Coke oven flue gas ultra-low emission treatment system

Abstract

The utility model provides a kind of coke oven flue gas ultra-low emission treatment system, be set on coke oven exhaust flue, nitrogen removal unit, waste heat boiler unit, desulfurization unit and dust removal unit are sequentially communicated, the desulfurization unit includes first CFB desulfurization tower, bypass flue being set to parallel with first CFB desulfurization tower and high activity calcium adding device being set on desulfurization flue;The desulfurization flue one end communicates the export of waste heat boiler unit, other end and first CFB desulfurization tower and the import of bypass flue are communicated, by nitrogen removal unit as first purification link, first to the nitrogen oxides in flue gas removal, after nitrogen removal treatment, flue gas enters waste heat boiler unit, by waste heat boiler unit to flue gas heat absorption flue gas cooling, ensure the temperature condition required for subsequent desulfurization reaction, also can carry out the recovery of energy in high-temperature flue gas, reach energy-saving effect, then after waste heat, flue gas enters desulfurization unit and completes sulfide removal, finally, after the removal of dust by dust removal unit, it is discharged up to standard.

Description

Technical Field

[0001] This utility model relates to the field of coke oven flue gas treatment technology, and in particular to an ultra-low emission treatment system for coke oven flue gas. Background Technology

[0002] Coke oven flue gas contains heavy pollutants such as nitrogen oxides, sulfides, and particulate matter. According to environmental protection requirements, the flue gas needs to be treated before being discharged. Currently, the flue gas treatment method is to treat nitrogen oxides through a catalytic bed, and then treat the flue gas again through a desulfurization tower and a waste heat recovery device. The desulfurization tower can treat the sulfides in the flue gas, and the waste heat recovery device recovers the waste heat in the flue gas. After dust removal, the flue gas is discharged through a chimney, which can meet the flue gas treatment requirements.

[0003] However, with the gradual increase in environmental protection requirements, the above-mentioned flue gas treatment methods cannot meet the emission requirements, and targeted improvements to the flue gas treatment system are needed to meet the emission requirements. Utility Model Content

[0004] The purpose of this invention is to solve the above-mentioned problems by providing an ultra-low emission treatment system for coke oven flue gas.

[0005] To achieve the above objectives, the technical solution of this utility model is as follows: an ultra-low emission treatment system for coke oven flue gas, installed on the coke oven exhaust flue, including a denitrification unit, a desulfurization unit, a waste heat furnace unit, and a dust removal unit, wherein the denitrification unit, the waste heat furnace unit, the desulfurization unit, and the dust removal unit are connected sequentially; the desulfurization unit includes a first CFB desulfurization tower, a bypass flue connected in parallel with the first CFB desulfurization tower, and a highly active calcium addition device installed on the desulfurization flue; one end of the desulfurization flue is connected to the outlet of the waste heat furnace unit, and the other end is connected to the inlet of the first CFB desulfurization tower and the bypass flue.

[0006] Furthermore, a first valve is provided at both ends of the first CFB desulfurization tower, and a second valve is provided between the bypass flue and the desulfurization flue.

[0007] Furthermore, the dust removal unit includes a bag filter, a hopper pump installed in the ash hopper of the bag filter, and a desulfurization waste ash hopper connected to the discharge port of the hopper pump. The discharge hopper of the desulfurization waste ash hopper is equipped with a desulfurization waste ash injection path. One end of the desulfurization waste ash injection path is connected to the desulfurization flue, and the other end is connected to the Roots blower.

[0008] Furthermore, the bag filter includes two sets arranged in parallel, each set of bag filters is equipped with multiple ash hoppers, and each ash hopper is equipped with a hopper pump.

[0009] Furthermore, the denitrification unit includes two SCR reactors arranged in parallel.

[0010] Furthermore, both SCR reactors are equipped with ammonia injection grids, and the feed pipes of both ammonia injection grids are connected to the main feed pipe, with an electrically controlled valve installed on each feed pipe.

[0011] Furthermore, a hot air blower is also provided at the input end of the denitrification unit.

