EP0693169A1 - Process for burning solids with a sliding firebar system - Google Patents

Abstract

PCT No. PCT/CH95/00026 Sec. 371 Date Dec. 6, 1995 Sec. 102(e) Date Dec. 6, 1995 PCT Filed Feb. 6, 1995 PCT Pub. No. WO95/21353 PCT Pub. Date Aug. 10, 1995A process for burning solids on a sliding fire grate system where each of the combustion control criteria are measured and controlled individually for each grate plate comprising the grate system.

Description

 Process for burning solids on a thrust

Combustion grate system

The present invention relates to a method for combusting solids on a thrust combustion grate system. The solids can be all conceivable combustible solids, for example fossil fuels such as lignite, hard coal and the like material. In particular, however, the method is suitable for incinerating waste or garbage in large plants, the incineration being optimized in many ways thanks to this method. To operate this process, a new type of thrust combustion grate system is required, which is presented here first to explain the process operated with it later.

In contrast to the conventional combustion grates, the grate steps of which are composed of a large number of grate bars made of cast chromium steel, such a grate step in the novel type of push-combustion grate consists of a hollow grate plate made of, for example, two welded sheet steel shells. A suitable medium can flow through the individual grate plates through one or more liquid circuits and thus be tempered. With this measure, it is possible to keep the grate at a low temperature by cooling, or to preheat it if necessary. Preferably, the medium for Cooling or water used for heating. Another contrast to the conventional combustion grates is the thrust movement options of the new grate type. In conventional thrust combustion grates, every second grate level is designed to be movable, while the others are installed in a stationary manner. However, the movable grate steps are firmly coupled to one another and can therefore only perform a parallel movement, that is to say either all the movable steps do not move or all move uniformly forwards or backwards. Depending on the manufacturer, the strokes measure between approx. 150mm to approx. 400mm. With the movement of these grate steps, therefore, in the conventional sliding grates, a transport movement of the items to be burned on the grate is always and necessarily connected. In the new sliding grate type, every second grate level is also designed to be movable, but in the large subclass of the conventional design, each such movable grate level is individually movable independently of all other movable grate levels, specifically with regard to the direction of travel, the travel and the speed of travel . The third major difference to conventional grates made of chrome steel grate bars is the new grate type made of hollow grate step plates with a large number of supply nozzles for the primary air supply to the fire. This new grate construction opens up new possibilities for controlling and regulating the combustion.

It is therefore the object of the present invention to provide a method for burning solids on one To specify thrust combustion grate system which can optimize the combustion processes in many ways. In particular, the method includes a number of control measures that ensure that the combustion chamber spectrum can continue to approach an ideal spectrum and can be kept close to it during operation, so that a further optimized burnout of all combustion residues is achieved, thereby the boiler efficiency increases and boiler erosion can be reduced, and as a result the flue gas values, in particular the CO and NO content, can also be further reduced and the measures for the downstream flue gas treatment can thus be made less complex.

The invention solves the problem with a method for burning solids on a thrust combustion grate system comprising a plurality of grate stages, each of which is separately flowed through by a cooling liquid and half of which is individually movable, and which is characterized by the features according to patent claim 1 .

The method according to the invention is described and its effect is explained on the basis of the following description of a thrust combustion grate required for carrying out this method:

It shows: Figure 1: A single grate in the form of a water-cooled grate plate;

FIG. 2: a single grate plate of a combustion grate with chicanes, partially cut open;

FIG. 3: A supply air siphon to be installed below the combustion grate with grate diarrhea container and device for its remote-controlled emptying;

Figure 4: A perspective view of the grate step drive of a single grate plate;

Figure 5: A cross section of the grate stage drive seen from the side;

Figure 6: The energy profile of an ideal waste incineration;

FIG. 7: A diagram for evaluating the combustion quality, that is to say the flue gases G and the system efficiency E as a function of the 0 _{2 part} in the flue gas G; FIG. 8: a block diagram of a control and regulating system for operating the method according to the invention.

In FIG. 1, a single grate plate 1 of a combustion grate with a circuit for cooling or generally for temperature control is shown in perspective. This design of a grate plate 1 consists of two chrome steel sheet metal shells, namely a shell for the top side of the grate plate 2 and a shell for the bottom side of the grate plate 3. The two sheet metal shells 2, 3 are welded to one another. For this purpose, their edges are advantageously shaped in such a way that the two shells 2, 3 can be slipped into one another with their edges. The two end faces of the hollow profile thus created are tightly welded with end plates. In the drawing, the rear end plate 4 is inserted, while the front end face 5 is still free and allows an insight into the interior of the hollow profile. After both end faces have been closed, a cavity sealed to the outside is formed in the interior of the grate plate 1. On the underside of the grate plate 3 there are two connecting pieces 6, 7 for connecting a supply and discharge line for a medium to be flowed through the grate plate 1. This medium is basically used for tempering the grate plate 1 and must fundamentally be a flowable medium, ie a gas or a liquid. It is therefore possible to let a cooling liquid flow through the grate plate 1, for example. The coolant can be water, for example or oil or other liquid suitable for cooling. Conversely, a liquid or a gas can also be used to heat the grate plate 1. Depending on the choice of the medium, it can be used for cooling as well as for heating, that is to say in general for tempering the grate plate 1. On the grate plate top 2 and on the grate plate bottom 3 there are openings 8, 9, the openings 8 on the top 2 being smaller than the openings 9 on the bottom 3. The ones on the grate plate top 2 and the Grate plate underside 3 opposite openings 8, 9 are tightly connected to one another with tubular elements 21, for example conical tubes 21 with a round, elliptical or slot-shaped diameter, each of these elements 21 in the grate plate upper side 2 and and the underside of the grate plate 3 is welded tight. The funnel-shaped bushings thus formed through the grate plate 1 enable targeted ventilation of the firing material lying on the grate by air flow from the underside of the grate plate 3. For this purpose, supply pipes or hoses for the primary air to be blown are connected to the individual openings of the continuous pipes on the underside 3 of the grate plate 1. The grate plate 1 shown here has such a cross section that on the. Top 2 of the plate 1, a largely flat surface 2 is formed, on which the kiln is intended to lie. The lower side 3 has bevels, so that feet 10, 11 are formed to a certain extent. Along the one foot 10, which here contains a can 12, runs inside this cannula 12 a round rod 13 on which the grate plate 1 rests here. The other foot 11 is flat at the bottom and is intended to rest on the adjacent grate plate, which is of the same shape.

