EXAMINING THE FATE OF EMULSION BREAKERS USEDFOR DECANTING

摘要

Skimmers operating in waves often recover a large amount ofrnwater, both in the form of water-in-oil emulsions and free water.rnRecovered water dramatically reduces the temporary storagerncapacity available for oily fluids offshore. The addition of chemicalrnemulsion breakers to the recovery system has been shown tornincrease the amount of water that can be quickly decanted whenrnrecovering emulsions. A significant potential impediment to thernapplication of emulsion breakers to extend temporary storagerncapacity is the ultimate fate of the emulsion breaking chemical(s).rnIf they end up in the separated water, they will be discharged intornthe marine environment when the water is decanted.rnThe objective of this study was to research the partitioning ofrnemulsion breakers injected into an oil spill recovery system atrnboth lab-scale and mid-scale, at Ohmsett. The experiments wererndesigned to simulate the conditions in an offshore oil spill recoveryrnoperation. The ability of emulsion breaker addition to reducernwater contents of the recovered fluid and the effects of demulsifierrnaddition of the oil content of decanted water were also assessed.rnThe formation of micelles by the surfactants in the water at highrnconcentrations and the resulting limitations of the analytical techniquernused to measure high concentrations of the demulsifiers inrnthe decanted water make definitive, quantitative conclusions aboutrnthe partitioning of the demulsifier between oily and water phasesrnimpossible. The following general conclusions could be made:rn? A large fraction of the demulsifier injected into the recoveredrnfluid stream appears to end up in the decanted water.rn? The concentrations of demulsifier in the decanted waterrnare well in excess of 100 ppm and could be as high asrn1000's of ppm.rnThe use of a demulsifier injected into a recovery system, combinedrnwith decanting, substantially reduced the volume of water inrntemporary storage tanks and the water content of emulsions forrndisposal/recycling. The efficacy of the demulsifier was a strongrnfunction of free water content: if the free water content exceededrnapproximately 55%, the effect of the surfactant was substantiallyrnreduced. The degree of emulsion breaking increased with increasingrnmixing energy applied to the fluid. Increasing the flow ratern(and hence turbulence level) and increasing the length of the flowrnpath both resulted in increased emulsion breaking. Primary breakrnoccurred in only a few minutes: the application of demulsifier did not appear to affect the time required compared to previous testsrnwithout demulsifiers. The results indicated that the use of a demulsifierrnincreased oil droplet concentrations in the decanted water byrnapproximately a factor of two compared to similar tests withoutrndemulsifier.