CN-114073882-B - Process technology and device for simultaneously recycling hydrogen, methane and other gases from petrochemical exhaust tail gas

CN114073882BCN 114073882 BCN114073882 BCN 114073882BCN-114073882-B

Abstract

The invention relates to a process technology and a device for simultaneously recycling various gases such as hydrogen, methane and the like from petrochemical exhaust tail gas. The volume percentage of hydrogen in the tail gas is 28-55%, the volume percentage of hydrocarbon in the tail gas is 30-56%, and the process technology uses a vacuum pressure swing adsorption-pressure swing adsorption composite integrated device, and comprises (a) a hydrocarbon gas-vacuum pressure swing adsorption stage for separating hydrocarbon gas product gas from the tail gas and generating intermediate gas by using a vacuum pressure swing adsorption device, and (b) a hydrogen gas-pressure swing adsorption stage for separating hydrogen gas product gas from the intermediate gas generated in the step (a) by using a pressure swing adsorption device. The process technology can simultaneously produce high-purity hydrogen, hydrocarbon gas and carbon-rich fuel gas with higher heating value.

Inventors

LIU MINGSHENG
XIAO YUEZHU
XUE DING
LIU MINGSHENG
WU BINBIN
SUN XUEFENG
LIU SHUANGMIN
JIA SHUJUN

Assignees

戴莫尔科技有限公司
天津联博化工股份有限公司

Dates

Publication Date: 20260508
Application Date: 20200820

Claims (13)

