CN111559736B - Low-temperature separation synthesis gas preparation H2Method and device for gas and CO gas - Google Patents
Low-temperature separation synthesis gas preparation H2Method and device for gas and CO gas Download PDFInfo
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- CN111559736B CN111559736B CN202010435096.XA CN202010435096A CN111559736B CN 111559736 B CN111559736 B CN 111559736B CN 202010435096 A CN202010435096 A CN 202010435096A CN 111559736 B CN111559736 B CN 111559736B
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
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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
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- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
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- C01B2203/046—Purification by cryogenic separation
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Abstract
The invention discloses a method for preparing H by low-temperature separation of synthesis gas2Gas and CO gas method and apparatus. The method for separating the synthesis gas at the low temperature comprises the steps of firstly, separating a first gas phase and a first liquid phase from a raw material gas under the conditions that the pressure is 2.4-5.9 MPa and the temperature is not lower than-182 ℃; step two, separating out H-rich from the first liquid phase2A second gas phase and a second liquid phase; step three, separating a third gas phase rich in CO and high-purity CH from the second liquid phase under the conditions that the pressure is 0.3-0.5 MPa and the temperature is-174 to-182 DEG C4A third liquid phase of (a); said third liquid phase portion is recycled back to steps one and two; the temperature at the bottom of the tower is 20-40 ℃ higher than that at the top of the tower; and step four, separating the third gas phase under the conditions that the separation pressure is 0.4-0.5 MPa and the temperature is-184-179 ℃ to obtain a fourth gas phase and CO gas. The invention can improve the purity and yield of CO and obtain high-purity H2The effect of qi.
Description
Technical Field
The invention relates to the field of chemical industry, in particular to a device for low-temperature separation of synthesis gas and preparation of H by adopting the low-temperature separation of the synthesis gas2Gas and CO gas.
Background
The synthesis gas uses carbon monoxide and hydrogen as main components and is mostly used as chemical raw material gas. The raw material of the synthesis gas is widely selected, can be generated by gasifying solid raw materials such as coal or coke, can be prepared from light hydrocarbons such as natural gas and naphtha, and can be produced by heavy oil through a partial oxidation method; in terms of synthesis gas production, the composition (in vol%) of the finally obtained synthesis gas differs greatly with respect to the above different feedstocks and processes, but essentially falls within the following ranges: h2 32～67、CO 10～57、CO2 2～28、CH4 0.1～25、N2 0.6～23。
The synthesis gas has many uses, such as synthesis of ammonia, and can also be used for producing methanol, glycol, formic acid, oxalic acid, acetic acid, phosgene and the like. However, no matter what kind of substance is used for synthesis, the composition purity and the proportion of the synthesis gas directly prepared from the raw materials cannot meet the requirements of subsequent synthesis products, and therefore, the synthesis gas needs to be further adjusted. The prior art discloses the use of shift reactions to adjust the hydrogen to carbon ratio and then the purification of the gas to remove sulfur (H)2S, COS), decarburization (CO)2) And further high concentrations of H are obtained respectively2、 CO、CH4Or high-purity synthesis gas with a certain hydrogen-carbon ratio, and finally, respectively utilizing the prepared various gases to synthesize subsequent products. The CO gas is the core raw material for developing one-carbon chemistry, such as low-carbon alcohol and high-carbon alcohol produced by oxo synthesis, phosgene and its derivatives (TDI, MDI), ethylene glycol, acetic acid, carbonate and the like.
At present, there are many methods for separating CO from purified syngas, including cryogenic separation, membrane separation, pressure swing adsorption, and the like. Currently, the cryogenic separation method is most commonly used, and usually H2The low-temperature separation of the CO component mainly adopts a low-temperature condensation method to directly obtain low-temperature condensate (CO-rich liquid) and non-condensable gas (H-rich gas containing about 10 percent of CO component)2A gas); then the CO-rich liquid is processed for dehydrogenation, demethanization and denitrification to obtain a high-purity CO gas product rich in H2The gas is directly sent out after reheating. H-rich separated by conventional condensation separation process2The gas contains a large amount of CO gas (not less than 10%), because part of CO in the raw material gas is enriched in H2The gas is carried away from the condensation separation step, resulting in a lower yield of CO actually separated in the condensation separation step. In addition to obtaining high purity H2Gas and CO yield are improved, and H enrichment is realized through a pressure swing adsorption device2H in gas2And (3) completely separating CO, wherein the obtained CO-rich normal pressure gas is pressurized and recycled to the raw material gas of the low-temperature separation device.
Disclosure of Invention
The invention aims to solve the problems that the yield of CO separated by the existing condensation separation technology is not high and high-purity H cannot be obtained2The problem of (2); the invention provides a low-temperature separation method capable of effectively improving the yield of separated CO and discloses a separation system suitable for the method.
