EP1855055A2 - Device for combusting and gasifying ball or bundle-shaped and pasty or solid fuels - Google Patents

Abstract

The device has a feed channel (0) for fuel (1). Outlets (26) are provided for oxygenated gas that is directed towards the fuel. The outlets are partly pressurized with recirculated flue gas. A support device (51) is arranged below a reaction zone (20) for the entry of the fuel falling down from the reaction zone. The outlets of the support device are assigned an oxidation gas, partly consisting of recirculated flue gas.

Description

The invention relates to a device for burning and gasifying bale or bundle-shaped and pasty or puncture resistant fuels, in particular biomass, arranged with at least one opening into a primary reaction zone feed channel for the fuel and towards the free end of the feed channel, directed against the fuel Outlets for oxygen-containing gas.

The use of straw and hull-like energy plants in bale or bundle form results from the need for transportation and storage.

Many power plants tear and crush these bales before burning, which causes high plant costs, high maintenance and repair costs and high (electrical) energy costs. This technology is used occasionally for smaller heating plants and also - to a limited extent - in larger power plants, also as co-incineration with coal as main fuel.

In the whole-bale combustion plants of straw, the so-called cigar firing is known: when the bale enters the combustion chamber, a small amount of air is supplied to the circumference, ie laterally to the imaginary bale end face; By burning the packing cords, the bale disintegrates into parts of different sizes, which are burned on a conventional grate (usually: inclined grate, vibrated and water-cooled). This rust is space consuming and expensive, as it is to be interpreted to the full firing capacity and the maximum part size.

In the document PCT / DE85 / 00220 a whole bale burning plant based on straw is proposed, in which the insertion channel is heated, so that there already a drying and pre-gasification of the bale should take place. Because of the low heat conduction of the straw, such an arrangement is only for very small Bale dimensions conceivable - apart from the risk of burnback in the insertion channel.

In the document DD 282 063 A5 a straw-based whole-bale-burning plant is proposed, in which the bale is impaled before entry into the combustion chamber by a conical hollow body through which combustion air and recycled hot gas pass through holes in the bale. Presumably facilities of this type would significantly increase the feed force of the plunger in the feed channel and favor the fire / burn-back in the feed channel; a uniform gasification within the bale is rather difficult to achieve.

In the EP 1 070 918 B1 a device of the initially characterized type is described in which a focal spot on the fuel ball is generated by air jets. Although this device has significant advantages, it could not fully satisfy.

Biomass, and particularly halm-type fuels, have a low ash melting point - far below the combustion chamber temperature of conventional coal-fired boilers - and it must now be attempted to drive the combustion temperature at any point just below the ash softening. In all of the procedures mentioned, the approach of controlling the local combustion temperature in order to control the problem of slagging is lacking.

The subject invention has set itself the task of avoiding the above-mentioned disadvantages. This is achieved by the features characterized in the claims.

• Fig. 1 einen schematischen Schnitt durch eine erfindungsgemäße Vorrichtung;
• Fig. 2 einen Schnitt nach der Linie A-A in Fig. 1;
• Fig. 3 eine Variante der Brennstoffförderung;
• Fig. 4 einen Drallapparat;
• die Fig. 5 und 6 Beispiele der Wandausbildung;
• Fig. 7 und 7a eine mögliche Ausbildung der Rückhaltevorrichtung;
• Fig. 8 eine Variante einer Vorrichtung nach der Erfindung;
• Fig. 9 das Verfahrensfließbild;
• Fig. 10, 11 und 12 Gestaltungsmöglichkeiten der Koks-Nachverbrennungszone;
• Fig. 13 eine Variante.

The subject invention is described and illustrated by way of example in the following figures, without being limited to these examples. Showing:

• 1 shows a schematic section through a device according to the invention;
• Fig. 2 is a section along the line AA in Fig. 1;
• Fig. 3 shows a variant of the fuel delivery;
• 4 shows a twisting apparatus;
• Figures 5 and 6 show examples of wall formation;
• Fig. 7 and 7a a possible embodiment of the retaining device;
• Fig. 8 shows a variant of a device according to the invention;
• 9 shows the process flow diagram;
• 10, 11 and 12 design possibilities of the coke post-combustion zone;
• Fig. 13 shows a variant.

