CN111253975A - Method for grading and utilizing low-rank coal - Google Patents
Method for grading and utilizing low-rank coal Download PDFInfo
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- C10J3/00—Production of combustible gases containing carbon monoxide from solid carbonaceous fuels
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- C10J2300/00—Details of gasification processes
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Abstract
The invention relates to a method for preparing and grading low-rank coal, which is characterized in that the low-rank coal is treated by a gasification reduction process to obtain upgraded coal with temperature and an oil-gas mixture, the upgraded coal with temperature is treated by a cold slag humidifying process to obtain upgraded coal, the oil-gas mixture is subjected to a purification process to obtain mixed gas and coal tar, and the mixed gas contains CO and H2And hydrocarbons, wherein the gasification reduction process is a chemical reaction process for heating low-rank coal under the condition of no oxygen or micro oxygen, and the gasification reduction process is two-stage; the mixed gas is treated by partial hydrocarbon reforming conversion process to obtain the mixed gas containing CO and H2The synthesis gas of (2). In the invention, the obtained products have multiple types, the yield of the coal tar is high, the yield of the synthesis gas is high, and the synthesis gas is hotThe value is high, the volatile components in the obtained upgraded coal are less, and the effective resources in the low-rank coal are fully and effectively utilized.
Description
Technical Field
The invention relates to the technical field of clean utilization of coal substances, in particular to a method for grading and utilizing low-rank coal.
Background
More than half of the coal reserves already explored in China are low-rank coals, and the volatile components in the low-rank coals are equivalent to 1000 hundred million tons of oil and gas resources. The low-rank coal mainly has the characteristics of high moisture and high volatility, flame is long and has smoke during combustion, the coalification degree is low, and typical coal types are brown coal and long flame coal. The coal-rich, oil-less and gas-deficient coal in China becomes a major subject of the clean coal technology at present by how to efficiently utilize low-rank coal. However, both combustion power generation and modern coal chemical utilization have extremely low comprehensive utilization efficiency due to the three characteristics of high water content, high ash content and low calorific value.
At present, the utilization mode of low-rank coal is mainly direct combustion or gasification, wherein direct combustion power generation is one of the most common utilization modes, and according to incomplete statistics, more than 90% of lignite in China is used for power station boilers and various industrial boilers. The direct combustion of the low-rank coal not only wastes rich oil and gas resources contained in the coal, has low efficiency, but also pollutes the environment, easily causes a large amount of greenhouse gases such as SOx and NOx, and causes severe weather environments such as acid rain. The modern coal chemical technology uses coal gasification as a technical tap, and primary raw materials CO and H required by chemical synthesis are obtained by gasification2However, the coal gasification technology has not developed to date, and a mature large-scale commercial low-rank coal gasification technology has not yet been formed. In the prior art, low-rank coal gasification is used for preparing CO and H2Generally, low-rank coal is pyrolyzed to obtain raw coal gas and upgraded coal, and the pyrolysis is generally carried out in the presence of a large amount of oxygen (or air), wherein a part of coal is reacted with oxygen to supply heat and generate a large amount of CO2. Due to CO2The crude gas is not combusted, belongs to invalid gas, and because of aerobic combustion, the nitrogen content in the crude gas is too high, so that the energy density of the crude gas is reduced, the calorific value of the crude gas is reduced, the crude gas produced by pyrolysis has other economic values except for return combustion, and the utilization rate of oil gas resources in coal is low. And heat is supplied because a part of coal and oxygen are combustedFormation of CO2The quantity of upgraded coal is less, coal resources in low-rank coal are greatly wasted, and no related integrated equipment is available, so that the low-rank coal can be used for continuously producing gas, upgraded and prepared coal tar, and continuous large-scale production can be realized.
Disclosure of Invention
In view of the above, the present invention provides a method for low-rank coal production and graded utilization, which comprises preparing oil-gas mixture and solid upgraded coal with temperature by carrying out coal gasification, reduction, grading and graded separation on low-rank coal under an oxygen-free or micro-oxygen condition, cooling and humidifying the upgraded coal with temperature to prepare upgraded coal with certain moisture and normal temperature, wherein the upgraded coal has low volatile content and high quality; the oil-gas mixture is further processed to obtain coal tar and mixed gas, and the yield of the obtained coal tar is high; reforming and converting the mixed gas to prepare CO and H rich gas2The synthetic gas has high yield and high heat value, the obtained products have various types, and the effective resources in the low-rank coal are fully and effectively utilized.
