Selection and maintenance technology of light burned magnesia powder

It is widely used in domestic hazardous waste disposal industry. The quality of refractories affects the stable operation of rotary kiln. This paper analyzes the selection and maintenance of refractories for the rotary kiln of hazardous waste treatment with Haicheng light burning powder for reference of specific engineering application. According to the definition of the national list of hazardous wastes, hazardous wastes are corrosive, toxic, inflammable, reactive, infectious and other hazardous characteristics. It may cause harmful effects on the environment or human health, which need to be managed according to hazardous waste. Among them, the heat treatment (incineration) of hazardous waste can not only completely remove the toxicity and harmfulness of waste, but also reduce the volume of hazardous waste to the greatest extent, which is the most powerful means of harmless and reduction of waste. At present, most of the newly built hazardous waste incineration and disposal projects in China prefer rotary kiln as the type of hazardous waste treatment furnace, which can effectively deal with different shapes and phases of hazardous waste.

Rotary kiln incinerator, also known as rotary kiln, is a slightly inclined steel hollow cylinder lined with refractory bricks. Most waste materials are heated by the gas generated in the combustion process and the heat transmitted by the kiln wall. The solid waste is sent into the kiln from the front end for incineration to achieve the purpose of mixing the waste by rotating. Proper inclination shall be maintained during rotation to facilitate the sliding of solid waste. In addition, waste liquid and waste gas can be sent to the kiln head or secondary combustion chamber, and even the whole barrel of waste can be sent to the rotary kiln incinerator for combustion.

Rotary kiln incineration technology is the most mainstream technology in the current hazardous waste incineration technology, which is the most widely used furnace type. Light burned magnesium powder is a multi-purpose incinerator with strong adaptability, which can burn a variety of solid, semi-solid, liquid and gas wastes. All kinds of combustible wastes of different types and shapes (particle, powder, block and barrel) can be sent into the rotary kiln for incineration.

The burning of hazardous waste in rotary kiln generally involves several stages, such as drying, pyrolysis, combustion and burnout. After these stages, the harmful components in the hazardous waste are fully decomposed and destroyed under the high temperature, forming high temperature flue gas and slag. These high temperature flue gas and slag will cause corrosive damage to the refractories built in the rotary kiln.

(1) High temperature resistance. It can operate in high temperature environment above 800 ℃ for a long time.

(2) High strength and excellent wear resistance. The refractories in the rotary kiln need to have certain mechanical strength to withstand the expansion stress at high temperature and the stress formed by the deformation of the kiln shell.

(3) Good chemical and thermal stability, to resist the corrosion of chemical substances in flue gas, and to withstand the alternating thermal stress in the burning state.

(4) The stability of thermal expansion is good. Although the thermal expansion coefficient of the shell of the rotary kiln is greater than that of the refractories of the rotary kiln, the shell temperature is generally about 150-300 ℃, and the temperature of the refractories is generally above 800 ℃, which may cause the refractories to expand more than the shell of the rotary kiln and fall off easily.

(5) The porosity should be low. High porosity will make the flue gas easily penetrate into the refractory and corrode the refractory body.