RI |bureau of mines

report of investigations 6054

t

PERFORMANCE OF TABLES

IN CLEANING ALASKA COALS

By M. R. Geer, Michael Sokaski, and P. S. Jacobsen

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UNITED STATES DEPARTMENT OF THE INTERIOR

BUREAU OF MINES

1962
PERFORMANCE OF TABLES

IN CLEANING ALASKA COALS

By M. R. Geer, Michael Sokaski, and P. S. Jacobsen

I

+ 4 * * * 4 * · + report of investigations 6054

UNITED STATES DEPARTMENT OF THE INTERIOR

Stewart L. Udall, Secretary

BUREAU OF MINES

Marling J. Ankeny, Director

The work upon which this report is based was done under a cooperative agreement between the Bureau of Mines,

U.S. Department of the Interior, and the School of Mineral Engineering, University of Washington.
Geer, Max Richard, 1912-

Performance of tables in cleaning Alaska coals, by M. R.

Geer, Michael Sokaski, and P. S. Jacobsen. [Washington]

U.S. Dept. of the Interior, Bureau of Mines [1962]

26 p. illus., tables. 27 cm. (U. S. Bureau of Mines. Report of

inve stigations, 6054)

Based on work done in cooperation with the School of Mineral

Engineering, University of Washington.

1. Coal washing. 2. Coal-Alaska. I. Title. (Series)

TN23.U7 no. 6054 622.06173

U. S. Dept. of the Int. Library

This publication has been cataloged as follows:
CONTENTS

Page

Introduction and summary .................... .......... 1

Acknowledgments ............................ 2

Description of coals and plants ..... ................... 2

Sampling and test procedure ............................. 4

Evaluation of results........ ......... ............... 4

Dependent criteria............... ............... 6

Sharpness of separation .. ..... ................. 9

Density of separation ........................ 10

Influence of size composition .................... 11

Prediction of cleaning results ....................... 12

Bibliography................................. 13

Appendix. - Summary of performance...... . ...... ,..... 15

ILLUSTRATIONS

1. Relation between recovery efficiency and amount of

near-gravity material...... .. ................. 8

2. Relation between recovery efficiency and yield..... 8

TABLES

1. Specific-gravity analyses of coals................. 3

2. Identification of tests and summary of principal

performance data............................... 5

3. Comparison of dependent criteria, percent........ 7

4. Comparison of sharpness-of-separation criteria... 9

5. Average distribution data, percent............... 11

A-1. Test Noo 1, 7B lower bed ......................... 15

A-2. Test No. 2, 7B lower bed ......................... 16

A-3. Test No. 3, 7B lower bed......................... 17

A-4. Test No. 4, 7C bed............................... 18

A-5. Test No. 5, 7C bed.............................. 19

A-6. Test No. 6, 7C bed.....................*........ 20

A-7. Test Noo 7, 7C bed....044 0.......0.. ... ......... 21

A-8. Test No. 8, 7C bed....................... . 22

A-9. Test No. 9, 5 bed......................... 23

A-10. Test No. 10, 5 bed.............................. 24

A-ll. Test No. 11, 5 bed........... .............. 25

A-12. Test No. 12, Mrak bed............................. 26
PERFORMANCE OF TABLES IN CLEANING ALASKA COALS'

by

M. R. Geer, 2 Michael Sokaski, 3 and P. S. Jacobsen4

INTRODUCTION AND SUMMARY

Information on the performance of coal-cleaning equipment is necessary to

provide a basis for evaluating the performance of existing plants and projecting that of new plants. Performance data can contribute greatly to the wise

selection and effective use of coal-washing equipment.

The Bureau of Mines has published information on the performance of

several commercial plants, as well as of some laboratory-scale equipment,5

(2-9, 11, 12, 17-19, 21-25) from time to time for a number of years. A more

intensive program to provide such information for all the principal types of

cleaning equipment is underway. The present evaluation of table performance

is part of this program.

A total of twelve performance tests was made in two Alaska plants, both

of which are in the Matanuska Valley field. The five coals cleaned in these

plants cover a wide range in washability. Some of the tests involved sampling

the table products incrementally over a full shift of operation to show average performance. In others, single-increment zone samples were collected that

could be combined as desired to show the influence of changing the cut point

between washed coal and refuse.

The separation between coal and impurity in the sizes coarser than 20-

mesh generally was reasonably sharp, as detonated by error areas of 50 to 60

and probable errors of about 0.100. In the intermediate size range, 20- to

48-mesh, elimination of heavy impurity generally was satisfactory, but coal

was lost in the refuse. In the finest fraction, 48- to 200-mesh, the separation between coal and impurity was far less sharp. Efficiency also was

iWork on manuscript completed December 1961.

2 Chief, Seattle Coal Research Laboratory, Bureau of Mines, Seattle, Wash.

3 Mining methods research engineer, Seattle Coal Research Laboratory,

Bureau of Mines, Seattle, Wash.

4 Research chemist, Seattle Coal Research Laboratory, Bureau of Mines,

Seattle, Wash.

EUnderlined numbers in parentheses refer to items in the bibliography.
2

influenced by size, sometimes exceeding 99 percent for the coarser material

but dropping significantly with decrease in particle size. Thus the proportion of extreme fines in the feed to tables has an important bearing on the

overall cleaning results.

As with most cleaning devices, sharpness of separation increased as the

density of separation decreased. However, any reduction in the density of

separation of coals of this type results in a relatively large sacrifice in

efficiency.

The amount of heavy impurity (sink at 1.80 specific gravity) in the table

feed ranged from 18 to 29 percent. As impurity content increased, efficiency

dropped. In fact, efficiency correlates more closely with impurity content

than with the amount of near-gravity (+0.10) material in the feed, which is

an index that is used widely to show relative difficulty of washing.

ACKNOWLEDGMENTS

This investigation was conducted at the Seattle Coal Research Laboratory

of the Bureau of Mines, which functions in cooperation with the School of

Mineral Engineering of the University of Washington. The authors are indebted

to officials and operating personnel of the Evan Jones Coal Co. and the Mrak

Coal Co., in whose plants the test work was done, for their assistance in the

fieldwork.

DESCRIPTION OF COALS AND PLANTS

Table 1 shows specific-gravity analyses of the one coal tested in the

Mrak plant and the three coals tested in the Evan Jones plant. The coal from

the No. 5 bed is by far the most difficult of the group to clean. It contains

almost as much impurity heavier than 1.80 specific gravity as float at 1.30;

it also contains considerable material of intermediate density. All the other

coals contain less heavy impurity and somewhat less material of intermediate

density and are therefore more amenable to treatment.

In both plants the raw coal is wet-screened at 1/4-inch; the oversize

goes to the coarse-coal circuit, and the undersize comprises the table feed.

In neither plant is the feed deslimed or thickened; that is, all the water

used in screening is used for push water to the tables. Raw-coal storage at

both plants is limited to a few truckloads. Table-washed coal in the Evan

Jones plant is recovered by a screw-type classifier, cyclones, and a vibrating

screen; in the Mrak plant a settling tank and vibrating screen are used.