1. The process for simultaneously recovering hydrogen and hydrocarbon gas from petrochemical exhaust tail gas is characterized in that the volume percentage of hydrogen in the tail gas is 28% -55%, the volume percentage of hydrocarbon gas in the tail gas is 30% -56%, the pressure of the tail gas is 5-600kPa in gauge pressure, and the process uses a vacuum pressure swing adsorption-pressure swing adsorption composite integrated device, and comprises the following steps: (a) A hydrocarbon gas-vacuum pressure swing adsorption stage of separating a hydrocarbon gas product gas from the tail gas and producing an intermediate gas using a vacuum pressure swing adsorption unit; (b) A hydrogen-pressure swing adsorption stage of separating a hydrogen product gas from the intermediate gas produced in step (a) using a pressure swing adsorption apparatus; Wherein, the The tail gas is not subjected to compression treatment before being adsorbed in the hydrocarbon gas-vacuum pressure swing adsorption stage, the hydrocarbon gas-vacuum pressure swing adsorption stage recovers hydrocarbon gas product gas through a desorption step, the hydrocarbon gas-vacuum pressure swing adsorption stage comprises a light reflux step after the desorption step, the vacuum pressure swing adsorption device comprises more than two vacuum pressure swing adsorption device adsorption towers filled with a first adsorbent and circularly operates in a coupling mode, and the pressure swing adsorption device comprises more than four pressure swing adsorption device adsorption towers filled with a second adsorbent and circularly operates in a coupling mode; The hydrocarbon gas-vacuum pressure swing adsorption stage comprises: a-1) feeding and adsorbing, namely, enabling the tail gas to enter a first adsorption tower from the bottom of the tower, enabling the hydrocarbon gas to be adsorbed by an adsorbent in the first adsorption tower, and converting the tail gas into an intermediate gas of hydrocarbon-lean and hydrogen-rich gas; a-2) a first concurrent decompression step of stopping the tail gas from entering the first adsorption tower, opening the connection between the first adsorption tower and the top of the adsorption tower or an intermediate gas buffer tank for carrying out a light reflux step or a countercurrent pressurization step, and enabling the intermediate gas to enter the adsorption tower or the intermediate gas buffer tank for carrying out the light reflux step or the countercurrent pressurization step; a-3) a second concurrent decompression step of closing the connection between the first adsorption tower and the top of the adsorption tower or the intermediate gas buffer tank which is used for carrying out the light reflux step or the countercurrent pressurization step in the step a-2), opening the connection between the first adsorption tower and the intermediate gas buffer tank or the top of the other adsorption tower which is used for carrying out the light reflux step or the countercurrent pressurization step, and leading the exhaust gas to enter the adsorption tower or the intermediate gas buffer tank which is used for carrying out the light reflux step or the countercurrent pressurization step; a-4) a desorption step of closing the connection between the first adsorption tower and the top or middle gas buffer tank of the adsorption tower performing the light reflux step or the countercurrent pressurization step in the step a-3), connecting the first adsorption tower with a hydrocarbon product gas tank, then starting a vacuum pump, and recovering hydrocarbon gas product gas to the hydrocarbon product gas tank, wherein the pressure in the adsorption tower in the desorption step is 10-50 kPa in absolute pressure; a-5) a light reflux step, namely, maintaining the communication of a vacuum pump, and communicating the top of the first adsorption tower with an intermediate gas buffer tank or the top of an adsorption tower subjected to a first or second concurrent decompression step, wherein hydrocarbon-lean hydrogen-rich gas in the adsorption tower subjected to the intermediate gas buffer tank or the concurrent decompression step enters the first adsorption tower; a-6) a countercurrent pressurization step, namely closing the communication of a vacuum pump, and communicating the top of the first adsorption tower with the top of the adsorption tower in the first or second concurrent depressurization step so as to equalize the pressure of the first adsorption tower and other adsorption towers; a-7) a repressurization step of introducing a gas lift column pressure in the off-gas or the intermediate gas buffer tank to the first adsorption column; a-8) repeating the above steps; Wherein at least a portion of the gas in the intermediate gas buffer tank enters the hydrogen-pressure swing adsorption stage, and when the first adsorption column is connected to the intermediate gas buffer tank in step a-2), the first adsorption column is not connected to the intermediate gas buffer tank in step a-3); the ratio of the duration of the light reflux step to the duration of the repressurization step is between 1:6 and 1:8.
2. The process according to claim 1, wherein the tail gas is a tail gas of a petrochemical refinery alkane olefin recovery treatment device.
3. The process according to claim 2, wherein the hydrocarbon olefin recovery processing unit is a C2 hydrocarbon pressure swing adsorption system.
4. The process of claim 1 wherein the tail gas comprises hydrogen, oxygen, nitrogen, carbon monoxide, hydrocarbon gases and water.
5. The process of claim 1, wherein the adsorbent in the feed adsorption step is selected from the group consisting of activated carbon, activated alumina, zeolite A, zeolite X, zeolite Y, a metal-organic framework material, silica gel, and combinations thereof.
6. The process according to claim 1, wherein the pressure in the adsorption column of the feed adsorption step is 5 to 600kPa gauge pressure and the temperature of the tail gas is less than 60 ℃.
7. The process of claim 5, wherein the ratio of the duration of the feed adsorption step to the duration of the first concurrent depressurization step or counter-current pressurization step is between 3:1 and 3:2.
8. The process of claim 1 wherein the hydrocarbon gas-vacuum pressure swing adsorption stage further comprises a hydrocarbon product gas purge step, the hydrocarbon product gas purge step being between steps a-2) and a-3).
9. The process of claim 8 wherein the ratio of the duration of the feed adsorption step to the duration of the first forward pressure reduction step or reverse pressure pressurization step is between 3:1 and 3:2, the ratio of the duration of the hydrocarbon gas product gas purge step to the duration of the desorption step is between 1:4 and 1:8, and the ratio of the duration of the light reflux step to the duration of the repressurization step is between 1:6 and 1:8.
10. The process of claim 1, wherein the hydrogen in the intermediate gas produced in the hydrocarbon gas-vacuum pressure swing adsorption stage has a purity of 88% to 99%.
11. The process of claim 1, wherein said intermediate gas is compressed to a gauge pressure of 10-24 bar for said hydrogen-pressure swing adsorption stage.
