Suspended calcination method and device for reducing content of sulfur and COD (Chemical Oxygen Demand) in powder

Abstract

The invention discloses a suspension calcination method and a suspension calcination device for reducing the content of sulfur and COD (Chemical Oxygen Demand) in powder, which are used for reducing the content of sulfur and COD in a powder raw material. The calcining method comprises the following steps: step 10, preheating a powder raw material; step 20, feeding the preheated powder raw material into a roasting furnace, and carrying out suspension calcination; 30, powder obtained after suspension calcination in the roasting furnace and generated flue gas are fed into a fourth cyclone separator to be subjected to gas-solid separation, the separated powder is cooled through a cooling device to form a finished product, airflow is heated through the separated flue gas through a heat exchange device, preheating treatment is conducted on the powder raw material in the step 10 through the airflow, and the flue gas obtained after heat exchange utilization is used for recycling the powder raw material in the step 10. And discharging into the atmosphere after dust removal and desulfurization treatment.

Description

Technical Field

[0001] The present invention belongs to the field of powder industrial processing, and in particular relates to a suspension calcination method and device for reducing sulfur and COD contents in powder. Background Art

[0002] In existing suspension calcination, the powdered material, suspended within the furnace, experiences extremely high heat exchange rates with the high-temperature flue gas, resulting in more uniform heating. This allows for calcination at lower temperatures to produce products that meet product requirements. During calcination in the calciner, the flow of the powdered material is driven by the flue gas. Compared to rotary kilns and shaft kilns, this results in a smoother, more compact process, fewer moving equipment, and lower maintenance costs. In suspension calcination, the powdered material is typically preheated before being fed into the calciner for suspension calcination. Finally, the powdered material and the resulting flue gas are separated into solids and gases in a cyclone separator. The separated flue gas is then discharged into a preheating unit to heat the powdered material. This fully utilizes the heat source in the separated flue gas. However, for powders containing sulfur and COD, the flue gas during suspension calcination contains high concentrations of SO₂, resulting in high temperatures of 950-1050°C and a high concentration of SO₂. When flue gas flows into the preheating device, the SO₂ in the flue gas reacts with the powdered raw materials to form a reverse sulfur-fixing reaction, which is detrimental to their desulfurization. In the production of new calcium-silicon materials like glass, the raw material's COD (Chemical Oxygen Demand) affects the melting, clarification, and homogenization of the molten glass, thereby affecting glass quality. Therefore, the need to calcine powdered raw materials to reduce COD and provide high-quality raw materials is becoming increasingly urgent. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a suspension calcination method and device for reducing the sulfur and COD contents in powder, so as to reduce the sulfur and COD contents in the powder raw material.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions: In one aspect, the present invention provides a suspension calcination method for reducing sulfur and COD contents in powder, the method comprising: Step 10: preheating the powder raw material; Step 20: feeding the preheated powder raw material into a roasting furnace for suspension calcination; Step 30: The powder and the generated flue gas after suspension calcination in the roasting furnace are fed into the fourth cyclone separator for gas-solid separation. The separated powder is cooled by a cooling device to form a finished product. The separated flue gas is heated by a heat exchange device and the air flow is used to preheat the powder raw material in step 10.

[0005] As a preferred example, the separated flue gas is subjected to a heat exchange device to process the heated airflow, and the airflow is used to preheat the powder raw material in step 10, including: using a heat exchange device to exchange heat between the flue gas flowing into the tube side and the airflow flowing into the shell side, the airflow temperature is increased, the flue gas temperature is decreased, the airflow with increased temperature enters the preheating device to preheat the powder; the flue gas with decreased temperature does not enter the preheating device.

[0006] As a preferred example, the roasting furnace includes a main furnace and an auxiliary furnace, and the top of the main furnace and the top of the auxiliary furnace are connected by a connecting pipe; the lower part of the main furnace is provided with a first layer of burners and a second layer of burners arranged up and down, and the middle part is provided with a third layer of burners; the upper part of the auxiliary furnace is provided with a fourth layer of burners; the step 20 specifically includes: at the first layer of burners and the second layer of burners, a reducing combustion atmosphere is adopted for the powder, and the air coefficient is less than 1; at the third layer of burners and the fourth layer of burners, a weak oxidizing combustion atmosphere is adopted.

[0007] As a preferred example, in step 30, the separated powder is cooled by a cooling device to form a finished product, the powder temperature is reduced, and the air flow temperature is increased; according to demand, the air flow with increased temperature in the cooling device is used as combustion air and passed into the third layer burner and the fourth layer burner, and the excess air flow is passed into the circulating fan.

[0008] As a preferred example, the method further includes step 40, using a circulating fan to send the airflow discharged from the preheating device into the shell side of the heat exchange device to form an airflow circulation.

[0009] On the other hand, the present invention also provides a suspension calcination device for reducing the sulfur and COD content in powder, comprising a roasting furnace, a preheating device, a fourth cyclone separator, a cooling device, a primary heat exchanger, a circulating fan, and a first fan, wherein a tube side is provided in the inner cavity of the primary heat exchanger, a shell side is provided in the shell of the primary heat exchanger, and the shell side is provided with a first air inlet, a first air outlet and a first material outlet; the tube side is provided with a second air inlet, a second air outlet and a second material outlet; the material outlet of the preheating device is connected to the material inlet of the roasting furnace, and the outlet of the roasting furnace is connected to the inlet of the fourth cyclone separator. The air outlet of the fourth cyclone separator is connected to the second air inlet of the tube side of the first-stage heat exchanger, the second air outlet of the tube side is connected to the first fan through a pipeline, and the second material outlet is located at the bottom of the tube side; the material outlet of the fourth cyclone separator is connected to the inlet of the cooling device, the air outlet of the cooling device is connected to the combustion air inlet at the bottom of the roasting furnace, and the cooling device is provided with a finished product outlet; the air outlet of the preheating device is connected to the air inlet of the circulation fan, the air outlet of the circulation fan is connected to the first air inlet of the shell side of the first-stage heat exchanger, and the first air outlet of the shell side of the first-stage heat exchanger is connected to the air inlet of the preheating device.

[0010] As a preferred example, the roasting furnace includes a main furnace and an auxiliary furnace, the top of the main furnace and the top of the auxiliary furnace are connected by a connecting pipe, and the bottom of the auxiliary furnace is the outlet of the roasting furnace; in the inner cavity of the main furnace, a first layer of burners, a second layer of burners and a third layer of burners are provided from bottom to top; and a fourth layer of burners is provided in the inner cavity of the auxiliary furnace.

[0011] As a preferred example, the first layer of burners and the second layer of burners are located at the lower part of the main furnace, the third layer of burners is located in the middle part of the main furnace; the fourth layer of burners is located at the upper part of the auxiliary furnace; when working, the first layer of burners and the second layer of burners adopt a reducing combustion atmosphere, and the air coefficient is less than 1; the third layer of burners and the fourth layer of burners adopt a weak oxidizing combustion atmosphere.

