Solids Handling Study Bench

Solids Handling Bench

I.

Introduction

5

II.

Equipment Schedule

7

III. Installation and Commissioning

8

IV. Sieving

9

V.

20

Bulk Density and Angle of Repose

VI. Flow from a Hopper

21

VII. Solids Mixing

23

VIII.Non-Standard VIII.Non-Standard Electrical Supplies

27

IX. Graphical Representation

30

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Solids Handling Bench – the latest equipment for Solid Handling Study Bench, a size reduction with a ball mill can also be studied.

– handling of bulk solids forms an important part of many process operations, particularly in the fertilizer, coal, etc.













– for Solid Mixing with its efficient hightorque impeller generates high mixing forces for the preparation of high viscosity materials and the dissolution and dispersion of concentrated powders in liquid. – a remotely controlled relay that is placed which consume large amounts of electricity and controller unit of the equipment. – method often requires extensive cutting of individual framing members or solids and a practical, code approved solution to many for mixing materials form the bends that make the shapes. – converts electrical – converts energy into mechanical energy and operate through the interaction of magnetic fields and currentcarrying conductors to generate force. – is a closed container designed to hold gases, solids or liquids at a pressure substantially different from the ambient pressure.













The handling of bulk solids forms an important part of many process operations, particularly in the fertilizer, coal, pharmaceutical, food and mineral processing plant. The arm-field bench introduces students to many aspects of solids behaviour, including measurement of bulk density, angle of response, sieving and particle size analysis, flow of solids from hoppers and solids mixing. In later versions (1977 onwards), size reduction with a ball mill can also be studied. The apparatus is essentially self-contained, and allows more than one experiment to be conducted at any one time, this increase the economic range of the solids handling bench.

(Armfield Technical Education Co. Ltd) The characterization new Solids Handling Study Bench of the solids in bulk form an important part in the process industries, particularly in the handling of fertilizers, cement, crystals, pharmaceutical, and foodstuffs. The Armfield Solids Handling Study Bench contains a number of simple items of equipment designed to introduce students to the basic understanding of solids and its behaviour. Each experiment may be undertaken separately from the others, so increasing the economic benefit of the Bench as experimental capabilities, description of equipment, and exclusions

1. Study of sieving techniques, including size distribution plots, effect of sieve load on screen blinding, etc. 2. Angle of repose measurements. 3. Efflux rates from storage hoppers, as affected by hopper load, exit geometry,













5. The apparatus is also a useful vehicle for demonstrating the application of statistical techniques.

Specification: The basic bench consists of a framework containing storage drawers and a table top for experimentation. Services Required: Electrical and single phase about 220-240 Volts, 50 Hz Shipping Specification: Volume of 4 metre and gross weight of 400 kilogram Overall Dimensions: Width at 2 metre, Height at 1.5 metre, Depth at 1 metre The following equipment is provided: 1. Set of standard sieves and sieve shaker. 2. Storage hopper, together with interchangeable exit orifice and solids collecting vessel. 3. 0 – 5 – 5 kilogram balance with weights. 4. Cylindrical vessel for solids mixing, driven by a variable speed electric drive and sampling equipment. 5. An alternative shaped mixing vessel to to replace the cylinder. 6. Conductivity cell and meter/.metre for concentration measurement of particular mixture of solids e.g. salt and a nd sand mixtures.



Supply of distilled or deionisid water, approximately 5 L per experiment



Sand and salt for mixing studies, although any ither materials may be used.













supply available in the laboratory must be quoted at the time of ordering.

1. Partial Inspection- The arm-field advice notes sent with the equipment provide a detailed list of the component parts of the equipment as packed for shipping. This list must be checked against the individually packed and labelled items immediately on arrival. Any breakage or omissions must be reported to the company within 3 days of arrival. 2. The main functional items of equipment, with their specification are as follows, (refer to drawing); a. Main support frame and bench, on which are mounted the following follo wing items  

Variable speed belt-driven motor and pulley. Two alternative (drum and V-arm) mixers, the drum type having a protractor arrangement for angle of repose measurement.



