EP0347519B1 - Process for eliminating waste products resulting from the recycling of waste paper in the paper and cardboard industry - Google Patents

Abstract

To eliminate waste and residual products resulting from the recycling of waste paper in the paper and cardboard industry, the waste products are predehydrated. Storage problems are avoided virtually completely if the predehydrated waste materials are dried in a drier (6) to a residual water content of 25 % by weight in relation to the solid quantity and are subsequently stratified continuously on a vibrating grid (2), overlaid with the residual products and burnt with underblast, to form slag, in an associated combustion furnace (1) with a slag collector (8). The combustion gases are used especially in a convential steam generator (9) for steam generation. <IMAGE>

Description

The invention relates to a method for removing trapping and residual materials occurring in the paper and cardboard industry during the recycling of waste paper, the trapping materials being dewatered (see e.g. DE-B-2 339 591).

In waste paper recycling, the raw material, i.e. the paper fiber damaged. A paper fiber can be reused four to six times before it breaks. The resulting pieces of fiber accumulate in the production water and are collected via flotation plants. The concentrate mainly consists of wood and cellulose fibers, which are called capture materials. The residues consist of more than 95% by weight of plastic in the form of adhesive tapes, foils, etc., which are separated directly from the recycling process and are usually taken to the capture materials independently. In the context of the present invention, residual substances are also understood to mean what is known as a “reject”.

As part of the known measures of the type mentioned at the outset, the trapping materials have only been dewatered mechanically to a dry content of about 35% and then sent to a landfill. The residues were also deposited independently of this. Taking into account that about 10% of the waste paper used is in the form of catch and residues, whereby the weight ratio of catch materials to residues is about 9: 1, and for ecological reasons an increased use of waste paper is required and on the other hand the available landfill capacities become scarcer, it becomes immediately clear that other ways of eliminating the catch and residues must be found.

The invention has for its object to find measures for eliminating the catch and residues that are no longer burdened by disposal or landfill problems.

In order to achieve this object, the invention teaches in procedural terms that the pre-dewatered capture materials are dried to a residual water content of at least 25% by weight, based on the amount of capture material, and then continuously stratified, covered with the residues and burned with underwind to form slag will.

The invention is based on the knowledge that the pre-dewatered capture materials after further drying without any problems, i.e. can be burned with the residual materials without primary energy if the combustion takes place in the form of a stratification, the lower layer being formed by the catching materials and the upper layer being formed by the residual materials. The resulting slag can be used for other purposes, in any case it does not represent a landfill problem anymore.

There are several possibilities for the further configuration within the scope of the invention. Thus, according to a preferred embodiment, the combustion gases formed during the combustion of the trapping and residual materials are subjected to heat recovery, in particular used for generating steam; here the resulting heat of combustion is used. It is advisable to dry the pre-dewatered capture materials to a residual water content of at least 20% by weight, based on the amount of capture material; then the process is not as sensitive to the combustion of the residues.

The water vapor generated can be used in papermaking, but it is also possible, as in the preferred embodiment, to pre-dry the pre-dewatered capture materials by heating with at least some of the water vapor generated. Alone or in combination, however, the pre-dewatered capture materials can also be dried with at least some of the combustion gases generated during the combustion of the capture and residual materials. In this context, one can get rid of possible exhaust air problems in a particularly simple manner by subjecting the exhaust air generated during the drying of the trapping materials to a post-combustion together with the combustion gases generated during the combustion of the trapping and residual materials. The dried and layered capture materials can be covered with up to 100% by weight of residual materials, based on the amount of solids, and fed to the combustion; optimal conditions are, however, provided that the dried and layered capture materials are covered with a maximum of 15 wt. The combustion gases are expediently subjected to dedusting. In any case, it is advisable to incorporate fly ash from the combustion gases into the slag. In any case, this slag can easily be used as a building material, so that there are no more landfill problems at all.

The invention is explained in more detail below with reference to a drawing.

