阅读说明：本技术 一种合成气的干法脱硫工艺 (Dry desulfurization process for synthesis gas ) 是由 *** 俞天明 吕彬峰 金飞伟 王建中 薛安克 于 2019-11-27 设计创作，主要内容包括：本发明公开一种合成气的干法脱硫工艺,包括合成气净化工序和合成气精脱硫工序,所述精脱硫工序包括加氢步骤和干法脱硫步骤,所述加氢步骤包括一级加氢和二级加氢,所述一级加氢为在铁钼催化剂的作用下,所述二级加氢为流经铁钼催化剂后的所述合成气,再流经镍钼催化剂,将所述合成气中的H<Sub>2</Sub>S脱除到含量低于<0.1ppm。本发明的干法脱硫工艺,保证后续煤加工工艺的顺利进行,从而使得人们充分利用了低阶煤中宝贵的挥发分和煤质；本发明中的系统,操作简单可行,运行成本较低,适合工业化生产。(The invention discloses a dry desulfurization process of synthesis gas, which comprises a synthesis gas purification process and a synthesis gas fine desulfurization process, wherein the fine desulfurization process comprises a hydrogenation step and a dry desulfurization step, the hydrogenation step comprises primary hydrogenation and secondary hydrogenation, the primary hydrogenation is carried out under the action of an iron-molybdenum catalyst, the secondary hydrogenation is carried out under the action of an iron-molybdenum catalyst, the synthesis gas flows through the iron-molybdenum catalyst, then flows through a nickel-molybdenum catalyst, and H in the synthesis gas is subjected to 2 S is removed to a content lower than<0.1 ppm. The dry desulfurization process ensures the smooth proceeding of the subsequent coal processing process, thereby fully utilizing valuable volatile components and coal quality in the low-rank coal; the system provided by the invention is simple and feasible to operate, low in operation cost and suitable for industrial production.)

1. The dry desulfurization process of the synthesis gas is characterized by comprising a synthesis gas purification process and a synthesis gas fine desulfurization process, wherein the synthesis gas purification process comprises an oil-removing and naphthalene-removing working section and a crude desulfurization working section, the oil-removing and naphthalene-removing working section comprises the step of absorbing oily condensable substances comprising naphthalene and tar in the synthesis gas by using an oil absorbent to ensure that the tar and the naphthalene content in the removed synthesis gas are reduced to below 1mg/Nm3, the crude desulfurization working section adopts a pre-desulfurization catalyst to absorb and remove inorganic sulfur in the synthesis gas, the synthesis gas fine desulfurization process comprises a hydrogenation step and a dry desulfurization step, the hydrogenation step comprises primary hydrogenation and secondary hydrogenation, and the hydrogenation step comprises primary hydrogenation and secondary hydrogenationThe first-stage hydrogenation is to react unsaturated hydrocarbon and organic sulfur compound contained in the synthesis gas with hydrogen under the action of an iron-molybdenum catalyst, the unsaturated hydrocarbon is converted into saturated hydrocarbon, and the organic sulfur is converted into H₂S, the synthesis gas flows through the iron-molybdenum catalyst after the secondary hydrogenation, and then flows through the nickel-molybdenum catalyst, so that unsaturated hydrocarbon and organic sulfur compounds contained in the synthesis gas react with hydrogen, the unsaturated hydrocarbon is converted into saturated hydrocarbon, and the organic sulfur is converted into H₂S, the dry desulfurization step, namely, desulfurization is carried out by utilizing a fine desulfurization catalyst containing ZnO, and H in the synthesis gas is removed₂S is removed to a content lower than<0.1ppm, thereby obtaining a desulfurized syngas.

2. The dry desulfurization process according to claim 1, wherein, in the hydrogenation step, the synthesis gas flows through an iron-molybdenum catalyst, or through a nickel-molybdenum catalyst, and also through a resistance wire, so that the H contained in the synthesis gas is introduced under energization₂S is ionized to elemental sulfur.

3. The dry desulfurization process of claim 2, wherein the resistance wire comprises chromium and nickel.

4. The dry desulfurization process according to claim 1, wherein, in the hydrogenation step, the synthesis gas flows through an iron-molybdenum catalyst or through a nickel-molybdenum catalyst and also through an electrode, on which a direct voltage higher than 10KV is applied, so that H contained in the synthesis gas is generated₂S is ionized to elemental sulfur.

5. The dry desulfurization process according to claim 1, wherein the synthesis gas is preheated to 35-60 ℃ before entering the fine desulfurization process of the synthesis gas, compressed under a pressure of 1.5-3MPa, and then passed through an oil filtering device to remove oily condensable substances in the synthesis gas.

6. The dry desulfurization process of claim 5, wherein there are at least two oil filtration devices, and the oil filtration devices can be in parallel and in series.

