Work starting method and device for heating process medium

Abstract

The invention relates to a starting method and device for heating a process medium. The method comprises the following steps: when the content of carbon dioxide in the furnace top flue gas reaches or is higher than a second set threshold value, dividing the furnace top flue gas into flue gas to be converted and circulating flue gas, feeding the flue gas to be converted into a carbon dioxide electrochemical catalytic conversion unit, and carrying out electrochemical catalytic conversion reaction to obtain synthesis gas and circulating gas, and the circulating flue gas is mixed with external oxygen and the circulating gas to serve as combustion-supporting gas. The device comprises a gas-gas mixer, a combustor, an industrial furnace body, a heat exchange unit and an electrochemical catalytic conversion unit. The problems that in the prior art, single air combustion-supporting start-up generates a large amount of nitric oxide, the radiation heat transfer efficiency is low, the smoke exhaust heat loss is large, the concentration of CO2 is low, and trapping and utilization are not facilitated are solved.

Description

Technical Field

[0001] This invention relates to the field of energy engineering, and more specifically, to a method and apparatus for starting up a heating process medium. Background Technology

[0002] Rapid industrial development has brought convenience to people's lives. Combustion is currently our primary way of obtaining energy from natural resources. However, the development of the petrochemical industry has also brought increasingly serious environmental problems.

[0003] Traditional process heating uses air as the combustion-supporting gas. However, the presence of large amounts of nitrogen and carbon dioxide in the air leads to incomplete combustion, resulting in exhaust gas containing significant amounts of carbon dioxide, nitrogen oxides, and non-combustible nitrogen, causing substantial heat loss. Currently, methods to design more efficient heating process media are being developed to achieve carbon dioxide enrichment and utilization, as well as energy conservation and emission reduction. CN103234213A discloses a method and apparatus for utilizing heat from oxygen-enriched combustion. The method includes the following steps: Step A: The boiler outlet flue gas is divided into a first part, a second part, and a third part. The first part preheats the oxygen fed into the boiler, the second part heats the circulating flue gas fed into the boiler, and the third part heats the feedwater. Step B: The first, second, and third parts of the flue gas are mixed after heat exchange and sent to a flue gas condenser. After drying and condensing to room temperature, they are divided into two parts: one part is sent as circulating flue gas to a circulating flue gas preheater, and the other part is sent to a flue gas compressor.

[0004] However, existing methods for heating process media have problems such as generating a large amount of nitrogen oxides during single-air combustion start-up, low radiative heat transfer efficiency, large heat loss in flue gas, and low CO2 concentration which is not conducive to capture and utilization. Summary of the Invention

[0005] To overcome the above-mentioned defects and solve the problems of generating a large amount of nitrogen oxides, low radiation heat transfer efficiency, large exhaust heat loss, and low CO2 concentration which are not conducive to capture and utilization, this invention provides a starting method and apparatus for heating the process medium.

[0006] The first aspect of this invention provides a method for starting a heated process medium, the method comprising: S1, feeding fuel gas and combustion-supporting gas into a burner for ignition and combustion to obtain high-temperature flue gas; the combustion-supporting gas containing external oxygen and external carbon dioxide; feeding the high-temperature flue gas into an industrial furnace body for heat exchange with the process medium to be heated to obtain furnace top flue gas and the heated process medium; S2, when the carbon dioxide content in the furnace top flue gas does not reach a first set threshold, mixing the furnace top flue gas with the external oxygen and external carbon dioxide as combustion-supporting gas and returning to step S1; S3, when the furnace top flue gas... When the carbon dioxide content in the gas reaches the first set threshold but not the second set threshold, the input of external carbon dioxide gas is stopped, and the flue gas at the top of the furnace is mixed with external oxygen as combustion-supporting gas and returned to step S1; S4, when the carbon dioxide content in the flue gas at the top of the furnace reaches or exceeds the second set threshold, the flue gas at the top of the furnace is divided into flue gas to be converted and circulating flue gas. The flue gas to be converted is sent to the carbon dioxide electrochemical catalytic conversion unit for electrochemical catalytic conversion reaction to obtain syngas and circulating gas. The circulating flue gas is mixed with external oxygen and the circulating gas as combustion-supporting gas and returned to step S1.

[0007] Preferably, a carbon dioxide concentration detector is used to detect the carbon dioxide content in the flue gas at the top of the furnace; the first set threshold is any value within the range of 10v%-20v%; the second set threshold is any value within the range of 25v%-90v%.

[0008] Optionally, in step S2, the flue gas at the top of the furnace is heat-exchanged to obtain circulating flue gas, and the circulating flue gas, together with the external oxygen and the external carbon dioxide, is sent into the burner as combustion-supporting gas. In step S3, the flue gas at the top of the furnace is heat-exchanged to obtain circulating flue gas, and the circulating flue gas and the external oxygen are sent into the burner as combustion aid. In step S4, the flue gas at the top of the furnace is heat-exchanged to obtain circulating flue gas and flue gas to be converted; the flue gas to be converted is sent to the electrochemical catalytic conversion unit and completely converted into syngas and circulating gas; the circulating flue gas is mixed with the external oxygen and the circulating gas as combustion-supporting gas and sent to the burner.

[0009] Preferably, the oxygen content in the combustion-supporting gas is detected using an oxygen concentration detector, and the oxygen content in the combustion-supporting gas varies within the range of 21v% to 50v% as the industrial furnace burns; the oxygen content in the circulating gas varies within the range of 60v% to 100v%.

