EP0693306A1 - Method for fabrication of secondary row materials from waste - Google Patents

Abstract

Process to recycle waste materials by bringing them directly, along with at least one additive material contg. a glass or ceramic forming combustible substance, into the flame of a burner operating with oxygen or a gas contg. a higher amt. of oxygen than air. A combustion gas and molten combustion particles are formed, which are transformed in subsequent cooling into a glass like and/or basalt like and/or ceramic like mass. The waste materials are mixed with the combustible substance to a mixt. of mixing ratio 20-40 to 40-80 wt.%, and the mixt. is burnt in the flames at 1250-1500 deg.C and ambient pressure.

Description

The invention relates to a method for recycling waste materials by introducing the waste materials together with at least one self-combustible additive containing glass and / or ceramic-forming substances directly into the flame of a burner operated with technical oxygen or with a gas having a higher proportion of oxygen than air, whereby a combustion gas and molten combustion particles are formed, which are subsequently converted into a glass-like and / or basalt-like and / or ceramic-like mass by cooling.

Landfills are becoming increasingly scarce and environmental regulations are becoming increasingly difficult to dispose of, particularly industrial waste. The waste is usually burned or deposited in landfills. The valuable materials contained in the waste are irretrievably lost.

The disposal of residues resulting from waste treatment is particularly problematic. If waste is incinerated, for example, furnace slag and boiler dust are left over as residues. Waste incineration is usually followed by flue gas cleaning, in which further solid residues are created. Depending on the type of flue gas cleaning, this includes filter dust, evaporation residues from flue gas washing water or flue gas cleaning residues. Airborne dusts that are retained in filter systems must be disposed of in a manner that is safe from leaching due to their elutability.

In particular, the residues from hazardous waste incineration plants represent a significant disposal problem. Laws make it increasingly difficult or even forbidden to deposit the residues in above-ground landfills. Disposal in underground landfills or as backfill material in hard coal mining requires lengthy geological investigations and approval procedures and is uneconomical and ecologically unsatisfactory.

There has been no lack of attempts to make the waste incineration residues mentioned inert. For example, glazing these residues is a technique that has been discussed recently. It should be possible to convert filter dusts into inert, eluate-resistant glasses. The disadvantage of this process is a high energy input, which increases due to the necessary additives.

Various methods are known from glass production for converting mixtures of substances that can be glazed into a glass matrix. For this purpose, the substance mixtures must consist predominantly of silicon oxide, calcium oxide and aluminum oxide.

For example, in the production of bulk glasses, it is customary to melt the raw materials required for glass production in a melting furnace that is indirectly heated with fossil fuels. However, transferring this known method to the vitrification of waste materials is problematic since large exhaust air flows occur which can contain dangerous pollutants. Effective removal of these pollutants is made difficult or very expensive by dilution of the exhaust air streams by combustion gases.

In addition, no residues from special waste incineration plants can be processed with such a method, since these residues contain hardly any glass-forming substances.

From DE-OS 41 11 917 a method for recycling combustible residues contaminated with heavy metals by partial oxidation is known. As residues, e.g. B. sewage sludge, which are fed together with gypsum from flue gas desulfurization plants an oxygen burner. The substances used are partially oxidized under increased pressure, producing a CO and H₂-rich raw gas. The mineral components of the sewage sludge are transferred to a molten slag, which solidifies into granules after cooling in a water bath.

The present invention has for its object to provide a process for the recycling of waste materials with which the waste materials can be converted into an unrestrictedly usable product in an economical manner.

This object is achieved in that the waste materials are mixed with the self-combustible additive to form a starting material mixture with a mixing ratio of waste materials to additive of 20 to 40 to 80 to 60 percent by mass, and the starting material mixture in the flame at temperatures of 1250 to 1500 ° C and ambient pressure is completely burned.

With the proposed procedure, an unrestricted return to the economic cycle is opened for waste materials for which there are only limited or no recycling possibilities.

The invention is based on the knowledge that a particularly effective conversion of the waste into a basalt-like product, in which the pollutants contained in the waste are safely enclosed, can be achieved if the waste in a certain mixing ratio together with glass-forming substances directly into the flame a burner, in particular a solid burner provided for the combustion of solids, and are completely oxidized at ambient pressure. Since the glass-forming reactions take place directly in the flame, much higher sales are achieved compared to conventionally directly or indirectly heated melting furnaces.

The use of technical oxygen or a gas enriched with oxygen, in particular air enriched with oxygen, ensures that the required high temperatures are maintained.

The technical oxygen is expediently produced in an air separator or a pressure swing adsorption system (PSA system).

