CN110131742B - Boiler exhaust gas full component treatment and resource recovery method based on waste heat drive - Google Patents

Abstract

A boiler smoke exhaust full-component treatment and recycling recovery mode based on waste heat drive belongs to the technical field of smoke treatment and circular economy. Aiming at the problems that the current boiler flue gas contains a large amount of water vapor and waste heat resources thereof, the tail feather carries more particle pollutants, particularly a large amount of penetrable particles and acid gas, a high-temperature dust remover is adopted to recycle smoke dust, meanwhile, a cascade condensation water film pollution removal mode is adopted to recycle condensed water, a large amount of sulfur dioxide and other acid gas in the flue gas tail feather, filterable particles, flocculable particles in penetrable particles, soluble particles and the like, the condensed water is carried and finally comprehensively recycled by a waste heat evaporation salt-separating crystallization device and the like, the condensed water is converted into building materials, industrial raw materials and the like, the recycled waste heat is used for driving the flue gas resource development process, and the recycled waste heat is used for heating, heating process water or combustion air and the like to realize the comprehensive resource utilization of hot, wet and dangerous wastes, and realize near zero-cost operation and even produce energy-saving and resource-saving economic benefits.

Description

Boiler exhaust gas full component treatment and resource recovery method based on waste heat drive

Technical Field

The invention relates to a method for treating all components of boiler exhaust gas and recycling them based on waste heat drive, and belongs to the technical field of flue gas treatment and circular economy.

Background technique

The exhaust gas of boilers and various industrial kilns that use fossil fuels such as coal and natural gas for heating contains a large amount of water vapor and many gaseous and solid pollutants, becoming an important source of pollutants affecting the atmospheric environment. At present, the control of haze and visual whitening are the focus of environmental protection issues of the public and policy departments, and enterprises are also concerned about the technical feasibility and economic feasibility of its realization and the secondary pollution problems in operation, that is, the further treatment methods and costs of waste liquid and solid waste. However, the current understanding and understanding of the causes of haze, the mechanism and degree of the impact of exhaust on haze, etc., needs to be deepened, so the direction, mode and method of coal-fired boiler exhaust control need to be deeply studied, and the supporting solutions and systems of industry enterprises, technical effects, investment and operation economy and enterprise tolerance need to be further investigated. At present, there are several important issues and phenomena in the field of flue gas treatment of boilers or kilns, including: first, the mechanism and degree of the impact of boiler exhaust on haze; second, the flue gas composition after ultra-low emission treatment of boiler exhaust, and the mechanism of its impact on haze; third, the technical approach to deep flue gas treatment to fundamentally eliminate or at least significantly reduce its contribution to haze; fourth, how to deal with the associated waste liquid and solid waste, whether there is the possibility of resource utilization and its technical approach; fifth, whether the key technologies and key equipment for realizing the technical approach are feasible, whether the technical effects and the impact on haze or de-whitening can be confirmed, and whether there are technical, economic conditions and policy environment for industrial promotion.

Several important background technologies of the present invention are described as follows.

1. Technical research background on the causes of haze.

In order to facilitate the discussion of technical solutions to the problem, it is necessary to first summarize the general understanding and analysis of haze. Haze weather is a state of atmospheric pollution. Haze is a general description of the excessive content of various suspended particulate matter in the atmosphere. Haze is an aerosol system composed of dust, sulfuric acid (salt), nitric acid (salt) and other particles in the air, which causes visual impairment. Among them, particulate matter is the culprit for aggravating haze weather pollution. It is not only a pollutant, but also a carrier of toxic substances such as heavy metals and polycyclic aromatic hydrocarbons. The distribution of haze particles is relatively uniform, and the scale of haze particles is relatively small, ranging from 0.001 microns to 10 microns, with an average diameter of about 1 to 2 microns. The particles floating in the air cannot be seen by the naked eye. The chemical composition of aerosol is very complex. It contains various trace metals, inorganic oxides, sulfates, nitrates and oxygen-containing organic compounds. Sulfate formed by the conversion of sulfur dioxide in the atmosphere is one of the main components of aerosol. Sulfur is the most important element in aerosol, and its content can reflect the global migration, transmission and distribution of pollutants. The formation mechanism of nitrates and organic matter in aerosols is yet to be studied. Aerosols come from various elements in industrial areas (such as chlorine, tungsten, silver, manganese, cadmium, zinc, antimony, nickel, arsenic, chromium, etc.), and there are large regional differences. Meteorological experts said that the formation of smog weather is affected by meteorological conditions and is also related to the increase in atmospheric pollutant emissions. The sources of smog are varied, such as automobile exhaust, industrial emissions, construction dust, garbage incineration, volcanic eruptions, etc., and smog weather is usually formed by the mixed effects of multiple pollution sources.

Haze is harmful to the human body after being inhaled into the human respiratory tract. If inhaled for a long time, it can lead to death in severe cases. From the perspective of the harm to the human respiratory tract, particles larger than 10 microns are often retained in the nasal cavity and nasopharynx; most of the particles between 2 and 10 microns are retained in the upper respiratory tract, and the rate of retention of particles below 2 microns in the lungs increases as the particle size decreases, and the rate of attachment of particles below 0.1 microns in the bronchi increases as the particle size decreases. Since the diameter of the fine powder-like floating particles in haze is generally less than 0.01 microns, they can directly enter the bronchi and even the lungs through the respiratory system. Therefore, the greatest impact of haze is on the human respiratory system, and the diseases caused are mainly concentrated in respiratory diseases, cerebrovascular diseases, nasal inflammation and other diseases.

To sum up, haze is a relatively stable aerosol state in the atmosphere under certain meteorological conditions. It is the result of the combined action of acidic gases such as sulfur dioxide, nitrogen oxides, and particulate matter. Particulate matter with smaller particle sizes, i.e. particles in the range of 0.001-0.1 microns, are more likely to form a relatively stable aerosol state, which is also one of the main factors in the formation of haze. At the same time, it is generally believed that it poses a more serious threat to human health, and is of course one of the main directions of haze removal efforts.

(II) New findings on the impact of boiler exhaust on haze and its research progress.

In recent years, multiple rounds of universal environmental protection emission reduction and efficiency improvement have been implemented for polluting enterprises such as coal-fired power plants, and great results have been achieved. In particular, thermal power plants have generally achieved ultra-low emission indicators, that is, smoke dust is not higher than 5mg/Nm³, sulfur dioxide is not more than 35mg/Nm³, and nitrogen oxides are not more than 50mg/Nm³. However, air pollution has not been fundamentally solved, and heavy haze pollution weather still occurs from time to time. At present, my country's existing national standard for particulate matter measurement (GB16157-1996) only measures particles larger than 0.45 microns (PM0.45). So will particles smaller than PM0.45 be another major cause of haze? The white flue gas produced by the wet desulfurization device contains a large number of dissolved particles (TDS—Total Dissolved Solids), which refers to the sum of solid particles dissolved in liquid, and its particle size is usually between a few nanometers and several hundred nanometers (most of which are smaller than the current monitoring scale PM0.45). The flue gas at the outlet of the wet desulfurization device contains a large amount of supersaturated water vapor, which causes the chimney to have a "white plume mist trailing" phenomenon. Actual measurements have shown that it contains a large amount of water vapor, as well as a large amount of dissolved particles and harmful heavy metals. After being discharged from the chimney, it floats in the air. As the water evaporates, it suspends in the atmosphere for a long time as extremely fine particles. Usually PM2.5 particles can suspend in the atmosphere for 100 hours, PM1 particles can suspend in the atmosphere for 1000 hours, and these smaller particles (below PM0.45) suspend for a longer time and are more difficult to settle. As the meteorological conditions and humidity conditions are suitable, they quickly aggregate to form aerosols (Aerosol), causing haze pollution.

From August 15 to August 30, 2017, the No. 1 unit of Tianjin Guodian Jinneng Thermal Power Co., Ltd. was carefully measured. The unit's denitrification, dust removal, desulfurization and other environmental protection facilities were put into operation on August 12, 2009, at the same time as the main project. The unit's environmental protection test has met the standard (particulate matter emission is less than 10mg/Nm3). Through the method of washing with distilled water, three sets of data were obtained from the test. Based on this, it is reasonable to infer that dissolved particles are an important reason why haze has not been cured for a long time. The actual measurement results are analyzed as follows.

