International Research Journal of Engineering and Technology (IRJET)
e-ISSN: 2395-0056
Volume: 04 Issue: 07 | July -2017
p-ISSN: 2395-0072
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CFD investigation of coal gasification: Effect of particle size Sonal Bhadauria#%, Sreepriya Vedantam*, Shriram Prasad$1, Anish P. Jacob$2 #PG
scholar, Madhav Institute of Science and Technology, Gwalior (MP) Scientist, %Chemical engineering division CSIR-IICT Hyderabad (TS) 1Associate Professor, $Department of Chemical Engineering, M.I.T.S, Gwalior, M.P 2Assistant Professor, $Department of Chemical Engineering, M.I.T.S, Gwalior, M.P ---------------------------------------------------------------------***--------------------------------------------------------------------*Project
Abstract - The present work studies the effect of different
energy equations along with empirical and theoretical correlations which give better understanding, requires supercomputers and is less time consuming. In coal gasification efficiency is mainly concerned with chemical reactions and energy transfer, therefore a hydrodynamic study is important to improve the process as it gives insight of distribution of phases and species involved. XiZhong Chen [3] studied the effect of distributor shape, solid particle size, and operational gas velocity and feed manner on the flow behavior in the polymerisation reactor. Caterina Goncalves Philippsen [1] also presented a review on fluidised bed technology giving importance of hydrodynamics. Process parameters play an important role in improving efficiency and the effect of one such parameter i.e. coal particle size is being studied in the present work. An Eulerian Eulerian CFD model with kinectic theory of granular flow is being used in this study
particle size diameter on fluidised bed hydrodynamics with different fluidization velocity. This study of operational parameters of hydrodynamics can form a basis for integration of kinectic into CFD model. The contours of solid volume fraction at different velocity with two particle size are shown. A range of velocity between minimum fluidization velocity and terminal velocity are studied to see the repeatability and observed that at high velocity there is no significant effect of particle size other than height of bed expansion for larger paricle diameter. Key Words: Coal gasification, fluidised bed, coal particle size, CFD
1. INTRODUCTION Energy crisis is the major threat the entire world is facing today, depletion of the fossil fuel being the major reason. Among the variety of fossil fuel present coal is said to be the clean energy of the future. Fluidised bed coal gasification is one of the potential sources for the production of clean and eco friendly fuel. In coal gasification instead of burning fossil fuel it is chemically transformed to syngas which is a combination of hydrogen, carbon monoxide and very less carbon di oxide. The syngas produced has variety of applications ranging from use in fertilizers to production of electricity. The fluidized bed technology allows efficient gas–solid contact; therefore it is widely used in covering particles, drying, granulation, blending, combustion and gasification processes [1].In this type of flow understanding the process and insight of the gasifier is a complex phenomenon due to particle-particle interaction and chemical reactions. So there is need of mathematical models that develop better understanding of the processes. Mathematical modeling of gas flow in fluidised bed began in 60s with Kunni and Levenspiel [2] being the major pioneer to analyze bubble motion, system instability and mass transfer.
2. EQUIPMENT AND MATERIAL 2.1 Fluidised Bed The simulated case is a bubbling fluidised bed coal gasifier designed and built for studying the gasification of Columbian coal [3]. The schematic view of the gasifier is shown in Fig-1 the reactor has an internal diameter of 0.22 m and a height of 2m. A uniform velocity is assumed at the air and the steam inlet. The geometry for the model is created in ANSYS FLUENTdiscretized into 9981 quadrilateral cells as shown. The air and the steam flow into from the bottom of the gasifier. The outlet pressure is fixed at atmosphere. The bed is initially assumed to be filled with coal particles up to 1m with a solid volume fraction of 0.48[4]
2.2 Materials Two coal particles size is used in the present study in the size range of 0.00062m and 0.01m. The density of the particles (coal) was taken to be 1250 kg/m3. The value of particle sphericity was assumed to be equal to one
Computational fluid dynamics is a branch of fluid mechanics which is widely used to predict the physical and chemical processed inside a fluidised bed technology.CFD uses mathematical models based on mass, momentum and
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