Plexiglas hopper, with 4 alternative orifice and shut-off valve, plus 2 litres plastic collecting beakers for collecting solids.

b. Separately packed 

Automobile sieve shaker with timer



6 British standard sieves of sizes 8, 16, 22,30,44,60.



Lid-and base units for sieve stacking

c. Conductivity cell and meter, for analyzing concentration of dissolved solids when sampling solids mixing experiment. d. Solids sampler means hollow tubes to be connected to a vacuum water ejector, for solids mixing experiment.















f. In the 1977 a ball mill, cylindrical steel type with porcelain balls. This fits into the same urunnious as Plexiglas mixers.

A part from identifying the separate items of equipment and their experimental use, the only installation work needed is to wire the single phase supply for the motor the bench, and separately, the automobile sieve shaker. Care should be taken to observe the equipment wire colour coding: co ding: Brown-Live

Blue-Neutral

Green-Earth

Yellow-Earth

The sieve shaker is extended not to the used on the bench, but on the floor of the laboratory as there is considerable variation during operations. Commissioning involved running the variable speed meter and laminar with the various for the meter derives urunnion meaning. Calibration of the conductivity cell with accurately made up solutions of sodium chloride in distilled or deionised water is also necessary, in order that solids mixing experimentally with salt and sand can be analyzed for the mixing experiment. Practice at taking solid samples of a fixed and known bulk volume with the samples should also be undertaken.













A test sieve is an instrument which is used for the measurement of particle size in its most common form; it consists of a woven wire screen, with square apertures, rigidly mounted in a shallow cylinder metal frame. For coarse sieving range down to 4 mm, and round whole sieves down to about 1 mm apertures. The sizes of solid particles from 125mm (5in) down to 38 microns can be measured rapidly and efficiently by means of a test sieve. Special screens with apertures, smaller than as microns are available, but it should be appreciated that the liner screen. It is the more easily with certain types of particulate solids tend to block or blind the openings. Particle size as measured by test sieving, may be specified simply by quoting the size of two screens, one through which the particles have passed, and the other on which they are retained., However, the most frequent use of test sieving is for measuring the size spread, and the particle size distribution. Choice of sieve sizes: For most size analyses it is usually impracticable, and indeed quite unnecessary, to use all the available screens in any standard sieve series. However, for best number of sieves to use a given test can present a problem. Broadly speaking, it sieves in the mind range of a given series are employed, not more than













A 16

18

22

B 16

22

C 16

22

D 16

25

30

36

30 25

30

18

44

52

60

44

60

36

44

60

36

44

60

a. Consecutive sieves which obey the 2 raise to ¼ relationships. Necessary only for detailed size analysis over the whole range. b. Alternate sieves which obey the 2 raise to ½ relationships. Adequate for most purposes. This is the series chosen for this equipment bench. c. Bad choice, random selection, difficult to interpret for this equipment in tabular form or graphically. The weight of the simple must not be allowed to change during the test. Damp materials should be dried in an oven if necessary, but care must be taken not to alter the physical characteristics of the material. If the material has been heated in an oven it should be cooled in the atmosphere before the test. Samples of desecrater, and then sieved with the minimum amount of exposure content during the test, the weights of the charge and the sieve fractions should be corrected to their dry weights. The recommended weights are shown in the given table.













