Method for preparing natural gas by upgrading coal

文档序号：1425484 发布日期：2020-03-17 浏览：287次中文

阅读说明：本技术 一种提质煤制天然气的方法 (Method for preparing natural gas by upgrading coal ) 是由王建中黄成侃陈锋江何巍蒋贤武吕彬峰于 2019-12-02 设计创作，主要内容包括：本发明公开一种提质煤制天然气的方法,包括以下步骤,(1)通过气化还原将备煤系统送来的低阶煤,制备得到提质煤,在800-1300℃条件下,提质煤与饱和水蒸气反应,使得提质煤在无氧或微氧条件下,制备得到包含CO和H2的合成气；(2)通过预脱硫工艺,脱除合成气中的硫,得到预脱硫合成气；(3)通过加氢工艺将预脱硫合成气的所有不饱和烃转变成对应的饱和烃类,同时将有机硫转变成H2S,得到加氢合成气；本发明的方法,通过将低阶煤中气化还原获得提质煤,再将提质煤气化制备成天然气合成所需的原料CO、CO2和H2等气体,所制备天然气中的杂质少,充分有效地利用了低阶煤中的煤质,符合国家煤炭综合利用方向。(The invention discloses a method for preparing natural gas by upgrading coal, which comprises the following steps of (1) preparing upgraded coal from low-rank coal supplied by a coal preparation system through gasification reduction, and reacting the upgraded coal with saturated water vapor at the temperature of 800- 2 The synthesis gas of (2); (2) removing sulfur in the synthesis gas through a pre-desulfurization process to obtain pre-desulfurized synthesis gas; (3) all unsaturated hydrocarbons of the pre-desulfurized synthesis gas are converted into corresponding saturated hydrocarbons by means of a hydrogenation process, while organic sulfur is converted into H 2 S, obtaining hydrogenated synthesis gas; according to the method, the quality-improved coal is obtained by gasifying and reducing the low-rank coal, and then the quality-improved coal is gasified and prepared into the natural coalRaw materials CO and CO required by gas synthesis 2 And H 2 When the gas is used, the impurities in the prepared natural gas are few, the coal quality in the low-rank coal is fully and effectively utilized, and the method conforms to the national comprehensive utilization direction of the coal.)

1. A method for upgrading coal to natural gas is characterized by comprising the following steps,

(1) preparing upgraded coal from low-rank coal sent by a coal preparation system through gasification reduction, and reacting the upgraded coal with saturated steam at the temperature of 800-₂The synthesis gas of (2);

(2) removing sulfur in the synthesis gas through a pre-desulfurization process to obtain pre-desulfurized synthesis gas;

(3) converting all unsaturated hydrocarbons of the pre-desulfurized syngas to the corresponding saturated hydrocarbons by means of a hydrogenation process, while converting organic sulfur to H₂S, obtaining hydrogenated synthesis gas;

(4) removing sulfur in the hydrogenated synthesis gas through a desulfurization process to obtain desulfurized synthesis gas;

(5) and (2) subjecting the desulfurized synthesis gas to a shift conversion process to obtain shift conversion gas, wherein the molar ratio of hydrogen to CO in the shift conversion gas is (3-10): 1;

(6) and removing carbon dioxide in the converted gas through a decarburization process to obtain natural gas synthetic gas, so that the hydrogen-carbon ratio in the natural gas synthetic gas is (2.95-3.05): 1;

(7) the natural gas synthesis gas is subjected to a methane synthesis process in which at least 4 methanation reactors are connected in series, so that carbon monoxide, carbon dioxide and hydrogen in the desulfurized synthesis gas react in the presence of a methanation catalyst to synthesize methane, and a methane product material flow is obtained;

(8) and introducing the methane product material flow into a liquefaction process, and producing methane with volume percentage not less than 90% by using a cryogenic liquefaction process to obtain the LNG product.

2. The method as claimed in claim 1, wherein the upgraded coal is reacted with water vapor at 800-.

3. A method according to claim 2, characterised in that the resistance wire contains nickel and chromium.

4. The method as claimed in claim 1, wherein the steam is preheated to 800-1300 ℃ before reacting with the upgraded coal.

5. The method of claim 1, wherein the pre-desulfurization process comprises using a pre-desulfurization solution, the syngas enters from a lower portion of a first desulfurization unit and is countercurrently contacted with a pre-desulfurization solution sprayed from an upper portion of the first desulfurization unit, thereby removing hydrogen sulfide from the syngas, and the pre-desulfurization solution comprises a PDS catalyst.

6. The method as claimed in claim 1 or 5, wherein the pre-desulfurization process comprises a second desulfurization unit using at least one of a resistance wire comprising nickel and chromium and a pre-desulfurization catalyst comprising at least one of basic copper carbonate, copper oxide, copper hydroxide, basic zinc carbonate, zinc oxide, zinc hydroxide, the syngas is passed into the second desulfurization unit, the resistance wire heats the syngas to 200-₂And decomposing S into elemental sulfur, and filtering to remove the elemental sulfur to obtain the pre-desulfurization synthesis gas.

7. The method of claim 1, wherein the pre-desulfurization process comprises using a filtration device loaded with a composition comprising an adsorbent material and the pre-desulfurization catalyst.

8. The method of claim 1, wherein the particulate matter in the syngas is removed by a dust removal process prior to entering the pre-desulfurization process.

