Detailed Sub-Product Analysis
Understanding the nature of the coker liquid product is the key to maximizing the possible profits from the coker since certain liquids are more valuable than others. The sub-products from the coker fractionator are typically sent to downstream processing units; therefore, knowing the properties of these sub-fractions is valuable to ensure that they are fit to be sent to these units. The combined coker product liquid from the pilot unit is distilled in a Batch Reactor distillation unit to collect heavy naphtha, light coker gasoil (LCGO) and heavy coker gasoil (HCGO) fractions. These are then characterized, and the yields correlated. PIONA is carried out on the heavy naphtha fraction while API, viscosity and sulfur are analyzed on all fractions. The effect of recycle on the sub-product distribution is also studied. The Vacuum Distillation Unit and the Vapor Liquid Separation Device are also used for sub-product analysis.
High temperature & low pressure in the pilot coker decreased the naphtha fraction while the HCGO increased. On the other hand, low temperature & high pressure increased naphtha fraction while the HCGO decreased. Correlations were generated to predict the PIONA as a function of temperature, pressure and feedstock properties. The viscosity and API gravity were also correlated as functions of operating conditions and feed properties. The sulfur correlated mostly with feed sulfur but very weakly with run conditions. Recycle seemed to decreases the end-point and the sulfur content in the HCGO fraction. It also affects the MCR and API of the coker liquid product, increases the naphtha and LCGO, and decreases the HCGO.
The detailed liquid sub-product study is very valuable for modelling the delayed coker as a part of a refinery model. The accurate experimental information generated by this project will help further the correct modeling of the coker.