Government Engg. College Valsad Branch :- Chemical Sem :- 5 th Group No. :- 6

Subject : Mechanical Operation ( 2150502 ) Topic : Size Reduction Presented By : Akash Patel : 130190105064 Ankit Patel : 130190105065 Dimple Patel : 130190105067 Divyesh Patel : 130190105068

Size Reduction Commonly Used Method For Size Reduction: Compression Impact Attrition Cutting

Principle For Size Reduction: Criteria For Size Reduction An Ideal Crusher Would, Have a large Capacity, Require a Small Power Input Per Unit Of Product; and Yield a Product of the Single Size Distribution Desired. Energy and power requirement in size reduction : The cost of power is a major expensive in crushing and grinding, so the factor that control this cost are important.

Crushing Efficiency : Empirical Relationship of Rittinger’s Law & Kick’s Law The work required in crushing is proportional to the new surface created. This is equivalent to the statement that the crushing efficiency is constant and, for a giving machine and material, is independent of the sizes of feed and product. If the sphericities F a (before size reduction) and F b (after size reduction) are equal and the machine efficiency is constant, the Rittinger’s law can be written as Where Kr is Rittinger’s Co-efficient.

Kick’s Law : the work required for crushing a given mass of material is constant for the same reduction ratio, that is the ratio of the initial particle size to the finial particle size Where P is power required, m is a feed rate of Crusher, DS2 is a average particle diameter before crushing, DS1 is average particle diameter after crushing, Kk is Kick’s Co-efficient.

Bond Crushing law & Work Index : The work required to form particles of size Dp from very large feed is proportional to the square root of the surface-to-volume ratio of the product, sp/vp. Since F s = 6/Dp, it follows that where Kb is a constant that depends on the type of machine and on the material being crushed.

The Work Index Wi, Is define as the gross energy required in KWH per tone to reduce a very large feed to such a size that 80%of the product passes a 100µ m screen. If Dp is in millimeters, P in Kw, and m in tone per hour, then If 80% of the feed passes a mesh size of Dpa millimeters and 80% of the product a mesh of Dpb millimeters, it follows that

Size Reduction Equipment : Size reduction equipment is divided into crushers, grinders, ultrafine grinders, and cutting machines. Crusher do the heavy work of breaking large pieces of solid material into small lumps. A primary crusher operates on run-of -mine material accepting anything that comes from mine face and breaking it into 150 to 250 mm lumps. A secondary crusher reduces these lumps into particles perhaps 6mm in size.  Grinders reduce crushed feed to powder. The product from an intermediate grinder might pass a 40-mesh screen; most of the product from a fine grinder would pass a 200-mesh screen with a 74m m opening. An ultrafine grinder accepts feed particles no larger than 6mm and the product size is typically 1 to 5m m. Cutters give particles of definite size and shape, 2 to 10mm in length.

The principal types of size-reduction machines are as follows: A. Crushers (coarse and fine) Jaw crushers Gyratory crushers Crushing rolls B. Grinders (intermediate and fine) Hammer mills; impactors Rolling-compression mills

Attrition mills Tumbling mills C. Ultrafine grinders Hammer mills with internal classification Fluid-energy mills Agitated mills D. Cutting machines Knife cutters; dicers; slitters