A boiler tail gas cooling device

Abstract

The invention discloses a boiler tail gas temperature reduction and cooling device, comprising a flue gas cooling tower. At least three-stage flue gas cooling devices are arranged in the flue gas cooling tower. The flue gas cooling device comprises a packing layer. Flue gas and circulating liquid are directly contacted and heat exchanged in the packing layer. The circulating liquids used by the flue gas cooling devices near the flue gas inlet and the flue gas cooling devices near the flue gas outlet are both calcium chloride solutions. The circulating liquid outlets of the flue gas cooling devices near the flue gas inlet and the flue gas cooling devices near the flue gas outlet are both connected to a mixing tank through a pipeline. The invention mixes the calcium chloride solution with reduced water content in the first-stage cooling spray device and the calcium chloride solution with increased water content in the fourth-stage cooling spray device together, and transports them back to the flue gas cooling tower after reaching water balance. Compared with the traditional calcium chloride solution dehydration method generally using a desiccant drying or a direct heating evaporation method, the method does not increase the system energy consumption and avoids energy waste.

Description

Technical Field

[0001] The invention belongs to the technical field of flue gas cooling, and in particular relates to a boiler tail gas cooling device. Background Art

[0002] In the field of integrated removal of low-temperature flue gas pollutants, in order to increase the adsorption capacity of unit adsorbent and reduce the filling volume of adsorbent, it is necessary to cool the flue gas from high temperature to sub-zero temperature in stages. Due to the water content in the flue gas, when the flue gas continues to cool below zero degrees Celsius, if the method of indirect heat exchange between the flue gas and the calcium chloride solution is adopted, as the operation time increases, the water in the flue gas will freeze on the flue gas side of the heat exchanger, increasing the resistance of the heat exchanger and even clogging it. If the method of direct heat exchange between the flue gas and the calcium chloride solution is adopted, as the operation time increases, the calcium chloride solution will be diluted by the water in the flue gas, resulting in an increase in the freezing point of the calcium chloride solution, and it is necessary to supplement or replace fresh calcium chloride solution, which affects the stability of system operation, and the consumption of calcium chloride solution increases, and the operating cost increases.

[0003] The traditional dehydration method of calcium chloride solution generally adopts the method of drying with a desiccant or directly heating and evaporating. In the process of regenerating the desiccant after absorbing water or heating and evaporating, a large amount of heat energy is consumed, resulting in energy waste, and a series of heating and cooling equipment need to be added, and the process is relatively cumbersome. Therefore, we propose a boiler tail gas cooling device. Summary of the invention

[0004] The purpose of the present invention is to improve and innovate the shortcomings and problems existing in the background technology and provide a boiler exhaust gas cooling device.

[0005] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a boiler exhaust gas cooling device, comprising a flue gas cooling tower, wherein at least three stages of flue gas cooling devices are arranged in the flue gas cooling tower, wherein the flue gas cooling device comprises a packing layer, and the flue gas and the circulating liquid are in direct contact and heat exchange in the packing layer, and the circulating liquid used by the flue gas cooling device near the flue gas inlet and the flue gas cooling device near the flue gas outlet are both calcium chloride solutions, and the circulating liquid outlets of the flue gas cooling device near the flue gas inlet and the flue gas cooling device near the flue gas outlet are both connected to a mixing tank through a pipeline, and the circulating liquid in the mixing tank is then respectively connected to the circulating liquid inlets of the flue gas cooling device near the flue gas inlet and the flue gas cooling device near the smoke gas outlet through two pipelines.

[0006] A further solution is that the circulating liquid inlet of the flue gas cooling device near the flue gas inlet is connected to the mixing tank through a first circulating liquid inlet pipe, and the circulating liquid outlet of the flue gas cooling device near the flue gas inlet is connected to the mixing tank through a first circulating liquid outlet pipe; the mixing tank is connected to the circulating liquid inlet of the flue gas cooling device near the flue gas outlet through a fourth circulating liquid inlet pipe via a refrigerator, and the mixing tank is connected to the circulating liquid outlet of the flue gas cooling device near the smoke gas outlet through a fourth circulating liquid outlet pipe.

[0007] A further solution is that a plurality of liquid collecting pans are arranged in the flue gas cooling tower, which can allow the flue gas to enter the upper flue gas cooling device from the lower flue gas cooling device, but cannot allow the circulating liquid of the upper flue gas cooling device to enter the lower flue gas cooling device.

