Fluid Particle Operations: - PowerPoint Presentation

1. Fluid Particle Operations:Unit 1By: Sarmad Rizvi

2. IntroductionGeneral Perception of Chemical Engineering is to, “convert or separate raw materials into useful products.” How?Some processes and industries where chemical engineering is essential:Manufacturing of inorganic and organic chemicals. (Ex: Sodium Hydroxide, Sulphuric Acid, Methyl alcohol, etc.),Petroleum Refining. (Separation of Crude oil into different products such as kerosene, gasoline, diesel, etc.),Polymer processing industry,Food Industry,Pharmaceutical Industry,Textile Industry, etc.

3. …Chemical Plants, in general, are defined as industries whose purpose is to convert raw materials into useful/value-added chemical products. They consist of Unit Operations and Unit Processes, combined in a systemic arrangement so as to yield the required products in a safe, efficient and economical manner.Unit Operations are the operations where only physical or mechanical changes occur, mainly due to some mechanical forces or by molecular transport mechanism. Ex: Heat Transfer Operations, Mass Transfer Operations, Fluid Flow Operations, etc.Unit Processes are processes where reactions are taking place, i.e., chemical changes occur. In general, there are few unit processes as compared to unit operations being used in any chemical plant.And as such, “Fluid Particle Operations”, also referred to as Mechanical Unit Operations, is a core course for Chemical Engineering as well as Petrochemical Engineering.

4. Chemical PlantUnit OperationsUnit OperationsUnit Process

5. Introduction to Particulate SolidsUnit Operations can be classified based on the phases interacting as:Solid-Solid Operations (Crushing, Grinding, Sieving, Compaction, Cutting, storage, and transport of bulk solids, etc.)Solid-Fluid Operations (Filtration, Sedimentation, Centrifugation, Floatation, Cyclone Separators, etc.)From a Chemical Engineering perspective, particulate solids (small solids suspended in a fluid medium) are of utmost importance.Understanding the characteristics/properties of particulate solids is essential for designing the processes and equipments dealing with streams containing small solids.

6. Unit operations involving particulate solidsSeparation of Solids from a suspension by Filtration,Fractionation of solids of wide size distribution based on size by gravity settling or differential settling methods,Separation of immiscible liquids by centrifugation (or decanting) and separation of solids from liquids by centrifugation,Heat/Mass transfer and/or mixing of solids in fluidized beds,Drying of solids,Cyclone Separators,…….and so on!!

7. …..Gravity Settling CentrifugeCyclone Separator

8. Properties of Particulate SolidsBefore we can discuss the operations for handling and storage of particulate solids, we must understand the properties of solids.Solid particles are characterized by their:Shape,Size, and Density.For regular particles, such as sphere or cubes, size and shape are easily specified.But, for irregular particles, such as sand grains or mica flakes, the terms size and shape are not so clear and thus, must be arbitrarily defined.

9. …..The way that we measure a particle size is as important as the value of the measured size. For example, how would you quantify yourself if measured by Circumference around your waist? Diameter of a sphere of the same displacement volume as your body? Length of your longest chord (height)? As you can deduce, the measured values have different meanings and will be important relative to those meanings. If you are sizing a life jacket belt, you would be interested in the first size. If you are buying a sleeping bag, I suggest the last one.

10. Size of irregular particlesMartin’s diameter: According to this definition, the size of the irregular particle is defined as length of the line bisecting the maximum cross-sectional area of the particle.Feret’s Diameter: This is defined as the distance between the two most extreme points on the particle surface.In other definitions, the size of irregular particles is defined by the second longest dimension of the particle.Another definition defines the size of irregular particles as average of longest and second longest dimension on the surface of the particle. The simplest shape of any particle is sphere because of its symmetry in all dimensions, and hence the size of irregular particles is frequently defined in terms of size of an equivalent sphere.x here can be equal to dv, ds, dvs, dsv, dt,…and so on.where,dv, ds, dvs, dsv, dt …and so on are the diameter of the equivalent sphere w.r.t different equivalency criterias.

