Precalciner

What is precalciner in cement plant? The precalciner is also called cement calciner, calciner in cement plant, etc. as the thermal equipment for cement rotary kiln, and it can be used for fuel combustion, heat exchange, and decarbonation.

Why the precalciner is necessary for cement plants? The reason why a precalciner is arranged in the cement production line is that the precalciner can uniformly distribute the raw materials so that the raw materials do not form an accumulation phenomenon. The material can be complete when the temperature rises, and because the material has a relatively high melting point and a short residence time in the equipment, the material cannot be completely decomposed, resulting in more impurities in the calcined clinker. The calciner in cement plant can not only extend the residence time of the materials in the equipment but also improve the fuel combustion rate so that the temperature of the equipment can always be maintained in the specified range during cement production line.

Types of precalciner

According to the structure and working principle, the cement calciner can be divided into following four types:

• Spiral-flow type calciner: it is characterized by the swirling motion of gases and materials in the furnace.
• Calciner with preheating chamber: it is characterized by a preheating chamber, ensure the steady combustion of fuel and raw material decomposition.
• Spouted calciner: it is characterized by suspension movement of material and gases produced by air blowing.
• Boiling calciner: high pressure fan produce air and send into air chamber, pass through the smoke cap and make the material, fuel boiling.

Structure of precalciner

• The body of precalciner is used for fuel consumption and material decomposition;
• The feeding device for fuel and materials
• Air inlet and outlet is good for air moving and suspension of fuel and materials, which make heat transfer and decompose fast.

Working principle of precalciner

The cement calciner makes the raw meal spread and suspension in the air flow, and ensure the fuel consumption and decarbonation happens in a short time. In the precalciner, the fuel combustion is carried out at the same time with the material endothermic reaction under the condition of turbulence, the fine particles of fuel float on one side and burn on the other side, making the whole furnace almost become the combustion zone. Therefore, no visible flame can be formed, but at a low temperature of 820-900℃ flameless combustion state.

Precalcining technology

The precalcining technology is a technical leap of cement calcining process, with a series of excellent properties and characteristics such as high quality, high efficiency, and low consumption.

Add a precalciner between the preheater and the rotary kiln, or use the uptake flue at kiln end, and set up a fuel injection device to make the combustion and exothermic process of fuel and the carbonate decomposition and endothermic process of raw materials suspended or fluidized in the precalciner, the decomposition rate of raw materials into the kiln can be improved.

Features of precalcining

• Decarbonation task move out,
• A small part of the fuel is added from the kiln head, and most of fuel is added from the precalciner, which reduces the heat load of the calcination zone in the rotary kiln, extends the use life of the lining, reduces the size of the rotary kiln and enlarges the cement production.
• Fuel combustion exotherm, suspension heat transfer and endothermic decomposition of materials are closely combined.