[0012] As a preferred example, the preheating device includes a first cyclone separator, a second cyclone separator, and a third cyclone separator. The air outlet of the first cyclone separator is connected to the air inlet of the circulating fan, the material outlet of the first cyclone separator is connected to the first connecting air pipe, one end of the first connecting air pipe is connected to the inlet of the second cyclone separator, and the other end of the first connecting air pipe is connected to the air outlet of the third cyclone separator; the air outlet of the second cyclone separator is connected to the inlet of the first cyclone separator through the second connecting air pipe, and the powder material adding pipe is connected to the second connecting air pipe; the material outlet of the second cyclone separator is connected to the inlet of the third cyclone separator, and the material outlet of the third cyclone separator is connected to the material inlet of the roasting furnace; the air inlet of the third cyclone separator is connected to the first air outlet of the shell side of the first heat exchanger.

[0013] As a preferred example, the cooling device includes a sixth cyclone separator, a fifth cyclone separator, a seventh cyclone separator, a fluidized bed cooler, a second fan and a finished product conveying device. The material outlet of the fourth cyclone separator is connected to the third connecting air pipe, one end of the third connecting air pipe is connected to the outlet of the sixth cyclone separator, and the other end of the third connecting air pipe is connected to the inlet of the fifth cyclone separator. The air outlet of the fifth cyclone separator is respectively connected to the combustion air inlet at the bottom of the roasting furnace, the third layer burner, the fourth layer burner, and the inlet of the circulating fan. The material outlet of the fifth cyclone separator is connected to the fourth connecting air pipe, one end of the fourth connecting air pipe is connected to the air inlet of the sixth cyclone separator, and the other end of the fourth connecting air pipe is connected to the air outlet of the seventh cyclone separator. The material outlet of the sixth cyclone separator is connected to the material inlet of the fluidized bed cooler; the air outlet of the second fan is connected to the air inlet of the fluidized bed cooler, and the gas-solid outlet of the fluidized bed cooler is connected to the gas-solid inlet of the seventh cyclone separator; the material outlet of the seventh cyclone separator is opposite to the finished product conveying device.

[0014] As a preferred example, the suspension calcining device further comprises a first vertical mill device, which is connected to the air outlet of the circulating fan, and the air volume of the circulating fan entering the first vertical mill device and the primary heat exchanger is controlled by the valve opening.

[0015] As a preferred example, the suspended calcination device also includes a secondary heat exchanger, a second vertical mill device and a third fan. The secondary heat exchanger is located between the primary heat exchanger and the first fan. The inner cavity of the secondary heat exchanger is provided with a tube side, the shell is provided with a shell side, the shell side is provided with a third air inlet and a third air outlet, and the tube side is provided with a fourth air inlet, a fourth air outlet and a fourth material outlet; the third air inlet of the shell side of the secondary heat exchanger is connected to the third fan, and the third air outlet of the shell side of the secondary heat exchanger is connected to the air inlet of the second vertical mill device; the fourth air inlet of the secondary heat exchanger tube side is connected to the second air outlet of the primary heat exchanger tube side through a pipeline, and the fourth air outlet of the secondary heat exchanger tube side is connected to the air inlet of the first fan.

[0016] As a preferred example, the suspended calcination device also includes a kiln tail dust collector, a kiln tail dust removal fan, a wet desulfurization device and a dust conveying device. The air outlet of the first fan is connected to the air inlet of the kiln tail dust collector, the discharge port of the kiln tail dust collector is opposite to the dust conveying device, the air outlet of the kiln tail dust collector is connected to the air inlet of the kiln tail dust removal fan, and the air outlet of the kiln tail dust removal fan is connected to the air inlet of the wet desulfurization device.

[0017] As a preferred example, the fourth material outlet of the secondary heat exchanger tube side and the first material outlet of the primary heat exchanger shell side are connected to the feed inlet of the dust conveying device through the main pipeline, and the second material outlet of the primary heat exchanger tube side is connected to two branch pipes containing control valves, one of which is connected to the main pipeline, and the other is connected to the third connecting air pipe.

[0018] Compared with the prior art, the suspension calcination method and apparatus of the present invention can effectively reduce the sulfur and COD content in powder raw materials. The method includes step 10, preheating the powder raw materials; step 20, feeding the preheated powder raw materials into a roasting furnace for suspension calcination; step 30, feeding the powder and the generated flue gas after suspension calcination in the roasting furnace into a fourth cyclone separator for gas-solid separation, the separated powder is cooled by a cooling device to form a finished product, and the separated flue gas is heated by a heat exchange device to form an airflow, and the airflow is used to preheat the powder raw materials in step 10. The method exchanges heat between the high-temperature flue gas separated by the fourth cyclone separator and another airflow in the heat exchange device. The airflow absorbs heat from the high-temperature flue gas and heats up, and the high-temperature flue gas releases heat and cools down. The heated airflow enters the preheating device to preheat the powder raw materials. The high-temperature flue gas does not enter the preheating device. This not only utilizes the high temperature heat of the high temperature flue gas, but also avoids the sulfur in the high temperature flue gas from undergoing solid sulfur adsorption reaction on the powder raw materials in the preheating device, effectively reducing the sulfur and COD in the powder raw materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a structural diagram of an embodiment of the present invention.

[0020] The figure includes: roasting furnace 1, main furnace 101, auxiliary furnace 102, first layer burner 103, second layer burner 104, third layer burner 105, fourth layer burner 106, preheating device 2, first cyclone separator 201, second cyclone separator 202, third cyclone separator 203, fourth cyclone separator 3, cooling device 4, fifth cyclone separator 401, sixth cyclone separator 402, seventh cyclone separator 403, fluidized bed cooler 404, second fan 405, primary heat exchanger 5. First air inlet 51, first air outlet 52, first material outlet 53, second air inlet 54, second air outlet 55, second material outlet 56, circulating fan 6, first fan 7, first vertical mill device 8, secondary heat exchanger 9, third air inlet 91, third air outlet 92, fourth air inlet 93, fourth air outlet 94, fourth material outlet 95, second vertical mill device 10, kiln tail dust collector 11, kiln tail dust removal fan 12, wet desulfurization device 13, dust conveying device 14, third fan 15. DETAILED DESCRIPTION

[0021] The technical solution of the present invention is described in detail below with reference to the accompanying drawings.

[0022] In the present invention, powder is suspended and calcined in a roasting furnace 1. The powder contains sulfur and COD. For example, the powder may be blast furnace slag powder, silica sand powder, dolomite powder, limestone powder, feldspar powder, etc. When used as raw materials for high-performance calcium silicate materials, these powders have very stringent requirements for sulfur and COD content.

[0023] The embodiment of the present invention provides a suspension calcination method for reducing sulfur and COD content in powder, comprising: Step 10: preheating the powder raw material; Step 20: feeding the preheated powder raw material into the roasting furnace 1 for suspension calcination; In step 30, the powder and the generated flue gas after suspension calcination in the roasting furnace 1 are fed into the fourth cyclone separator 3 for gas-solid separation. The separated powder is cooled by a cooling device to form a finished product. The separated flue gas is heated by a heat exchange device and the powder raw material in step 10 is preheated by the air flow.