[0008] A further solution is that the liquid collecting tray includes a tray body installed on the flue gas cooling tower, and a plurality of outlet pipes with openings at both ends are installed on the tray body. The top ends of the outlet pipes are fixedly connected to a liquid collecting tank through connecting rods, and the projection of the liquid collecting tank on the bottom surface of the flue gas cooling tower is larger than the projection of the outlet pipes on the bottom surface of the flue gas cooling tower, and a plurality of notches are opened on the side walls of the liquid collecting tank.

[0009] A further solution is that a four-stage flue gas cooling device is arranged in the flue gas cooling tower, the bottom of the third-stage flue gas cooling device is connected with the upper part of the second-stage flue gas cooling device through an overflow pipe, an external discharge pipe is arranged at the bottom of the second-stage flue gas cooling device, and the top height of the overflow pipe is lower than the top height of the outlet pipe in the third-stage flue gas cooling device, and the height of the external discharge pipe is lower than the top height of the outlet pipe in the second-stage flue gas cooling device.

[0010] A further solution is that a second circulating liquid inlet pipe is provided at the circulating liquid inlet of the second-stage flue gas cooling device, and a second circulating liquid outlet pipe is provided on the disk of the second-stage flue gas cooling device; a third circulating liquid inlet pipe is provided at the circulating liquid inlet of the third-stage flue gas cooling device, and a third circulating liquid outlet pipe is provided on the disk of the third-stage flue gas cooling device.

[0011] A further solution is that a plurality of trough distributors are installed in the flue gas cooling tower, and the trough distributors are located directly above the packing layers and correspond one to one with the packing layers.

[0012] A further solution is that a demister is provided on the top of the flue gas cooling tower, and the flue gas is discharged from the flue gas cooling tower after moisture is removed from the flue gas through the demister.

[0013] Compared with the prior art, the present invention has the following beneficial effects: (1) the present invention mixes the calcium chloride solution with reduced water content in the first-stage flue gas cooling device with the calcium chloride solution with increased water content in the fourth-stage flue gas cooling device, and then transports them back to the flue gas cooling tower for countercurrent heat exchange with the flue gas after reaching water balance. Compared with the traditional calcium chloride solution dehydration method which generally adopts desiccant drying or direct heating evaporation method, the present method does not increase the energy consumption of the system, thus avoiding energy waste;

[0014] (2) The bottom end of the third-stage flue gas cooling device is connected to the upper end of the second-stage flue gas cooling device through an overflow pipe, so that the circulating liquid cooling water precipitated from the third-stage flue gas cooling device can overflow into the second-stage flue gas cooling device. On the one hand, it can replenish cooling water for the second-stage flue gas cooling device, and on the other hand, it can transport the cold energy to the second-stage flue gas cooling device, avoiding the waste of energy caused by the discharge of cooling water;

[0015] (3) Through the coordination of the disc, the air outlet pipe, the liquid collecting tank, the notch and the connecting rod, the air outlet pipe can allow the flue gas to enter the upper flue gas cooling device from the lower flue gas cooling device, while the liquid collecting tank can prevent the circulating water of the upper flue gas cooling device from entering the lower flue gas cooling device, thereby ensuring that the circulating water of each level of the flue gas cooling device is independent of each other. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the structure of the present invention;

[0017] Figure 2 The present invention Figure 1 A schematic diagram of the partially enlarged structure at center A;

[0018] Figure numerals: flue gas cooling tower 1, mixing tank 2, flue gas inlet pipe 3, first-stage flue gas cooling device 4, second-stage flue gas cooling device 5, third-stage flue gas cooling device 6, fourth-stage flue gas cooling device 7, demister 8, first circulating liquid inlet pipe 9, first circulating liquid outlet pipe 10, second circulating liquid inlet pipe 11, second circulating liquid outlet pipe 12, third circulating liquid inlet pipe 13, third circulating liquid outlet pipe 14, fourth circulating liquid inlet pipe 15, fourth circulating liquid outlet pipe 16, trough distributor 17, overflow pipe 18, external discharge pipe 19, liquid collecting tray 20, outlet pipe 201, liquid collecting tank 202, notch 203, connecting rod 204. DETAILED DESCRIPTION

[0019] The following is combined with Figures 1-2 The present invention is described in further detail.

