This research work delves into the fascinating world of simulating and understanding the behavior of coal slurry in thermal pipelines. This groundbreaking book takes you on a journey through the intricate realm of computational modelling, uncovering the key factors and additive effects that influence the flow dynamics of coal slurry.
Through meticulous research and advanced simulations, this book provides a comprehensive exploration of the thermal aspects involved in coal slurry transportation. Gain invaluable insights into the role of additives and their impact on the overall performance of pipeline systems, as you examine the complex interactions between thermal factors, flow rates, and rheological properties.
With a focus on accuracy and precision, this book equips readers with the necessary tools to tackle challenges encountered in the field of thermal pipeline engineering. Explore various computational techniques, numerical methods, and advanced algorithms, empowering you to predict, analyze, and optimize the transport of coal slurry in thermal pipelines.
Whether you are a seasoned researcher, engineer, or a curious enthusiast, "Computational Modelling of Thermal Pipelines" offers a valuable resource for understanding the intricacies of slurry flow and the additive effects in coal transportation. Expand your knowledge, unravel the complexities, and unlock new possibilities in the realm of thermal pipeline systems.
Slurry pipelines are used to transport solid materials using water for short or long distance. These pipelines are used in many industrial application involving transportation of coal and disposal of slurry in thermal power plant. Transportation through slurry pipeline is a safe, pollution free and reliable method. In the present book, rheological properties of bottom and fly ash are studied to know the flow behavior of coal ash slurry. Numerical simulation is performed on the slurry flow through straight pipe and 90° pipe bend for the evaluation of pressure drop per 100 meter length. Modeling of Straight pipe and 90° pipe bend is generated in Gambit version 2.2.30 and Fluent version 6.2.16 is used for the numerical evaluation. Simulation has been performed on various concentrations (10%, 20%, 30%, 40% & 50%), with additive (40% & 50%) for bottom and fly ash slurries at various flow velocities (10, 20, 30, 32, 40, 41m/s).
Contents
ACKNOWLEDGEMENT
ABSTRACT
LIST OF CONTENTS
LIST OF FIGURES
LIST OF TABLES
NOMENCLATURE
CHAPTERS
1 INTRODUCTION
1.1 COAL ASH
1.1.1 Fly Ash
1.1.2 Bottom Ash
1.2 ASH HANDLING SYSTEM
1.2.1 Bottom Ash Handling System
1.2.2 Fly Ash Handling System
1.3 SLURRY
1.3.1 Non-Settling Slurry
1.3.2 Settling Slurry
1.4 SLURRY TRANSPORTATION SYSTEM
1.5 DIFFERENT TYPES OF LOSSES IN PIPELINE
1.5.1 Losses in Straight Pipe
1.5.2 Losses in Bend
1.6 PIPE MATERIAL
1.7 SURFACTANT
1.7.1 Classification of Surfactant
1.7.2 Triton X-100
1.7.2.1 Benefits of Triton X-100
1.7.2.2 Applications of Triton X-100
2 LITERATURE REVIEW
2.1 LITERATURE REVIEW
2.2 GAPS IN LITERATURE
3 PROBLEM FORMULATION AND OBJECTIVES
3.1 PROBLEM FORMULATION
3.2 OBJECTIVES
4 RHEOLOGICAL CHARACTERISTIC OF BOTTOM AND FLY ASH
4.1 PARTICLE SIZE DISTRIBUTION
4.2 SETTLING PROPERTY
4.3 pH VALUE
4.4 SPECITIC GRAVITY
4.5 RHEOMETER
4.6 GRAPHICAL REPRESENTATION OF PROPERTIES OF BOTTOM AND FLY ASH
5 COMPUTATIONAL SIMULATION OF PIPELINE
5.1 METHODOLOGY
5.1.1 Initial Design
5.1.2 Geometry Generation
5.1.3 Mesh Generation
5.1.4 Pre-Processing
5.1.5 Solver
5.1.6 Postprocessor
5.2 PIPE MODELING
5.3 ASSUMPTION FOR SIMULATION
5.3.1 Boundary Condition
5.3.2 Solution Parameters
5.4 SIMULATION RESULTS OF STRAIGHT PIPE
5.5 PIPE BEND MODELING
5.6 SIMULATION RESULTS OF 90° PIPE BEND
6 CONCLUSION AND FUTURE SCOPE
6.1 CONCLUSIONS
6.2 FUTURE SCOPES
REFERENCES
APPENDIX
Acknowledgements
We wish to express our thanks to Mr. Naveen Saini, Mechanical Engineering Department, M M University (Mullana), for their guidance and encouragement. The present book is the convergence of their ideas. Working under their guidance is of immense pleasure and very worthful in the context of knowledge.
