Combined caustic and ammonium chloride drying apparatus and method

Abstract

This invention discloses a drying apparatus and method for ammonium chloride in a combined alkali and sodium chloride system. The apparatus includes: a fluidized bed and its unloader; a powder flow cooler with its inlet connected to the unloader and its outlet connected to a dry ammonium chloride conveyor belt; a return bucket elevator with its inlet connected to the unloader and its outlet connected to a return scraper conveyor; a premixer with its dry ammonium chloride inlet connected to the return scraper conveyor and its mixing outlet connected to the fluidized bed; a cyclone separator with its inlet connected to the tail gas outlet of the fluidized bed and its outlet connected to both a bag filter and the dry ammonium chloride conveyor belt; a bag filter with its outlet connected to the dry ammonium chloride conveyor belt; an air preheater with its high-temperature tail gas inlet connected to the tail gas outlet of the bag filter, its condensate outlet connected to a washing tank, and its hot air outlet connected to a preheating section air heater; a preheating section air heater with its preheated air outlet connected to the fluidized bed; and a drying section air heater with its dry air outlet connected to the fluidized bed. This invention can reduce steam consumption, alleviate tail gas treatment pressure, and improve energy utilization.

Description

Technical Field

[0001] This invention belongs to the field of soda ash production technology, specifically relating to a soda ash ammonium chloride drying device and method. Background Technology

[0002] Currently, ammonium chloride drying in soda ash production utilizes a combined hot and cold fluidized bed dryer. The production principle involves heating air with steam, then using a blower to blow the hot air into the fluidized bed, causing the wet ammonium to fluidize. The hot air and internal heat exchanger then dry the ammonium to obtain dry ammonium. A cooling section is located at the fluidized bed outlet, using a cold method combined with an internal cooler to cool the ammonium chloride. While this process boasts high production capacity, it relies on air as the heating and cooling medium, generating a large amount of exhaust gas. Simultaneously, a large volume of cold air enters the fluidized bed exhaust gas, resulting in low exhaust gas temperatures and wasted heat. Furthermore, the existing equipment returns cooled ammonium chloride, requiring it to be cooled before being reheated, leading to significant energy waste and hindering efforts to reduce steam consumption in the fluidized bed.

[0003] The soda ash industry is currently facing increasingly fierce competition. Natural soda ash is gaining market share due to its cost advantage. The combined soda ash process needs to reduce costs and increase efficiency in order to survive in the increasingly competitive market. Therefore, it is crucial to reduce costs through technological means. Summary of the Invention

[0004] Technical problem solved: In view of the above-mentioned technical problems, the present invention provides a soda ash ammonium chloride drying device and method, which can reduce steam consumption, alleviate tail gas treatment pressure, and improve energy utilization.

[0005] Technical solution: A soda ash ammonium chloride drying device, comprising: The fluidized bed includes a preheating section and a drying section. The preheating section is equipped with a feed inlet and a preheating air inlet, and the drying section is equipped with a drying air inlet, an exhaust gas outlet, and a discharge outlet. The unloader is located at the discharge port of the fluidized bed; The powder flow cooler has its inlet connected to the outlet of the unloader, and its outlet connected to the dry ammonium belt conveyor. The return material bucket elevator has its inlet connected to the outlet of the unloader, and its outlet connected to the return material scraper conveyor. The premixer is equipped with a wet ammonium inlet, a dry ammonium inlet, and a mixing outlet. The dry ammonium inlet is connected to the discharge port of the return scraper conveyor, and the mixing outlet is connected to the feed port of the fluidized bed. The cyclone separator has its inlet connected to the exhaust gas outlet of the fluidized bed, and its outlet connected to the bag filter and the dry ammonium belt conveyor, respectively. The bag filter dust collector has its discharge port connected to a dry ammonium belt conveyor. The air preheating heater is equipped with an air inlet, a high-temperature exhaust gas inlet, a condensate outlet, and a hot gas outlet. The high-temperature exhaust gas inlet is connected to the exhaust gas outlet of the bag filter, the condensate outlet is connected to the water inlet of the washing tank, and the hot gas outlet is connected to the hot gas inlet of the preheating section air heater. The preheating section air heater is equipped with a steam inlet, a hot gas inlet, and a preheated air outlet, and its preheated air outlet is connected to the preheated air inlet of the fluidized bed; The air heater in the drying section is equipped with an air inlet, a steam inlet, and a dry air outlet, with the dry air outlet connected to the dry air inlet of the fluidized bed.

