Chinese
Causes and Prevention of Rotary Kiln and Red Kiln Failures
  • Time:Jan 19, 2023
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      The service life of the refractory bricks lining the rotary kiln is one of the important factors that determine the kiln operation cycle, and the damage to the refractory bricks causes the red kiln to be shut down for a long time, and the resulting economic losses are also relatively large, which affects the company's profitability. economic benefits. Therefore, how to improve the service life of refractory bricks, extend the kiln operation period, and avoid abnormal consumption of refractory bricks is the key content of Zhengzhou Zhenjin Company's research and development of refractory bricks from the aspects of performance, masonry, production organization and maintenance. 

1. Causes of red kiln failure

(1) Mechanical load

      The mechanical load of the rotary kiln is mainly due to the relative movement and heat transfer of the cylinder body, refractory materials, materials, and dust-containing gas during the calcination of the clinker, the mechanical load generated by the relative movement of the kiln lining, and the gravity and abrasion from the materials. When the mechanical load on the refractory in the kiln exceeds its own strength, it will cause damage to the refractory. The specific causes of mechanical load or mechanical stress include kiln shell distortion and deformation, axis deviation, and irregular masonry, etc. The main damage forms of refractory bricks are raised head burst, brick body fracture, and refractory bricks rotating along the kiln. The direction of twisting and shifting and the appearance of axial grooves, etc.

      Among the causes of damage to refractory bricks due to mechanical loads, irregular masonry is a relatively common cause. Therefore, in order to avoid such reasons, Zhengzhou Zhenjin Company will send special personnel to the site to guide the masonry when the user is building the kiln. To avoid problems such as too large or too small reserved expansion joints, too tight or too loose brick locking area, and too many steel plates used.

(2)Heat load

      The heat load mainly refers to the thermal expansion of the refractory bricks due to high temperature during the operation of the rotary kiln, causing them to be squeezed and damaged; local overheating of the refractory bricks leads to melting pits and thermal stress due to sudden changes in temperature, resulting in peeling and cracking of the brick surface. The specific reasons for the heat load include insufficient expansion joints reserved in the refractory brick masonry, the fire point of the burner is too biased towards the refractory brick, and the frequent start and stop of the kiln or the sharp change in temperature caused by a large reduction in production.

(3) Chemical attack

      Chemical erosion is one of the important factors affecting the life cycle of refractory bricks in kilns, and the application of cement kiln co-processing projects puts forward higher requirements on the performance of refractory bricks. The mechanism of chemical erosion is relatively complicated. Some studies have concluded that sulfur, alkali metals, sodium salts and other components in the liquid phase of clinker react with minerals on the surface of refractory bricks to form copolymers with low melting points on the surface of refractory bricks. The low-eutectic material formed on the surface of the brick has low strength and is easy to fall off under the action of material movement and friction, gradually forming a thinning of the refractory brick.

      Harmful substances such as sulfur, alkali metals, and chloride ions in the clinker liquid phase are not only from the raw materials, but also the harmful substances in the solid and hazardous waste production line that are co-processed will intensify the progress of refractory bricks being subjected to chemical erosion.

2. Preventive measures

      In the after-sales service of ZHENJIN REFRACTORIES, according to the working conditions, it provides customers with masonry guidance, and proposes daily maintenance measures for customers to help users avoid the phenomenon of red kilns and improve the safe operation cycle of rotary kilns.

(1) Daily management of refractory bricks

      Establish a refractory brick replacement ledger to record the use cycle, so that it can be replaced in time after the cycle. In daily operation, the surface temperature measurement of the kiln shell is strengthened. In addition to using the kiln shell scanner, the on-site temperature measurement of the kiln mouth, the kiln tail and the inner side of the wheel belt should also be carried out regularly.

      Regularly record key data such as slippage of the kiln wheel belt and vibration of the large ring gear to grasp changes in mechanical stress in a timely manner and make targeted adjustments. In addition, the ellipticity of the kiln shell needs to be tested before the planned maintenance of the production line, and the center line of the kiln needs to be tested for abnormal deviations, so as to reduce the abnormal consumption of refractory bricks caused by mechanical stress.

(2) Inspection of refractory brick kiln shutdown

      ZHENJIN REFRACTORIES requires the user's process professional management personnel to check and measure the actual loss of refractory bricks in the kiln after the production line is shut down. Carry out a comprehensive inspection of the area, record the minimum thickness, maximum thickness, average thickness, and refractory brick distortion, etc., and then form a replacement opinion based on the inspection situation and the service cycle of the refractory brick, and analyze the reasons for the replacement that has not reached the service cycle to avoid Prolonged cycle of nausea.

(3) Refractory brick construction and acceptance management

      Strengthen the management of the refractory brick construction process, from the tools and equipment used in the refractory brick masonry, the measurement of the ellipticity of the cylinder at the brick replacement site, to the pressure of the gas source used in the masonry, the sealing pressure, and the number of sealing bricks used for each ring of bricks, iron The number of boards, etc. shall be carried out in strict accordance with the refractory brick masonry specifications, and special personnel shall be arranged to supervise and record; the quality acceptance management of refractory brick construction shall be done well. After the masonry in the kiln is completed, check the locked brick area block by block. After the inspection, the rotary kiln is idling, and then a comprehensive inspection is carried out after idling to ensure that the construction quality is qualified.

(4) Designate a reasonable kiln heating curve

      According to the replacement of refractory bricks in the kiln, a reasonable kiln temperature rise curve is formulated, and the principle of "slow temperature rise, no turning back" is adhered to, and the system equipment is fully cleaned before ignition and heating to ensure stable operation of each host equipment after ignition and feeding.

      The service life of refractory bricks in the kiln is a key factor in determining the kiln operation period. Therefore, in order to improve the kiln operation period, it is very important to standardize the construction of refractory bricks, strengthen the refined management of process operation, and pay close attention to the temperature of the kiln shell. To this end, ZHENJIN REFRACTORIES continues to pay attention to the use and replacement of refractory bricks in each production line of users, constantly analyzes and summarizes the reasons for the abnormal consumption of refractory bricks in the production line, actively strengthens technical support, optimizes the configuration of refractory bricks, and is committed to reducing or avoiding abnormal consumption of refractory bricks The kiln shutdown caused by continuous improvement of kiln continuous operation cycle.

镁铁

One of the main products of ZHENJIN REFRACTORIES: magnesia-iron spinel bricks, which have excellent kiln skin-hanging properties, excellent corrosion resistance, and excellent thermal shock resistance stability. They are ideal refractory bricks for cement kiln rotary kilns.

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