Method and device for recovering hydrogen from mixed gas under multiple variable conditions

Abstract

The application provides a method and device for recovering hydrogen from mixed gas under multiple working conditions, and relates to the technical field of separating hydrogen from mixed gas containing hydrogen. The method comprises multiple-stage membrane separation of the mixed gas, which includes initial-stage membrane separation, any number of intermediate-stage membrane separation including zero, and terminal-stage membrane separation; the permeate of the initial-stage membrane separation is subjected to PSA treatment to obtain product hydrogen, and the permeate of the intermediate-stage membrane separation and the terminal-stage membrane separation can be sent to any stage of membrane separation or discharged; the permeation side pressure of the initial-stage membrane separation is adjusted to adjust the concentration of the permeate of the initial-stage membrane separation. The device comprises the initial-stage membrane separator, any number of intermediate-stage membrane separators including zero, and the terminal-stage membrane separator arranged in sequence, and a PSA unit is in communication with the permeation side pipeline of the initial-stage membrane separator. The application realizes high recovery rate of hydrogen from mixed gas with fluctuating flow and components.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of separating hydrogen from a hydrogen-containing mixed gas, and in particular to a method and device for recovering hydrogen from a mixed gas under variable working conditions. BACKGROUND

[0002] In the prior art, hydrogen recovery from mixed nitrogen gas generally includes three processes of membrane separation, PSA (pressure swing adsorption), and a combination of membrane separation and PSA. The disadvantage of membrane separation is that the purity of the separated product, whether it is nitrogen or hydrogen, is difficult to reach 99.8% (V / V) or above. The disadvantage of PSA is low recovery rate and narrow application range. If the nitrogen content in hydrogen exceeds 30%, the hydrogen recovery rate under normal working conditions is difficult to exceed 50%. The disadvantage of the combination of membrane separation and PSA is that it can only be applied to fixed gas volume and components, otherwise the output gas index will change greatly.

[0003] Currently, for a chemical plant, displacement gas and pressure regulating vent gas are unstable and have certain time periodicity and uncertainty. Taking a polysilicon plant as an example, most of the displacement gas and pressure regulating vent gas are hydrogen and nitrogen, but the gas volume and components of these gases change when they leave a single device or system. For example, the amount of discharge gas in a certain polysilicon plant changes rapidly from 1500 to 6000 Nm³ / h, and the hydrogen content in the components changes rapidly from 8 to 54% (V / V). The time of multiple discharge points in the plant is relatively disordered. When the displacement gas and pressure regulating gas in the entire plant are discharged to the leaching device, the gas volume and components change rapidly and chaotically. Therefore, none of the above three hydrogen recovery schemes can adapt to such gases, and even if some hydrogen can be recovered, the recovery rate is low (hydrogen recovery rate below 60% or even lower). SUMMARY

[0004] The purpose of the present application is to develop a method and device for recovering hydrogen from a mixed gas with fluctuating flow and components under variable working conditions.

[0005] The present application is achieved by the following technical solutions:

[0006] A method for recovering hydrogen from a mixed gas under variable working conditions, comprising:

[0007] Pretreating the mixed gas to remove impurities;

[0008] Pretreated mixed gas is subjected to multi-stage membrane separation, which includes initial stage membrane separation, any number of intermediate stage membrane separation including zero, and terminal stage membrane separation;

[0009] The non-permeated gas of the preceding stage of membrane separation is sent to the following stage of membrane separation, and the non-permeated gas of the terminal stage of membrane separation contains less than 2% of hydrogen and is discharged;

[0010] The permeated gas of the initial stage of membrane separation is subjected to PSA treatment to obtain product hydrogen, and the permeated gas of the intermediate stage of membrane separation and the terminal stage of membrane separation can be pressurized and sent to the inlet of any stage of membrane separation or discharged;

[0011] The permeated side pressure of the initial stage of membrane separation is adjusted to adjust the concentration of the permeated gas of the initial stage of membrane separation, so that the concentration of the permeated gas tends to be constant.

[0012] Optionally, the hydrogen content in the mixed gas fluctuates between 5% and 80%, the gas volume of the mixed gas changes between 10% and 100%, the pressure of the pretreated mixed gas is controlled to be 1.5-4 MPa, and the permeated side pressure of the initial stage of membrane separation is 0.1-1 MPa.

[0013] Optionally, the adsorption column of the PSA is switched in time by using the cumulative gas flow method.

[0014] Optionally, before the PSA treatment, the permeated gas of the initial stage of membrane separation is pressurized to 0.8-2 MPa.

