Chemistry » Chemistry and the Real World » The Fertilizer Industry

Producing Hydrogen

Producing hydrogen: Coal gasification and steam reforming at Sasol

Fact:

Sasol is an international company that was founded in Sasolburg, South Africa, in 1950. It employs over \(\text{34 000}\) people in at least \(\text{38}\) countries and has interests in synthetic fuels, mining, oil, gas and chemistry.

In Nigeria, Sasol has a 10% interest in Escravos GTL, a 33 000-barrel-per-day gas-to-liquids project which began beneficial operation in June 2014. Other partners in the project include the Nigerian National Petroleum Corporation (NNPC) and Chevron Nigeria Limited.

Using Sasol’s Fischer-Tropsch process technology and Chevron’s ISOCRACKING technology, the plant is designed to process 325 million cubic feet per day of natural gas from the Escravos Gas Plant expansion. The capacity of the plant, currently stands at 34 000 barrels per day (5,400 m3/d) of synfuel.

Producing Hydrogen

Fossil fuels are the main source of industrial hydrogen. Hydrogen can be generated from natural gas or coal. These processes are used by Sasol at their Gas-to-Liquid (GTL) and Coal-to-Liquid (CTL) facilities. Hydrogen is usually produced by the steam reforming of methane gas (natural gas). At high temperatures (\(\text{700}\)\(\text{1 100}\)\(\text{°C}\)), steam (\(\text{H}_{2}\text{O}\)) reacts with methane (\(\text{CH}_{4}\)) in an endothermic reaction to yield syngas, a mixture of carbon monoxide (\(\text{CO}\)) and hydrogen (\(\text{H}_{2}\)).

Tip:

You are not required to know this information in as much depth as is provided here, but the extra information should help your understanding of the subject.

\(\text{CH}_{4}(\text{g}) + \text{H}_{2}\text{O}(\text{g})\) \(\to\) \(\text{CO}(\text{g}) + 3\text{H}_{2}(\text{g})\)

During a second stage, which takes place at a lower temperature of about \(\text{130}\)\(\text{°C}\), the exothermic reaction generates additional hydrogen. This is called a water gas shift reaction.

\(\text{CO}(\text{g}) + \text{H}_{2}\text{O}(\text{g})\) \(\to\) \(\text{CO}_{2}(\text{g}) + \text{H}_{2}(\text{g})\)

Essentially, the oxygen (O) atom is stripped from the additional water (steam) to oxidise \(\text{CO}\) to \(\text{CO}_{2}\). This oxidation also provides energy to maintain the reaction.

Coal can also be used to produce syngas in a similar way to natural gas. The reactions are shown below:

\(\text{C}(\text{s}) + \text{H}_{2}\text{O}(\text{g})\) \(\to\) \(\text{CO}(\text{g}) + \text{H}_{2}(\text{g})\)

\(\text{CO}(\text{g}) + \text{H}_{2}\text{O}(\text{g})\) \(\to\) \(\text{CO}_{2}(\text{g}) + \text{H}_{2}(\text{g})\)

Remember that yield describes the quantity of product in a container relative to the maximum product possible.

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