11. …..Different types of diameter of equivalent sphere can be obtained depending upon the property of the irregular particle and equivalent sphere equaled:Volume-Mean diameter(dv): if the property equaled is volume, i.e. Vp = Vs; thenSurface-Mean diameter(ds): if the property equaled is surface area, i.e. Sp = Ss; then 

12. …..Volume-Surface mean diameter(dvs): if the volume to surface area ratio is same or equal for both, thenSimilarly, based on other properties, the diameter of equivalent sphere can be obtained.  

13. Shape of irregular particlesSphericity(Фs): The shape of an individual particle is conveniently expressed in terms of the sphericity, which is independent of the particle size. It is defined as the ratio of the surface area of spherical particle having same volume as of the particle, to the surface area of the particle. dv can be found by equating the volume of the particle and sphere.It is also defined as the ratio of the surface to volume ratio of sphere to that of the particle, i.e.,Sphericity provides a measure of how far the particle shape is from being a sphere.  

14. Practice questionsFind out the sphericity of the Cylinder having length = diameter.Cube with side length dp.Cuboid with l:b:h :: 3:2:1.

15. Particle Size and Size Analysis of MixtureCase 1: When Particles are uniformly sizedIn a sample of uniform sized particles of diameter dp, the total volume of the sample is , where m and are the total mass of the sample and the density of the particles, respectively. And, Since the volume of one particle is Vp, the total number of particles in the sample is: (Total Volume / Volume of 1 particle)Equation 1.Given that Sp is the Surface area of a single particle, the total surface area of the sample is:Equation 2 

16. …..To apply the above equations to mixtures of particles having various sizes and densities, the mixture is sorted into fractions, each of constant density and approximately constant size.Each fraction can then be weighed, or the individual particles in it can be counted or measured by any one of a number of methods. And then, the above equations can be applied to each fraction and the results added.

17. Determining Particle SizeMethods of measurement of particle size depend on:The size range,The physical properties, andThe permissibility of dryness or wetness.The following methods, for example, are used in laboratory and control work:Microscope: For very small size particles (of the order of a few microns, m). Size may be determined by simple measurement of a photo micrograph of known magnification. Or, maybe determined directly by means of a filar micrometer. This device consists of a movable cross-hair built into a standard microscope eyepiece. The movement of cross-hair is actuated by a calibrated micrometer screw. The cross-hair is moved form one edge of the particle to the other edge and readings are noted. The difference in readings is a measure of the particle “diameter”. The difference divided by the optical magnification of the objective and eyepiece will give the true dimensions in microns or other units. 

18. …..Sedimentation: It is based on the principle that in a solution, particles whose density is higher than that of the solvent sink, and the particles that are lighter than it float to the top. The greater the difference in density, the faster they move. And for different sized particles of same density, rate of falling in a fluid will be directly proportional to its size. One method involves shaking the sample of solid in water and leave the sample for a definite length of time. After the mixture stands a definite length of time, portions are removed from different levels y means of pipette. These portions are evaporated to dryness, and the residues weighed.Elutriation: This method is also based on the velocity of settling. The sample material is placed in a rising stream of fluid having a fixed velocity. Particles whose normal falling velocity is less than the velocity of the fluid, they will be carried away by the fluid out of the vessel. The fractions obtained form a series of fluid velocities are collected and weighed, and as such size analysis is obtained via elutriation.

19. …..Centrifuging: Sedimentation is too slow for particles of diameter under 0.5µ. Therefore, centrifugal force is substituted for the normal force of gravity when the size of very small particles is to be determined.Screening: Perhaps the simplest method for sizing consists of passing the sample material successively over a series of screens or sieves, having progressively smaller openings. The size of a material which has passed through one screen and has been retained on a screen having openings of a smaller size is usually considered to be the arithmetic average of the two screen openings and is called the “average diameter”, davg.

