EP0693169B1 - 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

The present invention relates to a method for burning of solids on a thrust combustion grate system. At the solids can be any combustible imaginable Trade solids, for example fossil fuels like Brown coal, hard coal and the like material. Especially but the process is suitable for rubbish or rubbish in To burn large plants, the combustion thanks to this Process is optimized in many ways. For operation this method is a novel type of a push-grate system necessary. In the publication DE-U 93 09 198 becomes a grate plate for the production of such Thrust combustion grate system for burning rubbish disclosed. This thrust combustion grate system is here first presented, afterwards the one operated with him To explain the procedure.

In contrast to the conventional combustion grates, the grate levels from a variety of side by side Rust bars are made of cast chrome steel such grate level in the new type of push-combustion grate from a hollow grate plate from, for example, two welded sheet steel shells. The individual grate plates are through one or more fluid circuits can be flowed through by a suitable medium and thus tempered. With this measure it is possible to rust through Keep cooling at a low temperature, or keep it at Also need to preheat. Preferably, the medium for Cooling or water used for heating. Another Contrary to the conventional combustion grates in the thrust movement possibilities of the new type of grate. With conventional thrust combustion grates, everyone is second grate stage is movable while the others are installed stationary. The movable grate levels are however, firmly coupled and can therefore only one Carry out parallel movement, that is, either move all moving stages do not move or all move uniformly forward or backward. The strokes measure depending on Make between approx. 150mm to approx. 400mm. With the movement this grate level is therefore with the conventional sliding grates without exception and always a transport movement of the material to be burned on the grate. With the new one Sliding grate type is also movable every second grate level executed, but in big difference to the conventional In construction, each such movable grate level is independent individually movable from all other movable grate levels, with regard to the stroke direction, the stroke and the lifting speed. The third essential difference to conventional grates made of chrome steel grate bars new grate type made of hollow grate plates with a variety of supply nozzles for the primary air supply to the fire be. This new grate construction opened for the Control and regulation of combustion new opportunities.

It is therefore the object of the present invention to provide a method for burning solids on such a thrust combustion grate system, which can optimize the combustion processes in many ways. In particular, the process includes a number of control measures that ensure that the combustion chamber spectrum can continue to approach an ideal spectrum and be kept close to it during operation, so that a further optimized burnout of all combustion residues is achieved, which increases the boiler efficiency increases and the boiler erosion can be reduced, and as a result also the flue gas values, in particular the CO and the NO _x content, can 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 of solids on a thrust combustion grate system of several, each separately from a coolant flowed through and half individually movable grate levels, which is characterized by the features according to patent claim 1.

Based on the description below one to exercise this This will be the process of the necessary combustion grate Process described according to the invention and its effect explains:

Figur 1 :

Eine einzelne Roststufe in Form einer wassergekühlten Rostplatte;

Figur 2 :

Eine einzelne Rostplatte eines Verbrennungsrostes mit Schikanen, teilweise aufgeschnitten;

Figur 3 :

Ein unterhalb des Verbrennungsrostes anzubauender Zuluft-Siphon mit Rostdurchtallbehälter und Vorrichtung zu dessen ferngesteuerter Entleerung;

Figur 4 :

Eine perspektivische Ansicht des Roststufen-Antriebes einer einzelnen Rostplatte;

Figur 5 :

Einen Querschnitt des Roststufen-Antriebes von der Seite her gesehen;

Figur 6 :

Das Energie-Profil einer idealen Kehricht-Verbrennung;

Figur 7 :

Ein Diagramm zur Beurteilung der Verbrennungsqualität, das heisst der Rauchgase G und der Anlageneffizienz E in Funktion des O₂-Anteils im Rauchgas G;

Figur 8 :

Ein Blockschema eines Steuerungs- und Regelsystems zum Betrieb des erfindungsgemässen Verfahrens.

It shows:

Figure 1:

A single grate in the form of a water-cooled grate plate;

Figure 2:

A single grate plate of a combustion grate with chicanes, partially cut open;

Figure 3:

A supply air siphon to be installed underneath the combustion grate with grate passageway 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;

Figure 7:

A diagram for evaluating the combustion quality, that is, the flue gases G and the system efficiency E as a function of the O ₂ content in the flue gas G;

Figure 8:

A block diagram of a control and regulating system for operating the method according to the invention.

