WO1992016261A1 - Process for treating combustion residues and/or flue gas purification residues - Google Patents

Abstract

In a process for treating combustion residues and/or flue gas purification residues, the dried residues are homogenized to the most uniform possible particle size and microcoated with a paste or suspension of a thermoplastic, and the coated material is shaped and granulated with a plastic containing a thermoplastic in order to recover a reusable material. To obtain microcoatings and microgels, 10 to 15 wt. % of the homogenized residue, referred to the material used, is added to the paste or suspension made from a thermoplastic at a temperature of 80 to 85 C with vigorous stirring and the mixture is mixed for 10 to 15 minutes at the above-mentioned temperature. Paste or suspension containing 40 to 50 wt. % of polyvinyl chloride is used. The microcoated material is mixed with up to 30 wt. % of other plastics material, the mixture so formed is extruded at an operating temperature between 165 and 180 C and the strand formed is chopped into granules. The additive material for the extrusion can be a purified and crushed waste plastics material with a 35 % thermoplastics content.

Description

 Process for the treatment of combustion and / or flue gas cleaning residues.

The invention relates to a method for processing residues from combustion and / or flue gas cleaning systems, in particular fly ash.

« _Q The solid combustion residues, especially fly ash, that occur in considerable quantities during the combustion of fossil fuels continue to represent a considerable problem. It can be assumed, for example, that in a 750 MW power plant, depending on the operating conditions and the quality of the equipment used Fuel between 70,000 t and

l, o - 200,000 t ash, of which 60,000 to 150,000 t fly ash, in the Federal Republic of Germany a total of between 15 and 20 million tons a year, of which only about 6 million tons are reused, while the vast majority of about 10 million t is deposited, although it han hierbe is basically quite a valuable mineral raw material _0-punched. For example, between 300 and 500 million tonnes of comparable mineral materials are used in the construction industry alone, in relation to which the above-mentioned residues of the type mentioned occurring in the Federal Republic represent a negligible amount. Regardless of this and regardless of the significant with the deposit of this return

So far, no proceedings have become known about 25 related problems 9 _

which would allow a total and complex processing of these residues in such a way that they can be returned to the Wirtschaftskreisla.

- The present invention has for its object to provide a method that would allow a work-up of the mentioned combustion residues in such a way that they can be returned to the material cycle.

Q This object is achieved with the method described in claim 1.

The invention provides a method by means of which residues from the combustion of solid fossil fuels, which are to be regarded as a valuable secondary raw material, can be fed to an industrially valuable use, which means not only the use of primary raw materials, but also the use of them increasingly the environmental impact that occurs can be reduced. The simultaneous micro-coating, micro-gelation, i.e. the (complete Q coating of the individual grains of the material used, on the one hand achieves a hermetic encapsulation that excludes the exchange with the environment, and on the other hand gives the particles a consistency that enables them to be incorporated into other types of materials So there is not only the possibility of using it as a filler in the construction industry, there is also the possibility of (materially) integrating it into other plastic materials for the production of secondary granules. The process according to the invention thus allows the production of light mineral-filled plastic granules using waste materials, for which purpose the gelling micro-coated material is extruded together with other plastic material and the extruded strand is cut into granules. In this case, the added plastic material can also consist of waste plastic - cleaned and crushed for this purpose.

Due to the hermetic sealing of the individual grains of the residues due to the microgelling and thus preventing an exchange with the environment, it is in principle possible to use the residues without special preprocessing, in particular liberation from heavy metals and other environmentally harmful substances in the manner according to the invention. Regardless of this, however, the residues are advantageously worked up beforehand in such a way that they are ground to a grain size of 20 millimeters before the micro-coating and then by means of known physical and / or chemical processes from their constituents of heavy metal compounds, iron oxide and the water-soluble constituents (nitrate, sulfate, chlorine salts) are freed.

The invention is explained below on the basis of the flow diagram attached in the system.

The residues are collected in a large amount and then homogenized with air drying if necessary. Homogenization based on a larger amount has the purpose here partly that uniform conditions can be maintained for further processing over a longer period of time.