[0015] Optionally, the permeated side pressure of each stage of membrane separation gradually decreases from the initial stage of membrane separation to the terminal stage of membrane separation, and the hydrogen concentration of the permeated gas gradually decreases.

[0016] Optionally, the permeated side pressure of the terminal stage of membrane separation is controlled to be -0.05-0.05 MPa, and the hydrogen content in the permeated gas is 10-50%.

[0017] Optionally, the gas generated by the PSA, including the reverse gas and the suction vacuum gas, is sent back to become a component of the pretreated mixed gas, and then subjected to the initial stage of membrane separation.

[0018] A device for recovering hydrogen from mixed gas under variable working conditions, comprising:

[0019] An initial stage of membrane separator, any number of intermediate stages of membrane separator, and a terminal stage of membrane separator are sequentially arranged;

[0020] A PSA unit, which is in communication with the permeated side pipeline of the initial stage of membrane separator;

[0021] The non-permeated side of the preceding stage of membrane separation is in communication with the gas inlet pipeline of the following stage of membrane separation, and the permeated gas of the intermediate stage of membrane separation and the terminal stage of membrane separation can be pressurized and sent to the gas inlet pipeline of any stage of membrane separation or discharged;

[0022] The pipeline between the PSA unit and the primary stage membrane separator is provided with an adjusting valve, and the PSA unit is communicated with the primary stage membrane separator through a gas inlet pipeline.

[0023] Optionally, a first compressor is arranged before the primary stage membrane separator, and the first compressor adjusts the pressure of the gas entering the primary stage membrane separator.

[0024] Optionally, the pipeline between the PSA unit and the primary stage membrane separator is further provided with a hydrogen purity analyzer, a pressure monitoring device, a flow monitoring device and a second compressor.

[0025] The present application has the following beneficial effects:

[0026] The present application adjusts the pressure of the permeation side of the primary stage membrane separator and adjusts the permeation gas concentration in time, so as to realize a relatively constant permeation gas concentration. Even if the amount of the permeation gas of the primary stage membrane separator is unstable, the hydrogen content is high and the concentration is stable. By monitoring the cumulative flow of the permeation gas of the primary stage membrane separator entering the PSA, the switching of the PSA time sequence can be realized, the hydrogen recovery rate in the PSA process is maximized, the subsequent multi-stage membrane separation further guarantees the hydrogen recovery rate, the hydrogen content of the non-permeation gas of the terminal stage membrane separation is low enough, the high hydrogen recovery rate is realized, in addition, the reverse gas discharged from the regeneration of the adsorption column is recycled for membrane separation, the hydrogen in the reverse gas is recovered, and the hydrogen recovery rate is further improved. Therefore, even for the mixed gas with the lowest hydrogen concentration of 10% and fluctuating flow and components, the recovery rate of more than 80% can be met. In the entire hydrogen recovery process of the mixed gas, the lost hydrogen is only the non-permeation gas discharged from the terminal stage membrane separation, and the hydrogen content in the non-permeation gas is 0.2-2%. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained without creative labor on the basis of these drawings.

[0028] Figure 1 The device structure diagram when the number of intermediate stage membrane separators is zero.

[0029] The drawings show that: 1, the first compressor; 2, the primary stage membrane separator; 3, the terminal stage membrane separator; 4, the hydrogen purity analyzer; 5, the pressure monitoring device; 6, the adjusting valve; 7, the second compressor; 8, the flow monitoring device; 9, the PSA unit. DETAILED DESCRIPTION

[0030] In the following, certain exemplary embodiments are simply described. As those skilled in the art can recognize, the described embodiments can be modified in various different ways without departing from the spirit or scope of the present invention. Therefore, the drawings and description are to be regarded as being illustrative in nature rather than restrictive.

[0031] Furthermore, the terms "first", "second", etc. are used only for descriptive purposes and should not be construed as implying or suggesting relative importance or an indicated number of technical features. Thus, features defined with "first", "second", etc. can explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "a plurality" is two or more, unless otherwise explicitly and specifically limited.

[0032] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0033] The present invention discloses a method for recovering hydrogen from mixed gas under variable working conditions. The main components of the mixed gas are nitrogen and hydrogen. The mixed gas is pretreated to remove impurities. The pretreatment is to pressurize, condense and adsorb the mixed gas to remove easily condensable substances such as chlorosilane and hydrogen chloride contained therein.

[0034] The hydrogen content in the mixed gas fluctuates rapidly between 5% and 80%, and the gas volume of the mixed gas changes rapidly between 10% and 100%. When the gas volume of the mixed gas is 100%, the maximum mixed gas processing capacity of the process is reached.

