JPH08269516A - Operation method of fluidized bed furnace - Google Patents

Abstract

PURPOSE: To provide an operation method capable of changing the supply flow rate of products without fluctuating the holdup of respective fluidized bed furnaces of bubbling type fluidized bed furnaces of a multistage type. CONSTITUTION: The set value of the granular and powder material supply 13 rate into the system in the multistage fluidized bed furnaces of a granular and powder material bubbling type is equal to the sum of a product delivery 12 rate and the loss quantity in the system and the corrected hold up. The set value of product coarse particles 10 is equal to the value obtd. after the delivered particulate 11 quantity is subtracted from the set value of the total delivered granular and powder material (total delivered product) 12 quantity. The set value of the delivered particulate 9 quantity from the n-th stage (n: >=2) of the fluidized bed furnace (hereafter 'furnace') is set equal to the generated particulate 7 quantity (or the quantity obtd. by adding a prescribed quantity thereto). The set value of the delivered particulate 8 quantity from the n-th stage furnace is equal to the value obtd. after the corrected holdup (n+1 is required not to exceed the number of columns of the fluidized bed furnaces) within the (n+1)-th stage furnace is added to the value obtd. by subtracting the quantity of the particulates generated in the next stage furnace from the sum of the delivered coarse and fine particle quantity to the next stage furnace. As the result, the furnaces are operated by calculating the values of the set values of the granular and powder material input 13 quantity to the inside of the system, etc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a bubbling type fluidized bed furnace used for a catalytic reaction in a chemical plant, reduction of iron ore, etc. in a plurality of stages connected to each other in order to increase the reaction rate of the product. The present invention relates to a method for operating a fluidized bed furnace, which allows individual control of the amount of powder (or residence time) of powder or granules in a bed, and at the same time, the amount of supply of a finally manufactured product.

[0002]

2. Description of the Related Art As a conventional series multi-stage fluidized bed furnace, a device utilizing an overflow pipe such as a lime baking furnace has been devised. FIG. 6 is a schematic vertical sectional view showing an example of such an overflow tube type lime calcination furnace. In the figure, raw material limestone 19
Is supplied from the charging port 20 to the first preheating section 23. on the other hand,
The air supplied from the tuyere 21 provided at the lower part of the lime burning furnace burns the fuel supplied from the blowing port 22 at the lower part of the incineration chamber 26. The overflow pipe 27 passes through the first preheating section 23, the second preheating section 24, and then the third preheating section 25, and then,
The limestone introduced into the incinerator 26 is burnt and burned with quick lime 28.
Then, the quick lime 28 is introduced into the cooling unit 29 by the overflow pipe 27, cooled, and then discharged from the outlet 30.

However, such an overflow tube type device is effective only when the target raw material particle size is relatively uniform, for example, when handling particles having a wide particle size distribution such as iron ore. However, it is difficult to apply the method because the fine particles inevitably jump out of the fluidized bed under the condition that the coarse particles are fluidized.

Japanese Unexamined Patent Publication (Kokai) No. 58-341114 describes a method for producing reduced iron by keeping iron ore particles in a fluid state and contacting them with a high-temperature reducing gas (hereinafter referred to as prior art). That is, by supplying hydrocarbons to a fluidized bed preliminary reduction furnace that holds iron ore particles in a fluidized state to decompose and gasify a part of the hydrocarbons and partially reduce the iron ore particles, the by-produced carbon is generated as iron ore particles. Then, the carbon-deposited iron ore particles, the cracked gas and a part of the reduced iron from the subsequent fluidized bed furnace are supplied to the fluidized bed gas reforming furnace, and the cracked gas is mainly reduced gas containing CO and H _2. And then the iron ore particles and reduced iron discharged from the fluidized bed gas reforming furnace are supplied to the fluidized bed reducing furnace and brought into contact with the reducing gas while maintaining the fluidized state. A method of manufacturing is described. The fluidized bed preliminary reduction furnace, fluidized bed gas reforming furnace and fluidized bed reduction furnace in this prior art are all bubbling type fluidized bed furnaces.

