Economical and energy-saving iron phosphate drying and calcining system and method

Abstract

The application provides an economic and energy-saving iron phosphate drying and roasting system, which comprises a drying mechanism, a heating and roasting mechanism and a cooling mechanism. Compared with the prior art, the application provides an economic and energy-saving iron phosphate drying and roasting system, which adopts a mode of directly contacting a material with high-temperature airflow to heat and warm the material, even roasting, and has high heating efficiency, can effectively reduce the heating load of a roasting furnace, thereby reducing the number of roasting furnaces, reducing the floor area, and reducing the device investment; and the mode of directly contacting the material with the airflow is adopted to recover the heat of the high-temperature material, which is high in energy efficiency and can replace the previous indirect air cooling or water cooling process.

Description

Technical Field

[0001] This invention relates to the drying process of ferric phosphate, and in particular to an economical and energy-saving ferric phosphate drying and roasting system and method. Background Technology

[0002] Iron phosphate (FePO4) is a precursor to lithium iron phosphate (LFP), the cathode material for lithium-ion batteries. Due to its good thermal stability and ease of recycling, FePO4 is an ideal battery material for electric vehicles. Currently, iron phosphate is mostly produced using globally leading wet-process purification phosphoric acid technology. The produced iron phosphate is primarily in the form of dihydrate iron phosphate, generally containing 40-55% free water and about 20% water of crystallization. It requires drying, high-temperature dehydration at over 600℃, and calcination to produce qualified anhydrous iron phosphate products.

[0003] Traditional ferric phosphate drying and roasting processes employ a single-stage flash drying process to remove most of the free water, followed by further removal of bound water in a roasting furnace. While this process is simple, it results in low capacity per line. Currently, the maximum capacity of a single production line is typically 25,000 to 30,000 tons of ferric phosphate per year. For customers requiring a production line with an annual capacity of 50,000 to 100,000 tons, conventional processes using the largest roasting furnace size would necessitate two production lines. To achieve the same production capacity while reducing the number of production lines and equipment investment, and enhancing market competitiveness, the development of new processes is urgently needed. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides an economical and energy-saving iron phosphate drying and roasting system that can recover the heat from high-temperature materials as part of the roasting heat source. The gas is circulated in a closed loop, which reduces emissions and saves energy. This allows for a reduction in the number of production lines and lower equipment investment while expanding the scale of operations.

[0005] The technical solution adopted in this invention is as follows:

[0006] An economical and energy-saving iron phosphate drying and roasting system includes a drying mechanism, a heating and roasting mechanism, and a cooling mechanism. The drying mechanism includes a feeding device connected to an upstream system, a rotary flash dryer connected to the feeding device for inputting hot air to dry the raw materials, a rotary flash bag filter connected to the rotary flash dryer for dust removal and purification of the dried material, a rotary flash fan connected to the rotary flash bag filter for leading out a portion of the purified gas and inputting it into the rotary flash dryer, and a drying gas heater for heating the gas from the rotary flash fan. The heating and roasting mechanism includes a screw conveyor for receiving solid material filtered by the rotary flash bag filter, an airflow heating device for receiving and heating the material output from the screw conveyor, and a roasting furnace for receiving the material heated by the airflow heating device and roasting it. The cooling mechanism includes an air temperature cooling device for inputting external air to cool the high-temperature material output from the roasting furnace, a first blower for introducing air after passing through the air temperature cooling device into the airflow heating device, and a first heater for heating the gas drawn out by the blower. The first heater is connected to the airflow heating device.

[0007] Preferably, the tail gas outlet of the roasting furnace is connected to a tail gas bag filter for cooling and separating high-temperature tail gas and a small amount of dust by inputting air. The outlet of the tail gas bag filter is connected to a tail gas fan for leading out the filtered tail gas. The outlet of the tail gas bag filter is equipped with a rotary valve for controlling the discharge of tail gas powder. A gas flow regulating valve is provided on the tail gas outlet pipe of the roasting furnace.

