Method and apparatus for separating co2 and cos from a blast furnace gas after a gas resolution back end rectification

Abstract

The application discloses a method and device for separating CO2 and COS through high-temperature tail gas rectification after blast furnace gas desorption, and relates to the technical field of blast furnace gas desorption recycling; the application realizes the cryogenic liquefaction of CO2 and COS in the dehydrated blast furnace gas desorption gas by controlling temperature or temperature and pressure, separates the gas and liquid, uses the different boiling points to distill and separate the left liquid part, namely CO2 and COS, and then extracts the separated CO2 gas to supply the cryogenic liquefaction link as a refrigerant for recycling; the dehydrated gas pipe, the cryogenic liquefaction device, the gas-liquid separation device, the recovery liquid pipe and the low-temperature distillation separation tower are sequentially communicated; the low-temperature distillation separation tower is provided with an air extraction hole at an arbitrary position above the material liquid surface and is communicated with the refrigerant inlet end of the cryogenic liquefaction device through a cooling carbon dioxide gas pipe; the application is simple and reasonable, the recovered product has a high value, the separated CO2 is reasonably used as a refrigerant for cryogenic liquefaction, and the effective utilization of energy and resources is facilitated.

Description

Technical Field

[0001] This invention relates to the field of blast furnace gas desorption gas recovery and reuse technology, specifically to a method and apparatus for the downstream distillation separation of CO2 and COS from blast furnace gas desorption gas. Background Technology

[0002] In response to the problem of excessive SO2 levels in blast furnace gas produced as a byproduct of steel enterprises, some companies have begun to adopt source-based desulfurization methods for blast furnace gas. These methods mainly fall into two categories: dry and wet desulfurization. Dry desulfurization of blast furnace gas primarily utilizes adsorbents to adsorb sulfur from the gas. After the adsorbent material becomes saturated, the regeneration gas can be hot gas, which desorbs the adsorbed sulfides, thus regenerating the adsorbent material and allowing for multiple reuses.

[0003] In a dry desulfurization project for blast furnace gas, on-site measurements showed that the blast furnace gas desorbate contained 1% H2O, 58% N2, 1% O2, 18% CO, 20% CO2, and 2% COS. The temperature was approximately 220℃.

[0004] For the desorbed blast furnace gas, one treatment method is to transport it through pipelines to sintering users for combustion, utilizing existing sintering flue gas treatment equipment to meet emission standards. Another method is to install sulfur melting kettles and other equipment to produce sulfur, but the purity of the produced sulfur is not high. Neither of these two methods can effectively improve the added value of the blast furnace gas. If about 1% of the water is removed through condensation and gas-liquid separation, the high-value industrial gases CO2 and COS in the blast furnace gas could be separated for utilization or sale, which would be a win-win situation. However, there is no dedicated device for separating CO2 and COS from blast furnace gas in the current technology. Simply adding high-efficiency separation equipment would result in a waste of energy or resources, and the separation results might not outweigh the benefits. Summary of the Invention

[0005] The purpose of this invention is to provide a method and apparatus for the downstream distillation separation of CO2 and COS from blast furnace gas desorption gas, so as to reduce the waste of energy or resources during the separation process of blast furnace gas desorption gas.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for separating CO2 and COS by distillation at the downstream end of blast furnace gas desorption gas, comprising the following specific contents: by controlling the temperature or temperature and pressure, the CO2 and COS in the dehydrated blast furnace gas desorption gas are cryogenically liquefied; after gas-liquid separation, the remaining liquid portion, i.e., CO2 and COS, is distilled and separated by utilizing their different boiling points; and the separated CO2 gas is then extracted and supplied to the cryogenic liquefaction stage as a refrigerant for recycling.

[0007] Preferably, after gas-liquid separation, the gas portion is returned to the coal gas system for recycling.

[0008] Another technical solution provided by the present invention: a method and apparatus for separating CO2 and COS by post-distillation of blast furnace gas desorption gas, comprising a dehydrated gas pipe, the gas outlet of which is connected to the feed end of a cryogenic liquefaction device, the discharge end of which is connected to the feed end of a gas-liquid separation device; the upper end of the gas-liquid separation device is provided with a gas outlet and connected to a gas recovery pipe, and the lower end is provided with a liquid outlet and connected to a liquid recovery pipe, wherein the liquid recovery pipe is connected to the feed end of a cryogenic distillation separation tower; the cryogenic distillation separation tower is provided with an extraction hole at any point above the liquid surface of the material for extracting the separated gas, and the extraction hole is connected to the refrigerant inlet of the cryogenic liquefaction device through a cooling carbon dioxide gas pipe.

