Increasing the efficiency of tubular supercentrifuges

Abstract

with a conical rotor [3] and experimental studies carried out atMIKhMe using a VM-100 laboratory tubular centrifuge with a 100-ram-diameter perforated rotor. Three radial baffles, 20 mm high, which engaged the entire liquid layer along the radius of the rotor, were installed in the lower section of the rotor. The angular velocity of the liquid was measured by a hydrodynamic rotating vane using stroboscopy. Even at relatively high flow rates the liquid (water) lag did not exceed 1.5-2%, while for more viscous liquids lag was practically zero. The effectiveness of accelerating liquid at the inlet zone of the rotor was verified by experimental studies of the separation of an emulsion of dibutylphthalate-aqueous glycerine using a type $45-1 laboratory supercentrifuge. The capacity of rotors with radial baffles installed only at the liquid inlet zone was the same as for rotors with impellers along the entire length of the rotor for equivalent quality separation. It was shown earlier [4] that an increase (acceleration) of liquid angular velocity over the rotor velocity occurs during the flow of prerotated liquid in the smooth outlet channel from the wall to the axis of the rotor. A simple inlet device [5] was designed to utilize the acceleration phenomenon to increase centrifugal efficiency. This consists of low radial baffles and a disc installed in the lower section of the rotor (Fig. 1). These baffles impart an angular velocity to the liquid equal to the rotor velocity and the liquid, flowing around the disc, enters the main section of the rotor close to its walls. Moving toward the outlet, the liquid, in passing from a larger to a smaller radius, retains a part of the imparted peripheral velocity, which -esults in increasing angular velocity as the liquid approaches the discharge surface. In a smooth clarifying rotor with an inlet device all the liquid moving radially is subject to greater forces, since the discharge end radius is always smaller than the radius at the inlet to the separation zone of the rotor. In a separating rotor the light fraction flow is similar to that in a clarifying rotor when the feed is accelerated. The heavy fraction flow in a separating rotor is practically not accelerated. Therefore, acceleration, which is determined by the light fraction flow, is lower in a separating than in a clarifying rotor. An analytical solution of the problem of liquid flow in a smooth cylindrical rotor with acceleration is quite difficult, since one cannot neglect any of the liquid velocity components in making approximations. Preliminary experimental studies using a type VM-100 laboratory tubular centrifuge were therefore carried out to determine the profile of liquid angular velocities when using an inlet device. The expe riments were carried out over a wide range of varying throughput u sing liquids of varying viscosities at different angular velocities, heights, and radii of rotor liquid discharge. The disc dimensions