CN111253978A

CN111253978A - Method and system for preparing synthesis gas by using low-rank coal gas

Info

Publication number: CN111253978A
Application number: CN201811459069.5A
Authority: CN
Inventors: 冯振董; 金飞伟; 李正平; 吕彬峰; 马倩
Original assignee: Zhejiang Tianlu Environmental Technology Co ltd
Current assignee: Zhejiang Tianlu Environmental Technology Co ltd
Priority date: 2018-11-30
Filing date: 2018-11-30
Publication date: 2020-06-09

Abstract

A method for preparing synthesis gas by using low-rank coal is characterized in that the low-rank coal is sequentially subjected to a drying process and a gasification reduction process to obtain upgraded coal and an oil-gas mixture, and the oil-gas mixture is subjected to a purification process to obtain a mixture containing CO and H₂And hydrocarbon mixed gas, wherein the gasification reduction process is a chemical reaction process for heating the dried low-rank coal under the condition of no oxygen or micro oxygen; the mixed gas is treated by a separation process to obtain a mixed gas containing H₂And CO and a gas comprising hydrocarbons; production of a hydrocarbon-containing gas by a reforming conversion process to produce a hydrocarbon-containing gas comprising CO and H₂A second synthesis gas of (a); and mixing the first synthesis gas and the second synthesis gas to obtain the synthesis gas. The method in the inventionMethod and system for maximizing the volatile components in low-rank coal by using CO and H in multiple ways₂The form of (a) is retained and the yield of syngas is high.

Description

Method and system for preparing synthesis gas by using low-rank coal gas

Technical Field

The invention relates to the technical field of clean utilization of coal substances, in particular to a method and a system for preparing synthesis gas by using low-rank coal gas.

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. Direct combustion power generation is one of the most common utilization modes, and more than 90% of lignite in China is used for power station boilers and various industrial boilers according to incomplete statistics. 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 gas can not be 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; and the crude gas contains a large amount of CH₄Reducing CO and H in the synthesis gas₂The content of the (C) in the raw gas reduces the calorific value of the raw gas, the raw gas cannot be used as a first-grade raw material for chemical synthesis, the mixed gas produced by pyrolysis has no other economic value except for return combustion, and the utilization rate of the coal raw material is low; and no related integrated equipment can utilize low-rank coal to continuously produce gas and can realize continuous large-scale production.

Disclosure of Invention

In view of the above, the present invention provides a method and a system for preparing synthesis gas from low-rank coal, which are used for preparing a mixed gas from dried low-rank coal under an oxygen-free or micro-oxygen condition, and then obtaining hydrocarbons containing CO and H from the mixed gas by a separation process₂The gas part is used as synthesis gas, and then hydrocarbons are reformed to prepare the catalyst containing CO and H₂The synthesis gas increases the path for preparing the synthesis gas, and fully and effectively utilizes the volatile components in the low-rank coal.

In order to solve the technical problems, the invention provides the following technical scheme:

the invention provides a method for preparing synthesis gas by using low-rank coal, wherein the low-rank coal is subjected to a drying process and a gasification reduction process in sequence to obtain upgraded coal and an oil-gas mixture, and the oil-gas mixture is subjected to a purification process to obtain a mixture containing CO and H₂And hydrocarbon mixed gas, wherein the gasification reduction process is a chemical reaction process for heating the dried low-rank coal under the condition of no oxygen or micro oxygen;

the mixed gas is treated by a separation process to obtain a mixed gas containing H₂And CO and a gas comprising hydrocarbons;

the gas containing hydrocarbons is subjected to a reforming conversion process to produce a gas containing CO and H₂A second synthesis gas of (a);

and mixing the first synthesis gas and the second synthesis gas to obtain the synthesis gas.

The drying process removes most of moisture in the low-rank coal to obtain dried low-rank coal and waste gas, and the dried low-rank coal enters a gasification reduction process to react to obtain a high-temperature oil-gas mixture and upgraded coal with a certain temperature; oxygen-free or micro-oxygen environment adopted by gasification reduction processThe following cases are to be distinguished: (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 dried low-rank coal is preferably subjected to gasification reduction reaction in an oxygen-free environment, so that the condition that the dried low-rank coal and oxygen are subjected to combustion reaction in the reaction process of the gasification reduction process to generate a large amount of incombustible CO is avoided₂Thereby ensuring CO in the obtained high-temperature oil-gas mixture₂The volume percentage is smaller, which is beneficial to the subsequent preparation of the synthesis gas with high energy density, and the process steps are less, simple and easy to operate, so that the reaction can be safely carried out; the high-temperature oil-gas mixture contains CO and H₂、CO₂The method comprises the following steps of (1) removing impurity gases such as dust, coal tar and sulfur-containing compounds through a purification process to obtain purified mixed gas; the mixed gas contains CO and H₂Can be directly used as synthesis gas, so that the mixed gas is processed into H by using a separation process₂And CO and a gas comprising hydrocarbons; the obtained gas containing hydrocarbons is subjected to a reforming conversion process to prepare a gas containing CO and H₂A second synthesis gas of (a); and finally, mixing the first synthesis gas and the second synthesis gas to obtain the synthesis gas which is a target product, wherein the synthesis gas has high energy density and high heat value.

Preferably, the purification process comprises a dust removal process, a tar removal process and a desulfurization process. 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; then a large amount of tar and vapor are removed by using a tar removing device, so that the problems of blockage of the process pipeline, carbon deposition and the like caused by cooling and adhesion of the tar in the process pipeline are prevented; and finally, removing sulfur-containing compounds from the residual gas after the tar removal process through a desulfurization process, so as to prevent the sulfur-containing compounds from causing catalyst poisoning in the subsequent process.

