CN118851874A - A process for preparing ethanol using calcium carbide furnace tail gas, coke oven gas and dimethyl ether as raw materials - Google Patents

Abstract

The invention relates to a process for preparing ethanol by using calcium carbide furnace tail gas, coke oven gas and dimethyl ether as raw materials. After benzene washing, the coke oven gas is mixed with calcium carbide furnace tail gas, and sequentially enters a separation device through a wet desulfurization device, a TSA device, a deoxidization and unsaturated hydrocarbon removal reactor, a hydrodesulfurization reactor, a hydrolysis reactor and a desulfurization and decarburization device, high-purity CO and H ₂ are separated, then the CO reacts with dimethyl ether to generate methyl acetate, and the methyl acetate is hydrogenated to generate ethanol. The process fully utilizes the effective components in the tail gas of the calcium carbide furnace and the coke oven gas, has the characteristics of simple flow and high efficiency, and realizes the maximum utilization of resources.

Description

A process for preparing ethanol using calcium carbide furnace tail gas, coke oven gas and dimethyl ether as raw materials

Technical Field

The invention relates to a process for preparing ethanol by taking calcium carbide furnace tail gas, coke oven gas and dimethyl ether as raw materials, and belongs to the field of coal chemical industry.

Background Art

Every ton of calcium carbide produced will generate ⁴⁰⁰ ~500Nm3 of calcium carbide furnace tail gas, which contains 65%~88% CO and 5%~15% _H2 by volume. In addition to being used as fuel gas, it can also be used as a chemical raw material. After purification, it can be used to produce carbon chemical products such as synthetic ammonia, ethylene glycol, methanol, and sodium formate. However, when used alone as a chemical raw material, the problem of high carbon and low hydrogen limits its large-scale industrial application.

The production of 1t of coke produces ^400Nm3 of coke oven gas as a by-product. Coke oven gas contains about 60% _H2 and 10% _COX by volume, and the hydrogen-carbon ratio in the furnace gas is as high as 6, while the hydrogen-carbon ratio of downstream chemical products such as synthetic methanol and ethylene glycol is about 2.0. Therefore, when used alone as a chemical raw material, there is a problem of high hydrogen and low carbon. The main components and impurity contents of coke oven gas and calcium carbide furnace tail gas are shown in Table 1. As can be seen from Table 1, when coke oven gas and calcium carbide furnace tail gas are used to produce chemical raw materials, their hydrogen-carbon ratios are highly complementary.

Table 1. Main components and impurity contents of coke oven gas and calcium carbide furnace tail gas

The properties of dimethyl ether are similar to those of liquefied petroleum gas, so it can replace liquefied petroleum gas as a civilian fuel. Based on this property, the scale of dimethyl ether equipment in my country during peak hours is nearly 10 million tons. However, with the decline in the market price of liquefied gas, the price difference between the two has become smaller, and the advantages of dimethyl ether as an alternative fuel are no longer obvious, resulting in a shrinking demand for dimethyl ether, and a large number of equipment have been shut down or idled. It is urgent to find new downstream markets for it.

At present, the synthesis methods of ethanol mainly rely on grain fermentation and chemical synthesis. Grain fermentation is costly and has the risk of competing with others for food. Chemical synthesis is divided into two categories: petrochemical synthesis and coal chemical synthesis. Since my country's energy structure is "rich in coal and poor in oil", the preparation of ethanol from the coal chemical route has become the most promising process route in the future.

In view of the tight market situation of ethanol, the unsatisfactory carbon-hydrogen ratio of calcium carbide furnace tail gas and coke oven gas as chemical raw material gas and the idle waste of dimethyl ether devices, a process for producing ethanol using calcium carbide furnace tail gas, coke oven gas and dimethyl ether as raw materials has practical significance and extremely high economic value. As can be seen from Table 1, calcium carbide furnace tail gas and coke oven gas contain a large amount of sulfide, benzene, HCN, PH ₃ , etc., so desulfurization and purification are the focus of this process.