In Figure 1 is a single grate plate 1 of a combustion grate with circuit for cooling or in general for the temperature control shown in perspective. This version of a grate plate 1 consists of two chrome steel sheet shells, namely from a shell for the top of the grate plate 2 and a bowl for the bottom of the grate plate 3. The two metal shells 2, 3 are together welded. For this purpose, their edges are advantageously shaped that the two shells 2, 3 are slipped into each other with their edges can be. The two end faces of the resulting Hollow profiles are tightly welded with end plates. In the drawing, the rear end plate is 4th used while the front end 5 is still free and insight into the interior of the hollow profile. After Locking both end faces is inside the grate plate 1 an externally sealed cavity is formed. There are two connection sockets on the underside of the grate plate 3 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 to temper the grate plate 1 and must always be a flowable medium, so a gas or a liquid. So it is possible the grate plate 1 flow through with a coolant, for example allow. The coolant can be water, for example or oil or another liquid suitable for cooling be. Conversely, a liquid or a gas can also can be used to heat the grate plate 1. Depending on your choice of the medium, this can be used for both cooling and also for warming up, in general for tempering the Grate plate 1 are used. On the top of the grate plate 2 and on the bottom of the grate plate 3 there are openings 8,9, the openings 8 on the upper side 2 being smaller than the openings 9 on the underside 3. The on the grate plate top 2 and the bottom of the grate plate 3 opposite Openings 8.9 are with tubular elements 21, for example conical tubes 21 with a round, elliptical or slit-shaped diameter, close together connected, each of these elements 21 in the grate plate top 2 and and the underside of the grate plate 3 are welded tight is. The resulting funnel-shaped bushings through the grate plate 1 allow by inflow with Air from the grate bottom 3 a targeted Ventilation of the firing material lying on the grate. To do this to the individual mouths of the continuous pipes the bottom 3 of the grate plate 1 feed pipes or hoses connected for the primary air to be blown. This one shown grate plate 1 has such a cross section that on the top 2 of the plate 1 has a largely flat surface 2 is formed, on which the firing material is determined to lie is. The lower side 3 has bends, so to a certain extent Feet 10,11 are formed. Along one foot 10, which here contains a channel 12, runs inside this cannula 12 a round rod 13 on which the grate plate 1 rests here. The other foot 11 is flat and below determined on the neighboring grate plate, which of the same Form is to lie on.

In Figure 2, a grate plate is partially cut open shown. This grate plate is by means of a partition bulkhead 50 divided into two chambers 51, 52. It is this Grate plate around one in the first part of a combustion grate is installed in which not with primary air supply is incorporated, which is why the plate shown here differs contains no tubular elements to that in FIG and therefore has no openings. Combustion grates usually consist of three to five different ones Zones, each consisting of a number of several grate plates exist, with primary air only from the second zone is fed. There are baffles inside the two chambers 51, 52 53 installed, which is tight with the grate plate below are welded, but an air gap on the top from a few tenths of a millimeter to the inside of the top Leave the grate plate open so that it can pass through these air gaps Gas exchange within the baffle 53 formed Labyrinths can take place. Through the connector 6 a cooling medium is pumped into the grate plate chamber 52, which then as indicated by the arrows by that of the Baffles 53 formed labyrinth flows and finally flows out of the chamber through the nozzle 7. Because the cooling medium a larger as it flows through Finding area for heat absorption will be a better one Heat exchange achieved. Water, for example, can be used as the cooling medium be used. It looks exactly inside the chamber 51 the same. Of course, such a grate plate with inner labyrith but also of tubular elements be interspersed so that openings for blowing primary air available. On both side edges of the grate plate planks 54 are arranged, along which the movable Slide the grate plates back and forth. In the example shown each plank 54 consists of two superimposed square tubes 55, 56, the intermediate wall 57 thus formed one end is shortened so that there is a connection between the inside of the two square tubes 55,56 is formed. From A connection 58 becomes cooling medium through the plank 54 pumped, which then through the two square tubes 55.56 flows as indicated by the arrows, and finally flows out of the plank 54 through the nozzle 59. In addition, between the plank 54 and the grate plate a shielding plate, not shown here, is arranged be the plank 54 on the combustion plate side borders and as a wear element because of the between Grate plate and plank used friction.

During the heats for everyone to be tempered or too cooling grate plates in a single, common line can be summarized, the returns of the cooling water guided separately by each grate plate, and if the Grate plates each with a partition in two or more separate cooling chambers are divided, so result per Grate plate two or more returns. For these returns ordinary sanitary pipes can be used because the temperatures to be tolerated allow this without further ado.

The flow is separately for each cooling cavity of a flow meter in the individual back rings measured and by means of a valve for each individual return controlled. This allows the cooling medium to be finely distributed. When this valve is completely closed, the flow is interrupted, when it is completely open, you have maximum Flow for the medium supplied. Between these two Extreme settings can be varied continuously. The valves in the individual returns can be done using servo motors be remotely controlled. This is how the coolant flow can be regulate individually for each individual cooling chamber. Of the Coolant inflow can be done with a separate dosing unit being controlled. Optionally, the coolant supplied also passed through a heating system to the grate for starting up the system to the desired operating temperature preheat.