7. The dry desulfurization process of claim 6, wherein the synthesis gas is heated to 250-300 ℃ by passing through a first inter-stage temperature regulator, a steam heater, a product heat exchanger and a second inter-stage temperature regulator in this order before entering the fine desulfurization process of the synthesis gas.

8. The dry desulfurization process according to claim 1, wherein the hydrogenation step comprises passing the synthesis gas through a pre-hydroconversion interstage attemperator and a hydroconversion unit in this order, the temperature of the synthesis gas is raised to 300 ℃ to 400 ℃, and organic sulfur in the synthesis gas is converted into inorganic sulfur under the action of the iron-molybdenum catalyst or the nickel-molybdenum catalyst.

9. The dry desulfurization process of claim 8, wherein the hydrogenation step further comprises a temperature reduction step, wherein the temperature of the syngas in the hydroconversion vessel is higher than 420 ℃, and a quench control valve is opened to reduce the temperature of the syngas to 300 ℃ to 400 ℃.

10. The dry desulfurization process of claim 8, wherein the hydrogenation step further comprises an emergency shutdown step, wherein the hydrogenation step is stopped when the temperature of the syngas in the hydroconversion vessel is above 500 ℃.

Technical Field

The invention relates to the technical field of clean utilization of coal substances, in particular to a dry desulfurization process for synthesis 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.

The methane synthesis reaction mainly involved in the production of synthetic natural gas by using coke oven gas or coal-derived synthetic gas is a strong exothermic reaction, 1% of CO in raw material gas reacts, and the temperature rise of the gas can reach 72 ℃; 1% CO2 reacts, and the gas temperature rises to 60 ℃. Therefore, the contents of CO and CO2 in the raw material gas must be strictly controlled within the specified process index range so as to avoid sintering and deactivation of the catalyst. In addition, the methane synthesis catalyst has good activity and high selectivity, is sensitive to poison and easy to be poisoned and inactivated, wherein the poisoning of sulfide is the most serious.

Usually most of H in coke oven gas or coal-made synthesis gas₂S is removed in the wet desulfurization process, while organic sulfur in the form of carbonyl sulfide, mercaptans, sulfides, thiophenes, etc. needs to be removed after conversion to inorganic sulfur.

The process for removing organic sulfur is generally: hydrogenolysis of organic sulfur to inorganic sulfur H by hydroconversion₂S, desulfurizing with adsorbent such as zinc oxide, activated carbon, iron oxide, molecular sieve, etc. The hydrogenolysis reaction of organic sulfur is exemplified as follows:

COS+H₂→CO+H₂S

C₂H₅SH+H₂→C₂H₆+H₂S

CH₃SC₂H₅+2H₂→CH₄+C₂H₆+H₂S

C₄H₄S+4H₂→C₄H₁₀+H₂S

the prior methods can remove the sulfur content to a lower degree, but have the defects of complex process, high equipment investment, long driving investment time and poor environmental protection.

Patent CN1272398A discloses a method and a catalyst for hydrodesulfurization of hydrocarbon-containing gas and application thereof. The relevant catalyst takes TiO2 as a carrier and comprises a catalyst A containing nickel and molybdenum active components and a catalyst B containing cobalt and molybdenum active components. The method opens up a new way for the production process of hydrogen production and synthetic ammonia by taking refinery gas as raw material. However, the patented methodThe specific surface area of the catalyst is less than 200m²The catalyst has poor universality and is not suitable for being used as a catalyst for the hydroconversion and desulfurization of coke oven gas or coal-made synthesis gas.

Patent CN101199935A discloses a hydrodesulfurization catalyst with titanium-aluminum composite oxide carrier and a preparation method thereof. The obtained catalyst is mainly used for removing sulfur in diesel oil, does not relate to pre-methanation and deep desulfurization of coke-oven gas or coal-to-synthesis gas for preparing methane, is prepared by a sol-gel method, and has complex process and high cost.

Aiming at the defects of the prior art, the invention develops a process combining a composite catalyst and equipment, simplifies the desulfurization process, reduces the investment, saves the start-up time, prolongs the service life of the subsequent methanation catalyst and reduces the production load.

Disclosure of Invention

In view of the above, the present invention provides a dry desulfurization process for syngas, which comprises preparing low-rank coal containing CO and H under oxygen-free or micro-aerobic conditions₂The synthetic gas is subjected to a synthetic gas purification process and a synthetic gas fine desulfurization process to remove sulfur in the synthetic gas.

