Process for producing co and ultrafine carbon powder by low temperature plasma decomposition of co2

Abstract

The application discloses a process for producing CO and superfine carbon powder by low-temperature plasma decomposition of CO2, which comprises the following steps: S1: raw material gas is sent into a carbon dioxide decomposition reactor from the upper end by passing through a washing tower from bottom to top; S2: carbon dioxide in the raw material gas passes through and is decomposed in an electrified plasma channel to generate carbon monoxide, superfine carbon powder, oxygen and ozone; S3: the decomposition products in step S2 are introduced into a water washing unit to remove the superfine carbon powder, and the washing water flows into a second collecting tank from an overflow port and is discharged from the top end of the carbon dioxide decomposition reactor; and S4: the gas discharged in step S3 is separated into undecomposed carbon dioxide, CO product gas and tail gas by a refining unit, wherein the undecomposed carbon dioxide is returned into the carbon dioxide decomposition reactor by the action of a circulating gas compressor. The raw material gas after water washing is introduced into the carbon dioxide decomposition reactor to realize the decomposition and conversion of carbon dioxide, the whole process can be carried out at normal temperature, and any catalyst is not needed.

Description

Technical Field

[0001] This invention relates to the field of low-temperature plasma gas decomposition technology, specifically a process for producing CO and ultrafine carbon powder by low-temperature plasma decomposition of CO2. Background Technology

[0002] In recent years, my country has conducted several transformative technology research and development projects focusing on industries with persistent carbon emissions, aiming to break through existing production models and processes, reshape the high-carbon development model of traditional industries, and address or reduce carbon emissions at their source. In the chemical industry, my country has previously addressed the issues of fossil fuel-based production, heavy pollution, and high emissions by researching and exploring several transformative chemical routes and technologies from the perspectives of low-carbon energy and low-carbon resources. Flue gas is the polluting gaseous substance emitted from flues or chimneys after the combustion of fossil fuels, generally composed of carbon dioxide. Direct emission of carbon dioxide into the atmosphere contributes to the greenhouse effect and global warming. Currently, countries are researching the decomposition of carbon dioxide. Decomposing carbon dioxide into combustible carbon monoxide or other combustible gases can not only solve atmospheric carbon emissions but also enable the reuse of carbon dioxide. Typically, the conversion and decomposition of carbon dioxide requires high temperatures and the addition of other chemical substances as catalysts to promote the conversion. This process requires not only high temperatures but also the assistance of other chemical substances. Currently, with the extensive research on plasma, it is gradually being applied in the chemical industry. Plasma technology is divided into high-temperature plasma technology and low-temperature plasma technology. At present, high-temperature plasma technology is often used for the synthesis or decomposition of compounds, which requires very high temperatures and consumes a lot of energy, while low-temperature plasma technology is less used in the decomposition of carbon dioxide. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a process for producing CO and ultrafine carbon powder by low-temperature plasma decomposition of CO2, which realizes the conversion and utilization of carbon dioxide through the combined action of a low-temperature plasma unit and a water washing unit.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] The invention provides a process for producing CO and ultrafine carbon powder by low-temperature plasma decomposition of CO2, comprising the following steps:

[0006] S1: Open the water washing spray device inside the raw gas scrubbing tower. The raw gas enters from the bottom of the raw gas scrubbing tower, passes through the inside of the scrubbing tower from bottom to top, and is sent into the carbon dioxide decomposition reactor from the top.

[0007] S2: After the raw gas is dehydrated by the gas-liquid separation unit, it enters the plasma unit. Carbon dioxide passes through the energized plasma channel and decomposes to generate carbon monoxide, ultrafine carbon powder, oxygen, and ozone.

[0008] S3: the decomposition products in step S2 are introduced from the gas passage of the water washing unit into the water washing unit to remove superfine carbon powder by water washing, the washing water flows into the second collecting tank from the overflow port, and then is discharged from the top end of the carbon dioxide decomposition reactor;

[0009] S4: the gas discharged in step S3 is separated into undecomposed carbon dioxide, CO product gas and tail gas by the refining unit, wherein the undecomposed carbon dioxide is returned into the carbon dioxide decomposition reactor by the action of the circulating gas compressor.

