CN112279217B - Separation device and method for synthesis gas - Google Patents
Separation device and method for synthesis gas Download PDFInfo
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- CN112279217B CN112279217B CN202011208045.XA CN202011208045A CN112279217B CN 112279217 B CN112279217 B CN 112279217B CN 202011208045 A CN202011208045 A CN 202011208045A CN 112279217 B CN112279217 B CN 112279217B
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- C01B3/00—Hydrogen; Gaseous mixtures containing hydrogen; Separation of hydrogen from mixtures containing it; Purification of hydrogen
- C01B3/50—Separation of hydrogen or hydrogen containing gases from gaseous mixtures, e.g. purification
- C01B3/52—Separation of hydrogen or hydrogen containing gases from gaseous mixtures, e.g. purification by contacting with liquids; Regeneration of used liquids
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- C10L3/00—Gaseous fuels; Natural gas; Synthetic natural gas obtained by processes not covered by subclass C10G, C10K; Liquefied petroleum gas
- C10L3/06—Natural gas; Synthetic natural gas obtained by processes not covered by C10G, C10K3/02 or C10K3/04
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- C01B2203/00—Integrated processes for the production of hydrogen or synthesis gas
- C01B2203/04—Integrated processes for the production of hydrogen or synthesis gas containing a purification step for the hydrogen or the synthesis gas
- C01B2203/0465—Composition of the impurity
- C01B2203/048—Composition of the impurity the impurity being an organic compound
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Abstract
The invention provides a separation device and a separation method for synthesis gas. The separation device of the synthesis gas comprises: the device comprises a first washing tower, a second washing tower, a flash tower, a first separation tower, a second separation tower, a first separation tank and a second separation tank; the first separation tank is respectively communicated with the first washing tower and the flash tower; the second separation tank is respectively communicated with the second washing tower and the flash tower; the first washing tower is communicated with the flash tower, the second washing tower is communicated with the flash tower, the flash tower is communicated with the first separation tower, the first separation tower is communicated with the second separation tower, the second separation tower is communicated with the first washing tower, and the first separation tower is communicated with the second washing tower. The invention also provides a separation method completed by the separation device, and the separation device and the method can simultaneously prepare an OXO product and pure H2And pure CO product, pure H2And the purity of the pure CO product can reach more than 99 v%.
Description
Technical Field
The invention relates to a separation device and a separation method, in particular to a separation device and a separation method for synthesis gas, and belongs to the technical field of gas separation.
Background
At present, the processes widely used for cryogenic separation of synthesis gas comprise a partial condensation process, a methane washing process, a carbon monoxide washing process and the like, but when the raw material synthesis gas contains H2、CO、CH4、N2When the components are equal, the processes are combined with other processes to prepare the OXO (H) simultaneously2And CO mixture), pure H2And pure CO.
The existing methods for treating synthesis gas mainly comprise the following methods:
example 1: and (4) partial condensation process. Such as coal water slurry or dry coal powder gasification, whether or not the raw synthesis gas contains CH4、N2The content of the component or the components is high or low, and pure H can not be directly obtained by the process2(99 v% +), H-rich2The partial pressure of the CO component in the gas is such that pure H is obtained directly2(99 v% +) requires cooling to a lower temperature, which is very expensive, and therefore the partially condensed reheat is usually H-rich2The gas is directly sent to a pressure swing adsorption unit for further purifying H2And then sent to the downstream user.
Example 2: and (3) methane washing process. If the tail gas generated by the steam reforming of the natural gas contains more CH4, the content of CH4 is required to be kept not too low for preparing pure H2 and pure CO, the content of CH4 in the raw material gas is not lower than 2.5 v%, otherwise, a methane washing process cannot be adopted, if a conversion gas is directly extracted and sent to a methanol synthesis device, the circulating gas quantity, the conversion rate and the like of the methanol synthesis can be directly influenced by the too high content of an inert component CH4, and an OXO product cannot be directly obtained from a cold box by the process.
Example 3: carbon monoxide washing process. No matter the synthesis gas produced by hydrocarbon steam conversion, partial oxidation or coal gasification can be separated by the process, but the products are usually OXO product and pure CO product (99 v% +), and the process can not directly obtain pure H from a cold box2And (5) producing the product.
