Two-stage flue gas heat exchanger for incineration exhaust waste heat utilization
By designing a two-stage flue gas heat exchanger, the problem of high temperature requirements of the selective catalytic reduction unit is solved, waste heat recovery and industrial water saving are realized, and the energy efficiency and stability of the exhaust gas purification process are improved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- SHANGHAI CHEMICAL IND ZONE ANYUE SUEZ ENVIRONMENTAL TECHNOLOGY CO LTD
- Filing Date
- 2025-07-11
- Publication Date
- 2026-07-31
AI Technical Summary
In existing technologies, selective catalytic reduction units have high requirements for flue gas temperature, leading to energy waste, and require a large amount of industrial water to be used in the exhaust gas purification process.
A two-stage flue gas heat exchanger is adopted, which is connected to a bag filter, an alkaline scrubbing tower, an acid scrubbing tower and a selective catalytic reduction unit respectively. The flue gas temperature is reduced through two-stage flue gas exchange to meet the temperature requirements of the selective catalytic reduction reaction and to recover waste heat.
This approach enables full utilization of waste heat, reduces the industrial water consumption of the scrubbing tower, decreases energy consumption, and stabilizes the operation of the scrubbing tower.
Smart Images
Figure CN224580275U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to a flue gas heat exchanger, and more particularly to a two-stage flue gas heat exchanger for utilizing waste heat from incineration exhaust gas. Background Technology
[0002] With the development of the times, people are paying more and more attention to environmental pollution and governance, and the protection of the atmosphere, water, soil and other aspects is becoming increasingly strict. Therefore, new national and local standards are constantly being introduced to control the emissions of chemical enterprises. For hazardous waste incineration enterprises, the emission requirements for nitrogen oxides are also becoming increasingly stringent. However, since the removal of nitrogen oxides by a single selective non-catalytic reduction unit is limited, and the amount of waste that generates nitrogen oxides in hazardous waste is also increasing, there is a need to add selective catalytic reduction units to remove nitrogen oxides from the exhaust gas.
[0003] Selective catalytic reduction (SCR) units, due to their stringent requirements on flue gas, are designed to be placed at the final stage of exhaust gas purification. The flue gas temperature entering this stage is around 70°C. However, since the SCR reaction requires temperatures between 250-400°C, a significant amount of new energy is needed to meet these reaction temperatures, resulting in energy waste. Therefore, flue gas heat exchangers for utilizing waste heat from incineration exhaust gas have been a key research focus in this field and are continuously being improved. Utility Model Content
[0004] The technical problem to be solved by this utility model is to provide a two-stage flue gas heat exchanger for the utilization of waste heat from incineration exhaust gas, which can fully recover the waste heat and at the same time reduce the temperature of the exhaust gas entering the scrubbing tower through flue gas heat exchange, thereby reducing the industrial water consumption of the scrubbing tower.
[0005] The technical solution adopted by this utility model to solve the above-mentioned technical problems is to provide a two-stage flue gas heat exchanger for the utilization of waste heat from incineration exhaust gas, including a first flue gas heat exchanger and a second flue gas heat exchanger. The first inlet of the first flue gas heat exchanger is connected to the outlet of a bag filter to introduce primary hot flue gas. The second inlet of the first flue gas heat exchanger is connected to the outlet of an alkaline scrubbing tower to introduce primary cold flue gas. The first outlet of the first flue gas heat exchanger is connected to the second inlet of the second flue gas heat exchanger. The second outlet of the first flue gas heat exchanger is connected to the inlet of an acid scrubbing tower, and the outlet of the acid scrubbing tower is connected to the inlet of the alkaline scrubbing tower. The first outlet of the second flue gas heat exchanger is connected to the inlet of a selective catalytic reduction unit. The outlet of the selective catalytic reduction unit is connected to the first inlet of the second flue gas heat exchanger. The second outlet of the second flue gas heat exchanger is connected to a chimney to discharge secondary hot flue gas.
