Bulk Solids Handling: An Introduction to the Practice and Technology

ISBN-13: 9780751402957 / Angielski / Twarda / 1988 / 522 str.

C. R. Woodcock; J. S. Mason

Opis

An understanding ofthe properties and the handling characteristics of liquids and gases has long been regarded as an essential requirement for most practising engineers. It is therefore not surprising that, over the years, there has been a regular appearance of books dealing with the fundamentals of fluid mechanics, fluid flow, hydraulics and related topics. What is surprising is that there has been no parallel development of the related discipline of Bulk Solids Handling, despite its increasing importance in modern industry across the world. It is only very recently that a structured approach to the teaching, and learning, of the subject has begun to evolve. A reason for the slow emergence of Bulk Solids Handling as an accepted topic of study in academic courses on mechanical, agricultural, chemical, mining and civil engineering is perhaps that the practice is so often taken for granted. Certainly the variety of materials being handled in bulk is almost endless, ranging in size from fine dust to rocks, in value from refuse to gold, and in temperature from deep-frozen peas to near-molten metal.

Recenzje

Overall, the authors have succeeded in their objective to design the book as a practical source of reference for plan and process engineers, designers, project and maintenance engineers in industries where particulate or granular materials are handled in bulk. It is a highly readable book that engineering students can read and understand on their own. Drying Technology

