CN117739676A - Stay tank for reducing burning rate of powder material, calcining device and method - Google Patents

Abstract

The invention discloses a residence tank, a calcination device and a calcination method for reducing the burning rate of powder materials, which can continue calcination outside a suspension kiln and reduce the burning rate of the powder materials. The residence tank comprises a tank body provided with an inlet, a feed pipe and a first air pipe, a partition body is arranged in the inner cavity of the tank body, the partition body divides the inner cavity of the tank body into a fixed bed and a fluidized bed, and the lower part of the fixed bed is communicated with the lower part of the fluidized bed; the fixed bed is communicated with the feeding pipe; the bottom of the tank body is provided with an air chamber, and the top of the air chamber is provided with an air distribution plate; the first air pipe is communicated with the air chamber; the fluidized bed is provided with a discharge hole.

Description

Stay tank for reducing burning rate of powder material, calcining device and method

Technical Field

The invention relates to the field of roasting, in particular to a residence tank for reducing the burning rate of powder materials, a calcining device and a calcining method

Background

Calcined dolomite is used as a raw material for smelting magnesium by a silicothermic process, and the burning reduction rate is one of important factors influencing the magnesium yield in a reduction tank. The traditional dolomite calcination mainly depends on a rotary kiln, but the rotary kiln is replaced by a more advanced suspension kiln due to the defects of poor heat transfer condition, long calcination time, low raw material utilization rate, high emission concentration of nitrogen oxides and the like.

The suspension kiln adopts advanced suspension calcination technology, and the dolomite blocks are ground into fine powder and then calcined. As the powder is adopted for calcination, the decomposition reaction rate of dolomite is greatly increased, the calcination time is sharply shortened, and the energy consumption of unit product is obviously reduced. The utilization rate of dolomite ore is effectively improved. At the same time, the flame temperature of the suspension calcination is lower, and the amount of generated nitrogen oxides is also lower. The dolomite after calcination is calcined dolomite. The calcined dolomite prepared by the method generally has a burning loss rate of 0.6-3%. The burning rate refers to the rate of change of the mass of calcined dolomite after calcination and after calcination at a high temperature.

However, the dolomite particles fed into the suspension kiln are of different sizes, under the influence of the milling equipment. In a shorter calcination time, the small-particle dolomite can be decomposed completely, but the large-particle dolomite is difficult to burn through. If the flame temperature is increased, the energy consumption is greatly increased; if the suspension kiln length is prolonged, i.e. the calcination time is prolonged, the investment costs are greatly increased. Thus, there is an urgent need for an apparatus and process that reduces the burn rate of calcined dolomite in suspension kilns.

Disclosure of Invention

The technical problems to be solved by the invention are as follows: the residence tank, the calcination device and the calcination method for reducing the burning rate of the powder materials can continue to calcine outside the suspension kiln, and the burning rate of the powder materials is reduced.

In order to solve the technical problems, the invention adopts the following technical scheme:

in a first aspect, the embodiment provides a residence tank for reducing the burning rate of powder materials, which comprises a tank body provided with an inlet and a first air pipe, wherein a separator is arranged in an inner cavity of the tank body, the inner cavity of the tank body is divided into a fixed bed and a fluidized bed by the separator, and the lower part of the fixed bed is communicated with the lower part of the fluidized bed; the inlet of the tank body is arranged on the fixed bed; the bottom of the tank body is provided with an air chamber, and the top of the air chamber is provided with an air distribution plate; the first air pipe is communicated with the air chamber; the fluidized bed is provided with a discharge hole.

As a preferable example, the residence tank further comprises a first hood, and the air distribution plate is provided with holes; the first hood is connected with the holes of the air distribution plate.

As a preferable example, the air outlet speed of the first hood is 5-20 m/s; the sum of the areas of the first hood accounts for 15-30% of the sum of the horizontal sectional areas of the fixed bed and the fluidized bed.