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

a dry desulfurization process for synthesis gas comprises a synthesis gas purification process and a synthesis gas fine desulfurization process, wherein the synthesis gas purification process comprises an oil-removing and naphthalene-removing working section and a crude desulfurization working section, the oil-removing and naphthalene-removing working section comprises a step of absorbing oily condensable substances including naphthalene and tar in the synthesis gas by using an oil absorbent so as to reduce the content of tar and naphthalene in the removed synthesis gas to below 1mg/Nm3, the crude desulfurization working section adopts a pre-desulfurization catalyst to absorb and remove inorganic sulfur in the synthesis gas, the synthesis gas fine desulfurization process comprises a hydrogenation step and a dry desulfurization step, the hydrogenation step comprises primary hydrogenation and secondary hydrogenation, and the primary hydrogenation is to carry out the hydrogenation on unsaturated hydrocarbons and organic sulfur compounds contained in the synthesis gas and hydrogen under the action of an iron-molybdenum catalystA reaction takes place, the unsaturated hydrocarbon is converted into a saturated hydrocarbon, the organic sulfur is converted into H₂S, the synthesis gas flows through the iron-molybdenum catalyst after the secondary hydrogenation, and then flows through the nickel-molybdenum catalyst, so that unsaturated hydrocarbon and organic sulfur compounds contained in the synthesis gas react with hydrogen, the unsaturated hydrocarbon is converted into saturated hydrocarbon, and the organic sulfur is converted into H₂S, the dry desulfurization step, namely, desulfurization is carried out by utilizing a fine desulfurization catalyst containing ZnO, and H in the synthesis gas is removed₂S is removed to a content lower than<0.1ppm, thereby obtaining a desulfurized syngas.

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 low-rank coal dried by the drying process enters the gasification reduction process for reaction, and for one-step optimization process, 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 can be 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 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 rich gas are obtained, wherein the solid carbon is upgraded coal, and the volatile matter in the upgraded coal is 8-15 wt%. The high-temperature rich gas comprises CO and H₂、CO₂Hydrocarbon, coal tar, naphthalene, halide, dust, sulfur compounds, and the like.

The sulfur compounds are liable to cause poisoning and deactivation of the reforming conversion catalyst and the methane synthesis catalyst, so that the sulfur compounds in the purified rich gas need to be removed before the reforming conversion process. The purified rich gas enters a coarse desulfurization process for treatment, and H in the purified rich gas is removed₂S removal to 20mg/Nm³The following. Coarse desulfurizationThe process adopts wet coarse desulfurization, the wet flue gas desulfurization technology is a gas-liquid reaction, the reaction speed is high, the desulfurization efficiency is high and generally higher than 90%, the technology is mature, and the application range is wide. The wet desulphurization technology is mature, the production operation is safe and reliable, and the wet desulphurization technology always occupies the dominant position in a plurality of desulphurization technologies, and accounts for more than 80 percent of the total installed capacity of desulphurization. Therefore, the wet desulphurization firstly removes a large amount of H in the rich gas₂And (4) removing the S.

By adopting a wet-process crude desulfurization process, common equipment cannot be operated under certain pressure, so that the air flow which is not compressed and flows is large, and the occupied area of the equipment and the whole set of equipment are large. And the total sulfur content of the gas after the crude desulfurization can not meet the requirements of the subsequent reforming conversion catalyst and the methane synthesis catalyst on the sulfur content. Therefore, the gas treated by the coarse desulfurization process is treated by a first compression process to improve the gas pressure, and then enters a fine desulfurization process, wherein the pressure of the first compression process is 20-25kg, and the temperature is 300-400 ℃. The fine desulfurization process is generally dry desulfurization, can be operated under certain pressure, increases the effective components of sulfur in unit volume of treatment, greatly improves the removal rate of sulfur content, greatly reduces a fine desulfurization device, and improves the utilization rate of equipment.

And (4) treating the gas compressed by the first compression process in a fine desulfurization process to obtain the reforming conversion feed gas. The fine desulfurization process is dry desulfurization, and a solid desulfurizing agent is adopted to remove sulfide. The coarse desulfurization process removes most of the sulfide, and the remaining small amount of sulfide is reduced to 1mg/Nm through the desulfurizing agent³The method not only reduces the consumption of the desulfurizer in the fine desulfurization process, but also ensures that the fine desulfurization process and the coarse desulfurization process are matched to be a reliable means for high-precision desulfurization, reduces the total sulfur content in the purified rich gas as much as possible, and meets the requirements of the subsequent reforming conversion catalyst and the methane synthesis catalyst on the sulfur content.

