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To: Elroy Jetson who wrote (68180)	8/27/2005 9:34:54 PM
From: Slagle	Read Replies (2) \| Respond to of 74559

Elroy Re: "stack gasses" Entropy is the problem , Elroy. In laymans terms it is a sort of geometrically progressing law of diminishing returns. From a continuous process kiln or oven running at 1000F or more you have exhaust stack gas at say 400F which carries with it lots of low level heat. But what can you do with it? Sure, you can run it through a counterflow heat exchanger or a maybe a rotating media "heat wheel" and capture a small portion of the heat in the waste gas by preheating the make-up air to the process. This we do already do, this is standard practice in industry, here and elsewhere. So maybe you drop the temperature another 100F and it is now under 300F. There is still lots of heat, but here the geometric nature of the problem really begins to weigh. What use is waste heat in the exhaust gas at this low temperature? This is literal "unavailable energy" and not much use for anything. But anyway, whatever heat can be salvaged from this 300F exhaust from the final stage of the heat exchanger is all the improvement that can be made. And this is a small part of the original input. The original input provided the heat energy for the heat of vaporization, raising the process material to operating temperature and other endothermic reactions of the process. These might be considered a "fixed cost" of doing business and cannot be improved upon. All you can change is to reduce the radiant and convection losses from the equipment and try to make use of the low level heat in the exhaust. All of this we are already doing. Papermaking, glass, synthetic rubber, ceramics and hundreds of other industries are employing very evolved and mature technology. There will incremental improvements, to be sure. But the age of revolutionary improvement is over. Slagle