Characteristics of costs

The high C/H ratio for heavy fuels and their high levels of contaminants such as sulfur, water, and sediment, tend to reduce their NHV which can reach as low as 40,000 kJ/kg by comparison to the 42,500 kJ/kg for a conventional home-heating oil. This characteristic is not found in the specifications, but it is a main factor in price negotiations for fuels in terms of cost per ton. Therefore it is subject to frequent verification. 

Calculational methods. Associating the analysis, the knowledge of the property-structure relationships, and the calculation methods has made possible the replacement of costly and arduous test methods by quicker tests whose results are linked by calculations to the characteristic under study. Some examples are the cetane number, in some cases, the octane number, or the characteristics of LPG (refer to Chapter 3). 

Most characteristics of amphiphilic systems are associated with the alteration of the interfacial stnicture by the amphiphile. Addition of amphiphiles might reduce the free-energy costs by a dramatic factor (up to 10 dyn cm in the oil/water/amphiphile mixture). Adding amphiphiles to a solution or a mixture often leads to the fomiation of a microenuilsion or spatially ordered phases. In many aspects these systems can be conceived as an assembly of internal interfaces. The interfaces might separate oil and water in a ternary mixture or they might be amphiphilic bilayers in... 

The most desirable characteristics of a solvent for recrystalhsation are (a) a high solvent power for the substance to be purified at elevated temperatures and a comparatively low solvent power at the laboratory temperature or below (6) it should dissolve the impurities readily or to only a very small extent (c) it should yield well-formed crystals of the purified compound and (d) it must be capable of easy removal from the crystals of the purified compound, i.e., possess a relatively low boiling point. It is assumed, of course, that the solvent does not react chemically with the substance to be purified. If two or more solvents appear to be equally suitable for the recrystallisation, the final selection will depend upon such factors as ease of manipulation, inflammability and cost. 

We have not indicated the reagents employed in the reactions by which ethylene and propene are converted to the compounds shown Because of patent requirements different companies often use different processes Although the processes may be different they share the common characteristic of being extremely efficient The industrial chemist faces the challenge of producing valuable materials at low cost Success in the industrial environment re quires both an understanding of chemistry and an... 

Both melamine—formaldehyde (MF) and resorcinol—formaldehyde (RF) foUowed the eadier developments of phenol—, and urea—formaldehyde. Melamine has a more complex stmcture than urea and is also more expensive. Melamine-base resins requite heat to cure, produce colorless gluelines, and are much more water-resistant than urea resins but stiU are not quite waterproof. Because of melamine s similarity to urea, it is often used in fairly small amounts with urea to produce melamine—urea—formaldehyde (MUF) resins. Thus, the improved characteristics of melamine can be combined with the economy of urea to provide an improved adhesive at a moderate increase in cost. The improvement is roughly proportional to the amount of melamine used the range of addition may be from 5 to 35%, with 5—10% most common. 

Compressed Ga.s PropeIIa.nts. The compressed gas propellants, so named because they are gaseous in conventional aerosol containers, are nontoxic, nonflammable, low in cost, and very inert. When used in aerosols, however, the pressure in the container drops as the contents are depleted. Although the problem is lessened when the contents are materials in which the propellant is somewhat soluble, this pressure drop may cause changes in the rate and characteristics of the aerosol spray. A compressed gas aerosol system is illustrated in Figure 3. 

Comparing two or more complex alternatives is more difficult than examining equipment capacity or first cost. Characteristics of alternatives should be weighted for relative importance and measured on a common scale to aEow proper evaluation. Many characteristics such as first cost, capacity, space requirement, and annual energy use can be measured objectively and used for system comparisons. Experience has shown that items such as maintenance expense, component life, and downtime can also be rehably estimated. Other factors, eg, system maintainabEity, flexibEity, and comfort, are more arbitrary. 

