JPH0285690A - Temperature control for fluidized-bed furnace - Google Patents

Abstract

PURPOSE:To contrive higher productivity through a shortening of a treating time by a method wherein an upper set temperature for a heating chamber is set to be lower in the process from a step of heating a fluidized bed to a step of stabilizing the temperature of the fluidized bed. CONSTITUTION:In a heating step 22, heat is supplied from a heating chamber 3 to a fluidized bed 7', whereby the bed 7' is heated, and the temperature of a material being heated 14 is also raised accordingly. When the temperature of the fluidized bed 7 approaches a set temperature 13, the temperature of the heating chamber 3 is changed to a lower value. Thus, the quantity of heat supplied from the heating chamber 3 to the fluidized bed 7 is decreased. Therefore, the rise of the temperature of the fluidized bed 7' beyond a set temperature TB after the bed temperature reaches the set temperature is small, so that the time necessary for the over-raised temperature of the fluidized bed 7' to return to the set temperature TB is short. As a result of this effect, the temperature of the fluidized bed 7' is stabilized to a set temperature in a short time.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a fluidized bed furnace in which a heating chamber is attached to a retort with a fluidized bed inside, and a low-temperature heat-treated material is charged into the fluidized bed. The present invention relates to a temperature control method for a fluidized bed furnace in which the temperature of the heat-treated material is then brought to a predetermined temperature.

[Conventional technology]

As shown in FIG. 3, the upper limit set temperature TA" of the heating chamber is set higher than the set temperature TB' of the fluidized bed.

After the material to be heat treated is charged into the fluidized bed, the temperature of the fluidized bed is raised by supplying heat from the heating chamber to the fluidized bed.After the fluidized bed reaches the set temperature, The temperature TI' of the heating chamber is controlled by the temperature T2' of the fluidized bed.As a result, the temperature T2° of the fluidized bed is controlled as shown in (su).
gradually approaches the set temperature TB', and the temperature TB''
Stabilize at (eg ±3°C).

[Problem to be solved by the invention]

In this conventional temperature control method for a fluidized bed furnace, the temperature TA'
is set relatively high compared to the temperature TB''.

Therefore, after the temperature T2° of the fluidized bed reaches the set temperature TB' at the point in time (B), the temperature T2' increases (excessively rises) as shown in (T').Then, the temperature T2' becomes (CH). ), it takes a long time to return to the set temperature TB'.

As a result, there is a problem in that it takes a long time (the time for the constant temperature step 23°) to reach the point (S) through such repetition. In order to shorten the time of this step 23°, it may be possible to set the temperature TA' relatively low, but in this case, the amount of heat supplied from the heating chamber to the fluidized bed will decrease ( ) to (°) (temperature raising step 22°) is problematic. All of these methods have the problem of prolonging the step 21'' from raising the temperature of the object to be heat-treated to constant temperature, which impairs productivity.

The present invention has been made in view of the above points, and its purpose is to shorten both the temperature raising process and the temperature constant process, thereby improving productivity by shortening the processing time. It is an object of the present invention to provide a temperature control method for a fluidized bed furnace that can achieve the following.

[Means to solve problems]

In order to achieve the above object, the present invention takes the measures as described in the claims above, and its effects are as follows.

[Effect]

In the temperature raising step, heat is supplied from the heating chamber to the fluidized bed to raise the temperature of the fluidized bed, and the temperature of the object to be heat treated also rises accordingly. When the temperature of the fluidized bed approaches the set temperature, the temperature of the heating chamber is changed to a lower temperature. Therefore, the amount of heat supplied from the heating chamber to the fluidized bed is reduced. For this reason, after the fluidized bed reaches the set temperature, the excessive rise above the set temperature of the fluidized bed is small, and as a result, the time required for the excessively raised temperature of the fluidized bed to return to the set temperature is short. As a result of these actions, the temperature of the fluidized bed stabilizes at the set temperature in a short time.

〔Example〕

The drawings showing the embodiments of the present application will be described below.

In FIG. 1, ■ indicates a bunch-type fluidized bed furnace.

