Sulphur as an energy source

[By our guest columnist, 'Thiophilos']

The stimulus for these Last Words has been the ever present suspicion that, since the Oil Patch became the world’s major source of elemental sulphur through socially imposed requirements to get it out of oil, it has become a barely tolerable pain in the butt for its suppliers. Gone are the days when the miners, be they pick and shovel or the Frasch type, produced valued sulphur “because it was needed” not because they had to, or they couldn’t sell their oil - and that is where the money is; the sulphur product is viewed as very much an unfortunate necessity!

What seems to have missed the Oil Patch’s attention is that sulphur, like carbon, is a very important source of energy in its own right. The similarities are striking. We get energy out of sulphur (and its oil patch precursor hydrogen sulphide) by burning it just as we do hydrocarbon and coal (carbon). The product of the combustion is sulphur dioxide instead of carbon dioxide. Both of these combustion products are GHGs (green house gases - as if you didn’t know). Indeed Rachel Carson et al way back fifty years ago were well ahead of Al Gore and company in highlighting the ‘Inconvenient Truth’ of the combustion emissions from the energy recovery processes. Acid Rain came long before Global Warming but the oxidative mechanism that forms the GHGs is rooted in the same human demand – for energy.

So maybe the fact that sulphur has finished up in bed with its oil patch mate as a “dirty” commodity is not all that unusual. But let’s look at just what dirty old sulphur does for us energy-wise:

In its recovery from admixture and/or combination with the hydrocarbon of oil (and gas) it appears as hydrogen sulphide (like hydro-carbon) and is oxidised (burnt) in the Claus Process Reactor. This chemical step differs little from a methane (hydrocarbon) burning furnace and produces large quantities of high quality steam, much of which is used as a process energy source or to generate electrical energy. The parallel with hydrocarbon energy generation is clear. But in sulphur’s case we are just at the beginning of the energy production chain. The end product of sulphur’s combustion is sulphur dioxide, just as carbon/hydrocarbon produces carbon dioxide, the source of global warming. In sulphur’s case, however, we already have a “capture and sequestration” procedure in place. We make sulphuric acid from the sulphur dioxide “waste product” and that acid is one of the most widely used industrial chemicals known to humankind.

If it wasn’t for the millions of tonnes of sulphuric acid available annually for processing ‘phosrock’ ore the fertilizer industry would consume millions of kilowatts of ‘alternative energy’ (electrical) in getting the essential phosphate nutrient out of the rock and into the plant so that the essential human fuel called food would still be plentifully available. Hydrocarbon-based energy sources may have become the essential motivator for automobiles, but sulphur-based energy sources play an equally important role in providing the essential food for humans. The parallels continue!

But, say the critics, the relative amounts of commodities are vastly different. Are they really? Fifty million tonnes per annum of recovered sulphur is an appropriate round figure to use for the world sulphur trade. As recently as two years ago that sulphur touched $800/tonne on world markets. Simple arithmetic using these numbers values the overall sulphur business at forty billion dollars a year. Not a fortune in today’s marketplace, where debts in the trillions are not uncommon, but not to be sneezed at either. At $100/bbl for oil it amounts to the value of four hundred million barrels of oil, or well over a month’s supply of all the hydrocarbon energy imported by the world’s biggest user. That’s a lot of energy from dirty old sulphur.
So the old yellow element is just as deserving of some respect as the black one – coke, coal or the form with hydrogen attached – hydrocarbon. It is a significant energy source as we energy-hungry humans look for ever more of the stuff. And what is even more impressive, we have already found ways to “sequester” the emissions (of sulphur dioxide) and put them to do good additional work in fuelling ‘we the people’ by fertilising the food we eat. Can you think of a comparable end use for carbon dioxide? Soda pop might cause some undesirable burping problems!

‘Thiophilos’