9. The method of claim 1, wherein the desulfurization process comprises using a desulfurization solution, and the hydrogenated synthesis gas enters from the lower part of a third desulfurization device and is in countercurrent contact with the desulfurization solution sprayed from the upper part of the third desulfurization device, so that hydrogen sulfide in the hydrogenated synthesis gas is removed, and the desulfurization solution contains an NHD solvent.

10. The method according to claim 1, wherein in the desulfurization process, a pressurized gas is introduced so that the pressure is 0.2 to 1.0MPa and the temperature is maintained at 20 to 30 ℃.

Technical Field

The invention relates to the technical field of clean utilization of coal quality, in particular to a method for preparing natural gas by upgrading coal.

Background

China is a country rich in coal, poor in oil and less in gas, and the coal consumption accounts for more than 60% of the primary energy consumption, so that the energy structure mainly based on coal is difficult to change in a long period of time. From the ascertained coal mine quality, the proportion of low-rank coal in the coal in China is very large, so that the reasonable and efficient utilization of the low-and-medium-rank coal to produce high-quality chemical products is very important. In recent years, the continuous development of technologies such as coal gasification, coal pyrolysis, coal gas purification, coal gas separation and the like makes the clean and efficient utilization of medium-low-grade coal more and more important.

Natural gas is a highly efficient clean energy source. In recent years, with the successive construction and use of national grade fuel gas transportation projects such as Shanxi gas import Jing and Xiqidong gas transportation, the demand of natural gas is increased explosively. According to prediction, in 2015, the demand of Chinese natural gas reaches 1700 hundred million Nm 3-2100 hundred million Nm3, while the yield of the natural gas at the same time can only reach 1400 hundred million Nm3, and the supply and demand gaps are about 300 hundred million Nm 3-700 hundred million Nm 3. In order to solve the problem of contradiction between supply and demand of natural gas in China, other alternative ways are required to be found besides the domestic resources are established and natural gas resources in other countries in the world are actively utilized.

The low-rank coal in China is generally used for pyrolysis gasification to crude coal gas and quality-improved coal, the pyrolysis is generally carried out under the condition of a large amount of oxygen (or air), and a part of low-rank coal is used for supplying heat in the oxygen reaction during pyrolysis and generates a large amount of CO₂. Due to CO₂Can not be combusted, belongs to ineffective gas, and has over high nitrogen content due to aerobic combustion, thereby reducing H in the crude gas₂And CO energy density, so that the calorific value of the crude gas is reduced, and the crude gas produced by pyrolysis has other economic values except for return combustion. But also the quantity of upgraded coal due to aerobic pyrolysisThe quality-improved coal can not be obtained even if the coal is not recycled, the amount of natural gas finally prepared by the quality-improved coal is small and less, effective coal resources in low-rank coal are greatly wasted, and the utilization rate of the low-rank coal is low.

Disclosure of Invention

In view of the above, the present invention provides a method for producing natural gas from upgraded coal, which aims to overcome the defects of the prior art, and comprises the steps of obtaining upgraded coal by removing most of volatile matters from dried low-rank coal through gasification reduction under the oxygen-free or micro-oxygen condition, wherein the upgraded coal has less volatile matters and less impurities, has a certain temperature when losing, and preparing raw materials, namely CO and CO, required by natural gas synthesis from upgraded coal by gasification₂And H₂When the gas is used, the prepared natural gas has less impurities and high quality, and the coal quality in the low-rank coal is fully and effectively utilized.

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

a method for upgrading coal to natural gas comprises the following steps,

(2) removing sulfur in the synthesis gas through a pre-desulfurization process to obtain pre-desulfurized synthesis gas;

(4) removing sulfur in the hydrogenated synthesis gas through a desulfurization process to obtain desulfurized synthesis gas;

(5) and (2) subjecting the desulfurized synthesis gas to a shift conversion process to obtain shift conversion gas, wherein the molar ratio of hydrogen to CO in the shift conversion gas is (3-10): 1;

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 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 high-temperature synthesis gas and upgraded coal with a certain temperature.

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 enters 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 ℃, and the pressure is less than or equal to 30Kpa, a complex chemical reaction process is carried out, so that solid carbon and high-temperature synthesis gas are obtained, wherein the solid carbon is upgraded coal, and the volatile components in the upgraded coal are 8-15 wt%. The high-temperature synthesis gas comprises CO and H₂、CO₂Hydrocarbon, coal tar, naphthalene, halide, dust, sulfur compounds, and the like.

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 synthesis gas, 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 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.

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 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 upgraded coal with lower volatile matters can be obtained, wherein the content of the volatile matters in the upgraded coal is 3-8 wt%.

Upgraded coal and H₂The reaction of O (water vapor) is endothermic and the reaction equation is C + H₂O＝CO+H₂The upgraded coal obtained after the gasification reduction process reaction is the upgraded coal with temperature, and has higher latent heat because the upgraded coal has certain temperature which is generally 350-800 ℃, and the process is based on fully utilizing the latent heat of the upgraded coal, preferably, the steam is preheated to 800-1300 ℃ so that the upgraded coal reacts with the steam at the temperature of 800-1300 ℃. Preferably, the steam and the upgraded coal are preheated to 800-1300 ℃ before reacting. Preferably, the upgraded coal is heated by a resistance wire under the condition of no oxygen or micro oxygen, so that the upgraded coal reacts with water vapor at the temperature of 800-1300 ℃. Preferably, the resistance wire contains nickel and chromium.

