CN108795508B - Method for separating coke oven gas by utilizing expansion refrigeration of nitrogen and helium - Google Patents
Method for separating coke oven gas by utilizing expansion refrigeration of nitrogen and helium Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10K—PURIFYING OR MODIFYING THE CHEMICAL COMPOSITION OF COMBUSTIBLE GASES CONTAINING CARBON MONOXIDE
- C10K1/00—Purifying combustible gases containing carbon monoxide
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- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
- 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
- C10L3/10—Working-up natural gas or synthetic natural gas
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- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
- C10L2290/00—Fuel preparation or upgrading, processes or apparatus therefore, comprising specific process steps or apparatus units
- C10L2290/54—Specific separation steps for separating fractions, components or impurities during preparation or upgrading of a fuel
- C10L2290/543—Distillation, fractionation or rectification for separating fractions, components or impurities during preparation or upgrading of a fuel
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/10—Process efficiency
Abstract
The invention relates to a method for separating coke oven gas by utilizing nitrogen and helium expansion refrigeration, which comprises the following steps: 1) compressing and precooling coke oven gas, sending the coke oven gas into a primary nitrogen circulating expansion refrigeration system, further cooling, and sending the coke oven gas into a rectifying tower; 2) the methane discharged from the bottom of the rectifying tower is cooled and liquefied by a secondary helium circulating expansion refrigeration system, then is sent into a liquefied natural gas storage tank for storage, and the hydrogen discharged from the top of the rectifying tower is sent into a liquid hydrogen storage tank for storage after being sequentially subjected to first normal-para state conversion and second normal-para state conversion; the first normal and secondary state conversion process is provided with cold energy by a two-stage helium circulating expansion refrigeration system, and the second normal and secondary state conversion process is provided with cold energy by a three-stage helium circulating expansion refrigeration system. Compared with the prior art, the method prepares the liquefied natural gas and the liquid hydrogen from the coke oven gas through the low-temperature circulation of the expansion of the nitrogen and the helium, improves the utilization efficiency and the energy utilization rate of the coke oven gas, reduces the phenomenon of emptying the coke oven gas, and has little environmental pollution.
Description
Technical Field
the invention belongs to the technical field of comprehensive utilization of coke oven gas in the coking/steel plant industry, and relates to a method for separating coke oven gas by utilizing expansion refrigeration of nitrogen and helium.
Background
the coke yield of China is in the top of the world, 2.33 hundred million tons in 2006, 3.53 hundred million tons in 2009 and 4.43 hundred million tons in 2012, a large amount of coke oven gas is generated while coke is produced, if the coke oven gas is calculated according to 430m 3 produced by 1t of coke produced, the generation amount of the coke oven gas reaches 1905 hundred million m 3 in 2012 in China all the year, wherein about 70 percent of the coke oven gas is used for self-use, commercial and urban residents of enterprises, the rest coke oven gas is not utilized well basically, and some coke oven gas is even directly combusted and released into the atmosphere.
the recyclable products of the coke oven gas mainly comprise methane and hydrogen, and the recycling mode has several advantages:
(1) the coke oven gas is a byproduct in the coke production process, the price of the coke oven gas is very low, hydrogen mainly exists in the form of a compound in nature, the price of elemental hydrogen is about 1.26 yuan/m 3, the wellhead price of natural gas for natural gas liquefaction is about 0.9 yuan/m 3, the wellhead price of the natural gas for the U.S. currently reaches 1.99 yuan/m 3, and the production cost of the coke oven gas is mainly energy consumption cost, so the produced liquid hydrogen (LH 2) and Liquefied Natural Gas (LNG) are very competitive in price.
(2) And the energy consumption is advantageous. The current mainstream preparation method of the hydrogen is an electrolytic water or water gas method, the energy consumption is about 50kWh/kg and is relatively high, and the coke oven gas contains a large amount of simple substance hydrogen, so that the hydrogen in the coke oven gas is separated, and the energy consumption in the hydrogen preparation process can be greatly reduced.
(3) Methane and hydrogen are clean energy which is vigorously developed in the future energy structure of China, and the application prospect is wide. The methane is used as the main component of the natural gas and has the characteristics of high combustion heat value, less atmospheric emission, high energy utilization efficiency and the like; the hydrogen energy has the advantages of high heat value, recyclability and the like, and the characteristics of cleanness and no pollution of the hydrogen energy accord with the concept of sustainable development.
the Chinese patent with publication number CN106753628A discloses a method and a device for preparing LNG (liquefied natural gas) and co-producing methanol from coke oven gas, wherein the coke oven gas is pressurized by a compressor, then subjected to TSA pretreatment and PSA debenzolization to remove naphthalene, tar, NH 3, benzene and other heavy hydrocarbon compounds, pressurized by the coke oven gas compressor, sent to a hydrodesulfurization device for desulfurization, sent to an MDEA decarburization device for decarburization, and subjected to LNG cryogenic separation to obtain a product LNG, the process is too complex, the cost is high, the stability and reliability need to be further verified, and the technology mainly recovers the LNG product and does not effectively utilize H 2 with high content in the coke oven gas.
