Slurry dewatering

Improved grinding media and linings, roller mills, high-efficiency classifiers, wet process slurry Dewatering with filter presses... 

Mixing tank Slurry Bioreactors Slurry Dewatering... 

The phosphate concentration in the tailings is upgraded to a level adequate for commercial exploitation through removal of the nonphosphate sand particles by flotation [32], in which the silica solids are selectively coated with an amine and floated off following a slurry dewatering and sulfuric acid treatment step. The commercial quality, kiln-dried phosphate rock product is sold directly as fertilizer, processed to normal superphosphate or triple superphosphate, or burned in electric furnaces to produce elemental phosphorus or phosphoric acid, as described in Section 9.2. 

Our research on responsive gels has been carried out with applications in separations and drug delivery in mind. Except for the slurry dewatering process described in the next section, however, we have not focused on the development of specific applications. One novel idea which we pursued, however, was the me of temperature-sensitive PNIPAAm for the preparative gel electrophoresis, discussed in Sect. 7.2. 

The slurry dewatering experiments were simple in principle but required great care to complete with accuracy. 10 x 4 PNIPAAm gels were synthesized as... 

Fig. 21. Coal slurry dewatering capability by gel extraction using thermally responsive 10x4 PNIPAAm gel [117], The final solids contents rises as the ratio of gel to slurry increases, but plateaus due to reduced sorption capacities of gels in high solids content slurries. The maximum extent of dewatering declines as the particles become finer...

Wakeman, R. J., Modelling Slurry Dewatering and Cake Growth in Filtering Centrifuge, Filtration and Separation, pp. 75-81 (Jan/Feb 1994)... 

Metal and plastic wedge wire screens are commonly used in the construction of filters and other separators, as either the support for finer filter media or as the filtering medium itself. The screens have typical aperture sizes of >50 pm with an average tolerance of 10%. Metal, usually steel, screens are used in applications where separator robustness needs to be combined with slurry dewatering duties or when the solids are particularly coarse or abrasive. 

Wakeman R.J., 1994. Modelling slurry dewatering and cake growth in filtering centrifuges, Filtr. Sep., 31, 75-81. 

In many cases of slurry dewatering, and especially where the slurry is a waste needing treatment prior to safe disposal, the decanter can dewater such slurries to a high level of dryness. The extra-dry solids decanter has become an important feature of the decanter market, both to allow it to compete for business with some designs of filter, and to provide a good means of processing waste sludges ahead of incineration or land disposal. 

The protein fraction is filtered and dried to become high (60%) protein content com gluten meal. The starch slurry can be dewatered and dried to produce regular com starch. Dry starch can be sold as is or heat treated in the presence of acid catalysts to produce dextrins. Or, it is chemically modified before dewatering and drying to produce modified starches used in food and industrial appHcations. Lasdy, it can be hydroly2ed to produce corn sweeteners. 

Limestone slurry scmbs flue gas. SO2 absorbed, reacted to CaSO. Further ak-oxidized to CaSO settled/removed as sludge. Lower cost and simpler than other processes. Disadvantages abrasive/corrosive, plugging and scaling, poor dewatering of... 

Another mining process involves the recovery of sodium carbonate decahydrate from alkaline ponds. EMC mines this material from its solar evaporation pond using a bucket wheel dredge. The decahydrate slurry is dewatered, melted, and processed to soda ash. 

Most of the above apphcations are in clarification duties. The use of HGMS to dewater relatively concentrated, paramagnetic mineral slurries has been demonstrated on 2 to 12 wt % feed concentration of synthetic malachite (7) concentrated to 40%. The magnetic collection was optimized at flow velocities of 1 mm/s, and product concentrations greater than 40% were not possible unless the collected material could be removed from the matrix with less than the equivalent of one canister of washwater. 

As the vessel is only about half filled with slurry, the disks become coated with the cake when immersed, the cake is dewatered when the disks emerge from the slurry, and scraped or blown off, by reverse blow, into the central conveyor which takes the cake to one end of the vessel. The planetary action and the slow movement of the disks through the feed slurry ensure exceptionally good homogeneity of the cake which is critically important for good dewatering characteristics the typical speed of rotation of the planetary system of shafts is from 0.8 to 1 rpm. 

The vertical recessed plate automatic press, shown schematically in Figure 15 and described previously, is another example of a horizontal belt pressure filter. Cycle times ate short, typically between 10 and 30 minutes, and the operation is fully automated. The maximum cake thickness is about 35 mm washing and dewatering (by air displacement) of cakes is possible. Apphcations include treatment of mineral slurries, sugar, sewage sludge, and fillers like talc, clay, and whiting. 

D. Blankmeister and Th. Triebert, Dewatering Fltrafme Coal Slurries by Means of Pressure Filtration, Aufbereitungstechnik Nr. 1/1986, pp. 1—5. 

Most continuous vacuum filters are the constant pressure type. Their main use is in dewatering concentrated slurries such as concentrates. They belong to three classes the disk, dmm, and horizontal filters. Disk, and to a lesser extent, dmm filters, are the mainstay for most final dewatering. These filters remove most fine particles from a process stream. 

The disk filter is similar to the dmm in operation, but filtration is conducted using a series of large diameter filter disks that carry the filter medium on both sides of the disk. They are connected to the main horizontal shaft and partly immersed in the feed slurry. The central shaft is connected by a set of valves which serve to provide vacuum and air as in dmm filters. As the disk sections submerge during rotation, vacuum is appHed to form a cake on both sides of the disk. The cycle of operation is similar to that in a dmm filter. One unit can have as many as 12 disks of up to 5-m diameter. Disk filters, both compact and cost effective, are used extensively in the iron ore industry to dewater magnetite concentrates. 

The general manufacturing scheme for phosphate salts is shown in Figure 11. Condensed phosphates are prepared from the appropriate orthophosphate or mixture of orthophosphates, so the preparation of orthophosphates must be considered first for the manufacture of any phosphate salt. Phosphoric acid is neutralized to form a solution or slurry with a carefully adjusted acid/base ratio according to the desired orthophosphate product. The orthophosphate may be recovered either by crystallization from solution, or the entire solution or slurry may be evaporated to dryness. The dewatering (qv) method is determined by the solubihty properties of the product and by its desired physical properties such as crystal size and shape, bulk density, and surface area. Acid orthophosphate salts may be converted to condensed phosphates by thermal dehydration (calcination). 

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