The invention provides a method for grading and utilizing low-rank coal, which comprises the following steps: the method comprises the steps of treating low-rank coal through a gasification reduction process to obtain upgraded coal with temperature and an oil-gas mixture, treating the upgraded coal with temperature through a cold slag humidifying process to obtain upgraded coal, purifying the oil-gas mixture to obtain mixed gas and coal tar, wherein the mixed gas contains CO and H2And hydrocarbons, wherein the gasification reduction process is a chemical reaction process for heating low-rank coal under the condition of no oxygen or micro oxygen, and the gasification reduction process is two-stage;
the mixed gas is treated by partial hydrocarbon reforming conversion process to obtain the mixed gas containing CO and H2The synthesis gas of (2).
The method comprises the following steps of enabling low-rank coal to enter a first-stage gasification reduction process and then enter a second-stage gasification reduction process, enabling the low-rank coal to react in the first-stage gasification reduction process to obtain first-stage gas and first-stage solid, enabling the first-stage solid to enter the second-stage gasification reduction process to be continuously gasified to obtain second-stage gas and second-stage solid, enabling the second-stage solid to be upgraded coal with temperature, and enabling the first-stage gas and the second-stage gas to. Gasification and reductionThe oxygen-free or micro-oxygen environment adopted by the original process mainly comprises the following conditions: (1) the air carried in the gaps between the raw material low-rank coal and the materials; (2) a small amount of mixed air is leaked from a feed inlet, a discharge outlet and the like of the gasification reduction process; (3) under the explosion limit value, O accounting for 5 percent of the coal by mass can be slightly introduced into the gasification reduction process2Or (air), and further preferably, O in an amount of 3% by mass of the coal is introduced2Or (air), is beneficial to improving the temperature of the gasification reduction reaction, preventing coking and the like, and simultaneously ensures the safety and stability of the whole gasification reduction process reaction; the low-rank coal is preferably subjected to gasification reduction reaction in an oxygen-free environment, so that coal substances are prevented from being consumed by combustion reaction of the low-rank coal and oxygen in the reaction process of the gasification reduction process, and a large amount of CO which cannot be combusted is generated2Thereby ensuring CO in the obtained high-temperature oil-gas mixture2The volume percentage of the coal ash is small, the subsequent preparation of the synthesis gas with high energy density is facilitated, the yield of the upgraded coal with temperature is increased, the process steps are few, and the operation is simple and easy, so that the reaction can be safely carried out. The upgraded coal with the temperature obtained after the reaction is treated by the secondary gasification reduction process has a high temperature, generally the temperature is 350-800 ℃, and the upgraded coal with the temperature does not contain water and can not be directly transported and sold, so the upgraded coal with the temperature is prepared into the upgraded coal with the water content of about 10 wt% and normal temperature by cooling and humidifying through the cold slag humidifying process, and the upgraded coal with the temperature is convenient to store, transport and sell. The high-temperature oil-gas mixture contains CO and H2、CO2The high-temperature oil-gas mixture generated by each stage of gasification reduction process is respectively subjected to purification process to remove dust and recover impurity gases such as coal tar and sulfur-containing compounds, so that coal tar and purified mixed gas are obtained; preferably, mixed gas obtained after purifying the oil-gas mixture after each stage of gasification and reduction is mixed together and then enters a reforming conversion process; the high-temperature oil-gas mixture contains CO and H2、CO2Hydrocarbons, dust, coal tar, water vapor and sulfur-containing compounds, etc., removing dust by a purification process, and recovering coalTar and impurity gases such as sulfur-containing compounds, thereby obtaining coal tar and purified mixed gas; the mixed gas mainly contains CO and H2And hydrocarbons, CO and H being well known2Can be directly used as a primary raw material for chemical synthesis, and hydrocarbons can be reformed to generate CO and H2Therefore, part of hydrocarbons in the mixed gas is reformed and converted by the reforming and conversion process to obtain the mixed gas containing CO and H2Of the synthesis gas, CO and H in the synthesis gas2Part of the original CO and H in the mixed gas2The other part is derived from reforming and converting part of the hydrocarbons to obtain a product containing CO and H2Greatly improve CO and H in the synthesis gas2Total volume percent, heating value increased. The method not only can prepare the synthesis gas by adopting various ways, but also can obtain the product coal tar and upgraded coal, and effectively utilizes resources in the low-rank coal by classification and quality.
Preferably, the water content of the low-rank coal is less than 7 wt%. The low-rank coal mostly has higher moisture content, and the moisture content of the low-rank coal can be reduced after the low-rank coal is placed for a long time, for example, the low-rank coal is naturally aired in clear weather, so that the drying process is saved. Therefore, the raw material is preferably low-rank coal with low water content, so that the production cost is reduced.
Further preferably, the water content of the low-rank coal is less than 6 wt%.
