Foaming problems can occur during the high temperature processing of hydrocarbon fluids.  Crude oil towers and cokers operating at high temperatures can produce foam in their hydrocarbon products which in turn diminishes the efficiency of the tower or coker, degrading the quality of the overhead products such as gasoline and gas oils.  Severe foaming problems are often encountered in crude oils during separation of dissolved gases at the well-head. 
In the processing of various residual petroleum stocks into coke, a commonly used technique is the well known delayed coking process.  In the delayed coking process, heavy residual oils are heated to about 500.degree.  C. by pumping them at high velocity through a pipe furnace and then charging these oils to an insulated coking drum.  The delayed coking process produces a quantity of foam which is undesirable since it diminishes the efficient operation of the process. 
Other refinery processes that can experience foaming problems include crude units, vacuum units, vis breakers, delayed cokers and asphalt processing units.  Traditionally, silicone (dimethyl polysiloxane) based antifoam compounds were employed to treat these operations for foaming problems. 
The use of silicone-based defoaming compounds is economically attractive due to their low dosage levels in the hydrocarbons.  However, they pose a problem in being expensive with respect to using them in less expensive hydrocarbon fluids.  The silicone-based compounds also pose a problem due to their difficulty in dispersing in high temperature hydrocarbon systems.  The silicone-based compounds tend to react with the metal surfaces of the processing system.  Another problem that is significant to the oil industry is that silicone-based defoamers poison downstream catalysts with silicon carryover and residues.