JPH05180402A - Bed temperature control device of fluidized bed boiler - Google Patents

Abstract

PURPOSE:To make it possible to fix the bed temperature of a fluidized bed boiler definitely. CONSTITUTION:An actual bed temperature of a fluidized bed obtained from a bed temperature detector 15 is compared with a desired setting temperature by means of a comparator 17 where a master signal is corrected based on a differential temperature resultant from the comparison and forms a fuel correction section A which directs a fuel supply quantity command and the corrected fuel supply quantity command is compared with an actual fuel flow rate obtained from a fuel flow rate detector 23 by means of a comparator 22. A fuel control section B is installed, which increases and decreases the fuel flow rate, responding to the differential flow rate resultant from the above comparison. This construction makes it possible to maintain a constant bed temperature by increasing and decreasing the fuel flow rate even when the infection or collection of a bed material causes a temporary changes in the bed temperature of the fluidized bed 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluidized bed boiler for fluidizing a bed material and fuel in a boiler body to form a fluidized bed, and more particularly to a fluidized bed boiler for controlling the height of the fluidized bed. Is.

[0002]

2. Description of the Related Art In recent years, as a fluidized bed boiler, a pressurized fluidized bed boiler is being researched and developed which can burn fuel with high combustion efficiency and can be made compact, have a high desulfurization rate, and can improve plant thermal efficiency.

This fluidized bed boiler is, as shown in FIG.
High-pressure combustion air is introduced into the boiler main body b housed in the pressure vessel a, and the combustion air is used to fluidize and burn fuel, for example, powdery coal, with bed material made of ash, limestone, etc. under high pressure. That is, a part of the combustion heat in the fluidized bed c is recovered by the heat transfer pipe d provided in the fluidized bed c, and the generated steam is supplied to the steam turbine e to drive the generator f. Also, after the boiler exhaust gas is collected under high temperature and high pressure,
The gas turbine g is driven, and the gas turbine drives the combustion air compressor h and the generator i. Incidentally, j is an economizer and k is a chimney.

A bed material storage container d is provided in the pressure vessel a, and the bed material storage vessel m controls the height of the fluidized bed c in the boiler body b according to the load to collect heat. It is supposed to be adjusted. Specifically, by decompressing the upper portion of the bed material storage container m by the decompression means n, the bed material is recovered and stored from the fluidized bed c into the storage container m via the bed material discharge pipe p, and the fluidized bed c is obtained. Lowers the height. On the other hand, by supplying air to the bed material injection pipe (L valve) q below the bed material storage container m, the bed material of the storage container m is injected into the fluidized bed c, and the height of the fluidized bed c increases ( Kaihei 1-217108).

[0005]

By the way, in the above fluidized bed boiler, there is an optimum temperature range for desulfurization in the bed. That is, in the combustion reaction, nitrogen oxides (NOx
There is a demand from the plant side that the layer temperature should be maintained at, for example, 860 ° C. because of the restriction that the generation of gas) is suppressed and the performance of the gas turbine g attached downstream is not adversely affected.

In response to such a request, conventionally, on the basis of a master signal, that is, a plant output command r, the fuel flow rate of the fuel pump s is adjusted and the air is supplied to the bed material injection pipe (L valve) q or the pressure is reduced by the supply pressure reducing means n. The steam flow rate, which is the output of the boiler, is controlled by performing the adjustment of the bed material injection recovery amount by the operation independently.

However, if the fuel flow rate and the bed material injection / collection amount are directly controlled, the following inconveniences occur. That is, when the master signal is a plant output increase command, when the bed material is injected to increase the bed height correspondingly, the bed material is cold, so the fuel flow rate is increased according to the plant output command. Nevertheless, there is a problem that the layer temperature temporarily drops. Further, the interlocking relationship between the fuel flow rate and the bed material injection and recovery amount may be broken for some reason. For example, when increasing the plant output, the bed material may not be injected due to the imbalance between the two, and under such conditions only the fuel is increased,
It is conceivable that the layer temperature rises and exceeds the heat-resistant temperature of pipes and the like that is originally acceptable as a plant.

Therefore, the present invention has been made in view of such circumstances, and an object of the present invention is to provide a fluidized bed boiler capable of more reliably stabilizing the bed temperature in consideration of the actual bed temperature. It is to provide a control device.