[0005]

In the bubbling type fluidized bed furnace, the gas introduced into the air box part is uniformly introduced into the fluidized bed furnace through the perforated plate type gas dispersion plate, so that the gas is distributed on the dispersion plate. A fluidized bed region of the granular material is formed, and a so-called free-board region is formed above the fluidized bed region in which the granular material is scarcely present. This is for the following reason. That is, in the process in which the gas rises in the fluidized bed furnace, the particles having a certain particle diameter have a gas flow velocity at which the particles are in a stationary state in the gas flow due to the balance between the levitation force received from the rising gas flow and the gravity of the particles. That is, it has a so-called “end speed”. When the rising velocity of gas in the freeboard, that is, the superficial velocity exceeds a certain terminal velocity for particles, the particles cannot stay in the fluidized bed region and fly out of the fluidized bed furnace. However, since the granular material generally has a certain particle size distribution, it is divided into those that stay in the fluidized bed region and those that do not stay in the fluidized bed region and jump out from the fluidized bed furnace.

Generally, with respect to the particles (hereinafter, referred to as "generated fine particles") jumping out of the fluidized bed furnace as described above, they are collected and returned to the fluidized bed furnace again, or they are produced as a product in the next step. A cyclone is installed on the gas outlet side of the fluidized bed furnace for transfer. Therefore, in order to control the delivery flow rate and the retention amount of the product in the operation of the bag-limb type fluidized bed furnace, the particles (hereinafter,
In addition to the flow rate for extracting "coarse particles" from the fluidized bed region (hereinafter referred to as "delivery flow rate"), the flow rate for extracting particles (hereinafter referred to as "fine particles") collected by the cyclone from the cyclone (hereinafter referred to as ""Discharge flow rate") must be properly adjusted.

However, when the operating conditions such as the particle size distribution of the powder, the gas temperature, the gas amount and the pressure in the system change every moment, it is caused by the particle size distribution of the powder and the gas flow velocity in the freeboard. The proportion of fine particles changes. Therefore, for stable operation of the fluidized bed furnace, unless the flow rate of the generated fine particles is constantly grasped and the discharge flow rate of the coarse particles is adjusted accordingly, the discharge flow rate and the retention amount of the product will fluctuate. It becomes difficult to control.

Further, when a plurality of fluidized bed furnaces are connected in series, not all the fluidized bed furnaces have the same operating conditions. For example, in one fluidized bed furnace, particles that stay in the fluidized bed as coarse particles may jump out of the fluidized bed region as particles in another fluidized bed furnace and enter the cyclone, and vice versa. . Therefore, when adjusting the discharge flow rate of the coarse particles, the above-mentioned matters must be taken into consideration. In the case of a multi-stage fluidized bed furnace, it must be taken into consideration that there is a time delay before the operation change action performed in the upstream fluidized bed furnace affects the downstream fluidized bed furnace.

As described above, in the operation of the multi-stage bag-limbed type fluidized bed furnace, various operation factors influence each other, and if an operation action is taken for only a part of the factor change, it is transferred to the other part. Also, the control does not converge because it also affects. For example, the result is that the amount of residence in each fluidized bed furnace constantly changes.

On the other hand, neither the conventional overflow overflow furnace nor the prior art discloses a method for solving the above-mentioned problems.

Therefore, an object of the present invention is to solve the above-mentioned problems, so that in the operation of a multi-stage bag-limbed type fluidized bed furnace, the final stage fluidized bed furnace can be operated without changing the residence amount in each fluidized bed furnace. The operating method of the fluidized bed furnace is such that the delivery flow rate of the product, that is, the delivery flow rate of the product can be changed, or conversely, the retention amount in a predetermined fluidized bed furnace can be changed without changing the delivery flow rate of the product. To provide.