Chinese patent CN103289768B discloses a method for synthesizing natural gas from calcium carbide tail gas and coke oven gas, which includes first condensing and dusting the calcium carbide tail gas, cooling the coke oven gas, removing tar and naphthalene, then mixing the two gases, undergoing sulfur-resistant conversion, decarbonization, desulfurization, and synthesizing methane gas, and finally dehydrating and pressure swing adsorption to synthesize natural gas. Since the invention uses calcium carbide tail gas and coke oven gas to synthesize natural gas, the carbon-hydrogen ratio is not suitable, and a conversion process is required to adjust the carbon-hydrogen ratio. In addition, the hydrogen sulfide after hydrodesulfurization is absorbed by a zinc oxide desulfurizer, which will produce a large amount of hazardous waste.

Summary of the invention

Based on the shortcomings of the above technologies, the present invention has developed a process for producing ethanol using calcium carbide furnace tail gas, coke oven gas and dimethyl ether as raw materials. The whole process is simple and the layout is reasonable, which realizes the maximum utilization of resources. The process includes the following steps:

⑴ After washing with benzene, the coke oven gas is mixed with the tail gas of the calcium carbide furnace and enters the wet desulfurization device to remove most of the _H2S and acid gases such as HCl, HCN, and HF, and then enters the TSA (temperature swing adsorption) device to purify the gas;

⑵ The purified gas from TSA is heated to 220℃ and then enters the deoxygenation and deunsaturation reactor. The gas after deoxygenation and deunsaturation enters the hydrodesulfurization reactor to convert the organic sulfur therein into _H2S . The gas after hydrodesulfurization is cooled to 80℃ and enters the hydrolysis reactor to hydrolyze the COS that is not completely converted by hydrodesulfurization into _H2S ; the gas from the hydrolysis reactor is cooled to room temperature and then enters the amine desulfurization and decarbonization device to remove _H2S and _CO2 . The gas from the amine desulfurization and decarbonization device enters the gas separation device to separate _H2 and CO with a purity of 99.9%; then CO is mixed with dimethyl ether and enters the carbonylation reactor to react to generate methyl acetate; methyl acetate is mixed with _H2 and enters the methyl acetate hydrogenation reactor to generate ethanol.

The wet desulfurization adopts the complex iron method.

The TSA is equipped with four reactors in parallel, three of which are in operation and one is for regeneration. Each reactor is equipped with a corresponding switch valve for freely adjusting the order of the reactors. The TSA reactor is regenerated at different temperatures in batches at regular intervals, and the regeneration temperatures are cycled in intervals of 200°C, 220°C, and 280°C.

The TSA reactor is filled with an activated carbon desulfurizer loaded with active components for further removing hydrogen sulfide, a dephosphorization agent for removing PH ₃ , and blank activated carbon for removing benzene, naphthalene, and tar impurities. The blank activated carbon has an iodine value of 1000-1500 mg/g and a carbon tetrachloride value of 55-60%.

The deoxygenation and deunsaturation hydrocarbon reactor adopts a uniform temperature internal heat exchange reactor; the upper 1/4 of the deoxygenation and deunsaturation hydrocarbon reactor is filled with a protective agent, and the rest is filled with a deoxygenation and deunsaturation hydrocarbon catalyst, and the main active component of the protective agent is Na-Mo.

The hydrodesulfurization reactor is filled in upper and lower layers. By volume, the upper 1/2 is filled with Fe-Mo series catalysts, and the lower 1/2 is filled with Ni-MO series catalysts.

The hydrolysis reactor is filled with a hydrolysis catalyst with Al-Ti as a carrier and Na-K as an active component;

The alcoholamine used in the alcoholamine desulfurization and decarbonization device is a mixture of MDEA (N-methyldiethanolamine) and MEA (ethanolamine).

The gas separation device uses cryogenic or PSA (pressure swing adsorption) methods to separate gases.

The deoxygenation and deunsaturation catalyst and protective agent loaded in the oxygen deunsaturation reactor and the hydrodesulfurization catalyst loaded in the hydrodesulfurization reactor are pre-sulfurized catalysts outside the reactor or are used after on-site sulfurization.