[0006] Preferably, both the preheating section and the drying section of the fluidized bed are equipped with internal heaters, and the internal heaters are connected to the steam network through steam pipelines.

[0007] Preferably, the unloader is a star-shaped unloader.

[0008] Preferably, the powder flow cooler is provided with circulating water inlet and outlet.

[0009] Preferably, the air inlet of the air preheater is connected to the preheating section blower, and the air inlet of the drying section air heater is connected to the drying section blower.

[0010] Preferably, the air preheater is further provided with an exhaust gas outlet, which is connected to the air inlet of the exhaust gas scrubbing tower via an induced draft fan.

[0011] Furthermore, the top of the exhaust gas scrubbing tower is provided with a production water inlet, an exhaust gas outlet, and a circulating wash water inlet, and the bottom is provided with a circulating wash water outlet and a wash water outlet. The circulating wash water inlet and the circulating wash water outlet are connected by a circulating wash water pump, and the wash water outlet is connected to the water inlet of the wash water tank.

[0012] A method for drying ammonium chloride in a combined alkali system, specifically: After the wet ammonium chloride from the crystallization process and the dry ammonium chloride from the fluidized bed return material are mixed in the premixer, the mixed material is successively fed into the preheating section and drying section of the fluidized bed for drying. Part of the dried ammonium chloride is used as dry ammonium chloride for return material, and part is sent to the packaging process after being cooled by the powder flow cooler. The high-temperature exhaust gas from the fluidized bed passes sequentially through a cyclone separator and a bag filter. The separated dry ammonium gas enters the dry ammonium gas conveyor belt, while the remaining high-temperature exhaust gas enters the air preheater to exchange heat with the cold air in the preheating section to recover heat. The condensate entrained in the cooled exhaust gas is discharged to the washing water tank. The heated air enters the preheating section air heater and is heated again before entering the preheating section of the fluidized bed. At the same time, the air heated by the drying section air heater enters the drying section of the fluidized bed.

[0013] Preferably, the material temperature in the preheating section is controlled at 75~80℃, and the material temperature in the drying section is controlled at 85~90℃.

[0014] Preferably, the air temperature heated by the air heater in the preheating section and the air heater in the drying section is controlled to be 170~200℃.

[0015] Beneficial effects: Through process improvement, this invention comprehensively utilizes the heat generated during the drying process of ammonium chloride, thereby increasing steam utilization and reducing steam consumption; This invention reduces the amount of drying exhaust gas generated and alleviates the exhaust gas treatment pressure by modifying the fluidized bed used for ammonium chloride drying. This invention utilizes a powder flow cooler to replace the original fluidized bed cooling section, eliminating the need to maintain the fluidized state of the material in the cooling section, reducing the need for a cooling section blower, and decreasing power consumption. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of the ammonium chloride drying device of the present invention; The numbers in the diagram represent the following: 1. Fluidized bed, 2. Powder flow cooler, 3. Unloader, 4. Return bucket elevator, 5. Return scraper conveyor, 6. Premixer, 7. Exhaust fan, 8. Preheating section blower, 9. Air preheater, 10. Preheating section air heater, 11. Drying section blower, 12. Drying section air heater, 13. Cyclone separator, 14. Bag filter, 15. Screw conveyor, 16. Washing water tank, 17. Circulating washing water pump, 18. Tail gas scrubbing tower, 19. Dry ammonium belt conveyor. Detailed Implementation

[0017] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. Example 1

[0018] like Figure 1 As shown, a soda ash ammonium chloride drying device includes: Fluidized bed 1 includes a preheating section and a drying section. The preheating section is provided with a feed inlet and a preheating air inlet, and the drying section is provided with a drying air inlet, a tail gas outlet and a discharge outlet. Both the preheating section and the drying section of the fluidized bed 1 are provided with internal heaters, and the internal heaters are connected to the steam network through steam pipelines.

