Device for recovering carbon dioxide from flue gas generated after oxygen-fuel combustion of heating furnace

Abstract

The utility model provides a device for recovering carbon dioxide from flue gas generated after oxygen-fuel combustion of a heating furnace. The device comprises an oxygen-fuel heating unit; the external exhaust flue gas pipeline and the circulating flue gas pipeline are connected with the total oxygen heating unit in parallel through a smoke guide machine; the oxygen-flue gas heat exchanger and the flue gas-bituminous coal water heat exchanger are sequentially connected with a flue gas discharge pipeline; the water washing tower is connected with the flue gas-heat medium water heat exchanger; the drying unit, the buffering unit and the carbon dioxide collecting unit are sequentially connected with the water washing tower. According to the device, flue gas is led out through a flue gas leading machine and divided into two paths, and one path is mixed with oxygen subjected to heat exchange through a circulating flue gas machine to serve as a combustion-supporting medium to enter a total-oxygen heating furnace; and the other path enters the flue gas-oxygen heat exchanger to exchange heat with external combustion-supporting oxygen of the device, then enters the flue gas-heating medium water heat exchanger to exchange heat with heating medium water and recover waste heat, and then enters the adsorption unit to reduce the water content in the flue gas and purify carbon dioxide in the flue gas after further reducing the discharge temperature and removing water-soluble impurities through the washing unit.

Description

Technical Field

[0001] The utility model belongs to the technical field of flue gas recovery, and particularly relates to a device for recovering carbon dioxide from the flue gas after the oxy-fuel combustion of a heating furnace. Background Technique

[0002] For the combustion (post) exhaust gas, such as the typical flue gas condition, the components of the flue gas after the capture and separation of dust, atomized particles and oil droplets are 27% carbon dioxide, 70% nitrogen, 2% oxygen, 1% water, and trace amounts of carbon monoxide, methane and light hydrocarbon organic compounds. The temperature is 150 - 200 °C, and the pressure is normal pressure or slightly positive pressure. The pressure swing adsorption (PSA) process for recovering carbon dioxide utilizes the characteristics that the boiling point and polarity (a physical property of the adsorbability by the adsorbent) of carbon dioxide are quite different from those of nitrogen, oxygen, carbon monoxide and methane. Many adsorbents preferentially adsorb carbon dioxide, and the concentration of carbon dioxide as the preferentially adsorbed adsorbate is relatively high, meeting the conditions of the conventional pressure swing adsorption (PSA) process with relatively low energy consumption. Among them, the adsorbents used include silica gel, activated carbon, 13X molecular sieve, etc. The ability of these adsorbents to adsorb carbon dioxide increases in turn, but the desorption difficulty also increases in turn.

[0003] The PSA process obtains a carbon dioxide enriched gas from the adsorption phase, and its purity can be as high as 95 - 99%, and after being pressurized, it is output as a product gas for direct use, such as the welding protection gas for shipbuilding and large containers, the injection agent for secondary oil recovery, the working medium for supercritical power generation, the supercritical extractant and the food industry additive, etc., or further obtains a high-purity carbon dioxide liquid product with a purity of greater than 99.95 - 99.99% through catalytic reaction, deep drying and adsorption purification and then through a carbon dioxide low-temperature rectification or fractional condensation or flash evaporation system, etc., which can be used as an electronic grade product. Although the PSA process for recovering carbon dioxide from flue gas is mature and has been applied, there are still some very obvious technical and economic defects, which hinder the wide application of the PSA process. Content of the Utility Model

[0004] In view of this, the purpose of the utility model is to provide a device for recovering carbon dioxide from the flue gas after the oxy-fuel combustion of a heating furnace, which can recover carbon dioxide in the flue gas and replaces the pressurized adsorption process, greatly reducing the energy consumption.

[0005] The utility model provides a device for recovering carbon dioxide from the flue gas after the oxy-fuel combustion of a heating furnace, including:

[0006] An oxy-fuel heating unit;

[0007] An external exhaust gas pipeline and a circulating flue gas pipeline that are connected in parallel with the oxy-fuel heating unit through a smoke extraction fan;

[0008] An oxygen-flue gas heat exchanger and a flue gas-heat medium water heat exchanger connected in sequence to the external exhaust flue gas pipeline;

[0009] A water washing tower connected to the flue gas-heat medium water heat exchanger;

[0010] A drying unit connected to the water washing tower;

[0011] A buffer unit connected to the drying unit;

[0012] A carbon dioxide collection unit connected to the buffer unit.

