WO1995027802A1 - Method and installation for the heat treatment of materials - Google Patents

Abstract

The installation proposed includes a conveyor belt (7) on which a bulk sinter mixture is deposited by a device (9). The conveyor belt carries the sinter mixture through a sintering plant (1) at the entry to which is disposed an ignition oven (3). The oven ignites the upper surface of the sinter bed. An extractor (11) located below the sinter bed sucks the burning zone down into the sinter bed. Located below the sinter bed at the output end of the sintering plant (1) is a second ignition oven (4) which ignites the lower surface of the sinter bed. A second extractor (6) sucks the second burning zone upwards. The pollutant content of the exhaust gases is significantly reduced since, in the input zone, the uninserted material acts as a filter while, in the output zone, combustion of the pollutants produced takes place in the upper-surface combustion zone. An additional adsorption agent ensures that the pollutants emerge mainly in the output zone of the sintering plant.

Description

 Method and arrangement for heat treating a

Goods to be treated

The invention relates to a method for the heat treatment of a pourable material to be treated, in particular for sintering metallic materials according to the preamble of patent claim 1. Furthermore, the invention relates to an arrangement according to the preamble of patent claim 13.

The method and arrangement of the type used in the invention are first described with reference to FIG. A, in which a conventional sintering system with the first additional units is shown schematically as a treatment system.

The arrangement shown in FIG. A essentially consists of a sintering plant 1 with an ignition furnace 3 arranged at its inlet end, a sintering bed transport device 5 which has an endless sintering belt 7 guided through the sintering plant, a sintering mixture Feed device 9 and an exhaust gas extraction device 11, with the aid of which the pressure gradient for the sintering process, which runs from top to bottom through the sintering bed, is also built up.

The sintering mixture in the known sintering process described with reference to FIG. A consists of ores, additives, fuels, in particular coke breeze, quicklime and return material from the sintering process itself. A mixing and rolling drum 13 ensures an intimate mixture of the granular or pourable mixture components as well as a uniform grain size and shape of the sintered material. The feed device 9 is fed from the mixing and rolling drum 13 and pours the sinter mixture in a substantially uniform layer thickness onto the grate of the sintering belt 7. With the aid of an upstream feed device 15, a finished sintered layer is applied to the grate in this known system Sintered belt 7, which is arranged between the actual sintering bed, ie the sintering mixture layer and the grate and protects the grate from excessive temperature loads and stresses in the manner of a temperature barrier. The finished sintered layer remains in the This is unaffected by the subsequent sintering process in the sintering plant 1 and does not interfere with the postprocessing steps in a breaker 17, in a sinter cooler 19 and in a cold sieve station 21 until the usable finished sinter is obtained at the starting point 23.

The associated conventional sintering process takes place as follows: First, a suitable rust coating layer is applied uniformly to the sintering belt 7 via the feed device 15. The sintered mixture is poured onto the grate covering in a predetermined layer thickness over the full width of the bed as evenly as possible. The sintering belt 7 moves from the feeding point of the sintering mixture below the feeding device 9 to the left towards the sintering plant. The sintering bed is ignited by the ignition furnace 3 on the first side facing it when it enters the sintering plant 1. A pressure drop is built up in the entire sintering system 1 in the sintering bed through the extraction device 11 below the bed, through which combustion air is introduced into the combustible sintering mixture and exhaust gases are removed on the second sintering bed side (underside). After the carbon-containing fuel of the sintering mixture has been ignited, a combustion zone forms in the sintering bed, which moves from top to bottom in the sintering bed from right to left as the sintering bed progresses, the sintered material being sintered through in this zone and come to cake The course and the formation of the firing or sintering zone over the depth of the sintering bed can be seen from the length of the sintering belt in the interior of the sintering plant 1 from FIG. In this example, the bed depth is 500 mm. As can be seen from FIG. B, the firing or sintering zone reaches the bottom of the sintering bed at the end of the sintering process or shortly before it emerges from the sintering plant 1 and softens the material to be sintered there so far that the individual material Baking grains together (agglomerating).

As is known, this proven sintering method has the disadvantage that the exhaust gases drawn off from the sintered layer are contaminated with a high proportion of pollutants which are removed must be before the exhaust gases can be discharged into the surrounding atmosphere. Up to now, sintered exhaust gases have been cleaned in practice using secondary exhaust gas purification systems. The investment costs of secondary exhaust gas cleaning systems, which reduce the pollutant emissions to permissible values, are enormous, since the exhaust gas is heavily contaminated with pollutants over the entire length of the sintered bed and correspondingly large amounts of gas have to be dealt with during the cleaning. Exhaust gas cleaning has therefore been limited to the use of dust filters (belt dedusting in FIG. A) or a somewhat more extensive exhaust gas cleaning has been carried out, for example, in washing systems. The particularly critical organochlorine substances, heavy metals and. The like, however, were not removed for cost reasons.