The separation process of the synthesis gas, which is to prepare the synthesis gas by adopting natural gas or hydrocarbon conversion or hydrocarbon partial oxidation or fixed bed gasification technology and then prepare the ethanol by utilizing the synthesis gas, usually contains H2、CO、CH4、N2And (4) and the like.
Taking the partial oxidation of natural gas in the partial oxidation of hydrocarbons as an example, the contents of the main components in the synthesis gas are as follows:
H2＝65v％、CO＝28v％、C1＝6.5v％、N2＝0.45v％、AR＝0.10v％。
because the raw material synthesis gas contains more CH4The conventional cryogenic separation process cannot be the same as the conventional cryogenic separation processThen obtain OXO and pure H2Pure CO product, and pressure swing adsorption for preparing H2The unit can be implemented.
When the device scale is very large, the pressure swing adsorption is used for preparing H2The occupied area is huge, the system can not be arranged in a plant area with limited occupied area, and the system can be used for preparing H by pressure swing adsorption2The large scale of equipment, programmable valves, adsorbents, etc. makes the investment high and also makes the whole plant not economical.
Based on the above factors, it is necessary to design a reasonable synthesis gas separation process, which can simultaneously prepare an OXO product and pure H without adding too many devices2And pure CO products.
Disclosure of Invention
In order to solve the above technical problems, the present invention aims to provide a method for simultaneously preparing an OXO product and pure H2The product and the pure CO product, and a synthesis gas separation device of other further purification equipment is not required to be additionally arranged.
Another purpose of the invention is to provide a method for simultaneously preparing an OXO product and pure H2The product and the pure CO product, and the synthesis gas separation method has high efficiency.
In order to achieve any of the above objects, the present invention provides, in a first aspect, a separation apparatus for synthesis gas, comprising: a first washing tower, a second washing tower, a flash tower, a first separation tower and a second separation tower;
the first washing tower is communicated with the flash tower, the second washing tower is communicated with the flash tower, the flash tower is communicated with the first separation tower, the first separation tower is communicated with the second separation tower, the second separation tower is communicated with the first washing tower, and the first separation tower is communicated with the second washing tower.
The invention relates to a separation device of synthesis gas, belonging to a synthesis gas cryogenic separation double-washing process, comprising a synthesis gas cryogenic component adjusting and separating process, and capable of producing OXO and pure H simultaneously2And a pure CO product, wherein the synthesis gas is precooled to a certain temperature from the low-temperature plate-fin or wound-tube main heat exchanger and then enters a first washing tower and a second washing tower to respectively wash carbon monoxide and methane.
The separation device of the synthesis gas is arranged in the cold box. A second washing tower for washing methane is arranged in the cooling box, a first washing tower for washing carbon monoxide is additionally arranged at the same time, the synthesis gas respectively enters the two washing towers, and the two washing towers respectively prepare pure H2And OXO products; meanwhile, a flash tower is arranged in the cold box, the flash tower at least receives materials from two washing towers for gas-liquid separation, the two separation towers arranged in the subsequent working sections in the cold box are used for preparing pure CO, and the three gases after reheating can be directly used as products to be sent to downstream users.
In a specific embodiment of the present invention, the cold quantity supplement required by the cold box of the separation device of the present invention can be provided by refrigeration of a refrigeration compression cycle, and the refrigeration cycle can adopt a nitrogen cycle process and can also utilize a carbon monoxide cycle process.
In one embodiment of the present invention, the separation apparatus of the present invention further comprises a heat exchanger, and the raw syngas is divided into two or more streams at the hot end, middle part or cold section of the heat exchanger after entering the cold box, and the two or more streams enter the first scrubber and the second scrubber respectively. Wherein, the heat exchanger is respectively communicated with the first separation tank and the second separation tank.
In a specific embodiment of the invention, the separation apparatus further comprises a first separation tank and a second separation tank; wherein, the first separating tank is respectively communicated with the first washing tower and the flash tower; the second separation tank is respectively communicated with the second washing tower and the flash tower.
