Integrated multi-pollutant removal cooling system and method using flue gas waste heat

Abstract

The present invention discloses a multi-pollutant integrated removal cooling system and method utilizing flue gas waste heat. The flue gas in the boiler is cooled by a primary economizer and then connected to the flue gas inlet of an air preheater. The flue gas outlet of the air preheater is connected to the flue gas inlet of a dust collector. The flue gas outlet of the dust collector is connected to the flue gas inlet of a lithium bromide absorption refrigeration unit. The flue gas outlet of the lithium bromide absorption refrigeration unit is connected to the flue gas inlet of the lower section of a flue gas cooling and washing tower. The low-temperature flue gas after being sprayed and cooled by upper and lower sections of circulating washing liquid in the flue gas cooling and washing tower comes out from the top of the tower to the subsequent adsorption section. The present invention makes full use of the waste heat carried by the flue gas after dust removal to provide the required heat for the lithium bromide absorption refrigeration unit. The prepared chilled water is used for flue gas cooling. The energy is fully utilized, the power consumption is reduced, and thus the operating cost of flue gas environmental protection treatment is reduced, which has significant economic benefits.

Description

Technical Field

[0001] The present invention belongs to the technical field of flue gas pollutant treatment and purification, and in particular relates to a multi-pollutant integrated removal and cooling system and method utilizing flue gas waste heat. Background Art

[0002] In conventional flue gas multi-pollutant removal systems, flue gas cooling can generally be achieved by direct water cooling, indirect water cooling, indirect air cooling, and natural cooling. There are two methods for direct water cooling. One is to spray water directly into the high-temperature flue gas. A special spray cooling tower can be used. The cross-sectional wind speed of the cooling tower is usually 2-3.5 m / s. Another method is to use a cooling water pipeline installed in the gas transport pipeline. This method has a strong cooling capacity and occupies less space. However, the direct water cooling method has a large cooling water circulation volume, high energy consumption, and cannot cool the flue gas to a lower target temperature.

[0003] Indirect water cooling or air cooling methods generally involve installing a heat exchanger on the flue gas circulation pipeline, with flue gas flowing on one side and cooling water or air flowing on the other side. These cooling media are mostly driven by pumps or fans to form forced convection heat exchange. This method has a small cooling coefficient, a large heat exchange end difference, occupies a large space, and requires high corrosion resistance of the heat exchanger.

[0004] Natural cooling generally lengthens the length of the gas transport pipeline, and the convection and radiation heat dissipation between the pipeline and the surrounding air cools the gas. It is mostly used for metal pipelines. In order to lengthen the cooling area, the flue gas pipeline is often set to S-shape. This method is simple, the cooling is weaker, and it occupies more space. It is usually used in occasions where the cooling effect is not required. Summary of the invention

[0005] In order to overcome the defects of the prior art, the present invention provides a multi-pollutant integrated removal cooling system and method using flue gas waste heat.

[0006] In order to achieve the above object, the present invention adopts the following technical scheme:

[0007] An integrated multi-pollutant removal cooling system utilizing flue gas waste heat, including a boiler, a primary economizer, an air preheater, a dust collector, a lithium bromide absorption refrigeration unit, a chilled water regulating valve, a lower section circulating pump, a lower section cooling water heat exchanger, a lower section chilled water heat exchanger, an upper section circulating pump, an upper section low-temperature refrigeration unit, and a flue gas cooling scrubber;

[0008] A primary economizer is provided in the flue of the boiler, the flue outlet of the boiler is connected to the flue gas inlet of the air preheater, the flue gas outlet of the air preheater is communicated with the flue gas inlet of the dust collector, the flue gas outlet of the dust collector is communicated with the flue gas inlet of the lithium bromide absorption refrigeration unit, the flue gas outlet of the lithium bromide absorption refrigeration unit is communicated with the flue gas inlet of the lower section of the flue gas cooling and washing tower, and the low-temperature flue gas outlet at the top of the flue gas cooling and washing tower is connected to the subsequent adsorption section;

