Show laboratory TESTS AS AIDS TO MILL DESIGN Z by J M callow C E i laboratory experiments are not sufficiently appreciated by pr practical pra operators and it is not surprising irig considering how they are usually conducted to start with the sample for testing is invariably inaccurate it is grabbed from the dump or knobbed off some of the several openings of the mine and several pounds are sent to an assay office where in the case of u h M CALLOW c e it is a sulphide ore probably ground in a sample grinder to 20 or even a finer mesh concentrated in a pan and the different differ different eni portions assayed and an extraction figured from the tal tailings lings such information is absolutely valueless when it comes to the design design of a mill the parties may take tle the precaution to get a run in ill some nearby mill which may be a badly arranged one even tor for its re regular ular ore supply and even more so for the ore in question still it may be more or less adjusted to meet the case and the test proceeded with the results may not be perfectly satisfactory but yet near enough with certain further alterations to justify the erection of a plant for the ore the new ull is built the old one being taken as a 11 model ode with here and there a modification and thus too often old fashioned and defective designs are perpetuated from one mill ton another there may be to much refinement on one chand hand or too careless a handling on the other so that it is still an experiment peri ment and the ultimate outcome is never spoken of with any assurance until the new plant is running and then in the majority of cases the experimenting begins anew this is a marked contrast to the scientific methods of dealing with things in other departments of metallurgy cyanide chlorination or in fact any of the wet extraction methods are predetermined pre determined with accuracy the charges for the blast furnace are also predetermined pre determined by the aid of chemical analysis with the same positive of what the ultimate results will be and there is no reason why ore dressing or concentration cent ration determinations cannot be made with equal precision when conducted with equal intelligence it is the intention here to roughly illustrate a method of testing an ore for concentration tra tion which is unique and which it is believed cannot fall fail to recommend itself to both the practical operator and the theoretical student A concentration test should be a mechanical analysis so that the different elements in ill the problem being accurately known and understood can be turned about and switched around into a number of different combinations bi nations out of which by practical knowledge and experience we can select the most suitable one for our purpose ev every ry act or operation should he be a as s nearl nearly duplicated in the laboratory as it woul woula occur in practice if you are going to use crushers and rolls then their crush ings must be imitated in the laboratory it are to be used in the actual mill then you may use the sample grinder but even then it must be operated in such a way as to produce what would actual actually lk take place in the field if the ore is to bo be jigged then a jig must be used in the laboratory and not hand picked with a pair of forceps as the writer has seen done to make the separation in practice you will use both screen and hydraulic sizing and these must both be done in their proper places in the experiment A vanner may be imitated with a pan or plaque but if you propose to use precession tables then you must use a precession table in the laboratory the assay value of any particular sample is of little value unless you have the weight of this portion of the cri original ginal sample for it may run high in values es but be so inconsiderable in quantity that it may represent a mere fraction of the original contents of the ore or vice versa and this is one of the principal defects of the full sized mill test it is practically impossible to wt et any more than a part of the data necessary the most important factor viz the weights cannot be arrived at and after all all you get is heads tails and concentrates everything between is EM X you may have crushed and concentrated stuff that costs more than you ge get t out of it or have thrown particles to the creek that could have been re handled at a profit or put in crushing crushing and separating machines out of proportionate the requirements of the case sometimes too few and in as many other cases far in excess of what was really needed of course after running your new mill a mouth month or two or more you may eventually arrive at the correct solution but see what it has cost when alf all of these factors can be tried tested and determined in the laboratory on a scale it is a waste of effort to further dwell upon the absurdity of the prevailing methods of conducting these selfsame self seif same experiments on the fifty to one hundred thousand dollar scale some people think that the smallness of the sample in a laboratory test in some unexplained way makes the results less re lible than when many tons are treated it would be just as reasonable to refuse to accept an assay as correct made arom any quantity less than an avoirdupois ton instead of