Due to pronounced turbulence in the flame and in the vicinity of the flame, such substances that are not incorporated into the melt can be separated off much better than would be possible with directly or indirectly heated melting furnaces. The extensive separation of these non-glass-forming substances, which includes in particular anions such as fluoride, chloride and sulfate and volatile metals such as cadmium, zinc and mercury, enables a very high product purity of the glass. The recycling options are significantly improved by the excellent product quality achieved.

The use of technical oxygen or a gas or gas mixture containing a higher proportion of oxygen than air also minimizes the amount of exhaust gas that is produced, as a result of which the exhaust gas cleaning system is significantly reduced and thus more economical.

The combination of technical oxygen with the solid fuel burner also enables the use of low-energy additives for automatic melting in the flame without the addition of additional fuels.

Residues from waste treatment plants that are contaminated with heavy metals, not leach-resistant, and possibly also with organic contamination, are preferably used as waste materials.

Such substances should be used as additives that are self-combustible and ensure the desired product properties. Substances that contain silicon and aluminum compounds are particularly suitable. Low calorific value waste and / or residues with glass and / or ceramic-forming ash content are particularly advantageous.

Dry sewage sludge, which has to be disposed of anyway, is particularly suitable for this. The energy required for melting the waste can only be obtained from the sewage sludge incineration. An additional supply of another fuel to the burner is not required energetically after the start-up phase. The sewage sludge contains glass-forming substances in sufficient quantities to be able to produce a glass-like product of high quality even with residues from special waste incineration plants that contain little glass-forming substances. Additional emissions are avoided when sewage sludge is used as an additive, since the sewage sludge will have to be incinerated anyway in the future.

Another option is to use dry pyrolysis residues as additives. Pyrolysis residues have a calorific value which is too low for conventional combustion, but which is completely sufficient for the melting process according to the invention using the burner operated with technical oxygen or with oxygen-enriched gas. In addition, pyrolysis residues contain enough glass-forming substances so that an unrestrictedly usable glass-like product can be produced from the waste to be disposed of.

Incompletely burnt out lignite ashes can also be used as additives. Lignite ashes are comparable to pyrolysis residues in terms of calorific value and the content of glass-forming substances.

According to a further variant of the method according to the invention, the rust diarrhea of domestic waste incineration plants or finely comminuted shredder waste can also be used as an additive.

A further development of the inventive concept provides, in addition to the additive containing glass-forming and / or ceramic-forming substances, to introduce at least one additional additive, in particular asbestos waste, into the flame of the burner, which improves the quality of the glass-like melt. The proportion of this additive in the educt mixture should preferably not exceed 10 percent by mass.

The starting material mixture is expediently completely burned in a rotary kiln in the flame of the burner. This ensures long residence times of the exhaust gases and the resulting melt. The rotary kiln is preferably designed with a small cross section and a large axial length so that a sufficient residence time for the waste and the additives is achieved. The melted reaction products are deposited on the furnace wall. The substances that are not incorporated into the glass-like melt accumulate in the exhaust gas and are drawn off via a flue gas treatment device, which preferably consists essentially of a quench, a hot gas dust separation and a harmful gas separation. The resulting melt is preferably discharged in the liquid state through a discharge opening of the rotary kiln.

Instead of a rotary kiln, a rotary drum kiln or preferably a standing cyclone can also be used.

The waste and additives are expediently introduced into the flame of the burner by means of a gas. Low-nitrogen gases are preferably used, as a result of which excessive nitrogen oxide formation is avoided. A fuel gas, in particular natural gas, propane or butane, can also be used.

According to a further development of the inventive concept, contaminated gas, for example from landfill sites, or polluted exhaust air, for example from tank systems, is used to blow the waste and additives into the flame. Such gases must be disposed of anyway, so that two disposal problems or when using substances to be disposed of as a result of simultaneous treatment with the waste Additives, such as sewage sludge or pyrolysis residues, can even solve three disposal problems at the same time.

A dispersing and metering device is preferably used to blow the waste and additives into the flame of the burner.

The method according to the invention is suitable for the treatment of all conceivable waste, in particular industrial waste and especially residues from waste incineration plants. The process is particularly suitable for treating residues from hazardous waste incineration plants. Such residues, e.g. Filter dusts from the flue gas cleaning of the special waste system have high pollutant concentrations and can only be treated with conventional glazing processes with increased effort. The filter dust contains hardly any glass-forming substances. With the method according to the invention, even such residues can be used economically.

There are a number of advantages associated with the proposed method. The use of technical oxygen or gas enriched with oxygen significantly reduces the amount of exhaust gas, which significantly reduces the size of the exhaust gas cleaning system. In addition, after the start-up phase, no additional fuel in addition to the additives is energetically required. Additional emissions are prevented, since additives are used that have to be disposed of anyway. Since the glass-forming reactions take place directly in the flame, significantly higher conversion rates are achieved compared to conventional furnace heating. The investment costs are kept low by using a simple system that is not susceptible to faults. The selection and quality of the resulting glass-like products can be determined in a simple manner by varying the quantitative ratio of waste and additives and a suitable choice of these additives and, if appropriate, further additives.

