Energy comprehensive utilization flue gas purification system and method

Abstract

The application discloses a flue gas purification system with comprehensive energy utilization, and belongs to the technical field of energy saving and environmental protection, and comprises a boiler, a bag-type dust collector, an SCR denitration device, a flue gas induced draft fan, a first heat conducting oil heat exchanger, a second heat conducting oil heat exchanger, a third heat conducting oil heat exchanger, a fourth heat conducting oil heat exchanger, a first heat conducting oil circulating pump, a second heat conducting oil circulating pump, a first heat conducting oil expansion oil storage tank and a second heat conducting oil expansion oil storage tank. The application improves the denitration efficiency, improves the energy utilization rate, and is safe and reliable.

Description

Technical Field

[0001] This invention belongs to the field of energy conservation and environmental protection technology, and in particular relates to a flue gas purification system and method for comprehensive energy utilization. Background Technology

[0002] Thermal energy plays an important role in economic construction and social development. Improving energy utilization efficiency and researching how to improve the utilization rate of thermal energy are becoming increasingly important in production and daily life.

[0003] With increasingly stringent environmental protection requirements, achieving clean emissions of flue gas is a development trend. To meet national environmental standards for nitrogen oxide emissions, most manufacturers adopt a co-treatment approach for flue gas. Given the high dust content in boiler flue gas, a typical approach involves pre-dust removal, desulfurization, dioxin removal, dust removal, denitrification (SCR), followed by an induced draft fan and chimney. Selective catalytic reduction (SCR) technology, with its mature technology and high denitrification efficiency, has become the preferred solution for flue gas denitrification. Although SCR catalysts must possess characteristics such as high activity, good thermal stability, stable mechanical properties, and minimal pressure loss, the highly efficient activity temperature range for SCR catalysts is 280–500℃. Excessive sulfur content in the flue gas can easily lead to catalyst poisoning. The flue gas temperature after the boiler economizer is around 200℃. After dust removal and desulfurization, the temperature drops even faster, making it unsuitable for direct denitrification. Instead, the flue gas temperature in the reactor area must be increased to 280℃ or higher by supplementing heat to meet the process requirements of SCR reaction. Generally, the flue gas purification process usually uses the internal circulation of a rotary flue gas air heat exchanger to increase the flue gas temperature. Its heat exchange medium is flue gas and air, which has a small heat exchange coefficient and poses a risk of air leakage, thus affecting the denitrification efficiency of the flue gas denitrification device. Summary of the Invention

[0004] The technical problem solved by this invention is to overcome the shortcomings of the prior art and provide a flue gas purification system and method with comprehensive energy utilization, which improves denitrification efficiency, increases energy utilization, and is safe and reliable.

[0005] The objective of this invention is achieved through the following technical solution: a flue gas purification system for comprehensive energy utilization, comprising: a boiler, a bag filter, an SCR denitrification device, a flue gas induced draft fan, a first thermal oil heat exchanger, a second thermal oil heat exchanger, a third thermal oil heat exchanger, a fourth thermal oil heat exchanger, a first thermal oil circulation pump, a second thermal oil circulation pump, a first thermal oil expansion storage tank, and a second thermal oil expansion storage tank; wherein, the flue gas output end of the boiler is connected to one input end of the first thermal oil heat exchanger, and one output end of the first thermal oil heat exchanger is connected to the input end of the bag filter; the output end of the bag filter is connected to one input end of the second thermal oil heat exchanger, and one output end of the second thermal oil heat exchanger is connected to the input end of the SCR denitrification device; the output end of the SCR denitrification device is connected to one input end of the third thermal oil heat exchanger. One output end of the third thermal oil heat exchanger is connected to the input end of the flue gas induced draft fan; the output end of the first thermal oil expansion storage tank is connected to the input end of the first thermal oil circulation pump, the output end of the first thermal oil circulation pump is connected to the other input end of the first thermal oil heat exchanger, the other output end of the first thermal oil heat exchanger is connected to the other input end of the second thermal oil heat exchanger, and the other output end of the second thermal oil heat exchanger is connected to the input end of the first thermal oil expansion storage tank; the output end of the second thermal oil expansion storage tank is connected to the input end of the second thermal oil circulation pump, the output end of the second thermal oil circulation pump is connected to the other input end of the third thermal oil heat exchanger, the other output end of the third thermal oil heat exchanger is connected to the input end of the fourth thermal oil heat exchanger, and the output end of the fourth thermal oil heat exchanger is connected to the input end of the second thermal oil expansion storage tank.