(1) In this test, after limestone-gypsum wet flue gas desulfurization, 87 mg/Nm3 of dissolved particles were discharged; after passing through the wet electrostatic precipitator, there were still 76 mg/Nm3. These two data are far higher than the existing national standard for ultra-clean emissions, which requires particulate matter emissions to be less than 10 mg/Nm3. This shows that: 1) a large number of dissolved particles are generated and discharged after wet desulfurization; 2) the wet electrostatic precipitator has little effect on removing these dissolved particles and cannot be used as an equipment option for removing dissolved particles; 3) these dissolved particles are extremely fine and are missed, escaping people's sight, traveling unimpeded, and being "legally" discharged into the atmosphere.

(2) Calculation of dissolved particle emissions and pollution assessment. Based on the measured dissolved particle emissions of this unit (capacity 330MW), it can be calculated that the amount of dissolved particles emitted into the atmosphere is about 131 kg/hour; the amount of dissolved particles discharged from the boiler flue gas of a 1000MW unit is 397 kg/hour. The "bursting" concentration of haze is 500µg/m3. The amount of dissolved particles emitted by this power plant per hour, under poor diffusion conditions, can cause the atmospheric space of about 2km (length) x2km (width) x200m (height) to reach the "bursting" concentration.

(3) The total installed capacity of coal-fired power generation in my country is about 906.25 million kilowatts, and 99% of them are equipped with wet desulfurization equipment. According to the above data, the emission of dissolved particles from desulfurization of coal-fired power plants alone is as high as about 2.6 million tons/year. This does not include users such as coking, steelmaking, chemical, cement, and industrial boilers. In addition, "splash evaporation" cooling is also a major emitter of dissolved particles. If all of these are included, it is estimated that the emission of dissolved particles (TDS) will be close to or higher than 10 million tons/year. The total amount of this pollutant even exceeds the total amount of dust emissions we know, plus the longer suspension time. Therefore, it can be concluded that dissolved particles are another important cause of smog.

(4) Analysis of pH value of water vapor in flue gas. The measured pH value is usually 2-3. When this water vapor enters the atmosphere, it will form acid rain if it rains (the annual emission of this highly acidic water vapor is as high as more than 900 million tons). This is because catalytic denitrification (SCR) converts more SO2 in the flue gas into SO3. The current wet desulfurization is extremely difficult to remove SO3; coupled with the "ammonia escape" phenomenon in denitrification, the water vapor in the exhaust gas has "strong acidity".

In summary, the flue gas from coal-fired boilers after wet desulfurization contains a large number of dissolved particles with smaller particle sizes. When "ultra-low" emissions are achieved, the actual content reaches 70-100 mg/Nm³, which is equivalent to or even greater than the sum of the contents of the three types of detected pollutants that have achieved "ultra-low" emissions. Therefore, it is not truly ultra-low emission, but because it is not currently included in the monitoring scope, it has not attracted enough attention. However, it and the escaped acidic gas are difficult to be captured by the wet electrostatic precipitator behind the desulfurization tower, and are thus discharged into the atmosphere in large quantities, becoming one of the main factors affecting the atmospheric environment and the formation of haze in the current exhaust gas.

(III) Technical analysis on the concept, essence and value of flue gas abatement.

At present, more than a dozen provinces and cities, including Shanghai, Tianjin, and Hebei, have issued local standards for "eliminating white smoke". Among them, southern regions such as Shanghai often require that smoke exhaust be dispersed in a wider range of altitudes by increasing the smoke temperature, so as to reduce dust pollution on the ground and adjacent air, and achieve visual "elimination of white smoke". However, unlike the southern regions, the white smoke elimination standards in the north do not require the complete elimination of white visual pollution in winter. For example, the policy departments in Tianjin, Hebei and other places require the goal and essence of white smoke elimination: to effectively reduce the water vapor content and soluble salts and other haze pollutants through condensation heat exchange, and reduce the visual pollution of "white smoke".

The key issue, essence and environmental value of white fog elimination lies first in significantly reducing various pollutants such as soluble salts, heavy metals, acidic gases and other key factors that affect haze and endanger human health. Secondly, it is to reduce and eliminate the visual pollution of "white fog". If the visual pollution is mainly solved but the various pollutants contained in the flue gas cannot be effectively controlled, then this kind of "white fog elimination" will instead increase a lot of electricity, reheat steam heat, etc., which will only increase energy consumption and corresponding pollution emissions. It has no practical significance. It should be carefully demonstrated again, and even the so-called "white fog elimination" behavior that puts the cart before the horse and tries to catch fish in a tree should be cancelled.

(IV) Overview of the development of leading patented technologies.

(1) The latest development of flue gas waste heat deep recovery and deoxidation technology.

Tsinghua University and other research institutes have developed and promoted a variety of patented flue gas waste heat recovery technologies in conjunction with enterprises, including a series of patented technical achievements of "flue gas waste heat recovery and heating technology based on steam heat carrier circulation", including "boiler exhaust heat and moisture direct recovery method and device based on steam heat carrier circulation" (2017104371042), "a boiler exhaust full heat recovery and flue gas whitening device with integrated smoke tower" ( 2017206805342), etc., have been successfully verified through demonstration projects and included in the 8th batch of energy-saving technology promotion catalogue of Shandong Province in 2018. It adopts direct heat exchange instead of heat pump to reduce the exhaust temperature to about 30°C, while recovering a large amount of water vapor latent heat and its water resources, reducing the water vapor content in the flue gas by more than 70% to 80%, thereby achieving significant whitening; at the same time, it can reduce filterable particulate matter (flue gas online monitoring parameter) by 30% to 50%, and more importantly, it can basically reduce soluble acidic gases such as sulfur dioxide and hydrogen chloride to 0, and can reduce gypsum, soluble salts, heavy metals, etc. by more than 60% to 80%, which means that many key factors in the cause of haze have been significantly eliminated.

(2) The feasibility and technical approaches of resource utilization of water vapor and pollutants contained in flue gas.

Currently mature technical approaches include: recycling dust through dust collectors for use as raw materials for building materials, etc.; removing sulfur dioxide through desulfurization towers and converting it into gypsum.

After achieving ultra-low emissions, the flue gas pollutant components can be transferred to the circulating water through condensation or spray washing methods, but the overflow sewage needs to find a technical way to recycle it. The current situation is that industrial high-salt wastewater and hazardous waste salt seriously pollute the environment, and the current conventional treatment methods such as pretreatment + membrane treatment + MVR evaporation or multi-effect evaporation technology routes, but the biggest problem with this technology is: huge initial investment and high operating energy consumption and operation and maintenance costs, which makes it difficult for most companies to bear the cost of comprehensive resource recovery of sewage and hazardous waste salt.

Professor Li Xianting's team at Tsinghua University creatively adopted a waste heat-driven sewage evaporation, crystallization and resource recycling technology. The waste heat from thermal power plants and other industrial enterprises was used to replace conventional MVR evaporation electricity consumption, multi-effect evaporation steam consumption and other high-quality energy sources as the driving heat source, achieving evaporation and salt separation of high-concentration wastewater, and ultimately achieving zero sewage discharge through waste salt resource utilization. The main patent results include: "A wastewater zero discharge and resource recovery system driven by waste heat from thermal power plants (2018214627233)", "A desulfurization wastewater recovery and crystallization salt purification system driven by waste heat (2018214381695)", etc.

This technical approach can significantly reduce initial investment, significantly reduce energy operating costs, and at the same time save the original process system including water resource taxes, sewage fees, process operation and maintenance costs, etc.

The above-mentioned series of patented technologies for thermal wastewater zero discharge and resource recovery driven by waste heat provide a solid technical foundation for the full-component treatment of flue gas and the resource utilization of its pollutants.

(3) Accurate measurement of smoke composition and its impact on haze.

A team of experts including Shi Aijun from Beijing Institute of Environmental Sciences and Zhao Jianfei from Beijing Hechen Smart Energy Technology Co., Ltd. used new high-precision nano-scale particle detection instruments and measurement methods to conduct theoretical research and engineering measurements on the measurement methods and component characteristics of multi-morphological particulate matter in wet flue gas from desulfurization. The results showed that the distribution of 11 major ions in the exhaust gas is as follows: ions containing sulfate and sulfite account for more than 82% of the total mass and are the main source of PM2.5; the nitrite content is also relatively high, so it is necessary to include fugitive particulate matter such as soluble particulate matter in the monitoring and control scope.

(4) Technological development of high-temperature dust collectors.