As a preferred example, the residence tank also comprises a feeding pipe and a connecting pipe, wherein the connecting pipe is connected between the inlet of the tank body and the feeding pipe, and the connecting pipe is positioned above the fixed bed.

As a preferable example, the top end of the fixed bed is an opening, and the inlet of the tank body is an opening of the fixed bed; the pipe diameter or the cross section area of the feeding pipe is smaller than the diameter or the cross section area of the fixed bed, and the pipe diameter or the cross section length of the connecting pipe gradually increases from top to bottom.

As a preferred example, the residence tank further comprises an air duct assembly, wherein the air duct assembly comprises a main air duct, at least one second air duct and a second hood; the main air pipe is communicated with the second air pipe, the second air pipe is fixedly connected in the inner cavity of the fixed bed, and the upper surface of the second air pipe is provided with holes; the second hood is connected with the hole of the second air pipe.

As a preferable example, the wind outlet velocity of the second hood is less than 1m/s, so that the concentration of decomposed gas at the smoke outlet is less than 30%; the sum of the areas of the second hood accounts for 10-20% of the horizontal sectional area of the fixed bed.

As a preferable example, the main air pipe is provided with an adjusting valve; a channel is formed between the adjacent second air pipes, and powder materials in the groove body downwards flow through the channel.

As a preferable example, the distance from the second air pipe to the top of the fixed bed is 1/3-1/2 of the height of the fixed bed.

As a preferred example, the residence tank also comprises a smoke exhaust outlet, wherein the smoke exhaust outlet is positioned on the side wall of the fixed bed and is close to the top end of the fixed bed.

As a preferable example, the powder material is a powder material which is not completely decomposed after suspension calcination.

As a preferable example, the powder material is calcined dolomite, quicklime, beta-spodumene or ferric phosphate.

In a second aspect, an embodiment of the present invention provides a calcining apparatus, including a suspension kiln, the above-mentioned residence tank, where the residence tank is communicated with an outlet of the suspension kiln through a cyclone separator; during operation, the raw materials of powder materials are fed into the suspension kiln.

As a preferable example, when the raw material of the powder material is dolomite powder, the calcined dolomite temperature entering the residence tank is 900-950 ℃; the temperature of calcined dolomite flowing out from a discharge hole of the fluidized bed is 750-850 ℃; the retention time of the calcined dolomite in the retention tank is 30-60 min.

As a preferable example, the calcining device further comprises a cooling device, and the cooling device is communicated with a discharge hole of the fluidized bed.

In a third aspect, an embodiment of the present invention provides a method for reducing a burning loss rate of a powder material, including:

step 10, calcining raw materials of powder materials by using a suspension kiln;

step 20, closing the first air pipe and the second air pipe, and feeding the powder material calcined in the step 10 into a fixed bed of the residence tank;

step 30, after the powder materials are piled up to a preset height in the fixed bed, a first air pipe is opened, the powder materials in the fixed bed are sent into the fluidized bed, and then flow out from a discharge hole of the fluidized bed; and opening a second air pipe, diluting and discharging gas generated by decomposing the powder material from a smoke discharge outlet, and controlling the calcination atmosphere.

In a preferred example, in the step 30, the powder material is stacked to a preset height in a fixed bed, which means that: the powder materials are piled up in the fixed bed to 20 cm to 30cm away from a smoke exhaust outlet of the fixed bed.

In the step 30, the air outlet speed of the first hood on the first air duct is 5-20 m/s; the wind outlet speed of the second hood on the second wind pipe is less than 1m/s.

As a preferred example, the step 30 further includes: and maintaining the opening states of the first air pipe and the second air pipe, continuously feeding the calcined powder material into the residence tank through the suspension kiln, continuously discharging the powder material through a discharge hole of the fluidized bed, and keeping the powder material in a flowing state in the residence tank until the calcination is finished.

