CZ9904629A3 - Method of extending control range of boiler capacity with stationary fluid bed and boiler for carrying out this method - Google Patents

Abstract

In the present invention, there is disclosed a method of extending power control range of a stationary oxidation fluidized bed boiler, in which boiler the control is carried out by change of velocity of combustion air flow above a fluidized bed grate (4),wherein the combustion air flow velocity is achieved by the change of combustion air amount being supplied in the fluidized bed grate (4) nozzles (7) per a time unit. The invention is characterized by changing the size of area above the fluidized bed grate (4), above which combustion air flows in order to maintain fluidization. Disclosed is also a boiler intended for carrying out the above-described method, said boiler having a fluidized bed grate (4) and a stationary oxidation fluidized bed wherein the boiler is characterized in that said fluidized bed grate (4) is divided into individual sections (5ii), each being provided with an independent air supply wherein at least some sections (5ii) are provided with independently closeable fitting (6iin), wherein all the sections (5iin) are connected to a main combustion air piping (1) being provided with a fan (2) with continuously controllable and adjustable flow of combustion air. In a preferred embodiment, said fluidized bed grate (4) and sections (5ii) thereof are formed by pipes of general cross section with nozzles (7).

Description

A method for extending the range of power regulation of a stationary oxidation fluidized bed boiler and a boiler for carrying out this method

Technical field

BACKGROUND OF THE INVENTION The present invention relates to a method for extending the range of power regulation of a stationary oxidizing fluidized bed in which power control is performed by varying the rate of combustion air flow over a fluidized bed, and a stationary oxidizing fluidized bed boiler for carrying out the method.

BACKGROUND OF THE INVENTION

The output control range of the boiler largely depends on the ability to regulate the heat demand from the fluidized bed to the heat transfer surfaces of the boiler. In principle, heat removal to the fluidized bed takes place in two ways:

1) Through the flow of combustion air through the fluidized bed, the fluidized combustion air being heated and dissipating heat to the fluidized bed. Here, regulation is possible by varying the amount of air passing through the fluidized bed.

2) By varying the amount of heat removed from the fluidized bed by the heat transfer surfaces immersed in the fluidized bed.

In principle, for a stationary oxidizing fluidized bed, the control range is determined by varying the amount of flue gas passing through the fluidized bed of constant cross-section.

The boiler output is within the following limits:

The minimum boiler output is given by the minimum air flow going through the fluid grate into the fluidized bed, which ensures minimal, i.e., the lowest possible fluidization of the fluidized bed. The lowest possible fluidization of the fluidized bed is understood to mean a fluidization in which the fluidized bed is still held in the fluidized state.

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-The maximum boiler output of the stationary fluidized bed is given by the maximum air flow, which does not cause the fluidized bed to escape, ie to be abducted and thus to lose the fluidized bed. Another limiting condition for the maximum flow rate is the speed of the flue gas flow in the boiler, when the heat exchange surfaces of the boiler are abrasive at too high speeds.

Usually these limits allow the boiler's power control range to be only 50% 100% of the boiler's rated output. The cross-section or area of the fluidized bed is constant.

SUMMARY OF THE INVENTION

These disadvantages of the prior art are largely overcome by the method of extending the range of power regulation of a stationary oxidation fluidized bed boiler in which power control is accomplished by varying the rate of combustion air flow over the fluid grate by varying the amount of combustion air supplied to the fluid grate nozzles per unit. The principle of the invention is that the boiler output control is extended by varying the size of the area above the fluid grate above which the combustion air flows to maintain fluidization. The method is carried out in a stationary stationary oxidative fluidized bed boiler, the essence of the invention being that the fluid grate is divided into individual sections, each of which is provided with a separate air supply with a self-closing fitting, all self-closing fittings being connected to the main supply line. combustion air with fan with infinitely adjustable and adjustable combustion air flow. It is advantageous if the fluid grate and its sections consist of tubes of general cross section with nozzles.

