SK279573B6 - Process and plant for the thermal disposal of waste - Google Patents

Abstract

Waste is, without oxygen supply, carbonated at temperature app. 300 - 700 degrees Celsius, thus producing a gas and residue material which is divided into a fine portion and coarse portion, with the proviso that the coarse portion is excluded, and the fine portion and gas originating in the low-temperature carbonization is burnt at temperatures higher than 1200 degrees Celsius thus forming flue and molten slag. The fine portion and gas originating in the low-temperature carbonization is burnt together with dust waste and/or liquid waste. A plant for processing the above-described method consists of a reactor (2) for the low-temperature carbonization; discharge device (3) for the solid residue material connected to the reactor (2); outlet branch (4) delivering gas from the low-temperature carbonization and fine dust from a combustion chamber (8); sorting device (20) for dividing the residue material to fine and coarse portions; and a pipe (21) for transporting fine portion to the combustion chamber (8). A feed piping (33) for dust dry waste and/or a feed piping (32) for liquid waste is connected to the combustion chamber (8).

Description

Technical field

The invention relates to a process for the thermal treatment of waste, wherein the waste is virtually oxygen-free at a temperature of about 300 ° C to 700 ° C to form a gas and a residual material, the residual material being divided into a fine and a coarse fraction, it eliminates the coarse fraction and at temperatures above 1200 ° C, the fine fraction and the gas from the low-temperature carbonization are burned to form flue gases and molten slag. The invention further relates to an apparatus for carrying out the method.

BACKGROUND OF THE INVENTION

Such a heat treatment plant is known, for example, from DE-PS 24 32 504. With this plant, waste (e.g. domestic waste) is carbonized at a temperature between 300 and 600 ° C without air inlet and the gas resulting from this process is continuously fed. an incandescent coke bed formed from low-temperature carbonization coke and preheated fresh air. In the coke bed, the gas from low-temperature carbonization is converted into high-energy flue gas. In such a process, only as much oxygen (air) is added as is necessary to maintain the necessary temperature in the coke bed. Not only low-temperature carbonization coke is fed to the coke bed, but also possibly a high-quality carbon carrier such as brown coal or charcoal. The flue gas obtained contains little or no organic pollutants due to the long molecular chain splits caused by the passage through the combustion chamber and the incandescent coke bed. The flue gas may be cooled in a heat exchanger and subsequently cleaned in a gas scrubber. Then the flue gas can be used either for heating or for the operation of internal combustion engines. A peculiarity of such a waste heat treatment device is that it is usually not in the immediate vicinity of the appliance of this flue gas. Therefore, in addition to the cost of realizing the installation, there is an additional cost of realizing a voluminous gas network for each appliance. More importantly, however, the residual solids from the low-temperature carbonization are landfilled. However, there is a danger that the pollutants contained in these residual substances, such as heavy metal compounds, will be rinsed or leached over time and will penetrate into groundwater or watercourses. In addition, the thermal energy contained in these residual substances is lost.

In order to overcome these disadvantages, it is proposed in GB 1 562 492 to separate the residuals from low-temperature carbonization after grinding with a sieve into a coarser fraction (inorganic substances such as metals, ceramics, glass) and a fine fraction (higher fraction of hydrocarbon-containing components). Metals are separated from the coarser fraction. The finer fraction, together with the coal in the further crushed form, is combusted in a combustion chamber and in this way it is thermally utilized. The low-temperature carbonization gas is also fed to the combustion chamber from which the high-boiling oils and tars are first removed from the condenser. It should be noted that the combustion chamber in the known apparatus is merely the focus of the known coal combustion apparatus, and that the combustion chamber is part of the steam generator. Due to the cooling of the combustion chamber walls used in such a device, there is a danger that the pollutants from both low-temperature carbonization gas combustion and low-temperature carbonization residual combustion may at least partially escape from the combustion equipment used and get into the environment (into air, special landfills, soil, water). This applies, for example, to organic pollutants, but also to heavy metal oxides such as cadmium, zinc, mercury and thallium oxide. The use of a combustion chamber for residual substances is not mentioned here at all.

