JPH10132212A - Circulating particle size monitor for circulating fluidized-bed apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To continuously monitor information regarding a particle size of circulating particle during operating in a circulating fluidized-bed apparatus having a combustion chamber and a fluidized-bed type external heat exchanger receiving particles flowing out together with combustion gas from the chamber, cooling and then returning it to the chamber. SOLUTION: A temperature detecting end 26 and a heat transfer probe 27 are installed in a fluidized-bed type external heat exchanger 3. An output of the end 26 and a signal of a surface temperature of the probe 27 are sent to a calculator 28, which outputs a temperature difference. Power supplied to the probe 27 is regulated by a power regulator 29 so that the difference becomes a predetermined value. A heat transfer coefficient Kt between the surface of the probe 27 and a particle layer is calculated by a calculator 30 from energy given to the probe 27, temperature difference and area of a heating surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circulating fluidized bed apparatus having a fluidized bed type external heat exchanger that receives particles flowing out of a combustion chamber together with combustion gas, cools the particles, and returns the particles to the combustion chamber. The present invention relates to an apparatus for monitoring particle size.

[0002]

2. Description of the Related Art In a circulating fluidized bed apparatus such as a circulating fluidized bed boiler, it is necessary to grasp the particle size of circulating particles.
It is indispensable to ensure stable operation of the equipment and maintain good performance. However, there is no way to obtain information on the particle size of circulating particles continuously and easily during operation, and it is necessary to take out the particles as needed and measure the particle size distribution etc. Was in

[0003]

As described above, in order to know the particle size of circulating particles in a circulating fluidized bed apparatus, conventionally, particles are extracted from a particle circulation system of an operating apparatus and analyzed. We have gained information on particle size. However, this conventional method has the following problems. (1) Generally, there is a danger from handling a high temperature fluid material. (2) It is difficult to obtain data over time because analysis takes time.

The present invention relates to a circulating fluidized bed apparatus having a combustion chamber and a fluidized bed type external heat exchanger that receives particles flowing out of the combustion chamber together with the combustion gas, cools the particles, and returns the particles to the combustion chamber. It is an object of the present invention to provide a device capable of continuously monitoring information on the particle size of the device during operation of the device.

[0005]

According to the present invention, the heat transfer coefficient between the particle layer and the heat transfer surface changes when the particle diameter changes among the physical property values of the particles. A probe for measuring a change in the coefficient was provided in an external heat exchanger of a fluidized bed system, and the above-mentioned problem was solved by knowing the particle size from the obtained heat transfer coefficient.

That is, in order to solve the above-mentioned problems, the present invention obtains a heat transfer coefficient between the probe and the circulating particles by using a heat transfer probe installed in an external heat exchanger, thereby obtaining a change in particle size of the circulating particles. Provided is a particle size monitoring device, comprising a means for measuring a temperature difference between the probe and the circulating particles, and a means for measuring energy required to generate the temperature difference. .

In the particle size monitor according to the present invention, the heat transfer probe applies or removes energy from the outside, and generates a temperature difference between the probe surface and the particle layer. Then, the amount of the given or taken energy is obtained, and the generated temperature difference is obtained. This temperature difference and given to generate that temperature difference,
Alternatively, the heat transfer coefficient between the probe surface and the particle layer is calculated from the energy taken, and the change in the particle diameter is obtained from the relationship between the particle diameter and the heat transfer coefficient, which is separately provided.

In this way, the particle size of the circulating particles can be monitored, and according to the present invention, sampling of high-temperature particles becomes unnecessary, and safety is increased. Further, according to the present invention, since data on the particle size of the circulating particles can be obtained continuously and promptly, it is easy to grasp changes over time and feedback to operating conditions is also easy.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment in which the present invention is applied to particle size monitoring of circulating particles in a circulating fluidized bed boiler will be specifically described with reference to the drawings. The circulating fluidized bed boiler shown in FIG. 1 includes a combustion chamber 1, a cyclone 2, a fluidized bed type external heat exchanger 3, and main parts of a stand pipe 4.

[0010] Air for combustion is supplied from the blowers 5a, 5b, 5c, and in the combustion chamber 1, a fluid state called a high-speed fluidized bed is formed, and the fuel supplied from the fuel supply device 6 is burning. Fluid such as silica sand is present in the boiler, and circulates together with unburned fuel in a system formed by the combustion chamber 1, the cyclone 2, the external heat exchanger 3, and the stand pipe 4.

The combustion gas and the fluidized material are separated by the cyclone 2, and the gas is discharged from the chimney 10 through the convection heat transfer surface 7, the bag filter 8, and the induction fan 9. The separated fluidized material enters the fluidized bed type external heat exchanger 3, is cooled on the internal heat transfer surface, and is then recirculated to the combustion chamber 1.

Particles remaining in the combustion chamber 1 are discharged out of the system by an ash removing device 11 as needed. The fluidized bed type external heat exchanger 3 has a temperature detecting end 26 for the purpose of obtaining a heat transfer coefficient.
And a heat transfer probe 27 are attached, both of which are in a dipped state in the fluidized bed.

FIG. 4 shows an example of the structure of the heat transfer probe 27. A heater 31 is provided inside, and a thermocouple 32 is embedded at a position near the outer surface of the probe, and terminals connected to the outside are provided from the heater 31 and the thermocouple 32, respectively.