Figure 3 shows a supply siphon 30 as it is below the Combustion grate mounted to each primary air supply line can be. Because through the small openings in the grate plates inevitably drop some rusty diarrhea can, this rust diarrhea falls in the form of fine powder Slag in the primary air supply lines. It it is therefore necessary to provide such siphons 30 in which the rust diarrhea is caught, and with what at the same time ensures the unimpeded continuous air supply becomes. Such a siphon is, for example, similar to that below Form of an Erlenmeyer flask, the bottom of the Siphons is closed by a spring-loaded flap 31. The flap 31 is pivotable about a hinge 32 and one Spring 33 loads the flap 31 with its one leg 34 from below and with the other leg 35 the side wall of the Siphons. An actuating lever firmly connected to the flap 31 36 protrudes from hinge 32 and is located in Area of action of a solenoid 37. This electromagnet can when its coil 38 is energized will pull the operating lever 36 to its core 39, whereby the flap 31 is opened and the accumulated Rust diarrhea 40 falls into an underlying trough. The primary air supply line leads in the upper region of the siphon 30 41 into the interior of the siphon 30. This supply line leads sloping down into the siphon, so under no circumstances Rust diarrhea can fall into this supply line, because it has to not necessarily constantly flowed through by a strong air flow be. The neck 42 of the siphon is heat-resistant flexible line 43 with the lower mouth of a single conical tube connected by a grate plate 1 leads.

A ventilation duct that is central to the entire grate extends under the grate in the longitudinal direction, serves as a supply air duct for the primary air. Hoses branch off to the side of him that lead to the underside of the grate plates and there Appropriate openings are connected to the grate plates Push through conically towards the top. this makes possible by air flow from the underside of the grate plate targeted ventilation of the firing material lying on the grate.

The primary air supply is via individual hoses from the supply duct via siphons as already described for FIG. 3 to individual blown through the rust-penetrating ventilation tube. These hoses are also equipped with controllable valves, for example with solenoid valves. This execution allows a very fine and individual control of the primary air for a large number of individual small areas the rust. This makes it possible to control the fire very finely and to drive a practically geometric fire.

In Figure 4 is the drive of a single movable grate plate shown in more detail. The movable grate plate 16 lies laterally on two ball-bearing steel rollers 23 each attached to the side planks of the grate structure are. Is on the movable grate plate 16 shown here a stationary grate plate 14 with its front edge on the is shown here in dashed lines. This stationary grate plate 14 is at its rear end by means of claws 26 held a steel tube 22. This steel tube 22 is between the two planks of the rust track welded in. The moveable Grate plate 16 now has a semi-cylindrical on its underside Recess 68 on, which is about half in the Grate plate 16 extends into it. Through the recess runs a bolt 69 which is held in a sleeve can, which penetrates the grate plate there. At the bolt 69 is the piston rod 70 of a hydraulic cylinder-piston unit 71 attached, which inside a rinse cylinder 72nd is attached, which in turn with its outside in the Recess 68 fits and is fixed therein. The back 73 of the rinse cylinder 72 is via a rod 74 and a pipe clamp 75 firmly connected to the steel tube 22, which yes also the stationary one located over this entire drive Grate plate 14 holds. The rinse cylinder 72 is via an air supply line 76 constantly supplied with sealing air. Thereby air constantly flows through the flushing cylinder 72 in the direction against the bolt 69, whereby the contained in the rinse cylinder 72 hydraulic cylinder-piston unit 71 of one Coat is surrounded by pure air and therefore firstly is cooled and secondly not from the front end can dust up. The hydraulic cylinder-piston unit 71 itself is on both sides of the piston 77 by a flow line 78.80 and an associated return line 79.81 with Hydraulic oil is supplied and flows through. The control of the hydraulic cylinder-piston unit 71 then takes place by means of Block individual lines. By doing so permanent flow through the cylinder chamber becomes an additional one Cooling achieved. Thanks to the liquid cooling of the The temperature never rises below the grate the critical hydraulic oil temperature of around 85 ° C. The provided cylinder-piston units 71 with up to 250 bar hydraulic pressure operated, only have a content of about a liter of hydraulic oil and bring up to 5 tons Thrust, which is more than sufficient. This may be the following Show a rough calculation: With a conventional one For example, about 100 tons of rubbish per grate Rostbahn and day implemented. The lead time is thereby about 20 minutes. This gives a momentary weight load of approx. 1.4 tons on the entire rust track. Does this exist at Example of 10 grate plates or grate steps, results in a very low load of 140 kg per grate plate. Even with multiple loads, this would be for the Drive no problems. With the one described here Any movable grate plate or -control level completely individually. Not just whether and in what direction it is moving can be determined, but also at what speed. This is because between zero and a maximum speed by means of the stepless shut-off valves also infinitely adjustable.

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 which is movable here in turn rests on the next stationary grate plate 15 which in turn is held on the steel tube 22 at its rear end by means of the claw 26. Depending on the design, a grate made of such overlapping grate plates can either be horizontal as shown, declined in the direction of conveyance, or also inclined towards the bottom. The stroke lengths and grate plate inclinations can be selected so 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. The fired material is not pushed from the grate plate front onto the next plate in such a simple stoking movement. Only when carrying out larger strokes is the firing material transported as desired.