DE 38 11 820 A1 discloses a thermal waste disposal plant comprising a pyrolysis reactor in which waste is carbonized. In the pyrolysis reactor, low-temperature carbonization gas and residual pyrolysis are produced. This residue is divided into a fine and coarse fraction. The fine portion of the residual material, together with the low-temperature carbonization gas, is fed to a combustion chamber where it is combusted. According to DE 38 11 820, a part of the residual substances from the combustion chamber, for example ash from the dust filter, is returned to the combustion chamber.

The aim of any waste treatment must be to minimize pollution of the environment.

In particular, when low heating wastes are processed, the known plants do not guarantee automatic and complete waste incineration, so that unburnt pollutants can remain.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a process for the thermal treatment of waste of this kind, in particular the treatment of low-calorific waste, so that both organic and inorganic pollutants are virtually eliminated and residual materials are disposed of as little as possible. Furthermore, an inexpensive device must be provided for carrying out this method. Equally, the investment costs must be as low as possible and the overall efficiency of the equipment as high as possible.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a process for the thermal treatment of waste in which the waste is virtually oxygen-free at about 300 ° C to 700 ° C to form a gas and a residual material, the residual material being separated into a fines and a coarse fraction. eliminates the coarse fraction and at temperatures above 1200 ° C, the fine fraction and gas from the low-temperature carbonization are burnt, so that flue gases and molten slag are formed according to the invention which is based on the fine fraction and gas from the low-temperature carbonization and / or liquid waste.

According to a preferred embodiment, the waste is contaminated soil and / or contaminated coarse waste, and / or pasty waste, and / or liquid waste, and / or inert waste. The fine waste is preferably further comminuted. The fines and / or the dry dry waste and / or the liquid waste and the low-temperature carbonization gas are preferably combusted together with the auxiliary fuel.

In this case, it is advantageous if dust is separated from the flue gas and the dust is sealed into slag. For temperature control, the cleaned flue gas is admixed to a low-temperature carbonization gas for combustion. The fine portion is temporarily stored prior to incineration. It is preferably excluded from the flue gas

EN 279573 Β6 fly ash, enriched with heavy metal oxides, and used as a raw material for recycling heavy metal oxides. The combustion chamber is preferably partially cooled.

The apparatus for carrying out the process according to the invention is provided with a low-temperature carbonization reactor, which converts waste into gas and solid residue, with a solid-residual discharge device connected to the low-temperature carbonization reactor, with an outlet connection for the low-temperature carbonization and fine dust discharge. and a combustion chamber into which the low-temperature carbonization gas and fine dust are supplied, with a separator for separating the residual substances into coarse fractions and fines arranged at the discharge side of the residual substance from the discharge device, and with a fine-line conduit leading to a combustion chamber, the essence of which is that the combustion chamber is connected to an inlet pipe for dry dry waste and / or an inlet pipe for liquid waste.

Further advantageous embodiments of the invention are apparent from the subclaims.

The residual material separator connected to the low-temperature carbonization reactor apparatus carries out the separation or special screening of the residual material to a coarse fraction, for example with a grain size greater than 5 mm, and to a fine fraction, for example with a grain size of less than 5 mm. The fine dust occurring in the carbonization reactor, together with the low-temperature carbonization gas, is fed directly to the combustion chamber. By separating (for example by sieving) the residual substance from the low-temperature carbonization, separating the non-combustible components (such as stones, glass shards, porcelain residues, metal pieces) that steam to a coarse fraction from the practically combustible components (low-temperature carbonization coke of wood, parts) plastics, carbon fibers, but also fine particles such as glass or stone dust, etc.), which belong to the fines. This virtually complete separation of the non-combustible substances from the still further combustible substances, following the low-temperature carbonization process in the reactor, is a prerequisite for the combustible substances to be further burned virtually emission-free. At the same time, it is achieved that the non-combustible metals, stones, glass discharged from the low-temperature carbonization reactor remain in non-oxidized form, that is, they remain well usable.

