Device and method for co-processing multiple pollutants in high-temperature flue gas of furnace

Abstract

The invention discloses a device and a method for co-processing multiple pollutants in high-temperature flue gas of a furnace kiln. Comprising a bypass type cyclone separator, an SCR tower and high-temperature circulating fluidized bed equipment which are sequentially connected, wherein the bottom of the bypass type cyclone separator is provided with a centralized ash bin, and the ash bin collects finished product powder and then discharges the finished product powder; a double-fluid ammonia water atomizing spray gun is arranged at the center of the outlet section of the bypass type cyclone separator, and the spraying direction of ammonia water is consistent with the flow direction of flue gas. Beneficial components in high-temperature flue gas (about 250-400 DEG C) generated by a kiln are recovered through a dust recovery device, nitrogen oxides are removed through an SCR tower, finally, gaseous pollutants such as SO2 are removed and fine dust removal is performed through high-temperature circulating fluidized bed equipment, and the flue gas is discharged into the atmosphere after meeting the ultra-low emission standard. The whole device not only can recover beneficial components in the flue gas, but also can efficiently treat high-temperature and high-concentration flue gas, various pollutants can be synergistically treated, secondary pollution such as waste water is not generated, and the device has wide social and economic benefits.

Description

Technical Field

[0001] The present invention relates to the field of flue gas pollutant treatment, and in particular to a device and method for the coordinated treatment of multiple pollutants in high-temperature flue gas from a furnace. Background Art

[0002] A large number of furnaces have been built and put into operation in industries such as steel, cement, chemicals, glass, and new energy. Various types of furnaces produce a large amount of sulfur dioxide (SO2), nitrogen oxides (NOx), particulate matter, heavy metals and other pollutants during the roasting process, which are directly discharged into the atmosphere, seriously affecting the quality of the air environment, thereby causing serious harm to human health and the ecosystem, and becoming a major factor restricting the sustainable development of my country's economy and society. The treatment of pollutants and the compliance of emissions with standards are the focus of flue gas treatment in various industries.

[0003] As China continues to promote ultra-low emission transformation across various industries, various flue gas treatment technologies are emerging, providing positive solutions for air pollution control. However, furnace flue gas is characterized by high concentrations of pollutants, a wide variety of pollutants, coupled pollutants, high flue gas temperatures, and large flue gas fluctuations. A single process, or a simple combination of several processes, cannot achieve the desired emission of various pollutants. Therefore, the development of new devices or methods for the coordinated treatment of furnace flue gas has been put on the agenda.

[0004] Patent CN 211025768U discloses an integrated, coordinated treatment device for high-temperature flue gas with multiple pollutants. After the high-temperature flue gas from the furnace is temperature-controlled to 320-350°C by a heat exchanger, a desulfurizer (calcium hydroxide powder) and a denitrification reducing agent (ammonia) are sprayed into the flue gas. The flue gas then enters a ceramic filter element dust, sulfur, and sulfur removal device to remove dust, SO2, and nitrogen oxides. Specifically, the calcium hydroxide powder cake on the outer layer of the filter element removes dust and SO2. A ceramic filter tube that adsorbs the SCR catalyst is installed inside the filter element to complete the reduction reaction of nitrogen oxides. Finally, the purified flue gas is discharged into the atmosphere through a fan. This method has the following characteristics: first, the risk of failure is high; damage or failure of a single filter element can result in substandard emissions of multiple pollutants; second, the removal efficiency is low, making it difficult to achieve ultra-low emissions for high-concentration pollutants; and third, the filter element must be specially manufactured, resulting in high maintenance and operating costs. Therefore, research and development of devices and methods for the coordinated treatment of high-concentration high-temperature furnace flue gas with multiple pollutants to stably achieve ultra-low emissions has been put on the agenda. Summary of the Invention

[0005] In response to the above problems, the purpose of the present invention is to provide a device and method for the coordinated treatment of multiple pollutants in high-temperature flue gas from furnaces. The entire device can not only recover beneficial components in the flue gas, but also efficiently treat high-temperature and high-concentration flue gas. Multiple pollutants can be coordinated and treated without generating secondary pollution such as wastewater, and has broad social and economic benefits.