[0019] The unloader 3 is a star-shaped unloader 3, which is located at the outlet of the fluidized bed 1.

[0020] The powder flow cooler 2 is equipped with a circulating water inlet and outlet. Its inlet is connected to the outlet of the unloader 3, and its outlet is connected to the dry ammonium belt conveyor 19.

[0021] The return material bucket elevator 4 has its inlet connected to the outlet of the unloader 3, and its outlet connected to the return material scraper conveyor 5. The premixer 6 is equipped with a wet ammonium inlet, a dry ammonium inlet and a mixing outlet. The dry ammonium inlet is connected to the discharge port of the return scraper conveyor 5, and the mixing outlet is connected to the feed port of the fluidized bed 1. Cyclone separator 13 has its inlet connected to the exhaust outlet of fluidized bed 1, and its outlet connected to bag filter 14 and dry ammonium belt conveyor 19 respectively. The bag filter 14 has its discharge port connected to the dry ammonium belt conveyor 19. The air preheater 9 is equipped with an air inlet, a high-temperature exhaust gas inlet, a condensate outlet and a hot gas outlet. Its air inlet is connected to the preheating section blower 8, the high-temperature exhaust gas inlet is connected to the exhaust gas outlet of the bag filter 14, the condensate outlet is connected to the water inlet of the washing tank 16, and the hot gas outlet is connected to the hot gas inlet of the preheating section air heater 10. The preheating section air heater 10 is provided with a steam inlet, a hot gas inlet and a preheated air outlet, and its preheated air outlet is connected to the preheated air inlet of the fluidized bed 1. The air heater 12 in the drying section is provided with an air inlet, a steam inlet and a dry air outlet. Its air inlet is connected to the blower 11 in the drying section and its dry air outlet is connected to the dry air inlet of the fluidized bed 1.

[0022] The air preheater 9 is also provided with an exhaust gas outlet, which is connected to the air inlet of the exhaust gas scrubbing tower 18 via an induced draft fan 7. The exhaust gas scrubbing tower 18 has a production water inlet, an exhaust gas outlet, and a circulating wash water inlet at the top, and a circulating wash water outlet and a wash water outlet at the bottom. The circulating wash water inlet and the circulating wash water outlet are connected via a circulating wash water pump 17, and the wash water outlet is connected to the water inlet of the wash water tank 16.

[0023] The wet ammonium (6% moisture content) from the crystallization process enters the premixer 6 and is mixed with the returned 85°C dry ammonium to reduce the moisture content to about 3% while simultaneously increasing the temperature of the wet ammonium. Then, it enters the preheating section of the fluidized bed 1. The mixed material is fluidized in the fluidized bed 1 by hot air blown from the preheating section air heater 10, exchanging heat with the hot air. Simultaneously, the heaters within the fluidized bed 1 provide auxiliary heating, controlling the material temperature in the preheating section to be between 75 and 80°C. Because of the angle of the air distribution plate in the fluidized bed 1, the material continuously moves towards the drying section of the fluidized bed 1 during the drying process. Under the action of the hot air and the internal heater in the drying section, the material temperature in the drying section is maintained at 85~90℃, ensuring that the moisture content of the dry ammonium is <1%. The dry ammonium exits the fluidized bed 1 through the unloader 3. Part of it is returned to the premixer 6 via the return bucket elevator 4 and the return scraper conveyor. The remaining part enters the powder flow cooler 2, where it exchanges heat with the circulating water to reduce the temperature of the dry ammonium to about 60℃. It is then sent to the packaging process via the dry ammonium belt conveyor 19.