In the step 30, the residence time of the powder material in the residence tank is preferably 30 to 60 minutes.

Compared with the prior art, the technical scheme of the invention can continue to calcine outside the suspension kiln, and reduce the burning rate of powder materials. The residence tank comprises a tank body with an inlet and a first air pipe, wherein a separator is arranged in the inner cavity of the tank body, the separator divides the inner cavity of the tank body into a fixed bed and a fluidized bed, and the lower part of the fixed bed is communicated with the lower part of the fluidized bed; the inlet of the tank body is arranged on the fixed bed; the bottom of the tank body is provided with an air chamber, and the top of the air chamber is provided with an air distribution plate; the first air pipe is communicated with the air chamber; the fluidized bed is provided with a discharge hole. The residence time of the powder material in the high temperature area is prolonged, and the powder material is further decomposed in the residence tank by utilizing heat carried by the powder material, so that the burning rate of the powder material is reduced. The residence tank shortens the residence time of the raw materials of the powder materials in the suspension kiln and saves investment cost.

Drawings

FIG. 1 is a schematic view of a residence tank in accordance with an embodiment of the present invention;

FIG. 2 is a cross-sectional view A-A of FIG. 1;

fig. 3 is a schematic structural view of a calcining apparatus according to an embodiment of the present invention.

The drawings are as follows: the device comprises a feeding pipe 1, a connecting pipe 2, a tank body 3, a fixed bed 31, a fluidized bed 32, a smoke exhaust outlet 4, a second air pipe 5, a second hood 6, a partition body 7, a first air pipe 8, an air chamber 9, an air distribution plate 10, a first hood 11, a discharge hole 12, a suspension kiln 13, a stay tank 14 and a cooling device 15.

Detailed Description

The technical scheme of the invention is described in detail below with reference to the accompanying drawings.

As shown in fig. 1, a residence tank for reducing the burning rate of powder materials in this embodiment includes a tank body 3 provided with an inlet and a first air duct 8. And feeding the calcined powder material into the tank body 3 from the inlet. A separator 7 is arranged in the inner cavity of the tank body 3. The partition 7 divides the inner cavity of the tank body 3 into a fixed bed 31 and a fluidized bed 32, and the lower part of the fixed bed 31 is communicated with the lower part of the fluidized bed 32. The inlet of the tank 3 is provided in the fixed bed 31. The bottom of the tank body 3 is provided with an air chamber 9, and the top of the air chamber 9 is provided with an air distribution plate 10. The first air pipe 8 is communicated with the air chamber 9. The fluidized bed 32 is provided with a discharge opening 12.

In the above embodiment, the calcined powder material output from the suspension kiln may be discharged from the solid phase outlet of the cyclone separator of the suspension kiln, enter the fixed bed 31 through the feed pipe 1, after the residence time in the fixed bed 31 reaches the preset time, open the first air pipe 8, send air flow into the air chamber 9, the air flow passes through the air distribution plate 10, drive the powder material at the lower part of the fixed bed 31, and output from the discharge port 12 of the fluidized bed 32. The powder material is continuously calcined in the fixed bed 31 at its own high temperature. In this embodiment, the powder material is a powder material which is not completely decomposed after suspension calcination. The raw materials of the powder material are dolomite, limestone, spodumene or ferric phosphate dihydrate. The raw materials of the powder material are respectively subjected to suspension calcination to obtain the powder material which is calcined dolomite, quicklime, beta-spodumene or ferric phosphate.

The staying tank is arranged, so that the powder materials output from the suspension kiln are continuously calcined in the staying tank. Through setting up the stay groove, can prolong the calcination time, make the powder material calcine more abundant, the burning rate is lower. Of course, after part of the powder material passes through the residence tank, complete decomposition cannot be achieved. In addition, the residence time of the raw materials of the powder materials in the suspension kiln can be properly reduced, and the height of the suspension kiln is reduced, so that the manufacturing cost of the suspension kiln is reduced.

