1.0     INTRODUCTION

          Propeller agitator mixing is one of the most common operations carried out in chemical, processing and allied industries.  The terms “mixing” is applied to the processes used to reduce the degree of non uniformity or gradual of a property in a system such as concentration, viscosity, temperature and so on.

          Mixing is achieved by moving material from one region to  another. It may be of interests simply as a means of achieving a desired degree of homogeneity or it may be used two proote heat undergoing a chemical reaction.

          At the outset I t is useful to consider some common examples of problems encountered in industrial mixing operations, since this will nto only reveal the ubiquitous nature of the process but will also provide an appreciation of some of the associated.  Difficulties.  Several attempts have been made to classify mixing problems, and for example “REAVELL” used as a criterion for mixing of powders, the flowability of the final products, HARNEY et al based their classification on the phases present, that is liquid – liquid, solid – liquid and so on.  This is probably the most useful description of mixing as it allows the adoption of a unified approach to the problems encountered in a range of industries.

          The term agitation is applied to a variety of operations differing in the degree of homogeneity of the mixed material.  In chemical engineering, it is conventional to treat agitation and multi purpose operations for which the principles of equipment design and operation can be stated generally, such operations in agitation like crystallization, Ion exchange and colliding are advanced of this study and construction.

          In most homes, industries and chemical operations, two or more substances are required to be mixed for users demand, in mixing as a unit operation, the substance is fed into the vessel or mixing tank containing the agitator in either one form, liquid, solid or gas.  The product obtained should either be homogenous or heterogeneous depending on demand or desired product.

          The selection of a particular agitator for a particular purpose requirement, the flow properties of the process fluid, equipment cost and the construction material required must be considered.  Ideally, the equipment chosen should be that which has the lowest cost but meets all process requirement.  In a given problem, the agitator given must handle the material when it is in it’s worst condition and may not be so effective as other design during other parts of mixing cycle.  As with other equipments, the choice of an agitator for heavy material is always a compromise and arbitrary.

          Liquids are agitated for a number of purpose, depending on the objective of the processing step, soe of the purpose includes

1.                 Promoting heat transfer between the liquid and a coil or jacket

2.                 Blending immiscible liquids, for example, methyl alcohol and water.

3.                 Dispensing a second liquid, immiscible wt h the first to form an emulsion or suspension of fine drops

4.                 Suspending solid particles

5.                 Dispersing a gas through the liquid in the form of small bubbles.

A typical application of propeller agitator is in mixing of high viscosity liquids or solid in solids.  Most factories produce and products using blended liquids like in the confectionery industries, liquids food drinks like canned juices as well as canned and bottled drinks.

Many a times, one agitator serves several purposes at the same time, as in the catalytic hydrogenation of a liquid, in a hydrogenation vessel, the hydrogen gas is dispersed through the liquid in which solid particles of catalyst are suspended, with the heat of reaction simultaneously removed by a cooling coil or jacket.

1.1     OBJECTIVE OF THE PROJECT

          The objective of the project is to construct a portable propeller agitator with high efficiency and durability, which will be used for good mixing operation in smalls scale industries or in the laboratories and other applications such as domestic and pharmaceutical industries.

          The preferred choice of raw material of the construction is mild steel because of it’s excellent properties which included high resistance to corrosion, machineability, ductility, malleability, it resistance to react with the material or reactant when agitating as any reaction between the vessel and the material to be mixed will affect the product.  Moreover, it is cheap and available.

          The dimensions of the propeller agitator are length of handle = 320mm, diameter of gear teeth = 100mm, thickness of shaft = 20mm, thickness of gear = 12mm, size of blade = 50mm x 100mm, blade diameter = 63mm, inside diameter of pump = 12mm outside diameter of pump = 20mm, shaft height = 470mm, vessel diameter = 340mm and vessel height = 560mm.