Desulfurized flue gas heating system

Abstract

The utility model discloses a desulfurized flue gas heating system which comprises a flue gas main pipeline, the part, located at the front end of a heat exchanger, of the flue gas main pipeline communicates with a first flue, an adjusting air door is arranged on the first flue, the first flue communicates with a desulfurizer conveying pipeline through a second fan, and the front end of the desulfurizer conveying pipeline communicates with a desulfurizer feeding unit; and the rear end of the desulfurizing agent conveying pipeline is communicated with the desulfurizing tower. The system has the beneficial effects that the flue gas bypass flues are led out from the front and the back of the heat exchanger, and the pre-activation temperature of the desulfurizing agent is controlled by adjusting the flue gas amount in the bypass flues; when the system is in low load, sodium bicarbonate pre-activation is realized to obtain a high-reaction-activity desulfurizer to guarantee efficient desulfurization; reutilization of high-temperature flue gas heat in the system is achieved, and the heat utilization rate is increased; sodium bicarbonate consumption is reduced, and operation cost is reduced.

Description

Technical Field

[0001] This application belongs to the technical field of chemical environmental protection, and particularly relates to a flue gas heating system for desulfurization. Background Art

[0002] The sodium-based SDS dry desulfurization technology uses powdered or granular sodium bicarbonate (baking soda, NaHCO3) as a desulfurizing agent to remove SO2 from flue gas. It has the advantages of small floor area, simple equipment and process flow, low energy consumption, and no secondary pollution, and can be widely used in the tail gas purification processes of industries such as industrial silicon, iron and steel, glass, and cement.

[0003] During the desulfurization process of the sodium-based SDS dry desulfurization process, the flue gas temperature has a decisive influence on the desulfurization efficiency. Sodium bicarbonate has high activity in the flue gas temperature window range of 140 - 280 °C. Usually, a slightly excessive (1:1.1 - 1:2) amount of sodium bicarbonate can spontaneously and completely carry out chemical reactions with acidic pollutants in the flue gas. When the flue gas temperature rises above 140 °C, the desulfurization efficiency can reach 96%; when the temperature is less than 140 °C, the desulfurization efficiency drops significantly.

[0004] Therefore, the engineering application scenarios of the sodium-based dry desulfurization process are restricted by low-temperature flue gas, and it is often necessary to increase the flue gas temperature to ensure the desulfurization efficiency. Existing technical solutions for increasing the reaction temperature of sodium-based SDS dry desulfurization flue gas include methods such as reburning blast furnace gas, external flue gas heaters, and connecting external high-temperature waste gas to heat the flue gas at the inlet of the desulfurization tower to ensure the reaction temperature inside the desulfurization tower. However, all of the above solutions have the following problems: ① increasing the overall energy consumption of the system; ② poor uniformity of the flue gas temperature field; ③ reducing the economy of the dry desulfurization process. Therefore, an effective device that can both ensure the desulfurization efficiency of the SDS dry desulfurization and make full use of the waste heat of high-temperature flue gas needs to be set up. Utility Model Content

[0005] The purpose of this application is to provide a flue gas heating system for desulfurization. Based on the sodium-based SDS dry desulfurization technology, it can ensure high-efficiency desulfurization of the system at full load. At low / high loads, the reaction activity of sodium bicarbonate entering the desulfurization tower can be increased by introducing high-temperature flue gas, and the heat source for pre-activation of this system comes from within the system without the need for an external heat source, solving the problem of limited application scenarios of traditional desulfurization systems.

[0006] The purpose of this application is achieved through the following technical solutions:

[0007] A flue gas heating system for desulfurization includes a main flue gas pipeline. The front part of the main flue gas pipeline is connected to a first flue at the front end of a heat exchanger. An adjusting damper is provided on the first flue. The first flue is connected to a desulfurizing agent conveying pipeline through a second fan. The front end of the desulfurizing agent conveying pipeline is connected to a desulfurizing agent feeding unit, and the rear end of the desulfurizing agent conveying pipeline is connected to a desulfurization tower.

[0008] Further, the main flue gas duct is connected to the second flue at the rear end of the heat exchanger, and the second flue is connected to the desulfurizing agent conveying pipeline through a second fan.

[0009] Further, a first temperature measuring point and a first flow measuring point are provided on the first flue.

