Ball Mill

Group Members (A-2)

Aqeel Abbas(M08-PG01)Ayaz Mazari(M08-PG04)Sajjad Rasul Chaudhry(M08-PG12)Qaiser Abbas(M08-CE29)

OutlineIntroductionStructure Grinding mediaGrinding mechanismIndustrial applicationsExperimentationDiscussion on resultsConclusionRecommendationsQuestion & answers Session

IntroductionA ball mill is a type of grinder used to grind materials into extremely fine powder.It is an ultrafine grinder and accepts feed size of almost 6mm and the product size is typically 1-5mm.

StructureBall millis a cylindrical or conical shell rotating about a horizontal axis, Partially filled with a grinding medium such as natural flint pebbles, ceramic pellets or metallic balls.

Grinding mediaHigh density alumina (9095% alumina) or steel media is widely used in grinding operations.Non-sparking grinding media (lead, antimony, brass, or bronze) for black powder and other flammable materials.Non-contaminating and corrosion resistant media (ceramic & flint) is used for contamination-sensitive and corrosive materials.

Grinding mechanismThe material to be ground is added so that it is slightly more than fills the voids between the pellets. The shell is rotated at a suitable speed (0.5-.75 of critical speed) which will cause the pellets to cascade, thus reducing particle sizes by impact.

Grinding mechanism (cont.)

Industrial applicationsBall mill is suitable for wet as well as dry grinding and is used widely in:Cement industrySilicate productsOre processingFertilizer industryPaint manufacturingFood industry

ExperimentationObjectivesTo calculate the energy required only for grinding and also total energy.To report the results of screen analysis in the form of distribution plots.To analyze the effect of time of grinding on energy required and product size.

Experimentation (cont.)ProcedureFeed preparationRock salt of mesh size (-6 +8) and average size 2870 micronsGrinding processFor 30 minutesFor 45 minutesFor 60 minutesSieve analysisBulk properties determinationDetermination of the voidageDetermination of the bulk density

Discussion on resultsFor 30 minutes grinding:

Energy consumed for grinding = 5.75 kWh

Total energy required = 95.07 kWh

Fractional voidage = 0.6

Bulk density = 1.23 g/cm3

Bonds diameter =

Discussion on results (cont.)Fractional Distribution PlotCumulative Distribution Plot

Discussion on results (cont.)For 45 minutes grinding:

Energy consumed for grinding = 9.26 kWh

Total energy required = 141.97 kWh

Fractional voidage = 0.6

Bulk density = 1.25 g/cm3

Bonds diameter =

Discussion on results (cont.)Fractional Distribution PlotCumulative Distribution Plot

Discussion on results (cont.)For 60 minutes grinding:

Energy consumed for grinding = 13.35 kWh

Total energy required = 188.29 kWh

Fractional voidage = 0.6

Bulk density = 1.23 g/cm3

Bonds diameter =

Discussion on results (cont.)Fractional Distribution PlotCumulative Distribution Plot

Discussion on results (cont.)Energy comparison

Discussion on results (cont.)Comparison Between Bonds Diameter

ConclusionLaboratory ball mills grinding efficiency is extremely low as:A large fraction of product is of the same size as that of feed in each case.Bonds dia. of the product in each case is approximately same.More energy consumption for larger time period but still no increase in grinding efficiency.

Conclusion (cont.)Possible causes:

Mill is not rotating at suitable speed i.e(0.5-0.75) of critical speed.

Density of the grinding media is low.

RecommendationsMetallic balls (of High density material) should be used as no explosive material is ground in lab.A combination of different sized balls should be used as grinding media.A gear box or electrical speed regulator should be installed.

Thanks You For Your Patience.

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