Specification of equipment

Industrial chemical processes are determined by recipe and production route. The recipe is the specification of a sequence of processing steps for the transformation of raw materials into the desired product(s). Specifications include quantity and quality of raw materials, composition of feeds, sequence of additions to the reaction zone, rate of dosing, temperature-time dependencies, pressures, etc. The production route also includes the specification of equipment in which processing steps are performed. 

It is imperative that the processor utilize every advantage available to ensure success since the specification of equipment in an extrusion line also affects resin usage and labor. Thus, it is always more cost effective in the long run to design and install an extrusion line that (1) has a maximum rate capability of at least 25% more than the expected maximum rate, and (2) has a properly engineered line (that might have a higher capital cost) to achieve maximum profitability. 

The density of the liquid is very high at around 1.2 kg/litre conqtared to light fliel oil at around 0.85 kg/litre. This means that the liquid has about 42% of the energy content of fuel oil on a weight basis, but 61% on a volumetric basis. This has inplications on the design and specification of equipment such as pumps. 

In some countries the ambient temperature can vary significantly over a 24-hour period, and its average daily value can also vary widely over a 12-month period. The power plant designer should therefore ascertain the minimum and maximum ambient temperatures that apply to the plant. The maximum value will be used frequently in the sizing and specification of equipment. The minimum value will seldom be used, but it is very important when the sizing of generators and their prime movers are being examined. 

The aim here is simply to present an overview of the various features on offer. The range of instruments extends from differential scanning calorimeters in a suitcase for on-site use to spatially resolved micro-thermal analysis equipment for samples as minute as 2 x 2 fim. Between these rather extreme examples there is a wide choice of commercial DTA and DSC equipment which allows samples to be studied at temperatures ranging from — 150°C to about 1600°C. For higher temperature measurements (above 1600°C) the equipment becomes increasingly more specialised. The detailed specification of equipment is often difficult (sometimes impossible ) to decipher - there appears to be no common practice between manufacturers. Information can best be obtained by raising questions directly with the manufacturers. Even so, hands-on experience is to be recommended when choosing equipment. 

The conditions for commencing flow in a confined situation are completely different from those at which flow then continues. Power requirements are also sensitive to apparently minor features of the design. The specification of equipment and the selection of a suitable drive unit must, therefore, be carefully matched. Only in the most straightforward applications, such as screw conveyors, are well-proven formulas published relative to a wide range of duties and different bulk products handled. 

In processes consisting of several units (e.g., chemical reactors, equipment for mixing/purification, autoclaves, fermenters) the analysis gets more complex, but the material balance is still a must and, as we will explain later, conducted on each unit, thus enabling the following steps in the design and specification of equipment. 

GX Severe >2000 Only specially designed and packaged equipment would be expected to survive. Specification of equipment in this class is a matter of negotiation between user and supplier. 

Flooding correlations for packed liquid extractors have been developed in a manner similar to those used for gas/liquid systems. Just like the air/water system used to evaluate the maximum hydraulic capacity for a gas absorption operation, the capacities in liquid-liquid systems are based on hydraulic flow rates for immiscible solvents in the absence of any mass transfer. As has been stated, the transfer of a solute can change the properties of the extract and raffinate phases in a significant manner. For this reason, it may be that flooding has been experienced in commercial operations at flow rates well below those predicted by the flooding correlation. Clearly, more research is needed to explain the effect of mass transfer on the capacity of a liquid extractor. Nevertheless, the application of a widely used flooding correlation will be reviewed. However, the designer should consider the limitations of this correlation and apply appropriate safety factors in the specification of equipment. 

Specifications of equipment for purchase with design requirements. 

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