[0010] Optionally, in step S4, the flue gas to be converted and the first electrolyte are fed together into the cathode chamber of the electrochemical reactor in the electrochemical catalytic conversion unit, and the second electrolyte is fed into the anode chamber of the electrochemical reactor. An electrochemical catalytic conversion reaction is carried out in the electrochemical reactor to obtain a cathode gas-liquid mixture and an anode gas-liquid mixture. The cathode gas-liquid mixture is fed into a first gas-liquid separator for gas-liquid separation to obtain syngas and cathode electrolyte. The anode gas-liquid mixture is fed into a second gas-liquid separator for gas-liquid separation to obtain circulating gas and anode electrolyte. The cathode electrolyte and the anode electrolyte are fed into an electrolyte mixing tank for mixing, and then the first electrolyte and the second electrolyte are drawn out from the electrolyte mixing tank. Demineralized water is fed into the electrolyte mixing tank to replenish the water consumed in the electrolysis reaction. The electrolyte is an aqueous solution of alkali metal carbonates and / or alkali metal bicarbonates, with a concentration range of 0.2 mol / L - 10 mol / L.

[0011] Preferably, the electrochemical reactor operates at a temperature of 10℃-120℃ and an operating pressure of 0.05 MPa-2.0 MPa; the first gas-liquid separator and the second gas-liquid separator are vertical or horizontal gas-liquid separators; the operating temperature inside the first gas-liquid separator is 10℃-120℃ and the operating pressure is 0.05 MPa-2.0 MPa; the operating temperature inside the second gas-liquid separator is 10℃-120℃ and the operating pressure is 0.05 MPa-2.0 MPa.

[0012] Optionally, the method further includes passing the flue gas from the furnace top through the high-temperature section and the low-temperature section of the low-temperature cold source heat exchanger in sequence to exchange heat, thereby obtaining flue gas to be converted and condensate, mixing the condensate with demineralized water, and then sending it into the electrolyte mixing tank of the electrochemical catalytic conversion unit.

[0013] Another aspect of the present invention provides an apparatus for heating a process medium, the apparatus comprising: a gas-gas mixer, a burner, an industrial furnace body, a heat exchange unit, and an electrochemical catalytic conversion unit; the industrial furnace body includes a high-temperature flue gas inlet, a process medium inlet to be heated, and a furnace top flue gas outlet arranged sequentially from bottom to top; the heat exchange unit includes a reflux flue gas inlet, a circulating flue gas outlet, and a flue gas outlet to be converted arranged sequentially along the flue gas flow direction; the electrochemical catalytic conversion unit includes a flue gas inlet to be converted, a syngas outlet, and a circulating gas outlet arranged sequentially; the furnace top flue gas outlet of the industrial furnace body and the reflux flue gas inlet of the heat exchange unit are connected... A reflux flue gas pipeline is provided. A circulating flue gas pipeline is provided between the circulating flue gas outlet of the heat exchange unit and the circulating flue gas inlet of the gas-gas mixer. A flue gas pipeline to be converted is provided between the flue gas outlet to be converted of the heat exchange unit and the flue gas inlet to be converted of the electrochemical catalytic conversion unit. A circulating gas pipeline is provided between the circulating gas outlet of the electrochemical catalytic conversion unit and the circulating gas inlet of the gas-gas mixer. The combustion-supporting gas outlet of the gas-gas mixer is connected to the combustion-supporting gas inlet of the burner. The gas-gas mixer is also provided with an external carbon dioxide inlet and an external oxygen inlet. A carbon dioxide concentration detector is also provided on the flue gas pipeline to be converted.

[0014] Optionally, the electrochemical catalytic conversion unit includes an electrochemical reactor, a first gas-liquid separator, a second gas-liquid separator, and an electrolyte mixing tank arranged sequentially along the flue gas flow direction; the electrochemical reactor includes a cathode chamber and an anode chamber separated by an ion-exchange membrane; the electrochemical reactor includes a cathode electrolyte inlet, an anode electrolyte inlet, a flue gas to be converted inlet, a cathode gas-liquid mixture outlet, and an anode gas-liquid mixture outlet arranged sequentially; the heat exchange unit includes a high-temperature section of a low-temperature cold source heat exchanger, a reflux flue gas induced draft fan, and a low-temperature section of a low-temperature cold source heat exchanger arranged sequentially; the flue gas to be converted outlet of the low-temperature section of the low-temperature cold source heat exchanger is connected to the outlet of the electrochemical catalytic conversion unit. The conversion flue gas inlet is connected to the cathode gas-liquid mixture outlet, which is connected to the cathode electrolyte inlet of the first gas-liquid separator. The anode gas-liquid mixture outlet is connected to the anode electrolyte inlet of the second gas-liquid separator. The first gas-liquid separator also includes a syngas outlet and a cathode electrolyte outlet, with the cathode electrolyte outlet connected to the electrolyte mixing tank. The second gas-liquid separator also includes a recirculating gas outlet and an anode electrolyte outlet, with the recirculating gas outlet connected to the recirculating gas inlet of the gas-gas mixer and the anode electrolyte outlet connected to the electrolyte mixing tank. The first electrolyte outlet of the electrolyte mixing tank is connected to the cathode chamber, and the second electrolyte outlet is connected to the anode chamber.

[0015] Optionally, the heat exchange unit is provided with a low-temperature cold source pipeline, which sequentially connects to the low-temperature section and the high-temperature section of the low-temperature cold source heat exchanger and then returns to the low-temperature section of the low-temperature cold source heat exchanger. The low-temperature cold source outlet after heat exchange in the low-temperature section of the low-temperature cold source heat exchanger is connected to the demineralized water inlet of the electrochemical catalytic conversion unit. A circulating flue gas pipeline is provided between the flue gas outlet of the reflux flue gas induced draft fan and the gas-gas mixer. A low-temperature section inlet flue gas pipeline is provided between the flue gas outlet of the reflux flue gas induced draft fan and the low-temperature section inlet flue gas of the low-temperature section of the low-temperature cold source heat exchanger. A flue gas pipeline is provided between the flue gas to be converted in the low-temperature section of the low-temperature cold source heat exchanger and the flue gas inlet to be converted in the cathode chamber of the electrochemical catalytic conversion unit.