[0006] To achieve the above-mentioned object, the present invention provides a device for the coordinated treatment of multiple pollutants in high-temperature flue gas from a furnace, comprising a bypass cyclone separator, a selective catalytic reduction tower (SCR tower), and a high-temperature circulating fluidized bed device connected in sequence, and a fan connected to the circulating fluidized bed;

[0007] A centralized ash bin is installed at the bottom of the bypass cyclone separator, collecting the finished powder before discharging it. A dual-fluid ammonia atomizing spray gun is located at the center of the bypass cyclone separator's outlet section. The spray angle and droplet size meet denitrification requirements, and the ammonia spray direction aligns with the flue gas flow. The bypass cyclone separator and finished ash bin are constructed of heat-resistant steel.

[0008] Furthermore, the SCR tower adopts a top-inlet, side-outlet configuration, with guide plates, rake-type soot blowers, catalysts, and a bottom ash discharge device arranged in order from top to bottom. The catalyst is a honeycomb-shaped catalyst with a window temperature of 250-400°C and 15-30 holes. The number of catalyst layers is set based on the nitrogen oxide concentration at the flue gas inlet and the denitrification efficiency.

[0009] A dust removal device is installed at the bottom of the SCR tower, and the denitrification tower is made of heat-resistant steel.

[0010] Furthermore, the high-temperature circulating fluidized bed equipment includes a high-temperature circulating fluidized bed desulfurization tower, a high-temperature bag dust collector, an ash circulating device, and an external ash discharge device.

[0011] Furthermore, the high-temperature circulating fluidized bed desulfurization tower adopts a bottom-inlet, side-outlet configuration. From bottom to top, the desulfurizer feed pipe, venturi, high-pressure reflux spray gun, and desulfurization tower body are arranged in this order. The feed pipe is located at the venturi inlet, and pneumatic conveying is used for feed. The flow rate at the venturi throat is 25-50 m / s. The spray gun is located at the venturi outlet, and the angle between the spray direction and the flue gas flow is 75-95 degrees. The droplet size meets desulfurization requirements, and the flue gas reaction time in the cylinder is 2.3-5 seconds. The desulfurization tower is constructed of heat-resistant steel.

[0012] Furthermore, the high-temperature bag dust collector adopts a top-inlet and side-outlet form, with a guide plate and an anti-dust accumulation device at the inlet. The dust collector body is made of heat-resistant steel, and the filter bag is made of ceramic fiber filter tube with a temperature resistance of 400°C. The appropriate filtration wind speed is selected according to the dust concentration and the chimney outlet emission limit.

[0013] Furthermore, the ash circulating device includes a variable frequency screw feeder arranged at the bottom of the dust collector ash hopper, a return pneumatic plug-in valve, a weighing screw feeder, and a return chute.

[0014] The inlet of the variable frequency screw feeder is connected to the bottom of the ash hopper, and outlets are set in the middle and tail of the screw feeder, which are respectively connected to the return material pneumatic plug-in valve and the external ash discharge pneumatic plug-in valve.

[0015] Furthermore, the external ash discharge device includes an external ash discharge pneumatic plug-in valve and a silo pump. The valve is made of stainless steel, the silo pump is made of heat-resistant steel, and the valve and silo pump are externally insulated.

[0016] To achieve the above-mentioned object, the present invention provides a method for the coordinated treatment of multiple pollutants in high-temperature flue gas from a furnace, wherein the method is performed using the above-mentioned device for the coordinated treatment of multiple pollutants in high-temperature flue gas from a furnace, and comprises the following steps:

[0017] The high-temperature flue gas after furnace combustion first enters the bypass cyclone separator for gas-solid separation. The beneficial dust in the flue gas falls into the centralized ash bin and is then discharged to the finished product bin. Ammonia droplets (20% ammonia water) are sprayed at the outlet of the cyclone separator. The ammonia water evaporates quickly and mixes evenly with the flue gas before entering the selective catalytic reduction tower (SCR tower). In the SCR, the nitrogen oxides in the flue gas undergo an oxidation-reduction reaction with ammonia to complete the removal of nitrogen oxides. The remaining raw material dust in the flue gas is intercepted and falls into the bottom of the tower and is discharged to the finished product bin.

[0018] Furthermore, the denitrified flue gas enters the high-temperature circulating fluidized bed equipment from the bottom, where it is fully mixed with the added desulfurizer and desulfurization ash from the return chute. Pollutants such as HCL, HF, and SO3 are first removed from the flue gas. It is then accelerated through the venturi tube and enters the fluidized bed, generating intense turbulence and mixing. Atomized water is sprayed into the venturi outlet to cool the flue gas, converting the reaction between SO2 and Ca(OH)2 into an ionic reaction that can be completed instantly, achieving efficient SO2 removal. As the flue gas rises, some particles flow back to the circulating fluidized bed to continue the reaction, while some particles are carried out with the flue gas and passed through a high-temperature bag filter for gas-solid separation. The treated clean flue gas is discharged into the atmosphere through an induced draft fan and chimney.