Preferably, the drying process adopts water vapor for indirect drying, the pressure of the water vapor is 0.3-1.5Mpa, the temperature of the water vapor is 105-250 ℃, the water content of the outlet material of the drying process is not more than 7 wt%, and the temperature of the outlet material of the drying process is 50-150 ℃. If the low-rank coal contains a large amount of moisture, the heat consumption in the gasification reduction reaction process is large. The drying medium of the drying process can be flue gas or water vapor, and the drying can be divided into direct drying and indirect drying. When flue gas is used as a drying medium, although the drying efficiency of the flue gas in direct contact with low-rank coal is the highest, the volume percentage of oxygen in the drying process environment is strictly controlled to be below an explosion limit when the flue gas is used for drying so as to prevent deflagration, and the efficiency of flue gas indirect drying is not ideal, so that steam drying is preferred for production safety and drying efficiency. The direct drying of the water vapor is easy to cause the water vapor to react with the low-rank coal to consume resources, so the drying mode of indirectly drying the low-rank coal by the water vapor is adopted to prevent the moisture in the water vapor from entering the low-rank coal. In addition, if the pressure of the steam is too high in the drying process, the temperature caused by the steam is too high, so that partial volatile components in the low-rank coal can escape out in the drying process, on one hand, the escape of the volatile components can bring potential safety hazards, and on the other hand, the gas yield of a subsequent gasification reduction process can be influenced, therefore, the drying steam pressure is not too high in the drying process, the drying effect can be guaranteed, and the volatile components in the low-rank coal can be prevented from being gasified.

Preferably, the reaction temperature of the gasification reduction process is 350-800 ℃. At the temperature, volatile components in the dried low-rank coal escape from the low-rank coal to obtain a high-temperature oil-gas mixture, solid residues left after gasification reduction reaction are upgraded coal, and the content of the volatile components in the upgraded coal is 8-15 wt%. Wherein, the gasification reduction process can be one-stage or multi-stage. When a first-stage gasification reduction process is adopted, the temperature mainly aims to obtain most of high-temperature oil-gas mixture, and the subsequent gas production, the yield of upgraded coal and the temperature of first-stage upgraded coal are directly influenced by the temperature; when the multistage gasification reduction process is adopted, the multistage gasification reduction process mainly has the main function of continuously gasifying certain amount of high-boiling-point oily substances (such as similar asphalt and the like) which cannot be gasified in a certain retention time and cannot be separated out or the temperature cannot reach the polycondensation reaction conditions of phenolic compounds, aromatic hydrocarbon compounds and the like in the previous stage gasification reduction process, and continuously reacting and gasifying, so that the gas yield and the quality of upgraded coal are improved.

Preferably, the separation process is pressure swing adsorption. The mixed gas is generally separated by a pressure swing adsorption method, a low temperature method (or cryogenic method), or a membrane separation method. The low temperature method is a method for liquefying gas by a series of processes by utilizing different boiling points of components in the gas and separating different components by rectification. Since separation of these gases is performed in a low temperature environment of 100K or less as compared with conventional separation, it is called a low temperature process (or cryogenic process) and the operation cost is high, and therefore, pressure swing adsorption is preferable for separation of mixed gases.

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.

The partial catalytic oxidation adopts oxygen and a part of hydrocarbon to combust and directly supply heatUnder the action of catalyst, partial hydrocarbon in the gas containing hydrocarbon reacts with steam to produce CO and H₂(ii) a When in steam catalytic reforming conversion, external heat supply is adopted, and partial hydrocarbons in the gas containing the hydrocarbons 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

The non-catalytic reforming conversion reforming does not need a catalyst, pure oxygen is introduced into the gas containing the hydrocarbons, and part of the hydrocarbons in the gas containing the hydrocarbons 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 pure oxygen and steam are introduced into the gas containing hydrocarbons, and a part of the hydrocarbons in the gas containing hydrocarbons reacts with the steam at the temperature of 850 ℃ and 1300 ℃ in the presence of the catalyst to obtain CO and H₂。

Preferably, the reforming conversion process is steam catalytic reforming conversion, the steam catalytic reforming conversion is that steam is introduced into the gas containing hydrocarbons, under the conditions of indirect heat supply to make the temperature reach 850-1200 ℃, and in the presence of a catalyst, part of hydrocarbons in the gas containing hydrocarbons react with the steam to obtain CO and H₂。

Preferably, the reforming conversion process is non-catalytic reforming conversion, the non-catalytic reforming conversion is that pure oxygen is introduced into the gas containing hydrocarbons, and part of hydrocarbons in the gas containing hydrocarbons react with the pure oxygen to obtain CO and H₂。

The system using the method comprises a drying device, a gasification reduction device, a purification device, a separation device and a reforming conversion reactor, wherein the drying device is connected with the gas through a gasification feeding deviceThe gasification device is connected with the gasification feeding device, the upper end of the gasification feeding device is connected with the purification device, the purification device is connected with the separation device, and the separation device is connected with the reforming conversion reactor. The low-rank coal enters a drying device to be dried to obtain dried low-rank coal, the dried low-rank coal is gasified, dispersed and conveyed to a gasification reduction device through a gasification feeding device to be subjected to gasification reduction reaction, and high-temperature oil-gas mixture and upgraded coal with a certain temperature are obtained after the reaction; the oil-gas mixture enters a purification device from the upper end of a gasification feeding device to purify and remove dust, tar and sulfur-containing compounds to obtain mixed gas, and the mixed gas enters a separation device to be treated to obtain CO and H₂And a hydrocarbon-containing gas, the hydrocarbon-containing gas entering a reforming conversion reactor to convert a portion of the hydrocarbons to CO and H₂Obtaining a second synthesis gas; and finally, mixing the first synthesis gas and the second synthesis gas in a synthesis gas storage tank to obtain the synthesis gas.

Preferably, the gasification and reduction device is a rotatable horizontal reaction kettle, further preferably, the gasification and reduction device is a 360-degree rotatable horizontal reaction kettle, a first heating mechanism is arranged outside the horizontal reaction kettle, and a second heating mechanism is arranged inside the horizontal reaction kettle. Adopt this kind of structure can guarantee that the low order coal after the stoving overturns at horizontal reation kettle multi-angle, the heated area of the low order coal after the increase stoving for the low order coal after the stoving is heated simultaneously in horizontal reation kettle's inside and outside, is favorable to accelerating gasification reduction reaction.

Based on the technical scheme, the method provided by the invention gasifies the volatile components in the dried low-rank coal to prepare mixed gas under the oxygen-free or micro-oxygen condition, prepares the mixed gas into the synthesis gas mainly containing CO and H2 by different ways, and fully utilizes the precious volatile components in the low-rank coal; the system provided by the invention is simple and feasible to operate, is mostly the existing equipment, is low in operation cost, and is suitable for industrial production.

