| 摘要 |
<p>In a vapour-heated process system such as a falling film evaporation system (23), at least part of the vapour is generated by flashing of a hot liquid (20) which has been heated by heat exchange with exhaust gas (15) from an air heater (10) delivering air (14) for drying of a liquid product which is concentrated by evaporation in the process system. The liquid is typically water formed as a condensate from the heating vapour passed into the system and/or generated in the evaporation process. Exhaust gas is of a temperature of 100-400 DEG C, in particular 200-300 DEG C, and water subjected to the heat exchange has a temperature in the range of 40 - 80 DEG C, typically leaves the heat exchanger at a temperature of about 100 DEG C and is flashed into the system to a temperature of about 50-80 DEG C. Exhaust gas may be exhaust gas from an indirect air heater delivering heated air for spray drying the product concentrated in the evaporation system. Heat exchanger (17) is a finned tube heat exchanger. Method utilizes heat transfer from the relatively low temperature exhaust gas to the low temperature water to obtain hot water useful for supplementing primary vapour supply to the process system.</p> |