Low-temperature separation synthesis gas preparation H2A process for gas and CO gas comprising:
firstly, pre-cooling raw material gas to obtain low-temperature condensate and low-temperature non-condensable gas, wherein the low-temperature non-condensable gas is used for obtaining first gas under the conditions that the pressure is 2.2-5.9 MPa and the temperature is not lower than-182 DEG CA phase and a first liquid phase; the specific separation process is as follows: pre-cooling and partially condensing the feed gas to obtain low-temperature condensate and non-condensable gas, adding the non-condensable gas from the bottom of a hydrogen separation tower, controlling the pressure of the hydrogen separation tower to be 2.4-5.9 MPa, controlling the temperature of the top of the hydrogen separation tower to be not lower than-182 ℃, controlling the temperature of the bottom of the hydrogen separation tower to be 1-9 ℃ higher than that of the top of the hydrogen separation tower, and simultaneously circulating the high-purity CH back in the third step4The third liquid is subjected to washing mass transfer treatment relative to the non-condensable gas, and a first gas phase (overhead gas of high-purity H2) and a first liquid phase (kettle liquid with dissolved hydrogen) are separated from the hydrogen separation tower;
step two, separating H-rich from the low-temperature condensate and the first liquid phase2Second gas phase of gas and dehydrogenated2The separation pressure is about one third of the feed gas pressure;
step three, separating a third gas phase rich in CO and high-purity CH from the second liquid phase under the conditions that the pressure is 0.2-0.5 MPa and the temperature is-174 to-182 DEG C4A third liquid phase of (a); and the third liquid phase part is recycled to the first step and the second step. The third liquid phase can be taken as a liquid product to be extracted after being cooled to about minus 160 ℃, and can also enter a fuel gas system after being reheated;
and step four, separating the third gas phase under the conditions that the separation pressure is 0.4-0.5 MPa and the temperature is-179-184 ℃ to obtain a fourth gas phase and high-purity CO gas.
The third gas phase is at CO/N2Separation in a separation column, CO/N2The temperature of the bottom of the separation tower is 4-15 ℃ higher than that of the top of the separation tower. Preferably, CO/N2The temperature of the top of the separation tower is-179 to-184 ℃, and the temperature of the bottom of the separation tower is 4 to 8 ℃ higher than that of the top of the separation tower; or, preferably, CO/N2The temperature of the bottom of the separation tower is 10-15 ℃ higher than that of the top of the separation tower.
The process requires CH in the feed gas4The volume percentage content of the (B) is not less than 1.3 percent.
When CH is contained in raw material gas4When the volume percentage of the methane in the feed gas is less than 1.3 percent, the methane is supplemented into the feed gas until the volume percentage of the methane in the feed gas reaches more than 1.3 percent.
And (3) separating the low-temperature non-condensable gas in the first step by using a hydrogen separation tower. Gas enters from the bottom of the tower, third liquid-phase supercooling return liquid is used as cold reflux, and the temperature of the top of the tower is-179 to-182 ℃; preferably, the temperature at the top of the tower is-180 to-182 ℃, and the temperature at the bottom of the tower is 5 to 17 ℃ higher than that at the top of the tower.
And the low-temperature condensate and the first liquid phase in which the hydrogen component is dissolved in the second step are subjected to light component separation by adopting a flash tower, and the third liquid phase supercooling return liquid is used as cold reflux. The pressure in the flash tower is 1-2 MPa (generally about one third of the pressure of the raw material gas), and the temperature at the top of the tower is-168 to-180 ℃; preferably, the temperature of the top of the flash tower is-175 to-180 ℃, and the temperature of the bottom of the flash tower is 25 to 40 ℃ higher than that of the top of the flash tower.
The second liquid phase in the third step adopts CH4/CO separation column for CH4And separation of CO, said CH4The pressure in the/CO separation tower is 0.4-0.5 MPa, the temperature at the top of the tower is-175-180 ℃, and the temperature at the bottom of the tower is 20-40 ℃ higher than that at the top of the tower, preferably 30-40 ℃.
And the second gas phase is reheated and pressurized and then returns to the feed gas.
The invention application technology formed by the main technical steps further comprises facilities and systems for reheating CO gas, compressing circulation, precooling, condensing and expanding refrigeration, which are arranged for supporting realization of low-temperature energy transfer and conversion among the steps of the low-temperature system. The facilities and the systems are all the existing facilities and systems, and detailed description is omitted in the invention. The technology also supports the production of LNG products, and an MRC mixed refrigerant refrigerating system is required to be additionally arranged in a device with the LNG products to supplement cold energy to the device. This is the inseparable part that supports the inventive technique.
The process of the present invention is applicable to synthesis gas obtained from various feedstocks and processes, such as partially shifted and unshifted synthesis gas produced by fixed bed gasification, fluidized bed gasification, dry powder entrained flow water wall gasification, coal water slurry entrained flow hot wall gasification, coal water slurry entrained flow gasification, and the like, including but not limited to coke oven gas.
Low-temperature separation synthesis gas preparation H2A gas and CO gas plant comprising: sequential communication of hydrogenSeparation column, flash column, CH4CO separation column and N2A CO separation column; the CH4The liquid outlet of the/CO separation tower is communicated with the hydrogen separation tower and the flash tower through a return pipeline.
