EP0595067A1 - Burn-out device and process for fuels - Google Patents

Abstract

Burn-out device and process for grate installations, in particular step-grate installations with primary air supply, in particular from regions below the individual grate steps and secondary air supply, in particular from the region of the fire space constriction in the upper region of the main combustion zone (7), characterised by a blow-out design (1) which blows out a compressed-gas medium of up to 4 bar in a pulsed manner at high pressure onto the outgoing region (8) of the furnace zone or the region of the burn-out zone of the last grate step, and blows off the finest fraction. <IMAGE>

Description

The invention relates to a burn-out device for grate systems, in particular step grate systems with primary air supply, in particular from areas below the individual grate levels, and secondary air supply, in particular from the area of the combustion chamber constriction in the upper area of the main combustion zone.

The burnout qualities of solid residues from incineration plants for solid fuels such as coal, wood, residues and waste are to be improved. In view of the expected slag quality of the new TA municipal waste, the goal of every incineration, also for the best possible use of energy, must be to completely mineralize the thermally convertible organic ingredients. With gaseous, liquid or dusty fuels, optimal burnout is achieved by using suitable atomizing devices.

In the case of solid fuels, this generally makes difficulties due to their relatively small specific surface, so that special processes for processing or special combustion techniques with sufficiently long dwell times and temperatures are necessary.

The more heterogeneous or contaminated a combustion product is, the more difficult the thermal decomposition of the organic substances becomes, the quality of the burnout deteriorates. Since the residues from incineration plants, such as slag, ash, dusts, are generally to be recycled, they must meet certain quality requirements. According to the new TA municipal waste, for example, they may only have a very limited organic fraction. This is particularly problematic with coal, residues or waste, which can contain up to 0.4 mg residues / mg product.

The invention has for its object to achieve a burnout with the lowest possible proportion of organic substances for such solid fuels.

This problem is solved in that an additional inflator, which is pressurized with gaseous media causing the combustion, is arranged in the region of the burnout zone of the last grate stage and / or in the outflow region of the firing zone, for swirling, combustion and fractionation in coarse and fine fractions ; the inflator being arranged and operable in such a way that the fine fraction is returned to the main combustion zone for post-combustion and that this or a possibly further inflator (10), the latter ejects approximately in the region of the first, gaseous media in the interval mode of an orderly higher pressure, one of which if necessary, separate supply of the two media with different pressures (in the form of 2 or, if applicable, 10) is provided.

The inflator can be mounted to be movable, in particular rotatable.
A second burnout bar can also be provided.

The fine fraction is therefore returned to the discharge via the flue gas path.
The coarse fraction is discharged as slag in a manner known per se. Inflation of gaseous media under pressure in the area of the last grate, for example, results in the separation into fine and coarse fractions on the fuel itself. Above all, the inert residues are divided into a pollutant-rich fraction (dust) and a low-pollutant coarse fraction (slag). After their treatment, both fractions have practically no or only very small proportions of organic substances. The separation of the fine and coarse fractions is obviously of great advantage for the recycling of residues. The whirled up and separated fine fraction is returned to the main combustion zone, the organic dust particles burn, the polluted light particles are discharged with the raw gases.

The effect according to the invention can be significantly increased if a further inflator for the same or a different gaseous medium is provided somewhat in the region of the first one, which emits gaseous media of an order of magnitude higher pressure in the interval operation. The pressure of the first inflator can be, for example, 800 to 1000 mm water column, that of the interval operated, for example, up to 4 bar.

A method for burning out solid fuels that are already in the area of the outflowing firing zone of a firing system operated with primary and secondary air is characterized in that a gaseous medium of a pressing, in particular from 800 to 1000 mm water column at a speed of 80 to 120 m / sec on the still combustible parts on the burnout section is directed in such a way that whirling up, burnout, fractionation into fine and coarse fractions and return of the fine fraction to the main combustion zone is carried out.

For this purpose, an additional medium of significantly higher pressure can expediently be directed at the burnout material from the same area at intervals. In the case of a preferred method measure, the pulsed application of the medium of substantially higher pressure can be carried out in such a way that the supply of gaseous medium is pushed off in the manner described above.

It is not ignored that, for the purpose of liquefying slag, it is already known to design the last grate stage as a slag melt stage and to do this transversely arranged slag liquefaction pipe to be provided on the outside with ramming mass and water cooling between ramming mass and an air pipe (DE 39 37 866). However, this does not serve to whirl up: rather, it was intended not to return the dusts to the main combustion zone, but rather to incorporate them into the slag if possible. This tube already had outlet swirl nozzles, but most of all still supplied fuel and is not designed for the intended purpose.

It is also known (DE 30 38 875), for example in the region of the constriction of the combustion chamber, not to supply the secondary air at the constriction (the projections, etc.), but in the form of a nozzle box, the nozzles being parallel to one of the walls of the flue gas duct and partially are directed into the interior of the flowing flue gas stream. However, the present invention requires a normal grate system with the proven primary and secondary air supply. Such a nozzle box, as shown, would otherwise burn in a short time and has nothing to do with the idea on which the invention is based; it is more of a speculative construction.