The Chinese patent with publication number CN107446635A discloses a new method for utilizing coke oven gas, raw coke oven gas generated by a coke oven is mixed with methane according to a certain proportion, the generated mixed gas is introduced into a plasma thermal cracking reactor to generate mixed gas containing acetylene, hydrogen and carbon monoxide, and the mixed gas is purified and enters a separation and concentration device to be extracted to obtain acetylene products and tail gas; the tail gas enters a methanation reaction device through compression and preheating, the reacted gas passes through a pressure swing adsorption separation device to obtain hydrogen and synthetic methane, one part of the obtained synthetic methane and the coke oven gas are mixed and sent into a plasma cracking reactor, and the other part of the obtained synthetic methane is output as a product. The process can obtain three products of hydrogen, synthetic natural gas and acetylene, but has complex flow and relatively high energy consumption.
Chinese patent publication No. CN107261748A discloses a system for producing natural gas from coke oven gas, which uses a pressure swing adsorption method to treat coke oven gas and extract natural gas therefrom, but does not recover a large amount of hydrogen contained in coke oven gas.
the Chinese patent with publication number CN107512702A discloses a hydrogen production process by coke oven gas, the product is dry hydrogen, and methane is not recycled.
The Chinese patent with publication number CN106315510A discloses a hydrogen production process by coke oven gas, which introduces light hydrocarbon conversion and carbon monoxide medium temperature conversion processes on the basis of the traditional hydrogen production process by coke oven gas, so that light hydrocarbon components such as methane, ethane and the like in the raw material coke oven gas and carbon monoxide and the like all participate in hydrogen production reaction, and the consumption of hydrogen production raw material gas can be reduced.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a method for separating coke oven gas by using nitrogen and helium expansion refrigeration.
the purpose of the invention can be realized by the following technical scheme:
A method for separating coke oven gas by utilizing nitrogen and helium expansion refrigeration comprises the following steps:
1) Compressing and precooling coke oven gas, sending the coke oven gas into a primary nitrogen circulating expansion refrigeration system, further cooling, and sending the coke oven gas into a rectifying tower;
2) The methane discharged from the bottom of the rectifying tower is cooled and liquefied by a secondary helium circulating expansion refrigeration system, then is sent into a liquefied natural gas storage tank for storage, and the hydrogen discharged from the top of the rectifying tower is sent into a liquid hydrogen storage tank for storage after being sequentially subjected to first normal-para state conversion and second normal-para state conversion;
In the step 2), the first normal and secondary state conversion process is provided with cold energy by a two-stage helium circulating expansion refrigeration system, and the second normal and secondary state conversion process is provided with cold energy by a three-stage helium circulating expansion refrigeration system. The hydrogen in the coke oven gas is a mixture of orthohydrogen and parahydrogen, and the parahydrogen proportion is higher when the temperature is lower. On one hand, the conversion speed of the normal para-state is slow, and the normal liquefaction is finished, and the conversion of the normal para-state is not started basically; on the other hand, the process of normal to secondary conversion is an exothermic process, the heat release of which exceeds the latent heat of vaporization. Therefore, if the inversion of the normal state is not promoted to be completed simultaneously during liquefaction, the resulting liquid hydrogen product will slowly be lost. Meanwhile, the lower the temperature, the higher the energy consumption for providing the same refrigerating capacity, so the invention carries out one more normal-para conversion at higher temperature (generally near the temperature of liquid nitrogen) and one more normal-para conversion at the final liquid hydrogen temperature.
Further, in the step 1), the coke oven gas is composed of methane and hydrogen. The coke oven gas is pre-purified to only contain methane and hydrogen.
furthermore, after the coke oven gas is compressed and precooled, the pressure is 2.5-3.5MPa, and the temperature is 30-40 ℃. The compression and pre-cooling are carried out in a double-stage compression cooling device.
Further, the coke oven gas is sent into a rectifying tower after being further cooled to below-150 ℃.
Further, in the step 2), the methane is cooled and liquefied by a secondary helium circulating expansion refrigeration system to obtain high-pressure natural gas, and the high-pressure natural gas is throttled and depressurized to 0.08-0.12MPa and then is sent to a liquefied natural gas storage tank for storage.
