CN104230621B - A kind of method being produced methane coproduction low-carbon alcohols by carbonaceous material - Google Patents

Abstract

A kind of method being produced methane coproduction low-carbon alcohols by carbonaceous material, the method includes: the crude synthesis gas obtained after being gasified by carbonaceous material carries out purifying to remove the impurity in described crude synthesis gas, obtains clean synthesis gas；At least part of described clean synthesis gas is contacted with mixed catalyst with water, and the product obtained after contact is carried out gas-liquid separation, obtaining gaseous product and product liquid, described mixed catalyst contains water gas shift catalyst and converts synthesis gas to the catalyst of low-carbon alcohols；Being contacted with methanation catalyst by methanation gas raw material, described methanation gas raw material contains described gaseous product, the H in described methanation gas raw material₂The mol ratio of/CO is 2.8 3.5.Methane co-production low-carbon alcohols can be produced according to the method for the present invention, and the load of the hydrosphere transformation during effectively reducing, has saved energy consumption, improve the utilization ratio of carbon, and directly carry out on the methanogenic device of life of prior art, and without increasing equipment.

Description

Method for producing methane and co-producing low-carbon alcohol from carbonaceous material

Technical Field

The invention relates to a method for indirectly converting a carbonaceous material, in particular to a method for gasifying the carbonaceous material into synthesis gas, converting the synthesis gas into methane gas and co-producing low-carbon alcohol.

Background

Based on the consideration of energy source endowments and national energy safety, China is actively advancing the strategy of 'coal to petroleum' to convert coal into civil gas, transportation fuels, basic chemical raw materials and the like. The technology for preparing the natural gas from the coal is a process of preparing synthesis gas by gasifying low-order lignite, and then converting the synthesis gas into methane to be used as a gas fuel for replacing the traditional natural gas.

The process of preparing natural gas from coal has high energy efficiency, low water consumption and relatively mature technology, and has important significance for developing coal in remote areas in the western China, improving the living standard of people and reducing the emission of polluted gas.

The technical economy of the coal-to-natural gas process is an important factor affecting the development of the technology. The process for preparing methane from American large plain coal comprises using brown coal as raw material, adding product transportation and city management fees when the heat value of the brown coal is 4000kcal/kg and the coal price is 150 yuan/t, and the cost price of methane is 2.50 yuan/Nm³At present, the cost of methane is reduced mainly by selling byproducts such as ammonia, sulfur, naphtha, tar, phenols and the like in the American plain project, but the trouble of economic factors on enterprise operation cannot be eliminated fundamentally.

In addition, the gas consumption of urban gas in China is quite unbalanced, the gas consumption in northern areas is large in winter, the gas consumption in non-heating seasons is small, and the problem of peak regulation is quite serious. At present, the peak regulation means such as underground gas storage, fuel gas peak regulation power generation or LNG (liquefied natural gas) and the like are mainly adopted, and in addition, a coal-based natural gas plant can also be used for peak regulation, namely the coal-based natural gas plant can produce natural gas in winter, and can co-produce a part of liquid fuel, chemicals and the like in other seasons.

In order to solve the peak regulation problem, a series of catalysts for preparing methane and co-producing low-carbon alcohol by converting synthesis gas, such as catalysts disclosed in CN102553600A, CN102553613A and the like, are proposed by the institute of chemical and physical research of the college of science and academy of china, and it is pointed out that when these catalysts are used for producing methane by synthesis gas, liquid fuel can be co-produced, and reaction products mainly comprising methane or reaction products mainly comprising low-carbon alcohol can be obtained by adjusting reaction conditions according to requirements. Although the catalyst with double functions effectively solves the problem of peak regulation, the synthesis gas is subjected to water-gas shift reaction to regulate H before undergoing methanation reaction₂The mol ratio of/CO is suitable for methanation reaction, thereby increasing energy consumption and having a large amount of CO₂And the use efficiency of carbon is reduced. In addition, synthesizing H required by the reaction of low carbon alcohol₂The mol ratio of/CO to H required for the methanation reaction₂the/CO molar ratio is different, so that the bifunctional catalyst cannot have its optimum H₂Operating at the/CO molar ratio operating conditions results in a less efficient catalyst.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provide a method for producing methane and co-producing low-carbon alcohol from a carbonaceous material, which has the advantages of low energy consumption, low carbon dioxide emission and convenient operation.