[0006] The aforementioned flue gas purification system for comprehensive energy utilization also includes a chimney; wherein the output end of the flue gas induced draft fan is connected to the chimney.

[0007] In the aforementioned flue gas purification system that integrates energy utilization, sodium bicarbonate and activated carbon are injected sequentially into the pipeline between the first heat transfer oil heat exchanger and the bag filter to dry remove sulfur and dioxins from the flue gas.

[0008] In the above-mentioned flue gas purification system for comprehensive energy utilization, the first, second, third, and fourth thermal oil heat exchangers are all tubular heat exchangers.

[0009] In the aforementioned flue gas purification system for comprehensive energy utilization, both the first heat transfer oil circulation pump and the second heat transfer oil circulation pump are frequency converters.

[0010] A flue gas purification method based on an energy-integrated flue gas purification system includes: Pre-dust removal of hot flue gas discharged from the boiler; After passing through the first thermal oil heat exchanger, the flue gas enters the pipeline between the first thermal oil heat exchanger and the bag filter. Baking soda and activated carbon are injected successively in the pipeline between the first thermal oil heat exchanger and the bag filter to remove S and dioxins from the flue gas in a dry process, resulting in flue gas containing only N. The flue gas containing only N enters the second thermal oil heat exchanger after passing through the bag filter. The first hot oil circulation pump pumps the low-temperature heat transfer oil in the first heat transfer oil expansion tank into the first heat transfer oil heat exchanger. The low-temperature heat transfer oil exchanges heat with the hot flue gas. The heated heat transfer oil enters the second heat transfer oil heat exchanger. The heated heat transfer oil heats the flue gas containing only nitrogen to above the preset temperature. The flue gas then enters the SCR denitrification device for denitrification to obtain hot clean flue gas. The hot clean flue gas then enters the third heat transfer oil heat exchanger. The heat transfer oil in the third heat transfer oil heat exchanger exchanges heat with the hot clean flue gas. The clean flue gas enters the flue gas induced draft fan, and the second heat transfer oil circulation pump pumps the heated heat transfer oil in the third heat transfer oil heat exchanger into the fourth heat transfer oil heat exchanger.

[0011] In the above-mentioned flue gas purification method for comprehensive energy utilization, when the outlet temperature of the heat transfer oil of the first heat transfer oil heat exchanger is lower than the preset temperature, the first heat transfer oil circulation pump is frequency-controlled to increase the amount of heat transfer oil, and the first heat transfer oil heat exchanger removes excess heat to ensure that the inlet temperature of the bag filter does not exceed the second preset temperature.

[0012] In the above-mentioned flue gas purification method that integrates energy utilization, the temperature of the nitrogen-containing flue gas entering the bag filter is reduced to 190℃-210℃.

[0013] In the above-mentioned flue gas purification method for comprehensive energy utilization, the preset temperature is 280℃.

[0014] In the above-mentioned flue gas purification method for comprehensive energy utilization, the second preset temperature is 250℃.