[0012] Furthermore, the waste heat furnace unit includes two sets of waste heat furnaces arranged in parallel.

[0013] Furthermore, an induced draft fan is provided downstream of the dust removal unit, and the pump outlet of the induced draft fan is connected to the chimney.

[0014] The ultra-low emission treatment system for coke oven flue gas disclosed in this utility model has the following advantages compared with the prior art: the denitrification unit is used as the first purification stage to remove nitrogen oxides from the flue gas. The flue gas after denitrification enters the waste heat furnace unit, where the waste heat furnace unit absorbs heat from the flue gas to cool it down, ensuring the temperature conditions required for the subsequent desulfurization reaction. It can also recover energy from the high-temperature flue gas to achieve energy saving. Then, the flue gas after waste heat enters the desulfurization unit to remove sulfides. Finally, the dust removal unit removes dust and the flue gas meets emission standards. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the overall structure of a coke oven flue gas ultra-low emission treatment system according to the present invention.

[0016] Figure 2 This is a schematic diagram of the desulfurization waste ash recycling subsystem in a bag filter of a coke oven flue gas ultra-low emission treatment system according to this utility model.

[0017] Figure 3 This is a schematic diagram of the connection structure of the two ammonia injection grids in the first SCR reactor and the second SCR reactor of this utility model.

[0018] In the diagram: 1. Hot air blower; 20. First SCR reactor; 21. Second SCR reactor; 22. First valve; 23. Ammonia injection grid; 230. Feed pipe; 231. Second electrically controlled valve; 24. Main pipeline; 30. First waste heat boiler; 31. Second waste heat boiler; 40. Bypass flue; 41. First CFB desulfurization tower; 401. Second valve; 5. Bag filter; 50. Silo pump; 51. Desulfurization waste ash recovery path; 52. Desulfurization waste ash silo; 53. Roots blower; 530. Desulfurization waste ash injection path; 510. Interface; 6. Exhaust fan; 60. First induced draft fan; 61. Second induced draft fan; 9. Flue gas conveying channel. Detailed Implementation

[0019] The present invention will now be described in further detail with reference to the accompanying drawings. The drawings are simplified schematic diagrams, illustrating only the basic structure of the present invention, and therefore only show the components relevant to the present invention.

[0020] Please refer to Figure 1 This utility model provides an ultra-low emission treatment system for coke oven flue gas. As a specific embodiment, the system is installed on the coke oven exhaust flue and includes a denitrification unit, a desulfurization unit, a waste heat furnace unit, and a dust removal unit. The denitrification unit, waste heat furnace unit, desulfurization unit, and dust removal unit are connected sequentially. The desulfurization unit includes a first CFB desulfurization tower, a bypass flue 40 connected in parallel with the first CFB desulfurization tower, and a highly active calcium addition device installed on the desulfurization flue. One end of the desulfurization flue is connected to the outlet of the waste heat furnace unit, and the other end is connected to the inlet of the first CFB desulfurization tower and the bypass flue 40.

[0021] As a specific implementation method, refer to Figure 1 This coke oven flue gas ultra-low emission treatment system is connected in series downstream of the coke oven exhaust flue. The coke oven flue gas is collected and connected to the inlet of the flue gas conveying channel 9 of this system through the main flue gas pipeline. The system performs deep purification treatment on the flue gas containing nitrogen oxides, sulfides and dust discharged from the coke oven. The system first uses the denitrification unit as the first purification stage to remove nitrogen oxides from the flue gas. The flue gas after denitrification enters the waste heat furnace unit, where the waste heat furnace unit absorbs heat from the flue gas to cool it down, ensuring the temperature conditions required for the subsequent desulfurization reaction. It can also recover energy in the high-temperature flue gas to achieve energy saving. Then, the flue gas after waste heat enters the desulfurization unit to remove sulfides. Finally, the dust removal unit removes dust and the flue gas meets the emission standards.

