Precipitation efficiency

When corona occurs, current starts to flow in the secondary circuit and some dust particles are precipitated. As potential is increased, current flow and electric field strength increase until, with increasing potential, a spark jumps the gap between the discharge wire and the collecting surface. If this "sparkover" is permitted to occur excessively, destmction of the precipitator s internal parts can result. Precipitator efficiency increases with increase in potential and current flow the maximum efficiency is achieved at a potential just short of heavy sparking. 

Cementation. Cementation is the precipitation of copper from copper leach solutions by replacement with iron. It was formerly the most commonly used method of recovering copper from leach solutions but has been replaced by solvent extraction—electro winning. The type of iron used ia cementation is important, and the most widely used material is detinned, light-gauge, shredded scrap iron. This operation can be performed by the scrap iron cone (Keimecott Precipitation Cone) or a vibrating cementation mill that combines high copper precipitation efficiency and reduced iron consumption (41). 

Several investigators have attempted to modify the basic Deutsch equation so that it would more nearly describe precipitator performance. Cooperman ( A NewTheoiy of Precipitator Efficiency, Pap. 69-4, APCA meeting, New York, 1969) introduced correction fac tors for diffusional forces arising from variations in particle concentration along the precipitator length and also perpendiciilar to the collecting surface. Robinson [Atmos. Environ. 1(31 193 (1967)] derived an equation for collec tion efficiency in which two erosion or reentrainment terms are introduced. 

High-Presstire-High-Temperature Electrostatic Precipitation In general, increased pressure increases precipitation efficiency, although a somewhat higher potential is reqiiired, because it reduces ion mobihty and hence increases the potential reqiiired for corona... 

Comparison of Protein Precipitation Efficiencies of Precipitants upon Treatment with Human Plasma... 

Bennett, R.P., Kober, A.E., "Chemical Enhancement of Electrostatic Precipitator Efficiency", Symposium on the Transfer and Utilization of Particulate Control Technology,... 

Theoretical calculations will always overestimate precipitator efficiencies, probably because of reentrainment. This overestimation could be as large as a factor of 2 or more (Rose and Wood, 1966). Even so, drift velocity or effective migration velocity is the basis for all precipitator calculations and does provide a good base for the comparison of various designs. 

Precipitation efficiencies (precipitation/condensation) of naturally occurring convective clouds are quite variable, but may average about 50% (Slinn, 1982). Removal of aerosol may, however, be more efficient (Hobbs and Molenkamp, personal communications). Nothing is known about the rainout efficiencies of the fumulus clouds which are stimulated by the buoyancy of the fires. However, not all fires will cause such convective cloud formation. 

Polvelecfroivte. The nature of the polyelectrolyte plays a major role in the precipitation efficiency. Both the charge on the polymer as well as the charge density are important (5, 6,12,13). Steric factors, or the flexibility of the polyelectrolyte may also influence the effectiveness of the precipitation (6). 

Solution dH Several investigators (2, 12, 13) have indicated that the solution pH is an important determinant in the precipitation efficiency, and the optimum pH level will vary with both the protein (12) and the polyelectrolyte (5). However, the optimum pH for precipitation of protein by CMC did not change with the degree of substitution (DOS) of the CMC (12). This dependence is expected for the formation of an electrostatic complex. Changes in pH will affect the charge on the polyelectrolyte and the charge distribution on the protein. 

Ionic Strengths If the protein-polymer complex is formed as a result of electrostatic interactions, increased ionic strength should serve to reduce the attraction between the oppositely charged macromolecules, and decrease the precipitation efficiency. This is observed at pH 4.2 in Figures 3 and 4 for lysozyme and ovalbumin, respectively, and in Figure 5 for lysozyme at pH 5.8 and 7.5. 

Precipitation efficiency increases with protein charge. 

The addition of grinding aids leads to the increased mobility of cement, even of high fineness. The material becomes very transportable, easily flows out from silos and is without difriculties packaged into the bags. On the other side, the fine fraction content in cement increases the dustiness of the air venting the mill and worsening the electrostatic precipitators efficiency by the higher resistivity of cement, which rise from 10 to 10" cm is observed [151]. 

Ferric iron solution is now continuously added to both acid and neutral leaching. This has resulted in higher iron utilization and enhanced impurity precipitation efficiency. The addition of soluble iron to the acid leach promotes the precipitation of ferric arsenate, enhancing arsenic rejection to the residues and dramatically lowering the arsenic levels in the plant electrolytes. Previously, the arsenic concentration in the acid leach electrolyte was as high as 5 g/L. The arsenic concentration is now below one gram per liter. 

Changes in neutral leaching pH and the addition of iron solution were made to optimize the precipitation efficiency of impurity metals (including germanium) while minimizing the acid soluble content in the leach residue. 

---