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 schematic flow diagram of a process for producing synthesis gas using low-rank coal gas according to the present invention;

FIG. 2 is a schematic diagram of a system for preparing synthesis gas by using low-rank coal gas according to the present invention;

FIG. 3 is a schematic diagram of the structure of a gasification feed apparatus in an embodiment of the invention;

FIG. 4 is a schematic structural diagram of a gasification reduction apparatus according to an embodiment of the present invention;

FIG. 5 is a front partial sectional view of a gasification reduction apparatus according to an embodiment of the present invention.

Reference numerals: 1. the device comprises a horizontal reaction kettle, 2, a feed inlet, 3, a discharge outlet, 4, a driving mechanism, 41, a toothed ring, 42, a riding wheel, 43, a motor, 44, a transmission gear, 5, a first heating mechanism, 51, a heater, 52, a heating box, 53, a heating pipeline, 54, a heating air outlet, 6, a second heating mechanism, 7, a guide plate, 9, a dynamic and static sealing device, 10, a gasification reduction device, 11, a gasification feeding device, 111, a spiral blade, 112, a gasification motor, 100, a drying device, 200, a purifying device, 210, a dust removal device, 220, a tar removal device, 230, a desulfurization device, 300, a reforming conversion reactor, 500, a synthetic gas storage tank, 600 and a separating device.

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, the raw materials and equipment used are commercially available or commonly used in the art, unless otherwise specified. The methods in the following examples are conventional in the art unless otherwise specified.

As shown in fig. 1-5, the present inventionThe method for preparing the synthesis gas by using the low-rank coal is provided, the low-rank coal is sequentially subjected to a drying process and a gasification reduction process to obtain upgraded coal and an oil-gas mixture, and the oil-gas mixture is subjected to a purification process to obtain a mixture containing CO and H₂And hydrocarbon mixed gas, wherein the gasification reduction process is a chemical reaction process for heating the dried low-rank coal under the condition of no oxygen or micro oxygen;

production of a hydrocarbon-containing gas by a reforming conversion process to produce a hydrocarbon-containing gas comprising CO and H₂A second synthesis gas of (a);

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 a raw material, on one hand, the pulverized coal does not need to be crushed and screened, so that the process steps are saved, the heating area is large during drying, the drying efficiency is high, and on the other hand, the pulverized coal is low in price compared with lump coal. Pulverized coal having a particle size of less than 20mm is preferably used, and pulverized coal having a particle size of less than 6mm is still more preferably 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.

If the low-rank coal contains a large amount of moisture, the heat consumption in the gasification reduction reaction process is large, so the technical scheme of the invention preferably treats the low-rank coal through a drying process. The drying medium of the drying process can be flue gas or water vapor, and the drying can be divided into direct drying and indirect drying. When flue gas is used as a drying medium, although the drying efficiency of the flue gas in direct contact with low-rank coal is the highest, the volume percentage of oxygen in the drying process environment is strictly controlled to be below an explosion limit when the flue gas is used for drying so as to prevent deflagration, and the efficiency of flue gas indirect drying is not ideal, so that steam drying is preferred for production safety and drying efficiency. The direct drying of the water vapor is easy to cause the water vapor to react with the low-rank coal to consume resources, so the drying mode of indirectly drying the low-rank coal by the water vapor is adopted to prevent the moisture in the water vapor from entering the low-rank coal. In addition, if the pressure of the steam is too high in the drying process, the temperature caused by the steam is too high, so that partial volatile components in the low-rank coal can escape out in the drying process, on one hand, the escape of the volatile components can bring potential safety hazards, and on the other hand, the gas yield of a subsequent gasification reduction process can be influenced, therefore, the drying steam pressure is not too high in the drying process, the drying effect can be guaranteed, and the volatile components in the low-rank coal can be prevented from being gasified. Therefore, preferably, the drying process adopts indirect drying by using water vapor, the pressure of the water vapor is 0.3-1.5Mpa, the temperature of the water vapor is 105-250 ℃, the water content in the low-rank coal can be reduced to the maximum extent under the process condition, even the water content in the low-rank coal discharged from a discharge port of the drying process can be reduced to be below 7 wt%, the temperature of an outlet material of the drying process is 50-150 ℃, and the water removed by the drying process forms waste gas along with dust such as coal dust and the like in the drying process in the form of the water vapor; still further preferably, when the pressure of the water vapor is 0.6-1.2Mpa and the temperature of the water vapor is 120-200 ℃, the water content of the dried low-rank coal is reduced to below 6 wt%, and the temperature of the outlet material of the drying process is 80-130 ℃.

The drying process can be one-stage or multi-stage, because if the water content of the low-rank coal after the first-stage drying process still does not meet the process requirement, multi-stage drying such as secondary drying, tertiary drying and the like can be adopted to continue further drying until the water content of the dried low-rank coal meets the process condition. In addition, the multistage drying process can be arranged in series or in parallel, the drying effect can be enhanced when the multistage drying process is connected in series, and the treatment capacity of the drying process can be increased when the multistage drying process is connected in parallel, so that the design that the multistage drying process is connected in series or in parallel or in series and in parallel can be adjusted according to the actual situation according to the requirement of the actual production process as long as the same technical effect can be achieved, and specifically, for example, when the feeding capacity of the drying process is calculated by low-rank coal of 20-30t/h, a one-stage steam drying process can be adopted; when the feeding amount of the drying process is calculated by a low level of 50-70t/h, a secondary steam drying process can be adopted, so that the method is more economical and reasonable.

