Improving efficiency

A column s efficiency improves with an increase in the number of theoretical plates or a decrease in the height of a theoretical plate. 

Another important characteristic of a gas chromatographic column is the thickness of the stationary phase. As shown in equation 12.25, separation efficiency improves with thinner films. The most common film thickness is 0.25 pm. Thicker films are used for highly volatile solutes, such as gases, because they have a greater capacity for retaining such solutes. Thinner films are used when separating solutes of low volatility, such as steroids. 

AlCl efficiency (based on g resin/g catalyst) can be markedly improved by polymerizing dry feeds (<10 ppm H2O) with an AlCl /anhydrous HCl system. Proceeding from 250 ppm H2O down to 10 ppm H2O, catalyst efficiency improves from 30.6 to 83.0 (26). Low levels of tertiary hydrocarbyl chlorides have been shown to gready enhance the activity of AlCl, while yielding resins with narrow molecular weight distributions relative to systems employing water or HCl (27). 

Fig. 5. Efficiency improvements in photovoltaic cells where ( ) corresponds to GaAs (—) InP ( ) CdS ( ) CdTe ( ) amorphous siUcon and...

Fig. 29. Theoretical regenerative cycle at 16 MPa (160 bar), showing reheat and efficiency improvement resulting from regeneration, where ( ) is the region removed from cycle ( ), vaporization (x x x), superheating ( " ) turbine expansion (----), heat rejection (-), reheating and ( ), regeneration.

The compressor can be driven by electric motors, gas or steam turbiaes, or internal combustion (usually diesel) engines. The compressor can also be a steam-driven ejector (Fig. 7b), which improves plant reUabiUty because of its simplicity and absence of moving parts, but also reduces its efficiency because an ejector is less efficient than a mechanical compressor. In all of the therm ally driven devices, turbiaes, engines, and the ejector mentioned hereia, the exhaust heat can be used for process efficiency improvement, or for desalination by an additional distillation plant. Figure 8 shows a flow diagram of the vertical-tube vapor compression process. 

The total world market for the use of ionophores for feed efficiency improvement in mminants is approximately 80— 90 million. The United States is the largest market. Lasalocid and monensin are the only members of this class cleared for use. Outside the United States, salinomycin is used in limited quantities. Worldwide usage is about 1.5 million kg. 

Energy Related Applications. Much research, with regard to the use of cesium in energy related processes, has resulted in Httle commercial apphcation. The heightened awareness of the environmental degradation caused by fossil fuel power stations has resulted in increased research both into efficiency improvements for existing plants and into alternative power generation (qv) methods. 

Fig. 20. Dryer efficiency improvement over time (19). To convert W/(m -K) to Btu/(h-ft -°F), multiply by 0.176.

References 1 and 2 give target excess oxygen to shoot for as a guide in heater efficiency improvement. Table 1 summarizes the recommended targets. 

Figure 4-21. Efficiency improvement with variable volume ratio screw compressors [4].

The team should be realistic about the time required to see improvements in end-of-pipe measures in most cases the pilot project success will be measured on efficiency improvements and other in-process measures alone. In this case it is important to demonstrate that all PSM and ESH issues are being managed. You should consider having a management systems audit (validation) conducted by a group independent of the integration project team. This may be done in conjunction with the next scheduled audit. This may be a corporate or divisional audit function or a consultant engaged specifically for this task. 

The pilot study is likely to use all the same Quality Management tools that were used for the integration framework development (Chapter 5). However, the limited scope of the pilot study enforces some limitations and compromises—it will not be possible to make changes outside of the department covered by the pilot. Any existing interfaces with other departments must remain the same. This will impact the design phases of the work. For example, Material Safety Data Sheets (MSDS) may currently be prepared locally, in the overall project it might be proposed to develop these centrally. However, for the pilot study it will not be possible develop the central resource so the pilot would have to continue to rely on local resources and there will be no efficiency improvement. 

The integration program was most likely supported by senior management because they saw opportunities to improve performance that is, better end-of-pipe performance and more efficient management. In most cases, improvements in end-of-pipe performance will take a considerable time to become evident. Measuring efficiency improvements and leading indicators of improved end-of-pipe performance must start as early as possible. 

Eigure 13.57 discusses in some detail the use of mobile-phase modifiers to prevent adsorption on PDVB resins. These concepts are very valuable in developing methods. Eor example, note how the observed column efficiencies improve for paraben analysis in the order of methanol < acetonitrile < 50/50 methanol/acetonitrile < THE. Eurthermore, when THE is used the chromato-... 

This act selected some dozen key residential appliances and proposed industry-tvide voluntary targets for energy efficiency improvement. If industry could not meet these volnntary targets, which averaged a 20 percent reduction in energy use compared to then-current figures, mandatory standards wonld be estab-... 

Market transformation involves coordination between large numbers of market players. It recognizes that because of returns to scale in manufacturing, uniform specifications are necessary to create the climate liccessai y to make investment in energy efficiency improvements. This coordination was devel-... 

The benefits from appliance efficiency improvements have been substantial to date. As of mid-2000. 

Energy-efficiency improvements have offset much of the increased demand from these new appliances. But demand has increased, and will continue to increase, as the combination of continually increasing disposable income and cheap energy accelerates ever more novel inventions and innovations requiring energy. 

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