Further, in step 2), the first ortho-para state conversion process and the second ortho-para state conversion process are both performed in a catalytic converter.
further, in the step 2), after the hydrogen subjected to the first normal-para state conversion is cooled and liquefied by the three-level helium circulating expansion refrigeration system, the second normal-para state conversion is performed.
further, in the step 2), after the hydrogen is cooled and liquefied by the three-stage helium circulating expansion refrigeration system, high-pressure hydrogen is obtained, and after the high-pressure hydrogen is throttled and reduced in pressure to 0.08-0.12MPa, second normal-state conversion is performed.
further, in the step 2), the refrigerant in the primary nitrogen circulating expansion refrigeration system is nitrogen, and the refrigerants in the secondary helium circulating expansion refrigeration system and the tertiary helium circulating expansion refrigeration system are helium. In the invention, in order to produce liquid hydrogen products, extremely low cold energy needs to be provided, helium is a good low-temperature refrigerant, and the low temperature of about 100K and mK can be obtained by using the low-temperature refrigerant, so that the refrigerants of the low-temperature section (a two-stage helium circulating expansion refrigeration system and a three-stage helium circulating expansion refrigeration system) are helium. Considering that the cost of the refrigerant helium is higher, and the adiabatic index of the refrigerant helium is larger than that of the conventional refrigerant nitrogen, so that the unit compression work is increased, the high-temperature section (the primary nitrogen cycle expansion refrigeration system) of the invention selects nitrogen as the refrigerant, thereby saving the cost and reducing the energy consumption.
Furthermore, a helium gas compression pre-cooling system is arranged between the second-stage helium circulating expansion refrigeration system and the third-stage helium circulating expansion refrigeration system, and the helium gas compression pre-cooling system is respectively communicated with the second-stage helium circulating expansion refrigeration system and the third-stage helium circulating expansion refrigeration system. And the helium gas compression precooling system compresses and precools the helium gas after the cyclic temperature rise and then sends the helium gas into the second-stage helium cyclic expansion refrigeration system and the third-stage helium cyclic expansion refrigeration system again.
the invention relates to a technology for separating and liquefying low-temperature gas with a rectification module, which is used for liquefying and separating coke oven gas, and a three-stage cycle expansion refrigeration system is established by utilizing nitrogen and helium as refrigerants to respectively provide cold energy for a high-temperature section and a low-temperature section, wherein a low-temperature working medium of a first-stage expansion cycle is nitrogen, and a low-temperature working medium of the other two-stage expansion cycle is helium. The rectifying tower in the system can realize the effective separation of methane and hydrogen in the coke oven gas. Performing primary nitrogen expansion low-temperature circulation on coke oven gas after compression and precooling, cooling to-160 ℃ or lower, then feeding the coke oven gas into a rectifying tower, and respectively obtaining hydrogen and methane products with the purity of more than 99.5% from the top and the bottom of the rectifying tower; the secondary helium expansion low-temperature cycle provides cold energy for the liquefaction of natural gas, a condenser in a rectifying tower and primary normal-state and secondary-state conversion in the hydrogen liquefaction process; the three-stage helium expansion low-temperature cycle provides cold energy for the hydrogen liquefaction and the secondary normal-para state conversion in the liquefaction process. The whole system realizes good energy integration, all expansion work is recycled by a compressor in a corresponding circulating expansion refrigeration system, and energy transmitted by a condenser and a reboiler in a rectifying tower is integrated by the system. Compared with the prior art, the invention realizes the obtaining of two high-purity liquid products from the coke oven gas for the first time, and is a breakthrough in the process development in the aspect of coke oven gas utilization.
the coke oven gas is a byproduct in the coke production process, so the system provided by the invention basically has no energy consumption for preparing raw material gas, and two gases are directly separated and liquefied at low temperature from low-cost mixed gas, thereby obtaining two high-purity liquid products. In the technology for preparing liquefied natural gas and liquid hydrogen by the traditional process, because hydrogen elements mainly exist in the form of compounds in nature, no method for preparing simple substance hydrogen with lower energy consumption exists at present, so compared with the technology for preparing liquefied natural gas and liquid hydrogen by the traditional process, the same product energy consumption by the traditional process comprises three parts of hydrogen preparation, hydrogen liquefaction and natural gas liquefaction, and the total energy consumption is greatly higher than that of the system for preparing liquefied natural gas and liquid hydrogen from low-cost coke oven gas.
compared with the prior art, the invention has the following characteristics:
1) The method fully utilizes the characteristic that the coke oven gas is rich in hydrogen and methane, prepares Liquefied Natural Gas (LNG) and liquid hydrogen (LH 2) from the coke oven gas through the expansion low-temperature circulation of nitrogen and helium, and verifies that the recovery rates of methane and hydrogen can respectively reach 97.92 percent and 99.68 percent through the simulation calculation of Aspen HYSYS software widely adopted in the petrochemical industry, thereby greatly improving the utilization efficiency and energy utilization rate of the coke oven gas, reducing the emptying phenomenon of the coke oven gas and effectively reducing the environmental pollution;
2) The traditional coke oven gas treatment method is to obtain LNG products through purification, methanation, PSA (pressure swing adsorption) and pressurization refrigeration, but the method directly enters a low-temperature system without adopting the PSA mode, and directly obtains high-purity liquid hydrogen and LNG products by adding a low-temperature rectifying tower.