Dry desulfurization is classified into three types according to its properties and desulfurization mechanism: hydrogenation type conversion catalyst, such as iron-molybdenum, nickel-molybdenum, etc., absorption type conversion absorbent, such as ZnO, ferric oxide, manganese oxide, etc., adsorption type, such as activated carbon, molecular sieve, etc. For exampleIn the invention, iron and molybdenum are adopted to catalyze and hydro-convert organic sulfur (COS and the like) and ZnO desulfurizer is used to absorb generated H₂S, the total sulfur in the purified rich gas is reduced to be below 0.1ppm, so that the catalyst poisoning in the subsequent process caused by the sulfide is prevented, and the requirements of the catalyst of the subsequent reforming conversion process and the catalyst of the methane synthesis process on the sulfur content are met. For example, at the temperature of 300-400 ℃, the organic sulfur in the purified rich gas is subjected to catalytic hydro-conversion by adopting iron and molybdenum, and the generated H is absorbed by a ZnO desulfurizer₂S, the total sulfur in the purified rich gas is reduced to be below 0.1ppm, and the requirements of the reforming conversion catalyst and the methane synthesis catalyst on the sulfur content are met.

The substances which cause poisoning and deactivation of the methane synthesis catalyst include chlorides, metal carbonyls and the like. In the fine desulfurization process, dechlorinating agent and cleaning agent for removing carbonyl metal compound can be added simultaneously to remove these harmful substances. Chlorine-containing compounds are liable to react with metal ions and to permanently poison the metal ions, and dry dechlorination is generally carried out using dechlorinating agents whose main components are basic oxides such as CaO, ZnO and Na₂O, etc., the content of chlorine in the purified rich gas obtained after purification is less than 0.1 x10^-6. The metal carbonyl compound in the methane synthesis gas needs to be removed to O.1x10^-6The metal carbonyl compound is mainly Fe (CO)₅、Ni(CO)₄In the form, a purifying agent for removing carbonyl metal is added in the fine desulfurization process to achieve the purpose of reducing carbonyl iron and carbonyl nickel in the purified rich gas.

Preferably, in the hydrogenation step, the synthesis gas flows through an iron-molybdenum catalyst and then flows through a nickel-molybdenum catalyst, so that unsaturated hydrocarbons and organic sulfur compounds contained in the synthesis gas are reacted with hydrogen, the unsaturated hydrocarbons are converted into saturated hydrocarbons, and the organic sulfur is converted into H₂S。

Further, in the hydrogenation step, the synthesis gas flows through an iron-molybdenum catalyst or a nickel-molybdenum catalyst and also flows through a resistance wire, so that H contained in the synthesis gas is introduced under the condition of electrification₂S is ionized to elemental sulfur.

Further, the resistance wire comprises chromium and nickel.

Further, in the hydrogenation step, the synthesis gas flows through an iron-molybdenum catalyst or a nickel-molybdenum catalyst and also flows through an electrode, and a direct current voltage higher than 10KV is applied to the electrode, so that H contained in the synthesis gas₂S is ionized to elemental sulfur.

Preferably, before entering the fine desulfurization process of the synthesis gas, the synthesis gas is preheated to 35-60 ℃, compressed under the pressure of 1.5-3MPa, and then flows through an oil filtering device to remove oily condensable substances in the synthesis gas.

Preferably, the number of the oil filtering devices is at least two, and the oil filtering devices can be connected in parallel.

Further, before the synthetic gas enters the fine desulfurization process of the synthetic gas, the synthetic gas sequentially flows through a first section temperature regulator, a steam heater, a product heat exchanger and a second section temperature regulator and is heated to 250-300 ℃.

Further, the hydrogenation step comprises the step that the synthesis gas sequentially flows through a pre-hydrogenation converter inter-segment temperature regulator and a hydrogenation converter, the temperature of the synthesis gas is increased to 300-400 ℃, and organic sulfur in the synthesis gas is converted into inorganic sulfur under the action of the iron-molybdenum catalyst or the nickel-molybdenum catalyst.

Preferably, the hydrogenation step further comprises a cooling step, wherein the temperature of the synthesis gas in the hydrogenation converter is higher than 420 ℃, a chilling regulating valve is opened, and the synthesis gas is cooled to 300-400 ℃.

Further, the hydrogenation step further comprises an emergency shutdown step, wherein the hydrogenation step is stopped when the temperature of the synthesis gas in the hydroconversion unit is higher than 500 ℃.

Further, the hydrogenation step also comprises a medium-temperature desulfurization step, wherein the synthesis gas flows out of the hydrogenation converter and flows into a medium-temperature desulfurization tank, so that the inorganic sulfur in the synthesis gas is absorbed and removed.

Preferably, the hydrogenation step further comprises flowing the synthesis gas out of the hydroconversion section and into a zinc oxide desulfurization tank to remove H from the synthesis gas₂S。

Based on the technical scheme, the dry desulfurization process prepares the dried low-rank coal into the synthesis gas mainly containing CO and H2 under the condition of no oxygen or micro oxygen, and removes the sulfur in the synthesis gas to the content of less than 0.1ppm in a dry desulfurization mode, so that the smooth proceeding of a subsequent coal processing process is ensured, and precious volatile components and coal quality in the low-rank coal are fully utilized by people; 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.