So the essential material requirements for given the exercise of the present procedure. Before the procedure is presented and explained in detail, here is the basic problem of combustion are shown using two diagrams.

FIG. 6 shows the energy profile 89 of an ideal waste incineration, like they only do on a water-cooled grate can be approximated. The energy curve 89 is one here bell curve and gives the product of temperature x flow of the Cooling water. Below the grate 98 are the different ones Rust zones indicated 90-94, with the distribution 88 of the Primary air supply. At the very beginning of the grate, immediately after the feed 97, there is the drying zone 90. Here the kiln is first dried on the grate 98, what if possible without any primary air supply. With a conventional, non-water-cooled grate comes one should not, however, around the air supply, because it becomes needed to cool the grate. Inevitably, through this air, which is actually used as cooling air, is the fire fanned and the cooling air inevitably also acts as Primary air. So with these conventional grates necessarily at the beginning of rust and therefore much too early Air added. The air is also in the remaining rust area often supplied in the wrong amount and in the wrong place, because at all cannot be dosed specifically. In the described water-cooled The grate system, on the other hand, is the primary air supply functions and rust cooling fundamentally and totally different from each other Cut. It is therefore possible to place the grate 98 in the drying zone without operating 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 closes then the main burning zone, which is divided into two sections 92 and 93 is divided. Then comes the burnout zone 93, which extends to the end of the grate 98. Like in Diagram shown takes the amount of primary air supplied practically steadily over the first half of the grate length, reaches a maximum in the second main combustion zone 93 and then decreases sharply. Only then will there be air in the burnout zone fed when this is necessary, that is, when it is there anything to burn at all. Above the fire secondary air is supplied from the side in order to burn out the flue gas ensure. Then the flue gases get in the boiler 96 and the downstream devices for the Flue gas treatment.

1. Die Beschickung erfolgt nicht kontinuierlich. Das in Portionen auf den Rost fallende Brenngut bewirkt ein unregelmässig hohes Brennbett. Darüberhinaus wird bei jeder Beschickung viel Asche und Staub aufgewirbelt. Das stört das Feuer und beschlägt die Kesselwände.

2. Weil die Kühlung der nicht-wassergekühlten Roste von der zugeführten Primärluft übernommen wird, sind die Funktionen Kühlung und Primärluftzufuhr nicht getrennt. Die Dosierung der Primärluftzufuhr wird vom Kühlertordernis stark eingeschränkt und man arbeitet deshalb generell mit einem zu hohen Sauerstoff-Ueberschuss. Der Sauerstoff-Ueberschuss bewirkt einen unnötig hohen NO_x-Gehalt und weil zuviel Luft den Rost durchströmt, trägt diese zur Verwirbelung und zur Staubentwicklung oberhalb des Rostes bei, mit allen unliebsamen Folgeerscheinungen. Die Verbrennung ist nicht optimal und die Kesselwände werden beschlagen.

3. Weil die Funktionen der Schürung und des Transportes auf konventionellen Rosten nicht getrennt werden können, kann das Brennbett nicht ausgeglichen werden und entsprechend kann es nicht gelingen, ein geometrisches Feuer auch nur annähernd zu erreichen. Man hat unweigerlich immer von Brenngut unbedeckte Rostbereiche und andererseits solche, auf denen das Brennbett zu hoch ist.

4. Weil die Art und Anzahl der Steuerungs-Parameter bei konventionellen, nicht wassergekühlten Rosten sehr begrenzt ist, kann die Verbrennung nur in einem sehr bescheidenen Rahmen beeinflusst werden.

