Analysis of installation and commissioning of cement rotary kiln BY Amanda Lee

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Analysis of installation and commissioning of cement rotary kiln BY Amanda Lee

 

 

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First, the structure of rotary kiln equipment In the cement production process,

the calcining kiln is the heart equipment, the calcination quality of the calcining kiln determines the quality and grade of the cement. The calcining kiln currently has vertical kiln, wet rotary kiln, hollow dry kiln and the new type of dry rotary kiln with preheating decomposer currently in common use. The quality of the installation and commissioning of the rotary kiln determines the operating rate of the rotary kiln, and the quality of the installation and commissioning of the rotary kiln determines the economic benefits of the enterprise. when

The front rotary kiln has been developed to a large scale. The daily output of a single kiln has reached more than 15,000 tons, and the total weight of a single plant has reached 1,500 tons. It is a high-precision equipment with long construction requirements. The rotary kiln equipment is mainly composed of the following components: kiln cylinder, supporting rotating supporting wheel, retaining wheel, transmission mechanism, kiln hood, kiln tail chamber, kiln head kiln seal, pulverized coal combustion device, firing belt cooling device, etc. .

The kiln cylinder is made of thick steel plate, and the refractory brick is built inside, which has a dip angle of 3~4%. It is placed on the roller set and rotates slowly. The normal rotation speed is generally 3~5 revolutions per minute. The kiln cylinder is provided with a heat-resistant steel material, and a wheel belt is arranged at the support wheel. The transmission part is equipped with a large gear, and a sealing device is arranged respectively at the interface between the kiln head cover and the kiln tail chamber.

The supporting kiln cylinder is a supporting wheel, and the supporting wheel and the supporting seat are in contact with a copper alloy bearing bush, and are equipped with a lubricating oil and a water cooling system. Due to the large size of the kiln, the axial thrust generated by the kiln is increased. By adjusting the angle of the supporting roller to offset the axial force, the hydraulic retaining wheel controlled by the hydraulic system is basically replaced. In addition to the full axial thrust of the kiln, the kiln is slowly reciprocated along the axis.

The transmission of the rotary kiln mainly includes large gears, small gears, gearboxes, main drive high-voltage DC speed-regulating motors, and transmission-assisted transmission motors. The positioning of the pinion is very important here.

The kiln hood and the kiln tail chamber are static equipments that are connected with the front and rear equipment of the rotary kiln; the pulverized coal combustion device transfers the heat to the cement raw material by burning pulverized coal to achieve the purpose of calcination and firing; Safety and control automatic control system, automatic reciprocating scanning temperature monitor is added in the kiln hood, kiln exhaust chamber, belt parts and kiln barrel firing zone. When the temperature exceeds the normal range, the monitor is automatically DCS. Control, adjust the kiln operation control parameters, or command the kiln to stop and overhaul.

Second, the working principle of rotary kiln equipment calcination

The calcining process of the rotary kiln is a process of calcining and decomposing the limestone ore which has reached a certain grade by the ingredients, and is a complicated physical chemical reaction process. According to the physical and chemical reaction process of the material, the rotary kiln can be divided into pre-tropical zone, decomposition zone and firing zone. The material enters the rotary kiln from the preheating decomposer at the kiln end. At this time, the material is in a molten state and the temperature reaches 850 ° C or higher. The temperature of the kiln material is mentioned to a certain height by the action of the preheating decomposer, thereby shortening the rotation. The preheating process in the kiln shortens the pre-tropical zone and enters the decomposition zone earlier, thereby improving the calcination efficiency and output of the rotary kiln. Actually, some materials have entered the preheating decomposer.

solution status. The material moves forward in the kiln according to the inclination of the kiln cylinder and the rotation of the kiln, and enters the firing zone. Under the action of high temperature flue gas in the rotary kiln, the temperature is above 1200 °C, fully calcined into cement clinker, and finally from the kiln. The hood is dropped into the grate cooler. The kiln head pulverized coal is burned by the burner, and a large amount of heat fumes are generated. Under the action of the kiln tail fan, the kiln is fully contacted with the material to complete the physical chemical reaction and enter the preheating decomposer.

Rotary kiln as the carrier of the above complex physical and chemical reaction process, on the one hand is the combustion equipment, in which the pulverized coal is burned to generate heat; at the same time, it is also the calcining equipment, the raw material absorbs the heat of the gas for calcination; the fuel combustion, calcination and material movement It must be properly coordinated. Only by ensuring the normal operation rate of the rotary kiln can the above process be ensured to be efficient and continuous, so as to achieve high production, high quality and low consumption.