The low-rank coal dried by the drying process is conveyed to the gasification reduction process for reaction, and a gasification feeding process can be added before the dried low-rank coal enters the gasification reduction process, so that the dried low-rank coal can rapidly enter a gasification reduction device, 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 the dried low-rank coal under the condition of no oxygen or micro oxygen. The dried low-rank coal is conveyed to a gasification reduction process, under the heating of heating media such as flue gas and the like, additives and other substances are not needed to be added in the reaction process, the temperature is generally 350-800 ℃, the pressure is less than or equal to 30Kpa, a complex chemical reaction process is carried out, solid carbon and a high-temperature oil-gas mixture are obtained, wherein the solid carbon is upgraded coal, the temperature of the upgraded coal is 350-800 ℃, and the volatile matter in the upgraded coal 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) below the explosion limit, gasification reductionO accounting for 5 percent of the coal by mass can be slightly introduced into the 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 explosion limit of the mixture of CO and air is 12-74.2 percent; 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 of the dried low-rank coal is preferably performed 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 the primary gasification reduction process is adopted, the temperature mainly aims to obtain most of high-temperature oil-gas mixture, the subsequent gas production rate, the yield of upgraded coal and the temperature of the primary upgraded coal are directly influenced, the reaction temperature of the gasification reduction process is 350-800 ℃, the volatile content in the upgraded coal is 8-15 wt%, and further the reaction temperature of the gasification reduction process is preferably 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 and a certain amount of high-boiling-point oily matters such as asphalt and the like which cannot be gasified within a certain retention time, and is favorable for improving the gas yield and the quality of upgraded coal.

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 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 preferably adopted, the materials dried by the drying process enter a first-stage gasification reduction process and then enter a second-stage gasification reduction process, the dried low-rank coal enters the first-stage gasification reduction process to obtain first-stage gas and first-stage solid, the first-stage solid 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; 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 ℃, and the gas outlet temperature is 450-700 ℃. When the two-stage gasification reduction process is adopted, the aim is to completely gasify most of volatile matters, so that a large amount of gas can be obtained, and upgraded coal with lower volatile matters can be obtained, wherein the content of the volatile matters in the upgraded coal is 3-8 wt%.

The high-temperature oil-gas mixture obtained from the gasification reduction process enters a purification process to remove solid dust, tar, sulfur-containing compounds and the like so as to obtain mixed gas.

The purification process comprises a dust removal process, a tar removal process and a desulfurization process. 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; then a large amount of tar and vapor are removed by using a tar removing device, so that the problems of blockage of the process pipeline, carbon deposition and the like caused by cooling and adhesion of the tar in the process pipeline are prevented; and finally, removing sulfur-containing compounds from the residual gas after the tar removal process through a desulfurization process, so as to prevent the sulfur-containing compounds from causing catalyst poisoning in the subsequent process.

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 hydrogen addition process can be added after the desulfurization process to convert the unsaturated hydrocarbon into saturated hydrocarbon so as to prevent carbon deposition; and a denitration process or a dechlorination process can be added after the desulfurization process to realize further purification.

In the invention, a two-stage gasification reduction process is preferably adopted, and each stage of gasification reduction process is respectively connected with a respective dust removal process, a tar removal process, a desulfurization process and the like in sequence; the dust amount in the high-temperature oil gas generated after gasification and reduction is larger, so in order to further optimize the process, each stage of gasification and reduction process is firstly connected with the respective dust removal process, and the dust removal process of each stage is sequentially connected with the same set of tar removal process and desulfurization process, so that the process links are saved.

The mixed gas obtained after the purification process mainly comprises CO and H₂、CO₂And comprises CH₄As is clear from Table 1 below, the mixed gas contained a large amount of hydrocarbons and H₂。

Table 1: the range of the volume percentage of each component in the mixed gas 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 N₂Water vapor, etc., the sum of the volume percentages of the components in the mixed gas is 100%.

The mixed gas is generally separated by a pressure swing adsorption method, a low temperature method (or cryogenic method), or a membrane separation method. The method is characterized in that the gas is liquefied through a series of processes by utilizing the difference of the boiling points of all components in the gas, and the different components are separated through rectification. Since separation of these gases is performed in a low temperature environment of 100K or less as compared with conventional separation, it is called a low temperature process (or cryogenic process) and the operation cost is high, and therefore, pressure swing adsorption is preferable for separation of mixed gases.

Pressure swing adsorption, abbreviated as PSA, is often performed under pressure, and pressure swing adsorption proposes a method of combining pressure and pressure reduction, which is usually an adsorption-desorption system consisting of pressure adsorption and pressure reduction. Under the condition of isothermality, the process combines the pressure adsorption and the pressure reduction desorption into an adsorption operation cycle process. The amount of adsorption of the adsorbent to the adsorbate increases with increasing pressure and decreases with decreasing pressure, and the adsorbed gas is released during depressurization (to atmospheric pressure or evacuation) to regenerate the adsorbent, which can be done without the need for external heat supply. Therefore, pressure swing adsorption is called isothermal adsorption, and also called heatless regenerative adsorption. The most common adsorbents for pressure swing adsorption are molecular sieves and activated carbon, usually in combination. For example, activated alumina is a highly pure porous alumina that is physically and chemically stable, is characterized by wear resistance, is inert to all corrosive gases and liquids, and has excellent thermal stability. In the PSA process, activated alumina may be loaded as an auxiliary adsorbent at the bottom of the adsorbent, with the feed first contacted to remove water vapor and aromatics from the feed. Silica gel is amorphous silica, chemically inert and non-corrosive, and is generally filled at the bottom of an adsorber in PSA process for purifying heavy hydrocarbons and acid gases.

The mixed gas in the invention is pressurized at normal temperature to ensure that the pressure in the pressure swing adsorption device reaches more than 8kg, so that most of the hydrocarbon and CO containing methane₂Adsorbed by the adsorbent, and simultaneously the adsorbent can adsorb a small amount of CO, and the unadsorbed gas mainly comprises CO and N₂And H₂The unadsorbed portion of the gas is the first syngas, and the first syngas contains CO and H₂The sum of the volume percentages of (A) is 80-90%; then decompressing to make the hydrocarbon and small amount of CO to be resolved from the adsorbent to obtain CO₂And the gas containing the hydrocarbons is obtained by still being adsorbed by the adsorbent, wherein the volume percentage of the hydrocarbons in the gas containing the hydrocarbons is 70-85%, and the rest gas is mainly CO.

Table 2: values in the range of the volume percentages of the individual components in the hydrocarbon-containing gas:

components	Comprising CH₄Of (2)	CO	Others
				Content (wt.)	75-90％	8-25％	0.1-5％

The sum of the volume percentages of the components in the hydrocarbon-containing gas is 100%.

It is further preferred that the hydrocarbon containing gas is compressed prior to entering the reforming process to better facilitate the reforming reaction.