A grate plate is shown partially cut open in FIG. This grate plate is divided into two chambers 51, 52 by means of a partition bulkhead 50. This grate plate is one that is installed in the first part of a combustion grate, in which no primary air supply is used, which is why the plate shown here, in contrast to that in FIG. 1, does not contain any tubular elements and thus also has no openings. Combustion grates usually consist of three to five different zones, each consisting of a number of several grate plates, primary air being supplied only from the second zone. In the interior of the two chambers 51, 52, chicanes 53 are installed, which are welded tightly to the bottom of the grate plate, but on the upper side leave an air gap of a few tenths of a millimeter open to the inside of the top of the grate plate, so that these air gaps allow gas exchange within the the baffles 53 formed labyrinths can take place. A cooling medium is pumped through the connection stub 6 into the grate plate chamber 52, which then flows as indicated by the arrows through the labyrinth formed by the baffles 53 and finally flows out of the chamber through the stub 7. Because the cooling medium is larger during the flow If there is an area for heat absorption, a better heat exchange is achieved. For example, water can be used as the cooling medium. Inside the chamber 51, it looks exactly the same. Of course, such a grate plate with an inner labyrith can also be penetrated by tubular elements, so that openings are provided for blowing in primary air. Planks 54 are arranged on both lateral edges of the grate plate, along which the movable grate plates slide back and forth. In the example shown, each plank 54 consists of two superimposed square tubes 55, 56, the intermediate wall 57 thus formed being shortened at one end, so that a connection is formed there between the inside of the two square tubes 55, 56. Cooling medium is pumped from a connection 58 through the plank 54, which then flows through the two square tubes 55, 56, as indicated by the arrows, and finally flows out of the plank 54 again through the connecting piece 59. A shielding plate (not shown here) can also be arranged between the plank 54 and the grate plate, which surrounds the plank 54 on the side of the combustion plate and serves as a wear element because of the friction occurring between the grate plate and the plank.

While the supply lines for all the cooling plates to be tempered or cooled can be combined in a single, common line, the returns of the cooling water are routed separately from each cooling plate, and if the cooling plates are each divided into two or more by a partition separate cooling chambers are subdivided, so there are even two or more returns per grate plate. Ordinary sanitary pipes can be used for these returns because the temperatures to be tolerated allow this without further ado.

The flow is measured separately for each cooling cavity by means of a flow measuring device in the individual returns and controlled for each individual return by means of a valve. The cooling medium can thus be finely distributed. If this valve is completely closed, the flow is interrupted, if it is completely open, the flow of medium supplied is maximum. You can continuously vary between these two extreme settings. The valves in the individual returns can be remotely controlled by means of servomotors. In this way, the coolant flow can be regulated individually for each individual cooling chamber. The coolant inflow can be controlled with a separate metering unit. Optionally, the supplied coolant can also be passed through a heating system to preheat the grate to the desired operating temperature for starting up the system.

Figure 3 shows a supply siphon 30, as it can be mounted below the combustion grate to each primary air supply line. Because the small openings in the grate plates can inevitably cause some rust diarrhea to fall down, this grate diarrhea falls into the feed lines for the primary air in the form of fine-powder slag. It it is therefore necessary to provide such supply siphons 30 in which the rust diarrhea is collected and which at the same time ensures the unimpeded continuous air supply. Such a siphon is designed at the bottom, for example, similar to the shape of an Erlenmeyer flask, the bottom of the siphon being closed by a spring-loaded flap 31. The flap 31 is pivotable about a hinge 32 and a spring 33 loads the flap 31 with its one leg 34 from below and with the other leg 35 the side wall of the siphon. An actuating lever 36 fixedly connected to the flap 31 protrudes away from the hinge 32 and is located in the effective range of a solenoid 37. This electromagnet, when its coil 38 is energized, can attract the actuating lever 36 to its core 39. whereby the flap 31 is opened and the accumulated grate diarrhea 40 falls into an underlying trough. In the upper area of the siphon 30, the primary air supply line 41 leads into the interior of the siphon 30. This supply line leads downwards into the siphon, so that rusty diarrhea can under no circumstances fall into this supply line, since this does not necessarily have to be from a strong one Airflow flows through it. The neck 42 of the siphon is connected via a heat-resistant flexible line 43 to the lower mouth of a single conical tube which leads through a grate plate 1.