Reference numeral 2 denotes a furnace body in a fluidized bed furnace, and a heating chamber 3 is provided inside. 4 is a burner attached to the furnace body 2 as an example of a heat source; 5 is a heating room temperature sensor provided in the heating chamber 3; for example, a thermocouple is used; 6 is a retort in a fluidized bed furnace; A fluidized bed chamber 7 is provided, and a pressure chamber 8 is further provided below the fluidized bed chamber 7 with a dispersion plate 9 in between. Heat-resistant granular material is stored in the fluidized bed chamber 7. 10 is a fluidizing gas supply port communicating with the pressure chamber 8. 11 is a lid that can be opened and closed; 12 is a fluidized bed temperature sensor provided in the fluidized bed chamber 7;
For example, a thermocouple is used. Reference numeral 13 denotes a lifting rod, which is raised and lowered by means of a lifting i' device (not shown). Reference numeral 14 indicates an object to be heat-treated, which is placed in a basket suspended from the lifting rod 13, for example.

In the above-described structure, fuel is burned in the heating chamber 3 by the burner 4, and the temperature of the heating chamber 3 increases. The heat is transferred to the retort 6, and the powder and granular material in the fluidized bed chamber 7 becomes hot. Further, the fluidizing gas supplied to the pressure chamber 8 from the supply port 10 is blown into the fluidized bed chamber 7 through the dispersion plate 9, and the above-mentioned granular material in the fluidized bed chamber 7 is fluidized by the gas, forming a so-called fluidized bed. be done. In this state, when the heat-treated material 14 is put into the fluidized bed 7, it comes into contact with the granular material which is heated to a high temperature and is in a fluidized state.
The powder itself receives heat and its temperature rises.

Next, temperature control and changes in temperature of each part in the case of the above operation will be explained based on FIG. 2.

Detection signals from the sensors 12 and 5 are given to a control device (not shown), and the operation of the burner 4 is controlled by the control device. The control is such that the detected value of the temperature of the fluidized bed 7° by the sensor 12 is the set temperature TB of the fluidized bed 7° (for example, 780°C).
), the burner 4 is activated (or the output is increased), and when the temperature is higher, the burner 4 is stopped (or the output is decreased), that is, the temperature of the fluidized bed 7° is maintained at the set temperature. be. In addition, sensor 5
This control stops the operation of the burner 4 when the detected value of the temperature of the heating chamber 3 exceeds the upper limit setting temperature TA (for example, 1050° C.) of the heating chamber, that is, the control suppresses the upper limit of the temperature of the heating chamber 3. Note that the upper limit set temperature TA is set higher than the set temperature TB of the fluidized bed.

In this control mode, before the material to be heat treated is placed in the fluidized bed, the temperature T1 of the heating chamber 3 and the temperature T2 of the fluidized bed are in the state shown in (a) in FIG. 2, respectively. . In other words, the temperature T2 is stable at the set temperature TB (
For example, ±3°C), and the temperature TI is higher than the set temperature TB and stable by an amount sufficient to replenish the fluidized bed with the amount of heat removed from the fluidized bed 7' by the flow of the fluidizing gas. are doing.

In this state, the object to be heat treated 14 which is at a low temperature at the time of (b)
is charged into the fluidized bed at 7°. Then, the object to be heat-treated receives heat from the fluidized bed, and its temperature T3 rises as shown in the figure (c). On the other hand, in the fluidized bed, as the heat is applied to the object to be heat treated, the temperature T2 thereof decreases as shown in the figure. Heat is also taken from the heating chamber 3 by the fluidized bed whose temperature has been reduced, and its temperature TI decreases as shown in the figure. In this state, since the temperature detected by the sensors 12 and 5 is low, the burner 4 is naturally in the operating state. Due to the operation of the burner 4, the temperature T1 of the heating chamber 3 eventually rises as shown in (d). Note that the upper limit of the temperature ↑l is suppressed by the upper limit set temperature TA as described above. When the temperature of the heating chamber increases as described above, the temperature T2 of the fluidized bed and the temperature T3 of the object to be heat treated also increase.

As shown in the figure (
(e) When it reaches the temperature TO which is lower than the set temperature TB by a predetermined temperature ΔL, the upper limit set temperature of the heating chamber is set at the temperature TA within a range higher than the set temperature TB. to a lower temperature TC (e.g. 9
50°C). In short, when the temperature of the fluidized bed increases, approaches the set temperature, and reaches a temperature lower than the set temperature by a predetermined temperature, the upper limit set temperature of the heating chamber is changed to the set temperature of the fluidized bed. Change lower within the range higher than the temperature. This change is automatically made by the control device, but may also be made manually. Above temperature Δt
is preferably determined experimentally, taking into consideration the time constant of heat transfer from the heating chamber to the fluidized bed, which varies depending on the shape and scale of the fluidized bed furnace l, and is, for example, 3 to 10°C. After changing the upper limit set temperature above, the temperature of the heating chamber will be the same temperature T.
The upper limit is controlled by C.