We are also wish thanks to Dr. N.K. Batra, Head of Department, Mechanical Engineering Department, M.M.D.U. Mullana, Ambala.
We would like to thank to all the faculty members and employees of Mechanical Engineering Department, for their everlasting support.
We are very obliged to our parents, friends and colleagues for their encouragement and support in building up this Book.
Dr. Subhash Malik Dr. Bikram Jit Singh
Preface
Slurry pipelines are used to transport solid materials using water for short or long distance. These pipelines are used in many industrial application involving transportation of coal and disposal of slurry in thermal power plant. Transportation through slurry pipeline is a safe, pollution free and reliable method. In the present book, rheological properties of bottom and fly ash are studied to know the flow behavior of coal ash slurry. The rheological properties of coal ash depend on a number of factors such as particle size distribution, pH value and settling characteristics. Bottom and fly ash for the current investigation are collected from the Guru Gobind Singh thermal power plant, Ropar. Rheometer is used for the shear rate and shear stress variation for the different concentration of bottom and fly ash slurry. Numerical simulation is performed on the slurry flow through straight pipe and 90° pipe bend for the evaluation of pressure drop per 100 meter length. Modeling of Straight pipe and 90° pipe bend is generated in Gambit version 2.2.30 and Fluent version 6.2.16 is used for the numerical evaluation. Simulation has been performed on various concentrations (10%, 20%, 30%, 40% & 50%), with additive (40% & 50%) for bottom and fly ash slurries at various flow velocities (10, 20, 30, 32, 40, 41m/s). It is found that pressure drop increases with increase in flow velocity and concentrations of bottom and fly ash slurries. Triton X-100 is used to lower the viscosity and pressure drop of slurry.
The significance of this book lies in its ability to address critical challenges and advance knowledge in the field of thermal pipeline engineering. Here are the key aspects that make this book significant like ; Advancing Computational Modelling, Understanding Additive Effects, Practical Relevance, Optimizing Pipeline Systems and Implications for Industry and Sustainability respectively. In summary, "Computational Modelling of Thermal Pipelines: Analysing the Additive Effects in Coal Slurry Flow" has significant implications for the field of thermal pipeline engineering. It advances computational modelling techniques, explores additive effects, offers practical insights, enables optimization, and contributes to industry sustainability.
