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How to convert PPMw (by weight) to PPMv(Volume) for H2S & moisture(H2O) in gas mixture?
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Submitted Chris Haslego, Nov 21 2011 11:21 AM | Last updated Nov 21 2011 01:29 PM

Category:	Refining
Question:	How can steam be utilized to reduce coking in crude furnaces?
Keywords:	steam,injection,reduce,coking,crude,furnaces,point,determine,determination
Answer:	The steam should be injected into each individual pass of the heater. Injecting steam in the common line will cause problems with the individual pass control valves since they are not suited to controlling two phase flow. The hard part is determining where, exactly, to put the steam into the passes. Injection too far upstream may lead to a high pressure drop across the heater that you may not be able to tolerate. Injection too far downstream may be too late to prevent coking as oil may have already started cracking. Steam should be injected just upstream of where oil vaporization starts to suppress high film temperatures. There is not a rule on how much steam you need; that would be determined specifically at the same time that the injection location would be determined. Finally, the steam pressure is dictated by the pressure at the injection point. You just need to have a high enough steam source to get it into the heater while allowing for pressure drop across a control valve.