In a visbreaker unit, it is necessary to quench the furnace or soaker effluent temperatures to minimise both further thermal cracking reactions and coke deposition in the fractionator flash zone and residue stripping trays. Usually a distillate quench is used, which is recycled over the fractionation section, increasing the flash zone liquid load and promoting foaming. In the vacuum flasher, the liquid load is higher by nature, potentially due to recycle, increasing the potential for foaming.
In either of these areas of the process, foaming results in the degradation of distillation efficiency and may result in black gas oil cuts, which are very costly.
To minimise these impacts, Nalco Water has developed antifoam agents that are stable, so the antifoam stays in the fractionator residue and is not entrained in lighter streams. Our antifoam programs reduce costly impacts of foam on throughput and side stream quality.