The successful development of filter materials made of basalt and other materials and their bag-type dust removal devices, as well as the development and successful promotion of static cleaning bag-type dust collector technology, can achieve efficient, stable and reliable dust removal in medium and high temperature flue gases, i.e. around 300-350°C, which can significantly improve the catalytic effect of subsequent medium and high temperature denitrification catalysts, thereby improving denitrification performance indicators, avoiding catalyst poisoning, and effectively reducing its investment and operating costs.

(5) Development of efficient and low-cost interlayer heat exchange technology.

The successful development of an extruded aluminum fin heat exchanger using graphene for surface corrosion protection can replace the existing heat exchangers made of expensive metals or special materials such as fluoroplastics. It has the characteristics of resistance to strong acid and alkali corrosion, low material consumption, long service life, and low maintenance. It is suitable for use in conditions where boiler flue gas is highly corrosive or even under deep condensation conditions.

In summary, the current technical research and promotion results on the preliminary technology of flue gas waste heat recovery, in-depth analysis of flue gas components and their impact on haze, flue gas waste heat recovery technology and wastewater zero discharge driven by waste heat and its resource recovery, etc., provide important technical conditions for the realization of full-component control of flue gas haze prevention and the development of pollutant resource recovery technology.

Summary of the invention

The purpose and task of the present invention is to adopt a hierarchical treatment system technology and a variety of key new technological achievements to achieve high-temperature and high-efficiency dust removal, high-efficiency denitrification, waste heat-driven cascade full-component treatment, waste heat-driven zero discharge of sewage and its resource recovery and other process flows in response to the above-mentioned boiler exhaust smoke full component analysis showing that there is a large amount of soluble salt escape, which significantly affects the formation of haze and air pollution. The present invention effectively reduces the existing fugitive pollutants such as water vapor, soluble salts, acidic gases in the exhaust gas, thereby achieving fundamental anti-haze and whitening treatment of boiler exhaust gas, and recycling the removed pollutants for resource utilization, achieving environmental protection benefits and circular economy at the same time, and transforming the environmental protection treatment of flue gas into sustainable economic development of developing flue gas resources.

The haze removal mechanism, flue gas resource development principle and technical approach based on the present invention are briefly described as follows. First, the flue gas is first dedusted by a high-temperature dust collector and then sent to a medium- and high-temperature denitrification device to improve the denitrification efficiency and further reduce the NOx content, avoid catalyst poisoning, reduce the excessive ammonia injection range and reduce the ammonia escape. Second, it helps to reduce the desulfurization agent poisoning in the desulfurization tower and ensure the stability of the desulfurization system operation and the stability of the desulfurization effect. Third, the deep dust reduction process no longer uses a wet electrostatic precipitator that has no substantial effect on the deep removal of dissolved particles and acidic gases, but instead uses a new stepped condensation water film decontamination module. The mechanism used includes: the flue gas at the outlet of wet desulfurization is in an oversaturated aerosol state with both fog and haze properties, and part of the nano-particles (0.001 to 0.1 microns) and acidic gases are formed into a mixture of sedimentable size by collision and condensation with droplets and larger particles, and are removed by removing this part of the liquid-solid mixture; through condensation heat exchange, various types of particles and acidic gases in the flue gas are removed. The body is removed with the condensed water; the water bath principle, that is, the particles in the flue gas, especially the dissolved particles and acidic gases, are washed by the circulating water spraying action; the water film dust removal principle, that is, by creating a large number of wall liquid films in direct contact with the flue gas, inertial collisions such as baffle scouring, Brownian motion and direct absorption, a large number of particles in the flue gas, especially dissolved particles and acidic gases, are adsorbed and absorbed; the chimney thermal pressure and high-altitude diffusion principle, that is, the flue gas with greatly reduced flue temperature and water vapor content is heated again to increase buoyancy and thermal pressure difference, and the air flow at the chimney mouth is increased. The purification emission effect of high-altitude diffusion, etc. Fourth, the resource development of flue gas pollutants, in addition to conventional dust collectors, is to recycle its water resources and waste heat resources through waste heat drive, and transform solid waste into industrial raw materials, building materials, etc. through flocculation precipitation, salt separation crystallization, etc. for resource utilization.

The specific description of the present invention is: a method for treating all components of boiler exhaust gas and recycling resources based on waste heat drive, a haze removal system and a resource recovery process system composed of a set of process flows for treating all components of flue gas and recycling resources are adopted to significantly reduce water vapor in flue gas, fugitive particles including nano-scale soluble salts and filterable particles, and acid gases including sulfur dioxide and hydrogen chloride, comprehensively eliminate or effectively inhibit the atmospheric haze influencing factors caused by exhaust gas, and realize the haze removal process and resource conversion and recovery process driven by waste heat recovery, characterized in that: the method for treating all components of boiler exhaust gas and recycling resources and its system process flow include high-temperature or medium-low temperature dust removal process, step-condensation waste heat recovery and water film decontamination process, medium-temperature flue gas heat recovery process, condensate reuse for desulfurization water replenishment and desalted water water production process, desulfurization wastewater zero discharge and resource recovery process, wherein the specific process flow is as follows:

i. First, a high-temperature dust collector 2 is provided at the flue gas outlet of the medium-temperature flue gas heating surface 1a of the tail heating surface of the boiler 1, where the outlet flue gas temperature is between 300 and 350°C. The flue gas after high-temperature dust removal is sent to the denitration device 3, eliminating the technical conditions for poisoning the denitration catalyst and achieving high-efficiency, low-cost, stable medium- and high-temperature denitration. During this period, the high-temperature dust collector 2 recovers dust resources used as building materials;

ii. Secondly, the primary purified flue gas after high-temperature dust removal and medium-high temperature denitrification enters the existing medium-low temperature flue gas heating surface 1b of the boiler and performs efficient and stable heat exchange under the technical conditions of avoiding dust scaling, and then enters the medium-temperature flue gas heat recovery device 6 to recover the sensible heat of the primary purified flue gas and serve as the heating heat source for the waste heat air preheater 4 and the waste heat evaporation crystallizer 8b, wherein the waste heat air preheater 4 performs the second stage sensible heat preheating on the boiler combustion air;

iii. Third, the flue gas continues to enter the desulfurization tower 7 for desulfurization, and the desulfurization wastewater is sent to the desulfurization wastewater waste heat evaporation and salt crystallization module 8 to recover water resources, industrial raw material resources including industrial grade sodium chloride, and building material raw material resources including gypsum and heavy metal stabilized compounds;

iv. Fourthly, the flue gas after desulfurization is sent to the flue gas inlet of the stepped condensed water membrane decontamination module 9 for deep purification, and passes through the flue gas inlet section 9k and the multi-stage washing condensed water membrane decontamination device from bottom to top, and is sent to the atmosphere for diffusion and discharge through the top smoke outlet of the stepped condensed water membrane decontamination module 9. During this period, water vapor in the flue gas, escaped particles including nano-scale soluble salts and filterable particles, and acid gases including sulfur dioxide and hydrogen chloride are absorbed, adsorbed and intercepted by the spray circulating water and condensed water, and sink to the water pool 9l at the bottom of the tower. The excess condensed water in the water pool 9l at the bottom of the tower is used as the circulating water replenishment of the desulfurization tower and the process replenishment in the plant, including the desalted water water production process;

v. Fifth, the high-temperature waste water in the water pool 91 at the bottom of the tower is sent to the waste heat user heater 10 to preheat the heating return water and process return water. A part of the waste water after cooling is then sent to the full-heat air preheater 11 to perform the first-stage full-heat preheating of the boiler combustion air, thereby realizing the cascade recovery and utilization of flue gas waste heat resources, especially latent waste heat;

vi. Sixth, the remaining part of the waste hot water after the temperature reduction of the waste heat user heater 10 is used as a medium-low temperature cold source and then sprayed by the circulating spray device 9f to drive the lower washing heat exchanger 9g to perform condensation heat exchange and wash the flue gas. The waste hot water outlet of the full heat air preheater 11 is used as a low temperature cold source and then sprayed by the washing spray device 9c to drive the upper washing heat exchanger 9d to perform deeper condensation heat exchange and wash the flue gas. At the same time, part of the heat user return water H0 is sent to the partition condenser 9h as a medium-low temperature cold source to perform partition condensation heat exchange on the flue gas, and the condensed water of the flue gas forms a water film on the outer wall surface of the partition condenser 9h to purify the flue gas through absorption and adsorption.

vii. Seventh, the secondary steam Q on the sewage side of the waste heat evaporation crystallizer 8b is sent to the secondary steam heat recovery device 8c, where it releases heat and condenses to recover the condensed water QN. The secondary waste water outlet J2 on the heated side is sent to the deoxidation heat exchanger 9a as a reheating heat source to achieve reheating and heating of the low-temperature and low-humidity purified flue gas, improve its buoyancy, and then diffuse it into the air for discharge.