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 gratings is carried out by the primary air supplied, the cooling and primary air supply functions are not separated. The metering of the primary air supply is severely restricted by the cooler requirement and therefore one generally works with an excess of oxygen that is too high. The excess of oxygen causes an unnecessarily high NO _x content and because too much air flows through the grate, it contributes to the turbulence and dust development 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 stoking and transport cannot be separated on conventional grates, the combustion bed cannot be compensated and accordingly it is not possible to even reach a geometric fire even close. Inevitably, you always have rust areas that are not covered by firing material and, on the other hand, areas where 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 evaluating the combustion quality, that is to say the flue gases G and the system efficiency E as a function of the O ₂ content in the flue gas G. The CO value is considered as a superordinate measure of the combustion quality. Now you can see from this diagram that the CO limit value (CO _max ) is maintained over a relatively wide range of the O ₂ content in the flue gas. With a decreasing O ₂ proportion, the NO _x proportion also decreases and the efficiency E of the incineration plant increases with a simultaneously decreasing gas volume flow V. However, if the O ₂ proportion is further reduced to a certain extent, the CO increases -Very suddenly steep. The aim of the combustion control must therefore be to keep the O ₂ value so low that the NO _x content becomes minimal and at the same time the CO limit value is just maintained. Such an ideal working point is shown in the diagram. In addition to the flue gas values to be achieved, it also guarantees high system efficiency. Because of the lower O ₂ content 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 overarching goal of the present method is to achieve combustion that is as stoichiometric as possible. On the way to this, the O ₂ content 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 procedure for achieving these goals is as follows described and explained: characteristic of the process it is that the current fire data is returned via the Cooling energy are recorded and then this data for control and control of the fire can be used. Depending on the data situation is then separated as needed or not stoked and / or transported separately and / or the grate is loaded with new firing material, exactly according to the specifications of control and regulation. Stoking can be done locally a single or multiple grate plates are restricted and the poker stroke and the lifting speeds are variable, thus of course the stroke frequencies. Further allows this grate construction in cooperation with the Control and regulation, the primary air as required and targeted dosed according to discrete locations on each grate level Add quantity and time-dependent. Through this targeted Primary air supply is optimal with primary air supplied so that its calorific value is used in the best possible way and its combustion is as complete as possible. For this purpose, the temperature spectrum in the combustion chamber above the Combustion grate additionally using a variety of temperature measuring probes be determined. These probes can for example built into the surface of the grate plates be. On the other hand, the temperature spectrum can also be determined using of a pyrometer can be determined. Through the targeted Dosage of the primary air supply for each individual supply line succeeds in the current temperature spectrum in the combustion chamber approach the optimal spectrum. For individual Control of the primary air supply for each supply line can, for example, use solenoid valves in the supply lines be made by a central microprocessor can be controlled in which the optimal selected furnace temperature range can be saved. As a regulation parameter As mentioned, the dissipated cooling energy is based on flow and temperature used in the returns. By the constant measurement of the real spectrum and comparison with that ideal spectrum, a control loop can be formed, according to which the individual solenoid valves individually finely dosed something more or less open and primary air through let the individual supply lines flow. The primary air supply done through one or more powerful Compressors or fans. Such a fine and very complex set of rules can be built, which by means of an electronic evaluation of the combustion by individual Control of all coolant runs, all Drive elements for moving and loading the grate, as well optimally ensures all individual primary air supplies. This makes the energy content of the fired material even better use, the slag diarrhea is further minimized and above all, are the basics for further minimizing the unwanted flue gas components created.

The medium used for temperature control can be exchanged in a heat with the primary air to be supplied. For this a commercially available heat exchanger can be used works on the countercurrent principle. By means of one Heat exchanger it is possible to preheat the primary air, what an optimal combustion with certain combustibles is beneficial. Especially with organic waste components, for example with rotten or rotten Vegetables or fruits, is a preheat of the primary air very much desirable because it improves combustion. On the other hand is it is also possible to use the combustion grate to start a combustion process to warm up the grate as soon as possible to drive to the optimal operating temperature. For this the temperature control medium can already remove the heat from the exhaust air absorb the incineration, and then 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 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 amounts of air no longer flow locally uncontrolled through the grate and the firing material, but local oxygen is gently fed into the firing material in a targeted amount, i.e. at a low flow rate. As a result, no unnecessary flue gas volume is generated, the flue gas speed is considerably reduced and the amount of fly ash is also generated. The small portion of fly ash is also no longer whirled up into the kettle. All this allows the boiler and all downstream system components to be dimensioned much smaller and therefore more cost-effectively. A nitrogen wash in the course of the flue gas treatment could be completely omitted if pure oxygen was added. In practice, you will probably work with less dramatic reductions. In principle, oxygen, for example, 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 flow required to achieve the desired burnout. For example, if you have 50,000 m ^{3 of} air flow per hour in a conventional system, then of the approx. 10,000 m ^{3 of} oxygen it contains, approx. 5,000 m ^{3 of} oxygen are available for combustion and approx. 5,000 m ³ as a combustion reserve. If you want to reduce this air throughput by half with the same combustion, the following rough calculation results: In 25,000 m ^{3 of} ambient air you still have 5,000 m ^{3 of} oxygen, of which approx. 2,500 m ³ for combustion and approx 2,500 m ^{3 are available} as a combustion reserve. By adding another 5,000 m ^{3 of} oxygen gas, the required values for the desired burnout and the necessary combustion reserve can be achieved. The 5,000 m ^{3 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 design and in particular nitrogen washing and flue gas cleaning 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 can be a uniformly high burning bed achieve and maintain. The control of the grate plate movements can also be controlled with the temperature. Once the temperature of a grate plate or area of a grate plate indicates that the burning bed height there is too low or no material on it Rust plate location. By automatically initiated combustion can immediately compensate for the burning bed become. The control measures mentioned here are advantageous controlled by a microprocessor, using as control variables including the temperatures of the individual coolant returns will be charged. These show quickly a change in the fire on the grate area in question on.

In Figure 8 is the basic block diagram of a controller and regulation for the method according to the invention shown. This control and regulation consists of the following Subsystems, which are each listed in a column: Whole on the left is the sensor system, that is, all Recordable data are listed based on 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 incinerator. The next column to the right names the facilities for the realization of superordinate links and the The column on the far right contains a list of the individual Actuators.