The inventor of the present invention has found through research and analysis that the H in the clean synthesis gas obtained by gasifying and purifying a carbon-rich material such as coal as a raw material₂The mol ratio of/CO is lower and is between 0.5 and 2.0. While the production of natural gas from clean syngas requires the H of clean syngas₂The molar ratio/CO is preferably between 3.0 and 3.1. Therefore, to adjust the H of the net syngas₂The mol ratio of/CO is suitable for preparing natural gas by methanation reaction, and the pure synthetic gas must be subjected to H by a water-gas shift process₂the/CO molar ratio is adjusted from H₂Conversion of clean syngas with a/CO molar ratio of 0.5-2.0 into H₂The work load of the water-gas shift process of the gas with the mol ratio of/CO of 3.0-3.1 is very large, the energy consumption is very high, and the economical efficiency is low.

The inventor of the invention researches and discovers that H in tail gas generated in the process of preparing low-carbon alcohol from synthesis gas₂The mol ratio of/CO is generally higher than that of raw material synthetic gas and is between 2.0 and 3.0, and the mixed catalyst obtained by mixing the water-gas shift catalyst and the catalyst for converting the synthetic gas into low-carbon alcohol can realize water-gas shift and can synthesize the low-carbon alcohol, namely the water-gas shift catalyst in the mixed catalyst can still keep the original water-gas shift function, and the catalyst for converting the synthetic gas into the low-carbon alcohol can still keep the original function of converting the synthetic gas into the low-carbon alcohol, so that the function of a single catalyst can not be obviously reduced. Thus, the inventors of the present invention have envisaged that the net synthesis gas produced by gasification and purification of carbonaceous material is first subjected to a methanation reactionThe clean synthesis gas is firstly contacted with the mixed catalyst obtained by mixing the water-gas shift catalyst and the catalyst for converting the synthesis gas into the lower alcohol, so that the synthesis gas H can be treated₂The mol ratio of the/CO is adjusted, a part of low-carbon alcohol can be produced, the product types are enriched, the advantage complementation of various coal-based products is realized, and the economic benefit and the integral risk resistance capability of a coal-based natural gas project are effectively improved. And the tail gas for synthesizing the low-carbon alcohol is compared with the H of the raw material synthesis gas₂The mol ratio of/CO is increased, thereby compared with the prior art that all the synthesis gas is directly subjected to water-gas shift and then is contacted with the bifunctional catalyst to produce methane and coproduce low-carbon alcohol, the H adjustment by the water-gas shift is realized at the same time₂The mol ratio of/CO and the CO-production of lower alcohol, thereby leading the methanation catalyst to be in proper H₂The catalytic reaction is carried out under the mol ratio of/CO, and the working efficiency is improved.

Based on the above findings, to achieve the aforementioned objects of the present invention, the present invention provides a method for producing methane and co-producing lower alcohols from carbonaceous material, wherein the method comprises: (1) purifying the crude synthesis gas obtained after gasifying the carbonaceous material to remove impurities in the crude synthesis gas to obtain a clean synthesis gas; (2) contacting at least part of the purified synthesis gas and water with a mixed catalyst, and carrying out gas-liquid separation on a product obtained after the contact to obtain a gas product and a liquid product, wherein the mixed catalyst contains a water-gas shift catalyst and a catalyst for converting the synthesis gas into low-carbon alcohol; (3) under the condition of methanation reaction, contacting a methanation gas raw material with a methanation catalyst, wherein the methanation gas raw material contains the gas product, and H in the methanation gas raw material₂The molar ratio of/CO is 2.8-3.5.

The method can produce methane and CO-produce low-carbon alcohol, effectively reduces the load of water-gas shift in the process, saves energy consumption, and reduces CO in the shift process₂The carbon utilization rate is improved. Because the energy-saving heating device can effectively save energy while co-producing low-carbon alcohol, the heating device is particularly suitable for being used in winter of China because of large heating gas consumption and non-heating seasonsCompared with the traditional hard peak regulation method for directly shutting down and reducing load when natural gas is used in a valley in non-heating seasons, the method of the invention can not generate the defects of large equipment damage, low equipment utilization rate, large operation fluctuation and the like.

