Agitation is important because maximum efficiency and energy saving are constant goals in chemical engineering.

In the relentless race for efficiency in which every company must compete, a careful analysis of needs and a correct assignment of priorities are essential if investments are to be optimised. Often, for a small marginal cost, a new agitator, carefully chosen, will make a big contribution to the improved performance of an existing system (quality, efficiency and productivity). In the same way, it is possible to reduce electricity consumption of a new or existing installation, kilowatt by kilowatt, agitator by agitator. In today's environment, these economies cannot be neglected, moreover, extending equipment life and reducing maintenance procedures are a constant matters.
Everyday, the science of agitation is evolving. This evolution is giving designers and builders a better selection of agitation equipment not only for common liquids, but also for liquids with special rheological properties (rheopectic, thixotropic, pseudo-plastic or viscoelastic liquids or solutions).
A good definition of the problem is the beginning of a good solution. To achieve this, close collaboration between user and designer-builder is the golden rule. The experience of both partners plays a key role in setting specifications which are ambitious but achievable: mixing time, coefficients of transfer (mass and heat), rate of renewal, size of crystals, distribution of granules, level of homogeneity. A good specification should also define a suitable test programme, run on a pilot scale by the user or by the builder.
A good solution must meet all the requirements (homogenisation, keeping in suspension, gas-liquid or gas-liquid-solid reaction, heat transfer) taking into account special characteristics of each job: chemical kinetics, the effect on micro-organisms, abrasive action, corrosion.

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Milton Roy Mixing (ex-Robin Industries) is based in Avon Cedex, France. www.miltonroymixing.com