[0024] Because the powder contains sulfur and COD, in step 30 of the above method, the fourth cyclone separator 3 performs gas-solid separation on the powder and flue gas discharged from the roasting furnace 1. Taking blast furnace slag powder as an example, the temperature of the powder and flue gas discharged from the roasting furnace 1 can reach as high as 1100°C. The flue gas contains SO2, which is generated by the suspended calcination of the powder in the roasting furnace 1. Since the flue gas contains SO2, if it is directly returned to the preheating device to preheat the powder raw material, the SO2 in the flue gas will undergo a solid sulfur adsorption reaction with the powder raw material, and the sulfur will be circulated and enriched in the powder raw material. The method of this embodiment exchanges heat between the high-temperature flue gas separated by the fourth cyclone separator 3 and another airflow in a heat exchange device. The airflow absorbs heat from the high-temperature flue gas and heats up, while the high-temperature flue gas releases heat and cools down. The heated airflow enters the preheating device to preheat the powder raw material. The high-temperature flue gas does not enter the preheating device. This not only utilizes the high temperature heat of the high temperature flue gas, but also avoids the sulfur in the high temperature flue gas from undergoing a solid sulfur adsorption reaction on the powder raw materials in the preheating device, effectively reducing the sulfur in the powder raw materials.

[0025] Preferably, in step 30, the separated flue gas is heated by a heat exchanger, and the airflow is used to preheat the powder raw material in step 10. This includes: using the heat exchanger to exchange heat between the flue gas flowing into the tube side and the airflow flowing into the shell side, increasing the airflow temperature and decreasing the flue gas temperature. The heated airflow enters the preheating device to preheat the powder; the decreased flue gas does not enter the preheating device. In this preferred embodiment, the heat exchanger can be a shell-and-tube heat exchanger, comprising a shell side and a tube side. The flue gas flowing into the tube side and the airflow flowing into the shell side do not directly contact each other; heat exchange occurs only during the flow of the flue gas. The airflow absorbs heat from the flue gas, increasing its temperature. The flue gas releases heat, decreasing its temperature. In one embodiment, the high-temperature flue gas has a temperature of approximately 950°C before entering the heat exchanger and a temperature of approximately 750°C when it exits the heat exchanger. The airflow (from the circulating fan) has a temperature of approximately 300°C before entering the heat exchanger and a temperature of approximately 550°C when it exits the heat exchanger. The flue gas with reduced temperature does not enter the preheating device, but can be passed into the kiln tail dust collector through the first fan for flue gas dust removal treatment.

[0026] To reduce the COD content in the powder, the roasting furnace 1 preferably includes a main furnace 101 and a secondary furnace 102, with the tops of the main furnace 101 and the secondary furnace 102 connected by a connecting pipe. The lower portion of the main furnace 101 is provided with a first layer of burners 103 and a second layer of burners 104 arranged vertically, and a third layer of burners 105 is provided in the middle portion. The upper portion of the secondary furnace 102 is provided with a fourth layer of burners 106. Step 20 specifically includes: adopting a reducing combustion atmosphere for the powder at the first layer of burners 103 and the second layer of burners 104, with an air coefficient of less than 1; adopting a weakly oxidizing combustion atmosphere at the third layer of burners 105 and the fourth layer of burners 106, and introducing sufficient combustion-supporting air to completely burn the fuel supplied by the third layer of burners 105 and the fourth layer of burners 106, and to completely burn the remaining fuel in the ascending flue gas in the roasting furnace 1.

[0027] In this preferred embodiment, the roasting furnace 1 is divided into a main furnace 101 and a secondary furnace 102. Four layers of burners are installed in the main furnace 101 and the secondary furnace 102. The first layer of burners 103 and the second layer of burners 104 are located in the lower portion of the main furnace 101, the third layer of burners 105 is located in the middle portion of the main furnace 101, and the fourth layer of burners 106 is located in the upper portion of the secondary furnace 102. The burners introduce dye into the roasting furnace 1 and, under the action of combustion-supporting air, burn the powder in the roasting furnace 1, causing the sulfides in the powder to decompose and produce SO2, CO2, and oxides. The powdered material enters the main furnace 101 of the roasting furnace 1, flows upward from the bottom, and then enters the secondary furnace 102 through a connecting pipe. In the secondary furnace 102, the powdered material flows downward from the top. The powdered material enters the main furnace 101 of the roasting furnace 1, flows upward from the bottom, and then burns in the first layer of burners 103 and then in the second layer of burners 104. A reducing combustion atmosphere is applied to the powder at the first and second burners 103, 104, with an air coefficient less than 1. The air coefficient refers to the ratio of the actual amount of air supplied for fuel combustion to the theoretical air quantity (i.e., the minimum amount of air required for complete fuel combustion). Insufficient combustion air is supplied to the first and second burners 103, 104. In a reducing atmosphere of CO or H₂, the reducing combustion atmosphere consumes O₂, driving the sulfate reaction in the powder forward, producing SO₂, CO₂, and oxides. After passing through the first and second burners 103, 104, the powder continues upward, passing sequentially through the third and fourth burners 105, 106. A weakly oxidizing combustion atmosphere is applied to these burners, with sufficient combustion air supplied to completely combust the fuel supplied by these burners 105, 106, and any remaining fuel in the ascending flue gas from the roasting furnace 1. In an oxidizing atmosphere, the reaction temperature rises, and the third and fourth burners 105 and 106 further promote the sulfate reaction, generating SO₂, CO₂, and oxides. The sulfur in the powder is oxidized through four combustion stages in calciner 1. This calcination reduces the sulfur content in the powder. The flue gas contains SO₂. Simultaneously, as the powder is calcined in the high-temperature environment of calciner 1, the organic matter contained therein is also calcined, reducing the COD.

[0028] Preferably, in step 30, the separated powder is cooled in a cooling device to form a finished product, reducing the powder temperature and increasing the airflow temperature. As needed, the heated airflow in the cooling device is used as combustion air and passed into the third-layer burner 105 and the fourth-layer burner 106. Excess airflow is fed into the circulating fan 6. Under the influence of the fan, external airflow is introduced into the cooling device. The airflow exchanges heat with the high-temperature powder separated by the cooling device and the fourth cyclone separator 3, cooling the high-temperature powder and increasing the airflow temperature. A portion of the heated airflow is passed into the combustion air inlet at the bottom of the roasting furnace 1, providing combustion air for the first-layer burners 103 and the second-layer burners 104. Another portion is passed into the third-layer burners 105 and the fourth-layer burners 106, providing sufficient combustion air for the burners. Any excess airflow is passed into the circulating fan 6. The flow direction and volume of the airflow are controlled by a valve according to process requirements. This effectively utilizes the heated airflow in the cooling device and avoids the waste of heat and environmental pollution caused by the discharge of high-temperature air.

[0029] Preferably, the method further comprises step 40, wherein the circulating fan 6 is used to feed the airflow discharged from the preheating device into the shell side of the heat exchange device, thereby forming an airflow circulation. After the airflow exchanges heat with the high-temperature flue gas in the heat exchange device, its temperature increases. The heated airflow is fed into the preheating device, where it comes into contact with the powder material in the preheating device. During its flow, the airflow heats the powder material. As the airflow flows out of the preheating device, its temperature decreases. Under the action of the circulating fan 6, the cooled airflow is fed back into the shell side of the heat exchange device, where it exchanges heat with the high-temperature flue gas in the tube side. The heated airflow is then fed into the preheating device, thereby forming an airflow circulation flow. The airflow circulates between the preheating device, the circulating fan 6, and the heat exchange device. In the heat exchange device, the airflow exchanges heat with the high-temperature flue gas, thereby increasing its temperature. In the preheating device, the airflow drives the powder material to flow, heating it and cooling it.