sieving (cm3) 22.4

25

1800

900

20

1600

800

1400

700

1000

500

800

400

800

400

10

600

300

6.3

500

250

400

200

5.6

400

200

4

350

150

2.8

240

120

2

200

100

1.4

160

80

1

140

70

Microns

120

60

700

100

50

500

80

40

250

70

35

180

60

30

125

50

25

16

12.5

12.2 8

355













divided into two or more charges if the quantity of material remaining on the sieve at the end of the sieve process exceeds the quantity stated in column 4. Sieve tests can be carried out by the hand or on machine designed to impart the necessary shaking, rotating, vibrating or jolting motion to the material on the screens. In general, the mechanical method of testing has many advantages over the hand method. Reproducible results are usually obtained in a much shorter time. Mechanically, with much lower expenditure of human effort. Procedure: The chosen nest of sieves is assembling with the coarsest mesh at the top the finest at the bottom and the bottom have measured on a receiver pan. The weighted sample is transferred to the top sieve, and the nest is shaken with a rotating section and continually tapped by hand of a 10 minutes. When dusty samples are being handled, the top sieve should be fitted with a lid. The top sieve is then removed from the nest and inverted over sieve piece of glossy paper. All the material is discharged from it, first by gently tapping the frame and then by brushing the gauge with a special brush. The material is then transferred back to the cleaned sieves which is now material on another receiver pan, and screened to an “end“end point” as follows.















Sieved through each sieve turn, for particles larger than about 25mm the test sieves serves essentially as a gauge. The appropriate charges may be screened gently and the particles remaining on the sieve are then checked, one by one, by presenting them in favourable attitudes to the sieve apertures. Those that do not pass through the apertures are rejected and become the sieve residue. Cleaning of test sieves: Sieves should be used with care, cleaned, regularly and stored in a dry safe place. It should always be remembered that a sieve is a measuring instrument and should not be maltreated. Particles should not be forced through a test sieve. Even the gentle brushing of material through the liner or finer meshes is undesirable, but this procedure is occasionally unavailable for certain materials that are otherwise difficult to sieve. If brushing is found necessary, care should be taken to avoid particle breakdown. In any case, the brush pressure must never be allowed to













each of the sieves used in the test can be listed as percentages of the original less sample weight. This is probably the most widely used (but not necessarily the best) method or recording sieve test data. A brief glance at the relevant column of table 2 brings out such facts as the sieves and the bulk f the material was confined to the 1200-300 microns range. In the second and third tubular methods, the cumulative percentage (i. e. running totals) of oversize and undersize material are listed. Either of these methods can be used to provide information not readily gathered from the fractional tables. The percentages of materials larger, or a smaller than a certain mesh size can be roughly estimated from cumulative tables. For example, referring to table 2 it can be seen that 70.7 percent of the material was liner than 850 microns and 88.9 percent was coarser than 300 microns. It can also be roughly estimated that the quantity that would have passed through a 5oo microns sieve, is about 37 percent (arithmetic mean of 46.3 and 27.8: the quantities referring to the 600 and 420













72

210

5.9

88.9

11.1

100

130

3.9

92.8

7.2

150

105

2.7

95.5

4.5

-150

4.5

Graphical Methods: The full significance of a sieve test can most readily be assessed when the data are recorded in graphical form. Trends which are frequently obscured in mass of figures in a table are easily seen in a graph. The extra-effort involved in graphical plotting is usually rewarded by the additional amount of useful information obtained. Graphical techniques are very useful aids for routine test sieving. It is much easier, for instance, to compare the data from several tests one graph than it is by trying to compare tables of figures. Again, by the use of certain graphical techniques, described sieves used in a test to 2 or 3, with a subsequent and valuable













On semi-logarithmic paper and scale is marked off in equal intervals (arithmetic or linear scale) and the other on a logarithmic scale. On this latter scale the spacing between 1 and 10, 10 and 100, 100 and 1000 are the same. These intervals are called “cycles” and usually 2 cycle paper sill suffice for most tests. However, to cover the entire fine-mesh range 3 cycle paper would be required. Log-Log Paper: In this type of graph paper both scales are marked off logarithmically. For most sieves test work 2x2 cycle paper is used, but again if the full fine-mesh size range is to be covered one cycle scale is necessary. Some of the uses of the above types of graph paper will now be described briefly. For illustration purpose the same sieve test data (Table 2) are used in every case. It must be understood, however, that all the methods described here will not necessary be applicable to any