The particle size of upgraded coal also affects syngas generation, and preferably, the upgraded coal is subjected to a pulverization process such that the upgraded coal has a particle size between 100 mesh and 300 mesh.

To facilitate the generation of syngas by allowing water vapor to adhere to the upgraded coal particles and within the interstices thereof, the water vapor is preferably passed through electrodes to which a direct current voltage in excess of 10KV is applied, causing the water vapor to become charged.

The upgraded coal is preferably upgraded coal with small particle size, the upgraded coal with large strength can be sold directly, the upgraded coal with small particle size is easy to cause dust and is not easy to transport, and is easy to cause environmental pollution, and the synthesis gas is preferably prepared by using the pulverized upgraded coal with small particle size after screening the upgraded coal. Preferably, the upgraded coal is subjected to a comminution process such that the upgraded coal has a particle size of between 50 mesh to 1000 mesh. Preferably, the upgraded coal is subjected to a pulverization process such that the upgraded coal has a particle size of between 100 mesh and 300 mesh.

Major impurities in syngasThe gas is CO₂、H₂S, COS, and a small amount of dust. The pre-desulfurization process, the hydrogenation process and the desulfurization process are required to remove relevant impurities to obtain the purified desulfurized synthesis gas. Preferably, the particulate matter in the synthesis gas is removed by a dust removal process before the synthesis gas enters the pre-desulfurization process. Preferably, the pre-desulfurization process comprises the use of a filtration device loaded with a composition comprising an adsorbent material and the pre-desulfurization catalyst. Preferably, the pre-desulfurization process comprises using a pre-desulfurization solution, wherein the synthesis gas enters from the lower part of the first desulfurization device and is in countercurrent contact with the pre-desulfurization solution sprayed from the upper part of the first desulfurization device, so that hydrogen sulfide in the synthesis gas is removed, and the pre-desulfurization solution comprises a PDS catalyst. Further, the pre-desulfurization process comprises a second desulfurization device using at least one of a resistance wire and a pre-desulfurization catalyst, wherein the resistance wire comprises nickel and chromium, the pre-desulfurization catalyst comprises at least one of basic copper carbonate, copper oxide, copper hydroxide, basic zinc carbonate, zinc oxide and zinc hydroxide, the synthesis gas is introduced into the second desulfurization device, the resistance wire heats the synthesis gas to 200-500 ℃, and H in the synthesis gas is enabled to react with hydrogen₂And decomposing S into elemental sulfur, and filtering to remove the elemental sulfur to obtain the pre-desulfurization synthesis gas. Preferably, the desulfurization process comprises using a desulfurization solution, wherein the hydrogenated synthesis gas enters from the lower part of a third desulfurization device and is in countercurrent contact with the desulfurization solution sprayed from the upper part of the third desulfurization device, so that hydrogen sulfide in the hydrogenated synthesis gas is removed, and the desulfurization solution contains an NHD solvent. Further, in the desulfurization process, pressurized gas is introduced so that the pressure is 0.2 to 1.0MPa, and the temperature is maintained at 20 to 30 ℃.

The effective component in the natural gas and the synthetic gas is H₂、CO、CO₂The requirement for the hydrogen-carbon ratio in the natural gas and the synthetic gas has the following expression: r ═ H₂-CO₂)/(CO+CO₂) Wherein, the hydrogen-carbon ratio R of the natural gas and the synthetic gas is 3.0, and the optimal value is 2.95-3.05. The R value of the hydrogen-carbon ratio in the prepared converted gas generally can not just meet the R value of less than 2.953.05, so that the hydrogen-carbon ratio R value of the obtained natural gas synthesis gas is adjusted to be 2.95-3.05 by adjusting the hydrogen-carbon ratio of the converted gas through one or more of a decarburization carbon-supplementing process, a shift conversion process and a hydrogen-supplementing process. Preferably, in the step (3), the converted gas is firstly subjected to a conversion process to obtain converted gas, and the converted gas is then subjected to a decarburization carbon supplement process to obtain natural gas synthesis gas. Because of CO + H in the upgrading coal gasification process₂The theoretical ratio of (1: 1) and the conversion CO content is too high, and the conversion reaction is carried out by transformation:

can increase H₂Volume percent of CO, volume percent of CO reduction, if CO is caused₂The redundant components are easy to remove. The converted gas obtained after the quality-improved coal gasification contains a certain amount of unreacted H₂O (water vapour), using the H contained in the reformed gas₂O (water vapour) or externally supplemented H₂O (water vapor) can be directly subjected to conversion reaction under certain conditions. Determining the choice of the conversion process according to the R value of the converted gas, and directly and quickly adjusting the R value through the subsequent decarburization carbon-supplementing process without adopting the conversion process when the R value is generally close to 2.95-3.05; when the R value is far less than 2.95-3.05, the conversion process is added, so as to increase the R value.

Preferably, the shift conversion process is to pass CO in the converted gas with H₂Conversion of O into H₂And CO₂The process of (1).

Preferably, in the decarbonization and carbon supplement process in the step (3), when the hydrogen-carbon ratio R value of the converted gas is greater than 3.1, CO is introduced₂Adjusting the R value to 2.95-3.05; when the hydrogen-carbon ratio R value of the converted gas is less than 2.95, removing CO₂So that the R value is adjusted to 2.95-3.05. When the R value of the converted gas is more than 3.1, the converted gas represents more hydrogen and less carbon, and CO is introduced into the converted gas through a carbon supplementing process₂Or CO of high purity₂And obtaining the natural gas synthetic gas meeting the standard. When in useWhen the R value of the reformed gas is less than 2.95, the reformed gas represents less hydrogen and more carbon, and a part of CO in the reformed gas is removed by pressure swing adsorption or solution absorption₂The R value range of the natural gas and the synthetic gas is adjusted to be 2.95-3.05.