[0016] Through the above technical solutions, this invention increases the flexibility of equipment startup by using a combination of various combustion-supporting fuels. The combustion environment of the device provided by this invention is almost free of nitrogen, greatly reducing the generation of pollutants such as nitrogen oxides; nitrogen oxide emissions are nearly zero, which is beneficial to environmental protection. Simultaneously, this invention uses pure oxygen-assisted combustion to achieve efficient fuel combustion, improving heat transfer efficiency. By using circulating flue gas and circulating gas as combustion-supporting fuels, it fully utilizes the combustion flue gas generated during the combustion process, reducing the amount of exhaust gas and minimizing heat loss. By electrochemically catalytically converting carbon dioxide, the carbon dioxide recovery rate is improved, and the carbon dioxide in the combustion flue gas is almost completely converted into syngas and regenerated flue gas, significantly reducing greenhouse gas emissions and generating high-value-added product gases, thus reducing environmental pollution while increasing the economic value of combustion.

[0017] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0018] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof. In the drawings: Figure 1 This is a schematic diagram of an oxygen-enriched combustion and carbon dioxide enrichment device according to one embodiment of the present invention. Figure 2 This is a schematic diagram of the device within an electrochemical catalytic conversion unit according to one embodiment of the present invention.

[0019] Explanation of reference numerals in the attached figures 1-Burner, 2-Industrial furnace body, 3-High-temperature section of low-temperature cold source heat exchanger, 4-Recirculating flue gas induced draft fan, 5-Low-temperature section of low-temperature cold source heat exchanger, 6-Gas-gas mixer, 7-Blower, 8-Electrochemical catalytic conversion unit, 81-Electrochemical reactor, 801-Cathode chamber, 802-Anode chamber, 82-First gas-liquid separator, 83-Second gas-liquid separator, 84-Electrolyte mixing tank, 9-Chimney, 11-Regulating valve one, 12-Regulating valve two, 13-Regulating valve three, 14-Regulating valve four, 15-Regulating valve five, 16-Regulating valve six, 17-Pure oxygen regulating valve; 101-Fuel gas, 102-Top flue gas, 103-Recirculating flue gas, 104-Flue gas after heat exchange, 105-Flue gas before low-temperature section, 106-High-purity carbon dioxide flue gas, 107-Flue gas to be converted, 108-Flue gas after carbon dioxide concentration detector, 109-Exhaust flue gas, 110-Condensate, 111-Demineralized water, 112-Synthesis gas, 113-Circulating gas, 114-Low-temperature cold source, 115-Low-temperature cold source after heat exchange, 116-External oxygen, 117 - Circulating flue gas, 118-First mixed gas, 119-External carbon dioxide gas, 120-Second mixed gas, 121-Combustion-supporting gas, 122-Mixed gas before burner, 123-Process medium to be heated, 124-First electrolyte, 125-Second electrolyte, 126-Cathode gas-liquid mixture, 127-Anode gas-liquid mixture, 128-Cathode electrolyte, 129-Anode electrolyte, AI1-Oxygen concentration detector, AI2-Carbon dioxide concentration detector. Detailed Implementation

[0020] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0021] The first aspect of the present invention provides a method for starting a heated process medium, the method comprising: S1, feeding fuel gas 101 and combustion-supporting gas into a burner 1 for ignition and combustion to obtain high-temperature flue gas; the combustion-supporting gas containing external oxygen and external carbon dioxide; feeding the high-temperature flue gas into an industrial furnace body 2 for heat exchange with the process medium 123 to be heated, to obtain furnace top flue gas 102 and the heated process medium; S2, when the carbon dioxide content in the furnace top flue gas 102 does not reach a first set threshold, mixing the furnace top flue gas 102 with the external oxygen and external carbon dioxide as combustion-supporting gas and returning to step S1; S3, when the furnace top flue gas 102... When the carbon dioxide content in the flue gas reaches the first set threshold but not the second set threshold, the input of external carbon dioxide gas is stopped, and the flue gas 102 at the top of the furnace is mixed with external oxygen as combustion-supporting gas and returned to step S1; S4, when the carbon dioxide content in the flue gas 102 at the top of the furnace reaches or exceeds the second set threshold, the flue gas 102 at the top of the furnace is divided into flue gas to be converted 107 and circulating flue gas 117. The flue gas to be converted 107 is sent to the carbon dioxide electrochemical catalytic conversion unit 8 for electrochemical catalytic conversion reaction to obtain syngas and circulating gas. The circulating flue gas 117 is mixed with external oxygen and the circulating gas as combustion-supporting gas and returned to step S1.

[0022] In this preferred embodiment, the present invention utilizes multiple mixed combustion-assisted start-up methods corresponding to the carbon dioxide concentration within the device. By mixing combustion flue gas with external oxygen, external carbon dioxide, and the device's circulating gas to assist combustion, the fuel gas is fully combusted. The combustion environment is almost free of nitrogen, greatly reducing the generation of nitrogen oxides, with nitrogen oxide emissions approaching zero. At the same time, the carbon dioxide generated during combustion is fully recovered and utilized, significantly reducing pollutant emissions. Ultimately, the device can achieve complete fuel combustion and full recovery and utilization of carbon dioxide without the need for external combustion-assisted gas supply, realizing the recycling of combustion flue gas.

