On plant

Hydrogen selenide in a concentration of 1.5 ppm is intolerable to man. Selenium occurs in some solid in amounts sufficient to produce serious effects on animals feeding on plants, such as locoweed, grown in such soils. Exposure to selenium compounds (as Se) in air should not exceed 0.2 mg/m3 (8-hour time-weighted average - 40-hour week). 

Specification tests are performed on plant streams once or twice per worker shift, or even more often if necessary, to assure the continuing quahty of the product. The tests are also performed on a sample from an outgoing shipment, and a sample of the shipment is usually retained for checking on possible subsequent contamination. Tests on specialty types of acetone may require sophisticated instmments, eg, mass spectrometry for isotopicaHy labeled acetone. 

The price differential at which coal becomes competitive with gas depends on plant size and the cost of capital, but based on estimates by the International Energy Agency (21) the required price ratio for gas to coal in North America falls into the range of 3.1 to 3.7 on an equivalent energy basis ( /MJ). Current prices give a gas/coal cost ratio nearer 1.5 to 2.0. As a result, all projected new methanol capacity is based on natural gas or heavy oil except for the proposed coal-based plant in China. 

Environmental impact studies on NE have been performed. Although undiluted NE inhibits seed growth, no effect on plant growth was observed when exposed to 6, 000 ppm-min of NE and only minor effects were observed at the 60, 000 ppm-min exposure level (41). Exposure of microbial populations to 25% NE in air for seven hours showed normal growth. NE is not an o2one-depleting gas (20). 

Ice formation is both beneficial and detrimental. Benefits, which include the strengthening of food stmctures and the removal of free moisture, are often outweighed by deleterious effects that ice crystal formation may have on plant cell walls in fmits and vegetable products preserved by freezing. Ice crystal formation can result in partial dehydration of the tissue surrounding the ice crystal and the freeze concentration of potential reactants. Ice crystals mechanically dismpt cell stmctures and increase the concentration of cell electrolytes which can result in the chemical denaturation of proteins. Other quaHty losses can also occur (12). 

Pseudomonas. These gram-aegative bacteria are a diverse group of microbes that iahabit plants, water, and sod. Pseudomonads are metabohcaHy versatile, capable of carrying out chemical transformations, mineralization of organic compounds, and colonization on plant roots (16). The use of Pseudomonads strains ia the clean up of chemical wastes and od spills has drawn considerable attention. 

The 1990 price of anhydrous HCl was about 330/t the 1993 price of 20° Bh (31.4% HCl) was about 73/t (77). Prices depend on plant location, transportation burden, and on-site demand. These factors all influence the selling price significantly, sometimes carrying zero or negative value. 

The viscosity of the spray oil, as measured by the Saybolt test, also determines its safety on plants. Other properties being equal, oils of low viscosity ate safer to use on foHage than those of high viscosity. For dormant sprays on deciduous trees, oils with viscosities between 100 and 200 Saybolt universal seconds (SUs) at 37.8°C are considered satisfactory. A lower range is often used in colder and a higher range in warmer areas. 

In the past, commodity chemicals were generally priced on the basis of ROl. Capital cost was the most critical item, and those elements that ate related to capital cost were the principal factors in the selling price (excluding taw material cost in some cases). On this basis, a satisfactory ROl resulted in acceptable values for other criteria such as ROS or sales margin. Many analysts favor ROS as a benchmark for comparison because it is up to date and simple and because it is increasingly difficult to determine a tme ROl based on what profits might be on plants built under indation and expensive capital and constmction costs. 

Values depend on plant-specific design and operating procedures for steam plant. 

A relatively small number of studies have reported on the effects of cumene on plants, fish, and other organisms. Studies of the effects of cumene on fresh and saltwater fish indicate the lowest reported toxic concentration (LC q) for fishes was 20 to 30 mg/L (18). The solubiUty of cumene is about 50 mg/L (19). Among invertebrates, the lowest reported concentration that was toxic to test organisms was 0.012 mg/L after 18 hours (20). The only available data on the effect of cumene on aquatic plants indicate that the photosynthesis of several species was inhibited at concentrations from 9 to 21 mg/L (19). 

