CHAPTER ONE
1.0 INTRODUCTION
1.1 BACKGROUND OF STUDY
Circulating fluidization is a promising technology for designing efficient coal combustors with higher solid throughputs. Excellent contacting is achieved as solids are entrained in a vertical riser column by a stream of reactive gases at high velocity. Unfortunately, limited understanding of circulating fluidized beds (CFB) renders design extrapolations from pilot reactors to full scale plants both empirical and expensive. In particular, the behavior of large-scale units is unclear.
The hostile environment makes measurements challenging in CFB power plants. Even essential flow variables like overall solid fluxes are seldom recorded. In contrast, cold facilities can produce detailed hydrodynamic data. However, because the density and viscosity of cold gases are markedly different than that of typical combustion products, the hydrodynamics of cold units may not be relevant to CFB combustors. To avoid this problem, several researchers have employed dimensional analysis to match the hydrodynamics of bubbling and CFB combustors in cold laboratory facilities.
Because vessel geometry greatly affects CFB flow behavior, Horio, et al., (2010) have carefully matched the aspect ratios of CFB units of increasing sizes before comparing their hydrodynamics. In contrast, we have quantified hydrodynamic scale-up effects directly using a single facility. To this end, we have constructed a cold CFB with the ability to recirculate –rather than discard– fluidization gas mixtures of adjustable density and viscosity. Using dimensional similitude, this cold CFB riser with diameter of 20cm, operating with different gas and solid systems, is made to simulate generic coal-burning CFB risers of 32cm and 46cm diameter.
1.2 STATEMENT OF RESEARCH PROBLEM
Several attempts to develop models for steady-state production, and for coarse-mesh simulations that require similar equation closures, have been presented in the literature. Agrawal et al. (2001) and Andrews et al. (2005) studied the average drag and stress terms through simulations in small domains with periodic boundary conditions. Zhang & VanderHeyden (2002) suggested an added-mass force closure for the correlation between fluctuations of the pressure gradient of the continuous phase and fluctuations of solids volume fraction. De Wilde (2007) analyzed the same term from simulations and accounted also for the drag force in the derivation of a new closure. Zheng et al. (2006) presented a two-scale Reynolds stress turbulence model for gas-particle flows.
1.3 AIMS AND OBJECTIVES OF STUDY
The main aim of the research work is to examine the experimental hydrodynamic on real circulating fluidinized bed (CFB) riser using a developed DC motor. Other specific objectives of the study are:
- to examine the hydrodynamic behavior of CFB
- to enhance the efficiency of the fluidinized bed (CFB) riser using developed DC motor
- to investigate on the factors affecting the use of DC motor in hydrodynamic on real circulating fluidinized bed (CFB) riser
- To proffer solution to the problem associated with the use of developed DC motor for experimental hydrodynamic on real circulating fluidinized bed (CFB) riser
1.4 RESEARCH QUESTION
The study came up with research questions so as to ascertain the above stated objectives of the study. The research questions for the study are:
- What is the hydrodynamic behavior of CFB?
- In what ways can the efficiency of the fluidinized bed (CFB) riser using developed DC motor be enhanced?
- What are the factors affecting the use of DC motor in hydrodynamic on real circulating fluidinized bed (CFB) riser?
1.5 ORGANISATION OF STUDY
This section deals with the organization of the research work in chapters; the chapter one of the research work will cover the background of the study, the statement of problem, the aims and objectives of study, significance and the scope of study, the chapter two will deal with the review of related literature on the effect of solar power. The chapter three of the research work will cover the areas of materials and method. The chapter four will cover the area of experiment; while the chapter five will cover the summary, conclusion and possible recommendation for the research work.
1.6 SIGNIFICANCE OF STUDY
The study on the experimental hydrodynamic on real circulating fluidinized bed (CFB) riser using a developed DC motor will be of immense benefit to the engineering sector of Nigeria, the state, the federal government and other researcher that desire to carry out similar research on the above topic because the findings of the study will educate the above audience on the importance of the use of developed DC motor for experimental hydrodynamic on real circulating fluidinized bed (CFB) riser. The study will discuss the factors affecting the use of developed DC motor. Finally the study will contribute to the body of existing literature and knowledge in this field of study and provide a basis for further research.
1.7 SCOPE OF STUDY
The study will focus on the use of DC motor in hydrodynamic on real circulating fluidinized bed (CFB) riser. The study will cover the importance of the use of developed DC motor for experimental hydrodynamic on real circulating fluidinized bed (CFB) riser. The study will discuss the factors affecting the use of developed DC motor
1.8 DEFINITION OF TERMS
FLUID: a fluid is a substance that continually deforms under an applied shear stress.
HYDRODYNAMIC: a branch of physics that deals with the motion of fluids and the forces acting on solid bodies immersed in fluids and in motion relative to them