12. An apparatus for carrying out the process for simultaneously recovering hydrogen and hydrocarbon gases from petrochemical tail gas as claimed in any one of claims 1 to 11, said apparatus being a vacuum pressure swing adsorption-pressure swing adsorption composite integrated apparatus comprising a hydrocarbon gas-vacuum pressure swing adsorption apparatus for separating a hydrocarbon gas product gas from the tail gas and producing an intermediate gas of hydrocarbon-lean hydrogen-rich gas, and a hydrogen-pressure swing adsorption apparatus for separating a hydrogen product gas from said intermediate gas, wherein, The hydrocarbon gas-vacuum pressure swing adsorption device comprises an exhaust buffer tank, more than two vacuum pressure swing adsorption device adsorption towers, a first program control valve group, a vacuum pump and a first pipeline system, wherein the first program control valve group comprises a first air inlet valve, a first air outlet valve, a first tower top valve and a first tower bottom valve, the first pipeline system comprises an exhaust pipeline, an intermediate gas outlet pipeline, a first communication pipeline, a first exhaust pipeline and a hydrocarbon product gas pipeline, a first adsorbent is placed in each vacuum pressure swing adsorption device adsorption tower, a first splitter plate is arranged at the bottom of each vacuum pressure swing adsorption device adsorption tower, and each vacuum pressure swing adsorption device adsorption tower circularly operates in a coupling mode; The hydrogen-pressure swing adsorption device comprises an intermediate gas compressor, an intermediate gas buffer tank, more than four pressure swing adsorption device adsorption towers, a second program control valve group and a second pipeline system, wherein the second program control valve group comprises a second air inlet valve, a second air outlet valve, a second tower top valve and a second tower bottom valve, the second pipeline system comprises an intermediate gas inlet pipeline, a second waste gas pipeline and a hydrogen product gas pipeline, a second adsorbent is placed in each pressure swing adsorption device adsorption tower, a second flow dividing plate is arranged at the bottoms of the pressure swing adsorption device adsorption towers, and the pressure swing adsorption device adsorption towers are circularly operated in a coupling mode; In the hydrocarbon gas-vacuum pressure swing adsorption device, one end of the tail gas buffer tank is connected with a tail gas pipeline, the other end of the tail gas buffer tank is connected with the bottom of the adsorption tower of the vacuum pressure swing adsorption device through the first air inlet valve, in the feeding adsorption step, the tail gas enters the adsorption tower of the vacuum pressure swing adsorption device from the tail gas buffer tank through the bottom of the adsorption tower of the vacuum pressure swing adsorption device without compression treatment, the hydrocarbon gas is adsorbed by the first adsorbent in the adsorption tower of the vacuum pressure swing adsorption device, and the tail gas is converted into hydrocarbon-lean hydrogen-rich gas, and the top of each adsorption tower of the vacuum pressure swing adsorption device is connected with the bottom of the adsorption tower through the intermediate gas exhaust pipeline, the first exhaust valve, The intermediate gas compressor is connected with the intermediate gas buffer tank and used for recovering intermediate gas and balancing the pressure in the vacuum pressure swing adsorption device adsorption towers in a forward flow decompression step or a reverse flow pressurization step, the tops of the vacuum pressure swing adsorption device adsorption towers are mutually communicated through the first tower top valve, the gas between the vacuum pressure swing adsorption device adsorption towers flows mutually through controlling the first tower top valve, in the forward flow decompression step, the first air inlet valve is closed, the tail gas is stopped from entering the vacuum pressure swing adsorption device adsorption towers, the first tower top valve at the tops of the vacuum pressure swing adsorption device adsorption towers and the first tower top valve at the tops of the vacuum pressure swing adsorption device adsorption towers are opened, the lean hydrocarbon rich hydrogen gas in the vacuum pressure swing adsorption device adsorption towers is discharged from the tops of the vacuum pressure swing adsorption device adsorption towers into the other vacuum pressure swing adsorption device adsorption towers, the pressure of the vacuum pressure swing adsorption device adsorption towers is balanced through controlling the first tower top valve, in the reverse flow pressurization step, the first tower top valve at the bottoms of the vacuum pressure swing adsorption device is closed, the vacuum pressure swing adsorption device is kept to be in the vacuum pressure swing adsorption device top of the vacuum adsorption towers and the other vacuum pressure swing adsorption device adsorption towers, the first vacuum pressure swing adsorption device is kept in the top pressure swing adsorption device is in the pressure swing adsorption device top of the vacuum adsorption device is balanced, and the other vacuum pressure swing adsorption device is in the top pressure swing adsorption device is in the pressure swing adsorption device, the top pressure swing adsorption device is in the vacuum device, the hydrocarbon-lean and hydrogen-rich gas enters the adsorption towers of the vacuum pressure swing adsorption devices from the adsorption towers of other vacuum pressure swing adsorption devices so as to increase the pressure of the adsorption towers, and the bottom of each adsorption tower of the vacuum pressure swing adsorption device is connected with the gas inlet through the first tower bottom valve, The vacuum pump is communicated with the hydrocarbon product gas pipeline, in the desorption step, a first tower top valve at the top of the vacuum pressure swing adsorption device adsorption tower is closed, a first tower bottom valve at the bottom of the vacuum pressure swing adsorption device adsorption tower is opened, the vacuum pressure swing adsorption device adsorption tower is communicated with the hydrocarbon product gas pipeline, and then the vacuum pump is opened to recover hydrocarbon product gas; In the hydrogen-pressure swing adsorption device, one end of the intermediate gas compressor is connected with the intermediate gas discharge pipeline, the other end of the intermediate gas compressor is connected with the intermediate gas buffer tank, one end of the intermediate gas buffer tank is connected with the intermediate gas compressor, the other end of the intermediate gas buffer tank is connected with the bottom of the pressure swing adsorption device adsorption tower through the second air inlet valve, the top of each pressure swing adsorption device adsorption tower is connected with a hydrogen product gas pipeline through the second air outlet valve and is communicated with other pressure swing adsorption device adsorption towers through the second tower top valve, and the bottom of each pressure swing adsorption device adsorption tower is connected with the intermediate gas buffer tank through the second air inlet valve and is communicated with the second waste gas pipeline through the second tower bottom valve.
13. The apparatus of claim 12, wherein the first adsorbent is selected from one of activated carbon, activated alumina, zeolite a, zeolite X, zeolite Y, metal-organic framework material, silica gel, or a combination thereof.

