Glass manufacturing – Processes of manufacturing fibers – filaments – or preforms – With charging or pretreatment of batch material
Patent
1995-07-21
1998-01-20
Mayes, Melvin
Glass manufacturing
Processes of manufacturing fibers, filaments, or preforms
With charging or pretreatment of batch material
651346, 651347, 651348, 651359, 651361, 651363, 65335, 65475, 65502, 65540, 65 28, C03B 3702, C03B 302
Patent
active
057097283
DESCRIPTION:
BRIEF SUMMARY
The invention concerns a method for the production of mineral wool by using wool waste as a recycled starting material and a device for producing such mineral wool.
BACKGROUND OF THE INVENTION
The large-scale use of mineral wool waste as a recycled starting material in the production of mineral wool has been aimed at for a long time. The intention is to utilise production scraps inherently arising in this system e.g. when trimming mineral wool webs, and refuse rejected by quality control. Not least the aim should also be to recover and utilise already used mineral wool products following their use by the purchaser. The mineral wool waste for recycling thus arises in varying amounts, and the arising amount may be as much as half of the starting material charged for producing the molten mass; it may therefore be in a 1:1 or higher ratio to the molten fresh mixture of raw materials.
Renewed melting of the mineral wool waste, however, is confronted by a variety of technological problems. A major problem resides in the fact that the larger part of the mineral wool waste contains organic substances, such as the binding agent used in producing a mineral wool felt, a mineral wool panel, or organic remainders stemming from its use, such as e.g. leftovers of roots. It is basically possible to introduce the associated carbon content into the molten mass when producing rock wool, however this unfavorably modifies the composition of the molten mass and attacks the refractory material of the melting tub; when producing glass wool, a substantial introduction of carbon into the molten mass is not permissible at all. In this latter case, it is possible to add an oxidising agent which, however, increases the starting material cost and affects exhaust gas emission, with the consequence that the addition of carbon-containing waste is in any case limited to low values.
In order to remove the carbon content of the mineral wool waste prior to melting in the melting tub, it is known from EP0 410 889A1 to subject the mineral wool waste to pyrolysis in a tunnel oven. To this end, the shredded waste is penetrated by a hot gas flow at a certain height of layer inside the tunnel oven and thereby annealed. The pyrolysis gas is inert or comprises an oxygen content reduced in comparison with air only to such an extent as to preclude the formation of combustion zones having such lively combustion that due to excessive release of energy melting of the starting material might take place, while organic impurities are enclosed in the molten mass. On the other hand, organic gases carried along in the pyrolysis gases are to be burnt in the process cycle to thus supply energy from the process itself to the pyrolysis gas before again being conducted through the mineral wool waste.
In view of the long sojourn times of the mineral wool waste in the pyrolysis oven, possibly extending to e.g. one hour, there results a reduced performance of the facility in exchange for a given expense of investment. As furthermore external energy is required which is lost prior to insertion into the molten mass due to cooling, this also results in relatively high energy costs. Altogether this method is satisfactory in a technical context, not however in an economic one.
From EP-A-389 314, on the other hand, it is known to melt the mineral wool waste in a melting unit and thereby burn the organic impurities. Pure oxygen or air strongly enriched with oxygen is utilised to attain a high-temperature combustion above the liquid level of the molten mass, such that the organic impurity material is burnt there as completely as possible before the heat generated in this combustion causes melting of the mineral wool waste in this location. Apart from start-up or auxiliary burners, the overwhelming part of the melting energy is derived from high-temperature combustion of the organic impurities.
Besides relatively high costs of investment, considerable costs--with the exception of relatively low fuel costs--are incurred for the oxygen. Handling the oxygen in the rough product
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Fleckenstein Hermann
Hornung Helmut
Isover Saint-Gobain
Mayes Melvin
LandOfFree
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