Economic Consideration

Due to environment and economic considerations, uses of pure sulphur trioxide in gaseous or liquid form were investigated. The main consideration was to tame the exothermic reaction and avoid unwanted co-products. 

In 1960 in India, the production of Liquid Sulphur Trioxide was less than 100 tonnes per annum (TPA). Today there are plants in India, which produce more than 100 TPD of liquid or gaseous sulphur trioxide with purity of 99-99.5 %. The total production of pure sulphur trioxide in India can be estimated as about 300,000 MTs in the year 2003. 60 % of the production is for captive use. 

The manufacture of liquid or gaseous SO3 is carried out by boiling of 25-32 % Oleum as in the case of manufacturing 65 % Oleum. The sulphur trioxide can be liquefied by condensing at 43 5 °C. Care should be taken to prevent any moisture ingress in the plant as it may cause serious operating problems. 

The liquefied SO3 is then taken to a product storage tank from which tankers are filled using Intermediate Lorry Filing Tanks. 

For any Sulphuric Acid plant, the production of liquid SO3 is more profitable and hence the objective is to maximise the production of SO3. Two important considerations for this are as follows  

The Declaration also exhorts the general principle that further economic liberalization must be implemented in a way so as to ensure that there is a clear point of responsibility for each of safety and security in a clearly identified State or other regulatory authority designated by that State for any given aircraft operation. 

The situation with regard to economic considerations has been so well stated in the First Report of the British Royal Commission on Environmental Pollution (1) that this section contains an extensive quotation from that report. 

Our survey of the activities of the Government, industry and voluntary bodies in the control of pollution discloses several issues which need further enquiry. The first and most difficult of these is how to balance the considerations which determine the levels of public and private expenditure on pollution control. Some forms of pollution bear more heavily on society than others some forms are cheaper than others to control and the public are more willing to pay for some forms of pollution control than for others. There are also short and long-term considerations in the short-term the incidence of pollution control on individual industries or categories of labor may be heavy but. . . what may appear to be the cheapest policy in the short-term may prove in the long-term to have been a false economy. 

As air pollution management moves forward, economics has a major role in reducing pollution. Multimedia considerations are forcing a blend of traditional emission reduction approaches and innovative methods for waste minimization. These efforts are directed toward full cost accounting of the life cycle of products and residuals from the manufacturing, use, and ultimate disposal of materials. 

The economics of each technology depend on the conditions and requirements of each project and must be studied on a case-by-case basis. Some of the most important considerations are as follows 

Engineering practice involves using scientific principles to design components and systems that perform reliably and satisfactorily. Another critical driving force in engineering practice is that of economics simply stated, a company or an institution must realize a profit from the products that it manufactures and sells. The engineer may 

Fnrthermore, in today s world and the global marketplace, economics does not always mean jnst the final cost of a product. Many countries have specific regulations regarding the chemicals used, CO2 emissions, and end-of-life procedures. Companies must consider a myriad of such factors. For example, in some instances, deleting toxic chemicals (which are regulated) in a product results in a cheaper fabrication process. 

Only a brief overview of important economic considerations as they apply to the materials engineer are provided. The student may want to consult references provided at the end of this chapter that address engineering economics in detail. 

The extraction costs of solids depend on several factors. One is the specific solvent ratio, kg C02/kg raw material, which is required to achieve the intended extraction result under optimised process conditions. The usual aim is to separate 85-95% of the valuable extract components a more complete extraction might not be economic. The solvent ratio is determined by the amount and the solubility of the extract to be separated from the starting material. In most cases the solvent ratio used for extraction is between 5 and 50 kg C02/kg material. 

Eor economic reasons it is best to do the extraction as fast as possible by increasing the flow rate of the supercritical gas. This is, however, limited by the pressure drop from inlet to outlet of the extractor which should not exceed 10 bar in order to avoid compaction and chaimelling. The maximal flow depends on the geometry of the extractor and on the nature and particle size of the material. Other limiting factors especially towards the end of the process are diffusion and mass transfer kinetics which require time rather than large amounts of solvent. 

For low solvent ratios and very fast extractions, e.g. if the raw material contains only 1 % of essential oil to be removed, it should be considered that the exchange of spent vs. new material including de- and re-pressurisation takes 45-90 minutes depending on the size of the extractor even if baskets are used for material handling. In such cases were the extraction time is shorter than the handling time the gas flow can be reduced for energy savings. 

