Document GK7O1maDEk3n14bQMwG98pXnN

280 W. N. WITHERIDGE detectors and alarms for heat, fire, or smoke should be installed in a "fail-i manner. E. COST ANALYSIS A comprehensive cost analysis for air or gas cleaning will include njiost the following items: j 1. Noninstalled cost per unit air-flow capacity. . j 2. Installation cost including discharge stack. j 3. Amortization based on known service life. j 4. Fixed charges on space required by equipment. 5. Initial costs for disposal equipment. j 6. Operating costs for disposal of wastes. 7. Preventive and corrective maintenance costs. j j 8. Scrubbing liquid costs. i 9. Power or utility costs. 10. Recovery or salvage value of constituents. Approximate information on the first item appears in Table 3. These d TABLE 3 Cost of Air or Gas Cleaners" (Dollars per 1000 c.f.m.) Type of cleaner Minimum noninstalled; Baffle chambers (gravity-inertial) Cyclones (single, large diameter) Cyclone3 (multiple, small diameter) Fan-type (dry) Filters " Cloth baghouse (above 10,000 c.f.m.) Reverse-jet cleaned (above 10,000 c.fm.) Unit air-supply ("throwaway") Conveyorized impingement type Active carbon (odor removal) Electric precipitators Single-stage high-voltage (above 100,000 c.f.m.) Two-stage, low-voltage (air conditiofimg) Scrubbers and washers' Spray'diaitibers Cyclone scrubbers (stationary) Mechanical or dynamic Packed'tOWgrB'Cchemical absorbers) "Disintegrator" scrubbers 50 100 400 200 500 800 10 100 200 500 .................... ........ 200' 100 300 500 1000 3000 "Approximate minimum noninstalled costs, using ordinary steel construction; insl costs, complete with necessary auxiliaries, may be at least twice the figures given here;, on 1955 prices. AIR CLEANING 281 Tgiven to indicate the wide range of costs encountered by the application engi- a't?$3and serve as a warning against hasty estimates. Even greater ranges'of r^are experienced when the items mentioned above are included in the F. POWER REQUIREMENTS Bphe energy consumed in cleaning air or gas is largely the power required to Ji.the fluid through the system against the resistance of numerous obstructions di:in the stream to stop the air-borne matter. Table 4 presents the order of Ipitude of pressure drop encountered with the several types of cleaning equip- Along with pressure drop is given the estimate of power required, in' kilo* to force 1000 cubic feet of air through the equipment in one minute against pecified resistance. lit is evident that no simple correlation exists between power consumption Mparation ability for fine particles. However, for those mechanisms depend|p)|imarily on centrifugal force, the power requirement will rise as separation increases, resulting in more effective performance against the smallest lies. TABLE 4 Power Requirements for Air-Cleaning Equipment Equipment type Pressure drop (in. HjO) Kilowatts required per 1000 ci.rn. air capacity* Gravity settling chambers Jipray chambers Electric precipitators Jinpingement filters "acked towera (wet) ^Absolute" filters 4oth arrestors -yklone separators -High-velocity centrifugals ntensive scrubbers 0.05-0.2 0.05-0.2 0.05-0.5 0.5 -1 0.5 -5 1-5 2-5 1-5 3-15 2-30 0.02-0.1 0.02-0.1 0.02-0.2 0.2 -0.5 0.2 -2 0.3 -2 0.5 -2 0.3 -2 1-5 1-10 'nat.include_power_to force,air through duct system, or to disintegrate.scrubbing liquid by al or hydraulic methods. General References hciui Chemical Society, Symposium on Atmospheric Contamination and Purification: Dlpoaition of aerosol particles from moving gas streams, H. F. Johnstone and M. N. Bg-te, (b) Development of the Venturi scrubber, W. P. Jones, (e) Electrical precipitagiand mechanical dust collection, W. A. Schmidt, (d) Agglomeration of smoke, fog, or Hparticles by sonic waves, H. W. St. Clair, (e) Industrial sonic agglomeration and hjtion systems, H. W. Danser and R. Neumann, Ind. Eng. Chem., 41, 2383-2493' 'November, 1949).