Spis treści

1 Characterization, Flow and Storage.- 1 The nature of bulk solids.- 1.1 Introduction.- 1.2 Sampling.- 1.2.1 Obtaining a gross sample.- 1.2.2 Preparing laboratory and test samples.- 1.3 Voidage and bulk density.- 1.4 Particle density.- 1.5 Particle size.- 1.5.1 Definition of ‘size’ and ‘size distribution’.- 1.5.2 Measurement of particle size.- 1.6 Particle shape.- 1.7 Surface area.- 1.8 Particle hardness.- 1.9 Cohesion and adhesion.- 1.9.1 Angle of repose.- 1.9.2 Shear strength.- 1.9.3 The shear cell as a means of determining shear strength.- 1.9.4 Wall friction.- 1.9.5 Measurement of wall friction.- 1.9.6 Arching phenomena.- 1.10 Moisture content.- 1.11 Explosiveness.- 1.12 Notation.- References and bibliography.- 2 Gravity flow of bulk solids.- 2.1 Introduction.- 2.2 Pressure distribution in a bulk solid.- 2.2.1 Bulk solid at rest.- 2.2.2 The effect of flow on the pressure distribution.- 2.3 Flow of bulk solids from hoppers.- 2.3.1 Introduction.- 2.3.2 Core flow.- 2.3.3 Mass flow.- 2.3.4 Obstructions to gravity flow.- 2.3.5 Predicting the solids discharge rate.- 2.4 Flow of bulk solids in chutes.- 2.4.1 Introduction.- 2.4.2 Flow patterns in straight inclined chutes.- 2.4.3 Flow patterns in curved chutes.- 2.4.4 Chute design.- 2.5 Flow of bulk solids in vertical pipes.- 2.5.1 Introduction.- 2.5.2 Mode of flow.- 2.5.3 Flow control—J-valves and L-valves.- 2.6 Notation.- References and bibliography.- 3 Dynamics of fluid/solids systems.- 3.1 Introduction.- 3.2 Flow through beds of fixed particles.- 3.2.1 Characteristics of flow in porous media.- 3.2.2 The prediction of pressure-drop across a fixed particulate bed.- 3.3 Settling behaviour of particles.- 3.3.1 Motion of a spherical particle settling in a stationary fluid.- 3.3.2 The settling of non-spherical particles.- 3.3.3 The settling of concentrations of particles (hindered settling).- 3.3.4 Classification and sorting of particles.- 3.4 Fluidization.- 3.4.1 The fluidization process.- 3.4.2 The prediction of minimum fluidizing velocity.- 3.4.3 Entrainment of particles from a fluidized bed.- 3.4.4 The porous membrane, or distributor.- 3.4.5 The influence of particle size and density.- 3.5 Spouted bed behaviour.- 3.6 Gas/solids flow in pipes.- 3.6.1 Introduction.- 3.6.2 The flow of gas/solids suspensions in horizontal pipes.- 3.6.3 The flow of gas/solids suspensions in vertical pipes.- 3.6.4 Flow around 90° bends.- 3.6.5 The prediction of pressure-drop in flowing gas/solids suspensions.- 3.7 Liquid/solids flow in pipes.- 3.7.1 Flow characteristics of liquid/solids mixtures (slurries).- 3.7.2 Non-Newtonian flow models for homogeneous suspension.- 3.7.3 The modelling of heterogeneous suspensions.- 3.8 Notation.- References and bibliography.- 4 The design of storage bins and hoppers.- 4.1 Introduction.- 4.2 Hopper geometry.- 4.2.1 Shape.- 4.2.2 Overall dimensions.- 4.3 Outlet size and cone angle.- 4.3.1 Jenike’s ‘flow—no flow’ criterion.- 4.3.2 Flow Functions and flow factors.- 4.3.3 Outlet dimension and cone angle.- 4.4 Period of storage and time consolidation effects.- 4.4.1 Caking.- 4.4.2 Testing for time consolidation.- 4.4.3 Practical ways of minimizing time consolidation.- 4.5 The effect of moisture.- 4.6 Overcoming space limitations.- 4.6.1 The use of low-friction linings.- 4.6.2 Changing hopper shape.- 4.7 Structural design.- 4.8 Control and measurement of discharge rate.- 4.9 Feeders.- 4.9.1 Introduction.- 4.9.2 Belt feeders.- 4.9.3 Apron feeders and rotary feeders.- 4.9.4 Rotary table feeders.- 4.9.5 Screw feeders.- 4.9.6 Vibratory feeders.- 4.10 Discharge aids.- 4.10.1 Introduction.- 4.10.2 Pneumatic methods.- 4.10.3 Vibrational methods.- 4.10.4 Mechanical methods.- 4.11 Notation.- References and bibliography.- 5 Dust control.- 5.1 Introduction.- 5.2 Dust as a hazard to health.- 5.2.1 Dust particle size.- 5.2.2 Dust concentration limits.- 5.3 Dust suppression.- 5.3.1 Elimination of dust.- 5.3.2 Control of dust dispersion.- 5.4 Gravity and inertial separators.- 5.5 Air cleaners—cyclones.- 5.5.1 Principle of operation.- 5.5.2 Prediction of collecting efficiency.- 5.5.3 Prediction of pressure-drop.- 5.5.4 Cyclone selection.- 5.6 Air cleaners—wet washers or scrubbers.- 5.6.1 Principle of operation.- 5.6.2 Low pressure-drop wet washers.- 5.6.3 High pressure-drop wet washers.- 5.7 Air cleaners—filters.- 5.7.1 Mechanism of filtration.- 5.7.2 Filter media.- 5.7.3 Bag filters-design and selection.- 5.7.4 Filter cleaning.- 5.8 Air cleaners—electrostatic precipitators.- 5.9 Notation.- References and bibliography.- 6 Explosion hazards.- 6.1 Introduction.- 6.2 Characteristics of dust explosions.- 6.2.1 Ignition.- 6.2.2 Explosibility limits.- 6.2.3 Expansion effects and explosion pressures.- 6.3 Measurement of explosion parameters.- 6.4 Explosion risks and system design.- 6.4.1 Minimizing sources of ignition and prevention of ignition.- 6.4.2 Containment.- 6.4.3 Explosion relief venting.- 6.4.4 Detection and suppression.- 6.5 Static electricity.- 6.6 Conclusion.- References and bibliography.- 2 Mechanical Handling.- 7 Belt conveyors.- 7.1 Introduction.- 7.2 Features of belt conveyors.- 7.2.1 Belt construction.- 7.2.2 Idlers.- 7.2.3 Drive arrangements.- 7.2.4 The power unit.- 7.2.5 Loading and discharge arrangements.- 7.2.6 Belt cleaners.- 7.3 Belt conveyor design.- 7.3.1 The bulk solid to be transported.