Fume scrubbers

Table 14-2 illustrates the observed variations in values for different packing types and sizes for the COg-NaOH system at a 25 percent reactant-conversion level for two different liquid flow rates. The lower rate of 2.7 kg/(s-m ) or 2000 lb/(h-ft ) is equivalent to 4 (U.S. gal/min)/ft and is typical of the liquid rates employed in fume scrubbers. The higher rate of 13.6 kg/(s-m ) or 10,000 lb/(h-fU) is equivalent to 20 (U.S. gal/min)/ft and is more typical of absorption towers such as are used in CO9 removal systems. For example. We note also that two different gas velocities are represented in the table, corresponding to superficial velocities of 0.59 and 1.05 m/s (1.94 and 3.44 ft/s). 

Wet scrubbers rely on a liquid spray to remove dust particles from a gas stream. They are primarily used to remove gaseous emissions, with particulate control a secondary function. The major types are venturi scrubbers, jet (fume) scrubbers, and spray towers or chambers. Venturi scrubbers consume large quantities of scrubbing liquid (such as water) and electric power and incur high pressure drops. Jet or fume scrubbers rely on the kinetic energy of the liquid stream. The typical removal efficiency of a jet or fume scrubber (for particles 10 g. or less) is lower than that of a venturi scrubber. Spray towers can handle larger gas flows with minimal pressure drop and are therefore often used as precoolers. Because wet scrubbers may contribute to corrosion, removal of water from the effluent gas of the scrubbers may be necessary. 

Figure 4-62. Spray scrubber— fume scrubber arranged for vertical downflow. Courtesy of Schutte Koerting Co.

DESUPERHEATER LIQUID MIXING EDUCTOR FUME SCRUBBER... 

Fume scrubber water recycle. The steel finishing industry uses fume scrubbers to capture acid gases from pickling tanks. Scrubber water, which may contain a dilute caustic solution, is neutralized and recirculated continuously to adsorb the acid. Makeup water is added to replace water lost through evaporation and water that is blown down to end-of-pipe metals treatment. 

The waste pickle liquor, rinse water discharges, and fume scrubber effluent can be combined in an equalization tank for subsequent treatment. Basically, three methods are used to treat the WPL ... 

There are two basic evaporator designs that are typically used atmospheric and vacuum evaporation (Metals Handbook 1987). Atmospheric evaporation principles are similar to those of a heated open tank, with the exception that the heated liquid is sprayed over plastic packing in order to increase its surface area and accelerate evaporation. Atmospheric evaporators on chrome plating lines have sometimes been used simultaneously as evaporators and as plating bath fume scrubbers. Atmospheric evaporators are considerably less expensive than vacuum evaporators. Typical atmospheric evaporator capital costs range from 2500 to 4000, while vacuum evaporator costs can be an order of magnitude or more higher. In atmospheric evaporator systems, however, vaporized water is not recovered, as it can be in vacuum systems. 

Marine Industry Corrosion resistant linings for fume scrubbers and cooling pipelines. Wear resistant linings for dredging pipelines. Ebonite or hard rubber for corrosion resistance. Soft natural rubber for wear resistance. 

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... 

Once the reaction is over, lead and slag are sequentially cast from the casting hole in the middle of the kiln. Molten lead and slag are cast in ladles on a train perpendicular to the kiln and kept under suction.The whole cycle- charging, reactions and casting -lasts about 3 hours. The fumes are conveyed to a fume scrubber, before sending them to a filter. Sometimes, a special scrubber for SO2 is also used, to eliminate possible excess. 

There is no hazardous waste generated when lithium batteries are recycled at Toxco Inc. There is no municipal sewer system in the processing area and air emissions are collected via a direct-capture-system over each of the reaction areas. These fumes are processed through three air filters coimected in series the first is a wet bed fume scrubber which removes particulate material, the second is a traveling bed filter to further remove particulate material, and the third treats the emissions chemically. Each year Toxco is required to hire an outside environmental audit firm to test the emissions for conformance with their permit. The 1999 results are presented in Table 1. As one can see the emissions are quite minor in comparison to the allowable limits. 

A GRP fume scrubber and outlet ducts, shown in Fig. 9.14, have now been dismantled after 8 years of trouble free service at the tin smelting plant of Capper Pass Ltd., Humberside, UK. The scrubber, installed in 1982, was... 

Figure 9.14 GRP fume scrubber, dismantled after 8 years of trouble free service. The resins used were vinyl esters, including a brominated fire retardant grade. Dimensions 11m high, 5m diameter...

BC-7 Belt conveyor GR-a Disintegrator BC-9 Belt conveyor T-10 Storage pile S-11 Fume scrubber... 

X-7 Slat conveyor cor-fcinuous DEN BC-8 Bel-fc conveyor S-9 Fume scrubber T-ID Superphosphate stor ge pile... 

Packed fume scrubbers operate on the principle of presenting a large surface area wetted by a liquid (usually water) over which the air flows... 

This graphical design procedure will apply to most fume scrubbers that operate at atmospheric pressure. 

For a liquid-film-controlled system, the effect of gas rate on the overall Koa value is small and will not significandy alter graphical calculations. The plots in Figures 5-1, 5-2, and 5-3 permit rapid determination of the packed height required for fume scrubbers in such systems. As can be seen, the packed depth necessary for a given solute removal efficiency becomes greater with increasing gas rate. 

In a gas-film-controlled system, the effect of liquid rate on the overall Koa value is essentially the same as for a liquid-film-controlled system, such as that shown in Table 5-6. In addition, in such a system the gas rate has a significant effect on the overall mass transfer coefficient. Similarly, Figures 5-4, 5-5, and 5-6 allow a rapid determination of the packed depth required for fume scrubbers in gas-film-controlled systems. In these plots, the overall K a value has been corrected for the effect of the gas flow rate. Because the K a value increases with an increasing gas flow rate, the solute removal efficiency drops only slightly for a fixed packed depth as the gas rate is increased in such a system. 

It must be remembered that a fume scrubber merely removes a contaminant from a gas stream but does not destroy it. The scrubber liquid effluent will contain all of these scrubbed contaminants thus, it will present a water pollution potential [7]. Particulates can be settled, or filtered, out of this discharged liquid for recovery or sludge disposal. Chemical... 

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