20. …..

21. Particle Size and Size Analysis of MixtureCase 2: When particles Are non-uniform in sizeAfter the mixture of different sized particles has been sorted into different fractions of constant density and approximately constant size, information from such particle-size analysis is tabulated to show the mass or number fraction in each size increment as a function of the average particle size (or size range) in the increment. An analysis tabulated in this way is called a differential analysis.A second way to present the information is through a cumulative analysis obtained by adding, consecutively, the individual increments, starting with that containing the smallest particles, and tabulating or plotting the cumulative sums against the maximum particle diameter in the increment.The differential analysis provides the plot between the mass fraction of the particles retained on the screens to the avg. diameter of the particle.Cumulative Oversize: Plot between mass fraction of size more than dpi vs dpi.Cumulative Undersize: Plot between mass fraction of size smaller than dpi vs dpi.

22. …..Calculations of average particle size, specific surface area, or particle population of a mixture may be based on either a differential or a cumulative analysis.In principle, methods based on the cumulative analysis are more precise than those based on the differential analysis, since when the cumulative analysis is used, the assumption that all particles in a single fraction are equal in size is not needed.The accuracy of particle-size measurements, however is rarely great enough to warrant the use of cumulative analysis, and calculations are nearly always based on the differential analysis.

23. Specific surface of mixtureIf the particle density and sphericity are known, the surface area of the particles in each fraction may be calculated from Equation 2 and the results for all fractions added to give As, the Total surface area. If and are constant, As is given by:And, Specific Surface (Aw, the total surface area of a unit mass of particles) is given by: 

24. …..Where, mi = mass of particles collected in a given increment,xi = mass fraction collected in a given increment,n = number of increment, = average particle diameter, taken as arithmetic average of smallest and largest particle diameters in the increment. 

25. Average Particle sizeThe average particle size for a mixture of particles is defined in several different ways. Volume-Surface Mean Diameter (Sauter Mean diameter): Most widely used definition for calculating avg. diameter. Mass-Mean Diameter: Volume-Mean Diameter: Arithmetic Mean Diameter:  

26. No. of particles in a mixtureTo calculate, from the differential analysis, the number of particles in a mixture, Equation 1 is used to compute the number of particles in each fraction, and Nw, the total population in one unit mass of sample, is obtained by summation over all the fractions.For a given particle shape, the volume of any particle is proportional to its “diameter” cubed, or where a is the volume shape factor. From Equation 1, then, assuming that a is independent of size, 

27. Screen Analysis:Standard Screen Series

28. Tyler Standard Series

29. Procedure for Screen Analysis:

30. Practice Question:See example 28.1 related to Screen Analysis from “Unit Operations in Chemical Engineering” book and try to understand it.(If incase, anyone faces any difficulty understanding the problem, then contact me via text and resolve that before the next class.)

31. Screen EffectivenessEffectiveness of screen is a measure of how effectively the screen separates the oversized and undersized material present in the feed. In case of a perfectly functioning screen, all the oversize material will be in overflow and all the undersize material will be in underflow.Let us consider the feed consists of oversize A and undersize B.D and W are overflow and underflow flowrates.XF, XD, XW are the mass fractions of oversized material in feed, overflowand underflow respectively.(1-XF), (1-XD), and (1-XW) will then be the mass fraction of undersizedmaterial in feed, overflow and underflow respectively.F (Kg/m){A/B}D (Kg/m)W (Kg/m)

32. …..Overall Mass Balance:Component A-balance:Component B-balance:Effectiveness of Screen based on oversized material, also called as Recovery of oversized material: 

33. …..Effectiveness of Screen based on undersized material, also known as Rejection of undersized material:Also, Rejection =  

34. Overall efficiency of screenWe know that, F = D + W and FXF = DXD + WXWOn simplification, we get: Which implies:Overall Effectiveness/Efficiency of screen = (Recovery*Rejection) = EA*EB 

35. Capacity of ScreenCapacity of screen is defined as the mass of feed handled in unit time through unit area of screen, and can be simply controlled by varying the feed rate to the equipment.The capacity of screen and effectiveness of screen are inversely proportional to each other.Overall chance of passage of a given undersize particle is a function of:Number of times the particle strikes the screen surface, andThe probability of passage during a single contact.If the screen is overloaded, then number of contacts between particles and screen surface would be less and as such the chances of passage will be reduced.