[0019] Furthermore, the original flue gas temperature is 250-400°C, the temperature drops by about 30°C after passing through the cyclone dust collector, the temperature drops by about 20°C after passing through the SCR tower, and the temperature drops by about 50-120°C after passing through the circulating fluidized bed equipment. The treated flue gas is discharged into the atmosphere at a temperature 20°C higher than the dew point temperature.

[0020] The beneficial effects of the present invention are:

[0021] 1) The present invention can not only recover beneficial components in furnace flue gas and realize the separation of furnace dust and desulfurization by-products, but also perform graded dust removal, reduce the risk of subsequent denitrification tower catalyst clogging and deactivation, and ensure stable and efficient operation of the system.

[0022] 2) The present invention can treat a variety of pollutants, including dust, SO2, SO3, nitrogen oxides, dioxins, thallium, mercury, etc., reducing the risk of subsequent engineering modifications, lowering investment and operating costs, and reducing site occupation.

[0023] 3) The present invention can adopt different forms of combination according to the actual flue gas working conditions. It can be operated as a single device or in combination with multiple devices to collaboratively remove multiple pollutants in the flue gas, thereby improving the flexibility of the device.

[0024] 4) The present invention can process a wide range of flue gas temperatures (250-400°C), and is suitable for furnace flue gas with a large flue gas fluctuation range (40% to 110%). It can maintain a 100% synchronization rate with furnace equipment, thereby improving the adaptability and stability of the device.

[0025] 5) The present invention is suitable for treating flue gas with high pollutant concentration, and the particle concentration is less than 15g / Nm 3 , SO2 concentration <4000mg / Nm 3 , nitrogen oxide concentration <800mg / Nm 3 , the export chimney can stably meet the ultra-low emission standards of various industries. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of the structure of an embodiment of the present invention.

[0027] 1: Furnace; 2: Bypass cyclone separator; 3: Centralized ash silo; 4: Ammonia spray gun; 5: SCR tower; 6: Catalyst; 7: Rake soot blower; 8: Guide plate; 9: New material feeding pipe; 10: Venturi tube; 11: High-pressure reflux spray gun; 12: Desulfurization tower body; 13: High-temperature bag filter; 14: Ceramic fiber filter cartridge; 15: Variable frequency screw feeder; 16: Silo pump; 17: Weighing screw feeder; 18: Return chute; 19: Return pneumatic plug-in valve; 20: External ash discharge pneumatic plug-in valve; 21: Fan; 22: Chimney. DETAILED DESCRIPTION

[0028] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0029] In the description of the present invention, it should be understood that the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention.

[0030] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the technical features being referred to. Thus, a feature specified as "first" or "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0031] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood broadly. For example, they may refer to fixed connections, detachable connections, or integral connections; they may refer to direct connections, indirect connections through an intermediary, or internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0032] Example 1

[0033] As shown in the figure, this embodiment provides a device for the coordinated treatment of multiple pollutants in high-temperature flue gas from a furnace, including a bypass cyclone separator 2, a selective catalytic reduction tower (SCR tower) 5 connected to the bypass cyclone separator, a high-temperature circulating fluidized bed device connected to the SCR tower, and a fan 21 connected to the high-temperature circulating fluidized bed device.

[0034] A centralized ash bin 3 is installed at the bottom of the bypass cyclone separator 2. A set of dual-fluid ammonia atomizing spray guns 4 is set at the center of the bypass cyclone separator outlet section, with a spray angle of about 28 degrees, an average droplet size of about 30μm, and a spray direction consistent with the flue gas flow direction.

[0035] From top to bottom, the SCR tower 5 is equipped with a guide plate 8, a rake soot blower 7, and a catalyst 6. The catalyst is a honeycomb type with a window temperature of 260-320°C and 25 holes. One layer of catalyst is initially installed, with one layer reserved. From bottom to top, the high-temperature circulating fluidized bed desulfurization tower is equipped with a desulfurizer feed pipe 9, a venturi 10, a high-pressure reflux lance 11, and a desulfurization tower body 12. The flow rate at the venturi throat is approximately 35 m / s, and the lance's spray direction forms an 85-degree angle with the flue gas flow.

