Low-concentration carbon dioxide feed gas recovery device

Abstract

The utility model discloses a low-concentration carbon dioxide feed gas recovery device which comprises a residual cold recoverer A, a residual cold recoverer B and a rectifying tower, low-concentration carbon dioxide raw materials are subjected to primary residual cold recovery through the residual cold recoverer A and the residual cold recoverer B and then are overheated and fed into the rectifying tower; liquid carbon dioxide in the rectifying tower flows out from a liquid carbon dioxide outlet formed in the bottom, and non-condensable gas in the rectifying tower flows out from a non-condensable gas outlet formed in the top to a residual cold recoverer B and a residual cold recoverer A for further residual cold recovery. The low-concentration carbon dioxide in the feed gas can be effectively recovered, the process is simple, the number of equipment is small, and the cost is low.

Description

Technical Field

[0001] The utility model belongs to the field of carbon dioxide recovery, and in particular relates to a low-concentration carbon dioxide raw gas recovery device. Background Art

[0002] In the late regeneration stage of the decarbonization liquid in the low-temperature methanol decarbonization unit and the early regeneration stage of the adsorbent in the PSA decarbonization unit, a tail gas with a medium to low carbon dioxide concentration (75% to 85%) is generated. Due to its low concentration, recovery is difficult and costly, and it does not have a market advantage. In most cases, it is not recovered and is directly vented. Against the backdrop of global climate change, as one of the main greenhouse gases, the reduction and recycling of carbon dioxide is particularly important. The utility model aims to propose a high-yield, low-energy-consumption, sustainable carbon recovery process that can reduce greenhouse gas emissions and recycle waste gas resources, turning waste into treasure and realizing a circular economy.

[0003] The utility model proposes a recovery process for tail gas with low carbon dioxide concentration (75% to 85%), which is energy-saving, simple in process, requires less equipment and has low operating costs. Utility Model Content

[0004] The purpose of the utility model is to provide a low-concentration carbon dioxide raw gas recovery device, which can effectively recover low-concentration carbon dioxide in the raw gas, has a simple process, a small number of equipment and a low cost.

[0005] In order to achieve the above purpose, the utility model adopts the following technical solutions:

[0006] The low-concentration carbon dioxide raw gas recovery device includes a waste cooling recovery device A, a waste cooling recovery device B and a distillation tower. The low-concentration carbon dioxide raw material first passes through the waste cooling recovery device A and the waste cooling recovery device B for initial waste cooling recovery and then is superheated and fed into the distillation tower. The liquid carbon dioxide in the distillation tower flows out from the liquid carbon dioxide outlet provided at the bottom, and the non-condensable gas in the distillation tower flows out from the non-condensable gas outlet provided at the top to the waste cooling recovery device B and the waste cooling recovery device A for further waste cooling recovery.

[0007] The low-concentration carbon dioxide raw material passes through the waste cooling recovery device A and the waste cooling recovery device B to recover the low-pressure non-condensable gas waste cooling and the high-pressure non-condensable gas waste cooling respectively, and then is distilled through the distillation tower. After distillation, the liquid carbon dioxide is recovered from the bottom, and the non-condensable gas flows from the top into the waste cooling recovery device B and the waste cooling recovery device A for waste cooling recovery again.

[0008] Furthermore, the distillation tower includes, from top to bottom, a top condensation section, a first packing layer, a middle condensation section, a second packing layer, a third packing layer and a built-in reboiler. A distillation tower air inlet is provided between the second packing layer and the third packing layer, and the low-concentration carbon dioxide raw material after the first residual cooling recovery enters the distillation tower from the distillation tower air inlet.

[0009] The low-concentration carbon dioxide raw material after the initial recovery of residual cold enters the distillation tower as superheated feed. The low-concentration carbon dioxide raw material is condensed through the top condensation section and the middle condensation section in the distillation tower to generate liquid carbon dioxide raw material. The liquid carbon dioxide material flows out from the bottom of the distillation tower, and the non-condensable gas flows out from the top and passes through the residual cold recovery device B and the residual cold recovery device A for further residual cold recovery.

[0010] The packing layer and reboiler are important components of the distillation process. Within the distillation tower, gas-liquid two-phase materials transfer mass and heat within the packing layer. By utilizing the different physical properties of the mixture's components and continuously repeating the gas-liquid equilibrium, the components of the mixture are separated and purified. The reboiler provides power support for the entire distillation process. After process optimization, the built-in reboiler does not require much reboil heat, greatly reducing the size of the reboiler and enabling its integration. The built-in reboiler can simplify the process and integrate equipment, reducing equipment cost and footprint.

[0011] Furthermore, the distillation tower is connected to a refrigeration system, which includes a compressor, a first-level liquid refrigerant and a liquid carbon dioxide refrigerant. The first-level liquid refrigerant first heats the built-in reboiler, then evaporates and cools the middle condensation section, and then enters the compressor for compression and liquefaction.

[0012] The first-stage liquid refrigerant heats and reboils the liquid carbon dioxide material in the built-in reboiler. The first-stage liquid refrigerant itself is supercooled, which is beneficial to improving the circulation efficiency of the refrigeration system. Then the first-stage liquid refrigerant goes to the middle condensation section to evaporate and cool the gaseous carbon dioxide raw material.