A ventilation duct that is central to the entire grate and extends under the grate in the longitudinal direction serves as supply air duct for the primary air. Hoses branch off to the side of it, which lead to the underside of the grate plates and are connected there to corresponding openings which pass through the grate plates in a conically tapering manner. This allows targeted ventilation of the firing material lying on the grate by air flow from the underside of the grate plate.

The primary air supply is blown through individual hoses from the supply channel via siphons, as already described for FIG. 3, into ventilation tubes penetrating the grate. These hoses are also provided with controllable valves, for example with solenoid valves. This design allows a very fine and individual control of the primary air for a large number of small individual areas on the grate. This makes it possible to control the fire very finely and thus drive a practically geometric fire.

The drive of a single movable grate plate is shown in more detail in FIG. The movable grate plate 16 rests laterally on two ball-bearing steel rollers 23, which are attached to the side planks of the grate structure. On the movable grate plate 16 shown here lies a stationary grate plate 14 with its front edge, which is shown here in broken lines. This stationary grate plate 14 is held at its rear end by means of claws 26 on a steel tube 22. This steel tube 22 is welded between the two planks of the grate track. The moveable The grate plate 16 now has a semi-cylindrical recess 68 on its underside, which extends approximately halfway into the grate plate 16. A bolt 69 runs through the recess and can be held in a bushing which passes through the grate plate there. The piston rod 70 of a hydraulic cylinder-piston unit 71 is fastened to the bolt 69, which is fastened inside a flushing cylinder 72, which in turn fits with its outside into the recess 68 and is fastened therein. The rear side 73 of the rinsing cylinder 72 is fixedly connected to the steel tube 22 via a rod 74 and a pipe clamp 75, which also holds the stationary grate plate 14 located over this entire drive. The rinsing cylinder 72 is constantly supplied with sealing air via an air supply line 76. As a result, air constantly flows through the flushing cylinder 72 in the direction against the bolt 69, as a result of which a jacket of pure air flows around the hydraulic cylinder-piston unit 71 contained in the flushing cylinder 72 and is therefore cooled firstly and secondly not from the front, which is open Can dust in the end. The hydraulic cylinder-piston unit 71 itself is supplied on both sides of the piston 77 with a flow line 78, 80 and an associated return line 79, 81 with hydraulic oil and flows through it. The hydraulic cylinder-piston unit 71 is then controlled by blocking individual lines. Additional cooling is achieved through the permanent flow through the cylinder space in this way. Thanks to the liquid cooling of the grate, the temperature below the grate never rises the critical hydraulic oil temperature of around 85 ° C. The intended cylinder-piston units 71 are operated with up to 250 bar hydraulic pressure, have only a content of about one liter of hydraulic oil and thus bring up to 5 tons of thrust, which is more than sufficient. This may be shown by the following rough calculation: In the case of a conventional grate, for example, about 100 tons of rubbish are moved per grate track and day. The lead time is approximately 20 minutes. This results in a current weight load of approx. 1.4 tons on the entire rust track. If this consists of 10 grate plates or grate steps, for example, there is still a very low load of 140 kg per grate plate. Even with multiple loads, this would not pose any problems for the drive. With the construction described here, each movable grate plate or step can be completely individually controlled. Not only can it be determined whether and in which direction it is moving, but also at what speed. This is namely infinitely variable between zero and a maximum speed by means of the stepless shut-off valves.

FIG. 5 shows the drive in a cross section seen from the side, the same elements as already described in FIG. 4 being shown. The grate plate that is movable here in turn rests on the next stationary grate plate 15, which in turn is held at its rear end by means of the claw 26 on the steel tube 22. Depending on the design, a grate can overlap from such the grate plates either horizontally, as shown, declined in the conveying direction upwards, or also inclined downwards. The stroke lengths and grate plate inclinations that are carried out can be selected such that the strokes of the grate plates are either merely stoking movements. These then make up about 1/4 to 1/3 of a normal transport stroke. A transport stroke, for example, measures around 250mm, and the stroke frequency can vary between 0.5Hz and 2Hz. Pure puffing strokes ensure that the firing material, which slowly moves downwards on the grate plate surface due to the force of gravity, is always pushed back somewhat and thereby rearranged. This rearrangement or agitation is very conducive to complete combustion. With such a mere stoking movement, the firing material is therefore not pushed from the grate plate front onto the next plate. Only when carrying out larger strokes is the firing material transported as desired.

This means that the essential material requirements for the exercise of the present procedure are met. Before the process is presented and explained in detail, the basic problem of combustion is to be shown here using two diagrams.

