Everything Science Grade 12

5.2 CHAPTER 5. THE CHEMICAL INDUSTRY

Sasol today: Technologyand produc-

tion

ESCCG

Today, Sasol is an oil and gas company with diverse chemical interests. Sasol has

three main areas of operation: Firstly, coal to liquid fuels technology, secondly the

production of crude oil and thirdly the conversion of natural gas to liquid fuel.

1. Coal to liquid fuels
   Sasol is involved in mining coal and convertingit into synthetic fuels, using the
   Fischer-Tropsch technology. Figure 5.1 is a simplified diagram of the process that
   is involved.

Coal mining

Coal

gasification

(Sasol/Lurgi

process)

Crude synthesis

gas

Gas

purification

Condensates from the gas are cooled

to produce tars, oils andpitches.

Ammonia, sulphur andphenolics are

also recovered.

SAS

reactor

C 1 to C 20

hydrocarbons

Figure 5.1: The gasification of coal to produce liquid fuels

Coal gasification is also known as the Sasol/Lurgi gasification process, and in-

volves converting low grade coal to a synthesisgas. Low grade coal has a low

percentage carbon, andcontains other impurities. The coal is put under ex-

tremely high pressure and temperature in thepresence of steam andoxygen.

The gas that is producedhas a high concentrationof hydrogen (H 2 ) and carbon

monoxide (CO). That iswhy it is called a ’synthesis gas’, because it is amixture

of more than one gas.

In the Sasol Advanced Synthol (SAS) reactors, the gas undergoes a high temper-

ature Fischer-Tropsch conversion. Hydrogen and carbon monoxide react under

high pressure and temperature and in the presence of an iron catalyst,to pro-

duce a range of hydrocarbon products. Below isthe generalised equationfor the

process. Don’t worry too much about the numbers that you see in front of the

reactants and products.It is enough just to see that the reaction of hydrogen and

carbon monoxide (the two gases in the synthesis gas) produces a hydrocarbon

and water.