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.

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. The terms "first," "second," and the like in the present disclosure are used for distinguishing between descriptions and not to imply or imply relative importance.

Preparation example

A dry desulfurization process of synthesis gas is characterized by comprising a synthesis gas purification process and a synthesis gas fine desulfurization process, wherein the synthesis gas purification process comprises an oil-removing and naphthalene-removing working section and a crude desulfurization working section, the oil-removing and naphthalene-removing working section comprises the step of absorbing oily condensable substances comprising naphthalene and tar in the synthesis gas by using an oil absorbent to ensure that the tar and the naphthalene content in the removed synthesis gas are reduced to below 1mg/Nm3, the crude desulfurization working section adopts a pre-desulfurization catalyst to absorb and remove inorganic sulfur in the synthesis gas, the synthesis gas fine desulfurization process comprises a hydrogenation step and a dry desulfurization step,the hydrogenation step comprises primary hydrogenation and secondary hydrogenation, wherein the primary hydrogenation is to react unsaturated hydrocarbon and organic sulfur compound contained in the synthesis gas with hydrogen under the action of an iron-molybdenum catalyst, the unsaturated hydrocarbon is converted into saturated hydrocarbon, and the organic sulfur is converted into H₂S, the synthesis gas flows through the iron-molybdenum catalyst after the secondary hydrogenation, and then flows through the nickel-molybdenum catalyst, so that unsaturated hydrocarbon and organic sulfur compounds contained in the synthesis gas react with hydrogen, the unsaturated hydrocarbon is converted into saturated hydrocarbon, and the organic sulfur is converted into H₂S, the dry desulfurization step, namely, desulfurization is carried out by utilizing a fine desulfurization catalyst containing ZnO, and H in the synthesis gas is removed₂S is removed to a content lower than<0.1ppm, thereby obtaining a desulfurized syngas.

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.

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. Conveying the dried low-rank coal to a gasification reduction process, under the heating of heating media such as flue gas and the like, adding other substances such as additives and the like in the reaction process, generally performing a complex chemical reaction process at the temperature of 350-800 ℃ and the pressure of less than or equal to 30Kpa to obtain solid carbon and high temperatureWherein the solid carbon is the 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.

The sulfur compounds are liable to cause poisoning and deactivation of the reforming conversion catalyst and the methane synthesis catalyst, so that the sulfur compounds in the purified rich gas need to be removed before the reforming conversion process. The purified rich gas enters a coarse desulfurization process for treatment, and H in the purified rich gas is removed₂S removal to 20mg/Nm³The following. The coarse desulfurization process adopts wet coarse desulfurization, the wet flue gas desulfurization technology is a gas-liquid reaction, the reaction speed is high, the desulfurization efficiency is high and generally higher than 90%, the technology is mature, and the application range is wide. The wet desulphurization technology is mature, the production operation is safe and reliable, and the wet desulphurization technology always occupies the dominant position in a plurality of desulphurization technologies, and accounts for more than 80 percent of the total installed capacity of desulphurization. Therefore, the wet desulphurization firstly removes a large amount of H in the rich gas₂And (4) removing the S.

By adopting a wet-process crude desulfurization process, common equipment cannot be operated under certain pressure, so that the air flow which is not compressed and flows is large, and the occupied area of the equipment and the whole set of equipment are large. And the total sulfur content of the gas after the crude desulfurization can not meet the requirements of the subsequent reforming conversion catalyst and the methane synthesis catalyst on the sulfur content. Therefore, the gas treated by the coarse desulfurization process is treated by a first compression process to improve the gas pressure, and then enters a fine desulfurization process, wherein the pressure of the first compression process is 20-25kg, and the temperature is 300-400 ℃. The fine desulfurization process is generally dry desulfurization, can be operated under certain pressure, increases the effective components of sulfur in unit volume of treatment, greatly improves the removal rate of sulfur content, greatly reduces a fine desulfurization device, and improves the utilization rate of equipment.

And (4) treating the gas compressed by the first compression process in a fine desulfurization process to obtain the reforming conversion feed gas. The fine desulfurization process is dry desulfurization, and a solid desulfurizing agent is adopted to remove sulfide. The coarse desulfurization process removes most of sulfide and little remainsThe amount of sulfide passing through the desulfurizing agent is reduced to 1mg/Nm³The method not only reduces the consumption of the desulfurizer in the fine desulfurization process, but also ensures that the fine desulfurization process and the coarse desulfurization process are matched to be a reliable means for high-precision desulfurization, reduces the total sulfur content in the purified rich gas as much as possible, and meets the requirements of the subsequent reforming conversion catalyst and the methane synthesis catalyst on the sulfur content.

