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Advanced Power Cycles with Mixtures as the Working Fluid Maria Jonsson Doctoral Thesis Department of Chemical Engineering and Technology, Energy Processes Royal Institute of Technology Stockholm, Sweden, 2003 Advanced Power Cycles with Mixtures as the Working Fluid Maria Jonsson Doctoral Thesis Department of Chemical Engineering and Technology, Energy Processes Royal Institute of Technology Stockholm, Sweden, 2003 TRITA-KET R173 ISSN 1104-3466 ISRN KTH/KET/R--173--SE ISBN 91-7283-443-9 Contact information: Royal Institute of Technology Department of Chemical Engineering and Technology, Division of Energy Processes SE-100 44 Stockholm Sweden Copyright © Maria Jonsson, 2003 All rights reserved Printed in Sweden Universitetsservice US AB Stockholm, 2003 Advanced Power Cycles with Mixtures as the Working Fluid Maria Jonsson Department of Chemical Engineering and Technology, Energy Processes Royal Institute of Technology, Stockholm, Sweden Abstract The world demand for electrical power increases continuously, requiring efficient and low-cost methods for power generation. This thesis investigates two advanced power cycles with mixtures as the working fluid: the Kalina cycle, alternatively called the ammonia-water cycle, and the evaporative gas turbine cycle. These cycles have the potential of improved performance regarding electrical efficiency, specific power output, specific investment cost and cost of electricity compared with the conventional technology, since the mixture working fluids enable efficient energy recovery. This thesis shows that the ammonia-water cycle has a better thermodynamic performance than the steam Rankine cycle as a bottoming process for natural gas- fired gas and gas-diesel engines, since the majority of the ammonia-water cycle configurations investigated generated more power than steam cycles. The best ammonia-water cycle produced approximately 40-50 % more power than a single- pressure steam cycle and 20-24 % more power than a dual-pressure steam cycle. The investment cost for an ammonia-water bottoming cycle is probably higher than for a steam cycle; however, the specific investment cost may be lower due to the higher power output. A comparison between combined cycles with ammonia-water bottoming processes and evaporative gas turbine cycles showed that the ammonia-water cycle could recover the exhaust gas energy of a high pressure ratio gas turbine more efficiently than a part-flow evaporative gas turbine cycle. For a medium pressure ratio gas turbine, the situation was the opposite, except when a complex ammonia- water cycle configuration with reheat was used. An exergy analysis showed that evaporative cycles with part-flow humidification could recover energy as efficiently as, or more efficiently than, full-flow cycles. An economic analysis confirmed that the specific investment cost for part-flow cycles was lower than for full-flow cycles, since part-flow humidification reduces the heat exchanger area and humidification tower volume. In addition, the part-flow cycles had lower or similar costs of electricity compared with the full-flow cycles. Compared with combined cycles, the part-flow evaporative cycles had significantly lower total and specific investment costs and lower or almost equal costs of electricity; thus, part-flow evaporative cycles could compete with the combined cycle for mid-size power generation. Language: English Keywords: power cycle, mixture working fluid, Kalina cycle, ammonia-water mixture, reciprocating internal combustion engine, bottoming cycle, gas turbine, evaporative gas turbine, air-water mixture, exergy List of Appended Papers This thesis is based on the following papers, referred to by the Roman numerals I- VIII: I. Jonsson, M., Thorin, E. and Svedberg, G. (1999). Gas Engine Bottoming Cycles with Ammonia-Water Mixtures as Working Fluid. In: Proceedings of the 1999 International Joint Power Generation Conference, Burlingame, California, USA, July 25-28, 1999. PWR-Vol. 34, 55-65. II. Jonsson, M. and Yan, J. (2000). Diesel Engine Bottoming Cycles with Ammonia-Water Mixtures as Working Fluid. In: Proceedings of the 2000 Spring Technical Conference of the ASME Internal Combustion Engine Division, San Antonio, Texas, USA, April 9-12, 2000. ICE-Vol. 34-1, 55-64. ASME Paper No. 2000-ICE-257. III. Jonsson, M. and Yan, J. (2000). Exergy and Pinch Analysis of Diesel Engine Bottoming Cycles with Ammonia-Water Mixtures as Working Fluid. International Journal of Applied Thermodynamics, 3(2), 57-71. Adapted from a paper published in: Proceedings of ECOS 2000, Enschede, The Netherlands, July 5-7, 2000. IV. Jonsson, M. and Yan, J. (2001). Ammonia-Water Bottoming Cycles: A Comparison between Gas Engines and Gas Diesel Engines as Prime Movers. Energy, 