Wherein, the gasification reduction process can be one-stage or multi-stage. When a first-stage gasification reduction process is adopted, mainly aiming at obtaining most of high-temperature oil-gas mixture, the temperature directly influences the subsequent gas production, the yield of the upgraded coal with temperature and the temperature of the first-stage upgraded coal with temperature, the reaction temperature of the gasification reduction process is 350-800 ℃, the volatile content in the upgraded coal with temperature is 8-15 wt%, and further preferably, the reaction temperature of the gasification reduction process is 400-750 ℃; still more preferably 450-700 ℃. When the multi-stage gasification reduction process is adopted, the multi-stage gasification reduction process mainly has the function of continuously gasifying solid matters (including gasified pulverized coal, solid impurities and the like) which cannot be gasified in the previous stage gasification reduction process, a certain amount of oily matters with high boiling points, such as asphalt and the like, which cannot be gasified within a certain retention timeThe gasification and retention time is short enough to separate out or the temperature can not reach the polycondensation reaction conditions of phenolic compounds, aromatic compounds and the like, the reaction and gasification are continued, and the gas yield and the quality of the upgraded coal with temperature are improved. Therefore, preferably, the gasification reduction process comprises a primary gasification reduction process and a secondary gasification reduction process, the low-rank coal is sequentially treated by the primary gasification reduction process and the secondary gasification reduction process to obtain upgraded coal with temperature and an oil-gas mixture, and the mixed gas contains CO and H2And hydrocarbons. Still further preferably, the feeding temperature of the primary gasification reduction process is 80-120 ℃, the reaction temperature of the primary gasification reduction process is 450-650 ℃, the gas outlet temperature of the primary gasification reduction process is 180-550 ℃, and the discharging temperature of the primary gasification reduction process is 350-600 ℃; the feeding temperature of the secondary gasification reduction process is 350-600 ℃, the reaction temperature of the secondary gasification reduction process is 550-800 ℃, the discharge temperature of the secondary gasification reduction process is 450-750 ℃, the gas outlet temperature of the secondary gasification reduction process is 450-700 ℃, under the process conditions, most of volatile components in the low-rank coal are completely gasified, the yield and gas quantity of an oil-gas mixture are increased, the volatile components in the obtained upgraded coal with temperature are reduced, and the volatile component content in the obtained upgraded coal with temperature is 3-8 wt%.
The purification process comprises a dust removal process, a cooling process, an oil-water separation process and a desulfurization process, wherein the oil-gas mixture is sequentially treated by the dust removal process, the cooling process and the desulfurization process to obtain a mixed gas and an oil-water mixture, and the mixed gas contains CO and H2And hydrocarbons, wherein the oil-water mixture is treated by an oil-water separation process to obtain coal tar. The high-temperature oil-gas mixture contains a large amount of dust, coal tar, water vapor, sulfur-containing compounds and the like; firstly, a dust removal process is utilized for removing dust, so that the temperature of an oil-gas mixture is prevented from being reduced in the dust removal process, and coal tar, water vapor and the like are condensed into liquid and adhered with a large amount of dust to cause the blockage of a subsequent process pipeline and the reduction of the dust removal effect; condensing the gas coal tar and water vapor in the oil-gas mixture into a liquid oil-water mixture by using a cooling processThe mixture is not mutually dissolved in oil and water, and the oil-water mixture is treated by an oil-water separation process to obtain the coal tar product, wherein the coal tar is brown and has a relative density of about 0.85kg/m3The main components are cyclane, alkane, aromatic compound and the like; and finally, removing sulfur-containing compounds from the residual gas after the cooling process through a desulfurization process, so as to prevent the sulfur-containing compounds from causing catalyst poisoning in the subsequent process.
Preferably, the mixed gas is subjected to a partial hydrocarbon reforming conversion process, so that the components of the gas in the mixed gas are directly reformed and converted into CO and H without separation2Because the reforming conversion is only intended to convert hydrocarbons to CO and H2The mixed gas already contains a part of CO and H2Therefore, the hydrocarbon does not need to be separated from the mixed gas and then reformed and converted, and the operation saves the process steps and has high economic benefit.
Reforming conversion mainly includes partial catalytic oxidation, steam catalytic reforming conversion, and non-catalytic reforming conversion. The catalyst is needed for partial catalytic oxidation and steam catalytic reforming conversion, the catalyst for reforming conversion process is mostly a load type catalyst, and the active components are mainly non-metals such as Ni, Co, Fe, Cu and the like and noble metals such as Rh, Ru, Pt and the like. Reforming conversion generally requires heat supply, and direct heat supply or indirect heat supply can be adopted. CO and H in syngas2The source of the (C) is two parts, one part is CO and H obtained by catalytic conversion of partial hydrocarbons in the mixed gas2The other part is original H in the mixed gas2And CO.