FIG. 6 shows the energy profile 89 of an ideal waste incineration combustion, as can only be approximated on a water-cooled grate. The energy curve 89 is a parabola here and gives the product of temperature x flow rate of the Cooling water. Below the grate 98, the various grate zones 90-94 are indicated, with the distribution 88 of the primary air supply. At the very beginning of the grate, immediately after the feed 97, is the drying zone 90. Here, the firing material is first dried on the grate 98, which should be done without any primary air supply if possible. With a conventional, non-water-cooled grate, you cannot avoid the air supply, because this is needed to cool the grate. This air, which is actually used as cooling air, inevitably ignites the fire and the cooling air inevitably also acts as primary air. With these conventional grates, air is forced to be added at the beginning of the grate and thus much too early. In the rest of the grate area, too, the air is often supplied in the wrong amount and in the wrong place, because it is not possible to meter in a targeted manner. In the water-cooled grate system described, however, the functions of primary air supply and grate cooling are fundamentally and totally separate from one another. It is therefore possible to operate the grate 98 in the drying zone without any air supply. The cooling takes place solely through the water flowing through the grate 98. The fired material is ignited in a second zone 91. Primary air is metered in here for the first time. It then connects to the main combustion zone, which is divided into two sections 92 and 93. This is followed by the burnout zone 93, which extends to the end of the grate 98. As shown in the diagram, the amount of primary air supplied increases practically continuously over the first half of the grate length, reaches a maximum in the second main combustion zone 93 and then decreases sharply. Air is only supplied in the burnout zone if this is necessary, that is, if there is anything left to burn. Above the fire, secondary air is supplied from the side to ensure the flue gas burnout. Then the flue gases get into the boiler 96 and the downstream devices for the flue gas treatment.

The disadvantage of conventional burns can be seen in various aspects:

1. The loading is not continuous. The firing material falling onto the grate in portions creates an irregularly high firing bed. In addition, a lot of ash and dust is whirled up with each loading. This bothers the fire and fogs the boiler walls.

2. Because the cooling of the non-water-cooled grids is carried out by the primary air supplied, the functions of cooling and primary air supply are not separated. The metering of the primary air supply is severely restricted by the cooling requirement and therefore one generally works with an excess of oxygen that is too high. The excess of oxygen causes an unnecessarily high NO content and because too much air flows through the grate, it contributes to turbulence and dust formation above the grate, with all the undesirable secondary effects. The combustion is not optimal and the boiler walls are steamed up. 3. Because the functions of the stoking and the transport cannot be separated on conventional grates, the combustion bed cannot be compensated and accordingly it is not possible to reach a geometric fire even close. One always has inevitably rust areas uncovered by firing material and, on the other hand, those on which the firing bed is too high.

4. Because the type and number of control parameters for conventional, not water-cooled grates is very limited, the combustion can only be influenced to a very limited extent.

FIG. 7 shows a diagram for assessing the combustion quality, that is to say the flue gases G and the system efficiency E as a function of the 0 ₂ component in the flue gas G. The C0 value is regarded as a superordinate measure of the combustion quality. Now you can see from this diagram that the CO limit value (CO) is maintained over a relatively wide range of the 0 ₂ content in the flue gas. With a decreasing 0 ₂ portion, the NO portion also decreases and the efficiency E of the incineration plant increases with a simultaneously decreasing gas volume flow V. However, if the 0 ₂ portion is further reduced to a certain extent, the CO value suddenly rises steeply. The aim of the combustion control must therefore be to keep the 0 ₂ value so low that the NO portion becomes minimal and at the same time the CO limit value is just maintained. Such an ideal working point is in The diagram is drawn. In addition to the flue gas values to be achieved, it also guarantees high system efficiency. Because of the smaller 0 ₂ ~ fraction compared to the current value, less air has to be blown through the firing material. This also means that there is less dust ejection. The dust particles are also less fast. This reduces the erosion of the boiler walls. Fast and many dust particles treat the boiler walls like sandblasting. The overriding aim of the present method is to implement combustion that is as stoichiometric as possible. On the way to this, the 0 ₂ portion in the flue gas should be reduced to a value of around 4 percent by volume, whereas today, due to the systems, one has to operate at about 10 percent by volume.

The process for achieving these goals is described and explained below: It is characteristic of the process that the current fire data about the recirculated cooling energy is recorded and then this data is used to control and regulate the fire. Depending on the data situation, it is then stoked and / or transported separately or not separately, and / or the grate is loaded with new firing material, exactly in accordance with the control and regulation specifications. The stoking can be limited locally to a single or several grate plates and the stoking stroke and the lifting speeds are variable, so of course the lifting frequencies. Furthermore, this grate construction in cooperation with the Control and regulation, the primary air as required and targeted to discrete locations on each grate level in a metered amount and time-dependent. This targeted primary air supply optimally supplies the firing material with primary air, so that its calorific value is used in the best possible way and its combustion takes place as completely as possible. For this purpose, the temperature spectrum in the combustion chamber above the combustion grate can also be determined using a large number of temperature measuring probes. These measuring probes can be installed in the surface of the grate plates, for example. On the other hand, the temperature spectrum can also be determined using a pyrometer. The targeted metering of the primary air supply for each individual supply line enables the current temperature spectrum in the combustion chamber to be approached approximately to the optimum spectrum. For individual control of the primary air supply for each supply line, for example, solenoid valves can be used in the supply lines, which are controlled by a central microprocessor, in which the optimally selected combustion chamber temperature spectrum can be stored. As mentioned, the cooling energy dissipated on the basis of flow and temperature in the returns is used as the regulation parameter. By constantly measuring the real spectrum and comparing it with the ideal spectrum, a control loop can be formed, according to which the individual solenoid valves are individually opened in a slightly more or less precise manner and allow primary air to flow through the individual supply lines. The primary air supply is provided by one or more powerful ones Compressors or fans. A fine and very complex set of rules can be set up in this way, which optimally ensures combustion by means of electronic evaluation by individually controlling all cooling medium runs, all drive elements for moving and charging the grate, and all individual primary air supplies. As a result, the energy content of the combustion material can be used even better, the slag diarrhea is further minimized and, above all, the foundations are laid for further minimizing the undesired flue gas components.