More specifically, compared with the prior art, the beneficial effects of the invention are mainly reflected in the following aspects:

firstly, the method provided by the invention can realize the preparation of methane gas and low carbon alcohol (generally low carbon mixed alcohol) from carbon materials through synthesis gas in the same process flow, enrich the types of coal-made natural gas products, effectively avoid the market risk of single coal-made natural gas products, simultaneously realize the co-production of the two products by adjusting the process conditions according to the market demand conditions of the products, and enable the selectivity of the two products to be adjustable in a larger range without influencing the stable operation of a production device, and the low carbon mixed alcohol has a wide market both as high-performance fuel and as basic chemical raw materials, thereby improving the economic benefit of the process to a certain extent.

Secondly, the method provided by the invention can realize water-gas shift and low-carbon alcohol coproduction in one reactor, reduce the investment of equipment and simplify the operation, and the tail gas of the low-carbon alcohol coproduction is compared with the H of the raw material synthesis gas₂The ratio of the/CO is high, thereby reducing the workload of water-gas shift and acid gas removal processes, and being beneficial to reducing the energy consumption of the process flow and CO₂The carbon utilization rate is improved.

Thirdly, the method provided by the invention is used for co-producing the low-carbon mixed alcohol and the gaseous product (methane), and the low-carbon mixed alcohol is liquid at normal temperature and normal pressure, has high density, is easy to store, and is easy to separate from gas, so that the process method can be realized without adding excessive separation equipment, and the additional investment is small.

The method provided by the invention can be used for the technological process of preparing methane by gasifying various carbonaceous materials (including coal but not limited to coal), and can also be used for improving the utilization of synthetic tail gas by preparing low-carbon mixed alcohol from the carbonaceous materials with the market demand of natural gas through a device for preparing low-carbon mixed alcohol from synthetic gas.

Detailed Description

The invention provides a method for producing methane and co-producing low carbon alcohol by using carbonaceous materials, wherein the method comprises the following steps: (1) purifying the crude synthesis gas obtained after gasifying the carbonaceous material to remove impurities in the crude synthesis gas to obtain a clean synthesis gas; (2) contacting at least part of the purified synthesis gas and water with a mixed catalyst, and carrying out gas-liquid separation on a product obtained after the contact to obtain a gas product and a liquid product, wherein the mixed catalyst contains a water-gas shift catalyst and a catalyst for converting the synthesis gas into low-carbon alcohol; (3) under the condition of methanation reaction, contacting a methanation gas raw material with a methanation catalyst, wherein the methanation gas raw material contains the gas product, and H in the methanation gas raw material₂The molar ratio of/CO is 2.8-3.5.

According to the process of the invention, preference is given to methanation of H in the gas feed₂The mol ratio of/CO is 2.9-3.3.

In the present invention, H in the methanation gas raw material is preferable₂The total content of CO and CO is 50-99 vol%, and can be adjusted according to the requirement.

In the specific use process, the water-gas shift catalyst and the catalyst for converting the synthesis gas into the low-carbon alcohol are mixed and then are filled into the reactor to be used as the catalyst bed layer, or the water-gas shift catalyst and the catalyst for converting the synthesis gas into the low-carbon alcohol are not mixed, and the two catalysts are directly filled into the reactor to be used as the catalyst bed layer according to the proportion in a layering mode or in a staggered layering mode.

According to the method of the invention, the products after the contact in the step (2) mainly comprise CO and H₂、CO₂And hydrocarbons with carbon number less than 5, lower alcohol with carbon number of 1-6, unreacted synthesis gas, gaseous hydrocarbons with carbon number less than 5, liquid hydrocarbons with carbon number greater than 4, other organic oxygen-containing compounds, water, etc.

According to the method of the invention, the gas product in the step (2) mainly contains CO and H₂、CO₂And hydrocarbons with carbon number less than 5, wherein the liquid product mainly contains lower alcohol with carbon number of 1-6, hydrocarbons with carbon number greater than 4, other organic oxygen-containing compounds and water.

