What is DICE?

Direct injection carbon engine; a diesel engine which has been modified to enable combustion of water-based slurry of micronised refined carbon fuel (MRC). The engine modifications allow MRC fuel to be injected directly into the cylinders in a similar manner to the heavy fuel oils used in conventional large diesel engines. This method of fuel delivery ensures excellent control of the heat release rate, and highly efficient combustion for a wide range of MRCs. A standard diesel engine cannot use MRC - the fuel pump and atomiser needle/cut off valve will jam within seconds (amongst other problems)!

What is MRC?

Micronised refined carbons. These include a range of carbon-based fuels (black and brown coals, lignite, biomass, biochars, and solid bitumen) that are finely ground, refined to reduce the ash content and improve micronising and other properties.  For black coals, refining would mostly involve deashing via flotation or selective agglomeration.  For porous and lower calorific value carbons such as brown coals and biomass, refining would include densification, hydrothermal treatment or carbonisation to improve micronising and the energy content of the MRC.  The refined carbons are mixed with water to produce a stable, low viscosity slurry with as high a solids content as practical - with the aid of surfactants. The specific energy is typically 15-25 MJ/L, and the viscosity 200-500mPa.s @100/s. The particle size will vary according to the type of carbon (in particular its effective volatiles content), the occurrence of the mineral mater, method of processing, and the speed of the engine. For low speed engines, current experience suggests -50µm for medium volatile black coals and -75µm for brown coals.


What is CWF?

Coal water fuel - a generic term for water-based slurry fuels containing finely ground coal. Other terms include coal water slurry (CWS) and coal water mixture (CWM).

What is the difference between MRC and other coal water fuels/slurries?

The term MRC has been used to differentiate fuel for DICE from the less refined/higher ash (mostly 3-8%), higher viscosity (1-2 Pa.s @ 100/s) coal water fuels and slurries produced for boilers and gasifiers.

Why has the meaning of DICE and MRC been changed to refer to carbon fuels?

A key advantage of DICE is the potential to efficiently utilise a range of biomass, which could include treated biomass, biochars and algal concentrates. Acceptable ignition of biochar has been confirmed in recent tests by the CSIRO, especially if ignition characteristics are sweetened with a small addition of coal. Therefore the terminology has been broadened with the "C" in DICE and MRC now referring to carbon.

What is DCFC?

A direct carbon fuel cell. This is a type of "carbon-battery" with the ability to generate electricity from carbons at extremely high thermal efficiency. For example, a sample of Yancoal UCC was used by Lawrence Livermore Laboratories to generate at a reported 74% thermal efficiency in 2003. The cell is presently being developed for military applications, but larger scale units have been projected from 2035. The DCFC would use low ash carbons similar to DICE - though via dry feed. The DCFC avoids key thermodynamic limitations of the hydrogen fuel cell.

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Can DICE really reduce the CO2 emissions from coal fired generation by 50% within 5 years?

No!!!  DICE has the potential to provide an alternative, cleaner coal technology within 5 years, one that has 50% lower CO2 emissions (kg CO2/MWh)  than from current brown coal power plants (and 30% lower emissions than most current black coal power plants).  So DICE can only reduce CO2 emissions by 50% when it is deployed to replace generation from older brown coal plants.

Compared to new conventional technology under Australian conditions, DICE is expected to provide a 30% reduction in emissions over new brown coal plants, and a 20% reduction over new black coal power plants - including ultra supercritical.

However, this does not take into account other benefits possible from the higher flexibility of DICE, which could provide additional CO2 savings from providing higher efficiency support for renewables, and have an increased ability for integration into a carbon optimised energy system for both electricity and transportation.

What are the main technical challenges for DICE and how are they being de-risked?

As fuel production and logistics would use commercially available equipment, the main technical challenges involve DICE. The USDOE program identified these as achieving efficient and consistent atomisation of MRC, and armouring the engine against abrasive wear. Engineering solutions were demonstrated for both of these issues by GE, Cooper Bessemer and SwRI for medium speed engines, with around 2,000 hours of engine operation (including in a GE Dash 8 locomotive). Also, these tests (which used black coals) were undertaken without any indication of potential longer term issues such as engine fouling by ash. The success of the earlier developments has been acknowledged by the largest engine companies, MAN and Wärtsilä, who believe that DICE could be commercialised within a few years given the appropriate resources to implement suitable engine technology for DICE.