Even after the temperature T2 of the fluidized bed reaches the temperature T8, the fluidized bed receives heat from the heating chamber, so the temperature T2 further increases and eventually reaches the set temperature TB as shown in (v). Temperature T
After the temperature 2 reaches the set temperature TH, it continues to rise due to the supply of heat from the heating chamber 3. However, since the temperature TI of the heating chamber has become low as a result of the upper limit set temperature being changed to a lower value as described above, the excessive rise value of the temperature T2 is small as shown in (g). Therefore, the temperature T2 becomes the set temperature T in a short time as shown in (H).
Return to B. After the temperature T2 repeats such excessive rise and return, it eventually stabilizes at the set temperature TB (for example, ±3° C.) as shown in (S).

As a result of the temperature T2 being stabilized as described above, the temperature of the object to be heat treated is also stabilized at the same temperature. When this state is achieved, the object to be heat-treated is subjected to the next treatment step (for example, a soaking step or a cooling step, although it differs depending on the #1 type of object to be heat-treated).

In this specification, the process from charging the low-temperature heat-treated material into the fluidized bed to stabilizing the temperature T2 of the fluidized bed to the set temperature TB, that is, the process indicated by the reference numeral 21 in the figure, is the temperature raising process. Also called temperature constant process.

Further, the process indicated by the reference numeral 22 from when the material to be heat treated is charged into the fluidized bed until the temperature T2 of the fluidized bed is raised to the set temperature TB is also referred to as a temperature raising process. Then, until the temperature T2 of the fluidized bed is constant at the set temperature TB,
The process indicated by the reference numeral 23 is called a constant temperature process.

In the case of the above temperature conditions, step 21 takes, for example, 28 minutes (step 22 takes 20.5 minutes, step 23 takes 7.5 minutes).
), the conventional step 21'' takes 50 minutes (step 22''
(20 minutes for step 23' and 30 minutes for step 23'), an improvement of 1.8 times in productivity is achieved.

〔Effect of the invention〕

As described above, in the present invention, the low-temperature heat-treated object 14
When the heat-treated material 14 is charged into the fluidized bed 7 and raised in temperature, the heat-treated material 14 comes into contact with the fluidized powder and granules and receives heat, so the temperature of the heat-treated material 14 is raised extremely quickly. Of course, this has the effect of increasing the temperature of the fluidized bed 7° by rapidly supplying heat from the high temperature heating chamber 3 to the fluidized bed 7°, so it can be set in an extremely short time. It has the effect of reaching the temperature.

Moreover, the upper limit temperature of the heating chamber is changed to a lower value in the process from the temperature raising process to the constant temperature process of the fluidized bed, so after reaching the set temperature as described above, the heating chamber 3 is changed to the fluidized bed 7. The heat supplied is reduced, and the excessive rise in temperature of the fluidized bed at 7° above the set temperature is small, and as a result, the time required for the excessively raised temperature to return to the set temperature is shortened. be. This has the effect of stabilizing the temperature of the object to be heat treated 14 at the set temperature in a short time.

In this way, the present invention can raise the temperature of a low-temperature object to be heat-treated in a short time, and after raising the temperature, can stabilize the temperature at a set temperature in a short time. The processing time required to reach the temperature can be significantly shortened compared to the above-mentioned conventional technology, which is useful in improving productivity.

[Brief explanation of the drawing]

The drawings show an embodiment of the present application, and FIG. 1 is a longitudinal sectional view of a fluidized bed furnace, and FIG. 2 is a graph showing temperature changes in a heating chamber, a fluidized bed, and a material to be heat treated. Figure 3 is a second diagram showing a conventional example.
Figure and equivalent figure. 3... Heating chamber, 6... Retort, 7''... Fluidized bed, 14... Material to be heat treated. 1 ■ Figure 2 Figure 3

Claims (1)

[Claims] A heating chamber is attached to the retort, which has a fluidized bed inside.
The upper limit temperature setting of the heating chamber is set higher than the setting temperature of the fluidized bed, and after charging the material to be heat treated into the fluidized bed,
A temperature control method for a fluidized bed furnace, in which the temperature of the fluidized bed is raised by supplying heat from the heating chamber to the fluidized bed, and after the fluidized bed reaches a set temperature, the temperature of the heating chamber is controlled by the temperature of the fluidized bed. A temperature control method for a fluidized bed furnace, characterized in that the upper limit set temperature of the heating chamber is changed to a lower value in the process from the step of raising the temperature of the fluidized bed to the subsequent step of constant temperature.