DESCRIPTION

The flow and handling characteristics of granular materials are relevant to many process industries, particularly in the handling of powders, pellets, crystals and aggregates. The CEN-MKII introduces students to the behaviour of granular materials and is available as three units that can be purchased separately or as a complete set, as follows:

CEN-MKII-11 SOLIDS HANDLING

The equipment consists of interchangeable ball mill and Vee blender assemblies that are operated inside a protective enclosure. The enclosure, constructed from solid PVC, incorporates an electric motor with quick release coupling and manually adjustable speed control. A single-piece transparent hinged cover over the top and front of the enclosure allows access to the mill or blender and allows the user to safely observe the operation of the equipment. A safety interlock prevents the motor from operating when the cover is raised.

Ball Mill

The ball mill is a type of grinder that is used to reduce the size of solid materials using porcelain balls as the grinding medium. The ball mill can also be used to mix different powdered / granular materials. The mill supplied consists of a PVC cylindrical drum that rotates in the horizontal plane. The two ends of the drum are constructed from clear acrylic to aid viewing of the milling operation.

Vee Blender

The Vee blender is the most gentle and cost effective way to blend powdered materials together. The blender supplied consists of a shallow V shaped vessel that is constructed from clear acrylic to aid viewing of the blending / mixing operation.

CEN-MKII-12 POWDER HANDLING

The equipment consists of several different pieces of apparatus, mounted on a common backboard that is constructed from solid PVC.

Hele-Shaw Cell

The maximum stable slope of a pile of granular material is called the angle of repose and this will vary with different materials and the moisture content. The Hele-Shaw cell consists of two parallel clear acrylic plates between which the granular material is poured showing a section through the conical pile and allowing the slope to be measured. The behaviour of mixtures of solids with different grain sizes can also be observed.

Hopper Discharge

The apparatus supplied consists of a pyrex glass cylindrical hopper with a conical base that terminates in a circular outlet. A disk mounted adjacent to the outlet allows the flow of granular material through four different sizes of orifice to be tested by timed collection using a stopwatch (not supplied).

Pneumatic Conveying and Cyclone separation

It is common in industrial processing for granular materials to be moved from one location to another using compressed air as the conveyor and a cyclone to separate the material from the air stream at the final destination. The apparatus supplied provides a visual demonstration of the principles of pneumatic conveying using the cylindrical hopper as the cyclone. The low pressure created by a stream of compressed air from an external source (not supplied) through a Venturi is used to draw the granular material into the conveying system.

CEN-MKII-13 VIBRATORY SHAKER AND SIEVES

The granular materials with different particle sizes can be separated/graded using a stack of sieves with different mesh sizes mounted on a vibratory shaker. After a period of operation the different ‘fractions’ can be collected from each of the sieves and weighed using a suitable balance (supplied with CEN-MKII-00 only).

CEN-MKII-00 COMPLETE SOLIDS HANDLING STUDIES BENCH

This option consists of a CEN-MKII-11, CEN-MKII-12 and CEN-MKII-13 with the addition of a 5kg digital balance for weighing samples.

TECHNICAL SPECIFICATIONS

CEN-MKII-11

Blender

Speed – Variable from 0 to 50 RPM
Total volume – 1.2 litres
Working volume – 0.35 litres

Ball mill

Speed – Variable from 0 to 50 RPM
Total volume – 3.5 litres
Grinding medium – Porcelain balls – 3.5kg supplied

CEN-MKII-12

Hele-Shaw cell

Internal width – 20mm
Construction – Clear acrylic

Cylindrical hopper

Construction – Pyrex glass
Inside diameter – 99mm
Parallel height – 258mm
Orifice diameters – 5mm, 10mm, 15mm & 20mm

CEN-MKII-13

Vibratory shaker

Process timer – 1 to 60 mins. or continuous
Vibrations per min – 3000 at 50Hz, 3600 at 60Hz

Sieves

Construction – Brass frame with stainless steel mesh
Standards – BS410-1 / ISO3310-1
Mesh sizes – 0.25mm, 0.355mm, 0.5mm, 0.71mm, 1mm, 2mm

EXPERIMENTAL CONTENT

• CEN-MKII-11 – Solids handling

  • Reducing the size of granular material using a ball mill (comminution)
  • Dry blending using a ball mill
  • To examine the efficiency of mixing of granular materials (powder to powder) in a Vee blender

  CEN-MKII-12 – Powder handling

  • Measuring bulk density, particle density and porosity (voidage) of granular materials
  • To determine the bulk density of various solids and to examine the influence of moisture content and compaction of the bulk density
  • To determine the natural angle of repose for a variety of materials using a Hele-Shaw cell and to examine the influence of moisture content on the repose angle
  • To observe the natural stratification and agglomeration of various materials using a Hele-Shaw cell
  • To investigate how the discharge (flow) rate of solids from a hopper is related to the diameter of the issuing orifice and whether the head of material over the orifice has any effect on the flow rate
  • To demonstrate the operation of a pneumatic conveying system for solids and to show how a cyclone is used to separate the solids from the air stream

  CEN-MKII-13 – Solids handling

  • To determine and analyse the size distribution of a fixed granular solid by using a test sieve stack and a vibratory shaker

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