When the synthesis gas contains a gas-liquid two-phase, the synthesis gas can be subjected to gas-liquid separation through the first separation tank and the second separation tank. Wherein, the gas phase directly enters a first washing tower and a second washing tower, and the liquid phase is sent to a flash tower. Or directly entering the tower kettles of the first washing tower and the second washing tower to carry out gas-liquid separation in the tower kettles.
In the separation device of the present invention, the first scrubber is used for scrubbing (adsorbing) carbon monoxide. The first washing tower is filled with low-temperature carbon monoxide liquid and used as a tower top washing agent of the first washing tower to wash the ascending gas, and CH in the ascending gas4、N2Ar and CO are gradually washedAbsorbing with the agent until H in the OXO gas in the gas phase at the top of the tower2The proportion of the oxygen gas to the CO component and the impurity content meet the product specification requirement, and the OXO gas is reheated by a cold box heat exchanger and then sent to a product pipe network. The synthetic gas at the bottom of the first washing tower is cooled by a first intercooler and then enters a flash tower.
In the separation apparatus of the present invention, the second washing column is used for washing (adsorbing) methane. The second washing tower is filled with low-temperature methane liquid and used as a tower top washing agent of the second washing tower to wash the ascending gas, and CO and N in the ascending gas2Ar and CH4The components are gradually absorbed by the absorption detergent until pure H in the gas phase at the top of the tower2The impurity components in the product meet the product specification requirement, and the gas is reheated by the self-cooling box heat exchanger and then sent to a product pipe network. And the synthetic gas at the bottom of the second washing tower is cooled by a second intercooler and then enters the flash tower.
In the separation device, the liquid at the bottom of the first washing tower and the liquid at the bottom of the second washing tower are partially reheated and then sent to the flash tower for hydrogen desorption, so that the temperature of the top of the subsequent separation tower is stably controlled, the temperature of the top of the separation tower is reduced due to the high hydrogen content, and the energy consumption is increased.
Wherein, the inlet of the bottom liquid of the first washing tower entering the flash tower can be positioned at the upper part or the lower part of the inlet of the bottom liquid of the second washing tower entering the flash tower. If the CO yield needs to be improved, the inlet of the tower bottom liquid of the first washing tower into the flash tower needs to be arranged at the middle lower part of the flash tower, and the inlet of the tower bottom liquid of the second washing tower into the flash tower needs to be arranged at the middle upper part of the flash tower.
In a specific embodiment of the invention, a first intercooler is arranged in the first washing tower, a second intercooler is arranged in the second washing tower, and a first reboiler is arranged in the flash tower; a first condenser is arranged at the top of the first separation tower, and a second reboiler is arranged at the bottom of the first separation tower; a second condenser is arranged at the top of the second separation tower, and a third reboiler is arranged at the bottom of the second separation tower.
The first intercooler is used as a heat exchanger for removing the absorption heat and needs an external cold source for providing cold energy, and the external cold source canTo circulate CH4Or recycled CO liquid or liquid nitrogen. The second intercooler is used as a heat exchanger for removing the absorption heat and needs an external cold source for providing cold, and the external cold source can be a circulating CH4Or recycled CO liquid or liquid nitrogen. The first reboiler is used for removing the dissolved hydrogen component from the liquid at the bottom of the flash tower so as to reduce the load at the top of the subsequent separation tower and stabilize the temperature at the top of the subsequent separation tower. A second reboiler for separating CO and CH4And (3) removing CO components in the liquid methane, and purifying the liquid methane at the bottom of the first separation tower. A third reboiler for separating CO and N2Component (C) removing N in tower bottom liquid CO of the second separation tower2And (4) purifying CO.
In the separation device, part of the low-temperature carbon monoxide generated by the second separation tower is reheated by a cold box heat exchanger and sent to downstream users of the product CO after meeting the requirements of pure CO product pressure and impurity content; if necessary, the product CO can be pumped by a carbon monoxide compressor and pumped out of an interstage or final stage to a downstream user of the product CO.
In the separation device, part of the low-temperature methane generated by the first separation tower is reheated by the cold box heat exchanger and then sent to a raw material natural gas pipe network or a fuel gas pipe network, or is subcooled by the cold box heat exchanger and then sent to the LNG storage tank under reduced pressure.
