General

Rotary kiln is a barrel-like rotary indurating equipment for heat treatment of bulk material and slurry material. This equipment is for the induration process of oxide pellet.
Rotary kiln is a thin wall barrel(hereinafter called kiln shell) installed on a supporting device with a certain inclination and rotated slowly by driving device. Material go in from the charging end(kiln tail). Due to the inclination of the kiln shell, material inside the kiln will move along the axial line while rolling peripherally, and flow slowly from the tail of the kiln cross the whole kiln shell and go out of the kiln shell at the discharging end(head of kiln). Fuel will be injected from head of kiln into high temperature zone inside kiln for combustion and flow to the tail of kiln. Hot fume flow counter-current with material. Material undergo high efficient heat exchange and complicated physical and chemical changes and complete induration process while rolling and moving inside the kiln shell.
This rotary kiln is used to produce oxide pellet. Preheated pellet from the traveling grate is charged through charging end of the rotary kiln and discharged from the discharging end of the rotary kiln after 1250~1350ºC induration inside the rotary kiln and delivered to the annular cooler for cooling. Finally the product pellet is obtained after cooling.

Equipment composition 

The rotary kiln is comprised of kiln shell, supporting device, hydraulic retaining roller(including kiln position detecting device), driving device, sealing device, fixed screen, kiln head sealing hood, kiln tail sealing hood, lubrication system, hydraulic piping system and structure cooling. The refractory, spillage collection device and controlling system which are related to the rotary kiln are not included the range of this unit.

Working principle of rotary kiln

Rotary kiln is composed of gas flow, fuel combustion, heat transfer and material movement, etc. Rotary kiln is how the fuel can be fully burned, the heat from fuel combustion can be effectively transferred to the material, and a series of physical and chemical changes will take place after the material receives the heat, and finally the finished clinker is formed.


Characteristics and application range of rotary kiln

Technical features of lime rotary kiln: the vertical preheater with advanced structure and low pressure loss can effectively improve the preheating effect after preheating
Metallurgical rotary kiln: metallurgical chemical kiln is mainly used for metallurgical industry iron and steel mill poor iron ore magnetization roasting;Chromium and nickel-iron oxide roasting.
Rotary kiln is mainly used for magnetizing roasting of lean iron ore in metallurgical industry.Silicon thermal smelting of magnesium;Chromium and nickel-iron ore oxidation roasting;The active lime and calcined dolomite used in refractory factories and ferroalloy factories.


Working principle of rotary kiln

In the working process of rotary kiln, materials and fuels enter from different ends of the kiln respectively, that is, materials enter from the high-end kiln tail of the cylinder body, and fuel is sprayed into the kiln head.With the tilting of the cylinder and the slow rotary action, the material rolls in the circumferential direction and moves from the high end to the low end in the axial direction. At the same time, the heat generated by the fuel under the action of wind and coal spraying pipe will be transferred from the kiln head to the kiln tail. Finally, the waste gas generated by combustion will be exchanged with the material and exported from the kiln tail.Finally, the generated clinker is cooled by the cooler through the kiln head cover.This collision process between heat and material constitutes calcining of material.
The use of wind in rotary kilns
It can be seen that the heat transfer of the rotary kiln is the core of the whole calcination. So, what is the heat transfer through? The answer is wind.Next, we will study the rotary kiln with the wind way.
The air entering the rotary kiln mainly comes from the leakage of the cooling machine, the coal spraying pipe and the system.The main wind from the rotary kiln is three times wind and kiln tail waste gas.
The wind coming into the rotary kiln is easy to understand, and the three winds coming out of the rotary kiln are highlighted below.
1, a wind.It is generally provided by a primary fan and transported coal powder into the kiln through pipelines.It not only transports pulverized coal, but also provides enough oxygen for coal in the initial combustion.However, the proportion of the primary air volume in the total air volume is not easy to be too much, and the increase of the proportion of the primary air volume will correspondingly reduce the proportion of the secondary air, which will affect the clinker cooling and increase the heat loss of the clinker.Generally, the primary air volume accounts for 15-25% of the total air volume is appropriate.
2. Secondary wind.It is generally provided by the blower and heated by the air preheater. The generated hot air is fed into the kiln through the separate passage of the burner and gradually converges with the primary wind.Secondary e wind provides oxygen for the combustion of carbon, and can strengthen the turbulence of airflow, promote the return of high-temperature flue gas, promote the mixture of combustible and oxygen, and provide conditions for complete combustion.
Three winds.The source of tertiary and secondary air is the same, which is the hot air after the clinker cooler cools the clinker.But the direction is different, secondary wind into the kiln to help combustion, three wind into the decomposition furnace.However, the purpose of secondary wind is the same, all for improving thermal efficiency.It contains about 10 fine coal powder in the third wind, and the air volume accounts for about 15 of the total air volume.
It can be seen from the above that the three times of wind plays a crucial role in the whole system of the rotary kiln, which can be said to be the heart of the rotary kiln. If the "heart" stops beating, the whole rotary kiln will not work.Therefore, when we operate, we must strictly grasp the amount of the three times of wind, so that the rotary kiln is in a healthy state.
 







