Acceptance efficiency

Small solid particles, present in dust and grit emissions, have very low settling velocities (Table 4.4) The collection efficiencies of simple cyclones are tlierefore, as shown in Figure 17.3, relatively low. Fabric filters, electrostatic precipitators or wet scrubbers may be required to remove particles <5 pm in size with an acceptable efficiency. Therefore the cost of pollution control inevitably increases when dealing with particle size distributions skewed towards the lower end. 

Provide an acceptable efficiency of collection for the air contaminant involved ... 

A tray is in balance when it operates wth acceptable efficiency under conditions at or very near those of design. 

A tray is flexible when it operates with acceptable efficiency under conditions which deviate significandy from those established for design. The usual changes affecting flexibility are vapor and/or liquid loading. A tray may operate down to 50% and up to 120% of vapor load, and down to 15% and up to 130% of liquid load and still be efficient. Beyond these points its efficiency may fall off, and the flexible limits of the tray would be established. 

A tray is stable when it can operate with acceptable efficiencies under conditions that fluctuate, pulse, or surge, developing unsteady conditions. This type of operation is difficult to anticipate in design, and most trays will not operate long without showing loss in efficiency. 

The pressure drop of these trays is usually quite low. They can be operated at an effective bubbling condition wnth acceptable efficiencies and low pressure drops. For more efficient operation the clear liquid height on the tray appears to be. similar to the sieve tray, i.e., 1.5-2-in. minimum. This is peculiar to each system, and some operate at 1 in. with as good an efficiency as when a 2-in. is used. When data is not available, 2 in. is recommended as a median design point. 

Many plants do not consider machine or systems efficiency as part of the maintenance responsibility. However, machinery that is not operating within acceptable efficiency parameters severely limits the productivity of many plants. Therefore a comprehensive predictive maintenance program should include routine monitoring of process parameters. 

A scalable algorithm is one that will execute with acceptable efficiency on large numbers of processors. One way to assess this attribute is through construction of a model for the execution of the code that combines costs from all parts of the algorithm. The result is a function such as... 

Natural-gas fueled fuel cells are more efficient than the conventional hydro-gen-oxygen (air) fuel cells since they reduce capital costs and simplify the process by eliminating the external source of hydrogen supply. Acceptable efficiencies also have been found for these processes. With the developing technology, new electrode materials and catalytic materials could be used to further improve this technique of alternate electricity generation from natural gas [28]. 

Demonstrated stable operation for >1200 hours in small reversible stacks at acceptable efficiency. 

Not aU the available methods extract the mercury species from solid samples (soil, sediment or biological material) with acceptable efficiency. The procedure giving the best recovery for methyl mercury from soil (95 4%) is the distillation method, and from fish tissue it is alkaline digestion using tetramethylammonium hydroxide with focused microwave power (95 to 105%). There is no standardized method to assess the extraction efficiency of a particular method, but several options are described in the subchapter on extraction efficiencies. 

The gaseous explosions give efficiencies between about 60 and 80%, which conflicts with the accepted efficiency of nearer 20%, but no reason is advanced at present for the... 

Two usual definitions of partial efficiency are the "rejection efficiency" and the "acceptance efficiency" or recovery index. The rejection efficiency, relevant in classification of powders, is considered as the mass of coarse product greater than the cut size (the limiting size dividing a particle size distribution into fines and coarse fractions) related to the mass of feed solids greater than the same cut size. According to this, in Equation 10.21 Xj would represent the cut size (X50) and X2 would be the maximum particle size in the feed. The rejection efficiency E, can be expressed as a function of cumulative oversize (coarse) percentage and the cumulative percentage of coarse fraction in the feed F, as... 

With regard to the acceptance efficiency, it may be considered opposite to the rejection efficiency in the sense that the undersized particles are those considered as the reference for defining such efficiency. In this case, Xi in Equation 10.21 would represent zero, while X2 would be taken as the cut point. The acceptance efficiency can be expressed as a function of cumulative undersized (fines) percentage Ff and the cumulative percentage of fines fraction in the feed F, as... 

A special case of acceptance efficiency is the one known as screen or sieve efficiency E, which assumes a perfectly formed screen so that the underflow is free from particles larger than the equivalent screen diameter x. According to this criterion. Equation 10.23 can be reexpressed as... 

Energy (ML / P), overall screen efficiency Acceptance efficiency Coating efficiency... 

Although experimental values of E can be obtained from the test data via the grade efficiency curve (from which X50 is determined—see chapter 3, Efficiency of Separation ), industrialists prefer to measure the fraction of solids unsedimented (1 — Ei) and plot this against the ratio of the measured flow rate and the calculated E value (which can be varied by changing the speed of rotation). This curve, which often comes out as a straight line on log-probability paper, is naturally a function of the size distribution of the feed but can be used to find the ratio of Q/IL for acceptable efficiency with the given feed material. Extrapolation of the data over the linear parts of the graph can be made with caution. 

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