[0010] Further, in step S1, the washing water in the first collecting tank is pumped into the water washing spray device by the first water washing pump to realize the recycling use of the washing water, and fresh water needs to be supplemented into the first collecting tank from time to time; in step S3, the electrode adsorption device is arranged in the second collecting tank to remove the superfine carbon powder in the washing water, and then the washing water in the second collecting tank is pumped into the washing water inlet of the water washing unit by the second water washing pump to realize the recycling use of the washing water.

[0011] Further, when the bubble cap tray structure is selected for water washing in step S3, the washing water is first flooded into the bubble cap tray structure, then the gas is introduced from the gas passage and overflowed from the periphery of the circular bubble cap, and the overflowed gas passes through the washing water and continues to move upward; when the lift cap-spray structure is selected for water washing, the spray head is opened, the washing water is atomized and sprayed from top to bottom, the gas is introduced from the gas passage and hits the lower side of the umbrella-shaped lift cap, and the gas is dispersed to the periphery to achieve the purpose of water washing.

[0012] Further, the decomposition of carbon dioxide by the plasma unit in step S2 is carried out at room temperature, direct current is adopted, and the voltage is above 1kV; when multiple plasma units and water washing units are arranged, the mixed gas discharged from the water washing unit in step S3 is directly introduced into the second-stage plasma unit, and then introduced into the second-stage water washing unit after the action of the second-stage plasma unit; until the last-stage plasma decomposition and water washing are completed, the gas is discharged from the top end of the carbon dioxide decomposition reactor.

[0013] Compared with the prior art, the present application has the following beneficial effects:

[0014] (1) the raw gas after water washing is introduced into the carbon dioxide decomposition reactor to realize the decomposition and conversion of carbon dioxide, the raw gas is widely sourced, which can come from the wet decarbonization device or the boiler flue gas, if the raw gas comes from the wet decarbonization device, the temperature is usually 20-45 DEG C, if the raw gas comes from the boiler flue gas, the temperature is usually 140-200 DEG C, and part of particulate matter is contained, the particulate matter can be removed by water washing while cooling, the cooled raw gas is introduced into the carbon dioxide decomposition reactor, and the carbon dioxide is decomposed and converted in the plasma channel under the condition of power supply at normal temperature, the process does not need to be carried out in a high-temperature environment, the safety of the operating personnel is ensured, and the energy consumption is reduced, in addition, any catalyst is not added in the application, and the subsequent separation and purification process can be simplified, the gas obtained through the carbon dioxide decomposition reactor is refined through the refining unit, and the undecomposed carbon dioxide, CO product gas and tail gas can be separated, wherein the undecomposed carbon dioxide is returned to the carbon dioxide decomposition reactor for decomposition through the action of the circulating gas compressor.

[0015] (2) after the carbon dioxide in the raw gas is decomposed by plasma, superfine carbon powder is mixed in the decomposition product, the superfine carbon powder is removed through the water washing unit, the structure for water washing of the mixed gas is a bubble cap tray structure or a gas hat-spraying structure, the former realizes water washing by making the gas pass through the washing water, and the latter realizes water washing by dispersing the gas and then spraying, the superfine carbon powder in the decomposition product can be effectively removed, the washing water after washing is collected in the liquid collecting tank, and the electrode adsorption device is arranged in the liquid collecting tank, so that the superfine carbon powder can be completely adsorbed, and the recycling of the washing water is realized. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 it is the whole structure schematic diagram of the application;

[0017] Figure 2 it is the structure diagram of one embodiment of the carbon dioxide decomposition reactor of the application;

[0018] Figure 3 it is the structure diagram of one embodiment of the water washing unit in the carbon dioxide decomposition reactor of the application;

[0019] Figure 4 it is the structure diagram of another embodiment of the carbon dioxide decomposition reactor of the application;

[0020] Figure 5 it is the structure diagram of another embodiment of the water washing unit in the carbon dioxide decomposition reactor of the application.

[0021] The corresponding names of the attached figures are as follows: 1-Raw gas scrubbing tower, 2-Gas-liquid separation unit, 3-Water washing spray device, 4-First liquid collection tank, 5-First water washing pump, 6-Plasma unit, 7-Water washing unit, 8-Gas inlet, 9-Gas outlet, 10-Spray head, 11-Washing water inlet, 12-First gas channel, 13-Circular bubble cap, 14-Overflow port, 15-Umbrella-shaped gas lift cap, 16-Second liquid collection tank, 17-Electrode adsorption device, 18-Bubble cap tray structure, 19-Gas lift cap-spray structure, 20-Second gas channel, 21-Second water washing pump, 22-Circulating gas compressor, 23-Refining unit. Detailed Implementation

[0022] The present invention will be further described below with reference to the accompanying drawings and embodiments. The embodiments of the present invention include, but are not limited to, the following embodiments.

