Continuous-operation centrifuge drum for concentrating suspended solids

#The present invention relates to a continuous-operation centrifuge drum for concentrating suspended solids, wherein the concentrated solids are conveyed through channels from a solids space in the outer region of the drum into a chamber toward the center of the drum, from which the concentrated solids are continuously extracted.

#A centrifuge drum of this type is known, for example from German Pat. No. 2 701 624. The amount of solids extracted from the drum is regulated by varying the flow cross-section of the channels by means of valves provided with flexible-tube diaphragms and positioned therein. Since, however, diaphragms of this type are sensitive to abrasive solids, they cannot be employed in many applications. If the valves are exploited to regulate the concentration of the extracted solids, the controls technology involved will be relatively expensive because the viscosity of the extracted solids must be measured and a proportional fluid pressure exerted on the diaphragms from outside.

#The object of the present invention is to provide a centrifuge drum for concentrating suspended solids wherein the amount of extracted solids can be automatically regulated in the drum as a function of viscosity.

#FIG. 1 is a partial section through the drum according to the invention,

#FIG. 2 illustrates the unribbed annular space positioned in the insert,

#FIG. 3 illustrates a drum with two communicating unribbed annular spaces,

#Channels 3, with constrictions 4, extend through the lid 2 of the centrifuge drum 1 illustrated in FIG. 1. Channels 3 extend from a solids space 5 and open into an unribbed annular space 6 at its outer surface 7. Unribbed annular space 6 communicates at its inner surface 8 with a central chamber 10 through an annular gap 9. A skimmer 11 is accommodated in central chamber 10. Another skimmer 13, accommodated in a chamber 12, leads to an outflow line 14. A pressure-regulation valve 15 is positioned in line 14. A product feed 16 opens into an intake chamber 17.

#The centrifugate conveyed through product feed 16 is clarified in drum 1, and the precipitated solids are collected in solids space 5, whence they are conveyed into unribbed annular space 6 through channels 3 and constrictions 4. As long as the solids concentrate is fluid, it will increase its peripheral velocity as accelerated at constrictions 4 as it travels radially in through unribbed annular space 6, generating a relatively high flow resistance in the space. Thus the cross-section of constrictions 4 can be relatively large, and the constrictions can even be eliminated, in which case the basal volume of the diverted solids will be established by the inside diameter of unribbed annular space 6. As the viscosity of the solids increases, the increased friction on the walls of the unribbed annular space 6 will impose the inwardly decreasing peripheral speed on the solids, whereupon the fluid pressure at constrictions 4 will be decreased and the volume of solids diverted will be increased. This leads again to a decrease in the concentration of solids and hence in viscosity. As the viscosity of the solids increases, the volume diverted will automatically increase, whereas, as the viscosity decreases, the volume diverted will automatically decrease. This corresponds to the known regulating behavior of conventional controls positioned outside the drum.

#FIG. 2 shows unribbed annular space 6 mounted in a replaceable insert 18, making it possible to adapt the drum to various conditions more rapidly. At constant diameters the radial extension of unribbed annular space 6 can easily be varied, if another annular space 20 provided with ribs 19 is positioned upstream, by rotating the ribs backward for example. Constrictions 4 and 4' can also be oriented in insert 18 along different limbs 21 and 22, to which different channels 3 and 3' lead, and the insert can be rotated to align either the constrictions 4 on outer limb 21 or the constrictions 4' on inner limb 22 with their associated channels 3 and 3', releasing them for extracting the solids through.