Full-temperature-range simulated rotating moving bed pressure swing adsorption process for separating and extracting H2/CO from synthesis gas

Abstract

The invention discloses a full-temperature-range simulated rotating moving bed pressure swing adsorption process for separating and extracting H2 / CO from synthesis gas, which is based on pressure swing adsorption and comprises a multi-tower middle temperature pressure swing adsorption concentration system, a multi-tower middle temperature intermediate gas pressure swing adsorption system, a methane hydrogen hydrogen extraction pressure swing adsorption system and a concentrated gas temperature swing adsorption system, a full-temperature-range simulated rotating moving bed pressure swing adsorption FTrSRMPSA system for deacidifying synthesis gas and separating and extracting H2 and CO product gas with high purity and high yield is formed, so that cyclic operation of multiple steps of adsorption and desorption in simulated rotating moving bed pressure swing adsorption and temperature swing adsorption on the basis of axial flow fixed bed pressure swing adsorption is realized; the device is suitable for fluctuation working conditions of flow, component concentration, pressure or temperature corresponding to synthesis gas while realizing'high yield and purity 'and avoiding deep adsorption, and overcomes the defects of fixed bed, circulating bed, fluidized bed, rotating wheel adsorption and simulated moving bed processes in the prior art.

Description

technical field [0001] The present invention relates to hydrogen (H 2 ) and carbon monoxide (CO) synthesis gas for the separation of H by pressure swing adsorption (PSA) 2 In the field of CO, more specifically, it involves a full temperature range simulated rotary moving bed pressure swing adsorption process for the separation and extraction of H2 / CO from syngas. Background technique [0002] Syngas is hydrogen (H 2 ) and carbon monoxide (CO) as the main component of mixed gas, mainly used to produce synthetic ammonia, methanol, dimethyl ether, ethylene glycol, natural gas, acetic acid (anhydride), butanol, synthetic oil, fuel gas, and methanol-based chemicals, synthetic olefins and materials. Syngas is the basic raw material for carbon-one chemical industry. [0003] Syngas is mainly obtained through the gasification of fossil raw materials, such as coal, natural gas and petroleum. Among them, coal gasification is the most important preparation method of syngas, which i...

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Problems solved by technology

However, if the processing capacity increases, due to the limitation of the diameter or height of the vertical adsorption tower, generally more adsorption towers can only be connected in series or in parallel, the occupied area will increase, and the loading capacity of the adsorbent will also increase accordingly.

[0010] ②Axial flow fixed-bed adsorption tower has a relatively large height-to-diameter ratio and good dynamic effect, generally 3 to 6. The higher the product purity requirement, the greater the height-to-diameter ratio, but the bed resistance is greater , it is necessary to control the radial diffusion, and increase the number of adsorption towers when the processing capacity increases or the number of pressure equalizations increases to increase the yield, and the corresponding number of program control valves or regulating valves for each adsorption tower also increases, resulting in a large investment cost The amplitude increases, and it will also lead to a decrease in the stability and reliability of the entire device

[0011] ③A product with higher purity can be obtained, but the yield is reduced due to the high dead space rate in the adsorption tower due to the high amount of adsorbent filled in the adsorption tower. There is a more obvious "the higher the product purity, the lower the yield." Contradiction of the "purity is inversely proportional to yield" relationship the lower the

[0012] ④The AFB adsorption bed process can achieve multiple pressure equalizations by increasing the number of adsorption towers to make full use of the pressure of each tower and the recovery of effective components in the dead space in the adsorption tower, further utilizing the pressure energy and improving the yield. To a certain extent, the contradiction of "purity and yield are inversely proportional" is alleviated, but the number of corresponding adsorption towers, program-controlled valves, regulating valves, pipelines and other equipment also increases, equipment investment increases, and operational stability decreases.

At the same time, the increase in the number of pressure equalizations does not increase the yield. For example, for the synthesis gas PSA deacidification gas separation H 2 / CO process, in the range of adsorption pressure 2.0-3.0MPa, when the number of pressure equalization is more than 3 times, the marginal yield will decrease every time the pressure equalization is increased, but the equipment investment will increase greatly. Therefore, the pressure equalization The technology with more than 3 times is not economical

[0013] ⑤Switching of the program control valves matched to each AFB bed will cause instantaneous pulses of the flowing gas in the adsorption bed, which will cause a large disturbance to the uniform laminar flow or advection airflow distribution required for mass transfer, and affect the mass transfer efficiency , the higher the switching frequency, the more frequent the disturbance, and the more affected the mass transfer process

[0014] ⑥The adsorption model and design that the AFB bed relies on are relatively mature, and are generally suitable for systems with relatively large relative adsorption and separation coefficients, for example, CO, the main acidic component in syngas 2 with nonadsorbate H 2 The separation coefficient between / CO is greater than 3, and it is easier to remove the acidic component CO by using the AFB bed 2 , but for H with a small relative separation coefficient 2 As far as the / CO system is concerned, the separation efficiency of the AFB bed layer is relatively low, and a larger aspect ratio is required, and a higher adsorption pressure is also required, so that a small amount of acidic impurity components that have not been completely removed are in the H 2 / CO height-to-diameter ratio The deep adsorption in the high-pressure adsorption tower is intensified, resulting in H 2 / CO separation efficiency is greatly reduced, including H 2 with CO purity affected

However, the FCPSA process also has obvious disadvantages: 1) technical monopoly

Therefore, when there is a large fluctuation in the raw material composition or flow or pressure, the adsorption separation efficiency of SMB will be greatly affected

Even though the rotary valve can adapt to this volatility by adjusting the rotation rate and the opening and closing of the porous connection opened by the channel, the number of sections and the period of entry and exit of the SMB adsorption bed can not be adjusted. This is also one of the reasons why the operating flexibility of the SMB process unit is relatively small; 4) The SMB adsorption process is not suitable for PSA separation and purification, because the conventional pressure swing operation cannot simultaneously realize "fast adsorption and purification" in the SMB bed layer. Rapid desorption" to achieve the "steady state" of mass transfer; 5) It is difficult to obtain high-purity products, especially gas products, through the SMB adsorption process

This is due to the regular cross-flow of various process streams in the channel of the multi-channel rotary valve. Even if one or more flushes are introduced, the "cross-contamination" generated by the cross-flow cannot be avoided, and this "cross-contamination" is introduced into the SMB bed In order to realize the mass transfer "steady state" of "rapid adsorption and rapid desorption" in the SMB bed, the bed itself can no longer play the additional "cross-contamination" of further adsorption and desorption; 6) Domestic industrialization still needs a lot Hardware and control problems need to be solved through research and development, including the expansion of SMB adsorption tower (to overcome axial dispersion), the manufacture of multi-channel rotary valve (MPV) supporting SMB, the selection of supporting high-efficiency adsorbent and desorbent, and the high cost of introduction Wait

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