Delayed coking: Industrial and laboratory aspects

Abstract

Delayed coking is a thermal process to convert petroleum residues to a solid coke material. Processes occurring in a delayed coker are complicated and attempts have been made, at the laboratory level, to simulate industrial delayed coking. Although the latter studies are useful, it is impossible to scale-down to the laboratory level. Industrial delayed coking is a turbulent process and such movements cannot be simulated easily in the laboratory. Of industrial importance are the multiphase systems i.e. volumes of unreacted isotropic pitch residue, transported through the bulk, fluid anisotropic mesophase, so creating ordering into acicular structures in the vicinity of the multiphase systems. Four petroleum residues were analysed chemically. Pyrolyses were carried out under pressures of up to 1.0 MPa. Complete mass balances were obtained and the semicokes examined by optical microscopy. Feedstocks for delayed cokers can be blends of petroleum residues, some of which can produce considerable amounts of volatile materials. Volatile evolution, at the optimum operating condition of the delayed coker, can bring about improvements in resultant coke quality. In industrial delayed coking it is important not only to consider the chemistry of the feedstocks, but attention must also be given to the physico-chemical aspects of coker operation.