Device for capturing and removing CO2 from exhaust gas of power plant

Abstract

The utility model discloses a device for capturing and removing CO2 from exhaust smoke of a power plant. Cooling and circulating water is used for CO2 absorption and CO2 desorption in the fuel preheating and drying process and the gas-water heat exchange process, and the water is kept clean enough to the maximum extent. According to the invention, two or more than two quasi-cylinders provided with one or two rotatable shaftless / shaftless strip-shaped spiral bodies with ripples on the surfaces are used as a CO2 absorber and a CO2 desorber; water is used as a CO2 absorbent and a CO2 desorption agent to realize physical absorption and desorption of CO2, and a common chemical method for absorbing CO2 absorbent regeneration is not needed, so that new environmental problems are avoided. Environment energy is utilized to the maximum extent, and the cost is controlled through the process and the device.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of CO2 capture and removal device, in particular to a device for capturing and removing CO2 from flue gas of power plant. BACKGROUND

[0002] The current global temperature is rising, which is threatening the future of life, and it has become a consensus that CO2 emissions must be reduced. Currently, chemical methods are commonly used to capture CO2 from boiler flue gas, but these methods have complex process, high energy consumption due to temperature changes during capture process, and uneven CO2 capture rate. In addition, the capture process may produce harmful substances and have new adverse effects on the environment. For example, the energy consumption of the process in patent CN202310480584.6 is declared to be low, but it still corresponds to an energy consumption of about 1.5 gigajoules per ton of CO2 captured, and the CO2 capture process often increases CO2.

[0003] And when the current known chemical method is used to capture and extract CO2, or even when the physical method is used to capture CO2, the accompanying substances in the boiler flue gas will accumulate in the CO2 absorbent, so purification treatment must be carried out and a large amount of fresh water resources may be consumed. At present, there is no low-cost process and device for using water instead of chemicals as an absorbent to absorb and capture CO2 from gas, especially large-scale power plant waste heat flue gas. SUMMARY

[0004] The task of the present application is to capture and remove CO2 from the flue gas of power plant based on the principle of physical absorption, using water as an absorbent to absorb and remove CO2 from the flue gas of boiler, and a safe and simple device is proposed to reduce the temperature of the flue gas of power plant to below 20℃, and the device does not need to consume other chemical reagents except water for the regeneration of CO2-absorbed aqueous solution and the removal of CO2, so that the present application can be used not only for capturing CO2 from the flue gas of power plant, but also for capturing and removing CO2 from gas from steelmaking, cement or other sources.

[0005] The invention comprises a kind of cylindrical device, which can be arranged in pairs of openings according to the needs, one or two rotatable, surface corrugated, axial / axle-free ribbon spirals can be arranged in the longitudinal direction inside the cylindrical device, the surface outer edges of the ribbon spirals are parallel and equidistant to each other in the longitudinal direction of the cylindrical device, there is a certain gap between the surface outer edges of the ribbon spirals and the outer shell of the cylindrical device, and the ribbon spirals can be partially immersed in the solution inside the cylindrical device, so that the gas and liquid on the surface of the ribbon spirals can flow together. The invention comprises two or more cylindrical devices arranged with "ribbon spirals" connected in sequence, one or more of the cylindrical devices are used as CO2 absorbers for dissolving and absorbing CO2 in the gas under the pressure of 24000 Pa, and the other one or more of the cylindrical devices are used as CO2 desorbers for desorbing and releasing CO2 from the CO2-rich liquid under the pressure of -450 Pa.

[0006] The invention also includes a fuel preheating dryer, a modular flue gas-water heat exchanger composed of two or more front flue gas-steam heat exchange modules and one end flue gas-steam heat exchange module, one or more CO2 absorbers, one or more CO2 desorbers, a condensing chimney, and an evaporative cooler combined with a cold water storage tank.

