NL8401701A - SECONDARY RAW MATERIAL FOR CEMENT. - Google Patents

Description

VO 6335

Title:. Secondary raw material for cement

The invention relates to the use of secondary raw materials, which are obtained during combustion according to the fluidized bed principle, for the preparation of cement.

The raw materials used for the preparation of cement must contain the 5 main components lime, silicic acid, clay earth and iron oxide.

For this purpose, natural raw materials preferably use lime marl and marl with a calcium carbonate content of about 60 - 80%.

In cases where lime marl or marl is not available, high-quality limestone moorings and clay quarries must be quarried.

The fluidized bed combustion principle is particularly suitable for the burning of inferior fuels and even industrial residues, which would otherwise have to be deposited at high cost and under environmental stress, such as flotation mountains, laundries, coal sludge dough sludge and clarification sludge; according to this method, of course, other fuels such as high-quality coal, ballast coal, peat and oil slate can also be burned. Although the waste incineration does mitigate the problem of their depot, it has hitherto not been successful to use the residues of the fluidized bed incineration economically. They have yet to be deposited again. Attempts have been made only to use residues specially formed from the combustion of flotation mountains for the manufacture of bricks, as an additive for moth binders and for the preparation of a lightweight concrete aggregate.

The residues from the combustion of flotation mountains, however, because of their physico-chemical similarity to natural raw materials (eg clays), represent a separate case which cannot be transferred to combustion residues of other substances and in particular to coal and therefore is saved after this. In particular, no application possibilities currently exist for residues from the combustion of fossil fuels according to the fluidized bed principle.

The residues obtained by fluidized bed combustion can differ completely in their physico-chemical properties.

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This depends on - the nature of the substance to be burned, - the combustion process, - the substance used for desulphurisation and the degree of desulphurisation, 5 - the discharge points of the equipment (e.g. ash behind the liquid bed, shaft behind the cyclone, shaft behind the filter).

Moreover, the residues from different disposal sites still differ in their grain size distribution.

Nor are these residues comparable to ashes from equipment with other combustion techniques, such as grate, dust or melt-chamber combustion, because they burn here at considerably higher temperatures (> 1000 ° C). While residues from grate, dust or melt chamber burnings have a glass content (glassy components) usually above 90%, residues from the fluidized bed combustion are in a predominantly crystalline state, which works against their use in many areas of the building materials industry.

It is therefore an object of the invention to solve the residue problem of fluidized bed combustion and at the same time to relieve deposits of high-quality raw materials.

To this end, it has been proposed according to the invention to use the residues obtained during the combustion according to the principle of the fluidized bed as a secondary raw material for the cement preparation, their weight contents of the total starting powder mixture 1-60 wt.%, Preferably 5- 40 wt%. Depending on the chemical composition, the residues (fluidized bed, cyclone dust, filter dust) obtained in the fluidized bed combustion at various locations can be used individually, in pairs or in a three-dry mix.

It is possible to use the secondary raw material in different ways. It can be fed together with the natural raw materials to the usual and known reprocessing equipment and finally grind it together into cement starting powder. In addition, it is particularly advantageous when residues with elevated carbon contents are used, the latent energy of which is used in clinker fires. According to the invention, it is also possible in this case to utilize the lime component, which is not used from a direct desulfurization with calcium-containing absorbents, as a main component of the cement starting powder.

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According to the invention, the lime surplus content is between 0.1 and 34% by weight, preferably between 1.5 and 15% by weight.

Furthermore, according to the invention, the raw material can be fed to a finished burnt cement clinker in contents of 5-30 wt.%, Preferably 10-15 wt.%, And be ground with it. For this it is particularly advantageous to use the fine parts of the residue after preliminary separation at 90 µm. Namely, it has surprisingly been found by tests that the CaSo 4 (anhydrite II) component essentially enriches in this range of fine grains.

The anhydrite simultaneously serves the later regulation of the hardening of the cement and in this way can replace all or part of the addition of a sulphate carrier.

If necessary, the secondary raw material can also be ground up alone and added in this form to the cement starting powder.

A decisive advantage achieved by the invention consists in that, when the residues obtained from the fluidized bed combustion are added to the cement starting powder, the properties of the finished cement meet the standards. This economic factor is further enhanced by the fact that at the same time a high cost with depot entailing is eliminated and, moreover, high-quality deposits are spared; .140 1 70 1 ................'.............__.............. ....................................... ".......... ............................

Claims (9)

1. Use of secondary raw materials for cement, characterized in that they consist of combustion residues according to the fluidized bed principle. Secondary raw material according to claim 1, characterized in that it is removed as a bed ash behind the fluidized bed and is used as a raw material without mixing with other residues of the fluidized bed combustion. Secondary raw material according to claim 1, characterized in that it is removed as fine material behind a cyclone separator and is used as raw material without mixing with other residues of the fluidized bed combustion. Secondary raw material according to claim 1, characterized in that it is removed behind a filter and is used as raw material without mixing with other residues of the fluidized bed combustion. 15-5. Secondary raw materials according to claims 1 to 4, characterized in that these residues obtained from the individual disposal sites are wholly or partially mixed dry into a single residue. Secondary raw materials according to claims 1-5, characterized in that they contain 1-40 wt.%, Preferably 3-20 wt.%, CaSO4 in the form of anhydrite II. Secondary raw materials according to claims 1-6, characterized in that they contain 0.1-34% by weight, preferably 1.5-15% by weight, of free CaO. 8. "Secondary raw materials according to claims 1-7, characterized in that the anhydrite and CaO and residual carbonate are predominantly present in the grain size ^ 90 µm. Secondary raw materials according to claims 1-8, characterized in that they are ground together with a cement starting material at levels of 1-60% by weight, preferably 5-40% by weight, into cement starting powder. Secondary raw materials according to claims 1-8, characterized in that after firing the starting powder with a content% of 5-30% by weight, preferably 10-15% by weight, together with the burnt cement clinker Λ are ground into cement. 8 4 0 1 7 0 1 ........................, .................. ............. t -5- Secondary raw materials according to claims 1 to 5 and 9 and / or 10, characterized in that they are divided into granular fractions before their addition. 8 4 0 1 7 0 1 ........................-...........-...... -..........................................-...... ....................... -.....-.................... ............