These flowsheets are more or less typical of many small-tonnage plants and

some large ones.
3

t

TABLE 1. - Specific-gravity analyses of coalsl

Specific Weight- Ash, Cumulative

Bed gravity percent percent Weight- Ash,

_ _ _ percent percent

Mrak.................... Under 1.30 56.1 2.9 56.1 2.9

1.30 to 1.40 15.8 11.7 71.9 4.8

1.40 to 1.50 4.7 24.5 76.6 6.0

1.50 to 1.60 2.5 34.6 79.1 6.9

1.60 to 1.70 2.0 43.5 81.1 7.8

1.70 to 1.80 1.4 50.9 82.5 8.6

Over 1.80 17.5 79.3 100.0 21.0

No. 5 ............... Under 1.30 30.9 2.0 30.9 2.0

1.30 to 1.40 19.7 10.1 50.6 5.2

1.40 to 1.50 7.7 23.1 58.3 7.5

1.50 to 1.60 5.1 33.7 63.4 9.6

1.60 to 1.70 4.2 42.4 67.6 11.7

1.70 to 1.80 3.5 49.7 71.1 13.5

Over 1.80 28.9 74.4 100.0 31.1

7B Lower......o** ............ Under 1.30 52.0 1.7 52.0 1.7

1.30 to 1.40 18.6 7.2 70.6 3.1

1.40 to 1.50 5.1 20.4 75.7 4.3

1.50 to 1.60 3.2 32.9 78.9 5.5

1.60 to 1.70 2.9 41.8 81.8 6.8

1.70 to 1.80 2.2 48.7 84.0 7.9

Over 1.80 16.0 69.8 100.0 17.8

7C...................... Under 1.30 49.5 1.5 49.5 1.5

1.30 to 1.40 13.1 7.9 62.6 2.8

1.40 to 1.50 3.7 20.8 66.3 3.8

1.50 to 1.60 2.6 33.5 68.9 5.0

1.60 to 1.70 2.8 42.8 71.7 6.4

1.70 to 1.80 2.7 50.0 74.4 8.0

Over 1.90 25.6 77.3 100.0 25.8

13- to 200-mesh.

The feed rate in the Evan Jones plant ranged from 5.5 t<

hour per table, disregarding the solids finer than 200-mesh.

the double-deck table in the Mrak plant was fed at 8.5 tons I

water-coal ratios (considering both push and dressing water)

following tabulation:

3 8.5 tons per

Each deck of

per hour. The

are shown in the

Test:

9 to 11.............

12..................

1 to 3................

4 to 6................

7 and 8.............o

Ratio of water to coal

2.5

3.3

3.6

3.9

5.0
4

In both plants, the amount of water required for screening rather than ideal

table adjustment dictated the amount of water used. In most tests the watercoal ratio was somewhat greater than that recommended by the manufacturer.

SAMPLING AND TEST PROCEDURE

Two types of performance tests were made. In one test, samples of the

feed, washed coal, and refuse were collected in increments over a shift of

plant operation. In the other test, single simultaneous zone samples were

collected with special sample launders that divided the side of the table into

six equal zones of 33 inches and the end of the table into two zones of 44

inches each. These zone samples were later combined as desired for laboratory

examination.

Regardless of type, all samples included both the solids and the water

discharged by the table. The samples were wet-screened at 48-mesh immediately,

and the oversize was dried to minimize degradation of the shale. An aliquot

portion of the material finer than 48-mesh was wet-screened at 200-mesh, and

the material coarser than 48-mesh was rescreened dry at 20-mesh in preparation

for the float-and-sink examination. Material coarser than 20-mesh was tested

in zinc chloride solutions at each 0.1 interval in specific gravity from 1.30

to 1.80. The 20- to 48- and 48- to 200-mesh fractions were tested at the same

densities in organic solutions. Each density fraction obtained was analyzed

for ash content.

Only the amount and ash content of the 200-mesh to 0 material was determined. The circulating water in both plants contain so much suspended clay,

which contaminated the 200-mesh to 0 fraction of the samples, that including

this size in the examination would have clouded the performance picture. The

amount of minus 200-mesh material in the feed samples (including contaminating solids from the water) ranged from 9 to 24 percent, and the average ash

content of this material exceeded 50 percent.

EVALUATION OF RESULTS

Table 2 identifies the individual tests and provided comparisons based

on some of the more widely used performance criteria. Additional criteria and

information on individual size groups are given in the tables in the appendix.

All of the various performance criteria used have been discussed in the

literature (15) and therefore will merely be defined. Recovery efficiency,

called organic efficiency in Europe and widely known as Fraser and Yancey

efficiency in this country, is the ratio, expressed in percent, of the yield

of washed coal to that of float coal of the same ash content shown to be

present in the feed (composite or reconstituted) by specific-gravity analysis.

Ash error is the difference in ash content, expressed in percent, between

the washed coal and a float coal at a yield equaling that of the washed coal.

Yield error is the difference between the yield of washed coal and the floatcoal yield at the same ash content. The float-coal yield and ash are derived

from the specific gravity-analysis of the composite feed.
TABLE 2. - Identification of tests and summarv of principal performance data

Type Zones Ash, percent Effi- Specific

Test Plant Bed of to Feed Washed Refuse Yield, ciency, ±0.10 gravity Error

sample washed coal percent percent of sepa- area

coal ration

1...... Evan Jones 7B lower Zone 1-6 17.8 7.3 59.4 79.8 96.4 5.0 1.715 81

2...... do. do. do. 1-3 17.8 6.0 48.5 72.2 90.1 6.6 1.562 74

3...... do. do. do. 1-2 17.8 5.3 34.5 57.1 72.9 10.5 1.458 70

4...... do. 7C do. 1-6 21.5 6.9 67.0 75.7 97.1 4.7 1.700 82

5...... do. do. do. 1-2 21.5 5.8 51.6 65.7 86.4 5.2 1.570 81

6...... do. do. Shift - 23.6 5.8 63.3 69.1 94.4 4.5 1.613 76

7...... do. do. Zone 1-6 25.8 6.1 64.5 66.4 93.3 5.5 1.620 82

8...... do. do. do. 1-2 25.8 5.2 52.7 56.8 81.8 6.2 1.511 72

9...... do. 5 Shift - 31.1 18.7 70.0 75.7 94.0 7.8 1.967 102

10...... do. 5 Zone' 1-6 34.8 20.4 74.1 73.1 94.9 8.7 1.964 99

11...... do. 5 do.i 1-2 34.8 16.0 64.4 61.1 88.0 7.7 1.826 122

12...... Mrak Mrak Shift - 21.0 9.3 70.7 81.1 97.0 3.6 1.687 107

13- to 48-mesh.

Un
6

Misplaced material is the sink in the washed coal and the float in the

refuse at the specific gravity of separation, expressed as a percentage of the

feed.

All of the foregoing are classed as dependent criteria, because they are

affected directly by the difficulty of the separation.

The specific gravity of separation is read from the distribution curve at

the 50-percent ordinate and is the specific gravity of material that is

divided equally between washed coal and refuse.

Error area and probable error, relating to the sharpness of the separation between washed coal and refuse, are determined from the distribution

curve, which is a plot showing what proportion of each density fraction of

the raw coal was recovered in the washed product. Error area is the area

between this distribution curve and one representing perfect separation; the

curves are plotted to a fixed scale. Probable error is one-half of the density interval in which the curve passes between the ordinated representing

25- and 75-percent recovery in the washed product. Both of these criteria are

regarded as substantially independent of the density composition of the raw

coal; therefore, they are the most useful of the various criteria in comparing

the cleaning of dissimilar coals.

Imperfection also relates to sharpness of separation and is regarded by

some as less affected by density of separation than are error area and probable error. Numerically, imperfection is the quotient of probable error

divided by the density of separation minus one.

All of these criteria are tabulated for the individual tests in the

appendix.

