DE2918580A1 - Domestic or industrial refuse incineration - injects powdered lime into one or more feed-hoppers or chutes - Google Patents

Abstract

The incineration of domestic and/or industrial refuse is intended for waste containing different substances with clarifying slurry added, and finds application particularly in incinerators with tilting step grates. For this purpose lime, pref. calcium hydroxide or carbonate, in powder form is injected under and/or on top of the charge in the feed hopper, and/or in the feed duct, and/or into the uncooled combustion zone above the grate elements, and/or into the last of the dust collectors behind the heat exchangers. The injection pref. uses air, steam or water spray and suitably designed nozzles.

Description

Process for multi-fuel combustion and stepped swivel grate arrangement

tion for its implementation The invention relates to a method for multi-fuel incineration, especially for the common disposal of industrial waste and / or household waste existing waste and sewage sludge and / or another Type of waste, especially with the use of stepped swivel grates.

The invention also has a stepped swing grate arrangement for implementation this procedure is the subject.

It is known to pollutants such as hydrochloric acid HCl, hydrogen fluoride HF and sulfur dioxide SO2 dry with the help of powdery additives such as calcium carbonate To absorb or adsorb CaC03 or hydrate lime Ca (OH) 2. Because of the essential hydrated lime is preferred for larger surfaces. For this purpose, the Introduce lime in dust form into the flue gas flow at temperatures below 3000C (Chemie-Technik 7th year (1978) No. 7, pages 291-297), mostly below 2000C. Here, however, the reaction between pollutants and lime is already significantly reduced. In addition, there is only a short way to the electrostatic precipitator, so that the statistical Possibility of combining molecules and particles of the pollutants in the flue gas on the one hand and in the lime on the other hand is considerably reduced.

Attempts have been made to inject lime dew in the high temperature range and been discarded again. The reaction or sorption is more effective and the residence time of the lime particles in the flue gas stream in the high temperature range longer. However, certain temperature ranges must not be exceeded. the Heating surface contamination was excessive.

It is also known (DE-AS 22 42 012) industrial waste initially in one Coking the furnace, adding sewage sludge to this coke, acidifying it if necessary, to heat slightly below 800C and then neutralize with lime, this Mixture is fed to the combustion. The lime is in this known measure added essentially to neutralize the previously added acid. Obviously, only a low level of sorption can be achieved with this type of milk of lime addition the pollutants can be reached.

The invention is based on the object from the combustion process resulting pollutants, especially in the case of the step swivel grate at a higher level Degree to be included than before and the pollution of the heating surfaces to a tolerable level Measure to press.

This is achieved with a method of the type mentioned at the beginning Surprisingly because lime in the area before the task, in particular the feed lock, on the material to be fired and / or on the shut-off valves at the bottom of the sluice and / or is added in the uncooled combustion chamber and / or at the end of the heating surfaces.

The lime is preferably sprayed in.

The lime is expediently distributed by means of air, steam or finely Water sprayed.

According to another embodiment, it is possible to use the lime in the different areas to inflate.

In general, lime is used in the form of hydrate lime Ca (OH) 2 or calcium carbonate, both in the form of dust, injecting According to a practical embodiment of the invention on a stepped swivel grate are provided: Lime dust feed in the filling funnel and / or above the double butterfly valves and / or above the stepped swivel grate elements in the uncooled Firebox and / or in the last dust funnel behind the boiler heating surfaces.

The nozzles in the are useful for blowing in wood chips common designs.

The measure according to the invention surprisingly results in a degree of integration from 60 to 70% achieved. In the downstream electrostatic precipitator it is possible to use the To practically completely eliminate lime and the pollutants below the tolerance limits to lower.

When injecting it is also possible to use water vapor as a carrier for the Use lime in finely divided form. This increases the electrical conductivity and the liquid increases the ability to bind.

According to another form of realization, one can also use water vapor Blow off lime. Steam flow and lime flow can also intersect. The distribution is excellent.

At the first addition of the lime on the double opening flaps on the one hand and on the feed material in the filling funnel takes place by falling down in the feed chute and then by being transported through the metering gate and moving on the stepped swing grids a good mix. The lime dust remains bound with the fuel. The sorption takes place at higher temperatures during the combustion process. Water vapor is released, which favors sorption again. On the other hand takes place the binding of the dust particles with the ashes through constant stirring and stirring through the stepped swivel grate elements and through discharge into the ash container.

The injection in the uncooled combustion chamber is particularly interesting, i.e. at the highest occurring temperature, i.e.

at the place where the pollutants are released from the material to be fired will. This is where the reaction is most violent. The swirl is greatest. on the other hand It is also possible to provide lime injections on the auxiliary burners, if necessary by guiding the lime with the carrier air to the burner. This allows the Burner temperatures are reduced. The combination of lime injection is particularly beneficial and the special design of the step swivel grate. The lime / flue gas mixture enters the cooled furnace (radiant heating surfaces), the one with smooth surfaces is formed, the walls of which are lined, for example, with welded fin walls are.