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BRIEF DESCRIPTION OF THE DRAWINGS

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described in more detail with reference to the accompanying drawings, in which: Figure 1 shows a flow diagram of a fluidized bed grate for a stationary oxidation fluidized bed boiler for carrying out the process; Fig. 1.

DETAILED DESCRIPTION OF THE INVENTION

In an exemplary embodiment of the method of the invention, the boiler output control is carried out continuously by varying the flow rate of the combustion air over the fluid grate, and in steps by varying the area above the fluid grate above which the combustion air flows to maintain fluidization. Continuous control is accomplished by varying the rate of combustion air flow over the fluid grate by changing the amount of combustion air supplied to the fluid grate nozzles per unit of time. The flow rate of the combustion air above the fluidized bed is possible in a fluidized bed boiler within the limits defined so that the lowest possible flow rate of the combustion air is that of the combustion air at which the fluidized bed is still held high, while the highest possible flow rate. The combustion air velocity is the combustion air velocity at which the fluidized bed is not yet leaked, i.e. the abduction and thus the fluidized bed is lost. The resulting regulation is then given by the joint action of the two control elements.

FIG. 1 shows a flow chart of a fluidized bed for a stationary oxidation fluidized bed boiler according to the invention. The combustion air supply line 1 is connected to a fan 2 controlled by a frequency converter (not shown). The outlet of the fan 2 is connected to the main shut-off fitting 3, the outlet of which is connected to the inlet of the fluid grate 4. Fluid grate 4

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It is divided into six sections 50, of which the first to third sections 5j to S3 are each provided with an auxiliary control valve 61 to 63 for controlling the combustion air supply to the fluid grate nozzles 7.

Fig. 2 shows a schematic diagram of a stationary oxidative fluidized bed boiler with a built-in fluid grate of Fig. 1. At the bottom of the combustion chamber 8 is a fluidized bed grate with nozzles 7. The fluidized bed 4 is divided into six sections 5j, the third sections 5i to Sj are each provided with an auxiliary control valve 61 to 63 for regulating the combustion air supply to the fluid grate nozzles 7. The combustion air supply line 1 is connected via a fan (not shown) to an air heater 9 located in the flue gas exit area of the boiler. The water heater 10 located in the same space is connected to the inlet of the boiler drum 11, the outlet of which is connected via the steam superheater 12 to the outlet line 13 of the superheated steam.

In the operation of a stationary fluidized bed oxidant fluidized bed boiler according to the invention, its output is controlled in a manner known per se by controlling the amount of combustion air supplied to the fluidized bed nozzles 7 by means of the main shut-off valve 3. 63, which pass the combustion air into the first to third sections 5i to 5g or stop the supply thereof, thus decommissioning the first to third sections 5j to Sj. By decommissioning the first to third sections 5j to 53, the area of the fluidized bed is reduced and the heat transfer to the boiler is reduced. Two phenomena are used: stopping the combustion air supply to the first to third sections 5j to Sj reduces the amount of air entering the boiler and thereby decreases the amount of flue gas, which reduces the boiler output, and reducing the area above the fluid grate above which combustion air flows, the direct washing or heat transfer of the fluidized bed into the heat transfer surface of the boiler is reduced, which also reduces the boiler output. This dual effect is then combined with the effect of controlling the amount of combustion air supplied to the nozzles 7

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Claims (3)

Patent claims CLAIMS 1. A method for extending the range of boiler power control with a stationary oxidative fluidized bed, wherein the power control is performed by varying the rate of combustion air flow over the fluid grate by changing the amount of combustion air supplied to the fluid grate nozzles per unit time. boiler output control is extended by varying the size of the area above the fluid grate above which the combustion air flows to maintain fluidization. A fluidized bed boiler with a stationary oxidative fluidized bed for carrying out the method according to claim 1, wherein the fluidized bed is divided into individual sections, each of which is provided with a separate air supply with a self-closing fitting, all self-closing fitting they are connected to the main combustion air supply pipe with a fan with a continuously controllable and adjustable combustion air flow. Boiler according to claim 1, characterized in that the fluid grate and its sections are formed by tubes of general cross section with nozzles.