The invention is therefore based on the object of removing the pollutants produced in heat treatment processes of the generic type as far as possible and with comparatively little investment, preferably with a reduction in the volume of exhaust gas to be cleaned.

In solving this problem, the invention is based on the knowledge that the conventional sintering process described already inherently contains numerous properties and phases which favor exhaust gas cleaning, which could not previously be suitably used. This is only possible according to the invention, namely in terms of the method with the features of claims 1, 2, 3, 4 and 6 and in terms of arrangement with the features of claims 13, 14, 15 and 16.

The invention is based on the secondary-side exhaust gas purification measures for very large gas volumes which are burdened with extremely high investment costs. In all alternative solutions, it essentially integrates exhaust gas purification into the primary sintering process. Here, the invention is based on the consideration that, in the known type of heat treatment, a strongly adsorbing filter layer is connected downstream of the combustion zone as long as the combustion zone has not yet broken through to the flue gas side opposite the ignition side. The Reini- The effect of this "natural" adsorption view is used in the invention. Before the cleaning effect disappears due to the combustion of the carbon-containing (adsorbable) fuel and the combustion zone penetrates to the other side, the pressure drop is reversed in the first solution according to the invention and counter-combustion is generated. In this way, the second burning zone migrating into the bed from the other side is in turn followed by a layer which can initially act as a filter layer. Before the union of the two firing zones, organic chlorine substances released, for example dioxins or furans, are burned in the second firing zone under the influence of the high temperature of the first firing zone or adsorbed by remaining carbon particles and subsequently burned in the same way.

In another solution according to the invention, the exhaust gases emerging from the treatment bed are collected and passed into the ignition furnace. In this case, either all of the gases emerging in the treatment system can be recycled or only the gases from partial phases which have a critical pollutant content, in particular the end phase of the treatment process. The pollutants contained in the exhaust gases are destroyed by the influence of the high temperature in the ignition furnace. The exhaust gases are then passed through the treatment bed under the influence of the pressure gradient applied to the treatment bed. They are exposed to extremely high temperatures in the area of the firing zone and are further cleaned in this way. The "natural" cleaning layer formed in the treatment bed behind the firing zone also adsorbs residual pollutants remaining in the exhaust gas.

In an alternative treatment method, the exhaust gases emerging from the treatment bed in the final phase of the process are collected and passed through the treatment bed together with the gases required for heat treatment in the initial and / or middle phase of the process. The exhaust gases can be distributed over a large area over the treatment bed and passed through it. The pollutants So they are not concentrated in the area of the ignition furnace, but can be supplied together with combustion air in a lower concentration. The pollutants contained in the exhaust gases, for example dioxins and furans, are in turn destroyed under the influence of the high temperature when the gas mixture passes through the combustion zone. The cleaning action of the "natural" adsorption layer formed behind the firing zone is also used in this method alternative. Only minor technical conversion measures are required to implement the method, so that the costs incurred are comparatively low.

In a further alternative treatment method, the pressure drop and thus the burning of the fuel layers within the bed is maintained from the beginning to the end of the treatment process. While the burning zone is moving from top to bottom, the relatively cool, untreated mixture layer underneath acts as an adsorption filter. Their filter effect is enhanced by the lowest (first) layer made of adsorptive material, especially coke. This layer is protected from ignition by the second layer of inert material acting as a temperature barrier. It is therefore an adsorption filter layer carried in the primary process. Instead of lumpy or granular coal or coke, other lumpy or granular materials can be used which have comparable adsorption or filter properties.

The last-mentioned alternative method makes a change to the conventional treatment system superfluous. The adsorbent-forming coke is poured onto the grate supporting the layer sequence as the first layer and accompanies the actual treatment process as a primary filter. This layer of coke is not lost; because on the one hand the coke can be largely separated from the remaining layers at the end of the treatment process and can possibly be recycled and reused, and on the other hand it can be used as a Top layer uses coke in the blast furnace to replace other coke feed materials.

In a further method alternative, the pollutants are concentrated on the system section in which the exhaust gas temperature is particularly high by a targeted shift of the pollutant profile in the direction of the profile of the exhaust gas temperature and in particular by superimposing the associated profile maxima. The cleaning of the exhaust gases can therefore be limited to a correspondingly short section of the treatment area in which the pollutant concentration and exhaust gas temperature are at a maximum. In this way, cleaning plants of small capacity are sufficient to operate an entire treatment plant with very low pollutant emissions.