- 7.3.2 Belt speed.- 7.3.3 Belt width.- 7.3.4 Belt tension.- 7.3.5 Idler spacing.- 7.3.6 Power requirements.- 7.4 Belt conveyor variants.- 7.4.1 The cable belt conveyor.- 7.4.2 Belt conveyors without idlers.- 7.4.3 Closed-belt or pipe conveyors.- 7.4.4 Sandwich belts.- 7.5. Notation.- References and bibliography.- 8 Bucket elevators.- 8.1 Introduction.- 8.2 Principal types of bucket elevator.- 8.2.1 Centrifugal discharge elevators.- 8.2.2 Continuous bucket elevators.- 8.2.3 Pivoted buckets.- 8.2.4 Profiled-belt elevators.- 8.3 Design and selection of bucket elevators.- 8.3.1 Design features.- 8.3.2 Loading.- 8.3.3 Discharge.- 8.3.4 Capacity.- 8.3.5 Driving power.- 8.4 Notation.- References and bibliography.- 9 Chain and flight conveyors.- 9.1 Introduction.- 9.2 Drag conveyors.- 9.3 En-masse conveyors.- 9.3.1 Design features.- 9.3.2 Performance calculations.- 9.3.3 Applications of en-masse conveying.- 9.4 Tubular drag conveyors.- 9.5 Apron conveyors.- 9.6 Aerial ropeways.- 9.7 Notation.- References and bibliography.- 10 Screw conveying.- 10.1 Introduction.- 10.2 Principle of operation of screw conveyors.- 10.3 The enclosed screw or ‘auger’ conveyor.- 10.3.1 Constructional features.- 10.3.2 Prediction of the performance of an auger conveyor.- 10.4 The industrial screw conveyor or ‘U-trough’ conveyor.- 10.4.1 Constructional features.- 10.4.2 The conveyed product.- 10.4.3 Conveyor selection.- 10.4.4 Conveyor power.- 10.4.5 Inclined screw conveyors.- 10.5 Vertical screw conveyors.- 10.6 Conclusion.- 10.7 Notation.- References and bibliography.- 11 Vibratory conveyors.- 11.1 Introduction.- 11.2 Movement of a bulk solid in a vibrating trough.- 11.2.1 The motion of the trough.- 11.2.2 The motion of bulk material in the trough.- 11.2.3 Average conveying velocity.- 11.2.4 The influence of the design parameters.- 11.2.5 Two-phase trough motion.- 11.3 Design features.- 11.3.1 Drive mechanism.- 11.3.2 Mounting systems.- 11.4 Applications of vibratory conveying.- 11.5 Spiral elevators.- 11.6 Notation.- References and bibliography.- 3 Pneumatic and Hydraulic Transport.- 12 Basic pneumatic conveying systems.- 12.1 Introduction.- 12.2 Modes of conveying—dilute-phase and dense-phase.- 12.3 Low-pressure pneumatic conveying systems.- 12.3.1 Positive-pressure systems.- 12.3.2 Negative-pressure (vacuum) systems.- 12.3.3 Combined negative/positive pressure systems.- 12.4 High-pressure systems.- 12.4.1 General features.- 12.4.2 Single blow tank systems.- 12.4.3 Twin blow tanks and continuously operating systems.- 12.4.4 Long-distance conveying.- 12.5 Low-velocity conveying and the use of supplementary air feeds.- 12.5.1 General features.- 12.5.2 Plug-forming systems.- 12.5.3 Plug-limiting systems.- 12.5.4 Air-injection and booster systems.- References and bibliography.- 13 Components of pneumatic conveying systems.- 13.1 Introduction.- 13.2 The air supply.- 13.2.1 General requirements.- 13.2.2 Fans and turbo-blowers.- 13.2.3 Roots-type blowers.- 13.2.4 Sliding-vane rotary compressors.- 13.2.5 Screw compressors.- 13.2.6 Reciprocating compressors.- 13.2.7 Vacuum pumps.- 13.3 Feeding devices.- 13.3.1 Rotary valves.- 13.3.2 Screw feeders.- 13.3.3 Venturi feeders.- 13.3.4 Gate lock valves.- 13.3.5 Blow tanks.- 13.3.6 Entrainment devices for vacuum systems.- 13.4 The pipeline.- 13.5 Disengaging and collecting devices.- 13.6 Notation.- References and bibliography.- 14 Pneumatic conveyor design.- 14.1 Introduction.- 14.2 General design procedure.- 14.2.1 Conveying velocity and volumetric air flow rate.- 14.2.2 Solids mass flowrate and solids loading ratio.- 14.2.3 Pipeline diameter.- 14.2.4 Pressure-drop.- 14.2.5 Stepped pipelines.- 14.2.6 Selection of the air mover.- 14.3 Summary of preliminary design procedure for dilute-phase systems.- 14.4 Designing from available test data.- 14.4.1 Conveying characteristics.- 14.4.2 Scaling for pipe size and conveying distance.- 14.5 Notation.- References and bibliography.- 15 Air-assisted gravity conveying.- 15.1 Introduction.- 15.2 The flow of fluidised solids.- 15.3 Practical air-assisted gravity conveying.- 15.4 Design parameters for air-gravity conveyors.- 15.4.1 Slope of channel.- 15.4.2 Conveying distance.- 15.4.3 Width of conveying channel.- 15.4.4 Air requirement.- 15.5 Properties of bulk solids for air-gravity conveying.- 15.6 Air-float conveyors for horizontal and upward transport.- 15.7 Energy consumption of air-gravity conveyors.- 15.8 Notation.- References and bibliography.- 16 Hydraulic conveying.- 16.1 Introduction.- 16.2 Components of a hydraulic conveying system.- 16.2.1 Pumps.- 16.2.2 Slurry preparation plant.- 16.2.3 The pipeline.- 16.2.4 De-watering equipment.- 16.3 System design.- 16.3.1 General design approach.- 16.3.2 Flow characreristics and pressure-drop.- 16.4 Recent development.- References and bibliography.- 17 Capsule transport.- 17.1 Introduction.- 17.2 Capsule transport in a pneumatic pipeline.- 17.2.1 General features of a pneumo-capsule system.- 17.2.2 The capsules.- 17.2.3 The pipeline.- 17.2.4 The air supply.- 17.2.5 Loading and unloading stations.- 17.3 Capsule transport in a hydraulic pipeline.- 17.3.1 General features of a hydro-capsule system.- 17.3.2 The capsules.- 17.3.3 The pipeline.- 17.3.4 The water supply and pump system.- 17.3.5 Injection and ejection of capsules.- 17.4 Size of capsule fleet.- 17.5 Notation.- References.