The partial catalytic oxidation adopts oxygen and partial hydrocarbon to burn and directly supply heat, and partial hydrocarbon in the mixed gas reacts with steam to generate CO and H under the action of the catalyst2(ii) a When the steam catalytic reforming conversion is carried out, external heat supply is adopted, and partial hydrocarbons in the mixed gas react with steam to generate the steam under the action of a catalystCO and H2(ii) a The main reaction mechanism of the two methods is:
(1)CmHn+mH2O＝mCO+1/2(n+2m)H2main reaction, endothermic reaction
(2)CO+H2O＝CO2+H2Side reactions, endothermic reactions
The non-catalytic reforming conversion reforming does not need a catalyst, pure oxygen is introduced into the mixed gas, and part of hydrocarbons in the mixed gas react with the pure oxygen to obtain CO and H2The main reaction mechanism is as follows: CH (CH)4+1/2O2→CO+2H2Hydrocarbons other than methane with methane and O2The reaction mechanism of (3) is similar.
Therefore, preferably, the reforming conversion process is a partial catalytic oxidation, wherein the partial catalytic oxidation is to introduce pure oxygen and steam into the mixed gas, and a part of hydrocarbons in the mixed gas react with the steam at the temperature of 850-1300 ℃ and in the presence of a catalyst to obtain CO and H2。
Preferably, the reforming conversion process is steam catalytic reforming conversion, the steam catalytic reforming conversion is to introduce steam into the mixed gas, under the conditions of indirect heat supply to make the temperature reach 850-2。
Preferably, the reforming conversion process is non-catalytic reforming conversion, the non-catalytic reforming conversion is that pure oxygen is introduced into the mixed gas, and part of hydrocarbons in the mixed gas react with the pure oxygen to obtain CO and H2。
After the reforming conversion process is adopted for treatment, H in the obtained synthesis gas2The volume ratio percentage of the CO and the CO is greatly improved, and the heat value of the synthetic gas is high.
Preferably, the low-rank coal is firstly subjected to a gasification feeding process and then subjected to a gasification reduction process to obtain a temperature-bearing upgraded coal and oil-gas mixture, and the low-rank coal can be gasified and dispersed by adopting the process, so that the heating area of the low-rank coal in the gasification reduction process is increased.
Based on the technical scheme, the method for preparing and utilizing the low-rank coal in a grading manner is used for preparing upgraded coal, synthesis gas and coal tar by developing and utilizing the low-rank coal in a grading manner, the product types are multiple, and the obtained upgraded coal is low in volatile content and high in quality; the yield of the obtained coal tar is high; the obtained synthesis gas has high yield and high heat value, and fully and effectively utilizes effective resources in low-rank coal.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, it is obvious that the drawings in the following description are only some embodiments described in the present invention, and other drawings can be obtained by those skilled in the art according to the drawings.
Fig. 1 is a process flow diagram of a method for graded utilization of low-rank coal.
Detailed Description
The present invention is further illustrated by the following examples, which are not intended to limit the invention to these embodiments. It will be appreciated by those skilled in the art that the present invention encompasses all alternatives, modifications and equivalents as may be included within the scope of the claims.
In the present invention, unless otherwise specified, the processes in the following methods are all conventional in the art, unless otherwise specified.
As shown in fig. 1, the invention provides a method for grading and utilizing low-rank coal, which comprises the following steps: treating low-rank coal through a gasification reduction process to obtain upgraded coal with temperature and an oil-gas mixture, treating the upgraded coal with temperature through a cold slag humidifying process to obtain upgraded coal, purifying the oil-gas mixture to obtain mixed gas and coal tar, wherein the mixed gas contains CO and H2And hydrocarbons, wherein the gasification reduction process is a chemical reaction process for heating the low-rank coal under the condition of no oxygen or micro oxygen, and the gasification reduction process is at least one stage;
the mixed gas is treated by partial hydrocarbon reforming conversion process to obtain the product containing CO and H2The synthesis gas of (2).
The raw material low-rank coal can be pulverized coal or lump coal, and when the low-rank coal adopts the lump coal, the pulverized coal with smaller granularity can be obtained by crushing and screening the oversize lump coal. The pulverized coal is preferably used as the raw material, on one hand, the pulverized coal does not need to be crushed and screened, so that the process steps are saved, and on the other hand, the pulverized coal is low in price compared with lump coal. Preferably, pulverized coal having a particle size of less than 20mm is used, and still more preferably pulverized coal having a particle size of less than 6mm is used.