[0035] The pressure of the pretreated mixed gas is controlled to be 1.5-4 MPa, and then initial stage membrane separation is performed. The permeate side pressure in the initial stage membrane separation is 0.1-1 MPa. The permeate gas (mainly hydrogen, the same below) of the initial stage membrane separation is treated by PSA (pressure swing adsorption), and the product hydrogen with a purity of more than 99.9% can be obtained after the PSA adsorption process. The non-permeate gas (mainly nitrogen, the same below) of the initial stage membrane separation is output and subjected to terminal stage membrane separation. The initial stage membrane separation adjusts the permeate side pressure to adjust the permeate gas concentration in time, so that the permeate gas concentration is always relatively constant.

[0036] The permeate side pressure of the terminal stage membrane separation can be controlled to be -0.05-0.05 MPa, and the hydrogen content in the permeate gas changes between 10% and 50%. The permeate gas in the terminal stage membrane separation is sent back to become a component of the pretreated mixed gas, and then subjected to initial stage membrane separation. The non-permeate gas in the terminal stage membrane separation contains less than 2% of hydrogen and is discharged. When the hydrogen concentration in the permeate gas of the terminal stage membrane separation is low, it can also be directly discharged.

[0037] Before PSA treatment, the permeated gas of the initial stage membrane separation is pressurized to 0.8-2 MPa, the adsorption column of the PSA is switched in time according to the total gas flow, that is, the maximum capacity of nitrogen adsorption is determined according to the total gas flow, so that the adsorption column is regenerated and other adsorption columns are switched to continue adsorption, the reverse gas or vacuum air for regeneration of the adsorption column is sent back to become the pretreated mixed gas component, and then the initial stage membrane separation is performed.

[0038] One or more intermediate stage membrane separations can be performed between the initial stage membrane separation and the terminal stage membrane separation, the initial stage membrane separation, the intermediate stage membrane separation and the terminal stage membrane separation are performed in sequence, and the permeation side pressure is gradually reduced in each stage of membrane separation, and the hydrogen concentration of the permeated gas is gradually reduced, the non-permeated gas of the previous stage of membrane separation is sent to the subsequent stage of membrane separation, and the permeated gas of the intermediate stage membrane separation and the terminal stage membrane separation can be pressurized and sent to the inlet of any stage of membrane separation or discharged.

[0039] As shown in Figure 1 The application further discloses a device for recovering hydrogen from mixed gas under variable working conditions, which comprises a first compressor 1, an initial stage membrane separator 2 and a terminal stage membrane separator 3 which are sequentially connected, the first compressor 1 pressurizes the mixed gas of hydrogen and nitrogen and sends the mixed gas into the gas inlet pipeline of the initial stage membrane separator 2, the non-permeation side of the initial stage membrane separator 2 is connected with the gas inlet pipeline of the terminal stage membrane separator 3, and the non-permeation side of the terminal stage membrane separator 3 is connected with a discharge pipeline.

[0040] The permeation side pipeline of the initial stage membrane separator 2 is connected with a second compressor 7, the second compressor 7 is connected with a PSA unit 9, and the PSA unit 9 is further connected with the first compressor 1.

[0041] The PSA unit 9 comprises a plurality of parallel adsorption columns, and the adsorption columns are provided with adsorption fillers.

[0042] The pipeline, in which the second compressor 7 is connected with the PSA unit 9, is provided with a flow monitoring device 8, and the flow monitoring device 8 monitors the gas flow entering the PSA unit 9. The pipeline, in which the second compressor 7 is connected with the initial stage membrane separator 2, is provided with a hydrogen purity analyzer 4, a pressure monitoring device 5 and a regulating valve 6.

[0043] The permeation side of the terminal stage membrane separator 3 is connected with the pipeline of the first compressor 1, and the permeated gas of the terminal stage membrane separator 3 is pressurized by the first compressor 1 and then enters the gas inlet pipeline of the initial stage membrane separator 2.

[0044] One or more intermediate stage membrane separators can be arranged between the initial stage membrane separator 2 and the terminal stage membrane separator 3, the initial stage membrane separator 2, the intermediate stage membrane separator and the terminal stage membrane separator 3 are arranged in sequence, the non-permeation side of the former stage membrane separator is communicated with the gas inlet pipeline of the latter stage membrane separator, the permeation side of the intermediate stage membrane separator and the terminal stage membrane separator 3 is provided with a permeation gas pipe, the permeation gas pipe can be communicated with the gas inlet pipeline of any stage membrane separator or communicated with the outside.

