Scaling, resource

Overall MCRs are a big step towards the ideal synthesis, which, according to Wender et al. can be measured by parameters such as the step count, overall yield, selectivity, cost, scale, resource requirements, waste stream, development time, execution time and personnel [8], The discovery of novel IMCRs are explained and several conceptually different approaches towards this goal, with an emphasis on our recent contributions in this area are shown. 

Considering that in 1970 there were 232 municipalities in the United States with populations ranging from 50,000 to 100,000, and 455 municipalities with populations ranging from 25,000 to 50,000, it appears that there are many potential users for small-scale resource recovery systems (15). The above two groups of municipalities represented a total population in 1970 of over 30 million people and probably generated close to 40,000 tons/day of MSW. 

Figure 7 The resources for the preparative task. The need to engage larger-scale resources depends on the scope of the preparative task, which can vary widely (Table 1 and Fig. 8).

Martin, AE, Small-Scale Resource Recovery Systems, Noyes Data Corporation, Park Ridge, MN, 1982. 

The problem with most quantum mechanical methods is that they scale badly. This means that, for instance, a calculation for twice as large a molecule does not require twice as much computer time and resources (this would be linear scaling), but rather 2" times as much, where n varies between about 3 for DFT calculations to 4 for Hartree-Fock and very large numbers for ab-initio techniques with explicit treatment of electron correlation. Thus, the size of the molecules that we can treat with conventional methods is limited. Linear scaling methods have been developed for ab-initio, DFT and semi-empirical methods, but only the latter are currently able to treat complete enzymes. There are two different approaches available. 

Product innovation absorbs considerable resources in the fine chemicals industry, in part because of the shorter life cycles of fine chemicals as compared to commodities. Consequently, research and development (R D) plays an important role. The main task of R D in fine chemicals is scaling-up lab processes, as described, eg, in the ORAC data bank or as provided by the customers, so that the processes can be transferred to pilot plants (see Pilot PLANTS AND microplants) and subsequently to industrial-scale production. Thus the R D department of a fine chemicals manufacturer typically is divided into a laboratory or process research section and a development section, the latter absorbing the Hon s share of the R D budget, which typically accounts for 5 to 10% of sales. Support functions include the analytical services, engineering, maintenance, and Hbrary. 

Pilot-plant start-up is different from principal process plant start because of the smaller scale of the unit, smaller resources committed, lack of advance start-up planning, and limited experience with the pilot-plant process and operation. 

Economy of time and resources dictate using the smallest sized faciHty possible to assure that projected larger scale performance is within tolerable levels of risk and uncertainty. Minimum sizes of such laboratory and pilot units often are set by operabiHty factors not directly involving internal reactor features. These include feed and product transfer line diameters, inventory control in feed and product separation systems, and preheat and temperature maintenance requirements. Most of these extraneous factors favor large units. Large industrial plants can be operated with high service factors for years, whereas it is not unusual for pilot units to operate at sustained conditions for only days or even hours. 

The future success of recyling largely depends on how governments respond to the problems described above. There are serious questions as to whether it is wise for the government to interefere further in recycling markets. Indeed, in many instances, collection programs should be scaled back to collect only those materials for which there is demand. Moreover, recycling rates should not be the proxy for how well society utilizes its resources. The... 

Not all of the gas is wasted. About 300 MW of electricity is generated from landfills. A variety of electric generation systems have been employed by a small number of developers. Most projects use simple technology and are small (2—10 MW). However, an EPRI study has estimated that landfill gas resources in the United States could support 6,000 MW of generation if utilized in 2-MW-sized carbonate fuel cells. Constmction on the world s first utihty-scale direct carbonate fuel cell demonstration was begun in California. If successful, EPRI estimates that precommercial 3-MW plants based on this design could become available by the end of this decade at an installed cost of 17,000/kW. 

Membrane Chemistry Three chemical families dominate the RO-NF membrane industry. Many other products are made on a small scale, and the field continues to attract significant R D resources. But three types command most of the market. 

Today resource limitations have caused the United States Environmental Protection Agency (USEPA) to reassess schedules for new rules. A 1987 USEPA survey indicated there were approximately 202,000 public water systems in the United States. About 29 percent of these were community water systems, which serve approximately 90 percent of the population. Of the 58,908 community systems that serve about 226 million people, 51,552 were classified as "small" or "very small." Each of these systems at an average serves a population of fewer than 3300 people. The total population served by these systems is approximately 25 million people. These figures provide us with a magnitude of scale in meeting drinking water demands in the United States. Compliance with drinking water standards is not... 

Medical surveillance programs range from support contracts with local hospitals or physicians to full-scale on-site occupational health organizations that include physicians, nurses, and technicians who are employed by prime contractors. The option selected depends on the size of the project, the nature of the hazards involved, the capabilities of local facilities, and the resources available. 

CBA relies heavily on the costs of environmental impacts. Some impacts may be easily expressed in monetary values, like crop loss or even increased morbidity among people. Others, like impact on biodiversity and the depletion of natural resources, are more difficult to describe in terms of monetary values. Large time scales and global impacts also complicate the methodology and confuse the understanding of the results. Some of the environmental consequences of today s activities appear only after several hundred or thousand yeats. Even low interest rates tend to diminish these types of impact, even if they are very large. 

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