Preferably, the decarbonization process comprises the use of decarbonization liquid, the hydrogenated synthesis gas enters from the lower part of a decarbonization device and is in countercurrent contact with decarbonization liquid sprayed from the upper part of the decarbonization device, so that carbon dioxide in the hydrogenated synthesis gas is removed, and the decarbonization liquid contains NHD solvent. Furthermore, in the decarburization process, pressurized gas is introduced so that the pressure is 0.3 to 1.0 MPa.

And finally, producing methane with the volume percentage not less than 90% by a cryogenic liquefaction process through a liquefaction process to obtain the LNG synthesis gas product, so that the natural gas product is obtained, the impurities are few, the quality is high, and the requirement of natural gas quality index is met.

Based on the technical scheme, the method obtains the upgraded coal through gasification reduction in the low-rank coal, the upgraded coal has less volatile components and less impurities, and the upgraded coal is gasified and prepared into the raw materials of CO and CO required by natural gas synthesis₂And H₂When the gas is used, the prepared natural gas has less impurities and high quality, the coal quality in the low-rank coal is fully and effectively utilized, and the method conforms to the national comprehensive utilization direction of the 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, 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.

A method for upgrading coal to natural gas comprises the following steps,

(1) preparing low-rank coal from coal preparation system by gasification and reductionAt the temperature of 800-1300 ℃, the upgraded coal reacts with saturated steam, so that the upgraded coal is prepared to contain CO and H under the oxygen-free or micro-oxygen condition₂The synthesis gas of (2);

(2) removing sulfur in the synthesis gas through a pre-desulfurization process to obtain pre-desulfurized synthesis gas;

(4) removing sulfur in the hydrogenated synthesis gas through a desulfurization process to obtain desulfurized synthesis gas;

(5) and (2) subjecting the desulfurized synthesis gas to a shift conversion process to obtain shift conversion gas, wherein the molar ratio of hydrogen to CO in the shift conversion gas is (3-10): 1;

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 a low degree of coalification, but the low-rank coal having a fixed carbon content of 40% to 60% is preferred.

The drying process can only remove most of the free water in the low-rank coal, but not remove the bound water in the low-rank coal, so that the low-rank coal is treated by the drying process to obtain the dried low-rank coal and waste gas, the dried low-rank coal still contains a certain amount of moisture, and the residual moisture can be gasified to form steam in the subsequent gasification reduction process. 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 firstly treats the low-rank coal through a drying process and removes a part of moisture in the low-rank coal. 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 steam can easily cause the steam to be mixed into the low-rank coal, thereby not only causing the consumption of reaction coal resources, but also reducing the drying efficiency, and therefore, the drying mode of indirectly drying the low-rank coal by the steam is adopted to prevent the moisture in the steam 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 below 7 wt%, most of the water escapes from the low-rank coal along with dust such as coal dust and enters the waste gas generated after drying in the form of the water vapor, and the temperature of the material at the discharge port of the drying process is 50-150 ℃; 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 enters the gasification reduction process to react, 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 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 the dried low-rank coal under the condition of no oxygen or micro oxygen. The dried low-rank coal enters a gasification reduction toolUnder the heating of heating media such as flue gas and the like, additives and other substances are not required to be added in the reaction process, the temperature is generally 350-800 ℃, and the process of complex chemical reaction is carried out under the pressure of less than or equal to 30Kpa, so as to obtain solid carbon and high-temperature synthesis gas, wherein the solid carbon is upgraded coal, and the volatile component in the upgraded coal is 8-15 wt%. The high-temperature synthesis gas comprises CO and H₂、CO₂Hydrocarbon, coal tar, naphthalene, halide, dust, sulfur compounds, and the like.

Wherein, the oxygen source of the oxygen-free or micro-oxygen environment adopted by the gasification reduction process is mainly divided into the following situations: (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 explosion limit of the mixture 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 coal₂To ensure the whole gasification reduction processThe safety and stability of the 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.

Upgraded coal and H₂The reaction of O (water vapor) is endothermic and the reaction equation is C + H₂O＝CO+H₂The upgraded coal obtained after the gasification reduction process reaction is upgraded coal with temperature, and has high latent heat because the upgraded coal has certain temperature which is generally 350-800 ℃, and O can be introduced firstly on the basis of fully utilizing the latent heat of the upgraded coal₂A part of the upgraded coal is burnt to release heat, the environmental temperature quickly reaches 800-₂The obtained gas is synthetic gas which mainly comprises CO and CO₂And H₂. Preferably, the upgraded coal is reacted with water vapor at the temperature of 800-1300 ℃ by heating through a resistance wire. Further, the resistance wire contains nickel and chromium. Preferably, the steam is preheated to 800-. Syngas is produced continuously by continuously introducing steam so that upgraded coal reacts with the steam.