[0009] Preferably, the cryogenic distillation separation tower also has a gaseous product outlet and a liquid product outlet, which are used to collect carbon dioxide products and carbonyl sulfide products, respectively.

[0010] Preferably, the low-temperature distillation separation tower is also equipped with refrigeration equipment to provide the working temperature for distillation separation.

[0011] Preferably, the refrigeration equipment is a booster expander.

[0012] Preferably, a gas extraction pump is installed on the cooling carbon dioxide gas pipe to extract gas from the cryogenic distillation separation tower.

[0013] Preferably, the cryogenic liquefaction device has an internal pressure higher than 1 atm and a cooling temperature of -50℃ to -85℃, and is used to liquefy CO2 and COS.

[0014] Preferably, the gas recovery pipe is connected to the gas pipeline network for recycling.

[0015] Compared with the prior art, the beneficial effects of the present invention are:

[0016] The method and apparatus for separating CO2 and COS from blast furnace gas by downstream distillation is simple in procedure and has a reasonable structure. It can separate high-value-added CO2 and COS from blast furnace gas by cryogenic liquefaction, gas-liquid separation and distillation, and can also recover and utilize the remaining CO, N2 and O2. In this process, the method and apparatus for separating CO2 and COS from blast furnace gas by downstream distillation also makes reasonable use of the separated CO2 as a refrigerant for cryogenic liquefaction, so that energy and resources are better utilized. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of the present invention.

[0018] In the diagram: 1. Gas pipe after dehydration; 2. Gas recovery pipe; 3. Liquid recovery pipe; 4. Carbon dioxide cooling gas pipe; 5. Cryogenic liquefaction device; 6. Gas-liquid separation device; 7. Low-temperature distillation separation tower; 8. Refrigeration equipment. Detailed Implementation

[0019] The method for separating CO2 and COS by downstream distillation of blast furnace gas desorbed gas includes the following specific steps: By controlling the temperature or temperature and pressure, the CO2 and COS in the dehydrated blast furnace gas desorbed gas are cryogenically liquefied. After gas-liquid separation, the remaining liquid portion, i.e., CO2 and COS, is distilled and separated using their different boiling points. The separated CO2 gas is then extracted and supplied to the cryogenic liquefaction stage as a refrigerant for recycling. Furthermore, since the main components of the remaining gas after gas-liquid separation are CO, N2, and O2, it can also be returned to the gas system for recycling as a high-calorific-value gas.

[0020] To achieve the above method, the following structure can be used: a device for the downstream distillation and separation of CO2 and COS from blast furnace gas desorption gas, such as... Figure 1 As shown, it includes a dehydrated gas pipe 1, the gas outlet of which is connected to the feed end of the cryogenic liquefaction device 5, and the discharge end of the cryogenic liquefaction device 5 is connected to the feed end of the gas-liquid separation device 6; the gas-liquid separation device 6 has a gas outlet at the upper end and is connected to a gas recovery pipe 2, and a liquid outlet at the lower end and is connected to a liquid recovery pipe 3, wherein the liquid recovery pipe 3 is connected to the feed end of the cryogenic distillation separation tower 7; the cryogenic distillation separation tower 7 has an exhaust port at any point above the liquid surface of the material for extracting the separated gas, and the exhaust port is connected to the refrigerant inlet of the cryogenic liquefaction device 5 through a cooling carbon dioxide gas pipe 4.

[0021] In addition to the evacuation port, the low-temperature distillation separation tower 7 is also equipped with a gas product outlet and a liquid product outlet, which are used to collect carbon dioxide products and carbonyl sulfide products, respectively. Generally, the gas product outlet is located at the top and the liquid product outlet is located at the bottom.

[0022] The low-temperature distillation separation tower 7 is generally equipped with a refrigeration device 8 to provide the working temperature for distillation separation; optionally, the refrigeration device 8 can be a booster expander.