Third, the installation and commissioning analysis of the rotary kiln

Due to its large size, heavy weight and high precision requirements, the rotary kiln is generally transported to the installation site by semi-finished products of segmented and sub-components. The installation and commissioning of the rotary kiln is a process with a long cycle and multiple types of work. The quality of the installation and commissioning directly affects the normal operation rate and even the service life of the rotary kiln. Based on my company’s and my many years of experience, I will explain from the installation and commissioning process of the rotary kiln:

1. Installation of the bearing pad and oil temperature control:

The rotary kiln cylinder is rotated on the supporting wheel set by the wheel belt, and the journals at both ends of each supporting wheel are respectively supported in the supporting wheel seat, and the copper alloy tile in the journal and the wheel bearing seat is used for rolling friction movement, copper alloy tile It is fixed on the spherical tile in the roller seat, and the spherical tile and the steel base are used for sliding balance adjustment movement. Under normal circumstances, the above-mentioned roller seat is filled with a certain height of grease (24-saturated cylinder oil). In the cold state, the saturated cylinder oil of No. 24 is viscous. In the hot state, as the operating environment temperature rises, The rolling friction of the roller shaft and the copper alloy is heated, and the oil is gradually diluted. A cooling circulating water pipe is arranged in the spherical tile and the fixed supporting wheel seat, and a thermocouple is arranged in the lower part of the oil chamber of the wheel bearing seat, and the oil temperature is transmitted to the DCS system at any time. When the oil is in normal operation, the oil temperature is 30-40 ° C. If the temperature exceeds 50 °C, the DCS system of the control room will automatically alarm and even stop the kiln, causing the operation to be abnormal. The installation of all the bearing pads and the oil temperature are closely related, that is, the installation of various indicators is in place. , can effectively control the oil temperature and ensure the operating rate of the rotary kiln.

During normal operation, the oil returning spoon at the end of the journal pulls the lubricating oil from the lower part of the inner part of the roller seat to the upper part, and is poured on the oil pan. The oil pan is evenly spread on the surface of the journal along the axial direction, along with the journal. The rotation of the journal forms an oil film on the surface of the journal. The journal carries the oil film and the copper alloy tile to roll and rub. The oil film acts mainly to lubricate and reduce the friction coefficient. The second is to cool and dissipate heat. The running-in of the journal and the copper alloy tile is an important work in the installation and commissioning process, and is one of the key factors for the normal operation of the rotary kiln. “Cement Machinery Installation Engineering Construction and Acceptance Specifications” (JCJ03-90) requires copper alloy tile and

The side clearance (per side) of the journal is 0.001~0.0015D (D is the diameter of the journal), and the top clearance is 0.0015~0.002D. It has been proved that this gap can be set to 0.003D during installation because of the copper alloy tile. After gradually wear, the gap will gradually decrease, which will cause the contact angle between the journal and the copper alloy tile to be too large, the oil film will be destroyed, and the copper alloy tile will be burned. The contact circumferential angle between the journal and the copper alloy tile, the “Construction and Acceptance Specifications for Cement Machinery Installation Engineering” (JCJ03-90) is 60~75°. It is proved that the angle should be 60° or even 50°. Because the contact angle between the journal and the copper alloy tile with 1~2 points/CM2 is within the contact angle, if the circumferential angle is slightly smaller, the damage time of the oil film affected by the above contact movement can be reduced, and at the same time, it can withstand The rotary kiln equipment and load weight can effectively ensure the probability of damage and heat generation of the copper alloy tile. In the course of practice, it is found that there is a unit that sets the contact circumferential angle to 30°, which is also undesirable. Although it theoretically satisfies the probability of oil film reduction and heat generation, the weight of the rotary kiln equipment and the load is too large. If the weight of each copper alloy tile is too large, it will cause serious wear. In the process, the equipment may not have major problems in the initial stage of operation, but soon the copper alloy tile will wear too fast, causing the contact circumferential angle to be fully contacted. The oil film is completely destroyed in the contact circumferential angle, thereby heating and burning the tile.

2. Center adjustment of the cylinder

With the increase of the production capacity of single kiln, the diameter and length of the rotary kiln are gradually increasing. Due to the limitation of transportation height, the kiln drum is embodied in a single cylinder (about 2~3 meters in length). At the installation site, the segmentation group is paired at the installation site. Finally, on the correct roller set, the segmented cylinders are hoisted into an integral rotary kiln cylinder. Regardless of the segment group pair or the overall group pair, the centers of all sections and sections of the rotary kiln cylinder must be concentric, so as to ensure the smooth operation of the rotary kiln. The longitudinal centerline of the cylinders of each section and section will be adjusted into a straight line, and the cylinders will be aligned with the wrong mouth. If the kiln is not in place, the consequences are very serious: the center of the cylinders of each section and section are inconsistent, resulting in dynamic imbalance of the cylinder, excessive running jitter, increased running load, resulting in the failure of the entire equipment to operate normally; the roller and the belt wear Uneven, wear and tear, the temperature of the roller oil is high, and even the kiln cylinder is subjected to unbalanced load, which causes the barrel welding and the base material to tear, which seriously affects the service life of the rotary kiln.

The methods for adjusting the kiln include common methods such as external centering method, lighting method, and infrared method. The outer circle centering method is to fix a pin at the outer circle of the kiln cylinder interface, let the cylinder rotate, and measure the pin to the cylinder distance.