Aqueous media, such as emulsion, suspension, and dispersion polymerization, are by far the most widely used in the acryUc fiber industry. Water acts as a convenient heat-transfer and cooling medium and the polymer is easily recovered by filtration or centrifugation. Fiber producers that use aqueous solutions of thiocyanate or zinc chloride as the solvent for the polymer have an additional benefit. In such cases the reaction medium can be converted directiy to dope to save the costs of polymer recovery. Aqueous emulsions are less common. This type of process is used primarily for modacryUc compositions, such as Dynel. Even in such processes the emulsifier is used at very low levels, giving a polymerization medium with characteristics of both a suspension and a tme emulsion. 

The third characteristic of interest grows directly from the first, ie, the high thermal conductance of the heat pipe can make possible the physical separation of the heat source and the heat consumer (heat sink). Heat pipes >100 m in length have been constmcted and shown to behave predictably (3). Separation of source and sink is especially important in those appHcations in which chemical incompatibilities exist. For example, it may be necessary to inject heat into a reaction vessel. The lowest cost source of heat may be combustion of hydrocarbon fuels. However, contact with an open flame or with the combustion products might jeopardize the desired reaction process. In such a case it might be feasible to carry heat from the flame through the wall of the reaction vessel by use of a heat pipe. 

Combinatorial. Combinatorial methods express the synthesis problem as a traditional optimization problem which can only be solved using powerful techniques that have been known for some time. These may use total network cost direcdy as an objective function but do not exploit the special characteristics of heat-exchange networks in obtaining a solution. Much of the early work in heat-exchange network synthesis was based on exhaustive search or combinatorial development of networks. This work has not proven useful because for only a typical ten-process-stream example problem the alternative sets of feasible matches are cal.55 x 10 without stream spHtting. 

Evolutionary. The evolutionary approach to network development starts with a good network developed by some alternative means and proceeds to change it into an optimal network from the standpoint of cost. The success of any evolutionary method depends gteatiy on the starting network. Evolutionary methods ate specific to starting network characteristics and ate usually matched with the method used to develop the initial network, eg, TI followed by ED. There ate two extremes for possible starting networks. 

For substrates of WORM and EOD(PCR) disks the industry in the future wants polymers that have a markedly improved resistance to heat softening compared to BPA-PC and, if possible, a lower water absorption and lower birefringence, but otherwise maintain the good characteristics in toughness, production, and cost (194). This goal is being approached in different ways further modification of BPA-PC, newly developed polymers, improvement of the processing characteristics of uv-curable cross-linked polymers, and development of special copolymers and polymer blends, eg,... 

The concentration of most metals in the earth s cmst is very low, and even for abundant elements such as aluminum and iron, extraction from common rock is not economically feasible. An ore is a metallic deposit from which the metal can be economically extracted. The amount of valuable metal in the ore is the tenor, or ore grade, usually given as the wt % of metal or oxide. Eor precious metals, the tenor is given in grams per metric ton or troy ounces per avoirdupois short ton (2000 pounds). The tenor and the type of metallic compounds are the main characteristics of an ore. The economic feasibihty of ore processing, however, depends also on the nature, location, and size of the deposit the availabihty and cost of a suitable extraction process and the market price of the metal. 

ASTM D883 defines a filler as "...a relatively inert material added to a plastic to modify its strength, permanence, working properties, or other quaHties or to lower costs." EiHers (qv) that modify the properties and characteristics of epoxies are employed in epoxy resins for a variety of reasons. Then principal functions are to control viscosity, reduce shrinkage and the coefficient of thermal expansion, effect a cost reduction, and color the epoxy resins. 

Proprietary blend formulations based on polysulfone, polyethersulfone, and polyphenylsulfone are sold commercially by Amoco Corporation to meet various end use requirements. The blends based on polysulfone are sold under the MINDEL trademark. A glass fiber-reinforced blend based on PES is offered under the trade name RADEL AG-360. This offers most of the performance characteristics of 30% glass fiber-reinforced polyethersulfone but at a lower cost. Two blend product lines are offered based on PPSF. These are designated as the RADEL R-4000 and R-7000 series of products. The former is a lower cost alternative to RADEL R PPSF homopolymer offering most of the performance attributes unique to PPSF. The R-7000 series of resins have been formulated for use in aircraft interiors for civil air transport. They exhibit a very high degree of resistance to flammabihty and smoke release. 

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