Dry desulfurization is classified into three types according to its properties and desulfurization mechanism: hydrogenation type conversion catalyst, such as iron-molybdenum, nickel-molybdenum, etc., absorption type conversion absorbent, such as ZnO, ferric oxide, manganese oxide, etc., adsorption type, such as activated carbon, molecular sieve, etc. For example, in the present invention, organic sulfur (COS, etc.) is catalytically hydroconverted using iron and molybdenum, and the generated H is absorbed by ZnO desulfurizer₂S, the total sulfur in the purified rich gas is reduced to be below 0.1ppm, so that the catalyst poisoning in the subsequent process caused by the sulfide is prevented, and the requirements of the catalyst of the subsequent reforming conversion process and the catalyst of the methane synthesis process on the sulfur content are met. For example, at the temperature of 300-400 ℃, the organic sulfur in the purified rich gas is subjected to catalytic hydro-conversion by adopting iron and molybdenum, and the generated H is absorbed by a ZnO desulfurizer₂S, the total sulfur in the purified rich gas is reduced to be below 0.1ppm, and the requirements of the reforming conversion catalyst and the methane synthesis catalyst on the sulfur content are met. Preferably, in the hydrogenation step, the synthesis gas flows through an iron-molybdenum catalyst and then flows through a nickel-molybdenum catalyst, so that unsaturated hydrocarbons and organic sulfur compounds contained in the synthesis gas are reacted with hydrogen, the unsaturated hydrocarbons are converted into saturated hydrocarbons, and the organic sulfur is converted into H₂And S. Further, in the hydrogenation step, the synthesis gas flows through an iron-molybdenum catalyst or a nickel-molybdenum catalyst and also flows through a resistance wire, so that H contained in the synthesis gas is introduced under the condition of electrification₂S is ionized to elemental sulfur. Further, the resistance wire comprises chromium and nickel. Further, in the hydrogenation step, the synthesis gas flows through an iron-molybdenum catalyst or a nickel-molybdenum catalyst and also flows through an electrode, and a direct current voltage higher than 10KV is applied to the electrode, so that H contained in the synthesis gas₂S is ionized to elemental sulfur.

Lead to the firstThe substances deactivated by the catalyst for synthesizing alkane include chloride, carbonyl metal compound, etc. In the fine desulfurization process, dechlorinating agent and cleaning agent for removing carbonyl metal compound can be added simultaneously to remove these harmful substances. Chlorine-containing compounds are liable to react with metal ions and to permanently poison the metal ions, and dry dechlorination is generally carried out using dechlorinating agents whose main components are basic oxides such as CaO, ZnO and Na₂O, etc., the content of chlorine in the purified rich gas obtained after purification is less than 0.1 x10^-6. The metal carbonyl compound in the methane synthesis gas needs to be removed to O.1x10^-6The metal carbonyl compound is mainly Fe (CO)₅、Ni(CO)₄In the form, a purifying agent for removing carbonyl metal is added in the fine desulfurization process to achieve the purpose of reducing carbonyl iron and carbonyl nickel in the purified rich gas.

Preferably, before entering the fine desulfurization process of the synthesis gas, the synthesis gas is preheated to 35-60 ℃, compressed under the pressure of 1.5-3MPa, and then flows through an oil filtering device to remove oily condensable substances in the synthesis gas.

Preferably, the number of the oil filtering devices is at least two, and the oil filtering devices can be connected in parallel.

Further, before the synthetic gas enters the fine desulfurization process of the synthetic gas, the synthetic gas sequentially flows through a first section temperature regulator, a steam heater, a product heat exchanger and a second section temperature regulator and is heated to 250-300 ℃.

Further, the hydrogenation step comprises the step that the synthesis gas sequentially flows through a pre-hydrogenation converter inter-segment temperature regulator and a hydrogenation converter, the temperature of the synthesis gas is increased to 300-400 ℃, and organic sulfur in the synthesis gas is converted into inorganic sulfur under the action of the iron-molybdenum catalyst or the nickel-molybdenum catalyst.

Preferably, the hydrogenation step further comprises a cooling step, wherein the temperature of the synthesis gas in the hydrogenation converter is higher than 420 ℃, a chilling regulating valve is opened, and the synthesis gas is cooled to 300-400 ℃.

Further, the hydrogenation step further comprises an emergency shutdown step, wherein the hydrogenation step is stopped when the temperature of the synthesis gas in the hydroconversion unit is higher than 500 ℃.