[0008] Preferably, the airflow heating device includes a first Venturi for receiving solid material conveyed by a screw conveyor and hot gas from a second cyclone separator for gas-solid mixing; a first bag filter connected to the first Venturi for separating the solid material after the first heating and the gas after the third cooling; a second Venturi connected to the first bag filter for receiving solid material after the first heating and hot gas from a third cyclone separator for gas-solid mixing; a second cyclone separator connected to the second Venturi for separating the solid material after the second heating and the gas after the second cooling; and a first heater. The system is connected to the second cyclone separator for receiving hot gas heated by the first heater and solid material heated for the second time for gas-solid mixing, and to the third cyclone separator for separating solid material heated for the third time and gas cooled for the first time. The outlet of the second cyclone separator is connected to the inlet of the first cyclone separator, the outlet of the third cyclone separator is connected to the inlet of the second cyclone separator, the outlet of the third cyclone separator is connected to the inlet of the roasting furnace, and the outlet of the first bag filter is connected to a third blower for drawing out the gas cooled for the third time.

[0009] Preferably, the air cooling device includes a fourth venturi for receiving high-temperature material from the roasting furnace outlet and first-heated air from the fifth bag filter for gas-solid mixing; a fourth bag filter for separating the first-cooled solid material and the first-heated air; a fifth venturi for receiving external cold air and first-cooled solid material for gas-solid mixing; and a fifth bag filter for separating and outputting the second-heated air and the second-cooled solid material. The outlet of the fifth bag filter is connected to the fourth venturi via a fourth blower, and the outlet of the fourth bag filter is connected to the first blower.

[0010] More preferably, the air cooling device further includes a second blower for introducing external air, a molecular sieve adsorption tower connected to the second blower for adsorbing moisture in the air, and a gas filter connected to the molecular sieve adsorption tower for filtration, the gas filter being connected to a fifth venturi.

[0011] This invention also provides a drying and roasting method for an economical and energy-saving iron phosphate drying and roasting system, comprising the following steps:

[0012] 1) Raw materials from the upstream system enter the rotary flash dryer from the top of the rotary flash dryer shell via the feeding device;

[0013] 2) In the rotary flash dryer, after the material is dried by direct contact with hot air, it enters the rotary flash bag filter for dust removal and purification. The purified gas is partly used as the circulating hot air for drying by the rotary flash fan, and then led out to the drying gas heater by the rotary flash fan and then enters the rotary flash dryer. The part is directly discharged to maintain the system balance.

[0014] 3) The solid material filtered by the flash bag filter enters the screw conveyor through the rotary valve at the bottom of the flash bag filter, and enters the airflow heating device for heating from the outlet of the screw conveyor. The purified gas is discharged through the third blower.

[0015] 4) After being heated by the airflow heating device, the material enters the roasting furnace for further heating, temperature maintenance, and roasting;

[0016] 5) The high-temperature material at the outlet of the roasting furnace is cooled by the air cooling device and then output as a product; the air after heat exchange enters the airflow heating device to heat the dried material.

[0017] 6) The high-temperature exhaust gas and a small amount of dust in the roasting furnace are mixed with the ambient air and cooled down by the gas flow regulating valve before entering the exhaust gas bag filter. The exhaust gas is discharged after being purified and filtered by the exhaust gas bag filter, and the collected powder is recycled.

[0018] Preferably, in step 2), the gas purified from the vortex bag filter is mixed with the supplementary gas from the make-up air filter and then led out by the vortex fan. Part of the gas is discharged out of the system to maintain system balance, and the remaining gas is used as circulating gas to enter the dry gas heater and heated to a certain temperature before entering the rotary flash dryer to heat the material.

[0019] Preferably, the specific heating steps of the airflow heating device in step 3) are as follows:

[0020] 3.1) The solid material conveyed by the screw conveyor and the hot gas from the second cyclone separator enter the first venturi for gas-solid mixing. After mixing, the solid material that is heated for the first time and the gas that is cooled for the third time enter the first bag filter for dust removal and separation. After separation, the solid material that is heated for the first time enters the second venturi, and the gas that is cooled for the third time is led out by the third blower.

[0021] 3.2) In step 3.1), hot gas from the third cyclone separator is continuously introduced into the second venturi to mix with the first heated solid material. After mixing, the second heated solid material and the second cooled gas enter the second cyclone separator for separation. The separated second heated material enters the third venturi, and the separated second cooled gas enters the first venturi in step 3.1).

[0022] 3.3) In step 3.2), the third venturi continues to be fed with the gas heated by the first heater and mixed with the solid material heated for the second time. The solid material heated for the third time and the gas cooled for the first time enter the third cyclone separator for separation. The separated material heated for the third time enters the roasting furnace, and the gas cooled for the first time enters the second venturi in step 3.2).

