Process liquor

Additional operations essential to commercial bauxite processing are steam and power generation, heat recovery to minimise energy consumption, process liquor evaporation to maintain a water balance, impurity removal from process liquor streams, classification and washing of ttihydrate, lime caustication of sodium carbonate [497-19-8] to sodium hydroxide [1310-73-2] repair and maintenance of equipment, rehabiUtation of mine and residue disposal sites, and quaUty and process control. Each operation in the process can be carried out in a variety of ways depending upon bauxite properties and optimum economic tradeoffs. 

At the alumina plant, the bauxite ore is further crushed to the correct particle size for efficient extraction of the alumina through digestion by hot sodium hydroxide liquor. After removal of "red mud" (the insoluble part of the bauxite) and fine solids from the process liquor, aluminum trihydrate crystals are precipitated and calcined in rotary kilns or fluidized bed calciners to produce alumina (AljOj). Some alumina processes include a liquor purification step. 

Brick lining (40-65 mm thick) is used for reducing the temperature at the membrane. This protects the membrane from deteriorating with free access of the process liquors and prevents its erosion and other mechanical damage [51,52]. 

Red and blue acid-resistant bricks are resistant to all inorganic and organic chemicals, except for hydrofluoric acid and hot concentrated caustic alkalis. Acid-resistant fireclay bricks are used for conditions involving elevating temperatures and corrosive condensates. Highly vitrified materials such as chemical stoneware, porcelain and basalts are used for extremely severe duties or where contamination of the process liquors is undesirable. 

Organic coatings are applied mainly to mild steel structures and equipment. They are also used on aluminum, zinc-sprayed and galvanized steel, but to a lesser extent. The applications for organic coatings can be divided into three areas corrosion by atmospheric pollution, protection from splash by process liquors, and linings for immersion in process liquors [70-74]. 

Paints based on phenolic resins are oil modified to permit drying at ambient temperatures. They are very suitable for most industrial atmospheres. Paints with a higher standard of chemical resistance are required for equipment that is splashed by corrosive process liquors. 

The axial and mixed flow impellers are used primarily for very high capacities at relatively low heads as show n in Table 3-2. They are usually applied to services such as water distribution to a large system, waste water disposal, recirculating large process liquor flows, and the like. 

Solids should be removed from process liquors and vessels should be designed so that deposition of solids does not occur, e.g. by avoiding sharp corners and stagnant areas by providing facilities for complete drainage of the process liquor. 

Accurate monitoring of bleaching processes is essential for efficiency, economy and protection of the environment. The importance of checking raw materials, including the substrate, should be obvious. There is also a need to monitor the actual process liquors and to evaluate the results obtained on the substrate. A useful account of such procedures is available [143]. 

Pletcher D, Walsh FC, Whyte I (1990) The application of electrochemical techniques to the treatment of industrial process liquors, I Chem E Symp Ser, No 116 195, 35 refs Chem Abstr 114 (1991) 170419h... 

The application of ion exchangers to dextrose process liquors involved considerable experimental work because of a number of factors which do not enter into their application to water purification. The accumulation of fats and proteins on the resin surfaces must be guarded against by proper clarification of the liquors to be treated. Such accumulation may result from precipitation as the neutralization progresses, and may soon destroy the effective acid-removing capacity of the anion exchange resin. This difficulty can effectively be eliminated by prior precipitation of thfe refinery residue from the acid liquor by bentonite, a colloidal clay of opposite electrical charge to the colloids,21 followed by filtration. 

A typical recipe for alkaline scouring processes (liquor ratio 1 10) is as follows ... 

Hydroseparator The efllnent from the oxidizer column next flows to a hydroseparator in which any lime grit, catalyst, or coke lines are physically removed. The solids are sent to a horizontal vacnnm belt filter, and the overhead liquor from this separator will be further treated to reclaim most of the process liquor and to produce a filter cake for disposal. 

Waste Clarifier This clarifier will treat the overhead liquor from the hydroseparator to concentrate any solids and to reclaim process liquor for reuse in the process. The overflow from this clarifier will be retnrned to the process and the underflow will be filtered to prodnce a filter cake for disposal. The filtrate from the filter press will be returned to the process. 

Horizontal Belt Vacuum Filter The final piece of equipment is the horizontal belt filter, in which the nnderflow from the hydroseparator (basically gypsum diluted with process liquor) will be filtered to produce marketable gypsum of -12% moisture. The filter cake will be washed to reduce the amount of dissolved solids and will be conveyed to a prodnct gypsnm storage area. Filtrate from this filter will be disposed of as an aqneons pnrge stream. 

Amine reagents also extract thorium from carbonate solutions and the use of a primary amine, RNH3C1, where R = C10 to Cl3 alkyl, as a 20% solution in kerosene allowed the concentrations of impurities in the extracted thorium to be reduced by factors of 33.8 for UVI, 111.4 for MoVI, 18.9 for Zrlv and 6167 for Mg11.177 The extracted thorium species was shown to be of the composition (RNH3)4Th(C03)4(H20)x. Di(tridecyl)amine has been used to extract thorium from barren uranium process liquors in the Blind River plant in Canada147 and flowsheets for the recovery of lanthanides, U03 and high-purity Th(S04)2 from the Elliot Lake area in Ontario using Primene/isodecanol have been described.178... 

Determination of noninorganic surfactants (NS) in environmental water samples or in samples relevant to environmental water quality (sewage, processing liquors in sewage treatment plants, and treated sewage) is difficult because of the complexity of the matrix, the multicomponent nature of the NS mixture in the aquatic environment, and the limited stability of samples.133... 

Regeneration Options for Water-based Process Liquors... 

To simultaneously recover the metal and sulfuric acid from spent process liquors of nickel electrolysis, Xu and Yang [95] tested diffusion dialysis successfully. The membrane used was surface-cross-linked with aqueous ammonium to decrease waste volume expansion caused by the water osmosis. They could control nickel leakage within 4% and recover about 70% of the add. 

For ionic liquid based process liquors, the contrary can be assumed. Due to their relatively high prices and anticipated costs for discharge of spent liquors a breakthrough of ionic liquids in plating applications can be expected to be linked... 

The process starting from lignin has faced serious problems, such as reduced availability and environmental impact. The availability is reduced because the new process for making paper paste yields less liquor. As a result, it is likely that the larger companies will not reinvest in new factories to process liquors to meet demand. The process s environmental impact is also problematic because over 160 t of caustic waste are produced for every ton of vanillin manufactured. 

Alcohol is distilled up to a content of 96% in one or more stages. About 1 % of ethanol consists of fusel oils (degradation products of amino acids) which can be used as solvents for lacquers and resins. Solids from the processed liquor containing proteins, carbohydrates, mineral salts, riboflavin and other vitamins are used in poultry, swine and cattle feeds. C02 and H2 produced in butanol-acetone-butyric acid production can be used for the chemical synthesis of methanol and ammonia, or are burned. 

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