The low-rank coal generally has 20-55% of volatile components, about 3-15% of tar, 30-60% of fixed carbon, 10-40% of water and the balance of other impurities such as dust. The low-rank coal has low coalification degree but contains abundant oil and gas resources, and the volatile components in the low-rank coal are very beneficial to extracting the synthesis gas, so that the low-rank coal with the volatile components between 30% and 55% is preferred. The low-rank coal mostly has higher moisture content, and the moisture content of the low-rank coal can be reduced after the low-rank coal is placed for a long time, for example, the low-rank coal is naturally aired in clear weather, so that the drying process is saved. Therefore, the raw material is preferably low-rank coal with the water content of less than 7 wt% as the raw material so as to reduce the production cost; still more preferably, low-rank coal having a water content of less than 6 wt% is used as the raw material.
A gasification feeding process can be added before the low-rank coal enters the gasification reduction process, so that the low-rank coal can rapidly enter the gasification reduction process, the surface area of the material is increased, and the gasification reduction reaction is accelerated.
Wherein, the gasification reduction process is a chemical reaction process for heating low-rank coal under the condition of no oxygen or micro oxygen. Conveying the low-rank coal to a gasification reduction process, heating by heating media such as flue gas, and the like, wherein additives and other substances are not required to be added in the reaction process, the temperature is generally 350-800 ℃, and the pressure is less than or equal to 30Kpa, so that a complex chemical reaction process is carried out, and a high-temperature oil-gas mixture is obtained, wherein solid carbon is the upgraded coal with temperature, and the volatile matter in the upgraded coal with temperature is 8-15 wt%. The high-temperature oil-gas mixture contains CO and H2、CO2Hydrocarbon, coal tar, dust, sulfur compounds, and the like.
Wherein, the oxygen-free or micro-oxygen environment adopted by the gasification reduction process is mainly divided into the following conditions: (1) air entrained in the gaps inside the raw material low-rank coal and the gaps between the materials, and O in the air2Reacts with coal immediately to generate CO in high-temperature environment in gasification reduction process2Or CO; (2) a small amount of mixed air, oxygen of the air and trace O are leaked from a feed inlet, a discharge outlet and the like of the gasification reduction process2Reacts with coal immediately to generate CO in high-temperature environment in gasification reduction process2Or CO; (3) under the explosion limit value, O accounting for 5 percent of the coal by mass can be slightly introduced into the gasification reduction process2Alternatively (air), this operation has the advantages of ① increased temperature and energy utilization in the gasification reduction process, ② increased char conversion, ③ prevention of coal coking, ④ small amount of O2The incomplete combustion with low-rank coal generates more CO, and more synthesis gas is brought to follow-up. Because the internal temperature of the gasification reduction process is higher, a small amount of O is introduced2Oxidation reactions (including combustion reactions) occur instantaneously, and the ignition point of many combustibles is below the reaction temperature of the gasification reduction reaction. Because the mixed explosion limit of CO and air is 12-74.2%; h2The explosion value is 4-75%. O is2The duty ratio is 21%. The upper explosion limit value of the converted pure oxygen is about 6 percent. By theoretical calculation, 100kg of coal will yield about 80Nm3CO and H of2. Therefore, introducing O accounting for 5 percent of the coal by mass2Is safe; further preferably, introducing O accounting for 3 percent of the mass of the coal2So as to ensure the safety and stability of the whole gasification reduction process reaction. However, when the temperature of the gasification reduction reaction meets the process requirements, oxygen may not be introduced, and the gasification reduction reaction is preferably performed on low-rank coal in an oxygen-free environment, so that the reaction can be safely performed.
Wherein, the gasification reduction process can be one-stage or multi-stage. When a first-stage gasification reduction process is adopted, mainly aiming at obtaining most of high-temperature oil-gas mixture, the temperature directly influences the subsequent gas production, the yield of the upgraded coal with temperature and the temperature of the first-stage upgraded coal with temperature, the reaction temperature of the gasification reduction process is 350-800 ℃, the volatile content in the upgraded coal with temperature is 8-15 wt%, and further preferably, the reaction temperature of the gasification reduction process is 400-750 ℃; still more preferably 450-700 ℃. When the multistage gasification reduction process is adopted, the multistage gasification reduction process mainly has the main effects that solid matters (including gasified pulverized coal, solid impurities and the like) which cannot be gasified in the previous stage gasification reduction process and a certain amount of high-boiling-point oily matters such as similar asphalt and the like which cannot be gasified in a certain retention time are continuously gasified, the retention time is short and precipitation is not reached or the temperature does not reach the polycondensation reaction conditions of phenolic compounds, aromatic hydrocarbon compounds and the like, the reaction and gasification are continuously carried out, and the gas yield and the quality of upgraded coal are favorably improved.
