CN101776270A - Method for performing mixed incineration on agricultural and forestal wastes, sludge and household refuses by using fluidized bed - Google Patents

Abstract

The invention relates to the technical field of energy and environmental engineering, and provides a method for performing mixed incineration on agricultural and forestal wastes, sludge and household refuses by using a fluidized bed. In the method, a fluidized bed incinerator needed by incineration is provided, and the agricultural and forestal wastes, the household refuses and the sludge after crushing treatment are mixed and incinerated in the incinerator. The agricultural and forestal wastes are used for igniting; when the temperature in the incinerator rises to 850 DEG C, the household refuses and the sludge are added into the incinerator to realize mixed incineration, wherein the agricultural and forestal wastes account for less than or equal to 40 percent of the mass of mixed fuel, and the sludge accounts for less than or equal to 30 percent of the mass of the mixed fuel; the incinerating temperature in the fluidized bed incinerator is controlled to between 850 and 950 DEG C; and smoke generated by the incineration is controlled to stay in the incinerator for more than 2 seconds. The method has low cost, improves the incineration efficiency of the refuse incinerator, solves the problem of pollution caused by the sludge, utilizes the agricultural and forestal wastes as resources, reduces the emission of pollutants, particularly heavy metal and dioxin, and reduces the consumption of fossil energy.

Description

Method for mixed incineration of agricultural and forestry waste, sludge and domestic waste by using fluidized bed

technical field

The invention belongs to the technical field of energy and environment engineering, and in particular relates to a method for treating agricultural and forestry waste, sludge and municipal solid waste by utilizing fluidized bed mixed incineration.

Background technique

With the development of economy and the process of urbanization, the output of municipal solid waste is increasing day by day. A large amount of municipal solid waste has caused great pressure and harm to people's living environment and urban development. How to realize the "three modernizations" of harmless, reduction and resource utilization of municipal solid waste has become the focus of research. In 2008, the volume of domestic waste removal in my country reached 174 million tons, the average daily domestic waste disposal volume was 315,300 tons, and the harmless treatment rate of domestic waste reached 66.03%. One of environmental pollution.

The usual disposal methods of urban waste include landfill, composting and incineration. Practice has proved that landfilling and composting not only occupy a large amount of land, but also take a long time, and the leachate of the waste will have a negative impact on the surrounding environment of the landfill and the composting field. Cause serious impact and destroy the ecological environment. The use of incineration to treat municipal solid waste is a relatively advanced waste treatment method at home and abroad. It can effectively make waste treatment harmless, reduce and recycle, and can use the energy generated by it for power generation, so it has become Today's mainstream of municipal solid waste.

By the end of 2007, the total number of waste incineration power plants in China had reached 75, of which 50 were completed and 25 were under construction. In 2008, Shanghai 100 million kWh waste-to-energy project, Chengdu Jiujiang environmental protection power plant, Wenling 35 kV waste incineration power plant, Handan landfill gas recovery and utilization power generation project and other projects have started construction one after another. According to statistics, more than 70% of municipal solid waste in Japan is treated by incineration, and 151 waste fluidized bed incinerator power plants are in operation. However, due to the low calorific value and high moisture content of urban domestic waste in my country, it is difficult to catch fire when incinerated in an incinerator, the burnout degree is low, the incineration condition is unstable, and the effect of volume reduction and volume reduction and pollutant emission control is poor. Waste incineration companies often need to add a certain amount of coal and municipal solid waste to co-burn or inject fuel into the furnace to support combustion, so as to achieve the expected waste treatment effect and emission indicators.

Using fluidized bed combustion technology to treat municipal solid waste is a simple, effective and feasible waste treatment method. In particular, the calorific value of waste in my country is relatively low. To achieve efficient and stable combustion, fluidized bed incineration technology is undoubtedly the best choice. On the one hand, it greatly reduces the volume and quantity of municipal solid waste, realizes reduction, and makes it harmless; on the other hand, it also recovers part of the heat of municipal solid waste itself to achieve harmless treatment.

Sludge is a kind of solid, semi-solid and liquid waste, which contains a large amount of organic matter, heavy metals, pathogenic bacteria and pathogenic bacteria, etc. If it is discharged without treatment, it will cause serious pollution to the environment. According to incomplete statistics, my country's sewage treatment plants currently produce about 9 million tons of wet sludge every year, and it is estimated that 27 million tons of wet sludge will be produced every year in the next five years. At present, most of the sewage treatment plant sludge in China adopts simple disposal methods such as discarding and landfilling. Sludge incineration power generation treatment can achieve the effects of reduction, harmlessness and resource utilization that cannot be achieved by other methods, and has become the leading direction of sludge resource utilization.