Drawings
FIG. 1 is a schematic process flow diagram of the present invention.
Detailed Description
the invention is described in detail below with reference to the figures and specific embodiments. The present embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation manner and a specific operation process are given, but the scope of the present invention is not limited to the following embodiments.
example 1:
The embodiment of the process for preparing Liquefied Natural Gas (LNG) and liquid hydrogen (LH 2) from coke oven gas by using nitrogen and helium expansion low-temperature cycles is shown in figure 1, wherein a gas expansion cycle refrigerant is pure nitrogen and helium, a low-temperature working medium of a first stage expansion cycle is nitrogen, a low-temperature working medium of the other two stages of expansion cycles is helium, the flow rates of the three stages of expansion cycle refrigerants are respectively 5000kmol/H, 5000kmol/H and 5500kmol/H, the raw material coke oven gas comprises the following components in molar fraction of 50% CH 4 + 50% H 2, the pressure of the coke oven gas is 0.2MPa, the temperature is 35 ℃, the flow rate is 1000kmol/H, and the process for preparing the liquefied natural gas and the liquid hydrogen from the coke oven gas comprises the following specific steps:
1) introducing purified coke oven gas COG-101 with the mole fractions of CH 4 and H 2 of 50% into a double-stage compression cooling device (a compressor C-101, a water cooler WC-101, a compressor C-102 and a water cooler WC-102), compressing the coke oven gas to 3.0MPa, reducing the temperature to 35 ℃, and consuming 2692kW in the process;
2) introducing the coke oven gas compressed in the step 1) into a primary nitrogen circulating expansion refrigeration system to cool to-160 ℃, wherein the gasification rate of the mixed gas is 0.5216, the working medium compression final pressure of the primary nitrogen circulating expansion refrigeration system is 1.03MPa, and the energy consumption in the process is 8094 kW;
3) introducing the coke oven gas cooled in the step 2) into a rectifying tower T-100, and respectively obtaining hydrogen and methane products with the purity of more than 99.5% from the top and the bottom, wherein the flow rates are 498.8kmol/h and 501.2kmol/h, the temperatures are-223 ℃ and-97.92 ℃, and the gasification rates are 0.999 and 0 respectively;
4) Introducing CH 4 separated in the step 3) into a secondary helium circulating expansion refrigeration system for cooling and liquefying, wherein the working medium compression final pressure of the secondary helium circulating expansion refrigeration system is 0.22MPa, and the energy consumption in the process is 2487.4 kW;
5) Introducing the high-pressure natural gas liquefied in the step 4) into a throttle valve VLV-701, and reducing the pressure to 0.1MPa of storage pressure;
6) Introducing H 2 separated in the step 3) into a catalytic converter CON-101 for normal-state conversion, wherein the cold quantity required in the process is 88.26kW and is provided by a secondary helium circulating expansion refrigeration system;
7) Introducing H 2 subjected to the first normal-state and normal-state conversion in the step 6) into a three-level helium circulating expansion refrigeration system for cooling and liquefying, wherein the final compression pressure of a three-level helium expansion low-temperature circulating working medium is 3.4MPa, and the energy consumption in the process is 37772.9 kW;
8) introducing the high-pressure hydrogen liquefied in the step 7) into a throttle valve VLV-100, and reducing the pressure to 0.1MPa of storage pressure;
9) Introducing H 2 liquefied in the step 8) into a catalytic converter CON-102 for secondary normal-state conversion, wherein the required cold quantity in the process is 48.64kW and is provided by a three-stage helium circulating expansion refrigeration system;
Introducing the liquefied natural gas and the liquid hydrogen product liquefied in the steps 5) and 9) into a storage tank for storage.
Wherein, the first-stage nitrogen circulating expansion refrigerating system, the second-stage helium circulating expansion refrigerating system and the third-stage helium circulating expansion refrigerating system in the step 2), the step 4) and the step 7) are three independent circulating expansion refrigerating systems. The refrigerant is in closed cycle and is an expansion refrigeration system with regenerative cycle, wherein the output work of the expander is recycled by the compressor of the low-temperature cycle in which the expander is located.
according to the simulation calculation, in the process flow for preparing the liquefied natural gas and the liquid hydrogen by using the coke oven gas, the recovery rates of methane and hydrogen are respectively as high as 98.44% and 99.66%, the total energy consumption is 51046.3kW, compared with the process flow for preparing two products by using the traditional process, the energy consumption required for obtaining the same yield is about 70852.2kW (50 kWh/kg for preparing hydrogen, 12.5-15kWh/kg for liquefying hydrogen, and 0.7kWh/kg for liquefying natural gas), and the energy consumption is reduced by 27.95%.