A 3 X 500 litre multipurpose extraction plant which is operated 250 days, for 24 hours each day, and with a change of raw material every two weeks has a capacity of 500-600 tons of botanical material a year and the extraction expenses are estimated to be 3 ( 30%)/kg feed in total. Costs of the raw material and raw material conditioning have to be added, as well as the costs of analysis and marketing if applicable. This price can be considerably reduced to about 1/kg solid feed or less if there are no product changes, if the hardware layout is adjusted to the feed material to be processed, if the extract separation from the gas is optimised and if the scale of the installation is increased. 

A breakdown according to cost centres reveals that investment costs (interest and depreciation) are the major cost factor of production at about 40%, followed by personnel, energy, consumables, maintenance and administration expenses. A more detailed description including plant price indices, operating expenses and profitability as well as more details on supercritical extraction mechanisms and modelling of solid botanical matrices and a presentation of the Latin American scenario are given in a recent review article [11]. 

Feedback control can be enforced on the heat exchanger using only three elements transmitter, controller, and valve. Adding feedforward control requires another temperature transmitter, two flow transmitters, two square root extractors, a steam flow controller, a summer, a multiplier, and a lead lag unit nine items. Such an expense must be justified. 

Although the heat exchanger serves as a convenient demonstration of feedforward control, only in rare instances would such refined control be justified for this type of application. Management likes to see investments such as advanced control systems pay for themselves in less than two years. If improved temperature control had no value, there would be no payout. But if it prolonged the life of the exchanger, or saved steam, or reduced maintenance, it would have a measurable worth. 

Economic incentive for improved control is most likely to be found where consistent quality of a valuable product is important. Many unit operations are conducted at reduced capacity or low recovery, or use excessive amounts of utilities to ensure that quality will surpass specifications even with poor control. Naturally, the rate of payout from these sources will vary directly with the production rate of the plant. Large plants therefore encounter reduced risks. 

But the payout of a control system is as much a factor of cost as of savings. A control system can be too perfect-that is, its cost can be out of proportion to the job to be done. In the control system for the heat exchanger, for example, both flow and inlet temperature were accepted as load changes. If inlet temperature were nearly constant, or subject only to slow variations, it could be eliminated from the system as long as feedback trim were available. This would reduce cost by saving a transmitter and a summer. 

There are three principal areas where feedforward control can produce results unobtainable with any other technique  

From the chemicals revealed in 2004 as the top 12 value-added products, only a few can be considered big sellers today. 

As reported in the U.S. Department of Energy study Top Value-Added Chemicals from Biomass. Vol. II, Results of Screening for Potential Candidates from Biorefinery Lignin, the biomass production in the United States is capable of supplying all necessary raw materials for the complete chemical industry [17]. 

0-10 years Ethylene glycol, propylene glycol, iso-propanol, acetone, butylene, methyl ethyl ketone, ethyl tert-butyl ether (ethylene, vinylchloride) 

10-20 years Acrylic acid, acrylonitrile, acrylamide, e-caprolactam, ethylene, vinylchloride 20-30 years Aromatics (benzene, toluene, xylene) 

As Table 2.2.1 demonstrates, the chemical industry step by step has reached a point where fine chemicals are produced from biomass, especially by means of biotechnology. Beginning with the production of bulk chemicals, not only biotechnology but also chemocatalysis is needed to convert renewable feedstock into products in the high quantities characteristic of bulk chemicals. 

The price of crude oil can materially affect the transportation/shipment costs of raw sulfur to the manufacturing plants which, in turn, inaeases the cost of manufacturing sulfuric acid from solid/molten sulfur compared to by-product acid from ferrous/non-ferrous metallurgical plants based on sulfide ores. 

2 Options Available to Management for Improving Economic Viability 

A sulfuric acid plant generally produces technical grade acid. However, plant management can explore the markets for the following products since they can realise much higher prices and they can be produced by adding on certain equipment as outlined below. This will improve the financial profitability of the organization. 

Ashar and K.R. Golweilkar, A Practical Guide to the Manufacture of Sulfuric Acid, Oleums, and Sulfonating Agents, DOI 10.1007/978-3-319-02042-6 9, 

Before deciding whether the waste should be processed by incineration, consideration shall be given to the following factors  

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Some Economic Considerations Affecting Drug Design... 

Bromination of methane is exothermic but less exothermic than chlorination The value calculated from bond dissociation energies is AH° = -30 kJ Al though bromination of methane is energetically fa vorable economic considerations cause most of the methyl bromide prepared commercially to be made from methanol by reaction with hydrogen bromide... 