[0015] Compared with the prior art, the present invention has the following advantages: (1) The high-temperature flue gas of the present invention transfers heat through low-temperature heat transfer oil. The heat transfer oil can achieve a very high operating temperature (below 350°C is liquid) under almost normal pressure conditions; and the heat transfer is uniform, the heat dissipation is fast, and the operation safety is high. (2) Along the flue gas direction, the present invention provides two heat transfer oil heat exchangers. The first one absorbs the heat in the flue gas, heats the heat transfer oil, and reduces the temperature of the flue gas. The second one releases the energy of the heat transfer oil, heats the flue gas, and increases the temperature of the flue gas, which greatly reduces the initial investment and operating cost of the denitrification system. (3) The heat transfer oil heat exchange device of the present invention has stable heat exchange performance, easy temperature control, no moving parts, and the system is safe and reliable. Attached Figure Description

[0016] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings: Figure 1 This is a schematic diagram of a flue gas purification system for comprehensive energy utilization provided in an embodiment of the present invention. Detailed Implementation

[0017] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the disclosure to those skilled in the art. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0018] Figure 1 This is a schematic diagram of a flue gas purification system for comprehensive energy utilization provided in an embodiment of the present invention. Figure 1 As shown, the comprehensive energy utilization flue gas purification system includes: a boiler 1, a bag filter 2, an SCR denitrification device 3, a flue gas induced draft fan 4, a first thermal oil heat exchanger 6, a second thermal oil heat exchanger 7, a third thermal oil heat exchanger 8, a fourth thermal oil heat exchanger 9, a first thermal oil circulation pump 10, a second thermal oil circulation pump 11, a first thermal oil expansion tank 12, and a second thermal oil expansion tank 13. Among them, The flue gas outlet of boiler 1 is connected to one input of the first thermal oil heat exchanger 6, and one output of the first thermal oil heat exchanger 6 is connected to the input of the bag filter 2; the output of the bag filter 2 is connected to one input of the second thermal oil heat exchanger 7, and one output of the second thermal oil heat exchanger 7 is connected to the input of the SCR denitrification device 3; the output of the SCR denitrification device 3 is connected to one input of the third thermal oil heat exchanger 8, and one output of the third thermal oil heat exchanger 8 is connected to the input of the flue gas induced draft fan 4; the output of the first thermal oil expansion storage tank 12 is connected to the input of the first thermal oil circulation pump 10, and the first hot oil circulation... The output end of pump 10 is connected to the other input end of the first thermal oil heat exchanger 6, the other output end of the first thermal oil heat exchanger 6 is connected to the other input end of the second thermal oil heat exchanger 7, and the other output end of the second thermal oil heat exchanger 7 is connected to the input end of the first thermal oil expansion tank 12; the output end of the second thermal oil expansion tank 13 is connected to the input end of the second thermal oil circulation pump 11, the output end of the second thermal oil circulation pump 11 is connected to the other input end of the third thermal oil heat exchanger 8, the other output end of the third thermal oil heat exchanger 8 is connected to the input end of the fourth thermal oil heat exchanger 9, and the output end of the fourth thermal oil heat exchanger 9 is connected to the input end of the second thermal oil expansion tank 13.

[0019] The flue gas purification system also includes a chimney 5; wherein the output end of the flue gas induced draft fan 4 is connected to the chimney 5.

[0020] Baking soda and activated carbon were injected sequentially into the pipeline between the first heat transfer oil heat exchanger 6 and the bag filter 2 to dry remove sulfur and dioxins from the flue gas.

[0021] The first thermal oil heat exchanger 6, the second thermal oil heat exchanger 7, the third thermal oil heat exchanger 8, and the fourth thermal oil heat exchanger 9 are all tubular heat exchangers.

[0022] Both the first heat transfer oil circulation pump 10 and the second heat transfer oil circulation pump 11 are frequency converters.

[0023] The flue gas output end of boiler 1 is connected to the input end of bag filter 2. Sodium bicarbonate and activated carbon are sprayed sequentially in the pipeline between the two to remove sulfur and dioxins from the flue gas. The output end of bag filter 2 is connected to the input end of SCR denitrification device 3. A heat exchanger 7 is installed on the pipeline between the two to increase the temperature of the flue gas. The output end of SCR denitrification device 3 is connected to the input end of flue gas induced draft fan 4. A heat exchanger 8 is installed on the pipeline between the two to convert excess heat of the flue gas for other uses, improve heat utilization rate, and ensure that the flue gas meets emission standards.