[0009] The bottom washing liquid outlet of the flue gas cooling washing tower is connected to the washing liquid inlet of the lower cooling water heat exchanger, the washing liquid outlet of the lower cooling water heat exchanger is connected to the washing liquid inlet of the lower freezing water heat exchanger, and the washing liquid outlet of the lower freezing water heat exchanger is connected to the washing liquid inlet of the lower section of the flue gas cooling washing tower;

[0010] The upper spray liquid outlet of the flue gas cooling and washing tower is connected to the spray liquid inlet of the upper low-temperature refrigeration unit, and the spray liquid outlet of the upper low-temperature refrigeration unit is connected to the upper spray liquid inlet of the flue gas cooling and washing tower;

[0011] After being cooled by the lithium bromide absorption refrigeration unit, the chilled water is divided into two paths, one path is connected to the chilled water inlet of the lower chilled water heat exchanger, and the other path is connected to the chilled water inlet of the upper low-temperature refrigeration unit. The chilled water outlet of the upper low-temperature refrigeration unit and the chilled water outlet of the lower chilled water heat exchanger are combined into one path connected to the chilled water inlet of the lithium bromide absorption refrigeration unit.

[0012] Furthermore, the washing liquid outlet at the bottom of the flue gas cooling and washing tower is connected to the washing liquid inlet of the lower circulating pump, and the washing liquid outlet of the lower circulating pump is connected to the washing liquid inlet of the lower cooling water heat exchanger.

[0013] Furthermore, the upper spray liquid outlet of the flue gas cooling and washing tower is connected to the spray liquid inlet of the upper circulating pump, and the spray liquid outlet of the upper circulating pump is connected to the spray liquid inlet of the upper low-temperature refrigeration unit.

[0014] Furthermore, the upper low-temperature refrigeration unit is provided with an inlet and an outlet for circulating cooling water.

[0015] Furthermore, the flue gas cooling and washing tower is a packed tower.

[0016] Furthermore, the flue gas cooling and washing tower is arranged in two sections, and the two sections of the flue gas cooling and washing tower are connected by an air lifting cap.

[0017] Furthermore, the air preheater is provided with a cold air inlet and a hot air outlet.

[0018] Furthermore, a chilled water regulating valve is provided between the chilled water outlet of the lithium bromide absorption refrigeration unit and the chilled water inlet of the lower chilled water heat exchanger.

[0019] The multi-pollutant integrated removal and cooling method using flue gas waste heat, the flue gas generated in the boiler furnace is cooled successively by the primary economizer and the air preheater and dedusted by the dust collector, and then enters the lithium bromide absorption refrigeration unit to provide it with the heat required for producing chilled water, and further cooled down, enters the flue gas cooling scrubber for spray cooling and deep cooling; the chilled water is divided into two paths after being cooled by the lithium bromide absorption refrigeration unit, one path goes to the lower chilled water heat exchanger to cool the scrubbing liquid in the lower section of the flue gas cooling scrubber to the target temperature, and the other path goes to the upper low-temperature refrigeration unit to cool the refrigerant, the two paths of chilled water are combined into one path returning to the chilled water inlet of the lithium bromide absorption refrigeration unit, the deep cooling of the flue gas in the flue gas cooling scrubber is divided into two sections, the scrubbing liquid in the lower section is used to cool the flue gas to 5-10°C, and the spray liquid in the upper section is used to cool the flue gas to -20--5°C, and the cooled low-temperature flue gas comes out from the top of the flue gas cooling scrubber to the subsequent adsorption section.

[0020] Furthermore, the upper low-temperature refrigeration unit is provided with an inlet and an outlet for circulating cooling water, and the cooling capacity required by the upper low-temperature refrigeration unit is provided by the surplus chilled water of the lithium bromide absorption refrigeration unit and the external circulating cooling water.