Because most of volatile components, tar and the like are gasified and removed in the gasification reduction process stage, the content of coal quality in the obtained upgraded coal is high, and therefore, the content of impurity gas in the synthesis gas obtained by using the upgraded coal is less. The upgraded coal is preferably upgraded coal with small particle size, the upgraded coal with large strength can be sold directly, the upgraded coal with small particle size is easy to cause dust and is not easy to transport, and is easy to cause environmental pollution, and the synthesis gas is preferably prepared by using the pulverized upgraded coal with small particle size after screening the upgraded coal.

The main impurity gas in the synthesis gas is CO₂、H₂S, COS, and a small amount of dust.

The acid-removed gas and a small amount of dust and other impurities in the synthesis gas are removed by a purification process to obtain purified converted gas. The purification process comprises a physical absorption method, a chemical absorption method and a physical and chemical absorption method. Physical absorption methods include low temperature natural gas scrubbing, the dimethyl ether of polyethylene glycol, the N-2 methyl pyrrolidone process, and the like. Among them, the physical absorption method is more economical and mature, and is widely applied to industrial production, and the representative methods include a low-temperature natural gas scrubbing method (Rectisol) and a polyethylene glycol dimethyl ether method (NHD). The low-temperature natural gas washing process takes cold natural gas as an absorption solvent and utilizes natural gas to treat acid gas (CO) at low temperature₂、H₂S, COS, etc.) and is a physical absorption method for removing acid gases from synthesis gas. The low-temperature natural gas washing process is the most economic gas purification technology with high purification degree which is recognized at home and abroad at present, and has the characteristics that other desulfurization and decarburization technologies cannot be replaced, such as: high quality of purified gas, high purification degree, and selective absorption of CO₂、 H₂The characteristics of S and CO, cheap and easily obtained solvent, low energy consumption, low running cost, stable and reliable production and operation, and the like. Therefore, the purification process is preferably a low temperature natural gas scrubbing process to remove acid gases from the syngas. Conversion of CO from gas₂Volume percent about 32.1%, volume percent CO about 19.02%, H₂S volume percent about 0.23%, H₂The volume percent was about 46.02%.

Preferably, the particulate matter in the synthesis gas is removed by a dust removal process before the synthesis gas enters the pre-desulfurization process. Preferably, the pre-desulfurization process comprises the use of a filtration device loaded with a composition comprising an adsorbent material and the pre-desulfurization catalyst. Preferably, the pre-desulfurization process comprises using a pre-desulfurization solution, and the synthesis gas enters from the lower part of a first desulfurization device and goes up from the first desulfurization deviceAnd part of the sprayed pre-desulfurization solution is contacted in a countercurrent manner, so that hydrogen sulfide in the synthesis gas is removed, and the pre-desulfurization solution comprises a PDS catalyst. Further, the pre-desulfurization process comprises a second desulfurization device using at least one of a resistance wire and a pre-desulfurization catalyst, wherein the resistance wire comprises nickel and chromium, the pre-desulfurization catalyst comprises at least one of basic copper carbonate, copper oxide, copper hydroxide, basic zinc carbonate, zinc oxide and zinc hydroxide, the synthesis gas is introduced into the second desulfurization device, the resistance wire heats the synthesis gas to 200-500 ℃, and H in the synthesis gas is enabled to react with hydrogen₂And decomposing S into elemental sulfur, and filtering to remove the elemental sulfur to obtain the pre-desulfurization synthesis gas. Preferably, the desulfurization process comprises using a desulfurization solution, wherein the hydrogenated synthesis gas enters from the lower part of a third desulfurization device and is in countercurrent contact with the desulfurization solution sprayed from the upper part of the third desulfurization device, so that hydrogen sulfide in the hydrogenated synthesis gas is removed, and the desulfurization solution contains an NHD solvent. Further, in the desulfurization process, pressurized gas is introduced so that the pressure is 0.2 to 1.0MPa, and the temperature is maintained at 20 to 30 ℃.

The value of the hydrogen-carbon ratio R in the converted gas obtained after the purification process treatment cannot meet the requirement that the value of the hydrogen-carbon ratio R in the raw material gas synthesized by natural gas is 2.95-3.05, so the value of the R needs to be adjusted.

The effective component in the gas required for natural gas synthesis is H₂、CO、CO₂The following expression is required for the hydrogen-carbon ratio in natural gas synthesis gas:

R＝(H₂-CO₂)/(CO+CO₂) Wherein the hydrogen-carbon ratio R of the natural gas and the synthetic gas is (H)₂-CO₂)/(CO+CO₂) The theoretical value is 3.0, and the optimal value is 2.95-3.05.

The natural gas synthetic gas contains a certain amount of CO₂Can increase the catalytic activity of the catalyst for synthesizing natural gas, reduce the heat effect of reaction, make the catalytic temperature easy to control, reduce the thermal deactivation of the catalyst caused by overtemperature, thus prolong the service life of the catalyst, but CO₂The content of (A) must be appropriate. If CO is present₂The content of (a) is too large,the water content of the product will increase, which will reduce the compression capacity of the compressor and increase the energy consumption of the gas compression and rectification process. CO2₂The optimal content in the natural gas synthetic gas is adjusted according to the catalyst used for natural gas synthesis and the natural gas synthesis operation temperature.

When the R value of the natural gas synthetic gas is more than 3.1, the natural gas synthetic gas represents more hydrogen and less carbon, at the moment, the circulating gas quantity of a natural gas synthetic loop is large, the power consumption of a circulating gas compressor is large, the purge gas quantity of natural gas is also large, and a plurality of raw materials are used for preparing useful H through multiple processes₂、CO、 CO₂And methane and the like are sent into a fuel system along with the purge gas of the natural gas to be burnt, so that serious resource waste is caused, and the consumption of raw materials is increased. When the R value of the natural gas synthetic gas is less than 2.95, the requirement of natural gas synthesis cannot be met. Therefore, the R value of the converted air needs to be adjusted.

