JPS59225209A - Control method for height of fluidized bed and device thereof - Google Patents

Abstract

PURPOSE:To maintain the height of a fluidized bed at a specified value and to ensure a stable combustion state, by a method wherein the height of the fluidized bed is computed through a measurement of a pressure loss per unit height of the fluidized bed, and control is made on the height of the fluidized bed such that the height thereof is decreased through removal of a fluidized medium from the fluidized bed or the height of the fluidized bed is increased through charging of the fluidized medium to a fluidized floor. CONSTITUTION:In a fluidized-bed boiler 1, pressure sensors A1 and A2 are mounted to a freeboard part at an upper fluidized bed and the inlet part of a dispersion plate at the bottom of a fluidized bed, respectively, and pressure sensors B1 and B2 are attached at a distance of a specified layer height in the arbitrary position of the fluidized bed. A differential pressure between the pressure sensors B<1> and B2 is a differential pressure at a specified distance which varies with the particle size, particle distribution, and density of a fluidized medium, and a difference in height is a unit height (d). The detecting values of sensors B1 and B2 and the detecting values of the pressure sensors A1 and A2 are measured by differential pressure detectors B and A, respectively, the two measurements are inputted to a computer 6, and an instruction is sent from an instruction device 7 to a fluidized medium discharge valve 8 or a fluidized medium feeder 9.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for maintaining a constant height of a fluidized bed in a fluidized bed boiler so as to achieve moderate heat exchange.

A fluidized bed boiler is a combustion chamber filled with a fluidized medium made of inert granular material such as sand, and fluidized air is injected into the combustion chamber from the bottom of the combustion chamber, so that the fluidized medium is heated as if the liquid were boiling. A fluidized bed is formed in a state where it is almost fluidized, and combustible materials from coal ponds are fed into this fluidized bed formation area and combusted. Heat is exchanged between the fluid passed through the heat tube and the heat generated by the combustible material supplied into the fluidized bed region to generate hot fluid or steam. In FIG. 1, a fluidized medium 2 filled in a combustion chamber 1 forms a fluidized bed with fresh air supplied to a wind box 3, and a fuel supply pipe 4
The coal supplied by the plant is burned as fuel. By arranging heat transfer tubes 5 in the fluidized bed to avoid heat exchange, it functions as a boiler. While a normal boiler uses gas contact,
In this boiler, since the fluidized bed is in solid contact, a heat transfer efficiency of about 10f8 compared to a normal boiler can be obtained. Therefore, development of fluidized bed boilers has recently progressed.

The height of the fluidized bed in a fluidized bed boiler is related to the operation of the boiler.
If the fluidized medium is small, the heat exchanger tubes will be exposed and heat exchange will not be carried out sufficiently.

It can also be a cause of death. Furthermore, if the height of the flowing medium is too high, heat is lost by the water-cooled wall around the fluidized bed, which lowers the temperature of the fluidized bed and increases the generation of SOx. In this way, whether the height of the fluidized bed is high or low, the P match is poor. For these reasons, it is most desirable to maintain the height of the fluidized bed at a constant level.

The height of the fluidized medium in conventional fluidized beds was detected only by the pressure loss between the treeboard section and the bottom scattering plate inlet of the fluidized bed. The bed height also changes due to pressure horn loss; in other words, as the density decreases, the bed height increases, and as the density increases, the bed height decreases. Furthermore, since a desulfurizing agent is included in the fluid medium,
When the desulfurization agent absorbs sulfur, the density increases and the bed height of the fluidized bed changes. Therefore, it has the disadvantage that it is not possible to measure the actual bed height using pressure drop measurements.

This invention makes it possible to know the actual height of the fluidized bed, which has not been possible, and aims to provide a method and apparatus for this purpose. This invention detects the pressure in the freeboard part above the fluidized bed and the pressure at the bottom of the fluidized bed in a fluidized bed boiler, and also detects the pressure per unit height of the fluidized bed.
J Measure the loss, calculate the height of the fluidized bed, and based on the oil cylinder result, remove the C fluidized medium from the fluidized bed or put the fluidized medium into the fluidized bed to maintain the fluidized bed at the optimal height. An embodiment of the present invention is shown in FIG. 2 and will be described below.