Sludge incineration can be mainly divided into two categories: one is to send dewatered sludge directly to the incinerator for incineration. Usually, the moisture content of sludge is as high as 98%, and the moisture content after dehydration is about 80%, so that the calorific value is improved to a certain extent, but it still cannot reach the level of self-sustaining combustion, and it is necessary to add a certain amount of coal and sludge for co-firing. , to improve the efficiency of sludge incineration and reduce pollutant emissions, but at the same time consume valuable resources such as coal. The other is to directly incinerate the sludge after deep dehydration, but the cost of deep dehydration is too high, which directly increases the cost of sludge treatment.

Agricultural and forestry waste is a by-product of agricultural and forestry production, with a large output and wide distribution. It is an important renewable and clean energy. The annual output of agricultural waste in my country reaches 750 million tons, mainly including rice stalks, wheat stalks, corn stalks, cotton stalks, rice husks and peanut shells. The annual output of forestry waste in my country is about 560 million tons, mainly including fruit tree branches, leaves, waste wood and sawdust. For a long time, the utilization of agricultural and forestry wastes has not attracted much attention, and the waste phenomenon is very serious. They are mainly used for cooking, some are used for feed and papermaking raw materials, and some are used for stacking and returning to the field. There are still about 220 million tons of remaining straw that have not been rationally utilized, most of which are burned by farmers on the spot, resulting in a large waste of resources. For many years, during the summer and autumn harvest seasons, villages are lit on fire, and smoke is emitted everywhere, endangering traffic safety and the health of residents. The burning of straw in the fields has become a major social hazard. Therefore, the utilization of agricultural and forestry waste is not only a matter of environmental protection and comprehensive utilization of resources, but also concerns the health of the people and the safety of life and property.

Contents of the invention

Technical problem: The technical problem to be solved by the present invention is to provide a low-cost, can significantly improve the combustion efficiency of fluidized bed waste incinerator, solve the pollution problem caused by sludge, resource utilization of agricultural and forestry waste, reduce pollutants especially Disclosed is an easy-to-implement method for treating agricultural and forestry waste, sludge and urban domestic waste by using fluidized bed mixed incineration to discharge heavy metals and dioxins and reduce consumption of fossil energy.

Technical solution: In order to solve the above technical problems, the technical solution provided by the invention is:

A method of using a fluidized bed to incinerate agricultural and forestry waste, sludge and domestic garbage, providing a fluidized bed incinerator required for incineration, and mixing and burning agricultural and forestry waste, sludge and domestic garbage in the fluidized bed incinerator , use agricultural and forestry wastes to ignite, when the temperature in the furnace reaches 850°C, add domestic garbage and sludge into the furnace to realize co-firing; wherein the mass percentage of agricultural and forestry wastes in the mixed fuel is within 40%, and the mixed combustion of sewage The mass percentage of mud in the mixed fuel is within 30%, the combustion temperature in the fluidized bed incinerator is controlled at 850°C to 950°C, and the residence time of the flue gas generated in the furnace is controlled at more than 2 seconds.

Preferably, the agricultural and forestry wastes are agricultural wastes such as straw or chaff or chicken manure, or forestry wastes such as fruit tree branches or leaves or waste wood or bagasse or sugar residue or sawdust.

Preferably, the sludge is municipal sludge or industrial sludge.

Preferably, the sludge can be co-fired with agricultural and forestry waste and urban domestic waste without deep dehydration.

Preferably, domestic waste must be sorted and crushed before entering the furnace, and after being crushed to less than 150 mm, it is sent to the dense phase area of the fluidized bed for incineration through a screw feeder.

Preferably, before the agricultural and forestry wastes are put into the furnace, they should be crushed to a size smaller than 150 mm and sent to the dense phase zone of the fluidized bed by a screw feeder for incineration.

Preferably, an inclined air distribution plate with an appropriate inclination angle and a large slag discharge port are used, and non-uniform air distribution is adopted at the same time, and a certain lateral movement of the bed material is formed in the bed layer by using the differential velocity of the fluidized air to push the large non-combustible materials to the discharge. The slag port moves to realize continuous slag discharge.

Preferably, adding limestone into the furnace can realize desulfurization and chlorine fixation.

Beneficial effect:

1. In the fluidized bed waste incinerator, realize the co-combustion of agricultural and forestry waste, sludge and urban domestic waste to generate electricity. While providing a clean and new energy utilization method, comprehensive resource treatment of urban domestic waste, sludge and agricultural and forestry Waste, save coal and other valuable fossil energy, and save investment in new sludge and straw incineration power plants, with fast cycle and strong operability.

2. Sludge can be co-burned with agricultural and forestry waste and urban domestic waste without deep dehydration, which greatly saves the cost of sludge incineration for power generation.