[0006] Furthermore, the second outlet of the second flue gas heat exchanger is equipped with an induced draft fan connected to the chimney.
[0007] Furthermore, the temperature of the primary hot flue gas is 200°C, and the temperature of the primary cold flue gas is 66°C. After the primary hot flue gas and the primary cold flue gas exchange heat through the first flue gas heat exchanger, the temperature of the secondary hot flue gas entering the acid washing tower drops to 110°C-120°C, while the temperature of the primary cold flue gas at the outlet of the alkali washing tower increases to 130-140°C.
[0008] Furthermore, the flue gas temperature delivered to the inlet of the selective catalytic reduction unit by the second flue gas heat exchanger is 260°C, thereby raising the flue gas temperature at the outlet of the selective catalytic reduction unit to 240°C.
[0009] Furthermore, the temperature of the secondary hot flue gas discharged from the second outlet of the second flue gas heat exchanger to the chimney is 162°C.
[0010] Compared with the prior art, the present invention has the following advantages: The two-stage flue gas heat exchanger for the utilization of waste heat from incineration exhaust gas provided by the present invention recovers the heat of the exhaust gas and supplies it to the selective catalytic reduction unit by adding the two-stage flue gas heat exchanger; thus, the waste heat can be fully reused, and at the same time, the temperature of the exhaust gas entering the scrubbing tower can be reduced by reducing the industrial water consumption of the scrubbing tower through flue gas heat exchange. Attached Figure Description
[0011] Figure 1 This is a schematic diagram of the two-stage flue gas heat exchanger for utilizing waste heat from incineration exhaust gas according to this utility model.
[0012] The diagram is marked as follows:
[0013] 1. Alkali washing tower; 2. Acid washing tower; 3. First flue gas heat exchanger; 4. Second flue gas heat exchanger; 5. Chimney; 6. Selective catalytic reduction unit; 7. Exhaust fan. Detailed Implementation
[0014] The present invention will be further described below with reference to the accompanying drawings and embodiments.
[0015] Figure 1 This is a schematic diagram of the two-stage flue gas heat exchanger for utilizing waste heat from incineration exhaust gas according to this utility model.
[0016] Please see Figure 1The present invention provides a two-stage flue gas heat exchanger for utilizing waste heat from incineration exhaust gas, comprising a first flue gas heat exchanger 3 and a second flue gas heat exchanger 4, each heat exchanger having two inlets and two outlets; the first inlet of the first flue gas heat exchanger 3 is connected to the outlet of a bag filter to introduce primary hot flue gas, the second inlet of the first flue gas heat exchanger 3 is connected to the outlet of an alkaline scrubbing tower 1 to introduce primary cold flue gas, the first outlet of the first flue gas heat exchanger 3 is connected to the second inlet of the second flue gas heat exchanger 4, the second outlet of the first flue gas heat exchanger 3 is connected to the inlet of an acid scrubbing tower 2, and the outlet of the acid scrubbing tower 2 is connected to the inlet of the alkaline scrubbing tower 1; the first outlet of the second flue gas heat exchanger 4 is connected to the inlet of a selective catalytic reduction unit 6, the outlet of the selective catalytic reduction unit 6 is connected to the first inlet of the second flue gas heat exchanger 4, and the second outlet of the second flue gas heat exchanger 4 is connected to a chimney 5 to discharge secondary hot flue gas.