[0020] A boiler tail gas cooling device comprises a flue gas cooling tower 1, wherein a flue gas inlet pipe 3 is arranged at the bottom of the flue gas cooling tower 1, so that the boiler flue gas can enter from the bottom of the flue gas cooling tower 1. The flue gas cooling tower 1 is provided with four-stage flue gas cooling devices, which are a first-stage flue gas cooling device 4, a second-stage flue gas cooling device 5, a third-stage flue gas cooling device 6 and a fourth-stage flue gas cooling device 7 from bottom to top. The flue gas cooling device comprises a packing layer, wherein the packing layer of the first-stage flue gas cooling device 4 adopts 50 ball ring random packing, and the remaining packing layers adopt 250X packing. The flue gas and the circulating liquid are in direct contact with each other in the packing layer for heat exchange, and the packing layer slows down the flow speed of the flue gas, increases the contact time between the flue gas and the circulating liquid, and enables the flue gas and the circulating liquid to fully exchange heat. The circulating fluids used in the first-stage flue gas cooling device 4 and the fourth-stage flue gas cooling device 7 are both calcium chloride solutions, and the circulating fluids used in the second-stage flue gas cooling device 5 and the third-stage flue gas cooling device 6 are both cooling water. Since the temperature of the flue gas in the first-stage flue gas cooling device 4 is relatively high and the water content in the flue gas is not saturated, the flue gas will take away the water in the calcium chloride solution. When the temperature of the flue gas in the fourth-stage flue gas cooling device 7 is reduced to below 0°C, a large amount of water in the flue gas will precipitate, which will cause the water content of the circulating fluid calcium chloride solution in the fourth-stage flue gas cooling device 7 to increase. The circulating liquid outlet of the first-stage flue gas cooling device 4 is connected to the mixing tank 2 through the first circulating liquid outlet pipe 10, and the circulating liquid outlet of the fourth-stage flue gas cooling device 7 is connected to the mixing tank 2 through the fourth circulating liquid outlet pipe 16, so that the calcium chloride solution with reduced water content in the first-stage flue gas cooling device 4 and the calcium chloride solution with increased water content in the fourth-stage flue gas cooling device 7 are mixed together, so that the water content of the two is balanced, thereby automatically reducing the water content of the circulating liquid of the fourth-stage flue gas cooling device 7, and then transported back to the flue gas cooling tower 1 through the first circulating liquid inlet pipe 9 and the fourth circulating liquid inlet pipe 15 respectively, wherein a refrigerator is arranged in the middle of the fourth circulating liquid inlet pipe 15, and the refrigerator is not shown in the figure. The refrigerator is used to provide cooling capacity for the circulating liquid of the fourth-stage flue gas cooling device 7.

[0021] Furthermore, a plurality of liquid collecting trays 20 are arranged in the flue gas cooling tower 1, and the liquid collecting trays 20 are respectively arranged between the first flue gas cooling device 4 and the second-stage flue gas cooling device 5, the second-stage flue gas cooling device 5 and the third-stage flue gas cooling device 6, and the third-stage flue gas cooling device 6 and the fourth-stage flue gas cooling device 7. The liquid collecting tray 20 includes a tray body installed on the flue gas cooling tower 1, and a plurality of outlet pipes 201 with openings at both ends are installed on the tray body. The top of the outlet pipe 201 is fixedly connected to a liquid collecting tank 202 by a connecting rod 204, and a plurality of notches 203 are opened on the side wall of the liquid collecting tank 202. The projection of the liquid collecting tank 202 on the bottom surface of the flue gas cooling tower 1 is larger than the projection of the outlet pipe 201 on the bottom surface of the flue gas cooling tower 1. It can be understood that, with such a configuration, the outlet pipe 201 can allow the flue gas to enter the upper flue gas cooling device from the lower flue gas cooling device, while the liquid collecting tank 202 prevents the circulating water of the upper flue gas cooling device from entering the lower flue gas cooling device, thereby ensuring that the circulating water of each stage of the flue gas cooling device is independent of each other.

[0022] Furthermore, the bottom of the third-stage flue gas cooling device 6 is connected to the upper part of the second-stage flue gas cooling device 5 through an overflow pipe 18, and an external discharge pipe 19 is provided at the bottom of the second-stage flue gas cooling device 5, and the top height of the overflow pipe 18 is lower than the top height of the outlet pipe 201 located in the third-stage flue gas cooling device 6, and the height of the external discharge pipe 19 is lower than the top height of the outlet pipe 201 located in the second-stage flue gas cooling device 5. The overflow pipe 18 can overflow the circulating liquid cooling water precipitated from the third-stage flue gas cooling device 6 into the second-stage flue gas cooling device 5, which can replenish cooling water to the second-stage flue gas cooling device 5 on the one hand, and transport the cold to the second-stage flue gas cooling device 5 on the other hand, avoiding the waste of energy caused by the external discharge of cooling water. The external discharge pipe 19 can discharge the excess cooling water of the second-stage flue gas cooling device 5 out of the flue gas cooling tower 1, avoiding the cooling water from entering the outlet pipe 201.