[0012]

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, the present invention provides a multi-stage fluidized bed furnace and a mass balance for each system of each fluidized bed furnace. The amount of loss in the system and the "corrected retention amount" obtained by applying a predetermined correction to the retention amount in each system are included, and the operation of the fluidized bed furnace is controlled based on this. It has the characteristics and has the following configuration.

That is, the operating method of the fluidized bed furnace according to the present invention is such that a gas introduction portion for fluidizing the powder or granular material, a dispersion plate for dispersing the gas, and a fine particle powder that is entrained in the gas and jumps out from the fluidized bed. In the operation of a multi-stage fluidized bed furnace in which two or more fluidized bed furnaces provided with a cyclone for collecting particles are connected in series, the following steps (a) to (d): (a) the whole fluidized bed furnace , The input flow rate setting value (Fin of the granular material into the system is
s) is added to the output flow rate of the granular material to the outside of the system, a value for correcting the difference between the set value and the measured value in the loss amount in the system and the total residence amount in the system. The step of calculating the input flow rate set value (Fin s), which is regarded as equal to the value obtained by (b) the flow rate set value Fc out s of the coarse-grained particles discharged from the final stage fluidized bed furnace.
Is considered to be equal to the value obtained by subtracting the flow rate of the fine particulate material discharged from the final stage fluidized bed furnace from the flow rate setting value of the total powder or granular material output from the system, Step of calculating the flow rate set value Fc out s of the coarse-grained powder, (c) n-th stage (however, n is a natural number of 2 or more, and the same hereinafter) fine-grained powder discharged from a fluidized bed furnace The flow rate setting value Fn f out s of the above is considered to be equal to the flow rate of the generated fine-grained powder or granular material in the n-th fluidized bed furnace or equal to the value obtained by adding a predetermined amount to the above, and The step of calculating the flow rate set value Fn f out s of the fine powder particles and the flow rate set value (Fn c out s) of the coarse particles discharged from the (d) nth stage fluidized bed furnace are the n-th From the sum of the flow rates of the coarse particles and the fine particles discharged from the first-stage fluidized bed furnace to the n-th fluidized bed furnace, the n-th fluidized bed is obtained. The value obtained by subtracting the flow rate of the generated fine particles in the inside is a value for correcting the difference between the set value and the measured value in the retention amount in the (n + 1) th stage fluidized bed furnace (where n + 1 is the multistage fluidized bed furnace If the number of towers of the fluidized bed furnace is exceeded, the corrected residence amount is regarded as equal to the value obtained by adding 0) and the flow rate setting value (Fn c out s) of the coarse particles is regarded as Calculation process,
By performing the above, the retention amount in each fluidized bed furnace is controlled, and the delivery flow rate of the product manufactured in the multi-stage fluidized bed furnace is controlled.

[0014]

FIG. 1 is a schematic flow chart showing a general form of a fluidized bed furnace used in the operating method of the present invention. Less than,
The operation and effect of the present invention will be described based on FIG. The gas for flowing the powder and granules enters the wind box 5 from the gas introduction part 16 in the lower part of the first-stage fluidized bed furnace 1 and causes the powder and the granules supplied to the first-stage fluidized bed furnace to flow therethrough, and then on the dispersion plate 14. Then, the coarse particle fluidized bed 6 is formed. The coarse particle fluidized bed 6 is formed in the same manner in the second and subsequent final fluidized bed furnaces.

As shown in the figure, a plurality of bubbling type fluidized bed furnace groups connected in series are considered to be one system, and the following equation (1): However, Fin s: Set value of the input flow rate of the granular material into the system α: Correction coefficient based on the loss (for example, dust loss) Fout: Output flow rate of the granular material outside the system Wi s: i-th fluidized bed furnace Residual amount setting value in WI: Actual amount of residual amount in i-th fluidized bed furnace T: By the amount of residual amount correction value, linked to the actual value Fout of 12 output of the granular material It is possible to control the set value Fin s of the amount 13 of input of the granular material into the inside.