De-risking is being achieved by a staged program for low speed engines (crosshead 2-stroke engines) starting with the development of an MRC atomiser, combustion tests in a small demonstration engine (single cylinder, 1 MW), component refinement and testing, and the design of a prototype engine for a near commercial scale demonstration of DICE.

How long will development take, out to the first commercial installation?

About 5 years, though this timing could be reduced to possibly 3 years with appropriate funding and additional contributors to development.  Implementation after this time would obviously depend on the need to replace old capacity and for new capacity (and being competitive with alternative technologies).  A number of factors make this short development time possible, in particular the ability to adapt existing commercial technologies for fuel production and the engines:

On the fuel side, there already exist commercial plants for producing coal water fuels (also called coal water mixtures and coal water slurries), with over 40 Mtpa presently being produced in China.  These fuels have also been traded internationally in the past as a heavy fuel oil replacement, with various means of transportation via road, pipeline and sea.  Only relatively small changes to the method of production are required to produce MRC for DICE.  It is noted that Australia has developed a number of leading technologies to further improve the economics of MRC fuel production - the Isamill and Jameson Cell.  Although MRC fuel production is initially likely to be by captive MRC plants from coal supplied by conventional infrastructure (Glencore XT already has package plant concepts for MRC production), it is most likely that DICE fuel will be ultimately be transported and traded in a similar manner to fuel oils.

On the engine side, compared to other cleaner coal technologies, DICE has potentially a very short development time and low development cost.  For example the time to develop an engine has been estimated (by MAN and others) at less than 5 years and for less than $60M - including demonstration.  This compares with many billions of dollars and 20 years for ultra supercritical coal (IEA data).

Much of the short lead time for DICE is due to the relatively short time for the manufacture of large engines (around 6 months), and the ability for incremental retrofit with improved technologies as development progresses – this is key to rapid development past the first demonstration plant.  For example, there is no need to wait for a major plant outage (for large coal power plants this may only occur every 12 months) to introduce improved components:  engines can be taken off line for incremental upgrades and be back on line within a few hours, greatly facilitating development.

DICE is very suitable for providing incremental and replacement coal capacity at much smaller unit capacity than for supercritical coal plants.  This greatly reduces the capital hurdles and commercial risks involved in establishing new plant, further reducing the time for deployment.

As DICE is applicable to a wide range of coals (and biomass) development costs can also be shared across all coals.  It is anticipated that this development will include international efforts.  For example there are presently consortia being established in South Korea to develop DICE for MRC produced from low rank coals in Victorian and Indonesia, and also in China from bituminous coals.

The above attributes should therefore enable DICE to have a shorter development time between pilot and full commercial application than other cleaner coal technologies.  BHP Billion data (below) shows that this has been achieved for other technologies - given appropriate support.


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Business basis

What are the advantages expected from DICE?

It is proposed that DICE could assist the transition to a lower emissions energy sector by providing a cost-competitive, lower emissions technology in its own right. Further reductions in CO2 emissions could be achieved by providing back-up and load-following power to enable the cost-effective and increased use of intermittent renewables. DICE could provide a number of benefits, especially for Australia:

  • DICE could facilitate a higher penetration of intermittent renewables by providing rapid response power (with rapid start and load change capability) when renewable generators are unable to meet demand, thereby decreasing the cost and increasing the effectiveness of renewables.
  • DICE could facilitate a higher penetration of intermittent renewables by providing rapid response power (with rapid start and load change capability) when renewable generators are unable to meet demand, thereby decreasing the cost and increasing the effectiveness of renewables.
  • DICE provides an option for customers seeking new power generation capacity. It is modular (10-100 MW) and requires half the capital investment and is well suited to Australia's current energy market environment.
  • DICE technology could assist in the uptake of carbon capture and storage (CCS), delivering a 30-40% cost advantage compared to conventional coal and gas power generation technology.
  • MRC fuel could also become a new global commodity for cost effective low emission power - especially relevant to Victoria with the potential to efficiently convert vast reserves of the brown coal at around 1/3 the cost of LNG.
  • MRC fuel is lower cost than fuel oil and the higher cost gas, and could reduce power generation costs for remote or decentralised generators. This would also enable lower cost electricity for off-grid communities (especially in developing countries) and assist sustainable mining development by providing cost effective power for mines and communities.
  • DICE could also provide users of gas with the option of installing multi-fuel gas engines now, and retrofitting with a DICE conversion kit later when gas prices become uneconomic – preventing stranding of assets (not an option for gas turbines).
  • The efficiency, flexibility and modularity of DICE provides the option for a pathway to energy systems with net negative CO2 emissions. This could be achieved via optimal use of a range of carbon management strategies – as system inputs, energy conversion, and system outputs.

What is the market potential?

In summary, the international market potential is large at well over 175 GW, with significant upside both nationally and internationally.

The market potential of fuel for DICE is effectively any coal generation, with the easiest market entry being replacement of smaller/old inefficient capacity (especially where this capacity is needed to support intermittent renewables), and large remote diesel fuelled capacity (mine sites or in developing countries). This is followed by incremental new generation capacity and marine:

The current small scale/old capacity is around 175 GW (~508 Mtpa coal equivalent).

Current remote generation (off-grid) capacity is estimated at around 3% of the total generation worldwide.

Marine capacity is estimated at an equivalent 85 GW (250 Mtpa coal equivalent).

In the USA, DICE would require some co-firing of biomass MRC, or partial (say 20%) CCS to meet the recent USDOE limit of 1100 lb CO2/MWh (burner tip).

Why haven't the coal industry produced MRC before?

In short, there is no current market for MRC. Although the production of coal water fuels and slurry-based transportation have been considered in the past for boiler markets, the world coal industry is presently based on producing dry “lump” coals. There has been no market for ultra-fine wet coal, in fact, as drying and briquetting of this material for sale into conventional markets is costly and energy intensive, any fine wet coal produced during coal processing is usually disposed of in tailings dams.

As DICE requires ultra-fine coal slurry, it provides the industry with opportunities to produce value added ultra-low ash products (the efficiency of coal cleaning actually increases as the coal size decreases). This includes the ability to produce MRC from tailings - with incentives to reprocess existing tailings dams.

What is the cost of development relative to ultra-supercritical coal?

Substantially less, based on the findings of the USDOE DICE program over 1978-92, and recent IEA cost estimates for ultra-supercritical coal.

The cost of development of DICE is expected to be 1/50th of that required for advanced ultrasupercritical pf (AUSC), and requiring 1/5th of the development time. This is because of metallurgical issues. Advanced ultra supercritical requires new materials that can operate at high temperature/pressure conditions for practical service lifetimes without failure. The EU, USA, Japan, India and China all have extensive material research programs aiming for steam temperatures of 700°C. At a development cost of billions of dollars, it is anticipated that the earliest that a commercial unit could be brought on-line is 2031 (Nicol, IEACCC/229).

Commercialisation of AUSC will therefore be strongly impacted by the cost of exotic nickel alloys, making the increasing capital cost of advanced ultra-supercritical a particular concern. For example, the extreme alloys and cost of fabrication required for the high pressure steam pipes (including reheat) alone could account for over 80% of the cost of the boiler, unless measures to reengineer the boiler-turbine layout to minimise the length of these pipes is achieved.

In contrast, while the combustion conditions in the diesel engine are far more extreme in terms of the temperature and pressure of the working fluid (which contributes to its higher thermodynamic efficiency), the diesel cycle is a batch process:  High temperature conditions are present for less than 10% of the time, which avoids the need for large amounts of exotic alloys.  The adaptations required to fire MRC are bolt-on, and together with the ability to make cylinder-based incremental improvements, should greatly reduce the development time for DICE (thereby providing DICE with a much faster development compared to other clean coal technologies).