[0023] Example 1

[0024] like Figures 1 to 3 As shown, this invention provides a process for producing CO and ultrafine carbon powder by low-temperature plasma decomposition of CO2. This process uses a carbon dioxide gas decomposition device, which includes a raw gas scrubbing tower 1 for washing the raw gas with water, and a carbon dioxide decomposition reactor connected to the raw gas scrubbing tower 1. A water washing spray device 3 is installed at the upper part of the interior of the raw gas scrubbing tower 1. The internal components of the raw gas scrubbing tower 1 can be selected from random packing, structured packing, tray structure, or empty tower structure according to actual conditions. Furthermore, the cross-section of the raw gas scrubbing tower 1 can be square or circular. A first liquid collection tank 4 is connected to the bottom of the raw gas scrubbing tower 1. The first liquid collection tank 4 and the water washing spray device 3 are connected by a pipe equipped with a first water washing pump 5. The first water washing pump 5 can transport the washing water in the first liquid collection tank 4 to the water washing spray device 3, realizing the recycling of the washing water.

[0025] The raw gas, after being washed in the scrubbing tower, is introduced into a carbon dioxide decomposition reactor. From bottom to top, the carbon dioxide decomposition reactor consists of a gas-liquid separation unit 2 with a gas inlet 8, a plasma unit 6 for plasma decomposition of carbon dioxide, and a water washing unit 7 for washing the decomposition products to remove ultrafine carbon powder. A gas outlet 9 is located at the top of the carbon dioxide decomposition reactor. The gas-liquid separation unit 2 removes liquid free water from the raw gas, and the removed water enters a second collection tank. The plasma unit 6 uses the plasma carbon dioxide treatment system disclosed in patent JP2023010045A by the Future Science Institute Co., Ltd. of Japan. The plasma unit decomposes carbon dioxide at room temperature using direct current with a voltage of 1kV or higher. In the plasma unit, carbon dioxide passes through an energized plasma channel and decomposes into carbon monoxide, ultrafine carbon powder, oxygen, and ozone.

[0026] The water washing unit 7 comprises a washing water inlet 11 arranged at the upper end of the water washing unit 7, an overflow port 14 arranged at the lower end of the water washing unit 7 and capable of discharging washing water, and a bubble cap tray structure 18 capable of realizing water washing of the gas (as shown in Figure 3 The bubble cap tray structure 18 comprises a first gas channel 12 capable of conveying the gas from the plasma unit 6 to the water washing unit 7 and a circular bubble cap arranged at the first gas channel 12 and capable of overflowing the gas. The mixed gas obtained by the decomposition of the plasma unit 6 enters the water washing unit 7 through the first gas channel 12 to wash away the superfine carbon powder, and the washing water flows into the second collecting tank 16 through the overflow port 14. The second collecting tank 16 is provided with an electrode adsorption device 17 for removing the superfine carbon powder in the washing water. The washing water in the second collecting tank 16 is conveyed to the washing water inlet 11 at the upper end of the water washing unit 7 by the second water washing pump 21, so as to realize the recycling of the washing water. According to the test, the single-pass conversion rate of the plasma unit in the decomposition and conversion of carbon dioxide is 5% to 85%, so the plasma unit 6 and the water washing unit 7 can be arranged in multiple according to the actual situation. It should be noted that the plasma unit and the water washing unit need to be distributed at intervals (as shown in Figure 2 The water washing unit 7 and the plasma unit 6, and the gas-liquid separation unit 2 and the plasma unit 6 are connected by flanges in the shortest distance. The direct connection by the flanges can shorten the length of the pipeline, reduce the resistance, save the space and reduce the investment of the equipment. The CO2 gas decomposition device provided in the embodiment further comprises a refining unit 23 for separating the gas after the decomposition of the carbon dioxide decomposition reactor. A circulation pipeline capable of conveying the undecomposed CO2 back to the carbon dioxide decomposition reactor is arranged between the refining unit 23 and the carbon dioxide decomposition reactor, and a circulation gas compressor 22 is arranged on the circulation pipeline.

