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Enron Mail |
After the Topock line has been cleaned and placed back in service, I
recommend immediate flushing with diesel. The existing Selexol tank and injection system can be used for this purpose. HYSIM simulations verify the existing high pressure injection pump is a good fit for the quantity of diesel to be added on a continuous basis, (approximately 1 B/D). Inject 1 or 2 barrels of diesel in front of each pig to begin with. I would buy diesel No. 2 because it has a wider boiling point range than No. 1. The diesel should be analyzed for PCB content before we purchase /inject. The above guideline should be adjusted based on the actual volume of liquids seen at the meter station filter separator. If you can keep a small but continuous amount of free liquids at this separator , the gas will be saturated with heavy hydrocarbons which will dilute and flush PG&E's downstream system. 1 to 2 Barrel per day of diesel injected into 200 MMSCF/D has a major effect on the C7+ concentration in the gas stream and on the hydrocarbon dew point. Most of the hydrocarbons in diesel are naturally ocurring to some extent in natural gas. The carbon number for diesel ranges from about C10 to C 20 with a corresponding boiling point of 350 oF to 650 oF. It is anticipated that some of the heavier hydrocarbons in the C18 to C20 range will drop out along with compressor oil carryover to substantially increase the amount of liquid PG&E sees in their downstream drips. The net effect of this is a substantial reduction of the PCB concentration. I would expect that after 30 to 60 days of continuous injection the PCB contaminant level should drop by an order of magnitude. The reason I would not inject Selexol after the pipeline has been cleaned is because you would leave a finite quantity of Selexol coating the pipeline which could then absorb and concentrate any potential PCB contaminant in the gas and potentially recontaminate downstream equipment. I will be on vacation from June 19 to June 26. If you have any questions please call.
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