Dependent Criteria

Table 3 shows all the dependent performance criteria for the tests,

grouped by whether the split between washed coal and refuse was made at the

corner or on the side of the table. This group divides the tests, with a few

exceptions, into high and low densities of separation. In the high-density

group, the recovery efficiency ranged from 93 to 97 percent and in the lowdensity group from 73 to 90 percent. The values for yield error parallel

those for efficiency because these two criteria are related arithmetically.

The values for ash error and misplaced material, on the other hand, deviate

somewhat from efficiency in ranking individual tests.

The efficiencies for these tests are comparable with those reported by

other investigators (1O, 13, 36). The index used most frequently to indicate

difficulty of separation is the amount of material within ±0.10 of the specific gravity of separation (13). Gandrud (10) generalized that a welloperated table should provide an efficiency of at least 95 percent if the

amount of +0.10 material in the feed did not exceed 10 percent, recognizing,

however, that the density of the separation and the size composition of the

feed modified the relationship between efficiency and near-gravity material.
7

Gandrud's rule-of-thumb generalization is overoptimistic for the present group

of tests because only three have efficiencies exceeding 95 percent, and only

one contained more than 10-percent of ± 0.10 material.

TABLE 3. - Comparison of dependent criteria, percent

Test Washed- Yield ±0.10 Effi- Yield Ash Misplaced

_ _ coal split ciency error error material

1........... Corner 79.8 5.0 96.4 3.0 1.0 5.8

4........... do. 75.7 4.7 97.1 2.3 1.2 5.3

6........... do. 69.1 4.5 94.4 4.1 1.8 6.5

7........... do. 66.4 5.5 93.3 4.8 2.1 7.6

9....... do. 75.7 7.8 94.0 4.8 2.4 10.8

10 ...... . do. 73.1 8.7 94.9 3.9 2.4 10.7

12..*o**.... . do. 81.1 3.6 97.0 2.5 1.5 5.9

2........... Side 72.2 6.6 90.1 7.9 2.6 10.3

3........... do. 57.1 10.5 72.9 21.2 3.4 22.7

5d........ do. 65.7 5.2 86.4 10.3 3.2 12.4

8........... do. 56.8 6.2 81.8 12.6 3.1 14.3

11 ........... do. 61.1 7.7 88.0 8.3 4.8 13.3

1 3- to 48-mesh.

Figure 1 illustrates the approximate nature of the correlation between

efficiency and ±0.10. The points exhibit considerable scatter, indicating

clearly that factors other than near-gravity material have a bearing on

efficiency.

The data in table 3 suggest that both efficiency and yield error are

related to the yield of washed coal. Figure 2 shows the relation between

efficiency and yield for the present tests and also for those in the references (10, 13, 26). Both the present data and those of the other investigators show that efficiency correlates better with yield than with amount of

near-gravity material. Moreover, figure 2 demonstrates that the efficiencies

found in the present investigation are conformable with those found in other

plants.

The dependence of efficiency on yield is not illogical. Some proportion

of the heavy impurity (sink at 1.80 specific gravity) in the feed always

reports in the clean product; as the amount of such impurity in the feed

increases, more impurity enters the washed coal and thus impares efficiency.

Also, as the bed of impurity on the table increases, the chances for mechanical entrapment and loss of fine coal are greater. Thus the table is unable

to operate as efficiently with dirty feeds as with cleaner ones.

The inability of the table to cope effectively with unusually dirty feeds

is illustrated by the results obtained in tests 9, 10, and 11 on the No. 5

bed. When the cleaner coals were treated in the Evan Jones plant, only a

small part of the impurity heavier than 1.80 entered the washed coal when the

split between coal and refuse was made at the corner of the table, whereas in

treating the No. 5 coal, about 35 percent of the 3- to 20-mesh sink at 1.80
75

Z

ca

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z

UWIL

a

1 90

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95

Inn

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I 1 I.

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70

75

80

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IL- ir

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o Present data

I~ -n - .

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A Noone A

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0 ° 0 0

0 0

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a * * .0 *' * I I

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2 4 6 8 10 12 100 90 80 70 60 50

NEAR GRAVITY MATERIAL + 10, percent of feed YIELD, percent

FIGURE 1. - Relation Between Recovery FIGURE 2. - Relation Between Recovery

Efficiency and Amount of Efficiency and Yield.

Near-Gravity Material.

specific gravity reported in the cleaned product. Most of this coarse impurity that contaminated the washed coal was discharged in zones 3 and 4. However, even in test 11, in which zones 1 and 2 comprised the washed coal,

nearly 13 percent of the coarse sink at 1.80 specific gravity was included

in the washed product.

The tables were not readjusted when the feed was changed from the cleaner

beds to the dirtier No. 5 bed. Removal of sink at 1.80 specific gravity might

have been improved if either the end elevation or the cross slope had been

decreased or if the stroke had been lengthened; however, all these measures

tend to move the clean coal farther toward the end of the table and therefore

might not have improved overall performance. Thus the comparison between

operation on the No. 5 coal and the cleaner beds clearly illustrates what

happens to table performance during periods of dirty feed, and may be indicative of the results to be expected with unusually dirty feed even under

optimum table adjustments.

Under fixed adjustments the table appears to be capable of stratifying

and eliminating only so much heavy impurity. When the amount of impurity

exceeds this critical value, the proportion entering the washed coal increases

sharply. This is illustrated in the following tabulation of sink at 1.80

specific gravity:
9

In feed, tons per hour:

1.41.....................

1.37 .....................

2.47.....................

Reporting in

washed coal,

percent

2.7

3.4

26.8

Sharpness of Separation

In table 4 the individual table tests are compared in terms of the three

criteria used to measure the sharpness of the separation between coal and

impurity. In a general way, error area, probable error, and imperfection all

rank the tests in about the same order of sharpness. However, notable exceptions occur. For example, tests 1, 2, and 3 comprise a series in which zone

samples are combined to give progressively lower densities of separation.

Error area shows a steady improvement in sharpness of separation as density

of separation decreases. Probable error, in contrast, indicates that the test

at lower density was the least sharp of the group.

TABLE 4. - Comparison of sharpness-of-separation criteria

Washed- Specific Error Probable

Test coal split gravity of area error Imperfection

separation

1.............. Corner 1.715 81 0.121 0.169

4 .. ............ do. 1.700 82 .122 .174

6 .............. do. 1.613 76 .125 .204

7....... . do. 1.620 82 .137 .221

9.............. do. 1.967 102 - -

10.............. do. 1.964 99 -

12............. do. 1.687 107 .198 .288

2............... Side 1.562 74 .101 .180

3.* ........... do. 1.458 70 .127 .277

5.............. do. 1.570 81 .129 .226

8.............. do. 1.511 72 .112 .219

11 .............. do. 1.826 122 .236 .286

Note that imperfection varies over fully as wide a range as either error

area or probable error. Imperfection is widely used in Europe and is generally regarded as being a constant for a given type of equipment operating

under comparable conditions of adjustment and loading. Thus imperfection

would have been expected to be constant for tests 1, 2, and 3.

The distribution curves for the 3- to 20-mesh size generally were regular

in form, with both tails approaching the axes. The curves for the intermediate size, 20- to 48-mesh, were distinctly poorer; the low-density segments

mostly did not approach the axis closely. The curves for the 48- to 200-mesh

material were distinctly irregular; generally the high-density segment was

displaced from the axis. The composite curves for the 3- to 200-mesh coal were

generally inferior to those characterizing cyclones, jigs, and dense-medium
10

cleaning. Therefore, the various criteria of sharpness of separation probably

are not as significant and reliable for tables as they are for most other

cleaning methods. Tromp (14) suggested that the distribution curve for tables

does not take the usual form because tabling represents a series of retreatment steps occurring at each riffle.