[0027] The process for producing CO and superfine carbon powder by low-temperature plasma decomposition of CO2 provided in the embodiment comprises the following steps:

[0028] S1: Turn on the water washing spray device inside the raw gas washing tower. The raw gas enters from the lower part of the raw gas washing tower, passes through the inside of the washing tower from bottom to top, and the particulate matters in the raw gas are washed away and cooled. The raw gas is sent into the carbon dioxide decomposition reactor from the upper end. The washing water is collected into the first collecting tank, and then is pumped into the water washing spray device by the first water washing pump to realize the recycling of the washing water. Fresh water needs to be supplemented into the first collecting tank from time to time.

[0029] S2: The raw gas enters the gas-liquid separation unit from the gas inlet at the lower end of the carbon dioxide decomposition reactor, and after removing the liquid saturated water, enters the plasma unit. The voltage of the plasma unit is above 1 kV. The carbon dioxide passes through the electrified plasma channel and decomposes to generate a mixed gas containing carbon monoxide, superfine carbon powder, oxygen and ozone.

[0030] S3: The mixed gas in step S2 is introduced into the water washing unit from the gas channel of the water washing unit to remove the superfine carbon powder by water washing. The washing water flows into the second collecting tank from the overflow port, and then is discharged from the top end of the carbon dioxide decomposition reactor. In this embodiment, the bubble cap tray structure is used for water washing of the gas. The washing water is first flooded into the bubble cap tray structure, and then the gas enters from the gas channel and overflows from the periphery of the circular bubble cap. The gas after overflowing passes through the washing water and continues to move upward. When the gas passes through the washing water, the superfine carbon powder in the gas can be washed away.

[0031] S4: The gas discharged in step S3 is separated into undecomposed carbon dioxide, CO product gas and tail gas by the refining unit. The undecomposed carbon dioxide is returned to the carbon dioxide decomposition reactor by the action of the circulating gas compressor. The refining unit mainly uses the deep cooling or adsorption method to separate the undecomposed carbon dioxide and the CO product gas. Finally, the remaining gas is discharged as tail gas.

[0032] S5: The second collecting tank is provided with an electrode adsorption device for removing the superfine carbon powder in the washing water. By providing a second water washing pump, the washing water in the second collecting tank can be pumped into the washing water inlet of the water washing unit to realize the recycling use of the washing water.

[0033] It should be noted that in the above embodiment, only one plasma decomposition is carried out, and the conversion rate of carbon dioxide is 5% to 85%. According to the actual situation, multiple plasma units and water washing units can be provided. When multiple units are provided, the mixed gas discharged from the water washing unit directly enters the second-stage plasma unit, and after the action of the second-stage plasma unit, it enters the second-stage water washing unit. Until the last-stage plasma decomposition and water washing are completed, the gas is discharged from the top end of the carbon dioxide decomposition reactor.

[0034] Example 2

[0035] As Figure 4 and 5As shown, on the basis of Embodiment 1, the bubble cap tray structure 18 can also be replaced by a riser cap-spraying structure 19, which comprises a spraying head 10 connected with the washing water inlet 11, a second gas passage 20 capable of conveying gas from the plasma unit 6 to the water washing unit 7, and an umbrella-shaped riser cap 15 arranged on the second gas passage 20 and capable of dispersing the gas. The mixed gas generated by the plasma unit enters the water washing unit through the second gas passage 20, and the gas moves upward and collides with the lower side of the umbrella-shaped riser cap 15 to realize the dispersion of the gas, and then the ultrafine carbon powder in the mixed gas is washed away by the spraying water, which can make the gas fully contact with the water and prevent the washing water from entering the plasma unit, and finally the washing water flows into the second liquid collecting tank 16 from the overflow port 14.

