When selecting a ras flow rate, keep in mind the following process goals. Some of key features of the mbe high rate thickener are the hrt is designed specificallyto operate with flocculantsand hence optimises flocculant consumption. Hi rate thickeners type typical thickener dimensions they produce a wide variety of thickeners, size up to dia. Feed densities up to 55 % discharging underflow at 70 % solution could be halved no other thickener can compare. The purpose of such an override is correction for errors in the mass control signal as well as for changes. Outotec directional autodil and outotec turbodil are the first thickening systems to autodilute feed while optimizing performance and flocculant consumption. The reliability and performance of delkor thickeners means. 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. Ras flow rates often are adjusted within the aforementioned range in response to sludge blanket depths. In high rate thickener hrt designs the rise rate or solids loading will dictate the required tank diameter for any given throughput. Today the definitions of high capacity or high rate thickeners is used to describe equipment, where mineral particles are thoroughly mixed with flocculant within a feedwell and then injected uniformly into the hindered settling zone of the thickener with largely radial motion. That signal is fed to a thickener controller which also monitors mass flow of the underflow. They differ from conventional thickeners in feed well design, size and control.
The increase in flocculation efficiency realised in high rate thickeners may increase in a bulk settling rate 2 to 10 times over that obtained in a conventional thickener, thus reducing the unit area requirements by a similar factor. High torque thickener clarifier monroe environmental. As mentioned previously most of the high rate thickeners subassemblies are similar to those of conventional thickeners except for lifting devices that are not available on all units due to design restrictions. The basic design of a high rate thickener is below. The thickening process is the primary method of producing high solids. Highshear effective hases can also be the sole or primary thickener for some acrylic semigloss paints. Thickeners are beneficial in a variety of applications, including areas where water is in short supply or very expensive, recirculated water is not suitable for reuse in a plant, ponds are located on minable reserves, or ponds must be. Thickeners and clarifiers complete range of reliable and.
The advantages of sludge thickening in reducing the volume of sludge to be handled are substantial. The critical difference is the use of feed dilution and flocculation in high rate thickeners over conventional thickeners. Thickening is a procedure used to increase the solids content of sludge by removing a portion of. A wide variety of high rate thickener options are available to you, there are 181 suppliers who sells high rate thickener on, mainly located in asia. Thickener tanks, rakes and feedwells are custom designed.
Optimal control of clarifierthickeners diva portal. Rake thickener tws also offers a range of rake style, high rate thickeners which allow for minimal feed height, facilitating gravity feed from upstream cyclone based washing systems. A well operated thickener will have a solids recovery of about 95 % 3. Pdf understanding the thickening process researchgate. In developing our highrate thickeners, we draw upon decades of experience in flocculation, feed dilution, and sedimentation technology from eimco and dorr. The reliability and performance of delkor thickeners means that they are well represented throughout the world. Many of these are easily measured, while some can be difficult. Having a higher sidewall tank to provide enhanced compression effects a steeper floor slope to assist in moving solids to the discharge area a low profile rake structure combined with pickets to enhance the bed dewatering a rake drive suitable. Design of thickeners the thickening process takes place in a settling tank with longenough solids retention time. The thickener area is also required for this calculation. High torque thickener clarifier for gypsum sludge challenge. Much higher handling rate, tnd lower capital cost are obvious advantages of high. For oldstyle conventional thickeners, conversion to a high. To facilitate us in giving you a proposal we would like the.
The altaflo ultra highrate thickener is a rakeless thickener that provides mixing, flocculation and internal dilution followed by clarification and positive sludge collection and removal in a single tank. Furthermore, they are normally positioned far away from the center of the plant so to allow. Which value of impact factor is recommended in sizing a high rate thickener. We can also offer conventional thickeners, high compression thickeners and clarifiers. They are highly effective in coal refuse thickening, gold recovery, ccd circuits, copper leaching, molybdenum processing and other mining and chemical flowsheets. Control systems take care of most of the operation. Similar to both the high rate and paste thickeners, the high density thickener depends on the feedwell to create the optimal free settling characteristics. The development and use of high handling capacity of these thickeners by several to ers. Highrate thickener andritz process engineering will determine the optimum percentage of feed solids for the specific application during laboratory or pilot plant test work. Take advantage of our pioneering thickening and clarifying methods with the outotec high rate thickener, including advances such as lowprofile triangular rake arms to reduce rake torque. Thickener design configuration s usually consider the high rate or paste thickener options, with a tradeoff between capital cost and process performance. Hence, for a given sluny rate, selection of a high plint of the thickener. In high compression hct and paste pt applications the bed depth or the mass of solids in the thickener must also be selected to ensure the desired underflow density from the thickener is achieved. The key advantages of a high rate thickener over a conventional thickener are as follows.