[0023] In a preferred embodiment, a carbon dioxide concentration detector AI2 is used to detect the carbon dioxide content in the flue gas 102 at the top of the furnace; the first set threshold is any value within the range of 10v%-20v%; and the second set threshold is any value within the range of 25v%-90v%.

[0024] In this preferred embodiment, the present invention controls the direction of gas within the device and the supply of external combustion-supporting gas by using the detection results of the carbon dioxide concentration detector AI2, thereby achieving complete combustion of fuel gas under various operating conditions.

[0025] In an optional embodiment, in step S2, the flue gas 102 at the top of the furnace is heat-exchanged to obtain circulating flue gas 117, and the circulating flue gas 117, together with the external oxygen 116 and the external carbon dioxide 119, is fed into the burner 1 as combustion-supporting gas 121; in step S3, the flue gas 102 at the top of the furnace is heat-exchanged to obtain circulating flue gas 117, and the circulating flue gas 117, together with the external oxygen 116, is fed into the burner 1 as combustion-supporting gas 121; in step S4, the flue gas 102 at the top of the furnace is heat-exchanged to obtain circulating flue gas 117 and flue gas to be converted 107; the flue gas to be converted 107 is fed into the electrochemical catalytic conversion unit 8 and completely converted into syngas 112 and circulating gas 113; the circulating flue gas 117, together with the external oxygen 116 and the circulating gas 113, is mixed as combustion-supporting gas 121 and fed into the burner 1.

[0026] In the above optional embodiments, the device can be flexibly used in multiple operating modes. When the carbon dioxide content in the flue gas 102 at the top of the furnace reaches the set threshold of the carbon dioxide concentration detector AI2, the flue gas at the top of the furnace is divided into flue gas to be converted 107 and circulating flue gas 117. The flue gas to be converted 107 is catalytically converted by the electrochemical catalytic conversion unit 8 to obtain syngas and circulating gas. The syngas includes hydrogen and carbon monoxide and is sent to the downstream utilization device for use. The circulating gas contains regenerated oxygen and is sent to the gas-gas mixer to mix with the circulating flue gas as combustion aid, so as to achieve the recycling of flue gas in the device. The carbon dioxide produced by the combustion of the device is completely absorbed and converted. The carbon dioxide of the electrochemical catalytic conversion unit can be completely converted.

[0027] In a preferred embodiment, an oxygen concentration detector AI1 is used to detect the oxygen content in the combustion-supporting gas 121, the oxygen content in the combustion-supporting gas varying from 21v% to 50v% with industrial furnace combustion; the oxygen content in the circulating gas 113 varies from 60v% to 100v%.

[0028] In the preferred embodiment described above, increasing the oxygen content in the combustion-supporting gas enables oxygen-enriched combustion of the fuel gas, thereby improving fuel combustion efficiency, reducing the generation of combustion flue gas, and reducing heat loss caused by flue gas emissions. At the same time, the oxygen in the circulating gas and the carbon dioxide in the circulating flue gas are fed back into the burner as combustion-supporting gas, ultimately achieving the goal of eliminating the need for external carbon dioxide supplementation and reducing the external oxygen supply, thereby reducing fuel combustion costs and efficiently utilizing combustion flue gas.

[0029] In an optional embodiment, the method further includes: in step S4, the flue gas 107 to be converted and the first electrolyte 124 are fed together into the cathode chamber 801 of the electrochemical reactor 81 in the electrochemical catalytic conversion unit 8, and the second electrolyte 125 is fed into the anode chamber 802 of the electrochemical reactor 81, where an electrochemical catalytic conversion reaction is carried out in the electrochemical reactor 81 to obtain a cathode gas-liquid mixture 126 and an anode gas-liquid mixture 127; the cathode gas-liquid mixture 126 is fed into a first gas-liquid separator 82 for gas-liquid separation to obtain syngas 112 and cathode electrolyte 128. The anode gas-liquid mixture 127 is fed into the second gas-liquid separator 83 for gas-liquid separation to obtain circulating gas 113 and anode electrolyte 129. The cathode electrolyte 128 and the anode electrolyte 129 are fed into the electrolyte mixing tank 84 for mixing. Then, the first electrolyte 124 and the second electrolyte 125 are drawn out from the electrolyte mixing tank 84. Demineralized water 111 is fed into the electrolyte mixing tank 84 to replenish the water consumed in the electrolysis reaction. The electrolyte is an aqueous solution of alkali metal carbonate and / or alkali metal bicarbonate, and the concentration range is 0.2 mol / L-10 mol / L.

[0030] In a preferred embodiment, the electrochemical reactor 81 operates at a temperature of 10°C-120°C and an operating pressure of 0.05 MPa-2.0 MPa; the first gas-liquid separator 82 and the second gas-liquid separator 83 are vertical or horizontal gas-liquid separators; the operating temperature inside the first gas-liquid separator 82 is 10°C-120°C and the operating pressure is 0.05 MPa-2.0 MPa; the operating temperature inside the second gas-liquid separator 83 is 10°C-120°C and the operating pressure is 0.05 MPa-2.0 MPa.

[0031] In an optional embodiment, the method further includes passing the flue gas 102 from the furnace top through the high-temperature section 3 and the low-temperature section 5 of the low-temperature cold source heat exchanger in sequence to exchange heat, thereby obtaining flue gas 107 to be converted and condensate 110. The condensate 110 is then mixed with demineralized water 111 and then sent to the electrolyte mixing tank 84 of the electrochemical catalytic conversion unit 8.