There are many specific methods for obtaining the heat transfer coefficient Kt [W / m ² · k] between the particle layer and the surface of the heat transfer probe 27. Here, the following method is used. First, energy E is applied to the probe so that a certain temperature difference occurs between the heating surface provided in the fluidized bed (here, the surface of the heat transfer probe 27) and the particle layer temperature. Temperature T ₂ of the temperature of the heating surface at this time T ₁ particle layer, the energy added E, the heat transfer coefficient Kt and the area of the heating surface and A is determined by the following equation.

[0015]

(Equation 1)

The specific operation of the present apparatus is as follows.
The output of the temperature detecting end 26 for measuring the temperature of the particle layer and the signal of the surface temperature of the heat transfer probe 27 enter the calculator 28 and output the temperature difference T ₁ -T ₂ . The power supplied to the heat transfer probe 27 is adjusted by the power regulator 29 so that the temperature difference T ₁ -T ₂ becomes a preset value. The heat transfer coefficient Kt between the surface of the heat transfer probe 27 and the particle layer is calculated by the arithmetic unit 3
At 0, it is obtained by the equation (1) as described above.

Now, consider a case where the particle size distribution of circulating particles changes in a fluidized bed apparatus to which the present invention is actually applied. FIG. 3 shows the relationship among the particle diameter dp, the porosity ε, and the heat transfer coefficient Kt (the figure shows VDI-WAERMEA).
(TLAS 4th edition). According to this, if the porosity ε is fixed, the heat transfer coefficient also changes with a change in the particle diameter.

Therefore, when the heat transfer coefficient is determined by the apparatus of the present invention, a change in the particle diameter (a value as a representative diameter determined from the heat transfer characteristics) can be obtained from the change amount. Vacancy rate ε
Is a value defined by the following equation (2), but becomes substantially constant within a practical range in a fluidized bed heat exchanger of a circulating fluidized bed apparatus.

[0019]

(Equation 2)

[0020] The present invention and the target at the illustrating a flow material properties an example of using a fluidized bed apparatus which is (assuming), particle density [rho _p = 2
700 kg / m ³ , particle layer bulk density ρ _b = 1200 kg / m
³ (in flux). Therefore, the void ratio ε = 1− (ρ
_b / ρ _p ) = 1− (1200/2700) = 0.56, and this value can be handled as the value of the void ratio. With respect to the bulk density of the flowing particle layer, it is possible to use conventional knowledge, for example, a value estimated by the following equation (3).

[0021]

(Equation 3)

As a specific example, consider a case where the circulating particle diameter is coarsened. Generally, coarsening of circulating particles in a circulating fluidized bed apparatus often causes various performance degradations because the amount of circulating particles is reduced. In this case, the coarsening of the particles is indicated by a decrease in the heat transfer coefficient. In this case, it is possible to take measures such as replenishment of the fine fluid material and discharge of the coarse particles out of the system.

FIG. 2 is a diagram showing another embodiment obtained by modifying the embodiment of FIG. In this embodiment, in addition to the configuration shown in FIG. 1, the pressure loss per unit length of the particle layer can be measured by the differential pressure gauge 33 for the purpose of accurately knowing the porosity ε of the particle layer (fluidized bed). It is. Assuming that the length of the part where the pressure loss is measured is L and the measured pressure loss is Δp, the bulk density ρ _b of the particle layer is obtained by the following equation (4), so that the change in the particle diameter can be more accurately estimated. become.

[0024]

(Equation 4)

[0025]

As described above, according to the present invention, in a circulating fluidized bed apparatus, a heat transfer probe installed in a fluidized bed type external heat exchanger determines a heat transfer coefficient between the probe and circulating particles. This is a particle size monitoring device that knows the change in the particle size of the circulating particles, and has the following effects.

Since the change in the physical properties of the circulating particles in the circulating fluidized bed apparatus can be continuously and promptly grasped, it is possible to easily detect the occurrence of a trouble due to the fluctuation in the physical properties of the circulating particles. And contributes to the improvement of the performance and reliability of the circulating fluidized bed apparatus, for example, by being able to specifically evaluate the effects of various driving operations, and is very useful in practical use.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a circulating fluidized bed boiler according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a circulating fluidized bed boiler according to another embodiment.

FIG. 3 is a diagram showing a relationship between a void ratio, a particle diameter, and a heat transfer coefficient.

FIG. 4 is a sectional view showing a structural example of a heat transfer probe used in the apparatus of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Combustion chamber 2 Cyclone 3 External heat exchanger 4 Stand pipe 5a, 5b, 5c Blower 6 Fuel supply device 7 Convection heat transfer surface 8 Bag filter 9 Attraction fan 10 Chimney 11 Ash extraction device 26 Temperature detection end 27 Heat transfer probe 28 Calculation Unit 29 power regulator 30 operation unit 31 heater 32 thermocouple

Claims (1)

[Claims] 1. A circulating fluidized bed apparatus having a combustion chamber and a fluidized bed external heat exchanger that receives particles flowing out of the combustion chamber together with combustion gas, cools the particles, and returns the particles to the combustion chamber. Using a heat transfer probe installed in the vessel to determine the heat transfer coefficient between the probe and the circulating particles, a particle size monitoring device that knows the change in particle size of the circulating particles, the temperature between the probe and the circulating particles Means for measuring the difference,
And a means for measuring the energy required to generate the temperature difference.