[0036] The high-temperature bag filter inlet features a guide plate and dust accumulation prevention device. The collector body is constructed of heat-resistant steel, and the filter bags utilize ceramic fiber filter tubes with a temperature resistance of 380°C. The filtration velocity is 0.7-0.9 m / s. The ash circulation system includes a variable-frequency screw feeder 15 at the bottom of the dust collector's ash hopper, a pneumatic return gate valve 19, a weighing screw feeder 17, and a return chute 18. The variable-frequency screw feeder inlet is connected to the bottom of the ash hopper, with outlets located in the middle and rear of the screw feeder, connected to the pneumatic return gate valve and the external ash discharge gate valve, respectively. The external ash discharge system includes the external ash discharge gate valve and a silo pump with a capacity of 0.5 cubic meters.

[0037] Example 2

[0038] This embodiment uses the device of Example 1 to treat the flue gas from the lithium mica roasting kiln of a new material company. The flue gas flow rate at the inlet of the device is about 73,000 Nm 3 / h (standard dry flue gas), flue gas temperature is 260-320℃, inlet SO2 concentration is 1200-2800mg / Nm 3 , the particle concentration is 5000mg / Nm 3 , the inlet nitrogen oxide concentration is 220-400mg / Nm 3 This case is designed based on extreme values.

[0039] After calcination, the high-temperature lithium mica first enters the bypass cyclone separator for gas-solid separation. The lithium mica powder in the flue gas falls into the centralized ash bin and is discharged to the finished product bin. Ammonia droplets (20% ammonia water) are sprayed at the outlet of the cyclone separator. The ammonia water quickly evaporates and mixes evenly with the flue gas before entering the selective catalytic reduction tower (SCR tower). In the SCR tower, the nitrogen oxides in the flue gas undergo an oxidation-reduction reaction with ammonia to complete the removal of nitrogen oxides. The remaining lithium mica powder in the flue gas is intercepted and falls to the bottom of the tower and is discharged to the finished product bin.

[0040] After denitrification, the flue gas enters the high-temperature circulating fluidized bed equipment from the bottom, where it is fully mixed with the added desulfurizer and the circulating ash from the return chute. Pollutants such as HCL, HF, and SO3 are first removed from the flue gas. It is then accelerated through the venturi tube and enters the fluidized bed, generating intense turbulence and mixing. Atomized water is sprayed into the venturi outlet to cool the flue gas, converting the reaction between SO2 and Ca(OH)2 into an ionic reaction that can be completed instantly, achieving efficient SO2 removal. As the flue gas rises, some particles flow back to the circulating fluidized bed to continue the reaction, while some particles are carried out with the flue gas and passed through a high-temperature bag filter for gas-solid separation. The treated clean flue gas is discharged into the atmosphere through an induced draft fan and chimney.

[0041] The original flue gas temperature is 260-320℃. After passing through the cyclone dust collector, the temperature drops by about 30℃. After passing through the SCR tower, the temperature drops by about 20℃. After passing through the circulating fluidized bed equipment, the temperature drops by about 50-120℃. The treated flue gas is discharged into the atmosphere at a temperature 20℃ higher than the dew point. After treatment, the SO2 concentration at the chimney outlet is <30mg / Nm 3 , nitrogen oxide concentration <40mg / Nm 3 , particle concentration <8mg / Nm 3 , which is better than the national ultra-low emission standards.

[0042] In the description of this specification, specific features, structures, materials or characteristics may be combined in an appropriate manner in any one or more embodiments or examples.

[0043] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A device for the coordinated treatment of multiple pollutants in high-temperature flue gas from a furnace, characterized in that: It includes a bypass cyclone separator, an SCR tower and a high-temperature circulating fluidized bed device connected in sequence; Among them, a centralized ash bin is installed at the bottom of the bypass cyclone separator, which collects the finished powder and then discharges it outside; a dual-fluid ammonia atomizing spray gun is set at the center of the bypass cyclone separator outlet section, and the ammonia spray direction is consistent with the flue gas direction.

