EP0576955B1 - Method and device for controlling the combustion of fuel on a grate of a furnace - Google Patents

Description

The invention relates to a method for controlling the combustion of Fuel on a grate of the type mentioned in the preamble of claim 1.

A generic method is known from WO 90/09552, in which with the help of a detector device in the form of a thermography or Infrared camera or a variety of individual detectors the temperature of the surface area formed on the grate is detected, d. H. on two-dimensional temperature profile is shown in individual rust zones and depending on the area distribution of the detected Measured values (temperature image) the supplied to the individual zones Combustion air and / or the transport speed of the fuel in is regulated in the individual zones.

When burning garbage, the garbage composition changes frequently and the detection of the bed temperature is sufficient for optimal control of the Combustion process not necessarily with regard to pollutant emissions out.

From the DE-Z. "CT Magazine for Computer Technology", special print, 1991, issue 3, The essay "Fuzzy Logic - The Sharp Theory of Fuzzy Sets" is that Fuzzy logic itself and the regulation according to the fuzzy logic in particular the Regulation of the combustion of methane in a combustion chamber is known. Of further components belonging to a fuzzy control system, such as fuzzy computers, Fuzzy chips and fuzzy logic arrays are described.

Fuzzy control offers a way to control processes automatically and can be used in an advantageous manner if due to complex Process variables of conventional controllers are not sufficient. The fuzzy control system allows to design a rule algorithm and in to implement a working controller, which is the one from the fire chamber measuring system provided data about the state of fire is analyzed and from it Control instructions are generated as they are without automatic regulation of the Surgeon based on his experience and judgment would give.

From the Z. "Elsevier Science Publishers", B.V. North Holland, 1989, p. 193 - 206, essay "Combustion control of refuse incineration plant by Fuzzy-Logic" by H. Ono et al., a method is known in which the incineration of waste on a fire grate of a waste incineration plant based on fuzzy logic is regulated. In doing so, the amount of refuse that is Transport speed of the garbage on the grate, the amount of combustion air and the combustion air temperature depending on the amount of steam Flue gas composition of the thickness of the garbage bed on the grate that Waste quality and / or the furnace temperature regulated. The fuel bed is transported as a whole by a transport device. The Combustion air is split up into individual streams along the grate section Channels covering rust are fed to the fuel bed. The setting of the Total air flow is through throttling devices, each of the channels are assigned and all adjusted equally via a servomotor become. The fact that the combustion of the fuel along the The grate section is defined as a whole, and so is the combustion process can only be influenced as a whole, there is a risk that the Combustion zone from the grate to the waste disposal or from the grate to the Ashtray migrates, which ultimately leads to an uncontrolled combustion leads to high pollutant emissions.

It is the object of the present invention, a generic method to specify the combustion, where the regulation regarding pollutant emissions are further improved.

This object is achieved in that the composition of the exhaust gases over the individual combustion zones and the amount of individual combustion air flows is regulated according to the fuzzy logic.

The exhaust gas composition, in particular the O ₂ , CO, CO ₂ and / or NO _x content, in addition to the bed temperature, also characterizes the advance of the combustion of the fuel in the individual zones.

The control of the combustion process on the fire grate according to the fuzzy logic allows for the consideration of a multitude of indeterminate ones conditional factors, such as the burnout behavior of the fuel, different fuel composition, the fuel temperature below Inclusion of empirical values, as otherwise from an experienced The operator would have to be brought in manually for the regulation.

As the proposed scheme the combustion process on the grate stabilized and as such subordinate to an overall regulation, the overall control of the amount of steam or heat output, the Flue gas composition and the flue gas temperature with the manipulated variables Total air quantity, secondary air quantity and fuel quantity of one cheaper, conventional regulation.

A further improvement of the method is achieved in that the Transport speed of the fuel in the individual zones after Fuzzy logic is regulated. The zone-by-zone regulation of the Transport speed of the fuel bed offers the possibility of the bed stretch or compress as needed.

The invention is also directed to a device for regulating the Combustion of the type mentioned in the preamble of claim 3.

This device is characterized in that the Detector device detects the composition of the exhaust gas and the said devices are components of a fuzzy control system that the amount of the individual combustion air flows according to the area Distribution of the measured values regulates.

The detector device can have at least one thermography or Infrared camera for simultaneous detection of radiation across several zones exhibit. The detector device can also have at least one gas analyzer with a gas sampling device for simultaneous detection of the Have exhaust gas composition over several zones.

The method according to the invention and one operated according to this method Device is now based on the accompanying figure, the one Waste incineration plant in longitudinal section with control and regulation technology Facilities shows are described in more detail.

The FIG. shows a furnace 1 of a furnace 2 with a step feed grate 3, as in the prospectus "Combustion technology feed grate" (P 8303-05-13 / 1.Dg) der L & C Steinmüller GmbH, D-51641 Gummersbach (DE) is described.

The feed grate 3 has four combustion zones A, B, C and D, with zones B and C through a stage 4 are separated from each other. The movable grate bars of the individual zones A - D are rust slides A5 - D5 assigned. The rust slides A5 - D5 are about schematic shown adjusting devices A6 - D6 back and forth slidable.

Zones A - D are combustion air ducts A7 - D7, respectively assigned to those primary streams via line A8 - D8 Combustion air via control flaps A9 - D9 with Actuators A10 - D10 and flow measuring devices A11 - D11 can be fed.

The total amount of primary combustion air is over a Line 8 with a control valve 9 with actuating device 10 and a flow measuring device 11 supplied. The dated Combustion grate 3 rising smoke gases can still over a line 8 'with control valve 9' with adjusting device 10 'and flow measuring devices 11' secondary air over several nozzles 12 are supplied.