The gas mainly containing hydrocarbons obtained from the separation process enters a reforming conversion process to be treated to obtain a gas containing CO and H₂Of the second synthesis gas. 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.

The partial catalytic oxidation adopts oxygen and part of hydrocarbons in the hydrocarbon-containing gas to burn and directly supply heat, so that the reaction temperature reaches 850-1300 ℃, and part of hydrocarbons in the hydrocarbon-containing gas reacts with steam to generate CO and H under the action of the catalyst₂(ii) a When in steam catalytic reforming conversion, external heat supply is adopted, and partial hydrocarbons in the gas containing the hydrocarbons 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+H₂0→CO+3H₂Generation of H₂The molar ratio of CO to CO is 3:1, and the ratio is large, so that the preparation of the second synthesis gas is very favorable.

The non-catalytic reforming conversion reforming does not need a catalyst, pure oxygen is introduced into the gas containing the hydrocarbons, and part of the hydrocarbons in the gas containing the hydrocarbons 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 2:1 molar ratio, facilitating the production of the second synthesis gas. Hydrocarbons other than methane with methane and O₂The reaction mechanism of (3) is similar.

Table 3: values for the ranges of the volume percentages of the individual components after reforming conversion of the hydrocarbon-containing gas:

components	Comprising CH₄Of (2)	CO+H₂	Others
				Content (wt.)	5-15％	80-95％	0.1-5％

The sum of the volume percentages of the components in the reformed hydrocarbon-containing gas is 100%.

As can be seen from tables 2 and 3, the gas containing hydrocarbonsThe volume percentage of hydrocarbon after reforming is reduced to 5-15% from 75-90% to obtain the second synthetic gas containing CO + H₂The sum of the volume percentages of (a) is 85-95%, the conversion of hydrocarbons is high, and the calorific value of the second synthesis gas is high.

Finally, mixing the first synthetic gas and the second synthetic gas to obtain a product synthetic gas, wherein CO and H in the synthetic gas₂The energy density is larger, the heat value of the synthesis gas is improved, and the synthesis gas can be used as a first-grade raw material for chemical synthesis.

As shown in fig. 2 to 5, the present invention also provides a system for preparing synthesis gas from low-rank coal gas, comprising a drying device 10, a gasification reduction device 10, a purification device 200, a separation device 600 and a reforming conversion reactor 300, wherein the drying device 100 is connected to the gasification reduction device 10 through a gasification feeding device 11, the upper end of the gasification feeding device 11 is connected to the purification device 200, the purification device 200 is connected to the separation device 600, and the separation device 600 is connected to the reforming conversion reactor 300.

When the raw material low-rank coal is pulverized coal, the low-rank coal can directly enter the drying device 100 through the conveying device to be dried. When the low-rank coal is lump coal, large particles need to be crushed by a crusher and screened by a screening machine to obtain low-rank coal with smaller particle size, and then the low-rank coal enters the drying device 100 for drying by the conveying device.

Wherein, the drying device 100 comprises a roller, a conveying device, a plurality of heating pipes and a driving mechanism which run through the roller, a feed inlet, a discharge port and an air outlet are arranged on the roller, low-rank coal enters the roller from the feed inlet, the driving mechanism is used for driving the roller to rotate, heating media such as water vapor and the like indirectly transfer heat with the low-rank coal in the roller through the heating pipes, a lifting blade is arranged on the inner wall of the roller and is distributed around the inner wall of the roller, the heating pipes are distributed inside the roller in a vertical and horizontal alternating manner, the roller can be horizontally or obliquely arranged, when the roller is obliquely arranged, the roller and a horizontal plane are set to be a certain inclination, one end of the roller provided with the discharge port is at a low position, the height of the front end of the roller is ensured to be higher than that of the rear end of the roller, the dried low-rank coal can, the conveying device is preferably a sealed conveying device to prevent external air from mixing into the dried low-rank coal in the conveying process and consuming coal resources; and waste gas such as raised dust, water vapor and the like generated in the drying process is discharged from the air outlet of the roller.

At least one or more than one roller of the drying device 100 may be provided, the installation heights of the plurality of rollers are the same, and the plurality of rollers may be connected in series or in parallel. The inner and outer diameter sizes and the lengths of the rollers can be determined according to the actual processing capacity of the low-rank coal processing system. The drying device 100 is at least one-stage, so as to ensure that the water content of the low-rank coal meets the production requirement. When the drying device 100 is multi-stage, the multi-stage drying devices 100 are connected in parallel or in series.

As shown in fig. 3-5, the low-rank coal treated by the drying device 100 is connected to the gasification reduction device 10 through the gasification feeding device 11, the gasification feeding device 11 is a screw conveying device, the dried low-rank coal passes through the gasification feeding device 11 from the discharge port of the drying device 100 and then enters the feed port of the gasification reduction device 10, and the gasification feeding device 11 is a conveying device for the dried material, so that the dried low-rank coal can further be dispersed into uniform particles in the gasification reduction device 10, and is uniformly heated to facilitate the reaction; but also improves the temperature of the dried low-rank coal entering the gasification reduction device 10.

The gasification feeding device 11 comprises a gasification feeding cavity, a helical blade 111 arranged in the gasification feeding cavity, and a gasification motor 112 driving the helical blade 111 to rotate, wherein the cross section of the helical blade 111 is not larger than the inner diameter cross section of the gasification feeding cavity.

The gasification feeding device 11 may be disposed at the discharge port 3 or the feed port 2 of the gasification reduction device 10. The upper end of the gasification feeding device 11 is connected with the purification device 200, when the gasification feeding device 11 is arranged at the discharge port 3 of the gasification reduction device 10, the dried low-rank coal enters the gasification reduction device 10 through the conveying device, the oil-gas mixture generated by the gasification reduction device 10 enters the upper end of the gasification feeding device 11 through the discharge port 3 and then enters the purification device 200, then the upgraded coal generated in the gasification reduction device 10 is conveyed to the next system through the gasification feeding device 11 from the discharge port 3, and the gasification feeding device 11 is only an oil-gas mixture conveying channel and an upgraded coal conveying device after the gasification reduction reaction.