If the formula (1) is not adopted and only the control action is taken to balance the entire balance without looking at the partial fluctuation in the amount of stay in the fluidized bed furnace, the total amount of stay will increase or decrease. However, as a result, the balance of control of the retention amount of other fluidized bed furnaces is lost. Also, in equation (1),
Since it is considered to correct the error between the set value ΣWi s (i = 1 to n) and the measured value ΣWi s (i = 1 to n) of the total amount of stay, the cause of some cause of the fluidized bed furnace Even if the amount of residence changes, or if the amount of residence set value of any fluidized bed furnace is changed, the total amount of total residence in the system is controlled so as to always be the total amount of residence set value. .

Next, in order to control the set value of the product delivery 12 flow rate from the final stage fluidized bed furnace 3, that is, the total delivery flow rate set value Fout s of the granular material to the outside of the system, the coarse particles are used. It is necessary to control the total flow rate of the discharge 10 flow rate and the particulate discharge 11 flow rate. However, in the case of fine particles, since it does not have a retention layer as a buffer in operation, the following formula (3): Fn f out s = Fn f out + β -------------------- ---------------- (3) However, Fn f out s: Set value of discharge amount of fine particles from n-th fluidized bed furnace Fn f out: N-th fluidized bed furnace Flow rate β of fine particles generated from: As shown in the correction coefficient, the set flow rate Fn f out s of fine particles is set.
Must be adjusted to the flow rate Fn f out of the generated fine particles 7 from the fluidized bed. When the discharge flow rate is less than or equal to the generated flow rate, the fine particles stay in the cyclone 4. vice versa,
If the delivery flow rate is greater than or equal to the generated flow rate, the delivery of the fine particles will be intermittent. On the other hand, the flow rate F of the generated fine particles 7
Since nf out fluctuates due to fluctuations in operating conditions, it lacks controllability as an industrial device.

Therefore, in the present invention, the set value Fout s of the product discharge 12 flow rate from the final stage fluidized bed furnace should be controlled by the coarse particle discharge 10 flow rate having a retention layer as an operation buffer. . That is, the following equation (2): Fc out s = F out s -Ff out ------------------------------ (2) However, Fc out s: Set value of flow rate of coarse particles discharged from the final stage fluidized bed furnace F out s: Set value of flow rate of total particle discharge to the outside of the system Ff out: Fine particle of powder outside the system As shown in the dispensing flow rate of No. 1, the product dispensing flow rate set value Fout s may be a value obtained by removing the fine particle dispensing 11 flow rate Ffout as the coarse particle dispensing 10 flow rate set value Fc out s. As a result, when the product delivery 12 flow rate set value Fout s is changed, the retention amount temporarily fluctuates, but the set value Fin s of the granular material flow rate input into the system by the equation (1) is also changed. Since it is changed, the flow rate of the fine particles 7 is generated Fn f out
Also changes and stabilizes with a new balance.

The control of the retention amount of the powder or granules in each fluidized bed furnace should be performed by the same logic for all fluidized bed furnaces except the final stage fluidized bed furnace 3 in which the product delivery flow rate control is prioritized. This logic is described in (4) below.
Formula: Fncouts = Fn-1cout + Fn-1fout-α'Fnfout + (Wn + 1s-Wn + 1r) / T ---------- (4) However, Fn c out s: Set value for discharging coarse particles from n-th fluidized bed furnace Fn-1 c out: Flow rate for discharging coarse particles from n-1 st fluidized bed furnace Fn-1 f out: n -Flow rate of fine particles discharged from the 1st-stage fluidized bed furnace α ': Correction coefficient based on loss (for example, dust loss) Fn f out: Flow rate of fine particles generated from the nth-stage fluidized bed furnace Wn + 1 s: n + 1 stage Set value of residence amount in the fluidized bed furnace Wn + 1 r: Actual value of residence amount in the n + 1 th fluidized bed furnace T: Residence amount correction value As shown in the table, supply of fine particles and coarse particles to the fluidized bed furnace 1 or 2 A value obtained by subtracting the flow rate Fn f out of the generated fine particles 7 from the flow rate of 13 or 8 + 9 and correcting the error of the retention value set value Wn + 1 s and the actual value Wn + 1 r of the fluidized bed furnace in the next process A furnace Payout rate setting value F of the coarse particles
You can use nc out s.