Further, the hydrogenation step also comprises a medium-temperature desulfurization step, wherein the synthesis gas flows out of the hydrogenation converter and flows into a medium-temperature desulfurization tank, so that the inorganic sulfur in the synthesis gas is absorbed and removed.

Preferably, the hydrogenation step further comprises flowing the synthesis gas out of the hydroconversion section and into a zinc oxide desulfurization tank to remove H from the synthesis gas₂S。

The components of the obtained desulfurized syngas and the energy consumption per kilogram of desulfurized syngas are analyzed by comparative experiments, thereby analyzing the technical progress of the dry desulfurization process of the present invention.

Experimental example 1

A dry desulfurization process of synthesis gas, which comprises a purification process of the synthesis gas and a fine desulfurization process of the synthesis gas, the synthetic gas purification process comprises an oil-removing and naphthalene-removing working section and a crude desulfurization working section, wherein the oil-removing and naphthalene-removing working section comprises the steps of absorbing oily condensable substances comprising naphthalene and tar in the synthetic gas by adopting an oil absorbent, so that the tar and naphthalene content in the removed synthesis gas is reduced to below 1mg/Nm3, the coarse desulfurization section adopts a pre-desulfurization catalyst to adsorb and remove inorganic sulfur in the synthesis gas, the fine desulfurization process of the synthesis gas comprises a hydrogenation step and a dry desulfurization step, the hydrogenation step comprises primary hydrogenation and secondary hydrogenation, wherein the primary hydrogenation is to carry out the hydrogenation on unsaturated hydrocarbon and organic sulfur compound contained in the synthesis gas under the action of an iron-molybdenum catalyst, reacting with hydrogen, converting the unsaturated hydrocarbon into saturated hydrocarbon, and converting the organic sulfur into H.₂S, the synthesis gas flows through the iron-molybdenum catalyst after the secondary hydrogenation, and then flows through the nickel-molybdenum catalyst, so that unsaturated hydrocarbon and organic sulfur compounds contained in the synthesis gas react with hydrogen, the unsaturated hydrocarbon is converted into saturated hydrocarbon, and the organic sulfur is converted into H₂S, the dry desulfurization step, namely, desulfurization is carried out by utilizing a fine desulfurization catalyst containing ZnO, and H in the synthesis gas is removed₂S is removed to a content lower than<0.1ppm, thereby obtaining a desulfurized syngas.

In Experimental example 1, a rich gas from a compression sectionThe temperature is 20-50 ℃, the pressure is 1.5-5.0MPa, the pyrolysis gas firstly enters two oil filtering tanks which can be connected in parallel and in series to remove oil in the pyrolysis gas, the pyrolysis gas at the outlet of the oil filtering tank is heated to 150-fold-by-400 ℃ through a first section temperature regulator, a steam heater, a product heat exchanger and a second section temperature regulator in sequence, the pyrolysis gas sequentially enters a first pre-hydrogenation converter section temperature regulator and a first-stage hydrogenation converter, under the action of an iron-molybdenum catalyst, unsaturated hydrocarbon, organic sulfur compounds (COS, thioether, mercaptan and the like), oxygen and the like in the pyrolysis gas react with hydrogen, the unsaturated hydrocarbon in the pyrolysis gas is converted into saturated hydrocarbon, and the organic sulfur is converted into H which is easy to remove₂S, the temperature is increased to 200-500 ℃, when the temperature exceeds the set value of the bed temperature of the first-stage hydrogenation converter, the cold shock regulating valve is opened to reduce the temperature, and the production is reduced or stopped when necessary.

The gas from the first-stage hydrogenation converter enters two series-parallel medium-temperature desulfurization tanks after being subjected to heat exchange by the inter-stage temperature regulator II, and the inorganic sulfur is absorbed at the temperature of about 300-400 ℃.

The pyrolysis gas from the medium-temperature desulfurization tank still cannot meet the requirement of a liquefaction working section on sulfur content, and needs further hydrogenation and fine desulfurization treatment. The pyrolysis gas enters a secondary hydrogenation converter, is further subjected to hydrogenation conversion under the action of a nickel-molybdenum catalyst and is almost completely converted into inorganic sulfur at the temperature of about 300-400 ℃.

The pyrolysis gas at the outlet of the second-stage hydrogenation converter passes through two zinc oxide desulfurization tanks connected in series and in parallel to carry out H₂S absorption; finally, the desulfurized synthetic gas which is finally discharged from the zinc oxide desulfurization tank is subjected to heat exchange by a product heat exchanger and a product cooler, the temperature is 20-50 ℃, the pressure is about 1.5-5.0MPa, and the purified desulfurized synthetic gas is conveyed to the next working section.

