Figure 1. CRC on Coal and sustainable Development programme structure and effort map.
Some people say that coal in sustainable development is an oxymoron. We take the view that sustainable development is a continuously developing process,” says John Hart, CEO of Australia’s Co-Operative Research Centre (CRC) on Black Coal Utilisation. “If you look a hundred years in the future, coal and oil will be phased out for most people. But if you look at a 50-year timeframe, realists have difficulty seeing how coal can be phased out before then.”
“There are limitations on other forms of energy and on how quickly they can be phased in,” adds Hart, who is overseeing a new CRC on Coal and Sustainable Development. “Coal has been a large part, and will subsequently be a smaller part, of our energy. But it is an essential transitional ingredient in our long-term spectrum of development.”
Since 1995 Hart’s CRC has been a major plank of Australia’s programme on clean coal development. CRCs are part of a federal government research programme which begun in the early 1990s that aims to get more value for each research dollar by getting research bodies, universities, state funding bodies and the private sector to co-operate.
“The programme is focused on high-profile national priority research,” explains Mark O’Neill of the Australian Coal Association. “Every year potential CRC groups bid for available funding. The Federal Minister for Science and Industry assesses the bids according to national priorities and the value of the group. The winners are each funded for seven years.”
Most of the funding for CRC programmes comes from the members. In the case of the CRC on Black Coal Utilisation, for example, CRC members provided A$25 million ($12.6 million) and federal funding added another A$10 million.
A sustained drive
Figure 2. Basic schematic plan of the ultra clean coal (UCC) process.
The CRC on Black Coal was due to end in 2002 but earlier this year it won a renewal grant, allowing the participants to undertake a further seven years research. “If you apply for a renewal grant you must demonstrate that it is not just more of the same,” says Hart. “So we have broadened the emphasis of the programme to include sustainable development. Hence the change in the programme’s name.”
The renewed CRC has won more funding – totalling A$60 million – and has also pulled new partners into the group. It will include four universities, as well as BHP Research and Australia’s premier research organization CSIRO, along with the Australian Coal Association Research Programme (ACARP). Industry participants include four power generation utilities from Queensland, New South Wales and Western Australia, the Queensland Government, and six mining companies.
The organizations represent Australia’s entire black coal industry – a powerful group in a country whose largest export is coal, and where 85 per cent of electricity generation is provided from coal. Outside the programme are brown coal producers based mainly in Victoria: they belong to a separate CRC on Clean Power from Lignite.
The new CRC on Coal in Sustainable Development will “have a new ‘driver programme’ for economic, social and environmental assessment,” says Hart. “It will use tools like life cycle analysis so we can determine where our efforts can be applied for the best effect in the chain from mining to utilization to waste.
The system approach extends to power generation. “Previously we looked technically at coal behaviour as the end-point,” Hart says. “Now the direction has changed to consider coal use in a system sense – enhancing system performance is not just about coal but about the power station as a whole. We are not power generation experts but we have a strong co-operation with Japan’s research organization CREIPI and the boiler manufacturers at Ishikawa Hatima Ikari Heavy Industries.
“So far we don’t have their US or European counterparts, but increasingly as we broaden our interest in the system we will have to work with world providers like ABB. We are in discussions with the US Electric Power Research Institute. With them we are looking at scenario development and risk analysis.”
Hart says risk management is an important tool underlying any new developments. “The coal industry as a whole is very conservative,” he says. “When you build investments worth millions of dollars you have to be conservative, but the power industry is very resistant to new developments like IGCC.”
But he says there is real risk involved in increasing efficiencies. “Our first pulverized coal fired boilers were 20-30 MW and over time were scaled up to 100, 200, 350 and now 500 MW. It’s a very comfortable way to develop commercially and safely. Compare that with requirements for new technology now, where you have to go from 5-10 MW to a commercial plant of more than 300 MW. There have been problems in IGCC in the Netherlands and the USA, but fortunately government has been willing to put in more money. Similarly the PFBC has been scaled from a 75 MW pilot plant in Japan to the next stage at 250 MW and 350 MW. Both have had problems.
“The risk management programme will explore ways of examining and reducing risk, and part of the answer is technical and part of it is financial. Look at the IGCC which integrates a gasifier and combined-cycle system. In Europe Siemens went for high integration to maximize efficiency. In the US they were more technically cautious – you might call it cruder – it certainly had lower efficiency, but it was safer and easier to operate. That approach has been vindicated. How much you integrate the systems is a matter of risk management.”
Clean power from lignite
Brown coal is a ‘lower ranked’ fuel than Australia’s high-quality black coal, but in Victoria it is the first option for power generation, providing around 94 per cent of the state’s power. Victorian lignite is very cheap to mine and is very low in sulphur and ash, but it is very wet, and that means thermal efficiencies in the state are very low – below 30 per cent – even for the most efficient of the plants. That is why the CRC on Clean Power from Lignite has put a large effort into research and development of drying technologies for its coal.
The Clean Power from Lignite CRC has been in operation since June 1993 and it was renewed in 1999. Its members include the utilities burning brown coal as well as research organizations and Alstom Power Australia.
The CRC’s research manager is Peter Jackson. He says the CRC has focused on understanding how Victorian coals behave in commercial gasification or advanced burning processes.