Fig. 1 shows the basic principle. The introduced via the feed opening 2 in the feed channel 3 bale or bundle-shaped fuel 1, z. B. straw, is introduced via a feed channel 0 in the primary reaction zone 20, where it emits the vaporized fuel moisture by contact with the at least partially made of oxidizing gases directed free-jet 27 and decomposes into coke. In the process, volatile, still flammable gases escape. The coke and the incompletely degassed solid fuel particles are finally burned in the coke post-combustion zone 40, leaving ash behind. The volatile gases and the flue gases from the post-combustion zone 40 are post-combusted in the gas post-combustion zone 60 to flue gas.

The figure already shows essential features of the formation of the primary reaction zone: The oxidizing gas is supplied via a free jet or a free jet bundle 27 frontal on the end face of the introduced fuel 1 and distributed as evenly as possible in order to achieve a surface burnup. The outlet openings for the free jets 27 extend approximately parallel to the respective end face of the fuel 1.

Fig. 2 shows the fuel supply in section AA in Fig. 1. In addition to or instead of the feed channel 0 for bale or bundle-shaped fuels 1 with a plunger 4 can also be used for pasty fuels, eg. B. sewage sludge, are introduced by means of a screw conveyor 5. At the respective fuel inlet 21 Each fuel feed is supplied with own free jets or free bundles 27 with oxidizing gases.

Fig. 3 shows another option of fuel delivery: here driver 6 are provided, the z. B. on a chain or rollers or even go back and forth, in the latter case, the driver 6 in the conveying direction the fuel 1 form-fit or frictionally capture (standing or pinching) and let go in the backward movement of the fuel 1.

Fig. 4 shows a twisting apparatus 28 for the free jet 27 of the oxidizing gas to give it more stability.

Fig. 5 shows a detail of the lining of the primary reaction zone 20. In order to make the reaction efficient and to maintain the necessary reaction temperature, cooling in this zone, e.g. B. by Kesselheizflächen, not useful. This is rather provided with a thermal insulation or at best weakly cooled. In the figure, a conventional lining 30 made of refractory material is shown as thermal insulation.

6 shows another possibility of lining the primary reaction zone 20. Here, the primary reaction zone 20 is lined by roof shingle-like elements 22, which are suspended by means of hooks 31. Since these are not gas-tight, a sealing skin 29 (made of sheet metal) is provided in the outward direction; between the roof shingle-like elements 22 and the sealing skin 29 is a thermal insulation 30 'or just a stagnant gas gap to reduce the heat flow to the outside.

FIG. 7 shows the coke afterburning zone 40, equipped with a fuel retaining device 51 designed as a rotary grate, in order to ensure the necessary residence time. The rotary grate is offset from the center of the coke post-combustion zone 40. Upon rotation, therefore, the edge of the rotary grate pushes the fuel on it to the center ( Figure 7a ). The ashes will be over one Discharge opening 55 transported to an ash sluice 56. The oxidizing gas is introduced via a gas distributor. Bulk type additional fuel may be introduced via a bulk fuel entry 42.

8 shows an alternative arrangement: the gases from the coke post-combustion zone 40 flow directly together with the gases of the primary reaction zone 20 to the common gas post-combustion zone 60. The axis of the gas post-combustion zone 60 may be inclined (as shown). or horizontally. In front of the gas post-combustion zone 60, a coarse dust separator 61 may be provided to enhance burnout and reduce sparking. After the coarse dust separator 61, the gases pass into a chamber 62, which is supplied with oxidizing gas via openings 65 of a ring line 64. The oxidizing gas enters the loop 64 at 63. At 66, the flue gases escape.

9 shows the overall process flow diagram for combusting fuels: The flue gas outlet opening from the furnace is connected via a hot gas pipeline 66 to a boiler 72, which cools down the flue gas in a useful manner. Instead of a boiler, be it a steam boiler or a hot water boiler, a heat exchanger, for. B. for thermal oil or hot air generation or a drying process can be used as a heat sink.