In experimental example 1, a rich gas obtained by using low-rank coal according to quality was used as a raw material gas, and the component of the rich gas included 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 300-800ppm, and the oil condensable matter comprising naphthalene and tar is 2000-6000ppm, and the dust is 2000-6000 ppm. After wet desulfurization in the previous section, the gas flows into rich gas in the dry desulfurization section, H₂The S content is between 20 and 200 ppm.

The energy consumption from the low rank coal to the desulfurized syngas stage is recorded and calculated.

Experimental example 2

Experimental example 2 referring to experimental example 1, except that, in the hydrogenation step of experimental example 2, the synthesis gas was passed through an iron-molybdenum catalyst, or through a nickel-molybdenum catalyst, and also through a resistance wire, so that H contained in the synthesis gas was supplied with electricity₂S is ionized to elemental sulfur.

Experimental example 3

Experimental example 3 referring to experimental example 1, except that, in the hydrogenation step of experimental example 3, the synthesis gas was passed through an iron-molybdenum catalyst or through a nickel-molybdenum catalyst and also through an electrode to which a direct current voltage of more than 10KV was applied, so that H contained in the synthesis gas was H₂S is ionized to elemental sulfur.

Comparative example 1

The desulfurization method for preparing natural gas from rich gas by using 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 obtain semi-coke, coal tar and rich gas as byproducts, wherein the component of the rich gas comprises CH₄28-40 percent of content, 10-15 percent of CO, 25-40 percent of H2, 5-10 percent of CO2, 2-8 percent of C2H6, 1-4 percent of C2H4, 0.5-3 percent of C3H6, 0.4-2.5 percent of C3H8, 0.2-2 percent of C4H8, 2000-6000ppm of H2S and NH₃The content is 300-800 ppm;

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

(3) all unsaturated hydrocarbons in the coal gas are converted into corresponding saturated hydrocarbons by the hydrogenation unit 3While converting organic sulfur into H₂S, obtaining hydrogenated rich gas; the hydrogenation unit is used for reacting unsaturated hydrocarbon and organic sulfur compound contained in the synthesis gas with hydrogen under the action of an iron-molybdenum catalyst, wherein the unsaturated hydrocarbon is converted into saturated hydrocarbon, and the organic sulfur is converted into H₂S；

(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, desulfurized syngas was obtained.

TABLE 1 compositional analysis tables of desulfurized syngas produced in test examples 1-3 and comparative example 1^*1

Composition of	Experimental example 1	Experimental example 2	Experimental example 3	Comparative example 1
					CH4	29.88	26.72	29.43	26.38
H2	30.62	34.77	31.12	26.42
					CO	14.85	18.64	15.26	14.60
CO2	14.21	10.21	13.94	16.96
					N2	1.08	1.10	1.06	1.52
H2O	1.94	1.93	1.96	6.72
					Others	7.41	6.62	7.22	7.40
Sulfur content	0.09ppm	0.04ppm	0.01ppm	139.4ppm

Note: 1. the content is volume percentage content;

2. others include other alkanes and ammonia.

TABLE 2 energy consumption analysis tables for desulfurized Synthesis gases of test examples 1 to 3 and comparative example 1

Composition of	Experimental example 1	Experimental example 2	Experimental example 3	Comparative example 1
					Energy consumption/kJ	1058	1152	1007	1086

Note: the energy consumption analysis is stopped by that the temperature of the desulfurized synthetic gas is 20-50 ℃ and the pressure is about 1.5-5.0MPa after the desulfurized synthetic gas is subjected to heat exchange through a product heat exchanger and a product cooler, and the purified desulfurized synthetic gas is conveyed to the front of the next working section.

From the results of tables 1 and 2, analyzing the components of the produced desulfurized syngas, we can obtain that, firstly, the sulfur content in the desulfurized syngas and the energy consumption can be effectively reduced due to the syngas purification process and the hydrogenation process of the present invention, the sulfur content is reduced from 139.4ppm of comparative example 1 to 0.09ppm of experimental example 1, and the energy consumption is reduced from 1086kJ of comparative example 1 to 1058kJ of experimental example 1; secondly, the hydrogenation step comprises the use of resistance wires, so that the sulfur content in the pre-desulfurized gas can be obviously reduced from 0.09ppm of experimental example 1 to 0.04ppm of experimental example 2, but the energy consumption is slightly increased from 1058kJ of experimental example 1 to 1152kJ of experimental example 2; thirdly, the sulfur content in the gas after pre-desulfurization can be obviously reduced by arranging an electrode in the hydrogenation step, the sulfur content is reduced from 0.09ppm of experimental example 1 to 0.01ppm of experimental example 3, the energy consumption is obviously saved due to the fact that the basic energy consumption of the electrode is low, and the energy consumption is reduced from 1058kJ of experimental example 1 to 1007kJ of experimental example 3.

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 and coal quality 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.