The homogenized material can now either - in another? known manner - to remove the heavy metals, iron oxides, dioxin compounds and water-soluble sal contained in it chemically processed (left branch) and / or encapsulated in the manner according to the invention by microgelation, for which purpose the material is a paste made of thermoplastic Plastic, for example PVC paste, in a quantity of 10 to 15% by weight corresponding approximately to the waste material used, is mixed intensively for a time between 10 and 15 minutes at temperatures between 60 and 80 ° C (right branch)

The material micro-gelled in this way can be used as a wholefood filler in the construction industry, but it also allows further processing into a high-quality secondary raw material, for which purpose it is mixed with an inorganic filler such as calcium carbonate and then with a other extruded plastic or waste plastic mixture containing at least 35% thermoplastic material. The extruded material is cut into granules, which can be further processed in the usual known manner by injection molding, pressing or rolling into articles of daily use, such as containers of all kinds, such as refuse containers, (sound) insulation materials, floor coverings, pipes and fittings, apparatus housings or the like. - D

Example:

1000 g of fly ash a from a coal incinerator are processed in the manner described above. For this purpose, the ground fly ash, which has been freed from the constituents above 20 mu, is freed of its iron oxide content (116.7 g) in a manner known per se and then leached out to remove the water-soluble constituents (183.8. From the remaining residue (699.5 g) Heavy metals (107.6 g) are also removed quantitatively in a manner known per se. The recovered components can be reused in the respective species-specific processes, such as the iron oxide and the heavy metals by smelting, the water-soluble salts for the production of chlorine bez potash fertilizers.

The remaining fly ash residue of 591.9 g is further processed to "thermoplastic pellets" and for this purpose 15 minutes with an equal amount of 65.0 g of polyvinyl chloride paste 50/50 mixed intensively at a temperature of 80 ° C. After processing and cooling, 845.6 g of micro-coated grain material result, which is sealed in an environmentally friendly manner due to the micro-coating and can be processed together with other plastic material to form secondary granules for the production of various everyday objects.

Claims

Claims 1. Process for the preparation of combustion and / or flue gas cleansing residues, characterized in that the dry residues homogenized to a possibly uniform grain size are micro-coated with the aid of a paste or suspension made of a thermoplastic and the material thus coated is molded and granulated with a plastic containing a thermoplastic component to obtain a material that can be used for reuse. 2. The method according to claim 1, characterized in that the homo genized residue for the purpose of micro-coating and micro-gelling the paste or suspension made of a thermoplastic plastic in an amount between 10 to 15 wt .-%, based on the used Material, at a temperature between 80 and 85 ° C with vigorous stirring and the mixture is mixed for a time between 10 and 15 minutes while maintaining the specified temperature. 3. The method according to claim 1 or 2, characterized in that a paste or suspension containing 40 to 50 wt .-% polyvinyl chloride is used. 4. The method according to claim 2 or 3, characterized in that de micro-coated material in another plastic material Amount up to 30 wt .-% admixed and the mixture thus formed at one Working temperature between 165 and 180 ° C extruded and formed o - strand is cut into granules. 5. The method according to claim 4, characterized in that as an additive material for extrusion cleaned and crushed waste plastic material with at least 35% thermoplastic components is used 0 5. The method according to claim 4 or 5, characterized in that de microgelled material together with the plastic material an inorganic cal filler, for example calcium carbonate, is added in an amount up to z 15% of the microgelled waste material used. 5 7. The method according to any one of claims 4 to 6, characterized in that as plastic material for extrusion low-pressure polyethylene high-pressure polyethylene, styrene polymers or poly-vinyl chloride au waste, in particular household waste, are used. 8. The method according to any one of claims 1 to 7, characterized in that the residues are ground to a grain size of 20 M before the micro-coating, then by means of physical and / or chemical methods known per se from their constituents of heavy metal compounds iron oxide and the water-soluble constituents (Nitrate, sulfate, chlorine salts) are exempted.