The R value of the converted gas can be realized by one or more of a decarburization carbon supplement process, a change conversion process and a hydrogen supplement process.

The decarbonization and carbon supplement process comprises a decarbonization process and a carbon supplement process, namely removing CO₂And make-up of CO₂The process of (1). The converted gas is treated by a decarburization and carbon supplement process to obtain the natural gas synthesis gas with the R value of 2.95-3.05. When the R value of the converted gas is more than 3.1, the converted gas represents more hydrogen and less carbon, and CO is introduced into the converted gas through a carbon supplementing process₂Or CO of high purity₂And obtaining the natural gas synthetic gas meeting the standard. When the R value of the converted gas is less than 2.95, the converted gas represents that the hydrogen is less and the carbon is more, and a part of CO in the converted gas is removed by a decarburization process₂The R value range of the natural gas and the synthetic gas is adjusted to be 2.95-3.05.

Removal of CO industrially₂There are many methods of (1), which can be broadly divided into two broad categories: one is solvent absorption and the other is Pressure Swing Adsorption (PSA). The solvent absorption method includes physical absorption method, chemical absorption method and physical-chemical absorption method, the physical absorption method such as low temperature natural gas washing method, polyethylene glycol dimethyl ether method, propylene carbonate method; chemical absorption, generally like NaOH, KOH, Ba (OH)₂The alkali liquor with stronger equialkalinity can effectively absorb CO₂Gas, the principle of which is due to CO₂The gas is dissolved in water to generate carbonic acid, and a small part of hydrogen ions generated by ionization of the carbonic acid react with hydroxide ions in the alkali liquor to generate water, so that CO can be removed₂. The PSA method utilizes the characteristic that the adsorbent has different adsorption capacities, adsorption speeds and adsorption forces to adsorbates under different partial pressures and has selective adsorption to each component of a separated gas mixture under a certain pressure to remove impurity components in raw gas by pressure adsorption and remove the impurities by decompression so as to regenerate the adsorbent₂The new technology has wide prospect. In addition, the process works to remove CO₂And can be recycled.

When the R value of the converted gas is less than 2.95, H can be supplemented by a hydrogen supplementing process₂The method replaces the decarburization process to adjust the R value of the converted gas so that the R value is between 2.95 and 3.05. Adding a proper amount of external H₂Or H of high purity₂Introducing into converted gas to make R value in the range of 2.95-3.05, so as to save decarbonization process and reduce technological process. Here H₂Or H of high purity₂Can be purchased directly from the outside, and can also recover purified H from the natural gas purge gas remaining after the subsequent natural gas synthesis process₂Preferably, purified H from natural gas purge gas is used₂And the reformed gas and the converted gas enter a subsequent compression process, so that the resource recycling is realized, and the process cost expenditure is saved.

Before the converted gas is subjected to the decarburization and carbon supplement process to obtain the natural gas synthetic gas, the converted gas is subjected to a conversion process to obtain converted gas. When the R value of the hydrogen-carbon ratio in the converted gas is generally less than 2.05, the converted gas represents more carbon and less hydrogen, and the components cannot meet the requirements of synthesizing natural gas. Carbon is excessive and hydrogen is insufficient, and the optimization focuses on how to obtain more hydrogen. The converted gas is subjected to a conversion process to obtain converted gas, the converted gas is subjected to a decarburization carbon supplement process to obtain natural gas synthetic gas, and the hydrogen-carbon ratio R value of the natural gas synthetic gas is adjusted to be 2.95-3.05.

A certain amount of H₂Introducing O (water vapor) into the converted gas to perform conversion reaction to obtain converted gas. The main reactions in the shift conversion process are:

thermal effect of this reaction H₂Depending on the state of O, an endothermic reaction is obtained in the case of liquid water, and an exothermic reaction is obtained in the case of steam. The change reaction is a reversible reaction whose equilibrium constant decreases with increasing pressure. The converted gas is treated by the conversion process to obtain the converted gas, and H can be increased₂Volume percent of CO, while increasing CO₂Therefore, the shift conversion process is generally followed by a decarburization process for removing CO₂. The transformation conversion process is used for increasing the effective component H₂At the same time, the CO is increased₂Volume percent, but CO₂Is easy to remove, and a great amount of CO in the shift gas is obtained after the shift conversion process₂Can be treated by a decarburization carbon supplementing process. Determining the choice of the conversion process according to the R value of the converted gas, and directly and quickly adjusting the R value through the subsequent decarburization carbon-supplementing process without adopting the conversion process when the R value is generally close to 2.95-3.05; when the R value is far less than 2.95-3.05, the conversion process is added to increase the R value, and the R value is adjusted by the decarburization carbon-supplementing process after reuse. Because the prepared converted gas contains a certain amount of unreacted H₂O (water vapor), and does not need to supplement H externally when changing₂O (water vapor) can be directly subjected to conversion reaction under certain conditions.

