Process contact

Preparation of Sulphuric Acid by the Contact Process. Assemble an apparatus as shown in Fig. 72. Fill gas meter 1 with oxygen and 

Check the tightness of the apparatus and fill it with oxygen. Put a small amount of sulphur into a boat, ignite it in the air, and put it into tube 6. Regulate the oxygen stream from the gas meter so 

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Sulphur trioxide, SO3, m.p. 17 C, b.p. 49 C. Formed SO2 plus O2 over a catalyst (contact process - see sulphuric acid). The solid exists... 

Since the catalyst is in the gaseous state, it is being continually removed from the mixing chambers. Its recovery, and the necessity of continual charging of the incoming gases with it, make the lead chamber plant complicated by comparison with that of the Contact process. 

The conversion of sulphur trioxide to sulphuric acid arises as a separate reaction only in the Contact process. 

In the finely divided state platinum is an excellent catalyst, having long been used in the contact process for producing sulfuric acid. It is also used as a catalyst in cracking petroleum products. Much interest exists in using platinum as a catalyst in fuel cells and in antipollution devices for automobiles. 

In 1875, a paper by Winkler awakened interest in the contact process, first patented in 1831. Winkler claimed that successfiil conversion of SO2 to SO could only be achieved with stoichiometric, undiluted ratios of SO2 and O2. Although erroneous, this beUef was widely accepted for more than 20 years and was employed by a number of firms. Meanwhile, other German firms expended a tremendous amount of time and money on research. This culminated in 1901 with Knietsch s lecture before the German Chemical Society (3) revealing some of the investigations carried out by the Badische Anilin-iind-Soda-Fahrik. This revealed the abandonment of Winkler s theory and further described principles necessary for successfiil appHcation of the contact process. 

Sulfuric acid may be produced by the contact process from a wide range of sulfur-bearing raw materials by several different process variants, depending largely on the raw material used. In some cases sulfuric acid is made as a by-product of other operations, primarily as an economical or convenient means of minimising air pollution (qv) or disposing of unwanted by-products. 

In early years the contact process frequentiy employed only two or three catalyst stages (passes) to obtain overall SO2 conversions of approximately 95—96%. Later, four pass converters were used to obtain conversions of from 97% to slightiy better than 98%. For sulfur-burning plants, this typically resulted in sulfur dioxide stack emissions of 1500—2000 ppm. 

Process Details and Flow Sheets. The stoichiometric relation between reactants and products for the contact process may be represented as foUows ... 

EPA has compiled significant data on values of k and n for environmentally significant pollutants with typical activated carbons. Assuming equilibrium is reached, the isotherm provides the dose of carbon required for treatment. In a concurrent contacting process, the capacity is set by the required effluent concentration. In a countercurrent process, the capacity of the carbon is set by the untreated waste pollutant concentration. Thus countercurrent contacting is preferrea... 

Particulate emissions from zinc processing are collected in baghouses or ESPs. SO2 in high concentrations is passed directly to an acid plant for production of sulfuric acid by the contact process. Low-concentration SO2 streams are scrubbed with an aqueous ammonia solution. The resulting ammonium sulfate is processed to the crystalline form and marketed as fertilizer. 

The contact process which replaced the chamber process reacts the products using a platinum or a vanadium catalyst. 

I. Jensen. Critical behavior of the three dimensional contact process. Phys Rev A 45 R563-R566, 1992. 

E. V. Albano. Irreversible phase transitions in contact processes with Levy exchanges and long-range interactions. Phys Rev E 54 3436-3441, 1996. 

Contact process for SO3/H2SO4 patented by P. Philips of Bristol, UK (tlie original platinum catalyst was. subsequently replaced by ones ba.sed on V2O5). 

The emergent SO2 is then fed into a contact process for H2SO4 (p. 708). Alternatively, ammonia and CO2 can be passed into a gypsum slurry to give ammonium sulfate for use in fertilizers ... 

Aerated 0.5kW-150kW Larger sizes (yes) N gas, LP gas 20 mbar-1 bar <20 1 Non-luminous shape depends on apphcation Wide use in heating and direct-contact process apphcations... 

Sulfuric acid is made commercially by a three-step contact process. First, elemental sulfur is burned in air to form sulfur dioxide ... 

The newer process uses a solid catalyst for reaction (19). Either finely divided platinum or vanadium pentoxide, V205, is effective. Because catalysis occurs where the gas contacts the surface of the catalyst, this process is called the contact process. 

Reaction (19) is carried out at a high temperature (about 500°C in the contact process). How does temperature affect equilibrium, according to Le Chatelier s Principle In view of your answer, propose an explanation of why the temperature is kept high. 

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