An important further constraint is the fact that economic considerations ia the constmction of deposition equipment normally lead to a preference for an ambient temperature deposition chamber. Control of deposition temperature is possible, but it adds both equipment expense and operational complexity. 

Economic Considerations. The principal economic consideration is, of course, total installed system cost, including the initial cost of the flow primary, flow secondary, and related ancillary equipment as well as material and labor required for installation. Other typical considerations are operating costs and the requirements for scheduled maintenance. An economic factor of increasing importance is the cost of disposal at the end of normal flow meter service life. This may involve meter decontamination if hazardous fluids have been measured. 

Evaluations of fuel resources or total fuel supply focus on critical economic and environmental issues as well as existence. These issues include avadabihty, utilisation patterns, environmental consequences, and related economic considerations. 

The total world consumption of energy in all forms is only about 300 EJ (300 quads) thus the earth s heat has the potential to supply all energy needs for the foreseeable future (5). Economic considerations, however, may preclude the utilisation of all but a small part of this potential resource. Only a miniscule fraction of this energy supply has been tapped. 

Mill Tailings. Recovery efficiency in ore processing is not 100%. Accumulated mill tailings contain tens of thousands of metric tons of uranium. Whereas improved techniques have been employed to recover some of this uranium, the recovery rate is still generally low, approximately 35—50%, owing to metallurgical problems and economic considerations (33). 

Increasing fuel costs and sizes of industrial and utiUty installations have forced the emphasis in economical considerations to shift to high thermal efficiency, rehabiUty, and avadabihty. The investment, operating, maintenance, transmission, insurance, and other costs as well as depreciation must also be considered, but these are often less important. 

Economic considerations in the 1990s favor recovering butadiene from by-products in the manufacture of ethylene. Butadiene is a by-product in the C4 streams from the cracking process. Depending on the feedstocks used in the production of ethylene, the yield of butadiene varies. Eor use in polymerization, the butadiene must be purified to 994-%. Cmde butadiene is separated from C and C components by distillation. Separation of butadiene from other C constituents is accomplished by salt complexing/solvent extraction. Among the solvents used commercially are acetonitrile, dimethyl acetamide, dimethylform amide, and /V-methylpyrrolidinone (13). Based on the available cmde C streams, the worldwide forecasted production is as follows 1995, 6,712,000 1996, 6,939,000 1997, 7,166,000 and 1998, 7,483,000 metric tons (14). As of January 1996, the 1995 actual total was 6,637,000 t. 

High Water Velocities. The abiUty of high water velocities to minimize fouling depends on the nature of the foulant. Clay and silt deposits are more effectively removed by high water velocities than aluminum and iron deposits, which are more tacky and form interlocking networks with other precipitates. Operation at high water velocities is not always a viable solution to clay and silt deposition because of design limitations, economic considerations, and the potential for erosion corrosion. 

Decahydrate, Pentahydrate, and Anhydrous Borax and Bulk Calcium Borates. The bulk borate products, borax decahydrate and pentahydrate, anhydrous borax, boric acid and oxide, and upgraded colemanite and ulexite, account in both toimage and monetary terms for over 99% of sales of the boron primary products industry (6). Economic considerations for all these products are highly interrelated, and most production and trade statistics do not distinguish the various products. 

Wear is an economic consideration. Wear resistance generally, but not always, is inversely related to friction level and other desirable performance charactenstics within any class of friction matenal. The objective is to provide the highest level of wear resistance in the normal use temperature range, a controlled moderate increase at elevated temperatures, and a return to the original lower wear rate when temperatures again return to normal. Contrary to common behef, maximum wear life does not require maximum physical and mechanical properties. 

Process Economics. Relative economics of various ceU culture processes depend heavily on the performance of the ceU line in a system and on the cost of raw materials, particularly the medium. Models are usuaUy developed for the various processes using productivity data obtained from smaU-scale experiments (see Pilot AND MiCROPLANTs). Often, for high value products, the process which ensures the shortest time to market may be the process of choice because of other economic criteria. This is especially tme for pharmaceuticals (qv). RehabUity concerns also often outweigh economic considerations in choosing a process for a high value product. 

This quantity is minimised when the stage is operated at a pressure ratio across the barrier corresponding to r = 0.285. Furthermore, if power were the only economic consideration, the stage would be operated at this pressure ratio. However, as the value of ris decreased from this optimum, although the cost of power is increased, the number of stages required and hence the capital cost of the plant is decreased. Thus, ia practice a compromise between these factors is made. 