Because the criteria of sharpness of separation has limited significance,

examination of the complete distribution data is even more important in evaluating table operation than with some other types of cleaning devices.

Density of Separation

Except for the high-ash slimes discharged principally next to the headmotion end, ash content along the side and around the end of a table increases

progressively. Thus the ash content of the washed coal, and the density of

separation, can be adjusted simply by changing the position of the split

between washed coal and refuse. Tests 1, 2, and 3 show the effect of progressively moving the position of the splitter from the corner of the table toward

the head-motion end. As shown in the following tabulation, in test 1, with

the entire side of the table representing washed coal, a product analyzing 7.3

percent ash was obtained at a yield of 79.8 percent.

Test

1 2 3

Zones to washed coal................... 1-6 1-3 1-2

Yield .......................... percent 79.8 72.2 57.1

Ash in washed coal ..... ,..........do... 7.3 6.0 5.3

Efficiency ....................... do. 96.4 90.1 72.9

±0.10 ..........................do... 5.0 6.6 10.5

Specific gravity of separation ......... 1.715 1.562 1.458

Error area............................. 81 74 70

Probable error .............................. .121 .101 .127

In test 2, with only the first three zones constituting the washed coal, a

reduction in ash content of 1.3 percentage points occurred, but the yield

dropped to 72.2 percent. This reduction in yield represented a decline in

efficiency from 96.4 to 90.1 percent. In test 3, with only the first two

zones constituting the washed coal, the yield was reduced to only 57.1 percent, and the efficiency was reduced to 72.9 percent. Thus, with coals of

this type, operating at a specific gravity as low as 1.46 entails a drastic

reduction in efficiency. The modest increase in amount of near-gravity material with decrease in density in this series of tests could hardly account

for the drastic decrease in efficiency. Thus these data show that the ±0.10

criteron is not always a reliable indication of the efficiency to be expected

in tabling.

As pointed out earlier, when some cleaning devices are used, the sharpness of separation between coal and impurity tend to increase as the density

of separation decreases. If error area is used to evaluate sharpness of separation, the present data indicate that the same relationship holds for tables,

although the improvement in sharpness of separation with decrease in density

is modest.
11

Influence of Size Composition

Tables, like all other cleaning devices, are unable to effect as sharp a

separation between coal and impurity in the finer portions of the feed as in

the coarse material. Table 5 shows the average distribution data by individual size groups for all the cleaning trials. A distinct impairment in sharpness of separation with decrease in particle size is evident. Neither the

recovery of coal nor the removal of impurity is as good in the smaller sizes

as in the coarser material.

TABLE 5. - Average distribution data, percent

Specific-gravity ____ _ Screen size, mesh

interval 3 to 20 20 to 48 48 to 200 3 to 200

-0.70 o.. ............. 99.5 - 95.1 -

.65................. 99.3 - 91.9 -

.60................ 99.1 - 89.3-

.55*......,..... 98.6 - 87.3 -

.50............... 96.5 - 85.4 -

.45................ 97.3 - 83.8 95.9

.40,.............. 96.6 96.7 86.9 96.0

.35............... 96.7 94.0 84.2 95.1

.30............... 94.7 87.8 79.9 91.9

.25................ 91.4 88.1 77.4 87.9

.20 .............. 86.3 83.7 71.2 82.5

.15............... 80.4 77.5 65.9 76.5

.10................ 72.4 69.3 60.9 69.5

- .05................ 61.8 59.8 55.2 60.4

0.................... 50 50.0 50.0 50.0

+ .05................ 39.0 41.4 45.2 39.6

.10................ 28.4 34.0 41.3 29.3

.15................ 20.2 27.5 38.1 21.4

.20............. . 16.2 22.1 34.5 16.6

.25................ 9.6 17.9 31.1 13.5

.30............... 7.7 14.7 28.6 9.8

.35................ 6.1 12.4 26.3 8.3

.40................ 5.0 10.7 24.3 7.2

.45................ 3.3 9.4 22.5 6.3

.50.......,..,.... 2.4 8.3 20.9 5.7

.55................ 1.9 7.5 18.0 5.2

.60................ 1.3 6.4 16.6 5.0

.65................ .7 5.1 14.1 3.9

.70................ .6 4.7 10.3 3.1

.75................ .4 4.2 - -

- 480..0.......... 40 -

- 385....5..... 3.5 - - -

Because sharpness of separatj

recovery efficiency in the 20- to

mesh size in every test. In some

ion decreases as particle size decreases, the

48-mesh size was lower than in the 3- to 20-

tests the efficiency in the 48- to 200-mesh

size was still lower, but in other tests the minimum efficiency was in the
12

intermediate size. Efficiency reflects primarily loss of coal, and generally

this loss was highest in the intermediate size range. This probably reflects

the fact that the finest coal particles, those below perhaps 65-mesh, are

largely entrained in the dressing water and carried to the side of the table,

whereas some of the intermediate-size coal particles are mechanically entrapped

in the refuse.

Both yield error and misplaced material exhibited about the same trend as

efficiency; that is, they generally show the poorest result in the intermediate rather than finest size range. In contrast, in all the tests, ash error

increased progressively as particle size decreased.

The magnitude of the decrease in sharpness of separation with decrease in

particle size and the consequent impairment in efficiency highlight the importance of the size composition of table feed and its effect on overall table

performance. Treatment of the finer sizes is so inferior to that of the material coarser than 20-mesh, that the proportion of finer material in the feed

has an important bearing on table operation. This fact is recognized by many

operators, and in a number of the more modern preparation plants material

finer than 100-mesh is removed from the table feed. In a few of the most

recent plants material finer than 48-mesh is removed for separate treatment

in flotation cells.

In all the present cleaning tests, the minimum density of separation

occurred in the 20- to 48-mesh range. In some tests the density of the separation in the 48- to 200-mesh was higher than that in the 3- to 20-mesh material, but in others it was not.

PREDICTION OF CLEANING RESULTS

With dense-medium units, including the dense-medium cyclone, and jigs,

the performance of a new cleaning plant can be projected with considerable

accuracy by using the distribution curves representing operation of similar

equipment under comparable conditions (16). The amount of detailed performance data on table operation available has not been sufficient to determine

whether the same technique could be used in predicting table results. The

variation in distribution data for the present group of tests, when expressed

on a basis of equal density difference as in table 5, suggests that such predictions of table performance would be far less accurate than that for densemedium cleaning, and probably distinctly less reliable than the predictions

that can be made for jig operation. Thus the average distribution factors

shown in table 5 should be used with due caution in predicting table performance on other coals. In view of the marked decrease in sharpness of separation with decrease in particle size, the use of the appropriate distribution

curves for individual size components of the feed would materially enhance the

accuracy of the predicted results.

Most investigators have concluded that the distribution curves for densemedium cleaning and jig operation are substantially independent of the density

composition of the raw coal. The present data do not demonstrate that this is

true for table operation, and until more data are available, the validity of

such an assumption is open to question.
13

BIBLIOGRAPHY

1. BIRD, B. M. Interpretation of Float-and-Sink Data. Proc. 2d Internat.

Conf. on Bituminous Coal, vol. 2, 1929, pp. 82-111.