Specification for Rotary Kiln(Φ4.0mx30m)
1  Product Description
1.1  Technical Parameter
1.1.1  Application:for spheric agglomeration roasting
1.1.2  Size:Φ4mx30m
1.1.3  Production capacity:≥90 t/h
1.1.4  Slope:3.5%( value)
1.1.5  revolution speed:
a) Main drive speed:0.16~1.60 r/min
b) Auxiliary drive speed:0.05 r/min
1.1.6  Supporting device:supporting with two stoppers
1.1.7  Retainer wheel device:hydrulic wheel
1.1.8  Sealing type: scale seal for kiln head & kiln tail
1.1.9   Cooling type for kiln head and tail:wind cooling
1.1.10  Rotary direction of the kiln:clockwise viewed form kiln head to kiln tail
1.1.11  Filling rate:7~8%
1.1.12  Roasting time:30~35 minutes

2  Basic structure and composition of equipment
2.1  Rotary kiln consists of:
Rotary kiln shaft one set, supporting device two sets, retainer wheel four sets, large gear device and gear cover one set, driver one set, kiln head seals and tail seals (including cooling air bustle pipes) one set for each, kin head hood one set, piping of oil pump station of the retainer wheel one set, lubrication system one set, special tools for rotary kiln one set and anchor bolts.
2.2  Drivers are equipped with emergent power supply. Two lines of power supply shall be provided, with one additional small power station installed for usage during power off. Auxiliary driving system must be provided for slow movement during kiln shaft failure.
2.3  Hydraulic automatic kiln play technology is used
Hydraulic automatic kiln play technology is adopted and the kiln can stably rotate. The support roller bearings are 10 sets of imported rolling bearing (performances not lower than that of Swedish SKF bearings). The stiffness and stability of the two roller sections that support the shaft shall be fully considered. Technical conditions of steel plates shall conform to the specifications of Boiler Plates GB13-1977 and cut-to-length wide plates shall be used as long as possible. The two backing ring sections and one gear ring section shall be treated by aging and meet construction, process and mechanical requirements. The connection of gear ring, support roller and shaft shall conform to process and mechanical requirements.
2.4  Centralized greasing station
The centralized greasing system is used for periodic automatic greasing of support bearing and retaining bearing of 1# and 2# support device.
Electric greasing system DDGY-RH-1: lubrication of the greasing system is executed by the 20Mpa pump station, which automatically supplies grease to various greasing points with the pressure at the connection port of greasing points not less than 2Mpa. Grease to be used: composite sodium base grease.
The greasing system and the oil injection system are installed with dual-pump system (one in operation and one standby). The pump station is around 20m from lubrication points. Except for lubrication points of the support roller bearing (total 8), all other lubrication points shall be installed with one section of hose.
The greasing system is installed with two electric greasing pumps, one in operation and one standby. Lubrication time of the greasing system should be adjustable and with automatic start up and shut down. The electric control system shall provide the upper computer with operation signals, light failure signals, heavy failure signals and operation control interfaces. The system shall have automatic control and manual control states.

3  Scope of supply
3.1 Rotary kiln shaft:          one set
The rotary kiln shaft, rolled and welded by steel plates, is φ4m×30 m, 30mm thick for shaft steel plates, 75mm thick for steel plates under rolling ring, and 45mm thick for steel plates under gear ring and of transitional belt.
3.2 Supporting device:                    two sets
The supporting device is composed of 1# and 2# supporting devices.
3.3 Supporting roller device:                four sets
The supporting roller device is composed of support roller, main shaft, bearing, bearing block, etc.
3.4 Large gear and gear cover:             one set
3.5 Driver                               one set
3.6 Kiln head seals and tail seals (including cooling air bustle pipes): one set for each.
3.7 Kiln head hood                      one set
3.8 Retaining roller oil pump station piping system    one set
3.9 Centralized greasing station           one set
3.10 Shaft temperature measuring device   one set
3.11 Rotary kiln special tools       one set
3.12 Anchor bolts                       one set