The main part of the reaction occurs here in the cooled furnace Lime dust and flue gas. Even before the flue gases laden with lime dust enter the contact heating surfaces, that is, the superheater packets, enter, the whole becomes Flue gas is introduced into a dust collecting funnel that looks like a cyclone. A large Part of the particles are deposited there. It is this measure that gives a relative Keeping the heating surfaces clean is guaranteed. Even after being deflected by the flue gas these are passed through each time before it flows through the next pipe packs (evaporator) out a dust funnel. This is done again when the feed water preheater exits, before the flue gases are fed to the electrostatic precipitator. However, in the last Dust funnel are once again sprayed with lime dew in a manner known per se. The heating surfaces can be cleaned while the soot is being blown.

An exemplary embodiment of the invention should now be referenced to be explained in more detail on the accompanying drawing.

Before the fuel is fed into the feed sluice, which is controlled by a gate valve 1, hopper 2 and double butterfly valves 3 are formed, lime dew at 30 is abandoned. The arrows drawn are only intended to signal a task and 0 should be on rotated by 90. Now the gate valve 1 opens; the fuel is placed in the hopper 2. After closing the gate valve 1 is lime dew (from 30) is added to the fuel in the hopper 2, so that lime dew lies on both the fuel and below the fuel.

If the double shut-off valve 3 is opened, the lime dust falls with it the fuel in the feed shaft 4 and mixes with this. The fuel falls on the feed grate 6 and is already mixed with lime dew. The allocator 5 now conveys the fuel mixed with lime dust onto the individual swivel grates. As a result of the intense poking and tumbling movements of the swivel grids, ash and the like are removed. Lime dust over the air distribution funnel and over the burn-out grate (without reference number) carried out. A corresponding reaction takes place in the uncooled combustion chamber 7 the lime dust in the flue gas. Here it is particularly favorable in this to infuse lime dust again into the uncooled furnace at 34. The smoke gases come out then into the cooled furnace 8, which is shown with welded fin walls is lined.

It is essential that the surfaces in the cooled furnace (radiant heating surfaces) are smooth. According to the illustration, the fin walls also extend in the area in'dem the contact heating surface packages hang. Before entering the contact heating surfaces the flue gases are diverted into a dust funnel 9, in which there is a cyclone-like Effect. At least a coarse dust separation takes place here. After passage The flue gases are again due to the superheater packages in the second and third pass passed into a dust funnel 9. After passing through the evaporator tube bundle and the pipe stacks of the feedwater preheater in the fourth and fifth Train, the flue gases enter another dust funnel, in which this one Embodiment at 36 a further addition of lime dust takes place. In the one built into the fox The final separation takes place in the electrostatic precipitator. The requirements of environmental protection corresponding flue gases leave the boiler system.

The measure according to the invention results in extremely low pollution of the heating surfaces with simultaneous high efficiency of the sorption in the high temperature range achieved.

In this embodiment, too, it is possible to fine the lime dust Add sprayed water. Instead of using the nozzles 34, it is also possible to use lime dew to be blown into the uncooled combustion chamber 7 via the pitot tube 10. The scope of the lime dust is always between 600 and 9000C.

According to an alternative embodiment, the allocation takes place Lime by means of a lock wheel; the injection takes place with the help of transport air via wide-ranging nozzles.

Claims (7)

"Lime injection" method for multi-fuel combustion and stepped swivel grate arrangement for its implementation PATENT CLAIMS process for multi-fuel combustion, in particular for the joint disposal of existing industrial and / or household waste Waste and sewage sludge, especially with the use of stepped swivel grates, thereby g e k e n n n z e i c h -n e t that lime in the area before the task, in particular the feed sluice, on the material to be fired and / or on the shut-off valves at the bottom of the Lock and / or in the hopper in the uncooled combustion chamber and / or at the end of the Heating surfaces is added. 2. The method according to claim 1, characterized in that g e k e n n z e i c h -n e t that lime is being injected. 3. The method according to any one of the preceding claims, characterized in g c It is not noted that the lime was dispersed by means of air, water vapor or finely Water is injected. 4. The method according to any one of claims 1 or 2, characterized g e k e n I do not point out that the lime is puffed up. 5. The method according to any one of the preceding claims, characterized g e it is not stated that the lime in the form of hydrated lime Ca (OH) 2 or calcium carbonate, both in dust form, is injected. 6. Step swivel grate arrangement for carrying out the method according to one of claims 1 to 5, g e k e n n -z e i c h n e t by supplying lime dust (30) in the hopper (2) and / or above the double shut-off valves (3) and / or in (32) feed shaft (4) and / or above the stepped swivel grate elements in the uncooled Firebox (7) and / or in the last dust funnel (9) behind the boiler heating surfaces. 7. step swivel grate arrangement according to claim 6, characterized in that g e k e n n notices that the nozzles are in the normal position for blowing in wood chips Types are trained.