36. Factors affecting the efficiency of screensClogging (Blinding) of ScreensAbility of the device/equipment to avoid clogging/blinding is the one of the most important factors.In dry screeningMoisture or dampness in material reduces efficiency.Feed contains high proportion of material of size slightly smaller than size of screen openings, called “near mesh”, reduces the efficiency significantly for the same capacity.Ratio of open surface of screen to total surface of screen.

37. Properties of Solid MAssesMany of the properties of masses of solid particles, especially when they are dry and not sticky, resemble that of a fluid.They exert pressure on the sides and walls of a container,They flow through openings or down a chute.However, they differ from liquids and gases in several ways, because the particles interlock under pressure and cannot slide over one another until the applied force reaches an appreciable magnitude.Unlike most fluids, granular solids permanently resist distortion when subjected to a moderate distorting force.When the force is large enough, failure occurs and one layer of particles slide over another, but between the layers on each side of the failure, there is appreciable friction.

38. …..Solid Masses have the following distinctive properties:Pressure is not the same in all directions. In general, a pressure applied in one direction creates some pressure in other directions, but it is always smaller than the applied pressure, and is a minimum at right angles to the applied pressures.In homogenous masses, the ratio of the normal pressure to applied pressure is a constant K´ (this constant is a characteristic of the material) (K´ = PL/Pv). This constant depends on the shape, the interlocking tendencies of particles, stickiness of particles, and on how tightly the material is packed.The constant is nearly independent of particle size until the grains become very small and the material is no longer free flowing.Non-cohesive materials which flow freely often have K´ value ranging from 0.35 to 0.6, whereas for cohesive materials which are characterized by their reluctance to flow through openings, K´ value approaches to 0.

39. …..Shear Stress applied at surface of a solid mass of particles is transmitted throughout a static mass of particles until failure occurs.Density of solid masses vary depending on the degree of packing of grains.The density of each individual particle is a function of temperature and pressure, but the bulk density of mass is not.The bulk density is minimum when the mass is “loose”.The bulk density is maximum when the mass is packed by vibrating or tamping.For a mass of tightly packed particles to flow, it must increase in volume to permit interlocking grains to move past one another, without such dilation flow is not possible.Sides of granular solids piled up on a flat surface are at a definite reproducible angle (Angle of Repose) with the horizontal. For free-flowing granular solids, it is often between 15-30ͦ˚

40. Storage of Solids:Bulk and Bin StorageOutdoor Storage or Bulk Storage:Many solid masses which are coarse such as coal are stored outside in large piles without any protection from weather.Such type of outdoor storage is very economical especially when hundreds or thousands of tons of material is involved.On requirement, these bulk solids are removed from piles by dragline or tractor ad delivered to conveyor or to process of interest.However, such outdoor storage leads to environmental problems (dusting or leaching of soluble materials from piles).