Finally, a separate mixture of the low-temperature carbonization residue and the fine particles will generate additional heat as they burn.

According to a preferred embodiment of the invention, the fines can first be separated from the coarse particles by screening and / or blowing (pneumatic sorting) from the residual material separator. At the same time, the heavier coarser fractions remain difficult to be deposited and can therefore be excluded separately. This separation method is reliable and inexpensive. Only blowers with higher pressure from the flue gas or air duct are required for blowing.

The combustion chamber emitting the molten slag is a combustion chamber of conventional construction. Combustible materials are fed into the pipeline or other transport equipment.

According to a preferred embodiment of the invention, the combustion chamber emitting the molten slag can be sized as a high temperature combustion chamber, i.e. to a wall temperature above 1200 ° C and can also be operated at this temperature. At such a high temperature, all organic pollutants disintegrate, occur in the molten state and can be removed. Preferably, also fine particles are fed to the high temperature combustion chamber with the residual substances from the low-temperature carbonization and the low-temperature carbonization gas. Powdered dry waste and liquid waste such as chemical solutions can be directly fed into the combustion chamber. Additional fuel such as fuel oil or natural gas may also be supplied to the burner of the combustion chamber if the calorific value of the waste is not sufficient for combustion. The low-temperature carbonization gas combustion chamber and the low-temperature carbonization residual combustion chamber may also be different combustion chambers. However, both can be designed as melting combustion chambers. The harmful gases still contained in the flue gas can be separated in a conventional flue gas cleaning plant.

The apparatus described and the method described are enormously suitable for the recovery of waste from both a substance and an energy point of view. Thus, with a small amount of residual emissions, an environmentally friendly waste treatment is generated. Halogenated hydrocarbons such as dioxin or furan and other organic pollutants contained in the low-temperature carbonization gas are disposed of. The solid residue from low-temperature carbonization is, as the surveys have shown, practically free of organic pollutants. However, it contains heavy metals such as cadmium and mercury which cannot be disposed of in landfills by the prior art. Organic pollutants, which are contained in the residual carbonation or in liquid form, are fed directly to the combustion chamber, burned there and are therefore destroyed.

The non-combustible solid constituents from the low-temperature carbonization are partly coarser form and can be further used under certain circumstances, partly transforming into molten slag. This is achieved by a sufficient length of elongation in the combustion chamber. The slag has a glassy form upon cooling. Substances contained in the slag, for example heavy metals, are confidently closed, for example they cannot be leached. Another advantage is the generation of only a small amount of waste gas and good thermal utilization of the supplied waste. By waste is meant in the present case waste materials and mixtures which, unlike domestic waste, are generally referred to as special waste, such as contaminated soil which may be contaminated with organic or inorganic pollutants, paste and liquid waste such as spent oil, contaminated wood, road accident waste, sludge of any kind, plastics and mixtures thereof.

The term low-temperature carbonization includes thermal decomposition of, in particular, organic substances at elevated temperatures, for example 300 to 700 ° C. Low-temperature carbonization is carried out without oxygen.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be explained in more detail by way of example with reference to the accompanying drawing, in which a plant for the thermal treatment of waste according to the invention is shown schematically.

SK 279573 Β6

DETAILED DESCRIPTION OF THE INVENTION

The figure shows the construction and mutual cooperation of the individual components of the waste heat treatment plant. A feed and metering device 1 is provided for supplying solid and pasty waste to the low-temperature carbonization reactor 2. For example, the solid waste may be contaminated soil, which must be removed. Contamination can be carried out with heavy metals, organic substances of any kind, or inorganic substances containing HCl or CN. The soil may come from industrial areas or may be contaminated by traffic accidents. This contaminated soil can be mixed upstream of the reactor 2 with, for example, pasty waste added thereto. In the exemplary embodiment, the reactor 2 is a conventional low-temperature carbonization drum operating at temperatures of 300 to 700 ° C and operating virtually oxygen-free, and besides the volatile gas, a solid residual material is formed by the low-temperature carbonization.