[0009]

In order to achieve the above object, the present invention forms a fluidized bed by fluidizing bed material and fuel in a boiler main body, and raises the fluidized bed height according to a master signal. In a fluidized bed boiler that controls the temperature by injecting the bed material from the storage container and collecting the bed material in the storage container, the temperature of the fluidized bed obtained from the bed temperature detector is compared with a desired set bed temperature,
A temperature correction unit that corrects the master signal with the temperature difference to make the fuel supply amount command, and compares the actual fuel flow rate obtained from the fuel flow rate detector with respect to the corrected fuel supply amount command,
A fuel control unit that increases or decreases the fuel flow rate according to the flow rate difference is provided.

[0010]

When the bed temperature of the fluidized bed is temporarily changed by injecting or collecting the bed material, it is detected as a temperature difference with respect to the desired set bed temperature by the temperature correction unit, and the master signal is corrected by this temperature difference and corrected. The specified fuel supply amount command is output. The corrected fuel supply amount command is compared with the actual fuel flow rate in the fuel control unit, and the fuel flow rate is increased or decreased according to the difference. As a result, even if the bed temperature of the fluidized bed temporarily changes due to the injection or recovery of the bed material, the fuel flow rate is increased or decreased to compensate for the change, so the bed temperature is maintained constant.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings.

In FIG. 1, reference numeral 1 denotes a boiler main body housed in a pressure vessel 2, and a bed material made of ash, limestone, dolomite or the like and a granular material are provided on an air dispersion plate 3 in the lower part of the boiler main body. Fuel such as coal is supplied. Of these, the fuel is supplied by the fuel pump 4 through the fuel supply pipe 5.

An air supply pipe 6 is connected to the pressure vessel 2, and high-pressure air from the air supply pipe 6 is supplied to the air dispersion plate 3.
Through which the bed material and fuel are fluidized on the air dispersion plate 3 under high temperature and high pressure to form a fluidized bed 7.

In the pressure vessel 2, a fluidized bed 7 is provided depending on the load.
A bed material storage container 8 for controlling the height of the gas is stored in the boiler main body 1 in parallel, and the upper portion of the bed material storage container 8 is connected to the fluidized bed 7 via a bed material discharge pipe 9 and the gas content in the container 8 is It is connected to a gas discharge pipe 11 equipped with a pressure reducing device 10a for discharging and reducing the pressure inside the container 8 and a control valve 10b.
Further, the lower portion of the storage container 8 is connected to the boiler body 1 via a bed material pipe (L valve) 12 formed in an L shape at a substantially right angle.
Is connected below the fluidized bed 7 and is connected in a substantially U-shape as a whole. The L-shaped corner portion of the bed material pipe 12 is connected to the pressure vessel 2 by an air carrying pipe 14 having a control valve 13, and when the load rises, a part of the air in the pressure vessel 2 is connected to the bed material pipe 12. And the bed material in the storage container 8 is supplied to the fluidized bed 7.

The control valve 10b and the control valve 13 inject bed material when the plant output should be increased according to the content of the master signal 19 of the plant, that is, the value of the bed height corresponding to the plant output or load. Therefore, the bed height of the fluidized bed 7 is increased, and when the bed height is to be decreased, the bed material is reduced and the bed height is decreased. In this case, in order to obtain the corresponding boiler steam amount, it is necessary to make the fuel flow rate suitable for the output of the plant. However, if the fuel flow rate supplied from the fuel pump 4 is directly adjusted according to the master signal 19, it is not possible to cover a temporary fluctuation of the bed temperature due to the injection or recovery of the bed material, and the bed temperature is not constant. That is, when the bed material is injected to increase the bed height, the bed temperature is lowered by the injected bed material. Further, when the bed height is lowered due to the recovery, the bed material is less than the input fuel, so the bed temperature rises. Therefore, the control device described below controls the fuel flow rate so that the actual bed temperature is constant, and as a result, the output of the plant is controlled.

The controller has a bed temperature detector 15 for detecting the actual bed temperature, and a fuel flow rate detector 23 for detecting the actual fuel supplied. In this embodiment, the bed temperature detector 15 is composed of a plurality of thermocouples for detecting the bed temperature of the fluidized bed 7 of the boiler body 1, and detects the average temperature of the fluidized bed 7. On the other hand, the fuel flow rate detector 23 detects the slurry flow rate of the fuel supply pipe 5.