The medium used for temperature control can be in a heat exchange with the primary air to be supplied. A commercially available heat exchanger can be used for this, which works according to the counterflow principle. By means of such a heat exchanger it is possible, for example, to preheat the primary air, which is conducive to optimal combustion with certain combustible goods. Especially with organic waste components, for example with rotten or rotten vegetables or fruits, a preheating of the primary air is very desirable because it improves the combustion. On the other hand, it is also possible to heat the combustion grate to start a combustion process in order to bring the grate to the optimum operating temperature as quickly as possible. For this purpose, the temperature control medium can absorb the heat from the exhaust air from the combustion that is already taking place and then introduce it into the grate plates of the combustion grate. With regard to the primary air supply, it is of particular importance that the cooling of the thrust combustion grate is carried out exclusively by a cooling liquid and that the supplied primary air is, apart from an inevitable part of its cooling effect, exclusively effective combustion air. Because of this functional separation, the primary air in a variant can be specifically metered with combustion-promoting substances or it can consist exclusively of such substances. This combustion air could theoretically be limited to pure oxygen, which is fed through the primary air supply lines 41 to the material to be burned on the grate. It is immediately clear that the air throughput of the grate could be reduced to a fifth of the previous air volume. This means that large quantities of air no longer flow locally uncontrolled through the grate and the material to be fired, but rather local oxygen is supplied very gently in a targeted amount, that is to say at a low flow rate, to the material to be fired. As a result, no unnecessary flue gas volume is generated, the flue gas speed is considerably reduced, and thus the occurrence of fly ash. The small portion of fly ash is also no longer whirled up into the kettle. All this makes it possible to dimension the boiler and all the downstream system components much smaller and therefore more cost-effectively. A nitrogen wash in the course of the flue gas treatment could be completely eliminated when pure oxygen is supplied. In practice, however, you will probably be less dramatic Reductions work. In principle, oxygen can be added in a suitable amount to the primary air, which is intended to act exclusively as combustion air. The higher the oxygen content of the primary air, the lower the air throughput required to achieve the desired Ausbran¬ des. In a conventional system, for example

3 50 * 000 air flow per hour, there are about 5 * 000 m3 of oxygen out of the approx. 10,000 m 3 oxygen contained therein

3 available for combustion and about 5,000 m as

Combustion reserve. If you want to reduce this air flow by half with the same combustion, you get

3 the following rough calculation: in 25,000 m

3 exercise air still has 5,000 m of oxygen, of which again approx. 2,500 m 3 are available for combustion and approx. 2,500 m3 as a combustion reserve. By dosing

3 further approx. 5,000 m of oxygen gas, the required values for the desired burnout and the necessary combustion reserve can be achieved. The 5,000 m of oxygen per hour corresponds to approximately 6,000 liters of liquid oxygen. That would be 6,840 kg of liquid oxygen. Now it is a matter of calculating the cost / benefit ratio of adding oxygen. The optimum may be anywhere between zero and 100% metering, depending on the system-specific criteria. In any case, however, a great deal can be achieved with a corresponding metering that is optimized on such a characteristic curve: you have much less flue gas volume, you achieve a significantly reduced flue gas speed, much less fly ash and as a result the entire boiler can be tion and in particular the nitrogen washing and flue gas cleaning can be dimensioned much smaller. The reduction in these dimensions translates into reduced amortization and thus reduced operating costs. A part of this cost reduction is of course consumed by the costs of metering in these combustion-promoting substances, but the bottom line is that considerable savings can be achieved.

With the movable grate plates with infinitely variable speed, a uniformly high combustion bed can be achieved and maintained. The control of the grate plate movements can also be regulated with the temperature. As soon as the temperature of a grate plate or a region of a grate plate rises, this indicates that the combustion bed height there is too low or there is no material at all on this grate plate location. The combustible bed can be compensated immediately by appropriate automatically initiated stoking. These control measures mentioned here are advantageously controlled by a microprocessor, the control variables being used, inter alia, to calculate the temperatures of the individual cooling medium returns. These quickly indicate a change in the fire on the grate area in question.

FIG. 8 shows the basic block diagram of a control and regulation for the method according to the invention. This control and regulation consists of the following Subsystems, each of which is listed in a column: The sensor system is to be indicated on the far left, that is to say all the data which can be recorded are listed on the basis of the associated sensors. The column to the right lists the setpoint transmitters. Then comes the actual regulation and control for the individual physical components of the entire combustion system. The next column on the right names the devices for realizing superordinate links and the column on the far right finally includes a list of the individual actuators.

