1、BRITISH STANDARD BS 7067:1990 Guide to Determination and presentation of float and sink characteristics of raw coal and of products from coal preparation plants UDC 552.574:662.66.002.612:662.8.053.346:620.11BS7067:1990 This British Standard, having been prepared under the directionof the Solid Mine
2、ral Fuels Standards Policy Committee, was published underthe authority of the BoardofBSI and comes into effecton 29June1990 BSI 01-2000 The following BSI references relate to the work on this standard: Committee reference SFC/5 Draft for comment85/55079DC ISBN 0 580 170446 Committees responsible for
3、 this BritishStandard The preparation of this British Standard was entrusted by the Solid Mineral Fuels Standards Policy Committee (SFC/-) to Technical Committee SFC/5, upon which the following bodies were represented: Association of British Mining Equipment Companies British Coal Corporation Coal P
4、reparation Plant Association Minerals Engineering Society Amendments issued since publication Amd. No. Date of issue CommentsBS7067:1990 BSI 01-2000 i Contents Page Committees responsible Inside front cover Foreword ii 1 Scope 1 2 Definitions 1 3 Sampling 1 4 Comprehensive plant efficiency tests 2 5
5、 Size analysis 2 6 Pilot testing 3 7 Float and sink testing 3 8 Presentation of results 10 Appendix A Procedure for a centrifugal float and sink test 14 Appendix B Typical procedure for the treatment and testing ofa sampleofarawcoal 14 Appendix C Practical hints on float and sink testing 15 Figure 1
6、 Sectional elevation of a2L measuring vessel for the determinationofrelative density of solids in aqueous suspension 6 Figure 2 Suitable cylindrical float and sink apparatus for separationofcoarsesize fractions 7 Figure 3 Float and sink bench 8 Figure 4 Suitable float and sink apparatus for separati
7、on of4mmto0.5mmsize fractions 9 Figure 5 Suitable float and sink apparatus for separation of size fractionsfinerthan0.5mm 10 Figure 6 Example of washability curves 12 Figure 7 Example of M-curve 13 Figure 8 Typical scheme for the treatment and testing of a sampleofrawcoal 16 Table 1 Recommended mini
8、mum mass of raw coal for a givensize fraction 1 Table 2 Example of results of size analysis 2 Table 3 Typical physical properties of organic liquids used in floatandsinktesting 4 Table 4 Suitable solids for aqueous suspensions 5 Table 5 Typical presentation of float and sink data and calculationforw
9、ashability curves 11 Publications referred to Inside back coverBS7067:1990 ii BSI 01-2000 Foreword This British Standard has been prepared under the direction of the Solid Mineral Fuels Standards Policy Committee. It is based on a draft International Standard, ISO/DIS7936 which is being prepared by
10、the International Organization for Standardization (ISO). The results of float and sink tests, presented in tabular and graphical form, are the basis for the provision of washability data and are of use when designing and redesigning coal preparation plants and in predicting, controlling and assessi
11、ng the performance of such plants. This British Standard provides guidance on float and sink testing, rather than specifying the full methods and the means of presenting the results, because of the various purposes for which the tests might be carried out and the wide range of conditions which might
12、 apply. It is essential that, before tests other than those for routine control purposes are to be carried out, detailed information concerning the size ranges and relative density fractions to be examined and the accuracy required is provided in order to establish the scope of the test. A British S
13、tandard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cov
14、er, an inside front cover, pages i and ii, pages1 to 16, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.BS7067:1990 BSI 01-2000 1 1 Scope This
15、 British Standard provides guidance on the apparatus and procedures for separation methods, based on differences in relative density, for determining the float and sink characteristics of raw coal and of products from coal preparation plants. It also provides guidance on the presentation, in tabular
16、 and graphical form, of the results of such tests. A procedure using a centrifuge to separate coals with a maximum particle size of less than1mm is described inAppendix A. A typical procedure for the treatment and testing of a sample of raw coal is described inAppendix B and some practical hints on
17、float and sink testing are given inAppendix C. NOTEThe titles of the publications referred to in this standard are listed on the inside back cover. 2 Definitions For the purposes of this British Standard the definitions given in BS3323 and BS3552 apply, together with the following. 2.1 top size the