2. YANCEY, H. F. The Effect of Certain Operating Variables on the Efficiency

of the Coal Washing Tables. Bureau of Mines Rept. of Investigations

3111, 1931, 13 pp.

3. YANCEY, H. F., AND PORTER, C. B. Pneumatic Tabling of Coal; Effect of

Specific Gravity, Size, and Shape. Bureau of Mines Tech. Paper 536,

1932, 18 pp.

4. YANCEY, H. F., AND GEER, M. R. Performance of a Baum-Type Coal-Washing

Jig. Bureau of Mines Rept. of Investigations 3371, 1938, 18 pp.

5. YANCEY, H. F., AND GEER, M. R., AND SHINKOSKY, H. E. Performance of a

Pulsator-Type Coal-Washing Jig. Bureau of Mines Rept. of Investigations

3372, 1938, 19 pp.

6. GANDRUD, B. W., COE, Go D., AND HAGER, H. J. Classification and Tabling

of Table Middlings at the Colta Coal Washery. Bureau of Mines Rept. of

Investigations 3448, 1939, 13 pp.

7. GEER, M. R., AND YANCEY, H. F. Washability Characteristics and Washing of

Coals From the Matanuska Field of Alaska. Bureau of Mines Rept. of

Investigations 3840, 1946, 17 pp.

8. YANCEY, H. F., AND GEER, M. R. Coal-Cleaning Performance--Comparison of

Pneumatic Jig, Pneumatic Table, and Baum-Type Jig. Trans. AIME, vol.

168, 1946, pp. 208-223.

9. GEER, M. R., AND YANCEY, H. F. Preliminary American Tests of a Cyclone

Coal Washer Developed in the Netherlands. Trans. AIME, vol. 177, 1948,

pp. 220-235.

10. GANDRUD, B. W. Concentrating Tables. Chap. in AIME, Coal Preparation,

1950, pp. 435-469.

11. GEER, M. R., YANCEY, H. F., ALLYN, G. L., AND ECKHOUSE, R. R. Laboratory

Performance Tests of the Humphreys Spiral as a Cleaner of Fine Coal.

Trans. AIME, vol. 187, 1950, pp. 1057-1067.

12. GANDRUD, B. W., AND RILEY, H. L. Recent Developments in Combination

Cleaning and Dewatering of Fine Sizes of Coal. Bureau of Mines Rept.

of Investigations 4707, 1950, 28 pp.

13. ZIMMERMAN, R. E. The Cleaning of Fine Sizes of Bituminous Coal by Concentrating Tables. Trans. AIME, vol. 187, 1950, pp. 956-966.

14. TROMP, K. F. Discussion. Trans. AIME, vol. 190, 1951, p. 998.
____

14

15. YANCEY, H. F., AND GEER, M. R. Efficiency and Sharpness of Separation in

Evaluating Coal-Washery Performance. Trans. AIME, vol. 190, 1951,

pp. 507-517.

16. GEER, M. R., How to Predict Results of Washing a New Coal: Coal Age,

vol. 57, June 1952, pp. 96-97.

17. GEER, M. R., OLDS, W. A., AND YANCEY, H. F. Cleaning Various Coals in a

Drum-Type Dense Medium Pilot Plant. Trans. AIME, vol. 196, 1953,

pp. 696-705.

18. GEER, M. R., AND YANCEY, H. F. Cleaning Characteristics and Cleaning

Tests of Montana Coal. Bureau of Mines Rept. of Investigations 5103,

1955, 47 pp.

19. PALOWITCH, E. R., JOLLEY, T. R., AND SOKASKI, M. Use of Pulverized Rock

as Dense Medium for Salvaging Coal From Pittsburgh-Bed Refuse. Bureau

of Mines Rept. of Investigations 5184, 1955, 33 pp.

20. YANCEY, H. F., AND GEER, M. R. Some Practical Aspects of Appraising CoalWashing Results. Bureau of Mines Rept. of Investigations 5153, 1955,

15 pp.

21. PALOWITCH, E. R., SOKASKI, MICHAEL, AND JOLLEY, T. R. Dense-Medium PilotPlant Performance Tests on Coal. Bureau of Mines Rept. of Investigations

5212, 1956, 52 pp.

22. YANCEY, H. F., AND GEER, M. R. Laboratory Cleaning Trials on a Pennsylvania Anthracite in a Baum-Type Jig and a Dense-Medium Pilot Plant.

Bureau of Mines Rept. of Investigations 5308, 1957, 23 pp.

23. GEER, M. R., AND YANCEY, H. F. Operating Results With the Feldspar FineCoal Jig. Bureau of Mines Rept. of Investigations 5412, 1958, 14 pp.

24. GEER, M. R., SOKASKI, MICHAEL, AND YANCEY, H. F. Plant Performance Tests

of the Tromp Dense-Medium Coal-Cleaning Process. Bureau of Mines Rept.

of Investigations 5619, 1960, 34 pp.

25. GEER, M. R., SOKASKI, MICHAEL, JACOBSEN, P. STANLEY, AND YANCEY, H. F.

Performance of Dense-Medium Cyclone in Cleaning Fine Coal. Bureau of

Mines Rept. of Investigations 5732, 1961, 22 pp.

26. NOONE, W. H. Effect of Continuous Mining Equipment on Cleaning Plant

Performance. Min. Cong. Jour., vol. 47, November 1961, pp. 34-41.
Screen analysis:

Feed ........................ percent

Washed coal....................do...

Refuse ............ do...

Ash:

Feed ........... ......... .... do...

Washed coal....................do...

Refuse ... .............. do...

Yield of washed coal ............. do...

Theoretical yield................do...

Recovery efficiency ............ do...

Yield error .... ............ do...

Ash error......... .. ...... do...

Misplaced material, percent of feed:

Washed coal........................

Refuse ........ . ...... ..*.......

Total. ... o.. o..... ... .. . . .

Near gravity material ± 0.10, percent

of feed ................... .........

Distribution, percent to washed coal:

Under 1.30........................

1.30 to 1.40 . ......................

1.40 to 1.50 ................. ....

1.50 to 1.60 .......... ..............

1.60 to 1.70........................

1.70 to 1.80....... ....... ........

Over 1.80........................

Specific gravity of separation ........

Error area.......................

Probable error........................

Imperfection ........................

3 to 20

75.5

79.8

58.4

16.1

7.1

64.1

84.4

84.8

99,5

0.4

0.2

1.2

1.9

3.1

5.0

99.8

99.6

97.2

90.1

73.0

46o8

3.7

1.738

63

0.098

0.133

. . , ,Y c

15

APPENDIX. - SUMMARY OF PERFORMANCE

TABLE A-1. - Test No. 1. 7B lower bed

C-I q m0oh

20 to 48

16.5

13.4

28.6

21.6

5.6

51.2

64.9

74.0

87.7

9.1

2.7

3.2

8.3

11.5

8.3

92.4

81.0

57.9

36.7

23.3

12.5

4.4

1.488

79

0.127

0.260

48 to 200

8,0

6.8

13.0

26.3

12.3

55.1

67.4

78.6

85.8

11.2

6.7

7.4

9.5

16.9

4.5

90.3

86.3

75.0

60.9

52.6

47.1

22.2

1.682

144

0.331

0.485

3 to 200

100.0

100.0

100.0

17.8

7.3

59.4

79,8

82.8

96.4

3.0

1.4

1.8

4.0

5.8

5.0

97.9

96.7

90.0

79.8

64.5

42.2

6.3

1.715

81

0.121

0.169

1'~ " 1
Screen analysis:

Feed ....................... percent

Washed coal ................... do...