3. The mixed burning of agricultural and forestry waste and sludge reduces the ignition point of urban domestic waste, and solves the combustion problem caused by high moisture content and unstable composition of urban domestic waste. Increase the furnace temperature of the waste incinerator so that the combustion temperature of the furnace is in the appropriate range of 850°C to 950°C, and improve the stability of the waste incineration working condition.

4. The volatile content of agricultural and forestry waste is high, the content of sulfur and nitrogen is low, and its own chlorine and sulfur fixation characteristics, blending agricultural and forestry waste can significantly reduce SO ₂ , NOx, HCl, heavy metals and dioxins in the incineration flue gas The discharge of pollutants such as British British Columbia is in line with the national policy of developing circular economy.

5. Solve the problem of environmental pollution caused by open burning of agricultural and forestry waste.

6. Solve the problem of environmental pollution caused by sludge.

Description of drawings

Figure 1 is a diagram of a waste fluidized bed incinerator mixed with agricultural and forestry waste and sludge power generation system diagram.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings.

The invention relates to a system for generating electricity by using a grate furnace to incinerate agricultural and forestry waste, sludge and urban domestic waste. As shown in Figure 1, the hybrid incineration method provided by the present invention is used for the system of generating electricity and mainly includes:

Fuel storage, transportation and crushing system: the main function is to collect, store and transport agricultural and forestry waste, sludge and urban domestic waste to the incineration power plant, and sort the domestic waste to make it uniform in size and condition, and crush it to less than 150mm; crush agricultural and forestry wastes to less than 150mm.

Incineration system: Send agricultural and forestry waste, sludge and urban domestic waste into the incinerator in a certain proportion. In the fluidized bed incinerator, the combustible components of the materials are burned and converted into heat energy, and the non-combustible components are converted into ash and collected after discharge. Comprehensive utilization.

Energy conversion system, heat energy is converted into electric energy: the heat energy generated by the combustion of mixed materials is absorbed into high-quality steam through the medium water, and the steam drives the steam turbine to drive the generator to generate electricity to realize the conversion of heat energy into electric energy.

Flue gas treatment system: Purify the flue gas generated by the combustion of mixed materials, and discharge it up to the standard. Ash and slag resource processing system: collect the ash and slag generated by the combustion of mixed materials for resource treatment and utilization.

Main cycle process: agricultural and forestry waste, sludge and urban domestic waste → collected to incineration power plant → unloaded into storage bin → sorting and crushing of urban domestic waste, crushing of agricultural and forestry waste → according to a certain proportion Put into the incinerator → the mixed material is burned in the incinerator to generate heat energy → the medium water absorbs heat energy and becomes steam → the steam continues to absorb heat in the superheating system to improve the quality of soda water → qualified steam enters the steam turbine through the steam pipeline to drive the steam turbine to do work → the steam turbine drives the generator Generate electricity and finally convert it into electric energy → output through transformers and transmission lines to meet the production and living needs of residents.

Implementing this invention in a waste incineration power plant can realize the mixed combustion power generation of agricultural and forestry waste, sludge and urban domestic waste without special large-scale technical improvement and equipment modification. The present invention finds through a large number of tests and researches that agricultural and forestry waste, sludge and municipal solid waste are mixed and burned, and all operating data and indexes achieve good results.

The method of using a fluidized bed for mixed incineration of agricultural and forestry waste, sludge and domestic garbage provided by the present invention is: providing a fluidized bed incinerator required for incineration, and putting agricultural and forestry waste, sludge and domestic garbage in the fluidized bed incinerator Internal mixed combustion, using agricultural and forestry waste to ignite. When the temperature in the furnace reaches 850°C, domestic garbage and sludge are added to the furnace to achieve mixed combustion; the mass percentage of agricultural and forestry waste in the mixed fuel is within 40%. The mass percentage of blended sludge in the mixed fuel is within 30%, the combustion temperature in the fluidized bed incinerator is controlled at 850°C to 950°C, and the residence time of the flue gas generated in the furnace is controlled at more than 2 seconds.

In a preferred embodiment, the agricultural and forestry wastes are agricultural wastes such as straw or chaff or chicken manure, or forestry wastes such as fruit tree branches or leaves or waste wood or bagasse or sugar residue or sawdust.

In a preferred embodiment, the sludge is municipal sludge or industrial sludge.

In a preferred embodiment, the sludge can be co-fired with agricultural and forestry waste and urban domestic waste without deep dehydration.

In a preferred embodiment, domestic waste must be sorted and crushed before entering the furnace, and after being crushed to less than 150mm, it is sent to the dense phase area of the fluidized bed for incineration through a screw feeder.

In a preferred embodiment, the agricultural and forestry wastes should be crushed to less than 150 mm before they are put into the furnace, and then sent to the dense phase zone of the fluidized bed for incineration through a screw feeder.

