Leaching design

The observed metal phosphate phases agree with thermodynamic models of the ash system described here. These phases control leaching in pH-stat systems and are present after aggressive leaching designed to remove available or leachable fractions. These phases are also similar to ones observed in soil, sediment, smelter dust, industrial wastewater, and slag systems. 

D.T. Kinard and A.A. Schweizer, Engineering Properties of Agglomerated Ore in a Heap Leach Pile, Geotechnical Aspects of Heap Leach Design (1987) 55-64. 

M and A R Leach 1994. Current Methods for Site-Directed Structure Generation. Journal of nputer-Aided Molecular Design 8 467-475. 

A. R. Leach, Molecular Modelling Principles and Applications Longman, Essex (1996). G. A. Jeffrey, J. F. Piniela, The Application of Charge Density Research to Chemistry and Drug Design Plenum, New York (1991). 

Uranium is present in small (50—200 ppm) amounts in phosphate rock and it can be economically feasible to separate the uranium as a by-product from the cmde black acid (30% phosphoric acid) obtained from the leaching of phosphate for fertilizers (qv). The development and design of processes to produce 500 t U Og per year at Ereeport, Louisiana have been detailed (272). 

Tipping pan and horizontal filters are also used for leaching the modus operand of the Rotocel extractor resembles that of a tipping pan filter, although the details of its design differ slightly. 

Sintering has been used to produce a porous polytetrafluoroethylene (16). Cellulose sponges are the most familiar cellular polymers produced by the leaching process (123). Sodium sulfate crystals are dispersed in the viscose symp and subsequently leached out. Polyethylene (124) or poly(vinyl chloride) can also be produced in cellular form by the leaching process. The artificial leather-tike materials used for shoe uppers are rendered porous by extraction of salts (125) or by designing the polymers in such a way that they precipitate as a gel with many holes (126). 

AH operating facilities shear the spent fuel elements into segments several centimeters long to expose the oxide pellets to nitric acid for dissolution. This operation is often referred to as chop-leach. The design and operation of the shear is of primary importance because (/) the shear can be the production botdeneck, and (2) the shear is the point at which tritium and fission gases are released. 

Impeller-agitated tanks These can be operated as continuous leaching tanks, singly or in a series. If the sohds feed is a mixture of particles of different setthng velocities and if it is desirable that all particles reside in the leaching tank the same lengths of time, design of a continuous stirred leach tank is difficult and uncertain. 

A somewhat similar but simpler design uses a horizontal screw section for leaching and a secona screw in an inclined sec tion for washing, draining, and discharging the extrac ted solids. 

At the heart of a leaching plant design at any level—conceptual, pre-liminaiy, firm engineering, or whatever—is unit-operations and process design of the extraction unit or hne. The major aspects that are particular for the leaching operation are the selection of process and operating conditions and the sizing of the extrac tion equipment. 

The proposed method can be applied to the speciation analysis of environmental solids for risk assessment of their contaminants as well as to design of effective leaching schemes. 

---