A flue gas treatment system

Abstract

The application discloses a flue gas treatment system and relates to the technical field of environmental protection. The system comprises a boiler, a high-temperature side of a flue gas heat exchanger, a coal economizer, a desulfurization device, a bag-type dust collector, a low-temperature side of the flue gas heat exchanger, a low-temperature SCR denitration device, a heat exchanger, an induced draft fan and a chimney which are sequentially connected along a flue gas flow. The core of the system is that the low-temperature SCR denitration device is arranged after dust removal and desulfurization, and clean low-temperature flue gas at the outlet of the bag-type dust collector is led back to the flue gas heat exchanger to exchange heat with high-temperature original flue gas at the outlet of the boiler, so that the clean flue gas is heated to a low-temperature denitration reaction temperature of 190-210 DEG C. The application solves the problems that traditional high-dust arrangement of an SCR catalyst is prone to blockage, poisoning and abrasion, prolongs the service life of the catalyst, realizes energy gradient recovery through internal heat exchange of the system, meets the denitration temperature requirement without additional energy, and has the advantages of high purification efficiency, low operation cost and remarkable energy-saving effect.

Description

Technical Field

[0001] This utility model relates to the field of environmental protection technology, specifically to a flue gas treatment system. Background Technology

[0002] With increasingly stringent environmental protection requirements, the purification and treatment of industrial boiler flue gas has become particularly important. Traditional flue gas treatment systems typically employ a process flow of "SCR (Selective Catalytic Reduction) denitrification → dust removal → desulfurization." The SCR denitrification unit requires operation at high temperatures (typically 300-400℃) to ensure catalyst activity. Therefore, this system usually places the SCR denitrification unit in the high-temperature flue gas section at the boiler outlet, before the economizer and air preheater.

[0003] However, this traditional process has many drawbacks. First, the high concentration of fly ash in the flue gas at the boiler outlet makes the catalyst channels of SCR denitrification units with high ash concentrations prone to blockage, leading to increased system resistance. Furthermore, heavy metals in the fly ash (such as arsenic and lead) can poison and deactivate the catalyst, significantly shortening its lifespan and increasing operating and maintenance costs. Second, the high-dust flue gas causes severe wear on the catalyst. Third, to meet the high-temperature reaction environment required for SCR denitrification, the system cannot fully utilize the high-temperature heat in the flue gas, resulting in low energy efficiency.

[0004] To overcome the aforementioned problems, a technical concept has emerged of placing SCR denitrification units in the low-dust, low-temperature flue gas environment after dust removal and desulfurization. However, the activity of conventional medium- and high-temperature SCR catalysts decreases significantly at low temperatures (especially below 200°C), making it impossible to guarantee denitrification efficiency. Therefore, developing an integrated treatment system that can adapt to low-temperature environments, avoid the adverse effects of high-dust flue gas, and efficiently recover waste heat from the flue gas has become an urgent technical problem to be solved in this field. Utility Model Content

[0005] The purpose of this invention is to provide a flue gas treatment system to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, this utility model provides a flue gas treatment system, characterized in that it includes:

[0007] boiler;

[0008] A flue gas heat exchanger, the high-temperature side of which is connected to the high-temperature flue gas at the boiler outlet;

[0009] An economizer is connected to the flue gas heat exchanger; a desulfurization device is located after the economizer.

[0010] A bag filter is located after the desulfurization device, and the low-temperature side of the flue gas heat exchanger is connected to the low-temperature flue gas after the bag filter.

[0011] The low-temperature SCR denitrification device uses a low-temperature catalyst and has a reaction temperature range of 190-210℃. It is located after the bag filter.

[0012] A heat exchanger, located after the low-temperature SCR denitrification device, is used to further reduce the flue gas temperature and recover waste heat;

[0013] An induced draft fan is connected to the heat exchanger;

[0014] Chimney, connected to the induced draft fan.

[0015] As a further improvement to this technical solution, the desulfurization device adopts a dry desulfurization process.

[0016] As a further improvement to this technical solution, the economizer is used to reduce the flue gas temperature to 160-180℃.

[0017] As a further improvement to this technical solution, the working fluid of the heat exchanger is water or other media that can recover heat.

[0018] As a further improvement to this technical solution, the inlet of the induced draft fan is connected to the outlet of the heat exchanger.

[0019] As a further improvement to this technical solution, the inlet of the chimney is connected to the outlet of the induced draft fan.

[0020] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0021] 1. By placing the low-temperature SCR denitrification device after the bag filter and desulfurization device, the flue gas entering the denitrification reaction is in a clean state with low dust and low sulfur, which completely avoids the problems of fly ash in the flue gas clogging, wear and poisoning of the catalyst, significantly extends the service life of the catalyst and reduces the replacement and maintenance costs.

[0022] 2. This invention utilizes a low-temperature catalyst with a reaction temperature range of 190-210℃, enabling the SCR denitrification reaction to occur at a lower temperature range after the flue gas has been cooled by the economizer. This not only reduces the requirement for the initial temperature of the flue gas, but also, through coordinated temperature regulation with the flue gas heat exchanger and economizer, precisely controls the flue gas within the optimal activity temperature window of the catalyst, ensuring high denitrification efficiency. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of this utility model.

