Petroleum coke is a flammable solid product after coking Petroleum residuum and asphaltum. The features of delayed coking are as follows. Residuum passes through furnace tube at a high velocity of flow. When heated to about 500 degree centigrade, the residuum immediately enters into a coking tower which is tens of meters high and start coking reaction in it depending on its own heat. Then, much gas-liquid product is emitted from the top of the tower, and coke remains. The amount of coke takes 10%~20% of the residuum which has entered into the tower. Delayed coking unit generally includes one heating furnace and two coking towers. The residuum which has been heated to specified temperature enters into one of the two towers. When coke is generated and accumulated to certain height, the hot residuum will be moved into the other coking tower. As to the recovery and fractionation system of gas-liquid products outside the coking tower, it is continuous manufacturing. As to two coking towers, just one tower is in the state of coking, while the other is in the state of preparation. It takes about 24 hours for residuum coking in the tower. According to the different property of residuum and recycle ration, the capacity of every tower is different. Finally, hydraulic decoking equipment is used to cut and discharge the generated coke in the tower. The main raw materials of delayed coking are vacuum residuum and secondary processing residuum, while sometimes crude oil is directly used for delayed coking. Above all, the quality of Pet coke is related to the content and property of crude oil or residuum. Various crude oil have different properties, so residuum that is obtained by distillation also has different properties. Even if the crude oil is same, the property of residuum is still different after crude oil passing different processing units. In China, the raw material is mainly the vacuum residuum whose density is smaller than one and coking value isn’t high. Owing to more colloid and asphaltene and less aromatic hydrocarbon existing in the vacuum residuum, much alveolate or sponge coke and little low-level needle coke generate when coking. As a result, this kind of the Pet coke has high resistivity and coefficient of thermal expansion.
Petroleum coke is a product which takes distilled or other heavy oil as the raw material. China mainly uses vacuum residuum. Heavy oil passes through the furnace tube that is about 500 degree centigrade at a high velocity of flow so that cracking reaction and condensation reaction happen in the coking tower. Finally generated green coke goes through cooling cook and decoking.
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