502 scrubbing

Leaking phosgene gas can be destroyed by spraying the contaminated zone with large volumes of water. Although the reaction is slow, the excess of water helps to suppress dispersion [1318]. Water should not be sprayed directly onto phosgene cylinders, however, since this may increase the size of the leak as a result of the formation of corrosive HCI [1318,1486]. 

Small quantities of phosgene (e.g. 1%) may be conveniently removed from inert gas streams by saturating with water vapour and passing through a column of high surface area active carbon at 25 C [565aa]. 

Solutions of phosgene in water-immiscible solvents should be destroyed with ethanolic ammonia [1C121]. Decontamination of rubber tubing may be carried out by immersion into aqueous ammonia before disposal [1C121]. 

A scrubber design for the control of phosgene emissions [2068aa]. 

It is recommended that any plant which makes or uses phosgene in large quantities should be provided with two separate scrubber systems. A fume scrubber (to handle low phosgene concentrations diluted with a large volume of inerts) and a caustic scrubber (to handle higher phosgene concentrations). The fume scrubber is a general suction service for 

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Benfield process Removal of carbon dioxide from fuel gases, such as those obtained by gasifying coal in the Lurgi process, by countercurrent scrubbing of the gases by hot potassium carbonate solution. 

Catacarb process An extraction process used to remove carbon dioxide from process gases by scrubbing the hot gases with potassium carbonate solution containing additives which increase the hydration rate of the gas in the solution. The Vetrocoke process is similar. See Benfield process. 

Fieser s solution An aqueous alkaline solution of sodium anthraquinone -sulphonale (silver salt) reduced with sodium dithionite, Na2S204, and used as a scrubbing solution for partially removing O2 from, e.g., N2. 

Hahner G and Spencer N D 1998 Rubbing and scrubbing Phys. Today September, 22-7... 

Hold-up of column. The hold-up of liquid should be reduced to a minimum compatible with scrubbing effectiveness and an adequate column capacity. The ratio of charge of the still to the hold-up of the... 

Flue gas handling Flue gas scrubber Flue-gas scrubbers Flue-gas scrubbing FlueUite Fluent... 

These reactions are used industrially for scrubbing operations and for selective removal of H2S from natural gas containing CO2. 

Flue Gas Desulfurization and SulfuricMcidProduction Uia Magnesia Scrubbing U.S. Environmental Protection Agency, Technology Transfer, EPA 625/2-75/077, Washington, D.C., 1975. 

Ethylene chain growth Flash, TEA scrub, hydrolysis, depolymer... 

Decomposition by Caustic Scrubbing. The waste gas stream is led through packed towers where a sodium hydroxide solution is introduced at the top of the towers. Venturi scmbbers can also be used. Makeup sodium hydroxide is added under pH control (32). 

Scrubbing andDesliming. Sylvinite ores in North America contain 1—6 wt % water-insoluble clays. A significant portion of these clays is less than 0.002 mm in diameter. If not removed or controUed in some manner, clay bodies that are dispersed in the flotation solution, ie, brine saturated with KCl and NaCl, absorb the amine coUector, which is added to effect flotation separation, and the coUector is rendered ineffective. Clay is the most troublesome impurity encountered in the processing of sylvinite ore. 

Theie aie several lime-scrubbing processes being marketed. The generalized process is described hy ibsorption... 

Copper—Liquor Scrubbing. Cuprous ammonium salts of organic acids form complexes with carbon monoxide. 

A surgical hand scrub is a nonirritating antimicrobial-containing preparation that significantly reduces the number of microorganisms on the intact skin. A surgical hand scmb should be broad-spectmm, fast-acting, and persistent. 

Recovery of iodine hy action of sulfur dioxide on aqueous sodium iodate Hydrogenation of vegetable oils with gaseous hydrogen Desulfurization of gases by scrubbing with aqueous ethauolamiues... 

Liquid Coolers and Condensers Dirty water can be used as the cooling medium. The top of the cooler is open to the atmosphere for access to tubes. These can be cleaned without shutting down the cooler by removing the distributors one at a time and scrubbing the tubes. 

F — 50)° (Standiford, Chemical Engineers Handbook, 4th ed., McGraw-Hill, New York, 1963, p. 11-35). Higher values of/c (to about 0.15) can be tolerated in the falhng-film evaporator, where most of the entrainment separation occurs in the tubes, the vapor is scrubbed by liquor leaving the tubes, and the vapor must reverse direction to reach the outlet. 

The exhaust gases are generally discharged into dust and fume knockdown equipment to avoid contamination of the atmosphere. Gas-cleaning equipment includes cyclones, setthng chambers, scrubbing towers, and electrical precipitators. Heat-recoveiy devices are utilized both within and outside the lain. These result in an increase in lain capacity or a decrease in fuel consumption. Waste-heat boilers, grates, coil systems, and chains are used for this purpose. 

Example 3 illustrates the use of Eq. (14-8) for scrubbing chlorine from air with aqueous caustic solution. For this case one can make the simplifying assumption that y, the interfacial partial pressure of chlorine over the aqueous caustic solution, is zero owing to the rapid and complete reaction of the chlorine after it dissolves. We note that the feea gas is not dilute. 

AP is the pressure drop, cm of water p and Pg are the density of the scrubbing liquid and gas respectively, g/cm L/g is the velocity of the gas at the throat inlet, cm/s QtIQg is the volumetric ratio of liquid to gas at the throat inlet, dimensionless It is the length of the throat, cm Coi is the drag coefficient, dimensionless, for the mean liquid diameter, evaluated at the throat inlet and d[ is the Sauter mean diameter, cm, for the atomized liquid. The atomized-liquid mean diameter must be evaluated by the Nuldyama and Tanasawa [Trans. Soc Mech Eng (Japan), 4, 5, 6 (1937-1940)] equation ... 

Ejfect of Gas Saturation in Scrubbing If hot unsaturated gas is introduced into a wet scrubber, spray particles will evaporate to cool and saturate the gas. The evaporating liquid molecules moving away from the target droplets will repel particles which might collide with them. This results in the forces of diffusiophoresis opposing particle... 

W scrubs the extract free from the unwanted second solute. The second solute leaves the contac tor in the raffinate stream. 

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