The individual system components are described from top to bottom: For sensors, this starts with those for measuring the amount of steam QD, then those for measuring the temperatures T ₁ ... T _{n of} the cooling water at the individual measuring points i. The flow rate Q ₁ ... Q _{m is also} measured in each return i. The temperature TF in the combustion chamber is measured using a pyrometer, for example. Optionally, the burning bed height H ₁ ... H _k can be measured at different points i. An ultrasound measurement from above onto the grate surface can be used for this purpose. With O ₂ is meant the oxygen content in the flue gas, which is measured with special measuring probes, or instead of O ₂ the. In addition, the inverse value of carbon dioxide CO ₂ in the flue gas was measured. Finally, one also measures the carbon monoxide content CO in the flue gas, 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 setpoints, which are listed in the second column. On the one hand, this is the target steam quantity, which arises from the design of the system itself, but in practice, based on experience as the maximum for each firing material, results as the theoretically optimal specification SDR (= setpoint generator steam quantity). Then it is the optimal values for the cooling water temperatures T ₁ ... T _{n of} the individual returns i, those for the optimal flow rates Q ₁ ... Q _{m of} the individual returns i, as well as the optimal combustion bed heights H ₁ ... H _k der individual grate plates i. These values result in certain setpoints for a profile SPR (= setpoint generator 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 steam regulator DR. This compares the effective steam quantity recorded with the target steam quantity. The temperatures T _i , flow rates Q _i and possibly the combustion chamber temperature TF and the combustion bed heights H _i are included in the profile controller PR. The measured values for O ₂ and CO ₂ 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 O ₂ or CO ₂ value in the flue gas and the CO value in the flue gas are included in the minimization calculator SBR for the ratio between O ₂ and CO ₂ . The calculated value then also influences the loading controller. The output signals of these various regulators just presented are linked and processed in the control devices listed in the fourth column. The block diagram provides the following higher-level link options, which are listed in this fourth column. Starting from the top, this is once the air distributor LV, which is fed by the output signal of the steam controller DR and the profile controller 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 is managed by the cooling water distributor WV by the directional valves WWS for the different returns of the cooling water system, the freshly fed Cooling water dosed using the WDS dosing unit is fed, and finally the heating system for the cooling water WHS is provided, depending on whether and how strong that Cooling water is tempered.

The coordination computer BFSK provides the drive elements for the grate movements and for loading the grate. These include the conveyor drives for determining the Hubes FRH of the individual cylinder-piston units of the movable Grate plates and the conveyor drives for the determination the lifting speeds FRG of the individual cylinder-piston units the movable grate plates. In the same way also the loading via the conveyor drives for the FBH hub and the lifting speed FBG of the loading device is set. The loading can be carried out continuously by the solids in the feed chute initially from two to different Retractable hydraulic locking grids portioned and retained so that on the Only one such portion at a time Solids lies. The lock window to be passed to Combustion chamber is then from this portion of solids always tightly closed and through this window is a continuous promotion on the combustion grate possible. This continuous promotion is possible by the carrier surface of the loading device from several longitudinal webs formed by alternating, slow strokes, which, seen from the side, describe a rhomboid, the solids lying thereon uniformly through the window convey onto the combustion grate.

1. Die Dampfregelung, mittels der Luftverteilung

2. Die O₂- oder die dazu inverse CO₂-Regelung, und zwar als

2.1. Beschickungssteuerung und/oder

2.2. Fördersteuerung und/oder

2.3. Schürsteuerung

3. Die Gasausbrandregelung mittels der CO/O₂-Minimierung

4. Die Steuerung der Verbrennungsposition, und zwar als

4.1. Steuerung der Primärluft-Verteilung und/oder

4.2. Steuerung der Kühlwasser-Energie-Umverteilung

5. Die Müllbett-Profilsteuerung

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 O ₂ - or the inverse CO _{2 control} , namely 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 / O 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 listed one after the other explains:

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

The steam control is carried out via the sensor QD for the amount of steam, the setpoint generator SDR, the steam controller DR and a Air distributor LV realized via the air system LS. For the The controller is the controlled system of the entire grate, the controlled variable is the steam output or one related to the steam output Size. The guide variable is also the steam output or a size associated with it. As a manipulated variable acts the primary air volume with constant distribution and as Actuators the individual actuators of the primary air system, which is the supply of primary air for each one Determine the primary air zone under the grate plates. In general The following applies: The smaller the measured steam output in comparison to the setpoint, the more primary air must be supplied.

2. The O ₂ - or the inverse CO _{2 control}

Another essential control system includes the O ₂ / CO _{2 control} . These two values are inverse to each other. In many cases, the O ₂ content in the flue gas is measured. The O ₂ / CO _{2 control} is carried out via a sensor for the O ₂ and / or CO ₂ value, a setpoint generator SBR, a loading controller BR and a conveyor control FS, a stoking controller SS and a coordinator BFSK for the grate conveyor drives FRH and FRG as well as for the feed drives FBH and FBG.