[0007] The task of the present application is mainly achieved by the following process: firstly, the CO2-rich waste heat flue gas (generally at 120-140℃) from the combustion system of a power plant boiler is blown through a fuel preheating and drying device and the temperature of the waste heat flue gas is reduced to about 52-56℃, and then the waste heat flue gas is sent into a modularized flue gas-water heat exchanger for further temperature reduction. The above modularized flue gas-water heat exchanger is composed of two or more front flue gas-water heat exchange modules and one end flue gas-water heat exchange module, which are fastened together by flanges with bolts. The waste heat flue gas reduced to about 52-56℃ is cooled by the heat exchange tubes made of corrosion-resistant and high-heat-transfer-efficiency materials such as silicon carbide, which are suitable for high-speed flue gas. The above flue gas-water heat exchange modules are separated by intermediate partitions, which have a certain number of micropores. Under normal conditions, cooling water at different temperatures is mainly distributed in different heat exchange modules, but when the cooling water is under certain pressure, it can pass through the micropores on the intermediate partitions of the flue gas-water heat exchange modules and flow in the opposite direction of the flue gas flow at a speed of up to 3 meters per second. At this time, the cooling water will form a turbulent flow around the silicon carbide heat exchange tubes, thereby improving the gas-water heat exchange efficiency. The temperature of the cooling water in the modularized flue gas-water heat exchange modules decreases from the front end to the back end, and the cooling water temperature in the last heat exchange module is the lowest and can cool the waste heat flue gas to below 20℃. The waste heat flue gas cooled to below 20℃ by the modularized flue gas-water heat exchanger enters the CO2 absorber through the gas inlet, and the CO2 in the waste heat flue gas is dissolved in water to generate CO2-rich liquid under the action of pressure, and the gas after absorbing and dissolving CO2 is discharged from the gas outlet. The CO2-rich liquid in the CO2 absorber enters the CO2 desorber and completes the desorption and release of CO2 under variable pressure conditions, and the desorbed and released CO2 is discharged from the gas outlet. The CO2-lean liquid after desorption and release of CO2 in the CO2 desorber leaves the CO2 desorber and is pumped into the CO2 absorber again and used in the closed cycle of CO2 absorption / desorption, or used to cool fresh air entering the evaporative cooler. Through the above process, the absorption and capture of CO2 in the waste heat flue gas and the desorption and release of CO2 are completed.

[0008] In the present application, water is used as the absorbent to complete the CO2 absorption and desorption process, so that the regeneration of the absorbent is not required in the CO2 absorption and desorption process of the flue gas from the power plant, and the CO2 absorption, desorption and release from the flue gas are completed without generating chemical absorption or CO2 byproducts.

[0009] The exhaust heat flue gas from the boiler of a power plant is cooled in the fuel preheating drying process and reaches a near-saturation state, so a considerable amount of condensed water is produced in the further cooling process, which can be recycled in the CO2 absorption process without purification. Long and thick corrugated polypropylene cooling pipes are coiled into a vertical cylindrical shape with spacer plates and loaded into the evaporative cooler. The low-temperature cooling water cooled in the evaporative cooler is sent to the flue gas-water heat exchange module arranged at the end. The impurities, especially the scale produced by surface evaporation, do not adhere to the polypropylene cooling pipes when the cooling water in the evaporative cooler flows through the thick polypropylene cooling pipes.

[0010] The cold water storage tank can store low-temperature cold water, and in winter, only a common gas-water heat exchanger and an evaporative cooler without water spray cooling are needed to produce low-temperature cold water meeting the temperature requirements of the present application, even near the freezing point.

[0011] The consumption of water used as the absorbent in the present application is determined by the CO2 capture rate in the gas and the cycle number of the set period of absorption / desorption release. The goal of the present application is to achieve the absorption and capture of more than 60% of CO2 from the flue gas of a power plant and the like. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 A cross-sectional view of a cylindrical device containing a rotatable, corrugated surface, axial / non-axial ribbon spiral is shown.