At the outlet or discharge side of the reactor 2 is connected a discharge device 3 provided with a low-temperature carbonization gas outlet neck 4 for its evacuation and a conveying device or a pipeline 5 for removing the solid residual material from the low-temperature carbonization. The low-temperature carbonization gas discharge line 6, which is connected to the discharge port 4 of the discharge device 3, is connected to the burner 7 of the high-temperature combustion chamber 8.

The high temperature combustion chamber 8 is designed for a temperature above 1200 ° C. It is uncooled for a certain length. Thus, it is ensured that the elongation of the introduced gas is sufficiently large in the temperature range above 1000 ° C (even on the walls) to cause thermal decomposition of the organic pollutants. The elongation length is approximately 1 to 5 seconds depending on the flame burn out. The combustion chamber 8 is provided with thermal insulation

9. A flue gas outlet pipe 10 is connected to the high-temperature combustion chamber 8, to which are connected in series in a specified sequence: a waste steam generating plant 11, a dust filter device 12, a flue gas cleaning device 13 and a stack 14. The burner 7 of the high temperature combustion chamber 8 is supplied with fresh air by a line 15 supplied with fresh air from the air inlet 15a via an air compressor 16. This fresh air may also be preheated, but this is not shown.

As can be seen in the figure, downstream of the dust filter device 12, at the connection point 17, a branch 18 is provided for the flue gas line 10 to which the flue gas recirculation line 19 is connected. Through this recirculation line 19, the flue gas, which has already been cooled and free of dust, is led to a temperature control or regulation on the burner 7 of the high temperature combustion chamber 8. Alternatively or additionally, the flue gas can be blown into the flame of the burner 7.

The exhaust gas vapor generating device 11 cools and transfers the transferred heat, for example to a steam power plant or district heating, or to another appliance for further use of steam.

The conveying device or the residual substance piping 5 from the discharge device 3 leads to a separating device 20. In this separating device 20, which is designed as network and / or pneumatic, the withdrawn residual substance from the low-temperature carbonization is divided into a fine and a coarse fraction. The fines include, for example, combustible fine dust and fine particles. The coarse fraction contains essentially non-combustible components such as stones, glass shards, porcelain remnants and metal parts.

The residual material separator 2 is provided with two discharge lines, namely a fine-line line 21 and a coarse-line line 22, in which the particle diameter is greater than 5 mm. The fine-line conduit 21 leads to the comminution device 23. From there, the conduit 24a leads to the buffer reservoir (intermediate storage) 25 for the comminuted fine component. A line 24b extends from the buffer reservoir 25. The duct 24b leads directly to the combined gas and dust burner 7. Instead, however, the duct 24c (shown in broken lines) may lead to a separate dust burner 7a. A dispensing device 26 is provided in the conduit 24b, for example in the form of a controlled means of transport, in order to control the temperature or the heating capacity of the combustion chamber 8.

The pipe 22 for the particularly heavy coarse portion leads to the container 37. Here, mostly stones, glass, ceramics, but also metal parts are collected. These substances may be reintroduced for reuse. The coarse pipe 22 may also lead to a metal separation device (not shown) in which pieces of metal are separated into stones and glass and ceramic fragments.

The fly ash (dust) present in the dust filter device 12 and possibly also in the waste steam plant 11 can be blown back through the return line 28 into the high-temperature combustion chamber 8, or fed back by dotted line 29 from the return line 28 to the reactor 2. For ventilation, the return line 28 is fed through the valve 30 and the compressor 31 to the outlet of the dust filter device 12 through the flue gas line 10. The dust can also be conveyed pneumatically by air.

Liquid wastes such as used oil and transformer oil can be directly fed to the burner. The liquid waste supply line 32 serves for this purpose. Dust and dry waste, for example pulverulent chemicals, can be fed directly through the waste duct 33 to the duct 24b, which typically terminates in the burner 7. In the event that the feed materials are not sufficient to operate the burner 7, the duct 34 can be fed to the burner 7. additional fuel such as fuel oil or natural gas.