Preferably, the residence tank further comprises a first hood 11, and the air distribution plate 10 is provided with holes; the first hood 11 is connected with the holes of the air distribution plate 10. In order to make the air flow velocity more uniform, a first hood 11 is provided on the air distribution plate 10. At the same time, the first hood 11 is arranged, so that powder materials in the fixed bed 31 and the fluidized bed 32 can be prevented from falling into the air chamber 9. More preferably, the first hood 11 is uniformly disposed on the air distribution plate 10.

Preferably, the air outlet speed of the first hood 11 is 5-20 m/s; the sum of the areas of the first hood 11 is 15 to 30% of the sum of the horizontal sectional areas of the fixed bed 31 and the fluidized bed 32. The air flow velocity from the first hood 11 cannot be too low, otherwise it is difficult to drive the powder material from the fixed bed 31 to the discharge port 12 of the fluidized bed 32. The air flow velocity from the first hood 11 cannot be too high because an excessive flow velocity would destroy the fixed bed. In the preferred embodiment, the air outlet speed of the first hood 11 is 5-20 m/s. The sum of the areas of the first hood 11 is 15 to 30% of the sum of the horizontal sectional areas of the fixed bed 31 and the fluidized bed 32. This achieves fluidized conveying of the powder material.

The inner cavity of the tank body 3 is divided into a fixed bed 31 and a fluidized bed 32 by a separator 7. As illustrated in fig. 1, the left chamber is a fixed bed 31 and the right chamber is a fluidized bed 32. The bottom of the residence tank is provided with a first air pipe 8 and an air chamber 9. An air distribution plate 10 and a first hood 11 are arranged above the air chamber 9. The air flow speed sprayed by the first hood 11 is 5-20 m/s, the powder material carried at the bottom of the fixed bed bypasses the separator 7 to enter the fluidized bed at the right side, and leaves from the discharge port 12 in a fluidization mode. At the same time, feed tube 1 was continuously fed. Under the action of gravity, the gap generated by carrying the fixed bed can be filled with the new powder material above, so that continuous discharging is realized.

Preferably, the residence tank further comprises a feeding pipe 1 and a connecting pipe 2, wherein the connecting pipe 2 is connected between the inlet of the tank body 3 and the feeding pipe 1, and the connecting pipe 2 is positioned above the fixed bed 31. Preferably, the top end of the fixed bed 31 is an opening, and the inlet of the tank body 3 is an opening of the fixed bed 31. The opening diameter or cross-sectional area of the fixed bed 31 and the pipe diameter or cross-sectional area of the feed pipe 1 tend to be different, so the connection pipe 2 serves to connect the opening of the fixed bed 31 and the feed pipe 1. More preferably, the pipe diameter or cross-sectional area of the feed pipe 1 is smaller than the diameter or cross-sectional area of the fixed bed 31, and the pipe diameter or cross-sectional area of the connecting pipe 2 is gradually increased from top to bottom. The pipe diameter or cross-sectional area of the connecting pipe 2 is gradually changed so that the powder material flowing out of the feed pipe 1 can flow more uniformly to the fixed bed 31.