The individual system components are described in each case from top to bottom: in the case of the sensors, this begins with those for detecting the amount of steam QD, then those for measuring the temperatures ^τ _ι --- ^τ _{n of} the cooling water at the individual measuring points i. The flow rate Q .... Q is also measured in each return i. The temperature TF in the combustion chamber is measured using, for example, a pyro meter. Optionally, the burning bed height H -... H can be measured at different points i. An ultrasound measurement from above onto the grate surface can be used for this purpose. 0 _{2 means} the oxygen content in the flue gas, which is measured with special measuring probes, or instead of 0 ₂ the. the inverse value of carbon dioxide C0 ₂ measured in the flue gas. Finally, the carbon monoxide content CO in the flue gas is also measured, which is prescribed by law for a combustion system to be operated as a maximum value. All values measured in this way are compared with target values, listed in the second column. This is the target amount of steam, which arises from the design of the system itself, but in practice, based on experience as a maximum for each fired product, results as the theoretically optimal specification SDR (= setpoint generator steam tight). Then there are the optimal values for the cooling water temperatures T -... T of the individual returns i, those for the optimal flow rates Q -... Q of the individual returns i, and the optimal combustion bed heights H -... H, the individual grate plates i. These values result in certain desired values for a ^'profile SPR (= target value transmitter profile). The third column shows the individual regulation and control units that connect the measurement data with the target values and then pass them on for the higher-level links for billing. In the third column, this begins with the DR steam regulator. This compares the detected effective steam quantity with the target steam quantity. The temperatures T., flow rates Q. and, if appropriate, the combustion chamber temperature TF and the combustion bed heights H. are incorporated in the profile controller PR. The measured values for 0 ₂ or CO- serve as parameters for the stoke control SS, the conveyor control FS and the loading controller BR. The combustion chamber temperature TF and the measured 0 ₂ ~ or C0 ₂ ~ value in the flue gas and the CO value in the flue gas are included in the minimization computer SBR for the ratio between 0 ₂ and C0 ₂ . The calculated value then also influences the feed controller. The output signals of these various controllers just presented are listed in the control devices in the fourth column are linked and further processed. The block diagram provides the following higher-level linking options, which are listed in this fourth column. Starting from the top, this is the air distributor LV, which is fed by the output signal of the steam regulator DR and the profile regulator PR. This is followed by the cooling water energy distributor WV, which receives its data from the profile controller PR. This is followed by a BFSK coordination computer for the coordination of loading, funding and stoking movements. The individual links made arithmetically based on programs then control the actuators. The air distributor has a determining effect on the air system and / or, if necessary, also on the air heating system, in the event that the primary air is to be preheated, or if preheated air is to be supplied to dry the combustion material.

The cooling water management is carried out by the cooling water distributor WV, in that the directional valves WWS are set for the different returns of the cooling water system, the freshly fed cooling water is metered in by means of the metering unit WDS, and finally the heating system for the cooling water WHS is set depending on whether and how much the cooling water is tempered.

The BFSK coordination computer provides the drive elements for the grate movements and for loading the grate. These include the conveyor drives for determining the Strokes FRH of the individual cylinder-piston units of the movable grate plates and the conveyor drives for determining the stroke speeds FRG of the individual cylinder-piston units of the movable grate plates. In the same way, the loading is set via the conveyor drives for the stroke FBH and the lifting speed FBG of the loading device. The loading can be carried out continuously, in that the solids in the feed shaft are first portioned and retained by two hydraulic barrier grids which can be moved in at different heights, so that only just such a portion of solids lies on the loading device. The lock window to be passed to the combustion chamber is then always tightly closed by this portion of solids, and continuous delivery to the combustion grate is possible through this window. This continuous conveying is possible in that the carrier surface of the loading device is formed from several longitudinal webs which, through alternating, slow strokes, which describe a rhomboid when viewed from the side, uniformly convey the solids lying thereon through the window onto the combustion grate .

The following different control and regulation tasks are fulfilled with these different subsystems:

1. The steam control, by means of the air distribution

2. The 0 ₂ - or the inverse C0 ₂ ~ control, as

2.1. Feed control and / or

2.2. Funding control and / or 2.3. Stoking control

3. The gas burnout control by means of CO / 0 ₂ ~ minimization

4. The control of the combustion position, namely as

4.1. Control of primary air distribution and / or

4.2. Control of cooling water energy redistribution

5. The garbage bed profile control

The individual control systems are explained in sequence below:

1. The steam control by means of the air distribution. The steam control is implemented via the sensor QD for the steam quantity, the setpoint generator SDR, the steam controller DR and an air distributor LV via the air system LS. For the controller, the controlled system is the entire grate, the controlled variable is the steam output or a quantity associated with the steam output. The command variable is also the steam output or a quantity associated with it. The quantity of primary air with constant distribution acts as the manipulated variable and the individual actuators of the primary air system, which determine the supply of primary air for each individual primary air zone under the grate plates, act as actuators. In general, the following applies: the smaller the measured steam output compared to the desired value, the more primary air has to be supplied. 2. The 0 -, - or the inverse CO -, - control Another essential control system includes the 0 ₂ / C0 ₂ ~ control. These two values are inverse to each other. In many cases the 0 ₂ ~ fraction in the flue gas is measured. The 0 ₂ / CO -, - control is via a sensor for the 0, - and / or C0 -, - value, a setpoint generator SBR, a loading controller BR and a conveyor control FS, a stoking control SS and a coordinator BFSK for the grate conveyor drives FRH and FRG as well as for the feed drives FBH and FBG realized.

2.1. Feed control

The controlled system for the loading controller BR is the loading device and / or the portioning device. The control and guide variable is the 0 ₂ ~ and / or C0 ₂ ~ content and the manipulated variable is the length of the drawer and the thrust speed of the individual movable loading elements for the continuous loading of the grate. The actuators contain the drive systems for these strokes.