[0013] In an embodiment of the present utility model, the all-oxygen heating unit is an all-oxygen heating furnace;

[0014] A fuel gas inlet and an oxygen inlet are provided at the bottom of the all-oxygen heating furnace.

[0015] In an embodiment of the present utility model, the oxygen after heat exchange in the oxygen-flue gas heat exchanger is connected to the oxygen inlet of the all-oxygen heating unit through an oxygen delivery pipeline.

[0016] In an embodiment of the present utility model, a flue gas baffle is provided at the top of the all-oxygen heating furnace.

[0017] In an embodiment of the present utility model, the drying unit is an adsorption tank or a coalescer.

[0018] In an embodiment of the present utility model, the buffer unit is a gas holder.

[0019] In an embodiment of the present utility model, a recycle gas fan is provided on the recycle flue gas pipeline.

[0020] In an embodiment of the present utility model, an adsorbent is provided in the adsorption tank, and the adsorbent is a water-absorbing molecular sieve.

[0021] The utility model provides a device for recovering carbon dioxide from flue gas after oxy-fuel combustion in a heating furnace, comprising: an oxy-fuel heating unit; an exhaust flue gas pipe and a circulating flue gas pipe which are connected in parallel with the oxy-fuel heating unit through a smoke-drawing machine; an oxygen-flue gas heat exchanger and a flue gas-heated coal water heat exchanger which are sequentially connected to the exhaust flue gas pipe; a water washing tower connected to the flue gas-heated medium water heat exchanger; a drying unit connected to the water washing tower; a buffer unit connected to the drying unit; and a carbon dioxide collection unit connected to the buffer unit. The high-temperature flue gas in the convection section of the device is led out by a smoke-drawing machine and divided into two paths. One path is mixed with the heat-exchanged oxygen through a circulating smoke machine as a combustion-supporting medium for fuel. After being fully and evenly mixed by a gas mixer, the combustion-supporting medium enters the oxy-fuel heating furnace. The other path enters the flue gas-oxygen heat exchanger to exchange heat with the combustion-supporting oxygen from outside the device, and then enters the flue gas-heated medium water heat exchanger to exchange heat with the heated medium water. After recovering the waste heat, it enters the water washing unit to further reduce the exhaust temperature and remove the impurities easily soluble in water, and then enters the adsorption unit to reduce the water content in the flue gas and purify the carbon dioxide in the flue gas. Description of the Drawings

[0022] Figure 1 It is a schematic diagram of the device for recovering carbon dioxide from flue gas after oxy-fuel combustion in a heating furnace provided by the utility model. Detailed Embodiments

[0023] The utility model provides a device for recovering carbon dioxide from flue gas after oxy-fuel combustion in a heating furnace, comprising:

[0024] An oxy-fuel heating unit;

[0025] An exhaust flue gas pipe and a circulating flue gas pipe which are connected in parallel with the oxy-fuel heating unit through a smoke-drawing machine;

[0026] An oxygen-flue gas heat exchanger and a flue gas-heated coal water heat exchanger which are sequentially connected to the exhaust flue gas pipe;

[0027] A water washing tower connected to the flue gas-heated medium water heat exchanger;

[0028] A drying unit connected to the water washing tower;

[0029] A carbon dioxide storage unit connected to the drying unit.

[0030] The oxy-fuel heating unit provided by the utility model is an oxy-fuel heating furnace; a fuel gas inlet and an oxygen inlet are arranged at the bottom of the oxy-fuel heating furnace. The utility model uses oxygen with a concentration > 99% to replace air for combustion with fuel, and nitrogen is not introduced during the combustion process, thereby increasing the concentration of carbon dioxide in the flue gas. The fuel gas inlet conveys fuel gas, such as methane; the oxygen inlet conveys oxygen. The molar ratio of fuel gas to oxygen is 1:2.

