Precipitator dust

The electric furnace process generates four streams that can be considered by-products slag, ferrophos, precipitator dust, and carbon monoxide off-gas. The approximate composition of the slag and precipitator dust are given in Table 3. These vary somewhat among different phosphoms manufacturers. 

Precipitator dust often contains concentrated amounts of minor ore components that make it attractive. The potassium, phosphate, and 2inc content have resulted in its use in ferti1i2er, and the sdver and gallium content have been the subject of some recovery efforts (see Recycling). 

St. Joe Minerals Corporation uses a fluid-bed roaster to finish the roasting at 950°C of material that has been deleaded in a modified multiple-hearth furnace operated with insufficient oxidation (34). First, sulfur is reduced from 31 to 22% and lead from 0.5 to 0.013%. Somewhat aggregated, the product is hammer-milled before final roasting. Half of the calcined product is bed overflow and special hot cyclones before the boiler remove the other half total sulfur is ca 1.5%. Boiler and precipitator dusts are higher in sulfur, lead, etc, and are separated. 

FIG. 17-73 Normal (perpendicular) rapping efficiency for various precipitated dust layers having about 0.03 g diist/cm (0.2 g diist/in ) as a function of maximum acceleration in multiples of g, Curve 1, fly ash, 200 or 300°F, power off. Curve 2, fly ash, 70°F, power off also 200 or 300°F, power on. Curve 3, fly ash, 70°F, power on. Curve 4, cement-ldln feed, 300°F, power off. Curve 5, cement dust, 300°F, power off. Curve 6, same as 5, except power on. Curve 7, cement-ldln feed, 300°F, power on. Curve 8, cement dust, 200°F, power off. Curve 9, same as 8, except power on. Curve 10, cement-ldln feed, 200°F, power off. Curve 11, same as 10, except at 70°F. Curve 12, cement-ldln feed, 200°F, power on. Curve L3, cement-ldln feed, 70°F, power on. °C = (°F — 32) x %. [Spioull, Air Polliit. Control Assoc. J., i.5, 50 (1965).]... 

Precipitation inhibitors, dispersants contrasted, 3 686 Precipitation leachate procedure, synthetic, 25 868-869 Precipitation reactions, for niobium and tantalum determination, 27 142-143 Precipitation reagents, protein, 22 133 Precipitation with compressed antisolvent (PCA) process, 24 17, 18 Precipitator dust, in phosphorus manufacture, 19 12 Precipitators, electrostatic, 23 180 Precision agriculture, 23 328 26 269-270 Precision measurement techniques, noble gases in, 27 370 Precision scales, 26 245 Preconcentration, of uranium ores, 25 401 Pre-crosslinked polychloroprene grades, 19 852... 

These data show that the ash content of the dried aqueous extracts tend to be higher than the original for all three types of samples. The increase is especially high for the condenser trash samples and is quite similar to the behavior of plant parts (21). There is also a trend that as the particle size becomes smaller, the ash content increases. The ash content of the electrostatic precipitator dust was particularly high (41.3%). 

TABLE VIII Minerals Identified in Electrostatic Precipitator Dusts Collected in a Model Card Room (16) ... 

Fertilizer - [AMMONIUMCOMPOUNDS] (Vol2) -ammoniumsulfate [AMMONIUMCOMPOUNDS] (Vol2) -castor pomace as [CASTOR OIL] (Vol 5) -iron compounds m [IRON COMPOUNDS] (Vol 14) -from lignite and brown coal [LIGNITE AND BROWN COAL] (Vol 15) -lime fillers [LIME AND LIMESTONE] (Vol 15) -magnesiumnitrate [MAGNESIUM COMPOUNDS] (Vol 15) -molybdenum compounds as [MOLYBDENUMAND COMPOUNDS] (Vol 16) -phosphorus precipitator dust as [PHOSPHORUS] (Vol 18) -raw material for [SULFAMIC ACID AND SULF AMATES] (Vol 23) -sodium nitrate as [SODIUM COMPOUNDS - SODIUM NITRATE] (Vol 22) -vanadium as by-product [VANADIUM AND VANADIUM ALLOYS] (Vol 24)... 

The need for series sectionalization in a precipitator arises mainly because power input needs differ at various locations in a precipitator. In the inlet sections of a precipitator, concentrations of particulate matter will be relatively heavy. This requires a great deal of power input to generate the corona discharge required for optimal particle charging heavy concentrations of dust particles tend to suppress corona current. On the other hand, in the downstream sections of a precipitator, dust... 

High-voltage electrostatic precipitator dust diameter 0.01 to 5 pm and conducting particles feed concentration <25 g/m with pressures <7 MPa and temperature <800 °C gas phase Ap = 0.02 to 0.1 kPa mass collection efficiency 99.5% power usage... 

Environmental regulations can influence the selection of agglomeration equipment in several ways. A first concern is always the finely divided particulate nature of the feed materials. Often, these are precipitated dusts or solids removed from fluids in pollution control devices. Recontamination of the environment is an obvious concern and is typically regulated. The equipment must provide dust control and be completely enclosed, particularly if the material is hazardous or toxic. Many of the growth agglomeration methods, for example, drums or discs, do not easily fulfill these requirements. 

Mazumder, M. K., E-SPART Analyzer Its Performance and Application to Powder and Particle Technology Processes, KONA, No. 11, 1993, pp. 105-118. Mazumder, M. K., R. E. Ware, T. Yokoyama, B. J. Rubin, and D. Kamp, Measurement of Particle Size and Electrostatic Charge Distributions on Toners Using E-SPART Analyzer, IEEE Trans. Ind. Appl., 27, 1991, pp. 611-619. McLean, K. J., Cohesion of Precipitated Dust Layer in Electrostatic Precipitators, J. Air Pol. Contrl. Assoc., 27, 11, Nov. 1977, pp. 1100-1103. Misev, T. A., Powder Coatings, Chemistry and Technology, Wiley, NY, 1991, p. 292. 

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