Figures
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Tables
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Nomenclature
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CHAPTER 1 INTRODUCTION
Slurry transportation through pipeline provides better effect on material transportation system. Transportation of bottom and fly ash in thermal power plants through pipeline is best example of slurry transportation system. [21] This system has various advantages such as very less pollution and less noise. So, there is requirement of detailed study of pipeline slurry transportation system to improve its performance. [2]
1.1 COAL ASH
Ashes coming out after the combustion of pulverized coal in thermal power plants are divided into two main categories:
- Fly Ash
- Bottom Ash
1.1.1 Fly Ash
Fly ash is the finest of coal ash particles. It is called fly ash because it is transported from the combustion chamber by exhaust gases. Fly ash is the fine powder formed from the mineral matter in coal, consisting of the non combustible matter in coal plus a small amount of carbon that remains from incomplete combustion. Fly ash is generally light in color and consists mostly of silt-sized and clay-sized glassy spheres. [23]
Illustrations are not included in the reading sample
Figure 1.1 Fly Ash [33] This gives fly ash a consistency somewhat like talcum powder. Properties of fly ash very significant with coal composition and plant-operating conditions. Fly ash can be referred to as either cementations or pozzolanic. A cementations material is one that hardens when mixed with water. A pozzolanic material will also harden with water but only after activation with an alkaline substance such as lime. These cementations properties are what make some fly ashes useful for cement replacement in concrete and many other building applications. [26]
1.1.2 Bottom Ash
Coal bottom ash and fly ash are quite different physically, mineralogical, and chemically. Bottom ash is a coarse, granular, incombustible product that is collected from the bottom of furnaces. Bottom ash is coarser than fly ash, with grain sizes spanning from fine sand to fine gravel. The type of product produced depends on the type of furnace used to burn. [8]
Illustrations are not included in the reading sample
Figure 1.2 Bottom Ash [34]
Main components of bottom ash are Nickel, Chromium, Arsenic and Sulphur. The concentrations of Ar, Cr and Ni are higher for bottom ashes from high Sulphur feed coals. [27]
1.2 ASH HANDLING SYSTEM
Ash handling refers to the method of collection, conveying, storage and load out of various types of ash residue left from solid fuel combustion processes. The most common types of ash include bottom ash and fly ash resulting from the combustion of coal. Ash handling systems may employ pneumatic ash conveying or mechanical ash conveyors. [6]
1.2.1 Bottom Ash Handling System
Bottom ash resulting from the combustion of coal in the boiler shall fall onto the ground, refractory lined, water impounded, maintained level, double V-Section type, W- Section type steel- fabricated bottom ash hopper having a hold up volume to store bottom ash and economizer ash of maximum allowable condition. [24] The slurry formed shall be transported to slurry sump through pipes. The Sulphur and Carbon contents of pulverized bottom ash are 0.03 to 2.32 weights % age and 0.19 to 6.62 weights % age respectively.
1.2.2 Fly Ash Handling System
Fly ash is considered to be collected in electrostatic separator hoppers. Fly ash from electrostatic separator hoppers extracted by vacuum pumps transported to intermediate surge hopper cum bag filter for further dry conveying of fly ash. [20] Under each surge hopper ash vessels shall be connected with Oil free screw compressor for conveying the fly ash from Intermediate Surge Hopper to silo. Total fly ash generated from each unit will be conveyed through streams operating simultaneously and in parallel. [28]
1.3 SLURRY
The mixture of solids and liquids is known as slurry. The physical characteristics of slurry are dependent on many factors such as particle size distribution, solid concentration in the liquid phase, turbulence level, temperature, conduit size, and viscosity of the carrier. Slurry is a mixture of a solid particles and fluid held in suspension. [15] Water is the most commonly used fluid. The speed of slurry flow is sufficiently high to maintain the particles in suspension. The mixture resists flow in highly viscous mixtures because of excessively low shear rate in the pipeline. [29] There are two types of slurry:
1.3.1 Non-Settling Slurry
The solid particles in slurry do not settle in the bottom, but remain in suspension for a long time. A non-settling slurry acts in a homogeneous, viscous manner, but the characteristics are nonNewtonian. Non-settling slurry can be defined as a homogeneous mixture of solids and liquid in which the solids are uniformly distributed. [30]
1.3.2 Settling Slurry
Setting slurry settled down rapidly with the time relevant of the process, but can be kept in suspension by turbulence. Settling slurry can be defined as a pseudo homogeneous or pseudo heterogeneous mixture and can be completely or partly stratified. [17]
- Pseudo-Homogeneous Mixture: A mixture in which, all the particles are in suspension but where the concentration towards the bottom.