Preferably, the residence tank further comprises an air duct assembly, as shown in fig. 2, comprising a main air duct, at least one secondary air duct 5, and a secondary hood 6. The main air pipe is communicated with the second air pipe 5, the second air pipe 5 is fixedly connected in the inner cavity of the fixed bed 31, and holes are formed in the upper surface of the second air pipe 5. The second hood 6 is connected with the holes of the second air pipe 5. Ambient air is fed into the main air duct, and then the air flows into the second air duct 5, and flows from the second hood 6 to the fixed bed 31. The second ductwork 5 may be arranged side by side in a plurality, for example 3, 5 or 6. By arranging the air pipe assembly in the preferred embodiment, the gas generated by the decomposition reaction is continuously diluted, the partial pressure of the gas in the residence tank is reduced, and the decomposition reaction is promoted to continue. If no other gas is mixed in the fixed bed 31, the decomposition reaction speed of the powder material is seriously slowed down, and even the decomposition reaction is stopped. Taking calcined dolomite as an example, when the calcined dolomite in the residence tank is further decomposed to generate carbon dioxide gas, if no other gas is mixed, the decomposition reaction speed of the calcined dolomite is seriously affected if the partial pressure of carbon dioxide is high. Therefore, the smoke exhaust outlet 4, the second air pipe 5 and the second hood 6 are arranged in the fixed bed 31, air in the environment is sent into the fixed bed 31, gas generated by decomposing the powder material is diluted, and the diluted gas is exhausted from the smoke exhaust outlet 4, so that the powder material in the fixed bed 31 can be normally decomposed.

Preferably, the wind outlet velocity of the second hood 6 is less than 1m/s, so that the concentration of the decomposed gas at the smoke outlet 4 is less than 30%; the sum of the areas of the second hood 6 accounts for 10-20% of the horizontal sectional area of the fixed bed 31. The air flow from the second air cap 6 into the fixed bed 31 is small, the apparent flow rate in the fixed bed 31 is small, and the apparent flow rate is only about 0.01m/s, and the particle fluidization speed is not reached, so that the temperature of the powder material is not influenced, and the powder material is not carried by the air flow flowing out of the second air cap 6 to flow upwards.

Preferably, the main air pipe is provided with an adjusting valve; a channel is formed between the adjacent second air pipes 5, and powder materials in the groove body 3 can pass through the channel to flow downwards, so that the powder materials are prevented from being accumulated above the second air pipes 5. The main air pipe is provided with a regulating valve which can regulate the air flow.

Preferably, the distance from the second air pipe 5 to the top of the fixed bed 31 is 1/3-1/2 of the height of the fixed bed 31. Thus, the height of the powder material above the second hood 6 is smaller than the height of the powder material below the second hood 6. The ambient air flowing out from the second hood 6 flows upwards under the influence of resistance to dilute the gas generated by decomposing the powder material, so that the concentration of the gas generated by decomposing the powder material contained in the flue gas is reduced, and the decomposition reaction is promoted. Taking calcined dolomite as an example, for example, the ambient air flowing out from the second hood 6 flows upward to dilute the carbon dioxide gas generated by decomposition of the calcined dolomite, so that the concentration of the carbon dioxide gas contained in the flue gas is reduced to 30% or less, and the decomposition reaction is promoted.

Preferably, the residence tank further comprises a fume outlet 4, wherein the fume outlet 4 is positioned on the side wall of the fixed bed 31 and is close to the top end of the fixed bed 31. The air flowing out of the second air pipe 5 dilutes the gas generated by decomposing the powder material to form flue gas. The flue gas exits from the flue gas outlet 4. The powder material located in the residence tank does not leave the fume outlet 4.

As shown in fig. 3, an embodiment of the present invention also provides a calcination apparatus including a suspension kiln 13 and a residence tank 14. The residence tank 14 of the above embodiment or preferred example is employed as the residence tank 14. The inlet pipe 1 of the residence tank is communicated with the outlet of the suspension kiln 13. In operation, the suspension kiln 13 is fed with raw materials of powder materials. The raw materials of the powder materials are subjected to suspension calcination in a suspension kiln 13 to form the powder materials, and the powder materials enter a residence tank 14. In the stay tank 14, the powder material is at a higher temperature and continues to decompose, corresponding to prolonged calcination in the suspension kiln 13. By arranging the stay groove 14, the calcination time of the raw materials of the powder materials in the suspension kiln 13 is reduced, the length of the suspension kiln 13 is reduced, and the manufacturing cost of the suspension kiln is reduced. The method is applicable to most powder materials, and the burning rate of the powder materials is reduced by adjusting the calcination temperature of the suspension kiln 13 and the residence time of the residence tank 14.

