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Hypothetical: A hydrocarbon contamination is observed in the cooling water system for almost a month. Exchangers and pumps utilizing cooling water (CW) were inspected in the process area however, the cooling water supply is already hazy thus the CW return is also hazy already. The use of biodispersant is being considered to clean up the system. Laboratory testing of the hydrocarbon collected is also being done to determine the contaminant's quality. What more should be done to solve this contamination issue? Will the laboratory result be accurate? The cooling towers are open loop and evaporation of hydrocarbon may take place.
 
Answers
05/09/2017 A: Kenneth Gonzales, Petron Bataan Refinery, kpgonzales2@petron.com
What about the injection of emulsion breaker to clear up the water to easily find the leak via visual inspection of cooling water inlet and outlet of exchangers? Is that an acceptable approach? Is the use of oil and grease dispersant would also be beneficial in cleaning the cooling water system? By the way, the cooling water system serves all process units from pipestills to downstream.
We also inspected one exchanger and tested it for turbidty, TOC and oil&grease. There is significant difference in the turbidity of the cooling water inlet and outlet of the exchanger but none for TOC. For oil&grease, the inlet is around 6 ppm and the outlet is 11 ppm, is that significant enough? We also collected a sample of the exchanger's outlet and let it stay stagnant for a few days but no observed settling of hydrocarbon layer.
01/09/2017 A: Prakash Pimparkar, Environmental Consulting Services , prakash.pimparkar@yahoo.in
Appears to be contaminated with emulsified oil. Best option is to inject cationic polyelectrolyte at the rate of about 1 to 2 ppm ( wt basis ). concentration of solution < 1 %.A temporary arrangement can be made using a dosing skid.If the problem is recurring a permanent dosing system can be installed. If details are available such as.What type of service the CW is being used CDU/VDU/FCC ?) also present chemical dosing circulating water quality, quantity/h,% side stream filtration etc then a better solution can be given.But for time being dosing of poly in SSF will do the job.
01/09/2017 A: Sridhar Balakrishnan, Bharat Oman Refineries Limited , laksrid@yahoo.com
Laboratory testing of hydrocarbon will predict and quantify the oil & grease present in the cooling water syste by gravimetric method. These methods are APHA methods, basic and accurate . Most of the industries use this method to determine hydrocarbon in water systems.