[0024] The meanings of the labels in the diagram are as follows:

[0025] 1. Boiler; 2. Flue gas heat exchanger; 3. Economizer; 4. Desulfurization device; 5. Bag filter; 6. Low temperature SCR denitrification device; 7. Heat exchanger; 8. Exhaust fan; 9. Chimney. Detailed Implementation

[0026] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0027] In the description of this utility model, it should be understood that the terms "upper", "lower", "both sides", "horizontal", "center", "bottom", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0028] Furthermore, in the description of this utility model, "multiple" means two or more, unless otherwise explicitly specified.

[0029] Please see Figure 1 As shown, this utility model provides a flue gas treatment system. The system mainly includes the following components along the flue gas treatment process: boiler 1, flue gas heat exchanger 2, economizer 3, desulfurization device 4, bag filter 5, low-temperature SCR denitrification device 6, heat exchanger 7, induced draft fan 8, and chimney 9.

[0030] The system connections are as follows: The flue gas outlet of boiler 1 is connected to the high-temperature inlet of flue gas heat exchanger 2 via a flue. The high-temperature outlet of flue gas heat exchanger 2 is connected to the flue gas inlet of economizer 3. The flue gas outlet of economizer 3 is sequentially connected to desulfurization device 4 and bag filter 5. The clean flue gas outlet of bag filter 5 is connected to the low-temperature inlet of flue gas heat exchanger 2 via a flue. The low-temperature outlet of flue gas heat exchanger 2 is connected to the inlet of low-temperature SCR denitrification device 6. The outlet of low-temperature SCR denitrification device 6 is connected to the flue gas inlet of heat exchanger 7. The flue gas outlet of heat exchanger 7 is connected to the inlet of induced draft fan 8. The outlet of induced draft fan 8 is finally connected to chimney 9.

[0031] Working principle: The high-temperature flue gas (approximately 300-350℃) generated from boiler 1 first enters the high-temperature side of flue gas heat exchanger 2. Subsequently, the flue gas flows into economizer 3, where it exchanges heat with boiler feedwater. The flue gas temperature is further reduced to a suitable range of 160-180℃. This temperature protects downstream equipment and creates optimal working conditions for bag filter 5.

[0032] Subsequently, the flue gas passes sequentially through desulfurization device 4 (preferably a dry desulfurization process in this embodiment) and bag filter 5. During this stage, sulfur oxides and most particulate matter in the flue gas are effectively removed, forming clean, low-temperature flue gas. However, at this point, the flue gas temperature has dropped to below 200°C, which cannot directly meet the reaction temperature window (190-210°C) required by the low-temperature SCR denitrification device 6.

[0033] To achieve energy conservation and consumption reduction, this invention ingeniously designs a flue gas recirculation heat exchange path. The clean, low-temperature flue gas from the outlet of the bag filter 5 is guided back to the low-temperature side of the flue gas heat exchanger 2. Here, the low-temperature clean flue gas undergoes indirect heat exchange with the high-temperature raw flue gas from the boiler 1, and is heated to a precise temperature of approximately 200°C without consuming external energy, perfectly meeting the high-efficiency reaction requirements of the low-temperature SCR denitrification catalyst.

[0034] The heated clean flue gas enters the low-temperature SCR denitrification unit 6. Under the action of the catalyst, nitrogen oxides (NOx) react with the injected reducing agent (such as ammonia) and are efficiently reduced to nitrogen and water, thus completing the denitrification process.

[0035] After denitrification, the flue gas enters heat exchanger 7 (whose working medium can be water or other suitable media), where it exchanges heat with a cold working medium. The flue gas temperature is significantly reduced to near ambient temperature, thereby maximizing the recovery of waste heat from the flue gas for heating or production processes, thus improving the overall thermal efficiency of the system. Finally, the low-temperature, clean flue gas is transported to chimney 9 by induced draft fan 8 and discharged into the atmosphere in compliance with standards.

[0036] The foregoing has shown and described the basic principles, main features, and advantages of this utility model. Those skilled in the art should understand that this utility model is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the utility model. Various changes and modifications can be made to this utility model without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed utility model. The scope of protection of this utility model is defined by the appended claims and their equivalents.

Claims

1. A flue gas treatment system, characterized in that, include: boiler; A flue gas heat exchanger, the high-temperature side of which is connected to the high-temperature flue gas at the boiler outlet; Economizer, connected to the flue gas heat exchanger; The desulfurization unit is located after the economizer; A bag filter is located after the desulfurization device, and the low-temperature side of the flue gas heat exchanger is connected to the low-temperature flue gas after the bag filter. The low-temperature SCR denitrification device uses a low-temperature catalyst and has a reaction temperature range of 190-210℃. It is located after the bag filter. A heat exchanger, located after the low-temperature SCR denitrification device, is used to further reduce the flue gas temperature and recover waste heat; An induced draft fan is connected to the heat exchanger; Chimney, connected to the induced draft fan.

2. The flue gas treatment system according to claim 1, characterized in that: The desulfurization unit adopts a dry desulfurization process.

3. The flue gas treatment system according to claim 1, characterized in that: The economizer is used to reduce the flue gas temperature to 160-180℃.

4. The flue gas treatment system according to claim 1, characterized in that: The working fluid of the heat exchanger is water or other media that can recover heat.

5. The flue gas treatment system according to claim 1, characterized in that: The inlet of the induced draft fan is connected to the outlet of the heat exchanger.

6. The flue gas treatment system according to claim 1, characterized in that: The inlet of the chimney is connected to the outlet of the induced draft fan.

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