Introduction

Shaft kiln, just as its name implies, is a kiln with erected shape. Shaft kiln with modern new technology has environmental protection function, energy-saving function, high mechanization, and high automaticity. It also has the ability to turn waste into wealth.

Therefore, it can make full use of cheap energy, especially the pollution-carry gas such as converter gas, blast furnace gas, calcium carbide furnace tail gas, etc.

Shaft Kiln Working Principle

Shaft kiln is a cylindrical kiln. Materials are put into the kiln from kiln crown and are ejected from the bottom of the kiln. According to the different ranges of temperature, the kiln can be divided into three parts: preheating zone, calcining zone, and cooling zone. In the preheating zone, materials are preheated by smoke; In the calcining zone, materials are calcimined by fuel; In cooling zone, calcimined materials and blowed-in cold air process heating exchange to cool materials then heated air becomes combustion air in calcimining zone. To guarantee that materials process intact calcimining in every zone, the three zones should be maintained at a certain height and be stable. The motion of materials in kiln occurs under two circumstances:  first, materials’ volume shrinkage makes upper materials move; second, lower materials’ ejectment leads to the whole materials’ motion.

Shaft kiln, during the descent, materials process complicated heat exchange with hot coal gas while limestone is decomposing and the grains of quicklime is growing and developing. After the whole process, materials are cooled down by combustion air to 60-degree centigrade higher than environmental temperature. Then lime is dumped on belt conveyor outside the kiln without disc ash machine and sealing valve leaking combustion wind. Then the size of limes less than or equal to 5mm and the size more than 5mm are respectively discharged into different silos after hoisting and sieving.

Shaft kiln’s combustion air is blown into the furnace from the lower part of the furnace by a Roots blower then overcomes the resistance of the pellet while lifting from the lower part to the top of the furnace. Under the drawing of the dust extraction fan, the flue gas is transported to the dust collector through the pipeline for dust removal. Due to the effect of induced draft fan, a micro-negative pressure zone is formed above the material surface in the kiln (about -10 Pa). This micro-negative pressure ensures smooth airflow in the furnace, which is very beneficial for the decomposition of limestone in the calcimining zone. The induced draft fan introduces all the flue gas into the dust collector for purification and then discharges it from the chimney to the atmosphere.