Use of combined steam-water and organic rankine cycles for achieving better efficiency of gas turbine units and internal combustion engines

Abstract

Original Russian Text © M.A. Gotovskiy, M.I. Grinman, V.I. Fomin, V.K. Aref'ev, A.A. Grigor'ev, 2012, published in Teploenergetika. 236 Problems of achieving better energy efficiency and more efficient use of waste heat from energy intense production processes are nowadays very pressing ones. Considerable experience with construction of waste heat recovery systems has been gained at Ormat, Sie mens, Turboden, and other companies; however, real efficiencies of cycles that are implemented are limited to around 18%.The problem of rationally using energy resources has attracted great attention of specialists since the middle of the past century, the time when rapid growth of industrial production generated the need to make it more energy efficient. In many industries generating by products and fuel (e.g., black leach and wood in the pulp and paper industry, synthesis gas in the petroleum refining indus try, light gas mixtures obtained as a result of processing chemical substances, blasting gases in steel industries, etc.) it is possible to avoid losses of energy by utilizing it in one form or another. The problems of losses in systems using renewable sources of energy (solar, geo thermal, and wind energy) for generating electricity are usually considered separately.Losses exist also in energy conversion systems (e.g., in heat exchangers, industrial heaters, pumps, and motors), the efficiency of which is limited by thermal or mechanical factors.Of course, heat losses-i.e., the produced heat that could not be usefully utilized by the consumer and was rejected into the environment-occupy the main place in the wide spectrum of energy losses. It should be noted that more than 75% of industrial heat wastes have temperature below 800 K, due to which applica tion of usual technologies, e.g., the Rankine steamwater cycle, for producing electricity is inefficient. THE ORGANIC RANKINE CYCLEThere are a few basic technologies using which low temperature waste heat can be utilized. For exam ple, for the last 20 years energy has been generated on the basis of the organic Rankine cycle (ORC) at power stations with capacities ranging from 300 kW to 130 MW operating on different sources of heat [1, 2]. Other alternative versions are either technically impossible or economically inefficient. Leading pro ducers of ORC based installations have gained great experience from using low boiling organic substances for producing electricity and have demonstrated that this cycle is well suited for low temperature sources of heat. The ORC technology is applicable for recovering heat of medium size gas turbines (GTs), cement plants, and geothermal sources, and yields consider able advantages as compared with the use of low tem perature steam turbines. The majority of existing sys tems operating at higher temperatures are fitted with a recovery unit (Fig. 1) between the heat source itself and organic working fluid (e.g., high temperature oil). The efficiency of electricity generaton using recovered heat of industrial wastes in ORC based systems...

Concerning utilization of heat from low-potential sources

“…Energy-saving technology using the Rankine cycle allows generating electricity with efficiency of up to 18% depending on the temperature of the heating low-potential source. This means a significant increase in the efficiency of the energy complex, especially the steam-water cycle, when two cycles are combined into a single binary cycle, using the heat of sources with the temperature of ∼200 °C [3].…”

“…The main direction of Russian research is the practical increase in the energy efficiency of geothermal and gas-steam plants by creating the combined power units with organic working fluids [3,[6][7][8]. In [6], the creation of an experimental-industrial geothermal pilot power unit with a capacity of 2.5 MW at the Pauzhetskaya GeoPP (Kamchatka), operating in a binary cycle, is analyzed.…”

“…In [6], the creation of an experimental-industrial geothermal pilot power unit with a capacity of 2.5 MW at the Pauzhetskaya GeoPP (Kamchatka), operating in a binary cycle, is analyzed. The main idea of the authors' innovative concept [3] is the combination of a traditional steam-water turbine with back pressure with the ORC.…”