The temperature of the carbonylation reactor is 200-300°C, the pressure is 1.0-5.0MPa, and the carbonylation catalyst is SAPO-34 molecular sieve catalyst. The reaction temperature of methyl acetate hydrogenation is 150-250°C, the pressure is 3.0-8.0MPa, the hydrogen-ester molar ratio is 20-30, and the hydrogenation catalyst is Pt, Cu series catalyst.

Compared with the prior art, the present invention has the following advantages:

By making full use of the characteristics of high CO in calcium carbide furnace tail gas and high _H2 in coke oven gas, the conversion process of chemical raw material gas utilization is eliminated, which not only saves water resources but also reduces energy consumption.

Calcium carbide furnace tail gas and coke oven gas share a set of wet desulfurization. Since coke oven gas contains about 10000ppm of H ₂ S, wet desulfurization is generally used for rough desulfurization. The H ₂ S content in calcium carbide furnace tail gas is generally around 10ppm, and wet removal is not very economical. However, the acidic substances HCl, HF, and HCN contained in it need to be removed by water washing and alkali washing, which easily forms alkaline slag and wastewater that is difficult to treat. The two share a set of wet desulfurization system, which can not only remove H ₂ S from coke oven gas, but also the alkaline substances in the desulfurization liquid can effectively remove acidic substances such as HCl, HF, and HCN in the tail gas of calcium carbide furnace.

The TSA process adopts a graded loading scheme, fully considering the characteristics of adsorption and regeneration of H ₂ S, PH ₃ and various impurities. The upper part of the reactor is loaded with an activated carbon desulfurizer loaded with active components to fully absorb H ₂ S, and the middle part is loaded with a dephosphorization agent to fully absorb PH ₃ , which can effectively avoid the influence of H ₂ S and PH ₃ on the removal of benzene and tar from blank activated carbon. The constant regeneration temperature of the ordinary process is changed. The TSA reactor is regenerated at different temperatures in batches, and the S generated by H ₂ S and the P ₂ O ₃ generated by PH ₃ are regenerated at high temperature regularly, which not only saves energy consumption, but also maximizes the recovery of adsorbent performance.

The deoxygenation and deunsaturated hydrocarbon reactor adopts a uniform temperature internal heat exchange reactor, which can adapt to the changes in different oxygen contents in the feed gas. The upper layer is filled with protective agents to effectively remove the influence of tar, benzene, and naphthalene, and extend the service life of the oxygen deoxygenation and deunsaturated hydrocarbon agent. The hydrodesulfurization reactor uses the upper part to be filled with a cheap FeMo-based desulfurizer with weaker activity to remove more active organic sulfur such as COS, RHS, and RSR, and the lower part is filled with a NiMO-based hydrodesulfurization catalyst with stronger activity and higher price to remove RSSR, C ₄ H ₄ S, etc., which can achieve the purpose of desulfurization and minimize production costs.

A hydrolysis reactor is set up after the hydrodesulfurization reactor to hydrolyze COS that is not completely converted by hydrodesulfurization. Industrial practice shows that hydrodesulfurization cannot completely convert COS or a small amount of COS will be generated during the hydrodesulfurization process. By completely converting COS into _H2S through hydrolysis, sulfides can be completely removed and the total sulfur can meet the requirements of technical indicators.

Traditional coke oven gas desulfurization requires a large amount of zinc oxide desulfurizer, which is a hazardous waste after use. The amine desulfurization and decarbonization device removes H ₂ S and CO ₂ at the same time. The entire process does not require the use of zinc oxide desulfurizer, which saves costs and reduces the generation of hazardous waste. It is an environmentally friendly process.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a process flow chart of preparing ethanol from calcium carbide furnace tail gas, coke oven gas and dimethyl ether;

Among them, 1 is a benzene washing unit; 2 is a wet desulfurization unit; 3 is a TSA unit; 4 is a deoxygenation and desaturation reactor; 5 is a hydrodesulfurization reactor; 6 is a hydrolysis reactor; 7 is an amine desulfurization and decarbonization unit; 8 is a gas separation unit; 9 is a carbonylation reactor; and 10 is a methyl acetate hydrogenation reactor.