[0031] The device provided by the present utility model includes an exhaust gas pipeline and a circulating gas pipeline that are connected in parallel with the all-oxygen heating unit through a smoke extractor. The components of the exhaust gas from the all-oxygen heating unit include 63-64% carbon dioxide, 30.01-30.1% water, 2.07-2.2% oxygen, and 4.72-5.0% nitrogen. An oxygen on-line analyzer is provided on the pipeline connecting the all-oxygen heating furnace and the smoke extractor.

[0032] A flue damper is provided at the top of the all-oxygen heating furnace. The flue gas generated from the all-oxygen heating unit is branched after passing through the flue damper. One branch is exhausted, and the other branch is used as circulating flue gas to be mixed with oxygen as a combustion-supporting medium. The volume ratio of the circulating flue gas to the exhaust flue gas is (6.5-7.5):(2.5-3.5).

[0033] The device provided by the present utility model includes an oxygen-gas heat exchanger and a gas-heat medium water heat exchanger that are sequentially connected to the exhaust gas pipeline. The flue gas transported through the exhaust gas pipeline sequentially passes through the oxygen-gas heat exchanger and the gas-heat medium water heat exchanger for heat exchange. The temperature of the exhaust flue gas is 350-370°C. After passing through the oxygen-gas heat exchanger, the temperature of the flue gas drops to 170-190°C. The heat-exchanged oxygen is mixed with the circulating flue gas as a combustion-supporting medium for fuel. The combustion-supporting medium enters the all-oxygen heating furnace after being fully mixed and homogenized through a gas mixer.

[0034] After further heat exchange through the gas-heat medium water heat exchanger, the temperature of the flue gas drops to about 65-75°C. The present utility model uses low-temperature heat medium water at 60°C to exchange heat with the flue gas to generate heat medium water at about 95°C, and the heat medium water enters the heat medium water pipe network.

[0035] After the flue gas passes through the oxygen-gas heat exchanger and the gas-heat medium water heat exchanger, the temperature decreases, and moisture will also condense and be removed.

[0036] The device provided by the present utility model includes a water washing tower connected to the gas-heat medium water heat exchanger; the water washing tower is used to remove impurities soluble in water in the flue gas and further reduce the temperature of the flue gas. The flue gas enters from the bottom of the water washing tower, and water flows from the top to the bottom by gravity for countercurrent contact.

[0037] The device provided by the present utility model includes a drying unit connected to the water washing tower; the drying unit is an adsorption tank or a coalescer. An adsorbent is provided in the adsorption tank, and the adsorbent is a water-absorbing molecular sieve. The adsorption unit is used to reduce the water content in the flue gas and purify carbon dioxide in the flue gas.

[0038] The device provided by the present utility model includes a carbon dioxide storage unit connected to the drying unit; the carbon dioxide storage unit is a gas holder; the gas holder is used for storing the raw material gas of the carbon dioxide device, stabilizing the device feed, controlling the pressure at 0 KPa to 10 KPa, maintaining the liquid level above 5 meters, and controlling the temperature not exceeding 40°C. After the above treatment, the concentration of the collected carbon dioxide reaches more than 90%, replacing the pressurized adsorption process and being converted into a liquid carbon dioxide product with high added value.

[0039] In the prior art, only part of the heat in the flue gas is recovered through an air preheater, resulting in waste. In the present utility model, most of the flue gas is circulated to the heating furnace to directly recover heat. After the discharged flue gas fully recovers heat by exchanging heat with oxygen and low-temperature heat transfer medium water, it then exchanges heat with circulating water to remove the moisture in the flue gas and enrich the carbon dioxide concentration.

[0040] The device provided by the present utility model enables the flue gas to meet the gas source index requirements for producing liquid carbon dioxide products, thereby recovering the carbon dioxide in the flue gas and producing industrial-grade liquid carbon dioxide products, turning waste into treasure.

[0041] In order to further illustrate the present utility model, the following describes in detail a device for recovering carbon dioxide from the flue gas after all-oxygen combustion of a heating furnace provided by the present utility model in conjunction with embodiments, but they should not be construed as limiting the protection scope of the present utility model.