As microprocessor-based controls displaced hardwired electronic and pneumatic controls, the impac t on plant safety has definitely been positive. When automated procedures replace manual procedures for routine operations, the probability of human errors leading to hazardous situations is lowered. The enhanced capability for presenting information to the process operators in a timely manner and in the most meaningful form increases the operator s awareness of the current conditions in the process. Process operators are expected to exercise due diligence in the supervision of the process, and timely recognition of an abnormal situation reduces the likelihood that the situation will progress to the hazardous state. Figure 8-88 depicts the layers of safety protection in a typical chemical jdant. 

Distribution costs depend on plant location, physical state of the material (whether liquid, gas, or sohd), nature of the material (whether corrosive, explosive, flammable, perishable, or toxic), freight rates, and labor costs. Distribution costs may be affected by any of the following new methods of materials handling, safety regulations, productivity agreements, wage rates, transportation systems, storage systems, quality, losses, and seasonal effects. 

Analysis of Drying Data Tests on Plant Dryers. 12-34... 

ANALYSIS OF DRYING DATA TESTS ON PLANT DRYERS... 

Tests on plant-scale dryers are usually carried out to obtain design data for a specific material, to select a suitable diyer type, or to check present performance of an existing diyer with the objective of determining its capacity potential. In these tests overall performance data are obtained and the results used to make heat and material balances and to estimate overall drying rates or heat-transfer coefficients. 

Two-fluid nozzles do not operate efficiently at high capacities and consequently are not used widely on plant-size spray diyers. Their chief advantage is that they operate at relatively low pressure, the hq-uid being 0 to 400 kPa/m" pressure, while the atomizing fluid is usually no more than 700 kPa/m" pressure. The atomizing fluid may be steam or air. Two-fluid nozzles nave been employed for the dispersion of thick pastes and filter cakes not previously capable of being handled in ordinaiy atomizers [Baran, Ind. Eng. Chem., 56(10), 34-36 (1964) andTurba, Brit. Chem. Eng., 9(7), 457-460 (1964)]. 

Costs based on plant processing 26,105 Mg/d (28,776 US ton/d) of Ilbnois No. 6 coal. Source Direct Coal Liquefaction Baseline Design and Systems Analysis, prepared by Bechtel and Amoco under DOE contract no. DE-AC22-90PC89857, March 1993. 

Symposium on Earthquake Effects on Plant and Equipment (Vols I and II), Organized by BHEL energy system group Hyderabad, India, and Indian Society of Earthquake Technology, Roorkee, India (1984). 

Another way of interpreting absolute risk estimates is through the use of benchmarks or goals. Consider a company that operates 50 chemical process facilities. It is determined (through other, purely qualitative means) that Plant A has exhibited acceptable safety performance over the years. A QRA is performed on Plant A, and the absolute estimates are established as calibration points, or benchmarks, for the rest of the firm s facilities. Over the years, QRAs are performed on other facilities to aid in making decisions about safety maintenance and improvement. As these studies are completed, the results are carefully scrutinized against the benchmark facility. The frequency/consequence estimates are not the only results compared—the lists of major risk contributors, the statistical risk importance of safety systems, and other types of QRA results are also compared. As more and more facility results are accumulated, resources are allocated to any plant areas that are out of line with respect to the benchmark facility. 

When the power defieit is eovered by an eleetrie motor, the initial motor load may be a multiple of its normal power output beeause the expander is unable to eontribute any power at startup. Depending on plant design and startup requirements, a motor power of 50%-75% of the rated eompressor power is suffieient for startup purposes. Careful engineering studies are always appropriate in this ease. 

Depending on plant size, the hot gas expander is supplied either with (Figure 4-40) or without variable inlet guide vanes. Adjustment features are not required in small plants where throughput at eonstant or full-load eapaeity is antieipated. 

The effects of air pollution on plants range from subtle to catastrophic, as shown in Fig. 8-1. Historically, these effects have been classified as... 

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