The shift in the pollutant concentration profiles is achieved by enriching the treatment bed with pollutant adsorbing agents which retain the pollutants up to the last section of the treatment area (e.g. the sintering machine). Only at the end of the treatment area, when the capacity of the pollutant-adsorbing agent is exhausted and the combustion zone reaches those lower layers in which the pollutants have been retained in a highly concentrated manner, does the concentration of the pollutants in the exhaust gas increase sharply. This portion of the exhaust gases which is heavily polluted can then be cleaned separately.

Instead of introducing additional pollutant-adsorbing agents into the treatment bed, agents with improved adsorption properties can be used in the applications in which the treatment process requires the use of pollutant-adsorbing agents in the treatment bed. A larger specific surface of the individual adsorbent particles can, for example, already lead to the desired shift in the pollutant concentration profiles.

The pollutant-adsorbing agents are advantageously mixed with the material to be treated and then poured onto the grate before they are introduced into the treatment area. So it succeeds almost without additional technical effort, that Distribute pollutant adsorbents evenly in the treatment bed.

In a further development of the invention, it is provided that the pollutant-adsorbing agents are present in a higher concentration in the lower region of the treatment bed than in the upper region of the treatment bed. Different concentration ratios between pollutant-absorbing agents and the material to be treated can be produced during mixing. In order to achieve a particularly steep concentration profile of the pollutants, it is favorable to gradually increase the concentration of the pollutant-adsorbing agent from top to bottom in the treatment bed. Instead, several two layers with different concentration ratios can be provided.

A preferred embodiment is characterized in that the collected exhaust gases are catalytically cleaned using their high temperature. Effective catalytic cleaning is only possible at temperatures above 300 ° C. By superimposing the pollutant concentration max a with the temperature maximum, the high temperature required for catalytic cleaning is reached in most heat treatment processes. No additional thermal energy has to be supplied; instead, the heat energy released in the heat treatment process is collected and sufficient as a heat supplier. It is also advantageous that the heat is not released into the environment as waste heat. Various types of pollutants can be removed from the exhaust gas by catalytic cleaning; For example, organochlorine substances such as dioxins and furans can be reduced using suitable reduction catalysts. Nitrogen oxides can also be easily reduced at these temperatures. A catalytic oxidation is possible, for example, for pollutants such as SO2. SO2 becomes SO3 through oxidation.

As an advantageous further development of the invention, it is provided that the pollutant-adsorbing agents and their concentrations in the treatment bed are selected such that the concentrations tion profiles of the pollutants arising in the treatment process and in particular their maxima are brought to overlap in the end section of the treatment area. The more concentration profiles of different pollutants can be overlapped with one another and the steeper the concentration peaks, the smaller the partial volume of the exhaust gas to be cleaned and the more effectively the method according to the invention works.

In a further development, the exhaust gases emerging from the treatment bed in the last phase are subjected to particle separation. A normal electrostatic filter can be used for this purpose. In order to achieve a particularly high cleaning effect, it is favorable to use catalytic cleaning after the particle separation.

Instead of the particle separation, the exhaust gas can be washed with adsorbent and water after the catalytic cleaning. This is done, for example, with the aid of a spray dryer, in which dust-like carbon-containing adsorbent and water are introduced into the flue gas stream. The water introduced reduces the exhaust gas temperature to such an extent that, for example, salts and chlorides can crystallize out. In order to further improve the quality of the exhaust gas, an activated coke system can be used instead of or in addition to a spray dryer.

After cleaning with adsorbent and water, the exhaust gas is advantageously subjected to particle separation.

A part of the solids resulting from the particle separation can be recycled and used again as an adsorbent for cleaning. Since the adsorbent-containing solids cannot fully utilize their absorption capacity of pollutants on their first passage through the exhaust gas, the recycling makes it possible to load the adsorbent with pollutants up to its capacity limit and to keep the operating costs low. Carbonaceous, pourable material, for example coke breeze and / or activated coke, is advantageously used as the pollutant adsorbent. This material is inexpensive to purchase. In the case of heat treatments above the ignition temperature of coke breeze, it ignites and releases the heat of combustion released as additional heat to the treatment bed. No disturbing foreign substances remain in the treatment bed.

The method according to the invention is preferably used in the sintering of metallic materials.

Appropriate developments and refinements of the invention are characterized in the subclaims.