2.2. Funding control

In the conveyor control, the control section includes all movable grate plates. The 0 -, - and / or C0 -, - content serves as the control and guide variable and the manipulated variables are the drawer lengths and the pushing speeds of the individual movable grate plates. 2.3. Stoking control

In the case of the stoke control SS, the control section again includes all movable grate plates. The 0 ₂ ~ and / or C0 ₂ ~ content serves as control and guide variable and the manipulated variables for this are again the reduced drawer lengths and the pushing speeds of the individual movable grate plates. If, for example, the C0 ₂ ~ content begins to decrease, or the inverse 0 ₂ ~ content in the flue gas begins to increase, fueling begins. If this fueling does not help, the system knows that there is no firing material on the grate at that point. Firing material must therefore be transported.

The coordinator BFSK has the task of separately and / or superimposing the movements to be brought about by the stoke control SS, conveyor control FS and / or the loading control BR, simultaneously or in succession to the actuators of the actuators.

3. The gas burnout regulation by means of the CO / 0 -.- minimization

A very important parameter for any waste incineration plant is the gas burnout. This can be regulated very finely by means of the method according to the invention, specifically via the chain of the feed control by the CO / O ₂ minimization computer SBR as setpoint generator for the feed controller BR. Most waste incineration plants are operated with a volume fraction of approx. 10% oxygen in the flue gas. This excess air is necessary in order to use conventional Systems to ensure the flue gas burnout. It is accepted that the NO Λ value is high in this operating mode. The ratio of CO to NO is opposite and only optimal in a narrow 0, - band. The CO / 0 ₂ ~ minimization calculator automatically probes the lowest possible 0 ₂ ~ content, at which an almost complete gas burnout is still guaranteed. It would previously have been possible to push the NO value down, only with the previous control and air distribution options it was not possible at the same time to ensure that the CO value was still maintained at a low 0 ₂ ~ content. However, the present method according to the invention now makes it possible to reduce the 0, - fraction in the flue gas and, thanks to the fine rules and regulations, to bring the combustion closer to an optimal working point. This operating point is characterized by a lower 0 ₂ ~ value with a simultaneous significant reduction in the NO content, and all this with reliable compliance with the permissible CO value, even with a significant reduction in this CO value. In order to achieve this operating point, the setpoint generator reduces the 0 ₂ setpoint for the charge controller until the actual CO value of the raw gas is below the legally permissible CO setpoint with a minimum 0 ₂ content. The combustion chamber temperature, which is simultaneously monitored via the temperature sensor TF, limits a further reduction in the 0 ₂ content at a maximum value. For the gas burnout control, the controlled system is the charging and portioning device, and the controlled variable is the 0, - and / or the CO ₂ content. This serves as a benchmark Ratio between CO and 0 ₂ - The actuating variable is the thrust speed and / or the stroke length of the actuators, namely the loading device and / or the movable grate plates.

4. The control of the combustion position

The combustion positioning is a further variable in comparison to the method operated with conventional systems. This combustion positioning is carried out via the temperature sensors ^τ _ι - * ^τ _{n of} ^the cooling water temperatures of the grate, via the flow rate sensors Q, ... Q of the cooling water flow rates of the grate, via the temperature sensor TF of the combustion chamber temperature, via a cooling water energy distributor WV, via a cooling water path distribution System WWS, a cooling water metering system WDS, a cooling water heater on the one hand and / or realized via the air distributor LV, the air system LS and an air heating LHS on the other hand as primary air distribution control and / or cooling water energy redistribution control.

4.1. Control of primary air distribution

For the primary air distribution control, the control sections are the primary air zones, which, however, can still be divided into local areas on the grate plates by a large number of supply air nozzles. The control variable is the primary air distribution, that is, how much air gets where and at what time. The guide variable is given by the ideal temperature profile of the cooling water. As manipulated variables the air volumes to the individual primary air zones or to the individual supply air nozzles are used for this. The actuators to be operated are the drives for the primary air supply, which consist of fans or compressors, and / or an air heater. If, for example, the cooling water temperature in the burnout zone of the grate does not drop compared to the main fire zone, primary air is also supplied there, which is otherwise avoided.

4.2. Control of the cooling water energy redistribution The cooling water energy redistribution control has the grate cooling system as the control section and the cooling water energy distribution as the control variable. The optimal cooling water energy profile serves as a guide. The manipulated variable is the cooling water path and / or the cooling water quantity and / or the cooling water energy. The drives of the cooling water path system and / or the cooling water metering system and / or a cooling water heater serve as the actuators to be operated.

5. The garbage bed profile control

The present method also opens up the possibility of controlling the profile of the garbage or combustion bed itself. This is done via the temperature sensor T -... T of the cooling water temperature of the grate, the temperature sensor TF for the combustion chamber temperature, the garbage or combustion bed height sensor H -... H, the profile computer PR, and the coordination computer BFSK, the grate conveyor drives FRH and FRG as well as the feed drives FBH and FBG realized. The control route is the grate conveyor and loading system. The tax base is the garbage bed profile. The guide variable is given by the cooling water temperature profile and / or the directly measured garbage bed profile. The drawer lengths and thrust speeds of the loading and the movable grate plates that form the actuators act as the manipulated variable.