According to the technical scheme, the content of the water-gas shift catalyst and the catalyst for converting the synthesis gas into the low-carbon alcohol in the mixed catalyst can be selected from a wide range and can be adjusted according to requirements, for example, when the methane consumption is low, such as the south of China, or the time is not the typical summer season, for example, when the methane is produced according to the method of the invention, because the methane consumption is low, the content of the catalyst for converting the synthesis gas into the low-carbon alcohol can be increased, the content of the water-gas shift catalyst can be reduced, so that the low-carbon alcohol can be co-produced as much as possible, on one hand, the low-carbon alcohol can be co-produced as much as possible, and on the other hand, the H of the tail gas of the synthetic₂H/CO molar ratio compared to neat syngas₂The mol ratio of/CO is more suitable for methanation reaction, thereby effectively saving energy consumption. In general, the mixed catalyst may contain 60 to 90 wt% of a water gas shift catalyst and 10 to 40 wt% of a catalyst for converting synthesis gas into lower alcohols.

When methane is produced by the method of the present invention in a place where the amount of methane is large, such as north of China, or at a time such as a typical heating season, for example, in winter, the load of the reaction for synthesizing lower alcohols in step (2) can be reduced because the amount of methane is large, for example, the amount of a catalyst for converting synthesis gas into lower alcohols can be reduced and the amount of a water gas shift catalyst can be increased to produce as much methane as possible. In the above case, the mixed catalyst may generally contain 60 wt% or more of the water gas shift catalyst and 90 wt% or less, and in the above case, the mixed catalyst may generally contain 10 wt% or more of the water gas shift catalyst and 40 wt% or less of the catalyst for synthesizing lower alcohols.

Based on the above description, it is generally preferred that the weight ratio of water gas shift catalyst to synthesis gas to lower alcohols in the mixed catalyst is from 1 to 8:1, preferably from 2 to 6: 1. And then adjusted within the above range as needed.

As can be seen from the above description, the method of the present invention can effectively realize CO-production and can flexibly adjust according to the amount of methane used, and the energy consumption is effectively saved and CO is reduced in the process₂The carbon utilization rate is improved.

According to the process of the present invention, the amount of the net synthesis gas in step (2) may be adjusted as desired, for example, part of the net synthesis gas and water may be contacted with a mixed catalyst, while another part of the remaining net synthesis gas is used for other purposes or subjected to other treatments, and for the main purpose of the present invention, the whole net synthesis gas is contacted with a mixed catalyst in step (2), preferably, when the methanation gas feedstock in step (3) contains only the gas product.

According to the method of the present invention, in step (2), the conditions of the contacting are wide in the optional range, and the object of the present invention can be achieved by the conditions capable of achieving the aforementioned requirements, and for the present invention, it is preferable that the conditions of the contacting in step (2) include: the temperature is 150-^-1The molar ratio of water to carbon monoxide is 0.5-1.3: 1.

In the present invention, the molar ratio of water to carbon monoxide refers to the molar ratio of water to carbon monoxide in the net synthesis gas.

According to the method of the invention, the water gas shift catalyst can be selected conventionally in the field, for example, the water gas shift catalyst can be an Fe-Cr catalyst containing active component elements including Fe and Cr, wherein the content of the active component in the Fe-Cr catalyst is 60-95 wt% calculated by oxide, and the content of the auxiliary agent is 5-40 wt%; for another example, the catalyst can be a Cu-Zn catalyst containing active component elements of Cu and Zn, wherein the content of the active component in the Cu-Zn catalyst is 45-90 wt% and the content of the auxiliary agent in the Cu-Zn catalyst is 10-55 wt% in terms of oxide; for another example, the catalyst may be a Co-Mo catalyst containing Co and Mo as active component elements, wherein the content of the active component is 60 to 85 wt% and the content of the auxiliary agent is 15 to 40 wt% in terms of oxide in the Co-Mo catalyst. Wherein the adjuvant component may be conventional in the art and the present invention will not be described in detail herein.