[0024] Thermal oil circulation system 1: The output end of thermal oil expansion tank 12 is connected to the input end of thermal oil circulation pump 10, the output end of thermal oil circulation pump 10 is connected to the input end of thermal oil heat exchanger 6, the output end of thermal oil heat exchanger 6 is connected to the input end of thermal oil heat exchanger 7, and the output end of thermal oil heat exchanger 7 is connected to the input end of thermal oil expansion tank 12.

[0025] Heat transfer oil circulation system 2: The output end of the heat transfer oil expansion tank 13 is connected to the input end of the heat transfer oil circulation pump 11. The output end of the heat transfer oil circulating pump 11 is connected to the input end of the heat transfer oil heat exchanger 8, the output end of the heat transfer oil heat exchanger 8 is connected to the input end of the heat transfer oil heat exchanger 9, and the output end of the heat transfer oil heat exchanger 9 is connected to the input end of the heat transfer oil expansion tank 13.

[0026] This embodiment also provides a flue gas purification method for comprehensive energy utilization, the method comprising: Pre-dust removal is performed on the hot flue gas discharged from boiler 1; After passing through the first thermal oil heat exchanger 6, the flue gas enters the pipeline between the first thermal oil heat exchanger 6 and the bag filter 2. Sodium bicarbonate and activated carbon are injected successively in the pipeline between the first thermal oil heat exchanger 6 and the bag filter 2 to remove sulfur and dioxins from the flue gas, resulting in flue gas containing only nitrogen. The flue gas containing only nitrogen enters the second thermal oil heat exchanger 7 after passing through the bag filter 2. The temperature of the flue gas containing only nitrogen entering the bag filter 2 is reduced to 190℃-210℃. The first hot oil circulation pump 10 pumps the low-temperature heat transfer oil in the first heat transfer oil expansion storage tank 12 into the first heat transfer oil heat exchanger 6. The low-temperature heat transfer oil exchanges heat with the hot flue gas. The heated heat transfer oil enters the second heat transfer oil heat exchanger 7. The heated heat transfer oil heats the flue gas containing only nitrogen to a preset temperature (above 280°C) and enters the SCR denitrification device 3 for denitrification to obtain hot clean flue gas. The hot clean flue gas enters the third heat transfer oil heat exchanger 8. The heat transfer oil in the third heat transfer oil heat exchanger 8 exchanges heat with the hot clean flue gas. The clean flue gas enters the flue gas induced draft fan 4, and the second heat transfer oil circulation pump 11 pumps the heated heat transfer oil in the third heat transfer oil heat exchanger 8 into the fourth heat transfer oil heat exchanger 9.

[0027] When the outlet temperature of the heat transfer oil in the first heat transfer oil heat exchanger 6 is lower than the preset temperature, the first heat transfer oil circulation pump 10 is frequency-controlled to increase the amount of heat transfer oil, and the first heat transfer oil heat exchanger 6 removes excess heat to ensure that the inlet temperature of the bag filter 2 is not higher than the second preset temperature; wherein, the second preset temperature is 250℃.

[0028] Specifically, the method includes the following steps: S1: The hot flue gas discharged from the waste heat boiler is first pre-dust removed to reduce the dust content and ensure the desulfurization efficiency of subsequent dry desulfurization.

[0029] S2: After passing through the heat exchanger 6, the temperature of the flue gas drops to about 200℃ when it enters the bag filter 2.

[0030] S3: Before the flue gas enters the bag filter 2, sodium bicarbonate and activated carbon are injected successively in the pipeline to remove sulfur and dioxins from the flue gas. The flue gas at the outlet of the bag filter 2 contains only nitrogen.

[0031] S4: The heat transfer oil circulation pump 10 pumps the low-temperature heat transfer oil in the heat transfer oil expansion storage tank 12 into the heat exchanger 6, where it indirectly exchanges heat with the high-temperature flue gas. The heated high-temperature heat transfer oil enters the heat exchanger 7, which heats the desulfurized low-temperature flue gas to above 280°C, and then enters the SCR denitrification device 3 for denitrification.