[0013] Figure 2 A longitudinal partial cross-sectional view of a cylindrical device containing a rotatable, corrugated surface, axial / non-axial ribbon spiral is shown.

[0014] Figure 3 A schematic diagram of a device for extracting CO2 from 80000 Nm 3 / h, about 120-140℃, 10% CO2-containing exhaust heat flue gas from a 15 MW biomass power plant is shown.

[0015] Figure: 1-8 exhaust flue gas, 2- fuel preheating dryer, 3- waste heat flue gas, 4- front end flue gas / water heat exchanger module, 5- evaporative cooler, 6- cold water storage tank, 7- ordinary flue gas / water heat exchanger, 8- fan, 9- CO2 absorber, 10- air pressure control valve, 11- condensing chimney, 12- CO2 desorber, 13- water pressure control valve, 14- pump with check valve, 15- evaporation channel, 16- fresh air, 17- sprinkling water, 18- end flue gas / water heat exchanger module, 19- heat exchange tube, 20- intermediate partition, 21- desorbed CO2, 22- induced draft fan, 23- waste water, 24- waste gas, 25- cooling tube, 26- partition, 27- solution tank, 28- solution, 29- ribbon spiral, 30- gas inlet, 31- gas outlet, 32- solution inlet, 33- solution outlet, 34- outer housing, 35- motor, 36- modular flue gas / water heat exchanger, 37- waste heat flue gas inlet. DETAILED DESCRIPTION

[0016] The present application will be described in detail by an embodiment, Figure 1 Figure: shows a schematic view of a cross section of a cylindrical device containing a rotatable, surface corrugated, axial / non-axial ribbon spiral.

[0017] Two pairs of openings (30, 31, 32, 33) can be arranged on the cylindrical device and the position of the openings can be selected as desired. A rotatable, surface corrugated, axial / non-axial ribbon spiral (29) is arranged in the longitudinal direction in the cylindrical device. The outer edges of the ribbon spiral (29) are parallel to each other at equal distances in the longitudinal direction of the cylindrical device. There is a gap between the outer edges of the ribbon spiral (29) and the outer housing (34) of the cylindrical device. The ribbon spiral (29) can be partially immersed in the solution (28) in the cylindrical device, so that the gas at the surface of the ribbon spiral (29) and the solution (28) flow together.

[0018] Figure 2 Figure: shows a longitudinal partial sectional view of a cylindrical device containing a rotatable, surface corrugated, axial / non-axial ribbon spiral. The ribbon spiral (29) is driven by a motor (35).

[0019] Figure 3 Figure: shows a schematic view of a device for extracting CO2 from waste heat flue gas from a 15 MW biomass power plant with a capacity of 80000 Nm3 / h, at a temperature of about 120-140°C, containing 10% CO2. 3 Figure: shows a schematic view of a device for extracting CO2 from waste heat flue gas from a 15 MW biomass power plant with a capacity of 80000 Nm3 / h, at a temperature of about 120-140°C, containing 10% CO2.

[0020] The embodiment first blows the flue gas (1) from a 15 MW biomass power plant at about 120-140℃, containing 10% CO2, into a fuel preheating dryer (2) and cools the flue gas (1) into waste heat flue gas (3) at a temperature of about 52-56℃.

[0021] The waste heat flue gas (3) flowing out of the fuel preheating dryer (2) is then sent into a modular flue gas-water heat exchanger (36). The modular flue gas-water heat exchanger (36) of the embodiment is composed of three front flue gas-water heat exchange modules (4) and one end flue gas-water heat exchange module (18). Intermediate partitions (20) are arranged between the flue gas-water heat exchange modules (4, 18). The flue gas-water heat exchange modules (4, 18) are connected together by flanges and bolts.