What is the link between DICE and the DCFC?

Both DICE and the direct carbon fuel cell (DCFC) require ultra-low ash carbons as fuel – so a fuel cycle developed now for DICE could be used to supply fuel for the DCFC in the longer term (projected after 2035). The DCFC could give a further 20% reduction in CO2 intensity over DICE, and be even more suitable for decentralised and distributed generation, and for tri-generation. DICE, the DCFC and renewables therefore provide an alternative pathway for very low CO2 emissions electricity generation without depending on major CO2 capture and storage.

Why is a diesel engine being developed to use MRC and not a gas turbine?

Better efficiency, fuel tolerance and flexibility: Size for size, the diesel engine has the highest thermal efficiency of any heat engine. Being a piston engine (ie a having a batch or cyclic combustion process), it is also more flexible and fuel tolerant, and is scalable to give any capacity via multiple cylinder units (this enables maximum generation efficiency over a much wider load range).

In particular, the batch combustion of the diesel engine enables very high combustion temperatures and pressures to maximise thermal efficiency, whilst maintaining relatively low metal temperatures (<400°C), and avoiding the high temperature fouling or corrosion issues that occur in gas turbines with impure fuels.

Although diesel engines use an expansion turbine to drive the turbo compressor, the metal temperatures are low (<400°C) compared to gas turbines (>1200°C), which dramatically reduces fouling tendency and allows the use of a wider range of harder materials to protect against particle abrasion.

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Technical – fuel production

What are the implications of coal type and coal properties?

These have yet to be defined. However, a wide range of coals have been tested and shown to give good ignition and combustion under diesel engine conditions - providing that reasonable atomisation is achieved.

For example, ignition delays (at 600°C) for Bulga, Wambo, Lithgow, Moolarben, Walloon, Loy Yang, Yallourn, Kalimantan, and Rhenish coals are in the range of 3-7 ms, which is very acceptable for low speed, and the larger medium speed diesel engines.

Only charcoal-based MRC gave unacceptable ignition - but this could be dramatically improved with a small proportion of coal or other higher volatile fuel, or the use of pilot fuel (as is used for many gas engines).

It is speculated that the extremely high heating rates in a diesel engine (up to 300,000°C/s, or 10-20x faster than in pf boilers or gasifiers) together with the high pressure (around 120-150 bar) results in enhanced volatiles formation which promotes ignition even for lower volatile coals.

Doesn’t micronising of the carbon fuel use a lot of energy?

No: Nearly all solid fuels are micronised to some degree before combustion (eg coal is milled to a mass mean size of around 65-70 µm for boilers). For DICE, extra fine micronising is required, with a mass mean size of around 15 µm being required (giving a top size of around 50-70µm). This increases the energy penalty for micronising to around 0.6% points – about 3x that for coal fired boilers.

However, recent R&D has shown that the ignition and combustion characteristics of MRC are most strongly affected by the quality of atomisation (more so than by particle size or water content). It is therefore expected that improved combustion could actually be obtained from the use of coarser grinds, which give a lower viscosity and easier to atomise MRC for a given solids loading. Obtaining an optimum grind could reduce the energy for micronising by as much as 50%, and give other benefits across the DICE fuel cycle.

Note that the micronising energy penalty for DICE is actually much smaller than for some other power plant ancillaries:  For example, current dry cooling of steam generation plant reduces the efficiency by 1.5-2% points, and a similar efficiency penalty can accrue from NOx and SOx emissions control.

What is the recovery of coal during the cleaning step?

Coal recovery is dependent on the cleaning methods used, and the production mix of the preparation plant. For flotation, a combustible recovery of 85-90% is readily achievable in producing MRC (this has been achieved for a wide range of coals). However, this does not necessarily mean a loss of 10-15% of the recoverable coal, as the tailings streams from the MRC cleaning steps can be utilised for higher ash products. In addition, MRC can also be produced from tailings (with extensive pilot scale experience by Glencore/XT, Yoon, Tradd Barrow, CSIRO etc), which effectively increases the overall grade recovery.

The reason for the increase in combustibles recovery is due to micronising, which significantly increases the degree of liberation/separation of mineral matter from the coal.