[0032] In the preferred embodiment described above, an ion-exchange membrane is disposed between the cathode chamber 31 and the anode chamber 32. The ion-exchange membrane is selectively permeable, preferably having a high permeability for alkali metal cations and a low permeability for other ions or molecules, such as at least one of hydrogen ions, hydroxide ions, carbonate ions, bicarbonate ions, carbon monoxide molecules, and carbon dioxide molecules. The ion-exchange membrane allows the free movement of alkali metal cations within the circuit of the electrochemical reactor and isolates hydrogen and oxygen generated during the electrocatalytic process. During electrolysis, the transport of alkali metal cations between the anode and cathode can only occur through the ion-exchange membrane. By separately feeding the anode gas-liquid mixture and the cathode gas-liquid mixture of the electrochemical reactor into different separators, the separation efficiency of the gas-liquid mixture generated by the reaction is improved, the reaction process is accelerated, the gas purification rate and the electrolyte circulation rate during the reaction are promoted, and no additional electrolyte replenishment is required. The water lost by the electrochemical catalytic conversion unit is replenished using condensate and external demineralized water, achieving the goal of reducing equipment operating costs and maximizing equipment utilization.

[0033] Another aspect of the present invention provides an apparatus for heating a process medium, the apparatus comprising: a gas-gas mixer 6, a burner 1, an industrial furnace body 2, a heat exchange unit, and an electrochemical catalytic conversion unit 8; the industrial furnace body 2 includes a high-temperature flue gas inlet, a process medium inlet to be heated, and a furnace top flue gas outlet arranged sequentially from bottom to top; the heat exchange unit includes a reflux flue gas inlet, a circulating flue gas outlet, and a flue gas outlet to be converted arranged sequentially along the flue gas flow direction; the electrochemical catalytic conversion unit 8 includes a flue gas inlet to be converted, a syngas outlet, and a circulating gas outlet arranged sequentially; a space is provided between the furnace top flue gas outlet of the industrial furnace body 2 and the reflux flue gas inlet of the heat exchange unit. A flue gas recirculation pipeline is provided. A flue gas recirculation pipeline is provided between the circulating flue gas outlet of the heat exchange unit and the circulating flue gas inlet of the gas-gas mixer 6. A flue gas pipeline to be converted is provided between the flue gas outlet to be converted of the heat exchange unit and the flue gas inlet to be converted of the electrochemical catalytic conversion unit 8. A circulating gas pipeline is provided between the circulating gas outlet of the electrochemical catalytic conversion unit 8 and the circulating gas inlet of the gas-gas mixer 6. The combustion-supporting gas outlet of the gas-gas mixer 6 is connected to the combustion-supporting gas inlet of the burner 1. The gas-gas mixer 6 is also provided with an external carbon dioxide gas inlet and an external oxygen gas inlet. A carbon dioxide concentration detector AI2 is also provided on the flue gas pipeline to be converted.

[0034] In the above preferred embodiments, the device using the heating process medium of the present invention can significantly improve the flexible operation of the device in multiple operating modes. The device does not produce nitrogen oxides at all, increases the concentration of CO2 which is beneficial to the capture and utilization of CO2, has extremely low carbon dioxide content in the exhaust gas, has high radiative heat transfer efficiency, and significantly reduces exhaust heat loss, thus achieving the purpose of environmental protection.

[0035] In one optional embodiment, the electrochemical catalytic conversion unit 8 includes an electrochemical reactor 81, a first gas-liquid separator 82, a second gas-liquid separator 83, and an electrolyte mixing tank 84 arranged sequentially along the flue gas flow direction; the electrochemical reactor 81 includes a cathode chamber 801 and an anode chamber 802 separated by an ion-exchange membrane; the electrochemical reactor 81 includes a cathode electrolyte inlet, an anode electrolyte inlet, a flue gas inlet to be converted, a cathode gas-liquid mixture outlet, and an anode gas-liquid mixture outlet arranged sequentially; the heat exchange unit includes a high-temperature section 3 of a low-temperature cold source heat exchanger, a reflux flue gas induced draft fan 4, and a low-temperature section 5 of a low-temperature cold source heat exchanger arranged sequentially; the flue gas outlet of the low-temperature section 5 of the low-temperature cold source heat exchanger is connected to the electrochemical catalytic conversion unit. The flue gas to be converted in unit 8 is connected to the cathode gas-liquid mixture outlet, which is connected to the cathode electrolyte inlet of the first gas-liquid separator 82. The anode gas-liquid mixture outlet is connected to the anode electrolyte inlet of the second gas-liquid separator 83. The first gas-liquid separator 82 also includes a syngas outlet and a cathode electrolyte outlet, with the cathode electrolyte outlet connected to the electrolyte mixing tank 84. The second gas-liquid separator 83 also includes a circulating gas outlet and an anode electrolyte outlet, with the circulating gas outlet connected to the circulating gas inlet of the gas-gas mixer 6 and the anode electrolyte outlet connected to the electrolyte mixing tank 84. The first electrolyte outlet of the electrolyte mixing tank 84 is connected to the cathode chamber 801, and the second electrolyte outlet is connected to the anode chamber 802.

[0036] In one optional embodiment, the heat exchange unit is provided with a low-temperature cold source pipeline, which sequentially connects the low-temperature section 5 and the high-temperature section 3 of the low-temperature cold source heat exchanger and then returns to the low-temperature section 5 of the low-temperature cold source heat exchanger. The low-temperature cold source outlet of the low-temperature section 5 after heat exchange is connected to the demineralized water inlet of the electrochemical catalytic conversion unit 8. A circulating flue gas pipeline is provided between the flue gas outlet of the reflux flue gas induced draft fan 4 and the gas-gas mixer 6. A low-temperature section inlet flue gas pipeline is provided between the flue gas outlet of the reflux flue gas induced draft fan 4 and the low-temperature section inlet flue gas of the low-temperature section 5 of the low-temperature cold source heat exchanger. A flue gas pipeline is provided between the flue gas to be converted in the low-temperature section 5 of the low-temperature cold source heat exchanger and the flue gas inlet of the cathode chamber 801 in the electrochemical catalytic conversion unit 8.

