Green Petroleum Coke (GPC) is calcined at high temperatures in a rotary kiln. The cooled Calcined Coke is routed to bulk storage and bagged for shipment to customers.
GPC is a byproduct of delayed coking in crude oil distillation units of Oil Refineries. It is used to produce anodes for aluminium, steel and titanium smelting industry.
A calcining process of petroleum coke is used to remove impurities like moisture, volatile matter and sulfur from the carbonaceous material. This is done by heating it at a temperature of about 1300. It also changes the structural and physicochemical properties of petroleum coke. It improves its graphitization degree, mechanical strength, density and electrical conductivity, while reducing its hydrogen content.
The calcined coke produced is widely used as anode for aluminium production and steel recarburizing. It is also a crucial ingredient in the manufacture of titanium dioxide which is a key component of sunscreens, plastics and many other industrial products.
The rotary kiln process is more energy efficient than shaft coke calcination and is preferred by most smelters. However, the different porosity and bulk density profiles of shaft and rotary cokes cause large variations in pitch level and anode density if they are processed on a campaign basis. Therefore, smelters are increasingly blending CPC from different sources to achieve more consistent anode quality.
The calcining process is typically done in rotary kilns which are steel shells lined with high-temperature refractory brick. The coke is heated to temperatures between 1200 °F and 1350 °F and then cooled by water quenching in a rotary cooler. The coke is then conveyed on a conveyor and into the storage godowns.
Aluminum smelters consume the most CPC in the world; each ton of aluminum produced requires about 0.4 pounds of anode grade coke. Rain Carbon supplies anode-grade coke to the global aluminum industry. The physical and electrical conductivity of anode-grade coke makes it a key component in the aluminum production process.
Fuel-grade petcoke can be burned in industrial boilers to produce steam or hot water for various processes. It’s a cheaper fuel than natural gas and can reduce energy costs. With stricter emissions regulations, more and more calciners are adding SO2 scrubbing to their plants. The resulting scrubbed coke is used to manufacture graphite electrodes and other carbon products, and it’s also being explored as an alternative fuel for power cells.
The process of calcining petroleum coke starts with the crude oil being refined in a refinery. During the refining process, heavy fractions are produced which will later be converted to petcoke (calcined petroleum coke). The petcoke is then used in various industrial processes such as producing carbon anodes for aluminum smelting and as a fuel for power generation.
While calcining, the petroleum coke goes through complex physical and chemical changes. The coke gets contracted when it is cooled down, and the size of contraction depends on the temperature during calcining. The lower the temperature is during calcining, the smaller the size of the contraction is.
The calcined coke has to be transported from the kiln to the storage area where it will be kept in different bunkers. It is then packed in HDPE bags which are weighed before loading. Since CPC is a highly sensitive product, AIPL ensures that it is stored in a proper way.
The coke is a highly brittle, oily substance that contains high levels of carbon. It can cause a fire or explosion. Workers handling coke need to be trained in the engineering and work practice controls, such as immediate housekeeping and explosion/deflagration suppression systems. OSHA’s National Emphasis Program for Coke Oven Emissions and Control requires specific engineering and work practice controls to prevent combustible dust explosions.
The calcining process transforms sponge coke into a solid fuel called calcined petroleum coke, or CPC. This is used for making graphite electrodes, foundry cores, and in open hearth furnace linings. It also is used in steel, glass, paper, brick, and fertilizer manufacturing.
Independent or merchant calciners (those not integrated with refineries) blend different quality GPCs to produce CPCs that meet anode specifications for S, V, and Ni, as well as the Hardgrove grindability index. They also test the CPC for other mechanical properties, such as its coefficient of thermal expansion, which influences the ability to withstand extreme temperature variations in the arc furnace, and its apparent density, which affects binder content for electrode paste.
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