Preferably, when the raw material of the powder material is dolomite powder, the calcined dolomite temperature entering the stay tank 14 is 900-950 ℃; the temperature of calcined dolomite flowing out from the discharge port 12 of the fluidized bed 32 is 750-850 ℃; the retention time of the calcined dolomite in the retention tank 14 is 30 to 60 minutes. When the temperature of the calcined dolomite entering the residence tank 14 is 900-950 ℃, the calcined dolomite can continue to carry out decomposition reaction, and meanwhile, the calcining temperature in the suspension kiln 13 is not required to be too high, so that the energy consumption of the suspension kiln 13 is reduced. Since the temperature of the calcined dolomite flowing out from the discharge opening 12 of the fluidized bed 32 is relatively high, the calcining apparatus further comprises a cooling device 15, and the cooling device 15 is communicated with the discharge opening 12 of the fluidized bed 32. The cooling device 15 is used for cooling the calcined dolomite.

The residence tank of the embodiment prolongs the residence time of the powder material after suspension calcination in a high temperature zone, reduces the temperature required by the suspension kiln and the residence time of the powder material raw material in the suspension kiln, and reduces the operation cost and the investment cost. Through setting up the stay groove, reduced the calcination temperature of suspension kiln, can protect the refractory, reduce scattered heat loss and the heat loss of discharging fume, can also reduce the flue gas volume flow under the operating mode simultaneously, reduce equipment size. By providing a residence tank, the calcination time in the suspension kiln is reduced, and the suspension kiln length can be reduced.

By adopting the residence tank structure of the above embodiment, the embodiment further provides a method for reducing the ignition rate of powder materials, comprising:

step 10, calcining raw materials of powder materials by using a suspension kiln;

step 20, closing the first air pipe 8 and the second air pipe 5, and feeding the powder material calcined in the step 10 into a fixed bed 31 of a residence tank through a feed pipe 1;

step 30, after the powder materials are piled up to a preset height in the fixed bed 31, opening the first air pipe 8, feeding the powder materials in the fixed bed 31 into the fluidized bed 32, and then flowing out from the discharge hole 12 of the fluidized bed 32; and opening a second air pipe 5, diluting and discharging the gas generated by calcining the powder material from a smoke discharge outlet 4, and controlling the calcining atmosphere.

In the above method, the raw material of the powder material is calcined by the suspension kiln, and then the powder material is fed into the fixed bed 31 of the residence tank. The powder material output from the suspension kiln has a high temperature and is always in the decomposition reaction after entering the fixed bed 31. The powder material falls downward from the upper part of the fixed bed 31 and is accumulated in the fixed bed 31. After being piled up to a preset height, the first air pipe 8 is opened, powder materials in the fixed bed 31 are sent into the fluidized bed 32, and then flow out from the discharge hole 12 of the fluidized bed 32. The powder materials in the fixed bed 31 are conveyed to the discharge port 12 of the fluidized bed 32 by the air flowing out of the first air pipe 8. At the same time, the second air duct 5 is opened, and the second air duct 5 is filled with ambient air to feed the ambient air to the fixed bed 31. The ambient air dilutes the gas generated by decomposing the powder material, and the gas generated by decomposing is discharged from the smoke discharge outlet 4 to control the calcination atmosphere.

Preferably, in the step 30, the powder material is accumulated to a preset height in the fixed bed 31, which means that: the powder material is deposited on the fixed bed 31 to a distance of 20-30 cm from the smoke outlet of the fixed bed 31. If powder materials are accumulated to or above the smoke exhaust outlet, the smoke cannot be exhausted. If the powder material is deposited too far into the fume outlet, the fixed bed 31 will not be maximally utilized.