The waste heat-driven boiler exhaust gas full component treatment and resource recovery system includes high-temperature or medium-low temperature dust removal module, cascade condensation waste heat recovery and water film decontamination module, medium-temperature flue gas heat recovery module, condensate reuse for desulfurization water replenishment and desalted water water production module, desulfurization wastewater zero discharge and resource recovery module. The specific process systems are as follows:

i. The flue gas inlet of the high-temperature dust collector 2 is connected to the flue gas outlet of the medium-temperature flue gas heating surface 1a of the tail heating surface of the boiler 1, where the outlet flue gas temperature is between 300 and 350°C. The flue gas outlet of the high-temperature dust collector 2 is connected to the flue gas inlet of the denitrification device 3, and the flue gas outlet of the denitrification device 3 is connected to the flue gas inlet of the medium- and low-temperature flue gas heating surface 1b. The bottom of the high-temperature dust collector 2 is provided with a discharge port for dust discharge D;

ii. The outlet flue gas of the medium and low temperature flue gas heating surface 1b is connected to the flue gas inlet of the medium temperature section flue gas heat recovery device 6 through the flue gas outlet after the boiler body air preheater, and the flue gas outlet of the medium temperature section flue gas heat recovery device 6 is communicated with the flue gas inlet of the desulfurization tower 7, and the heated water outlet of the medium temperature section flue gas heat recovery device 6 is respectively connected to the high temperature side water inlet of the waste heat air preheater 4 and the high temperature side water inlet of the waste heat evaporation crystallizer 8b, and the heated water inlet of the medium temperature section flue gas heat recovery device 6 is respectively connected to the high temperature side water outlet of the waste heat air preheater 4 and the high temperature side water outlet of the waste heat evaporation crystallizer 8b, the outlet of the combustion air outlet (A2) of the waste heat air preheater 4 is connected to the combustion air inlet of the boiler body air preheater, and the inlet of the combustion air inlet (A1) of the waste heat air preheater 4 is connected to the combustion air outlet of the full heat air preheater 11;

iii. The outlet water S of the desulfurization tower 7 enters the buffer tank 7a, and the outlet pipe of the desulfurization circulating return water SH at the circulating water outlet of the buffer tank 7a is connected to the inlet pipe of the desulfurization makeup water B2 and the inlet pipe of the desulfurization circulating supply water SG. The buffer tank 7a is also provided with a discharge port for gypsum SS and a drain port for desulfurization wastewater P1, wherein the drain port of desulfurization wastewater P1 is connected to the feed port of the wastewater pretreatment tank 8a of the desulfurization wastewater waste heat evaporation and salt separation crystallization module 8. The wastewater pretreatment tank 8a is also provided with a dosing inlet of the reagent G, a discharge port for desulfurization solid waste SP of building materials including gypsum and heavy metal stabilized compounds, and an outlet for desulfurization wastewater pretreatment water P2. The outlet of the treated water P2 is connected to the feed port of the waste heat evaporation crystallizer 8b, and the waste heat evaporation crystallizer 8b is also provided with a discharge port of industrial-grade sodium chloride NC and an outlet of secondary steam Q on the sewage side, and the outlet of secondary steam Q on the sewage side is connected to the steam inlet of the secondary steam heat recovery device 8c, and the secondary steam heat recovery device 8c is also provided with a water outlet of secondary steam condensed water QN and an inlet and outlet of heated water on the low-temperature side, wherein the outlet of the secondary waste hot water outlet J2 of the secondary steam heat recovery device 8c is connected to the water inlet of the de-whitening heat exchanger 9a, and the inlet of the secondary waste hot water inlet J1 of the secondary steam heat recovery device 8c is connected to the water outlet of the de-whitening heat exchanger 9a;

iv. The flue gas outlet of the desulfurization tower 7 is connected to the flue gas inlet of the stepped condensed water film decontamination module 9. The internal scaling of the stepped condensed water film decontamination module 9 includes the following condensation washing purification process structures or devices from bottom to top: a flue gas inlet section 9k and a multi-stage washing condensed water film decontamination device. The upper flue gas outlet of the multi-stage washing condensed water film decontamination device is connected to the external atmosphere through the tower top smoke outlet of the stepped condensed water film decontamination module 9. A tower bottom water pool 9l is provided at the lower part of the flue gas inlet section 9k;

v. The high-temperature waste water outlet of the tower bottom water pool 91 is respectively connected to the outlet pipe of the make-up water B, the inlet of the high-temperature side water inlet R1 of the waste heat user heater 10, and the circulating water inlet of the cooling tower after passing through the circulating water pump. The outlet pipe of the make-up water B is connected to the make-up pipe of the desulfurization make-up water B2 and the make-up pipe of the process make-up water B1 in the plant including the desalted water water production. The outlet of the high-temperature side outlet water R2 of the waste heat user heater 10 is respectively connected to the medium and low temperature cold source through the water inlet of the circulating spray device 9f and the water inlet of the full heat air preheater 11. The low-temperature side inlet of the waste heat user heater 10 is respectively connected to the return pipe of the hot user return water H0 and the water inlet of the partition condenser 9h. The outlet of the low-temperature side outlet water H2 of the waste heat user heater 10 is respectively connected to the outlet of the outlet water H2 of the partition condenser 9h and the outlet pipe of the hot user return water H3 after preheating;

vi. The water outlet of the bottom water pool of the full heat air preheater 11 is connected to the water inlet of the washing spray device 9c, the air inlet of the full heat air preheater 11 is connected to the boiler air inlet A0, and the air outlet of the full heat air preheater 11 is connected to the inlet of the combustion air inlet A1 of the waste heat air preheater 4.

The multi-stage washing condensate water film decontamination device inside the stepped condensate water film decontamination module 9 includes the following condensate washing purification process and devices from bottom to top: washing condensate rain area 9j, one-way rectifier 9i, partition condenser 9h, lower washing heat exchanger 9g, circulating spray device 9f, washing demister 9e, upper washing heat exchanger 9d, washing spray device 9c, demister 9b, dewhitening heat exchanger 9a, and the upper air outlet side of the dewhitening heat exchanger 9a is connected to the tower top smoke outlet of the stepped condensate water film decontamination module 9.

The high temperature dust collector 2 adopts a bag dust collector structure with basalt filter material.

The full-heat air preheater 11 adopts a direct contact spray heat exchange tower structure with the function of heating and humidifying the boiler combustion-supporting air.

The medium-temperature flue gas heating surface 1a, the medium-low temperature flue gas heating surface 1b, the waste heat air preheater 4, the medium-temperature flue gas heat recovery device 6, the deoxidizing heat exchanger 9a, and the partition condenser 9h adopt an extruded aluminum fin heat exchange tube structure covered with graphene material.

The lower washing heat exchanger 9g and the upper washing heat exchanger 9d are both made of condensing heat exchange materials that are resistant to strong acid and alkali corrosion and scaling and clogging.

The inlet washing solution Na of the washing spray device 9c adopts a dilute sodium hydroxide solution with a pH value of 7 to 10.

Aiming at the problem that the tail plume of boiler flue gas carries a lot of particulate pollutants, especially a large number of penetrable particulate matter (PM0.3 and below) and acidic gases, which is one of the main causes of haze and pollutes the adjacent ground environment, the present invention adopts a high-temperature dust collector to improve the efficiency of the denitrification device and eliminate the root cause of poisoning, and adopts a cascade condensation water membrane decontamination module to greatly reduce water vapor, sulfur dioxide, acidic gases such as hydrogen chloride, filterable particulate matter (FPM), condensable particulate matter (CPM) and soluble particulate matter (DPM) in penetrable particulate matter (EPM), and the clean exhaust gas is diffused and discharged at high altitude, which fundamentally reduces or basically eliminates the substantial adverse effects of boiler exhaust gas on the formation of haze and the surrounding air environment.

