Decanter scroll discharge machine

One of the main reasons why decanter centrifiiges are becoming more popular for apphcations which were not beheved practicable until recently is the development of shear-resistant flocculants. This has opened up the market of thickening biological sludges, which without these special flocculants would lead to very finely broken up particles of material only shghtly heavier than water and, therefore, very difficult to dewater. Other applications are discussed below. 

Aplication Feed cone %wt Cake cone % wt Centrate clarity, ppm Polymer dosage, kgt Capacity, m n 

The capacity varies with the size of the machine enq)loyed the values given in Table 8.2 represent the range in feed flow rates that may be expected om commercial machines. 

Some modem decanter centrifuge designs are claimed to eliminate the need for polymer flocculant, notably in the water treatment industries, but centrate quality usually suffers. During flocculation the very fine particles can become adsorbed on the larger agglomerates, enhancing centrate quality. Some polymers marketed for use in centrifuges claim to increase the solid content of the cake. 

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Decanter centrifuges, for process applications, are typically solid bowl scroll-discharge machines, capable of continuous sohd and centrate discharge. They are ideally suited to handling high feed solids concentrations and delivering dry solid products. They are generally able to convey the soft solids often encountered in the pharmaceutical and fermentation industries. 

At one end of the bowl a conical section is attached giving a smaller diameter. The liquid runs round the helical scroll and is discharged over weir plates fitted at the parallel end of the bowl. The solids are moved by the conveying action of the helical scroll up the gentle slope of the conical section, out of the liquid and finally out of the machine. Decanters of this type are known as solid bowl decanters. 

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