Care needs to be taken with the nomenclature of conventional or high rate thickeners. In table i of the july article, improve clarifier and thickener design and operation, by joel christian pp. As already discussed previously thickeners are a major component in a plant layout and occupy large spaces which may be saved by introducing highrate machines. 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.
Magra highrate thickener presentation 2011 free download as powerpoint presentation. We work with you to address your specific process challenges that affect your thickener and clarifier selection. High rate thickeners high rate thickeners are designed specifically to maximise the flocculation efficiency of flocculants. Which method is superior recommended in sizing a high rate thickener. High rate solid contact clarifier reactor type full bridge with side feed. The rise rate during testing must allow for dilution systems which can result in high localised convention effects. Integration of mclanahan high rate thickeners into a plant is simple. Highdensity thickeners can be considered an intermediate case between highrate thickeners and paste thickeners. Chapter 3 sludge thickening thickening is a procedure used to increase the solids content of sludge by removing a portion of the liquid fraction. The corresponding volume may be 4 to 15 times smaller than with conventional thickeners in the same application. The top countries of suppliers are china, india, and pakistan, from which the percentage of. The highrate thickeners became popular in the mid 1980s and are relatively newcomers to the sedimentation line of equipment. Conventional thickeners, high compression thickeners and clarifiers. Laboratory testing for design of thickener circuits joseph m.
In most cases, if these requirements are met and proper test work is done, highrate thickeners may replace conventional thickeners and depending on the application they are capable of delivering a throughput that is 510 higher than with a conventional machine of equal size. The following is a short cut to designing your own thickener. The circular class of high capacity thickener is similar in general form to a conventional circular basin thickener, but cylinder diameters are limited to between 4 and 18 m see figure 1. Unlike conventional thickeners, high rate thickeners must use flocculants. Like the high rate thickener, the paste thickener uses high floccu lant dosage and optimised feed. Sizing a high rate thickener thickening, filtering, ccd. Quiescent hydraulic flows are required, as the designed rates of settling. Several iterations of area may be required to achieve a practical thickener size and pumping rate.
High rate thickener feed wells are designed to disperse flocculants thoroughly into the feed end to admit the flocculated slurry into the settling zone of the thickener without destruction of the newly formed floccules. Dorr oliver high capacity thickener with high capacity clarifier feed. The new and improved andritz interstage mixing and dilution system for ccd circuits helps to reduce the. Existing slant plate clarifiers were misapplied to the process and were unable to properly separate the dense, sticky solids contained in the liquid stream. The most common solidsliquid sl unit operation is thickening. Instrumentation and control of sedimentation equipment abstract some of the process variables that are commonly monitored on a thickener are torque, rake height, bed level, bed pressure, feed rate and density, underflow rate and density, settling rate, and overflow turbidity. John dorr patented the continuous thickener in 1906, which included a circular tank and a set of rakes. Westech hiflo highrate thickeners are used in many types of process circuits to separate liquids and solids at very high rates. During the last decade, various methods have been utilized in sizing a thickener such as coe and clevenger, talmage and fitch and wilhemnaide. Schoenbrunn 20 paste 2011, perth, australia 2 development of thickening technology thickeners were invented in the early 1900s though batch settling tanks go back much further. Units are constructed from steel and include a cylindrical top portion, an inverted cone bottom section and an angled rake system mounted on a central. High density thickeners deeper sidewall and more robust drive paste thickeners ultra high rate thickeners our units are available in a variety of sizes starting from 3ft diameter pilot scale to 300ft diameter. Our main product offeringis the high rate thickener hrt which has several special features that provide advantages over conventional thickeners.
However, fluctuation of an interface level between clear and unclear areas of the thickener can effect flow rate adjustment. A concentration of 20% solids, which might be achieved by mechanical dewatering discussed in the next section, results in a 95% reduction in volume, with resulting savings. The optimum percentage of feed solids will ensure proper flocculation and achievement of maximum fluxes tm 2 d. Highrate thickeners, or clarifiers, recover immediately reusable process water for mineral and aggregate producers, as well as environmental contractors. Sludge thickening an overview sciencedirect topics.