In one embodiment of the invention, a first air pressure pump is arranged on a communication pipeline of the second separation tower and the first washing tower; and a second pneumatic pump is arranged on a communication pipeline of the first separation tower and the second washing tower.
The first air pressure pump is used for pressurizing carbon monoxide liquid flowing out of the bottom of the second separation tower, and the pressurized liquid-phase carbon monoxide enters the top of the first washing tower and is used as a carbon monoxide washing (adsorbing) agent of the first washing tower.
The second pneumatic pump is used for pressurizing methane liquid flowing out of the bottom of the first separation tower, and the pressurized liquid-phase methane enters the top of the second washing tower and is used as a methane washing (adsorbing) agent of the second washing tower.
In one embodiment of the invention, if some CO retention is desired in the OXO product2ComponentsWhen H is required in the synthesis gas, as required in a methanol synthesis plant2Mixed gas with CO in accordance with the stoichiometric coefficient (H)2-CO2)/(CO+CO2) 2.05-2.10, required CO2A by-pass gas can be introduced from an upstream matched decarburization process, and the by-pass gas does not enter the separation device of the invention, is directly mixed with the gas which is discharged from the cold box at the top of the first (carbon monoxide) scrubber and reheated, and then is sent to a downstream OXO user.
In one embodiment of the present invention, the acid gas or syngas decarbonization process can be performed by amine or low temperature methanol or pressure swing adsorption or other decarbonization process, and the by-pass gas is pumped from the lower portion of the upper portion of the scrubber/absorber or adsorber to retain a portion of the CO2Component (b) can also ensure H2S and other components which easily poison the downstream catalyst do not exceed the standard.
The invention also provides a separation method of the synthesis gas, which is completed by the separation device of the synthesis gas.
In one embodiment of the present invention, the separation method comprises:
feeding raw material synthesis gas into a first washing tower and a second washing tower respectively;
scrubbing CH in the ascending gas in a first scrubber4、N2Ar and CO, separating the tower top to obtain OXO gas, and introducing the liquid-phase synthesis gas at the tower bottom into a flash tower;
scrubbing CO and N in the rising gas in a second scrubbing tower2Ar and CH4(liquid methane from the bottom of the first separation tower enters from the top of the second washing tower, and CO and N in the synthesis gas entering from the bottom of the second washing tower are separated2Ar is directly washed and absorbed), pure H is obtained at the tower top2Sending the liquid-phase synthetic gas obtained at the bottom of the tower to a flash tower for flash dehydrogenation;
in the flash tower, the liquid phase synthesis gas at the bottom of the first washing tower and the second washing tower is decompressed and enters the flash tower from the middle part of the flash tower to be used as reflux liquid, the flash steam is discharged from the top of the flash tower, and the material flow at the bottom of the flash tower is sent to a first separation tower;
in a first separation tower, separating methane and carbon monoxide from the material flow at the bottom of a flash tower in the first separation tower, sending crude carbon monoxide gas obtained at the top of the first separation tower into a second separation tower, obtaining liquid-phase methane at the bottom of the first separation tower, directly collecting one part of the liquid-phase methane as LNG gas, and sending the other part of the liquid-phase methane into a second washing tower after pressurization to be used as circulating methane washing liquid;
in the second separation tower, crude carbon monoxide gas flowing out of the top of the first separation tower enters from the middle part of the second separation tower; the tower top reflux liquid is provided by total reflux after the ascending gas is liquefied, and the noncondensable gas in the ascending gas is directly collected; one stream of liquid-phase carbon monoxide at the bottom of the tower is pressurized and then sent to the top of the first washing tower to be used as a cold source at the top of the tower, the evaporated carbon monoxide is directly sent to the main heat exchanger to be reheated and then sent out of the cold box to obtain pure CO, and the other stream of liquid-phase carbon monoxide is pressurized and then sent to the top of the first separation tower to be used as a circulating carbon monoxide washing liquid.
In a specific embodiment of the invention, when the raw material synthesis gas has a gas-liquid two-phase state, the synthesis gas is subjected to gas-liquid separation through a first separation tank and a second separation tank, the gas phase enters a first washing tower and a second washing tower, and the liquid phase enters a flash tower;
preferably, the depressurized liquid-phase synthesis gas at the bottom of the first separation tank and the second separation tank enters the flash tower from the lower part of the flash tower as reflux liquid.
