As long as thickening area demand is not controlling, this costs nothing. On the basis of the currently used Coe and Oevenger model of compression, they would not therefore be expected to increase compression capacity. 31 shows a typical unit, long used in water treatment, that does have a flocculation compartment. Just how much has, at this time, to be determined by piloting. As noted earlier, such designs become impractical in large diameters. This is what is observed experimentally. The unit size will then increase with increased underflow recirculation. Learn more about managing your data and your rights. Since the solids are fully flocculated, there is no retention time demand, and since the floe structure is well-formed, it has a high settling rate. Via G. Cespi, 2 61032 Rosciano di Fano, ITALY, Copyright 2020 COGEDE srl. However, we know the model is faulty. If the boundary is not level, the film of clarified liquid is squeezed by hydrostatic forces along the boundary in a The internal sludge recirculation schemes embodied in the designs discussed above tend not to break down floccules existing in the settled sludges. High Rate thickener with central drive unit. Figure 34 shows an older design using the same principle. The principles of particulate clarification are treated more fully under the section on classification.). High rate Thickener are used to concentrate as much as possible the solid in the bottom of the Thickener. Where and to the extent that removals are governed by settling rates, such baffles increase the capacity of a space into which they are introduced. Recycled floccules are maintained in suspension by gentle agitation and augment the rate at which feed fines are collected. Laboratory Testing Consulting & Engineering Process Equipment. Whether a locally formed stream of clarified liquid remixes to some extent or is joined in the overflow by some streaming elements of unclarified flow, depends upon flow patterns. ANDRITZ process engineering will determine the optimum percentage of feed solids for the specific application during laboratory or pilot plant test work. The purpose is to increase the rate at which new feed solids are incorporated into the floe structure and/or to form a floe structure firm enough so that fines do not segregate from it in the feed layer. +33 (0) 1 77 92 99 79. Solutions you can count on in the chemicals industry, Unique flat, counter-current circuit design, Three levels of protection against overloading, Fully automated, including automatic load sensing for consistent underflow quality, Reversible or variable speed hydraulic units, Copper/cobalt, nickel, gold, uranium, coal, lead, zinc, iron ore, chrome, titanium sands. They tie up less suspension in inventory, which may be of economic value if either solids or liquid are valuable. Structural design of engineered tanks aimed at weight reduction (static and dynamic F.E.M.
This design, however, relies on a sloping bottom to discharge solids. 33 the new feed is jetted into the thickening zone in such a way as to mix it thoroughly with the surrounding settled solids. They do not increase its volume, so do not increase solids removal where it is governed by flocculation rate and hence by retention time. Instrumentation & Control aimed at process optimization and Opex OPEX reduction. They probably cannot produce and handle underflows at as high a solids content as conventional thickeners, and underflows must be much more closely controlled to prevent build-up and overflow of solids. High rate thickeners - Diemme Filtration. In small sizes they are portable. Whether you need spare parts, rentals, local service, repairs, upgrades, or modernization of your equipment. There are two basic types of high rate thickener units: They contain space-cutting baffles that intercept settling paths at many levels. Obviously such recycling increases the load on the thickener. New feed (plus flocculants and/or reactants) is introduced through orifices along hollow arms rotating below the top of a sludge blanket. It was originally conceived that the new- feed would be filtered through the sludge blanket, and in a loose sort of way it may be so explained, but if the new feed were not dispersed and locally mixed into the sludge blanket, it would channel to the top in low- density currents. Where the mixed feed reflocculates quickly enough to avoid segregation of fines in the feed zone, external recirculation should accomplish much of what internal circulation does, with less cumbersome mechanical configurations. For clarification, the long tube test should predict removals, but note that the long tube is now very short because the vertical height of any flow compartment is small. If the centrifuge overflow is then recycled to thickener feed, the recirculating load of fines which forms may in some cases become large enough to overload the thickener. Moreover our High rate thickener have a system that allow us to measure continuously the effort on the rake and by a system of hydraulic jacks to move up and down the thickeners Rake in order to have constant concentration thickener output and to avoid any mechanical problem on the mechanism. Their applicability for thickening follows a similar pattern. The last technology of high rate thickener or thickener plant developed by Cogede allow to optimize the consumption of polyelectrolyte by special feed well design. (This has happened a number of times in industrial practice.) Solids from settling compartment A return to a flocculating chamber B where they are mixed with new feed. Remixing settled solids into new feed increases the thickening load and hence the area demand for thickening. Thus the initial cost of a unit, installed, filled, and ready to go, may be low. From Monday to Friday: 9am-6pm Feed solids concentration is the single most important variable affecting the sedimentation properties of given slurry. Industry's new products straight in your inbox! Powered by Gostec snc. Diemme Filtrations High Rate thickeners are an advanced product derived from our extensive experience in solid/liquid separation applications, such as mining, chemical, waste water and more, coupled with our technical research to continuously improve and optimize sedimentation in filtration plants. Industry Plaza: products, services and industrial equipment. Thus lamina type units would seem best suited for particulate clarification. Solids recirculation units comprise many types. A solid-bowl centrifuge, for example, acts in almost all cases as a classifier, in that coarse solids segregate to some degree from fines in the machine, and the fines report selectively to the overflow. So the mechanism is probably just recirculation and mixing of sludge solids into the various feed streams to bring them into the line settling regime. Circulation may be external, internal, or may consist of mixing new feed locally into the thickening zone, as in certain types of sludge blanket filtration units. Figure 32 shows a competing design, similar inprinciple but different in configuration. At some amount of recirculation thickening, area demand will become larger than that for clarification. The increase is usually insignificant, but if the subsequent processing selectively returns fines, an augmented recirculating load of fines will form. List your products and services to enhance your web presence and receive qualified enquiries. The hydrodynamically rough handling of the underflow stream undoubtedly damages the existing floe structure. A suitable fraction of the underflow stream is diverted into an external mixing chamber and/or flocculation compartment where it is mixed with new feed. In the design of Fig. In applying long tube data, any areas filled with compressing solids would have to be subtracted from total overflow area to obtain that available for clarification. Flow patterns in a lamina-type settler are complex because of density effects. Unit Operations Handbook: Volume 2by John J. McKetta Jr. Complete LAB & SITE testing (flocculants type and dosage selection, static and dynamic test, rheology test, sensitivity analysis). So if the use of a solid-bowl centrifuge or any other classifying device is being considered for dewatering thickener underflow, or if there is selective recycle of solids to the thickener from any process source, a detailed material balance for all solids size fractions should be calculated to determine what the steady-state operating conditions will be. INTERNET USERS ALSO CONSULTED ON THE CATEGORY SLUDGE DIGESTION, Check out all the products from category sludge digestion. (This is settlement unaccompanied by flocculation. Proper efficiency factors to use with this type of unit are not generally known, but might be expected to be low. WASTEWATER & SLURRY TREATMENT PLANTS, THICKENERS, FILTER PRESS. Where, as in cane sugar juices, the line settling rate of the mixed feed exceeds the overflow rate necessary for simple clarification of unmixed feed, such a unit produces clean overflow at higher ratein some cases much higher. In this way the thickener plant is able to guarantee automatically constant settling performance.