This cooled flue gas can be passed through a coarse separator 74 for the purpose of partial dedusting. A portion of this cooled and optionally partially dedusted flue gas is passed through a flue gas recirculation means 80 and recirculated with combustion air from the combustion air supply means 90 in a gas mixing and metering device 100 to the furnace, in zones, via the oxidizing gas inlet openings 23, 43rd and 63 for the primary reaction zone 20, the Koksnachverbrennungszone 40 and the gas post-combustion zone 60. The remaining, so to speak surplus, subset of this cooled flue gas via an exhaust gas discharge device 110, consisting for. B. from a Saugzuggebläse, a flue gas cleaning system (not shown) and a chimney discharged to the environment.

The purpose of the gas mixing and metering device 100 is to provide, for each zone, the right amount of oxidizing gas with the right mixture of recirculated flue gas and combustion air. For this purpose, as shown in the figure, throughput-controllable gas conveying devices 101, 104 and 107 can be provided for the recirculated flue gas and flow-controllable gas conveying devices 102, 105 and 108 for the combustion air and the individual gas flows in mixing devices 103, 106 and 109 to the oxidation gases of the primary Reaction zone 20, the Koksnachverbrennungszone 40 and the gas post-combustion zone 60 are mixed. The flow-controllable gas conveying devices may, for. B. variable speed or swirl or throttle controlled blower or it can also be a blower for the recirculation gas and a fan for the combustion air are provided and the allocation of the individual zones done by control valves.

FIGS. 10, 11 and 12 show a further design possibility of the coke afterburning zone 40.

FIG. 10 shows the elevational view of this variant of the coke afterburning zone 40. The fuel retaining device is here designed or operated in such a way that a backflow of the fuel takes place. It is synonymous for the invention, whether now the backlogged material in the form of a bed (a fixed bed) is present or - due to the intensive gasification and gasification - in the form of a fluidized bed. In the illustrated case, for example, the lower part of the coke afterburning zone - such as a silo or bunker - fed and the material is supported on a turntable 52 from. Upon rotation of the turntable 52, the material (which consists predominantly of ash and has only small amounts of unburned) begins to flow and flows out of the ash discharge opening 55 over the edge of the turntable 52 of the (not shown) ash lock to. Of course, the discharge device shown is not the only one possible: Depending on the nature of the material, z. As well as discharge screws, rotary valves, clearing or sliding discharge - as they are known from mechanical engineering - to.

The required for the oxidation or gasification oxidation gas is introduced via a distribution box via so-called Lutten 54 (Gasverteilleitungen blowing out down, in the present case in the emptied bed) in the retained material, which depends on the Durchgasungs amount and the grain properties present as a fixed bed or fluidized and forms a fluidized bed. Fig. 11 shows - as a detail of Figure 10 - a Lutte 54; It consists of a roof-shaped element and side walls and is open at the bottom. The oxidizing gas is passed through the duct 54 and flows down into the sloped bed.

FIG. 12 shows the plan view and the plan view, respectively, of FIG. 10. In this view, the formation of oxidizing gas supply can be seen in more detail. For example, the coke post-combustion zone has a square cross-section and the lower part is a tapered transition piece from a square to a circular hole. The oxidation gas required for the oxidation or gasification is via a horizontal distribution box 53 in z. B. 3 horizontal Lutten 54 branches and introduced into the retained material. Of particular importance is the uniform distribution in the bed itself. In general, the gas tends to flow preferably on the wall (along the lining), which can be counteracted by avoiding a near-wall entry of the oxidation gas. Therefore, the wall distance of the outer Lutten 54 is greater than half of the transverse distribution of the Lutten 54 inside the backlogged material.

FIG. 13 shows a variant - using the example of the primary reaction zone 20 - in which the mixing devices were laid towards the confluence with the reaction zone. Combustion air succeeded via an air supply space 23a via an annular air inlet opening 24a directly into the reaction zone; the recirculation gas also passed directly into the reaction zone via a recirculation gas supply space 23b via a circular and concentric recirculation gas inlet opening 24b. The actual mixture of the two gas streams takes place in its own free jet 27 or only when the free jet impinges on the bale surface or also when dissolving the free jet in the reaction zone. Of course, the gas streams can be reversed, so that the combustion air via the circular and concentric inlet opening 24b and the recirculation gas via the annular inlet opening 24a are introduced into the reaction zone.

