821 How to Conduct the Survey

The survey should be carried out as an integral part of the energy audit of the plant. The survey consists of a systematic study of the sources of waste heat in the plant and of the opportunities for its use. The survey is carried out on three levels. The first step is the identification of every energy-containing nonproduct that flows from the plant. Included are waste streams containing sensible heat (substances at elevated temperatures); examples are hot inert exhaust products from a furnace or cooling water from a compressor. Also to be included are waste streams containing chemical energy (waste fuels), such as carbon monoxide from a heat-treatment furnace or cupola, solvent vapors from a drying oven, or sawdust from a planing mill: Figure 8.7 is an example of a survey form used for listing waste streams leaving the plant.

The second step is to learn more about the original source of the waste-heat stream. Information should be gathered that can lead to a complete heat balance on the equipment or the system that produces it. Since both potential savings and the capital costs tend to be large in waste-heat recovery situations, it is important that the data be correct. Errors in characterization of the energy-containing streams can either make a poor investment look good, or conversely cause a good investment




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