The atmospheric and vacuum distillation columns bottoms, or residuum, can be further processed into more desirable products. This is accomplished by running the resid through a Coker Unit.
Cokers are one of two types, either fluid cokers or delayed cokers. Both operate at pressures slightly higher than atmospheric and at temperatures greater than 900oF. Under these conditions, the resid with be thermally cracked into products such as gas oil, naphtha, and other distillates, and leaves behind the solids commonly referred to as Petroleum Coke. Dependent on the length of coking time and the temperature of the coking operation, the coke is sold either as fuel or undergoes an extra heating process, commonly called calcining, to produce a petroleum coke that is anode-grade for the aluminum and steel industry.
With a delayed coker, the residual oil is heated to its thermal cracking temperature in a furnace. This cracks the long chain hydrocarbons into coker gas oil, naphtha, and other distillates, plus the petroleum coke. The cracking process starts in the furnace and continues in the transfer line to the coke drums, where the cracking process is completed.
Two or more large reactors are utilized to hold, or delay, the feed until the cracking process is complete. The gas oil and lighter products are created in a vapor phase, and exit the drums through the overhead to a fractionator for further separation by boiling point. The coke is deposited in the coke drum as a solid, and is typically removed by hydraulically cutting the coke with high pressure water sprays.
Fluid coking is an expensive process, and as such has a small share of the coker market. The feed is charged to a heated reactor where the cracking takes place. The produced coke is transferred to a heater as a fluidized solid. Here it is burned to obtain the necessary heat for the initial cracking process. Remaining coke is collected. An ExxonMobil license process called Flexicoking takes this one step further by adding a third gasifier which converts the coke to a low BTU fuel gas.
MEI Maverick Engineering, a wholly owned subsidiary of Triple 5 Worldwide, can be of assistance with your Coker projects. MEI can provide the complete range of services, including front-end engineering design, detail engineering, procurement, construction management, start-up and operator training, to insure a successful project. Our expertise yields shorter project schedules, industry superior cost control, and minimal client risk.
Coker Units: Projects
A partial listing of MEI Engineering experience with Coker Units is provided below:
- Design of a Water Wash Tower unit to remove contaminants from the Coker off-gas stream ahead of the Amine Contractor.
- Feasibility study to revamp an 18,000 BPD Delayed Coker, included Norm Lieberman, Process Improvement Engineering.
- HAZOP review for grass-roots 50,000 BPD Delayed Coker Unit.
- Engineering design for a 40,000,000 SCFD Coker gas plant.
- Mechanical design on a 70,000 BPD four drum Delayed Coker.