18、size corresponding to the5 percentile on the cumulative size distribution curve of a material, i.e.the size above which5% of the material is retained 2.2 bottom size the size corresponding to the95 percentile on the cumulative size distribution curve of a material, i.e.the size above which95% of the
19、 material is retained 3 Sampling 3.1 General Sampling should be carried out in accordance with BS1017-1. The mass of the bulk sample, and consequently the degree of accuracy obtained in a float and sink test, may be varied according to the purpose for which the test is being carried out. The three m
20、ain categories of tests are as follows: a) investigations of the characteristics of raw coal; b) comprehensive plant efficiency tests (seeclause4); c) plant control tests. 3.2 Raw coal The mass of the bulk sample should be such that the number of discrete particles in any size fraction is not less t
21、han2000. A size fraction is defined by the aperture size of the square-hole sieve through which all the particles will just pass and the aperture size of the sieve on which they will all be retained. Examples of size fractions are given in Table 1 together with the recommended minimum mass of each s
22、ize fraction. The masses will generally be sufficient to ensure that there are at least2000 particles in each size fraction for raw coal, but some values have been adjusted to take account of practical considerations. Table 1 Recommended minimum mass of raw coal for a given size fraction In order th
23、at there is sufficient material for subsequent analysis, each relative density fraction should have a mass of at least20g and should contain at least10discrete particles. Because some coals give low yields in the intermediate relative density fractions, it may be necessary to take a much larger bulk
24、 sample than that based on the recommendations inTable 1. Other size fractions, replacing or supplementing those in Table 1, may be chosen: the minimum mass for each size fraction will then depend on the number of separations to be made and the quantitative distribution of the components in terms of
25、 relative density. It is better to take a bulk sample which is too large than to risk not having sufficient material. When testing coal that includes the larger sizes inTable 1, the bulk sample may have to be10tonnes or more. From a newly opened mine or a trial shaft, and in other similar circumstan
26、ces, the mass of the bulk sample should always be at least10tonnes. Size fraction Mass of coal mm kg 250.0 W 125.0 W 63.0 W 31.5 W 16.0 W 8.0 W 4.0 W 2.0 W 1.0 W 125.0 63.0 31.5 16.0 8.0 4.0 2.0 1.0 0.5 1000 350 180 90.0 33.0 7.0 3.0 1.5 1.0 4m 500 W 63 0.5BS7067:1990 2 BSI 01-2000 For bore cores it
27、 is usually impracticable to obtain the masses recommended inTable 1. For this reason, core plies or sections as large as possible should be selected and sub-division of a crushed ply or section prior to float and sink testing should be avoided. Both the size distribution and the ash of the raw coal
28、 coming from a working coal face or a mine will vary during a shift as well as from day to day. It is essential that the duration of sampling should be long enough to cover such variations. 3.3 Plant products The minimum mass of clean coal in a given size fraction should normally be50% greater than
29、that for raw coal, to ensure that adequate amounts of misplaced material are available. Since the relative densities of discard, middlings, etc. are greater than that of clean coal, the minimum mass of samples containing these components should be increased proportionately. This will ensure that the
30、se samples contain approximately the same number of particles as the corresponding clean coal sample and that consequently a similar degree of accuracy will be obtained in the test. Samples should be taken as soon as possible after the material leaves the cleaning unit in order to minimize breakage
31、and disintegration. Testing should then commence as soon as possible. When sampling pulp, the mass of the (dried) solids should meet the recommendations inTable 1. Increments should be taken at regular time intervals over the total cross section of the pulp stream either manually or by mechanical me
32、ans, using a sampling device having a capacity equal to at least twice the recommended minimum mass of increment. Care should be taken to ensure that none of the sample is lost by splashing. 3.4 Samples for plant control testing Routine samples should be taken regularly for the purpose of determinin
33、g the average efficiency of a cleaning plant. They may represent daily, weekly or even longer periods of operation. The mass taken may be less than that based on the recommendations inTable 1, depending on the reason for the test, but if any dispute arises concerning the accuracy of the results then
34、 the mass of the sample should meet all the relevant recommendations in3.2 and3.3. 4 Comprehensive plant efficiency tests A comprehensive plant efficiency test involves a systematic mass balance of all materials entering and leaving the coal cleaning plant. In this case the mass and moisture content
