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Wasted energy
In doing early research for a group of articles coming in our October issue, I have been hunting for stories related to interesting sources of energy. Wind, solar and the like are compelling in themselves, but I have found discussions of capturing waste energy particularly fascinating. The idea of capturing heat from a power plant's condensers to distill ethanol seems so basic, I wonder when every utility boiler will have some type of co-located facility to use that energy rather than just dissipating it into the atmosphere or a nearby river.
In an earlier life, I worked with a company that built gas cooling systems. We would spray atomized water into a hot gas stream to cool and humidify the gas before it reached a baghouse or electrostatic precipitator. One project I remember particularly was a double lime kiln. The incoming gas temperature was around 1,100 degrees F and we were cooling it to about 500 degrees F. When either kiln was running at normal production, we had to inject about 100 gallons of water per minute to make that temperature change. If you have a moment, do the math and figure out how many BTUs of heat it takes to flash 200 gallons of water per minute into steam. Add to that the horsepower needed to spray that much water through nozzles at about 600 psi. Add to that the horsepower needed to pump 288,000 gallons of water every day out of the local well. Add to that the BTUs still present in the gas when it is down to 500 degrees, and that is a whole lot of energy going to waste. Recovering it is tricky in that the gas is heavily dust loaded, but it would be interesting to see how many megawatts such an installation could produce and save if we could capture even half of it.
Of course all this costs money, but given the price of energy currently, things that may have seemed uneconomical a few years ago probably look very different today. Let's do some creative engineering and make it happen.
Wasted energy
June 28, 2007
In doing early research for a group of articles coming in our October issue, I have been hunting for stories related to interesting sources of energy. Wind, solar and the like are compelling in themselves, but I have found discussions of capturing waste energy particularly fascinating. The idea of capturing heat from a power plant's condensers to distill ethanol seems so basic, I wonder when every utility boiler will have some type of co-located facility to use that energy rather than just dissipating it into the atmosphere or a nearby river.In an earlier life, I worked with a company that built gas cooling systems. We would spray atomized water into a hot gas stream to cool and humidify the gas before it reached a baghouse or electrostatic precipitator. One project I remember particularly was a double lime kiln. The incoming gas temperature was around 1,100 degrees F and we were cooling it to about 500 degrees F. When either kiln was running at normal production, we had to inject about 100 gallons of water per minute to make that temperature change. If you have a moment, do the math and figure out how many BTUs of heat it takes to flash 200 gallons of water per minute into steam. Add to that the horsepower needed to spray that much water through nozzles at about 600 psi. Add to that the horsepower needed to pump 288,000 gallons of water every day out of the local well. Add to that the BTUs still present in the gas when it is down to 500 degrees, and that is a whole lot of energy going to waste. Recovering it is tricky in that the gas is heavily dust loaded, but it would be interesting to see how many megawatts such an installation could produce and save if we could capture even half of it.
Of course all this costs money, but given the price of energy currently, things that may have seemed uneconomical a few years ago probably look very different today. Let's do some creative engineering and make it happen.
Posted by Peter Welander on June 28, 2007 | Comments (0)
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