[0030] like Figure 1As shown, an embodiment of the present invention further provides a suspension calcination device for reducing the sulfur and COD content in powder, comprising a calciner 1, a preheating device 2, a fourth cyclone separator 3, a cooling device 4, a primary heat exchanger 5, a circulating fan 6, and a first fan 7. A tube side is provided in the inner cavity of the primary heat exchanger 5, and a shell side is provided in the shell side. The shell side is provided with a first air inlet 51, a first air outlet 52, and a first material outlet 53; the tube side is provided with a second air inlet 54, a second air outlet 55, and a second material outlet 56. The material outlet of the preheating device 2 is connected to the material inlet of the roasting furnace 1, the outlet of the roasting furnace 1 is connected to the inlet of the fourth cyclone separator 3, the air outlet of the fourth cyclone separator 3 is connected to the second air inlet 54 of the tube side of the first-stage heat exchanger 5, the second air outlet 55 of the tube side is connected to the first fan 7 through a pipeline, and the second material outlet 56 is located at the bottom of the tube side; the material outlet of the fourth cyclone separator 3 is connected to the inlet of the cooling device 4, the air outlet of the cooling device 4 is connected to the combustion air inlet at the bottom of the roasting furnace 1, and the cooling device 4 is provided with a finished product outlet; the air outlet of the preheating device 2 is connected to the air inlet of the circulating fan 6, the air outlet of the circulating fan 6 is connected to the first air inlet 51 of the shell side of the first-stage heat exchanger 5, and the first air outlet 52 of the shell side of the first-stage heat exchanger 5 is connected to the air inlet of the preheating device 2.

[0031] In the apparatus of the above embodiment, the roasting furnace 1 has sufficient reaction space and residence time for the powder to ensure proper reaction. The space and calcination time of the roasting furnace 1 meet the requirements for removing sulfur and COD from the powder. In this apparatus, the powder feedstock is preheated in the preheating device 2. After preheating, the powder feedstock is fed into the roasting furnace 1 for suspension calcination. The suspended calcined powder and the resulting flue gas are fed into the fourth cyclone separator 3 for gas-solid separation. The separated powder is cooled by the cooling device 4 to form the finished product. The separated flue gas exchanges heat with the airflow through the primary heat exchanger 5, increasing the airflow temperature and reducing the flue gas temperature. The heated airflow is used to preheat the powder feedstock in the preheating device. The cooled flue gas undergoes dust removal and desulfurization before being discharged. The airflow is circulated between the preheating device and the primary heat exchanger 5 using power provided by the circulation fan 6. The flue gas discharged from the fourth cyclone separator 3 is directed to the primary heat exchanger 5 using power provided by the first fan 7.

[0032] In the apparatus of the above embodiment, the heat required for powder calcination is provided by the combustion of coal gas (natural gas and blast furnace gas). After calcination and decomposition, the powder is transported with the airflow to the fourth cyclone separator 3 for solid-gas separation. The separated product then enters the cooling device. Since the separated flue gas has a high temperature of 950-1050°C and contains a high concentration of SO₂, if it were to enter the preheating device directly, the SO₂ in the flue gas would react with the powder feedstock to form a reverse sulfur-binding reaction, which would be detrimental to the desulfurization of the powder. Therefore, in this embodiment, the flue gas from the outlet of the fourth cyclone separator 3 is introduced into the primary heat exchanger 5 for heat recovery.

[0033] In the device of the above embodiment, in the first-stage heat exchanger 5, the high-temperature flue gas containing SO2 discharged from the fourth cyclone separator 3 serves as the heat medium. A portion of the mixed airflow of the hot air separated by the preheating device and the hot air separated by the cooling device serves as the refrigerant. The heat medium and the refrigerant exchange heat in the first-stage heat exchanger 5. Before the heat medium enters the first-stage heat exchanger 5, a portion of cold air can be added to make the flue gas temperature ≤950°C. After being heated by the first-stage heat exchanger 5, the refrigerant enters the preheating device to heat the powder raw material. A portion of the mixed airflow of the hot air separated by the preheating device and the hot air separated by the cooling device serves as the refrigerant and enters the first-stage heat exchanger 5 again, and the cycle continues. The temperature of the heat medium decreases after passing through the first-stage heat exchanger 5, but the temperature is still as high as 600-650°C. This high-temperature flue gas serves as the heat medium for the second-stage heat exchanger 9.

[0034] Preferably, the roasting furnace 1 includes a main furnace 101 and a secondary furnace 102. The tops of the main furnace 101 and the secondary furnace 102 are connected by a connecting pipe, and the bottom of the secondary furnace 102 serves as the outlet of the roasting furnace 1. The main furnace 101 is taller than the secondary furnace 102. The connecting pipe can be a gooseneck tube. Compared to using only the main furnace 101, this preferred embodiment uses a main furnace 101 and secondary furnace 102 structure, which increases the furnace capacity, prolongs the calcination and decomposition reaction time, and is more conducive to the full reaction of the powder. The inner cavity of the main furnace 101 is provided with a first layer of burners 103, a second layer of burners 104, and a third layer of burners 105 from bottom to top; the inner cavity of the secondary furnace 102 is provided with a fourth layer of burners 106. Preferably, the first layer of burners 103 and the second layer of burners 104 are located at the bottom of the main furnace 101, the third layer of burners 105 is located in the middle of the main furnace 101, and the fourth layer of burners 106 is located at the top of the secondary furnace 102. During operation, the first layer burner 103 and the second layer burner 104 adopt a reducing combustion atmosphere with an air coefficient of less than 1; the third layer burner 105 and the fourth layer burner 106 adopt a weak oxidizing combustion atmosphere.

[0035] In this preferred embodiment, the powdered raw material enters the main furnace 101 of the roasting furnace 1, flows upward from bottom to top, and then enters the auxiliary furnace 102 through a connecting pipe. In the auxiliary furnace 102, the powdered raw material flows downward from top to bottom. The powdered raw material enters the main furnace 101 of the roasting furnace 1 and flows upward from bottom to top, first undergoing combustion reactions in the first-layer burners 103 and then in the second-layer burners 104. A reducing combustion atmosphere with an air coefficient of less than 1 is applied to the powder in the first and second-layer burners 103, 104. This prevents insufficient combustion-supporting air from entering the first and second-layer burners 103, 104. The reducing combustion atmosphere consumes O2, driving the sulfate reaction in the powder forward, producing SO2, CO2, and oxides. After passing through the first and second-layer burners 103, 104, the powder continues upward, passing through the third and fourth-layer burners 105, 106, respectively. A weak oxidizing combustion atmosphere is adopted at the third layer burner 105 and the fourth layer burner 106, and sufficient combustion-supporting air is introduced, which can completely burn the fuel supplied by the third layer burner 105 and the fourth layer burner 106, and can completely burn the remaining fuel in the ascending flue gas in the roasting furnace 1.

