EP0458822B2 - Process and device for controlling the combustion of a fuel in a grate incinerator - Google Patents

Description

The invention initially relates to a method for detecting essentially one after the other in the conveying direction of the grate Combustion zones of the grate of outgoing radiation and regulation of the combustion process depending on the radiation detected by changing the transport speed and the supplied to the individual combustion rust zones Primary air.

Such a method is known from WINTRICH, F.:"Development and first operating experiences with a new fire performance control concept for waste incineration plants "in" Lectures of the VGB Conference, Waste Incineration 1988 of September 28, 1988, Essen ", in which the wavelengths are used by means of highly integrated pyrodetectors the H ₂ O and CO ₂ bands are selectively detected, whereby a small number of detectors with a large integrating single field of view are directed at the surface of the grate and a small number of mean value signals are derived from their output signals, which give a rough indication of the fire situation in the Allow rust zones. The detection of the gas bands and the measurement of the gas band radiation integrating over large individual fields of view are not sufficient for the detection of a surface temperature distribution and thus for a sufficiently precise determination of the combustion progress.

From Patent Abstracts of Japan, Vol. 10, No. 191 (M-495) (2247) July 4, 1986, & JP-A-61 36611 (Kawasaki Heavy Ind.) February 21, 1986 such a method is known in which a Gas or flame radiation is recorded and from this a two-dimensional temperature distribution over the combustion zone is derived, namely the imaging of flame parts in a striking contrast the background surrounding them. The analog image signals are converted into digital signals. With their Help will depend on the distribution of the constant amount of primary air supplied to the individual zones the position of the actual burnout point determined by means of the temperature distribution relative to predetermined burnout point. The feed rate is the same for all combustion zones. At In the known method, the bed temperature and thus the location of particularly hot combustion points can cannot be detected safely since the flames can be displaced by gas flow over the bed do not show the burns safely. The flame radiation itself represents a phenomenon with faster change over time, which is poorly suited to regulating the air supply and / or transport speed is. For the rest, a regulation of the primary air is sufficient with the transport speed remaining the same Doesn't always rust.

From Patent Abstracts of Japan, Vol. 5, No. 80 (M-70) (752) May 26, 1981, & JP-A-56 27816 (Unitika) March 18 In 1981 a method for controlling the combustion in a grate furnace is known, in which the primary air supply to individual of the successive combustion zones and the transport speed in the individual combustion zone depending on the one arranged at the upper part of the combustion chamber Temperature sensor measured combustion gas temperature is regulated as a reference variable.

From Patent Abstracts of Japan, Vol. 8, No. 154 (M-310) (1591) July 18, 1984, & JP-A-59 52105 (Babcock Hitachi) March 26, 1984 is a process for regulating the combustion of a fuel in a stationary Fluidized bed firing is known, in which the fluidized bed is operated in several adjacent partial beds can be. An infrared camera is aimed at the top of the fluidized bed. On a monitor the material bed temperature distribution over the partial beds is shown in order to regulate it, which is not described in detail to enable the temperatures in the individual partial beds of the fluidized bed. It is assumed, that an operator is supplying swirl air and / or supplying fuel to the individual Manually controls partial beds.

In from Patent Abstracts of Japan, Vol. 5, No. 93 (M-74) (765) June 17, 1981, & JP-A-56 40018 (Takuma) 16 April 1981 known method for regulating the combustion of waste in a grate is the Radiation emanating from two points on the discharge edge of the grate is detected in the visible or UV range and from this a combustion energy gradient is calculated to determine the transport speed of the fuel in the combustion zone assigned to the discharge edge and the air supply in this combustion zone to regulate.

Finally, from Patent Abstracts of Japan, Vol. 10, No. 191 (M-495) (2247), July 4, 1986, & JP-A-61 36612 (Kawasaki Heavy Ind.) A process for burning fuel in successive swirl zones known to which primary air is supplied from below. Flame pictures are made using a color television camera in the wave range of color blue and in the range of shorter wavelengths detected to overheated vortex zones to determine. To lower the temperature in an overheated vortex zone, the temperature of the primary air supplied to the individual vortex zone. The amount of primary air supplied is also regulated. The transport from one fluidized bed to the other is carried out by the swirling process.