By adopting the logical operations represented by the above equations (1) to (4), the amount of residence in each fluidized bed furnace is controlled in the operation of a complicated multi-stage fluidized bed furnace, and the final product is obtained. It becomes possible to relatively easily perform the payout flow rate control.

[0021]

Next, the present invention will be described in more detail with reference to Examples. FIG. 2 is a diagram showing a schematic flow of the fluidized bed furnace used in the embodiment of the operating method of the present invention.

The equipment shown in the figure is a two-stage bubbling fluidized bed furnace for preheating and pre-reducing iron ore in a smelting reduction equipment, and the logic shown in the above equations (1) to (4) is calculated by a computer. It is automatically executed by the control system. The correction coefficients α, α ′ and β used for this control are as follows. α: 0.95 to 1.05 α ': 0.95 to 1.05 β: 10 kg / min

In the fluidized bed furnace shown in the figure, the temperature generated from a smelting reduction furnace (not shown) is 500 to 800 ° C.
A gas having a dipressure of 1.6 kg / cm ² G was used for the final stage fluidized bed furnace 3
Was introduced from the gas introduction part 16b at a flow rate of 4000 Nm ³ / min for bubbling as well as for preheating and pre-reduction, and then passed through the wind box 5b and the dispersion plate 14b to obtain a tower height of 9
m, the coarse particle fluidized bed 6 of the final stage fluidized bed furnace 3 with a tower diameter of 2.7 m
The gas introduced into b and thus introduced into the coarse particle fluidized bed 6b is passed through the cyclone 4b and the gas communication duct 17, and then the gas of the first-stage fluidized bed furnace 1 having a tower height of 5 m and a tower diameter of 2.5 m. Bubbling and introduction as preheating and pre-reducing gas from the introduction part 16a, then the air box 5a, the dispersion plate 14
After passing through a, it enters the coarse particle fluidized bed 6a for reuse, and is exhausted through the cyclone 4a.

On the other hand, the iron ore is the iron ore supply shoe 13
a to 300 to 500 kg / min for the first-stage fluidized bed furnace 1
Is supplied at the speed of
The following equation (1 ′) obtained when i = 1: Fin s = α × Fout + (ΣW1 s −ΣW1 r) / T --------- (1 ′) where α: 0.95 .About.1.05, and is adjusted by the powder or granular material flow rate adjuster 18a. In this way, the iron ore supplied to the first-stage fluidized bed furnace 1 is classified into coarse particles and fine particles by the gas rising after passing through the dispersion plate 14a. The quantitative ratio of the coarse particles to the fine particles is about 5: 5 to 2: 8.

The coarse particles classified in this manner form a coarse particle fluidized bed 6a of 5 to 10 tons on the dispersion plate 14a, are preheated and reduced, and then discharged from the first stage fluidized bed furnace 1. And is supplied to the final stage fluidized bed furnace 3. on the other hand,
The fine particles are carried by the gas and collected in the cyclone 4a. The collected fine particles are discharged from the cyclone 4a through the fine particle discharging shunt 9 according to the amount of the generated fine particles 7a, and are supplied to the final stage fluidized bed furnace 3.