At the same time, waste heat recovery is used as an important driving force for the cascade haze removal process. On the one hand, the flue gas releases heat to produce a large amount of condensed water to remove water vapor, while absorbing or adsorbing more acidic gases, fugitive particulate matter and filterable particulate matter; on the other hand, a part of the higher-grade waste heat is used to reheat the outlet flue gas to achieve visual de-whitening and improve its diffusion effect in the atmosphere, effectively reducing the pollutant concentration in the adjacent airspace; at the same time, the condensed water flushes the lower flow wall to remove adherent pollutants and further absorbs or adsorbs more pollutants through the water film; then, the temperature of the circulating water falling into the water pool at the bottom of the tower is increased, and its heat can be transferred to the return water of the downstream hot user through the heat exchanger to realize the utilization of waste heat, and the cooled water is transported by the water pump to the spray device to continue to deeply recover the flue gas condensed water and absorb or adsorb pollutants, and the excess condensed water is discharged and reused as desulfurization makeup water.

Furthermore, waste heat recovery is used as the main driving force for the zero discharge of sewage that contains flue gas pollutants and its resource recovery process, while all water resources are recovered and the contents are graded. Heavy metal ions are removed through chemical precipitation and converted into a stable chemical state that can be used as raw materials for building materials; phosphate is converted into gypsum and chloride is converted into industrial raw materials such as industrial-grade sodium chloride through waste heat evaporation and salt crystallization technology, thereby realizing the transformation of pollutants into resources.

Finally, a graded method is adopted to extract waste heat resources of different grades from flue gas, and these are used for the above-mentioned driving process, as well as for heating boiler combustion air to save coal, heating heating network return water or process water to save steam, etc., thereby producing more significant energy-saving benefits. Energy saving itself correspondingly reduces fuel consumption and its pollution emissions.

The above energy-saving and resource recovery benefits are significant, thus achieving multiple effects such as flue gas pollution control, resource utilization and energy-saving benefits, realizing the integrated management process of energy conservation and emission reduction, and thus realizing economically beneficial environmental protection investment and operation, and having significant technical and economic advantages in the field of deep energy-saving recovery and emission reduction management of boiler exhaust gas.

On the other hand, when the system has a large heating load demand in winter, a large amount of waste heat from condensation of water vapor can be used for heat recovery heating; but in the non-heating period, in addition to part of it being used to preheat the boiler air intake to save fuel, it is necessary to find downstream heat users such as process water heating to realize the benefits of waste heat utilization. Otherwise, when the waste heat cannot be utilized more, it can only rely on the installation of cooling towers to dissipate this part of the waste heat into the atmosphere, but at this time, a part of the make-up water, water pump and fan power consumption are still required, so as to realize the above-mentioned cascade condensation water film decontamination process to achieve the purpose of deeply reducing flue gas pollution emissions and visual whitening in summer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a system of the present invention.

The numbers and names of the components in Figure 1 are as follows.

Boiler 1, medium-temperature flue gas heating surface 1a, medium-low temperature flue gas heating surface 1b, high-temperature dust collector 2, conventional medium-low temperature dust collector 2d, denitrification device 3, waste heat air preheater 4, induced draft fan 5, medium-temperature flue gas heat recovery device 6, desulfurization tower 7, buffer tank 7a, desulfurization waste water waste heat evaporation salt crystallization module 8, waste water pretreatment tank 8a, waste heat evaporation crystallizer 8b, secondary steam heat recovery device 8c, step condensate water film decontamination module 9, whitening heat exchanger 9a, demister 9b, washing spray device 9c, upper washing heat exchanger 9d, washing demister 9e, circulating spray device 9f, lower washing heat exchanger 9g, partition condenser 9h, one-way rectifier 9i, washing condensation rain area 9j, flue gas inlet section 9k, tower bottom water tank 9l, waste heat user heater 10, full heat air preheater 11, boiler air inlet A0, combustion-supporting air inlet A1, combustion-supporting air outlet A2, make-up water B, process make-up water B1, desulfurization make-up water B2, dust discharge D, heat user return water H0, low-temperature side inlet and outlet water H1, partition condenser outlet water H2, preheating heat user return water H3, heating outlet water J1, heating inlet water J2, washing solution Na, ammonia NH3, sewage side secondary steam Q, condensate water QN, hot water R, high-temperature side inlet water R1, high-temperature side outlet water R2, cooling tower inlet water R3, cooling tower return water R4, desulfurization tower outlet water S, desulfurization cycle return water SH, desulfurization cycle water supply SG, separation pool sewage SS, high-temperature dust collector inlet flue gas Y1, high-temperature dust collector outlet flue gas Y2, denitrification device outlet flue gas Y3, boiler outlet flue gas Y4, desulfurization tower outlet flue gas Y5, cascade condensate water membrane decontamination module outlet flue gas Y6.

Detailed ways

FIG. 1 is a system schematic diagram and an embodiment of the present invention.

Specific embodiment 1 of the present invention is as follows. Based on the waste heat driven boiler exhaust full component treatment and resource recovery method, a haze removal system and a resource recovery process system composed of a set of process flows for full component treatment of flue gas and resource recovery are adopted to significantly reduce water vapor, fugitive particles including nano-scale soluble salts and filterable particles, and acid gases including sulfur dioxide and hydrogen chloride in the flue gas, comprehensively eliminate or effectively inhibit the atmospheric haze influencing factors caused by exhaust gas, and realize the waste heat recovery driven haze removal process and resource conversion and recovery process, which is characterized in that: the boiler exhaust full component treatment and resource recovery method and its system process flow include high temperature or medium and low temperature dust removal process, step condensation waste heat recovery and water film decontamination process, medium temperature flue gas heat recovery process, condensate reuse for desulfurization water replenishment and desalted water water production process, desulfurization wastewater zero discharge and resource recovery process, wherein the specific process flow is as follows:

i. First, a high-temperature dust collector 2 is provided at the flue gas outlet of the medium-temperature flue gas heating surface 1a of the tail heating surface of the boiler 1, where the outlet flue gas temperature is between 300 and 350°C. The flue gas after high-temperature dust removal is sent to the denitration device 3, eliminating the technical conditions for poisoning the denitration catalyst and achieving high-efficiency, low-cost, stable medium- and high-temperature denitration. During this period, the high-temperature dust collector 2 recovers dust resources used as building materials;

ii. Secondly, the primary purified flue gas after high-temperature dust removal and medium-high temperature denitrification enters the existing medium-low temperature flue gas heating surface 1b of the boiler and performs efficient and stable heat exchange under the technical conditions of avoiding dust scaling, and then enters the medium-temperature flue gas heat recovery device 6 to recover the sensible heat of the primary purified flue gas and serve as the heating heat source for the waste heat air preheater 4 and the waste heat evaporation crystallizer 8b, wherein the waste heat air preheater 4 performs the second stage sensible heat preheating on the boiler combustion air;

iii. Third, the flue gas continues to enter the desulfurization tower 7 for desulfurization, and the desulfurization wastewater is sent to the desulfurization wastewater waste heat evaporation and salt crystallization module 8 to recover water resources, industrial raw material resources including industrial grade sodium chloride, and building material raw material resources including gypsum and heavy metal stabilized compounds;

iv. Fourthly, the flue gas after desulfurization is sent to the flue gas inlet of the stepped condensed water membrane decontamination module 9 for deep purification, and passes through the flue gas inlet section 9k and the multi-stage washing condensed water membrane decontamination device from bottom to top, and is sent to the atmosphere for diffusion and discharge through the top smoke outlet of the stepped condensed water membrane decontamination module 9. During this period, water vapor in the flue gas, escaped particles including nano-scale soluble salts and filterable particles, and acid gases including sulfur dioxide and hydrogen chloride are absorbed, adsorbed and intercepted by the spray circulating water and condensed water, and sink to the water pool 9l at the bottom of the tower. The excess condensed water in the water pool 9l at the bottom of the tower is used as the circulating water replenishment of the desulfurization tower and the process replenishment in the plant, including the desalted water water production process;

v. Fifth, the high-temperature waste water in the water pool 91 at the bottom of the tower is sent to the waste heat user heater 10 to preheat the heating return water and process return water. A part of the waste water after cooling is then sent to the full-heat air preheater 11 to perform the first-stage full-heat preheating of the boiler combustion air, thereby realizing the cascade recovery and utilization of flue gas waste heat resources, especially latent waste heat;

vi. Sixth, the remaining part of the waste hot water after the temperature reduction of the waste heat user heater 10 is used as a medium-low temperature cold source and then sprayed by the circulating spray device 9f to drive the lower washing heat exchanger 9g to perform condensation heat exchange and wash the flue gas. The waste hot water outlet of the full heat air preheater 11 is used as a low temperature cold source and then sprayed by the washing spray device 9c to drive the upper washing heat exchanger 9d to perform deeper condensation heat exchange and wash the flue gas. At the same time, part of the heat user return water H0 is sent to the partition condenser 9h as a medium-low temperature cold source to perform partition condensation heat exchange on the flue gas, and the condensed water of the flue gas forms a water film on the outer wall surface of the partition condenser 9h to purify the flue gas through absorption and adsorption.

vii. Seventh, the secondary steam Q on the sewage side of the waste heat evaporation crystallizer 8b is sent to the secondary steam heat recovery device 8c, where it releases heat and condenses to recover the condensed water QN. The secondary waste water outlet J2 on the heated side is sent to the deoxidation heat exchanger 9a as a reheating heat source to achieve reheating and heating of the low-temperature and low-humidity purified flue gas, improve its buoyancy, and then diffuse it into the air for discharge.