Description

Process technology and device for simultaneously recycling hydrogen, methane and other gases from petrochemical exhaust tail gas Technical Field The invention relates to the field of tail gas separation and recovery, in particular to a process technology and a device for simultaneously recovering various gases such as hydrogen, methane and the like from petrochemical exhaust tail gas. Background The petrochemical industry consumes large amounts of hydrogen for hydrogen reforming, hydrocracking, oil and gas hydrogenation, and other processes. Since the early 80 s, pressure swing adsorption was proposed to be applied to synthesis gas separation, methane steam reforming and coal-to-synthesis gas reforming have become the main hydrogen production methods in the petrochemical industry. Meanwhile, petrochemical industry daily needs to produce or process large amounts of industrial effluent gases or off-gases containing hydrogen and carbon (such as methane (CH 4), carbon dioxide (CO 2), etc.), such as methane steam reforming hydrogen production off-gases, cracked dry gases, hydrogen production off-gases, and flare gases, etc. These off-gases contain a considerable amount of hydrogen, which is typically burned in a burner to provide heat. However, hydrogen (H 2) as a high value added energy carrier and chemical product should produce more economic benefits than simple combustion heat recovery. In addition, it is well known that the combustion of tail gases to produce significant amounts of CO 2,CO2 is a major greenhouse gas that can lead to climate change and global warming. Thus, the recovery of hydrogen and carbon-containing gases from petrochemical tail gas is both environmentally and economically beneficial. The world is currently in transition to low carbon emissions and many countries are or have evolved carbon tax/carbon trading plans to reduce carbon emissions and increase energy efficiency. Many techniques including cryocondensation, liquid absorption, solid adsorption, and membrane processes have been developed and used in response to various gas separation/purification requirements, but they all have their own advantages and disadvantages. Pressure swing adsorption/vacuum pressure swing adsorption (PSA/VSA) technology has been applied in many cases in different forms due to its recognized energy consumption advantages and compact material handling processes. When using these cyclic adsorption techniques, a raw material gas containing CH 4、CO2 and other gases is passed through a fixed/moving bed packed with an adsorbent material to adsorb gases such as CH 4/CO2/nitrogen (N 2)/water (H 2 O) onto the adsorbent. The carbon or hydrocarbon rich gas is produced by a depressurization process while producing an H 2 rich gas at the other end of the adsorption column. In these gas separation processes, the prior art typically employs a multistage compressor to pressurize the tail gas to a high pressure of 8-24 bar gauge and then begin the separation. High pressure PSA systems are commonly used to recover/remove carbonaceous component gases. In addition, some other process flows also use the off-gas from the high pressure water gas shift reaction unit as a feed gas in the high pressure PSA system to obtain H 2 -rich gas that is stripped of carbon-or hydrocarbon-containing gas prior to delivery to standard hydrogen PSA equipment to produce high purity hydrogen. For example, U.S. patent application 2010/0287981 A1 describes a process for recovery of H 2 and CO 2 in a steam reforming system. The target gas in the invention is a water gas shift product. After recovery of H 2 using conventional hydrogen PSA, the tail gas is compressed to a pressure and sent to a PSA system and/or membrane system for recovery of the carbonaceous or hydrocarbon components. However, no examples are disclosed in this invention, nor are specific procedures (cycles) or detailed performance. Likewise, in U.S. patent application US 2008/0074152 A1, a VPSA and PSA based process flow is used to separate CO 2 and H 2. The treatment objective of these prior art processes is the effluent gas after the water gas shift reaction. DIMER in australian patent AU2016201267, a highly efficient VSA/PSA coupling technology was developed to simultaneously capture and separate hydrogen from the tail gas of a methane steam reforming hydrogen production system of a petrochemical refinery process (which contains mainly about 31% hydrogen and 49.8% carbon dioxide). The technology can simultaneously produce 96% -99% purity CO 2 and 99.99% high purity H 2. U.S. patent application 2011/0011128 A1 describes a process for recovering carbon dioxide and hydrogen from a steam reforming unit. CO-feed/CO-purge is used in the PSA unit to produce high concentrations of CO 2, while producing high purity H 2 product. In addition, this patent application describes a conceptual CO 2 clean-up. The chinese patent of invention zl00132036.X, incorporated by reference, uses VPSA technol