[0023] Furthermore, a second circulating liquid inlet pipe 11 is provided at the circulating liquid inlet of the second-stage flue gas cooling device 5, and a second circulating liquid outlet pipe 12 is provided on the disk of the second-stage flue gas cooling device 5; a third circulating liquid inlet pipe 13 is provided at the circulating liquid inlet of the third-stage flue gas cooling device 6, and a third circulating liquid outlet pipe 14 is provided on the disk of the third-stage flue gas cooling device 6.

[0024] Furthermore, a plurality of trough distributors 17 are installed in the flue gas cooling tower 1. The trough distributors 17 are located directly above the packing layer and correspond one to one with the packing layer. The trough distributors 17 make the circulating liquid inlet evenly distributed in the packing layer.

[0025] Furthermore, a demister 8 is provided on the top of the flue gas cooling tower 1 . The demister 8 is a wire mesh demister. The flue gas is discharged from the flue gas cooling tower 1 after moisture is removed from the flue gas through the demister 8 .

[0026] Working principle of the present invention: When used specifically, the flue gas after dust removal from the high-temperature boiler is introduced into the flue gas cooling tower 1 through the flue gas inlet pipe 3. The flue gas first enters the first-stage flue gas cooling device 4 for countercurrent heat exchange with the calcium chloride solution to reduce the flue gas temperature from 80°C to 60°C. Since the flue gas temperature is relatively high at this time, the water content in the flue gas is not saturated, and the flue gas will take away the water content in the calcium chloride solution; then the flue gas enters the second-stage flue gas cooling device 5 to be cooled by cooling water, and the flue gas temperature is reduced from 60°C to 40°C; then the flue gas enters the third-stage flue gas cooling device 6 to continue to be cooled by cooling water, and the flue gas temperature is reduced from 40°C to 5°C. Since the flue gas temperature is relatively low, the water content in the flue gas will precipitate, thereby increasing the amount of cooling water in the third-stage cooling spray device 6, and the excess water content can overflow to the second-stage cooling spray device 5 through the overflow pipe 18; then the flue gas enters the fourth The first-stage cooling spray device 7 is in direct contact with the circulating liquid calcium chloride solution for countercurrent heat exchange, and the flue gas temperature will be reduced from 5°C to -20°C. During the heat exchange process, a large amount of moisture in the flue gas will be precipitated, which increases the water content of the circulating liquid calcium chloride solution in the fourth-stage flue gas cooling device 7. Finally, the flue gas is discharged from the flue gas cooling tower 1 after the moisture is removed by the demister 8; since the circulating liquid outlets of the first-stage flue gas cooling device 4 and the fourth-stage flue gas cooling device 7 are both connected to the mixing tank 2 through a pipeline, the calcium chloride solution with reduced water content in the first-stage flue gas cooling device 4 and the calcium chloride solution with increased water content in the fourth-stage flue gas cooling device 7 are mixed together, and then returned to the flue gas cooling tower 1 for countercurrent heat exchange with the flue gas after reaching water balance. Compared with the traditional calcium chloride solution dehydration method which generally uses desiccant drying or direct heating evaporation, this method does not increase the energy consumption of the system and avoids energy waste.

[0027] The above implementations are used to illustrate the technical solution of the present invention rather than to limit it. Those skilled in the art should understand that any modification, equivalent substitution or improvement of the technical solution of the present invention within the spirit and principles of the present invention are included in the protection scope of the present invention.

Claims

1. A boiler tail gas cooling device, comprising a flue gas cooling tower (1), characterized in that: At least three stages of flue gas cooling devices are arranged in the flue gas cooling tower (1), wherein the flue gas cooling device comprises a packing layer, and the flue gas and the circulating liquid are in direct contact with each other in the packing layer for heat exchange. The circulating liquids used in the flue gas cooling device near the flue gas inlet and the flue gas cooling device near the flue gas outlet are both calcium chloride solutions. The circulating liquid outlets of the flue gas cooling device near the flue gas inlet and the flue gas cooling device near the flue gas outlet are both connected to a mixing tank (2) through pipelines. The circulating liquid in the mixing tank (2) is then respectively connected to the mixing tank (2) near the flue gas inlet through two pipelines. The flue gas cooling device at the first stage (4) is connected to the circulating liquid inlet of the flue gas cooling device near the flue gas outlet, wherein the flue gas cooling device is divided into four stages, the circulating liquid outlet of the first stage flue gas cooling device (4) is connected to the mixing tank (2) through the first circulating liquid outlet pipe (10), the circulating liquid outlet of the fourth stage flue gas cooling device (7) is connected to the mixing tank (2) through the fourth circulating liquid outlet pipe (16), and then transported back to the flue gas cooling tower (1) through the first circulating liquid inlet pipe (9) and the fourth circulating liquid inlet pipe (15), respectively.

