Main Ways and Methods to Improve the Quality of Coke Oven Silica Bricks

In 1954, my country started the research on silica bricks for coke ovens. After decades of research, there was no breakthrough in the production process of silica bricks for coke ovens and the quality of their products from 1970 to 1978. Still maintained at a low level, the qualified rate of the produced silica bricks is very low and the quality is poor. Later, Baosteel introduced Japanese steel (including coking) production technology and various production equipment, including coke oven silica brick production technology. Chinese researchers conducted a detailed analysis of the silica bricks for coke ovens introduced from Japan, and then implemented technological innovations on the basis of them. Finally, at the end of the last century, large-scale production was carried out in Henan Luoyang Refractory Factory and Shanxi Xixiaoping Silica Brick Factory. In addition to the relatively high-quality silica bricks for coke ovens, the tridymite content can reach nearly 70% and the residual quartz content is less than 0.9%. Before, the tridymite content of silica bricks produced in my country was difficult to exceed 40%, and the residual quartz content was as high as 3% to 4%. The main reason is that the control of raw materials and the optimization of the process are not in place, and the core technology of its production technology is not mastered. Since then, my country has started in-depth research on silica raw materials, optimized the production process of silica bricks, formulated a more reasonable and efficient production process, and produced great progress in the quality of silica bricks.

silica brick

The trial production of silica bricks for coke ovens with compound ingredients was first proposed by Liu Jinming, and the conforming ingredients mainly include three kinds of silica (crystalline silica from Hebei Tangshan and Liaoning Shimen and cemented silica from Shanxi Wutai Mountain) with a critical particle size of 2.5mm, in ferrous oxide and calcium oxide. When used as a mineralizer, it was fired at 1380°C for 50 hours in a tunnel kiln to obtain high-quality silica bricks for coke ovens, in which the tridymite content was 75% and the residual quartz was less than 1%.

Zhou Wancheng, Hu Yanshu, etc. conducted an experimental study on the effect of A1203 content on the properties of silica bricks. The results show that A1203 affects the refractoriness, softening temperature under load, true density and mineral phase composition of silica brick products. There are few reports on the analysis of silica raw materials for coke oven silica bricks produced in southern provinces.

Gao Zhenxin et al. analyzed and studied the main ways and methods to improve the quality of coke oven silica bricks based on the phase diagram of SiO2 crystal transformation and the microstructure changes of coke oven silica bricks after use, and put forward their own views.

Summarizing the basic experience in the production of silica bricks for decades, mainly in the following aspects:

(1) Raw materials are the basis.

The raw materials should be of stable quality, not easy to loosen during firing and easy to control, and there should be considerable reserves for long-term use. Selecting appropriate raw materials can simplify the manufacturing process, facilitate the operation, stabilize the quality and reduce the cost. Bricks made of two or more kinds of mixed silica with different properties are gradually adopted by people. For example, Luonai, Shandong Ernai, Lengshuijiang Refractory Factory, etc. have all verified that the use of mixed silica is superior to that of single silica. Japanese silica bricks It is also used in combination with more than two or even four raw materials. Using mixed silica to make silica bricks has the following advantages: first, the chemical composition can be adjusted; second, the particle composition can be adjusted to achieve a reasonable gradation economically; third, it is easy to control the expansion and crystal transformation of the brick embryo during firing ( The expansion curve of each kind of silica when heated is not completely consistent, and this difference can be used to lengthen the temperature section where the expansion occurs, so that the expansion can be dispersed; the fourth is to reduce the cost.

(2) The particle size distribution should be reasonable.

The particle size distribution of silica bricks needs to consider two aspects: one is the pass rate, and the other is conducive to the crystal transformation of quartz to achieve the expected mineral composition. Most of the silica brick factories now use a smaller critical particle size of 2~2.5mm, a maximum of no more than 3mm, and a considerable proportion of fine powder. The research report of the Institute of Metal Research of the Chinese Academy of Sciences stated that when the critical particle size of recrystallized, dense, medium-speed silica is used, the sintering crack is serious when the critical particle size is greater than 3mm.

(3) Pay attention to mineralizers.

Mineralizer is a necessary factor for the formation of tridymite phase. The selection of mineralizer involves the formation of tridymite phase, which determines the performance of silica brick.

(4) Kneading should have a kneading effect.

The mixing process not only involves the problem of mixing, but the mud also requires a certain kneading property, which can increase the density of the brick, thereby optimizing the physical and chemical indicators of the silica brick to obtain a denser silica brick.

(5) Mechanization of embryo making.

Mechanized embryo making can ensure the quality of the green silicon brick and the stability of its performance.

(6) Brick embryos are dried at low temperature.

Low-temperature drying can improve the pass rate of silica bricks to a certain extent, and it is also a key step that cannot be ignored.

(7) Firing is the key.

To a certain extent, the true density of silica bricks can determine whether the performance of silica bricks is excellent or not. To obtain silica bricks with lower true density, a reasonable firing system must be adopted, including firing temperature, heating rate and holding time.

Through the research on the production process of silica bricks, it is found that in the production process of silica bricks, raw materials are a necessary condition for obtaining high-quality silica bricks, and it is the key point of the advantages and disadvantages of silica bricks. The quality of the bricks, and the firing system in the production process of silica bricks is the key.