Sulphur is an amazingly versatile element, as this blog never tires of telling people. Fellow poster Thiophilos reminds people of sulphur’s virtues as a power source, utilising the heat of combustion in electricity generation, as happens daily at countless sulphur-burning sulphuric acid plants around the world.
But sulphur is now also set to make other inroads into powering our lives, this time via battery technology. As the number and capability of portable electronic devices continues to increase, our appetite for portable power sources is also growing, and at a staggering rate. Battery technology has already had several step changes over the past few decades, from lead-acid through nickel-cadmium and alkaline cells, to lithium ion batteries, which are the new workhorses of the consumer electronics industry, especially for rechargeable applications like mobile phones, tablets and laptop computers. But the need to increase energy density continues, especially if we are to move to electrically-powered vehicles.
One of the problems is with the cathode of lithium ion batteries, which in the case of lithium oxides or lithium iron phosphate might only have fraction of the specific charge capacity of the silicon or graphite anode. Over the past few years, the focus of attention has turned to sulphur as a cathode – sulphur has a very high theoretical specific capacity. As a result, and also because of the relatively lightweight elements that constitute them, lithium sulphur (Li-S) batteries can have two to four times the energy density of lithium-ion batteries, both in weight and volume terms. However, one of the problems with using sulphur is its poor conductivity, and another is that it tends to form lithium polysulphides which are soluble in the battery electrolyte. This means that the Li-S batteries’ ability to be discharged and recharged rapidly degrades away over several charging cycles.
Commercial Li-S batteries have been under development by several companies, using coated sulphur and electrolytes which minimise the dissolution of the lithium polysulphides, but in the meantime work has been under way in research institutes around the world to completely overcome the issues with Li-S batteries, and now Dr Hailiang Wang and his team at Stanford University in the US say that they may have found a way. The technique that they use is a polyethylene glycol (PEG) coating on sub-micron particles of sulphur. The PEG coating traps polysulphides and prevents them dissolving away. Nanoengineering techniques are then use to wrap the coated particles in a ‘cage’ of graphene molecules. The interaction between the carbon and sulphur renders the particles electrically conducting, and also supports them as they swell and shrink during each charging cycle.
As the paper says: “it is worth noting that the graphene-sulphur composite could be coupled with silicon-based anode materials for rechargeable batteries with significantly higher energy density than currently possible.”
There is clearly a lot of work still to be done before such a technique can be first optimised and then performed on an industrial scale. However, in the meantime the first generation of lithium-sulphur batteries are already being used in demonstration applications. One was used in the world’s longest unmanned flight, using a solar-powered aircraft which stayed aloft for 14 days in July 2010. Companies like Oxis Energy and Sion Power are racing to commercialise Li-S batteries and within a few years it may well be that your mobile phone or tablet computer, and possibly even your car, will be powered by sulphur.
Tuesday 26 July 2011
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’
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’
Is the sulphur industry doing its environmental best?
[By our guest columnist, 'Thiophilos']
As we are daily reminded by the media and many others how dirty and polluting the lives we lead have become, it seems only fair that we pause amidst the muck for a moment and examine how much, if anything, we in the sulphur business have done to clean up the mess in, say, the last couple of generations. Not withstanding the black picture painted by the Greens, it turns out that, by and large, we have not been altogether asleep at the switch. It is more a matter that the faster the industry has become cleaner, the more the people who produce the emissions have grown larger in numbers. The result - more emissions.
In the specific case of elemental sulphur, the world’s annual production of the yellow stuff has blossomed from around 3 million t/a in 1940 to well over 50 million t/a in 2010. To be fair, that growth in sulphur is offset by a reduction in the amount of iron sulphide (pyrites) that is roasted to form sulphur dioxide; that source has been displaced by burning elemental sulphur to produce the same gas to feed sulphuric acid plants. But it is still a huge increase, and one that was enough to get Rachel Carson all upset in the 1960s about the negative effect that all of that fugitive sulphur dioxide was having on Mother Nature.
A good swift rap on the knuckles or boot in the pants never did much harm, and Rachel’s cry for decency on behalf of the industry had a salutary effect. Sulphur recovery plant efficiency rose from a 70-80% level in the 1960-1970 era to near 99% in the early years of the twenty-first century. Not a bad record, but still not enough to satisfy the bright Greens.