In the following, the invention is explained in more detail with reference to exemplary embodiments schematically shown in the drawing. The drawing shows:

1 shows a schematic representation of a sintering arrangement for carrying out a first sintering process according to the invention; 2 shows a schematic representation of a sintering arrangement for carrying out a second method alternative according to the invention; 3 shows a schematic representation of a sintering arrangement for carrying out a third method alternative according to the invention. 4 shows a schematic representation of a sintering arrangement for carrying out a fourth treatment method according to the invention; 5 shows a schematic representation of a sintering arrangement for carrying out a fifth method alternative according to the invention; 6 shows a schematic illustration of a sintering arrangement for carrying out a sixth method alternative according to the invention; 7a shows a schematic representation of a sintering arrangement; 7b shows a diagram of the exhaust gas temperature, plotted against the length of the sintering belt; 7c shows a diagram of the exhaust gas concentration of S02, plotted against the length of the sintering belt; 7d shows a diagram of the exhaust gas concentration of polychlorinated dibenzodioxins and polychlorinated dibenzofurans, plotted against the length of the sintered belt; 7e shows a diagram of the exhaust gas concentration of nitrogen oxides, plotted against the length of the sintered belt. The embodiment of the invention shown schematically in FIG. 1 differs from the conventional sintering arrangement in FIG. A on the one hand by a second ignition furnace 4, which is arranged near the outlet end of the sintering system 1 and ignites the sintering bed from the underside, and on ¬ on the other hand by a device for generating a pressure drop in the opposite direction, ie from the bottom of the bed to the top of the bed. This pressure gradient generating device has an exhaust gas exhaust hood 6 and a suction pump 10 arranged in a return line 8.

The exhaust gas discharged via the extractor hood 6 can be dedusted using a suitable filter 12. In a mixer 14, the exhaust gas is mixed with the combustion air required in the front or middle area of the sintering system 1 and is passed together with the combustion air through the hood 16 through the sintering bed from top to bottom. When passing through the firing zone or through the high temperature area of the sintered bed passed through the firing zone, the organochlorine substances are destroyed with sufficient reliability. Behind the firing zone, the exhaust gases which are recirculated or newly formed during sintering pass through the sintered mixture, in which the highly carbon-containing fuel is generally contained in fine form in the form of coke breeze. This fuel acts as an adsorbent, in which a substantial part of the pollutants is similar as in conventional secondary purification of exhaust gases in activated coke reactors.

In the schematic drawing according to FIG. 2, only the feed section of the sintered bed transport device 5 is shown schematically. Otherwise, the sintering arrangement corresponds to that according to FIG. A. As can be seen, the sintering belt 7 is assigned three feed devices in succession. In an additional first feed device 18, a thin adsorbent layer 20 is applied to the grate. A is arranged behind the device 18, the application device 15 already described with reference to FIG. A for the application of the finished sintered layer 22 to the adsorbent layer 20, and then the application device 9 for the application of the sintering mixture 24, which represents the actual sintering bed, follows. During the sintering process, the finished sintered layer 22, which can also consist of another material with essentially inert properties, forms a temperature barrier which prevents the firing zone from spreading into the adsorptive filter layer 20.

FIG. 3 shows a sintering arrangement which is basically similar to that of FIG. 1, but in which the second ignition furnace 4 is missing in the rear section of the sintering arrangement 1. Similar to the arrangement according to FIG. 1, an exhaust gas collection device 6 'is provided there, but is arranged at the normal pressure drop on the underside of the sintered bed. The exhaust gas collected there is returned to the mixing device 14 via the return line 8 and the suction pump 10, mixed there with combustion air and passed through the sintering bed via the hood 16 in the front and middle region of the sintering system 1. The cleaning effect of the sinter mixture located beyond the firing zone in the sinter bed is also used in this arrangement according to FIG. 3. The investment costs are primarily lower because the second ignition device is superfluous and the additional filter system 12 can also be omitted. The primary emission control measures described above can also be used in combination. The exhaust gas recirculation according to FIG. 3 can of course also be used when using the additional adsorbent layer 20 according to FIG. 2. In addition, the exhaust gas can be fed back only into the ignition furnace and only into the inlet-side or central section of the sintering system outside the ignition furnace. In the same way, however, it can be fed back into the ignition furnace area and a further area, for example into the middle section of the sintering plant. When returning the exhaust gas only into the ignition furnace, the mixer 14 and / or the hood 16 can be dispensed with. The invention also does not require any restrictions with regard to the sintered bed conveying device. The conventional sintering belt system can be replaced, for example, by a so-called push-through furnace, in which the sintering bed is moved in baskets arranged one behind the other and pushed through the sintering system 1. The conveyor belt can be driven both continuously and discontinuously.

In the system according to FIG. 4, the feed device 9 serves not only to supply the sinter mixture, but also an additional adsorbent. The sinter mixture consists in a known manner of ores, additives, fuels, in particular coke breeze, quicklime and return material from the sintering process itself. The adsorbent contains carbon and is granular or pourable.