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 O ₂ and / or CO ₂ content and the correcting variable is the length of the drawer and the thrust speed of the individual moving loading elements for the continuous loading of the grate. The actuators contain the drive systems for these strokes.

2.2. Funding control

The control section of the conveyor control includes all movable grate plates. The O ₂ and / or CO ₂ 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 SS stoke control, the control section in turn contains all movable grate plates. The O ₂ and / or CO ₂ content serves as the 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 CO ₂ content begins to decrease or the inverse O 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 stoking control SS, conveyor control FS and / or the feed control BR movements to be effected separately and / or superimposed, to the actuators simultaneously or in succession the actuators to switch.

3. The gas burnout control by means of CO / O ₂ 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 to ensure the flue gas burnout in conventional systems. It is accepted that the NO _x value is high in this operating mode. The ratio of CO to NO _x is opposite and only optimal in a narrow O ₂ band. The CO / O ₂ minimization computer automatically probes for the lowest possible O ₂ content, at which an almost complete gas burnout is still guaranteed. It would have been possible to push the NO _x down, but with the previous control and air distribution options it was not possible to ensure at the same time that the CO was still maintained with a low O ₂ content. However, the method according to the invention now makes it possible to reduce the O ₂ content in the flue gas and to bring the combustion closer to an optimal working point thanks to the fine rules. This operating point is characterized by a lower O ₂ value with a simultaneous significant reduction in the NO _x 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 O 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 O ₂ content. The combustion chamber temperature, which is simultaneously monitored via the temperature sensor TF, limits a further reduction in the O ₂ content at a maximum value. For the gas burnout control, the controlled system is the loading and portioning device, and the controlled variable is the O ₂ and / or the CO ₂ content. The ratio between CO and O ₂ serves as a benchmark. The thrust speed and / or the stroke length of the actuators, namely the loading device and / or the movable grate plates, serves as the manipulated variable.

4. The control of the combustion position

Combustion positioning is another variable compared to the process operated with conventional systems. This combustion positioning is carried out via the temperature sensors T ₁ ... T _{n of} the cooling water temperatures of the grate, via the flow rate sensors Q ₁ ... Q _{m 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, cooling water heating on the one hand and / or via the air distributor LV, the air system LS and an air heating LHS on the other hand realized as primary air distribution control and / or cooling water energy redistribution control.

4.1. Control of primary air distribution

The control sections are for the primary air distribution control the primary air zones, but still underneath through a variety of supply air nozzles in local areas on the Grate plates can be divided. The tax amount is the Primary air distribution, that is, where and at what time how much Air enters. The leader size is by the ideal Given the temperature profile of the cooling water. As manipulated variables the air volumes to the individual primary air zones serve this purpose or to the individual supply air nozzles. The actuators to be operated are the drives for the primary air supply that come from Fans or compressors exist, and / or air heating. For example, if the cooling water temperature in the Burnout zone of the grate not opposite the main fire zone drops, primary air is also supplied there, what else is omitted.

4.2. Control of cooling water energy redistribution

The cooling water energy redistribution control has as a control route the grate cooling system and as a control variable the cooling water energy distribution. The optimal is used as a guide variable Cooling water energy profile. The manipulated variable is the cooling water path and / or the amount of cooling water and / or the cooling water energy. The serve as the actuators Drives of the cooling water path system and / or the cooling water metering system and / or a cooling water heater.

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 using the temperature sensors T ₁ ... T _{n of} the cooling water temperature of the grate, the temperature sensor TF for the combustion chamber temperature, the waste or combustion bed height sensors H ₁ ... H _k , 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. The control section is the grate conveyor and loading system. The control variable 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 one control based on the return temperatures of the cooling medium, which then become manipulated variables for the movements of the grate plates. When the temperature drops locally, the concerned grate plate started and if the temperature does not rise again, additional firing material is added to this Transported to the site 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 rule network with increasing numbers Parameter becomes very complex. But the goal is always one to achieve stoichiometric combustion as possible. Bigger Significance is that with the present procedure immediately Practical experience can be gained, which in a short time lead to the flue gas volumes drastically reduced and therefore the downstream units designed for flue gas treatment smaller and cheaper can be. The boiler efficiency will continue increase due to the process-optimized combustion, boiler erosion as a result of better burnout reduced and the flue gas values will generally turn up level in with lower values. The disposal of filter ash, which is filtered out of the flue gas is increasingly expensive. That’s why it’s important to reduce the amount of filter ash, what means better combustion with the present Procedure is achieved.