[0021] Compared with the prior art, the present invention has the following beneficial technical effects:

[0022] The invention is suitable for treating flue gas pollutants of coal-fired power plants and the like. The flue gas generated in the boiler furnace is cooled successively by a primary economizer and an air preheater and dedusted by a dust collector, and then enters a lithium bromide absorption refrigeration unit to provide the flue gas with heat required for preparing chilled water. At the same time, after further cooling, the flue gas enters a flue gas cooling and washing tower for spray cooling and deep cooling. The method makes full use of the waste heat carried by the flue gas, has a significant energy-saving effect and can reduce the direct operating cost of the device. The chilled water is divided into two paths after being cooled by the lithium bromide absorption refrigeration unit. One path goes to a lower chilled water heat exchanger for cooling the washing liquid in the lower part of the spray tower to a target temperature, and the other path goes to an upper low-temperature refrigeration unit for cooling the refrigerant. The two paths of chilled water are combined into one path returning to the chilled water inlet of the lithium bromide absorption refrigeration unit. The deep cooling of the flue gas in the flue gas cooling and washing tower is divided into an upper and lower section. The washing liquid in the lower section is used to cool the flue gas to 5-10°C, and the spray liquid in the upper section is used to cool the flue gas to -20--5°C. The upper and lower sections are independent in circulation, and the power is provided by their respective circulation pumps.

[0023] Furthermore, the amount of chilled water going to the lower chilled water heat exchanger is controlled by a chilled water regulating valve.

[0024] Furthermore, the cooling capacity required by the upper low-temperature refrigeration unit can be provided by the surplus chilled water of the lithium bromide absorption refrigeration unit and the external circulating cooling water. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The drawings in the specification are used to provide further understanding of the present invention and constitute a part of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0026] Figure 1 This is a schematic diagram of a multi-pollutant integrated removal and cooling system utilizing flue gas waste heat according to the present invention.

[0027] Among them, 1. Boiler; 2. First-stage economizer; 3. Air preheater; 4. Dust collector; 5. Lithium bromide absorption refrigeration unit; 6. Chilled water regulating valve; 7. Lower section circulating pump; 8. Lower section cooling water heat exchanger; 9. Lower section chilled water heat exchanger; 10. Upper section circulating pump; 11. Upper section low-temperature refrigeration unit; 12. Flue gas cooling and washing tower. DETAILED DESCRIPTION

[0028] The embodiments of the present invention are described in further detail below:

[0029] like Figure 1 As shown, a multi-pollutant integrated removal cooling system utilizing flue gas waste heat comprises a boiler 1, a primary economizer 2, an air preheater 3, a dust collector 4, a lithium bromide absorption refrigeration unit 5, a chilled water regulating valve 6, a lower section circulating pump 7, a lower section cooling water heat exchanger 8, a lower section chilled water heat exchanger 9, an upper section circulating pump 10, an upper section low-temperature refrigeration unit 11 and a flue gas cooling and washing tower 12.

[0030] The flue gas generated in the furnace of the boiler 1 is cooled by the primary economizer 2 and then connected to the flue gas inlet of the air preheater 3, the flue gas outlet of the air preheater 3 is connected to the flue gas inlet of the dust collector 4, the flue gas outlet of the dust collector 4 is connected to the flue gas inlet of the lithium bromide absorption refrigeration unit 5, the flue gas outlet of the lithium bromide absorption refrigeration unit 5 is connected to the flue gas inlet of the lower section of the flue gas cooling and washing tower 12, and the low-temperature flue gas coming out of the top of the flue gas cooling and washing tower 12 goes to the subsequent adsorption section; the bottom washing liquid outlet of the flue gas cooling and washing tower 12 is connected to the washing liquid inlet of the lower section circulating pump 7, the washing liquid outlet of the lower section circulating pump 7 is connected to the washing liquid inlet of the lower section cooling water heat exchanger 8, the washing liquid outlet of the lower section cooling water heat exchanger 8 is connected to the washing liquid inlet of the lower section chilled water heat exchanger 9, and the washing liquid outlet of the lower section chilled water heat exchanger 9 is connected to the lower section washing liquid inlet of the flue gas cooling and washing tower 12; The upper spray liquid outlet is connected to the spray liquid inlet of the upper circulating pump 10, the spray liquid outlet of the upper circulating pump 10 is connected to the spray liquid inlet of the upper low-temperature refrigeration unit 11, and the spray liquid outlet of the upper low-temperature refrigeration unit 11 is connected to the upper spray liquid inlet of the flue gas cooling and washing tower 12; the chilled water is divided into two paths after being cooled by the lithium bromide absorption refrigeration unit 5, one path is connected to the chilled water inlet of the lower chilled water heat exchanger 9 through the chilled water regulating valve 6, and the other path is connected to the chilled water inlet of the upper low-temperature refrigeration unit 11, the chilled water outlet of the upper low-temperature refrigeration unit 11 is connected to the chilled water outlet of the lower chilled water heat exchanger 9, and the two paths of chilled water are combined into one path and connected to the chilled water inlet of the lithium bromide absorption refrigeration unit 5; the upper low-temperature refrigeration unit 11 is provided with an inlet and an outlet for circulating cooling water; the flue gas cooling and washing tower 12 generally adopts a packed tower, which is arranged in two sections, and the two sections are connected by a gas lift cap.

