Improvement of Exhaust Gas Heat Recovery from Marine Diesel Engines

Starting from the availability of performance data regarding a two-stroke marine diesel engine, the authors describe different options for the waste heat recovery from the exhaust gas of this type of engines, in order to be able to decide the solution ensuring the best fulfillment of the energy needs of an oil tanker. The Thermo Efficiency Systems (TES) here examined can adopt either steam turbine and gas turbine or simply steam turbine for power generation. As regards the steam plant, two basic layouts are considered, optimized and compared: the first plant scheme is a typical steam plant currently adopted for waste heat recovery purposes, the second one is a solution proposed by the authors. In this paper, by means of simulation, four TES configurations, applied to the mentioned diesel engine, are singly optimized and compared among them in order to find the most suitable plant layout and the steam cycle parameters that ensure its best operation at the engine normal continuous rating (NCR). The performance of the optimized TES systems is evaluated also by comparing them under off-design load conditions, in the engine power range between 50% and 100% of its maximum continuous rating (MCR).