[0022] Since the waste heat flue gas (3) is to be further cooled at a small temperature difference, an effective heat exchange process is required. The flue gas-water heat exchange modules (4, 18) of the embodiment have an outer diameter of 3.4 meters and a total length of about 14 meters. The flue gas-water heat exchange modules (4, 18) are arranged with 250 corrosion-resistant, high-heat transfer efficiency, wear-resistant and high-speed flue gas suitable silicon carbide heat exchange pipes (19) with an inner diameter of 88 mm passing through the intermediate partitions (20). The thermal conductivity of silicon carbide is about 120 W / mxK, which is several times that of steel. Intermediate partitions (20) are arranged between the flue gas-water heat exchange modules. Cooling water at different temperatures is input into different flue gas-water heat exchange modules. The lowest temperature cooling water is input into the end flue gas-water heat exchange module (18) to cool the waste heat flue gas (3) at the lowest possible temperature.

[0023] To ensure the rapid transmission of the waste heat flue gas (3), the flow rate of the waste heat flue gas (3) at the waste heat flue gas inlet (37) is controlled to be about 39 meters / second, and the flow rate of the waste heat flue gas (3) at the outlet of the heat exchange pipes (19) is about 34.6 meters / second.

[0024] The heat exchange pipes (19) of the flue gas-water heat exchange modules (4, 18) pass through the intermediate partitions (20). Cooling water at different temperatures is distributed in different flue gas-water heat exchange modules (4, 18). The micropores arranged on the intermediate partitions (20) allow the cooling water in the modular flue gas-water heat exchanger (36) to flow against the flow direction of the waste heat flue gas (3). By adjusting the width, number and arrangement of the micropores arranged on the intermediate partitions (20), the flow rate of the cooling water flowing against the flow direction of the waste heat flue gas (3) can be greater than 3 meters / second. The cooling water will generate turbulent flow around the heat exchange pipes (19), thereby improving the gas-water heat exchange efficiency.

[0025] The cooling water is operated in a closed system. In the present invention, in addition to the aforementioned modularized flue gas / water heat exchanger (36), an evaporative cooler (5) and a cold water storage tank (6), a common gas / water heat exchanger (7) and the pumps and pipes required by regulations are included.

[0026] Fresh air (16) is sucked into the evaporative cooler (5) by the fan through the evaporation channel (15), and the fresh air (16) is cooled by about 10-15℃ by the condensed water from the condensing chimney (11) in the evaporation channel (15) and the lean CO2 aqueous solution discharged through the opening of the CO2 desorber (12), and then used as the cooling air of the evaporative cooler (5), and the cooling water cooled by the evaporative cooler (5) is sent to the terminal flue gas / water heat exchanger module (18).

[0027] In summer, the temperature of the cooling water and the waste heat flue gas (3) will rise, and the evaporative cooling process through the evaporative cooler (5) is particularly necessary in summer, and we must cool the waste heat flue gas (3) to about 17℃, and the CO2 absorption capture rate in the waste heat flue gas (3) can reach more than 60%; In winter, only the common gas / water heat exchanger (7) or the evaporative cooler (5) without spraying cooling can make the temperature of the cooling water close to 10℃ or lower, and the CO2 absorption capture rate in the waste heat flue gas can reach more than 60%. In winter, antifreeze can be added to the closed cooling water circuit as needed.

[0028] The cooling water of the present invention is circulated in a closed cooling water circuit, and the flow of the cooling water can be controlled as needed by adjusting the frequency conversion water pump of the two closed water circuit systems.

[0029] The waste heat flue gas (3) cooled to about 17℃ by the aforementioned modularized flue gas / water heat exchanger (36) is pressurized to about 24000Pa by the fan (8) and enters the CO2 absorber (9) through the gas inlet (30), and is dissolved in the solution (28) as the absorbent after being repeatedly immersed and co-flowing with the solution (28) in the CO2 absorber (9) through the rotatable, corrugated, shafted / unsheathed ribbon spiral (29) ribbon surface.