To make the challenge to the industry to clean up their act a bit more ‘persuasive’, the folks that design and manufacture analytical testing equipment have moved ahead, by a few orders of magnitude. The sensitivity they can achieve when it comes to detecting the “stuff that got away” has skyrocketed. PPM limits have now become PPB and, at least in the nuclear world, PPTs are now the fashion and eminently measureable. What levels of what emissions are hazardous to your health? It is becoming close to a case of: “if we can measure it, it must be harmful”.
And then there are the bureaucrats who keep adding new regulations to old rules that were based on common sense. Recently the International Maritime Organization (IMO) told us that the cargoes of formed sulphur that we load by the millions of tons for ocean transportation must be “non-combustible”, or nearly so. This notwithstanding the fact that the first thing the buyer does with 95% of the stuff on receipt is to BURN it! Other regulatory bodies see fit to argue that storing formed elemental sulphur in open air stockpiles exposed to wind and rain is no less environmentally friendly than storing it under cover and protected from the other kind of ‘elements’. Who and what is a poor sulphur marketer to believe? The best of intentions may be the very stuff that public criticism is made of.
But there is one thing that sulphur peddlers can be assured of: if you stop trying to be good neighbours the criticism will only get louder. And there is much yet to be done by way of improving sulphur’s image in the eyes of society. Sulphur is a bit like the sun - everybody enjoys its benefits, but they can be brutally antagonistic when exposure to too much of it hurts. It all depends on how the sulphur or solar message is spun by the messenger with the story to tell. Winter holidays under a sun-filled sky are very much OK, but the fact that you are sitting under an unshielded monstrous nuclear reactor that is pouring out harmful radiation is seldom heard. With sulphur the soil acidifying evils and air polluting sulphur dioxide gas emissions are well publicised, but relatively little is heard of the critical role it plays in producing the fertilizer that grows the food which billions eat each and every year of their lives.
And there is even more opportunity for sulphur in the “better life” of the future if we the people would only take time to be more conscious of the chemistry that lies hidden within this common element. Mother Nature has made it a very central component of her photosynthesis systems where she captures all these nuclear sourced rays from the sun and uses the energy to build new living substances. The muscles in your body would not work very well if there were no sulphur-sulphur bonds to make and break in biochemical processes.
It all seems too heavy stuff for the ordinary bloke to be concerned about, but somebody will latch on to some aspect of the story that can be spun into a negative image. Maybe in this official World Year Of Chemistry, we in the sulphur business can do a little teaching of the truth about thios as part of our effort to persuade society that the industry is doing its best to protect the environment, not withstanding the tales of terror told by the television.
‘Thiophilos’
As we are daily reminded by the media and many others how dirty and polluting the lives we lead have become, it seems only fair that we pause amidst the muck for a moment and examine how much, if anything, we in the sulphur business have done to clean up the mess in, say, the last couple of generations. Not withstanding the black picture painted by the Greens, it turns out that, by and large, we have not been altogether asleep at the switch. It is more a matter that the faster the industry has become cleaner, the more the people who produce the emissions have grown larger in numbers. The result - more emissions.
In the specific case of elemental sulphur, the world’s annual production of the yellow stuff has blossomed from around 3 million t/a in 1940 to well over 50 million t/a in 2010. To be fair, that growth in sulphur is offset by a reduction in the amount of iron sulphide (pyrites) that is roasted to form sulphur dioxide; that source has been displaced by burning elemental sulphur to produce the same gas to feed sulphuric acid plants. But it is still a huge increase, and one that was enough to get Rachel Carson all upset in the 1960s about the negative effect that all of that fugitive sulphur dioxide was having on Mother Nature.
A good swift rap on the knuckles or boot in the pants never did much harm, and Rachel’s cry for decency on behalf of the industry had a salutary effect. Sulphur recovery plant efficiency rose from a 70-80% level in the 1960-1970 era to near 99% in the early years of the twenty-first century. Not a bad record, but still not enough to satisfy the bright Greens.