Example 2:
The embodiment of the process for preparing Liquefied Natural Gas (LNG) and liquid hydrogen (LH 2) from coke oven gas by using nitrogen and helium expansion low-temperature cycles is shown in figure 1, wherein a gas expansion cycle refrigerant is pure nitrogen and helium, a low-temperature working medium of a first stage expansion cycle is nitrogen, a low-temperature working medium of the other two stages of expansion cycles is helium, the flow rates of the three-stage expansion cycle refrigerant are respectively 5000kmol/H, 4800kmol/H and 4600kmol/H, the raw coke oven gas comprises the following components in molar fraction of 60% of CH 4 + 40% of H 2, the pressure of the coke oven gas is 0.2MPa, the temperature is 35 ℃, the flow rate is 1000kmol/H, and the process for preparing the liquefied natural gas and the liquid hydrogen from the coke oven gas comprises the following specific steps:
1) introducing purified coke oven gas COG-101 with the mole fractions of CH 4 and H 2 of 60% and 40% respectively into a two-stage compression cooling device (a compressor C-101, a water cooler WC-101, a compressor C-102 and a water cooler WC-102), compressing the coke oven gas to 3.0MPa, reducing the temperature to 35 ℃, and consuming 2676kW in the process;
2) introducing the coke oven gas compressed in the step 1) into a primary nitrogen circulating expansion refrigeration system to cool to-160 ℃, wherein the gasification rate of the mixed gas is 0.4137, the working medium compression final pressure of the primary nitrogen circulating expansion refrigeration system is 1.20MPa, and the energy consumption in the process is 8772 kW;
3) Introducing the coke oven gas cooled in the step 2) into a rectifying tower T-100, and respectively obtaining hydrogen and methane products with the purity of more than 99.5% from the top and the bottom, wherein the flow rates are 398.1kmol/h and 601.9kmol/h respectively, the temperature is-223 ℃ and-98.17 ℃, and the gasification rates are 0.999 and 0 respectively;
4) Introducing CH 4 separated in the step 3) into a secondary helium circulating expansion refrigeration system for cooling and liquefying, wherein the working medium compression final pressure of the secondary helium circulating expansion refrigeration system is 0.20MPa, and the energy consumption in the process is 2020.2 kW;
5) introducing the high-pressure natural gas liquefied in the step 4) into a throttle valve VLV-701, and reducing the pressure to 0.1MPa of storage pressure;
6) Introducing H 2 separated in the step 3) into a catalytic converter CON-101 for normal-state conversion, wherein the cold quantity required in the process is 70.43kW and is provided by a secondary helium circulating expansion refrigeration system;
7) Introducing H 2 subjected to the first normal-state and normal-state conversion in the step 6) into a three-level helium circulating expansion refrigeration system for cooling and liquefying, wherein the final compression pressure of a three-level helium expansion low-temperature circulating working medium is 3.13MPa, and the energy consumption in the process is 30186.8 kW;
8) Introducing the high-pressure hydrogen liquefied in the step 7) into a throttle valve VLV-100, and reducing the pressure to 0.1MPa of storage pressure;
9) Introducing H 2 liquefied in the step 8) into a catalytic converter CON-102 for secondary normal-state conversion, wherein the required cold quantity in the process is 38.82kW and is provided by a three-stage helium circulating expansion refrigeration system;
introducing the liquefied natural gas and the liquid hydrogen product liquefied in the steps 5) and 9) into a storage tank for storage.
Wherein, the first-stage nitrogen circulating expansion refrigerating system, the second-stage helium circulating expansion refrigerating system and the third-stage helium circulating expansion refrigerating system in the step 2), the step 4) and the step 7) are three independent circulating expansion refrigerating systems. The refrigerant is in closed cycle and is an expansion refrigeration system with regenerative cycle, wherein the output work of the expander is recycled by the compressor of the low-temperature cycle in which the expander is located.
According to the simulation calculation, in the process flow for preparing liquefied natural gas and liquid hydrogen by using coke oven gas, the recovery rates of methane and hydrogen are respectively 98.37% and 99.43%, the total energy consumption is 43655kW, compared with the process flow for preparing two products by using the traditional process, the energy consumption required for obtaining the same yield is about 58744.6kW (50 kWh/kg for preparing hydrogen, 12.5-15kWh/kg for liquefying hydrogen, and 0.7kWh/kg for liquefying natural gas), and the energy consumption is reduced by 25.69%.
Example 3:
A method for separating coke oven gas by utilizing nitrogen and helium expansion refrigeration comprises the following steps:
1) Compressing and precooling coke oven gas, sending the coke oven gas into a primary nitrogen circulating expansion refrigeration system, further cooling, and sending the coke oven gas into a rectifying tower;
2) the methane discharged from the bottom of the rectifying tower is cooled and liquefied by a secondary helium circulating expansion refrigeration system, and then is sent into a liquefied natural gas storage tank for storage, and the hydrogen discharged from the top of the rectifying tower is sequentially subjected to first normal-normal state conversion and second normal-normal state conversion, and then is sent into a liquid hydrogen storage tank for storage, wherein the first normal-normal state conversion process is provided with cold by the secondary helium circulating expansion refrigeration system, and the second normal-normal state conversion process is provided with cold by a three-level helium circulating expansion refrigeration system.