By enriching the sintered bed with adsorbent, pollutants are increasingly adsorbed, which develop in the front or middle section of the sintering plant 1. The pollutants are retained in the sintered bed so that the exhaust gases drawn off in the front sections are already of sufficient purity. The exhaust gases (exhaust line 25) drawn off in the front and middle sections of the sintering system with the exhaust gas extraction device 11 can, after particle separation with an electrostatic filter 25 ', pass to the ambient atmosphere without further cleaning steps be dissipated. The discharge drawn off by the exhaust gas extraction device 11 in the rear section of the sintering system 1 is conducted via a separate extraction line 26. In this section of the sintering plant, the temperature of the exhaust gas is naturally particularly high. Due to the enrichment with pollutant-adsorbing agents, the maximum concentration of all critical pollutants, for example any chlorine-organic substances, nitrogen oxides and sulfur dioxide, also lies in this last section. Particles such as fly ash are first separated out of the exhaust gas with the electrostatic filter 27. The exhaust gases are then catalytically cleaned with the addition of reducing agents. In the catalytic cleaning reactor 28, any dioxins and furans and nitrogen oxides that may be present are reduced with a reduction catalyst. An additional oxidation catalyst is used to oxidize SO2 to SO3. The catalytic treatment is favored by the high exhaust gas temperature. The catalytically cleaned exhaust gas can then be released into the ambient atmosphere without further purification (exhaust line 29).

The fifth embodiment of the arrangement according to the invention shown in FIG. 5 differs from the arrangement shown in FIG. 4 by the cleaning arrangement connected downstream of the exhaust gas discharge line 26. In this embodiment, the catalytic cleaning reactor 28 is acted upon directly by the pollutant-elastic exhaust gases. The exhaust gases are then cleaned in an adsorbent reactor 30, with the addition of adsorbent and water, of sulfur oxides, dust and organic substances. A fabric filter 31 connected downstream of the adsorbent reactor 30 separates the loaded adsorbent and other solids from the flue gas stream. The filtrate is partly returned to the reactor via the return line 32 in order to adsorb further pollutants there and to fully utilize the adsorption capacity of the particles.

After the fabric filter 31, the exhaust gas has a relatively high purity and can be discharged together with the exhaust gas from the exhaust line 25 into the ambient atmosphere. The exhaust gas in this embodiment also fills the ever stricter pollutant emission limits and is particularly environmentally compatible.

The adsorbent reactor 30 used can be designed to be very small, since by concentrating the release of pollutants on the rear section of the sintered area, only a small part of the exhaust gas removed during the heat treatment process has to be cleaned of pollutants. The construction effort remains low. By returning the adsorbent to the reactor, the operating costs are also kept low.

In the embodiment according to FIG. 6, the exhaust line 26 first leads to the electrostatic filter 27, in which solids, in particular fly ash, are separated. The actual cleaning again takes place in the catalytic cleaning reactor 28 at temperatures of approximately 300-400 ° C. The hot exhaust gas is then returned to the ignition furnace via a return line 33. There, the exhaust gas is mixed with combustion air and passed through the sintered bed again. The cleaning effect of the sintering mixture located beyond the firing zone in the sintering bed is used in order to achieve an even higher purity of the exhaust gas.

The exhaust gas purification measures described can also be used in combination. The exhaust gas recirculation according to FIG. 6 can of course also be used in addition to an adsorbent reactor. In addition, the adsorbent can be introduced in the lower layers of the sintered bed in a higher concentration than in the upper layers. The adsorbent and the sintered mixture can also be applied to the belt one after the other. A separate adsorbent layer can be provided separated from the sintered mixture by an insulation layer. Such an adsorbent layer can also be used in addition to enriching the material to be treated with adsorbable material.

The adsorbent itself can be an additive and / or one used in conventional sintering processes Be a mixture of substances whose pollutant-adsorbing properties are improved in the sense of the invention. It is important that the concentration profile of the pollutants is shifted to match the exhaust gas temperature profile. This is explained in more detail below with reference to FIG. 7.

The sintering process begins below the ignition furnace 3. The sintering belt 7 moves in the conveying direction, that is to the right in the drawing. Simultaneously with the conveying movement of the sinter bed, the sinter zone moves from top to bottom through the sinter bed.

7a shows a diagram of the exhaust gas temperatures, plotted against the sintering belt length. The solid line represents the curve for a conventional sintering process and the dashed line represents the curve for the method according to the invention. This also applies to diagrams b-e. The course of the exhaust gas temperature shows a strong maximum in the rear section of the sintering region, both in the known method and in the method according to the invention. The temperature profile is practically not affected by the invention.

7b shows the diagram of the concentrations of SO2 in the exhaust gas, plotted against the sintering band length. In known sintering processes (solid line), the SO2 concentration in the exhaust gas rises shortly behind the center of the sintering system. The Sθ2 ~ peak is very broad. In the method according to the invention, the exhaust gas concentration of the SO2 is constantly significantly lower in the front and middle sections and only increases significantly later with a relatively steep flank. The peak is shifted backwards and considerably narrower.