To make the challenge to the industry to clean up their act a bit more ‘persuasive’, the folks that design and manufacture analytical testing equipment have moved ahead, by a few orders of magnitude. The sensitivity they can achieve when it comes to detecting the “stuff that got away” has skyrocketed. PPM limits have now become PPB and, at least in the nuclear world, PPTs are now the fashion and eminently measureable. What levels of what emissions are hazardous to your health? It is becoming close to a case of: “if we can measure it, it must be harmful”.
And then there are the bureaucrats who keep adding new regulations to old rules that were based on common sense. Recently the International Maritime Organization (IMO) told us that the cargoes of formed sulphur that we load by the millions of tons for ocean transportation must be “non-combustible”, or nearly so. This notwithstanding the fact that the first thing the buyer does with 95% of the stuff on receipt is to BURN it! Other regulatory bodies see fit to argue that storing formed elemental sulphur in open air stockpiles exposed to wind and rain is no less environmentally friendly than storing it under cover and protected from the other kind of ‘elements’. Who and what is a poor sulphur marketer to believe? The best of intentions may be the very stuff that public criticism is made of.
But there is one thing that sulphur peddlers can be assured of: if you stop trying to be good neighbours the criticism will only get louder. And there is much yet to be done by way of improving sulphur’s image in the eyes of society. Sulphur is a bit like the sun - everybody enjoys its benefits, but they can be brutally antagonistic when exposure to too much of it hurts. It all depends on how the sulphur or solar message is spun by the messenger with the story to tell. Winter holidays under a sun-filled sky are very much OK, but the fact that you are sitting under an unshielded monstrous nuclear reactor that is pouring out harmful radiation is seldom heard. With sulphur the soil acidifying evils and air polluting sulphur dioxide gas emissions are well publicised, but relatively little is heard of the critical role it plays in producing the fertilizer that grows the food which billions eat each and every year of their lives.
And there is even more opportunity for sulphur in the “better life” of the future if we the people would only take time to be more conscious of the chemistry that lies hidden within this common element. Mother Nature has made it a very central component of her photosynthesis systems where she captures all these nuclear sourced rays from the sun and uses the energy to build new living substances. The muscles in your body would not work very well if there were no sulphur-sulphur bonds to make and break in biochemical processes.
It all seems too heavy stuff for the ordinary bloke to be concerned about, but somebody will latch on to some aspect of the story that can be spun into a negative image. Maybe in this official World Year Of Chemistry, we in the sulphur business can do a little teaching of the truth about thios as part of our effort to persuade society that the industry is doing its best to protect the environment, not withstanding the tales of terror told by the television.
‘Thiophilos’
So much for Peak Phosphorus?
Spring is always a season of conferences, and I seem to have been on my travels more than usual over the past few months, to San Antonio for the National Petroleum Refiners Association’s (NPRA) annual get-together, to Abu Dhabi for the Sour Oil and Gas Advanced Technology (SOGAT) conference, and to New York, where The Sulphur Institute (TSI) had its annual meeting. While picking out the highlights in terms of implications for the industry and the wider world, to my own mind one of the most significant things that I learned over the past two months is that we don’t need to worry about running out of phosphorus.
This is no idle concern; while for the sulphur industry phosphate fertilizers represent 55% of all sulphur and sulphuric acid demand, for the human race it is one of the key nutrients that goes to make up our own bodies – the most common mineral element in us apart from calcium. The Peak Phosphorus debate – like concerns about a number of strategic minerals – has come hard on the heels of Peak Oil fears, but the implications were always perhaps even more worrying; while it might be difficult and expensive, we can always find substitute fuels for oil, or other ways of getting about, but there is no substitute for the role that phosphorus plays in human health and nutrition.
