Most of the energy demand in the steel industry is used for heating purposes. The recovery of residual heat contributes to significant reductions in both production costs and greenhouse gas emissions. In this paper, the design, manufacture and testing of an innovative heat recovery system based on a Flat Heat Pipe heat exchanger (FHP) is described. The FHP system consists of stainless steel heat pipes linked by a bottom header and a shell and tube top header. The thermal performance of the FHP was investigated both in the laboratory and on an industrial plant and the energy recovered and the working temperatures of the FHP are reported. A theoretical modelling tool has been built to predict the performance of the device in the laboratory. Reasonable agreement has been obtained between experimental and theoretical results. It is concluded from the results that the HIP is an innovative high efficiency technology for waste heat recovery from such industrial applications. (C) 2017 The Authors. Published by Elsevier Ltd.