The waste heat-driven boiler exhaust gas full component treatment and resource recovery system includes high-temperature or medium-low temperature dust removal module, cascade condensation waste heat recovery and water film decontamination module, medium-temperature flue gas heat recovery module, condensate reuse for desulfurization water replenishment and desalted water water production module, desulfurization wastewater zero discharge and resource recovery module. The specific process systems are as follows:

i. The flue gas inlet of the high-temperature dust collector 2 is connected to the flue gas outlet of the medium-temperature flue gas heating surface 1a of the tail heating surface of the boiler 1, where the outlet flue gas temperature is between 300 and 350°C. The flue gas outlet of the high-temperature dust collector 2 is connected to the flue gas inlet of the denitrification device 3, and the flue gas outlet of the denitrification device 3 is connected to the flue gas inlet of the medium- and low-temperature flue gas heating surface 1b. The bottom of the high-temperature dust collector 2 is provided with a discharge port for dust discharge D;

ii. The outlet flue gas of the medium and low temperature flue gas heating surface 1b is connected to the flue gas inlet of the medium temperature section flue gas heat recovery device 6 through the flue gas outlet after the boiler body air preheater, and the flue gas outlet of the medium temperature section flue gas heat recovery device 6 is communicated with the flue gas inlet of the desulfurization tower 7, and the heated water outlet of the medium temperature section flue gas heat recovery device 6 is respectively connected to the high temperature side water inlet of the waste heat air preheater 4 and the high temperature side water inlet of the waste heat evaporation crystallizer 8b, and the heated water inlet of the medium temperature section flue gas heat recovery device 6 is respectively connected to the high temperature side water outlet of the waste heat air preheater 4 and the high temperature side water outlet of the waste heat evaporation crystallizer 8b, the outlet of the combustion air outlet (A2) of the waste heat air preheater 4 is connected to the combustion air inlet of the boiler body air preheater, and the inlet of the combustion air inlet (A1) of the waste heat air preheater 4 is connected to the combustion air outlet of the full heat air preheater 11;

iii. The outlet water S of the desulfurization tower 7 enters the buffer tank 7a, and the outlet pipe of the desulfurization circulating return water SH at the circulating water outlet of the buffer tank 7a is connected to the inlet pipe of the desulfurization makeup water B2 and the inlet pipe of the desulfurization circulating supply water SG. The buffer tank 7a is also provided with a discharge port for gypsum SS and a drain port for desulfurization wastewater P1, wherein the drain port of desulfurization wastewater P1 is connected to the feed port of the wastewater pretreatment tank 8a of the desulfurization wastewater waste heat evaporation and salt separation crystallization module 8. The wastewater pretreatment tank 8a is also provided with a dosing inlet of the reagent G, a discharge port for desulfurization solid waste SP of building materials including gypsum and heavy metal stabilized compounds, and an outlet for desulfurization wastewater pretreatment water P2. The outlet of the treated water P2 is connected to the feed port of the waste heat evaporation crystallizer 8b, and the waste heat evaporation crystallizer 8b is also provided with a discharge port of industrial-grade sodium chloride NC and an outlet of secondary steam Q on the sewage side, and the outlet of secondary steam Q on the sewage side is connected to the steam inlet of the secondary steam heat recovery device 8c, and the secondary steam heat recovery device 8c is also provided with a water outlet of secondary steam condensed water QN and an inlet and outlet of heated water on the low-temperature side, wherein the outlet of the secondary waste hot water outlet J2 of the secondary steam heat recovery device 8c is connected to the water inlet of the de-whitening heat exchanger 9a, and the inlet of the secondary waste hot water inlet J1 of the secondary steam heat recovery device 8c is connected to the water outlet of the de-whitening heat exchanger 9a;

iv. The flue gas outlet of the desulfurization tower 7 is connected to the flue gas inlet of the stepped condensed water film decontamination module 9. The internal scaling of the stepped condensed water film decontamination module 9 includes the following condensation washing purification process structures or devices from bottom to top: a flue gas inlet section 9k and a multi-stage washing condensed water film decontamination device. The upper flue gas outlet of the multi-stage washing condensed water film decontamination device is connected to the external atmosphere through the tower top smoke outlet of the stepped condensed water film decontamination module 9. A tower bottom water pool 9l is provided at the lower part of the flue gas inlet section 9k;

v. The high-temperature waste water outlet of the tower bottom water pool 91 is respectively connected to the outlet pipe of the make-up water B, the inlet of the high-temperature side water inlet R1 of the waste heat user heater 10, and the circulating water inlet of the cooling tower after passing through the circulating water pump. The outlet pipe of the make-up water B is connected to the make-up pipe of the desulfurization make-up water B2 and the make-up pipe of the process make-up water B1 in the plant including the desalted water water production. The outlet of the high-temperature side outlet water R2 of the waste heat user heater 10 is respectively connected to the medium and low temperature cold source through the water inlet of the circulating spray device 9f and the water inlet of the full heat air preheater 11. The low-temperature side inlet of the waste heat user heater 10 is respectively connected to the return pipe of the hot user return water H0 and the water inlet of the partition condenser 9h. The outlet of the low-temperature side outlet water H2 of the waste heat user heater 10 is respectively connected to the outlet of the outlet water H2 of the partition condenser 9h and the outlet pipe of the hot user return water H3 after preheating;

vi. The water outlet of the bottom water pool of the full heat air preheater 11 is connected to the water inlet of the washing spray device 9c, the air inlet of the full heat air preheater 11 is connected to the boiler air inlet A0, and the air outlet of the full heat air preheater 11 is connected to the inlet of the combustion air inlet A1 of the waste heat air preheater 4.

The multi-stage washing condensate water film decontamination device inside the stepped condensate water film decontamination module 9 includes the following condensate washing purification process and devices from bottom to top: washing condensate rain area 9j, one-way rectifier 9i, partition condenser 9h, lower washing heat exchanger 9g, circulating spray device 9f, washing demister 9e, upper washing heat exchanger 9d, washing spray device 9c, demister 9b, dewhitening heat exchanger 9a, and the upper air outlet side of the dewhitening heat exchanger 9a is connected to the tower top smoke outlet of the stepped condensate water film decontamination module 9.

The high temperature dust collector 2 adopts a bag dust collector structure with basalt filter material.

The full-heat air preheater 11 adopts a direct contact spray heat exchange tower structure with the function of heating and humidifying the boiler combustion-supporting air.

The medium-temperature flue gas heating surface 1a, the medium-low temperature flue gas heating surface 1b, the waste heat air preheater 4, the medium-temperature flue gas heat recovery device 6, the deoxidizing heat exchanger 9a, and the partition condenser 9h adopt an extruded aluminum fin heat exchange tube structure covered with graphene material.

If the high-temperature dust collector 2 is not set, a conventional medium-low temperature dust collector 2d is set, wherein the flue gas inlet of the conventional medium-low temperature dust collector 2d is connected to the flue gas outlet of the boiler 2, and the flue gas outlet of the conventional medium-low temperature dust collector 2d is connected to the flue gas inlet of the desulfurization tower 7 or the medium-temperature section flue gas heat recovery device 6.

If the desulfurization tower 7 for wet desulfurization is not set up, but a high-temperature dry or semi-dry desulfurization device is set up in the furnace, the circulating water outlet of the buffer tank 7a is changed to a water inlet connected to the outlet pipe of the make-up water B, and the discharge outlet of the desulfurization wastewater P1 of the buffer tank 7a is still connected to the feed inlet of the wastewater pretreatment tank 8a of the desulfurization wastewater waste heat evaporation and salt separation crystallization module 8 which is changed to perform zero sewage discharge and salt separation crystallization functions on a part of the external drainage from the make-up water B.

