The working principle and structure characteristics of rotary kiln

rotary kiln

 Xinguang Machinery is one of the leading manufacturers in producing high efficiency and energy-saving mining machinery in Henan Province, China. We mainly provide ball mills, rotary kilns , Vertical combination crusher , magnetic separators, floatation machines, pelletizers, vibrating feeders, vibrating screens, sand-washing machines, belt conveyors and driers.
1． Working principles：rotary kiln is the host device of cement production. 

Raw material is entered from high-end of kiln tail shell to the inner kiln shell for calcination. The inclination and slow rotation of kiln shell makes material roll along circumferential direction and along axial direction from high end to low end. Through decomposition, calcination, cooling and other technical process, the raw material is burnt to cement clinker and then discharged from the low end of kiln shell and entered cooler.  

The fuel is puffed from kiln head, burnt inside the kiln, and the heat giving out is used to heat the raw material, to make the raw material calcine to clinker. The hot air formed during the process of material heating exchange is entered from kiln feeding end to kiln tail system, and then vent the gas by chimney.

2．Structural features 

The rotary kiln is mainly consist of kiln shell, driving device, supporting device, thrust roller device, kiln head sealing device, kiln tail sealing device, kiln hood and so on. Please refer to structural diagram of rotary kiln.

 

(1)Kiln shell part 

Kiln shell is the main body of rotary kiln, and it is rolled and welded by steel plate. Kiln tail is obliquely installed many pairs of supporting rollers. The lower end of the kiln shell is equipped with high temperature and abrasion resistant kilneye guard plate and form sleeve space, and there is also air fan to cool for kilneye part. Several rectangle tyres have been set along the direction of kiln shell length, which bears the weight of kiln shell, kiln liner, material and other rotate parts, and spreads its weight to supporting device. There’s floating washer under the tyre, you can adjust or change it according to the clearance after operation, to gain the best clearance. The washer is used to enhance the rigidity of kiln shell, to avoid kiln shell suffering abrasion due to relative sliding between tyre and kiln shell along circumferencial direction

(2)  bull gear device  

Bull gear is fixed near the end part of kiln shell to transmit torque. The bull gear is connected with kiln shell by spring plate, because this connecting structure can make enough heat dissipation space between gear ring and kiln shell, and can also reduce kiln shell bending deflection, besides it can damping and buffer, which is good to prolong the life of kiln liner.

(3)  driving device 3.1  driving mode： 

a) Single drive：The driving system adopts single drive, and it is driven by a set of main     driving motor. 

b) Double drive：The driving system adopts double drive, and they are driven two sets of main driving motor. Two sets of transmission of the synchronization are achieved by adjusting the electrical equipment, so two systems can bear even stress.  c) 3.2  motor 

Except the small-scale rotary kiln can select Z2 series small-scale DC motor, the others all select ZSN4 DC motor - specialized for rotary kiln. ZSN4 DC motor is designed as per cement rotary kiln main drive working condition, with small size, light weight, high efficiency, and good performance.   3.3  Reducer  

It often selects hardened tooth-surface reducer for the reducer, because it has advanced technology, small size and light weight. 3.4  Assembled spring coupler 

Assembled spring coupler is used between pinion device and main reducer, because it has good flexibility, can absorb some impact and can also compensate for the larger radial deviation and axial stretch. 

(4) Supporting device 

Supporting device is an important part of rotary kiln. It carries the whole weight of the rotating part of kiln shell, and has the positioning function on shell to make shell and supporting roller rotate stably. Supporting device is Self-aligning sliding bearings structure, with compact structure and light weight. It also configured lubricating oil automatic heating and temperature control devices and measuring devices, which is reliable and adaptable.(5)thrust roller device 

According to the stress condition and action principle of thrust roller, it is divided into mechanical signal thrust roller and hydraulic thrust roller.  

a) Mechanical thrust roller: it is installed in pairs on the two sides of tyre near bull gear, to restrict kiln shell movement in axial direction.

b) Hydraulic thrust roller：it is set on lower side of tyre near bull gear. Trust roller is to force tyre and kiln shell reciprocate in certain speed and stroke along kiln centerline direction on the supporting roller, which can make the tyre and supporting roller wear evenly on the whole width to prolong lifetime.（6） kiln head sealing device 

Kiln head sealing device is the SM-type kiln head sealing device or the GP-type kiln head sealing device, which can meet the working condition and the user’s requirements. a) SM-type kiln head sealing device SM graphite is block radial contact and labyrinth assembly sealing mode. It can compensate runout during kiln shell operation automatically, and it has good sealing performance. 

b) GP-type kiln head sealing device is steel sheet radial contact sealing mode. It can compensate runout during kiln shell operation automatically, and it has good sealing performance. 

(7)  kiln tail sealing device 

a) QD-type kiln tail sealing device adopts cylinder compress endface contact, and the whole sealing rings can bear the even stress and eliminate harmful effect caused by installation and kiln shell flexivity. Besides, lubricating grease is fed into friction ring contact surface to lubricate by electrical dry oil pump, with little friction, little abrasion and good sealing.(8) kiln hood 

Kiln hood is welded by steel plate. It is located on kiln head operation platform by the supporting legs on the two sides. Its lower part is connected with cooler. Inside the kiln hood, there should be firebrick or heat resistant concrete. Two suspension movable kiln door are set at outer endface of kiln hood, so as to easily get into kiln for repairing and building kiln liner