ABSTRACT
The “bottom of the barrel” has become more of a problem for refiners because heavier crudes are being proc essed and the market for heavy residual fuel oils has been decreasing. Historically, the heavy residual fuel oils have been burned to produce electric power and to supply the energy needs of heavy industry, but more severe environmental restrictions have caused many of these users to switch to natural gas. Thus when more heavy residuals are in the crude there is more difficulty in economically disposing of them. Coking units convert heavy feed-stocks into a solid coke and lower boiling hydrocarbon products which are suit-able as feedstocks to other refinery units for conversion into higher value trans-portation fuels.