Refuse. ..................... do..

Ash:

Feed ......................... do...

Washed coal...................do...

Refuse.........................do...

Yield of washed coal........... do...

Theoretical yield.............d...

Recovery efficiency............do...

Yield error . ....................do...

Ash error .................. do...

Misplaced material, percent of feed:

Washed coal........................

Refuse ... .........................

Total ....................... ........

Near gravity material ± 0.10, percent

of feed.......... ...................

Distribution, percent to washed coal:

Under 1.30........................

1.30 to 1.40 .......................

1.40 to 1.50.......................

1.50 to 1.60 .......................

1.60 to 1.70. ....... ...... .........

1.70 to 1.80 ................. .....

Over 1.80 .................. ....

Specific gravity of separation.......

Error area ........ ...............

Probable error .......................

Imperfection ......................

3 to 20

75.5

80.2

63.3

16,1

5.4

50.9

76.6

80.9

94.7

4.3

1.4

1o7

5.5

7.2

6.7

96.6

92.0

81.4

57.1

27.9

9.8

009

1.574

61

0.086

0.150

- -

16

TABLE A-2. Test No. 2. 7B lower bed

Size. mesh

20 to 48

16.5

12.6

26.6

21.6

5.7

41.0

55.0

74.2

74.1

19.2

3.9

4.1

16.7

20.8

13.2

77.5

70.6

47.4

30.6

20.9

12.5

4.4

1.437

86

0.143

0.327

48 to 200

8.0

7.2

10.1

26.3

12.6

51.8

65.0

79.0

82.3

14.0

8.0

7.3

12.1

19.4

4.4

87.4

79.4

72.2

60.9

52.6

47.1

22.2

1.695

153

0.364

0.524

I

3 to 200

100.0

100.0

100.0

17.8

6.0

48.5

72.2

80.1

90.1

7.9

2.6

2.4

7.9

10.3

6.6

92.7

88.8

76.3

53.3

28.2

13.5

4.6

1.562

74

0.101

0.180
Screen analysis:

Feed . ............. ........ percent

Washed coal ...... .... .. .. ..... . do . ..

Refuse ....... .. .... ........ do ..

Ash:

Feed .. ....... . .. .......... do ...

Washed coal...................do...

Refuse .. ..... ...... 0....do.. > 

Yield of washed coal .......... d......

Theoretical yield ............... do..

Recovery efficiency.............do.o.

Yield error................... do...

Ash error .................. .. ... do..

Misplaced material, percent of feed:

Washed coal ....................... o

Refuse .............................

Total ..............................

Near gravity material + 0.10, percent

of feed .............................

Distribution, percent to washed coal:

Under 1.30.......................

1.30 to 1.40. ............ ........

1.40 to 1.50 .......................

1.50 to 1.60 ......................

1.60 to 1.70.......................

1.70 to 1.80 .......... ..........

Over 1.80 .......................

Specific gravity of separation.......

Error area...........................

Probable error.......................

Imperfection ........................

3 to 20

75.5

80.1

69.4

16.1

4.3

33.9

60.5

77.9

77.7

17.4

2.3

2.2

17.5

19.7

13.2

79.9

73.0

52.8

21.8

6.2

2.9

0.5

1.459

56

0.104

0.227

17

TABLE A-3. - Test No. 3. 7B lower bed

20 to 48

16.5

12.4

21.9

21.6

6.1

33.2

42.9

75.0

57.2

32.1

4.9

6.7

25.0

31.7

49.3

60.6

50.7

39.5

26.5

18.6

12.5

4.4

1.365

91

.. Size, mesh

48 to 200

8.0

7.5

8.7

26.3

13.5

40.9

53.4

80.4

66.4

27.0

11.2

8.0

21.9

29.9

5.3

71.7

57.8

58.3

52.2

47.4

41.2

20.9

1.588

162

3 to 200

100.0

100.0

100.0

17.8

5 .3

34.5

57.1

78.3

72.9

21.2

3.4

2.7

20.0

22.7

10.5

76.1

69.5

51.9

24.3

11.1

7.6

4.1

1.458

70

0.127

0.277 q -- -. - = -
Screen analysis:

Feed . .............. ..... percent

Washed coal ................... do...

Refuse ....................... do ..

Ash:

Feed .........................do...

Washed coal ................. do...

Refuse ........... ... . o.. ...do...

Yield of washed coal ............ do...

Theoretical yield...............do...

Recovery efficiency.............do...

Yield error ..................... do...

Ash error .................... do...

Misplaced material, percent of feed:

Washed coal ........................

Refuse........... ... 0 .o.. *.. .....

Total . .. ......

Near gravity material ± 0.10, percent

of feed ...................

Distribution, percent to washed coal:

Under 1.30.......................

1.30 to 1.40 .......................

1.40 to 1.50.......................

1.50 to 1.60 ......................

1.60 to 1.70.......................

1.70 to 1.80 .......................

Over 1.80 ................. ea...

Specific gravity of separation.......

Error area...........................

Probable error ......................

Imperfection......................... . u

3 to 20

78.7

83.0

65.0

18.8

6.2

68.8

79.9

80.6

99.1

0.7

0.4

1.4

1.9

3.3

4.7

99.8

99.2

93.0

83.2

68.1

42.5

3.7

1.720

68

0.104

0.144

18

TABLE A-4. - Test No. 4, 7C bed

20 to 48

15.1

11.9

25.3

29.4

7.0

62.3

59.3

66.3

89.4

7.0

3.4

4.2

5.9

10.1

6.2

94.2

87.2

57.9

45.9

28.6

21.1

5.9

1.507

93

0.149

0.294

Size, mesh

48 to 200

6.2

5.1

9.7

36.0

17.2

66.8

62.2

72.2

86.1

10.0

6.6

10.6

5.6

16.2

4.9

94.1

92.4

80.0

64.7

66.7

43.8

23.6

1.698

126

0.280

0.401

3 to 200

100.0

100.0

100.0

21.5

6.9

67.0

75.7

78.0

97.1

2.3

1.2

2.3

3.0

5.3

4.7

98.8

97.8

86.5

76.4

61.7

38.5

6.5

1.700

82

0.122

0.174- -

w - = = - - . . -
Screen analysis:

Feed ....................... percent

Washed coal .... , .......... do...

Refuse ...................... do...

Ash:

Feed .................... do...

Washed coal................... do..

Refuse..............................do..

Yield of washed coal ........... do...

Theoretical yield ........... d... ...

Recovery efficiency.............do...

Yield error .....................do...

Ash error ........... ....... do...

Misplaced material, percent of feed:

Washed coal.......................

Refuse................ ...........

Total.......... .......... ........

Near gravity material + 0.10, percent

of feed............ .................

Distribution, percent to washed coal:

Under 1.30.......................

1.30 to 1.40.......................

1.40 to 1.50.......................

1.50 to 1.60 .......................

1.60 to 1.70 .......................

1.70 to 1.80.......................

Over 1.80 ............... .......

Specific gravity of separation.......

Error area...........................

Probable error.....................

Imperfection......................