from an assay ton the results results in either case depend upon the accuracy of the sample submitted the larger the original sample broken from the mine the better it should not be picked or knobbed it should be mined exactly the same as under practical conditions so that the proper proportion of fines and coarse may be present in the test sample as it would be in the ore sent to the full size mill if the surfaces are large and the openings in the mine numer numerous busnot not less than five tons should be broken down and so on up in proportion these five tons should bo be sent to the sampling works and a sample cut out for a test some judgment is necessary here to determine the best method to pursue if the ore is such that no separation of mineral would take place until after crushing to 1 1 I then it may be screened on a grizzly and the oversize passed through a roll or crusher to 1 inch L cubes then aber a thorough mixing the sample of 1000 pounds cut out by alternate shoveling do not cone or quarter it this time honored method of sampling is not as accurate a one as taking each alternate sh ovel ful and repeating a sufficient number of gf timer imes until th the quantity of the sample is small enough if however there are large chunks of mineral that would in practice be hand sorted then our laboratory test must commence at this place and the big lot hand sorted and the first class ore weighed up sampled and assayed before commencing to crush for the test after bams 4 acae A it 67 0 27 i J I 1 w fr of fM y ficaia A alj 7 Y 7 Q 4 as r s t sy i D M 1 1 I N 7 at k 7 IN 1 i 03 sim av ael ga ing the results of a test on a sulphide lead ore this ore was low grade and difficult to mine clean the ore impregnating the country rock in very irregular fashion so go that it was impossible to recover or sever the ore cheaply from the mine without getting considerable barren country rock in D ore e ane mian pam tons pm af y aa ay ae VM Ws 0 10 2 ww f ft 4 63 0 1 71 11 9 17 74 4 2011 ae iza 3 tsa 32 MS sus nsf N af 02 st 6 6 11 0 2 OS OS sah 00 ayi W iff mii y zes e 3 1132 11 32 38 ftc 73 Z cas aa 0 o cef 46 aza ira 41 79 fa ifer 1 ass 46 za sap 9 1047 fa jes CO d 6 22 asaf irza SS 4 47 7 ar fla 2 17 I 1 j AZ 7 1773 64 aso S 7 22 11 S Q AT ass mss ass 14 ts asp syr ar 83 1940 37 r d ays as elsoy ili sen al 7 iab M N 71 xa 17 0 o JOS r a 39 fa 2 4 1776 ao 10 avo 0 ats si z 3 zefa sew 0 0 46 aa at 1 sm cr faife 9 alzaa 04 00 19 1132 0 73 fa ab Y 36 d 6 af za tubs as 10 pa Z tais ZY 34 02 9 M nsf cowf oo wf a az sms r AO aj a adz ba 1040 7 8 6 1 5 y ra sask WM eua 9 4 46 fern a 3 ZM 1 6 9 Z w 0 17 7 76 C 4 J SM sa ax 7 41 aza 7 P 11 so 40 ea ase 67 ar V aas 22 as lo 10 mal 9 ali ah 9 ess 13 3 yx 31 SOS ya 7 73 as YA 70 97 fm taw S za ass mss aa als 6 eez az 92 83 0 47 toil we of effs y baw 1 a yf ae fw zd 3 aso M aff asu 3 16 M s 36 6 af is us 0 o 92 J ss 9 hi Z sf wf fofi 92 S ac musj aj 17 gur 0 SO RIO J 7 7 be O ca 1497 97 toi 0 s f fie 2100 ats J 9 0 4 13 3 aes 16 73 gerass ze rass 0 o 77 4 46 6 4 17 JS as TO 70 at as i S auf 94 C 61 fe Z 7 9 9 he fa ef ss ea so 9 As a 2403 na 14 za zv M sa 0 efi ef ar i 47 go 90 Z 7 as aj tale 3 ea se ds azar J 49 in ra APA AP A te SOS e 02 A au PJ af S 4 t afsa Z if 4 4 46 60 1410 as a aaa PM P M JM 14 18 tabt A 6 aj grafl ts 7 P I 1 afi a fi im V a 33 asis bin fla 6 inyl adf xa afe at to fsr 23 faff 0 as f cai S taw KID III OD fc crushing the rejections from the hand sorting to say 1 inch duplicate halves should be made one cut down and crushed re for assay and the other for the test 1 the accompanying diagram and table liable shows without the necessity of many wards words the authors method of testing and hillur brat I 1 with it the lead was mostly cube galena some chunks being large enough to hand separate the object to be kept in view in the design of the plant was a mill mili to handle the largest amount of material with the least possible outlay of captian capt ial and the smallest jos possible sIbIe working expense water too was scarce the chief value of the mill was to be as an assistant assi tant in the cheap mining of the ore mining carefully enough to keep out all waste would be so expensive as to absorb the profits cheaper methods of mining reduced the grade of the ore with like results hand sorting was unprofitable as none but the coarsest hortings sor tings and the very finest screenings would pay to ship the rest being lost on the the dump with a mill they could mine roughly hence cheap ly and even if the mill extractions were low the sum of all the costs and losses would be far less than on the former plan the actual treatment is given in the diagram which a little study will readily explain in the actual mill but one separation was to be done on on the sorting belt the second class and the waste both being sent to the creek or dump two men on the belt would easily handle the forty tons per day delivered to it and sort out nearly two tons of first class going 40 per cent lead and fifteen ounces silver worth 40 these forty tons were handled by this means at a cost of 15 cents per ton for labor and all the loss that would have occurred in slimes if we had smashed up the cube lead in the fine rolls was avoided if these forty tons had all gone through the other department of