Preferably, in the step 30, the air outlet speed of the first hood 11 on the first air duct 8 is 5-20 m/s. The gas flow rate can drive the powder material to flow from the fixed bed 31 to the discharge port 12 of the fluidized bed 32. The wind outlet velocity of the second hood 6 on the second wind pipe 5 is less than 1m/s. The air flow velocity does not affect the temperature of the powder material, nor does it cause the powder material to be carried upward by the air flow flowing out of the second hood 6.

Preferably, the step 30 further includes: the opening state of the first air pipe 8 and the second air pipe 5 is kept, the calcined powder material is continuously fed into the residence tank through the suspension kiln, and continuously flows out of the powder material through the discharge port 12 of the fluidized bed 32, and the powder material is in a flowing state in the residence tank until the calcination is finished. After the first air pipe 8 and the second air pipe 5 are opened, the opened state is kept until the calcination is finished. After the first air pipe 8 and the second air pipe 5 are opened, the powder material in the stay groove is always in a flowing state. In the flowing process, the powder material is further decomposed, and the burning rate is reduced. Preferably, the residence time of the powder material in the residence tank is 30-60 min. By adjusting the air outlet speed of the first hood 11, the residence time of the powder material in the residence tank can be adjusted.

In the above method, in step 20 and step 30, the powder material calcined in the suspension kiln enters the fixed bed of the residence tank to be piled up. The heat on the surface of the particles is continuously conducted to the core parts of the particles under the action of temperature difference, so that the parts which are not decomposed in the powder materials are continuously decomposed. For example, the calcined dolomite is left in the residence tank for more than 30 minutes because the surface temperature of the calcined dolomite entering the residence tank is only about 900 ℃, so that the core part of the granule is further decomposed. In the stay tank, the powder material is further decomposed, so that the burning rate of the powder material is further reduced. By controlling the residence time of the powder material in the residence tank, the burning loss can be reduced to some extent.

The foregoing is merely a preferred embodiment of the present invention, and it should be noted that the specific embodiments described above are merely illustrative and not limiting of the present invention, as will be appreciated by those of ordinary skill in the art. Any modifications, equivalent substitutions and improvements will occur to those skilled in the art, and are intended to be included within the scope of the present invention.

Claims (20)

1. The residence tank is characterized by comprising a tank body (3) with an inlet and a first air pipe (8), wherein a separator (7) is arranged in an inner cavity of the tank body (3), the separator (7) divides the inner cavity of the tank body (3) into a fixed bed (31) and a fluidized bed (32), and the lower part of the fixed bed (31) is communicated with the lower part of the fluidized bed (32); the inlet of the tank body (3) is arranged on the fixed bed (31); an air chamber (9) is arranged at the bottom of the tank body (3), and an air distribution plate (10) is arranged at the top of the air chamber (9); the first air pipe (8) is communicated with the air chamber (9); the fluidized bed (32) is provided with a discharge port (12).

2. A stay tank according to claim 1, further comprising a first hood (11), said air distribution plate (10) being provided with holes; the first hood (11) is connected with the holes of the air distribution plate (10).

3. A stay tank according to claim 2, characterized in that the air outlet speed of the first hood (11) is 5-20 m/s; the sum of the areas of the first hood (11) accounts for 15-30% of the sum of the horizontal sectional areas of the fixed bed (31) and the fluidized bed (32).

4. A residence tank according to claim 1, characterized in that it further comprises a feed pipe (1) and a connecting pipe (2), said connecting pipe (2) being connected between the inlet of the tank body (3) and the feed pipe (1), said connecting pipe (2) being located above the fixed bed (31).

5. The residence tank according to claim 4, characterized in that the top end of the fixed bed (31) is an opening, and the inlet of the tank body (3) is an opening of the fixed bed (31); the pipe diameter or the cross section area of the feeding pipe (1) is smaller than that of the fixed bed (31), and the pipe diameter or the cross section length of the connecting pipe (2) is gradually increased from top to bottom.