[0022] In terms of the specific structural design of the desulfurization unit, the first CFB desulfurization tower adopts existing circulating fluidized bed technology. This means that the tower body is equipped with an air distribution device, a desulfurizing agent injection device, and a material circulation device. The air distribution device ensures that the flue gas forms a uniform fluidized state within the tower. The desulfurizing agent injection device injects ordinary calcium hydroxide powder into the tower to fully react with the sulfides in the flue gas. The bypass flue 40 is arranged in parallel with the first CFB desulfurization tower, and its pipe diameter is the same as the inlet flue diameter of the first CFB desulfurization tower, ensuring that the flue gas maintains a stable flow velocity in both flow paths. A high-activity calcium addition device is also included. Installed near the outlet of the waste heat furnace unit in the desulfurization flue, the device includes a high-activity calcium silo, a metering pump, and a spray grid. The silo is used to store high-activity calcium hydroxide dry powder with a particle size of 300-450 mesh. The metering pump automatically adjusts the delivery rate according to the real-time concentration of sulfur dioxide in the flue gas. The spray grid is optimized in layout through digital model calculation so that the high-activity calcium dry powder can be evenly sprayed into the desulfurization flue. It should be noted that the structure and control method of the above-mentioned high-activity calcium addition device are mature technologies in the prior art. The high-activity calcium addition device in this application adopts the prior art, which should be understood by those skilled in the art.

[0023] By configuring the first CFB desulfurization tower in parallel with the bypass flue 40, the problem of overall system shutdown due to a single equipment failure in traditional desulfurization systems is effectively solved. When the first CFB desulfurization tower requires maintenance, the flue gas can be switched to bypass flue 40 for circulation. At the same time, a highly active calcium desulfurizing agent is injected into bypass flue 40 through a highly active calcium additive device to ensure uninterrupted desulfurization process, continuous system operation, and compliance with environmental protection requirements for "emissions meeting standards at any time."

[0024] In actual operation, either the high-activity calcium additive device or the first CFB desulfurization tower 41 can operate for desulfurization, or the high-activity calcium additive device and the first CFB desulfurization tower can work synergistically to achieve flexible control of desulfurization efficiency. Under normal production conditions, the first CFB desulfurization tower uses ordinary calcium hydroxide powder as the desulfurizing agent. Utilizing the material circulation characteristics of the circulating fluidized bed, a desulfurization efficiency of over 98% can be achieved under a calcium-to-sulfur ratio of 1.2-1.6. Moreover, the procurement cost of ordinary calcium hydroxide is only about 30% of that of high-activity calcium hydroxide, significantly reducing operating costs. When environmental control requirements are further tightened or the concentration of sulfides in the flue gas suddenly increases, the high-activity calcium additive device is activated. The high-activity calcium desulfurizing agent has a higher reactivity with the sulfides in the flue gas, which can further improve the desulfurization efficiency and ensure that the sulfide emission concentration is stably controlled below 30 mg / Nm³, meeting the ultra-low emission requirements.

[0025] Furthermore, as another specific implementation method, refer to Figure 1The first CFB desulfurization tower is equipped with a first valve 22 at both ends, and a second valve 401 is provided between the bypass flue 40 and the desulfurization flue.

[0026] Specifically, the first valve 22 is a high-temperature and corrosion-resistant electric slide gate valve. Its valve body is made of 310S stainless steel, and the sealing surface uses a hard alloy welding process to ensure long-term stable operation in high-temperature flue gas (up to 280℃) and corrosive gas environments. Two first valves 22 are installed on the inlet and outlet flues of the first CFB desulfurization tower, respectively. The inlet valve 22 is located near the tee connection between the first CFB desulfurization tower and the desulfurization flue, while the outlet valve 22 is located near the connection between the first CFB desulfurization tower and the dust removal unit's inlet flue. Both the valves and their control utilize existing technology, employing remote automatic switching and opening adjustment. The second valve 401 also adopts an electric slide gate valve, and its specifications and models are the same as those of the first valve 22. It is installed at the connection port between the bypass flue 40 and the desulfurization flue, that is, at the starting position of the inlet of the bypass flue 40. The opening and closing status of the valve can be interlocked with the first valve 22 through the central control system. When the first valve 22 is closed, the second valve 401 automatically opens, and vice versa, to ensure that the flue gas can only flow through one path in the first CFB desulfurization tower or the bypass flue 40.