- Heterogeneous Mixture: A mixture of solids and liquid in which the solids are not uniformly distributed and tend to be more concentrated in the bottom of the pipe or containment vessel. [18]
1.4 SLURRY TRANSPORTATION SYSTEM IN THERMAL POWER PLANT
Illustrations are not included in the reading sample
Figure1.3 Slurry Transport System
All the available coals have some percentage of ash. When the coal is burnt in a boiler furnace, about 10 to 20% of quantity of coal used results in ash. In the modern large steam power plants where huge amounts of coal are used, the amount of ash may be go up to many thousands tonnes of ash per year. A slurry transport system is used to disposal the coal ash away from coal burning unit in thermal power plant. Bottom and fly ash slurries are pumped from the common ash slurry sump to the dyke area which is located near slurry pump house. Water and coal ash are mixed in slurry tank, after that slurry transportation takes place in slurry pipeline with the help of slurry pump. [5]
1.5 DIFFERENT TYPES OF LOSSES IN PIPELINE
When fluid flows through a pipe, it is subjected to hydraulic resistances which are of viscous frictional resistance and local resistance. Viscous frictional resistance associated with the fluid flow is called major loss of energy, where as local resistances are called losses of energy. [14] Local resistances are essentially due to change of velocity either in magnitude or direction, in which the portion of energy possessed by the flowing fluid gets dissipated as heat energy. Losses due to change in cross section, bends, valves and frictions of all types are categorized as minor losses. In short pipes, minor losses sometimes are more than the frictional losses. Losses due to the local disturbances of the flow in the conduits such as changes in cross-section, projecting gaskets, elbows, valves and similar items are called minor losses. So, minor losses can be defined as the losses that occur in pipelines due to bends, elbows, joints, valves, etc. In case of a very long pipe, these losses are usually insignificant in comparison to the fluid friction in the length considered. [22]
1.5.1 Losses in Straight Pipe
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Figure 1.4 Pressure Drop in Horizontal Pipe [37]
In horizontal pipe when z1 = z2 and diameter of pipe is constant, u1 = u2, hydraulic loss is equal to the head of pressure drop or head loss. [13]
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1.5.2 Losses Due to Bend
Bends are provided to change the direction of fluid flow through pipeline. An additional loss of the head due to fluid friction takes place in the course of fluid flow through pipeline bend. [32] The fluid takes a curved path while flowing through a pipe bend as shown:
Illustrations are not included in the reading sample
Figure 1.5 Losses in Bend [38]
Whenever a fluid flows in a curved path, there must be a force acting radically inwards on the fluid to provide the inward acceleration, known as centripetal acceleration [4]. Fluid particles in this region, because of their close proximity to the wall, have low velocities and cannot overcome the adverse pressure gradient and this leads to a separation of flow from the boundary and consequent losses of energy in generating local eddies. The additional loss of head (apart from that due to usual friction) in flow through pipe bends is known as bend loss and is usually expressed as: [1]
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The value of loss factor depends on the total length of the bend and the ratio of radius of curvature of the bend and pipe diameter. The radius of curvature R is usually taken as the curvature of the centre line of the bend. Loss factor varies slightly with Reynolds number (Re) in the typical range of encountered practice, but increases with surface roughness.
1.6 PIPE MATERIAL
Different types of pipes are used to transportation of slurry from one point to another such as carbon steel, cast iron, copper, galvanized iron pipe etc. In the present work, carbon steel pipe is used to transfer slurry from power plant to required place. [12] Inner and outer diameter of pipe is 381 mm, 400 mm respectively. Pipes are jointed with electric resistance welding. Working pressure of carbon steel pipe is 2902 k Pa according to ASTM.
1.7 SURFACTANT
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Figure 1.6 Surfactant [35]
Surfactants are compounds that lower the surface tension or interfacial tension between two liquids or between liquid and solid. Surfactants may act as detergents, wetting agents, emulsifiers, foaming agents and dispersants. [11]
1.7.1 Surfactant Classification
- Nonionic: A non-ionic surfactant has no charge groups in its head.
