Accurate pH Measurement of Refinery Wastewater

摘要

Refinery wastewaters contain challenging contaminants such as residual hydrocarbons, sulphur and chloride salts from sour crude refining, ammonia, cyanides, hydrofluoric acid, benzine and toluene. To eliminate these contaminants, the waste waters are subjected to a coagulation process where Alum and polymers are added - these create a "floc' that reduces the contaminates to a sludge. Accurate pH measurement and control is necessary to optimise the coagulation and floc. Bio-reactors remove VOC's - bacteria converts the VOC's to a non-hazardous sludge - Again Precise pH measurement and control is necessary to optimize this biological process. Challenges for pH/mV sensor include fouling of the porous reference junction is the main cause of high levels of maintenance and electrode failure, and H2S poisoning of the Ag/AgCl reference half cell and electrolyte occurs due to a precipitation between the H2S and AgCl - this forms AgS that completely blocks the reference junction and wrecks the mV stability of the Ag/AgCl half cell.