41. …..Confined Storage or Bin Storage:Valuable or too soluble solids are stored in bins, hoppers, or silos.In general, these are cylindrical or rectangular vessels of concrete or metal.Silos are tall and relatively smaller in diameter, whereas bins are not very tall and usually fairly wide.Hopper is a small vessel with a sloping bottom. It is for temporary storage before feeding solids to a process.Bins, Silos and Hoppers are loaded from top and discharging is generally done from the bottom.BinsSilosHopper

42. Pressure in bins and silosLateral pressure exerted on the walls at any point is less than the predicted pressure from head of the material above that point.Friction force is there between the solid materials and the wall, and this friction is felt throughout the mass because of the interlocking of particles. This friction force tends to offset the weight of the solids and reduces the pressure exerted by the mass on the bottom of the container.Therefore, the vertical pressure on the vessel floor or the packing support is much smaller than that exerted by a column of liquid of the same density and height.If height of solids column > 3 times the diameter of the container, then additional solids will have no effect on the pressure at the base and the additional mass will be carried by the walls and foundation, and not by the floor of the vessel.

43. …..Actual pressure from solids depend upon:Value of K´ for respective solids,Friction coefficient between solids and container walls, and The way solids are packed in the column (loose or tightly packed).Unlike in the case for liquids, for granular solids high pressure does not increase the tendency to flow, instead it leads to pack the grain tightly together and makes the flow more difficult.In extreme cases, combination of friction and gravitational forces at some point in the container causes the solids to arch or bridge, i.e., the mass do not fall under even though the material below them has fallen or removed.Usually all large bins contain an archbreaker – an upward pointing shallow metal cone set near the bottom.

44. Flow out of binsSolids can be flown out of storage vessels through any opening near the bottom (on the sides or on the floor).Best discharge option is via an opening on the floor.Flow through side openings:Uncertain and increases lateral pressure on the other side of the bin while solids are flowing.Flow through floor/bottom openings:Less likely to clog and maintains uniform pressure on the surface of the vessel.Factors affecting the flow pattern through the bottom:Steepness of the wall in the bottom section,Coefficient of friction between the wall and the solids,Discharge opening, andProperties of Solid.

45. Types of Flow patterns or modes developedThe following types of flow patterns are possible in symmetrical geometry:Mass Flow All the material is in motion, but not necessarily at the same velocity.Funnel or Tunnel FlowCentrally moving core, dead or non-moving annular region.

46. Mass Flow patternMass Flow pattern is possible in hoppers that have sufficiently steep (i.e., cone-bottomed bins with tall and steep cone) and smooth surfaces. Moreover, when the bulk solid is discharged through the whole outlet opening.It involves the flow of all solids present inside the vessel without stagnant regions during discharging.Mass Flow pattern gives the complete discharge at predictable flowrates.

47. Funnel or Tunnel or Core Flow PatternCore or Tunnel Flow occurs when the hopper is not sufficiently steep, and/or when the hopper is not smooth to force bulk solids to slide along the walls.It can also occur when the outlet of the bin is not fully effective which may be due to the poor design of the outlet.In funnel flow, initially only the vertical channel of bulk solid above the opening moves downward without disturbing the sides(stagnant or dead zones).Then, lateral flow begins first from the topmost layer of solids.A conical depression is formed in the surface of the mass. The solids at the bin floor, at or near the walls, are the last to leave.If additional material is added to the bin at the same rate as the material is flowing out, the solids near the bin walls remain stagnant and do not discharge nomatter how long the flow persists.

48. …..Major issues with Funnel Flow:Flushing: Uncontrolled flow from a hopper due to powder being in an aerated state. Occurs only in fine solids.Inadequate emptying: Usually occurs in funnel flow where the cone angle is insufficient to allow self draining of the bulk solid.Time-consolidating (Caking): Many powders will tend to cake as a function of time, humidity, pressure, temperature. Particularly a problem for funnel flow which are infrequently emptied completely.https://www.youtube.com/watch?v=w_Yd8or3PCk

49. Comparison of Mass and Tunnel Flow:AdvantagesDisadvantagesDisadvantages

50. ConveyingHandling of particulate solids in processing industries is concerned with movement of materials in different cases such as:from supply point to store or process, between stages during processes, or to packing and distribution after product formation.The movement of materials is a crucial activity which adds nothing to the value of the product, but can represent an added cost if not managed properly.It is important, therefore, for production executives to have a sound knowledge of the fundamentals of good handling practice.