The lower washing heat exchanger 9g and the upper washing heat exchanger 9d are both made of condensing heat exchange materials that are resistant to strong acid and alkali corrosion and scaling and clogging.

The inlet washing solution Na of the washing spray device 9c adopts a dilute sodium hydroxide solution with a pH value of 7 to 10.

The above-mentioned embodiment 1 is applicable to the comprehensive treatment and resource development and utilization of boiler smoke in new projects, and the deep haze removal and resource development and utilization of industrial kiln or process flue gas in new or expanded projects. However, for existing coal-fired boiler systems, the flue gas tail heating surface and even the denitrification device are integrated in the boiler body, and there is not enough space to install the high-temperature dust collector in the boiler body, or to lead the medium and high temperature flue gas to the high-temperature dust collector and then return it to the original flue. Therefore, it is difficult to apply it directly. It can be modified according to the method of the following specific embodiment 2.

Specific embodiment 2 of the present invention is as follows.

If it is not suitable to install the high-temperature dust collector 2 due to reasons such as on-site installation space, a conventional medium-low temperature dust collector 2d may be installed instead, wherein the flue gas inlet of the conventional medium-low temperature dust collector 2d is connected to the flue gas outlet of the boiler 2, and the flue gas outlet of the conventional medium-low temperature dust collector 2d is connected to the flue gas inlet of the desulfurization tower 7 or the medium-temperature section flue gas heat recovery device 6. Other system processes and features of this specific embodiment are the same as those of specific embodiment 1.

Specific embodiment 3 of the present invention is as follows.

If the existing boiler adopts dry or semi-dry desulfurization, that is, the wet desulfurization tower 7 is not set, the flue gas outlet of the medium-temperature flue gas heat recovery device 6 is changed to communicate with the flue gas inlet of the stepped condensation water membrane decontamination module 9. The other system processes and features of this specific embodiment are the same as those of the above-mentioned specific embodiment 1. At this time, the cleanliness of the flue gas after dry desulfurization, high-temperature dust removal and high-temperature denitrification is very high. After that, all kinds of heat exchangers on the flue gas channel, including the medium and low temperature flue gas heating surface 1b, the existing air preheater of the boiler, the flue gas side of the heat exchange element of the medium temperature flue gas heat recovery device 6, etc., have solved the inherent problems such as scaling and blockage, reduced efficiency, regular cleaning and maintenance, and accelerated corrosion.

It should be noted that the present invention proposes a method for deep treatment of all components of boiler exhaust gas and its resource recovery to eliminate the factors affecting haze and surrounding environmental pollution, and provides specific implementation methods, processes and implementation devices for how to achieve the above-mentioned purposes by adopting a stepped haze removal method, a waste heat utilization method and a resource return water method. According to this overall solution, there may be different specific implementation measures and specific implementation devices with different structures. The above specific implementation method is only one of them. Any other similar simple deformation implementation methods, such as adopting different heat exchange structures; adding or reducing several layers of stepped treatment measures; or simply adjusting the waste hot water system pipeline connection method, the inlet and outlet water sources and the number of grades; or performing deformation methods that ordinary professionals can think of, etc., or applying the technical method with the same or similar structure to different types of power equipment exhaust or exhaust, etc. and other similar applications, all fall within the protection scope of the present invention.

Claims (8)