In the fluidized bed boiler 1, a pressure sensor AI is installed in the freeboard section above the fluidized bed, and a pressure sensor A2 is installed at the inlet of the bottom diffuser plate of the fluidized bed. Attach B+ and B2. The pressure difference between the pressure sensors Bi and B2 is a pressure difference between fixed intervals that changes depending on the particle size, flow distribution, and density of the fluidizing medium, and this height difference is defined as a unit height d.

Sen'I)-B+, 32 (7) Detection (White area Differential pressure detection'
aB D. The detected values of the pressure sensors A+ and △2 are measured by the pressure detector A, and the constant values on both sides are inputted to the pi calculator 6, and sent from the command device 7 to the fluidizing medium discharge valve 8 or the fluidizing medium supply device 9. configured to command.

Next, to explain the operation of the present invention, the fluidized bed boiler 1
The height of the fluidized medium 2 during operation is considered to be equal to the pressure on the fluidized bed and the pressure in the flow layer, and the pressure loss △
P is measured as the differential pressure between pressure sensors 4 no Δ1 and Δ2. On the other hand, the pressure loss △Po between unit height 0, which changes depending on the particle size, distribution, and density of the fluidizing medium, is the pressure loss ΔPo between the pressure sensors [3+, 1
Since C is measured as a differential pressure of 3z, it can be considered that the relationship between bed height and pressure loss is proportional, so D-=P. The pressure detection IWA measures the pressure loss △P, and the pressure detector B measures the pressure loss Po, and inputs each information to the computer 6, which calculates the height D of the fluid medium based on the image information. This is then compared with the planned layer height Do, and the value is input to the command device 7, so the command device performs the calculation! Listen to the fluidized medium discharge valve 8 according to the information from 6 or drive the fluidized medium (j(tn) device 9. That is, if the height of the fluidized bed becomes too low, activate the fluidized medium supply position A medium is supplied to the fluidized bed to raise the bed height, and if the bed height becomes too high, the fluidized medium discharge valve is operated (the fluidized medium is discharged to maintain the bed height at the planned height).

In this way, this invention detects pressure loss by measuring the pressure in the freeboard part above the fluidized bed and the pressure at the bottom of the fluidized bed in a fluidized bed boiler, and also measures the pressure loss per unit height d of the fluidized bed. The height of the fluidized bed is calculated using the calculation result, and the fluidized medium forming the fluidized bed is extracted from the fluidized bed to lower the height of the fluidized bed, or the fluidized medium is placed in the fluidized bed. The height of the fluidized bed was controlled using a comb to maintain a constant bed height, so the particle size of the fluidized medium,
Even if the fluid distribution and density change, the fluidized bed can be reliably kept constant.

Therefore, the fluidized bed boiler can ensure stable combustion conditions. By implementing the present invention in this manner, combustion with less NOx and SOX generation can be obtained, and heat exchange peculiar to a fluidized bed boiler can be efficiently performed.

[Brief explanation of drawings]

Figure 1 is a schematic side sectional view showing the outline of a fluidized bed boiler;
The figure is a side view of a fluidized bed boiler including a system diagram for explaining the present invention. DESCRIPTION OF SYMBOLS 1... Fluidized bed boiler, 2... Fluidized medium, 3... Empty box, 4... Fuel supply pipe, 5... Heat exchanger tube, 6... Computing machine, 7... Command device , 8... Fluid medium discharge valve, 9
...Fluid medium supply device.

Claims (2)

[Claims] (1) Detecting the pressure at the freeboard part above the fluidized bed and the pressure at the bottom of the fluidized bed in a fluidized bed boiler,
A fluidized bed in which the height of the fluidized bed is determined by measuring the coercivity loss per unit height of the fluidized bed, and the fluidized medium is handled from or introduced into the fluidized bed based on the Song Dynasty. High control method. (2) Freeboard 1 above the fluidized bed of a fluidized bed boiler;
A pressure sensor installed at the bottom of the fluidized bed between d5 and 1,000 unit heights of the fluidized bed, a calculation device that inputs and calculates the detected value of the Group 1 soil calender, and a calculation result that controls the fluidic medium. A flow #J layer height control device comprising a command device for controlling either a discharge valve or a fluid medium feeding device.