The CRC has developed laser-based instrumentation for analyzing coal and is due to commercialize the development soon in a joint venture, known as Laser Analysis Technologies, with instrumentation company Automated Fusion Technology. “Our coal is low in sulphur and nitrogen, and it has less than three per cent ash, so it is very clean,” says Jackson. “Our biggest problem is that it is very young so it is very wet – 60-67 per cent water. Dewatering is our biggest programme area.”
“Most of the water, maybe 75-80 per cent, is in the interstitial structure and is actually free,” Jackson says. “It can be removed by squeezing the coal.” Around five years go researchers from the CRC found that if the coal was heated to 150-200°C the water could be squeezed out at very low pressure – a discovery made almost simultaneously at Germany’s Dortmund University.
“In Germany a demonstration plant has gone into operation at Neiderhaussen, based on flat presses like those used to make wood particle boards,” Jackson says. “In Australia we are working on a continuous process. It is basically the same process but using different equipment.”
In Australia the process has been successfully used in two pilot plants processing 100 kg/hr, and is now being patented. Jackson says the aim is to scale up the process quickly. “We have placed orders for a 1 t/yr pilot plant that should go into operation at the end of the year. When we have results from that we aim to move to a 15 t/hr design straight away – probably operating in 18 months. Stepping up from that to 100 t/hr will be equivalent to the feed rate for individual mills on Victoria’s largest stations,” he says.
The success of the dewatering project is limited by only one thing: at the moment it stands no chance of being used in Victoria because coal costs are just too low. “The process would have no impact on the economics of power stations here,” says Jackson, “coal is so cheap that it is a minimal part of the power station cost.”
Although wholesale power prices are increasing in the state, that situation is unlikely to change any time soon for operating plants. “The driver is carbon taxes and emissions trading,” Jackson says, “there must be substantial capital investment but in the absence of carbon trading there is no incentive – there is no payback in terms of coal.”
In Victoria the process is waiting for the demand-supply gap – already shrinking – to offer economic incentives for new plants. “When that happens dewatering is likely to be used in conjunction with supercritical burning to increase efficiencies from the current maximum of 29 per cent to 37-38 per cent, or even over 40 per cent if more advanced technologies are used,” Jackson says.
Ultra clean coal
While the CRCs aim to make the coal industry more efficient, a commercial programme is hoping to develop a new coal technology that will allow it to compete against gas in the market for ‘clean’ fuels.
There has always been interest in whether it is possible to burn fine coal in gas turbines. The problem is that when coal is burned ash remains, and in a turbine that means the blades suffer damage. Australia’s White Group and CSIRO have been working on a chemical process to remove ash from coal, and in November this year they expect to complete a demonstration plant that will provide test tonnages to Mitsubishi in Japan for full scale testing.
John Langley heads UCC Energy Ltd., a new subsidiary set up by White Group to develop and market the new process.
“The process is similar to the Bayer process,” he says. “Coal ground to 1 mm is treated with hot caustic soda at a temperature of 240°C and a 2.5 MPa pressure. That attacks the quartz and converts clay into an acid-soluble form. After the alkali phase the coal is washed in dilute acid, which removes more of the minerals, and then undergoes a final thorough washing to remove salts.”
Depending on the type of coal, the process reduces the ash level to 0.1-0.2 per cent but the coal retains the same size and shape characteristics. Mineral wastes are produced equivalent to 15-20 per cent of the original coal tonnage, depending on the original ash level, “but we think the mineral byproducts will have a market value,” Langley says.
After processing, the coal is milled to less than 10 µ in size and then injected into a conventional gas turbine. At 10 µ the combustion time is similar to that of the oil droplets when oil is co-fired in a gas turbine, minimizing the changes required to the turbine. The size of any residual ash particles will be less than 5 µ, and Langley says that at that size, and a level of 0.1 per cent “even under the electron microscope we can’t find any erosion or abrasion of the turbine blades. We can’t even find the particles”.
UCC Energy has turned to Japanese organizations for specialist turbine tests. “Japan is our major trading customer for coal and they have a large research capability,” Langley says. “We now have a co-operative agreement with the Centre for Coal Utilisation in Japan (CCUJ), along with the CSIRO. Through the CCUJ we have access to Mitsubishi Heavy Industries for turbine development and to Idimitsu Koasn Co. Ltd., We are also working with Kyushu Electric Power Co., as the first potential user.
“When we produce the test tonnages from the new plant, in the Hunter Valley (north of Sydney), Idumitsu will do coal characterization testing and the MHI will do the turbine testing. MHI has told us the only changes required in its conventional gas turbine will be modifications to the fuel nozzles, and possibly larger combustion baskets because coal burn is longer than gas.”
Langley says the new process can compete on equal terms with ‘clean’ fossil fuels. “On an equal energy basis,” he says, “it is cheaper than gas, cheaper than Type A fuel oil and marginally cheaper than Type C [high sulphur] fuel oil,” and because it allows coal to be used more efficiently it reduces greenhouse gas emissions. CSIRO figures estimate ultra clean coal (UCC) in a gas turbine with combined cycle would have a thermal efficiency of 53 per cent, compared to around 38 per cent for a conventional coal-fired station.
But perhaps as important, it offers coal an entry into the market for small distributed power systems. “This is a clean fuel,” Langley says, “it does not substitute for conventional coal: its major applications are in areas where coal cannot be used, and it is an alternative for heavy fuel oil and gas.”