[0024] After being drawn in by the preheating blower 8, the air enters the air preheating heater 9 to exchange heat with the high-temperature exhaust gas, and then enters the preheating air heater 10 for reheating. After reaching a temperature of 170~200℃, the air enters the fluidized bed 1 preheating section. After being drawn in by the drying blower, the air enters the drying air heater 12 and is heated to 170~200℃ before entering the fluidized bed 1 drying section.

[0025] The exhaust gas from fluidized bed 1 is drawn by the induced draft fan 7 to maintain a slight negative pressure within fluidized bed 1. Because the original cooling section of fluidized bed 1 is eliminated, the exhaust gas volume is reduced by about one-third. At the same time, the temperature of the exhaust gas increases from the original 70℃ to 110℃. The exhaust gas from fluidized bed 1 is separated by cyclone separator 13 to remove larger particles of ammonium chloride. The remaining exhaust gas enters bag filter 14 to separate fine ammonium chloride powder. The remaining high-temperature exhaust gas enters air preheater 9 to exchange heat with the cold air in the preheating section to recover heat. The condensate entrained in the cooled exhaust gas is discharged to washing water tank 16. The exhaust gas after heat exchange enters exhaust gas scrubbing tower 18 for treatment and is then discharged. Production water is added to the exhaust gas scrubbing tower 18 and pumped to the top of the tower by circulating washing water pump 17 to clean the exhaust gas. The high-concentration washing water is placed in washing water tank 16. The washing water in washing water tank 16 is sent to the soda ash mother liquor system according to the tank level. The dry ammonium separated by cyclone separator 13 and bag filter 14 enters dry ammonium conveyor belt 19 to be sent to the packaging process.

[0026] Steam at 1.3 MPa from the steam pipeline enters the preheating section air heater 10, the drying section air heater 12, the fluidized bed 1 preheating section heater, and the fluidized bed 1 drying section heater for heat exchange. The condensate after heat exchange enters the flash tank, and the 0.6 MPa steam and 0.6 MPa condensate after flashing enter the pipeline.

[0027] This invention offers significant improvements over the original drying process in terms of energy consumption and exhaust emissions. Firstly, the cooling section of fluidized bed 1 is eliminated, replaced by a powder flow cooler 2. Maintaining the fluidized state of the material in the cooling section is no longer necessary, reducing the need for a separate cooling section blower and thus lowering electricity consumption. Secondly, the absence of a cooling section allows for increased exhaust gas temperature from fluidized bed 1, laying the foundation for subsequent utilization of exhaust gas heat. The original exhaust gas temperature was 70°C, while the new process can reach 110°C. Furthermore, the original return material temperature was only 60°C, while the new process can reach 85°C, allowing for full utilization of the returned material's heat and reducing the amount of returned material. Eliminating the cooling section blower also reduces the amount of drying exhaust gas by approximately one-third, alleviating the pressure on exhaust gas treatment.