[0030] In the present invention, the CO2 capture rate in the waste heat flue gas (3) can be further improved by increasing the number of CO2 absorbers (9), and in the present embodiment, three CO2 absorbers (9) with a length of 10 meters, a width of 3 meters and a height of 3.4 meters are arranged.

[0031] The CO2-rich liquid absorbed into the CO2 absorber (9) is pumped into the CO2 desorber (12) arranged with a "ribbon spiral" through another opening of the CO2 absorber (9) and a water pressure control valve (13), and the CO2 (21) is desorbed and released from the CO2-rich liquid under the pressure of -450 Pa generated by the induced draft fan (22), which helps to accelerate the desorption and release of the CO2 (21) and improve the desorption rate of the CO2.

[0032] After the CO2 desorber (12) desorbs and releases the CO2 (21), the CO2-lean liquid is pumped into the CO2 absorber (9) again through another opening of the CO2 desorber (12) for recycling or used as the air coolant required by the evaporative cooler (5) through the evaporation channel (15).

[0033] The CO2 absorber (9) and the CO2 desorber (12) of the present application have a circulating solution (28) loop, and the solution (28) is circulated by a pump (14) with a check valve.

[0034] In the present embodiment, when the waste heat flue gas (3) is cooled to about 17℃ by the modular flue pipe type gas-water heat exchanger (36), the modular flue pipe type gas-water heat exchanger (36) and the CO2 absorber (9) can discharge about 20 tons of water per hour, which can basically meet the requirements of the operation of the evaporative cooler (5), so the present application can be installed anywhere, and it meets the future "green" resource principle requirement of adapting to nature. On the other hand, if fresh water resources are abundant and cheap, it is easy to integrate the cooled fresh water into the present application. The size of the cooling water storage tank (6) can be variable and can supply low-temperature cooling water conveniently to better utilize the potential of nature.

[0035] The function of the air pressure control valve (10) in the present application is to stabilize the gas pressure of about 24000 Pa in the CO2 absorber (9) and not affected by the change of gas flow rate, and it can also adjust the gas flow rate to the condensing chimney (11), and the gas flowing into the condensing chimney (11) can generate spray water (17) for the cooling of fresh air used in the evaporative cooler (5).

[0036] Because the water sprayed into the evaporation channel (15) or the evaporative cooler (5) will be more than the water absorbed by the cooling of fresh air, a certain cleaning effect can be achieved and the heat exchange surface of the evaporative cooler (5) can be kept clean.

[0037] The research found that the scale and other pollutants will not adhere to the polypropylene material during the continuous surface evaporation process, so this material is particularly suitable for use as a cooling tube (25) in the manufacture of the evaporative cooler (5). The cooling tube (25) together with the spacing plate (26) will be inserted into the vertical cylindrical space in the evaporative cooler (5) after being coiled. This cooling tube (25) is preferably made of a flexible corrugated polypropylene tube, and since the evaporative cooler (5) is always operated in a low temperature environment below 20℃, the service life of the polypropylene material cooling tube (25) will be longer.

[0038] Due to the low price of the material, the size of the evaporative cooler (5) can be made large to compensate for the heat conduction defects to better adapt to the low temperature difference heat exchange, and other components of the evaporative cooler (5) can also be made of plastic. Only a small part of the condensed water is discharged as waste water (23) that may contain impurities from the waste heat flue gas (3), and the above circulating process makes the present application have a certain self-cleaning function.

[0039] The present application can also be regarded as an efficient flue gas purification system, because the exhaust gas through the condensing chimney (11) is clean and odorless, and the dust and sulfide content in the exhaust gas can meet the emission standards.

[0040] The present application can recover most of the waste heat in the flue gas (1) of the power plant by preheating and drying the fuel, thereby reducing the cost of fuel procurement. In the embodiment, the fuel cost is expected to be reduced by 10%, and the saved funds are sufficient to invest and operate the device of the present application including fuel preheating and drying, and even possibly with a profit, which makes it easier to raise funds for CO2 capture, which is the key to immediately starting CO2 capture using the present application.