[0010] Further, a second flow measuring point and a second temperature measuring point are provided on the second flue.

[0011] Further, a second isolation damper is provided on the second flue.

[0012] Further, the first flue and the second flue merge in front of the second fan.

[0013] Further, a first isolation damper is provided between the second fan and the desulfurizing agent conveying pipeline.

[0014] Further, the desulfurizing agent feeding unit includes a sodium bicarbonate powder silo, a guide pipe, a mill and a first fan. The sodium bicarbonate powder silo extends to the feed inlet of the mill through the guide pipe, and the discharge outlet of the mill is connected to the desulfurizing agent conveying pipeline through the first fan.

[0015] Further, a desulfurizing agent pipeline temperature measuring point is provided on the desulfurizing agent conveying pipeline.

[0016] Further, the desulfurizing agent conveying pipeline extends into the desulfurization tower through a spray gun.

[0017] The object of the present application:

[0018] ① To provide a sodium-based SDS dry desulfurization system applicable to low-temperature flue gas containing sulfur dioxide. By introducing high-temperature flue gas before the heat exchanger to mix with the air conveying sodium bicarbonate, the temperature of the conveying gas is increased to realize the pre-activation of sodium bicarbonate, generating a mixture of highly reactive sodium carbonate and sodium bicarbonate, and improving the overall desulfurization efficiency of the system.

[0019] ② It can adapt to different load conditions of the system; when the temperature at the outlet of the heat exchanger is lower than 140 °C, by adjusting the opening degree of the flue damper, introducing the flue gas before the heat exchanger to mix with the desulfurizing agent conveying air, the temperature of the sodium bicarbonate conveying pipeline is increased to realize the pre-activation of sodium bicarbonate and thus ensure the high efficiency of the desulfurization reaction of the system; on the one hand, the flue gas volume control can be adjusted through valves and fans, which is beneficial to the control and operation at the engineering site; on the other hand, while improving the thermal utilization rate of the high-temperature flue gas, the system has a simple structure and low operating cost.

[0020] The beneficial effects of the present application:

[0021] ① Smoke bypass flues are led out before and after the heat exchanger. By adjusting the amount of flue gas in the bypass flue, the pre-activation temperature of the desulfurizer is controlled; when the system is at low load, the pre-activation of sodium bicarbonate is achieved to obtain a highly reactive desulfurizer to ensure efficient desulfurization.

[0022] ② The heat of the high-temperature flue gas in the system is reused to improve its thermal utilization rate.

[0023] ③ The amount of sodium bicarbonate used is reduced, and the operating cost is lowered.

[0024] The main solution of the present application and its various further alternative solutions described above can be freely combined to form multiple solutions, all of which are solutions that can be adopted and claimed in the present application; and in the present application, (each non-conflicting alternative) alternatives can be freely combined with each other and with other alternatives. Those skilled in the art can understand that there are various combinations according to the prior art and common general knowledge after understanding this solution, all of which are technical solutions to be protected in the present application and will not be enumerated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a schematic structural diagram of the present application.

[0026] In the figure: 1 - sodium bicarbonate powder bin, 2 - feeding pipe, 3 - mill, 4 - first fan, 5 - desulfurizer conveying pipeline, 6 - spray gun, 7 - desulfurization tower, 8 - heat exchanger, 9 - main flue gas pipeline, 10 - first temperature measuring point, 11 - first flow measuring point, 12 - first flue, 13 - regulating damper, 15 - second fan, 16 - first isolation damper, 17 - second flue, 18 - second flow measuring point, 19 - second temperature measuring point, 20 - desulfurizer pipeline temperature measuring point, 21 - second isolation damper. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] The present application will be further described below in conjunction with specific embodiments and the drawings.

[0028] Refer to Figure 1 As shown, a flue gas heating system for desulfurization includes a desulfurizer feeding unit, a desulfurizer pre-activation unit and a desulfurization tower 7. The desulfurizer feeding unit includes a sodium bicarbonate powder bin 1, a feeding pipe 2, a mill 3 and a first fan 4. The desulfurizer pre-activation unit includes a desulfurizer conveying pipeline 5, a spray gun 6, a heat exchanger 8, a main flue gas pipeline 9, a first temperature measuring point 10, a first flow measuring point 11, a first flue 12, a regulating damper 13, a second fan 15, a first isolation damper 16, a second flue 17, a second flow measuring point 18, a second temperature measuring point 19, a desulfurizer pipeline temperature measuring point 20 and a second isolation damper 21.