[0017] This invention employs a two-stage flue gas heat exchanger. The first stage of flue gas exchange involves the exchange of flue gas from the bag filter outlet (hot flue gas, approximately 200°C) and the flue gas from the alkaline scrubbing tower 1 outlet (cold flue gas, 66°C). This first stage of heat exchange reduces the temperature of the flue gas entering the acid scrubbing tower 2 from the bag filter outlet to 110°C-120°C, reducing industrial water consumption by 1.2 t / d. Simultaneously, the temperature of the flue gas exiting the alkaline scrubbing tower 1 is increased to 130-140°C. The second stage of flue gas exchange involves the exchange of flue gas (cold flue gas) heated to 130-140°C by the first flue gas heat exchanger 3 and the flue gas (hot flue gas, 260°C) passing through the selective catalytic reduction unit 6. Through the second stage of heat exchange, the temperature of the flue gas entering the selective catalytic reduction unit 6 is increased from 135°C to 240°C, while the temperature of the flue gas exiting the selective catalytic reduction unit 6 is reduced to 162°C before being discharged through the induced draft fan 7 to the chimney 5. After two stages of heat exchange, the required amount of heat source, converted into natural gas consumption, can be reduced by 10,000 m³. 3 / d of natural gas consumption.
[0018] The two-stage flue gas heat exchanger for utilizing waste heat from incineration exhaust gas provided by this utility model can fully recover the waste heat. At the same time, by reducing the temperature of the exhaust gas entering the scrubbing tower through flue gas heat exchange, the industrial water consumption of the scrubbing tower can be reduced. It has the following advantages:
[0019] 1. Two-stage heat exchange can fully utilize the heat in the flue gas, reduce the addition of new energy, and simultaneously achieve the purpose of flue gas purification;
[0020] 2. By reducing the flue gas temperature through the first-stage flue gas heat exchange, the water scrubbing tower can operate stably and avoid shutdowns due to large temperature fluctuations.
[0021] 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 some modifications and improvements without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the claims.
Claims
1. A two-stage flue gas heat exchanger for utilizing waste heat from incineration exhaust gas, characterized in that, The system includes a first flue gas heat exchanger (3) and a second flue gas heat exchanger (4). The first inlet of the first flue gas heat exchanger (3) is connected to the outlet of the bag filter to introduce primary hot flue gas. The second inlet of the first flue gas heat exchanger (3) is connected to the outlet of the alkaline scrubbing tower (1) to introduce primary cold flue gas. The first outlet of the first flue gas heat exchanger (3) is connected to the second inlet of the second flue gas heat exchanger (4). The second outlet of the first flue gas heat exchanger (3) is connected to the inlet of the acid scrubbing tower (2). The outlet of the acid scrubbing tower (2) is connected to the inlet of the alkaline scrubbing tower (1). The first outlet of the second flue gas heat exchanger (4) is connected to the inlet of the selective catalytic reduction unit (6). The outlet of the selective catalytic reduction unit (6) is connected to the first inlet of the second flue gas heat exchanger (4). The second outlet of the second flue gas heat exchanger (4) is connected to the chimney (5) to discharge secondary hot flue gas.
2. The two-stage flue gas heat exchanger for utilizing waste heat from incineration exhaust gas as described in claim 1, characterized in that, The second outlet of the second flue gas heat exchanger (4) is equipped with an induced draft fan (7) connected to the chimney (5).
3. The two-stage flue gas heat exchanger for utilizing waste heat from incineration exhaust gas as described in claim 1, characterized in that, The temperature of the primary hot flue gas is 200°C, and the temperature of the primary cold flue gas is 66°C. After the primary hot flue gas and the primary cold flue gas exchange heat through the first flue gas heat exchanger (3), the temperature of the secondary hot flue gas entering the acid washing tower (2) drops to 110°C-120°C, while the temperature of the primary cold flue gas at the outlet of the alkaline washing tower (1) rises to 130-140°C.
4. The two-stage flue gas heat exchanger for utilizing waste heat from incineration exhaust gas as described in claim 1, characterized in that, The flue gas temperature at the inlet of the second flue gas heat exchanger (4) to the selective catalytic reduction unit (6) is 260°C, which raises the flue gas temperature at the outlet of the selective catalytic reduction unit (6) to 240°C.
5. The two-stage flue gas heat exchanger for utilizing waste heat from incineration exhaust gas as described in claim 1, characterized in that, The temperature of the secondary hot flue gas discharged from the second outlet of the second flue gas heat exchanger (4) to the chimney (5) is 162°C.