the mill it would have cost at least per ton to handle it there the per cent of saving on the stuff that went to the belt it will be seen was 40 per cent and even if by sending it to the fine department we could have doubled the extraction it would still have been a losing game so that instead of having to design a ton plant all that was necessary was practically a 50 or a 60 ton plant this took a correspondingly spon smaller supply of water and the arrangement in every way fitted in without the aid of this information nearly twice as much capital would have gone into the plantford plant for the same capacity and twice as much water would have been necessary down on the jigs it will be seen that some were made but they went high enough it was afterwards found so that they could be sent to the concentrates the diagram shows three losses going to the creek wilfley tailings 54 waste and second class 57 jig tailings in the wilfley tails the loss was in the slimes the ore carried some carbonate nothing could be profitably done with the waste and second class for reasons given but the jig tails carried included grains of mineral though most of the value represented here was silver however they were all in the mill were all crushed to sizes between one quarter and one twentieth of a pound and could be re crushed for 25 cents cent sper per ton from these sizes to 16 mesh so of the three losses this was the only place where any good could be done they were accordingly crushed re as noted and increased the combined extraction 8 per cent viz to 75 per cent which though not a perfect saving by any means was one that would give the best commercial results under the conditions knowing the facts in relation to each other we were able to not only design the plant to treat the ore of this particular sample but to keep in view possible variations that might occur for instance the grade of the ore might so improve that the second class might be good enough to pay for milling so the belt was placed in such a position that these hortings sor tings could drop into the rolls or even drop the whole of the belt product direct to them or to another set designed especially for the purpose screen sizing is shown in conjunction with the wilfley tables in this case chiefly tor for the purpose of economizing water and incidentally by its use to throw the fine galena and carbonate slimes all on one of the two tables where thel their chances of recovery covery would be much better than when on the same table with the coarse sands each sample is numbered on the diagram and its weight value and other features are given in the accompanying table the figures written in the vertical position on the diagram represent weights or tons out of the figures written diagonally epitomize by expressing in dollars and cents the valuable contents of that particular sample it is written across thus giving at a glance a proper and clear conception of its relation to the rest of the operations all these figures etc are of the greatest assisi tance in the design and proportion of the plant the sorting belt must be large enough to have a capacity of 40 tons the rolls will be called upon to crush 32 tons per day 29 tons are already fine enough and have no need of going through the rolls the meshes of the revolving screens are predetermined pre determined by experiments peri ments so as to get a distribution of material to their several jigs in proportion to their relative capacities 28 tons going to the no I 1 and 18 tons to the no 2 if the jig tailings are thrown to the creek as shown we have 22 tons to go to the Wilf leys and by experimenting with different screens jn n the laboratory we find the correct mesh to give a proper to the two tables if we decide to regrind these jig tails we must provide at least three more tables for the 35 tons of this material that there is besides the necessary grinding mill an extra outlay of at least but as we would be making at least 30 per day by the operation after paying for all expenses of extra crushing it will pay for itself in days the diagram is divided into sections alphabetically designated which are referred to again in the table of assays essays and in the conduct of the test the authors rule and practice is that the sum of the contents of the several samples in any one section must check with the contents of the head sample before proceeding further any errors in weighing sampling or assaying can thus be easily detected in time and the correction ace accurately irately made A test similar to the one above will take ten days or two weeks of steady work to complete the sample of ore worked on may be from to pounds often two or three tests are run through and completed before a satisfactory combination is agreed upon the author does not wish to be understood as condemning the full size test in an actual mill such a test properly conducted is a valuable and wise precaution to take especially when a large outlay of capital is involved but he does insist that in every case a laboratory test such as the above should precede all operations of any kind on a full sized scale so that guided by the information obtained in the laboratory a really suitable plant can be selected and a full size run made with profit and to good purpose |