In a preferred embodiment, the inclined air distribution plate with an appropriate inclination and the large slag outlet are adopted, and the non-uniform air distribution is adopted at the same time, and the differential velocity of the fluidized air is used to form a certain lateral movement of the bed material in the bed layer to push the bulk Non-combustibles move to the slag outlet to realize continuous slag discharge.

In a preferred embodiment, adding limestone into the furnace can realize desulfurization and chlorine fixation.

Example 1:

Due to the high volatile content and low ignition temperature of agricultural and forestry waste, when the bed material is heated to 400°C, fuel such as straw or chaff with a length of less than 150mm can be added from the feeding port, and the fuel will be ignited after entering the furnace. The bed temperature rises rapidly, shut down and start the fuel (diesel or natural gas) system, and when the bed temperature rises to 850°C, add sludge and municipal solid waste according to a certain mass ratio to achieve co-combustion, adjust the primary and secondary air volumes, and gradually The bed temperature is adjusted to 850°C to 950°C.

Example 2:

Municipal solid waste has high moisture content and low calorific value. The moisture content and composition of sludge are complex, and the calorific value varies greatly. In the actual process of waste incineration, the specific blending ratio of agricultural and forestry waste should be flexibly adjusted according to the quality of waste and sludge. When the garbage in the north has high moisture content, low combustible components, and a calorific value of about 700kcal/kg, the blending ratio of agricultural and forestry waste such as wheat straw, rice straw, cotton straw, rice husk, and fruit tree branches can reach 30%-40%. The calorific value of the mixed fuel is increased to more than 1200kcal/kg; when the quality of garbage and sludge is good, when the calorific value is about 1200kcal/kg, the blending ratio of agricultural and forestry waste is within 10%; the combustion temperature in the incinerator is maintained at 850 In the range of ℃～950℃, the residence time of flue gas in the furnace is more than 2 seconds, so as to improve the burning rate of garbage, reduce pollutant emissions, and improve the combustion efficiency of boilers.

Claims (8)

1. A method utilizing a fluidized bed to incinerate agricultural and forestry wastes, sludge and domestic refuse, characterized in that: a fluidized bed incinerator required for incineration is provided, and the agricultural and forestry wastes, sludge and domestic refuse are fluidized The mixed combustion in the bed incinerator uses agricultural and forestry wastes to ignite. When the temperature in the furnace reaches 850°C, domestic garbage and sludge are added to the furnace to achieve mixed combustion; the mass percentage of agricultural and forestry wastes in the mixed fuel is 40% %, the mass percentage of blended sludge in the mixed fuel is within 30%, the combustion temperature in the fluidized bed incinerator is controlled at 850°C to 950°C, and the residence time of the flue gas generated in the furnace is controlled at more than 2 seconds . 2. The method of utilizing a fluidized bed to incinerate agricultural and forestry waste, sludge and domestic garbage according to claim 1, wherein the agricultural and forestry waste is agricultural waste such as straw or chaff or chicken manure, Or fruit tree branches or leaves or waste wood or bagasse or sugar residue or wood chips and other forestry waste. 3. The method for mixed incineration of agricultural and forestry waste, sludge and household garbage by using a fluidized bed according to claim 1, characterized in that: said sludge is municipal sludge or industrial sludge. 4. The method for mixed incineration of agricultural and forestry wastes, sludge and domestic waste by using a fluidized bed according to claim 1, characterized in that the sludge can be co-incinerated with agricultural and forestry wastes and urban domestic waste without deep dehydration. 5. The method of using a fluidized bed to incinerate agricultural and forestry wastes, sludge and domestic garbage according to claim 1, characterized in that: the domestic garbage must be sorted and crushed before being put into the furnace, and after being broken to less than 150mm It is sent to the dense phase area of the fluidized bed by a screw feeder for incineration. 6. The method of using a fluidized bed to incinerate agricultural and forestry wastes, sludge and domestic garbage according to claim 1, characterized in that: before the agricultural and forestry wastes are put into the furnace, they should be crushed to less than 150mm and fed by a screw The machine is sent to the dense phase zone of the fluidized bed for incineration. 7. The method of using a fluidized bed to incinerate agricultural and forestry wastes, sludge and domestic garbage according to claim 1, characterized in that: the inclined air distribution plate and the large slag discharge port with an appropriate inclination are adopted, and the non-uniform distribution is adopted at the same time. The wind uses the differential speed of the fluidized wind to form a certain lateral movement of the bed material in the bed, and pushes the large non-combustible materials to move to the slag discharge port to realize continuous slag discharge. 8. The method of using a fluidized bed to incinerate agricultural and forestry waste, sludge and domestic garbage according to claim 1, characterized in that: adding limestone into the furnace can realize desulfurization and chlorine fixation.