DE19817121A1 - Method and device for feeding the wind for the combustion of lumpy fuel - Google Patents

Abstract

The grid is formed of radial, hollow support arms (5) evenly spaced out over the grid and possessing blowing-holes pointed towards the fuel-supporting surface of the grid. An air source is pneumatically connected with the support arms, by means of a movable coupling arrangement (7,8). A post-combustion chamber (15) removes the flame gases, which are mixed with combustion air The solid fuel rests on a grid that has one surface area covered and one not covered by the fuel. Draught is introduced from underneath to the fuel in the combustion area. The flame gases emerging from the combustion zone are mixed with a top draught.

Description

To burn lumpy fuel on a rotie conical or cone-like combustion grate, it is known the combustion air as a downwind and upwind feed.

For feeding the underwind, it is known below the Rotating combustion grate to arrange fixed blowing channels openings that face the combustion grate, from which the underwind upwards towards the bottom of the ver blown rust is blown. The combustion grate has an opening between the grate bars forming it, through which the sub however, only a small part of the wind can flow, because the on the Combustion grate fuel partially covers these openings blocked. The greater part of the underwind is therefore used deflected laterally and downwards. The one on the cremation As a result, fuel lying in rust does not receive enough ver combustion air.

A significant disadvantage is also that in the in the pre called way swept underwind entrained gas and it contains dusty fuel that burns. The the resulting flame jets overheat and corrode the metallic material of the combustion grate, in particular its consisting of radial support arms and circular rings Support structure. As the heating value of the fuel increases such overheating and corrosion are more serious.  

For post-combustion of the ascending from the combustion grate Flame gases are known to supply this upper air. At known method, this was done in such a way that the flame gas flow sucked in the upper air by itself.

A disadvantage with such grate firing was still incomplete constant burnout of the fuel, which corresponds to one a correspondingly high proportion of CO in the combustion exhaust gases. Finally, they also contained a significant portion entrained solid particles, especially fly ash, the separation by means of filter systems and the like is required made. Grate firing of the type described, especially with Cones, therefore, have not become established in practice can.

The invention has for its object a method of im The preamble of claim 1 to specify the outlined type sufficient for the complete burnout of the fuel Air supply ensures overheating of the combustion prevents rust and without dust filtering the combustion gases gets along. In addition, one is said to carry out the procedure suitable device can be specified.

This task is carried out with regard to the procedure by the Claim 1, with respect to the device by the in claim 2 specified features solved. Advantageous embodiments of the Invention are the subject of the dependent claims.

The invention achieves the success it seeks on the one hand apparatus in that the support arms of the combustion grate are hollow executed and flowed through by the downwind, which makes them  be cooled. The downwind is forced on the top the combustion grate, d. H. directly on the fuel, so that the possibility of a distraction of the underwind under the ver burn rust is greatly reduced.

On the other hand, the aim of the invention is to achieve this target of the afterburning of the flame gases by the on the Combustion rust running out of burning fuel, special on attention given. According to the invention, the flame gases the upper air in the form of a high-speed flow leads, which surrounds the flame gases helically and itself propagates towards the combustion grate, the Increased diameter of this vortex. The waiter wind flow thus describes the surface of a truncated cone, whose larger diameter faces the combustion grate.

The headwind is due to the smaller diameter of this truncated cone blown in. This results in a negative pressure in the center, the sucks in the flame gases. Between the center of the towards this vacuum point flowing flame gas flow and this A zone is formed around the toroidal headwind current intense turbulence from where the flame gases with the headwind be mixed thoroughly. This zone of turbulence is outside of surrounded by a cold air flow of fresh head winds.

The head wind is at a speed of 40 to 100 m / s, preferably 60 to 80 m / s, which is thus so high, that the thereby acting on the particles in the flame gases Centrifugal force the particles into the cold air flow mentioned ejected, where they are cooled so far that they dry fail. This way not only the afterburn will be  exiting exhaust gas flow without the use of filters from Par Free items, but is also a slagging of the burns system avoided.

In fact, there is such a large amount of hot dedusting Flame gases that the exiting from the afterburner - z. B. when blowing out into the open - clear and visual to the eye appear dust-free, which at the current state of hot de-icing exercise technology has so far been considered impossible.

Experiments with waste wood in the form of wood chips as firing have shown that the above results with a Air flow can be achieved in which about 30 to 40% of the complete combustion of the fuel required air quantity can be fed as a downwind while the necessary Remaining portion of 70 to 60% of the air volume supplied as a headwind becomes. It can be seen from this that the afterburning also under an essential one from the point of view of fuel efficiency Importance.