In the step 1), the coke oven gas consists of methane and hydrogen; after the coke oven gas is compressed and precooled, the pressure is 2.5MPa, and the temperature is 40 ℃; further cooling the coke oven gas to below-150 ℃, and then feeding the coke oven gas into a rectifying tower.
in the step 2), the methane is cooled and liquefied by a secondary helium circulating expansion refrigeration system to obtain high-pressure natural gas, and the high-pressure natural gas is throttled and depressurized to 0.12MPa and then is sent to a liquefied natural gas storage tank for storage; the first and second ortho-para conversion processes are both performed in a catalytic converter; after the hydrogen subjected to the first positive-state and secondary-state conversion is cooled and liquefied by a three-level helium circulating expansion refrigeration system, performing second positive-state and secondary-state conversion; after the hydrogen is cooled and liquefied by a three-stage helium circulating expansion refrigeration system, high-pressure hydrogen is obtained, and after the high-pressure hydrogen is throttled and reduced in pressure to 0.08MPa, second normal-state and normal-state conversion is carried out; the refrigerant in the first-stage nitrogen circulating expansion refrigeration system is nitrogen, and the refrigerants in the second-stage helium circulating expansion refrigeration system and the third-stage helium circulating expansion refrigeration system are helium; and a helium gas compression pre-cooling system is arranged between the second-stage helium circulating expansion refrigeration system and the third-stage helium circulating expansion refrigeration system, and is respectively communicated with the second-stage helium circulating expansion refrigeration system and the third-stage helium circulating expansion refrigeration system.
example 4:
A method for separating coke oven gas by utilizing nitrogen and helium expansion refrigeration comprises the following steps:
1) compressing and precooling coke oven gas, sending the coke oven gas into a primary nitrogen circulating expansion refrigeration system, further cooling, and sending the coke oven gas into a rectifying tower;
2) The methane discharged from the bottom of the rectifying tower is cooled and liquefied by a secondary helium circulating expansion refrigeration system, and then is sent into a liquefied natural gas storage tank for storage, and the hydrogen discharged from the top of the rectifying tower is sequentially subjected to first normal-normal state conversion and second normal-normal state conversion, and then is sent into a liquid hydrogen storage tank for storage, wherein the first normal-normal state conversion process is provided with cold by the secondary helium circulating expansion refrigeration system, and the second normal-normal state conversion process is provided with cold by a three-level helium circulating expansion refrigeration system.
In the step 1), the coke oven gas consists of methane and hydrogen; after the coke oven gas is compressed and precooled, the pressure is 3.5MPa, and the temperature is 30 ℃; further cooling the coke oven gas to-170 ℃, and then sending the coke oven gas into a rectifying tower.
In the step 2), the methane is cooled and liquefied by a secondary helium circulating expansion refrigeration system to obtain high-pressure natural gas, and the high-pressure natural gas is throttled and depressurized to 0.12MPa and then is sent to a liquefied natural gas storage tank for storage; the first and second ortho-para conversion processes are both performed in a catalytic converter; after the hydrogen subjected to the first positive-state and secondary-state conversion is cooled and liquefied by a three-level helium circulating expansion refrigeration system, performing second positive-state and secondary-state conversion; after the hydrogen is cooled and liquefied by a three-stage helium circulating expansion refrigeration system, high-pressure hydrogen is obtained, and after the high-pressure hydrogen is throttled and reduced in pressure to 0.12MPa, second normal-state and normal-state conversion is carried out; the refrigerant in the first-stage nitrogen circulating expansion refrigeration system is nitrogen, and the refrigerants in the second-stage helium circulating expansion refrigeration system and the third-stage helium circulating expansion refrigeration system are helium; and a helium gas compression pre-cooling system is arranged between the second-stage helium circulating expansion refrigeration system and the third-stage helium circulating expansion refrigeration system, and is respectively communicated with the second-stage helium circulating expansion refrigeration system and the third-stage helium circulating expansion refrigeration system.
Example 5:
A method for separating coke oven gas by utilizing nitrogen and helium expansion refrigeration comprises the following steps:
1) compressing and precooling coke oven gas, sending the coke oven gas into a primary nitrogen circulating expansion refrigeration system, further cooling, and sending the coke oven gas into a rectifying tower;
2) The methane discharged from the bottom of the rectifying tower is cooled and liquefied by a secondary helium circulating expansion refrigeration system, and then is sent into a liquefied natural gas storage tank for storage, and the hydrogen discharged from the top of the rectifying tower is sequentially subjected to first normal-normal state conversion and second normal-normal state conversion, and then is sent into a liquid hydrogen storage tank for storage, wherein the first normal-normal state conversion process is provided with cold by the secondary helium circulating expansion refrigeration system, and the second normal-normal state conversion process is provided with cold by a three-level helium circulating expansion refrigeration system.
