Drying beds

The most overlooked hazard and contaminant is water (99). Water reacts with isocyanates at room temperature to yield both ureas and large quantities of carbon dioxide. The presence of water or moisture can produce a sufficient amount of CO2 to overpressurize and mpture containers. As Httle as 30 mL of water can result in 40 L of carbon dioxide which could result in pressures of up to 300 kPa (40 psi). For these reasons, the use of dry nitrogen atmospheres is recommended during handling. If a plant air system must be used, purification equipment, such as oil traps and drying beds, should be installed between the source and the isocyanate vessel. 

Noith American Chemi-cal Co. 218 Trona, Calif. Seades Lake dry bed... 

A pressure filter is a plate-and-frame press which operates on an intermittent time cycle. Drier cakes are generally attainable from a filter press. Sludge drying beds are usually used for smaller sludge volumes, which drain and dry rapidly. Thein appHcation is usually restricted to the more arid climates. 

Aerobically digested sludge usually has good dewatering characteristics. When applied to sand drying beds, it drains well and redries quickly if rained upon. 

The molecular sieve process uses synthetically manufactured. solid crystalline zeolite in a dry bed to remove gas impurities. The crystalline... 

Cic it rally, the adsorption capacity of a dry bed unit decreases as the pressure is lowered. If the dehydrators are operated well below the design presMirc. the desiccant will have to work harder to remove the water and to maintain the desired effluent dew point. With the same volume i i incoming gas, the increased gas velocity, occurring at the lower prcssLiic., could also affect the effluent moisture content and damage the desiccant,... 

Dry bed pressure drop values usually run 0.1 to 0.5 in. water/ft of packing [96]. Use Equation 9-3 IB when Lf is below 20,000. Packings operate essentially dry when Lf is below 1,500 (about 3 gpm/ft2) at Fp = 20. Pressure drop at flooding is suggested to be predicted by Kister and Gill s relationship [93] presented in this text. 

AP = specific pressure drop, in. water/ft of packing APpb = specific pressure drop through dry bed, in. water/ft of packing Vs = superficial gas velocity, ft/sec pg = gas density, Ib/ft ... 

AP(j = dry bed pressure drop, in. water/ft AP = operating pressure drop, in. liquid/ft e = base of natural logarithms Xi,X2 = curve fit coefficients for C2, Table 9-32. 

APpb = Specific pressure drop through dry bed, in. water/ft packing... 

AP = Air pressure loss, in. of water APflood = Pressure drop at flood point for all random packings, in. of water/ft of packing height APd = Dry bed pressure drop, in. water/ft packed height... 

Thermal inversions make winter the most unfavorable season for clean air. Vast differences in air quality are found in the industrialized north, and the residential southwest regions. Particulate matter influences mainly the north, where industries, landfills, and the dried bed of Texcoco Lake are located. Sulfur oxides impinge primarily on the northeast and southwest. High carbon monoxide concentrations are found in heavy traffic areas such as the northwest. Ozone affects predominantly the southwest at any season. We have selected air quality records from data generated by stations registering the higher pollutant levels, as follows ... 

Option 1 Emulsion breaking and oil separation by skimming, cyanide oxidation, chromium reduction, chemical precipitation and sedimentation, and sludge drying beds. 

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