[0029] The desulfurizer feeding unit is used to supply desulfurizer to the desulfurizer conveying pipeline 5. The desulfurizer is preferably sodium bicarbonate powder or granules. Similarly, other types of desulfurizer can also be selected. Specifically, the sodium bicarbonate powder silo 1 is used to store sodium bicarbonate. The bottom of the sodium bicarbonate powder silo 1 extends above the feed inlet of the mill 3 through the guide pipe 2, and the sodium bicarbonate is continuously conveyed to the mill 3 through the guide pipe 2 for grinding. The discharge port of the mill 3 is connected to the desulfurizer conveying pipeline 5 through the first fan 4. The first fan is preferably a centrifugal fan, which blows the ground sodium bicarbonate into the conveying pipeline.

[0030] The main flue gas pipeline 9 is a pipeline for the flow of high-temperature flue gas. A heat exchanger 8 is provided on the main flue gas pipeline 9. The heat exchanger 8 is used to absorb the heat of the high-temperature flue gas. Therefore, the flue gas temperature at the front end of the heat exchanger on the main pipeline is high, while the flue gas temperature at the rear end of the heat exchanger is low. Therefore, the front-end part of the main flue gas pipeline 9 located at the heat exchanger 8 is connected to the first flue 12, and the rear-end part of the main flue gas pipeline 9 located at the heat exchanger 8 is connected to the second flue 17, so as to adjust the operation of different flues according to different working conditions.

[0031] The first flue 12 is provided with a first temperature measuring point 10, a first flow measuring point 11 and a regulating damper 13. The first flue 12 is used to introduce high-temperature flue gas. The first temperature measuring point 10 and the first flow measuring point 11 are respectively used to measure the flue gas temperature and flow rate in the pipeline. The regulating damper 13 is used to adjust the flue gas flow rate to control the heat carried by the flue gas to meet the subsequent requirement of heating the desulfurizer.

[0032] The second flue 17 is provided with a second flow measuring point 18, a second temperature measuring point 19 and a second isolation damper 21. The second flue 17 is used to introduce low-temperature flue gas. The second temperature measuring point 19 and the second flow measuring point 18 are respectively used to measure the flue gas temperature and flow rate in the pipeline. The second isolation damper 21 is used to adjust the on / off of the pipeline.

[0033] The first flue 12 and the second flue 17 merge in front of the second fan 15, which can reduce the investment in equipment and pipelines. Similarly, the two flues can also be independently connected to the desulfurizer conveying pipeline 5. The first flue 12 is connected to the desulfurizer conveying pipeline 5 through the second fan 15, and the second flue 17 is connected to the desulfurizer conveying pipeline 5 through the second fan 15. Then, the high-temperature / low-temperature flue gas is mixed with the desulfurizer in the conveying pipeline to realize the pre-activation of the desulfurizer. A first isolation damper 16 is provided between the second fan 15 and the desulfurizer conveying pipeline 5 to control the on / off of the combined pipeline.

[0034] The front end of the desulfurizer conveying pipeline 5 is connected to the first blower 4 of the desulfurizer feeding unit, and the rear end of the desulfurizer conveying pipeline 5 is connected to the desulfurization tower 7. A desulfurizer pipeline temperature measuring point 20 is provided on the desulfurizer conveying pipeline 5. The desulfurizer conveying pipeline 5 extends into the desulfurization tower 7 through a spray gun 6 to uniformly spray the pre-activated desulfurizer at high temperature into the desulfurization tower, ensuring uniform mixing of the desulfurizer and the flue gas and improving the desulfurization efficiency.

