Energy Saving High Quality Rotary Kiln for Dolomite, Limestone, Cement

 1.rotary kiln brief introduction:

A rotary kiln is a pyroprocessing device used to raise materials to a high temperature (calcination) in a continuous process. Materials produced using rotary kilns include:

• Cement
• Lime
• Refractories
• Metakaolin
• Titanium dioxide
• Alumina
• Vermiculite
• Iron ore pellets

They are also used for roasting a wide variety of sulfide ores prior to metal extraction.

 

2.Rotary Kiln Principle of operation

The rotary kiln is a cylindrical vessel, inclined slightly to the horizontal, which is rotated slowly about its axis. The material to be processed is fed into the upper end of the cylinder. As the kiln rotates, material gradually moves down towards the lower end, and may undergo a certain amount of stirring and mixing. Hot gases pass along the kiln, sometimes in the same direction as the process material (co-current), but usually in the opposite direction (counter-current). The hot gases may be generated in an external furnace, or may be generated by a flame inside the kiln. Such a flame is projected from a burner-pipe (or "firing pipe") which acts like a large bunsen burner. The fuel for this may be gas, oil, pulverized petroleum coke or pulverized coal.

 

3.Rotary kiln structure:

The basic components of a rotary kiln are the shell, the refractory lining, support tyres (riding rings) and rollers, drive gear and internal heat exchangers.

rotary kiln Cylinder as heating pivoting department, made of high-quality carbon steel plate, is supported on the support device by tyre, and there is mechanical or hydraulic pressure catch wheel on the first or some gear in order to control the turning of cylinder. Place of the tyre Gearing gyrate according to process-required rotating speed by ring gear in the middle of cylinder. Because of the need By the required of installation and maintenance, the bigger rotary kiln has auxiliary gears, which makes cylinder gyrate more slowly. To prevent cold air come in and dust overflow, the reliable sealing equipment of kiln tail and head is installed on feeding hole and discharge hole.

 

Kiln shell:

This is made from rolled mild steel plate, usually between 15 and 30 mm thick, welded to form a cylinder which may be up to 230 m in length and up to 6 m in diameter. This will be usually situated on an east-west axis to prevent eddy currents.

Upper limits on diameter are set by the tendency of the shell to deform under its own weight to an oval cross section, with consequent flexure during rotation. Length is not necessarily limited, but it becomes difficult to cope with changes in length on heating and cooling (typically around 0.1 to 0.5% of the length) if the kiln is very long.

Refractory lining:

The purpose of the refractory lining is to insulate the steel shell from the high temperatures inside the kiln, and to protect it from the corrosive properties of the process material. It may consist of refractory bricks or cast refractory concrete, or may be absent in zones of the kiln that are below around 250 °C. The refractory selected depends upon the temperature inside the kiln and the chemical nature of the material being processed. In some processes, such as cement, the refractory life is prolonged by maintaining a coating of the processed material on the refractory surface. The thickness of the lining is generally in the range 80 to 300 mm. A typical refractory will be capable of maintaining a temperature drop of 1000 °C or more between its hot and cold faces. The shell temperature needs to be maintained below around 350 °C in order to protect the steel from damage, and continuous infrared scanners are used to give early warning of "hot-spots" indicative of refractory failure.

Tyres and rollers:

Tyres, sometimes called riding rings, usually consist of a single annular steel casting, machined to a smooth cylindrical surface, which attach loosely to the kiln shell through a variety of "chair" arrangements. These require some ingenuity of design, since the tyre must fit the shell snugly, but also allow thermal movement. The tyre rides on pairs of steel rollers, also machined to a smooth cylindrical surface, and set about half a kiln-diameter apart. The rollers must support the kiln, and allow rotation that is as nearly frictionless as possible. A well-engineered kiln, when the power is cut off, will swing pendulum-like many times before coming to rest. The mass of a typical 6 x 60 m kiln, including refractories and feed, is around 1100 tonnes, and would be carried on three tyres and sets of rollers, spaced along the length of the kiln. The longest kilns may have 8 sets of rollers, while very short kilns may have only two. Kilns usually rotate at 0.5 to 2 rpm, but sometimes as fast as 5 rpm. The Kilns of most modern cement plants are running at 4 to 5 rpm. The bearings of the rollers must be capable of withstanding the large static and live loads involved, and must be carefully protected from the heat of the kiln and the ingress of dust. In addition to support rollers, there are usually upper and lower "retaining (or thrust) rollers" bearing against the side of tyres, that prevent the kiln from slipping off the support rollers. Now rotary kiln length is 84 meters.

 

4. Rotary Kiln features:

1. Support device: advanced shaft structure, has automatic temperature measurement and electrical heating device ,meanwhile you can choose liquidity support . 
2. Catch wheel: mechanical wheel and hydraulic pressure 
3. Gearing: single driver or double driver. Control the revolution by YZD, DC motor and frequency variable motor. Be reliable, energy-saving, and efficient. 
4. Cylinder tyre bolster: bolster has three types: fixed type, adjustable type and floating type. The structure is simple; maintenance and replacement are convenient without hurting the cylinder. 
5. Sealing equipment: there are many different design of sealing style for choice according to kiln models, including air cylinder edge sealing, spring edge sealing, graphite block sealing and combination for above. The feather is adaptive for cylinder rotating and swing. And airproof performance is well.