The method of this method can play a certain role, but the ellipticity of the kiln cylinder is also included in the amount of swing, so the result is inaccurate and the error is large, generally in the early stage of adjusting the kiln. Used as a coarse adjustment method. The basic principles of the lighting method and the infrared method are similar, but there is a difference in finding a positive light source. The infrared light has the advantages of high brightness, strong directivity, and good monochromaticity, and is currently widely used in installation. The cylinders of each section have been fully rounded in the manufacturing plant, and the “M-shaped support” has been added to the installation site. Before adjusting the kiln, first determine the starting point of the wheel fulcrum at the feeding end as the starting point of the infrared kiln, and prepare the joint. Each interface uses the method of finding the approximate center to find the center of the circle; the center of the starting point of the kiln is drilled with a diameter of 2MM, and the other center of the interface is opened with a diameter of 50~80MM, which serves as the infrared starting channel, and the other interfaces are respectively added. A hinged metal insert plate is used to detect the size and direction of the center of each interface before the kiln is deflected. During the process of adjusting the kiln, when the different cores are measured, the platen bolts are used for adjustment, and the center deviation of the cylinder is controlled within the required range. In particular, when the segmented cylinders are paired, they are adjusted in advance and must be adjusted in place, otherwise the quality of the segmentation adjustment will be affected. When the segment pairs are paired, they can be adjusted by using the segmented cylinder weight and the crane lifting. “Code for Construction and Acceptance of Cement Machinery Installation Engineering” (JCJ03-90) requires that the radial runout of the center of the cylinder should not be greater than the following values: the center of the cylinder at the large ring gear and the wheel belt is 4MM, and the center of the cylinder at the rest is 12MM, 5MM at the kiln head and kiln tail, can only be welded after adjustment. In the actual operation process, there is welding operation after the completion of the adjustment of the kiln, and the welding must have welding deformation. In order to ensure that the jumps meet the above requirements of the acceptance specification after the completion of the welding, the requirements must be increased during the adjustment of the kiln. During the actual operation of the kiln, the center of each cylinder interface is controlled according to the following requirements: the different degrees of control of the large gear, the belt, the kiln head and the kiln are controlled within 2MM, and all other interfaces are controlled within 6MM. In the welding process, the influence of welding on the center concentricity must be fully considered, and effective control measures should be taken accordingly.

In the process of adjusting the kiln, the kiln cylinder must be rotated several times, so that the kiln cylinder can be stopped at different angles (can be divided into eight equal parts according to the circumference) to find the final quality of the kiln. At the same time, in the process of adjusting the kiln, it is necessary to take into account the external factors, especially the temperature (especially in the summer). Therefore, the general kiln work is selected at night or at the beginning of the day to effectively eliminate the deformation of the kiln due to the temperature. the elements of.

3. Size gear installation correction

In order to ensure the normal operation of the rotary kiln, the installation of transmissions such as large and small gears is also one of the key factors.

The connection between the large gear and the kiln cylinder is connected by elastic spring plates to reduce the impact of the cylinder bending, parking and driving. At present, the large rotary kiln is connected by tangential spring plates. There are three types of connection between the spring plate and the kiln cylinder: one is connected by rivets, the other is connected with a transitional matching screw, and the third is welded connection. At present, the welding connection method is more common. The key control point for the large gear installation is that the center of the large gear is consistent with the center of the kiln cylinder, and the tooth surface is required.

The longitudinal centerline of the cylinder is parallel. “Cement machinery installation engineering construction and acceptance specifications” (JCJ03-90) to correct the rotary kiln gear: (1) radial swing deviation should not be greater than 1.5MM; (2) end face swing deviation should not be greater than 1MM; (3) The deviation of the transverse centerline of the large ring gear from the adjacent wheel belt shall not exceed 3 mm. It is worth noting here that after the spring plate is welded, the radial oscillation of the large gear, the end surface oscillation, and the transverse center line must be detected again. If the detection exceeds the standard, it must be adjusted again, and the adjustment can be performed by jacking and welding.

Pinion installation, in addition to the control of the conventional tip clearance, parallelism, etc., the special need to specify here is the positioning of the radial centerline of the pinion. The pinion width is larger than the large gear. During normal operation, with the kiln cylinder The expansion, the upper and lower wheels are strung together, and the large gear must be in full contact with the pinion at full time. In practice, it is found that some of the side of the large gear exceeds the edge of the pinion and it falls, causing serious wear on the axial side of the large and small gears. , affecting the normal operation of the rotary kiln. To avoid the above phenomenon, the upper and lower limit positions of the large gears must be accurately calculated during installation, and the center line of the pinion gears should be positioned according to the above upper and lower limit positions. In the specific operation, the wheel belt of the kiln cylinder drive can be abutted against one end of the wheel, and then the stroke of the wheel belt can be measured to calculate the limit position of the big gear up and down.

Fourth, the conclusion

The installation and commissioning process of the rotary kiln, as well as basic acceptance, pallet alignment, cylinder hoisting, wheel set, cylinder welding, kiln kiln tail seal installation, firing zone cooling installation, pulverized coal combustion installation, The process of refractory masonry, cooling circulating water system installation, single-machine trial operation, etc., each process is a process that requires fine operation. Only through full implementation, from all aspects, can the effective operation rate of the rotary kiln be effectively improved. Therefore, it will also promote the sustained and stable development of cement enterprises in the era of low profit.

 

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