In one embodiment of the invention, the gas source pressure for the separation process is from 2.5MPaG to 3.5 MPaG.
In a particular embodiment of the invention, the operating temperature of the first scrubber is higher than-180 ℃; preferably, the operating temperature is from-175 ℃ to-165 ℃.
In a specific embodiment of the invention, the second scrubber is operated at a temperature above-180 ℃; preferably, the operating temperature is from-175 ℃ to-180 ℃.
In one embodiment of the invention, the raw synthesis gas is derived from synthesis gas containing hydrogen, carbon monoxide, methane produced by steam reforming of hydrocarbons, partial oxidation of hydrocarbons and fixed bed gasification. In particular to synthesis gas produced by methane steam conversion and acetylene tail gas produced by a device for producing acetylene by partial oxidation of natural gas.
The separation apparatus and separation method of synthesis gas of the present invention can be applied to a synthesis gas containing H2、CO、CH4、N2And (3) a separation process of the isocomponent synthesis gas. For example, the synthesis gas separation process is used for preparing the ethanol from the synthesis gas prepared by hydrocarbon steam conversion (natural gas or low-carbon hydrocarbon steam conversion) or hydrocarbon partial oxidation or fixed bed gasification technology.
The separation device and the method of the synthesis gas can simultaneously prepare the OXO product and the pure H2And pure CO product, pure H2And the purity of the pure CO product can reach more than 99v percent, and the pure CO product can completely meet the ethanol process or other chemical processes requiring the purity of the product.
The synthesis gas separation device can greatly simplify the configuration of the device, greatly reduce the number of synthesis gas separation equipment, has very compact floor area, and has smaller investment when the device has larger scale. For example, product demand:
OXO＝120000Nm3/h，(H2-CO2)/(CO+CO2)＝2.05-2.10
H2＝72000Nm3/h，99v％
CO＝40000Nm3/h，99v％
the conventional gas separation device can adopt a partial condensation process and pressure swing adsorption hydrogen production or membrane separation and pressure swing adsorption hydrogen production, but the investment is generally higher. The separation device and the method of the invention have the advantages that the investment of the device is similar to that of partial condensation process and pressure swing adsorption hydrogen production, the energy consumption is not greatly different, but the quantity of the device and the occupied area are greatly reduced.
Drawings
Fig. 1 is a schematic configuration diagram of a syngas separation apparatus in an embodiment of the present invention.
Description of the main figures:
t101, a carbon monoxide washing tower; t201, a methane washing tower; t202, a flash tower; t203, a methane/carbon monoxide separation tower; t204, a carbon monoxide/nitrogen separation tower; c101, a carbon monoxide washing tower intercooler; c201, a methane washing tower intercooler; c203, a methane/carbon monoxide separation column condenser; c204, a carbon monoxide/nitrogen separation tower condenser; b202, a flash tower reboiler; b203, a methane/carbon monoxide separation tower reboiler; b204, a carbon monoxide/nitrogen separation tower reboiler; v101, a first separation tank; v201, a second separation tank; p101, a carbon monoxide pump; p201 and a methane pump.
Detailed Description
The technical solutions of the present invention will be described in detail below in order to clearly understand the technical features, objects, and advantages of the present invention, but the present invention is not limited to the practical scope of the present invention.
Example 1
As shown in fig. 1, the present embodiment provides a separation apparatus of synthesis gas, which includes a carbon monoxide washing column T101, a methane washing column T201, a flash column T202, a methane/carbon monoxide separation column T203, a carbon monoxide/nitrogen separation column T204, a first separation tank V101, and a second separation tank V201.
Wherein, the carbon monoxide washing tower T101 is communicated with the flash tower T202, the methane washing tower T201 is communicated with the flash tower T202, the flash tower T202 is communicated with the methane/carbon monoxide separating tower T203, the methane/carbon monoxide separating tower T203 is communicated with the carbon monoxide/nitrogen separating tower T204, the carbon monoxide/nitrogen separating tower T204 is communicated with the carbon monoxide washing tower T101, and the methane/carbon monoxide separating tower T203 is communicated with the methane washing tower T201.