[0036] Preferably, the preheating device 2 includes a first cyclone separator 201, a second cyclone separator 202, and a third cyclone separator 203. The air outlet of the first cyclone separator 201 is connected to the air inlet of the circulating fan 6, the material outlet of the first cyclone separator 201 is connected to the first connecting air pipe, one end of the first connecting air pipe is connected to the inlet of the second cyclone separator 202, and the other end of the first connecting air pipe is connected to the air outlet of the third cyclone separator 203; the air outlet of the second cyclone separator 202 is connected to the inlet of the first cyclone separator 201 through the second connecting air pipe, and the powder material adding pipe is connected to the second connecting air pipe; the material outlet of the second cyclone separator 202 is connected to the inlet of the third cyclone separator 203, and the material outlet of the third cyclone separator 203 is connected to the material inlet of the roasting furnace 1; the air inlet of the third cyclone separator 203 is connected to the first air outlet 52 of the shell side of the first-stage heat exchanger 6.

[0037] In this preferred embodiment, three cyclone separators are used to preheat the powder raw materials. The airflow flowing out of the air outlet of the second cyclone separator 202 enters the first cyclone separator 201 through the second connecting air pipe. During this process, the powder material adding pipe adds powder raw materials to the second connecting air pipe. The powder raw materials flow into the first cyclone separator 201 along with the airflow in the second connecting air pipe, and the powder raw materials are heated during the flow. The first cyclone separator 201 can be equipped with two cyclone separators connected in parallel to increase work efficiency. The first cyclone separator 201 separates the powder raw material and the airflow, and the separated airflow enters the air inlet of the circulating fan 6, and the separated powder raw materials are fed downward into the first connecting air pipe. The airflow flowing out of the air outlet of the third cyclone separator 203 flows into the second cyclone separator 202 through the first connecting air pipe. Since the powdered material separated by the first cyclone 201 is fed into the first connecting air pipe, it flows along the airflow in the first connecting air pipe to the second cyclone 202. During this flow, the airflow further heats the powdered material, raising its temperature. The second cyclone 202 separates the powdered material and the airflow. The separated airflow flows through the second connecting air pipe to the first cyclone 201, where it is fed into the third cyclone 203. In the third cyclone 203, the heated airflow flows into the third cyclone 203, heating the powdered material for a third time, raising its temperature. The heated powdered material is then fed into the roasting furnace 1 through the material outlet of the third cyclone 203 for suspension calcination, completing the preheating of the powdered material before being fed into the roasting furnace 1. The airflow separated by the third cyclone 203 flows through the first connecting air pipe to the second cyclone 202. The flow of gas through the three cyclones achieves multiple preheating of the powdered raw material. The air inlet of the third cyclone 203 is connected to the first air outlet 52 of the shell side of the first heat exchanger 5. The air outlet of the first cyclone 201 is connected to the first air inlet 51 of the shell side of the first heat exchanger 5 via the circulation fan 6. Thus, powered by the circulation fan 6, the airflow circulates between the first cyclone 201, the second cyclone 202, the third cyclone 203, and the shell side of the first heat exchanger 5. Simultaneously, the airflow exchanges heat in the first heat exchanger 5, raising its temperature. The heated airflow then flows through the first cyclone 201, the second cyclone 202, and the third cyclone 203, heating the powdered raw material and lowering its temperature. The cooled airflow then recirculates to the first heat exchanger 5 for further heat exchange and temperature increase, continuing the cycle.

[0038] In the preheating device of the preferred embodiment, the heat medium comes from the hot air of the first-stage heat exchanger 5. Taking blast furnace slag powder raw material as an example, the blast furnace slag powder raw material flows from top to bottom with the hot air flow. During the heat exchange process with the hot air flow, the temperature gradually increases. After being separated by the third cyclone separator 203, the blast furnace slag powder raw material enters the roasting furnace 1 for high-temperature roasting. In the preheating device, the hot air flow flows from bottom to top during the heat exchange process with the blast furnace slag powder raw material, and the temperature gradually decreases. Finally, it is discharged from the outlet of the first cyclone separator 201. The cyclone preheating method adopted in the preferred embodiment has the effect of fully dispersing and mixing the gas and solid phases, rapidly exchanging heat, and efficiently separating them.

[0039] Preferably, the cooling device 4 includes a sixth cyclone separator 402, a fifth cyclone separator 401, a seventh cyclone separator 403, a fluidized bed cooler 404, a second fan 405 and a finished product conveying device, the material outlet of the fourth cyclone separator 3 is connected to the third connecting air pipe, one end of the third connecting air pipe is connected to the outlet of the sixth cyclone separator 402, the other end of the third connecting air pipe is connected to the inlet of the fifth cyclone separator 401, the air outlet of the fifth cyclone separator 401 is respectively connected to the combustion air inlet located at the bottom of the roasting furnace 1, the third layer burner 105, the fourth layer burner 106, the circulating fan 6, the material outlet of the fifth cyclone separator 401 is connected to the fourth connecting air pipe, one end of the fourth connecting air pipe is connected to the air inlet of the sixth cyclone separator 402, the other end of the fourth connecting air pipe is connected to the air outlet of the seventh cyclone separator 403, the material outlet of the sixth cyclone separator 402 is connected to the material inlet of the fluidized bed cooler 404; the air outlet of the second fan 405 is connected to the air inlet of the fluidized bed cooler 404, the gas-solid outlet of the fluidized bed cooler 404 is connected to the gas-solid inlet of the seventh cyclone separator 403; the material outlet of the seventh cyclone separator 403 is opposite to the finished product conveying device.

[0040] In this preferred embodiment, the second fan 405 draws in external air to form an airflow. The airflow flows in the cooling device 4. This airflow does not react with the powder material in the roasting furnace 1 and does not contain sulfur. The powder separated by the fourth cyclone separator 3 is fed into the third connecting air pipe from its material outlet. The airflow in the third connecting air pipe is the airflow flowing from the sixth cyclone separator 402 to the fifth cyclone separator 401. The powder separated by the fourth cyclone separator 3 flows from the third connecting air pipe to the fifth cyclone separator 401 along with the airflow. During the flow, the airflow absorbs heat from the powder to increase its temperature, and the powder releases heat to cool down. In the fifth cyclone separator 401, part of the separated gas flows into the roasting furnace 1 as combustion air to supply combustion air to the first layer burner 103 and the second layer burner 104; part of it is used as combustion air to supply combustion air to the third layer burner 105 and the fourth layer burner 106; and the remaining part flows into the circulation fan 6. Since this airflow does not contain sulfur, it passes through the circulating fan 6 and enters the shell side of the primary heat exchanger 5, where it participates in preheating the powder raw material and does not produce a solid sulfur adsorption reaction. In the fifth cyclone separator 401, the separated powder is fed into the fourth connecting air pipe.

[0041] The airflow in the fourth connecting air pipe flows from the seventh cyclone separator 403 to the sixth cyclone separator 402. The powder separated in the fifth cyclone separator 401 flows along with the airflow in the fourth connecting air pipe and flows to the sixth cyclone separator 402. During the flow, the airflow absorbs heat from the powder, increasing its temperature, while the powder releases heat, decreasing its temperature. In the sixth cyclone separator 402, the separated airflow enters the third connecting air pipe, and the separated powder enters the fluidized bed cooler 404. The airflow drawn from the outside by the second fan 405 flows into the fluidized bed cooler 404. After the powder is fully mixed and heat-exchanged with the fluidizing air and the side air in the fluidized bed cooler 404, the powder is further cooled and flows along with the airflow into the seventh cyclone separator 403. The powder separated in the seventh cyclone separator 403 is the finished product, and the separated airflow flows into the fourth connecting air pipe. Powered by the second blower 405, the air flows into the cooling device 4, where it cools the high-temperature powder separated from the fourth cyclone separator 3 multiple times, ultimately forming a finished product. During the cooling process, the heated airflow is used to provide combustion air for the first-layer burners 103, the second-layer burners 104, the third-layer burners 105, and the fourth-layer burners 106, and also serves as part of the airflow for the preheating device.