Claims (24)

Device for burning and gasifying bale- or bundle-shaped as well as pasty or puncture-resistant fuels, in particular biomasses, with at least one feed channel (0) for the fuel (1) and opposite the free end of the feed channel (0) opening into a primary reaction zone (20). arranged, directed against the fuel (1) outlet openings (26) for oxygen-containing gas, characterized in that the outlet openings (26) are at least partially acted upon by recirculated flue gas and below the primary reaction zone (20) a retaining device (51) for receiving the the primary reaction zone (20) is arranged down fallen fuel, wherein the retaining device (51) outlet openings for an oxidizing gas, at least partially consisting of recirculated flue gas is assigned. Apparatus according to claim 1, characterized in that the respective feed channel (0) is unheated or cooled. Apparatus according to claim 1 or 2, characterized in that the feed channel (0) has a reversible plunger (4). Device according to one of the preceding claims, characterized in that an insertion device for pasty fuels has a reversible piston or as a plug screw (5) is executed. Device according to one of claims 1 to 3, characterized in that an insertion device for pasty and water-rich fuels (eg sewage sludge) is designed as a dewatering plug screw (5). Device according to one of the preceding claims, characterized in that the outlet openings (26) for the free jets (27) are each approximately parallel to the respective end face of the fuel (1). Device according to one of the preceding claims, characterized in that the outlet openings (26) for the free jets (27) have twisting devices (28). Device according to one of the preceding claims, characterized in that the primary reaction zone (20) is uncooled, only slightly cooled or thermally insulated. Device according to one of the preceding claims, characterized in that the inside of the primary reaction zone (20) encloses in the circumferential direction, the junction (s) of the feed channel (0) and the feed channels, for example elliptical or polygonal. Device according to one of the preceding claims, characterized in that the inside of the primary reaction zone (20) is bricked or consists of pre-hung heat-resistant sheet metal elements (22), wherein the pre-hung sheet metal elements (22) on the back of a thermal insulation or a gap to a sealing skin (29) of the primary reaction zone (20). Device according to one of the preceding claims, characterized in that a Koksnachverbrennungszone (40) below the primary reaction zone (20) is arranged. Apparatus according to claim 11, characterized in that the Koksnachverbrennungszone formed as a rotary grate retention device (51). Apparatus according to claim 12, characterized in that the rotary grate is reversibly drivable in the direction of rotation. Device according to one of the preceding claims, characterized in that the rotary grate has a central ash discharge with an outlet opening (55). Device according to one of claims 12 to 14, characterized in that the rotary grate from the periphery with a bulk-like additional fuel is chargeable. Device according to one of claims 12 to 15, characterized in that the rotary grate is offset from the means of Koksnachverbrennungszone (40). Device according to one of the preceding claims, characterized in that a gas post-combustion zone (60) in the sense of the flue gas stream after the Koksnachverbrennungszone (40) is arranged. Device according to one of claims 1 to 17, characterized in that a Gasnachverbrennungszone (60) is arranged in the sense of the flue gas stream after the primary reaction zone (20). Device according to one of the preceding claims, characterized in that a common gas post-combustion zone (60) is provided for both the coke post-combustion zone (40) and the primary reaction zone (20). Device according to one of the preceding claims, characterized in that the gas post-combustion zone (60) before co-mixing with the oxidizing gas coarse dust separator (61). Device according to one of the preceding claims, characterized in that the oxidation gas for the reaction zones is a mixture of the recycled flue gas or the recirculated vapor of a downstream drying process and the combustion air is. Device according to one of the preceding claims, characterized in that the temperature in each reaction zone by adjusting the mixture ratio between flue gas or vapor and combustion air takes place. Device according to one of the preceding claims, characterized in that the combustion air for the primary (20) and the gas post-combustion zone (60) is preheated. Device according to one of the preceding claims, characterized in that the rotary grate performs an incomplete left-right rotation when starting with bulk-like fuels and also in partial load operation to merge already burning material with the supplied fresh fuel.

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