[0023] Preferably, the specific cooling steps of the air temperature cooling device in step 5) are as follows:

[0024] 5.1) The high-temperature material from the roasting furnace outlet and the first heated air from the fifth bag filter are mixed in the fourth venturi. The solid material after the first cooling and the air after the second heating enter the fourth bag filter for separation. The separated solid material after the first cooling enters the fifth venturi. The air after the second heating is introduced into the first heater by the first blower for heating.

[0025] 5.2) In step 5.1), the fifth venturi continues to be supplied with external air introduced by the second blower, which passes through the separation screen adsorption tower and gas filter in sequence, and mixes it with the first cooled solid material. The solid material after the second cooling is separated from the air after the first heating in the fifth bag filter. The separated second cooled solid material is output as the product, and the separated first heated air enters the fourth venturi through the fourth blower.

[0026] Preferably, in step 6), the exhaust gas purified and filtered by the exhaust gas bag filter is drawn out by the exhaust gas fan; the collected dust is recovered by the rotary valve at the bottom of the exhaust gas bag filter, and the flow rate of the mixed air is controlled by the mixed air flow regulating valve.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention provides an economical and energy-saving iron phosphate drying and roasting system, which uses a high-temperature airflow to directly contact the material to heat and even roast the material. The heating efficiency is high, which can effectively reduce the heating load of the roasting furnace, thereby reducing the number of roasting furnaces, reducing the floor space, and reducing equipment investment. Furthermore, by using airflow to directly contact the material, the heat of the high-temperature material is recovered, which is highly efficient and energy-saving, and can replace the previous indirect air cooling or water cooling process. Attached Figure Description

[0028] Figure 1 The flowchart below shows an economical and energy-saving iron phosphate drying and roasting system provided by the present invention.

[0029] Figure 2 The diagram below shows a block diagram of an economical and energy-saving iron phosphate drying and roasting system provided by the present invention. Detailed Implementation

[0030] The preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0031] Figures 1 to 2 This is a preferred embodiment of an economical and energy-saving iron phosphate drying and roasting system provided by the present invention. For example... Figures 1 to 2As shown, the economical and energy-saving iron phosphate drying and roasting system includes a drying unit 1, a heating and roasting unit 2, and a cooling unit 3. The drying unit 1 includes a feeding device 11 connected to the upstream system, a rotary flash dryer 12 connected to the feeding device for inputting hot air to dry the raw materials, a rotary flash bag filter 13 connected to the rotary flash dryer for dust removal and purification of the dried material, a rotary flash fan 14 connected to the rotary flash bag filter for leading out a portion of the purified gas and inputting it to the rotary flash dryer, and a drying gas heater 15 for heating the gas from the rotary flash fan. The heating and roasting unit 2 includes a screw conveyor 21 for receiving the solid material filtered by the rotary flash bag filter, an airflow heating device 22 for receiving and heating the material output from the screw conveyor, and a cooling device for receiving the material heated by the airflow heating device. The roasting furnace 23 heats the material for baking; the cooling mechanism 3 includes an air cooling device 31 for cooling the high-temperature material output from the roasting furnace by inputting external air, a first blower 32 for introducing the air after passing through the air cooling device into the airflow heating device, and a first heater 33 for heating the gas drawn out by the blower. The first heater 33 is connected to the airflow heating device 22. In this way, the material from the upstream system is dried by the drying mechanism 1 and then enters the heating and roasting mechanism 2 for heating, temperature control, and roasting. The high-temperature material then enters the cooling mechanism 3 for cooling, and the product is output. The heat from the high-temperature material is recovered as part of the heat source for roasting and recycled into the airflow heating device 22. This reduces emissions and saves energy, allowing for a reduction in the number of production lines and lower equipment investment while expanding the scale. A portion of the gas drawn out by the vortex fan is controlled by various means such as a vortex exhaust gas flow regulating valve or a manual valve. The drying gas heater can be an electric heater, a finned tube heater, or other types.