3 to 20

78.7

84.1

68.3

18.8

4.9

51.6

70.2

78.1

89.9

7.9

2.2

1.5

8.4

9.9

4.9

91.4

89.0

75.6

58.7

30.2

12.2

1.2

1.580

69

0.106

0.183

-- - x

19

TABLE A-5. - Test No. 5, 7C bed

Cln inc.1,

20 to 48

15.1

10.9

23.2

29.4

7.2

49.5

47.4

66.7

71.1

19.3

5.5

5.0

15.6

20.6

11.2

77.1

61.5

42.1

37.8

23.8

18.4

5.5

1.423

101

0.170

0.402

48 to 200

6.2

5.0

8.5

36.0

17.9

56.2

52.9

72.7

72.8

19.8

12.9

11.6

12.6

24.2

5.7

85.0

62.0

60.0

52.9

53.3

37.5

22.0

1.567

149

0.355

0,626

, LL--

3 to 200

100.0

100.0

100.0

21.5

5.8

51.6

65.7

76.0

86.4

10.3

3.2

2.3

10.1

12.4

5.2

89.1

85.2

69.9

54.3

31.3

14.1

4.5

1.570

81

0.129

0.226
Screen analysis:

Feed ....... . . ........... percent

Washed coal ................... do...

Refuse ...................... do...

Ash:

Feed .............. ......... .do...

Washed coal .................. do...

Refuse .......... .......... do...

Yield of washed coal ...........do...

Theoretical yield ...............do...

Recovery efficiency ............. do...

Yield error..................... do...

Ash error...................... do...

Misplaced material, percent of feed:

Washed coal ........................

Refuse .............................

Total ..............................

Near gravity material ± 0.10, percent

of feed.............................

Distribution, percent to washed coal:

Under 1.30.......................

1.30 to 1.40.......................

1.40 to 1.50.......................

1.50 to 1.60.......................

1.60 to 1.70 ......................

1.70 to 1.80 .......................

Over 1.80.......................

Specific gravity of separation.......

Error area ...........................

Probable error .......................

Imperfection .........................

3 to 20

79.4

86.7

63.1

20.2

5.4

65.7

75.4

77.3

97.5

1.9

0.9

1.6

2.8

4.4

4.4

99.0

95.6

86.6

71.2

48.3

24.0

2.3

1.640

68

0.108

0.169

20

TABLE A-6. - Test No. 6, 7C bed

20 to 48

14.0

10.2

22.5

30.2

5.5

55.3

50.4

62.4

80.8

12.0

3.2

2.8

10.6

13.4

11.0

84.0

76.0

44.4

28.1

16.7

8.8

1.8

1.432

71

0.112

0.259

Size. mesh

48 to 200

6.6

3.1

14.4

50.3

19.1

65.4

32.4

50.7

63.9

18.3

13.3

7.6

8.4

16.0

5.6

76.0

76.5

61.9

37.5

31.6

22.2

8.8

1.500

106

0.166

0.332

3 to 200

100.0

100.0

100.0

23.6

5.8

63.3

69.1

73.2

94.4

4.1

1.8

2.0

4.5

6.5

4,5

92.6

92.7

79.9

63.0

42.5

21.6

3.1

1.613

76

0.125

0.204 . P -
Screen analysis:

Feed ............ ........ ,.percent

Washed coal .. ...... do...

Refuse .......................do..

Ash:

Feed ....... ............ ........ do...

Washed coal...................do...

Refuse.... ................. ..do...

Yield of washed coal............do...

Theoretical yield ...............do...

Recovery efficiency.............do...

Yield error ....................do...

Ash error ................ .. ... do..o

Misplaced material, percent of feed:

Washed coal........................

Refuse..................... ..

Total . .. .......... .....

Near gravity material ± 0.10, percent

of feed ... .. ... 0..... ... . .........

Distribution, percent to washed coal:

Under 1.30......................

1.30 to 1.40 ............... .......

1.40 to 1.50......... .............

1.50 to 1.60 ............ ...........

1.60 to 1.70 ..................... ..

1.70 to 1.80 ......................

Over 1.80 .................... ...

Specific gravity of separation.......

Error area ..........................

Probable error ......................

Imperfection .. ........... ............

3 to 20

78.0

83.3

67.4

24.0

5.9

68.1

71.0

72.8

97.5

1.8

0.9

1.8

3.2

5.0

5.7

98.5

96.0

86.3

72.2

48.7

23.7

1.3

1.641

66

0.104

0.162

21

TABLE A-7. - Test No. 7, 7C bed

20 to 48

15.9

11.8

24.1

31.1

5.9

55.3

49.0

63.8

76.8

14.8

4.0

4.0

11.5

15.5

14.2

82.6

65.0

37.5

27.8

12.5

10.0

3.8

1.395

76

0.119

0.301

Size, mesh

48 to 200

6.1

4.9

8.5

35.5

11.4

63.0

53.2

65.5

81.2

12.3

7.9

7.1

8.4

12.2

4.7

88.7

71.7

64.7

42.9

46.2

33.3

11.7

1.531

130

0.258

0.486

3 to 200

100.0

100.0

100.0

25.8

6.1

64.5

66.4

71.2

93.3

4.8

2.1

2.3

5.3

7.6

5.5

95.5

91.7

78.3

64.0

44.5

22.9

2.7

1.620

82

0.137

0.221
Screen analysis:

Feed . ......................percent

Washed coal..............do...

Refuse ...... ....... do..

Ash:

Feed... o... ........ o.....o. do...

Washed coal .................. do...

Refuse ........ . ............. do ...

Yield of washed coal ............ do...

Theoretical yield...............do...

Recovery efficiency ..... ........do..

Yield error .............. do..

Ash error ...................... do...

Misplaced material, percent of feed:

Washed coal.......................

Refuse .. . ... .................

Total. . . .......................

Near gravity material + 0.10, percent

of feed .............................

Distribution, percent to washed coal:

Under 1.30......................

1.30 to 1.40 .......................

1.40 to 1.50.......................

1.50 to 1.60 ............ .........

1.60 to 1.70 .......................

1.70 to 1.80 ........ ... ...........

Over 1.80......................

Specific gravity of separation.......

Error area......o...........,.......

Probable error......................

Imperfection ........................

3 to 20

78.0

84.1

69.9

24.0

4,7

54.4

61.3

70.3

87.2

9.0

2.3

1.8

9.7

11.5

6.6

88.1

84.7

70.2

45.3

20.2

6.6

0.6

1.530

63

0.099

0.187

22

TABLE A-8. Test No. 8, 7C bed

20 to 48

15.9

11.0

22.4

31.1

6.5

47.0

39.2

64.8

60.5

25.6

5.2

5.3

19.2

24.5

59.3

65.1

50.4

32.1

25.0

12.5

10.0

3.6

1.355

74

Size, mesh

48 to 200

6.1

4.9

7.7

35.5

12.0

55.0

45.3

66.4

68.2

21.1

10.3

7.3

14.8

22.1

6.1

75.6

54.3

58.8

35.7

38.5

33.3

10.8

1.465

130

0.261

0.561

3 to 200

100.0

100.0

100.0

25.8

5.2

52.7

56.8

69.4

81.8

12.6

3.1

2.2

12.1

14.3

6.2

83.8

80.1

64.3

41.1

20.6

9.0

2.1

1.511

72

0.112

0.219
Screen analysis:

Feed . ..................... percent

Washed coal ................... do...

Refuse ........................ do...

Ash:

Feed.......................... do...

Washed coal ................... do...

Refuse ............... do..

Yield of washed coal............do...

Theoretical yield............... do...

Recovery efficiency.............do...

Yield error..................... do...

Ash error .......................do...

Misplaced material, percent of feed:

Washed coal.........................

Refus e.............................

Total ..............................