[0023] In addition, a vacuum pump can be installed on the carbon dioxide gas pipe 4 to extract gas from the cryogenic distillation separation tower 7.

[0024] The cryogenic liquefaction unit 5 uses a refrigerant-cooled cryogenic device. Under normal atmospheric pressure, it needs to be cooled to -80 to -85°C because CO2 and COS will liquefy at this temperature, while CO, N2, and O2 remain gases, allowing for gas-liquid separation. Commercially available cryogenic liquefaction devices usually have a pressurization function. Compared to simple cooling, achieving liquefaction separation through pressure and temperature control is more time-saving and energy-efficient. When using this common device, in a preferred embodiment, the internal pressure of the cryogenic liquefaction unit 5 is higher than 1 atm, and the cooling temperature is between -50°C and -85°C, which is sufficient to liquefy CO2 and COS. The recovered gas pipe 2 can be further connected to the gas pipeline network, and its main components are CO, N2, and O2, which can be recovered and utilized as high-calorific-value gas.

[0025] Furthermore, the cryogenic distillation separation tower 7 should employ vacuum distillation. By controlling the pressure and temperature within the tower, CO2 and COS can be separated based on their different boiling points (CO2 boiling point is -78.5℃ at atmospheric pressure, and COS boiling point is -50℃). The separated CO2 and COS can be obtained with higher purity for storage or export. Since vacuum distillation is used, the separation of CO2 and COS can generally be completed between -50℃ and -85℃. Therefore, the outlet temperature of the aforementioned vent can basically meet the cooling requirements of the cryogenic liquefaction unit 5. The energy loss in this process can generally be compensated by pressurizing the cryogenic liquefaction unit 5. However, under special circumstances, additional cryogenic carbon dioxide can be added as an external refrigerant depending on the operating conditions. Of course, the carbon dioxide gas after heat exchange flowing out of the cryogenic liquefaction unit 5 can be combined with the product gas from the cryogenic distillation separation tower 7 to form a carbon dioxide product.

[0026] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

[0027] Any aspects of this invention not described in detail are well-known to those skilled in the art.

Claims

1. A method for the separation of CO2 and COS in the back-end rectification of a coke oven gas after gas resolution, characterized in that, Includes the following: By controlling the temperature or temperature and pressure, the CO2 and COS in the dehydrated blast furnace gas are cryogenically liquefied. After gas-liquid separation, the remaining liquid portion, i.e., CO2 and COS, is distilled and separated using their different boiling points. The separated CO2 gas is then extracted and supplied to the cryogenic liquefaction stage for recycling as a refrigerant. The method employs the following apparatus: The device includes a dehydrated gas pipe (1), whose outlet is connected to the feed end of a cryogenic liquefaction device (5), and the outlet of the cryogenic liquefaction device (5) is connected to the feed end of a gas-liquid separation device (6); the gas-liquid separation device (6) has an outlet at the upper end and is connected to a gas recovery pipe (2), and a liquid outlet at the lower end and is connected to a liquid recovery pipe (3), wherein the liquid recovery pipe (3) is connected to the feed end of a cryogenic distillation separation tower (7); the cryogenic distillation separation tower (7) has an exhaust port located at any point above the liquid surface of the material for extracting the separated gas, and the exhaust port is connected to the refrigerant inlet of the cryogenic liquefaction device (5) through a cooling carbon dioxide gas pipe (4); the internal pressure of the cryogenic liquefaction device (5) is higher than 1 atm, and the cooling temperature is -50℃ to -85℃, which is used to liquefy CO2 and COS; The low-temperature distillation separation tower (7) is also equipped with a gas product outlet and a liquid product outlet, which are used to collect carbon dioxide products and carbonyl sulfide products, respectively.

2. The method of claim 1, wherein: The gas recovery pipe (2) is connected to the gas pipeline network. After gas-liquid separation, the gas portion is returned to the gas system for recycling.

3. The method of claim 1, wherein: The low-temperature distillation separation tower (7) is also equipped with a refrigeration device (8) to provide the working temperature for distillation separation.

4. The method of claim 3, wherein: The refrigeration equipment (8) is a booster expander.

5. The method of claim 1, wherein: A gas pump is installed on the cooling carbon dioxide gas pipe (4) to extract gas from the low-temperature distillation separation tower (7).

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