Besides ensuring reasonable temperature of the gasification reduction process, certain retention time in the gasification reduction process is ensured, the retention time is too short, volatile components are not completely escaped for gasification, and the quality of upgraded coal with temperature is influenced more while the gas yield is influenced; the residence time is too long, and although the product is guaranteed, the yield cannot be kept up to, so that maintaining a reasonable residence time for the gasification reduction reaction is critical to the yield and quality of the product. Due to different varieties of raw material low-rank coal, the retention time of materials in the general gasification reduction process is 30min-4 h.
According to the invention, a two-stage gasification reduction process is adopted, low-rank coal firstly enters a first-stage gasification reduction process and then enters a second-stage gasification reduction process, the low-rank coal firstly enters the first-stage gasification reduction process to obtain first-stage gas and first-stage solid, the first-stage solid then enters the second-stage gasification reduction process to be continuously gasified to obtain second-stage gas and second-stage solid, and the second-stage solid is upgraded coal with temperature; the feeding temperature of the primary gasification reduction process is 80-120 ℃, the gas outlet temperature is 180-550 ℃, the reaction temperature is 450-650 ℃, and the discharging temperature is 350-600 ℃; the feeding temperature of the secondary gasification reduction process is 350-600 ℃, the discharging temperature is 450-750 ℃, the reaction temperature is 550-800 ℃, the gas outlet temperature is 450-700 ℃, and the volatile content in the upgraded coal with temperature is 8-15 wt%. When a two-stage gasification reduction process is adopted, the method is mainly used for completely gasifying most of volatile matters, so that a large amount of gas can be obtained, and the warmed upgraded coal with lower volatile matters can be obtained, wherein the volatile matter content in the warmed upgraded coal is 3-8 wt%.
The temperature of the upgraded coal with the temperature obtained from the secondary gasification reduction process is higher, because the upgraded coal with the temperature contains a small amount of volatile components, and the obtained upgraded coal with the temperature is generally 45-65 wt% of the raw material, so that the yield of the obtained upgraded coal with the temperature is high. The temperature of the upgraded coal with the temperature is generally 350-800 ℃, and the upgraded coal with the temperature does not contain water, and the upgraded coal with the temperature is exposed in the air, so that the upgraded coal with the temperature is easy to react with oxygen in the air, and a large amount of coal substances are consumed, therefore, the upgraded coal with the temperature is cooled and humidified by a slag cooling and humidifying process to prepare the upgraded coal which is normal temperature and contains a certain amount of moisture, the moisture content in the upgraded coal is about 10 wt%, and the upgraded coal is convenient to store, transport and sell.
It is further preferred that the mixed gas is compressed before entering the reforming process, so as to better perform the reforming reaction.
The high-temperature oil-gas mixture obtained from the gasification reduction process enters a purification process for treatment. The purification process comprises a dust removal process, a cooling process, an oil-water separation process and a desulfurization process, wherein the high-temperature oil-gas mixture contains a large amount of dust, coal tar, water vapor, sulfur-containing compounds and the like; firstly, a dust removal process is utilized for removing dust, so that the temperature of an oil-gas mixture is prevented from being reduced in the dust removal process, and coal tar, water vapor and the like are condensed into liquid and adhered with a large amount of dust to cause the blockage of a subsequent process pipeline and the reduction of the dust removal effect; condensing the gas coal tar and water vapor in the oil-gas mixture into a liquid oil-water mixture by using a cooling process, and treating the oil-water mixture by using an oil-water separation process to obtain the coal tar product, wherein the coal tar is brown and has a relative density of about 0.85kg/m3The main components are cyclane, alkane, aromatic compound and the like, and the recovery rate of the coal tar is 80-95 percent, so that the yield of the obtained coal tar is high; finally, the residual gas after the cooling process is treated by a desulfurization process to remove the sulfur-containing compounds, thereby preventing the sulfur-containing compounds from causing catalyst poisoning in the subsequent process,by adopting the process, impurity gas and solid can be removed so as to obtain purified mixed gas, the impurity of the mixed gas is less, the subsequent process treatment is facilitated, and the stability of subsequent equipment is ensured.
In order to further optimize the process, an electric tar capturing process can be additionally arranged after the desulfurization process for capturing a small amount of tar so as to further reduce the amount of tar in the gas; if the volume fraction of the unsaturated hydrocarbon in the oil-gas mixture is too high, a hydrogenation process can be added after the desulfurization process to convert the unsaturated hydrocarbon into saturated hydrocarbon, so that the problems of carbon deposition and the like caused by the decarbonization of the unsaturated hydrocarbon are prevented; and a denitration process or a dechlorination process can be added after the desulfurization process to realize further purification.