[0032] S5, when the outlet temperature of the heat transfer oil in heat exchanger 6 is too low, the control system will adjust the frequency of the circulating pump 10 to increase the amount of heat transfer oil in the system, and the heat exchanger 6 will remove excess heat to ensure that the inlet temperature of the bag filter 2 is not higher than 250℃; at the same time, the heat exchanger 7 can meet the heat exchange requirements.

[0033] S6, heat exchanger 8 removes excess heat from the clean flue gas, heat exchanger 9 utilizes the heat brought back by the heat transfer oil, and heat transfer oil circulation pump 10 uses frequency conversion to adjust the circulation volume of heat transfer oil to match the emission of clean flue gas. As long as the local non-whitening temperature is reached, the emission is permitted.

[0034] In step S1, the purpose of pre-dust removal is to reduce the amount of baking soda used and improve desulfurization efficiency during dry desulfurization.

[0035] In step S1, the reaction is most vigorous when the dry desulfurization temperature is around 200℃.

[0036] In step S4, this process uses heat transfer oil to transfer the heat of the high-temperature flue gas at the front end of the system to the inlet flue gas of the SCR denitrification device, ensuring that the inlet temperature is not lower than 280°C.

[0037] In step S4, the flue gas undergoes dust removal and desulfurization processes in S1 and S3, which greatly improves the lifespan of the SCR denitrification catalyst.

[0038] In steps S5 and S6, the heat transfer in this process is accomplished through a heat exchanger. Except for system losses, the heat in the high-temperature flue gas is basically transferred out of the system through process S6 for other uses.

[0039] In this embodiment, the high-temperature flue gas transfers heat through low-temperature heat transfer oil. The heat transfer oil can achieve a very high operating temperature (liquid state below 350℃) under near-atmospheric pressure conditions; it also exhibits uniform heat transfer, rapid heat dissipation, and high operational safety. This embodiment features two heat transfer oil heat exchangers along the flue gas direction. The first absorbs heat from the flue gas, heating the heat transfer oil and lowering the flue gas temperature; the second releases the energy of the heat transfer oil, heating the flue gas and raising its temperature, significantly reducing the initial investment and operating costs of the denitrification system. The heat transfer oil heat exchange device in this embodiment boasts stable heat exchange performance, easy temperature control, no moving parts, and a safe and reliable system.

[0040] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solutions of the present invention by utilizing the methods and techniques disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the protection scope of the technical solutions of the present invention.

Claims

1. A flue gas purification system for comprehensive energy utilization, characterized in that... include: Boiler (1), bag filter (2), SCR denitrification device (3), flue gas induced draft fan (4), first thermal oil heat exchanger (6), second thermal oil heat exchanger (7), third thermal oil heat exchanger (8), fourth thermal oil heat exchanger (9), first thermal oil circulation pump (10), second thermal oil circulation pump (11), first thermal oil expansion tank (12), and second thermal oil expansion tank (13); among which, The flue gas output end of the boiler (1) is connected to one input end of the first thermal oil heat exchanger (6), and one output end of the first thermal oil heat exchanger (6) is connected to the input end of the bag filter (2). The output end of the bag filter (2) is connected to one input end of the second thermal oil heat exchanger (7), and one output end of the second thermal oil heat exchanger (7) is connected to the input end of the SCR denitrification device (3). The output end of the SCR denitrification device (3) is connected to one input end of the third thermal oil heat exchanger (8), and one output end of the third thermal oil heat exchanger (8) is connected to the input end of the flue gas induced draft fan (4). The output end of the first thermal oil expansion tank (12) is connected to the input end of the first thermal oil circulation pump (10), the output end of the first thermal oil circulation pump (10) is connected to the other input end of the first thermal oil heat exchanger (6), the other output end of the first thermal oil heat exchanger (6) is connected to the other input end of the second thermal oil heat exchanger (7), and the other output end of the second thermal oil heat exchanger (7) is connected to the input end of the first thermal oil expansion tank (12). The output end of the second thermal oil expansion tank (13) is connected to the input end of the second thermal oil circulation pump (11), the output end of the second thermal oil circulation pump (11) is connected to the other input end of the third thermal oil heat exchanger (8), the other output end of the third thermal oil heat exchanger (8) is connected to the input end of the fourth thermal oil heat exchanger (9), and the output end of the fourth thermal oil heat exchanger (9) is connected to the input end of the second thermal oil expansion tank (13).

