How to control the volume stability of refractory materials

Because of the non setting refractory material is used in the field of baking and burning, will appear dry shrinkage and firing shrinkage.

It is necessary to consider the measures to compensate the shrinkage in the design ofcomposition, that is, the total molar volume of the reaction product is greater than the total molar volume of the reaction product, and the volume expansion of the matrix is matched with the sintering shrinkage. The main methods are as follows:

(1) Thermal decomposition method, a mineral which is decomposed at high temperature and the molar volume of the product of its in situ thermal decomposition is more than the molar volume of the original mineral to compensate for the sintering shrinkage of the material. Such as in the A1203-SiO2 system unshaped refractory materials added a certain amount of kyanite, after high temperature calcinations into mullite and free silica (quartz), volume expansion and produces about 16% ~ 18% (calculated). There are sillimanite, andalusite and sillimanite minerals. The volume expansion after the decomposition of Kyanite is the largest, so it has been widely used.

(2) High temperature chemical reaction method is used to compensate for the volume expansion effect of the in-situ chemical reaction occurring during high temperature use. In the aluminum matrix such as magnesium or magnesium aluminum castables, ramming material or vibratory ramming material in. With high temperature MgO and in situ reaction to generate spinel and produce about 7.5% of the volume expansion, can be part of the compensation of the sintering shrinkage.

(3) In the process of heating, the transformation method of the crystal type can be used to produce the mineral, and the molar volume of the crystal is larger than the molar volume of the transformation. As in the trough of blast furnace A1203- SiC-C matter ramming material is added with appropriate amount of silica particles with quartz transformation of tridymite and cristobalite volume expansion effect (respectively 12.7% and 17.4% to compensate matrix of sintering shrinkage, reduce or eliminate the trough of the shrinkage cracking phenomenon.

Recovery and utilization of flue gas and heat in the production of refractory materials

Because of the kiln body structure and the thermal process of different, the intermittent kiln is more than 5 times higher than the flue gas produced by the tunnel kiln. In general, the higher the gas temperature, the greater the proportion of heat loss. Such as gas temperature of 1093, the heat loss of 55%, when the gas temperature of 1427 degrees, the heat loss was 70%. For hot gas intermittent sintering refractory down draft kiln, according to the relevant experimental data show that: heat from the flue gas from the furnace kiln accounted for about 35% to 40% of all caloric expenditure, in the absence of any heat recovery measures, the calculation results of heat balance, heat efficiency is in 10% ~ 15%This is a great loss of heat. Therefore, the use of gas heat is a very important energy recovery work.

Setting heat exchanger in the flue is an important method for waste heat recovery. Hot air through a heat exchanger obtained can be directly sent to the burner for combustion supporting air, can also be hot air diluted transported to the products of somatic embryos drying kiln drying medium or it, the kiln thermal efficiency reached 30% or higher.

When firing system by changing the preheated air to the heat exchanger, and the hot air do combustion the combustion air can not only increase the kiln thermal efficiency, reducing the consumption of fuel, energy-saving effect is achieved. And it can increase the temperature of the flame, increase the heating efficiency, and shorten the heating time (the period). And because of the volume expansion of hot air, the flow velocity of the burner is increased, the gas flow in the kiln is accelerated, and the temperature in the kiln is uniform. The relevant data shows that the fuel consumption can be reduced from 6% to 8% when the air temperature is 220 ~ 250. At the same time the combustion air of different temperatures, a very large impact on the flame temperature. Even in the case of no preheating gas, combustion temperature of gas increases significantly with increasing the preheating temperature of combustion air. Refractorymaterials not only can solve the problem of low firing temperature, but also plays an important role in the enterprise energy saving and reducing consumption.