A decarburization process for coal syngas

Abstract

The present application relates to a kind of coal synthetic gas decarburization process, comprising the following steps: S1: crude raw gas enters crude synthetic gas pretreatment device, and crude synthetic gas pretreatment device is pretreated to crude raw gas, and obtains raw gas, S2: raw gas is sent into carbon dioxide membrane separation device and is roughly removed carbon dioxide, and obtains high carbon dioxide content raw gas;The present application has the advantages of low energy consumption, low operating cost.

Description

Technical Field

[0001] This invention belongs to the field of coal syngas decarbonization technology, specifically relating to a coal syngas decarbonization process. Background Technology

[0002] Underground Coal Gasification (UCG) is a new technology for developing clean energy and chemical raw materials by controlling the combustion of underground coal to produce combustible gases. This technology extracts only the energy-containing components of the coal, leaving pollutants such as ash underground. This new technology integrates well construction, coal mining, and conversion processes, significantly reducing environmental damage caused by coal production and use, and greatly improving the utilization rate of coal resources. Given my country's resource endowment characteristics of "abundant coal but insufficient oil and gas," utilizing idle underground coal resources to produce methane, hydrogen, etc., is of great strategic significance for China's natural gas development. The crude syngas produced by UCG has a high CO2 content, which not only reduces the calorific value of the syngas but also causes severe corrosion to equipment and pipelines, requiring additional anti-corrosion measures; therefore, underground coal syngas needs to be decarbonized before utilization. In recent years, with the rapid development of industrial technology, numerous decarbonization processes have evolved, mainly including low-temperature distillation, solvent absorption, adsorption, and membrane separation technologies. Among them, membrane separation decarbonization technology, as an emerging, highly efficient, and green separation technology, has shown many unique advantages. Therefore, choosing membrane separation technology or membrane separation-based coupling technology for decarbonization of underground coal syngas has good development potential in industrial applications.

[0003] Chinese invention patent CN113862044A discloses a high-efficiency underground coal syngas surface treatment process, including a surface treatment process for underground coal syngas through crude gas pretreatment, MDEA desulfurization and decarbonization, molecular sieve dehydration, and dehydrogenation. This patent uses a single activated MDEA solution absorption method for the syngas decarbonization unit. The activator used in the activated MDEA solution has a low boiling point, and the activator is easily entrained in the purified gas and regenerated gas, resulting in significant losses. If the activator concentration is too high, it can easily corrode the equipment. Furthermore, because the reaction rate of MDEA with CO2 absorption is slow, increasing the circulation volume of the absorbent leads to high energy consumption and high operating costs.

[0004] Chinese invention patent CN113880092A discloses a CO2 capture, recovery, and liquefaction process, which includes a combined process of low-temperature distillation and adsorption separation for CO2 capture, recovery, and liquefaction. This patent mainly includes multi-stage pressurization, desulfurization, dehydration and mercury removal, and fractionation recovery processes. However, this technology requires high energy consumption and has high equipment costs. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a decarbonization process for coal syngas with low energy consumption and low operating costs.

[0006] The technical solution of the present invention is as follows:

[0007] A decarbonization process for coal syngas includes the following steps:

[0008] S1: The crude raw material gas enters the crude syngas pretreatment unit, which pretreatments the crude raw material gas to obtain the raw material gas.

[0009] S2: The feed gas is sent into a carbon dioxide membrane separator for rough removal of carbon dioxide to obtain permeate gas with a high carbon dioxide content.

[0010] S3: The permeate gas with low carbon dioxide content after passing through the carbon dioxide membrane separation unit is then sent to the MDEA decarbonization unit to obtain product gas.

[0011] S4: The permeate gas with a high carbon dioxide content and the product gas are mixed and sent to the hydrogen purification membrane separation unit. After the hydrogen in the permeate gas and the product gas are separated, they are sent to the carbon dioxide cryogenic distillation unit to obtain liquefied carbon dioxide.

[0012] Compared with the prior art, the beneficial effects of the present invention are:

[0013] 1. This invention removes carbon dioxide from coal syngas through a carbon dioxide membrane separation device and an MDEA decarbonization device, and removes hydrogen from the raw gas through a hydrogen extraction membrane separation device. Finally, liquefied carbon dioxide is obtained through a carbon dioxide low-temperature distillation device. This significantly reduces the scale of the amine absorption device, effectively reduces energy consumption, and achieves better carbon dioxide removal effect from coal syngas while minimizing investment and operating costs.

[0014] 2. The present invention uses a crude syngas pretreatment device to pretreat the crude raw gas, reducing the mechanical impurities, larger water droplets and oil droplets, as well as the damage to the membrane of the carbon dioxide membrane separator caused by fine fixed particles, water mist and oil mist in the crude raw gas, thereby increasing the service life of the membrane separation equipment.

[0015] In summary, the present invention has the advantages of low energy consumption and low operating cost.

[0016] Furthermore, the crude syngas pretreatment device includes a heat exchanger, a buffer tank, a first filter, a cyclone separator, a high-efficiency filter, and a second filter, wherein the heat exchanger, buffer tank, first filter, cyclone separator, high-efficiency filter, and second filter are connected in series.

[0017] Furthermore, the MDEA decarbonization device is specifically an alcohol amine absorption tower.

[0018] Furthermore, the permeate and product gas from the hydrogen purification membrane separation unit are then transported to the carbon dioxide cryogenic distillation unit after passing through a carbon dioxide compressor. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the crude syngas pretreatment device of the present invention;

[0020] Figure 2 For the present invention Figure 1 A schematic diagram of the decarbonization process.