1. A process flow of full-component treatment and resource recovery of boiler exhaust gas driven by waste heat, a haze removal system and a resource recovery process system composed of a set of process flows of full-component treatment and resource recovery of flue gas are used to significantly reduce water vapor, fugitive particles including nano-scale soluble salts and filterable particles, and acid gases including sulfur dioxide and hydrogen chloride in flue gas, comprehensively eliminate or effectively inhibit the factors affecting atmospheric haze caused by exhaust gas, and realize a process of haze removal and resource conversion and recovery driven by waste heat recovery, characterized in that: the process flow of full-component treatment and resource recovery of boiler exhaust gas includes a high-temperature or medium-low temperature dust removal process, a step-condensation waste heat recovery and a water film decontamination process, a medium-temperature flue gas heat recovery process, a condensate reuse for desulfurization water replenishment and desalted water water production process, a desulfurization wastewater zero discharge and resource recovery process, wherein the specific process flow is as follows: First, a high-temperature dust collector (2) is provided at the flue gas outlet of a medium-temperature flue gas heating surface (1a) having an outlet flue gas temperature between 300°C and 350°C in the rear heating surface of the boiler (1). The flue gas after high-temperature dust removal is sent to a denitration device (3), thereby eliminating the technical conditions for causing poisoning of the denitration catalyst and achieving high-efficiency, low-cost, stable medium- and high-temperature denitration. During this period, the high-temperature dust collector (2) recovers dust resources for use as building materials. Secondly, the primary purified flue gas after high-temperature dust removal and medium-high temperature denitrification enters the existing medium-low temperature flue gas heating surface (1b) of the boiler and performs efficient and stable heat exchange under the technical conditions of avoiding dust scaling, and then enters the medium-temperature flue gas heat recovery device (6) to recover the sensible heat of the primary purified flue gas and serve as a heating source for the waste heat air preheater (4) and the waste heat evaporation crystallizer (8b), wherein the waste heat air preheater (4) performs the second stage sensible heat preheating on the boiler combustion air; Thirdly, the flue gas continues to enter the desulfurization tower (7) for desulfurization, and the desulfurization wastewater is sent to the desulfurization wastewater waste heat evaporation and salt separation crystallization module (8) to recover water resources, industrial raw material resources including industrial grade sodium chloride, and building material raw material resources including gypsum and heavy metal stabilized compounds; Fourthly, the flue gas after desulfurization is sent to the flue gas inlet of the cascade condensation water membrane decontamination module (9) for deep purification, and passes through the flue gas inlet section (9k) and the multi-stage washing condensation water membrane decontamination device from bottom to top, and is sent to the atmosphere for diffusion and discharge through the top smoke outlet of the cascade condensation water membrane decontamination module (9). During this period, water vapor in the flue gas, escaped particulate matter including nano-scale soluble salts and filterable particulate matter, and acid gases including sulfur dioxide and hydrogen chloride are absorbed, adsorbed and intercepted by the spray circulating water and condensed water, and sink to the water pool (9l) at the bottom of the tower. The excess condensed water in the water pool (9l) at the bottom of the tower is used as circulating water replenishment for the desulfurization tower and process replenishment in the plant, including the desalted water water production process. Fifth, the high-temperature waste heat water in the water pool (91) at the bottom of the tower is sent to the waste heat user heater (10) for preheating heating return water and process return water. A portion of the waste heat water after cooling is then sent to the full-heat air preheater (11) for first-stage full-heat preheating of the boiler combustion air, thereby realizing the cascade recovery and utilization of flue gas waste heat resources, especially latent waste heat; Sixthly, the remaining part of the waste hot water after the temperature reduction of the waste heat user heater (10) is used as a medium-low temperature cold source and is sprayed by the circulating spray device (9f) to drive the lower washing heat exchanger (9g) to perform condensation heat exchange and flue gas washing. The waste hot water outlet of the full heat air preheater (11) is used as a low temperature cold source and is sprayed by the washing spray device (9c) to drive the upper washing heat exchanger (9d) to perform deeper condensation heat exchange and flue gas washing. At the same time, a part of the heat user return water (H0) is sent to the partition condenser (9h) as a medium-low temperature cold source to perform partition condensation heat exchange on the flue gas, so that the condensed water of the flue gas forms a water film on the outer wall surface of the partition condenser (9h) to purify the flue gas through absorption and adsorption. Seventh, the secondary steam (Q) on the sewage side of the waste heat evaporation crystallizer (8b) is sent to the secondary steam heat recovery device (8c) to release heat and condense to recover the condensate (QN) water resources. The secondary waste water outlet (J2) on the heating side is sent to the deoxidation heat exchanger (9a) as a reheating heat source to achieve reheating and heating of the low-temperature and low-humidity purified flue gas, improve the buoyancy, and then diffuse it into the high altitude for discharge. 2. A system for the full-component treatment and resource recovery process of boiler exhaust smoke driven by waste heat as claimed in claim 1, characterized in that the system for realizing the full-component treatment and resource recovery process of boiler exhaust smoke driven by waste heat includes a high-temperature or medium-low temperature dust removal module, a step condensation waste heat recovery and water film decontamination module, a medium-temperature flue gas heat recovery module, a condensate reuse module for desulfurization water replenishment and desalted water water production module, a desulfurization wastewater zero discharge and resource recovery module, wherein the specific process system is as follows: i. The flue gas inlet of the high-temperature dust collector (2) is connected to the flue gas outlet of the medium-temperature flue gas heating surface (1a) of the rear heating surface of the boiler (1) whose outlet flue gas temperature is between 300 and 350°C, the flue gas outlet of the high-temperature dust collector (2) is connected to the flue gas inlet of the denitrification device (3), the flue gas outlet of the denitrification device (3) is connected to the flue gas inlet of the medium- and low-temperature flue gas heating surface (1b), and a discharge port for dust exhaust (D) is provided at the bottom of the high-temperature dust collector (2); ii. The outlet flue gas of the medium and low temperature flue gas heating surface (1b) is connected to the flue gas inlet of the medium temperature section flue gas heat recovery device (6) through the flue gas outlet after the boiler body air preheater, the flue gas outlet of the medium temperature section flue gas heat recovery device (6) is connected to the flue gas inlet of the desulfurization tower (7), the heated water outlet of the medium temperature section flue gas heat recovery device (6) is respectively connected to the high temperature side water inlet of the waste heat air preheater (4) and the high temperature side water inlet of the waste heat evaporation crystallizer (8b), the heated water inlet of the medium temperature section flue gas heat recovery device (6) is respectively connected to the high temperature side water outlet of the waste heat air preheater (4) and the high temperature side water outlet of the waste heat evaporation crystallizer (8b), the outlet of the combustion air outlet (A2) of the waste heat air preheater (4) is connected to the combustion air inlet of the boiler body air preheater, and the inlet of the combustion air inlet (A1) of the waste heat air preheater (4) is connected to the combustion air outlet of the full heat air preheater (11); iii. The effluent (S) of the desulfurization tower (7) enters the buffer tank (7a). The outlet pipe of the desulfurization circulating return water (SH) at the circulating water outlet of the buffer tank (7a) is connected to the inlet pipe of the desulfurization makeup water (B2) and the inlet pipe of the desulfurization circulating supply water (SG). The buffer tank (7a) is also provided with a discharge port for gypsum (SS) and a drain port for desulfurization wastewater (P1). The drain port of desulfurization wastewater (P1) is connected to the feed port of the wastewater pretreatment tank (8a) of the desulfurization wastewater waste heat evaporation and salt separation crystallization module (8). The wastewater pretreatment tank (8a) is also provided with a dosing inlet for the reagent (G), a discharge port for desulfurization solid waste (SP) of building materials including gypsum and heavy metal stabilized compounds, and an outlet for desulfurization wastewater pretreatment water (P2). The outlet of the water pretreatment water (P2) is connected to the feed port of the waste heat evaporation crystallizer (8b), the waste heat evaporation crystallizer (8b) is also provided with an outlet of industrial-grade sodium chloride (NC) and an outlet of secondary steam (Q) on the sewage side, the outlet of the secondary steam (Q) on the sewage side is connected to the steam inlet of the secondary steam heat recovery device (8c), the secondary steam heat recovery device (8c) is also provided with an outlet of secondary steam condensed water (QN) and an inlet and outlet of heated water on the low-temperature side, wherein the outlet of the secondary waste hot water outlet (J2) of the secondary steam heat recovery device (8c) is connected to the water inlet of the descaling heat exchanger (9a), and the inlet of the secondary waste hot water inlet (J1) of the secondary steam heat recovery device (8c) is connected to the water outlet of the descaling heat exchanger (9a); iv. The flue gas outlet of the desulfurization tower (7) is connected to the flue gas inlet of the stepped condensed water film decontamination module (9), and the internal scaling of the stepped condensed water film decontamination module (9) includes the following condensation washing purification process structures or devices from bottom to top: a flue gas inlet section (9k) and a multi-stage washing condensed water film decontamination device, the upper flue gas outlet of the multi-stage washing condensed water film decontamination device is connected to the external atmosphere through the tower top smoke outlet of the stepped condensed water film decontamination module (9), and a tower bottom water pool (9l) is arranged at the lower part of the flue gas inlet section (9k); v. The high-temperature waste water outlet of the tower bottom water pool (9l) is connected to the outlet pipe of the make-up water (B), the inlet of the high-temperature side water inlet (R1) of the waste heat user heater (10), and the circulating water inlet of the cooling tower after passing through the circulating water pump. The outlet pipe of the make-up water (B) is connected to the make-up water pipe of the desulfurization make-up water (B2) and the make-up water pipe of the process make-up water (B1) in the plant, including the desalted water water production. The outlet of the high-temperature side outlet water (R2) of the waste heat user heater (10) is connected to the middle The low-temperature cold source is connected to the water inlet of the full-heat air preheater (11) through the water inlet of the circulating spray device (9f); the low-temperature side inlet of the waste heat user heater (10) is respectively connected to the return pipe of the hot user return water (H0) and the water inlet of the partition condenser (9h); the outlet of the low-temperature side outlet water (H2) of the waste heat user heater (10) is respectively connected to the outlet of the outlet water (H2) of the partition condenser (9h) and the outlet pipe of the hot user return water (H3) after preheating; vi. The water outlet of the water pool at the bottom of the full-heat air preheater (11) is connected to the water inlet of the washing spray device (9c), the air inlet of the full-heat air preheater (11) is connected to the boiler air inlet (A0), and the air outlet of the full-heat air preheater (11) is connected to the inlet of the combustion air inlet A1 of the waste heat air preheater (4); the multi-stage washing condensate film decontamination device inside the cascade condensate film decontamination module (9) includes the following condensate washing purification process and device from bottom to top: washing condensate rain area (9 j), a one-way rectifier (9i), a partition condenser (9h), a lower washing heat exchanger (9g), a circulating spray device (9f), a washing demister (9e), an upper washing heat exchanger (9d), a washing spray device (9c), a demister (9b), and a whitening heat exchanger (9a); the upper air outlet side of the whitening heat exchanger (9a) is connected to the tower top smoke outlet of the stepped condensation water film decontamination module (9); the high-temperature dust collector (2) adopts a bag dust collector structure with basalt filter material. 3. The system for the waste heat-driven boiler exhaust gas full-component treatment and resource recovery process as described in claim 2 is characterized in that the full-heat air preheater (11) adopts a direct contact spray heat exchange tower structure with the function of heating and humidifying the boiler combustion-supporting air. 4. The system for the waste heat-driven boiler exhaust full-component treatment and resource recovery process as described in claim 2 is characterized in that the medium-temperature flue gas heating surface (1a), medium-low temperature flue gas heating surface (1b), waste heat air preheater (4), medium-temperature section flue gas heat recovery device (6), deoxidizing heat exchanger (9a), and partition condenser (9h) adopt an extruded aluminum fin heat exchange tube structure coated with graphene material. 5. The system for the waste heat-driven boiler exhaust full-component treatment and resource recovery process as described in claim 2 is characterized in that if the high-temperature dust collector (2) is not provided, a conventional medium-low temperature dust collector (2d) is provided, wherein the flue gas inlet of the conventional medium-low temperature dust collector (2d) is communicated with the flue gas outlet of the boiler (1), and the flue gas outlet of the conventional medium-low temperature dust collector (2d) is communicated with the flue gas inlet of the desulfurization tower (7) or the medium-temperature section flue gas heat recovery device (6). 6. The system for the whole-component treatment and resource recovery process of boiler flue gas driven by waste heat as described in claim 2 is characterized in that if the desulfurization tower (7) is not set up, but a high-temperature dry or semi-dry desulfurization device is set up in the furnace, then the circulating water outlet of the buffer tank (7a) is changed to an inlet connected to the outlet pipe of the make-up water (B), and the outlet of the desulfurized wastewater (P1) of the buffer tank (7a) is still connected to the feed inlet of the wastewater pretreatment tank (8a) of the desulfurized wastewater waste heat evaporation and salt crystallization module (8) which is changed to perform zero sewage discharge and salt separation and crystallization functions on a part of the external drainage from the make-up water (B). 7. The system for the waste heat-driven boiler flue gas full-component treatment and resource recovery process as described in claim 2 is characterized in that the lower washing heat exchanger (9g) and the upper washing heat exchanger (9d) are both made of condensing heat exchange materials that are resistant to strong acid and alkali corrosion and scaling and fouling. 8. The system for the waste heat-driven boiler flue gas full-component treatment and resource recovery process as claimed in claim 2, characterized in that the inlet washing solution (Na) of the washing spray device (9c) adopts a dilute sodium hydroxide solution with a pH value of 7 to 10.