General
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Sulfuric Acid can be made in two different processes. One is called Lead Chamber and the other is called Contact. The Lead Chamber Process is the older process, and is used to produce the acid used in fertilizer, which is a more dilute acid. Contact is used to make purer Sulfuric Acid, but is more expensive, as it requires purer raw materials and more expensive catalysts. In both processes, sulfur dioxide is oxidized and dissolved in water.
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A Glover Tower Diagram and a Sulfuric Acid Plant |
Lead chamber
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Contact
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In this process, hot sulfur dioxide enters the bottom of a reactor called a GLOVER TOWER, and is washed with nitrous vitriol (H2So4 with NO and NO2 dissolved in it) then mixed with nitric oxide and nitrogen dioxide gases. Then the mixture of gases (including sulfur dioxide and trioxide, nitrogen oxides, nitrogen, oxygen and steam) is moved to a lead-lined chamber where it is reacted with more water. It is formed by a complex series of reactions. It condenses on the floor and walls of the chamber. This usually produces 62% to 68% H2So4. The remaining gases are then washed with cooled concentrated acid to form the nitrous vitriol used in the Glover Tower. The remaining waste gases are then discharged into the atmosphere.
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In this process purified sulfur dioxide and air are mixed, heated to about 450°C and passed over a catalyst. The sulfur dioxide is then oxidized to sulfur trioxide. The catalyst is usually platinum on a silica or asbestos carrier or vanadium pentoxide on a silica carrier. The sulfur trioxide is cooled and passed through two towers. In the first tower it is washed with oleum (fuming sulfuric acid, 100% sulfuric acid with sulfur trioxide dissolved in it). In the second tower it is washed with 97% sulfuric acid. 98% sulfuric acid is usually produced in this tower. Waste gases are usually discharged into the atmosphere. Acid of any desired concentration may be produced by mixing or diluting the products of this process, as this process creates a concentrated sulfuric acid.
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