Claims (10)

1. A process for burning solids on a sliding fire grate system made of a plurality of grate stages through which a cooling liquid flows separately and half of which are individually movable, the grate stages having a plurality of injection nozzles for the supply of the fire with primary air, characterized in that the following functions are, not necessarily depending on each other, are controlled and operated:

   a) cooling of the single grate stages,

   b) local and chronological supply of primary air, wherein if required combustion-enhancing materials are directedly metered into the same or wherein the same consists exclusivley of oxygen,

   c) the local and chronological stocking movements of the grate,

   d) the local and chronological conveying movements of the grate,

   e) the chronological feed movements for feeding the grate,

   wherein at least the cooling liquid temperatures of the individual grate stages are used as control variables for the control.
2. A process in accordance with claim 1, characterized in that the cooling liquid temperatures of the individual grate stages are used as control variables for controlling, on the one hand, the stoking and conveying movements of the individually movable grate stages, which are chronologically and locally independent of each other, as well as the feed movements and, on the other hand, as control variables for the primary air which is chronologically and locally metered and supplied separately for each grate stage.
3. A process in accordance with one of the preceding claims, characterized in that by means of variations in the stoking, conveying and feed movements the cooling water temperature distribution is approximated to a theoretical ideal, then, while maintaining this distribution as faithfully as possible, the primary air supply is reduced while maintaining the prescribed CO threshold value and reduction of the NO_x value until the CO value begins to rise, by means of which an operating point below the CO threshold value is defined, which is afterwards maintained by means of varying one or more of the functions a) to e) defined in claim 1.
4. A process in accordance with one of the preceding claims, characterized in that, in case of a falling cooling water temperature of one grate stage, stoking is immediately started there and, if the cooling water temperature does not increase thereafter, operation proceeds with a brief increase of the local primary air supply and, if the cooling water temperature still does not increase thereafter, a conveying movement is started in order to convey material to be burned to the respective grate stage, and that when a reference value of the cooling water temperature has been reached, the conveying movement is stopped and the primary air supply is returned to the initial value.
5. A process in accordance with one of the preceding claims, characterized by

   a) the detection of the data of the returned cooling energy and use of these data for controlling and regulating combustion;

   b) if required, feeding of the grate chronologically separated from the stoking and conveying of the material to be burned on the grate in accordance with the setting of the control and regulation;

   c) if required, chronologically and locally separate stoking and conveying of the material to be burned on the grate in accordance with the setting of the control and regulation;

   d) if required, directed supply of primary air to discrete locations on each grate stage, each in metered amounts and lengths of time;

   e) if required, individual temperature adjustment of each grate plate of the fire grate by means of the medium flowing through it.
6. A process in accordance with one of the preceding claims, characterized in that

   a) the fire data are determined by means of temperature sensors (T₁ ... T_n), flow-through measuring devices (Q₁ ... Q_m) and measuring devices (H₁ ... H_k) for determining the local garbage bed height, as well as by a combustion chamber thermometer (TF), and are subsequently computed in a temperature, energy and garbage bed profile computer (PR);

   b) feeding is controlled by a coordination computer (BFSK), which receives its data from the profile computer (PR) and a feed regulator (BR), which take into consideration the ratio of O₂ to CO in the flue gas, by varying the stroke and the stroke speed of the feed installation;

   c) the chronologically and locally separated stoking and/or conveying of the material to be burned on the grate is controlled by a variation of the stroke and the stroke speed of the grate plate drives by a coordination computer (BFSK), which receives its data from the profile computer (PR), and from a stoking (SS) and conveying control (FS) which take into consideration the ratio of O₂ to CO in the flue gas;

   d) the directed supply of primary air over a plurality of zones, each with separate air supply nozzles, takes place in the grate plates, wherein the respectively supplied amount of air is controlled by an air distributor (LV), which takes into consideration the data of a steam regulator (DR), which makes comparison between the reference value of the amount of steam and the effectively generated value;

   e) the separate grate plates are individually temperature- adjusted in that a cooling water distributor (WV) controls the directional control valves (WWS) of the individual liquid circuits of the individual grate plates, so that freshly supplied cooling liquid is metered in or that cooling liquid is heated, if required, wherein the regulated quantities are set by the temperature, energy and garbage bed profile computer PR.
7. A process in accordance with one of the preceding claims, characterized in that for the stoking, conveying and feed movements the respective stroke as well as the stroke speeds and stroke frequencies are varied respectively independently of each other and chronologically and locally separated.
8. A process in accordance with one of the preceding claims, characterized in that the operation in the drying zone of the grate is run without any supply of primary air and therefore cooling of the grate is exclusively provided by the medium flowing through it.
9. A process in accordance with one of the preceding claims, characterized in that in the final combustion zone of the grate the operation generally is run without primary air supply and that primary air is only supplied if in an exceptional case the cooling water temperature from the final combustion zone does not fall below that in the main combustion zone of the grate, wherein the supply of primary air is immediately stopped as soon as the cooling water temperature from the final combustion zone drops.
10. A process in accordance with one of the preceding claims, characterized in that pure oxygen is admixed with the primary air, or that the primary air exclusively consists of oxygen.

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