Where the units are being used for organics removal, such as in soils washing or lignite removal, the overflow will contain larger organics with the finer sand (equivalent weight particulates).
The denser underflow stream is typically directly fed to a Dewatering Screen. The dart style valve is fully rubber lined and features spring-to-close actuation in the event of loss of air (preventing the vessel from emptying).ĭilute Hydrosizer™ overflow containing the lighter /smaller fractions is typically dewatered using Hydrocyclones or Separators and further dewatered using Dewatering Screens. McLanahan’s latest development is a bespoke valve, which features a linear open/close profile for more accurate performance. While these have been functional, there are disadvantages associated with matching open area with required underflow capacity and, due to their non-linearity, greater difficulty tuning the control loop.
Typical of Hydrosizers™ of the past, underflow valves have been of a non-linear design such as pinch or butterfly design. On loss of water flow at shut down, the nozzles close and, along with a non-return valve, serve to prevent sand from entering into the teeter water piping.
Specially designed teeter water nozzles open when pressurised and provide an evenly distributed spray of water into the Hydrosizer™. There are no screen cloths to maintain, the unit automatically compensates for changes in feed rate, and the only moving part is the underflow valve.Ī valve and a flow meter is supplied with every unit so teeter water can be adjusted easily, either manually or automatically. All the operator has to do is set the water injection rate. The Hydrosizer™ control monitors the classification environment and adjusts the underflow valve to maintain a consistent performance. The McLanahan Hydrosizer™ maintains separation automatically through a simple PID control loop. Maintenance of this bed is easily done through a simple set of controls. This phenomenon slows down the settling rates of particles and allows them to be more critically reviewed as either a member of the coarse or fine fraction. Within this teetered bed, solids settle through the tank in an environment known as hindered settling. This accumulation is described as a teetered or fluidised bed, similar in many ways to quick sand.
Particles that are near the size of separation, being neither massive enough to migrate to the underflow cone nor small enough to be lifted out, begin to accumulate in the separation chamber. Coarser and denser particles pass downward through this current and are collected in the underflow cone to await discharge. As particles in the feed meet this rising current of water, finer and less dense fractions are lifted out and swept over the overflow weir. This water injection causes an upward rising current of water that flows over the peripheral weir and is collected in the overflow launder. Simultaneously, process water is injected through an array of pipes located near the bottom of the separation chamber. This phenomenon is the result of a fluidised (teetering) bed of particles or dense media created in the vertical-walled separation zone.įeed material (typically Hydrocyclone underflow) enters the top of the unit via a central feed-well. To make its sharp wet classification, Hydrosizers™ use the hindered settling principle.
0 kommentar(er)