Fig. 2 is a schematic diagram of a TSA device;

Among them, 1 is an activated carbon desulfurizer loaded with active components; 2 is a dephosphorization agent; 3 is blank activated carbon; R101A/B/C/D is a reactor.

DETAILED DESCRIPTION

The present invention is further described below in conjunction with FIG. 1 , FIG. 2 and embodiments, but the present invention is not limited to the embodiments.

Example 1

As shown in Figure 1, a certain unit in Shanxi Province has a 200,000/year dimethyl ether device, which transports 30,000 ^m3 /h of coke oven gas and 20,000 ^m3 /h of calcium carbide furnace tail gas from nearby factories through pipelines. The coke oven gas passes through the benzene washing device 1, mixes with the calcium carbide furnace tail gas, and enters the wet desulfurization device 2. The wet desulfurization adopts the complex iron method to remove most of the _H2S and acid gases such as HCl, HCN, and HF, and then enters the TSA device 3 to purify the gas;

The purified gas from TSA is heated to 220°C and then enters the deoxygenation and deunsaturation hydrocarbon reactor 4, which is a uniform temperature internal heat exchange reactor used to remove oxygen, acetylene, ethylene and other gases. The upper 1/4 (by volume, the same below) of the deoxygenation and deunsaturation hydrocarbon reactor is filled with protective agent, and the rest is filled with deoxygenation and deunsaturation hydrocarbon catalyst. The main active component of the protective agent is Na-Mo.

The gas after deoxygenation and removal of unsaturated hydrocarbons enters the hydrodesulfurization reactor 5. The hydrodesulfurization reactor 5 adopts an upper and lower layer filling method, with the upper 1/2 filled with Fe-Mo series catalysts and the lower 1/2 filled with Ni-Mo series catalysts. The gas after hydrodesulfurization is cooled to 80°C and enters the hydrolysis reactor 6. The hydrolysis reactor 6 is filled with a hydrolysis catalyst with Al-Ti as a carrier and Na-K as an active component;

The deoxygenation and deunsaturation catalyst and the protective agent loaded in the deoxygenation and deunsaturation reactor 4 and the hydrodesulfurization catalyst loaded in the hydrodesulfurization reactor 5 use an external presulfurized catalyst.

The gas from the hydrolysis reactor 6 is cooled to room temperature and then enters the alcohol amine desulfurization and decarbonization device 7, which uses a mixture of MDEA and MEA to remove _H2S and _CO2. The gas from the alcohol amine desulfurization and decarbonization device 7 enters the gas separation device 8, which uses deep cooling to separate _H2 and CO with a purity of 99.9%; CO is mixed with dimethyl ether and enters the carbonylation reactor 9 to react to generate methyl acetate. The temperature of the carbonylation reactor is 200°C, the pressure is 1.0MPa, and the carbonylation catalyst is SAPO-34 molecular sieve catalyst. _H2 and the generated methyl acetate enter the methyl acetate hydrogenation reactor 10 for hydrogenation to generate ethanol. The reaction temperature of methyl acetate hydrogenation is 250°C, the pressure is 8.0MPa, the hydrogen-ester molar ratio is 30, and the hydrogenation catalyst is a Cu-based catalyst.