[0037] In the preferred embodiments described above, the present invention utilizes an electrochemical catalytic conversion device to increase the CO2 concentration, which is beneficial for CO2 capture and utilization. Carbon dioxide in the combustion flue gas is almost completely converted into syngas and regenerated flue gas, significantly reducing CO2 in the emissions and generating high-value-added product gas. This reduces environmental pollution while increasing the economic value of combustion. The device provided by the present invention has almost no nitrogen in its combustion environment, greatly reducing the generation of pollutants such as nitrogen oxides. Nitrogen oxide emissions are nearly zero, which is beneficial for environmental protection. Simultaneously, the present invention uses pure oxygen-assisted combustion to achieve efficient fuel combustion, improving the heat transfer efficiency of combustion. By using circulating flue gas and circulating gas as combustion-supporting fuel, the combustion flue gas generated during the combustion process is fully utilized, reducing the amount of exhaust gas and minimizing heat loss.

[0038] The present invention will be further illustrated by the following embodiments, but the present invention is not limited to the embodiments.

[0039] Example This embodiment illustrates a start-up method for heating the process medium using the apparatus shown in the attached diagram, and efficiently utilizes the flue gas generated within the apparatus. The method in this embodiment includes: S1. Fuel gas 101 and combustion-supporting gas 121 are sent into burner 1 for ignition and combustion to obtain high-temperature flue gas; the combustion-supporting gas 121 contains external oxygen 116 and external carbon dioxide gas 119; the high-temperature flue gas is sent into industrial furnace body 2 to exchange heat with the process medium 123 to be heated to obtain furnace top flue gas 102 and heated process medium. S2. When the carbon dioxide content in the flue gas 102 at the top of the furnace does not reach the first set threshold, the flue gas 102 at the top of the furnace (flow rate of 28.93 kg / s, carbon dioxide content of 10 v%) is mixed with the external oxygen 116 and the external carbon dioxide gas 119 as combustion-supporting gas 121 and the process is returned to step S1. S3. When the carbon dioxide content in the flue gas 102 at the top of the furnace (flow rate of 28.93 kg / s, carbon dioxide content of 25%) reaches the first set threshold but does not reach the second set threshold, stop inputting external carbon dioxide gas 119, mix the flue gas 102 at the top of the furnace with external oxygen 116 as combustion-supporting gas 121 and return to step S1. S4. When the carbon dioxide content in the flue gas 102 (flow rate 28.93 kg / s, carbon dioxide content 54 v%) reaches or exceeds the second set threshold, the flue gas 102 is divided into flue gas to be converted 107 (flow rate 8.2 kg / s, carbon dioxide content 54 v%) and circulating flue gas 117 (flow rate 20.72 kg / s, carbon dioxide content 54 v%). The flue gas to be converted 107 is sent to the carbon dioxide electrochemical catalytic conversion unit 8 for electrochemical catalytic conversion reaction to obtain syngas 112 (composed of 4.96 kg / s carbon monoxide, 0.7 kg / s hydrogen and 4.66 kg / s carbon dioxide) and circulating gas 113 (oxygen flow rate 8.54 kg / s, carbon dioxide flow rate 2.31 kg / s). The circulating flue gas 117 is mixed with external oxygen 116 and the circulating gas 113 as combustion-supporting gas 121 and returned to step S1.

[0040] The carbon dioxide content in the flue gas 102 at the top of the furnace is detected using a carbon dioxide concentration detector AI2; the first set threshold is 15%; and the second set threshold is 52%.

[0041] The commencement method described in this embodiment also includes: The flue gas 107 to be converted (flow rate 8.2 kg / s, carbon dioxide content 54 vol%) and the first electrolyte 124 are fed together into the cathode chamber 801 of the electrochemical reactor 81 in the electrochemical catalytic conversion unit 8. The second electrolyte 125 is fed into the anode chamber 802 of the electrochemical reactor 81. An electrochemical catalytic conversion reaction is carried out in the electrochemical reactor 81 to obtain a cathode gas-liquid mixture 126 and an anode gas-liquid mixture 127 (reactor outlet temperature 63°C, operating pressure 0.15 MPa). The cathode gas-liquid mixture 126 is fed into the first gas-liquid separator 82 for gas-liquid separation to obtain syngas 112 (composed of 4.96 kg / s carbon monoxide, ... The anode gas-liquid mixture 127 (composed of 0.7 kg / s hydrogen and 4.66 kg / s carbon dioxide) and cathode electrolyte 128 are fed into a second gas-liquid separator 83 for gas-liquid separation to obtain circulating gas 113 (oxygen flow rate of 8.54 kg / s and carbon dioxide flow rate of 2.31 kg / s) and anode electrolyte 129. The cathode electrolyte 128 and the anode electrolyte 129 are then fed into an electrolyte mixing tank 84 for mixing (total flow rate of 13755 kg / s). Then, the first electrolyte 124 (flow rate of 3434.65 kg / s) and the second electrolyte 125 (flow rate of 9604 kg / s) are drawn out from the electrolyte mixing tank 84. Demineralized water 111 (flow rate of 8.0 kg / s) is fed into the electrolyte mixing tank 84 to replenish the water consumed in the electrolysis reaction; the electrolyte is preferably a sodium bicarbonate solution with a concentration of 3 mol / L; the electrochemical reactor 81 operates at a temperature of 60°C and a pressure of 0.15 MPa; the first gas-liquid separator 82 and the second gas-liquid separator 83 are vertical or horizontal gas-liquid separators; the first gas-liquid separator 82 operates at a temperature of 63°C and a pressure of 0.12 MPa; the second gas-liquid separator 83 operates at a temperature of 63°C and a pressure of 0.12 MPa.