51. Types of handling equipmentsBroadly speaking, the many types of handling equipment comprise conveyors, elevators, cranes/hoists, trucks, and pneumatic systems.The method of motion provides a convenient basis for subdividing the types of conveyors into:gravity or manually moved, such as chute, roller or skate-wheel conveyors; and power driven, such as roller, belt, slat, chain, vibratory, magnetic, screw, flight, and pneumatic conveyors.The above categories include all the possibilities of materials handling within a processing plant, that is, either in bulk or packed.For bulk particulate or powdered materials, a simpler and more convenient classification would comprise the following types of conveyors: belt, chain and screw, as well as pneumatic equipment.

52. Conveying of Bulk SolidsA proper categorization of the handling equipment for bulk particulate solids comprises the following:Belt Conveyors,Chain Conveyors (Scraper Conveyors, Apron Conveyors, and Bucket Elevators),Screw Conveyors, andPneumatic Conveyors (dense phase systems and dilute phase systems).The above classification groups the different types of conveying systems in virtue of their operating principle.

53. Belt ConveyorsThe belt conveyor consists, essentially, of an endless belt operating between two or more pulleys, friction driven at one end and carried on an idler drum at the opposite end.Belt conveyors are used for movement of bulk solids at distances varying from meters to kilometers and thus, belt and its load have to be supported on idlers on both conveying and return sections.Damage to the product in movement is slight because there is little or no relative motion, between the product being transported and the belt.The carrying capacity is high since relatively high speeds are possible when the whole system is operating.Conveys bulk solids mainly in the horizontal plane, though inclined conveying possible with restricted angle of elevation, 15-20˚.To avoid spillage or run-back, special belts with corrugated sidewalks and lateral ribs are used for steeper inclination up to 45˚.A properly designed and maintained belt system has a long service life, but the initial cost is high.

54. Elements of a belt conveying systemBelt: Stitched canvas, solid-woven balata, and rubber belts may be commonly used. Belts must be:flexible enough to conform to the pulleys,wide enough to carry the quantity and type of material required, have sufficient strength to stand up under the expected load and operating tension, and possess a resistant surface.Drive system,Tension elements,Idlers,Appropriate loading and discharging devices.

55. …..Tensors for belt conveyors: (a) gravity tensor, (b) sliding pulley.Idler pulleys for belt conveyorsTripper used for belt conveyor discharge.

56. Power calculations for belt conveyorsThe horsepower required for movement of material by belt conveyors can be calculated by conventional engineering methods by considering the frictional resistance of the belt, the lift, and the frictional resistance of the different pulleys and trippers.However, the constants used in such procedure may vary with change in operating conditions.Power to drive empty conveyors: Power to convey material on level: Power to lift material: Power to operate a tripper: Total Power required = Sum of all four powers calculated. Where, P : Power in Horsepower,F: friction factor, 0.03- 0.05,L: conveyor length in m,L0 : constant, 30.5-45.7,W: weight of moving parts of conveyor in Kg/m of overall length.v: conveyor speed in m/min,T: conveyor capacity in ton/h,H: height of lift in m,Y and Z: constants.

57. Chain ConveyorsCompared to belt conveying systems, chain conveyors present a series of contrasting characteristics:Economical construction,Noisy Operation,Slower movement,Mechanical inefficiency,No specialized skills required for their design, and Much more adaptable to different duties than belt conveyors.Main components of chain conveyors are:Chains, moving elements, and drives.

58. …..Types of chain commonly used in chain conveyors are the malleable detachable, malleable pintle, steel, roller, and combination.The malleable detachable chain is, possibly, the most common and is normally used for light intermittent service.Pintle chain, characterized by a pin which connects the links, is used for more rigorous service such as vertical grain elevators.Steel chain is used where high strength or good wearing qualities, or both, are needed.Roller chain is fitted with rollers or wheels to minimize friction and reduce wear. Combination chain is made in such a way that different features of the above three types are combined to provide certain definite performance characteristics.