As shown in Figure 2, the TSA device is equipped with four parallel reactors R101A/B/C/D, three of which are in operation and one is regenerated. Each reactor is equipped with a corresponding switch valve for freely adjusting the order of the reactors. The TSA reactor is regenerated at different temperatures in batches at regular intervals, and the regeneration temperature is 200°C, 220°C, and 280°C in turn. From top to bottom, 1/4 of the TSA reactor is filled with an activated carbon desulfurizer 1 loaded with active components, 1/4 is filled with a dephosphorization agent 2, and 1/2 is filled with blank activated carbon 3 with an iodine value of 1500 mg/g and a carbon tetrachloride value of 55%;

Example 2

As shown in Figure 1, a certain unit in Shanxi Province has a 200,000/year dimethyl ether device, which transports 30,000 ^m3 /h of coke oven gas and 20,000 ^m3 /h of calcium carbide furnace tail gas from nearby factories through pipelines. The coke oven gas passes through the benzene washing device 1, mixes with the calcium carbide furnace tail gas, and enters the wet desulfurization device 2. The wet desulfurization adopts the complex iron method to remove most of the _H2S and acid gases such as HCl, HCN, and HF, and then enters the TSA device 3 to purify the gas;

The purified gas from TSA is heated to 220°C and then enters the deoxygenation and deunsaturation hydrocarbon reactor 4, which is a uniform temperature internal heat exchange reactor. The upper 1/4 (by volume, the same below) of the deoxygenation and deunsaturation hydrocarbon reactor is filled with protective agent, and the rest is filled with deoxygenation and deunsaturation hydrocarbon catalyst. The main active component of the protective agent is Na-Mo.

The gas after deoxygenation and removal of unsaturated hydrocarbons enters the hydrodesulfurization reactor 5. The hydrodesulfurization reactor 5 adopts an upper and lower layer filling method, with the upper 1/2 filled with Fe-Mo series catalysts and the lower 1/2 filled with Ni-Mo series catalysts. The gas after hydrodesulfurization is cooled to 80°C and enters the hydrolysis reactor 6. The hydrolysis reactor 6 is filled with a hydrolysis catalyst with Al-Ti as a carrier and Na-K as an active component;

The deoxygenation and deunsaturation catalyst and protective agent loaded in the deoxygenation and deunsaturation reactor 4 and the hydrodesulfurization catalyst loaded in the hydrodesulfurization reactor 5 are used after being sulfurized on site.

The gas from the hydrolysis reactor 6 is cooled to room temperature and then enters the alcohol amine desulfurization and decarbonization device 7, which uses a mixture of MDEA and MEA to remove _H2S and _CO2. The gas from the alcohol amine desulfurization and decarbonization device 7 enters the gas separation device 8, which uses the PSA method to separate _H2 and CO with a purity of 99.9%; CO is mixed with dimethyl ether and enters the carbonylation reactor 9 to react to generate methyl acetate. The temperature of the carbonylation reactor is 300°C, the pressure is 5.0MPa, and the carbonylation catalyst is a SAPO-34 molecular sieve catalyst. _H2 and the generated methyl acetate enter the methyl acetate hydrogenation reactor 10 for hydrogenation to generate ethanol. The reaction temperature of methyl acetate hydrogenation is 150°C, the pressure is 3.0MPa, the hydrogen-ester molar ratio is 20, and the hydrogenation catalyst is a Pt-based catalyst.

As shown in Figure 2, the TSA device is equipped with four parallel reactors R101A/B/C/D, three of which are in operation and one is regenerated. Each reactor is equipped with a corresponding switch valve for freely adjusting the order of the reactor. The TSA reactor is regenerated at different temperatures in batches at regular intervals, and the regeneration temperature is 200°C, 220°C, and 280°C in turn. From top to bottom, 1/4 of the TSA reactor is filled with an activated carbon desulfurizer 1 loaded with active components, 1/4 is filled with a dephosphorization agent 2, _and 1/2 is filled with blank activated carbon 3 with an iodine value of 1000 mg/g and a carbon tetrachloride value of 60%.

The changes in the impurity content at the outlet of each section of Example 1 and Example 2 are shown in Table 2. As can be seen from Table 2, the process of the present invention efficiently removes various impurities in the impurity removal section, providing high-quality raw gas for the synthesis of ethanol.

Table 2. Changes in impurity content at the outlet of each section

The above is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent change made to the above embodiment according to the technical essence of the invention still falls within the protection scope of the technical solution of the present invention.