In terms of apparatus, the air duct described is achieved in afterburning ner with the help of a truncated cone-shaped afterburner into which the upper wind at the smaller end facing away from the combustion grate The same diameter is blown in via an introducer which is the upper wind tangential to the wall of the afterburner leads into this, where it is inclined at an angle to the Axis of the afterburning chamber spreads out in this. With the Einlei upwind in the afterburning chamber can also be from a flow direction obliquely from the outset by means of guide devices to the axis of the afterburner.  

Advantageously, only those arms of the Combustion grate fed under air on which fuel lies, and preferably according to the thickness of the fuel layer. The other brackets not covered by fuel get no air. You can also give them a little air supply quantity to prevent the penetration of corrosive fuel gases and to prevent fuel or ash particles. A minor one Flow through the support arms not covered by fuel ver also improves their cooling.

According to a development of the invention, each hollow support arm at least one other opening facing away from the fuel th side so that it has fallen through the combustion grate Ash or fine fuel in the combustion chamber Get air to burn out completely. Through this opening can also penetrate into the pipes fuel or Ash particles are blown out.

The combustion grate is advantageously covered by a jacket hollow (burning) cone, which rotates around a oblique axis executes. The afterburner is in this It is most conveniently arranged coaxially to the axis of rotation of the cone net. As a result, the flame emerging from the firing cone gases are particularly well directed to the center of the afterburner, where a reduced compared to the pressure prevailing in the firing cone Pressure prevails, which is the transition from the firing cone favoring and entering flame gases in the afterburning uncontrolled escape of these flame gases to the outside or in a the incinerator from the fuel cone and afterburner enclosing housing prevented.  

The coaxial arrangement of the afterburner chamber just above the burner cone also has the consequence that the heat radiation in the Afterburning chamber burning flame gases on the in the burning cone fuel acts advantageously and takes place there supports the charring and combustion process.

The lower diameter should suitably be the after combustion chamber slightly larger than the diameter of the upper edge of the fuel cone. This will make the near the night Dust blown down the combustion chamber wall from the afterburning chamber past the firing cone into the ash room below blown.

The invention is described below with reference to FIGS Illustrated embodiment illustrated in detail.

It shows:

Figure 1 is a partially sectioned side view of a kegelför shaped burner with an afterburner attached.

Fig. 2 shows a section through the conical part of the conical combustion grate of the burner of Fig. 1, and

Fig. 3 shows an enlarged section through the hollow supporting lug of the combustion grate of FIG. 2.

Fig. 1 shows a complete incinerator, consisting of a rotating cone about an inclined axis O fuel cone K and an afterburner N coaxially adjoining the outlet end of the fuel cone K, which are enclosed by a housing G.

The fuel cone K has a frustoconical section 1 , an adjoining it towards the open end cylindri's section 2 and an adjoining, narrowing in diameter section 3 . The combustion grate of this fuel cone K consists of grate bars 4 made of heat-resistant cast and of hollow, radial support arms 5 and ring carriers (not shown) which connect the support arms 5 to one another. The firing cone K is held at its end of smaller diameter by a plurality of hollow axially parallel legs 6 , which are connected to a Luftsam melkasten 7 , which has radial partition walls, each of which closes 5 an air collection chamber for each support arm. The air collection box 7 is firmly connected to a race 8 which is supported by a plurality of stationary rollers (not shown). The race 8 has one opening per support arm 5 .

Give the side facing the firing cone K of the race 8 is pressed by springs a slide ring 9 , which carries a plurality of connecting pieces which are connected via hose lines 10 with a common air supply chamber 11 . The number of connecting pieces is preferably as large as the number of hollow support arms 5 .

A shaft 12 is rigidly connected to the race 8 , which extends on the side of the race 8 facing away from the firing cone K and is supported in its free end region by means of a spherical roller bearing 13 . A drive motor 14 can also be seen, which sets the race 8 and thus the fuel cone K in rotation on the axis O via a spur toothing.

At a distance above the end of the larger diameter of the firing cone K is the frustoconical afterburner N, which is arranged coaxially to the firing cone K. The afterburner N has a truncated cone-shaped afterburner 15 , which widens in the direction of the firing cone K and whose lower edge 16 has a larger diameter than the free edge of the narrowing section 3 of the firing cone K. At the end of the smaller diameter of the afterburner 15 is followed by an air collection space 17 , in which radially adjustable guide vanes 18 are arranged. By adjusting the guide vanes 18 , the effective opening cross section of the air collecting space 17 can be changed. The air collection space 17 has an opening (not shown) through which upper air can be blown tangentially into the air collection space 17 . To the outside, that is to say on the side facing away from the afterburning chamber 15, a narrowed collar 19 adjoins the air collecting space 17 and leaves an outlet cross section 20 free.