Grant road, suite 106 tucson, arizona 85745 introduction feed dilution or solidsliquid weight the english word sedimentation ratio is derived from the latin verb sedere size and shape of the particulate meaning to sink down. Ts and vs at sludge level and 150 cm inside the gravity thickener equipped with annulus were still very high, ranging from 23,000 to 26,000 mgl. Magra highrate thickener presentation 2011 chemical. Table 5 shows the performance of a gloss paint thickened primarily with a highshear effective nsat to obtain good highshear viscosity, and cothickened with a lowshear effective nsat for stormer consistency. High rate thickener outotec high rate thickener take advantage of our pioneering thickening and clarifying methods with the outotec high rate thickener, including advances such as lowprofile triangular rake arms to reduce rake torque. Control of a high rate thickener on gold plant tailings ausimm. The object of a control system on a high rate thickener hrt, as on a conventional thickener, is to obtain the required underflow density and overflow. Instrumentation and control of sedimentation equipment. Made in the usa gpm 12001600 17002200 20004000 specifications tank dia. Improve clarifier and thickener design and operation. The new and improved andritz interstage mixing and dilution system for ccd circuits helps to reduce the footprint and consequently cut capex while maintaining low operating costs.
A gypsum manufacturing plant was having trouble effectively treating its plant wastewater. Chemicals like chlorine ci 2 need to be added to inhibit the biological activity. R h e o l o g i c a l a s s e s s m e n t a r o a d m a p f o r p l a n t d e s i g n e r s a n d o p e r a t o r s. It has a flocculent mix chamber, inclined settling plates and automatic sludge level control system. Jan 26, 2015 the most common solidsliquid sl unit operation is thickening. The principles of flocculation have been further adapted to a new design that will thicken. Conventional thickeners are generally incorporated in heavy duty applications when the underflow density is high and substantial torques are required to convey the settled solids from the periphery to the central outlet for pumping away.
Hiflo high rate thickener westech has a worldwide installation base with application experience across the spectrum for minerals and industrial high rate. Thus the diameter of the thickener is determined by selecting a rise rate at which acceptable solids carry over is produced, as demonstrated either by continuous dynamic test or by a factor over the free settling rate. High overflow rates and shorter detention time vs conventional clarifiers resulting in smaller footprint utilises the solids contact principle plus unique controlled recirculation bringing previously formed flocs in contact with the raw water. With reference to figure 93, a sludge with 1% solids thickened to 5% results in an 80% volume reduction since 5% 120. High rate conventional high density paste deep cone raked and unraked pin bed and dynamic bed clarifiers underground settlers we use a combination of design approaches including first principles and an inhouse developed iteration design program to arrive at the optimum design configuration for the thickener unit. A series of experiments showed that gravity thickener diameter of 315 mm, recycle sludge 50% equipped with annulus could produce vs decomposition rate up to 77%. Thickeners and clarifiers complete range of reliable and cost. Equitable clarifier influent flow distribution is a critical clarifier operational performance. Factor table 2 factors affecting gravity thickening performance effect nature of the solids feed freshness of feed solids high volatile solids concentrations high hydraulic loading rates solids loading rate temperature and variation in temperature of thickener contents high solids blanket depth solids residence time mechanism and rate of solids withdrawal chemical treatment presence of. Figure 3 forceddilution devices on the feed line to a 42 m high rate thickener.
High density thickeners can come as either elevated or onground tanks according to industry preference. Control of a high rate thickener on gold plant tailings. Hydraulic loading rate and solids load are the main design parameters. The thickener controller adjusts the mass flow rate of the underflow in response to the influent mass flow signal. Andritz thickening and clarification solutions are designed to achieve the highest production rates without compromising efficiency. Highrate thickeners in developing our highrate thickeners, we draw upon decades of experience in flocculation, feed dilution, and sedimentation technology from eimco and dorroliver. The feed conditions which may vary include volumetric and mass feed rate, pulp density, particle size and particle type. The westech hiflo highrate thickener is used in many types of process circuits to separate liquids and solids at very high rates.
High rate thickener andritz process engineering will determine the optimum percentage of feed solids for the specific application during laboratory or pilot plant test work. The similar components may be seen in the following links. It is highly effective in coal refuse thickening, gold recovery, ccd circuits, copper leaching, molybdenum processing, and other mining and. To my mind in a high rate thickener, solids concentration during flocculation is a powerful tool and we have to choose the solids concentration to achieve maximum flux concentration. The revolutionary outotec high rate thickener has pioneered and redefined thickening and clarifying methods around the world. In this condition selecting a safety factor would led to overcome variation in feed properties e. Pyrometallurgy towards clean metallurgical processing 2012. To illustrate, if waste activated sludge, which is typically pumped from secondary tanks with a content of 0. Ras rate is the volume of settled sludge collected from the bottom of the secondary clarifier and returned to the influent of the upstream aeration basins.
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