The only drawing figure shows schematically a device for removing trapping materials on the one hand and residual materials on the other hand, as they occur in the paper and cardboard industry in the recycling of waste paper. The capture materials are pre-dewatered in the usual form. A combustion furnace 1 with an inclined vibrating grate 2 and underwind feed 3 can be seen in the main. Above the upper grate end there is a feed metering device 4 for the capture materials, which is connected via a transport device 5 to a dryer 6 for the pre-dewatered capture materials. In addition to and looking downwards in the direction of the grating slope, a further feed metering device 7 is provided for the residue materials behind the feed metering device 4, which are fed in without further processing. A slag collector 8 can be seen under the vibrating grate 2. A heat recovery unit in the form of a steam generator 9 is connected downstream of the combustion furnace 1 in the flow direction of the combustion gases. This is connected to the dryer 6 via a schematically indicated line 10. In addition, it can be seen that the combustion furnace 1, seen in the flow direction of the combustion gases, is provided behind the vibrating grate 2 with a combustion gas branch line 11 led to the dryer 6 and the dryer 6 is connected with its exhaust air outlet to a post-combustion chamber 12 of the combustion furnace. This post-combustion chamber 12 can be provided with secondary air supplies (not shown) to reduce the CO content of the combustion gases and to support post-combustion. The steam generator 9 is followed by a conventional dry dedusting unit 13 and a chimney 14. The dry dedusting unit 13 and the steam generator 9 each have a fly ash outlet 15 and 16, respectively, which are connected to the combustion furnace 1 via a line 17. Line 17 opens in Slag area of the vibrating grate 2 in the incinerator 1. The fly ash returned to this extent is thus fed with secondary air in the area of the slag zone and integrated into the slag.

The mode of operation of the device described can easily be seen in the figure. The pre-dewatered capture materials are dried in the dryer 6 to a residual water content of at least 25% by weight, in particular 20% by weight, based on the amount of capture material. This drying can be dried by heating with at least a part of the water vapor generated and / or with at least a part of the combustion gases generated during the combustion of the capture and residual materials. The exhaust air produced in the latter case is then subjected to post-combustion together with the combustion gases in the post-combustion chamber 12. With the help of the feed meter 4, the dried capture materials are continuously layered and placed on the vibrating grate 2. Immediately above, based on the amount of solids, at most 100% by weight, preferably at most 15% by weight, the residues are covered with a layer and the whole is then incinerated with the formation of slag. The fly ash from the dry dedusting is added to this slag. The wet slag is used in the construction industry.

Claims (9)

1. A process for the disposal of trash substance and foreign materials arising during waste paper recycling in the paper and carton industries, the trash substance being partly dewatered, characterised in that the partly dewatered trash substance is further dried to a residual water content not exceeding 25% by weight of the trash substance and then continuously laid out on a grate, covered with a layer of foreign materials and incinerated with under-grate blast, to form a clinker.
2. A process as in Claim 1, characterised in that the waste gases from the incineration of the trash substance and foreign materials are utilized as a source of waste heat, more particularly for steam production.
3. A process as in Claim 1 or 2, characterised in that the partly dewatered trash substance is dried to a residual water content not exceeding 20% by weight of the trash substance.
4. A process as in Claim 2 or 3, characterised in that the partly dewatered trash substance is pre-dried by heating with at least a proportion of the steam produced.
5. A process as in any of Claims 1 to 4, characterised in that the partly dewatered trash substance is dried with the aid of at least a proportion of the waste gas produced by incinerating the trash substance and foreign materials.
6. A process as in Claim 5, characterised in that the spent air arising from the drying of the trash substance is subjected to after-burning together with the waste gases arising from the incineration of the trash substance and foreign materials.
7. A process as in any of Claims 1 to 6, characterised in that the dried trash substance on the grate is covered with a layer of foreign materials not exceeding 100% by weight of its solids content, and more particularly not exceeding 15% by weight of its solids content, and subjected to incineration.
8. A process as in any of Claims 1 to 7, characterised in that the fly ash contained in the waste gases from the incineration of the trash substance and foreign materials is incorporated in the clinker.
9. A process as in any of Claims 1 to 8, characterised in that the clinker is utilized as a building material.

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