Solid material costs

Economic evaluations of waste-reduction options should involve a comparison of operating costs to illustrate where cost savings would accrue. For example, a waste-reduction measure that reduces the amount of raw material lost down the drain during the process will reduce raw-material costs. Raw-material substitution or process changes may reduce the amount of solid waste that must be transported offsite, reducing the transport costs for waste disposal. 

Example 2.9 A solid polyethylene beam is 10 mm thick and IS mm wide. If it is to be replaced with a sandwich section with solid polyethylene in the two outer skins and polyethylene foam (density = 200 kg/m ) in the centre, calculate the dimensions of the sandwich beam if it is to have optimum stiffness at the same weight as the solid beam. If the foam material costs 20% more than the solid material, calculate the increase or decrease in cost of the sandwich beam. 

Wall sections in foam moulding are thicker than in solid material. Longer cycle times can therefore be expected due to both the wall thickness and the low thermal conductivity of the cellular material. In contrast, however, the injection pressures in foam moulding are low when compared with conventional injection moulding. This means that less clamping force is needed per unit area of moulding and mould costs are less because lower strength mould materials may be used. 

The optimum design of a hydrocyclone for a given function depends upon reconciling a number of conflicting factors and reference should be made to specialist publications. Because it is simple in construction and has no moving parts, maintenance costs are low. The chief problem arises from the abrasive effect of the solids materials of construction, such as polyurethane, show less wear than metals and ceramics. 

A number of zeolite syntheses result in incomplete conversion of all of the gel components to solid zeolite. In many cases the reactant Si/Al ratio is different than that of the product (usually higher), resulting in a silicate solution remaining behind. At the industrial scale this silicate solution is often recycled to minimize waste and raw material cost [34—36]. 

The question of choosing a PFTR or a CSTR will occur throughout this book. From the preceding arguments it is clear that the PFTR usuaUy requires a smaller reactor volume for a given conversion, but even here the CSTR may be preferred because it may have lower material cost (pipe is more expensive than a pot). We will later see other situations where a CSTR is clearly preferred, for example, in some situations to maximize reaction selectivity, in most nonisothermal reactors, and in polymerization processes where plugging a tube with overpolymerized solid polymer could be disastrous. 

In fact, production of solid materials of high quality and controlled properties (specific polymorphs) with important added value, could transform the traditional brine-disposal cost in a potentially new profitable market reducing, moreover, the environmental problems of the brine disposal [10]. 

A pre-condition for Hydrogen use is to solve the problem of its storage and circulation under acceptable conditions, taking into account also the costs of such operations. Hydrogen can be stored in the form of gas, cryogenic liquid or adsorbed gas in solid materials. The most ordinary type of storage involves confining the... 

Chlorinated by-products of ethylene oxychlorination typically include 1,1,2-trichloroethane chloral [75-87-6] (trichloroacetaldehyde) trichloroethylene [7901-6] 1,1-dichloroethane cis- and 1,2-dichloroethylenes [156-59-2 and 156-60-5] 1,1-dichloroethylene [75-35-4] (vinylidene chloride) 2-chloroethanol [107-07-3] ethyl chloride vinyl chloride mono-, di-, tri-, and tetrachloromethanes (methyl chloride [74-87-3], methylene chloride [75-09-2], chloroform, and carbon tetrachloride [56-23-5]) and higher boiling compounds. The production of these compounds should be minimized to lower raw material costs, lessen the task of EDC purification, prevent fouling in the pyrolysis reactor, and minimize by-product handling and disposal. Of particular concern is chloral, because it polymerizes in the presence of strong acids. Chloral must be removed to prevent the formation of solids which can foul and clog operating lines and controls (78). 

Figure 24.23 shows the layout of a typical suspension mix plant in which all the major suspension ingredients are received as solids. This is presently a popular mode of operation. Raw material costs for such a plant often are less than for bulk blending because nongran-ular materials can be used. Piping for the optional addition of phosphoric acid and ammonia is shown. Such addition develops heat, which hastens the disintegration of some solids. 

Oxidizer. The major component, by weight and volume, of composite solid propellants is the oxidizer. By far, the most important oxidizer used is AP, a crystalline solid material ground to exacting particle size distributions. This chemical possesses the desirable properties of high density, good thermal stability, and oxygen availability, and relatively low reactivity and cost. Properties of AP and several other materials that are used as oxidizers are summarized in Table 37.5. 

Catalysis has little direet impaet on transportation costs for a given produet. However eatalysis can be used to eonvert gaseous and solid materials that are expensive to transport into eheaper to transport liquids. Examples of this inelude the eonversion of methane in remote locations, via synthesis gas, into methanol or liquid hydroearbons [Sections 4.1.2 and 4.7]. 

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