The natural gas synthesis gas obtained from the decarburization carbon supplementing process is firstly compressed by a compression process, which is beneficial to the subsequent synthesis compression process of natural gas with the pressure of 40-50kg and the temperature of 200-350 ℃. Because the pressure of the gas treated by the compression process is 40-50kg, the natural gas is synthesized by adopting a low-pressure method. In order to realize isobaric natural gas synthesis, save a natural gas synthesis gas compressor and compression power consumption, and reduce investment cost and production cost, the production and purification of the natural gas synthesis gas are generally carried out under low pressure. The natural gas synthetic gas enters a natural gas synthesis process, a catalyst required by natural gas synthesis is added, and crude natural gas and natural gas purge gas are obtained after reaction. The natural gas synthesis catalyst can be generally divided into a zinc-chromium catalyst, a copper-based catalyst, a palladium-based catalyst, a molybdenum-based catalyst and the like, and the copper-zinc-aluminum-based catalyst is commonly used in industrial production. The purity of the crude natural gas in the invention is about 95%. The main chemical reaction formula of the synthetic natural gas is as follows:

the main chemical reaction formula of the synthetic natural gas is as follows:

because of the exothermicity in the natural gas synthesis process, a plurality of side reactions are generated, the side reactions generate a large amount of inert gases and are accumulated in the system continuously, the normal operation of the natural gas synthesis process is influenced, and the discharged gases are required to be discharged continuously, and the discharged gases are called natural gas purge gases. The main component of the natural gas purge gas is H₂、CO、H₂O and CH₄In the presence of an inert gas, wherein H₂And CH₄The volume percentage content is about 90 percent.

The invention at least adopts a methane synthesis process with 4 methanation reactors connected in series, so that carbon monoxide, carbon dioxide and hydrogen in the desulfurized synthesis gas react in the presence of a methanation catalyst to synthesize methane, and a methane product material flow is obtained, thereby reducing the discharge of natural gas purge gas, and fully utilizing the natural gas purge gas which needs to be discharged originallyH of (A) to (B)₂And the dual purposes of increasing the yield of natural gas, saving energy and reducing emission can be achieved.

The obtained synthesis gas components are analyzed through a comparative experiment, so that the technical progress of the quality-improved coal-to-natural gas production method based on the low-rank coal quality-based utilization is analyzed.

Experimental example 1

A method for upgrading coal to natural gas comprises the following steps,

(2) removing sulfur in the synthesis gas through a pre-desulfurization process to obtain pre-desulfurized synthesis gas;

(4) removing sulfur in the hydrogenated synthesis gas through a desulfurization process to obtain desulfurized synthesis gas;

(5) and (2) subjecting the desulfurized synthesis gas to a shift conversion process to obtain shift conversion gas, wherein the molar ratio of hydrogen to CO in the shift conversion gas is (3-10): 1;

In the embodiment 1, the low-rank coal is pulverized coal with the granularity of less than 20 mm;

in example 1, upgraded coal is prepared from low-rank coal through a gasification reduction process, and when the temperature of the upgraded coal is about 1000 ℃, 800-1300 ℃ steam is introduced to enable the upgraded coal to react with the steam under the oxygen-free or micro-oxygen condition to prepare the upgraded coal containing CO and H₂The synthesis gas of (2), in particular steam, is passed such that the upgraded coal and steam react at a temperature of about 1000 ℃.

Experimental example 2

Experimental example 2 reference is made to Experimental example 1, except that in Experimental example 2, the upgraded coal is heated by a resistance wire under oxygen-free or micro-oxygen conditions, so that the upgraded coal reacts with water vapor at the temperature of 800-1300 ℃. Specifically, upgraded coal is reacted with steam at a temperature of about 1000 ℃ to obtain syngas.

Experimental example 3

Experimental example 3 referring to Experimental example 1, except that the pre-desulfurization process in Experimental example 3 includes a second desulfurization unit using at least one of a resistance wire including nickel and chromium and a pre-desulfurization catalyst including at least one of basic copper carbonate, copper oxide, copper hydroxide, basic zinc carbonate, zinc oxide, and zinc hydroxide, the syngas is passed into the second desulfurization unit, the resistance wire heats the syngas to 200-500 deg.C, so that H in the syngas₂And decomposing S into elemental sulfur, and filtering to remove the elemental sulfur to obtain the pre-desulfurization synthesis gas. The specific second desulfurization device comprises a resistance wire and a pre-desulfurization catalyst.

Comparative example 1

The method for preparing the natural gas from the synthesis gas by using the low-rank coal in a quality-divided manner comprises the following steps:

(1) heating low-rank coal at the temperature of 600 ℃ by isolating air to produce semi-coke, coal tar and synthesis gas as byproducts, wherein the synthesis gas comprises the following componentsWith CH₄28-40% of content, 10-15% of CO content and H₂25-40% of CO₂Content 5-10%, C₂H₆Content 2-8%, C₂H₄Content 1-4%, C₃H₆0.5-3% of C₃H₈Content of 0.4-2.5%, C₄H₈0.2-2% of H₂S content 2000-₃The content is 300-800 ppm;

(2) through the spray washing purification process adopted by the washing purification unit 2, the pretreated synthesis gas is further purified, ammonia and sulfide in the synthesis gas are removed, so that the load of a subsequent desulfurization process is reduced, and the pre-desulfurized synthesis gas is obtained;

(3) all unsaturated hydrocarbons in the coal gas are converted into corresponding saturated hydrocarbons through the hydrogenation unit 3, and organic sulfur is simultaneously converted into H₂S, obtaining hydrogenated synthesis gas;