7c shows the exhaust gas concentrations of polychlorinated dibenzodioxins and dibenzofurans against the sintering band length. In the conventional sintering process, the concentration of organochlorine substances increases in the middle of the sintering process. Analogous to the peak of the SO2 exhaust gas concentration, the peak is very broad. In the method according to the invention, the exhaust gas loading with organochlorine substances in the front and middle sections is achieved by the additional The adsorption effect of the sintered bed was significantly reduced and the maximum shifted backwards with the formation of a sharper peak.

The exhaust gas concentrations of NO _{x are} plotted against the sintering belt length in FIG. 7e. In the conventional sintering process, the NO _x concentration is constant over almost the entire length of the sintering belt. Only at the end of the band does the NO _x concentration drop approximately linearly. The consequence of this is that up to now the entire exhaust gas volume had to be cleaned in order to remove the NO _x pollutants. The exhaust gas concentration of NO _x in the process according to the invention is negligibly low in the front and middle sections and only rises to a peak in the rear section of the sintering belt.

The method according to the invention thus enables the pollutants to be concentrated in the rear section of the sintering belt. The pollutant peaks are shifted backwards and the concentration maxima correspond to the maximum of the exhaust gas temperature. In this way, only a small part of the resulting exhaust gas volume needs to be cleaned. The partial exhaust gas quantity to be cleaned is collected in the rear section of the sintering machine, that is to say where the exhaust gas temperature has essentially reached the optimum temperature for catalytic cleaning.

Many possible variations are conceivable in the invention. In particular, the measures shown in FIGS. 1-6 can be combined with one another as desired. The process can be used for many heat treatment processes with similar advantages, in particular also for roasting processes, for example for the heat treatment of metal sulfides, in particular lead, zinc and nickel in an oxidizing atmosphere.