In the present invention, the catalyst for converting synthesis gas into lower alcohol may be selected conventionally in the art, and for example, may be a Zn — Cr catalyst in which active component elements include Zn and Cr, the content of the active component is generally 65 to 95 wt% and the content of the auxiliary agent is generally 5 to 35 wt% in terms of oxide, and the auxiliary agent element may be one or more of K, Li, Mg, Mn, Zr, Ce, La, Fe, Co, Pt and Pd; also for example, the catalyst can be a Cu-Zn-Al catalyst containing active component elements of Cu, Zn and Al, wherein the content of the active component in the Cu-Zn-Al catalyst is generally 55 to 97 weight percent and the content of the auxiliary agent is generally 3 to 45 weight percent, and the auxiliary agent component elements can be one or more of K, Li, Fe, Mn, Zr, Ce, La, Ni, Pt, Pd and Rh; for another example, the catalyst may be a Cu-Co catalyst containing Cu and Co as active component elements, wherein the content of the active component in the Cu-Co catalyst is generally 50 to 90 wt% and the content of the auxiliary agent is generally 10 to 50 wt%, and the auxiliary agent component element may be one or more of Cr, K, Li, Mn, Fe, Co, U, Rh, Pt, Zr, La and Nd; for example, it may be MoS₂Catalyst of said MoS₂The catalyst refers to a solid catalyst with S/Mo atomic ratio of 2 obtained by carrying out vulcanization treatment on molybdenum oxide; the catalyst can also be a Zn-Cr catalyst with active component elements containing Zn and Cr, wherein the content of the active component in the Zn-Cr catalyst is generally 75-99.5 wt% and the content of the auxiliary agent is generally 0.5-25 wt%, and the auxiliary agent component elements can be one or more of K, Fe, Li, Al, Mn and La.

According to the process of the present invention, the methanation reaction conditions may be conventionally selected, and for the present invention, it is preferred that the methanation reaction conditions comprise: the pressure is 0.2-5MPa, the temperature is 250-750 ℃, and the gas space velocity is 100-20000h^-1. The methanation reaction reactor has no special requirement, and can be a fixed bed, a moving bed or a fluidized bed, and preferably a fixed bed or a fluidized bed.

According to the method of the invention, the methanation catalyst can be selected conventionally in the field, wherein, preferably, the methanation catalyst is a supported catalyst, in the supported catalyst, the active component element is preferably Ni, and the carrier is preferably Al₂O₃. The methanation catalyst can be chemically modified, and the auxiliary component elements adopted in the chemical modification can be one or more of La, Fe, Mg and Ce.

According to the method of the present invention, the gas-liquid separation method can adopt various common gas-liquid separation methods in the prior art, and for the present invention, the gas-liquid separation method is preferably cooling separation, and the cooling temperature is preferably 5-40 ℃.

According to the method of the invention, the cooling method can be direct contact cooling or indirect heat exchange cooling, and the cooling medium can be water and/or petroleum fractions.

According to the method of the present invention, preferably the method of the present invention further comprises: removing carbon dioxide from the methanation gas raw material before the step (3) is carried out, so that the content of the carbon dioxide in the methanation gas raw material is lower than 2.0 mol%. The removal of carbon dioxide can be carried out with reference to the prior art and the present invention is not described in detail herein.

According to the process of the present invention, the impurities in the raw synthesis gas typically contain tar, water vapor, sulfur-containing species, and the like.

The process for purifying the raw synthesis gas obtained after gasification of carbonaceous material according to the process of the invention can be carried out with reference to the prior art, which can be based on raw synthesisThe impurities in the syngas are selected, and as mentioned above, the impurities in the raw syngas generally include one or more of tar, steam and sulfur-containing substances, and when the impurities in the raw syngas include tar, steam and sulfur-containing substances, the step of purifying the raw syngas obtained by gasifying the carbonaceous material in step (1) generally includes: the crude synthesis gas is sequentially cooled, detarred, subjected to crude desulfurization and subjected to fine desulfurization, and the obtained pure synthesis gas contains H₂20-40 mol%, CO15-70 mol%, CO₂3-35 mol%, CH₄0-15 mol%, and H₂S is less than 0.1 mu g/g. Wherein, the methods of cooling, tar removal, crude desulfurization and fine desulfurization can be selected conventionally in the field, and the invention has no special requirement for the method.