In the step 1), the coke oven gas consists of methane and hydrogen; after the coke oven gas is compressed and precooled, the pressure is 3MPa, and the temperature is 35 ℃; further cooling the coke oven gas to-160 ℃, and then sending the coke oven gas into a rectifying tower.
In the step 2), the methane is cooled and liquefied by a secondary helium circulating expansion refrigeration system to obtain high-pressure natural gas, and the high-pressure natural gas is throttled and depressurized to 0.1MPa and then is sent to a liquefied natural gas storage tank for storage; the first and second ortho-para conversion processes are both performed in a catalytic converter; after the hydrogen subjected to the first positive-state and secondary-state conversion is cooled and liquefied by a three-level helium circulating expansion refrigeration system, performing second positive-state and secondary-state conversion; after the hydrogen is cooled and liquefied by a three-stage helium circulating expansion refrigeration system, high-pressure hydrogen is obtained, and after the high-pressure hydrogen is throttled and reduced in pressure to 0.1MPa, second normal-state and normal-state conversion is carried out; the refrigerant in the first-stage nitrogen circulating expansion refrigeration system is nitrogen, and the refrigerants in the second-stage helium circulating expansion refrigeration system and the third-stage helium circulating expansion refrigeration system are helium; and a helium gas compression pre-cooling system is arranged between the second-stage helium circulating expansion refrigeration system and the third-stage helium circulating expansion refrigeration system, and is respectively communicated with the second-stage helium circulating expansion refrigeration system and the third-stage helium circulating expansion refrigeration system.
as shown in fig. 1 (in the figure, C is compressor, CON is catalytic converter, E is expander, HEX is heat exchanger, MIX is mixer, T is rectifying tower, TEE is separator, V is gas-liquid separator, VLV is throttle valve, WC is water cooler, Q represents heat quantity, W represents power), the whole process flow is:
The coke oven gas COG-101 is compressed and water-cooled for two times by a compressor C-101, a water cooler WC-101, a compressor C-102 and a water cooler WC-102 in sequence, cooled by a primary nitrogen circulating expansion refrigeration system, and then sent into a rectifying tower T-100; methane discharged from the bottom of the rectifying tower T-100 exchanges heat with helium in a secondary helium circulating expansion refrigeration system in a heat exchanger HEX-104 to be cooled and liquefied, and then enters a gas-liquid separator V-100 to separate Liquefied Natural Gas (LNG) after being throttled and depressurized by a throttle valve VLV-701 and then is sent to a liquefied natural gas storage tank to be stored; after a material discharged from the top of a rectifying tower T-100 enters a gas-liquid separator V-101 to be separated to obtain hydrogen, the hydrogen is sent to a catalytic converter CON-101 to be converted in a normal-secondary state, meanwhile, a second-stage helium circulating expansion refrigeration system is used for refrigerating the catalytic converter CON-101 to obtain high-pressure hydrogen, the high-pressure hydrogen exchanges heat with helium in a third-stage helium circulating expansion refrigeration system in a heat exchanger HEX-105 to be cooled and liquefied, then, the high-pressure hydrogen enters the catalytic converter CON-102 to be converted in the normal-secondary state for the second time after being throttled and depressurized by a throttle valve VLV-100, meanwhile, the third-stage helium circulating expansion refrigeration system is used for refrigerating the catalytic converter CON-102, and finally, the obtained liquid hydrogen product is sent to a.
In the primary nitrogen circulating expansion refrigeration system, nitrogen is subjected to two-stage heat exchange with coke oven gas in a heat exchanger HEX-102 and a heat exchanger HEX-101 after being subjected to two-stage expansion refrigeration in an expander E-201 and an expander E-202 in sequence, the coke oven gas is refrigerated, the nitrogen subjected to heat exchange is subjected to two-stage compression water cooling in a compressor C-203, a water cooler WC-201, a compressor C-204 and a water cooler WC-202 in sequence, and then circularly enters the expander E-201 and the expander E-202 for expansion refrigeration.
The helium gas precooled in the helium gas compression precooling system is divided into two parts in the separator TEE-301, and the two parts enter the second-stage helium circulating expansion refrigeration system and the third-stage helium circulating expansion refrigeration system respectively. In the secondary helium circulating expansion refrigeration system, helium sequentially passes through a heat exchanger HEX-501 and a heat exchanger HEX-502 and then enters an expansion machine E-501 for expansion refrigeration, then enters a catalytic converter CON-101 for refrigeration, and then sequentially passes through the heat exchanger HEX-503, the heat exchanger HEX-104 and the heat exchanger HEX-501 and then enters a mixer MIX-301, wherein the helium performs heat exchange refrigeration on the heat exchanger HEX-104 and methane discharged from the bottom of a rectifying tower T-100. In the three-stage helium circulating expansion refrigeration system, helium sequentially passes through a compressor C-401, a water cooler WC-401 and a heat exchanger HEX-401, then enters an expansion machine E-401 for expansion refrigeration, then enters a catalytic converter CON-102 for refrigeration, then sequentially passes through a heat exchanger HEX-105 and a heat exchanger HEX-401, and then enters a mixer MIX-301, wherein the helium performs heat exchange refrigeration with high-pressure hydrogen in the heat exchanger HEX-105. In the helium compression precooling system, helium entering the mixer MIX-301 sequentially passes through a water cooler WC-303, a compressor C-301, the water cooler WC-301, a compressor C-302 and the water cooler WC-302 to be compressed and cooled for multiple times, and then enters a separator TEE-301.