2. The flue gas purification system for comprehensive energy utilization according to claim 1, characterized in that... Also includes: Chimney (5); wherein the output end of the flue gas induced draft fan (4) is connected to the chimney (5).

3. The flue gas purification system for comprehensive energy utilization according to claim 1, characterized in that: Sodium bicarbonate and activated carbon were sprayed sequentially into the pipeline between the first heat transfer oil heat exchanger (6) and the bag filter (2) to dry remove sulfur and dioxins from the flue gas.

4. The flue gas purification system for comprehensive energy utilization according to claim 1, characterized in that: The first thermal oil heat exchanger (6), the second thermal oil heat exchanger (7), the third thermal oil heat exchanger (8) and the fourth thermal oil heat exchanger (9) are all tubular heat exchangers.

5. The flue gas purification system for comprehensive energy utilization according to claim 1, characterized in that: Both the first heat transfer oil circulation pump (10) and the second heat transfer oil circulation pump (11) are frequency converters.

6. A flue gas purification method for comprehensive energy utilization using a flue gas purification system according to any one of claims 1-5, characterized in that... include: Pre-dust removal is performed on the hot flue gas discharged from the boiler (1); After passing through the first thermal oil heat exchanger (6), the flue gas enters the pipeline between the first thermal oil heat exchanger (6) and the bag filter (2). Sodium bicarbonate and activated carbon are injected successively in the pipeline between the first thermal oil heat exchanger (6) and the bag filter (2) to remove S and dioxins from the flue gas and obtain flue gas containing only N. The flue gas containing only N enters the second thermal oil heat exchanger (7) after passing through the bag filter (2). The first hot oil circulation pump (10) pumps the low-temperature heat transfer oil in the first heat transfer oil expansion tank (12) into the first heat transfer oil heat exchanger (6). The low-temperature heat transfer oil exchanges heat with the hot flue gas. The heated heat transfer oil enters the second heat transfer oil heat exchanger (7). The heated heat transfer oil heats the flue gas containing only N to a preset temperature above the preset temperature. It then enters the SCR denitrification device (3) for denitrification to obtain hot clean flue gas. The hot clean flue gas enters the third heat transfer oil heat exchanger (8). The heat transfer oil in the third heat transfer oil heat exchanger (8) exchanges heat with the hot clean flue gas. The clean flue gas enters the flue gas induced draft fan (4), and the second heat transfer oil circulation pump (11) pumps the heated heat transfer oil in the third heat transfer oil heat exchanger (8) into the fourth heat transfer oil heat exchanger (9).

7. The flue gas purification method for comprehensive energy utilization according to claim 6, characterized in that: When the outlet temperature of the first heat transfer oil heat exchanger (6) is lower than the preset temperature, the first heat transfer oil circulation pump (10) is frequency-controlled to increase the amount of heat transfer oil, and the first heat transfer oil heat exchanger (6) removes excess heat to ensure that the inlet temperature of the bag filter (2) is not higher than the second preset temperature.

8. The flue gas purification method for comprehensive energy utilization according to claim 6, characterized in that: The temperature of the flue gas containing only N entering the bag filter (2) drops to 190℃-210℃.

9. The flue gas purification method for comprehensive energy utilization according to claim 6, characterized in that: The preset temperature is 280℃.

10. The flue gas purification method for comprehensive energy utilization according to claim 7, characterized in that: The second preset temperature is 250℃.

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