The frusto-conical wall 21 of the afterburning chamber 15 is surrounded by a jacket 22 which, with the wall 21, delimits a chamber through which coolant flows and can be part of the housing G. A feed shaft 23 extends through this jacket 22 and the wall 21 and lies vertically above the opening of the firing cone K and serves to feed fuel into the firing cone K. Suitable closing flaps (not shown) are arranged in the shaft 23 .

It can also be seen in Fig. 1 in the housing G below the Brennke gel K a screw conveyor arrangement 24 which serves to transport ash accumulating in the housing G into an ash outlet 25 .

It should be noted that the axis of the afterburning chamber 15 can be inclined against the axis of the firing cone K, in particular upwards, but the edge 16 of the afterburning chamber 15 should remain par allel to the opposite edge of the firing cone K in order to prevent the uncontrolled escape of flame gases avoid or at least reduce.

Fig. 2 shows a section through the conical section of the firing cone K. The support arms 5 can be seen , which are hollow and are arranged at uniform angular intervals. The reference numerals of the individual support arms 5 are provided with suffixes a to 1 for later explanation of the operational sequence. Between the support arms 5 are the grate bars 4 made of warm, firm greeting, which are essentially T-shaped in cross-section, the wide leg of the T forming the bearing surface for the fuel B, while the rib projecting therefrom not only the stiffening, but also dissipates heat. The grate bars 4 are at a mutual distance, which is chosen so that ash, but not too large pieces of fuel can fall through the space formed by the distance. The distance is expediently on the order of 4 mm.

In Fig. 3 one of the support arms 5 is shown enlarged in cross section. It can be seen that from the hollow interior of the same, openings 26 which are inclined at the top lead into the combustion chamber enclosed by the firing cone K. Another opening 27 may be formed on the opposite side. Their purpose will be explained later.

In operation, the firing cone K rotates around its axis O. This orbital movement is shown in Fig. 2 with the arrow. The fuel B located in the fuel cone K is thereby entrained by the Brennke gel, so that there is an inclined slope, as indicated in FIG. 2. This embankment becomes increasingly steep as the fuel cone K rotates and then collapses, with the result that the fuel B is constantly circulated in the fuel cone.

The fuel B is ignited at the beginning of the combustion process by an ignition flame which is supplied by a lance (not shown). If the fuel B burns sufficiently, there is no need to support the combustion by the pilot flame. With constant circulation due to the movement of the fuel cone, the fuel B burns in the fuel cone K. Fuel can be added through the shaft 23 at the appropriate time. The metering of the fuel per Zeitein unit is expediently carried out by monitoring the O ₂ content contained in the combustion exhaust gases.

The flame gases emanating from the firing cone K are sucked into the after combustion chamber 15 by the underpressure caused by the upstream flow, whereby they are mixed with the top wind whirling there intensely. Flammable components that are still flammable are completely burned out. Ash particles are thrown in the direction of the wall 21 and fall down at the edge 16 into the housing G.

For operation, it is useful if only the support arms 5 located in the combustion zone are supplied with a downwind.

These are shown in FIG. 2, the support arms 5 k, 5 l and 5 a to 5 d. This can be controlled in such a way that only those connecting pieces are supplied with sub-air, which are arranged at the positions which currently occupy the aforementioned support arms. With further rotation of the fuel cone in FIG. 2 counterclockwise, the support arm 5 j then enters the combustion zone, while the support arm 5 d leaves it. Then later the support arm 5 i enters the combustion zone while the support arm 5 c leaves it, etc. The other support arms not in the combustion zone, that is, in the situation shown in FIG. 2, the support arms 5 d to 5 h not or only weakly supplied with air, for example by using a suitable throttle This weak supply serves on the one hand a certain cooling, but mainly to prevent that particles penetrate into them through the openings 26 .

The design and arrangement of the firing cone K shows that the layer thickness of the fuel over the combustion grate is different. It is, for example, at the transition between the conical section 1 and the cylindrical section 2 at its largest and near the center of the conical section 1 , ie at its smallest diameter at the lowest. In order to take this into account during the combustion process, the openings 26 , which are arranged along each support arm 5 , can be designed in diameter and / or longitudinal distribution in such a way that the sum of the opening cross sections per unit length of each support arm is approximately proportional to the layer thickness of the respective unit length Support arm lying amount of fuel is. The different degrees of coverage of the support arms which result in the different height positions of the support arms during the rotation of the firing cone can be taken into account by correspondingly throttling the underwind supply at the somewhat higher connection piece.