the embodiments described above are described to facilitate an understanding and use of the invention by those skilled in the art. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above embodiments, and those skilled in the art should make improvements and modifications within the scope of the present invention based on the disclosure of the present invention.
Claims (10)
1. The method for separating the coke oven gas by utilizing the expansion refrigeration of the nitrogen and the helium is characterized by comprising the following steps of:
1) Compressing and precooling coke oven gas, sending the coke oven gas into a primary nitrogen circulating expansion refrigeration system, further cooling, and sending the coke oven gas into a rectifying tower;
2) The methane discharged from the bottom of the rectifying tower is cooled and liquefied by a secondary helium circulating expansion refrigeration system, then is sent into a liquefied natural gas storage tank for storage, and the hydrogen discharged from the top of the rectifying tower is sent into a liquid hydrogen storage tank for storage after being sequentially subjected to first normal-para state conversion and second normal-para state conversion;
In the step 2), the first normal and secondary state conversion process is provided with cold energy by a two-stage helium circulating expansion refrigeration system, and the second normal and secondary state conversion process is provided with cold energy by a three-stage helium circulating expansion refrigeration system.
2. The method for separating the coke oven gas by utilizing the expansion refrigeration of the nitrogen and the helium as claimed in claim 1, wherein in the step 1), the coke oven gas consists of methane and hydrogen.
3. The method for separating the coke oven gas by utilizing the expansion refrigeration of the nitrogen and the helium as claimed in claim 1, wherein in the step 1), the pressure of the coke oven gas is 2.5-3.5MPa and the temperature is 30-40 ℃ after the coke oven gas is compressed and precooled.
4. the method for separating the coke oven gas by utilizing the expansion refrigeration of the nitrogen and the helium as claimed in claim 1, wherein in the step 1), the coke oven gas is further cooled to below-150 ℃ and then is fed into a rectifying tower.
5. The method for separating the coke oven gas by utilizing the expansion refrigeration of the nitrogen and the helium according to claim 1, wherein in the step 2), the methane is cooled and liquefied by a secondary helium circulating expansion refrigeration system to obtain high-pressure natural gas, and the high-pressure natural gas is throttled and depressurized to 0.08-0.12MPa and then is sent to a liquefied natural gas storage tank for storage.
6. the method for separating the coke oven gas by utilizing the expansion refrigeration of the nitrogen and the helium as claimed in claim 1, wherein in the step 2), the first normal-state and the second normal-state conversion processes are both carried out in a catalytic converter.
7. The method for separating the coke oven gas by utilizing the expansion refrigeration of the nitrogen and the helium as claimed in claim 1, wherein in the step 2), the hydrogen after the first normal-state conversion is cooled and liquefied by a three-stage helium circulating expansion refrigeration system, and then the second normal-state conversion is carried out.
8. The method for separating the coke oven gas by utilizing the expansion refrigeration of the nitrogen and the helium as claimed in claim 7, wherein in the step 2), the hydrogen is cooled and liquefied by a three-stage helium circulating expansion refrigeration system to obtain high-pressure hydrogen, and the high-pressure hydrogen is throttled and reduced in pressure to 0.08-0.12MPa and then is subjected to second normal-state and secondary-state conversion.
9. the method for separating the coke oven gas by utilizing the expansion refrigeration of the nitrogen and the helium as claimed in claim 1, wherein the refrigerant in the primary nitrogen circulating expansion refrigeration system is nitrogen, and the refrigerants in the secondary helium circulating expansion refrigeration system and the tertiary helium circulating expansion refrigeration system are helium.
10. the method for separating the coke oven gas by utilizing the expansion refrigeration of the nitrogen and the helium as claimed in claim 9, wherein a helium compression pre-cooling system is arranged between the second-stage helium circulating expansion refrigeration system and the third-stage helium circulating expansion refrigeration system, and the helium compression pre-cooling system is respectively communicated with the second-stage helium circulating expansion refrigeration system and the third-stage helium circulating expansion refrigeration system.
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| CN114518015A (en) * | 2022-02-14 | 2022-05-20 | 杨兆铭 | Hydrogen liquefaction process adopting nitrogen turbine expansion precooling |
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