The gas outlet of the flash column is communicated with the feed gas inlet of the plant, i.e. with the feed gas inlet of the hydrogen separation column, via a compressor.
The technical scheme of the invention has the following advantages:
1. the invention discloses a method for preparing H by low-temperature separation of synthesis gas2The method for separating the gas and the CO gas adopts different separation temperature and pressure combination modes, and realizes the main gas component H in the raw material gas by setting the pressure and the temperature in different reaction towers2、CO、CH4The separation is carried out efficiently to the maximum extent. Most importantly, the third liquid phase part is quantitatively returned to the hydrogen separation tower and the flash tower through ingenious arrangement, cold energy is directly provided for the second tower, reverse mass transfer separation is carried out, and high-purity H is directly obtained2Gas and achievement H2The components are fully recovered, and the requirement of directly providing high-purity hydrogen to a downstream device is met. Tests show that H is in the first gas phase2The purity of the components can be not less than 99.0 percent, and the yield is not less than 99.0 percent. And simultaneously, the yield of CO is effectively ensured to be not lower than 90 percent and even reach 99 percent. The method disclosed by the invention can be suitable for separating various synthesis gases, and the application range is wider.
2. The method provided by the invention can obtain high-purity H2The gas obtained after the separation of the raw material gas can be directly used for the requirements of the subsequent ammonia synthesis process and the hydrogenation process, so that an SPA device is omitted, the cost is saved, the process is greatly simplified, and the production efficiency is greatly improved. Simultaneously eliminates CO and H richly produced in the PSA desorption process2The tail gas recycling system further simplifies the overall equipment investment of the factory.
3. The invention further discloses a corresponding device which comprises a hydrogen separation tower, a flash tower and CH4CO separation column and N2Combined arrangement of/CO separation columns for separating a first gaseous phase of high-purity hydrogen from a hydrogen separation column and for dissolving the hydrogenA first liquid phase with hydrogen, a second gas phase rich in hydrogen and concentrated CO and CH from the flash tower4A second liquid phase of the component and from CH4Separating a third gas phase rich in CO (or high-purity CO) and high-purity CH in a CO separation column4A third liquid phase of (a); the device of the invention realizes the production of high-purity hydrogen (H) in the same cold box environment2Concentration is more than 98.8 percent), high-purity LNG and high-purity CO gas, and the yield of each effective component is improved to more than 99 percent.
Detailed Description
The following examples are provided to further understand the present invention, not to limit the scope of the present invention, but to provide the best mode, not to limit the content and the protection scope of the present invention, and any product similar or similar to the present invention, which is obtained by combining the present invention with other prior art features, falls within the protection scope of the present invention.
Example 1
Low-temperature separation synthesis gas preparation H2A process for gas and CO gas comprising:
step one, the flow rate is 39765.0NM3And (3) feeding the HR purified feed gas into a low-temperature cold box, pre-cooling and partially condensing to obtain low-temperature condensate and non-condensable gas, and introducing the non-condensable gas into the bottom of the hydrogen separation tower. Controlling the pressure of the hydrogen separation tower to be 5.42MPa, the temperature of the top of the hydrogen separation tower to be-181 ℃, controlling the temperature of the bottom of the hydrogen separation tower to be 14-16 ℃ higher than that of the top of the hydrogen separation tower, and simultaneously performing CH separation in the third step4High-purity CH recycled from/CO separation tower4The third liquid of (2) is treated with respect to the non-condensable gas, and the first gas phase of high-purity hydrogen and the first liquid phase of dissolved hydrogen can be separated from the hydrogen separation column. The raw material gas in the case is purified synthesis gas provided by a coal water slurry gasification furnace, and the pressure is 5.51 MPa. The composition (mole percentage) is as follows: h246.7% of CO, 52.6% of CO, CH40.1% of N20.4% and Ar 0.2%. The composition of the first gas phase obtained from the hydrogen separation column is shown in Table 1, and the first gas phase can be directly used as H2The gas product can be used for standby, or can be directly used for preparing ammonia synthesis gas for subsequent ammonia synthesisTo equal, in this example H2The discharge flow rate of the gas product is 18708.1NM3/HR。
Step two, introducing the low-temperature condensate and the first liquid phase into a flash tower, and separating a second gas phase rich in hydrogen and CO and CH from the flash tower4、N2、H2An isocomponent second liquid phase; the flow rate of the second gas phase is 3647.0NM3and/HR. In the step, the pressure in the flash tower is controlled to be 1.93MPa, the temperature of the top of the flash tower is-177.6 ℃, and the temperature of the bottom of the flash tower is controlled to be 28-30 ℃ higher than that of the top of the flash tower. Wherein the second gas phase is returned to the feed gas of step one. Since the methane content in this step is lower than 1.3%, in this embodiment, the purchased natural gas is supplemented, the purchased natural gas is pretreated to obtain pure methane gas before the supplementation, then the second gas phase is returned to the step one, and simultaneously the pure methane gas and the second gas phase are returned to the step one, and the pure methane gas is added at a flow rate of 425.8NM3HR, the methane volume content in the supplemented gas is higher than 1.3%.
