在线清焦操作中弹丸焦产生的原因及预防

Causes of Production of Shot Coke in Inline Decoking Operation and Countermeasures

惠州炼化延迟焦化装置采用"两炉四塔"工艺路线,设计生焦周期为18h;设计循环比为0.3,可以实现灵活调节;加热炉可以实现在线清焦操作。2013年6月,延迟焦化装置进行在线清焦时,出现了弹丸焦。结合弹丸焦产生机理和在线清焦技术原理,分析认为,原料性质变差是产生弹丸焦的影响因素;快速变温清焦阶段的大流量注水产生高气速,是产生弹丸焦的主要原因;在生焦后期并料导致焦炭塔内气速突变、反应速度加快也是重要原因。为预防弹丸焦的形成,在清焦过程中,要严格控制注水流量,利用瓦斯压控阀和火嘴来控制炉出口温度,避免大量过热蒸汽进入焦炭塔,导致油气线速上升;同时,应尽量避免在生焦中后期进行并料操作。此外,还可以通过增大循环比、降低炉出口温度、提高焦炭塔压力等方式,预防弹丸焦的产生。

CNOOC Huizhou Refining and Petrochemicals Company＇s delayed coking unit uses a two furnace plus four column technical route,with a designed 0.3 and can be adjusted flexibly.The heating coke production cycle of 18 hours.The designed cycle ratio is furnaces allow inline decoking.In June 2013,when the company conducted an inline decoking operation for the delayed coking unit,shot coke was generated.Based on the mech- anisms behind the production of shot coke as well as the principle in inline decoking,technicians concluded that the deterioration of the quality of feedstock was the factor contributing to the production of shot coke, the high air speed resulting from high-rate water injection during the decoking phase where temperature was changed quickly was the main reason for the production of shot coke,and that the sudden changes in the air speed and the acceleration of reaction inside the coking column,caused by the mixing of materials in the late phase of coke production,also contributed to the generation of shot coke.In order to prevent the produc- tion of shot coke ,the flow rate of the water injected during decoking operation must be controlled strictly,the outlet temperature of furnace should be controlled with the use of gas prevent a large amount of superheated steam from entering the coking pressure control valves and nozzles to column to cause a rise in oil and gas linear speed.In addition,if possible,mixing of materials should be avoided in the medium and late phase of coke production.Other measures can also be taken to prevent production of shot coke such as increasing the cycle ratio, reducing the outlet temperature of furnace, and raising the pressure of the coking column.