[0032] The tail gas outlet of the roasting furnace 23 is connected to a tail gas bag filter 24 for cooling and separating high-temperature tail gas and a small amount of dust by inputting air. The outlet of the tail gas bag filter is connected to a tail gas fan 25 for leading out the filtered tail gas. The outlet of the tail gas bag filter 24 is equipped with a rotary valve 241 for controlling the discharge of tail gas powder. A gas flow regulating valve 231 is provided on the tail gas outlet pipe of the roasting furnace 23. In this way, the flow rate of the small amount of high-temperature gas discharged from the roasting furnace 23 is controlled by the gas flow regulating valve 231 on the tail gas outlet pipe. The flow rate is interlocked with the pressure transmitter on the tail gas outlet pipe. After the discharged high-temperature gas mixes with the ambient air and reaches a certain temperature, it enters the tail gas bag filter 24. The purified gas is discharged through the tail gas fan 25. The collected dust is recovered through the rotary valve 241 at the bottom of the tail gas bag filter. The flow rate of the mixed air is controlled by the mixed air flow regulating valve 26.

[0033] The airflow heating device 22 includes a first Venturi 221 for receiving solid material conveyed by a screw conveyor and hot gas from a second cyclone separator for gas-solid mixing; a first bag filter 222 connected to the first Venturi for separating the solid material after the first heating and the gas after the third cooling; a second Venturi 223 connected to the first bag filter 222 for receiving solid material after the first heating and hot gas from a third cyclone separator for gas-solid mixing; a second cyclone separator 224 connected to the second Venturi for separating solid material after the second heating and the gas after the second cooling; and a third Venturi connected to both the first heater and the second cyclone separator for receiving hot gas heated by the first heater 33 and solid material after the second heating for gas-solid mixing. 225 and a third cyclone separator 226 connected to the third venturi for separating the solid material after the third heating and the gas after the first cooling. The outlet of the second cyclone separator 224 is connected to the inlet of the first venturi 221. The outlet of the third cyclone separator 226 is connected to the inlet of the second venturi 223. The outlet of the third cyclone separator 226 is connected to the inlet of the roasting furnace 23. The outlet of the first bag filter 222 is connected to a third blower 227 for drawing out the gas after the third cooling. In this way, the hot air passing through the first heater 33 is cooled by three stages of heat exchange, and the air after heat exchange is drawn out by the third blower 227. The solid material conveyed from the screw conveyor is heated by three stages of heat exchange, and the heated solid material then enters the roasting furnace 23. It is worth noting that the airflow heating device consists of a Venturi mixer, a cyclone separator (and / or a bag filter) and a rotary valve; high-temperature gas enters the heated Venturi mixer and mixes with the material gas-solid mixture from the rotary valve at the bottom of the heated cyclone separator (or bag filter) to heat the material. Single-stage heating, two-stage heating or more can be used, and the number of heating stages is determined by the number of heated Venturi mixers.

[0034] The air cooling device 31 includes a fourth venturi 311 for receiving high-temperature material from the roasting furnace outlet and mixing it with the first heated air from the fifth bag filter; a fourth bag filter 312 for separating the solid material after the first cooling and the air after the second heating; a fifth venturi 313 for receiving external cold air and mixing it with the solid material after the first cooling; and a fifth bag filter 314 for separating and outputting the air after the first heating and the solid material after the second cooling. The outlet of the fifth bag filter 314 is connected to the fourth venturi 311 via a fourth blower 315, and the outlet of the fourth bag filter 312 is connected to the first blower 32. The cold air entering the fifth venturi 313 is heated twice and then introduced into the first heater 33 by the first blower 32 before entering the airflow heating device 22. The high-temperature material exiting the roasting furnace outlet is discharged from the system as a product after being cooled twice. It is worth noting that the air cooling device consists of a Venturi mixer, a cyclone separator (and / or a bag filter), a rotary valve, and a fan. Cooling gas enters the Venturi mixer and mixes with the material from the rotary valve at the bottom of the cyclone separator (and / or bag filter) to cool the material and recover its heat. Single-stage, two-stage, or higher cooling systems can be used, with the number of stages determined by the number of Venturi mixers.

[0035] The cooling mechanism 3 also includes a second blower 34 for introducing external air, a molecular sieve adsorption tower 35 connected to the second blower for adsorbing moisture from the air, and a gas filter 36 connected to the molecular sieve adsorption tower for filtration. The gas filter 36 is connected to a fifth venturi 313. External air is introduced through the second blower 34, then passes through the molecular sieve adsorption tower 35 to adsorb moisture and the gas filter 36 to filter impurities before entering the fifth venturi 313. Each flash bag filter and cyclone separator is equipped with a rotary valve at its bottom.