- Anionic: If the charge is negative then surfactant is called anionic.
- Cationic: If the charge is positive then surfactant is called cationic.
- Amphoteric: If a surfactant contains a head with two oppositely charged groups, it is termed as amphoteric. [28]
Abbildung in dieser Leseprobe nicht enthalten
Figure 1.7 Surfactant Classifications According to the Head: Nonionic, Anionic, Cationic, and Amphoteric [35]
1.7.2 Triton X-100 (C14H22O (C2H4O) N
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Figure 1.8 Structure of Triton X-100 [36]
It is a non-ionic surfactant which has a hydrophilic polyethylene oxide chain. [7] The "X" series of Triton detergents are produced from octylphenol polymerized with ethylene oxide. The number (100) relates only indirectly to the number of ethylene oxide units in the structure. Apart from laboratory use, Triton X-100 can be found in several types of cleaning compounds ranging from heavy-duty industrial products to gentle detergents. [3]
1.7.2.1 Benefits of Triton X-100
- Excellent detergent
- Dispersant & emulsifier for oil-in water systems
- Excellent wetting agent
- Readily biodegradable
1.7.2.2 Applications of Triton X-100
- Household & industrial cleaners
- Paints & coatings
- Textile
- Metalworking fluids
CHAPTER 2 LITERATURE REVIEW
2.1 LITERATURE REVIEW
The rheology of coal ash slurry and their characterization has received attention in recent years because of widespread application in industry and academic interest. To easy transportation of slurry attention has been taken on viscosity and rheology characteristics of solid material. The flow behavior and slurry characteristics are greatly influenced by the presence of additive (Triton X-100) in slurry. Simulation of fluid flow through pipeline has carried out in fluent.
Mukhtar et al. [1994] studied the bend pressure drop on two materials, namely slurries of iron ore and zinc tailings. These two materials have been chosen because they differed widely in specific gravity as well as particle size distribution. From there experiments they observed that bend loss coefficient for long radius 90° bend in the flow of multi sized particulate slurry is less than that of water. Their study reveals that bend loss coefficient relatively independent of solid concentration and specific gravity. From their experiments they came to the conclusion that as long as the mixture velocity exceeds the deposition velocity by at least 0.5 m/s, the value of bend coefficient can be assumed to be independent of flow velocities. [1]
Logos and Nguyen [1996] studied the rheological behavior of low-rank coal-water slurry as a function of solids concentration, particle size distribution. The significant improvement in the rheological behavior with changing the particle size distribution may be explained in terms of spatial rearrangement of the particles, and an apparent dilution effect. The results obtained in this study indicate that, with a careful control of the particle size distribution, it is possible to prepare an optimum coal-water slurry which has a low viscosity but with high solids loadings. [2]
Aktas and Woodburn [2000] studied the rheological properties of CWM depend on a number of factors such as the type of coal, the solid content and its size distribution, the temperature, the pH and the presence of electrolytes and chemical additives. The slurry viscosity was influenced significantly by initial surfactant loading, the particle size distribution and the ash content of the feeds. CWS of up to 60% prepared from bickers, coal samples with low ash contents could be produced at acceptable viscosities in the presence of a non-ionic surfactant (Triton X-405). To produce pump able slurries with more than 60% solid, it would be necessary first to achieve a significant level of demineralization, and to use high levels of reagent addition. The viscosities of the slurries with low ash content were significantly reduced by the surfactant addition which also altered the rheological characters of these slurries from non-Newtonian towards Newtonian fluids. [3]
[...]
- Quote paper
- Subhash Malik (Author), Bikram Jit Singh (Author), 2023, Computational Modelling of Thermal Pipelines. Analysing the Additive Effects in Coal Slurry Flow, Munich, GRIN Verlag, https://www.grin.com/document/1372508
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