High temperature air combustion
This book is a comprehensive and illustrated work on high temperature air combustion (here called HiTAC), which has revolutionized our paradigm on the use of all kinds of fossil, alternative, waste, and derived fuels for energy conversion and energy utilization in industry. Significant experimental knowledge and insights from many practical devices have resulted in the utilization of HiTAC technology for many applications. The traditional definition of flame is that which gives heat and light during chemical reaction between reactants. However, under certain conditions with some fuels, this definition of flame can be revised.
The text is oriented toward the person who wishes to gain a good understanding of the principles and practice of HiTAC. The text also allows one to apply this technology to achieve significant energy savings, to reduce the size of equipment and environmental pollution, including CO2, for specific applications. Combustion technology utilizing preheated combustion air in excess of 1000°C has drawn significant worldwide attention for many applications. The basic concept is that the combination of maximum waste heat recovery by high cycle regenerator and controlled mixing of highly preheated combustion air with burned gases yields uniform and relatively low temperature flames. Indeed, the revolutionary HiTAC technology has been demonstrated to provide simultaneous reduction of CO2 and nitric oxide emissions and to reduce energy consumption for a specific process or requirement. Specifically, HiTAC has been demonstrated to provide about 30% reduction in energy (and hence also CO2 emission), 50% reduction of pollutants, and about 25% reduction in the physical size of the facility compared with the conventional type of furnace design. Furthermore, extremely low levels of nitric oxide emissions, far below the present regulations, have been demonstrated in several field trials.
This book describes the development of HiTAC technology and its practical application to different kinds of furnaces of importance in industry. Future potential applications of this technology are also presented. Recognition of the vast scope and importance of HiTAC technology has prompted CRC Press to include the present text in their series of books on Environmental and Energy Engineering.
Other texts in the series delve deeply into other specific areas. This book focuses on all aspects and applications of HiTAC; good characterization of the combustion phenomena with high temperature combustion air is of prime concern. Particular reference is made to the work published in this area during the last decade. Other valuable information may be found in various research reports and journals in Japan and from international symposia and journals.
Chapter 1 describes the innovation of HiTAC, as well as the historical background and evolution of this combustion technology. Chapter 2 discusses the combustion phenomena associated with high temperature air combustion. A comprehensive view is provided of the fundamental differences in the thermal, chemical, and fluid dynamic characteristics of the flame. HiTAC technology provides significantly higher flame stability at all fuel–air mixtures (including very lean fuel mixtures), higher heat transfer, and low heat loss from the stack (waste heat). The fundamentals of gas, liquid, and solid fuel flames are also presented from the point of view of HiTAC. Also included here are the significantly different flame features, flame stability, reduced emissions, and significant energy savings with HiTAC. The flame color is found to be much different from the usually observed blue or yellow. Under certain conditions bluish green and green color flame has been observed using typical hydrocarbon fuels. In contrast, flameless (or colorless) oxidation of the fuel has also been observed. These characteristics of flames have not been cited before in the literature. In Chapters 3 and 4 the models for simulating high temperature air combustion as well as the impact of HiTAC on industrial furnace performance are presented. Chapter 5 provides the design guidelines for high performance industrial furnaces. General and optimal design guidelines for various kinds of furnaces, such as reheating furnaces, heat treatment furnaces, and melting furnaces, are presented from the point of view of higher heat transfer, reduced size, reduced pollution, and higher performance. Experience and field trials on different kinds of practical furnaces are also presented. In Chapter 6, potential applications of HiTAC to other energy-using sectors are presented. Some of the examples include the conversion of coals, biomass, and solid waste fuels to cleaner fuels, fuel reforming, stationary gas turbine engines, internal combustion engines, and many other advanced energy-to-power conversion systems. Reference data from several high performance industrial furnaces are also included as an appendix to the book.
This book is the first to be published on high temperature air combustion, including fundamental aspects, its practical use in furnaces and boilers, potential applications in other energy conversion systems, and projected developments and trends. We hope that our readers will be stimulated by the new developments in equipment for energy saving and low pollution for industry and commerce. The authors of any specialized text must select, abstract, and reframe the material that they find most suitable for exemplifying the principles and techniques. In this book we have selected the work of several prominent researchers. Nevertheless, a special attribute of this book is the strong practical emphasis of the portrayal of those concepts, which may be difficult to understand and apply. We have tried to strike the best balance among the physical, practical, and mathematical aspects, and to produce a text that appeals to students and practicing engineers in applying the latest available knowledge to solve their practical energy conservation needs and environmental pollution reduction.
The book is intended as a basis for engineers and researchers in the area of energy conversion using fuels, and also as a textbook for senior year undergraduate and graduate students. The scope of the book is to provide a solid foundation for those who intend to utilize HiTAC technology for their specific application for energy conservation and pollution reduction.
We wish to acknowledge the work of all those who contributed and collaborated on HiTAC research and development activities and of those who assisted in the preparation of this book. We are particularly grateful to our numerous colleagues in Japan and throughout the world who provided us with information for inclusion here. Specific acknowledgment to authors and sources is made in the text and in the lists of references. Special thanks are due to all the industries, institutions, and organizations listed in the Acknowledgments as well as the authors who have contributed to this book. Their help, support, encouragement, and friendship were most welcome. We wish to acknowledge the late Ryoichi Tanaka, President of NFK, for his vision and leadership on the development of HiTAC technology. All members of the technical community worldwide will remember him for his commitment and devotion to developing advanced furnaces. We are grateful for his lifelong dedicated efforts on the evolutionary and revolutionary burner and furnace technology developments. Finally, we most gratefully wish to thank CRC Press for their special cooperation in careful preparation of the book.