[0036] This invention also provides a drying and roasting method for an economical and energy-saving iron phosphate drying and roasting system, comprising the following steps:

[0037] 1) Raw materials from the upstream system enter the rotary flash dryer 12 from the upper part of the rotary flash dryer shell via the feeding device 11;

[0038] 2) In the rotary flash dryer 12, after the material is dried by direct contact with hot air, it enters the rotary flash bag dust collector 13 for dust removal and purification. The purified gas is partly used as the circulating hot air for drying by the rotary flash fan 14, and then led out to the drying gas heater 15 and enters the rotary flash dryer 12. The part is directly discharged to maintain the system balance.

[0039] 3) The solid material filtered by the flash bag filter 13 enters the screw conveyor 21 through the bottom rotary valve of the flash bag filter, and enters the airflow heating device 22 from the outlet of the screw conveyor for heating. The purified gas is discharged through the third blower 227.

[0040] 4) After being heated by the airflow heating device 22, the material enters the roasting furnace 23 for further heating, temperature maintenance, and roasting;

[0041] 5) The high-temperature material at the outlet of the roasting furnace is cooled by the air cooling device 31 and then output as a product; the air after heat exchange enters the airflow heating device 22 to heat and dry the material.

[0042] 6) The high-temperature exhaust gas and a small amount of dust in the roasting furnace are mixed with the ambient air and cooled down by the gas flow regulating valve 231 before entering the exhaust gas bag filter 24. The exhaust gas is discharged after being purified and filtered by the exhaust gas bag filter 24, and the collected powder is recycled.

[0043] In step 2), the gas purified from the vortex bag filter 13 is mixed with the supplementary gas from the make-up air filter 16 and then led out by the vortex fan 14. Part of the gas is discharged out of the system to maintain system balance, and the remaining gas is used as circulating gas to enter the dry gas heater 15 and heated to a certain temperature before entering the rotary flash dryer 12 to heat the material.

[0044] The specific heating steps of the airflow heating device 22 in step 3) are as follows: 3.1) The solid material conveyed by the screw conveyor and the hot air from the second cyclone separator enter the first venturi 221 for gas-solid mixing. After mixing, the solid material that has been heated for the first time and the gas that has been cooled for the third time enter the first bag filter 222 for dust removal and separation. The solid material that has been heated for the first time after separation enters the second venturi 223, and the gas that has been cooled for the third time after separation is led out by the third blower 227; 3.2) In step 3.1), the hot air from the third cyclone separator continues to be introduced into the second venturi 223 to mix with the solid material that has been heated for the first time. After mixing, the solid material that has been heated for the second time enters the first bag filter 222 for dust removal and separation. The material and the second cooled gas enter the second cyclone separator 224 for separation. The separated material after the second heating enters the third venturi 225, and the separated gas after the second cooling enters the first venturi in step 3.1). In step 3.3), the third venturi 225 in step 3.2) continues to be fed with gas heated by the first heater and mixed with the second heated solid material. The mixed solid material after the third heating and the first cooled gas enter the third cyclone separator 226 for separation. The separated material after the third heating enters the roasting furnace, and the separated gas after the first cooling enters the second venturi 223 in step 3.2).

[0045] The specific cooling steps of the air cooling device 31 in step 5) are as follows: 5.1) The high-temperature material from the roasting furnace outlet and the first heated air from the fifth bag filter are mixed in the fourth venturi 311. The solid material after the first cooling and the air after the second heating enter the fourth bag filter 312 for separation. The separated first cooled solid material enters the fifth venturi 313. The second heated air is introduced into the first heater by the first blower for heating. 5.2) The fifth venturi 313 in step 3.2) continues to be introduced with external air introduced by the second blower 34, which passes through the separation screen adsorption tower 35 and the gas filter 36 in sequence, and mixes with the first cooled solid material. The solid material after the second cooling and the first heated air are separated in the fifth bag filter 314. The separated second cooled solid material is output as a product. The separated first heated air enters the fourth venturi 311.

[0046] In step 6), the exhaust gas purified and filtered by the exhaust gas bag filter is drawn out by the exhaust gas fan 25; the collected dust is recovered by the rotary valve 241 at the bottom of the exhaust gas bag filter, and the flow rate of the mixed air is controlled by the mixed air flow regulating valve 26.