[0036] The raw material gas after water washing is introduced into the carbon dioxide decomposition reactor to realize the decomposition and conversion of carbon dioxide. The raw material gas can be obtained from a wet decarbonization device or a boiler flue gas. If the raw material gas is obtained from the wet decarbonization device, the temperature is usually 20-45℃. If the raw material gas is obtained from the boiler flue gas, the temperature is usually 140-200℃ and contains part of particulate matter. Through water washing, the particulate matter can be removed while cooling. The cooled raw material gas is introduced into the carbon dioxide decomposition reactor to realize the decomposition and conversion of carbon dioxide in the plasma passage under normal temperature. This process does not need to be carried out in a high-temperature environment, which ensures the safety of the operating personnel and reduces energy consumption. In addition, no catalyst needs to be added in the present application, which can simplify the subsequent separation and purification process. The gas obtained from the carbon dioxide decomposition reactor is refined in a refining unit, and the undecomposed carbon dioxide, CO product gas and tail gas can be separated. The undecomposed carbon dioxide is returned to the carbon dioxide decomposition reactor by the action of a circulating gas compressor to continue the decomposition.

[0037] The above embodiment is only one of the preferred embodiments of the present application and should not be used to limit the protection scope of the present application. Any modification or polishing without substantial meaning made within the main design idea and spirit of the present application, which still solves the technical problems consistent with the present application, should be included in the protection scope of the present application.

Claims

1. A process for producing CO and ultrafine carbon powder by low-temperature plasma decomposition of CO2, characterized in that, Includes the following steps: S1: Open the water washing spray device inside the raw gas scrubbing tower. The raw gas enters from the bottom of the raw gas scrubbing tower, passes through the interior of the scrubbing tower from bottom to top, and is sent into the carbon dioxide decomposition reactor from the top. The first water washing pump pumps the washing water in the first collection tank into the water washing spray device to realize the recycling of the washing water. S2: The raw material gas enters the gas-liquid separation unit from the gas inlet at the bottom of the carbon dioxide decomposition reactor. After the liquid saturated water is removed in the gas separation unit, the gas enters the plasma unit. The carbon dioxide passes through the energized plasma channel and decomposes to generate carbon monoxide, ultrafine carbon powder, oxygen and ozone. S3: The decomposition products from step S2 are introduced into the water washing unit through the gas channel of the water washing unit to remove the ultrafine carbon powder. The washing water flows into the second collection tank from the overflow port and then exits from the top of the carbon dioxide decomposition reactor. The water washing unit uses a bubble cap tray structure or a riser cap-spray structure to wash the mixed gas to remove the ultrafine carbon powder. The washed gas exits from the top of the carbon dioxide decomposition reactor, while the washing water carrying the ultrafine carbon powder flows into the second collection tank from the overflow port of the water washing unit. The second collection tank is equipped with an electrode adsorption device to remove the ultrafine carbon powder from the washing water. The second water washing pump then pumps the washing water from the second collection tank into the washing water inlet of the water washing unit to achieve the recycling of the washing water. S4: The gas discharged in step S3 is separated into undecomposed carbon dioxide, CO product gas and tail gas by the purification unit. The undecomposed carbon dioxide is returned to the carbon dioxide decomposition reactor by the action of the recirculating gas compressor.

2. The process for producing CO and ultrafine carbon powder by low-temperature plasma decomposition of CO2 according to claim 1, characterized in that, In step S1, fresh water needs to be added to the first collection tank from time to time.

3. The process for producing CO and ultrafine carbon powder by low-temperature plasma decomposition of CO2 according to claim 2, characterized in that, When using a bubble cap tray structure for water washing in step S3, the washing water first submerges the bubble cap tray structure. Then, the gas enters through the gas channel and overflows from the periphery of the circular bubble cap. The overflowing gas passes through the washing water and continues to move upward. When using a lift cap-spray structure for water washing, the spray head is opened, and the washing water is atomized and sprayed from top to bottom. The gas enters through the gas channel and impacts the lower side of the umbrella-shaped lift cap. The gas then disperses in all directions to achieve the purpose of water washing.

4. The process for producing CO and ultrafine carbon powder by low-temperature plasma decomposition of CO2 according to claim 3, characterized in that, In step S2, the decomposition of carbon dioxide in the plasma unit is carried out at room temperature, using direct current with a voltage of 1kV or higher. When multiple plasma units and water washing units are set up, the mixed gas discharged from the water washing unit in step S3 directly enters the second-stage plasma unit, and after being acted upon by the second-stage plasma unit, it enters the second-stage water washing unit. The gas is discharged from the top of the carbon dioxide decomposition reactor after the final stage of plasma decomposition and water washing is completed.

Images