Step three, introducing the second liquid phase into CH4/CO separation column from CH4Separating CO-rich third gas phase and high-purity CH in CO separation column4A third liquid phase of (a); returning the third liquid phase part to the hydrogen separation tower in the step one and the flash tower in the step two to respectively wash the first gas phase and the second gas phase, and separating the rest to obtain CH4Drainage as CH4The flow rate of the third liquid phase of the discharged liquid is 315.6NM3HR, CH in the third liquid phase4The molar purity of (a) was 99.4%. Control of CH in this step4The pressure of the/CO separation column was 0.43MPa, CH4The temperature of the top of the CO separation tower is-176 ℃, and CH is controlled4The temperature at the bottom of the column in the CO separation column is 36 ℃ higher than that at the top of the column. Also, the temperature of the third liquid phase returned to the hydrogen separation column and the flash column in this step was controlled to-178.5 ℃. Wherein the flow rate of the third gas phase is 21167.2NM3/HR。
Step four, introducing the third gas phase into CO/N2The pressure in the separation tower is 0.40MPa, the temperature at the top of the tower is-182.2 ℃, and the temperature at the bottom of the tower is 4 to E higher than the temperature at the top of the towerFurther separation is carried out at the temperature of 6 ℃, and the molar concentration of 99.5 percent and the flow rate of 20861.5NM can be effectively separated3HR CO product gas at a flow rate of 305.7 NM3The fourth gas phase of/HR (N-rich)2Tail gas, into the fuel gas system).
If CH is discharged in this embodiment4Gas circulation is to system benefit CH4According to the normal production requirement of component balance, the natural gas is only needed to be supplemented by 93.63NM3HR (pure methane gas). As a result of the detection, the compositions (mole percentages) of the respective substances detected as being discharged after returning the third liquid phase to the hydrogen separation column are shown in table 1.
TABLE 1
| First gas phase | Second gaseous phase | Third gas phase | The fourth gas phase | CO product gas | |
| H2 | 99.0844 | 98.2979 | 0.1671 | 11.5742 | 0 |
| N2 | 0.0473 | 0.0004 | 0.7754 | 38.0294 | 0.2296 |
| CO | 0.0005 | 0.0392 | 98.7698 | 50.3963 | 99.4784 |
| Ar | 0 | 0 | 0.2777 | 0.0002 | 0.2817 |
| CH4 | 0.8678 | 1.6624 | 0.0100 | 0 | 0.0102 |
The hydrogen and CO yields in this example were calculated. Wherein, the hydrogen yield (%) (hydrogen concentration in the first gas phase · flow rate of the first gas phase)/(hydrogen concentration in the feed gas · feed gas flow rate of the feed gas) · 100%; CO yield (%) — (CO concentration of CO product gas · flow of CO product gas)/(CO concentration in feed gas · feed flow of feed gas) · 100%.
The yield of hydrogen and CO in this example was found to be 99.81% and 99.25% by calculation.
Example 2
Low-temperature separation synthesis gas preparation H2A process for gas and CO gas comprising:
step one, the flow rate is 49871.1NM3And (3) introducing the/HR purified water into a low-temperature cold box, precooling and partially condensing to obtain low-temperature condensate and non-condensable gas, and introducing the non-condensable gas into the bottom of the hydrogen separation tower. Controlling the pressure of the hydrogen separation tower to be 3.36MPa, the temperature of the top of the hydrogen separation tower to be-181 ℃, controlling the temperature of the bottom of the hydrogen separation tower to be 10-12 ℃ higher than that of the top of the hydrogen separation tower, and simultaneously performing CH separation in the third step4High-purity CH recycled from/CO separation tower4The third liquid is treated relative to the non-condensable gas, so that a first gas phase of high-purity hydrogen and a first liquid phase in which hydrogen is dissolved can be separated from the hydrogen separation tower; this case is a coke-oven plant for the production of H2The gas and CO gas are used for hydrogenation, oxo synthesis and other devices, and are gasified to produce gas by using pulverized coal and crushed coke, and the pressure of the raw material gas is 3.46 MPa. The feed gas comprises the following specific components in percentage by mole: h245.9% of CO, 53.5% of CO, CH40.1% of N20.4% and Ar 0.1%. The composition of the first gaseous phase obtained from the hydrogen separation column is shown in Table 1, and the first gaseous phase can be directly discharged as H2The gas product is ready for use, or can be directly used for preparing ammonia synthesis gas for subsequent ammonia synthesis and the like, in the embodiment, H2The gas product flow rate is 23056.4NM3/HR。
Step two, introducing the low-temperature condensate and the first liquid phase into a flash tower, and separating a second gas phase rich in hydrogen and CO and CH from the flash tower4、N2、H2An isocomponent second liquid phase; the flow rate of the second gas phase is 2968.4NM3and/HR. In the step, the pressure in the flash tower is controlled to be 1.13MPa, the temperature of the top of the flash tower is controlled to be-177.7 ℃, and the temperature of the bottom of the flash tower is controlled to be 33-35 ℃ higher than that of the top of the flash tower. Wherein the second gas phase is returned to the feed gas of step one. Since the content of methane in this step is less than 1.3%, in this embodiment, the purchased natural gas is supplemented, the purchased natural gas is pretreated to obtain pure methane gas before the supplementation, and then the pure methane gas is returned to the first step while the second gas phase is returned to the first stepReturning to the first step together with the second gas phase, wherein the pure methane gas is added at 425.9NM3HR, the methane volume content in the supplemented gas is higher than 1.3%.