Near gravity material ± 0.10, percent

of feed .............................

Distribution, percent to washed coal:

Under 1.30.......................

1.30 to 1.40.......................

1.40 to 1.50.......................

1.50 to 1.60.......................

1.60 to 1.70............... ........

1.70 to 1.80.......................

Over 1.80.......................

Specific gravity of separation.......

Error area...........................

. Probable error.......................

Imperfection.......................

3 to 20

73.8

78.3

59.9

30.1

19.3

74.0

80.3

82.2

97.7

1.9

1.2

5.0

4.5

9.5

7.6

99.2

98.7

97.4

95.0

91.2

85.9

34.7

1.991

92

23

TABLE A-9. - Test No. 9, 5 bed

20 to 48

18.8

14.9

31.1

32.6

11.7

63.9

59.9

66.3

90.3

6.4

3..3

3.6

7.5

11.1

7.1

94.0

91.0

79.7

65.5

50.7

36.5

5.5

1.653

95

0.173

0.265

Size. mesh . . - - - ]

48 to 200

7.4

6.8

9.0

37.5

26.1

64.2

70.2

80.8

86.9

10.6

6.3

9.0

12.2

21.2

9.6

93.5

90.5

87.3

82.9

76.5

76.9

39.4

2.003

131

3 to 200

100.0

100.0

100.0

31.1

18.7

70.0

75.7

80.5

94.0

4.8

2.4

5.2

5.6

10.8

7.8

97.7

97.1

93.4

89.4

83.6

78.4

29.0

1.967

102
Screen analysis:

Feed.......... . ....... percent

Washed coal . ............... .do...

Refuse.................... ... do...

Ash:

Feed ....................... ... do...

Washed coal................... do...

Refuse.. ........ ...... . do...

Yield of washed coal ............do...

Theoretical yield .............. do...

Recovery efficiency............. do...

Yield error ......... ......... do...

Ash error . .................... .. do...

Misplaced material, percent of feed:

Washed coal........................

Refuse... .... ........ ... ......

Total ............. 0. . ........ ....

Near gravity material ± 0.10 percent

of feed .......... ...... 0...........

Distribution, percent to washed coal:

Under 1.30.......................

1.30 to 1.40...... .................

1.40 to 1.50........................

1.50 to 1.60 ........ .............

1.60 to 1.70.......................

1.70 to 1.80 ...... 09..............

Over 1.80 ...... , ..... ....

Specific gravity of separation.......

Error area.............. ... .o.... 

Probable error ............. ,.......

Imperfection .......... ..... ....... 

3 to 20

74.0

78.7

61.2

34.1

21.5

78.1

77.8

78.9

98.6

1.1

0.7

8.8

6.2

15.0

8.8

100.0

99.9

99.8

98.8

97.7

89.8

35.4

1.983

89

-

24

TABLE A-10. - Test No. 10. 5 bed

Size. -, = mesh

20 to 48

26.0

21.3

38.8

36.8

16.2

67.7

59.9

66.4

90.2

6.5

3.9

6.9

5.8

12.7

7.5

97.8

93.2

82.8

67.7

54.0

40.4

13.7

1.680

109

0.184

0.271

3 to 48

100.0

100.0

100.0

34.8

20,4

74.1

73.1

77.0

94.9

3.9

2.4

6.6

4.1

10.7

8.7

99.4

98.6

95.7

90.4

86.7

76.6

29.3

1.964

99
Screen analysis:

Feed ...... .. . ...... percent

Washed coal. ...... .......... do...

Refuse ............ ....... ... do...

Ash:

Feed, .....o.......... ....do...

Washed coal..,................do...

Refuse ............. do...

Yield of washed coal ............do...

Theoretical yield ............... do...

Recovery efficiency ............ do....

Yield error .................... do...

Ash error....................... do...

Misplaced material, percent of feed:

Washed coal......... ... ..........

Refuse ................ . ......

Total ..................... .

Near gravity material ± 0.10, percent

of feed ..........................

Distribution, percent to washed coal:

Under 1.30.......................

1.30 to 1.40 .......................

1.40 to 1.50 ........... ............

1.50 to 1.60 ........... ...........

1.60 to 1.70............... ........

1.70 to 1.80 ...................

Over 1.80 .......................

Specific gravity of separation.......

Error area....................... .

Probable error........o.....o*.....o

Imperfection ............ ...........

3 to 20

74.0

77.9

67.8

34.1

15.8

67.1

64.4

69.7

92.4

5.3

3,3

4.3

6.7

11.0

7.3

94.4

92.9

90.7

84.4

79.2

66.8

12.8

1.809

95

0.144

0.178

25

TABLE A-11. - Test No. 11, 5 bed

--- I Size. mesh- - ..

20 to 48

26.0

22.1

32.2

36.8

16.5

58.8

51.9

66.8

77.7

14.9

8.4

7.6

11.9

19.5

8.5

84.0

82.6

67.8

55.4

46.0

35.1

13.0

1.613

124

0.232

0.378

3 to 48

100.0

100.0

100.0

34.8

16.0

64.4

61.1

69.4

88.0

8.3

4.8

4.0

9.3

13.3

7.7

91.4

90.9

85.2

76.5

70.9

58.3

12.9

1.826

122

0.236

0.286
Screen analysis:

Feed ...... ..... .......... percent

Washed coal..... ............... do...

Refuse .......... o.o. ...... .do ..

Ash:

Feed................ ........ do...

Washed coal ................ do ...

Refuse ... .............. . ..... do. ..

Yield of washed coal ............do,..

Theoretical yield .............

Recovery efficiency.,..............

Yield error...........O....... do...

Ash error ..... o.........do... .. .. .

Misplaced material, percent of feed:

Washed coal .....................

Refuse...° ... .. ......... . .o ...o.o.

Total. .. .......... o............. o.

Near gravity material + 0.10, percent

of feed ................. ... .....

Distribution, percent to washed coal:

Under 1.30......................

1.30 to 1.40 ......................

1.40 to 1.50 ......... ..............

1.50 to 1.60 .. .......... ...........

1.60 to 1.70.......................

1.70 to 1.80 . .....................

Over 1.80............. ..........

Specific gravity of separation.......

Error area .............. ..........

Probable error .......... 0 ..........

Imperfection ........................

3 to 20

69.7

71.2

63.4

18.3

7.3

71.4

82.8

84.0

98.6

1.2

0.5

1.4

1.9

3.3

3.9

99.7

98.8

91.5

67.2

44.8

31.4

2.8

1.629

79

0.138

0.219

, J & C

26

TABLE A-12. - Test No. 12, Mrak bed

C 7PI m no

20 to 48

11.7

10.0

19.1

25.8

7.0

67.8

69.1

72.8

94.9

3.7

1.5

2.3

4.4

6.7

5.6

97.8

88.6

69.8

50.0

31.8

18.8

3.5

1.550

82

0.138

0.251

48 to 200

18.6

18.8

17.5

27.7

18.1

71.9

82.1

86.2

95.2

4.1

2.7

7.1

5.2

12.3

5.1

99.4

93.2

88.0

84.6

83.9

82.4

41.9

2.010

119

IlLttO 11

3 to 200

100.0

100.0

100.0

21.0

9.3

70.7

81.1

83.6

97.0

2.5

1.5

3,0

2.9

5.9

3.6

99.4

97.2

88.4

68.9

54.2

42.6

13.6

1.687

107

0.198 r

0.288 . - - -

INT..BU. OF MINES.PGH. ,PA, 4138

" C"