A carbon monoxide pump P101 is arranged on a communication pipeline for communicating the carbon monoxide/nitrogen separation tower T204 with the carbon monoxide washing tower T101; a methane pump P201 is arranged on a communication pipeline of the methane/carbon monoxide separation tower T203 and the methane washing tower T201.
A carbon monoxide washing tower intercooler C101 is arranged in the carbon monoxide washing tower T101, a methane washing tower intercooler C201 is arranged in the methane washing tower T201, and a flash tower reboiler B202 is arranged in the flash tower T202;
a methane/carbon monoxide separation column condenser C203 is provided at a top position in the methane/carbon monoxide separation column T203, and a methane/carbon monoxide separation column reboiler B203 is provided at a bottom position in the methane/carbon monoxide separation column T203;
a carbon monoxide/nitrogen separation column condenser C204 is provided at the top of the carbon monoxide/nitrogen separation column T204, and a carbon monoxide/nitrogen separation column reboiler B204 is provided at the bottom of the carbon monoxide/nitrogen separation column T204.
Wherein the first separation tank V101 is respectively communicated with a carbon monoxide washing tower T101 and a flash tower T202; the second separation tank V201 communicates with the methane wash column T201 and the flash column T202, respectively.
The embodiment also provides a separation method of the synthesis gas by using the separation device shown in fig. 1, which specifically comprises the following steps.
About 3.5MPaG of the raw syngas enters the cold box (not shown in FIG. 1) and is split at the hot end of the heat exchanger (not shown in FIG. 1) into two streams entering the first separation vessel V101 and the second separation vessel V201. Wherein the two discharges of the first separation tank V101 enter a carbon monoxide wash column T101 (gas phase) and a flash column T202 (liquid phase), respectively; the two discharge streams of the second separation tank V201 enter a methane washing tower T201 (gas phase) and a flash tower T202 (liquid phase) respectively, or directly enter a washing tower kettle to carry out gas-liquid separation in the tower kettle.
In a carbon monoxide washing tower T101, the synthesis gas rising from the bottom of the tower and a carbon monoxide liquid stream at about-170 ℃ entering from the top of the tower are in countercurrent contact, and after the mass transfer and the heat transfer are carried out step by step through each tower plate or filler, the CH in the synthesis gas is carried out by low-temperature CO4、N2And Ar and other components are absorbed to obtain OXO gas at the tower top, and the material flow is reheated by a heat exchanger and sent out of a cold box and directly sent to a product pipeline to a downstream OXO product user; such as a methanol synthesis unit. Liquid phase synthesis gas is obtained at the bottom of the tower, and the stream is decompressed by a valve and then sent to a flash tower T202 for flash dehydrogenation.
In the CO washing tower T101, an intercooler C101 of the CO washing tower is used as an external cold source for removing absorption heat, and a circulating CH can also be adopted4Or recycled CO liquid supply.
In a methane washing tower T201, liquid methane with the temperature of about-180 ℃ entering from the top of the tower is used for removing CO and N in the synthetic gas at the bottom of the tower2After the components such as Ar and the like are directly washed and absorbed, the purified pure H with the purity of more than 99v percent2Sent out from the top of the methane washing tower T201, and directly sent to a product pipeline to pure H at the downstream after being reheated by a heat exchanger and sent out of a cold box2And (5) a product user. And obtaining liquid-phase synthesis gas at the bottom of the tower, reducing the pressure through a valve, and sending the liquid-phase synthesis gas to a flash tower T202 for flash dehydrogenation.
In the methane washing tower T201, an intercooler C201 of the methane washing tower is used as an external cooling source for removing absorption heat, and circulating CH can also be adopted4Or recycled CO liquid supply.
In the flash tower T202, the liquid-phase synthesis gas decompressed at the bottoms of the carbon monoxide washing tower T101 and the methane washing tower T201 and the decompressed liquid-phase synthesis gas at the bottoms of the first separation tank V101 and the second separation tank V201 are taken as reflux liquid and respectively enter from the middle part and the lower part of the flash tower T202 (the load of a reboiler B202 of the flash tower can be reduced, partial cold energy is recycled through a throttling decompression part and a heat exchanger, and gas-liquid two phases enter the flash tower to save energy).