[0042] Embodiment 1

[0043] Methane and oxygen are introduced into the heating furnace at a molar ratio of 1:2. After all-oxygen combustion, flue gas is generated. The components of the flue gas include 63.2% carbon dioxide, 30.01% water, 2.07% oxygen, and 4.72% nitrogen; the flue gas is discharged, 70 vol% of the flue gas is circulated, and 30 vol% of the flue gas is exchanged heat through an oxygen-flue gas heat exchanger. The exchanged oxygen is mixed with the circulating flue gas and transported to the all-oxygen heating furnace as a combustion-supporting medium; the flue gas after heat exchange is further exchanged heat through a flue gas-heat transfer medium water heat exchanger, and the temperature of the flue gas drops to 70°C. After being exchanged heat with 60°C heat transfer medium water, it is heated to about 95°C; after heat recovery, it further reduces the discharged temperature and removes impurities easily soluble in water through a water washing tower, then enters an adsorption tank to reduce the water content in the flue gas and purify the carbon dioxide in the flue gas, and finally enters the gas holder for storing the raw material gas of the carbon dioxide device.

[0044] The concentration of the collected carbon dioxide reaches more than 90% (V PCT).

[0045] As can be seen from the above embodiments, the present utility model provides a device for recovering carbon dioxide from the flue gas after the oxy-fuel combustion of a heating furnace, including: an oxy-fuel heating unit; an external exhaust flue gas pipeline and a circulating flue gas pipeline that are connected in parallel with the oxy-fuel heating unit through a flue gas extractor; an oxygen-flue gas heat exchanger and a flue gas-bituminous coal water heat exchanger that are sequentially connected to the external exhaust flue gas pipeline; a water washing tower connected to the flue gas-bituminous coal water heat exchanger; a drying unit connected to the water washing tower; a buffer unit connected to the drying unit; and a carbon dioxide collection unit connected to the buffer unit. The high-temperature flue gas in the convection section of the device is led out by a flue gas extractor and divided into two paths. One path is mixed with the heat-exchanged oxygen through a circulating gas machine as the combustion-supporting medium of the fuel. After the combustion-supporting medium is fully and evenly mixed through a gas mixer, it enters the oxy-fuel heating furnace. The other path enters the flue gas-oxygen heat exchanger to exchange heat with the combustion-supporting oxygen from outside the device, and then enters the flue gas-bituminous coal water heat exchanger to exchange heat with the bituminous coal water. After the waste heat is recovered, it enters the water washing unit to further reduce the external exhaust temperature and remove the impurities that are easily soluble in water, and then enters the adsorption unit to reduce the water content in the flue gas and purify the carbon dioxide in the flue gas.

[0046] The above are only the preferred embodiments of the present utility model. It should be noted that for those of ordinary skill in the art in this technical field, without departing from the principle of the present utility model, several improvements and refinements can still be made, and these improvements and refinements should also be regarded as the protection scope of the present utility model.

Claims

1. An apparatus for recovering carbon dioxide from the flue gas after all-oxygen combustion in a heating furnace, comprising: An all-oxygen heating unit; An exhaust flue gas pipeline and a circulating flue gas pipeline which are connected in parallel with the all-oxygen heating unit through a flue gas blower; An oxygen-flue gas heat exchanger and a flue gas-heat medium water heat exchanger which are sequentially connected to the exhaust flue gas pipeline; A water washing tower connected to the flue gas-heat medium water heat exchanger; A drying unit connected to the water washing tower; A carbon dioxide storage unit connected to the drying unit.

2. The device according to claim 1, characterized in that, The all-oxygen heating unit is an all-oxygen heating furnace; A fuel gas inlet and an oxygen inlet are arranged at the bottom of the all-oxygen heating furnace.

3. The device according to claim 2, characterized in that, The oxygen after heat exchange in the oxygen-flue gas heat exchanger is connected to the oxygen inlet of the all-oxygen heating unit through an oxygen delivery pipeline.

4. The device according to claim 2, characterized in that, A flue damper is arranged at the top of the all-oxygen heating furnace.

5. The device according to claim 2, characterized in that The drying unit is an adsorption tank or a coalescer.

6. The device according to claim 5, characterized in that, The carbon dioxide storage unit is a gas holder.

7. The device according to claim 1, characterized in that, A circulating flue gas machine is arranged on the circulating flue gas pipeline.

8. The device according to claim 5, characterized in that, An adsorbent is arranged in the adsorption tank, and the adsorbent is a water-absorbing molecular sieve.

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