According to the invention, it is in principle possible to blow gaseous medium through a single tube once in normal operation at low pressure and once in interval operation at increased pressure.

However, a common burnout bar is preferably provided, in which two pipes, a medium inner pipe for 2 to 4 bar (interval), a second medium inner pipe for the pressure (continuously) of 800 to 1000 mm water are provided.

In general, the nozzles will be directed vertically downwards towards the burnout zone during pulse operation, different angles (vertically downwards or angles up to, for example, 30 ° deflection with respect to the vertical) may be interesting for the medium inner pipe for continuous outflow from the nozzles , especially to facilitate the deportation during interval operation.

Fig. 1

einen Ausbrennbalken für ein Mediumrohr gemäß der Erfindung zeigt;

Fig. 2

eine Anordnung des Ausbrennbalkens in einer Rostanlage darstellt; und

Fig. 3

einen Ausbrennbalken für Medien unterschiedlichen Drucks zeigt.

For example, embodiments of the invention will now be explained in more detail with reference to the accompanying drawings, in which:

Fig. 1

shows a burn-out bar for a medium pipe according to the invention;

Fig. 2

represents an arrangement of the burnout bar in a grate system; and

Fig. 3

shows a burn-out bar for media of different pressure.

Fig. 1 shows a burn-out bar for a medium pipe, which can be arranged at a variable distance, for example, possibly also rotatable, over the grate surface (burn-out zone) of a combustion system. The burnout bar 1 can be cooled, in particular water-cooled, and arranged across the entire grate width. The bar 1 consists of an inner tube 2, which is acted upon by compressed air. The bar is arranged across the entire grate width and has one or more rows of special air nozzles installed at a distance of approx. 5 to 30 cm, which are either arranged vertically or at any acute angle to the grate surface. The inner tube 2 is enclosed by a jacket tube 4, the ring cross section 5 of which contains a cooling medium or a positive action, for example Water or air has to give the bar 1 the necessary stability against thermal stresses. The casing tube 4 is bare or provided with a protective material, for example ramming material, to avoid corrosion and temperature stresses. The entire bar 1 can also be rotatably supported, so that the direction of the air outflow onto the grate can thereby be changed.

As far as the above-mentioned division of the inert residues into a pollutant-rich dust-like fine fraction and a low-pollutant coarse fraction is concerned, the fine substance fraction (to be seen in FIG. 2) is again passed through the main combustion zone 7. Here the organic dust particles burn, the pollutant light particles are discharged with the raw gases.

According to the design, the interval operation is higher in order of magnitude in pressure, there is practically a "blowing off" of the fuel. It must be added that the inner tube and outer tube are rigidly connected by spacers.

FIG. 3 shows two pipes for the discharge of gaseous media, which are arranged within a single oval pipe, which is encased by the ramming compound 6. According to FIG. 3, the air flow with 800-1000 mm WS can be permanently blown out via a separate air supply pipe 2 with air nozzles 3; the pulse air flow (interval air flow) is blown out, for example, at 2-4 bar via its own air supply pipe 10, the air nozzles of which can also be seen at 3. The oval cross-section 11 of the jacket tube is clearly recognizable, and the medium-carrying tubes in turn have a circular cross-section.

Only in the exemplary embodiment was air mentioned for the sake of simplicity. The gaseous, pressurized medium can be steam, enriched Act gases, warmed or not warmed, as well as untreated or contaminated air and / or a flue gas circulation. It is possible to install an automatic system that controls the blow-off process and can be controlled at any time via data acquisition and recording.

The burnout zone of the grate 8 can be horizontal, oblique or curved, movable or non-movable.

The system shown for example works as follows:
The air nozzles 3 of the burnout bar 1 are acted upon directly or indirectly by cold, heated and / or enriched air via a blower. This air has, for example, a pressure of about 800 to 1000 mm water column, an air outlet speed at the nozzles of about 80 to 120 m / s, so that even combustible parts are whirled up on the burnout path of the grate 8 and can burn out. Via a valve-controlled automatic circuit, for example, compressed air of approx. 2 to 4 bar is fed from the second air system to the air nozzles at intervals of around 3 to 6 minutes for short intervals, so that fine inert components and combustible light components on the fuel are blown off intensively . During the pulsed application of compressed air of 2-4 bar for a few seconds, the air supply line is shunted off from 800-1000 mm water. This burning off intensifies the burning process. The combustible and pollutant-containing dust components are passed into the main combustion zone 7, burned out there and discharged with the flue gas stream 9 depending on their mass and size. The increased dust content is separated in the flue gas dedusting system in a known manner.

According to FIG. 3, separate air supply pipes 2 and 10 for 800-1000 mm WS or for 2-4 bar with modified jacket pipe 11 can be used for both air flows.

There is a significant improvement in the burnout quality and also a division of the inert residues into a pollutant-rich fine fraction (dusts and the like) and a low-pollutant coarse fraction (slag). It is of great advantage that after their treatment, both fractions have practically no or only very small proportions of organic substances. This separation into fine and coarse fractions is of great advantage for the required recycling of residues.