[0027] Through the above configuration, the first valve 22 enables the independent isolation of the first CFB desulfurization tower. When a fault occurs inside the first CFB desulfurization tower, such as damage to the air distribution device or blockage of the desulfurizing agent injection device, closing the first valve 22 at both ends can isolate the first CFB desulfurization tower from the rest of the system, facilitating maintenance and repair without affecting the normal operation of the bypass flue 40, thus ensuring the continuous purification capacity of the system. The second valve 401 controls the opening and closing of the bypass flue 40, achieving a coordinated effect between the first CFB desulfurization tower and the bypass flue 40.

[0028] Furthermore, as another specific implementation, the dust removal unit includes a bag filter 5, a hopper pump 50 installed in the ash hopper of the bag filter 5, and a desulfurization waste ash hopper 52 connected to the discharge port of the hopper pump 50. The discharge hopper of the desulfurization waste ash hopper 52 is equipped with a desulfurization waste ash injection path 530. One end of the desulfurization waste ash injection path 530 is connected to the desulfurization flue, and the other end is connected to the Roots blower 53.

[0029] refer to Figure 1 , Figure 2The bag filter 5 adopts the existing pulse jet cleaning method. The ash hopper of the bag filter 5 is located at the bottom of the dust collector and has a conical structure, which facilitates the collection of desulfurization waste ash. The silo pump 50 is a pneumatic conveying silo pump 50, with one pump installed at the bottom of each ash hopper. The discharge port of the silo pump 50 is connected to the desulfurization waste ash silo 52 through the desulfurization waste ash recovery path 51, collecting and conveying the desulfurization waste ash to the desulfurization waste ash silo 52. The desulfurization waste ash silo 52 adopts existing technology, and its lower discharge port is connected to the desulfurization waste ash injection path 530. The desulfurization waste ash injection path 530 consists of an injection pipe and nozzles. One end of the injection pipe is connected to the outlet of the discharge hopper of the desulfurization waste ash silo 52, and the other end extends into the desulfurization flue. The nozzles are atomizing nozzles, installed in the desulfurization flue near the high-activity calcium addition device. The Roots blower 53 is a three-lobe Roots blower 53, and its outlet is connected to the injection pipe through a pipe to provide power for the injection of desulfurization waste ash. The speed of the Roots blower 53 can be adjusted by a frequency converter to control the amount of waste ash injected.

[0030] Through the above setup, desulfurization waste ash can be recycled. A portion of the waste ash is sent back to the desulfurization flue through the desulfurization waste ash injection path 530. The desulfurization waste ash collected by the bag filter 5 contains unreacted active calcium components. After being re-injected into the desulfurization flue, it can react with sulfides in the flue gas again, reducing the consumption of fresh desulfurizing agent. According to actual operation data, this design can increase the overall utilization rate of desulfurizing agent by more than 30%, significantly reducing the operating cost of the desulfurization system. The combined use of the silo pump 50 and the desulfurization waste ash silo 52 realizes the orderly collection and transportation of desulfurization waste ash.

[0031] Furthermore, as a preferred embodiment, refer to Figure 2 The bag filter 5 includes two sets arranged in parallel. Each set of bag filter 5 is equipped with multiple ash hoppers, and each ash hopper is equipped with a hopper pump 50.