[0013] Furthermore, a regulating valve is connected between the built-in reboiler and the middle condensing section, and the primary liquid refrigerant enters the middle condensing section through the regulating valve after being supercooled in the built-in reboiler.

[0014] The regulating valve reduces the pressure of the first-stage liquid refrigerant.

[0015] Furthermore, the liquid carbon dioxide refrigerant evaporates and cools the top condensation section and then enters the compressor for compression and liquefaction.

[0016] Furthermore, the packing in the first, second, and third packing layers is high-efficiency corrugated plate structured packing or high-efficiency surface-modified wire mesh structured packing. Packing is a critical component in the distillation process. Within the distillation tower, gas-liquid two-phase materials transfer mass and heat within the packing layers. By utilizing the different physical properties of the mixture's components and continuously reproducing gas-liquid equilibrium, the CO2 in the CO2 feed mixture is separated and purified.

[0017] Due to the adoption of the above technical solution, the utility model has the following beneficial effects:

[0018] The low-concentration carbon dioxide feedstock passes through Residual Cooling Recovery Units A and B, where the low-pressure non-condensable gas residual coolant and the high-pressure non-condensable gas residual coolant are recovered, respectively. The superheated feed then enters the distillation tower for distillation. After distillation, the liquid carbon dioxide is recovered from the bottom, and the non-condensable gas flows from the top into Residual Cooling Recovery Units B and A for further residual coolant recovery. The purpose of superheating the low-concentration carbon dioxide feedstock is to use the heat released by superheating to saturation to heat the liquid carbon dioxide material descending through the distillation tower, thereby reducing the external reboiler heat required in the tower bottom reboiler. This allows for sufficient reboilability without the need for an external heat source, relying solely on a primary liquid-phase ambient temperature refrigerant.

[0019] The specific beneficial effects are as follows:

[0020] (1) The process flow of this utility model is simple, the levels are clear, and the equipment configuration is small.

[0021] (2) The utility model is provided with a double waste cold recovery device, which avoids the blockage of pipes and equipment by dry ice generated after the high-pressure and low-temperature non-condensable gas is decompressed.

[0022] (3) The utility model optimizes the feed position of the distillation tower, greatly reducing the energy consumption of the distillation process (relative energy saving ~20%).

[0023] (4) The liquid phase refrigerant is used as the heat source of the reboiler to supercool the liquid phase refrigerant, thereby improving the thermal cycle efficiency and refrigeration coefficient of the refrigeration system and reducing the energy consumption of the refrigeration system (energy saving of ~6%). BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The present invention will be further described below with reference to the accompanying drawings.

[0025] Figure 1 This is the process flow chart of the low-concentration carbon dioxide raw gas recovery device. DETAILED DESCRIPTION

[0026] like Figure 1 The low-concentration carbon dioxide feed gas recovery device shown includes a residual cooling reclaimer A1, a residual cooling reclaimer B2, and a distillation tower 3. From top to bottom, the distillation tower 3 comprises a top condensing section 4, a first packing layer 5, a middle condensing section 6, a second packing layer 7, a third packing layer 8, and a built-in reboiler 9. A distillation tower air inlet 10 is located between the second and third packing layers 7, 8. A regulating valve 11 is connected between the built-in reboiler 9 and the middle condensing section 6.

[0027] The waste cooling unit A1 is equipped with a first air inlet a, a first air outlet b, a second air inlet c, and a second air outlet d. The waste cooling unit B2 is equipped with a third air inlet e, a third air outlet f, a fourth air inlet g, and a fourth air outlet h. The first air outlet b of the waste cooling unit A1 is connected to the third air outlet f of the waste cooling unit B2, while the second air outlet d of the waste cooling unit A1 is connected to the third air inlet e of the waste cooling unit B2. The third air outlet f of the waste cooling unit B2 is connected to the air inlet 10 of the distillation column.

[0028] The distillation column 3 is connected to a refrigeration system comprising a compressor (not shown), a primary liquid refrigerant 12, and a liquid carbon dioxide refrigerant 13. The primary liquid refrigerant 12 first heats the internal reboiler 9 before passing through a regulating valve 11 and entering the middle condensing section 6 for evaporative cooling. The liquid carbon dioxide refrigerant 13 then enters the compressor for compression and liquefaction. The liquid carbon dioxide refrigerant 13 evaporates and cools the top condensing section 4 before entering the compressor for compression and liquefaction.

[0029] The fillers in the first-stage packing layer 5 , the second-stage packing layer 7 and the third-stage packing layer 8 are high-efficiency corrugated plate structured packing or high-efficiency surface-modified wire mesh structured packing.

[0030] The recovery method using a low-concentration carbon dioxide raw gas recovery device comprises the following steps:

[0031] S1: The room temperature low concentration carbon dioxide raw gas of 3.3-3.5 MPa from the drying process enters the residual cooling recovery device A1 from the first air inlet a to recover the low pressure non-condensable gas residual cooling.