4  Equipment manufacturing requirements and inspection standards
4.1 Construction drawings, completed by Seller, shall subject to Buyer's review and signing. Only after that, can this drawing be followed for manufacturing. Such works as assembling, test and inspection are then performed in the manufacturing plant.
Main technical standards followed during manufacturing: General Technical Specifications on Heavy Machinery (JB/T15000.1~15).
4.2  Manufacturing, assembling and commissioning of the rotary kiln should meet the requirements of design drawings and documents and be provided with complete quality inspection reports. Supervisors for equipment manufacturing are entitled to check and review quality inspection reports and relevant documents.
4.3 Rotary Kiln Shaft
4.4 Rotary kiln support device
4.5 Refractory Materials in the Kiln (supplied by the buyer)
The service life of inside kiln refractory shall be advanced in China and more than 3 years, and that for the kiln head refractory be over 2 years. Such issues as refractory material, heat insulation material and connection integrity between shaft sections shall be fully considered to ensure the service life of refractory materials. The transformation of heat insulation materials due to periodic compression shall be taken into account of as well. Heat insulation materials between shaft shell and refractory materials shall be capable of ensuring the average temperature of shaft shell less than 100ºC.
4.6 The Large gear ring
4.7 The Rolling Ring
The material: ZG35SiMn or ZG35CrMo;The rolling ring requires ultrasonic fault detection in conformity to GB7233-85 standard's II level and the quality level requirements shall be qualified; the places that need overlaying welding shall conform to the related requirements of JB/ZA4000.6-86 (General technical requirements for steel casting's overlaying welding). The heat treatment of the rolling ring: normalizing HB=180~200; The rolling rings shall be delivered in the state of normalizing.
4.8 The Head and Tail Seal Devices
The seal devices adopt Elastic scale-like seal, which mainly consists of the scale and friction ring and so on. Along the circumferential direction, the friction rings can be divided into 24 pieces which are fastened at the head of the shaft and the tail of the air channel by briquetting. After the friction rings are fastened, no stairs shall exist between adjacent rings. Also, the coaxality of the friction rings' outer circle and the shaft shall meet the design requirements.
4.9 The Seal Devices of the Kiln Head and Kiln Tail
Seals of the kiln head and tail are composed of kiln head hood, kiln tail hood and scale seals. Scale seals are outsourced. Kiln head and tail hoods are welded parts. For easy construction of refractory materials on site, the head hood is designed as split type of upper part and lower part, which are welded into a complete piece after installation and site adjustment. Sealing hoods of the head and tail are equipped with ash hopper. As head and tail hoods are respectively installed with head sealing scale and tail sealing scale, the contact cone surface must be flat and meet the roundness and shaft coaxiality requirements. In addition, the head and tail hoods shall be stress eliminated and deformation corrected after welding.
4.10 Cooling air device
Coolers are set at the kiln's head and tail respectively so that they can send cold winds to these two places' seal friction ring and interlayer scale of the shaft respectively. Coolers are welded structures. Therefore, the welding stress shall be eliminated and the deformation shall be rectified after welding.
4.11 Hydraulic automatic kiln play technology is used
The kiln can stably rotate. The support roller bearings are 10 sets of imported rolling bearing (performances not lower than that of Swedish SKF bearings). The stiffness and stability of the two roller sections that support the shaft shall be fully considered. Technical conditions of steel plates shall conform to the specifications of Boiler Plates GB13-1977 and cut-to-length wide plates shall be used as long as possible. The two backing ring sections and one gear ring section shall be treated by aging and meet construction, process and mechanical requirements. The connection of gear ring, support roller and shaft shall conform to process and mechanical requirements.
4.12 Centralized greasing station
Designed and manufactured according to current effective national standards and norms, the components and parts selected by the system shall be reliable in quality, convenient for installation and overhauling.
Electric greasing system DDGY-RH-1: lubrication of the greasing system is executed by the 20Mpa pump station, which automatically supplies grease to various greasing points with the pressure at the connection port of greasing points not less than 2Mpa. Grease to be used: composite sodium base grease.
The greasing system and the oil injection system are installed with dual-pump system (one in operation and one standby). The pump station is around 20m from lubrication points. Except for lubrication points of the support roller bearing (total 8), all other lubrication points shall be installed with one section of hose.
The greasing system and oil injection system are installed with two electric greasing pumps, one in operation and one standby. Lubrication time of the greasing system should be adjustable and with automatic start up and shut down. The electric control system shall provide the upper computer with operation signals, light failure signals, heavy failure signals and operation control interfaces. The system shall have automatic control and manual control states.

5. Equipment installation requirements
5.1 The design drawing requirements and General Specifications on Machinery Installation, Construction and Acceptance (GB50231-98) shall be followed for construction, installation and acceptance of the rotary kiln.
5.2 Upon arrival of equipment on site, Seller shall send qualified technicians to the site to instruct installation. Seller shall repair and replace those defect equipment emerged during this period within specified period free of charge.
5.3 Seller shall send personnel to the site during installation period till equipment is conformed and accepted.
5.4 Kiln Shaft
5.5 Seals for kiln head and tail
Seals of the kiln head and tail are composed of kiln head hood, kiln tail hood and scale seal. Scale seals are outsourced. Kiln head and tail hoods are welded parts. For easy construction of refractory materials on site, the head hood is designed as split type of upper part and lower part, which are welded into a complete piece after installation and site adjustment. Sealing hoods of the head and tail are equipped with ash hopper. As head and tail hoods are respectively installed with head sealing scale and tail sealing scale, the contact cone surface must be flat and meet the roundness and shaft coaxiality requirements. In addition, stress of the head and tail hoods shall be eliminated and deformation corrected after welding.

6  Test run and performance test of equipment
The rotary kiln shall be generally assembled, no-load tested and load tested on site. The inspection and performance test shall conform to the followings:
6.1 The driver shall be running-in under no-load and gradually loading operation.
6.2 The rotary kiln is commissioned as a whole, which shall meet the drawing requirements.
6.3 The equipments should meet the requirements of the Φ4mx30m rotary kiln technical specification.
6.4 Seller shall send personnel to participate in no-load and load tests and to settle technical problems in relation with manufacturing that comes out during the test run.