2. A boiler tail gas cooling device according to claim 1, characterized in that: The circulating liquid inlet of the flue gas cooling device near the flue gas inlet is connected to the mixing tank (2) through a first circulating liquid inlet pipe (9), and the circulating liquid outlet of the flue gas cooling device near the flue gas inlet is connected to the mixing tank (2) through a first circulating liquid outlet pipe (10); the mixing tank (2) is connected to the circulating liquid inlet of the flue gas cooling device near the flue gas outlet through a fourth circulating liquid inlet pipe (15) via a refrigerator, and the mixing tank (2) is connected to the circulating liquid outlet of the flue gas cooling device near the flue gas outlet through a fourth circulating liquid outlet pipe (16).

3. A boiler tail gas cooling device according to any one of claims 1 to 2, characterized in that: A plurality of liquid collecting pans (20) are arranged in the flue gas cooling tower (1), and the liquid collecting pans (20) can allow flue gas from a flue gas cooling device at a lower level to enter a flue gas cooling device at an upper level, but cannot allow circulating liquid of the flue gas cooling device at an upper level to enter the flue gas cooling device at a lower level.

4. A boiler tail gas cooling device according to claim 3, characterized in that: The liquid collecting tray (20) comprises a tray body mounted on a flue gas cooling tower (1), a plurality of outlet pipes (201) with openings at both ends being mounted on the tray body, the top ends of the outlet pipes (201) being fixedly connected to a liquid collecting tank (202) via connecting rods (204), the projection of the liquid collecting tank (202) on the bottom surface of the flue gas cooling tower (1) being larger than the projection of the outlet pipes (201) on the bottom surface of the flue gas cooling tower (1), and a plurality of notches (203) being provided on the side walls of the liquid collecting tank (202).

5. The boiler tail gas cooling device according to claim 1, characterized in that: The flue gas cooling tower (1) is provided with four-stage flue gas cooling devices, the bottom of the third-stage flue gas cooling device (6) is connected to the upper part of the second-stage flue gas cooling device (5) through an overflow pipe (18), and the bottom of the second-stage flue gas cooling device (5) is provided with an external exhaust pipe (19).

6. A boiler tail gas cooling device according to claim 4, characterized in that: The flue gas cooling tower (1) is provided with four-stage flue gas cooling devices, the bottom of the third-stage flue gas cooling device (6) is connected to the top of the second-stage flue gas cooling device (5) through an overflow pipe (18), the bottom of the second-stage flue gas cooling device (5) is provided with an external discharge pipe (19), and the top height of the overflow pipe (18) is lower than the top height of the outlet pipe (201) located in the third-stage flue gas cooling device (6), and the height of the external discharge pipe (19) is lower than the top height of the outlet pipe (201) located in the second-stage flue gas cooling device (5).

7. The boiler tail gas cooling device according to claim 5, characterized in that: A second circulating liquid inlet pipe (11) is provided at the circulating liquid inlet of the second-stage flue gas cooling device (5), and a second circulating liquid outlet pipe (12) is provided at the circulating liquid outlet of the second-stage flue gas cooling device (5); a third circulating liquid inlet pipe (13) is provided at the circulating liquid inlet of the third-stage flue gas cooling device (6), and a third circulating liquid outlet pipe (14) is provided at the circulating liquid inlet of the third-stage flue gas cooling device (6).

8. The boiler tail gas cooling device according to claim 5, characterized in that: A second circulating liquid inlet pipe (11) is provided at the circulating liquid inlet of the second-stage flue gas cooling device (5), and a second circulating liquid outlet pipe (12) is provided on the disk of the second-stage flue gas cooling device (5); a third circulating liquid inlet pipe (13) is provided at the circulating liquid inlet of the third-stage flue gas cooling device (6), and a third circulating liquid outlet pipe (14) is provided on the disk of the third-stage flue gas cooling device (6).

9. The boiler tail gas cooling device according to claim 1, characterized in that: A plurality of trough distributors (17) are installed in the flue gas cooling tower (1), and the trough distributors (17) are located directly above the packing layer and correspond one to one with the packing layer.

10. The boiler tail gas cooling device according to claim 1, characterized in that: A demister (8) is provided on the top of the flue gas cooling tower (1), and the flue gas is discharged from the flue gas cooling tower (1) after moisture is removed from the flue gas through the demister (8).

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