[0045] The present application adjusts the pressure of the initial stage membrane separation permeation side and adjusts the permeation gas concentration in time, so that the permeation gas concentration is relatively constant, even if the permeation gas amount of the initial stage membrane separation is unstable, but the hydrogen content is high and the concentration is stable, by monitoring the cumulative flow of the initial stage membrane separation permeation gas entering the PSA, the switching of the PSA time sequence can be realized, the hydrogen recovery rate in the PSA process is maximized, the subsequent multi-stage membrane separation further guarantees the hydrogen recovery rate, so that the hydrogen content of the non-permeation gas of the terminal stage membrane separation is low enough, the high hydrogen recovery rate is realized, in addition, the reverse gas discharged by the regeneration of the adsorption column is recycled for membrane separation, the hydrogen in the reverse gas is recovered, the hydrogen recovery rate is further improved, therefore, even for the mixed gas with the lowest hydrogen concentration of 10% and fluctuating flow and components, the hydrogen recovery rate of more than 80% can be met, in the whole hydrogen recovery process of the mixed gas, the lost hydrogen is only the non-permeation gas discharged by the terminal stage membrane separation, the hydrogen content in the non-permeation gas is 0.2-2%.

[0046] The above embodiments are only the preferred embodiments of the present application, and are not the limitation of the technical solutions of the present application, as long as the technical solutions realized on the basis of the above embodiments without creative labor are considered to fall within the protection scope of the present application.

Claims

1. A method for recovering hydrogen from a mixed gas under varying conditions, characterized by, The method comprises the following steps: The mixed gas is pretreated to remove impurities; The pretreated mixed gas is subjected to multi-stage membrane separation, which comprises initial-stage membrane separation, any number of intermediate-stage membrane separations including zero, and terminal-stage membrane separation; In the multi-stage membrane separation, the non-permeated gas of the preceding stage is sent to the following stage, and the non-permeated gas of the terminal-stage membrane separation contains less than 2% hydrogen and is discharged; The permeated gas of the initial-stage membrane separation is subjected to PSA treatment to obtain product hydrogen, and the permeated gas of the intermediate-stage membrane separation and the terminal-stage membrane separation can be pressurized and sent to the inlet of any stage or discharged; The permeation side pressure of the initial-stage membrane separation is adjusted to adjust the concentration of the permeated gas of the initial-stage membrane separation, so that the concentration of the permeated gas tends to be constant; The adsorption column of the PSA is switched in time by using the cumulative gas flow method; The gases generated in the PSA regeneration, including reverse gas and suction vacuum gas, are sent back to become components of the pretreated mixed gas, and then subjected to initial-stage membrane separation.

2. The method of claim 1, wherein, The hydrogen content in the mixed gas fluctuates between 5% and 80%, the gas volume of the mixed gas changes between 10% and 100%, the pressure of the pretreated mixed gas is controlled between 1.5 MPa and 4 MPa, and the permeation side pressure of the initial-stage membrane separation is between 0.1 MPa and 1 MPa.

3. The method of claim 1, wherein the hydrogen is recovered from the mixed gas under multiple working conditions. Before PSA treatment, the permeated gas of the initial-stage membrane separation is pressurized to 0.8-2 MPa.

4. The method of claim 1, wherein, From the initial-stage membrane separation to the terminal-stage membrane separation, the permeation side pressure of each stage is gradually reduced, and the hydrogen concentration of the permeated gas is gradually reduced.

5. The method of claim 1, wherein the hydrogen is recovered from the mixed gas under multiple working conditions. The permeation side pressure of the terminal-stage membrane separation is controlled between -0.05 MPa and 0.05 MPa, and the hydrogen content in the permeated gas is between 10% and 50%.

6. A device for recovering hydrogen from a mixed gas under multiple working conditions, characterized by comprising: The method comprises the following steps: The initial-stage membrane separator, any number of intermediate-stage membrane separators including zero, and the terminal-stage membrane separator are sequentially arranged; The PSA unit is in communication with the permeation side pipeline of the initial-stage membrane separator; The non-permeated side of the preceding stage is in communication with the gas inlet pipeline of the following stage, and the permeated gas of the intermediate-stage membrane separator and the terminal-stage membrane separator can be pressurized and sent to the gas inlet pipeline of any stage or discharged; An adjusting valve is arranged on the pipeline between the PSA unit and the initial-stage membrane separator, and the PSA unit is in communication with the gas inlet pipeline of the initial-stage membrane separator; A hydrogen purity analyzer, a pressure monitoring device, a flow monitoring device, and a second compressor are further arranged on the pipeline between the PSA unit and the initial-stage membrane separator.

7. The apparatus for recovering hydrogen from a mixed gas under multiple working conditions according to claim 6, wherein, A first compressor is arranged before the initial-stage membrane separator, and the first compressor adjusts the pressure of the gas entering the initial-stage membrane separator.

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