Claims (10)

1. A process for preparing ethanol by using calcium carbide furnace tail gas, coke oven gas and dimethyl ether as raw materials is characterized in that: the process comprises the following steps:

⑴ After benzene washing, the coke oven gas is mixed with calcium carbide furnace tail gas, enters a wet desulfurization device, most of H ₂ S and HCl, HCN, HF acid gas are removed, and then enters a TSA device to purify the gas;

⑵ Heating the purified gas from the step ⑴ TSA to 220 ℃, then entering a deoxidization and de-unsaturated hydrocarbon reactor, allowing the deoxidization and de-unsaturated hydrocarbon gas to enter a hydrodesulfurization reactor to convert organic sulfur in the deoxidization and de-unsaturated hydrocarbon gas into H ₂ S, cooling the hydrodesulfurization gas to 80 ℃, and allowing the hydrodesulfurization gas to enter a hydrolysis reactor to hydrolyze COS which is not completely converted into H ₂ S;

⑶ Cooling the gas from the hydrolysis reactor in the step ⑵ to normal temperature, then entering an alcohol amine desulfurization and decarbonization device to remove H ₂ S and CO ₂, and entering a gas separation device from the alcohol amine desulfurization and decarbonization device to separate H ₂ and CO with the purity of 99.9 percent;

⑷ Mixing the CO obtained in the step ⑶ with dimethyl ether, and then entering a carbonylation reactor to react to generate methyl acetate;

⑸ Mixing methyl acetate obtained in the step ⑷ with H ₂ obtained in the step ⑶, and then entering a methyl acetate hydrogenation reactor for reaction to generate ethanol.

2. The process of claim 1, wherein: the wet desulfurization adopts a complex iron method.

3. The process of claim 1, wherein: the TSA is provided with four reactors connected in parallel, three reactors are operated, one is regenerated, and each reactor is provided with a corresponding switch valve for freely adjusting the front-back sequence;

the TSA reactor is periodically regenerated at different temperatures in batches, and the regeneration temperature is sequentially and circularly carried out at intervals in a mode of 200 ℃, 220 ℃ and 280 ℃.

4. A process according to claim 1 or 3, wherein: the TSA device reactor is filled with active carbon desulfurizing agent loaded with active components in 1/4 of the total volume of the TSA device reactor from top to bottom for further removing hydrogen sulfide, dephosphorizing agent in 1/4 of the total volume of the TSA device reactor is filled with dephosphorizing agent for removing PH ₃, and blank active carbon in 1/2 of the TSA device reactor is filled with blank active carbon for removing benzene, naphthalene and tar impurities;

The iodine value of the blank activated carbon is 1000-1500mg/g, and the carbon tetrachloride value is 55-60%.

5. The process of claim 1, wherein: the deoxidization and unsaturated hydrocarbon removal reactor adopts a uniform temperature internal heat exchange reactor; the upper 1/4 of the catalyst is filled with protective agent, and the rest is filled with deoxidized and unsaturated hydrocarbon catalyst;

the main active component of the protective agent is Na-Mo.

6. The process of claim 1, wherein: the hydrodesulfurization reactor adopts a mode of filling an upper layer and a lower layer, wherein the upper part is filled with Fe-Mo series catalyst by 1/2 and the lower part is filled with Ni-Mo series catalyst by 1/2 in terms of volume.

7. The process of claim 1, wherein: the hydrolysis reactor is filled with a hydrolysis catalyst which takes Al-Ti as a carrier and Na-K as an active component.

8. The process of claim 1, wherein: alcohol amine used in the alcohol amine desulfurization and decarbonization device is a mixture of MDEA and MEA.

9. The process according to claim 1, characterized in that: the gas separation device adopts a cryogenic or PSA mode to separate the gas.

10. The process according to claim 1, characterized in that: the deoxidized and unsaturated hydrocarbon catalyst filled in the deoxidized and unsaturated hydrocarbon reactor, the protective agent and the hydrodesulfurization catalyst filled in the hydrodesulfurization reactor are used after the catalyst is presulfided outside the reactor or is vulcanized on site.