System design and first operational experiences in a paper mill of a steam-generating Type II absorption heat pump
An Absorption Heat Transformer or Type II Absorption Heat Pump is a thermally driven heat pump that upgrades approximately half of its driving heat to a higher temperature level with almost negligible electric power consumption. Usually, such heat pumps recover waste heat from a renewable or waste heat source and upgrade it to a usable higher temperature. This work presents an integration scheme in which an upgraded hot water stream can be used with a flash tank to produce saturated steam for industrial processes. The subsystem for steam generation (steam generation module or SGM) has been expanded with a Thermocompressor, which allows for steam supply at higher pressures, if a driving high-pressure steam flow is available in the plant. Following the presented integration scheme, an industrial pilot heat pump delivering about 350 kW of steam at 3.3 bar(a) by using waste heat at 90 ºC has been designed and installed in a paper mill in Italy as part of a European project. The absorption heat pump has been designed based on a previous smaller unit designed for waste heat upgrade in a refinery. The present design has been modified to minimize the risk of crystallization under operation with high delivery temperature and low cooling water temperature. The expected performance for the absorption heat pump is discussed with regards to the steam generation, when operated together with a flash tank and a Thermocompression. The first operational results confirm the soundness of the heat recovery concept and its stable operation in a real environment.