When the gasification feeding device 11 is arranged at the feeding port 2 of the gasification reduction device 10, on one hand, the dried low-rank coal is conveyed by the gasification feeding device 11, gasified and dispersed into suspended uniform particles, and then enters the feeding port 2 of the gasification reduction device 10, meanwhile, an oil-gas mixture generated by the gasification reduction device 10 enters the upper end of the gasification feeding device 11 through the feeding port 2, and then enters the purification device 200, the high-temperature oil-gas mixture and the dried low-rank coal are subjected to heat exchange in the gasification feeding device 11, which is beneficial to improving the temperature of the dried low-rank coal entering the gasification reduction device 10, so that the gasification feeding device 11 is a conveying device for the dried material, and the dried low-rank coal is in the gasification reduction device 10 into dispersed uniform particles, and is uniformly heated and is convenient for reaction; but also improves the temperature of the dried low-rank coal entering the gasification reduction device 10. Preferably, the gasification feed device 11 is therefore arranged at the feed opening 2 of the gasification reduction device 10.

In order to further increase the sealing performance, a metal compensator and a dynamic and static sealing device 9 are arranged outside the gasification feeding cavity and the feeding hole 2 of the horizontal reaction kettle 1 so as to increase the sealing performance and the connection stability between the gasification feeding device 11 and the horizontal reaction kettle.

As shown in fig. 4-5, the gasification reduction apparatus 10 is a rotatable horizontal reaction vessel 1, and more preferably a 360 ° rotatable horizontal reaction vessel 1, the gasification reduction apparatus 10 includes a 360 ° rotatable horizontal reaction vessel 1, a first heating mechanism 5, and a driving mechanism 4 for driving the horizontal reaction vessel 1 to rotate, the first heating mechanism 5 is connected to the horizontal reaction vessel 1 to heat the dried low-rank coal in the horizontal reaction vessel 1; the horizontal reaction kettle 1 is provided with a discharge port 3 and a feed port 2, dried low-rank coal enters from the feed port 2, upgraded coal obtained by gasification reduction is output from the discharge port 3 through a guide plate arranged in the horizontal reaction kettle 1, and an oil-gas mixture generated in the horizontal reaction kettle 1 is discharged from the feed port 2.

The driving mechanism 4 includes a gear ring 41 disposed on the outer peripheral surface of one end of the horizontal reactor 1, a riding wheel 42 meshed with the gear ring 41, a transmission gear 44 and a motor 43, the motor 43 drives the transmission gear 44 to rotate, and further drives the riding wheel 42 to rotate, so as to drive the gear ring 41 and the horizontal reactor 1 to rotate again, where it should be noted that the driving mechanism 4 may also be another device as long as the same technical effect can be achieved.

The horizontal reaction kettle 1 rotates for 360 degrees, so that dried low-rank coal in the horizontal reaction kettle can be in a rotating state all the time, the heating area of a heating medium provided by the dried low-rank coal and the first heating mechanism 5 is increased, the gasification reduction reaction of the dried low-rank coal is accelerated, the first heating mechanism 5 continuously heats the dried low-rank coal in the horizontal reaction kettle 1 through the transmission heating medium and continuously performs gasification reduction, the dried low-rank coal can generate an oil-gas mixture and upgrade coal to the maximum extent, and the maximum coal energy utilization value is generated while the minimum heating resources are utilized.

The first heating mechanism 5 comprises a heater 51 and a heating box 52, wherein the heater 51 is connected with the heating box 52 through a heating pipeline 53, and the heating box 52 is sleeved outside the horizontal reaction kettle 1 and is connected with the horizontal reaction kettle 1 through a dynamic and static sealing device 9. By adopting the structural design, the heating medium is prevented from leaking to improve the energy utilization rate, and finally the heating medium is discharged through the heating gas outlet 54, so that the first heating mechanism 5 and the horizontal reaction kettle 1 form two sets of relatively independent mechanisms, therefore, the occupied space of the whole system can be better arranged according to actual production scenes, meanwhile, the heating medium can be enabled to perform continuous heat exchange with low-rank coal in the horizontal reaction kettle 1, in order to increase the stability of the first heating mechanism 5, the first heating mechanism 5 can be fixedly arranged, for example, the first heating mechanism 5 can be fixed on the ground or a support. Further preferably, a heat insulating device such as heat insulating cotton is provided outside the heating box 52 to prevent the temperature of the first heating means 5 from decreasing. Further preferably, the number of the heating pipes 53 may be multiple, and the multiple heating pipes 53 introduce the heating medium from different positions of the bedroom reactor 1 and heat the heating medium after heat exchange utilization to the heating air outlet 54, so as to accelerate the rate of the gasification reduction reaction.

Wherein, horizontal reation kettle 1 is inside to be equipped with second heating mechanism 6 for horizontal reation kettle 1 is inside to be heated evenly. Further, the second heating mechanism 6 uniformly heats the dried low-rank coal in the horizontal reaction kettle 1 by controlling the flow rate, temperature, pressure and the like of heating media such as flue gas and the like; first heating mechanism 5 heats the low order coal after drying from horizontal reation kettle 1's outside to realize the flow of heating medium inside and outside horizontal reation kettle 1, make the low order coal after drying contact a large amount of heats along with horizontal reation kettle 1 is rotatory simultaneously, with better gasification reduction reaction that carries on, improve gasification reduction reaction's efficiency and speed.

Wherein, the guide plate 7 is of a single-spiral structure and/or a double-spiral structure, the guide plate 7 which is obliquely arranged and is of the spiral structure and/or the single-spiral structure is arranged, the dried low-rank coal in the horizontal reaction kettle 1 is continuously gasified and reduced, simultaneously, the produced upgraded coal is conveyed to the discharge port 3 to be discharged, and then, the rotation of the horizontal reaction kettle 1 is matched, so that the low-rank coal can be more fully gasified and reduced in the conveying process through the guide plate 7, wherein, the guide plate 7 is divided into a guide steel plate and a guide stainless steel plate, the single-spiral structure or the double-spiral structure can be adopted, the spiral guide structure which is singly or doubly combined can be adopted for guiding flow, the structural design is adopted, in the rotating process of the horizontal reaction kettle 1, the dried low-rank coal in the horizontal reaction kettle 1 can move to the discharge port 3 under the action of the spiral guide plate, accelerating the discharge of the upgraded coal of the product after the gasification reduction reaction in the horizontal reaction kettle 1.