According to the method of the invention, the method for gasifying carbonaceous materials is conventionally selected and generally comprises: under the pressurized reaction condition, the carbonaceous material is contacted with a gasifying agent, and the gasifying agent is selected from one or more of air, oxygen and water vapor, and is preferably a mixed gas of oxygen and water vapor. The pressurized reaction conditions are conventionally selected and generally include: the temperature is 450 ℃ and 2000 ℃, and the pressure is 0.1-20 MPa. And according to the needs, before gasifying the carbonaceous material, the carbonaceous material is pretreated by drying, crushing, pulping, preheating, melting and the like, which are well known to those skilled in the art, and the detailed description of the invention is omitted.

According to the invention, the gasification is generally carried out in a gasification furnace, which can be selected from suitable operating modes such as fixed bed, moving bed, fluidized bed, entrained flow and the like, and can be selected according to the properties of the carbonaceous material, and the invention has no special requirements for this and is not described in detail herein.

According to the method of the present invention, the carbonaceous material is selected from a conventional variety, including but not limited to coal, typically low rank coal, preferably one or more of lignite, long flame coal, crushed coal, pulverized coal, lump coal, caking coal, peat and coal-water slurry, and for the purposes of the present invention, preferably the carbonaceous material is lignite and/or long flame coal.

According to the method of the present invention, preferably the method of the present invention further comprises: separating the liquid product obtained in the step (2) into low carbon alcohol with carbon number less than 7, liquid hydrocarbon with carbon number more than 4, water and the like. The separated water contains a certain amount of organic matters, and can be used as sewage to be sent to a water treatment unit for treatment and then used by a device or discharged.

According to the method of the present invention, preferably the method of the present invention further comprises: cooling the contacted product obtained in the step (3) to separate water to obtain a gas material, and separating the gas material to obtain a methane-rich gas and a purge gas. According to the method of the invention, the cooling method can be direct contact cooling or indirect heat exchange cooling, and the cooling medium can be water and/or petroleum fractions. The process for separating the gaseous material according to the invention can be carried out with reference to the prior art and can be, for example, a cryogenic separation process or a pressure swing adsorption process.

According to the process of the invention, the methane-rich gas may be tempered or fed directly into a pipe network. The purge gas typically contains lower hydrocarbons, CO and CO₂In order to improve the utilization rate of carbon and reduce the problem of air pollution caused by emission of purge gas, the purge gas can be returned to the step (3) for methanation reaction for recycling, or returned to the step (1) for gasification for recycling, or sent to a heating furnace as gas alcohol.

The following examples further illustrate the invention but are not intended to limit the invention thereto.

Example 1

This example illustrates the present invention for the co-production of lower alcohols from methane produced from carbonaceous materials.

Pulverizing brown coal with particle size of 5-50 mmSee table 1) using oxygen/steam as gasifying agent, gasifying into crude synthesis gas, cooling, removing tar, crude desulfurizing, and fine desulfurizing to obtain pure synthesis gas (composition shown in table 2), wherein (CO + H)₂) Content 63 vol%, H₂The mol ratio of/CO is 1.59;

dividing the clean synthesis gas into G1 and G2, wherein G1 is sent into a synthesis reactor after being subjected to heat exchange and temperature rise, and is contacted with a mixed catalyst fixed bed layer for reaction, the catalyst bed layer is formed by mixing a water-gas shift catalyst and a synthetic low-carbon alcohol catalyst, the mass ratio of the water-gas shift catalyst to the synthetic low-carbon alcohol catalyst is 3:1, wherein the water-gas shift catalyst is a Co-Mo catalyst (the manufacturer is Koli company, and the trade mark is QCS-01), and the synthetic low-carbon alcohol catalyst comprises the following components: 40 wt% CuO-37 wt% Co₂O₃-21 wt.% MnO-2 wt.% K₂O; the inlet temperature of the composite reactor is 228 ℃, the outlet temperature is 266 ℃, the pressure is 6.25MPa, and the gas space velocity is 5000h^-1The product after reaction is cooled to 40 ℃ by indirect heat exchange and is divided into a gas stream G_aAnd a liquid stream L_a(weight proportions are shown in Table 3), gas stream G_aIn (H)₂+ CO) content of 47% by volume, C1-C4 hydrocarbon content of 15% by volume, H₂A molar ratio/CO of 2.95, a liquid stream L_aThe proportion of the medium-low carbon mixed alcohol is 78 weight percent;

g is to be_aCO of₂Removed to 1.55 vol.% in the gas stream (H)₂+ CO) content of 65% by volume, then sent to a methanation reactor by further compression, heat exchange and temperature rise, with Ni/Al in an amount of 15% by weight, calculated as the element, of nickel₂O₃The catalyst is subjected to contact reaction, the inlet temperature is 304 ℃, the outlet temperature is 461 ℃, the pressure is 3.18MPa, and the gas space velocity is 2500h^-1And cooling the product obtained by the reaction through heat exchange, cooling to 40 ℃, and separating liquid water to obtain a gas product with the methane content of 74.3 vol%.

