Industrial drying operations are highly energy intensive, usually utilising a primary energy source to provide the necessary heat for the production of a wide range of materials. The use of hot air as the heat and mass transfer medium leads to a resultant loss of energy through the venting of humid exhaust streams. An absorption heat transformer pilot plant was designed and constructed to investigate the potential of recovering this waste heat. Using a two stage cycle, simulated dryer exhaust streams were successfully dehumidified and reheated. The first stage of the transformer employed a direct contact process which used a concentrated absorbent solution, in this case aqueous lithium bromide solution, to reduce the humidity of the gas stream. This stage was followed by an indirect contact process using a novel absorption column to reheat the 'dry' gas. It was found that, based on initial water vapour partial pressures of around 0.2 bar, exit partial pressures as low as 0.04 bar were achievable. Temperature lifts of 50 - 70°C were possible in the reheat column, while the maximum exit gas temperature achieved was 160°C. In conjunction with the experimental studies, a computer simulation program was also written. Results of the model show that the absorption process was extremely rapid, occurring within the first 5 cm (6%) of the absorption column. A good comparison between the experimental and computer results was achieved. A preliminary design of an industrial heat transformer was also proposed following an industrial case study of a spray drying operation.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:649032 |
| Date | January 1994 |
| Creators | Currie, John S. |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/13527 |
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