2. The device for collaboratively treating multiple pollutants in high-temperature flue gas from a furnace according to claim 1, characterized in that: The SCR tower adopts the top-inlet and side-outlet form, and is equipped with a guide plate, a rake soot blower, a catalyst, and a bottom soot discharge device from top to bottom. The catalyst adopts honeycomb type, the window temperature of the catalyst is 250-400℃, and the number of holes in the catalyst is 15-30; Among them, a dust discharge device is set at the bottom of the SCR tower.

3. The device for collaboratively treating multiple pollutants in high-temperature flue gas from a furnace according to claim 1, characterized in that: The high-temperature circulating fluidized bed equipment includes: a high-temperature circulating fluidized bed desulfurization tower, a high-temperature bag dust collector, a circulating ash device and an external ash discharge device.

4. The device for collaboratively treating multiple pollutants in high-temperature flue gas from a furnace according to claim 3, characterized in that: The high-temperature circulating fluidized bed desulfurization tower adopts the form of bottom inlet and side outlet, and the desulfurizer feeding pipe, venturi tube, high-pressure reflux spray gun, and desulfurization tower cylinder are arranged from bottom to top in sequence. The feeding pipe is arranged at the inlet end of the venturi tube, and the feeding is carried out by pneumatic conveying. The flow rate at the throat of the venturi tube is 25-50m / s. The spray gun is arranged at the outlet end of the venturi tube, and the angle between the injection direction and the flue gas flow direction is 75-95 degrees.

5. The device for collaboratively treating multiple pollutants in high-temperature flue gas from a furnace according to claim 3 is characterized in that: The high-temperature bag dust collector adopts a top-inlet and side-outlet form, and the inlet adopts a guide plate and a dust accumulation prevention device.

6. The device for collaboratively treating multiple pollutants in high-temperature flue gas from a furnace according to claim 3 is characterized in that: The ash circulating device comprises a variable frequency screw feeder, a return material pneumatic plug-in valve, a weighing screw feeder and a return material chute, which are arranged at the bottom of the dust collector ash hopper. Among them, the inlet of the variable frequency screw feeder is connected to the bottom of the ash hopper, and outlets are set in the middle and tail of the screw feeder, which are respectively connected to the return material pneumatic plug-in valve and the external ash discharge pneumatic plug-in valve.

7. A method for the coordinated treatment of multiple pollutants in high-temperature flue gas from a furnace, characterized in that: The method is accomplished using the furnace high-temperature flue gas multi-pollutant coordinated treatment device according to claim 1, and comprises the following steps: The high-temperature flue gas after kiln combustion first enters the bypass cyclone separator for gas-solid separation. The beneficial dust in the flue gas falls into the centralized ash bin and is then discharged to the finished product bin. Ammonia droplets are sprayed into the cyclone separator outlet, where they evaporate quickly and mix evenly with the flue gas before entering the SCR tower. In the SCR tower, nitrogen oxides in the flue gas undergo an oxidation-reduction reaction with ammonia, removing the nitrogen oxides. The remaining raw material dust in the flue gas is intercepted and falls to the bottom of the tower before being discharged to the finished product bin. The flue gas after denitrification enters the high-temperature circulating fluidized bed equipment from the bottom.

8. The method for collaboratively treating multiple pollutants in high-temperature flue gas from a furnace according to claim 7, characterized in that: The denitrified flue gas entering the high-temperature circulating fluidized bed equipment is fully mixed with the added desulfurizer and the desulfurization ash in the return chute, first removing pollutants such as HCL, HF, and SO3 from the flue gas. The flue gas is then accelerated through the venturi tube and enters the fluidized bed, generating intense turbulence and mixing. Atomized water is sprayed at the outlet of the venturi tube to cool the flue gas, converting the reaction between SO2 and Ca(OH)2 into an ionic reaction that can be completed instantly, thus completing the efficient removal of SO2. The flue gas rises, and some particles flow back to the circulating fluidized bed to continue reacting. Some particles are carried out with the flue gas and pass through the high-temperature bag dust collector for gas-solid separation. The treated clean flue gas is discharged into the atmosphere through the induced draft fan and chimney.

9. A high-efficiency double-tower double-circulating fluidized bed desulfurization and dust removal method according to claim 8, characterized in that: The temperature of the high-temperature flue gas after combustion in the furnace is 250-400°C. After passing through the cyclone dust collector, the temperature drops by about 30°C, after passing through the SCR tower, the temperature drops by about 20°C, and after passing through the circulating fluidized bed equipment, the temperature drops by about 50-120°C. The treated flue gas is discharged into the atmosphere at a temperature 20°C higher than the dew point.

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