The invention will be explained in more detail below using an exemplary embodiment:
Airborne dusts retained in filter systems of a special waste incineration plant, which contain pollutants such as mobilizable heavy metals, easily soluble neutral salts and organic pollutants, such as dioxins, furans fed to a rotary kiln. The rotary kiln has a ratio of axial length to diameter of at least 5 (L / D ≧ 5). A solid fuel burner for technical oxygen is used in the rotary kiln. For example, an air separator or a PSA system can be provided for the oxygen supply.

The fly dusts are mixed intensively outside of the rotary kiln with decayed, dry sewage sludge from an industrial sewage treatment plant. The resulting mixture of substances is blown into the flame of the solid fuel burner by means of a dispersing device at a flow rate of 9 m / s by means of exhaust air contaminated with pollutants, which accumulates in a pendulum gas device of a nearby tank farm for liquid hazardous waste. Due to the high temperature in the flame of over 1300 ° C, the substances contained in the filter dusts and the glass-forming substances in the sewage sludge, in particular silicon oxide, calcium oxide and aluminum oxide, react with a high reaction rate, whereby the filter dusts are incorporated into a glass-like matrix . This creates a product similar to basalt, in which the pollutants are sealed against leaching.

The feed materials are entrained by the gas flow prevailing in the rotary kiln, react on the path that runs axially to the rotary kiln, and the melted products finally deposit on the furnace wall. The melt thus formed is continuously discharged through a discharge opening of the rotary kiln. Depending on the intended use of the basalt-like product, different melting treatment processes can follow (e.g. defined cooling in specified time units and / or mechanical processing).

• Anionen wie Fluorid, Chlorid und Sulfat sowie flüchtige Metalle wie Cadmium, Zink und Quecksilber werden über das Abgas ausgetragen.
• Die zur Glasbildung befähigten Stoffe werden im flüssigen Zustand abgezogen.

The implementation of the relatively small particles enables a significantly improved mass and heat exchange compared to the previous processes. On the one hand, this means that the formation of basalt-like structures is significantly improved. On the other hand, this procedure enables a better separation into the melted and gaseous phase:

• Anions such as fluoride, chloride and sulfate as well as volatile metals such as cadmium, zinc and mercury are discharged through the exhaust gas.
• The substances capable of forming glass are removed in the liquid state.

It should be mentioned in this connection that the energy and material conversions are improved by the advantages described.

The flue gas cleaning essentially consists of a quench, a hot gas dust separator, a gas scrubber, a fixed bed adsorber and a blower.

The glass-like products resulting from the process can be used in road and path construction, for recultivation purposes, as additives in the concrete industry and the brick-making industry, as inert mining additives or as thermal insulation material.

Claims (7)

Process for recycling waste materials by introducing the waste materials together with at least one self-combustible additive containing glass and / or ceramic-forming substances directly into the flame of a burner operated with technical oxygen or with a gas having a higher oxygen content than air, whereby a combustion gas and Molten combustion particles are formed, which are subsequently converted into a glass-like and / or basalt-like and / or ceramic-like mass by cooling, characterized in that the waste materials with the self-combustible additive form an educt mixture with a mixing ratio of waste materials to additive of 20 to 40 to 80 up to 60 mass percent are mixed, and the starting material mixture is completely burned in the flame at temperatures of 1250 to 1500 ° C. and ambient pressure. Method according to claim 1, characterized in that residues from waste treatment plants are used as waste materials which are heavy metal contaminated, not leach resistant, and possibly also organic contaminated. A method according to claim 1 or 2, characterized in that a self-combustible additive is a low calorific value waste or residual material with glass and / or ceramic-forming ash content, in particular dry sewage sludge and / or dry pyrolysis residue and / or incompletely burned out lignite ash and / or finely shredded shredder waste, be used. Method according to one of claims 1 to 3, characterized in that at least one further additive, in particular asbestos waste, preferably in an amount of up to 10 percent by mass, is added to the educt mixture, which improves the quality of the glass and / or ceramic-like mass. Method according to one of claims 1 to 4, characterized in that the starting material mixture is completely burned in a rotary kiln. Method according to one of claims 1 to 5, characterized in that the starting material mixture is introduced into the flame of the burner by means of a nitrogen-poor gas. Method according to one of claims 1 to 6, characterized in that the starting material mixture is introduced into the flame of the burner by means of a gas to be disposed of.