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In Sulfuric Acid Plants |
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Larger acid mist particles are created in sulfuric acid drying and absorbing towers as a result of the splash and shear of liquid acid in the distributor and over the packing. These particles are entrained in the upward gas flow. More difficult to collect small acid particles are formed by the reaction of sulfur trioxide with any water vapor present and by the condensation of acid from the gaseous or vapor phase. These acid particles can corrode blowers, ductwork and heat exchangers, damage catalyst and cause atmospheric pollution.
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As an example, in a sulfuric acid plant, much of the mist is mechanically generated. The frothing action in the distributor along with bubbling in the downcomers generate spray particles. Also acid drops are stripped off the acid flowing over and through the tower packing
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In a sulfuric acid plant absorbing tower the gas stream contains SO3, H2SO4 vapor and H2O vapor. As the gas is cooled, H2SO4 vapor condenses and submicron particles are formed by the "shock cooling". In addition, the SO3 vapor and the H2O vapor react to form submicron H2SO4 mist.
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