[0032] S2: The low-concentration carbon dioxide raw gas flowing out of the first gas outlet b of the residual cooling recovery device A1 enters the residual cooling recovery device B2 through the third gas inlet e to recover the high-pressure non-condensable gas residual cooling.

[0033] S3: The low-concentration CO2 feed gas flowing out of the third outlet f of the residual cooling recovery unit B2 enters the distillation tower 3 through the distillation tower inlet 10 and is then subjected to superheated feed rectification. Within the distillation tower 3, the low-concentration CO2 feed gas merges with the ascending gaseous CO2 material through the third packing layer 8. It then undergoes mass and heat transfer with the descending liquid CO2 material in the second packing layer 7. The gaseous CO2 material then enters the middle condensing section 6 of the distillation tower 3 for a primary condensation at -25°C. The condensate then flows back to the second packing layer 7 by gravity. The -25°C gaseous CO2 material then ascends into the first packing layer 5, undergoing mass and heat transfer with the descending liquid CO2 material. After exiting the first packing layer 5, it ascends to the top condensing section of the distillation tower 3 for a secondary condensation at -45°C. Normal-temperature primary liquid refrigerant 12 from the refrigeration system serves as a reboiling heat source and enters the built-in reboiler 9 in the bottom of distillation tower 3, heating and reboiling the liquid carbon dioxide material in the bottom. This subcools the refrigerant, which is then throttled to -30°C by regulating valve 11 before being transported to the central condensing section 6 of distillation tower 3 for evaporative cooling. The resulting primary gaseous refrigerant is then fed into the refrigeration system for compression and liquefaction. The -20°C saturated liquid carbon dioxide refrigerant from the refrigeration system is depressurized to -50°C by regulating valve 11 before being transported to the top condensing section of distillation tower 3 for evaporative cooling. The resulting gaseous carbon dioxide refrigerant is then fed into the refrigeration system for compression and liquefaction.

[0034] S4: The bottom of the distillation tower 3 obtains a qualified liquid carbon dioxide product 14, and the 3.3-3.5 MPa, -45°C high-pressure non-condensable tail gas obtained at the top of the distillation tower 3 enters the residual cold recovery device B2 through the fourth air inlet g for residual cold recovery.

[0035] S5: The reheated non-condensable tail gas flowing out of the fourth outlet h of the residual cold recovery device B2 is reduced in pressure to 0.02 MPa through the regulating valve 11, and then flows into the second air inlet c of the residual cold recovery device A1 to further recover the residual cold. The reheated non-condensable tail gas is discharged to a safe place through the second outlet d.

[0036] The final yield of liquid carbon dioxide was 91.5%.

[0037] The above are only specific embodiments of the present invention, but the technical features of the present invention are not limited thereto. Any simple changes, equivalent substitutions, or modifications based on the present invention that solve essentially the same technical problems and achieve essentially the same technical effects are included within the scope of protection of the present invention.

Claims

1. Low concentration carbon dioxide raw gas recovery device, characterized by: It includes a waste cooling recovery device A, a waste cooling recovery device B and a distillation tower. The low-concentration carbon dioxide raw material first passes through the waste cooling recovery device A and the waste cooling recovery device B for initial waste cooling recovery and then is superheated and fed into the distillation tower. The liquid carbon dioxide in the distillation tower flows out from the liquid carbon dioxide outlet provided at the bottom, and the non-condensable gas in the distillation tower flows out from the non-condensable gas outlet provided at the top to the waste cooling recovery device B and the waste cooling recovery device A for further waste cooling recovery.

2. The low-concentration carbon dioxide feed gas recovery device according to claim 1, characterized in that: The distillation tower includes, from top to bottom, a top condensation section, a first packing layer, a middle condensation section, a second packing layer, a third packing layer and a built-in reboiler. A distillation tower air inlet is provided between the second packing layer and the third packing layer. The low-concentration carbon dioxide raw material after the first residual cooling recovery enters the distillation tower through the distillation tower air inlet.

3. The low-concentration carbon dioxide feed gas recovery device according to claim 2, characterized in that: The distillation tower is connected to a refrigeration system, which includes a compressor, a first-level liquid refrigerant and a liquid carbon dioxide refrigerant. The first-level liquid refrigerant first heats the built-in reboiler, then evaporates and cools the middle condensation section, and then enters the compressor for compression and liquefaction.

4. The low-concentration carbon dioxide feed gas recovery device according to claim 3, characterized in that: A regulating valve is connected between the built-in reboiler and the middle condensing section, and the primary liquid refrigerant enters the middle condensing section through the regulating valve after being supercooled in the built-in reboiler.

5. The low-concentration carbon dioxide feed gas recovery device according to claim 3, characterized in that: The liquid carbon dioxide refrigerant evaporates and cools the top condensation section and then enters the compressor to be compressed and liquefied.

6. The low-concentration carbon dioxide feed gas recovery device according to claim 2, characterized in that: The fillers in the first-stage filler layer, the second-stage filler layer and the third-stage filler layer are high-efficiency corrugated plate structured fillers or high-efficiency surface-modified stainless steel wire mesh structured fillers.

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