Making refractory materials from tailings

Overview

Refractory structural material is mainly used for thermal resistance in high temperature equipment and as a container or other member of the high-temperature inorganic non-metallic solid material.

The performance requirements of thermal equipment such as industrial furnaces and kiln for refractory materials are:

Refractoriness must be above 1580 ° C;

Cold crushing strength and high deflection temperature under load (or softening point load) is high, the general construction furnace load does not exceed 0.5 to 1 kg / cm ^2, for safe use requirements of the refractory material exceeds this index;

High thermal stability and low thermal expansion coefficient;

High chemical stability and strong slag resistance;

The shape is neat and the size is accurate.

The refractory material can be divided into various types according to the chemical mineral composition of the refractory matrix. In order to better use the tailings, two refractory materials which are close to the chemical composition of the tailings are described below.

First, silicon brick

Silica brick containing 93% or _more SiO refractory material is silica or silica-rich quartzite as a raw material, adding a small amount of lime as a binding agent, high temperature calcination of the silica into cristobalite and tridymite, and quartz, and residual The phase change structure in which the glassy matter formed at a high temperature coexists is an acidic refractory material.

The basic requirements for the manufacture of silicon brick raw materials are shown in Table 1.

Table 1 Basic requirements for silica brick raw materials at all levels

The raw materials are required to be pure and the impurities are evenly distributed. It is not possible to concentrate locally. Otherwise, the products of the fired buckle will be melted and melted, and will be damaged from these holes and melting smelts inside. The raw material must contain Al ₂ O ₃ and TiO ₂ low because a small amount of Al ₂ O ₃ or SiO ₂ can form a eutectic point of 1545 ° C with SiO ₂ , which seriously reduces the refractoriness and high temperature strength of the silica brick. If the raw materials contain soil, they should be washed clean.

Second, semi-silicon brick

Semi-silica bricks contain refractories of Al ₂ O ₃ +TiO ₂ <30% and SiO ₂ >65%, which are semi-acid products.

The manufacture of semi-silica bricks can utilize natural clay- bearing clay and kaolin resources, and the tailings obtained in the refractory clay , kaolin or quartzite beneficiation can also be used as semi-silica bricks.

The standards for clay and semi-silica refractory products for metallurgical coke ovens in China are shown in Table 2.

Table 2 Ministry of Clay and Semi-Silicon Refractory Products for Metallurgical Furnaces (YB402-63)

The Soviet Union has three levels of semi-silica bricks, and the quality indicators are shown in Table 3.

Table 3 Quality indicators of Soviet semi-silica bricks

About 60% to 70% of refractory materials in general industrial countries are used in the metallurgical industry. 55% to 65% is used in steel industry. Therefore, the refractory industry must be developed while developing the metallurgical industry. Constantly innovating refractory materials can create conditions for improving metallurgical technology. The manufacture of high quality refractory materials must start with the selection of quality raw materials. However, there are some thermal equipments that do not require high technical performance of refractory materials. It can be considered to use industrial waste residue. For example, metal mine tailings can be used when their mineral components basically conform to certain refractory components. As a raw material.

Anshan Jiaonan Design Institute used the tailings of a certain plant in Anshan and the clay near Anshan to test the refractory bricks in the silicon brick kiln.

Tailings and clay are physical and chemical compositions listed in Tables 4 and 5.

Table 4 Physical properties and chemical composition of tailings

Table 5 Physical properties and chemical composition of clay near Anshan

The tailings were mixed with clay by the four ratios in Table 6. They were pressed and formed by a friction brick press according to the standard brick size specified by the state, and sent to a silicon brick kiln for calcination, and the firing temperature was above 1300 °C. According to the preliminary test results, the ratio of tailings to clay is preferably 90:10. But not ideal enough, the main reason is that the iron in the tailings is too high.

Table 6 The ratio of tailings to clay and the ideal index of refractory bricks

A porcelain clay mine in Jiangsu Province uses the tailings of the plant to be fired with appropriate amount of coke gemstones , 4th porcelain clay and clinker and other raw materials to produce refractory bricks. The test results are as follows:

The hydrothermal alteration deposits based clay mineral, which is the main mineral kaolinite, followed by quartz, chalcedony, sericite, alunite, limonite, pyrite, galena, sphalerite and the like. The chemical composition of tailings after panning porcelain clay:

Tailings particle size: the largest particle is 0.5 mm, the fine particles are 0.2 to 3 mm, and the finest particles are less than 10 microns. The sieve was sieved through a 65-hole sieve (0.25 mm), the amount on the sieve was 37%, and the amount under the sieve was 63%. The tailings have a refractoriness of 1690 to 1710 ° C, a softening temperature of 1469 ° C, and a volume reduction ratio of 20%.

The chemical composition of No. 4 porcelain clay and self-burning clinker is shown in Table 7.

Table 7 Chemical composition of No. 4 porcelain clay and self-burning clinker

Four options were selected for the experiment and the results are shown in Table 8.

Table 8 Test of fire-resistant bricks fired from tailings in a porcelain clay mine in Jiangsu Province

In Table 8, the refractory products of the third and fourth schemes have basically reached the national standards.

The mine has produced more than 300 tons of refractory bricks from the kaolin tailings discharged, and two inverted kiln kiln, one at 20 ^m3 and the other at 30 ^m3 . The production process is shown in Figure 1.

Figure 1 Production process

1- Add water molding: hand-formed moisture 10% ~ 11%; machine molding moisture 6% ~ 8%; 2 - making brick blanks with slabs;

3-drying uses flue waste heat; 4- kiln roasting control temperature 1370 ~ 1380 ° C, heat preservation for four hours