Claims

claims 1. Process for the heat treatment of a pourable material to be treated in a treatment bed, in particular for sintering metallic materials with the addition of fuels with a high carbon content, the material to be treated being poured onto a movable grate in a predetermined minimum layer thickness; the grate moves with the treatment bed through a treatment area and the treatment bed when entering the Treatment area is ignited from a first side; thereafter, with supply of oxygen and a pressure drop from the ignition side through the treatment bed, a combustion zone starting from the ignition side is formed in the treatment bed; and the combustion zone is displaced in the course of the further transport of the material to be treated under the influence of the pressure gradient in the direction of a second side of the treatment bed opposite the first side in order to successively heat-treat the material to be treated, exhaust gases escaping from the treatment bed being removed, characterized in that a Counter-burning process is initiated by igniting the material to be treated from the second side of the treatment bed after the treatment bed has been transported a predetermined distance in the treatment system and the Firing zone has reached a certain depth of penetration in the treatment bed, but before the firing zone has broken through to the second side of the treatment bed; and that the treatment bed at the second ignition point is exposed to an opposite pressure drop, so that a second combustion zone is built up from the second side, which is driven through the treatment bed to such an extent that the fuel particles not yet detected by the first combustion zone are burned in it and the entire treatment bed is sintered through. 2. Process for the heat treatment of a pourable material to be treated in a treatment bed, in particular for sintering metallic materials with the addition of fuels with a high carbon content, the material to be treated being poured onto a movable grate in a predetermined minimum layer thickness; the grate with the treatment bed is moved through a treatment area and the treatment bed is ignited when entering the treatment area from a first side; thereafter, with supply of oxygen and a pressure drop from the ignition side through the treatment bed, a combustion zone starting from the ignition side is formed in the treatment bed; and the combustion zone is displaced in the course of the further transport of the material to be treated under the influence of the pressure gradient in the direction of a second side of the treatment bed opposite the first side in order to successively heat-treat the material to be treated, exhaust gases escaping from the treatment bed being removed, in particular according to claim 1 , characterized in that the exhaust gases emerging from the treatment bed in at least one phase of the treatment process are preferably fed together with the gases required for ignition when the treatment bed is ignited to remove pollutants in the ignition zone and / or when flowing through the treatment bed under the influence of the pressure drop in destroy the burning zone and / or adsorb in an adsorption layer formed in the treatment bed. 3. Process for the heat treatment of a pourable material to be treated in a treatment bed, in particular for sintering metallic materials with the addition of fuels with a high carbon content, the material to be treated being poured onto a movable grate in a predetermined minimum layer thickness; the grate with the treatment bed is moved through a treatment area and the treatment bed is ignited when entering the treatment area from a first side; thereafter, with supply of oxygen and a pressure drop from the ignition side through the treatment bed, a combustion zone starting from the ignition side is formed in the treatment bed; and the combustion zone is displaced in the course of the further transport of the material to be treated under the influence of the pressure gradient in the direction of a second side of the treatment bed opposite the first side in order to successively heat-treat the material to be treated, exhaust gases escaping from the treatment bed being removed, in particular according to claim 1 or 2, characterized in that the exhaust gases emerging from the treatment bed in the final phase of the treatment process are collected and passed through the treatment bed together with the gases required for heat treatment in the initial and / or middle phase of the treatment process in order to remove pollutants in the furnace ¬ destroy zone and / or adsorb in an adsorption layer formed in the treatment bed behind the firing zone. 4. Process for the heat treatment of a pourable material to be treated in a treatment bed, in particular for sintering metallic materials with the addition of fuels with a high carbon content, the material to be treated being poured onto a movable grate in a predetermined minimum layer thickness; the grate with the treatment bed is moved through a treatment area and the treatment bed is ignited when entering the treatment area from a first side; thereafter, with supply of oxygen and a pressure drop from the ignition side through the treatment bed, a combustion zone starting from the ignition side is formed in the treatment bed; and the firing zone in the course of the further transport of the material to be treated under the influence of the pressure gradient in the direction of a second side of the treatment opposite the first side. Lung bed is shifted to successively heat-treat the material to be treated, exhaust gases emerging from the treatment bed being removed, in particular according to claim 2 or 3, characterized in that the movable grate is covered with a multi-layer system consisting of a first layer of a highly adsorbable material , for example made of granular or lumpy coke or coal, an overlying layer forming a temperature barrier made of essentially inert material, in particular of sintered material, and a third layer made of the material to be treated; that the multilayer system is ignited on the third layer side; and that the firing zone is allowed to migrate to the second layer while maintaining the pressure gradient during ignition, the first layer consisting of highly adsorbable material until the treatment material in the third layer is completely burned out as a filter layer for the exhaust gases released in the firing zone is used. 5. The method according to any one of claims 1 to 3, characterized ge indicates that the material to be treated is deposited and distributed on a substantially inert sintered material layer and is supplied to the ignition point on the grate such that the ignition of the material to be treated on the (inert) Side facing away from the sintered material layer begins. 6. Process for the heat treatment of a pourable material to be treated in a treatment bed, in particular for sintering metallic materials with the addition of carbonaceous materials Fuels, the material to be treated being poured onto a movable grate in a predetermined minimum layer thickness; the grate moves with the treatment bed through a treatment area and the treatment bed when entering the Treatment area is ignited from a first side; thereafter, with supply of oxygen and a pressure drop from the ignition side through the treatment bed, a combustion zone starting from the ignition side is formed in the treatment bed; and the combustion zone is displaced in the course of the further transport of the material to be treated under the influence of the pressure gradient in the direction of a second side of the treatment bed opposite the first side in order to successively treat the material to be treated, exhaust gases escaping from the treatment bed being removed, in particular after one of claims 1 to 5, characterized in that the treatment bed before and / or in the treatment area is enriched with pollutant-adsorbing agents and pollutants are retained in the treatment bed under the influence of the pollutant-adsorbing agents in such a way that in at least one, preferably the last one Phase of the treatment process, the concentration profile of at least one type of pollutant is adapted to the profile of the exhaust gas temperature and in particular the associated profile maxima of exhaust gas temperature and type of pollutant (s) are overlapped and that in this phase Exhaust gases emerging from the treatment bed are collected. 