Claims

1. A drying device for ammonium chloride in a combined alkali system, characterized in that, include: The fluidized bed (1) includes a preheating section and a drying section. The preheating section is provided with a feed inlet and a preheating air inlet, and the drying section is provided with a drying air inlet, a tail gas outlet and a discharge outlet. The unloader (3) is located at the outlet of the fluidized bed (1); The powder flow cooler (2) has its inlet connected to the outlet of the unloader (3), and its outlet connected to the dry ammonium belt conveyor (19). The return material bucket elevator (4) has its inlet connected to the outlet of the unloader (3), and its outlet connected to the return material scraper conveyor (5). The premixer (6) is provided with a wet ammonium inlet, a dry ammonium inlet and a mixing outlet. Its dry ammonium inlet is connected to the outlet of the return scraper conveyor (5) and its mixing outlet is connected to the inlet of the fluidized bed (1). The cyclone separator (13) has its inlet connected to the exhaust outlet of the fluidized bed (1), and its outlet is connected to the bag filter (14) and the dry ammonium belt conveyor (19). The bag filter (14) has its outlet connected to the dry ammonium belt conveyor (19). The air preheating heater (9) is provided with an air inlet, a high-temperature exhaust gas inlet, a condensate outlet and a hot gas outlet. Its high-temperature exhaust gas inlet is connected to the exhaust gas outlet of the bag filter (14), the condensate outlet is connected to the water inlet of the washing tank (16), and the hot gas outlet is connected to the hot gas inlet of the preheating section air heater (10). The preheating section air heater (10) is provided with a steam inlet, a hot gas inlet and a preheated air outlet, and its preheated air outlet is connected to the preheated air inlet of the fluidized bed (1); The air heater (12) of the drying section is provided with an air inlet, a steam inlet and a dry air outlet, and its dry air outlet is connected to the dry air inlet of the fluidized bed (1).

2. The ammonium chloride drying apparatus according to claim 1, characterized in that, The preheating section and drying section of the fluidized bed (1) are both equipped with internal heaters, and the internal heaters are all connected to the steam network through steam pipelines.

3. The ammonium chloride drying apparatus according to claim 1, characterized in that, The unloader (3) is a star-shaped unloader (3).

4. The ammonium chloride drying apparatus according to claim 1, characterized in that, The powder flow cooler (2) is equipped with a circulating water inlet and outlet.

5. The ammonium chloride drying apparatus according to claim 1, characterized in that, The air inlet of the air preheater (9) is connected to the preheating section blower (8), and the air inlet of the drying section air heater (12) is connected to the drying section blower (11).

6. The ammonium chloride drying apparatus according to claim 1, characterized in that, The air preheater (9) is also provided with an exhaust gas outlet, which is connected to the air inlet of the exhaust gas scrubbing tower (18) via an induced draft fan (7).

7. The ammonium chloride drying apparatus according to claim 6, characterized in that, The tail gas scrubbing tower (18) is provided with a production water inlet, a tail gas outlet and a circulating wash water inlet at the top, and a circulating wash water outlet and a wash water outlet at the bottom. The circulating wash water inlet and the circulating wash water outlet are connected by a circulating wash water pump (17), and the wash water outlet is connected to the water inlet of the wash water tank (16).

8. A method for drying ammonium chloride using the apparatus described in claim 1, characterized in that, The method is specifically as follows: After the wet ammonium from the crystallization process and the dry ammonium from the fluidized bed (1) are mixed in the premixer (6), the mixed material is successively fed into the preheating section and drying section of the fluidized bed (1) for drying. Part of the dried ammonium chloride is used as the dry ammonium from the return material, and part is cooled by the powder flow cooler (2) and sent to the packaging process. The high-temperature exhaust gas from the fluidized bed (1) passes through the cyclone separator (13) and the bag filter (14) in sequence. The separated dry ammonium enters the dry ammonium belt conveyor (19). The remaining high-temperature exhaust gas enters the air preheating heater (9) to exchange heat with the cold air in the preheating section to recover heat. The condensate entrained in the exhaust gas after cooling is discharged to the washing water tank (16). The heated air enters the preheating section air heater (10) and is heated again before entering the preheating section of the fluidized bed (1). At the same time, the air heated by the drying section air heater (12) enters the drying section of the fluidized bed (1).

9. The drying method for ammonium chloride according to claim 8, characterized in that, The material temperature in the preheating section is controlled at 75~80℃, and the material temperature in the drying section is controlled at 85~90℃.

10. The drying method for ammonium chloride according to claim 8, characterized in that, The air temperature heated by the preheating section air heater (10) and the drying section air heater (12) is controlled to be 170~200℃.

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