Report on Test work conducted on the Fisher Air Separator

Transcription

1 Reprt n Test wrk cnducted n the Fisher Air Separatr Cnsidering the water limitatins at Leqhbng, and previus expsure t the Fisher Air Separatr a trial was undertaken in Lephalale (Ellisras) t cnsider the effectiveness f the separatr in the remval f ultra-fines frm a kimberlitic feed. The installed air separatr is currently being used fr the supply f aggregate and crusher dust fr the Medupi pwer statin. A sample f material was transprted t Lephalale fr the trial. Due t excessive rain in the area ver the December perid the sample was spread ut t dry and cvered at night. As a result the percentage misture was lwer than what wuld have been preferred. Principle f peratin The principle f peratin is simple and the unit has minimal mving parts The peratin invlves intrducing the feed material int a vertically rtating chamber. The uter wall f the chamber is s cnstructed that a cunter current air stream can pass frm the utside inwards. The rtatin f the chamber als acts as a fan, generating the cunter current air flw..

2 As the air passes thugh the chamber it cmes int cntact with the feed, which due t centrifugal frce is mving utward in the chamber. The air flw passes thugh the feed and in s ding remves all fines present in it. The fines with the air flw are circulated and depsited n the uter wall f the discharge cne. Carse material mves thrugh the rtating chamber and is discharged via an inner cne. General peratin f the unit prduces minimal dust, hwever at the start f peratin the unit generates a fair amunt f dust fr a few minutes. Test Wrk The test wrk was dne in tw stages. Primary feed was fed int the unit and a mass reductin calculated based n the units feed tns. Fines frm the test were sampled and then discarded. The primary carse prduct was retained and then used as a feed in a secnd separatin stage. It is cmmn practice t use tw separatrs in series.

3 Results As can be seen the sample cntained a high degree f fines which can be attributed t the handling and drying. The feed misture was 4% which was lwer than what wuld have been preferred. The machine is capable f perating at 10% misture with higher yields. The resulting yields are tabulated belw Primary yield 64.2 % Secnd Yield 78.7% Overall yield 50.5% The verall reductin f fines is impressive. Unlike a screening peratin the cut pint is determined by the velcity f the air stream. It is thus pssible t change the cut pint by increasing r decreasing the air velcity.

4 Cnsidering the distributins abve, the reductin in fines frm the feed t the primary prduct is very evident. The secnd reductin appears t be far less but due t n screen sizes being available in the fine ranges the prduct curves have been skewed. What in effect has happened is that the secnd separatin curve has mved dwn in the finer fractins. During the test wrk it is clear that the secnd pass cut pint was lwer than in the first pass and this wuld be in agreement with the cmment abve. A size distributin n the fines fractin will be cnducted t cnfirm the cut pint. It is als clear frm the test wrk that the unit remves fines belw 2mm with the bulk f the reductin being effected at 1.5mm 1 st pass prduct (carse)

5 1 st and 2 nd pass ultra-fines. Cnclusin Frm the test wrk it is clear that the unit is capable in the separatin f fines using a dry applicatin. Given the water and slimes dam cnstraints at Leqhbng as well as the assciated csts building slimes dams, this wuld certainly be a rute t pursue. I d nt see that the unit wuld entirely replace scrubbers in the prcess. There will always be a cmbinatin f bth. It may als be pssible t utilise the unit in the prcess during the dry winter mnths when water is at a premium. RK Prentice

6 II^ AT' IVIA I RO CAST - F?TiI?il:' - CIVILENG.LABORATORY SERVICES - VAT. Reg.N.: Reg.N.:2000/ a SANAS Accredited Testing Labratry, N. TO24S 4 HMrcT CLOSE, BRACKENDUST P.OBOX1106, BRACKENFELL Tel. : Fax : inf@matrcast.c.za TESTRESULTS KElTHPRENTICE Prject : LESOTHOMININGMATERTAL Attentin:MR K. PRENTICE YurRef OurRef DateReprted ':37824 : FOUNDATION (ASTMzD4221 INDICATOR SampleN. :C0619 MaterialDescriptin: DARK OLIVE SILTY H l en. :- Depth :- LiquidLimit(%) : 19 Clav (%) 9.6 Astm 9.6 BritishStandard 4. 8 Plasticitylndex : 5 LinearShrinkage(%) : 3.0 Pl f Whle Sample :5 P.R.A,Classificatin : A-4(2) Jenninqs sitt(%) Sand(%) Gravel(% CASAGMNDE PLASTICITYCHART ACTIVITYDIAGRAM x -9 q. c' -g (l, E c UnifiedSil Classificatir: SM-SC Classificatin SILTY S]LTY SILTY E Activity : 1.00 F(-, HeaveClassificatin : LOW GradingMdulus : 0.59 lg - Percentage(<0.002) : 5.0 MistureCntent(%) : 3.8 = d 1 0d LiquidLimit(%) Percentage (<0.002) P A R TIC LES IZED IS TR IB U TION 1 Lr,l 90 u.l (9 80 an 60 = 70 s 50 IIJ 40 If 30 = 20 :) 10 JENN CLAY ASTM CLAY BS CLAY S I L T Remarks : FORM: A6 MEDIUM SILT COARSE SILT MEDIUM MEDIUM COARSE SAMPLED ANDDELTVERED By CUSTOMER 3. 3R( ) 1.0 TechnicalSignatry:Raymndvan Niekerk MEDIUM COARSE