[0041] The purpose of the present application is to be able to capture CO2 at low cost and low power consumption throughout the year, including summer, and to achieve the goal of absorbing more than 60% of CO2 capture rate from flue gas and other gases from power plants.

[0042] Obviously, the above embodiments are only examples for the sake of clarity, and are not a limitation on the embodiments. Based on the above description, those skilled in the art can make other different forms of changes or variations. Here, it is not necessary and impossible to exhaust all embodiments. The obvious changes or variations derived therefrom are still within the scope of protection of the present application.

Claims

1. A device for capturing and removing CO2 from flue gas from a power plant, comprising a cylindrical device; characterized in that, Two pairs of openings (30, 31, 32, 33) can be arranged on the cylindrical device as needed, and the positions of the openings can be selected as needed. A rotatable, corrugated, shaftless / shafted ribbon-like spiral (29) is arranged longitudinally inside the cylindrical device. The outer edges of the surface of the ribbon-like spiral (29) are parallel and equidistant from each other in the longitudinal direction of the cylindrical device. There is a certain gap between the outer edge of the surface of the ribbon-like spiral (29) and the outer shell (34) of the cylindrical device. The ribbon-like spiral (29) can be partially immersed in the solution (28) inside the cylindrical device, so that the gas and solution (28) on the surface of the ribbon-like spiral (29) flow together.

2. The apparatus for capturing and removing CO2 from flue gas from a power plant according to claim 1, characterized in that, The device comprises two or more cylindrical devices arranged with ribbon-like helices (29) connected in sequence, wherein one or more of the cylindrical devices are used as CO2 absorbers (9) for dissolving and absorbing CO2 in a gas at a pressure of 24000 Pa, and the other one or more cylindrical devices are used as CO2 desorbers (12) for desorbing CO2 from a CO2-rich liquid at a pressure of -450 Pa.

3. The apparatus for capturing and removing CO2 from flue gas from a power plant according to claim 2, characterized in that, The solutions used for CO2 absorption and desorption in the CO2 absorber (9) and CO2 desorber (12) are water.

4. The apparatus for capturing and removing CO2 from flue gas from a power plant according to claim 1, characterized in that, Waste heat flue gas (3) from the fuel preheating dryer (2) flows into silicon carbide heat exchange tubes (19) arranged in the heat exchange modules (4, 18) of the modular flue gas-water heat exchanger (36). Cooling water in the heat exchange modules (4, 18) can flow against the flow direction of waste heat flue gas (3) through micropores on the intermediate partition wall (20).

5. The apparatus for capturing and removing CO2 from flue gas from a power plant according to claim 4, characterized in that, Cooling water flows through a modular flue gas-water heat exchanger (36) consisting of heat exchange modules (4, 18), the aqueous solution of which comes from an evaporative cooler (5) that operates using condensate from waste heat flue gas (3) and a conventional gas-water heat exchanger (7).

6. The apparatus for capturing and removing CO2 from flue gas from a power plant according to claim 5, characterized in that, The evaporative cooler (5) includes cooling tubes (25) made of corrugated polypropylene, which are arranged in a coiled manner together with a spacer plate (26) within the vertical cylindrical space of the evaporative cooler (5).

7. The apparatus for capturing and removing CO2 from flue gas from a power plant according to claim 6, characterized in that, The evaporative cooler (5) operates in combination with the cold water storage tank (6).

8. The apparatus for capturing and removing CO2 from flue gas from a power plant according to claim 1, characterized in that, The device includes a fuel preheating dryer (2), a modular flue gas-water heat exchanger (36) consisting of two or more front-end flue gas-water heat exchange modules (4) and an end flue gas-water heat exchange module (18), one or more CO2 absorbers (9), one or more CO2 desorbers (12), a condensation chimney (11), and an evaporative cooler (5) that operates in combination with a cold water storage tank (6).

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