[0042] In this preferred embodiment, after the powder is fully mixed and heat-exchanged with the fluidizing air and the sleeting air in the fluidized bed cooler 404, the gas-solid mixture enters the seventh cyclone separator 403 for separation, and the separated powder enters the finished product conveying device.

[0043] In this preferred embodiment, before the powder is conveyed out of the cooling device as a finished product, a second blower 405 draws ambient air at room temperature into the fluidized bed cooler 404 to exchange heat with the powder, further lowering the powder temperature. The combustion-supporting air used in the roasting furnace 1 utilizes heat exchanged air from the cooling device, thereby improving energy efficiency.

[0044] In this preferred example, in the cooling device, the high-temperature air after heat exchange with the powder has two flow directions after separation by the fifth cyclone separator 401. One of the flow directions is: flowing to the bottom (buffer smoke chamber), middle and upper parts of the roasting furnace, serving as the combustion air of the roasting furnace, and adjusting the air flow entering different areas of the roasting furnace according to the air coefficient requirements of different areas in the roasting furnace; the other flow direction is: the excess air flow is mixed with the air flow at the outlet of the first cyclone separator 201 to form a mixed air flow, which enters the circulating fan 6 to participate in the circulation and replacement of the preheated circulating air. A part of it is used as the heat medium of the first-stage heat exchanger 5, and the excess part is sent to industrial equipment, such as the first vertical mill device 8, as a drying heat source to realize waste heat utilization.

[0045] Preferably, the suspension calcining apparatus further includes a first vertical mill 8 , which is connected to the air outlet of a circulating fan 6 . The air volume flowing from the circulating fan 6 into the first vertical mill 8 and the primary heat exchanger 5 is controlled by the valve opening. A valve is used to distribute air between the first vertical mill 8 and the primary heat exchanger 5 . After the air volume required by the primary heat exchanger 5 is met, the circulating fan 6 discharges the excess air into the first vertical mill 8 . This fully utilizes the temperature of the airflow, providing a greater heat source for the industrial equipment.

[0046] In the preferred embodiment described above, the air discharged from the outlet of the first cyclone separator 201 mixes with excess hot air from the cooling device and enters the circulating fan 6. After being pressurized by the circulating fan 6, a portion of the airflow enters the primary heat exchanger 6 for heat exchange and temperature increase, serving as the heat medium for the preheating device. This prevents solid sulfur contamination of the powdered raw material and enables the recycling of the hot air. The remaining excess airflow is then delivered to industrial equipment as a heat source, such as the hot air inlet duct interface of the first vertical mill 8, for drying. In the preheating device, the circulating air is powered by the variable-frequency-controlled circulating fan 6.

[0047] To further reduce the temperature of the flue gas separated from the fourth cyclone separator 3, the suspension calcining device preferably further includes a secondary heat exchanger 9, a second vertical mill 10, and a third fan 15. The secondary heat exchanger 9 is located between the primary heat exchanger 5 and the first fan 7. The secondary heat exchanger 9 has a tube side in its inner cavity, a shell side in its housing, a third air inlet 91 and a third air outlet 92 in the shell side, and a fourth air inlet 93, a fourth air outlet 94, and a fourth material outlet 95 in the tube side. The third air inlet 91 of the shell side of the secondary heat exchanger 9 is connected to the third fan 15, and the third air outlet 92 of the shell side of the secondary heat exchanger 9 is connected to the air inlet of the second vertical mill 10. The fourth air inlet 93 of the tube side of the secondary heat exchanger 9 is connected to the second air outlet 55 of the tube side of the primary heat exchanger 5 via a pipeline, and the fourth air outlet 94 of the tube side of the secondary heat exchanger 9 is connected to the air inlet of the first fan 7.

[0048] In this preferred embodiment, the primary heat exchanger 5 and the secondary heat exchanger 9 can be shell-and-tube heat exchangers. The flow surfaces of both the primary heat exchanger 5 and the secondary heat exchanger 9 are coated with refractory material. The tube bundle of the primary heat exchanger 5 is made of 310S material, while the tube bundle of the secondary heat exchanger 9 is made of 321 material, meeting the requirements for operating with high-temperature, high-sulfur flue gas. The third fan 15 draws ambient air into the third air inlet 91 of the secondary heat exchanger 9, into the shell side of the secondary heat exchanger 9, and out through the third air outlet 92 of the secondary heat exchanger 9 into the second vertical mill 10, providing a heat source for the second vertical mill 10. The first fan 7 provides power to draw flue gas from the tube side of the primary heat exchanger 5 (i.e., the flue gas separated by the fourth cyclone separator 3) into the tube side of the secondary heat exchanger 9. The flue gas enters through the fourth air inlet 93 of the secondary heat exchanger 9 tube side and exits through the fourth air outlet 94 of the secondary heat exchanger 9 tube side, entering the first fan 7. In this process, the flue gas is cooled for the first time in the tube pass of the first-stage heat exchanger 5, and then flows into the tube pass of the second-stage heat exchanger 9 to be cooled again.

[0049] The sub-high temperature flue gas discharged from the primary heat exchanger 5 serves as a heat medium and enters the secondary heat exchanger 9. The refrigerant of the secondary heat exchanger 9 is the ambient air blown in by the third fan 12 with variable frequency speed regulation. The heat medium and the refrigerant exchange heat in the secondary heat exchanger 9. Taking blast furnace slag powder as an example, in the primary heat exchanger 5, the temperature of the heat medium is 950°C before entering the primary heat exchanger 5. After the heat medium is cooled by the primary heat exchanger 5, the temperature is about 550°C. In the secondary heat exchanger 9, the refrigerant is heated to a clean hot air temperature of 350-400°C, which can be used as a drying heat source for other industrial equipment. After heat exchange, the flue gas serving as the heat medium has its temperature reduced to about 220°C and is discharged through the first fan 7 to the subsequent flue gas dust removal and desulfurization device.

[0050] Preferably, the suspended calcination device further includes a kiln tail dust collector 11, a kiln tail dust removal fan 12, a wet desulfurization device 13 and a dust conveying device 14, the air outlet of the first fan 7 is connected to the air inlet of the kiln tail dust collector 11, the discharge port of the kiln tail dust collector 11 is connected to the feed port of the dust conveying device 14, the air outlet of the kiln tail dust collector 11 is connected to the air inlet of the kiln tail dust removal fan 12, and the air outlet of the kiln tail dust removal fan 12 is connected to the air inlet of the wet desulfurization device 13.