Step three, introducing the second liquid phase into CH4/CO separation column from CH4Separating CO-rich third gas phase and high-purity CH in CO separation column4A third liquid phase of (a); returning the third liquid phase part to the hydrogen separation tower in the step one and the flash tower in the step two to respectively wash the first gas phase and the second gas phase, and separating the rest to obtain CH4Drainage as CH4The flow rate of the third liquid phase of the discharged liquid is 230.5NM3HR, CH in the third liquid phase4The molar purity of (a) was 99.4%. Control of CH in this step4The pressure of the/CO separation column was 0.43MPa, CH4The temperature of the top of the CO separation tower is-176 ℃, and CH is controlled4The temperature of the bottom of the tower in the/CO separation tower is 35-36 ℃ higher than that of the top of the tower. Also, the temperature of the third liquid phase returned to the hydrogen separation column and the flash column in this step was controlled to-178.5 ℃. Wherein the flow rate of the third gas phase is 27010.1NM3/HR。
Step four, introducing the third gas phase into CO/N2The further separation is carried out in the separation tower under the conditions that the pressure is 0.45MPa, the temperature at the top of the tower is-182.0 ℃, and the temperature at the bottom of the tower is 4-6 ℃ higher than the temperature at the top of the tower, so that the effective separation can be carried out, the molar concentration is 99.4%, the flow rate is 26652.0NM3HR CO product gas with a flow rate of 358.1NM3A fourth gas phase of/HR (N2 rich tail gas, into the fuel gas system).
If CH is discharged in this embodiment4Gas circulation is to system benefit CH4According to the normal production requirement of the component balance, the external natural gas supplement only needs 205.65NM3HR (pure methane gas). As a result of the detection, the compositions (mole percentages) of the respective substances detected as discharged after returning the third liquid phase to the hydrogen separation column are shown in table 2.
TABLE 2
| First gas phase | Second gaseous phase | Third gas phase | The fourth gas phase | CO product gas | |
| H2 | 99.0411 | 98.3116 | 0.1523 | 11.4873 | 0 |
| N2 | 0.0346 | 0.0014 | 0.6809 | 35.3618 | 0.2151 |
| CO | 0.0005 | 0.0389 | 98.7435 | 53.1507 | 99.3559 |
| Ar | 0 | 0 | 0.2733 | 0.0002 | 0.2769 |
| CH4 | 0.9238 | 1.6481 | 0.1500 | 0 | 0.1521 |
The hydrogen and CO yields in this example were calculated. Wherein, the hydrogen yield (%) (hydrogen concentration in the first gas phase · flow rate of the first gas phase)/(hydrogen concentration in the feed gas · feed gas flow rate of the feed gas) · 100%; CO yield (%) — (CO concentration of CO product gas · flow of CO product gas)/(CO concentration in feed gas · feed flow of feed gas) · 100%.
The yield of hydrogen and CO in this example was found to be 99.82% and 99.28% by calculation.
Example 3
Low-temperature separation synthesis gas preparation H2A process for gas and CO gas comprising:
step one, the flow rate is 158742.2NM3Feeding HR raw material gas into a low-temperature cold box, pre-cooling and partially condensing to obtain low-temperature condensate and non-condensable gas, introducing the non-condensable gas into the bottom of a hydrogen separation tower, controlling the pressure of the hydrogen separation tower to be 2.36MPa, controlling the temperature of the top of the hydrogen separation tower to be-181 ℃, controlling the temperature of the bottom of the hydrogen separation tower to be 7-9 ℃ higher than that of the top of the hydrogen separation tower, and simultaneously performing CH condensation in the third step4High-purity CH recycled from/CO separation tower4The third liquid is treated relative to the non-condensable gas, so that a first gas phase of high-purity hydrogen and a first liquid phase in which hydrogen is dissolved can be separated from the hydrogen separation tower; wherein, the raw material gas for purification entering the low-temperature cold box uses the mixed clean of the Lurgi gasifier generated gas and the coke oven gasGasifying gas under the pressure of 2.43 MPa. The specific composition (mole percentage) of the feed gas is as follows: h255.9% of CO, 27.6% of CH414.8% of N21.4%, Ar0.2%, C2H6Is 0.1%. The composition of the discharged first gas phase is shown in Table 1, and the discharged first gas phase can be directly discharged as H2The gas product is ready for use, or can be directly used for preparing ammonia synthesis gas for subsequent ammonia synthesis and the like, in the embodiment, H2The discharge flow rate of the gas product is 89559.2NM3/HR。
Step two, introducing the low-temperature condensate and the first liquid phase into a flash tower, and separating a second gas phase rich in hydrogen and CO and CH from the flash tower4、N2、H2An isocomponent second liquid phase; the flow rate of the second gas phase is 4056.0NM3and/HR. In the step, the pressure in the flash tower is controlled to be 1.17MPa, the temperature of the top of the flash tower is controlled to be-179.2 ℃, and the temperature of the bottom of the flash tower is controlled to be 28-30 ℃ higher than that of the top of the flash tower. Wherein the second gas phase is returned to the feed gas of step one.