[0032] Specifically, Furthermore, the two sets of baghouse dust collectors 5 are arranged in parallel. The inlet of each set of dust collectors is connected to the outlet flue of the desulfurization unit through a branch pipe, and the outlet is connected to the inlet flue of the induced draft fan 6 through a branch pipe. In this design, the filtration area of ​​each set of baghouse dust collectors 5 is designed according to the maximum processing flow rate of the coke oven flue gas, ensuring that a single set of dust collectors can meet the dust removal requirements under normal operating conditions, and that the two sets of dust collectors can handle the peak flow rate of the flue gas when operating simultaneously. Specifically, each set of baghouse dust collectors 5 is equipped with three ash hoppers. The bottom of each ash hopper is connected to the inlet of a silo pump 50. The model of the silo pump 50 is matched according to the amount of waste ash discharged from the ash hopper. The three silo pumps 50 of each set of dust collectors are connected in series adjacent to each other through a desulfurization waste ash recovery path 51. The interface 510 of the desulfurization waste ash recovery path 51 is connected to the compressed air source, and the other end is connected to the desulfurization waste ash silo 52.

[0033] The parallel design of the two sets of bag filters 5 enables the dust removal system to be maintained without shutting down. When one set of bag filters 5 needs to replace filter bags, clean hoppers, or be repaired, the other set of dust collectors can be started to continue working, ensuring that the dust removal process is uninterrupted and avoiding the overall system shutdown due to dust removal equipment maintenance, thus improving the system's operational stability and continuity.

[0034] The design of equipping each ash hopper with a silo pump 50 avoids the problem of uneven conveying caused by multiple ash hoppers sharing a single silo pump 50; with one silo pump 50 for each ash hopper, the waste ash can be conveyed separately and in a timely manner, ensuring that the waste ash liquid level in each ash hopper is always within a safe range, thereby improving the dust removal efficiency and equipment reliability of the dust collector.

[0035] Furthermore, as a specific implementation method, refer to Figure 1 The denitrification unit includes two SCR reactors connected in parallel. Specifically, the two SCR reactors are the first SCR reactor 20 and the second SCR reactor 21, both adopting the same structural design and dimensional parameters. Both use existing mature structures, such as vertical reactors. The reactor interior is equipped with a flow guiding device, an ammonia injection grid 23, a rectifier, and a catalyst layer from top to bottom. Since the operating temperature of the SCR reactor is 180-280℃, even when emission requirements are high in winter and the hot air blower 1 cannot be used, the temperature of the coke oven flue gas under low load can still be maintained above 220℃. At this time, the SCR reactor can still operate normally and can effectively work without using the hot air blower 1 to heat the flue gas, thus meeting the high emission requirements in winter.

[0036] Both SCR reactors are equipped with electrically operated flap valves on their inlet and outlet branch pipes. The operation of the two reactors can be controlled by operating these two valves. The parallel operation of the two SCR reactors solves the problem of nitrogen oxides not being denitrified during equipment maintenance in traditional single-SCR reactor systems. When one SCR reactor needs catalyst replacement, internal ash cleaning, or equipment repair, its inlet and outlet flap valves can be closed to isolate the reactor, while the other reactor continues denitrification. This ensures that nitrogen oxides in the flue gas are always effectively removed, preventing excessive nitrogen oxide emissions due to equipment malfunction.

[0037] Further, refer to Figure 3Both SCR reactors are equipped with ammonia injection grids 23, and the feed pipes 230 of both ammonia injection grids 23 are connected to the main feed pipe, with each feed pipe 230 equipped with an electrically controlled valve. Specifically, the feed pipe is the main pipeline 24 supplying ammonia gas, and both ammonia injection grids 23 are connected to the main pipeline 24 via feed pipes 230. By installing second electrically controlled valves 231 on the feed pipes 230, the two valves can be controlled independently, facilitating the switching of ammonia injection between the two systems when operating the corresponding SCR reactors.

[0038] Furthermore, as a preferred embodiment, refer to Figure 1 The input end of the denitrification unit is also equipped with a hot air blower 1. Specifically, the hot air blower 1 is a centrifugal high-temperature hot air blower 1. By setting the hot air blower 1, the temperature of the flue gas collected from the coke oven can be raised to 240-280℃. When the heated flue gas enters the denitrification unit, it can ensure better denitrification effect and meet the ultra-low emission requirements of nitrogen oxides.

