Rotary kiln is the most commonly used equipment in the calcination of petroleum coke.Raw petroleum coke (commonly known as coke) flow into the rotary kiln in the kiln tail, in the kiln and countercurrent hot air contact heating, because the kiln body is tilted rotation, material rotates with the kiln body and move to the kiln head, and in turn after kiln preheating, calcining zone and cooling zone. Finally, from the head of the kiln outflow into the cooling machine.
Calcined petroleum coke
Calcined petroleum coke is mainly used in producing Graphite electrode. The calcined temperature is normally about 1300℃. The aim is to try to get rid of volatile petroleum coke. This can reduce the hydrogen content of petroleum coke products again, So that the degree of graphitization of petroleum coke increase and improve the high temperature and heat resistance of graphite electrode, and improve the conductivity of the graphite electrode. Calcined coke is also used carbon paste products, carborundum, food grade phosphate industry, metallurgical industry and calcium carbide.
Calcined petroleum coke as Φ2.2 * 45m rotary kiln an example, for example, yields about 5.5 tons / hour, the temperature is 1350 ℃, coke powder resistance is about 500-600μΩm, density 2-2.06g / cm3, burning carbonaceous loss of 9%.
- The rotation of the rotary kiln: 2.0-2.5r/min
- The temperature of the rotary head <900℃
- The temperature of the rotary kiln tail 900-1000℃
- Calcined temperature 1240-1300℃
- the negative pressure of the kiln 10-40pa
- The temperature of the cooling discharge 60-100℃
The process of the Calcined petroleum coke:
How it works
Coke calcining plants can be located in oil refineries, captive plants in aluminum smelters or merchant plants.
The petroleum green coke is fed into a refractory lined rotary kiln where the volatiles are driven off during the calcining process in an oxygen deficient atmosphere. Air can be injected through the kiln shell to burn a portion of the volatile matter in the kiln providing usable heat to the kiln.
Once the calcined coke is discharged from the kiln, the coke is cooled in a rotary cooler. At the feed end of the cooler, water is sprayed on the calcined coke to cool the coke to acceptable temperatures. The water is evaporated in the process.
The kiln exhaust gas is oxygen deficient and contains volatile matter released in the kiln. The kiln exhaust gas is directed to an afterburner (secondary combustion chamber) and air is injected to burn the volatiles and dust. A waste heat recovery boiler is used to produce steam from the heat contained in the afterburner exhaust gas.
Flexibility in operations
Metso rotary kilns can handle a wide range of green coke feeds including needle, sponge, shot, fluid or tar pitch green cokes. The rotary kiln is also able to optimize the coke calcining operating parameters, be it residence time, temperature gradient, and heat up rate, all of which impact product quality. Coke kilns can be fueled with: gas, heavy oil, oil, refinery gas, waste oil and solid fuel, fired independently or in combination.