26(1), 31-44. V. Jonsson, M. and Yan, J. (2001). Gas Turbine with Kalina Bottoming Cycle versus Evaporative Gas Turbine Cycle. In: Proceedings of the 2001 International Joint Power Generation Conference, New Orleans, Louisiana, USA, June 4-7, 2001. ASME Paper No. JPGC2001/PWR-19005. VI. Jonsson, M. and Yan, J. (2002). Exergy Analysis of Part Flow Evaporative Gas Turbine Cycles - Part 1: Introduction and Method and Part 2: Results and Discussion. In: Proceedings of ASME Turbo Expo 2002, Amsterdam, The Netherlands, June 3-6, 2002. ASME Paper Nos. 2002-GT-30125 and GT-2002-30126. VII. Jonsson, M. and Yan, J. (2003). Economic Assessment of Evaporative Gas Turbine Cycles with Optimized Part Flow Humidification Systems. Accepted for publication in: Proceedings of ASME Turbo Expo 2003, Atlanta, Georgia, USA, June 16-19, 2003. ASME Paper No. GT2003-38009. VIII. Jonsson, M. and Yan, J. (2003). Humidified Gas Turbines - A Review of Proposed and Implemented Cycles. Manuscript to be submitted for journal publication. The papers are appended after the summary. Table of Contents 1 Outline of the Thesis 1 2 Introduction 3 2.1 Background 3 2.2 Objective of the Thesis 4 3 Ammonia-Water Processes as Bottoming Cycles for Reciprocating Engines 5 3.1 Theory and Previous Work on Ammonia-Water Cycles 5 3.1.1 Properties of Ammonia-Water Mixtures 5 3.1.2 The Principle of the Ammonia-Water Cycle 6 3.1.3 Comparison of the Ammonia-Water and the Rankine Cycle 8 3.1.4 Previous Work on Ammonia-Water Cycles 9 3.1.4.1 Cycle Studies 9 3.1.4.2 Existing Ammonia-Water Cycle Power Plants 12 3.1.4.3 Properties of Ammonia-Water Mixtures 14 3.2 Reciprocating Engines for Power Generation 15 3.2.1 The Principle of Gas and Gas-Diesel Engines 15 3.2.2 Reciprocating Engine Power Plants 16 3.3 Studies of Ammonia-Water Bottoming Cycles for Gas and Gas-Diesel Engines 19 3.3.1 Method 19 3.3.1.1 Assumptions and Fixed Parameters 19 3.3.1.2 Cycle Configurations and Optimization 21 3.3.1.3 Exergy Analysis 23 3.3.2 Ammonia-Water Bottoming Processes for Gas Engines 23 3.3.3 Ammonia-Water Bottoming Processes for Gas-Diesel Engines 26 3.3.3.1 First Law Analysis 26 3.3.3.2 Second Law and Pinch Analyses 28 3.3.4 Comparison between Ammonia-Water Bottoming Processes for Gas and Gas-Diesel Engines 32 3.4 Discussion 33 3.4.1 Method and Assumptions 33 3.4.2 Economical and Technical Aspects 34 3.4.3 Results 35 3.4.4 Suggestions for Future Work 36 4 Part- and Full-Flow Evaporative Gas Turbines for Power Generation 37 4.1 Gas Turbines for Power Generation 37 4.2 Theory and Previous Work on Evaporative Gas Turbines 39 4.2.1 Gas Turbines with Air-Water Mixtures as the Working Fluid 39 4.2.1.1 Water-Injected Gas Turbines 40 4.2.1.2 Steam-Injected Gas Turbines 41 4.2.1.3 Evaporative Gas Turbines 42 4.2.2 Previous Work on Evaporative Gas Turbines 43 4.2.2.1 The Humid Air Turbine 44 4.2.2.2 The EvGT Project and Related Studies 46 4.2.2.3 Part-Flow Humidification 47 4.2.2.4 The Humidification Tower 48 4.2.2.5 Water Recovery and Water and Air Quality 49 4.2.2.6 Properties of Air-Water Mixtures 50 4.3 Studies of Evaporative Gas Turbines with Part- and Full-Flow Humidification 51 4.3.1 Method 51 4.3.2 A Comparison between Combined Cycles with Kalina Bottoming Processes and Evaporative Gas Turbines 52 4.3.2.1 Method and Cycle Configurations 53 4.3.2.2 Results 56 4.3.3 Exergy Analysis of Part-Flow Evaporative Gas Turbines 58 4.3.3.1 Method and Cycle Configurations 58 4.3.3.2 Results 58 4.3.4 Economic Analysis of Evaporative Gas Turbines 61 4.3.4.1 Method and Cycle Configurations 62 4.3.4.2 Results 65 4.4 Discussion 70 4.4.1 Method and Assumptions 70 4.4.1.1 Thermodynamic Analysis 70 4.4.1.2 Economic Analysis 71 4.4.2 Economical and Technical Aspects 72 4.4.3 Results 73 4.4.4 Suggestions for Future Work 75 5 Conclusions 77 6 References 79 7 Nomenclature 97 8 Acknowledgments 101 1 Outline of the Thesis The thesis is a summary of eight technical papers, which are appended to the thesis. In Chapter 2, the general background to the study, the two power cycles investigated, and the objective of the thesis are presented. In Chapter 3, the ammonia-water cycle is addressed. In Section 3.1, the properties of the ammonia-water working fluid, the principle of the ammonia- water cycle, the reasons for the high efficiency of the ammonia-water cycle compared with the steam Rankine cycle, and some of the previous work on ammonia-water cycles in different applications are discussed. In Section 3.2, reciprocating internal combustion engines for power production are described. The principles of spark-ignition gas engines and compression-ignition gas-diesel engines are explained and some examples of reciprocating engine power plants, where engine waste heat is recovered, are given.
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