(4) the fine desulfurization unit 4 adopts a dry desulfurization process, solid ZnO is used for desulfurization, and H in the feed gas is removed₂The S content is reduced to<0.1ppm, obtaining the desulfurized synthesis gas;

(5) passing the desulfurized gas through a pre-conversion unit 5, and pre-converting the desulfurized gas by using a hydrocarbon steam pre-conversion catalyst with high nickel content, wherein the NiO content in the catalyst is 48-68%, and the Al content in the catalyst is 48-68%₂O₃15-36% of La, 1.2-4.8% of MgO and₂O₃1.2-4.8% of CaO, 5-12% of CaO and K₂0.5-1.2% of O and 1.5-4.5% of graphite; the unit leads higher hydrocarbon above C2 in the coal gas to carry out pre-conversion reaction to generate methane under the conditions of pressure of 1.5-3.5MPa, temperature of 400-; wherein the coal gas after the pre-conversion reaction comprises the following components: CH (CH)₄30-50% of CO, 13-18% of H2, 10-15% of CO2 and a small amount of water vapor and other impurity gases;

(6) passing the pre-converted gas through a methanation unit 6, and adopting a methanation catalyst with low nickel content, wherein the components of the methanation catalyst comprise NiO content of 12-24%, Al2O3 content of 32-74%, MgO content of 1.2-4.8%, La2O3 content of 1.2-4.8%, CaO content of 5-12%, K2O content of 0.5-1.2%, and graphite content of 1.5-4.5%; the effective components in the raw material gas are: h2, CO and CO2 are subjected to methanation reaction, so that the concentration of the generated methane can reach 75-90%;

(7) and introducing the gas after the methanation reaction into a pressure swing adsorption unit 7, and producing high-concentration methane, namely a product LNG and high-purity hydrogen through a pressure swing adsorption process.

TABLE 1 analysis table of composition of syngas produced in test examples 1-3 and comparative example 1^*

Composition of	Experimental example 1	Experimental example 2	Experimental example 3	Comparative example 1
					CH₄	0.86	0.92	0.90	26.38
H₂	44.62	48.36	50.36	26.42
					CO	40.12	37.22	35.12	14.60
CO₂	1.68	1.45	1.28	16.96
					N₂	1.38	1.25	1.35	1.52
H₂O	10.68	10.26	10.46	6.72
					Others	0.59	0.54	0.53	7.40
Sulfur content	3600ppm	54ppm	36ppm	3500ppm
					H₂/CO	1.11	1.30	1.43	0.71

Note: 1. the content is volume percentage content;

2. others include other alkanes and ammonia.

From the results in table 1, the components of the obtained pre-desulfurized rich gas were analyzed, and we can obtain that, firstly, the sulfur content in the rich gas can be significantly reduced by using the PDS catalyst-containing desulfurization solution for pre-desulfurization, and secondly, the sulfur content in the pre-desulfurized gas can be significantly reduced by using the resistance wire and the pre-desulfurization catalyst, from 36.8ppm in experimental example 1 to 14.6ppm in experimental example 2; thirdly, the pre-desulfurization process is provided with the electrode, so that the sulfur content in the pre-desulfurized gas can be obviously reduced from 36.8ppm of experimental example 1 to 16.2ppm of experimental example 3.

TABLE 2 compositional analysis tables of the pre-desulfurized rich gas produced in test examples 1 to 3 and comparative example 1^*1

Composition of	Experimental example 1	Experimental example 2	Experimental example 3	Comparative example 1
					CH₄	27.67	26.17	27.86	26.38
H₂	28.53	32.66	29.43	26.42
					CO	14.70	17.20	15.58	14.60
CO₂	18.91	17.46	18.76	16.96
					N₂	1.08	1.12	1.06	1.52
H₂O	1.72	1.25	1.65	6.72
					Others	7.38	4.14	5.66	7.40
Sulfur content	36.8ppm	14.6ppm	16.2ppm	139.4ppm

Note: 1. the content is volume percentage content;

2. others include other alkanes and ammonia.

From the results of Table 2, analyzing the composition of the resulting syngas gas, we can obtain that, first, upgraded coal of Experimental examples 1, 2 and 3 was prepared to contain CO and H by reacting with steam under oxygen-free or micro-oxygen conditions₂So that in the synthesis gas, H₂CO, was higher than in comparative example 1, and the amount of carbon dioxide in the synthesis gas of experimental example 1, experimental example 2 and experimental example 3 was significantly lower than in comparative example 1. Secondly, we have surprisingly found that in experimental examples 2 and 3, the sulfur content in the obtained synthesis gas is significantly reduced, whereby the upgraded coal is heated by resistance wires such that the upgraded coal reacts with water vapor at a temperature of 800-₂S is ionized into elemental sulfur, which is reflected in the syngas with a significant reduction in sulfur content.

The crude natural gas obtained from the natural gas synthesis process is subjected to a natural gas liquefaction process to obtain a product natural gas, the recovery rate of the liquefaction process is about 99.5%, the obtained natural gas has few impurities and high quality, and the specification meets the requirements of natural gas quality indexes.

In conclusion, the method obtains the upgraded coal through gasification reduction of the low-rank coal, the upgraded coal has less volatile components and less impurities, and the upgraded coal is gasified and prepared into the raw materials CO and CO required by natural gas synthesis₂And H₂Isogas, is preparedThe natural gas prepared has less impurities and high quality, fully and effectively utilizes the coal quality in the low-rank coal, and accords with the national comprehensive utilization direction of 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.

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