The gasification reduction apparatus 10 is provided in at least one stage. Can set up the horizontal reation kettle of at least one-level as required to carry out more abundant complete gasification reduction to the low order coal, can also increase the feeding volume of gasification reduction low order coal simultaneously, 360 rotatable horizontal reation kettle can make the low order coal after its inside stoving be in the motion state all the time simultaneously, with more comprehensive even being heated. The preferable horizontal reaction kettle in the invention comprises a first-stage horizontal reaction kettle and a second-stage horizontal reaction kettle, wherein the first-stage horizontal reaction kettle and the second-stage horizontal reaction kettle are connected through a sealed conveying device, and the conveying device is a gasification feeding device 11. The dried low-rank coal is subjected to a first-level gas and a first-level solid after reaction from the first-level horizontal reaction kettle, the first-level gas enters the subsequent purification device 200 from the upper end of the gasification feeding device 11, the first-level solid enters the second-level horizontal reaction kettle through the gasification feeding device to continue to react to obtain a second-level gas and a second-level solid, the second-level solid is upgraded coal, and the second-level gas enters the subsequent purification device 200 from the upper end of the gasification feeding device 11.

Preferably, the capacity of the second-stage horizontal reaction kettle is smaller than that of the first-stage horizontal reaction kettle. After the low-rank coal after drying passes through the gasification reduction of one-level horizontal reaction kettle, can produce a certain amount of oil-gas mixture, the volume of remaining solid coal this moment will significantly reduce, after reducing the capacity of second grade horizontal reaction kettle so, can satisfy the gasification reduction once more of remaining solid coal better, consequently such design, more reasonable and abundant the capacity of having utilized the device to the occupation of land space has been saved, the rationality of system has been improved.

Wherein, after the low-rank coal is gasified and reduced by the first-stage horizontal reaction kettle, the volatile content in the upgraded coal is 8-15 wt%, and after the low-rank coal is gasified and reduced by the second-stage horizontal reaction kettle, the volatile content in the upgraded coal is 3-8 wt%. The main factors are related to the reaction temperature and the type of the low-rank coal, and are determined by the reaction temperature.

Wherein, horizontal reation kettle 1 is inside still to be equipped with a plurality of wireless temperature controller. The wireless temperature controller is used for monitoring the temperature in the horizontal reaction kettle 1 and transmitting a temperature signal to the background or the alarm device, so that workers can monitor the proceeding condition of the gasification reduction reaction in real time, and the controllability of the gasification reduction reaction and the safety of the reaction are improved. When the temperature of the discharge port 3 of the equipment does not reach the designated temperature, the temperature sensor transmits a signal to a computer and an alarm device to remind workers, which means that the product does not reach the qualified requirement, at the moment, the horizontal reaction kettle 1 can rotate reversely, so that solid materials which are fast to the discharge port 3 enter the horizontal reaction kettle 1 again to fully react, the retention time is prolonged, meanwhile, the heating is continued, the reverse rotation time of the horizontal reaction kettle 1 is unequal to 30min-4h, then the horizontal reaction kettle 1 rotates forwards, when the solid materials enter the discharge port 3, whether the temperature sensor alarms or not is observed, if the alarm is given, the horizontal reaction kettle 1 rotates backwards again, and the operation is repeated, and the qualified product is ensured to be off line. If the temperature sensor shows that the temperature reaches the standard, the reacted solid matter, namely the upgraded coal enters the discharge port 3 and is conveyed by the conveying device to be discharged from the discharge port of the horizontal reaction kettle 1.

The feeding port 2 of the gasification reduction device 10 in the high-temperature oil-gas mixture enters the purification device 200 from the upper end of the gasification feeding device 11.

As shown in fig. 2, the purification apparatus 200 mainly includes a dust removal apparatus 210, a tar removal apparatus 220, and a desulfurization apparatus 230, and the dust removal apparatus 210, the tar removal apparatus 220, and the desulfurization apparatus 230 are connected in this order. The high-temperature oil-gas mixture firstly enters a dust removal device 210 to remove a large amount of solid impurities such as dust and the like, then enters a tar removal device 220 system to remove a large amount of coal tar, and then enters a desulfurization device 230 to remove a large amount of sulfur-containing compounds; in order to further optimize the system, an electric tar capturing process can be additionally arranged after the desulfurization process for capturing a small amount of tar; more preferably, a hydrogenation device is additionally arranged; further optimization is carried out; a denitration device or a dechlorination device is additionally arranged to realize further purification. When two-stage gasification reduction devices are adopted, preferably, each stage of gasification reduction device is respectively and sequentially connected with the respective dust removal device 210, the tar removal device 220 and the desulfurization device 230, preferably, each stage of gasification reduction device is firstly connected with the respective dust removal process, and the dust removal device 210 of each stage is sequentially connected with the same tar removal device 220 and the same desulfurization device 230, so that equipment is saved, and the production cost expenditure is reduced.

The dust removing device 210 is connected with the upper end of the gasification feeding device 11, and the dust removing device 210 comprises one or more of a gravity dust removing device, a cyclone separating device and an electric dust removing device. Further preferably, the dust removing device 210 may be insulated with insulation cotton or the like to reduce the temperature of the oil-gas mixture as much as possible, and if the temperature is reduced too fast, the diesel oil or the like forms liquid, which causes the coal tar to adhere to the dust removing device 210 and causes blockage.

The tar removing device 220 includes a spray cooling tower and the like. The spray cooling tower utilizes cooled industrial wastewater or cooling media such as heavy oil to cool tar and water vapor in a high-temperature oil-gas mixture and then convert the tar and the water vapor into a liquid oil-water mixture, so that oil and water are separated from residual gas, and the residual gas is discharged from a gas outlet of the spray cooling tower and enters the next process for treatment.