[0051] In this preferred embodiment, the first fan 7 provides power to discharge the flue gas, which has been cooled in the secondary heat exchanger 9, into the kiln tail dust collector 11. In the kiln tail dust collector 11, the flue gas is subjected to dust removal. The dust-removed airflow, driven by the kiln tail dust removal fan 12, flows out of the kiln tail dust collector 11 and enters the wet desulfurization device 13 for desulfurization. The desulfurized clean air is discharged from the wet desulfurization device 13. The collected dust falls into the dust conveying device 14. This device performs two heat exchange and cooling operations on the high-temperature flue gas separated from the fourth cyclone separator 3 (flowing out of the roasting furnace 1 and containing sulfur), and then performs dust removal and desulfurization to meet the requirements for discharge to the outside.

[0052] Preferably, the fourth material outlet 95 of the secondary heat exchanger 9 tube side and the first material outlet of the primary heat exchanger 5 shell side are connected to the feed port of the dust conveying device 14 through the main pipeline, and the second material outlet 56 of the primary heat exchanger 5 tube side is connected to two branch pipes containing control valves, one of which is connected to the main pipeline, and the other is connected to the third connecting air pipe.

[0053] In this preferred embodiment, the high-temperature flue gas and powder flowing out of the roasting furnace 1 enter the fourth cyclone separator 3. The flue gas contains sulfur and is mixed with a small amount of powder. When the high-temperature flue gas separated by the fourth cyclone separator 3 releases heat through the first-stage heat exchanger 5, some powder will be deposited in the pipe process. If the quality of the powder meets the quality requirements of the finished product, then adjust the control valve and connect the powder to the third connecting air pipe through another branch pipe, so that this part of the powder and the powder in the cooling device flow together to cool down and be output as the finished product. If the quality of the powder does not meet the quality requirements of the finished product, then adjust the control valve and connect the powder to the main pipeline through a branch pipe, and it will be collected by the dust conveying device 14.

[0054] Ash removal devices are installed in both the tube bundle box and the outlet box of the primary heat exchanger 5. The ash in the tube bundle box comes from the settled ash of the refrigerant and is primarily composed of undesulfurized powder raw materials. It is discharged through the first material outlet 53 and then enters the powder raw material bin as raw material. The ash in the outlet box comes from the settled ash of the heat medium and is primarily composed of desulfurized powder (finished product). However, a reverse reaction occurs during the descent of the flue gas within the primary heat exchanger 5. Therefore, the ash in the outlet box of the primary heat exchanger 5 is split into two paths by a splitting valve: ① If the ash is found to be a qualified finished product after commissioning, it enters the discharge pipe of the fourth cyclone separator 3 through the second material outlet 56 and enters the cooling device together. ② If the ash is found to be unqualified after commissioning, it is discharged through the second material outlet 56 and then enters the powder raw material bin as raw material.

[0055] As the air flows through the preheating device, the flue gas separated from the first cyclone separator 201 may contain powdered raw materials. After the flue gas passes through the circulating fan 6 and enters the shell side of the primary heat exchanger 5, some dust may be deposited. This dust is then transported through the first material outlet of the shell side of the primary heat exchanger 5 via a main pipeline to the dust conveying device 14. The gas flowing out of the tube side of the primary heat exchanger 5 enters the tube side of the secondary heat exchanger 9. During the heat exchange process in the secondary heat exchanger 9, some dust may be deposited. This dust is then discharged through the fourth material outlet 95 of the secondary heat exchanger 9 into the main pipeline, and then from there into the dust conveying device 14.

[0056] In the above embodiment, the flue gas from the outlet of the fourth cyclone separator 3 is introduced into the primary heat exchanger 5, where the heat of the high-SO2 flue gas is recovered and utilized, and the high-SO2 flue gas is desulfurized by the wet desulfurization device 13. In the primary heat exchanger 5 and the secondary heat exchanger 9, the heat medium flows through the tube side, and the refrigerant flows through the shell side.

[0057] In the apparatus of the above embodiment, to prevent the reverse sulfur-fixing reaction during the preheating of the raw materials by the sulfur-containing, high-temperature flue gas from the roaster 1 outlet, a primary heat exchanger 5 is used to transfer heat from the high-temperature flue gas to clean circulating air, which is then used to preheat the raw materials in the preheating device. Furthermore, the circulating air flowing between the preheating device 2 and the primary heat exchanger 5 contains clean air from the third cyclone separator 203 of the refrigeration unit, reducing the sulfur content in the circulating air. This replaces high-sulfur air with low-sulfur air and prevents sulfur enrichment in the circulating air.

[0058] In the device of the above embodiment, a venting heat exchange device is provided to remove higher concentrations of SO2, thereby avoiding S circulation enrichment, causing SO2 in the flue gas to undergo a reverse sulfur fixation reaction with the raw material, which is not conducive to the desulfurization of slag powder.

[0059] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the specific embodiments described above. The specific embodiments and descriptions in the specification are only intended to further illustrate the principles of the present invention. Various changes and improvements are possible without departing from the spirit and scope of the present invention, and such changes and improvements fall within the scope of the invention as claimed.

Claims

1. A suspension calcination method for reducing sulfur and COD content in powder, characterized in that: The method comprises: Step 10: preheating the powder raw material; Step 20: feeding the preheated powder raw material into the roasting furnace (1) for suspension calcination; Step 30: The powder and the generated flue gas after suspension calcination in the roasting furnace (1) are fed into the fourth cyclone separator (3) for gas-solid separation. The separated powder is cooled by a cooling device to form a finished product. The separated flue gas is heated by a heat exchange device to form an air flow, and the air flow is used to preheat the powder raw material in step 10.

2. The method according to claim 1, characterized in that The separated flue gas is subjected to a heat exchange device to process the heated airflow, and the airflow is used to preheat the powder raw material in step 10, including: using the heat exchange device to perform heat exchange on the flue gas flowing into the tube side and the airflow flowing into the shell side, the airflow temperature is increased, and the flue gas temperature is decreased, the airflow with increased temperature enters the preheating device to preheat the powder; the flue gas with decreased temperature does not enter the preheating device.

3. The method according to claim 1, characterized in that The roasting furnace (1) comprises a main furnace (101) and an auxiliary furnace (102), wherein the top of the main furnace (101) and the top of the auxiliary furnace (102) are connected via a connecting pipe; a first layer of burners (103) and a second layer of burners (104) arranged vertically are provided at the lower portion of the main furnace (101), and a third layer of burners (105) is provided in the middle portion; and a fourth layer of burners (106) is provided at the upper portion of the auxiliary furnace (102); The step 20 specifically includes: At the first layer burner (103) and the second layer burner (104), a reducing combustion atmosphere is adopted for the powder, and the air coefficient is less than 1; at the third layer burner (105) and the fourth layer burner (106), a weak oxidizing combustion atmosphere is adopted.

4. The method according to claim 3, characterized in that In step 30, the separated powder is cooled by a cooling device to form a finished product, the temperature of the powder is reduced, and the temperature of the air flow is increased; according to demand, the air flow with increased temperature in the cooling device is used as combustion air and passed into the third layer burner (105) and the fourth layer burner (106), and the excess air flow is passed into the circulating fan (6).

5. The method according to claim 1, characterized in that The method further includes step 40, using a circulating fan (6) to send the airflow discharged from the preheating device into the shell side of the heat exchange device to form an airflow circulation.