[0031] During operation, the flue gas generated in the furnace of the boiler 1 is cooled successively by the primary economizer 2 and the air preheater 3 and dedusted by the dust collector 4, and then enters the lithium bromide absorption refrigeration unit 5 to provide the heat required for preparing chilled water. At the same time, after further cooling, the flue gas enters the flue gas cooling and washing tower 12 for spray cooling and deep cooling. After cooling by the lithium bromide absorption refrigeration unit 5, the chilled water is divided into two paths, one path goes to the lower chilled water heat exchanger 9 to cool the washing liquid in the lower section of the flue gas cooling and washing tower 12 to the target temperature, and the other path goes to the upper low-temperature refrigeration unit 11 to cool the refrigerant. The two paths of chilled water are combined into one path returning to the chilled water inlet of the lithium bromide absorption refrigeration unit 5. The deep cooling of the flue gas in the flue gas cooling and washing tower 12 is divided into two sections, the washing liquid in the lower section is used to cool the flue gas to 5-10°C, and the spray liquid in the upper section is used to cool the flue gas to -20--5°C. The cooled low-temperature flue gas comes out from the top of the flue gas cooling and washing tower 12 to the subsequent adsorption section.

[0032] The present invention is applicable to the pollutants in coal-fired flue gas generated by power and other industries, including SO 2、SO 3 ,NO,NO 2 , HCl, HF, Hg and VOCs, etc. The lithium bromide absorption refrigeration unit 5 uses the waste heat of the flue gas after dust removal as the heat source, and the obtained chilled water is mainly used to cool the washing liquid in the lower section of the spray tower that is first cooled by the circulating cooling water to the target temperature, and the surplus part is used to cool the refrigerant of the upper low-temperature refrigeration unit, which makes full use of the waste heat of the flue gas and reduces the power consumption, thereby reducing the operating cost of the flue gas environmental protection treatment, and has significant economic benefits.

[0033] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An integrated multi-pollutant removal and cooling system utilizing flue gas waste heat, characterized in that: It comprises a boiler (1), a primary economizer (2), an air preheater (3), a dust collector (4), a lithium bromide absorption refrigeration unit (5), a chilled water regulating valve (6), a lower section circulating pump (7), a lower section cooling water heat exchanger (8), a lower section chilled water heat exchanger (9), an upper section circulating pump (10), an upper section low-temperature refrigeration unit (11) and a flue gas cooling and washing tower (12); A primary economizer (2) is arranged in the flue of the boiler (1); the flue outlet of the boiler (1) is connected to the flue gas inlet of the air preheater (3); the flue gas outlet of the air preheater (3) is communicated with the flue gas inlet of the dust collector (4); the flue gas outlet of the dust collector (4) is communicated with the flue gas inlet of the lithium bromide absorption refrigeration unit (5); the flue gas outlet of the lithium bromide absorption refrigeration unit (5) is communicated with the flue gas inlet of the lower section of the flue gas cooling and washing tower (12); and the low-temperature flue gas outlet at the top of the flue gas cooling and washing tower (12) is connected to the subsequent adsorption section; The washing liquid outlet at the bottom of the flue gas cooling and washing tower (12) is connected to the washing liquid inlet of the lower cooling water heat exchanger (8), the washing liquid outlet of the lower cooling water heat exchanger (8) is connected to the washing liquid inlet of the lower chilled water heat exchanger (9), and the washing liquid outlet of the lower chilled water heat exchanger (9) is connected to the washing liquid inlet of the lower section of the flue gas cooling and washing tower (12); The upper spray liquid outlet of the flue gas cooling and washing tower (12) is connected to the spray liquid inlet of the upper low-temperature refrigeration unit (11), and the spray liquid outlet of the upper low-temperature refrigeration unit (11) is connected to the upper spray liquid inlet of the flue gas cooling and washing tower (12); After the chilled water is cooled by the lithium bromide absorption refrigeration unit (5), it is divided into two paths, one path is connected to the chilled water inlet of the lower chilled water heat exchanger (9), and the other path is connected to the chilled water inlet of the upper low-temperature refrigeration unit (11). The chilled water outlet of the upper low-temperature refrigeration unit (11) and the chilled water outlet of the lower chilled water heat exchanger (9) are combined into one path connected to the chilled water inlet of the lithium bromide absorption refrigeration unit (5); The washing liquid outlet at the bottom of the flue gas cooling and washing tower (12) is connected to the washing liquid inlet of the lower circulating pump (7), and the washing liquid outlet of the lower circulating pump (7) is connected to the washing liquid inlet of the lower cooling water heat exchanger (8); The upper spray liquid outlet of the flue gas cooling and washing tower (12) is connected to the spray liquid inlet of the upper circulating pump (10), and the spray liquid outlet of the upper circulating pump (10) is connected to the spray liquid inlet of the upper low-temperature refrigeration unit (11); A chilled water regulating valve (6) is provided between the chilled water outlet of the lithium bromide absorption refrigeration unit (5) and the chilled water inlet of the lower chilled water heat exchanger (9).

