CS228049B1 - Portland clinker firing mineralizer - Google Patents

Abstract

The invention relates to the cement industry, namely the firing of raw material flour or sludge into Portland clinker. The invention solves the problem of improving clinker firing by facilitating the formation of clinker minerals during the firing of Portland clinker. It consists in using waste industrial gypsum from the production of titanium white as a mineralizer, which contains approximately 60% CaSO^. 2H20, 12% Fe20^, 5.7o MgO, 8% SiC>2, 5% SiEg" and other oxides and salts in small quantities. These compounds have an effect on the easier formation of clinker minerals during the firing of cement raw material into Portland clinker. Improving mineralization during clinker firing has a positive effect on the weight of Portland cements and mixed cements produced from this clinker. The invention can only be used in the cement industry, during the firing of Portland clinker.

Description

The invention relates to the use of waste industrial gypsum resulting from the production of titanium dioxide.

This gypsum is produced in the Přerov Chemical Plant and is actually a waste product from the production of titanium white. It contains a mixture of salts and oxides in approximately the following amounts: 60%

CaS0 ₄ . 2H ₂ 0, 12% Pe^, 5% MgO, 8% SiO ₂ , 5% AlgO^, % SiPg and other oxides and salts in small quantities. The chemical composition is variable and depends on the composition of the neutralized input acidic systems.

During the firing of cement raw materials (in the form of raw material flour or raw material sludge), reactions occur at temperatures of 1200-1450°C between the basic oxides, namely silicon, aluminum, iron and calcium, which result in the formation of clinker minerals. Since these reactions take place at high temperatures, firing mineralizers are used to facilitate them, which either reduce the temperature of clinker mineral formation or achieve a more perfect course of clinker mineral formation. The result is therefore a reduction in thermal energy consumption or an improvement in the binding properties of the produced clinker. Clinker with increased binding properties practically means the possibility of coarser grinding of cements and thus saving electrical energy.

Fluorides and fluorosilicates are used as mineralizers for clinker firing. Their disadvantages are limited availability and, above all, high price, which exceeds the resulting savings. The above disadvantages are eliminated by the Portland clinker firing mineralizer, the essence of which is that industrial gypsum waste from the production of titanium white is used as mineralizers.

The use of the above-mentioned industrial waste gypsum as mineralizers for Portland clinker firing has been tested in operation. The industrial waste gypsum is added to the raw material mixture

228 049 in the amount of 0.5^1.5% by weight of the raw material mixture before the raw material mill, in which it is ground and homogenized together with the raw material mixture into raw material flour. Clinker was produced with approximately the same thermal energy consumption, but with a significantly higher binding capacity.

Long-term tests were carried out in the cement plant with the following results: sintering temperatures and kiln performances remained practically unchanged (kiln performance increased slightly), the quality of clinker and cements produced from it improved, mainly the initial setting (i.e. after 1 and 3 days).

The binding capacities of clinkers of identical chemical composition, made from raw materials without the addition of industrial waste gypsum and with the addition of industrial waste gypsum, were 3200 cm/g according to Blaine when ground:

Tensile/compressive strengths in MPa for 1 day 3 days 28 days clinker from raw material without industrial gypsum waste 1.95/ 9.0 4.25/23.3 6.50/48.5 clinker from raw material with industrial gypsum waste (1.0%) 3.28/13.7 5.39/28.3 7.52/53.6

Average binding capacities of commercially produced PC 400 cements, made from clinker fired without the addition of industrial waste gypsum and from clinker fired with the addition of industrial waste gypsum:

grinding fineness Tensile/compressive strength in MPa for

Blaine cm2/g 1 day 3 days 28 days PC 400 (clinker without gypsum) 3139 1.98/ 8.7 4.05/21.0 7.32/47.5 PC 400 (clinker with gypsum) 2849 2.30/10.4 4.30/21.7 6.93/43.8

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It has therefore been demonstrated that clinkers made from raw materials with the addition of industrial waste gypsum can be ground more coarsely for the production of cements _of the same class, thereby saving electrical energy. _The invention can be used in those kilns where raw materials with a low S content (up to 0.2%) are processed and fuel is also used that is low in S content.

Claims (1)

Use of waste industrial gypsum from titanium production %, which contains 60 wt. calcium sulfate dihydrate » 12 wt. % ferric oxide, 5 wt. % magnesium oxide, 8 wt. % silica, 5 wt. alumina, 5 wt.% silica fluoride, and other oxides and salts in small amounts, as a Portland clinker firing mineralizer.