The amount of coarse particles to be supplied to the final stage fluidized bed furnace 3 is expressed by the following equation (4 ') obtained by setting n = 2 in the equation (4): F2 c out s = F1 c out + F1 f out -Α'F2 f out + (W3s-W3r) / T --------- (4 ') However, based on α': 0.95 to 1.05, the flow rate regulator 18a 'Is adjusted. However, since the fluidized bed furnace in this embodiment is a two-stage type, there is no third stage fluidized bed furnace. Therefore, both W 3 s and W 3 r in the right side of the above equation (4 ′) are 0. The coarse particles and fine particles thus fed to the final stage fluidized bed furnace 3 are newly classified into coarse particles and fine particles according to the operating conditions of the final stage fluidized bed furnace 3.

The classified coarse particles form a coarse particle fluidized bed 6b on the dispersion plate 14b and are preheated / reduced to produce product coarse particles, while the classified fine particles are conveyed by a gas and cyclone. Captured at 4b.

The collected fine particles are discharged from the cyclone 4b according to the amount of the generated fine particles 7b.
Paid out from. On the other hand, the product coarse particles are expressed by the following formula (2): Fc out s = F out s -F f out ---------------------------- -Based on (2), while the flow rate is adjusted by the granular material flow rate adjuster 18b, the product coarse particle supply shoe 10 dispenses the product.

FIG. 3 is a correlation diagram between the product delivery flow rate set value and its actual value in the embodiment of the operation method of the present invention described above. As is clear from the figure, the actual product delivery flow rate value is within ± 15% of the set value, and is controlled accurately.

FIGS. 4 and 5 show retention amount set values and retention amount results in the first-stage fluidized bed furnace and the second-stage fluidized bed furnace (final stage fluidized bed furnace) in the embodiment of the operating method of the present invention described above. It is a graph which shows the time-dependent change of the deviation with a value. The actual amount of residence is calculated by measuring the pressure difference (fluidized bed differential pressure) at a predetermined position in the fluidized bed furnace using a differential pressure gauge, and
Formula: Actual amount of stay = Fluidized bed differential pressure x Fluidized bed cross section --------------------- (5) In this example, the fluidized bed differential pressure is 1000 to 2000 mmAq and the fluidized bed cross sectional area is 5.72.
It is 6 m ² . In the figure, the retention amount setting value of the first-stage fluidized bed furnace is set to 5 ton
It is a control result when it is turned on. As is clear from the figure, the standard deviation σ of the actual value with respect to the set value is within the range of 0.3 to 0.4 ton in any fluidized bed furnace, and is accurately controlled.

[0031]

As described above, according to the present invention, in the operation of the multi-stage bubbling type fluidized bed furnace in a chemical plant, an iron ore reduction plant, etc., the product amount can be controlled while controlling the retention amount of each fluidized bed furnace. When controlling the discharge flow rate, a complicated operation can be easily performed, and a method for operating a fluidized bed furnace that can be automatically performed by using a computer can be provided, which is extremely useful industrially. The effect is brought about.

[Brief description of drawings]

FIG. 1 is a schematic flow chart showing a general form of a fluidized bed furnace used in an operating method of the present invention.

FIG. 2 is a schematic flow diagram of a two-stage bubbling fluidized bed furnace used in an example of the operating method of the present invention.

FIG. 3 is a correlation diagram between a product payout flow rate set value and its actual value in the embodiment of the operating method of the present invention.

FIG. 4 is a graph showing a change with time of a deviation between a stay amount set value and a stay amount actual value in a first-stage fluidized bed furnace in an example of the operating method of the present invention.

FIG. 5 is a graph showing a change over time in the deviation between the retention amount set value and the retention amount actual value in the final stage fluidized bed furnace in the example of the operating method of the present invention.

FIG. 6 is a schematic vertical sectional view showing an example of a conventional series multi-stage fluidized bed furnace.

