Optimization of waste heat recovery from the exhaust gas of marine diesel engines

Abstract

In this article, some configurations of waste heat recovery systems are described, analysed and compared, in order to\ud find the optimal plant layout. Starting from the availability of performance data of a two-stroke diesel engine, adopted for\ud the propulsion plant of a crude oil tanker ship, the authors examined different solutions for the waste heat recovery\ud from the diesel engine exhaust gas ensuring the best fulfilment of the vessel needs in terms of mechanical, electric and\ud thermal energies. The considered waste heat recovery systems can adopt either steam turbine and gas turbine or simply\ud steam turbine for power generation. As regards the steam plant, two basic layouts are considered, optimized and compared:\ud the first plant scheme is a typical steam plant currently adopted for waste heat recovery purposes and the second\ud one is a solution proposed by the authors. Considering the different options, in this article, four different system layouts,\ud applied to the mentioned diesel engine, are singly optimized and compared between them in order to find the most suitable\ud plant and the steam cycle parameters that provide its best operation at the engine normal continuous rating. The\ud performance of the optimized waste heat recovery systems is evaluated also by comparing them under off-design engine\ud load conditions, in the engine power range between 50% and 100% of its maximum continuous rating

Comparison of Saturated and Superheated Steam Plants for Waste-Heat Recovery of Dual-Fuel Marine Engines

“…Many examples of WHR systems from marine diesel engines were presented in the literature, some of which are mentioned in references at the end of this paper [16][17][18][19][20][21][22][23][24][25][26][27][28]. Of the last two papers [27,28], the former is on the effects of the deterioration of steam-plant components on the performance of WHR systems, and the latter presents an interesting comparison of an organic and a steam Rankine cycle applied to WHR plants.…”

“…Following this observation, we carried out a thorough comparison between two single-pressure WHR plants, one characterized by saturated steam, the other by superheated steam, applied to the same DF four-stroke marine engine. Both WHR steam plants, characterized by a similar layout, were optimized by means of a simulation code, with a procedure presented by the authors in [24], aimed at achieving the best efficiency of the combined engine-WHR system with the engine running at Normal Continuous Rating (NCR). The WHR steam plants were then compared on the basis of energetic and exergetic considerations, with regard to the thermodynamic performance of the Heat Recovery Steam Generator (HRSG), the dimensions and weights of the steam generator as a whole and of its components (economizer, evaporator and superheater) in relation to the exchanged thermal powers, the Rankine cycle characteristics, and the efficiency of the combined DF engine-WHR plant.…”

Efficiency Improvement of a Natural Gas Marine Engine Using a Hybrid Turbocharger

“…An efficiency increase of the on-board systems using such engines can be obtained by the partial recovery of their waste heat, by means of a Heat Recovery Steam Generator (HRSG), able to feed a steam turbine generally for electric energy production, in order to reduce the on-board diesel-generator's power. To this purpose, different schemes of Waste Heat Recovery (WHR) steam plants, applied to marine diesel engines, are proposed in the literature [7][8][9][10][11][12][13][14][15][16][17][18], characterized by singleor dual-pressure steam plants.…”

“…This is possible thanks to the current high efficiency of the turbochargers used for marine applications. Indeed, to supply sufficient air to the engine cylinders, it is not necessary to send all the exhaust gas to the turbocharger turbine, but a portion (generally about 10%) can be sent to another turbine (power gas turbine), running in parallel to the turbocharger turbine, for electricity production [12,18]. Another way to increase the efficiency of WHR systems is to adequately exploit (by means of heat exchangers) the heat of the air at the turbocharger compressor outlet, as described in [19].…”

A Comparison of Organic and Steam Rankine Cycle Power Systems for Waste Heat Recovery on Large Ships

“…The results presented by Ma et al [3] indicated an engine efficiency increase from 48.5% to 53.8% when installing a single pressure SRC unit in combination with a power turbine unit. Benvenuto et al [4] suggested an alternative design of the dual pressure SRC unit and demonstrated 34% higher electricity generation at design (SRC stand-alone unit) compared to the dual pressure SRC system design typically used in industry. Dimopoulos et al [5] showed that the installation of a dual pressure SRC and power turbine-based WHR system is economically feasible with a positive net present value over a wide range of fuel prices and component costs.…”