With the not previously published older patent application EP 352 620 is a method for controlling the Combustion of a fuel has been proposed in which the infrared radiation corresponding to the material bed temperature detected and the primary air is regulated depending on this. A regulation of the transport speed the fuel in the individual zones is not provided.

It is first the object of the present invention to specify a generic method in which the bed temperature can be detected and the control can be improved.

This object is achieved in that the essentially of individual combustion rust zones of the Rusting outgoing infrared radiation corresponding to the material bed temperature in its area distribution captured simultaneously by means of a thermography or infrared camera and depending on the comparison of the captured area temperature distribution with a predetermined temperature distribution, the primary air supplied and Transport speed of the fuel is regulated in individual zones.

In the method according to the invention, it is not the gas or flame radiation, but the Radiation from the bed itself is detected. With the help of the zone-wise regulation of the primary air distribution and the Fuel transport is an improvement of the combustion process on the grate (burnout), a minimization of pollutant emissions and a reduction in the excess air, which according to the prevailing Opinion must also lead to a reduction in the formation of dioxins in the incineration of waste.

The zones can be divided not only in the conveying direction, but also across the conveying direction. To the grates in which the method according to the invention can be used include in particular the single-lane or multi-lane feed grates, where fixed and movable in each grate track Alternate grate bars. The zone division is achieved here by different primary air supply. Farther these include the single or multi-lane step feed grates, in which the grate gradations Overturning and breaking up of the fuel layer and each rust element cause a rust zone determined in which the primary air can be adapted to the respective burn progress. Such a zoning without gradation is also realized with the so-called burnout grates. The invention leaves but also with moving grates, roller grates, return grids, counter-rotating grids and Use shaking grates.

The invention is also directed to a device for detecting the at least one combustion zone of at least two spatially separated locations radiation emanating from a grate by means of a detector device, with one connected downstream of the detector device Evaluation device and the control device downstream of the evaluation device to influence the Combustion process by changing the primary air supply and the transport speed of the fuel,

According to the invention, this provides that the detector device for at least one thermography or infrared camera for simultaneous Detection of the infrared radiation corresponding to the material bed temperature in the conveying direction of the grate successive rust zones in their area distribution and the evaluation device the detected compares surface temperature distribution with a predetermined temperature distribution and that the Individual grate zones separately adjustable actuators for the supply of primary air and for the Transport speed of the fuel in the material bed through the individual grate zones are assigned.

In a preferred manner, two infrared cameras are provided, each of which has a side wall of the combustion chamber are assigned and cover the same bed surface. This is redundancy and therefore given increased security of the scheme.

FIG. 1

zeigt einen schematischen Schnitt durch einen Stufenvorschubrost mit fünf aufeinander folgenden Rostzonen,

FIG. 2

einen Blick auf die Rostzonen mit zwei seitlich angeordneten Infrarot- bzw. Thermographie-Kameras mit einer für die Verbrennung ungünstigen Isothermenverteilung und

FIG. 3

eine Ansicht vergleichbar FIG. 2 mit einer für die Verbrennung optimalen Isothermenverteilung und

The invention will now be explained in more detail with reference to the attached figures:

FIG. 1

shows a schematic section through a step feed grate with five successive grate zones,

FIG. 2nd

a look at the rust zones with two infrared or thermography cameras arranged on the side with an isothermal distribution that is unfavorable for the combustion and

FIG. 3rd

a view comparable to FIG. 2 with an optimal isothermal distribution for combustion and

The FIG. 1 shows a furnace 1 with a step feed grate 2, as shown in the brochure "Combustion technology - moving grate" (P 8303-05-13 / 1.DG) from "L. & C. Steinmüller GmbH, Gummersbach, DE "is described.

The feed grate 2 has five combustion zones A, B, C, D and E, with zones B and C and D respectively and E are separated from one another by a stage 3 or 4. In FIG. 1 is shown schematically that the movable grate bars of the individual zones A-E are each assigned to a grate slide 5.

The grate slides A5 - E5 can be moved back and forth via schematically illustrated hydraulic drives A6 - E6.

The combustible material, in particular garbage, is fed via a funnel 7 and a hydraulically operated one Dispenser 8 relinquished to grate 2, specifically to dispensing zone 8 '.