According to a further embodiment of the invention, which is not shown (both the burnout device and the method), it is also possible to drive at the location mentioned without basic air, i.e. without air with the low pressure. Precautions are only for pulse operation with compressed air, i.e. with high pressure up to 4 bar, the size of the pulse once and the interval between two pulses being essential and controllable.

The size of the pulse depends on the type of slag, the height of the bed of slag and the composition of the slag, called slag type.

The interval (short or long intervals between two pulses) depends on the rust rate and whether the material to be burned out is very rich in slag or not.

example

If, for example, books, newspapers or the like are burned, in order that the half or three-quarter burned book is finally burned, it can also be blown onto this book which is about to burn out for a certain period of time, as a result of which the book is expanded, for example.

With this procedure, you are no longer bound to a special burnout bar or a burnout device. A blow-out pipe (for compressed air or a so-called press medium pipe) is simply sufficient, since other media such as gas mixtures etc. are also possible. Blowing is again carried out across the grate width at the end of the grate, onto the burned-out slag just before it falls into the water bath.

Conditions like the wind sifter can be separated into fine and coarse fractions. For this purpose, pipes, which are to be called compressed air channels or air feeders, can be arranged outside the furnace wall. The burned parts are blown off. That is the essential. Temperature-resistant material can be used on the nozzles. The loss on ignition can be reduced by half compared to today's best values.

In the countercurrent furnace, the incoming slag is easily blown, at least with a row of nozzles or the like. The impulse nozzle outlets can be arranged in such a way that they briefly and strongly inflate from locations in the area of the slag shaft or in front of the slag shaft onto the burned-out material (the still glowing or no longer glowing slag). If the airflow is slightly inclined against the direction of flow in the case of countercurrent, it is inclined towards the main combustion zone in the case of direct current or medium flow, ie in the main combustion shaft against the first draft. This will the fine fraction is actually driven to the main combustion zone. In the case of a direct current furnace, secondary air is generally blown from the ceiling, so that the blowing out of the compressed air according to the invention is best provided directly in the cross section where the slag shaft goes off. As a result of blowing off the light fraction, that is the fine fraction, the loss on ignition is often only a third of the usual values. The air quantities that are used are extremely small in relation to the primary, secondary and, if applicable, tertiary air quantities of the furnace, ie they are negligible.
It can also be inflated specifically with lances or the like known for this purpose.

The term "push-off" mentioned above means the following: push-off can be carried out using solenoid valves. The continuous jet air, if there is one, is pushed off each time the system is switched to pulse operation, for example by actuating a solenoid valve, so as to prevent losses to the fan (for example running in the opposite direction) being prevented. Only now is high pressure pulse air given.

Claims (10)

Burn-out device for grate systems, in particular step grate systems with primary air supply, in particular from areas below the individual grate levels, and secondary air supply, in particular from the area of the combustion chamber constriction in the upper area of the main combustion zone, characterized in that in the area of the burnout zone of the last grate level (8) and / or in outgoing area of the firing zone, an additional inflator (1), which is pressurized with gaseous media causing the combustion, is arranged for fluidization, combustion and fractionation in coarse and fine fraction; the inflator being arranged and operable in such a way that the fine fraction is returned to the main combustion zone for post-combustion and that this or a possibly further inflator (10), the latter ejects approximately in the region of the first, gaseous media in the interval mode of an orderly higher pressure, one of which if necessary, separate supply of the two media with different pressures (in the form of 2 or, if applicable, 10) is provided. Burn-out device according to claim 1, characterized in that the inflator (1) is movably, in particular rotatably, mounted. Burn-out device according to one of the preceding claims, characterized in that the pressurized gaseous medium is steam, enriched gas, heated or unheated and untreated or contaminated air and / or a flue gas circulation. Burn-out device according to one of the preceding claims, characterized in that the position and the feed for the gaseous medium above the grate system are variable. Burn-out device according to one of the preceding claims, characterized by an automatic system for controlling the blow-off process, controlled at all times with data acquisition, in such a way that it can be represented by recordings. Burn-out device according to one of the preceding claims, characterized in that the burn-out zone of the grate (8) is horizontal, oblique or curved, movable or non-movable. Process for burning out solid fuels that are already in the area of the outflowing firing zone of a firing system operated with primary and secondary air, characterized in that a gaseous medium of a pressure of in particular 800-1000 mm WS with a nozzle speed of 80-120 m / sec is directed towards the still combustible parts on the burnout section in such a way that fluidization, burnout, fractionation into fine and coarse fractions and return of the fine fraction to the main combustion zone is carried out. A method according to claim 7, characterized in that an additional medium of substantially higher pressure is directed at the burnout material at intervals from the same area. Method according to claim 8, characterized in that the pulsed application of the medium of substantially higher pressure is carried out in such a way that the supply of gaseous medium is blocked off according to claim 7. Process for burning out solid fuels that are already in the area of the outflowing firing zone of a firing system operated with primary and secondary air, characterized in that a gaseous medium of high pressure, in particular up to 4 bar, is directed intermittently at the material to be burned out and the fine or Light fraction is blown off.

Images