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Posted by Tony Conner on August 18, 2002 at 05:52:55:
In Reply to: Re: what to do with over a billion pounds of steam? posted by Anonymous on August 15, 2002 at 23:34:19:
You can't necessarily say that. I know of a chemical plant that at least used to vent almost 100,000 #/hr of steam, depending on production conditions. Heat was generated from the process reactions, so they captured it, and made steam. They used they steam when they had a requirement (which was often), but they didn't always have a home for it. The plant "next door" was about a mile away. In addition to the distance, the intermittent supply made buying it more trouble than it was worth.
Some petro-chem & refinery operations have waste from process runs that have heating value, so they burn them. More often than not, these liquids and gases are burned not because they're wonderful fuels, but to simply get rid of them. The disposal costs are higher than firing them in a boiler that's already operating on-site. Even if they vent some steam, the overall cost is cheaper than hiring an environmental disposal outfit to pick the liquids up and handle them for disposal. Gases and vapours that were just vented in the past, are often a big environmental issue now. A lot of the time, the easiest, most effective means of handling them is to pipe them to a boiler, and burn them.
Other plants have very low pressure exhaust steam - 5 PSIG or less. You can do some on-site building heating/cooling with it, but again, that particular process has to be running to supply the steam. And if it's spring/fall, there's still no requirement for it. Up the vent it goes.
You can almost always capture exhaust heat. The tricky bit is in having a home for it, right after you've caught it, as it doesn't usually store very well.