3. The Production Process Historically, sulfuric acid production was based on the The Lead Chamber Process, involving the oxidation of sulfur dioxide by nitric acid and nitrogen oxides in the Production presence of water. This has been replaced by the Contact Process in which sulfur dioxide is oxidized by Process atmospheric air at high temperatures and in the presence of a vanadium pentoxide catalyst. Specifics will vary from one plant to another, but this description is provided as an overview of a typical Contact Process. The process begins with cleaning of the gas. The sulfur dioxide from smelting and roasting operations The critercriteriaia of purity and passes through a series of gas cleaning steps that acaccuracycuracy ofof gradeg are ththee primaryprimary goalsggo of sulfuriclf i acid id prproduction.oddu ThTThee Contact Process,Prooce Quench Tower: deddescribedscribed here,heerre, is Weak acid jets remove alaalmostlmost universallyuniverssaally used particulate matter from hot process gasses to cconvertono vert SSOO2 to H2SO4 tente on c Scrubber:Sccrubber: ts FurtherFurther contact wwithith f i oof its aciaacidd jjetsets provprovidesidesdedees rt Falco. pa or addiadditionaltionaallc ccoolingoooolo ingngg y N aandnd clccleaningleaeane ingngg n f a t o ce en du ns ro co ep n r r te o rit y w op r c rio ot p n e ill th w ut ou ho y it at w th er e ev re so ag at u h yo w t se en o m rp u pu oc y . d an co is r al th fo rF ng or o di N a rm Electrostatic © re fo y ny Precipitators: B a in Acid mist and remaining Weak Acid dust particles removed Pump Tank

Weak Acid Solution 98% Acid Stream 93% Acid Stream SO Gas Stream 6 3 SO2 Gas Stream Acid Pumps cool and remove almost all metallurgical dusts. Depending on the required product strength, The gas is then drawn through electrostatic acid from the absorption or drying towers can be precipitators where acid mist and any remaining stripped of SO2, cooled, and pumped to dust particles are removed. The wet gas is dried storage. Some acid is exchanged between the in a tower by direct contact with 93% sulfuric absorption and drying circuits to maintain acid acid and a blower then forces the gas through a strength. series of heat exchangers and converter beds, where, in the presence of vanadium pentoxide, the sulfur dioxide is oxidized to sulfur trioxide. The purpose of the heat exchangers is to utilize the heat of reaction in the converter beds to heat the incoming cool gas to the reaction temperature. The SO3 gas then passes through an absorption tower where it combines with the water in 98% sulfuric acid to make additional sulfuric acid.

Drying Tower: ToT StaStackckk Clean gasses are dried by contact with concentrated H2SO4

Converter: SO2 Stripper:S : AirA stream ts content SO2 in the clean dryy ggasas is removess excessexc s SOalco. converted to SOO3 rt of its c2 ppara or y NNorFalco n of To Drying a t Tower ce en du ns o co epr n r r te o y writ op r c rio ot p n e ill th w ut ou ho y it at w h er e t ev re so g at Heatu a h ExchangersExcyouy angers agag w t bbetweenween en each stages m of conversionc Drying u ppupurposeu wha Tower oc y . d n Pump o is r a Tank lc th fo Fa g r or in o N ad rm © re fo y ny B a in

Absorption Tower: 93% SO3 is absorbed by water in concentrated acid to 96% form more H2SO4

Absorption Tower 98% Pump Tank

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