2. The integrated multi-pollutant removal and cooling system utilizing flue gas waste heat according to claim 1 is characterized in that: The upper low-temperature refrigeration unit (11) is provided with an inlet and an outlet for circulating cooling water.

3. The integrated multi-pollutant removal and cooling system utilizing flue gas waste heat according to claim 1 is characterized in that: The flue gas cooling and washing tower (12) is a packed tower.

4. The integrated multi-pollutant removal and cooling system utilizing flue gas waste heat according to claim 3 is characterized in that: The flue gas cooling and washing tower (12) is arranged in two sections, and the two sections of the flue gas cooling and washing tower (12) are connected by a gas lifting cap.

5. The integrated multi-pollutant removal and cooling system utilizing flue gas waste heat according to claim 1 is characterized in that: The air preheater (3) is provided with a cold air inlet and a hot air outlet.

6. A method for integrated removal and cooling of multiple pollutants using flue gas waste heat, using the integrated removal and cooling system of multiple pollutants using flue gas waste heat as claimed in claim 1, characterized in that: The flue gas generated in the furnace of the boiler (1) is cooled successively by the primary economizer (2) and the air preheater (3) and dedusted by the dust collector (4), and then enters the lithium bromide absorption refrigeration unit (5) to provide the heat required for producing chilled water. At the same time, the flue gas is further cooled and enters the flue gas cooling and washing tower (12) for spray cooling and deep cooling. After the chilled water is cooled by the lithium bromide absorption refrigeration unit (5), it is divided into two paths. One path goes to the lower chilled water heat exchanger (9) for washing the lower part of the flue gas cooling and washing tower (12). The second cooling liquid is used to cool the flue gas to the target temperature, and the other cooling liquid is used to cool the refrigerant to the upper low-temperature refrigeration unit (11). The two cooling water paths are combined into one path to return to the chilled water inlet of the lithium bromide absorption refrigeration unit (5). The deep cooling of the flue gas in the flue gas cooling and washing tower (12) is divided into two sections, the washing liquid in the lower section is used to cool the flue gas to 5~10℃, and the spraying liquid in the upper section is used to cool the flue gas to -20~-5℃. The cooled low-temperature flue gas comes out from the top of the flue gas cooling and washing tower (12) to the subsequent adsorption section.

7. The multi-pollutant integrated removal and cooling method using flue gas waste heat according to claim 6 is characterized in that: The upper low-temperature refrigeration unit (11) is provided with an inlet and an outlet for circulating cooling water. The cooling capacity required by the upper low-temperature refrigeration unit (11) is provided by the surplus chilled water of the lithium bromide absorption refrigeration unit (5) and the circulating cooling water from the outside.

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