6. A suspension calcination device for reducing sulfur and COD content in powder, characterized in that: The device comprises a roasting furnace (1), a preheating device (2), a fourth cyclone separator (3), a cooling device (4), a primary heat exchanger (5), a circulating fan (6), and a first fan (7), wherein: The first-stage heat exchanger (5) has a tube side in its inner cavity, and a shell side in its shell. The shell side has a first air inlet (51), a first air outlet (52), and a first material outlet (53); the tube side has a second air inlet (54), a second air outlet (55), and a second material outlet (56); The material outlet of the preheating device (2) is connected to the material inlet of the roasting furnace (1), the outlet of the roasting furnace (1) is connected to the inlet of the fourth cyclone separator (3), the air outlet of the fourth cyclone separator (3) is connected to the second air inlet (54) of the tube side of the first heat exchanger (5), the second air outlet (55) of the tube side is connected to the first fan (7) through a pipeline, and the second material outlet (56) is located at the bottom of the tube side; the material outlet of the fourth cyclone separator (3) is connected to the inlet of the cooling device (4), the air outlet of the cooling device (4) is connected to the combustion air inlet at the bottom of the roasting furnace (1), and the cooling device (4) is provided with a finished product outlet; the air outlet of the preheating device (2) is connected to the air inlet of the circulation fan (6), the air outlet of the circulation fan (6) is connected to the first air inlet (51) of the shell side of the first heat exchanger (5), and the first air outlet (52) of the shell side of the first heat exchanger (5) is connected to the air inlet of the preheating device (2).

7. The suspension calcination device according to claim 6, characterized in that: The roasting furnace (1) comprises a main furnace (101) and an auxiliary furnace (102), the top of the main furnace (101) and the top of the auxiliary furnace (102) are connected via a connecting pipe, and the bottom of the auxiliary furnace (102) is the outlet of the roasting furnace (1); The inner cavity of the main furnace (101) is provided with a first layer of burners (103), a second layer of burners (104) and a third layer of burners (105) from bottom to top; the inner cavity of the auxiliary furnace (102) is provided with a fourth layer of burners (106).

8. The suspension calcination device according to claim 7, characterized in that: The first layer burner (103) and the second layer burner (104) are located at the lower part of the main furnace (101); the third layer burner (105) is located in the middle part of the main furnace (101); and the fourth layer burner (106) is located at the upper part of the auxiliary furnace (102); During operation, the first layer burner (103) and the second layer burner (104) adopt a reducing combustion atmosphere with an air coefficient less than 1; the third layer burner (105) and the fourth layer burner (106) adopt a weak oxidizing combustion atmosphere.

9. The suspension calcination device according to claim 6, characterized in that: The preheating device (2) comprises a first cyclone separator (201), a second cyclone separator (202), and a third cyclone separator (203); the air outlet of the first cyclone separator (201) is connected to the air inlet of the circulation fan (6); the material outlet of the first cyclone separator (201) is connected to the first connecting air pipe; one end of the first connecting air pipe is connected to the inlet of the second cyclone separator (202); the other end of the first connecting air pipe is connected to the air outlet of the third cyclone separator (203); The air outlet of the second cyclone separator (202) is connected to the inlet of the first cyclone separator (201) through the second connecting air pipe, and the powder material adding pipe is connected to the second connecting air pipe; the material outlet of the second cyclone separator (202) is connected to the inlet of the third cyclone separator (203), and the material outlet of the third cyclone separator (203) is connected to the material inlet of the roasting furnace (1); the air inlet of the third cyclone separator (203) is connected to the first air outlet (52) of the shell side of the first-stage heat exchanger (6).

10. The suspension calcination device according to claim 7, characterized in that: The cooling device (4) includes a fifth cyclone separator (401), a sixth cyclone separator (402), a seventh cyclone separator (403), a fluidized bed cooler (404), a second fan (405) and a finished product conveying device. The material outlet of the fourth cyclone separator (3) is connected to the third connecting air pipe, one end of the third connecting air pipe is connected to the outlet of the sixth cyclone separator (402), and the other end of the third connecting air pipe is connected to the inlet of the fifth cyclone separator (401). The air outlet of the fifth cyclone separator (401) is respectively connected to the combustion air inlet at the bottom of the roasting furnace (1), the third layer burner (105), the fourth layer burner (106), the circulating fan ( 6), the material outlet of the fifth cyclone separator (401) is connected to the fourth connecting air pipe, one end of the fourth connecting air pipe is connected to the air inlet of the sixth cyclone separator (402), the other end of the fourth connecting air pipe is connected to the air outlet of the seventh cyclone separator (403), the material outlet of the sixth cyclone separator (402) is connected to the material inlet of the fluidized bed cooler (404); the air outlet of the second fan (405) is connected to the air inlet of the fluidized bed cooler (404), the gas-solid outlet of the fluidized bed cooler (404) is connected to the gas-solid inlet of the seventh cyclone separator (403); the material outlet of the seventh cyclone separator (403) is opposite to the finished product conveying device.

11. The suspension calcination device according to claim 6, characterized in that: The invention also includes a first vertical mill device (8), the first vertical mill device (8) is connected to the air outlet of the circulation fan (6), and the air volume of the circulation fan (6) entering the first vertical mill device (8) and the first-stage heat exchanger (5) is controlled by the valve opening.

12. The suspension calcination device according to claim 10, characterized in that: The invention also includes a secondary heat exchanger (9), a second vertical mill device (10) and a third fan (15), wherein the secondary heat exchanger (9) is located between the primary heat exchanger (5) and the first fan (7), the secondary heat exchanger (9) has a tube side in its inner cavity, a shell side in its shell, a third air inlet (91) and a third air outlet (92) in its shell side, and a fourth air inlet (93), a fourth air outlet (94) and a fourth material outlet (95) in its tube side; The third air inlet (91) of the shell side of the secondary heat exchanger (9) is connected to the third fan (15), and the third air outlet (92) of the shell side of the secondary heat exchanger (9) is connected to the air inlet of the second vertical mill device (10); the fourth air inlet (93) of the tube side of the secondary heat exchanger (9) and the second air outlet (55) of the tube side of the primary heat exchanger (5) are connected through a pipeline, and the fourth air outlet (94) of the tube side of the secondary heat exchanger (9) is connected to the air inlet of the first fan (7).

13. The suspension calcination device according to claim 12, characterized in that: The invention also includes a kiln tail dust collector (11), a kiln tail dust removal fan (12), a wet desulfurization device (13) and a dust conveying device (14), wherein the air outlet of the first fan (7) is connected to the air inlet of the kiln tail dust collector (11), the material discharge port of the kiln tail dust collector (11) is opposite to the dust conveying device (14), the air outlet of the kiln tail dust collector (11) is connected to the air inlet of the kiln tail dust removal fan (12), and the air outlet of the kiln tail dust removal fan (12) is connected to the air inlet of the wet desulfurization device (13).

14. The suspension calcination device according to claim 13, characterized in that: The fourth material outlet (95) of the secondary heat exchanger (9) tube side and the first material outlet of the primary heat exchanger (5) shell side are connected to the feed port of the dust conveying device (14) through the main pipeline, and the second material outlet (56) of the primary heat exchanger (5) tube side is connected to two branch pipes containing control valves, one of which is connected to the main pipeline, and the other is connected to the third connecting air pipe.

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