The control unit consists of two parts. one,
The actual bed temperature of the fluidized bed 7 obtained from the bed temperature detector 15 is compared with a desired set bed temperature, for example, 860 ° C., and the master signal 19 is corrected by the temperature difference of the comparison result to give a fuel supply amount command. The temperature correction unit A includes a bed temperature detector 15, a temperature setting unit 16, a comparator 17, a PI (proportional integral) control unit 18, and an addition unit 21. The other one is a fuel control unit B that compares the corrected fuel supply amount command with the actual fuel flow rate obtained from the fuel flow rate detector 23 and increases or decreases the fuel flow rate according to the flow rate difference as a result of the comparison. The fuel flow rate detector 23, the comparator 22, the PI control unit 24, the automatic / manual switching unit 25, and the inverter 26.

The bed temperature detected by the bed temperature detector 15 is led to a comparator 17, where it is compared with a desired set bed temperature (860 ° C.) set by the temperature setter 16, and the temperature difference signal is compared. Is output. This temperature difference signal enters the adder 21 via the PI controller 18. The signal obtained by the PI controller 18 is a signal obtained by multiplying the temperature drop change by a linear function proportional to time. A signal obtained by converting the master signal of the plant into a linear function proportional to time by the function generator 20 is input to the addition unit 21, and the PI is added to the signal.
The signals from the control unit 18 are added. Therefore, the addition unit 2
In 1, the fuel supply amount command (target value) after being corrected by taking into consideration the actual bed temperature of the fluidized bed 7 is obtained.

The corrected fuel supply amount command from the adder 21 is compared with the actual fuel supply flow amount detected by the fuel flow amount detector 23 by the comparator 22, and the difference (flow amount difference) is output. It This difference appears when the fuel flow rate is manipulated in response to the master signal during the above-described injection and recovery of the bed material, and the amount of increase / decrease adjustment of the supplied fuel is insufficient. The difference, which is the shortage signal of the increase / decrease adjustment amount of the supplied fuel, is added to the drive inverter 26 of the fuel supply pump 4 via the PI control unit 24 and the automatic / manual switching unit 25. As a result, the fuel supply pump 4
Has its operating speed varied so as to compensate for the shortage of the increase / decrease adjustment amount of the supplied fuel. Thus, the bed temperature is kept constant even when the bed material is injected and collected.

Further, according to the above configuration, the inconvenience that the interlocking relationship between the fuel flow rate and the bed material injection / discharge amount is broken for some reason and only the fuel increases even if the bed material is not injected is avoided. ..

[0021]

In summary, according to the present invention, the temperature correction unit for detecting the change in the bed temperature of the fluidized bed and setting the master signal as the corrected fuel supply amount command, the corrected fuel supply amount command and the actual fuel are provided. Even if the bed temperature of the fluidized bed temporarily changes due to other factors such as injection or recovery of bed material, the change occurs because the fuel control unit that increases or decreases the fuel flow rate according to the difference with the flow rate is provided. The fuel flow rate is increased / decreased to compensate for the above, and the bed temperature is maintained constant.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a configuration diagram showing a fluidized bed boiler that has been conventionally researched and developed.

[Explanation of symbols]

 1 Boiler Main Body 2 Pressure Vessel 3 Air Dispersion Plate 4 Fuel Pump 5 Fuel Supply Pipe 6 Air Supply Pipe 7 Fluidized Bed 8 Bed Material Storage Container 9 Bed Material Discharge Pipe 10a Pressure Reducer 10b Control Valve 11 Gas Discharge Pipe 12 Bed Material Pipe 13 Adjustment Valve 14 Air carrier pipe 15 Layer temperature detector 16 Temperature setter 17 Comparator 18 PI control section 19 Plant master signal 20 Function generator 21 Addition section 22 Comparator 23 Fuel flow rate detector 24 PI control section 25 Automatic / manual switching Part 26 Inverter A Temperature correction part B Fuel control part

Claims (1)

[Claims] 1. A bed material and fuel are fluidized in a boiler body to form a fluidized bed, and the height of the fluidized bed is injected from a storage container to the bed and recovered to the storage container according to a master signal. In the fluidized bed boiler controlled by, the temperature of the fluidized bed obtained from the bed temperature detector is compared with a desired set bed temperature,
A temperature correction unit that corrects the master signal with the temperature difference to make the fuel supply amount command, and compares the actual fuel flow rate obtained from the fuel flow rate detector with respect to the corrected fuel supply amount command,
A bed temperature control device for a fluidized bed boiler, comprising: a fuel control unit that increases or decreases the fuel flow rate according to the difference in flow rate.