In the minimum case, only a control is implemented on the basis of the return temperatures of the cooling medium, which are then calculated into manipulated variables for the movements of the grate plates. When the temperature drops locally, the stoking of the grate plate in question is started, and if the temperature does not rise again, additional firing material is transported to this location by increasing the strokes. As a further option, more primary air is supplied to this point until the target temperature is reached.

It is clear that the control network becomes more complex as the number of parameters increases. But the goal is always to achieve as stoichiometric combustion as possible. It is of great importance that the present method can be used to immediately gain experience in practical operation, which in a short time leads to a drastic reduction in the flue gas volumes and, as a result, the downstream units for flue gas treatment can be designed to be smaller and less expensive . Furthermore, the boiler efficiency will increase due to the optimized combustion, the boiler erosion due to the better burnout achieved reduced and the flue gas values will generally level off at lower values. Disposing of filter ash, which is filtered from the flue gas, is increasingly expensive. It is therefore important to reduce the amount of filter ash which is achieved by means of better combustion with the present method.

Claims

claims

1. Method for burning solids on a thrust combustion grate system comprising a plurality of grate stages, each with a coolant flowing through them separately and half of which can be moved individually, characterized in that the following functions are not necessarily controlled and operated individually as a function of one another: a) the cooling of the grate, b) the local and temporal supply of primary air, the latter possibly being metered in with targeted substances which promote combustion or the latter consist exclusively of such substances, c) the local and temporal stoking movements of the grate, d) the local and temporal transport movements of the grate, e) the temporal loading movements for loading the grate, at least the coolant temperatures of the individual grate levels serving as control variables for control.

2. The method according to claim 1, characterized in that the cooling liquid temperatures of the individual rust fen serve as a control variable for controlling, on the one hand, the time and place independent stoking and transport movements of the individual movable grate levels and the loading movements of the grate system, and on the other hand as control variables for the primary air separately metered and supplied for each grate level.

3. The method according to any one of the preceding claims, characterized in that the cooling water temperature distribution is approximated to a theoretical ideal by means of variation of the stoking, transport and loading movements, then the primary air supply in compliance with the prescribed CO - Limit value and decrease in NO -

Value is reduced until the CO value begins to increase, which defines an operating point below the CO limit value, which is then maintained by varying all possible parameters.

4. The method according to any one of the preceding claims, that when the cooling water temperature of a grate level drops there is an immediate start, and if the cooling water temperature does not rise thereafter, a brief increase in the local primary air supply is carried out, and if the cooling water temperature still does not rise thereafter , a transport movement is used in order to convey firing material to the grate level in question. and that when the target value of the cooling water temperature is reached, the transport movement stops and the primary air supply is reset to the initial value.

5. The method according to any one of the preceding claims, characterized by a) capturing data of the returned cooling energy and using this data for controlling and regulating the combustion; b) if necessary, charging the grate separately from the stoking and transporting of the firing material on the grate in accordance with the requirements of the control system; c) if necessary, temporally and spatially separate shearing and transport of the firing material on the grate in accordance with the control and regulation specifications; d) if necessary, targeted supply of primary air to discrete locations on each grate level in each metered quantity and duration; e) if necessary, individual tempering of each grate plate of the combustion grate with the medium flowing through it.

6. The method according to any one of the preceding claims, characterized in that a) the fire data by means of temperature sensors (T -... T), flow meters (Q- ... Q) and measuring devices (H .... H.) For determining the local garbage bed height, as well as recorded by a furnace thermometer (TF) and then calculated in a temperature, energy and garbage bed profile calculator (PR); b) the loading is controlled by varying the stroke and the lifting speed of the loading device from a coordination computer (BFSK), which receives its data from the profile computer (PR) and from a loading controller (BR), which has the ratio 0 ₂ to CO in the flue gas considered; c) the spatially and spatially stoking and / or transporting of the firing material on the grate by varying the stroke and the stroke speed of the grate plate drives is controlled by a coordination computer (BFSK), which processes its data from the profile computer (PR) and receives from a stoking (SS) and conveyor control (FS), which take into account the ratio 0 ₂ to CO in the flue gas; d) the targeted primary air supply takes place via a plurality of zones, each with separate air supply nozzles in the grate plates, the air quantity supplied in each case being controlled by an air distributor (LV) which takes into account the data of a steam controller (DR), which compares the setpoint of the amount of steam and the effectively generated; e) the individual grate plates are individually tempered by a cooling water distributor (WV) Directional control valves (WWS) of the individual liquid circuits of the individual grate plates control so that newly added coolant is metered in or coolant is preheated if necessary, the manipulated variables being specified by the temperature, energy and waste bed profile computer PR.

7. The method according to any one of the preceding claims, characterized in that both the respective stroke as well as the stroke speeds and stroke frequencies are each varied independently of one another and in terms of time and location for the stoking, transport and loading movements.

8. The method according to any one of the preceding claims, characterized in that in the drying zone of the grate is driven without any primary air supply and thus the cooling of the grate is carried out exclusively by the medium flowing through it.

9. The method according to any one of the preceding claims, characterized in that in the burnout zone of the grate is generally run without primary air supply, and primary air is only supplied if the cooling water temperature from the burnout zone does not exceptionally drop compared to that in the main combustion zone of the grate, wherein the supply of primary air immediately is stopped again as soon as the cooling water temperature drops out of the burnout zone.

10. The method according to any one of the preceding claims, characterized in that pure oxygen is added to the primary air, or that the primary air consists exclusively of pure oxygen.