[0047] In summary, the technical solution of this invention can fully and effectively achieve the above-mentioned objectives. Furthermore, the structure and functional principles of this invention have been fully verified in the embodiments, achieving the expected effects and objectives. Without departing from the principles and essence of this invention, various changes or modifications can be made to the embodiments. Therefore, this invention includes all substitutions within the scope mentioned in the patent application claims, and any equivalent changes made within the scope of this patent application are within the scope of the patent application.

Claims

1. An economical and energy-saving iron phosphate drying and roasting system, characterized in that, The system includes a drying mechanism, a heating and baking mechanism, and a cooling mechanism. The drying mechanism includes a feeding device connected to the upstream system, a rotary flash dryer connected to the feeding device for inputting hot air to dry the raw materials, a rotary flash bag filter connected to the rotary flash dryer for dust removal and purification of the dried material, a rotary flash fan connected to the rotary flash bag filter for leading out a portion of the purified gas and inputting it into the rotary flash dryer, and a drying gas heater for heating the gas from the rotary flash fan. The heating and baking mechanism includes a screw conveyor for receiving solid material filtered by the rotary flash bag filter, an airflow heating device for receiving and heating the material output from the screw conveyor, and a roasting furnace for receiving the material heated by the airflow heating device and roasting it. The cooling mechanism includes an air cooling device for inputting external air to cool the high-temperature material output from the roasting furnace, a first blower for introducing air after passing through the cooling device into the airflow heating device, and a first heater for heating the gas drawn out by the blower. The first heater is connected to the airflow heating device. The tail gas outlet of the roasting furnace is connected to a tail gas bag filter for cooling and separating high-temperature tail gas and a small amount of dust by inputting air. The airflow heating device includes a first Venturi for receiving solid material conveyed by a screw conveyor and hot gas from a second cyclone separator for gas-solid mixing; a first bag filter connected to the first Venturi for separating the solid material after the first heating and the gas after the third cooling; a second Venturi connected to the first bag filter for receiving solid material after the first heating and hot gas from a third cyclone separator for gas-solid mixing; a second cyclone separator connected to the second Venturi for separating the solid material after the second heating and the gas after the second cooling; and a first heater and a second cyclone separator connected to the first cyclone separator for gas-solid mixing. The second cyclone separator is connected to a third venturi for receiving hot gas from the first heater and mixing solid material after the second heating, and to a third cyclone separator connected to the third venturi for separating solid material after the third heating and gas after the first cooling. The outlet of the second cyclone separator is connected to the inlet of the first venturi, the outlet of the third cyclone separator is connected to the inlet of the second venturi, and the outlet of the third cyclone separator is connected to the inlet of the roasting furnace. The outlet of the first bag filter is connected to a third blower for drawing out the gas after the third cooling.

2. The economical and energy-saving iron phosphate drying and roasting system according to claim 1, characterized in that: The outlet of the exhaust bag filter is connected to an exhaust fan for drawing out the filtered exhaust gas, and the outlet of the exhaust bag filter is equipped with a rotary valve for controlling the discharge of exhaust gas powder; the exhaust gas outlet pipe of the roasting furnace is equipped with a gas flow regulating valve.

3. The economical and energy-saving iron phosphate drying and roasting system according to claim 2, characterized in that: The cooling device includes a fourth venturi for receiving high-temperature material from the roasting furnace outlet and the first heated air from the fifth bag filter for gas-solid mixing; a fourth bag filter for separating the first cooled solid material and the first heated air; a fifth venturi for receiving external cold air and the first cooled solid material for gas-solid mixing; and a fifth bag filter for separating and outputting the second heated air and the second cooled solid material. The outlet of the fifth bag filter is connected to the fourth venturi via a fourth blower, and the outlet of the fourth bag filter is connected to the first blower.

4. The economical and energy-saving iron phosphate drying and roasting system according to claim 3, characterized in that: The cooling device also includes a second blower for introducing external air, a molecular sieve adsorption tower connected to the second blower for adsorbing moisture in the air, and a gas filter connected to the molecular sieve adsorption tower for filtration. The gas filter is connected to a fifth venturi.

