What Are The Causes Of Crusting And Blockage in Cement Rotary Kiln Systems?

There are numerous and complex factors contributing to the buildup and blockage of the new dry process cement rotary kiln system. Therefore, it is imperative to conduct thorough and meticulous analysis and research from the perspectives of process, raw materials and fuels, equipment, thermal regime, operation, and management. Based on the production experience of some cement enterprises, the primary reasons for buildup and blockage can be broadly categorized as follows:
① Blockage caused by skinning
Caking refers to the formation of hard layers of material adhering to the inner walls of the smoke chamber, rising ducts, and cones of various stages (mainly the third and fourth stages) of the cyclone. In severe cases, it presents as circular constrictions. This caking hinders the normal flow of material, with alternating processes of adhesion and melting, gradually increasing the number and thickness of the layers. It affects the ventilation within the kiln, alters the speed and direction of material and airflow within the preheater, and ultimately leads to blockages. There are three main reasons for this phenomenon: the impact of ash backflow, the influence of harmful elements, and local high temperatures causing caking and blockages.
② Blockage caused by air leakage
Air leakage is a major enemy of the external decomposing kiln. It not only reduces the separation efficiency of the cyclone tube and increases heat consumption, but also serves as a primary factor causing system blockage. Blockages caused by internal air leakage and those caused by external air leakage.
③ Blockage caused by improper operation
(1) Feeding is not timely.
(2) Improper exhaust air volume during kiln startup and shutdown.
(3) The feeding rate is not synchronized with the kiln speed.
(4) Improper control of exhaust air volume.
(5) Uneven distribution of airflow in kilns and furnaces, coupled with uncoordinated operations.
④ Blockage caused by foreign objects
The system should be inspected for any loose or collapsed door bricks; peeling of materials on the top cover and lining of the cyclone tube and decomposing furnace; burnt and fallen inner cylinder or spreading plate of the cyclone tube; burnt or malfunctioning ash discharge valve; and mechanical blockage of the preheater caused by refractory bricks, ironware, or other items left inside during maintenance.
⑤ Blockage caused by improper design and inherent deficiencies
The system design should create favorable conditions for production, and any inherent deficiencies caused by unreasonable design of certain parts must be avoided, as they can affect production. System blockages caused by inherent deficiencies are difficult to handle in production and must be avoided. For example, factors such as excessively long horizontal connecting pipes, excessively small angles of connecting pipes, a smaller height-to-width ratio of the air inlets of preheaters at various stages, smaller cone angles, excessively long inner cylinders, and uneven ash mixing will all affect production.