If the CO recovery rate is not strictly controlled, one part of the liquid-phase synthesis gas can be sent to the top of the flash tower, and the material flow at the top of the flash tower is finally used as the supplement OXO gas and sent to an OXO product pipe network after being reheated by a heat exchanger and sent out of a cold box.
The bottom stream of the flash column T202 may also be fed as a stream to a methane/carbon monoxide separation column T203 for separation of methane and carbon monoxide components. Crude carbon monoxide gas is obtained at the top of the methane/carbon monoxide separation tower T203, liquid-phase methane is obtained at the bottom of the tower, part of the gas is pressurized by a methane pump P201 and then used for circulating methane washing liquid in a methane washing tower, and the other part of the gas is sent out as by-product LNG as a cold box or as fuel gas after being reheated by a heat exchanger, and can also be returned to a hydrocarbon partial oxidation process raw material system or a fixed bed gasification pilot burner for use.
In the carbon monoxide/nitrogen separation tower T204, circulating carbon monoxide gas (introduced from the outside) and crude carbon monoxide gas (flowing out from the methane/carbon monoxide separation tower T203) respectively enter from the bottom and the middle of the tower, tower top reflux liquid is provided by total reflux after liquefaction of ascending gas, and non-condensable gas in the ascending gas is directly reheated by a heat exchanger and then is sent to a fuel gas or a flare system. One material flow after the liquid phase carbon monoxide at the bottom of the tower is extracted is used as a circulating washing liquid of the carbon monoxide washing tower T101, and is sent to the top of the carbon monoxide washing tower T101 after being pressurized by a carbon monoxide pump P101; and the other stream of carbon monoxide liquid is decompressed by a valve and then is sent into a shell of a thermosiphon heat exchanger at the top of the carbon monoxide/nitrogen separation tower T204 to be used as a cold source at the top of the tower, the evaporated carbon monoxide gas is directly sent to the heat exchanger for reheating and then is sent out of a cold box to be used as a pure CO product to be sent to downstream users, and part of the pure CO can also be used for circularly refrigerating and is sent to a carbon monoxide compressor for supercharging and circulating refrigeration.
The bottoms reboiling heat source for flash column T202, methane/carbon monoxide separation column T203, and carbon monoxide/nitrogen separation column T204 may be from circulating CO/circulating N2Raw material synthesis gas and the like; the cold source at the tower top can be circulated CO/circulated N2After liquefaction, specific embodiments are not further enumerated herein.
The heat exchange among the various material flows in the cold box needs to be completed in the low-temperature heat exchanger, the cold loss of the cold box can be supplemented by a carbon monoxide expander or a nitrogen expander or liquid nitrogen, and the part of the content is omitted in the figure 1.
1. The traditional partial condensation process can only obtain hydrogen-rich gas, generally H2The purity is about 85 v%, the purity of carbon monoxide is about 97 v% -99 v%, and OXO (H) can also be obtained2And CO mixtures) the purity can be adjusted.
2. The traditional methane washing process can only obtain hydrogen-rich gas, generally H2Purity of 93 v% -97 v% or 99 v% at most, pure carbon monoxide, CO purity of 97 v% -99 v% in general, and pure or methane-rich, 85 v% -92 v%, but no OXO product (H) is obtained2And CO mixtures).
The separating device of the embodiment can simultaneously obtain an OXO product and pure H2Product and pure CO product, and hydrogen canDirectly to H299 v% of the component, 99 v% of the CO component, the OXO gas OXO product, H2The ratio of/CO can be adjusted, and the gas demand of three gases is completely met. For example, the ethanol device requires gas consumption, the process configuration is simple, and the separation equipment is arranged in the cold box. And a pressure swing adsorption hydrogen purification facility arranged at the downstream of the partial condensation or methane washing process is not required to be arranged. The pressure swing adsorption usually occupies a large area, and when the gas amount is large, the occupied area is large, while the cold box is very compact, and even if the amount of the circulating compressor is increased, the occupied area is basically unchanged.