35、 of the raw feed, the mass and moisture content “as weighed” of all cleaned products, discard, etc., and the volume and solids content of the effluent will have to be determined. The mass of all materials is calculated to a uniform moisture basis and the raw coal feed entering the plant and the prod
36、ucts leaving the plant are balanced against each other. The efficiency of the cleaning plant is assessed from the actual and theoretical yields and grades. The analysis of the raw coal feed derived by the computation from the masses and analyses of all the products is used for the calculation of the
37、 theoretical yields. When a screen analysis of a plant product is made in connection with a cleaning plant efficiency test, it will be found that there is some material below the nominal bottom size being treated in the cleaning unit. The mass and particle size range of this undersize material shoul
38、d be recorded. 5 Size analysis The sample should be spread out on an impervious base, preferably under shelter, and allowed to dry sufficiently for sieving purposes. It should then be sieved using a suitable range of aperture sizes. Typical size fractions are given inTable 2. Oversize material may b
39、e broken by hand or machine crushed according to the nominal top size required. If applicable, the relevant part of the crusher circuit in a preparation plant may be simulated. Table 2 Example of results of size analysis Size fraction Mass of size fraction Cumulative oversize Cumulative undersize mm
40、 % % ( m/m) % ( m/m) W 125.0 125.0 W 63.0 W 31.5 W 16.0 W 8.0 W 4.0 W 2.0 W 1.0 W 0.5 63.0 31.5 16.0 8.0 4.0 2.0 1.0 0.5 Nil 11.9 12.1 12.8 15.7 12.5 10.2 7.5 5.6 11.7 Nil 11.9 24.0 36.8 52.5 65.0 75.2 82.7 88.3 100.0 100.0 88.1 76.0 63.2 47.5 35.0 24.8 17.3 11.7 Nil Total 100.0BS7067:1990 BSI 01-20
41、00 3 The quantity of material passing the63mm aperture sieve is usually more than the amount required and can be divided before proceeding to the next sieve. Further division may be necessary before sieving on some of the smaller aperture sieves. NOTEThe above sieving process may be preceded by a sa
42、mple treatment operation designed to simulate particle breakdown which may occur in a coal preparation plant. If it is not possible to carry out efficient sizing by dry sieving due to fine particles adhering to larger particles, then wet sieving should be used to ensure that the fine particles are c
43、ollected in the appropriate size fraction. 6 Pilot testing Pilot testing is frequently carried out on a smaller sample in order to determine the pattern of behaviour which the bulk sample will follow. This knowledge enables the operator to plan the actual test in such a way that unnecessary operatio
44、ns are avoided so that the test is carried out more quickly and with less effort. The pilot test, or previous experience, may indicate an advantage in commencing the separation at either the highest or lowest relative density. A sample which will give a high yield at either of these points should be
45、 separated at the point so that the bulk of the sample can be removed in one operation. In cases where there is only a low yield in one or both of two consecutive relative density fractions in the pilot test, it is better to combine these fractions in the main test. Such a combination will not affec
46、t the outcome of the test and will often improve its accuracy and reduce the time and effort involved. 7 Float and sink testing 7.1 Float and sink medium 7.1.1 Basis for selection. The medium which is to be used for the separation may be a mixture of organic liquids, aqueous solutions of inorganic s
47、alts, or solids in aqueous suspensions. The choice of medium is governed to some extent by the bulk and particle size of the coal being tested, its rank, its relative density and the purpose for which the separation is being carried out. The most suitable range of relative densities 1)for the test w
48、ill have to be determined by trial and error but would normally include1.3,1.4,1.5,1.6,1.7,1.8,1.9 and2.0. Relative densities lower than1.3 and higher than2.0 may be required. Additional separations at intermediate relative densities will be found useful if the cumulative ash is increasing rapidly i
49、n relation to the cumulative yield for successive relative density fractions. As stated in3.2, each relative density fraction should weigh at least20g and should contain at least10 discrete particles. If it is known or suspected that the sample will disintegrate or otherwise react on contact with water or aqueous solutions, separations will have to be carried out using organic liquids. However, the fact that the raw coal will react with water will affect its behaviour in the cleaning process and any information which will provide guidance should be