The invention adopts two-stage gasification reduction process, and each stage of gasification reduction process is respectively connected with respective dust removal process, cooling process, oil-water separation process, desulfurization process and the like; the dust amount in the high-temperature oil gas generated after gasification and reduction is large, so that in order to further optimize the process, each stage of gasification and reduction process is connected with the respective dust removal process, and the dust removal process of each stage is connected with the same set of cooling process, oil-water separation process and desulfurization process, so that the process links are saved.
The mixed gas obtained from the purification process enters a reforming conversion process for treatment to obtain the product containing CO and H2The synthesis gas of (2). Wherein the mixed gas comprises CO and H2、CO2And comprises CH4And the like.
The mixed gas is reformed and converted into CO and H through partial hydrocarbon to obtain the mixed gas with various components without separation2Because the reforming conversion is only intended to convert hydrocarbons to CO and H2The mixed gas already contains a part of CO and H2Therefore, the hydrocarbon does not need to be separated from the mixed gas and then reformed and converted, and the operation saves the process steps and has high economic benefit.
Reforming conversion mainly includes partial catalytic oxidation, steam catalytic reforming conversion, and non-catalytic reforming conversion. The partial catalytic oxidation and the steam catalytic reforming conversion both need to be catalyzedMost of catalysts of reforming conversion process are supported catalysts, and active components are mainly non-metals such as Ni, Co, Fe, Cu and the like and precious metals such as Rh, Ru, Pt and the like. Reforming conversion generally requires heat supply, and direct heat supply or indirect heat supply can be adopted. CO and H in syngas2The source of the (C) is two parts, one part is CO and H obtained by catalytic conversion of partial hydrocarbons in the mixed gas2The other part is original H in the mixed gas2And CO.
The partial catalytic oxidation adopts oxygen and partial hydrocarbon to burn and directly supply heat, so that the reaction temperature reaches 850-1300 ℃, and partial hydrocarbon in the mixed gas reacts with steam to generate CO and H under the action of the catalyst2(ii) a When the steam catalytic reforming conversion is carried out, external heat supply is adopted, the temperature is up to 850-1200 ℃, and partial hydrocarbons in the mixed gas react with steam to generate CO and H under the action of a catalyst2(ii) a The main reaction mechanism of the two methods is:
(1)CmHn+mH2O＝mCO+1/2(n+2m)H2main reaction, endothermic reaction
(2)CO+H2O＝CO2+H2Side reactions, endothermic reactions
With CH4For example, the main reaction equation is CH4+H2O→CO+3H2Generation of H2The molar ratio of CO to CO is 3:1, and the ratio is large, so that the method is very favorable for preparing the synthesis gas.
The non-catalytic reforming conversion reforming does not need a catalyst, pure oxygen is introduced into the mixed gas, and part of hydrocarbons in the mixed gas react with the pure oxygen to obtain CO and H2The main reaction mechanism is as follows: CH (CH)4+1/2O2→CO+2H2Generation of H2And CO in a molar ratio of 2:1, which is favorable for preparing the synthesis gas. Hydrocarbons other than methane with methane and O2The reaction mechanism of (3) is similar.
Table 1: the range value of the volume percentage of each component in the mixed gas before reforming conversion is as follows:
| components | H2 | Comprising CH4Of (2) | CO | CO2 | Others |
| Content (wt.) | 15-45％ | 10-52％ | 5-25％ | 5-25％ | 0.1-10％ |
The other component is N2And steam, etc., the volume percentages of the components in the mixed gas before reforming conversion are integrated to 100%.
Table 2: the range value of the volume percentage of each component in the mixed gas after reforming conversion is as follows:
| components | H2 | Comprising CH4Of (2) | CO | CO2 | Others |
| Content (wt.) | 30-70％ | 1-5％ | 10-30％ | 3-35％ | 0.1-10％ |
The other component is N2And steam, etc., the volume percentage of each component in the mixed gas after reforming conversion is integrated to be 100%.
As no external substances are basically added in the process of the gasification reduction process, the weight of the mixed gas obtained after the low-rank coal is treated by the gasification reduction process and the purification process is 15-50% of the volatile components of the low-rank coal according to the mass conservation law, so that the gas in the low-rank coal is basically completely gasified by using the method disclosed by the invention, and the yield of the obtained mixed gas is high. As can be seen from tables 1 and 2, the volume percentage of the hydrocarbons in the mixed gas is reduced from 10-52% to 1-5% after the mixed gas is treated by the reforming conversion process, the mixed gas after reforming conversion is the synthesis gas, and CO and H in the synthesis gas2The sum of the volume percentages of the components is 60-80%, and the heat value in the synthesis gas is greatly improved.
