The absorption heat exchanger (AHE) combined by an absorption heat pump (AHP) and a plate heat exchanger (PHE) is invented for replacing conventional plate heat exchangers at the heating substation in the district heating system, which could decease the return water temperature of primary pipe (PP) significantly when compared with the conventional PHE. The return water temperature of PP is much lower than that of secondary pipe (SP) in the AHE without consuming extra energy. The heating capacity of an original heating pipe is increased obviously, and it is much more convenient to recover different kinds of low grade industrial waste heat by the low temperature return water of PP. Meanwhile, inlet and outlet temperatures of PP and SP vary obviously during a whole heating period, therefore, the effect on heat exchange process caused by the LiBr (lithium bromide) solution circulating rate and the ratio of flow rates of PP and SP in the PHE is studied, which could ensure optimal performance of AHE under different working conditions. Operation regulation curves are given for regulation of the AHE during the whole heating period. (C) 2017 Elsevier B.V. All rights reserved.