Instruments measure the height of the interface between thickened slurry at the bottom of the thickener and the clarified liquor at the top. To illustrate, if waste activated sludge, which is typically pumped from secondary tanks with a content of 0. Thickening commonly produces sludge solids concentrations in the 3% to 5% range, whereas the point at which sludge begins to have the properties of. Improving thickener operation and control by means of a. In operation, the tank is full of whatever it is you are thickening, usually a pulp of ground ore, or tailing, and. The hindered settling zone consists of a pulp of fairly uniform consistency, which is near the same solids. To start at the beginning, lets see what a thickener is. The settling velocity of the solids within the free settling zone must be greater than up flow of water released expressed as the rise rate in m3hr. In table i of the july article, improve clarifier and thickener design and operation, by joel christian pp. Clarified liquor overflows to the top and settled solids undeflow is removed from the bottom. The basic operation of the gravity thickener is described in this lesson, focusing on the theory of operation,components found in. The operator has time to correct the operation without impacting on production or damage to the thickener internals. The etaq draws supernatant from the thickener surface and pumps into the radflow feed stream to achieve the perfect level of feed dilution for optimal focculation.
Jan 26, 2015 the most common solidsliquid sl unit operation is thickening. The excellent and reliable thickening performance of the gravity drum thickener is based upon 50 years of pulp dewatering experience. Thickener with central transmissionon this product details page, you can find 1,equipments purpose. Such jumbo thickeners, when centrally driven, require for most demanding applications extra heavy duty drive heads some of which reach a continuous operating torque of 3. They concluded that the actual capacity of a continuous thickener was deter mined by some solids concentration. Bed level is a frequently installed instrument and can be installed and serviced during normal thickener operation.
Suspension is fed into one or more basins or chambers and, whilst it is passing through, the solids settle out. Lastly, particletoparticle interactions between thickener and charged surfaces of system components bring about changes in rheological properties. The ease by which thickeners are effectively dispersed or dissolved in the solvent. When a thickener is in operation, the thick underflow produced in the unit.
Deflector plate feedwell radflow feedwell perturbed area feedwell type comparison in scale model thickeners both running at 3mhr rise rate. We have fixed up a couple of diagrams on this page to show you the inside of one,and, as you see, the main elements are the tank, the rake arms, and the drive mechanism. It also offers a description of thickener operation performance based upon the proposed method. The doublenip thickener is ideal for washing and removal of ink, clay and other contaminants from a variety of furnishes. Thickening is a process where a slurry or solidliquid mixture is separated to a dense slurry containing most of the solids and an overflow of essentially clear water or liquor in leaching processes. Thickener wire the black clawson doublenip thickener is a compact thickener which can wash and thicken stock up to 15% consistency. The top thickener design approach adds innovative features to the thickener to provide a b etter process solution. If you study thickener operation a little and think about it, you can make a really interesting job out of it. Attention is given to mathematics concepts which are used in. For example, achieving solidsliquid separation in settlingthickening tanks prior to. Technology 124 consideration in urban locations where space is limited, as it can reduce the required area of subsequent treatment steps.
Have an overiew of potential advantages and disadvantages of operating a settling thickening tank. On the control of sludge level and underflow concentration in. The system is designed with ease of operation, low maintenance, cost effectiveness and thickening efficiency in mind. Outotec thickening technologies leading edge technologies for thickening and clarifying outotec is a global leader in the design, fabrication and supply of thickening and clarifying solutions for the minerals industry. The clear zone, which is the clear overflow liquor, is essentially free of solids in. In many plants, thickener problems are a regular, daytoday operational event. Thickener operation figure shows a loglog relationship between underflow concentration and unit area at various. Zone b free settling zone zone ctransition zone zone dcompression zone coe and clevenger made the assump tion that the settling rate is a unique function of concentration in the free settling mode.
Start the filter disc drive and reactor stirrer with approx. At this time the maximum underflow solids concentration of the slurry at the base of the tank is attained. Transient batch settling test data for a normal settling test free settling. At the top there is what might be called clarified area, which has a low solids concentration leaking with the supernatant liquid from the weir. The high time for thickeners was in the 60s when the metallurgical industries were booming and sizes of up to 150 m diameter were constructed. This increase in thickener throughput due to raking the. Mip thickener design the following is a short cut to designing your own thickener. Rotamat disc thickener ros2s disk thickener start up starting the thickener start the thickener in semi. The thickening process, although operated successfully. This paper presents a development of thickening theory which provides a reliable and easytouse method for determining the size of continuous thickeners from batch settling tests.