The openings 26 and 27 in the support arms 5 are preferably dimensioned such that at full load the speed of the underwind emerging from them is between 20 and 60 m / s, preferably 40 m / s.

The latter openings 27 in the support arms 5 serve, on the one hand, to blow particles which have penetrated into the support arms 5 , on the other hand, to supply combustion air to the particles which have fallen into the ash receiving space in the housing G and which may not yet be completely burned out. Therefore, the openings 27 are formed on the outside of the firing cone K in the support arms 5 , and expediently at the point which is the deepest at the lowest surface line of the firing cone. In the example shown, this would be in the area of the transition between the conical section 1 and the cylindrical section 2 of the firing cone K.

Claims (9)

1. A method of supplying the wind for the combustion of particulate fuel, which lies on a combustion grate, which has a surface area located in a combustion zone, covered by the fuel and a surface area not covered by the fuel, and carries out an orbital movement which makes a rolling movement of the Causes fuel over the entire surface of the combustion grate, the fuel in the combustion zone wind is supplied from below (underwind) and the flame gases emanating from the combustion zone are mixed with an upper wind at a distance from the combustion zone, characterized in that
a first portion of the amount of combustion air required for the complete combustion of the fuel is blown under the fuel above the combustion grate under the fuel, and
a second portion of the amount of combustion air required for the complete burnout of the fuel is fed as a headwind at a speed of 40 to 100 m / s in a rotating flow that envelops the flame gases emanating from the combustion zone and in a helical path that runs expanded in diameter, directed towards the combustion zone. 2. The method according to claim 1, characterized in that the Underwind at a speed of 20 to 60 m / s the combustion grate fuel is supplied.   3. The method according to claim 1 or 2, characterized in that when using wood waste, especially wood chips, as fuel 30 to 40% of that for complete combustion the amount of air required as underwind and the The remaining portion of the required air volume is fed as a headwind become. 4. Apparatus for carrying out the method according to claim 1, comprising a movable combustion grate and a combustion zone which detects a partial area of the combustion grate, and a drive device which sets the combustion grate in a circular movement which successively passes through all partial areas of the combustion grate leads the combustion zone, characterized in that
the combustion grate is partially formed by radially extending support arms ( 5 ) which are evenly distributed and hollow over the combustion grate and each have a plurality of blowing openings ( 26 ) directed towards the surface of the combustion grate carrying the fuel,
an air source is provided which is pneumatically connected via a movable coupling device ( 7 , 8 ) at least to the support arms ( 5 ) for feeding underwind, which are respectively located in the combustion zone, and
Arranged above the combustion grate is an afterburning chamber ( 15 ) which is connected to an air source and which receives the flame gases rising from the combustion grate and mixes and burns out with combustion air freshly supplied as an upper wind. 5. The device according to claim 4, characterized in that the tightly located in the combustion zone support arms ( 5 ) are pneumatically connected to the air source via a throttling device. 6. Device according to one of claims 4 and 5, characterized in that the blowing openings directed against the fuel ( 26 ) on the support arms ( 5 ) are distributed and dimensioned such that the sum of the opening cross sections per unit length of each support arm ( 5 ) approximately is proportional to the nominal layer thickness of the amount of fuel lying on the relevant length section of the support arm. 7. Device according to one of claims 4 to 6, in which the combustion grate is the jacket of a cone (K) with the horizontal against the Hori obliquely extending axis of rotation (O) and the support arms ( 5 ) extend radially, characterized in that at least one of the fuel support surface of the combustion grate directed blow opening ( 27 ) is formed at that point of each support arm ( 5 ) which is lowest when the jacket line in which the support arm ( 5 ) lies, the lowest position during the rotation of the cone ( K) occupies. 8. The device according to claim 7, characterized in that the opening of the cone (K) at the base of a cylindrical or conically narrowing in the throughput direction, rotationally symmetrical post-combustion chamber ( 15 ) is coaxially opposed, the inlet opening ( 16 ) facing the cone (K) has a larger diameter than the opening of the cone (K), and which in the region of the outlet end facing away from the cone (K) has a device ( 17 , 18 ) for the tangential feeding of headwind, and in the direction of the outlet end to this device ( 17 , 18 ) connects a collar ( 19 ) which encloses an opening of smaller diameter than the narrowest cross-section of the afterburner chamber (N). 9. The device according to claim 8, characterized in that the device ( 17 , 18 ) for tangential feeding of the headwind has a variable opening cross-section.