59. …..Depending upon how chain and moving elements are mounted for a specific duty, several types of chain conveyors can be obtained.Scraper Conveyors, Apron Conveyors, and Bucket elevators.Scraper conveyors will have the moving element, or flight, fitted perpendicular between two strands of roller chains. https://www.youtube.com/watch?v=HEL33gqVLsM&ab_channel=HennigInc.Apron conveyors will have the moving elements, or pans, overlapped and mounted on the same plane of roller chains forming a continuous “apron.” https://www.youtube.com/watch?v=47xyFrFSc8g&ab_channel=moritoyamachanWhen buckets are fixed to two strands of roller chains mounted on a steep-sloped or vertical structure, Elevation of bulk solids can be possible in the so-called bucket elevators. https://www.youtube.com/watch?v=FEuv79KW7Cs&ab_channel=DavidKruse https://www.youtube.com/watch?v=ZEkzNY_k3bM&ab_channel=bikoserwis

60. …...Horizontal and Z-type Scraper Conveyors.Bucket elevators (a) centrifugal discharge-spaced buckets, (b)positive discharged-spaced buckets, (c) continuous buckets, (d) super capacity continuous bucket.

61. Screw ConveyorsOperate on the principle of a rotating helical screw moving a given material in a trough or a casing and used to handle:finely divided powders,damp materials,hot substances that may be chemically active, and granular materials of all type.It is also used for batch or continuous mixing and for feeding where a fairly accurate mass rate is required.

62. …..Components of a Screw Conveyor:Flight (Flights are made of stainless steel, copper, bras, aluminium or cast iron).Screw formed by mounting flights on axle, and Trough or casing.https://www.youtube.com/watch?v=Uo3qwJ4TXI4&ab_channel=PruthvirajDPScrew conveyor components: (a) flight, (b) screw formed by mounting flights on an axle, and (c) trough

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64. Pneumatic ConveyorsOne of the most important bulk solids handling techniques in a solids handling plant is the movement of material suspended in a stream of air over horizontal, inclined or vertical surfaces, ranging from a few to several hundred meters. This type of conveying is one of the most versatile, handling materials that range from fine powders through 6.35-mm pellets and bulk densities of 16 to more than 3200 kg/m3.As compared with previously discussed methods, pneumatic conveying offers the containment and flexibility of pipeline transport for bulk solids that, otherwise, will be exposed to direct contact with moving mechanical parts.Advantages in cleanliness and low contamination are reflected in the fact that if properly constructed and maintained, pneumatic systems can be virtually dust free.Pneumatic conveying has various drawbacks such as high power consumption, limitations in overall distance and capacity, as well as severe wear of equipment and attrition or degradation of the materials being conveyed. In terms of consumption, taken on the basis of cost per unit weight per unit distance conveyed, pneumatic conveying is by far the most expensive method of moving materials.

65. …..Pneumatic conveying can be categorized in a number of ways depending on their function, as well as type and magnitude of operating pressure. Based on relative solids loading and velocity of system, they can be classified as:Dense phase systems/conveying, also termed “non-suspension” conveying, is normally used to discharge particulate solids or to move materials over short distances. There are several types of equipment such as plug-phase conveyors, fluidized systems, blow tanks, and, more innovative, long-distance systems. https://www.youtube.com/watch?v=4_7Z5CfQuEs&ab_channel=Powder-Solutions%2CInc. Dilute-phase, or dispersed-phase conveyors, are more versatile in use and can be considered the typical pneumatic conveying systems as described in the literature. The most accepted classification of dilute-phase conveyors comprises: pressure, vacuum, combined, and closed-loop systems. https://www.youtube.com/watch?v=5mKvQHL_YI4&ab_channel=Powder-Solutions%2CInc.

66. Guide for conveyor selection