Example 2

The net syngas was prepared and composed as in example 1. The total net syngas was split into two streams, G1 and G2. Wherein, G1 is sent into a synthesis reactor after being heated by heat exchange to react with a mixed catalyst fixed bed layer, the catalyst bed layer is formed by mixing a water-gas shift catalyst and a synthetic low-carbon alcohol catalyst, the mass ratio of the water-gas shift catalyst to the synthetic low-carbon alcohol catalyst is 4:1, wherein the water-gas shift catalyst is a Co-Mo catalyst (manufacturer is Qingdao communication company, trade mark QDB-03), and the synthetic low-carbon alcohol catalyst comprises the following components: 50 wt% ZnO-47 wt% Cr₂O₃-3% by weight of K₂O; the inlet temperature of the composite reactor is 305 ℃, the outlet temperature is 342 ℃, the pressure is 10.33MPa, and the gas space velocity is 4500h^-1The product after reaction is cooled to 40 ℃ by indirect heat exchange and is divided into a gas stream G_aAnd a liquid stream L_a(weight proportions are shown in Table 3), gas stream G_aIn (H)₂+ CO) content 56% by volume, C1-C4 hydrocarbon content 13% by volume, H₂A molar ratio/CO of 5.09, a liquid stream L_aThe proportion of the medium-low carbon mixed alcohol is 92 percent by weight;

g2 and G_aMixing, namely mixing CO in the mixed gas₂It is removed to 1.48% by volume, at which time (H)₂The content of + CO) was 71 vol%, H₂The mol ratio of the Ni to the CO is 3.02, the mixture is further compressed, subjected to heat exchange and heated, and then sent to a methanation reactor, and mixed with Ni/Al with the content of 15 weight percent of nickel calculated by elements₂O₃The catalyst is subjected to contact reaction, the inlet temperature is 303 ℃, the outlet temperature is 449 ℃, the pressure is 3.94MPa, and the gas space velocity is 2500h^-1And cooling the product obtained by the reaction through heat exchange, cooling to 40 ℃, and separating out liquid water, wherein the content of methane in the obtained gas product is 90.2 vol%.

Comparative example 1

The net syngas was prepared and composed as in example 1. The obtained clean synthesis gas is directly sent to a water-gas shift unit, the catalyst is a Co-Mo catalyst (the manufacturer is Qingdao communication company, brand QDB-03), the inlet temperature of the reactor is 250-:1, the pressure is 3.8MPa, and water-gas shift gas is obtained. CO in it₂Stripping to 1.71% by volume (H)₂+ CO) content 86% by volume, H₂The mol ratio of the Ni to the CO is 3.03, the mixture is further compressed, subjected to heat exchange and heated, and then sent to a methanation reactor, and mixed with Ni/Al with the content of 15 weight percent of nickel calculated by elements₂O₃The catalyst is subjected to contact reaction, the inlet temperature is 304 ℃, the outlet temperature is 461 ℃, the pressure is 3.03MPa, and the gas space velocity is 2500h^-1And cooling the product obtained by the reaction through heat exchange, cooling to 40 ℃, and separating out liquid water, wherein the content of methane in the obtained gas product is 95.3 vol%.

TABLE 1

TABLE 2

Clean syngas principal component	(mol%)
		H2	38.7
CO	24.3
		CO2	26.5
CH4	8.3
		N2	1.2
AR	0.6
		C2+Hydrocarbons	0.5

TABLE 3

Note:

(1) total liquid amount = G1 × L_a/100

(2) Total gas quantity =100% -total liquid quantity

(3) The total water gas shift load reduction (Δ WGS in carbon dioxide emissions reduction) is calculated as:

wherein, $P_t=Y_0/100\×\frac{1}{R_0+1}\×\frac{R_3-R_0}{R_3+1}\×100\%$

Y₀-CO + H in the feed gas₂Volume percent of (d);

R₀-H in the feed gas₂The mol ratio of/CO;

R₃-H in methanation feed gas₂The mole ratio of/CO.