through an 850 microns sieve and was retained on a 6oo microns sieve, the mean particle size could be taken as the average of 850 and 600-725 microns. The main virtue of the arithmetic plot (Figure 2) is simplicity; no special graph paper is required. The main advantage a dvantage is that points in the region of the finer meshes tend to become congested. For instances, the data in table 2 were obtained from alternate sieves in the B. S. ranges, but it consecutive sieves had been used, some of this points would have crowded into one another on the graph. Congestion is avoided on the semi-logarithmic plot (in the figure 3). The points in the fine mesh region are spread out and those in the coarse mesh region closed in, with the result that the points are approximately equidistant and the columns are approximately of equal widths. Cumulative Percentage Graphs:















B.S. sieves had to be translated into values for sieves 14, 25, 45 and 80 mesh of the U.S. (ASTM) Standard Standard series. The corresponding apertures are 1410, 707, 354 and 177 microns, so it is an easy matter o read off values on either figures 4a or 4b to give the results 14 (97%), 25 (59%), 45 (21%), 80 (80%). Another valuable quantity q uantity readily obtained from graphs such as those shown in figure 4 is the median size of the sample. This defines the mid-point in the size distribution, half the particles are smaller than the median size and half are larger. The median size, therefore, is read off either graphs corresponding to 50 percent













Precision of Weighing: The fraction quantities retained on the sieves and the undesirable should be weighed with a precision of ±0.1 percent of the charge. The area of these weights should not differ by more than 2 percent from that of the test sample weight. The losses are to be recorded separately. The fraction weights should be converted into percentages of the sum total of the fraction weights, not of the original test sample weight.













being indicated by a protractor granular material is introduced into the container metal. It was approximately half bulk. The 3 surface is made level by shaking the container and the cylinder is rotated. The particles must begin to slide and the angle at which bulk being measure. The container is then rotated in the opposite direction until the 3 surface appear horizontal. From the reading in the position, the angle between the horizontal and justified sharpen surface can be found. This is the natural angle of repose. This procedure is repeated several times in order to obtain average values for the two materials. As it is different to as certain accurately when the surface is horizontal, a further set of runs should be made in which the angle is













In a narrow container the wall takes place of the region E and in the upper part paling. The central zone C of faster moving material occupies, most of the tube, with the result that the free surface of the material becomes a large cone (inverted). Most workers investigating this subject have related the discharge rate to the orifice diameter. Linear plots were obtained for graphs of log Q and log D usually with slope of 3 (i.e. Q=kD 3). The most recent work published is that of Crown and Richards who round that their results could be represented by Q= 2.24 D 2.5 ø where Q is measured in













The same orifice is then used again and the rates of efflux for convenient periods of the time again measured as above. However, in this experiment no attempt is made to level the surface from its inverted cone shape( caused by the flow of material), the measured height being that of base of the cone above the orifice. Again, no orifice or head on efflux rate should be detected. In order to investigate the effect of orifice diameter on the efflux rate, alternative orifice is used separately, and an each series the same line material should be used. Two runs for any one orifice can be carried out over a convenient period of time















It is difficult to express the degree of mixing, but any index should be related to the properties of the required ix, should be say to measured, and should be













When a material is partly mixed, then the degree of mixing can be represented by some term M, and several methods have been suggested for expressing M in terms of measurable quantities. It is obtained from examination or













Thus, with congestive mixing, L-M will depend on the sample size. The rate of mixing expressions for the rate of mixing can be developed for any on of the possible mechanism since mixing involves obtaining an equilibrium condition of













COULSON AND MAITRA have examined the mixing of the number of pairs in the materials in a sample drum mixer, and have expressed their results in the













The transformer supplied is of the “Auto” type with eight (8) alternative voltage tapping and will have been connected to the equipment in accordance with the frequency specified on the arm field technical Education Company acceptance of



















































Solids Handling Study Bench

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