Bypass, classifiers

Analysis of this type of classifier (15) suggests that the sharpness iadex is between 0.5 and 0.6, consistent with calculated results, because the degree of turbulence can be high ia these devices (16). A DSF Dorr classifier (1.8 m x 7 m), operating at 19 strokes per minute and having a weir depth of 100 cm and a slope of 19.4 cm/m, produced a cut size equal to 240 p.m, a sharpness iadex of 0.5, and an apparent bypass of approximately 26% when the water spht was 26% (15). 

Centrifuges. Sohd-bowl centrifuges have been proposed as an alternative classifying device to hydrocyclones for cut sizes below 10 pm. The results appear to be mixed (21). In one apphcation, where the cut size was 6.5 pm and the sharpness index 0.7, there was essentially no apparent bypass. However, in other apphcations operating at higher feed concentrations, the cut size ranged from 5—8 pm, but the sharpness index was between 0.3—0.5 and the apparent bypass between 10—30% or higher (22). Smaller cut sizes have also been reported (23). 

The yield is the sum of column 5 multipfled by (1 — a). Thus, if the operating apparent bypass of the classifier is 0.3, then the yield is 24.65% or 0.2465. The coarse mass values can be calculated by subtracting the fine mass values multipfled by (1 — a) from the feed interval values. The coarse interval values are then calculated by dividing the coarse mass values by the sum of the coarse mass values. 

Etibank is the sole producer of boron minerals and derivatives in Turkey, which is second in production only to the United States. The open-pit Kirka mine in the Eskisehir Province is the only source of Turkish sodium borate ore. A tincal concentrate is produced from ore that has been blasted and carried in tmcks to the concentration plant. The ore is screened and cmshed to reduce it to —100 mm and then hammer milled to —25 mm. The stockpiled material is further milled and screened to 6 mm. A fraction of +1 mm (+18 mesh, U.S. Standard) is washed and classified to remove fine clay. Clay is removed from the —1 mm faction bypassing it through cyclones and then through a classifier. This material is centrifuged and combined with the washed + 1 mm faction to produce a final product which is a —6 mm concentrate having 6—8 wt % moisture and 32% 2 3 1987 production was... 

Disc Two well-mixed tanks in series with classified exit Well-mixed tank and plug-flow in series with fines bypass Sastry Loftus [Pmc. 5th Int. Symp. Agglom., IChemE, 623 (1989)1 Ennis, Personal communication (1986)... 

Type A HE is induced by acute liver failure, Type B results from portal-systemic bypass without intrinsic liver disease, and Type C occurs with cirrhosis. HE may be classified as episodic, persistent, or minimal. 

Transfer optics The interface of the IR beam with the sample, especially in a classified hazardous environment, can be a major challenge. Gas samples are not too difficult although it is important to pay attention to the corrosivity of the gases, relative to the windows and any internal optics, as with a folded path length cell. Liquids offer different challenges. For on-line applications users prefer to minimize the use of valves, bypass streams and auxiliary pumps, especially over long distances between the stream and the analyzer. At times there is a benefit to sample the stream either directly or as close as possible... 

The bacterial toxins responsible for toxic shock syndrome are proteins that are classified as superantigens. These proteins bypass some of the steps normally involved in antigen-mediated immune response, thereby activating 5 to 30% of the T cell population, compared to 0.01 to 0.1% activated by conventional antigens. The consequence of the huge numbers of activated T cells is release of cytokines that cause capillaries to leak, resulting in many of the symptoms of the syndrome. 

A Safe Operating Procedure developed to create a uniform method to ensure that appropriate steps are taken prior to bypassing or removing an alarm, instrument, or shutdown system from service is offered. This procedure can provide an effective way of communicating the status of an impaired instrument. The procedure has been in use for over five years. It assumes that all instrumentation has been classified into three priorities. 

The other type of classifier inefficiency is apparent bypass, a. If, because of mutual interference or other reasons, some of the feed material bypasses the separation and reports to either the fine or the coarse streams, then a certain percentage of one of the product streams will have the same particle size distribution as the feed materiaL Both the apparent bypass and the sharpness index dictate the performance of classifiers. 

The effects of bypass on size selectivity are shown in Figure 4.15. Bypass reporting to the fine stream changes curve b to curve c. Bj ass reporting to the coarse stream moves from curve b to curve c. Comminution of the particles in a classifier will give rise to a size selectivity curve such as d. 

Analysis of various tj s of industrial classifiers has led to the observation that the sharpness index is essentially constemt for a classifier (with a fixed geometrical configuration) over its normal operating range. Assuming that bypass is minimal, only two things affect the size distribution of the fine stream the size distribution of the feed and the cut size. Hence, if the size distribution of the feed is constant, only the cut size (c 5o) will affect the size distribution of the fines. Bypass can be minimized by proper design and operation of the classifier. 

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