[Explanation of symbols]

 1 1st stage fluidized bed furnace 2 2nd stage fluidized bed furnace 3 Final stage fluidized bed furnace 4 Cyclone 4a Cyclone of 1st stage fluidized bed furnace of Example 4b Cyclone of final stage fluidized bed furnace of Example 5 Windbox 5a Implementation Example First Stage Fluid Bed Furnace Wind Box 5a Final Stage Fluid Bed Furnace Wind Box 6 Coarse Particle Fluidized Bed 6a Example First Stage Fluid Bed Furnace Coarse Particle Fluidized Bed 6b Final Stage Fluidization of the Example Coarse particle of fluidized bed fluidized bed 7 Particles generated 7a Particles generated in first stage fluidized bed furnace of Example 7b Particles generated in final stage fluidized bed furnace of Example 8 Coarse particle delivery shunt 8a Example of Example 1 Coarse particle delivery shunt 9 for staged fluidized bed furnace 9 Particle delivery shunt 10 Product coarse particle delivery shunt 11 Product particulate delivery shunt 12 Product delivery 13 Input of powder into the system 13a Iron ore supply shoe -T 14 Dispersion plate 14a First embodiment Dispersion plate 14b of the first-stage fluidized bed furnace Dispersion plate of the final stage fluidized bed furnace of the example 15 Freeboard 16 Gas introduction part 16a Gas introduction part 16b of the first stage fluidized bed furnace of the example 16b Final stage of the example Gas introduction part of fluidized bed furnace 17 Gas communication duct 18 Powder and granular material flow rate controller 18a Powder and granular material flow rate controller of first stage fluidized bed furnace of Example 18b Powder and granular material flow rate adjustment of final stage fluidized bed furnace of Example 18b Container 19 Limestone 20 Inlet 21 Tuyere 22 Blow-in 23 First 1st preheating section 24 2nd preheating section 25 3rd preheating section 26 Incinerator room 27 Overflow pipe 28 Quick lime 29 Cooling section 30 Discharge outlet

Claims (1)

[Claims] 1. A fluidized bed furnace provided with a gas introduction part for fluidizing powders and granules, a dispersion plate for dispersing the gas, and a cyclone for collecting fine particles that accompany the gas and fly out of the fluidized bed. In the operation of a multi-stage fluidized bed furnace in which two or more towers are connected in series, the following steps (a) to (d): (a) When all the fluidized bed furnaces are regarded as one system, Input flow rate setting value (Fin
s) is added to the output flow rate of the granular material to the outside of the system, a value for correcting the difference between the set value and the measured value in the loss amount in the system and the total residence amount in the system. The step of calculating the input flow rate set value (Fin s) by assuming that the flow rate set value (Fc out s) of the coarse particles discharged from the final stage fluidized bed furnace is From the flow rate setting value of the total powder or granular material output from the system, it is regarded as equal to the value obtained by subtracting the flow rate of the fine particles discharged from the final stage fluidized bed furnace, Flow rate setting value (Fc
out c), (c) nth stage (however, n is a natural number of 2 or more. The same applies below) Flow rate set value of fine particles discharged from a fluidized bed furnace (Fn
f out s) is regarded as equal to the flow rate of the fine particles generated in the n-th fluidized bed furnace or equal to a value obtained by adding a predetermined amount to the flow rate set value (F
nf out s) is calculated, and (d) the flow rate setting value (Fn c out s) of the coarse particles discharged from the nth stage fluidized bed furnace is calculated from the n-1st stage fluidized bed furnace. A value obtained by subtracting the flow rate of fine particles generated in the nth stage fluidized bed furnace from the sum of the flow rate of coarse particles and the flow rate of fine particles discharged to the nth stage fluidized bed furnace is the n + 1th stage fluidized bed. A value for correcting the difference between the set value and the measured value of the residence amount in the furnace (however, when n + 1 exceeds the number of towers of the fluidized bed furnace constituting the multi-stage fluidized bed furnace, the corrected residence amount is 0. The step of calculating the flow rate set value (Fn c out s) of the coarse particles by performing the step of calculating the flow rate set value (Fn c out s) of the coarse particles is controlled to control the residence amount in each of the fluidized bed furnaces. And controlling the delivery flow rate of the product produced in the multi-stage fluidized bed furnace. Method.