Normally, the surface should be relatively clear and free of solids and,gas. Sludge thickening is a process in which the solids concentration is increased and the total sludge volume is correspondingly decreased, but the sludge still behaves like a liquid instead of a solid. A lifting device promotes a dependable and continuous operation during plant upset conditions. Understand the fundamental mechanisms of how settling thickening tanks function. Edible thickeners are commonly used to thicken sauces, soups, and puddings without altering their taste. The belt thickener is designed for low polymer consumption, high throughput rates, and high solids content and is available in six standard sizes. In terms of thickener performance, raking the networked solids resulted in an order of magnitude increase in thickener throughput. For the rest of the time, however, thickener performance or lack of it seriously affects the rest of the operation. A well designed thickener provides storage and equalization, and reduces the costs associated with dewatering.
The 5 regimes model recognizes one clear regime free of solids at. The prs drum thickener is a simple, costefficient, and reliable filter for dewatering stock and broke, as well as for virgin and recycled fibers in a consistency range of 0. Operation of a thickener a thickener operates pretty much like a settling tank. Hydraulic power pack the reliability and ease of maintenance of hydraulics are legendary. The feed enters from the middle, are distributed radially, the settled sludge is collected from the underflow, the effluent exits over the weirs. Aldrum sludge thickener mini and midi alfa laval aldrum drum thickeners are ideal for mechanical thickening of sludge prior to digestion or dewatering, and for reducing sludge volume prior to storage or transportation. Sludge thickening an overview sciencedirect topics. Powerdrum pdr, drum thickeners for sludge thickening. Dunn 6 paste 2014, vancouver, canada compressive yield stress forces of the mud bed. A description of the sedimentation process during dynamic thickener operation a. The thickened solids are removed together with a portion of the liquid as thickened underflow.
Thickener can be adjusted to give a solids output in the range of 3% to 8% for was, or up to 16% for primary sludges. Thickeners are similar to other circular clarifiers in appearance and operation, but typically require higher operating torque and alternate sludge collection designs for optimal performance. Know the appropriate level of operations, maintenance and monitoring necessary to achieve solidsliquid separation in settling thickening tanks. Pdf understanding the thickening process researchgate. The gravity thickening design is similar to a clarifier. Chapter 3 sludge thickening thickening is a procedure used to increase the solids content of sludge by removing a portion of the liquid fraction. High speed dewatering of the stock allows efficient. Thickener definition of thickener by the free dictionary.
How a continuous thickener works as a feed stream enters the thickener, the solids settle to the bottom. Recall that gravity thickener operation varies between summer and winter due to the. In a continuously operated thickener, there are different zones of concentration. Raking within a thickener is currently performed at the base of the thickener in order to aid transport of the suspension. A wide variety of thickeners are used including conventional, deep well, paste, high rate and clarifiers which is a thickener subclass used for removing solids from turbid or very low % solids waters. Pdf the common thickener underpins the performance of most. Demonstrate an understanding of thickener operation and operator control. Application the alfa laval ash belt thickener is a gravity belt thickener used to thicken dilute sludge and slurries particularly those from biological and activated sludge processes. The aldrum drum thickener comes in two sizes, mini and midi, for capacities from 4 22 m3h 1897 gpm on the basis of.
A description of the sedimentation process during dynamic. The operation of the thickener must accommodate fluctuations control for. Thickeners in an operating mineral processing plant play a vital part in the. Start thethe washwash waterwater supplysupply continuouscontinuous washing. Three areas can be observed in the stationary operation of a thickener. Compaction of the bed is assumed to occur instantaneously and thus the density of the bed at any particular level depends only on the mass height of sediment above it. This classification permits the analysis of thickener design proce dures with a clear perspective of their applicability and limitations. Continuous thickening by an operation called sedimentation is the separation of suspended solid particles. A thickener is an equipment structure used for the continuous gravity settling sedimentation of solids in suspensions. The clear zone, which is the clear overflow liquor, is essentially free of solids in most applications. A thickening agent or thickener is a substance which can increase the viscosity of a liquid without substantially changing its other properties.
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