An important aspect of economic consideration is the prevention of egg and egg product loss to the drain or the atmosphere, eg, a checked or cracked egg may be broken in the washer, and the contents go down the drain with the wash water. Other measurable losses during egg product production are Hsted in Table 5. 

Economic Considerations. Gum production by Ethyl Corp. is under 20 metric tons per year. Products are sold primarily for use in U.S. and N.A.T.O. naval appHcations. The materials are sold as finished goods, and thus elastomer pricing is not appropriate. Ethyl Corp. has aimounced that it will either divest or exit this business. Atochem has developed their technology and has constmcted a pilot plant to produce aryloxyphosphazenes. 

In concentrated electrolytes the electric current appHed to a stack is limited by economic considerations, the higher the current I the greater the power consumption W in accordance with the equation W = P where is the electrical resistance of the stack. In relatively dilute electrolytes the electric current that can be appHed is limited by the abflity of ions to diffuse to the membranes. This is illustrated in Eigure 4 for the case of an AX membrane. When a direct current is passed, a fraction (t 0.85-0.95) is carried by anions passing out of the membrane—solution interface region and... 

The problem presented to the designer of a gas-absorption unit usually specifies the following quantities (1) gas flow rate (2) gas composition, at least with respect to the component or components to be sorbed (3) operating pressure and allowable pressure drop across the absorber (4) minimum degree of recoverv of one or more solutes and, possibly, (5) the solvent to be employed. Items 3, 4, and 5 may be subject to economic considerations and therefore are sometimes left up to the designer. For determining the number of variables that must be specified in order to fix a unique solution for the design of an absorber one can use the same phase-rule approach described in Sec. 13 for distillation systems. 

Recovery of the solvent, sometimes by chemical means but more often by distillation, is almost always required, and the recoveiy system ordinarily is considered an integral part of the absorption-system process design. A more efficient solvent-stripping operation normally will result in a less costly absorber because of a smaller concentration of residual dissolved solute in the regenerated solvent however, this may increase the overall cost of solvent recoveiy. A more detailed discussion of these and other economic considerations is presented later in this section. 

The actual liquid-to-gas ratio (solvent-circulation rate) normally will be greater than the minimum by as much as 25 to 100 percent and may be arrived at by economic considerations as well as by judgment and experience. For example, in some packed-tower applications involving veiy soluble gases or vacuum operation, the minimum quantity of solvent needed to dissolve the solute may be insufficient to keep the packing surface thoroughly wet, leading to poor distribution of the liquid stream. 

Computation of Tower Height The required height of a gas-absorption or stripping tower depends on (1) the phase equilibria involved, (2) the specified degree of removal of the solute from the gas, and (3) the mass-transfer efficiency of the apparatus. These same considerations apply both to plate towers and to packed towers. Items 1 and 2 dictate the required number of theoretic stages (plate tower) or transfer units (packed tower). Item 3 is derived from the tray efficiency and spacing (plate tower) or from the height of one transfer unit (packed tower). Solute-removal specifications normally are derived from economic considerations. 

The main objective for calculating the number of theoretical stages (or mass-transfer units) in the design of a hquid-liquid extraction process is to evaluate the compromise between the size of the equipment, or number of contactors required, and the ratio of extraction solvent to feed flow rates required to achieve the desired transfer of mass from one phase to the other. In any mass-transfer process there can be an infinite number of combinations of flow rates, number of stages, and degrees of solute transfer. The optimum is governed by economic considerations. 

Drying Fhiidized-bed units for drying solids, particularly coal, cement, rock, and limestone, are in general acceptance. Economic-considerations make these units particularly attrac tive when large tonnages of solids are to be handled. Fuel requirements are 3.3 to 4.2 MJ/kg (1500 to 1900 Btu/lb of water removed), and total power for blowers, feeders, etc., is about 0.08 kWh/kg of water removed. The maximum-sized feed is 6 cm (IV2 in) X 0 coal. One of the major advantages of this type of dryer is the close control of conditions so that a predeterminea amount of free moisture may be left with the solids to... 

The choice of size, shape, and type of electrode is based on economic considerations and is usually determined by the characteristics of the gas and suspended matter and by mechanical considerations such as flue arrangement, the available space, and previous experience with the electrodes on similar problems. The spacing between collecting electrodes in plate-type precipitators and the pipe diameter... 

Circular Clarifiers Circular units are available in the same three basic types as single-compartment thickeners bridge, center-column, and peripheral-traction. Because of economic considerations, the bridge-supported type is limited generally to tanks less than 20 m in diameter. 

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