Step three, introducing the second liquid phase into CH4/CO separation column from CH4Separating CO-rich third gas phase and high-purity CH in CO separation column4A third liquid phase of (a); returning the third liquid phase part to the hydrogen separation tower in the step one and the flash tower in the step two to respectively wash the first gas phase and the second gas phase, and supercooling the rest part to-160 ℃ to be used as an LNG product, wherein the flow rate of the third liquid phase as the LNG product is 22885.5 NM3HR, CH in the third liquid phase4The molar purity of (a) was 98.5%. Control of CH in this step4The pressure of the/CO separation column was 0.44MPa, CH4The temperature of the top of the CO separation tower is-176 ℃, and CH is controlled4The temperature at the bottom of the column in the CO-separation column is 39 ℃ higher than at the top of the column. Also, the temperature of the third liquid phase returned to the hydrogen separation column and the flash column in this step was controlled to-161.5 ℃. Wherein the flow rate of the third gas phase is 64118.7NM3/HR。
Step four, introducing the third gas phase into CO/N2In the separation tower, the pressure is 0.40MPa, the temperature at the top of the tower is-181.4 ℃, and the temperature at the bottom of the tower is 4-6 ℃ higher than the temperature at the top of the towerFurther separation is carried out under the condition that the molar concentration is 98.3 percent and the flow rate is 42298.1NM3CO product gas/HR, and a flow rate of 3222.5NM3A fourth gas phase of/HR (N2 rich tail gas, into the fuel gas system).
As a result of the detection, the compositions (mole percentages) of the respective substances detected as discharged after returning the third liquid phase to the hydrogen separation column are shown in table 3.
TABLE 3
The hydrogen, methane and CO yields in this example were calculated. Wherein, the hydrogen yield (%) (hydrogen concentration in the first gas phase · flow rate of the first gas phase)/(hydrogen concentration in the feed gas · feed gas flow rate of the feed gas) · 100%; methane yield (%) (methane and C in LNG product)2H6Is used as the flow rate of the LNG product)/(methane and C in the feed gas2H6Concentration x inlet flow rate of feed gas) 100%; CO yield (%) — (CO concentration of CO product gas · flow of CO product gas)/(CO concentration in feed gas · feed flow of feed gas) · 100%.
The yield of hydrogen, methane and CO in this example was 99.90%, 96.04% and 94.88%, respectively, as determined by calculation. This example is due to N in the feed gas2The component concentration is higher, the CO yield is lower, but the CO yield can still reach more than 90 percent.
All the data show that the concentration of the hydrogen separated by the method can be higher than 99%, the yield of the separated hydrogen is higher than 99%, the yield of the methane and the CO can reach the effect of simultaneously being higher than 90%, and the effect is very obvious.
In various embodiments of the present invention, the raw material gas used includes, but is not limited to, gas generated by gasifying coal or coal water slurry, such as coke oven gas, lurgi furnace gas, and german gas.
Taking coke oven gas as an example, the gas composition of the coke oven gas comprises 50-62% of hydrogen, 20-28% of methane, 3-9% of carbon monoxide and 1-5% of C2The unsaturated hydrocarbon, 0.5 to 5 percent of carbon dioxide, 0.1 to 1.0 percent of oxygen and 2 to 8 percent of nitrogen. Note that this gas is not suitable as a feed gas for CO gas production alone, but may be blended in proportions to supplement other gasification syngas feeds to supplement deficiencies in H2, CH4, etc.
Taking Lurgi furnace gas as an example, the gas composition of the Lurgi furnace gas is 32-43% of hydrogen, 8-15% of methane, 10-20% of carbon monoxide, 0.1-1.3% of hydrocarbons and 29-36% of carbon dioxide.
Taking Texaco gas as an example, the gas composition of the Texaco gas is 33-40% of hydrogen, 42-51% of carbon monoxide, less than 0.2% of methane and 13-23% of carbon dioxide. When the Texaco gas is adopted, because the content of methane is lower, when the method is adopted for separation, the natural gas can be used for supplementing methane in the raw material gas, so that the volume content of methane is higher than 1.3 percent.