The high temperature combustion chamber 8 is provided with a slag extraction 35. By this withdrawal 35, the molten slag is discharged into the water tank 36. Here it solidifies into the glassy granulate.

When heated in reactor 2, the waste is partially gasified at 300 ° C to 600 ° C. The gas produced and part of the fine dust generated are fed to the burner 7 of the high-temperature combustion chamber 8 through the discharge port 4 of the discharge device 3 and via the duct 6. There, the low-temperature carbonization gas containing organic and inorganic pollutants is combusted with fresh air. compressor 16 via line 15, i.e. with excess oxygen or air. In this case, the temperature in the high-temperature combustion chamber 8 is maintained above 1200 C. At this high temperature, all the long molecular chains of the organic pollutants disintegrate.

In order to keep the gases sufficiently long and stable at a temperature level of about 1200 ° C, a high-temperature combustion

In the illustrated embodiment, the chamber 8 is cooled in a certain length. The temperature control to a predetermined setpoint above 1200 ° C is performed (not shown) by a controller, for example by controlling the additional addition of low-temperature carbonization residual material by more or less vigorous blowing of cooled flue gas, even downstream of the waste steam generating device 11. downstream of the dust filter device 12, they branch off and are fed back to the burner via the recirculation line 19, or by additional combustion of additional fuel or heating liquid waste, for example, worn oil, etc.

As already mentioned, the cooled flue gas can be introduced directly into the burner 7 of the high temperature combustion chamber 8 in order to influence the temperature in the combustion chamber or the temperature of the flame. However, flue gases may also be blown alongside the flame. In the plant 11, steam is produced on the heating surfaces 37, which is used here as a process steam for internal and / or external appliances (not shown).

Built-in compressors 38 and 16 may be provided in the flue gas recirculation line 19 and in the fresh air line 15.

The solid residue discharged from the reactor 2 through the discharge device 3 is divided into a fines and a coarse fraction in the separator 20, the fines being fed to the comminution plant 23, which is in particular a roller crusher.

The return of the fly ash drawn from the dust filter device 12 and the waste steam generator 11 to the high temperature combustion chamber 8 via the return line 28 results in the fly ash being set up and mixed with the slag of the high temperature combustion chamber 8. In the same way, the fly ash is recycled via a branch 29 to the reactor 2 with the fly ash mixed with the residual material and transported to the combustion chamber 8 with either dusty gas or with the residual substance or its fines from low-temperature carbonization. The slag is discharged through a take-off 35 at the lower end of the high-temperature combustion chamber 8 and cooled in the water tank 36 of the wet deburring device. In the water bath, a granulate is formed which can be used for road construction and similar purposes.

By separating the coarse fraction of the low-temperature carbonization residue, in particular all metal fractions, from the fine fraction, i.e. from the combustible constituents and fine particles, it is achieved that the coarse fractions are available at this location of the plant before being introduced into the high-temperature combustion chamber. in a hygienically flawless and sorted condition and are therefore best suited for longer intermediate storage and for further transportation. The non-oxidized state of the metals is particularly advantageous for further processing. At the same time, stones, ceramic pieces and glass shards are separated from the residual material separator 20, which are then used without further problems or landfilled. This again contributes to the fact that the cost of the fines 23 is very low.

Heavy metals, such as mercury and cadmium, which have already evaporated at the carbonization temperature and are predominantly deposited on the low-temperature carbonization residue, are evaporated and oxidized in the high-temperature combustion chamber 8 during fine dust combustion. Heavy metal oxides are then partly present, such as cadmium oxide and zinc oxide, with fly ash as solids in plants 11 and 12, and partly, such as mercury oxide, in the precipitated solid downstream of the flue gas cleaning device 13.

By re-routing the fly ash through the return line 28 to the high-temperature combustion chamber 8, these heavy metals are recirculated until they are finally bound in the slag or discharged by the solid from the flue gas cleaning.