The allocation zone 8 'and the combustion zones A-E with movable grate bars are each underwind zones 9 or A9 - E9 assigned, to which 10 primary combustion air via control flaps via a line 9 'and A12-E12 can be supplied. The smoke gases rising from the combustion grate 2 can still Secondary air is supplied via a line 12 and control flaps 12 ′ and 12 ″ via a plurality of nozzles 13.

In the side walls 14a and 14b of the firebox there are two infrared and thermography cameras 15a and 15b arranged so that they cover essentially the entire rectangular area of zones B, C and D. cover in a measuring manner. This can be done with an illustration, not shown, but common in the field. and focusing optics can be achieved.

On the output side, the two thermography cameras 15 are connected to an evaluation circuit 16, the - as shown schematically by arrow S - the desired temperature profile in the area of the three monitored zones B, C, and D is specified. Monitoring can also be extended to the other zones will or be limited to two adjacent or separate zones; this depends on what you want Degree of monitoring and regulation.

On the output side is the evaluation circuit 16 with drives A6 - E6 for the feed and the flaps A12 - E12 connected for primary air supply. It is also possible that the evaluation circuit also the Flap 9 'for the primary air zone 9, the flap 10' for the total amount of primary air, the drive of the distributor 8 and the flaps 12 'and 12 "for the secondary air.

If it makes sense for the control, the measurement signals of the in FIG. 1 shown Flow rates measuring devices 17 of the evaluation circuit 16 are connected.

In the FIG. 2 shows a course of combustion along and across the feed direction VS of the grate, which does not lead to optimal combustion The temperature range with the highest assumed here Combustion temperature is too far ahead. H. essentially in the area of zone B, and in the area of Zone D is an area that is lower than the hot area, but should already be here a lower temperature can be reached. The combustion is therefore elongated.

The thermography cameras 15 record the two-dimensional radiation distribution in the area of the zones B - D and the evaluation circuit compares the resulting isotherms according to FIG. 2 with the predetermined target isotherms, as shown in FIG. 3 are shown.

By appropriate actuation of some or all drive units A6 - E6 for the rust zones, if necessary also the allocator 8, and one. appropriate adjustment of the primary air supply for the combustion zones and optionally the allocation zone 8 can be achieved that the combustion essentially the in FIG. 3 shows the isothermal curve shown, i. H. the combustion process leading to the highest isotherm 1200 ° C, is pushed to Zone C. At the same time, the second area becomes higher temperature mined in zone D All this leads to optimal combustion.

A complete coverage of the rectangular zones or tracks is shown in the figures. It is but quite conceivable that the desired goal of an improved regulation even with partial coverage, e.g. an elliptical or circular covering of the rectangular zones or tracks is achieved.

Claims (3)

1. Method of measuring of radiation being emitted substantially by individual combustion zones of a grate, which combustion zones lie one after the other in the transport direction of the grate and of controlling of the combustion process in depency of the measured radiation by varying the transport velocity and the primary air supplied to the individual combustion grate zones,
   characterized in that the infrared radiation emitted substantially from the individual combustion grate zones and corresponding to the material bed temperature is detected each in its superficial distribution simultaneously by means of a thermography resp. infrared camera and in dependency of the comparison of the measured superficial temperature distribution with a predetermined temperature distribution the supplied primary air and the transport velocity of the fuel in the individual zones is controlled.
2. Device for measuring of the radiation being emitted substantially by at least two spatially separated positions of at least one combustion zone of a grate by means of detector means, with evaluation means connected to the detecting means and actuation means connected to the evaluation means for affecting the combustion process by varying the primary air supply and the transport velocity of the fuel,
   characterized in that the detecting means comprises at least one thermography resp. infrared camera (15a; 15b) for the simultaneous measuring of the infrared radiation corresponding to the material bed temperature of a plurality of grate zones (A-E) in its spatial distribution, which grate zones lie one after the other in the transport direction of the grate (2), and the evaluation means compares the measured superficial temperature distribution with a predetermined temperature distribution and in that to the individual grate zones independently adjustable actuation means (A12-E12) for the supply of primary air and actuation means (A6-E6) for the transport velocity of the fuel in the material bed through the individual grate zones are associated.
3. Device according to claim 2,
   characterized in that two infrared cameras (15a, 15b) are provided, each of which is associated to a sidewall (14a, 14b) of the combustion chamber and detects the same material bed surface.

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