There are pulverized coal gasification gas and the like, and detailed description thereof is omitted.
Example 4
Low-temperature separation synthesis gas preparation H2A process for gas and CO gas comprising:
step one, the flow rate is 135128NM3And (3) introducing the HR purified gas into a low-temperature cold box, precooling and partially condensing to obtain low-temperature condensate and non-condensable gas, and introducing the non-condensable gas into the bottom of the hydrogen separation tower. Controlling the pressure of the hydrogen separation tower to be 3.80MPa, the temperature of the top of the hydrogen separation tower to be-181 ℃, controlling the temperature of the bottom of the hydrogen separation tower to be 10-12 ℃ higher than that of the top of the hydrogen separation tower, and simultaneously performing CH separation in the third step4High-purity CH recycled from/CO separation tower4The third liquid is subjected to a washing treatment with respect to the non-condensable gas, thereby making it possible to separate a first gas phase of high-purity hydrogen and a first liquid phase in which a hydrogen component is dissolved from the hydrogen separation column; in the case, the mixed gas of pulverized coal gasified gas and semi-coke gas is used as the raw material gas to prepare hydrogen and CO gas for a large-scale ethylene glycol device, and the pressure of the feeding purified gas is 3.80 MPa. Specific group of the raw material gasThe composition (mol percentage) is: h251.47% of CO, 46.74% of CH41.07% and the balance of N2And Ar. The composition of the first gaseous phase obtained from the hydrogen separation column is shown in Table 1, and the first gaseous phase can be directly discharged as H2Gas product, H in this example, for standby2The gas product flow rate is 70124 NM3/HR。
Step two, introducing the low-temperature condensate and the first liquid phase into a flash tower, and separating a second gas phase rich in hydrogen and CO and CH from the flash tower4、N2、H2And aliquoted as a second liquid phase. In the step, the pressure in the flash tower is controlled to be 1.23MPa, the temperature of the top of the flash tower is controlled to be-177.7 ℃, and the temperature of the bottom of the flash tower is controlled to be 33-35 ℃ higher than that of the top of the flash tower. Wherein the second gas phase is returned to the feed gas of step one.
Step three, introducing the second liquid phase into CH4/CO separation column from CH4Separating a third gas phase rich in CO and high-purity CH from the CO separation column4A third liquid phase of components; returning part of the third liquid phase to the hydrogen separation tower in the step one and the flash tower in the step two to respectively wash the first gas phase and the second gas phase, and taking the rest part of the third liquid phase as high-purity CH4Discharge, CH in the third liquid phase4The molar purity of (a) was 99.40%. Control of CH in this step4The pressure of the/CO separation column was 0.43MPa, CH4The temperature of the top of the CO separation tower is-176 ℃, and CH is controlled4The temperature of the bottom of the tower in the/CO separation tower is 35-36 ℃ higher than that of the top of the tower. Also, the temperature of the third liquid phase returned to the hydrogen separation column and the flash column in this step was controlled to-178.5 ℃. Wherein the flow rate of the third gas phase is 96029NM3/HR。
Step four, introducing the third gas phase into CO/N2The further separation is carried out in the separation tower under the conditions that the pressure is 0.45MPa, the temperature at the top of the tower is-182.0 ℃, and the temperature at the bottom of the tower is 4-6 ℃ higher than the temperature at the top of the tower, so that the molar concentration of 99.22 percent and the flow rate of 63136NM can be effectively separated3HR CO product gas with a flow rate of 1151 NM3The fourth gas phase of/HR (N-rich)2Tail gas, into the fuel gas system).
In this exampleCH in material-purified gas4The component concentration was 1.0653%, and no natural gas was added to the system during actual operation.
As a result of the detection, the composition (mole percentage) of each of the substances detected as being discharged after returning the third liquid phase to the hydrogen separation column and the flash column is shown in table 4.
TABLE 4
| First gas phase | Second gaseous phase | Third gas phase | The fourth gas phase | CO product gas | |
| H2 | 99.0515 | 98.0515 | 0.0967 | 8.0739 | 0.0000 |
| N2 | 0.0473 | 0.0056 | 0.8281 | 46.7405 | 0.2814 |
| CO | 0.0005 | 0.0393 | 98.5678 | 45.1855 | 99.2152 |
| Ar | 0 | 0.0000 | 0.3474 | 0.0001 | 0.3515 |
| CH4 | 0.9001 | 1.6655 | 0.1500 | 0 | 0.1518 |
The hydrogen, and CO yields in this example were calculated. Wherein, the hydrogen yield (%) (hydrogen concentration in the first gas phase · flow rate of the first gas phase)/(hydrogen concentration in the feed gas · feed gas flow rate of the feed gas) · 100%; CO yield (%) — (CO concentration of CO product gas · flow of CO product gas)/(CO concentration in feed gas · feed flow of feed gas) · 100%.
The yield of hydrogen in this example was 99.87% and the yield of CO was 99.17% by calculation.