[0042] The oxygen content in the combustion-supporting gas 121 is detected using an oxygen concentration detector AI1. The oxygen content in the combustion-supporting gas 121 varies within the range of 21v%-50v% as the industrial furnace burns. The oxygen content in the circulating gas 113 varies within the range of 60v%-100v%.

[0043] In the device described in this embodiment, the single-pass conversion rate of carbon dioxide in the electrochemical catalytic conversion unit 8 is 55%, and the comprehensive utilization thermal efficiency is 97.1%.

[0044] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0045] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0046] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A start-up method for heating a process medium, characterized in that, The method comprises: S1, sending fuel gas (101) and combustion-supporting gas (121) into a burner (1) to ignite and burn, to obtain high-temperature flue gas; the combustion-supporting gas (121) contains external oxygen (116) and external carbon dioxide gas (119); the high-temperature flue gas is sent into an industrial furnace body (2) to exchange heat with a process medium (123) to be heated, to obtain furnace top flue gas (102) and the heated process medium; S2, when the carbon dioxide content in the furnace top flue gas (102) does not reach a first set threshold, the furnace top flue gas (102) is mixed with the external oxygen (116) and the external carbon dioxide gas (119) as the combustion-supporting gas (121) to return to the operation of step S1; S3, when the carbon dioxide content in the furnace top flue gas (102) reaches the first set threshold and does not reach a second set threshold, the input of the external carbon dioxide gas (119) is stopped, and the furnace top flue gas (102) is mixed with the external oxygen (116) as the combustion-supporting gas (121) to return to the operation of step S1; S4, when the carbon dioxide content in the furnace top flue gas (102) reaches or is higher than the second set threshold, the furnace top flue gas (102) is divided into to-be-converted flue gas (107) and circulating flue gas (117), the to-be-converted flue gas (107) is sent into a carbon dioxide electrochemical catalytic conversion unit (8) to perform an electrochemical catalytic conversion reaction, to obtain synthesis gas (112) and circulating gas (113), and the circulating flue gas (117) is mixed with the external oxygen (116) and the circulating gas (113) as the combustion-supporting gas (121) to return to the operation of step S1.

2. The method of claim 1, wherein, The carbon dioxide content in the furnace top flue gas (102) is detected by using a carbon dioxide concentration detector (AI2); the first set threshold is any point value in the range of 10v%-20v%; and the second set threshold is any point value in the range of 25v%-90v%.

3. The method of claim 1, wherein, In step S2, the circulating flue gas (117) is obtained after the furnace top flue gas (102) is exchanged heat, and the circulating flue gas (117) is sent into the burner (1) as the combustion-supporting gas (121) together with the external oxygen (116) and the external carbon dioxide gas (119); In step S3, the circulating flue gas (117) is obtained after the furnace top flue gas (102) is exchanged heat, and the circulating flue gas (117) is sent into the burner (1) as the combustion-supporting gas (121) together with the external oxygen (116); In step S4, the circulating flue gas (117) and the to-be-converted flue gas (107) are obtained after the furnace top flue gas (102) is exchanged heat; the to-be-converted flue gas (107) is sent into the electrochemical catalytic conversion unit (8) to be completely converted into the synthesis gas (112) and the circulating gas (113); and the circulating flue gas (117) is mixed with the external oxygen (116) and the circulating gas (113) as the combustion-supporting gas (121) to be sent into the burner (1).

4. The method of claim 1, wherein, The oxygen content in the combustion-supporting gas (121) is detected by an oxygen concentration detector (AI1), and the oxygen content in the combustion-supporting gas (121) is in the range of 21v% to 50v%; The oxygen content in the circulating gas (113) is in the range of 60v% to 100v%.

5. The method of claim 1, wherein, The method further comprises: The flue gas to be converted (107) is sent into a cathode chamber (801) of an electrochemical reactor (81) of an electrochemical catalytic conversion unit (8) together with a first electrolyte (124), a second electrolyte (125) is sent into an anode chamber (802) of the electrochemical reactor (81), an electrochemical catalytic conversion reaction is carried out in the electrochemical reactor (81) to obtain a cathode gas-liquid mixture (126) and an anode gas-liquid mixture (127); the cathode gas-liquid mixture (126) is sent into a first gas-liquid separator (82) to carry out gas-liquid separation to obtain a synthesis gas (112) and a cathode electrolyte (128), the anode gas-liquid mixture (127) is sent into a second gas-liquid separator (83) to carry out gas-liquid separation to obtain a circulating gas (113) and an anode electrolyte (129), the cathode electrolyte (128) and the anode electrolyte (129) are mixed in an electrolyte mixing tank (84), and then the first electrolyte (124) and the second electrolyte (125) are led out from the electrolyte mixing tank (84); The desalted water (111) is sent into the electrolyte mixing tank (84) to supplement water consumed in the electrolysis reaction; the electrolyte is an aqueous solution of alkali metal carbonate and / or alkali metal bicarbonate, and the concentration is in the range of 0.2mol / L to 10mol / L.

