Economic limitations

The operating pressure is kept low to reduce air consumption. To obtain high capacities, the disks spin fairly fast (up to 2 or 3 rpm) and this leads to thin cakes which give Htde resistance to air flow the only way to keep this flow within economical limits is to reduce the air pressure in the vessel. 

Synthesis. Exploratory research has produced a wide variety of odorants based on natural stmctures, chemicals analogous to naturals, and synthetic materials derived from available raw materials and economical processing. As in most areas of the chemical industry, the search for new and useful substances is made difficult by the many materials that have been patented and successfully commercialized (4). In the search for new aroma chemicals, many new materials are prepared for screening each year. Chemists who perform this work are involved in a creative exercise that takes its direction from the commercial sector in terms of desirable odor types and specific performance needs. Because of economic limitations, considerations of raw material costs and available processing methods may play a role eady in the exploratory work. 

Special conditions affect the choice of thickener or clarifier type. For example, if a unit must be covered to conser ve heat, the bridge-supported type may be more economical up to about 45 m (150 ft) in diameter, although 30 m (100 ft) may be the economic limit for an uncovered unit. 

Metallic Palladium films pass H9 readily, especially above 300°C. Ot for this separation is extremely high, and H9 produced by purification through certain Pd alloy membranes is uniquely pure. Pd alloys are used to overcome the ciystalline instability of pure Pd during heat-ing-coohng cycles. Economics limit this membrane to high-purity apphcations. 

The Break Even Stripping Ratio (BESR) or the economic limit for surface operations in comparison with underground mining is therefore determined as ... 

Changing the wettability of reservoir rock surfaces from oil-wet to water-wet, increases the permeability of the formation to oil, decreases the permeability to water, decreases mobility ratio, increases sweep efficiency, increases the flowing fraction of oil at every saturation, and increases oil recovery at the economic limit of the waterflood. 

There is a practical economical limit to the size of enclosed ground flares. If the maximum effluent relief rate exceeds 100 tons/h, the feasibility of an enclosed ground flare becomes questionable, and at 500 tons/h, it is impractical (AIChE-CCPS, 1998). 

When as a result of the decomposition of the steam by the fuel mass, the temperature of the latter has fallen below the economic limit, the steam supply is shut off, and the air blast started again to raise the fuel temperature. When the temperature is again suitable, the air is shut ofif and steam again passed through the fuel, but on this occasion downwards from the steam supply S, die water gas passing out by the outlet I. 

Spare parts for common components such as heaters for barrels, transfer lines, and dies, thermocouples, pressure transducers, drive belts, and fuses should be kept in stock. Since the goal is to keep the line operational at all times, keeping these low-cost but necessary components in stock can reduce the amount of downtime due to simple failures. For operations where the resin is abrasive or corrosive, a spare screw should be kept in stock. As the screw wears in the extruder and the performance decreases beyond an economic limit, then the screw should be replaced with the spare screw and the worn screw should be sent to a screw manufacturer for refurbishment. 

The initial requirement in the development of a solvent extraction process for the recovery or separation of metals from an aqueous solution is knowledge of the solution composition, pH, temperature, and flow rate. Both pH and temperature can be adjusted, within certain economic limits, before feeding to the solvent extraction circuit, but only in a few cases can the leaching or dissolution conditions be dictated by the extraction process. Consequently, no serious development work on the extraction process can be carried out before the leaching conditions or the type of feed solution are established. 

The thermal cycle efficiency of a Brayton cycle can be increased by adding more intercoolers, compressors, reheaters, turbines, and regeneration. However, there is an economic limit to the number of stages of intercoolers, compressors, reheaters, and turbines. 

Obviously this objective is not unique to North Sea production platforms. Barring certain peculiar circumstances it is always desirable, within economic limits, to maximize the recovered barrels of stock tank oil per unit volume of well stream production. This has the effect of increasing the ratio of barrels of stock tank oil to barrels of reservoir oil, which is defined as the formation volume factor. 

From this equation It is evident that the parameters which control the falling velocity of water particle are the droplet else, density difference and viscosity of oil. Application of heat will reduce the oil gravity as well as viscosity. However, heat will cause loss of lighter crude fractions. Thus, adjusting the crude viscosity and gravity hy heat has economic limits. Therefore, the most practical approach would be to attempt to increase the particle size. 

The benefits of enhanced reaction rate and improved selectivity have to be seen in relation to the costs of working at higher pressures. The technical/economical limit for standard materials is somewhere around 300 bar. 

Nevertheless, there are natural or economic limits to the amount of tailoring possible by use of chemical or physical processes applied to the products per se. There comes a time when these processes can no longer yield products that meet the exacting requirements of the commercial and consumer equipment in which they are to be used. Or there comes a time when these exacting requirements can be met more economically in other ways. Nor does the situation ever become static it continuously becomes more critical as technological improvements in combustion equipment (including the development of new types) intensify old problems or create new ones. 

In distillation the water closest to the heating surface is hottest and it is there that calcium sulfate is least soluble. Thus, calcium sulfate deposits, forming an adhering film that increases the thermal resistance and decreases the heat flux. The scale is continuously deposited until the tubes are cleaned or become plugged. For scale deposition the local concentration must be at least saturated in calcium sulfate. At 100° C. this occurs in concentrated sea water at a concentration 3.1 times that of ordinary sea water. A plant has been successfully operated continuously without calcium sulfate deposition by taking only part of the available water from the sea water, so that the liquid in the evaporator is never more than 1.8 times the concentration of sea water and the wall temperature is below about 250° F. ( ). This imposes technical and economic limitations on distillation plants. Similar considerations hold for plants distilling brackish water containing calcium sulfate. 

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