Claims (7)
1. A syngas separation plant, comprising: the device comprises a first washing tower, a second washing tower, a flash tower, a first separation tower, a second separation tower, a first separation tank and a second separation tank;
the first washing tower is communicated with the flash tower, the second washing tower is communicated with the flash tower, the flash tower is communicated with the first separation tower, the first separation tower is communicated with the second separation tower, the second separation tower is communicated with the first washing tower, the first separation tower is communicated with the second washing tower, the first separation tank is respectively communicated with the first washing tower and the flash tower, and the second separation tank is respectively communicated with the second washing tower and the flash tower;
the first scrubber is a CO scrubber, the second scrubber is a methane scrubber, the first separation tower is a methane/carbon monoxide separation tower, and the second separation tower is a carbon monoxide/nitrogen separation tower.
2. The separation device of claim 1, further comprising a cold box for providing a cryogenic environment for the separation device.
3. The separation device according to claim 1, wherein a first pneumatic pump is arranged on a communication pipeline of the second separation tower and the first washing tower; and a second pneumatic pump is arranged on a communication pipeline of the first separation tower and the second washing tower.
4. The separation device of claim 1 wherein a first intercooler is disposed in the first scrubber, a second intercooler is disposed in the second scrubber, and a first reboiler is disposed in the flash column.
5. The separation device according to claim 1, wherein a first condenser is provided at a top position in the first separation column, and a second reboiler is provided at a bottom position in the first separation column.
6. The separation apparatus according to claim 1, wherein a second condenser is provided at a top position in the second separation column, and a third reboiler is provided at a bottom position in the second separation column.
7. A process for the separation of synthesis gas by a synthesis gas separation apparatus according to any one of claims 1 to 6; the separation method comprises the following steps:
carrying out gas-liquid separation on the raw material synthesis gas through a first separation tank and a second separation tank, enabling a gas phase to enter a first washing tower and a second washing tower, and enabling a liquid phase to enter a flash tower as reflux liquid to enter the flash tower from the upper part of the flash tower;
the raw material synthesis gas is synthesis gas containing hydrogen, carbon monoxide and methane generated by hydrocarbon steam reforming, hydrocarbon partial oxidation and fixed bed gasification; the air source pressure is 2.5MPaG-3.5 MPaG; scrubbing CH in the ascending gas in a first scrubber4、N2Ar and CO, separating the tower top to obtain OXO gas, and introducing the liquid-phase synthesis gas at the tower bottom into a flash tower; the operating temperature of the first scrubber is from-175 ℃ to-165 ℃;
scrubbing CO and N in the rising gas in a second scrubbing tower2Ar and CH4Pure H is obtained at the top of the tower2Sending the liquid-phase synthetic gas obtained at the bottom of the tower to a flash tower for flash dehydrogenation; the operating temperature of the second scrubber is from-175 ℃ to-180 ℃;
in the flash tower, the liquid phase synthesis gas at the bottom of the first washing tower and the second washing tower is decompressed and enters the flash tower from the middle part of the flash tower to be used as reflux liquid, the flash steam is discharged from the top of the flash tower, and the material flow at the bottom of the flash tower is sent to a first separation tower;
in a first separation tower, separating methane and carbon monoxide from the material flow at the bottom of a flash tower in the first separation tower, sending crude carbon monoxide gas obtained at the top of the first separation tower into a second separation tower, obtaining liquid-phase methane at the bottom of the first separation tower, directly collecting one part of the liquid-phase methane as LNG gas, and sending the other part of the liquid-phase methane into a second washing tower after pressurization to be used as circulating methane washing liquid;
in the second separation tower, crude carbon monoxide gas flowing out of the top of the first separation tower enters from the middle part of the second separation tower; the tower top reflux liquid is provided by total reflux after the ascending gas is liquefied, and the noncondensable gas in the ascending gas is directly collected; one stream of liquid-phase carbon monoxide at the bottom of the tower is pressurized and then sent to the top of the first washing tower to be used as a cold source at the top of the tower, the evaporated carbon monoxide is directly sent to the main heat exchanger to be reheated and then sent out of the cold box to obtain pure CO, and the other stream of liquid-phase carbon monoxide is pressurized and then sent to the top of the first separation tower to be used as a circulating carbon monoxide washing liquid.
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