Example 5
This example provides a cryogenic separation of syngas to produce H suitable for use in examples 1-4 above2A system for a gas and CO gas process comprising an existing hydrogen separation column, a flash column, CH, in serial communication4CO separation column and N2a/CO separation column. In the case of the present case where CH4the/CO separation column uses CO recycle as overhead cold wash.
The system of the present invention is distinguished from the existing systems in that the CH is4The liquid outlet of the/CO separation tower is communicated with the hydrogen separation tower and the flash tower through a return pipeline, and at the moment, the third liquid phase returns to the hydrogen separation tower through the return pipeline to wash the first gas phase, and the third liquid phase also returns to the flash tower through the return pipeline to wash the second gas phase. To obtain high purity hydrogen (first gas phase) and increase system H2Recovery of components, reduction of system H2And (4) loss.
The gas outlet of the flash tower is communicated with the raw material gas inlet of the hydrogen separation tower by adopting a circulating compressor, and the second gas phase is returned to the position of the raw material gas and enters the hydrogen separation tower together with the raw material gas for separation.
The invention adopts the CO compressor and the CO gas circulation system, and the arrangement effectively connects the cold energy of different grades generated and needed by each mass transfer unit in series, thereby realizing the sufficient cold energy conversion and transmission and greatly reducing the consumption of the cold energy.
It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications therefrom are within the scope of the invention.
Claims (8)
1. Low-temperature separation synthesis gas preparation H2 A method for producing gas and CO gas, comprising:
pre-cooling raw materials to obtain low-temperature condensate and low-temperature non-condensable gas, wherein the non-condensable gas is separated into a first gas phase and a first liquid phase under the conditions that the pressure is 2.4-5.9 MPa and the temperature is not lower than-182 ℃;
step two, separating rich liquid from the low-temperature condensate and the first liquid phase obtained in the step two under set conditionsH2Second gas phase of gas and dehydrogenated2A second liquid phase of (a); the second gas phase is returned to the feed gas after being pressurized; separating the low-temperature condensate and the first liquid phase by adopting a flash tower, wherein the pressure in the flash tower is 1-2 MPa, and the temperature at the top of the tower is-175 to-180 ℃;
step three, adopting CH as the second liquid phase4 /CO separation column for CH4And separation of CO, said CH4 The pressure in the/CO separation tower is 0.3-0.5 MPa, the temperature at the top of the tower is-174 to-182 ℃, the temperature at the bottom of the tower is 20-40 ℃ higher than that at the top of the tower, and CH is4 CO separation in a CO separation column4A third liquid phase of (a); said third liquid phase portion is recycled back to steps one and two;
and step four, separating the third gas phase under the conditions that the separation pressure is 0.4-0.5 MPa and the temperature is-184-179 ℃ to obtain a fourth gas phase and CO gas.
2. The cryogenic separation of syngas to produce H according to claim 12Process for the production of gas and CO gas, characterized in that the third gaseous phase is in CO/N2Separation in a separation column, CO/N2The temperature of the bottom of the separation tower is 4-15 ℃ higher than that of the top of the separation tower.
3. The cryogenic separation of syngas to produce H according to claim 12The method for preparing gas and CO gas is characterized in that CH in the raw material gas4The volume percentage content of the (B) is not less than 1.3 percent.
4. The cryogenic separation of syngas to produce H according to claim 12The method for producing gas and CO gas is characterized in that when CH is contained in raw material gas4When the volume percentage of the methane in the feed gas is less than 1.3 percent, the methane is supplemented into the feed gas until the volume percentage of the methane in the feed gas reaches more than 1.3 percent.
5. The low temperature separation of syngas to produce H according to any one of claims 1 to 42Process for the production of gas and CO gas, characterized in that the third liquid phase fraction is returned to step one andin step two, the remaining portion of the third liquid phase is subcooled to-160 ℃ and recovered as product.
6. The low temperature separation of syngas to produce H according to any one of claims 1 to 42The method for separating the gas and the CO gas is characterized in that a hydrogen separation tower is adopted for separation in the step one, low-temperature non-condensable gas enters from the bottom, and the temperature of the top of the tower is-180 to-182 ℃.
7. The low temperature separation of syngas to produce H according to any one of claims 1 to 42The method of gas and CO gas is characterized in that CH is adopted as the second liquid phase in the step three4 /CO separation column for CH4And separation of CO, said CH4 The pressure in the/CO separation tower is 0.4-0.5 MPa, the temperature at the top of the tower is-175-180 ℃, and the temperature at the bottom of the tower is 20-40 ℃ higher than that at the top of the tower.
8. Application of the low-temperature separation synthesis gas in any one of claims 1 to 7 to preparation of H2A device for a gas and CO gas process, characterized in that it comprises: sequentially communicated hydrogen separation tower, flash tower and CH4 CO separation column and N2 A CO separation column; the CH4 The liquid outlet of the/CO separation tower is communicated with the hydrogen separation tower and the flash tower through a return pipeline; and a gas outlet of the flash tower is communicated with a raw material gas inlet of the device through a compressor.
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