（4）CO₂The relative emission change Δ RCE is calculated as:

from the results of the examples and comparative examples, it can be seen that, compared to comparative example 1, by using the method of the present invention, methane gas and lower alcohols can be co-produced from lignite via a clean syngas. Compared with the comparative example, according to the operation methods of the example 1 and the example 2, the reaction tail gas is mixed with the rest of the net synthesis gas to generate methanation reaction, the water-gas shift load can be reduced by 17.2 percent and 17.0 percent respectively on the whole, and the production unit volume of CH can be reduced₄，CO₂The discharge amount of the catalyst is reduced by 1.7 percent and 1.6 percent respectively. Therefore, the method can realize the CO-production of the methane gas and the low carbon alcohol, and not only the total CO in the process₂Reduced emissions and production of CH per unit volume₄CO of₂The discharge amount is also reduced, which shows that the invention can also effectively improve the utilization rate of carbon and reduce the discharge of carbon in the process.

The preferred embodiments of the present invention have been described in detail, however, the present invention is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solution of the present invention within the technical idea of the present invention, and these simple modifications are within the protective scope of the present invention.

Claims (10)

1. A method for co-producing methane and lower alcohols from carbonaceous materials, the method comprising:

(1) purifying the raw synthesis gas obtained after gasifying the carbonaceous material to remove impurities in the raw synthesis gas;

(2) contacting at least part of the purified synthesis gas and water with a mixed catalyst, and carrying out gas-liquid separation on a product obtained after the contact to obtain a gas product and a liquid product, wherein the mixed catalyst contains a water-gas shift catalyst and a catalyst for converting the synthesis gas into low-carbon alcohol, the weight ratio of the water-gas shift catalyst to the catalyst for converting the synthesis gas into the low-carbon alcohol in the mixed catalyst is 1-8:1, and the low-carbon alcohol is the low-carbon alcohol with the carbon number of 1-6;

(3) under the condition of methanation reaction, contacting a methanation gas raw material with a methanation catalyst, wherein the methanation gas raw material contains the gas product, and H in the methanation gas raw material₂The molar ratio of/CO is 2.8-3.5.

2. The method of claim 1, wherein the catalyst for converting syngas to lower alcohols is a Zn-Cr catalyst, a Cu-Zn-Al catalyst, a Cu-Co catalyst, and MoS₂One or more of a catalyst.

3. The method of claim 1, wherein the water gas shift catalyst is one or more of a Fe-Cr catalyst, a Cu-Zn catalyst, and a Co-Mo catalyst.

4. The process of claim 1, wherein in step (2), all of the net syngas is contacted with a mixed catalyst; in the step (3), the raw material of the methanated gas is the gas product.

5. The method of claim 1, wherein in step (2), the contacting conditions comprise: the temperature is 150-^-1The molar ratio of water to carbon monoxide is 0.5-1.3: 1.

6. The method according to claim 1, wherein in the step (2), the gas-liquid separation method is cooling, and the temperature of the cooling is 5-40 ℃.

7. The process of claim 1, wherein in step (3), H in the methanated gas feedstock is₂The total amount of CO and CO is 50-99 vol%.

8. The process of claim 1, wherein in step (3), the methanation reaction conditions comprise: the pressure is 0.2-5MPa, the temperature is 250-750 ℃, and the gas space velocity is 100-20000h^-1。

9. The method according to claim 1, wherein the step of purifying the raw synthesis gas obtained by gasifying the carbonaceous material in step (1) comprises: cooling, tar removing, crude desulfurization and fine desulfurization are carried out on the crude synthesis gas in sequence, and the obtained pure synthesis gas contains H₂20-40 mol%, CO15-70 mol%, CO₂3-35 mol%, CH₄0-15 mol%, and H₂S is less than 0.1 mu g/g.

10. The method of claim 1, wherein the carbonaceous material is lignite and/or long-flame coal.