By further optimizing the system, the gas treated by the tar removing device 220 enters the desulfurizing device 230 for desulfurization to obtain the mixed gas. The cold gas desulfurization can be broadly divided into dry desulfurization, which is widely used in the iron oxide process and the activated carbon process, and wet desulfurization, which is typified by the arsenic-alkali process, ADA, modified ADA, and tannin extract process. In the wet desulfurization technology of producer gas, tannin extract desulfurization method is widely applied. It uses soda as absorbent, tannin extract as oxygen carrier and NaVO₂Is an oxidizing agent. The whole desulfurization and regeneration process of wet tannin extract desulfurization is a continuous online process, desulfurization and regeneration are carried out simultaneously, and a standby desulfurizing tower is not required to be arranged; the desulfurization and purification degree of the coal gas can be adjusted and timely controlled by adjusting the solution ratio according to the needs of enterprises, and H in the purified coal gas₂The S content is stable. In the present invention, wet tannin extract desulfurization is preferred, and the desulfurization apparatus 230 is a wet desulfurization tower.

The mixed gas obtained from the purification apparatus 200 is introduced into the separation apparatus 600. The separation device 600 is a pressure swing adsorption device, and an adsorbent is disposed in a pressure swing adsorbent of the adsorption device, and the adsorbent is commonly activated alumina, silica gel, or the like, and may be a single adsorbent or a mixed adsorbent. In the pressure swing adsorption device, the pressure is increased at normal temperature, and the hydrocarbon and CO in the mixed gas are absorbed by the adsorbent₂Adsorption of hydrocarbons and CO₂Etc. with CO, H₂And N₂CO and H which are not adsorbed after gas separation₂And N₂The part of gas can be directly used as first synthesis gas; CO and H in pressure swing adsorption device₂And N₂Gas dischargeThereafter, the pressure in the pressure swing adsorption unit is adjusted so that the hydrocarbons are desorbed from the adsorbent to form CO₂Still adsorbed in the adsorbent, thereby obtaining a gas comprising hydrocarbons.

The gas containing hydrocarbons enters the reforming conversion reactor 300, and the reforming conversion reactor 300 is provided with a gas inlet and a gas outlet. When partial catalytic oxidation conversion is adopted, oxygen and steam are introduced into the reforming conversion reactor 300 to be combusted for heat supply, and under the action of a catalyst, hydrocarbons such as methane in the gas containing the hydrocarbons react with the steam to generate the gas mainly containing CO and H₂A second synthesis gas of (a); when the steam catalytic reforming conversion is adopted, external heat supply is needed to heat the reforming conversion reactor 300, water vapor is introduced into the reforming conversion reactor 300 through the air inlet, and under the action of the catalyst, the gas discharged from the air outlet of the reforming conversion reactor 300 is the gas containing CO and H₂A second synthesis gas of (a); when non-catalytic reforming conversion is adopted, the reforming conversion reactor 300 is heated by external heat supply, oxygen is introduced into the reforming conversion reactor 300 to react with hydrocarbons in the gas containing hydrocarbons, and the obtained gas mainly contains CO and H₂To be stored in the syngas storage tank 500.

Finally, the obtained first synthesis gas and the second synthesis gas are mixed in the synthesis gas storage tank 500 to obtain the product synthesis gas.

In summary, the method and the system of the invention gasify the volatile components in the dried low-rank coal to prepare the mixed gas under the oxygen-free or micro-oxygen condition, and the mixed gas is prepared to mainly contain CO and H by different ways₂The synthesis gas fully utilizes precious volatile components in the low-rank coal; the system provided by the invention is simple and feasible to operate, is mostly the existing equipment, is low in operation cost, and is suitable for industrial production.

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

1. A method for preparing synthesis gas by using low-rank coal gas comprises the following steps: the low-rank coal is subjected to a drying process and a gasification reduction process in sequence to obtain upgraded coal and an oil-gas mixture, and the oil-gas mixture is subjected to a purification process to obtain a mixture containing CO and H₂And a hydrocarbon, characterized in that: the gasification reduction process is a chemical reaction process for heating the dried low-rank coal under the anaerobic or micro-aerobic condition;

2. The method for preparing the synthesis gas by using the low-rank coal gas as claimed in claim 1, wherein the method comprises the following steps: the purification process comprises a dust removal process, a tar removal process and a desulfurization process.

3. The method for preparing the synthesis gas by using the low-rank coal gas as claimed in claim 1, wherein the method comprises the following steps: the drying process adopts water vapor for indirect drying, the pressure of the water vapor is 0.3-1.5Mpa, the temperature of the water vapor is 105-250 ℃, the water content of the outlet material of the drying process is not more than 7 wt%, and the temperature of the outlet material of the drying process is 50-150 ℃.

4. The method for preparing the synthesis gas by using the low-rank coal gas as claimed in claim 1, wherein the method comprises the following steps: the reaction temperature of the gasification reduction process is 350-800 ℃.

5. The method for preparing the synthesis gas by using the low-rank coal gas as claimed in claim 1, wherein the method comprises the following steps: the separation process is pressure swing adsorption.

6. The method for preparing the synthesis gas by using the low-rank coal gas as claimed in claim 1, 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 the gas containing hydrocarbons, and react part of the hydrocarbons in the gas containing hydrocarbons with the steam at the temperature of 850-1300 ℃ in the presence of a catalyst to obtain CO and H₂。

7. The method for preparing the synthesis gas by using the low-rank coal gas as claimed in claim 1, 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 the gas containing hydrocarbons, under the conditions that the indirect heat supply temperature reaches 850-1200 ℃, and the catalyst exists, part of hydrocarbons in the gas containing hydrocarbons react with the steam to obtain CO and H₂。

8. The method for preparing the synthesis gas by using the low-rank coal gas as claimed in claim 1, 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 the gas containing hydrocarbons, and part of hydrocarbons in the gas containing hydrocarbons react with the pure oxygen to obtain CO and H₂。

9. A system using the method of any of claims 1-8, wherein: the device comprises a drying device, a gasification reduction device, a purification device, a separation device and a reforming conversion reactor, wherein the drying device is connected with the gasification reduction device through a gasification feeding device, the upper end of the gasification feeding device is connected with the purification device, the purification device is connected with the separation device, and the separation device is connected with the reforming conversion reactor.

10. The system of claim 9, wherein: the gasification and reduction device is a horizontal reaction kettle capable of rotating by 360 degrees, a first heating mechanism is arranged outside the horizontal reaction kettle, and a second heating mechanism is arranged inside the horizontal reaction kettle.