6. The method of claim 5, wherein, The operating temperature of the electrochemical reactor (81) is 10℃ to 120℃, and the operating pressure is 0.05MPa to 2.0MPa; The first gas-liquid separator (82) and the second gas-liquid separator (83) are vertical gas-liquid separators or horizontal gas-liquid separators; the operating temperature in the first gas-liquid separator (82) is 10℃ to 120℃, and the operating pressure is 0.05MPa to 2.0MPa; the operating temperature in the second gas-liquid separator (83) is 10℃ to 120℃, and the operating pressure is 0.05MPa to 2.0MPa.

7. The method of claim 1, wherein, The method further comprises: The flue gas (102) is sequentially sent through a high-temperature section (3) of a low-temperature heat source heat exchanger and a low-temperature section (5) of the low-temperature heat source heat exchanger to carry out heat exchange, to obtain the flue gas to be converted (107) and condensed water (110), the condensed water (110) is mixed into the desalted water (111), and then sent into the electrolyte mixing tank (84) of the electrochemical catalytic conversion unit (8).

8. An apparatus for heating a process medium, characterized by The device comprises a gas-gas mixer (6), a burner (1), an industrial furnace body (2), a heat exchange unit, and an electrochemical catalytic conversion unit (8); The industrial furnace body (2) comprises, from bottom to top, a high-temperature flue gas inlet, a process medium to be heated inlet, and a flue gas outlet at the top of the furnace; The device comprises a gas-gas mixer (6), a burner (1), an industrial furnace body (2), a heat exchange unit, and an electrochemical catalytic conversion unit (8); The heat exchange unit comprises, in sequence along the flow direction of the flue gas, a backflow flue gas inlet, a circulating flue gas outlet and a to-be-converted flue gas outlet; The electrochemical catalytic conversion unit (8) comprises, in sequence, a to-be-converted flue gas inlet, a synthesis gas outlet and a circulating gas outlet; A backflow flue gas pipeline is arranged between the flue gas outlet of the furnace top of the industrial furnace body (2) and the backflow flue gas inlet of the heat exchange unit, a circulating flue gas pipeline is arranged between the circulating flue gas outlet of the heat exchange unit and the circulating flue gas inlet of the gas-gas mixer (6), and a to-be-converted flue gas pipeline is arranged between the to-be-converted flue gas outlet of the heat exchange unit and the to-be-converted flue gas inlet of the electrochemical catalytic conversion unit (8); A circulating gas pipeline is arranged between the circulating gas outlet of the electrochemical catalytic conversion unit (8) and the circulating gas inlet of the gas-gas mixer (6), the combustion-supporting gas outlet of the gas-gas mixer (6) is in communication with the combustion-supporting gas inlet of the burner (1), and the gas-gas mixer (6) is further provided with an external carbon dioxide gas inlet and an external oxygen gas inlet; the to-be-converted flue gas pipeline is further provided with a carbon dioxide concentration detector (AI2).

9. The apparatus of claim 8, wherein, The electrochemical catalytic conversion unit (8) comprises, in sequence along the flow direction of the flue gas, an electrochemical reactor (81), a first gas-liquid separator (82), a second gas-liquid separator (83) and an electrolyte mixing tank (84); the electrochemical reactor (81) comprises a cathode chamber (801) and an anode chamber (802) separated by an ion diaphragm; The electrochemical reactor (81) comprises, in sequence, a cathode electrolyte inlet, an anode electrolyte inlet, a to-be-converted flue gas inlet, a cathode gas-liquid mixture outlet and an anode gas-liquid mixture outlet; The heat exchange unit comprises, in sequence, a low-temperature cold source heat exchanger high-temperature section (3), a backflow flue gas induced draft fan (4) and a low-temperature cold source heat exchanger low-temperature section (5); The to-be-converted flue gas outlet of the low-temperature cold source heat exchanger low-temperature section (5) is connected to the to-be-converted flue gas inlet of the electrochemical catalytic conversion unit (8), the cathode gas-liquid mixture outlet is connected to the cathode gas-liquid mixture inlet of the first gas-liquid separator (82), and the anode gas-liquid mixture outlet is connected to the anode gas-liquid mixture inlet of the second gas-liquid separator (83); the first gas-liquid separator (82) further comprises a synthesis gas outlet and a cathode electrolyte outlet, the cathode electrolyte outlet is connected to the electrolyte mixing tank (84); the second gas-liquid separator (83) further comprises a circulating gas outlet and an anode electrolyte outlet, the circulating gas outlet is connected to the circulating gas inlet of the gas-gas mixer (6), and the anode electrolyte outlet is connected to the electrolyte mixing tank (84); The first electrolyte outlet of the electrolyte mixing tank (84) is connected to the cathode chamber (801), and the second electrolyte outlet is connected to the anode chamber (802).

10. The apparatus of claim 9, wherein, The heat exchange unit is provided with a low-temperature cold source pipeline, which sequentially communicates the low-temperature section (5) of the low-temperature cold source heat exchanger, the high-temperature section (3) of the low-temperature cold source heat exchanger and returns to the low-temperature section (5) of the low-temperature cold source heat exchanger, and the outlet of the low-temperature cold source after heat exchange of the low-temperature section (5) of the low-temperature cold source heat exchanger is communicated with the desalted water inlet of the electrochemical catalytic conversion unit (8); A circulating flue gas pipeline is arranged between the flue gas outlet of the backflow flue gas induced draft fan (4) and the gas-gas mixer (6), a low-temperature section front flue gas pipeline is arranged between the flue gas outlet of the backflow flue gas induced draft fan (4) and the low-temperature section front flue gas inlet of the low-temperature section (5) of the low-temperature cold source heat exchanger, and a to-be-converted flue gas pipeline is arranged between the to-be-converted flue gas of the low-temperature section (5) of the low-temperature cold source heat exchanger and the to-be-converted flue gas inlet of the cathode chamber (801) of the electrochemical catalytic conversion unit (8).

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