Raw Coke. Image credit MedialWiki

Raw Coke. Image credit MedialWiki

ZIMSEC O Level Combined Science Notes: The manufacture of coke at Hwange

  • Coke is a hard prous residue formed when coking coal is heated to 1250°C in the absence of air
  • It is almost pure carbon
  • It is often used as a raw material by the metal industry

The process of making coke

  • Coaking coal is fed into a battery of long coke ovens
  • The ovens are lined with silica brick
  • The ovens are heated with coal gas
  • After 16 hours the coal is transformed
  • If 17 tonnes are fed into the ovens about 12 tonnes of coke are obtained
  • After the process is complete the red-hot coke is ejected from the ovens and drenched with water
  • When the coke is drained it is send to ZISCO and other metal extracting companies
  • Coking byproducts make up the difference between the mass of the coal input and the coal output

The by-products and their uses

  • Various by-products are given off by the coking process
  • Some of them are used as they are for example coal gas but some have to be refined
  • After they are refined these by-products have different uses
  • The table below shows the various by-products of the coking process and their uses
By-ProductRefining ProcessUses
Coke which is almost pure carbonDestructive distillation
  • fuel (heat energy)

  • smelting metal ores

  • to make fuel gases like water gas

AmmoniaDistillation
  • metal processing

  • fertilizers
BenzolFractional distillation to give oily liquid products with different boiling points ( benzene, toluene, xylene)
  • Solvents for grease, paint and varnish

  • Plastics

  • Disinfectants

  • Food flavouring

  • Perfumes

  • Drugs

  • Dyes

  • Insecticides
TarsDistillation
  • Tars which are used for road making

  • Naphthalene for the chemical industry

  • Creasolte for preserving and termite-proofing wood

Coal gasNone
  • Is used to fuel the coke ovens

To access more topics go to the Combined Science Notes page.

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