The fuel 13, in particular garbage, is via a Feed hopper 14 and a feed device 15 with Actuator 16 the grate 3 in the area of the first Grate zone A abandoned and along the grate section below Spread to a fuel bed covering the grate 3 17 by operating one or more Rust slide A5 - D5 transported.

It is also envisaged to design the grate 3 in multiple lanes. The individual tracks are parallel to each other arranged and designed in the same way.

The combustion process of the fuel 13 on the grate 3 becomes essential by the location of the combustion and the Distribution of the combustion on the grate 3 determined.

To influence the combustion process or the situation and the distribution of combustion and the The progress of combustion can, if necessary, be done by the individual Rust zones A - D more or less with primary Combustion air can be applied. In addition, by Operation of the individual rust slides A5 - D5 at each different speeds or by operating only single rust slide A5 - D5 the fuel bed 17 at Need to be compressed or stretched. With multi-lane It is possible to rust the fuel bed across the grate compress or stretch. By operating the Feeder 15 at different Speeds or different intervals or through the operation of only individual tappet rows 15 ', 15' ' the mass throughput or the bed thickness can vary can be set.

To record the combustion process on the individual Rust zones A - D are one above the furnace 1 Infrared camera 18 attached by the individual Zones A - D or radiation emanating from the fuel bed 17 detected. In a downstream of the camera 18 after the Fuzzy logic evaluation and control device 19 the individual radiation values or those on the Radiation-returning temperatures in each Rust zones A - D along or at a temperature profile appropriate measuring arrangement along and across the grate section summarized. The current state is then fuzzified, subjected to an inference procedure and then defuzzified.

Instead of the fuel bed surface over a large area capturing termography camera, it is also possible that the single detector device a variety of Includes individual detectors, which in groups or individually are assigned to the respective rust zones. As individual detectors come with photodiodes, photodetectors and gas analyzers upstream rake-like gas sampling device in Question.

To influence the combustion process, the Actuators A10 - D10 for adjusting the primary combustion air partial flows and / or the Actuators A6 - D6 for moving the Rust slide A5 - D5 for the transport of the Fuel 13, 17 according to the determined target values controlled. For a better overview is shown in FIG. each only one signal line shown completely. The individual primary combustion air partial flows each set so that it always exceeds the setpoint predetermined share of the total primary Combustion air. To regulate this are one flow controller FC and one Flow ratio controller FFC for signal adaptation switched on, representing only one Partial air flow are shown.

If required, the operation of the feed device 15 can also be carried out in whole or in part according to the fuzzy logic working regulation. The degree of Inclusion is via one of the evaluation and Control device 19 downstream control unit 20 fixed.

The fuzzy control to influence the The combustion process is one of the overall rules subordinate self-contained partial regulation.

As a stable controlled by the fuzzy control Burning on the grate can be achieved Main regulation a conventional and cheaper one Control system can be used.

The evaluation and control unit 21 provided for the main control detects the flue gas temperature and the O ₂ content of the flue gas at the end of the combustion chamber and the amount of steam by means of symbols 22, 23, 24 represented symbolically. Corresponding to the setpoints determined by the evaluation and control device 21 for the main control, the primary air flow is regulated via the control flap 9 with the actuating device 10 and the flow measuring device 11 and the secondary air quantity is regulated via the control flap 9 'with the actuating device 10' and the flow measuring device 11 '. Furthermore, provision is made to regulate the control of the fuel quantity in whole or in part by means of the control device 20 connected downstream of the evaluation and control device 21 for the main control.

Claims (4)

1. Method of regulating the combustion of fuel on a fire grate, which has successive combustion zones and onto which the fuel is delivered and transported along the grate path with spreading out into a fuel bed covering the grate, wherein the combustion zones are acted on zonally in each case by a combustion air part flow, wherein measurement values, which are associated with the combustion process, of at feast two zones are detected and wherein in dependence on the distribution in terms of area of the detected measurement values the combustion is regulated by regulating the quantity of the individual combustion air flows, characterised in that the composition of the exhaust gas over the individual combustion zones is detected and the quantity of the individual combustion air flows is regulated in accordance with fuzzy logic.
2. Method according to claim 1, characterised in that the transport speed of the fuel in the individual zones is regulated in accordance with fuzzy logic.
3. Device for regulating combustion in a combustion chamber of a furnace with delivery equipment for delivery of fuel onto a grate, at least one transport device for transport of fuel along the fire grate and combustion air channels, which are distributed substantially longitudinally of the grate path, are directed towards the grate and cover this in zones, with throttle elements for the feed of combustion air in combustion air part flows and with a regulating system for regulating the combustion process in dependence on at least one parameter able to be referred to the combustion, with at least one detector device for detection of the combustion process in at least two combustion zones by means of measurement values, which are associated with the combustion process at the individual grate zones, in their distribution in terms of area, an evaluating and control device, which is connected downstream of the detector device, for evaluation and conversion of the measurement values and individually controllable setting devices, which are connected downstream of the evaluating and control device, respectively associated with the individual throttle elements of the combustion air channels, wherein the regulating system regulates the quantity of the individual combustion air flows in accordance with the distribution in terms of area of the detected measurement values, characterised in that the detector device (18) detects the composition of the exhaust gas and the said devices (18, 19, A10-D10) are components of a fuzzy regulating system.
4. Device according to claim 3, characterised in that the zones (A-D) are each associated with a respective transport device (A5-D5) with a respective setting device (A6-D6) individually controllable by the evaluating and control device (19), and the setting devices (A6-D6) are similarly components of the fuzzy regulating system.

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