6. A stay tank according to claim 1, further comprising an air duct assembly comprising a main air duct, at least one second air duct (5), and a second hood (6); the main air pipe is communicated with the second air pipe (5), the second air pipe (5) is fixedly connected in the inner cavity of the fixed bed (31), and the upper surface of the second air pipe (5) is provided with holes; the second hood (6) is connected with the holes of the second air pipe (5).

7. The residence tank according to claim 6, characterized in that the outlet air velocity of the second hood (6) is less than 1m/s, so that the concentration of decomposed gas at the fume outlet (4) is lower than 30%; the sum of the areas of the second hood (6) accounts for 10-20% of the horizontal sectional area of the fixed bed (31).

8. The stay tank according to claim 6, wherein the main air pipe is provided with a regulating valve; a channel is formed between the adjacent second air pipes (5), and powder materials in the groove body (3) flow downwards through the channel.

9. A residence tank according to claim 6, characterized in that the distance from the second air duct (5) to the top of the fixed bed (31) is 1/3-1/2 of the height of the fixed bed (31).

10. A residence tank according to claim 6, characterized in that it further comprises a fume outlet (4), said fume outlet (4) being located on the side wall of the fixed bed (31) and near the top end of the fixed bed (31).

11. The residence tank of claim 1, wherein the powder material is a powder material that fails to completely decompose after suspension calcination.

12. The residence tank of claim 11, wherein the powder material is calcined dolomite, quicklime, beta-spodumene or iron phosphate.

13. A calcination apparatus characterized by comprising a suspension kiln (13), a residence tank (14) according to any one of claims 1 to 10, the residence tank being in communication with the outlet of the suspension kiln (13) through a cyclone; during operation, raw materials of powder materials are fed into the suspension kiln (13).

14. The calcination apparatus according to claim 13, wherein when the raw material of the powder material is dolomite powder, the temperature of calcined dolomite entering the residence tank (14) is 900 to 950 ℃; the temperature of calcined dolomite flowing out from a discharge hole (12) of the fluidized bed (32) is 750-850 ℃; the retention time of the calcined dolomite in the retention tank (14) is 30-60 min.

15. The calcination apparatus according to claim 13, further comprising a cooling device (15), wherein the cooling device (15) is in communication with the discharge opening (12) of the fluidized bed (32).

16. A method of reducing the burn rate of a powder material comprising:

step 10, calcining raw materials of powder materials by using a suspension kiln;

step 20, closing the first air pipe (8) and the second air pipe (5), and feeding the powder material calcined in the step 10 into a fixed bed (31) of the stay tank;

step 30, after powder materials are piled up to a preset height in a fixed bed (31), a first air pipe (8) is opened, the powder materials in the fixed bed (31) are sent into a fluidized bed (32), and then flow out from a discharge hole (12) of the fluidized bed (32); and opening a second air pipe (5), diluting, discharging gas generated by decomposing the powder material from a smoke discharge outlet (4), and controlling the calcination atmosphere.

17. The method according to claim 16, wherein in step 30, the powder material is deposited to a predetermined height in a fixed bed (31), which means: the powder materials are piled up in the fixed bed (31) to 20 cm to 30cm away from the smoke exhaust outlet (4) of the fixed bed (31).

18. The method according to claim 16, wherein in the step 30, the air outlet speed of the first hood (11) on the first air duct (8) is 5-20 m/s; the air outlet speed of the second hood (6) on the second air pipe (5) is less than 1m/s.

19. The method of claim 16, wherein the step 30 further comprises:

and (3) keeping the opening states of the first air pipe (8) and the second air pipe (5), continuously feeding the calcined powder material into the stay tank through the suspension kiln, continuously discharging the powder material through a discharge port (12) of the fluidized bed (32), and keeping the powder material in a flowing state in the stay tank until the calcination is finished.

20. The method of claim 16, wherein in step 30, the powder material is held in the holding tank for a holding time of 30 to 60 minutes.