[0035] The working process of this application: When the system is operating at low load and the flue gas temperature at the inlet of the desulfurization tower is low (<140 °C), open the regulating damper 13 and close the second isolation damper 21. Send the high-temperature flue gas (260 - 320 °C) at the front end of the inlet of the heat exchanger 8 into the desulfurizer conveying pipeline 5 through the second blower 15. Change the opening degree of the regulating damper 13 (0 - 100%) so that the temperature after mixing in the desulfurizer conveying pipeline can reach 140 - 150 °C. Subsequently, the ground sodium bicarbonate is transported to the desulfurizer conveying pipeline 5 through the first blower 4 to achieve pre-activation to generate highly reactive sodium bicarbonate, and finally enter the desulfurization tower 7 through the spray gun 6 for desulfurization reaction to achieve high-efficiency desulfurization of the system. When the system is operating at normal load and the flue gas temperature (≥140 °C) after the heat exchanger 8 meets the pre-activation temperature requirement for dry sodium bicarbonate desulfurization, at this time, the first flue can be disabled, the regulating damper 13 can be closed, the second isolation damper 21 can be opened, and the flue gas from the second flue is used to pre-activate the sodium bicarbonate.

[0036] The key points of this application:

[0037] 1. The first flue and the second flue are added before and after the heat exchanger. According to the different load conditions of the actual system, the flue gas in the front / rear section of the heat exchanger can be introduced into the desulfurizer conveying pipeline to increase the temperature of the desulfurizer conveying gas (≥140 °C). The specific surface area of the sodium bicarbonate after high-temperature activation increases, thereby improving the desulfurization efficiency.

[0038] 2. Valves are provided on the outlet flue, so that the flue gas can be led out through the flue as needed. At the same time, a blower is provided to adjust the flow rate of the led-out flue gas to ensure the stability of the desulfurizer conveying speed and temperature.

[0039] 3. The second flue provided can be opened or closed according to the actual operating conditions, and can also be increased or decreased according to the actual engineering situation.

[0040] The basic example of the present application and its various further selected examples can be freely combined to form multiple embodiments, all of which are the embodiments that can be adopted and claimed in the present application. In the solution of the present application, each selected example can be arbitrarily combined with any basic example and selected example.

[0041] The above are only the preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application shall be included within the protection scope of the present application.

Claims

1. A flue gas heating system for desulfurization, comprising a flue gas main duct (9), characterized in that: The flue gas main pipeline (9) is located at the front end of the heat exchanger (8) and is connected to the first flue (12). The first flue (12) is provided with an adjusting damper (13). The first flue (12) is connected to the desulfurizing agent delivery pipeline (5) through the second fan (15). The front end of the desulfurizing agent delivery pipeline (5) is connected to the desulfurizing agent feeding unit, and the rear end of the desulfurizing agent delivery pipeline (5) is connected to the desulfurization tower (7).

2. The flue gas heating system for desulfurization according to claim 1 is characterized in that: The flue gas main pipeline (9) is located at the rear end of the heat exchanger (8) and is connected to the second flue (17). The second flue (17) is connected to the desulfurizing agent delivery pipeline (5) through the second fan (15).

3. The flue gas heating system for desulfurization according to claim 1 or 2, characterized in that: The first flue (12) is provided with a first temperature measuring point (10) and a first flow measuring point (11).

4. The flue gas heating system for desulfurization according to claim 2 is characterized in that: The second flue (17) is provided with a second flow measurement point (18) and a second temperature measurement point (19).

5. The flue gas heating system for desulfurization according to claim 2 or 4, characterized in that: The second flue (17) is provided with a second isolation damper (21).

6. The flue gas heating system for desulfurization according to claim 2, characterized in that: The first flue (12) and the second flue (17) are combined at the front end of the second fan (15).

7. The flue gas heating system for desulfurization according to claim 1, characterized in that: A first isolation damper (16) is provided between the second fan (15) and the desulfurizing agent delivery pipeline (5).

8. The flue gas heating system for desulfurization according to claim 1, characterized in that: The desulfurizing agent feeding unit comprises a sodium bicarbonate powder bin (1), a material guide pipe (2), a mill (3) and a first fan (4); the sodium bicarbonate powder bin (1) extends to a feed port of the mill (3) through the material guide pipe (2); and the discharge port of the mill (3) is connected to a desulfurizing agent conveying pipeline (5) through the first fan (4).

9. The flue gas heating system for desulfurization according to claim 1, characterized in that: The desulfurizing agent delivery pipeline (5) is provided with a desulfurizing agent pipeline temperature measuring point (20).

10. The flue gas heating system for desulfurization according to claim 1 or 9, characterized in that: The desulfurizing agent delivery pipeline (5) extends into the desulfurizing tower (7) through the spray gun (6).

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