In conclusion, the invention provides a method for producing and utilizing low-rank coal in a grading manner, the method for treating the low-rank coal is used for developing and utilizing the low-rank coal in a grading manner to prepare upgraded coal, synthetic gas and coal tar, the product types are various, and the obtained upgraded coal has less volatile components and high quality; the yield of the obtained coal tar is high; the obtained synthesis gas has high yield and high heat value, and fully and effectively utilizes effective resources in low-rank coal.
The above-mentioned embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the same; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (10)
1. A method for preparing and grading low-rank coal for utilization comprises the following steps: the method comprises the steps of treating low-rank coal through a gasification reduction process to obtain upgraded coal with temperature and an oil-gas mixture, treating the upgraded coal with temperature through a cold slag humidifying process to obtain upgraded coal, purifying the oil-gas mixture to obtain mixed gas and coal tar, wherein the mixed gas contains CO and H2And hydrocarbons characterized by: the gasification reduction process is a chemical reaction process for heating low-rank coal under the condition of no oxygen or micro oxygen, and the gasification reduction process is two-stage;
the mixed gas is treated by the reforming conversion process of partial hydrocarbons to obtain a mixed gas containing CO and H2The synthesis gas of (2).
2. The method for classifying and utilizing low-rank coal as claimed in claim 1, wherein the method comprises the following steps: the water content of the low-rank coal is less than 7 wt%.
3. The method for classifying and utilizing low-rank coal as claimed in claim 2, wherein the method comprises the following steps: the water content of the low-rank coal is less than 6 wt%.
4. The method for classifying and utilizing low-rank coal as claimed in claim 1, wherein the method comprises the following steps: the feeding temperature of the primary gasification reduction process is 80-120 ℃, the reaction temperature of the primary gasification reduction process is 450-650 ℃, the gas outlet temperature of the primary gasification reduction process is 180-550 ℃, and the discharging temperature of the primary gasification reduction process is 350-600 ℃; the feeding temperature of the secondary gasification reduction process is 350-600 ℃, the reaction temperature of the secondary gasification reduction process is 550-800 ℃, the discharging temperature of the secondary gasification reduction process is 450-750 ℃, and the gas outlet temperature of the secondary gasification reduction process is 450-700 ℃.
5. The method for classifying and utilizing low-rank coal as claimed in claim 1, wherein the method comprises the following steps: the purification process comprises a dust removal process, a cooling process, an oil-water separation process and a desulfurization process, wherein the oil-gas mixture is sequentially treated by the dust removal process, the cooling process and the desulfurization process to obtain a mixed gas and an oil-water mixture, and the mixed gas contains CO and H2And hydrocarbons, wherein the oil-water mixture is treated by an oil-water separation process to obtain coal tar.
6. The method for classifying and utilizing low-rank coal as claimed in claim 1, wherein the method comprises the following steps: the mixed gas is reformed and converted into CO and H through partial hydrocarbon to directly reform and convert the partial hydrocarbon into the mixed gas without separating each component of the gas2The reforming conversion process of (1).
7. The method for producing and utilizing low-rank coal according to claim 6, wherein the method comprises the following steps: the reforming conversion process is partial catalytic oxidation, wherein the partial catalytic oxidation is to introduce pure oxygen and steam into mixed gas, and react partial hydrocarbons in the mixed gas with the steam at the temperature of 850-1300 ℃ in the presence of a catalyst to obtain CO and H2。
8. The method for producing and utilizing low-rank coal according to claim 6, wherein the method comprises the following steps: the reforming conversion process is steam catalytic reforming conversion, the steam catalytic reforming conversion is to introduce steam into mixed gas, under the conditions of indirect heat supply to make the temperature reach 850-1200 ℃ and the existence of catalyst, partial hydrocarbons in the mixed gas react with the steam to obtain CO and H2。
9. The method for preparing the synthesis gas by using the low-rank coal as claimed in claim 6, wherein the method comprises the following steps: the reforming conversion process is non-catalytic reforming conversion, the non-catalytic reforming conversion is to introduce pure oxygen into mixed gas, and partial hydrocarbons in the mixed gas react with the pure oxygen to obtain CO and H2。
10. The method for classifying and utilizing low-rank coal as claimed in claim 1, wherein the method comprises the following steps: and the low-rank coal is firstly subjected to a gasification feeding process and then subjected to a gasification reduction process to obtain a upgraded coal and oil-gas mixture with temperature.
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