Waste Packing Density

Tank Water from Packing Houses.—Sheep and calves will produce from 1)4 to 2 gal., hogs from 2) i to 3 gal. and beeves from 7 to 10 gal. of tank water, with a density of about 4°B6., and the quantity will be larger if the percentage of sohds is lower. In most cases, 3°B6. hquor is concentrated to about 27° in multiple-effect evaporators of the horizontal type having a capacity of 1.8 gal. per square foot, with a steam pressure of from 3 to 5 lb. and a vacuum of from 27 to 28 in. There is not much tendency to foam, but sometimes tank water will form a heavy scale on the tubes which has to be removed by boiling with alkaline solutions. Waste waters are sometimes slightly acid, and evaporators must have cast-iron shells and copper or brass tubes. 

Consider the following application of fixed-bed, activated carbon adsorption for the control of VOC emissions. An industrial waste gas consists of 0.5 vol% acetone in air at 300 K and 1 atm. It flows at the rate of 2.3 kg/s through a fixed bed packed with activated carbon. The bed has a cross-sectional area of 5.0 m2 and is packed to a depth of 0.3 m. The external porosity of the bed is 40%, its bulk density is 630 kg/m3, and the average particle size is 6 mm. The average pore size of the activated carbon particles is 20 A, the internal porosity is 60%, and the tortuosity factor is 4.0. A Langmuir-type adsorption isotherm applies with qm = 0.378 kg VOC/kg of carbon, K = 0.867 kPa-1. At the break point, the effluent concentration will be 5% of the feed concentration. Calculate ... 

Roll cell. These are sandwich constructions consisting of a packed stainless steel or titanium mesh cathode, separator and a screen anode rolled up like a swiss roll. These cells can operate with fluid velocities of 1-10 cm s and with apparent current densities of 10-200 mA cm at the separator. This type of cell is a concentrator device for metal ions, the metal is recovered from the cell by leaching or by anodic dissolution. An economic analysis [23] showed that waste water treatment with this cell is highly competitive with ion-exchange technology. Typical applications for metal ion removal are recovery of copper and Hg from waste stream recovery of Ag from a used fixer solution down to a silver concentration of 0.1 ppm and the treatment of zinc cyanide plating bath rinse waters which contain the Zn(CN)5 complex ion. 

EXAMPLE 12.3-1. Scale-Up of Laboratory Adsorption Column A waste stream of alcohol vapor in air from a process was adsorbed by activated carbon particles in a packed bed having a diameter of 4 cm and length of 14 cm containing 79.2 g of carbon. The inlet gas stream having a concentration of 600 ppm and a density of 0.00115 g/cm entered the bed at a flow rate of 754 cm /s. Data in Table 12.3-1 give the concentrations of the breakthrough curve. The break-point concentration is set at dCg = 0.01. Do as follows. 

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