So the prospect of running out of this vital nutrient should perhaps have raised far more global concern than it has done. Warnings began to emerge in 2006 that we would see peak phosphorus production before 2030, with the planet completely denuded of vital phosphate resources by 2050-2100, with the prospect of mass starvation ahead for humanity, and the price peak of 2008 helped give legs to the story. Well, if it did all pass you by, let me tell you that you can relax; it turns out we’re not running out of phosphorus after all. Steven Von Kauwenbergh, phosphate geologist and principal scientist with the International Fertilizer Development Centre, has spent the past couple of years reviewing the evidence for global phosphorus reserves, and at the TSI conference in New York he told me that concerns have been overblown. In fact even economically recoverable reserves – which he puts at 60 billion tonnes – should last us at least 375 years at current rates of usage, and he estimates that global phosphate resources probably total 290 billion tonnes; enough to last 1,800 years at present rates of use. And this is, he insists, a conservative estimate; Morocco alone may have 56 billion tonnes of mineable reserves and 140 billion tonnes of total resources.
The Hubbert Curve is of course a simple mathematical model, with no scope for new technological developments which can have dramatic consequences (such as the way shale gas has transformed the natural gas market). But it is also part of the more general problem of assuming that the future is amenable to a simple extrapolation from present trends. The idea that consumption will always continue to rise is one such. For example, per capita consumption of phosphorus is not rising, but in fact falling. In 1976 it was predicted that we would be using 210 million t/a of phosphates by 2000. The figure for 2000 was actually about 160 million, and like most fertilizer nutrients, consumption has been falling in the developed world since about 1990 as we find more efficient ways of using it. Peak usage in the developing world may not be too far down the line.
Dire predictions about the future, always advanced with the best of intentions, are nothing new. And they often draw our attention to a situation which if left unchecked could indeed be problematic, or contain within them sensible ideas that we should pay heed to. It would be very much to our advantage to continue to try to improve the efficiency of our use of phosphorus, for example. However, it is reassuring to know that this doomsday scenario in particular is not one we need lose much sleep over.
This is no idle concern; while for the sulphur industry phosphate fertilizers represent 55% of all sulphur and sulphuric acid demand, for the human race it is one of the key nutrients that goes to make up our own bodies – the most common mineral element in us apart from calcium. The Peak Phosphorus debate – like concerns about a number of strategic minerals – has come hard on the heels of Peak Oil fears, but the implications were always perhaps even more worrying; while it might be difficult and expensive, we can always find substitute fuels for oil, or other ways of getting about, but there is no substitute for the role that phosphorus plays in human health and nutrition.
So the prospect of running out of this vital nutrient should perhaps have raised far more global concern than it has done. Warnings began to emerge in 2006 that we would see peak phosphorus production before 2030, with the planet completely denuded of vital phosphate resources by 2050-2100, with the prospect of mass starvation ahead for humanity, and the price peak of 2008 helped give legs to the story. Well, if it did all pass you by, let me tell you that you can relax; it turns out we’re not running out of phosphorus after all. Steven Von Kauwenbergh, phosphate geologist and principal scientist with the International Fertilizer Development Centre, has spent the past couple of years reviewing the evidence for global phosphorus reserves, and at the TSI conference in New York he told me that concerns have been overblown. In fact even economically recoverable reserves – which he puts at 60 billion tonnes – should last us at least 375 years at current rates of usage, and he estimates that global phosphate resources probably total 290 billion tonnes; enough to last 1,800 years at present rates of use. And this is, he insists, a conservative estimate; Morocco alone may have 56 billion tonnes of mineable reserves and 140 billion tonnes of total resources.
The Hubbert Curve is of course a simple mathematical model, with no scope for new technological developments which can have dramatic consequences (such as the way shale gas has transformed the natural gas market). But it is also part of the more general problem of assuming that the future is amenable to a simple extrapolation from present trends. The idea that consumption will always continue to rise is one such. For example, per capita consumption of phosphorus is not rising, but in fact falling. In 1976 it was predicted that we would be using 210 million t/a of phosphates by 2000. The figure for 2000 was actually about 160 million, and like most fertilizer nutrients, consumption has been falling in the developed world since about 1990 as we find more efficient ways of using it. Peak usage in the developing world may not be too far down the line.
Dire predictions about the future, always advanced with the best of intentions, are nothing new. And they often draw our attention to a situation which if left unchecked could indeed be problematic, or contain within them sensible ideas that we should pay heed to. It would be very much to our advantage to continue to try to improve the efficiency of our use of phosphorus, for example. However, it is reassuring to know that this doomsday scenario in particular is not one we need lose much sleep over.
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