Abstract: A heat exchanger (10) including a hot process stream (14) fluidly connected to an industrial process, a cold process stream (16) fluidly connected to an industrial process, and a membrane distillation system (18). The membrane distillation system (18) includes a vapourising stream (12) comprising a mixture of components, a condensing stream (20), and a membrane (30) located between the vapourising stream (12) and the condensing stream (20). The vapourising stream (12) and condensing stream (20) are in fluid communication through the membrane (30). The membrane (30) facilitates transfer of at least one volatised component of the vapourising stream (12) into the condensing stream (20). The membrane distillation system (18) also includes a first heat transfer area (24) between the hot process stream (14) and the vapourising stream (12).