7. The method according to any one of claims 1 to 6, characterized in that the pollutant-adsorbing agent with the Treatment items are mixed and then poured onto the grate before they are introduced into the treatment area. 8. The method according to one of claims 1 to 7, characterized in that the pollutant-adsorbing agents are present in the lower region of the treatment bed in a higher concentration than in the upper region of the treatment bed. 9. The method according to any one of claims 1 to 8, characterized in that the collected exhaust gases are catalytically cleaned using their high temperature. 10. The method according to any one of claims 1 to 9, characterized ge indicates that the exhaust gases emerging from the treatment bed in the last phase are subjected to a particle separation, which is preferably preceded by the catalytic cleaning. 11. The method according to claim 9 or 10, characterized gekennzeich¬ net that the exhaust gas is cleaned after the catalytic cleaning with adsorbent and water. 12. The method according to any one of claims 1 to 11, characterized in that as a pollutant-absorbing agent kohl¬ containing, pourable material e.g. Coke greeting and / or activated coke is used. 13. Arrangement for the heat treatment of granular or pourable items to be treated, in particular for sintering metallic materials with the addition of fuels containing a large amount of carbon, with a treatment system (1), a treatment bed transport device (5) which places the treatment bed on a grate has a belt (7) moving horizontally through the treatment system, a device (9) for feeding the material to be treated (24) onto the grate before its point of entry into the treatment system, an ignition furnace (3) arranged in the region of the treatment system inlet Ignition of the treatment bed on a first side and an exhaust gas extraction device (11) effective on the second side of the treatment bed opposite the first side, characterized in that a second ignition furnace (4) is arranged in the outlet-side end section of the treatment system (1) the treatment bed ignites on the second side thereof; and that a separate differential pressure generating system (6, 8, 10) is effective in the area of the second ignition furnace Pressure drops from the second to the first side of the treatment bed are generated. 14. Arrangement for the heat treatment of granular or pourable material to be treated, in particular for sintering metallic materials with the addition of fuels containing a large amount of carbon, with a treatment system (lj, a treatment bed transport device (5) which places the treatment bed on a grate approximately horizontally belt (7) moving through the treatment plant, a device (9) for placing the treatment good (24) on the grate before its point of entry into the treatment plant, an ignition furnace (3) for ignition arranged in the area of the treatment plant inlet of the treatment bed on a first side and an exhaust gas extraction device (11) effective on the second side of the treatment bed opposite the first side, characterized in that three separate feed devices (18, 15, 9) are provided, a first of which (18) pour a pourable adsorbent (20) onto the grate t, a second (15) a non-reactive layer (22) serving as a temperature barrier, e.g. Finished sinter, gives up as a second layer and the third (9) pours up the material to be treated (24). 15. Arrangement for the heat treatment of granular or pourable treatment material, in particular for sintering metallic materials with the addition of high carbon fuels, with a treatment system (1), a treatment bed transport device (5) which places the treatment bed on a grate has a belt (7) moving horizontally through the treatment system, a device (9) for placing the material to be treated (24) on the grate before it enters the treatment system, an ignition furnace (3) arranged in the region of the treatment system inlet Ignite the treatment bed on a first side and one on the opposite side. set second side of the treatment bed effective exhaust gas extraction device (11), in particular according to claim 13 or 14, characterized in that a separate exhaust gas collection device (6 ') is arranged at least in the outlet-side end section of the treatment system; and that a return line (8) connects the separate exhaust gas collecting device (6 ') to the ignition furnace (3) in order to lead exhaust gas drawn off from the outlet-side end section of the treatment system into the ignition furnace (3). 16. Arrangement for the heat treatment of granular or pourable material to be treated, in particular for sintering metallic materials with the addition of fuels containing a large amount of carbon, with a treatment system (1), a treatment bed transport device (5) which places the treatment bed on a grate has a belt (7) moving horizontally through the treatment plant, a device (9) for placing the treatment good (24) on the grate before its point of entry into the treatment plant, an ignition furnace (3) arranged in the region of the treatment plant inlet Ignition of the treatment bed on a first side and an exhaust gas extraction device (11) effective on the second side of the treatment bed opposite the first side, in particular according to claim 13 or 14, characterized in that in the outlet-side end section of the treatment system a separate exhaust gas collection device ( 6 ') is arranged that a mixing device ( 14, 6) is provided for supplying the combustion air for the inlet-side and / or middle section of the treatment system (1); and that the mixing device is connected to the separate exhaust gas collecting device (6 ') in order to distribute exhaust gas withdrawn from the outlet-side end section of the treatment system through the treatment bed. 17. Arrangement according to one of claims 13 to 16, characterized in that an exhaust gas collection device is arranged in the end section of the treatment area and is coupled via a first exhaust line (26) to a catalytic cleaning reactor (28). 18. Arrangement according to one of claims 13 to 17, characterized in that the exhaust gas collecting device is followed by a first particle separator (27), in particular an electrostatic filter in the exhaust gas stream. 19. Arrangement according to one of claims 13 to 18, characterized in that the catalytic cleaning reactor (28) is followed by an adsorbent reactor (30). 20. The arrangement according to claim 19, characterized in that the adsorbent reactor (30) is followed by a second particle separator (31), in particular a fabric filter. 21. Arrangement according to one of claims 13 to 20, characterized in that the exhaust gas flow from the Abgassammelvorrich- device via the catalytic cleaning reactor (28) to the ignition furnace (3) is returned in the front section of the treatment area. 22. Arrangement according to one of claims 13 to 21, characterized in that a separate exhaust gas collecting device for collecting the exhaust gases is arranged in the front and middle sections of the treatment area and via a second exhaust line (25) with a third particle separator (25 '), in particular an electrostatic filter is connected. 23. Arrangement according to one of claims 13 to 22, characterized in that the second discharge line (25) is connected to the first discharge line (26) behind the electrostatic filter.