5. A drying and roasting method for an economical and energy-saving ferric phosphate drying and roasting system, using the economical and energy-saving ferric phosphate drying and roasting system as described in claim 4, characterized in that, Includes the following steps: 1) Raw materials from the upstream system enter the rotary flash dryer from the top of the rotary flash dryer shell via the feeding device; 2) In the rotary flash dryer, after the material is dried by direct contact with hot air, it enters the rotary flash bag dust collector for dust removal and purification. The purified gas is partially used as the circulating hot air for drying by the rotary flash fan, and is led out by the rotary flash fan to the drying gas heater before entering the rotary flash dryer. The remaining part is directly discharged to maintain the system balance. 3) The solid material filtered by the flash bag filter enters the screw conveyor through the rotary valve at the bottom of the flash bag filter, and enters the airflow heating device for heating from the outlet of the screw conveyor. The purified gas is discharged through the third blower. 4) After being heated by the airflow heating device, the material enters the roasting furnace for further heating, temperature maintenance, and roasting; 5) The high-temperature material at the outlet of the roasting furnace is cooled by the air cooling device and then output as a product; the air after heat exchange enters the airflow heating device to heat and dry the material. 6) The high-temperature exhaust gas and a small amount of dust in the roasting furnace are mixed with the ambient air and cooled down by the gas flow regulating valve before entering the exhaust gas bag filter. The exhaust gas is discharged after being purified and filtered by the exhaust gas bag filter, and the collected powder is recycled.

6. The drying and roasting method of the economical and energy-saving iron phosphate drying and roasting system according to claim 5, characterized in that: In step 2), the gas purified by the vortex bag filter is mixed with the supplementary gas from the make-up air filter and then led out by the vortex fan. Part of the gas is discharged out of the system to maintain system balance, and the remaining gas is used as circulating gas to enter the dry gas heater and heated to a certain temperature before entering the rotary flash dryer to heat the material.

7. The drying and roasting method of the economical and energy-saving iron phosphate drying and roasting system according to claim 5, characterized in that: The specific heating steps of the airflow heating device in step 3) are as follows: 3.1) The solid material conveyed by the screw conveyor and the hot gas from the second cyclone separator enter the first venturi for gas-solid mixing. After mixing, the solid material that is heated for the first time and the gas that is cooled for the third time enter the first bag filter for dust removal and separation. After separation, the solid material that is heated for the first time enters the second venturi, and the gas that is cooled for the third time is led out by the third blower. 3.2) In step 3.1), hot gas from the third cyclone separator is continuously introduced into the second venturi to mix with the first heated solid material. After mixing, the second heated solid material and the second cooled gas enter the second cyclone separator for separation. The separated second heated material enters the third venturi, and the separated second cooled gas enters the first venturi in step 3.1). 3.3) In step 3.2), the gas heated by the first heater is continued to be introduced into the third venturi and mixed with the solid material heated for the second time. The solid material heated for the third time and the gas cooled for the first time enter the third cyclone separator for separation. The separated material heated for the third time enters the roasting furnace, and the separated gas cooled for the first time enters the second venturi in step 3.2).

8. The drying and roasting method of the economical and energy-saving iron phosphate drying and roasting system according to claim 7, characterized in that: The specific cooling steps of the air temperature cooling device in step 5) are as follows: 5.1) The high-temperature material from the roasting furnace outlet and the first heated air from the fifth bag filter are mixed in the fourth venturi. The solid material after the first cooling and the air after the second heating enter the fourth bag filter for separation. The separated solid material after the first cooling enters the fifth venturi. The air after the second heating is introduced into the first heater by the first blower for heating. 5.2) In step 5.1), the fifth venturi continues to be supplied with external air introduced by the second blower, which passes through the separation screen adsorption tower and gas filter in sequence, and mixes it with the first cooled solid material. The solid material after the second cooling is separated from the air after the first heating in the fifth bag filter. The separated second cooled solid material is output as the product, and the separated first heated air enters the fourth venturi through the fourth blower.

9. The drying and roasting method of the economical and energy-saving iron phosphate drying and roasting system according to claim 8, characterized in that: In step 6), the exhaust gas purified and filtered by the exhaust gas bag filter is drawn out by the exhaust gas fan; the collected dust is recovered through the rotary valve at the bottom of the exhaust gas bag filter, and the flow rate of the mixed air is controlled by the mixed air flow regulating valve.

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