[0021] In the diagram, 1 is a buffer tank, 2 is the first filter, 3 is a cyclone separator, 4 is a high-efficiency filter, 5 is a heat exchanger, 6 is the second filter, 7 is a carbon dioxide membrane separation device, 8 is an MDEA decarbonization device, 9 is a carbon dioxide compressor, and 10 is a carbon dioxide cryogenic distillation device. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] like Figure 1-2 As shown, a decarbonization process for coal syngas includes the following steps:

[0024] S1: The crude raw gas with a carbon dioxide content greater than 50% is fed into the crude syngas pretreatment unit. The crude syngas pretreatment unit pretreatment the crude raw gas to remove mechanical impurities, larger water droplets and oil droplets, as well as fine solid particles, water mist and oil mist mixed in the crude raw gas, and obtain the raw gas.

[0025] S2: The feed gas is fed into the carbon dioxide membrane separator 7. After the feed gas enters the carbon dioxide membrane separator 7, the feed gas with high carbon dioxide content is enriched on the permeate side of the membrane to obtain carbon dioxide permeate gas with a content of 99%.

[0026] S3: The permeate gas with low carbon dioxide content after passing through the carbon dioxide membrane separation device 7 is then sent to the MDEA decarbonization device 8. The carbon content of the raw gas after passing through the carbon dioxide membrane separation device 7 is 12%. The MDEA decarbonization device 8 removes the raw gas with a carbon content of 12% to produce product gas with a carbon dioxide content of ≤73%.

[0027] S4: The permeate gas with a content of 99% carbon dioxide and the product gas with a carbon dioxide content of ≤73% are mixed and sent into the hydrogen purification membrane separation device 11. After separating the hydrogen from the permeate gas and the product gas, the mixture is sent into the carbon dioxide cryogenic distillation device 10. The carbon dioxide cryogenic distillation device 10 uses cryogenic separation technology to separate carbon dioxide from hydrocarbon components to obtain liquefied carbon dioxide.

[0028] The crude syngas pretreatment device removes mechanical impurities, larger water droplets and oil droplets, as well as fine solid particles, water mist and oil mist entrained in the crude raw gas, thus preventing damage to the membrane of the carbon dioxide membrane separator 7.

[0029] Hydrogen is removed from product gas and permeate gas by a hydrogen purification membrane separation device, thereby increasing the carbon dioxide content in product gas and permeate gas.

[0030] Most of the carbon dioxide in the raw gas is removed by the carbon dioxide membrane separator 7, thereby reducing the decarbonization load of the MDEA decarbonization unit 8 by more than 45%.

[0031] In this embodiment, the crude syngas pretreatment device includes a heat exchanger 5, a buffer tank 1, a first filter 2, a cyclone separator 3, a high-efficiency filter 4, and a second filter 6. The heat exchanger 5, buffer tank 1, first filter 2, cyclone separator 3, high-efficiency filter 4, and second filter 6 are connected in series. During use, because the temperature of the crude raw gas is high (>200℃), the crude raw gas needs to pass through the heat exchanger to reduce its temperature to 70℃ before entering the buffer tank 1. The buffer tank 1 buffers the flow of the raw gas and then filters the buffered flow through the first filter 2, cyclone separator 3, and high-efficiency filter 4 to remove mechanical impurities, larger water droplets and oil droplets, as well as fine solid particles, water mist, and oil mist mixed in with the crude raw gas. The gas is then filtered again through the second filter 6 to ensure that the gas entering the carbon dioxide membrane separator 7 does not contain mechanical particles, thereby preventing damage to the membrane of the carbon dioxide membrane separator 7.

[0032] In this embodiment, the MDEA decarbonization device 8 is specifically an alkanolamine absorption tower, which achieves the fine removal of carbon dioxide and ensures the removal of carbon dioxide.

[0033] In this embodiment, the permeate gas and product gas from the hydrogen purification membrane separation device 11 are transported to the carbon dioxide cryogenic distillation device 10 after passing through the carbon dioxide compressor 9.

[0034] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A decarbonization process for coal syngas, characterized in that: Includes the following steps: S1: The crude raw material gas enters the crude syngas pretreatment unit, which pretreatments the crude raw material gas to obtain the raw material gas. S2: The feed gas is sent into a carbon dioxide membrane separator for rough removal of carbon dioxide to obtain permeate gas with a high carbon dioxide content. S3: The permeate gas with low carbon dioxide content after passing through the carbon dioxide membrane separation unit is then sent to the MDEA decarbonization unit to obtain product gas. S4: The permeate gas with a high carbon dioxide content and the product gas are mixed and sent to the hydrogen purification membrane separation unit. After the hydrogen in the permeate gas and the product gas are separated, they are sent to the carbon dioxide cryogenic distillation unit to obtain liquefied carbon dioxide.

2. The decarbonization process for coal syngas according to claim 1, characterized in that: The crude syngas pretreatment unit includes a heat exchanger, a buffer tank, a first filter, a cyclone separator, a high-efficiency filter, and a second filter, all of which are connected in series.

3. The decarbonization process for coal syngas according to claim 2, characterized in that: The MDEA decarbonization device is specifically an alcohol amine absorption tower.

4. The decarbonization process for coal syngas according to claim 3, characterized in that: The permeate and product gas from the hydrogen purification membrane separation unit are then transported to the carbon dioxide cryogenic distillation unit after passing through a carbon dioxide compressor.

Images