The nitrogen oxide content of the flue gas can be kept low in this waste heat treatment plant. This is conditioned by mixing the cold flue gases directly into the burner 7 or next to the burner 7 into the high temperature combustion chamber 8 (flue gas recirculation).

Claims (19)

PATENT CLAIMS CLAIMS 1. A process for the thermal treatment of waste, wherein the waste is virtually oxygen-free at a temperature of about 300 ° C to 700 ° C to form a gas and residual material, the residual material being separated into a fines and a coarse fraction, the coarse fraction and at temperatures above 1200 ° C, the fine fraction and gas of the low-temperature carbonization are burnt to form flue gases and molten slag, characterized in that the fine fraction and gas of the low-temperature carbonization are burnt together with the dust and / or liquid waste Method according to claim 1, characterized in that the waste is contaminated soil and / or contaminated coarse waste, and ^from or pasty waste and / or liquid waste or inert waste. Method according to claim 1 or 2, characterized in that the fine waste is further comminuted. Method according to one of claims 1 to 3, characterized in that the fine fraction and / or the dry waste dust and / or the liquid waste and the low-temperature carbonization gas are burnt together with the auxiliary fuel. Method according to one of Claims 1 to 4, characterized in that dust is separated from the flue gases and the dust is sealed into slag. Method according to one of Claims 1 to 5, characterized in that, in order to control the temperature, the cleaned flue gas is admixed with a low-temperature carbonization gas for combustion. Method according to one of Claims 1 to 6, characterized in that the fines are temporarily stored prior to combustion. Method according to one of Claims 1 to 7, characterized in that the flue gas, which is enriched with heavy metal oxides, is excluded from the flue gas and is used as a raw material for the recycling of heavy metal oxides. Method according to one of Claims 1 and 8, characterized in that the combustion chamber is partially cooled. Apparatus for carrying out the method according to claim 1, with a low-temperature carbonization reactor (2) that converts waste into gas and a solid residue, with a solid-residue discharge device (3) connected to the low-temperature carbonization reactor (2), an outlet orifice (4) for evacuating the gas from the low temperature carbonization; and And a combustion chamber (8) into which low-temperature carbonization gas and fine dust are supplied, with a separating device (20) for separating the residual substances into coarse and fines arranged on the discharge side of the discharge substance. the apparatus (3), and with a fine-line conduit (21) leading to the combustion chamber (8), characterized in that the combustion chamber (8) is connected to a dry-waste feed line (33) and / or an inlet pipe (32) for liquid waste. Apparatus according to claim 10, characterized in that an additional fuel supply pipe (34) is connected to the combustion chamber (8). Apparatus according to claim 10 or 11, characterized in that the separating device (20) for separating the residual matter is connected by a fine-line duct (21) to a comminution device (23) which is connected to the combustion chamber (8). Apparatus according to one of Claims 10 to 12, characterized in that the combustion chamber (8) is designed for temperatures above 1200 ° C. Apparatus according to one of Claims 10 to 13, characterized in that an intermediate storage tank (25) is connected to the intermediate storage on the duct (21, 24a, 24b, 24c) connecting the separating device (20) to the combustion chamber (8). fines. Apparatus according to claim 14, characterized in that a metering device (26) is provided in the duct (24b) connecting the separating device (20) to the combustion chamber (8) for controlling, in particular, the heating capacity of the waste production plant (11). steam. Device according to one of Claims 10 to 15, characterized in that a return line (28) is connected to the combustion chamber (8) for the return of the fly ash removed from the flue gas. Device according to one of Claims 10 to 16, characterized in that a recirculation pipe (19) is led from the flue gas line (10) to the combustion chamber (8). Device according to one of Claims 10 to 17, characterized in that a metering device (1) for supplying the non-crushed waste is connected to the low-temperature carbonization reactor (2). Device according to claim 18, characterized in that the combustion chamber (8) is provided with thermal insulation (9), in particular in the form of uncooled masonry.