[0039] Furthermore, the waste heat furnace unit includes two sets of waste heat furnaces arranged in parallel. Specifically, the waste heat furnace unit includes a first waste heat boiler 30 and a second waste heat boiler 31 arranged in parallel. The inlets of both sets of pre-waste heat furnaces are connected to the outlet flue of the denitrification unit through branch pipes, and the outlets are connected to the desulfurization flue of the desulfurization unit through branch pipes. Electric gate valves are installed on both the inlet branch pipe and the outlet branch pipe.

[0040] Furthermore, as a specific implementation, an induced draft fan 6 is provided downstream of the dust removal unit, and the pump outlet of the induced draft fan 6 is connected to the chimney. Specifically, the induced draft fan 6 is a centrifugal high-temperature induced draft fan 6, and its motor power is designed according to the maximum flue gas resistance and flow rate of the system. Since this system is improved based on the original flue gas conveying pipeline, the pipeline resistance has increased. In order to ensure the flue gas discharge effect, a new induced draft fan 6 is added to the original induced draft fan 6. The original first induced draft fan 60 has a power of 1800kW, and the newly added second induced draft fan 61 has a power of 2500kW. By setting up two sets of induced draft fans 6, the use of any production load of the coke oven can be met.

[0041] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the protection scope of this invention.

Claims

1. A coke oven flue gas ultra-low emission treatment system, installed on the coke oven exhaust flue, comprising a denitrification unit, a desulfurization unit, a waste heat furnace unit, and a dust removal unit, characterized in that, The denitrification unit, waste heat furnace unit, desulfurization unit and dust removal unit are connected in sequence. The desulfurization unit includes a first CFB desulfurization tower (41), a bypass flue (40) connected in parallel with the first CFB desulfurization tower (41) and a highly active calcium addition device installed on the desulfurization flue. One end of the desulfurization flue is connected to the outlet of the waste heat furnace unit, and the other end is connected to the inlet of the first CFB desulfurization tower and the bypass flue (40).

2. The ultra-low emission treatment system for coke oven flue gas according to claim 1, characterized in that, The first CFB desulfurization tower is equipped with a first valve (22) at both ends, and a second valve (401) is provided between the bypass flue (40) and the desulfurization flue.

3. The ultra-low emission treatment system for coke oven flue gas according to claim 2, characterized in that, The dust removal unit includes a bag filter (5), a hopper pump (50) installed in the ash hopper of the bag filter (5), and a desulfurization waste ash hopper (52) connected to the discharge port of the hopper pump (50). The discharge hopper of the desulfurization waste ash hopper (52) is equipped with a desulfurization waste ash injection path (530). One end of the desulfurization waste ash injection path (530) is connected to the desulfurization flue, and the other end is connected to the Roots blower (53).

4. The ultra-low emission treatment system for coke oven flue gas according to claim 3, characterized in that, The bag filter (5) includes two sets arranged in parallel. Each set of bag filter (5) is equipped with multiple ash hoppers, and each ash hopper is equipped with a hopper pump (50).

5. A coke oven flue gas ultra-low emission treatment system according to any one of claims 1-4, characterized in that, The denitrification unit includes two SCR reactors connected in parallel.

6. The ultra-low emission treatment system for coke oven flue gas according to claim 5, characterized in that, Both SCR reactors are equipped with ammonia injection grids (23), and the feed pipes (230) of the two ammonia injection grids (23) are connected to the main feed pipe, and each feed pipe (230) is equipped with an electric control valve.

7. A coke oven flue gas ultra-low emission treatment system according to any one of claims 1-4, characterized in that, The input end of the denitrification unit is also equipped with a hot air blower (1).

8. A coke oven flue gas ultra-low emission treatment system according to any one of claims 1-4, characterized in that, The waste heat furnace unit includes two sets of waste heat furnaces arranged in parallel.

9. A coke oven flue gas ultra-low emission treatment system according to any one of claims 1-4, characterized in that, The dust removal unit is equipped with an induced draft fan (6) downstream, and the pump outlet of the induced draft fan (6) is connected to the chimney.

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