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Fertiliser Technology - Engineering

Q1:

Heating of coke, sand & phosphate rock in an electric furnace is done for the manufacture of

A phosphoric acid.

B superphosphate.

C phosphorous.

D triple superphosphate.

ANS:C - phosphorous.

Heating of coke, sand, and phosphate rock in an electric furnace is done for the manufacture of phosphorous. In this process, known as the electric furnace method or the thermal process, the reaction between phosphate rock (calcium phosphate) and coke (carbon) at high temperatures (typically around 1450°C) produces phosphorous vapor. The sand serves as a fluxing agent, helping to lower the melting point of the phosphate rock and facilitating the reaction. The overall chemical reaction can be represented as: 𝐶𝑎3(𝑃𝑂4)2+3𝐶→3𝐶𝑎𝑂+3𝑃+3𝐶𝑂Ca3​(PO4​)2​+3C→3CaO+3P+3CO In this reaction:

  • 𝐶𝑎3(𝑃𝑂4)2Ca3​(PO4​)2​ represents the phosphate rock.
  • 3𝐶3C represents the coke.
  • 3𝐶𝑎𝑂3CaO represents calcium oxide (lime), which forms as a by-product and reacts with the sand to form a slag.
  • 3𝑃3P represents the phosphorous vapor produced.
  • 3𝐶𝑂3CO represents carbon monoxide, another by-product of the reaction.
The phosphorous vapor is then condensed and collected to produce elemental phosphorous, which is used in various industrial applications, including the production of phosphoric acid, fertilizers, and detergents.