Overall, combustibles recovery should therefore be higher for MRC production than from the production of conventional washed coal products.

What about chemically cleaned MRC?

A number of processes have been developed to the pilot or small demonstration scale over the last 30 years to chemically clean coal for higher value applications, such as for electrode carbons, a fuel oil replacement for boilers and diesel engines, and an LNG replacement for gas turbines. The processes either dissolve the ash from the coal (Yancoal UCC, AMAX, Cenfuel/InterTech), or dissolve the coal from the ash to produce a solvent refined coal prill (Kobe Hypercoal, KIER SinEx).

As chemically cleaned coals can be produced with less than 0.5% total ash (and with mineral ash below 0.2%) they can make very high quality MRC, with properties superior to many heavy fuel oils, and at substantially lower cost - though the fluctuating price of crude over the last 30 years has made commercialisation of these processes difficult.

In general, the cost of chemical cleaning approximately doubles the processing costs to produce MRC, making this fuel most competitive for higher speed DICE (lower capital cost) for remote and intermittent generation, and large marine applications.

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Technical – engines

Doesn’t water in fuel reduce thermal efficiency?

Slightly: Water either in the fuel, or produced from the combustion of the hydrogen in the fuel, always decreases the achievable thermal efficiency due to the latent heat of steam in the exhaust gases. However, the overall effect of added water on efficiency can be significantly minimised in internal combustion engines.

It is noted that water is routinely added to diesel engines for NOx and soot emissions control – up to 50% by weight of the fuel. Methods include adding water to fuel to create oil-water emulsions, direct injection of water into the cylinder, or even more effectively by scavenge air moisturisation (evaporating hot sea water into the hot air after the turbo compressor to feed the cylinders with warm (70°C) saturated air). The effect on efficiency is small, usually less than 0.5% points.

For MRC, given a modest fuel preheat and taking into account the lower hydrogen content and higher oxygen content of MRC, the efficiency penalty is expected to be between 1-2% points relative to diesel fuel. This still provides DICE with a step increase in efficiency over conventional coal steam plants, due to the higher efficiency of the Diesel cycle.

It is noted that the previous USDOE program, fuelling medium speed 4-stroke engines with MRC containing 50% water showed little or no measurable reduction in thermal efficiency over diesel. Recent duration tests by CSIRO firing Yancoal UCC (52% water) into a small diesel engine with an electronic fuel injection system, gave identical efficiency to the base engine using diesel fuel.

What about ash fouling?

This has received scant attention, presumably because ash fouling has not been reported as an issue in any of the past engine tests totalling around 20,000 hours. A complete lack of fouling is unexpected, as coal cleaning processes only remove the bulk/extraneous mineral components in coal. This leads to flyash with proportionally higher amounts of deleterious elements (Na, K, S, Cl, Ca, Mg) from the original coal – a condition certain to cause fouling in other combustion devices. However, past engine tests, including continuous operation periods of over 100 hours (USDOE), have not observed cylinder or turbocharger fouling. Compared to boilers (and gas turbines), the lack of fouling has generally been attributed to the highly cyclic heat flux within reciprocating engines:  Cylinder surfaces are only exposed to gases (say above 800°C) for ~10% of the cycle, and the temperature of the metal surfaces is lower (mostly below 300°C).  Deposits in engines are also exposed to rapid pressure cycling, which is also expected to increase deposit sloughing via deposit panting.

Note that the lack of fouling in diesel engines was actually the main reason for terminating development of the coal fired gas turbine in favour of the diesel engine in the 1980s – which resulted in the comprehensive USDOE DICE program.

More recent tests involving a 40 hour engine test using Yancoal UCC (a chemically cleaned ultra low ash coal) in an 16 kW laboratory engine have given similar results. This is despite the UCC fuel used having an exceptionally high alkali:silicate ratio which would likely cause chronic fouling in other combustion devices.


What components need to be changed to adapt a diesel engine to DICE?

Previous developments, particularly under the USDOE program of 1978-92, showed that the main components to be changed to fire MRC in diesel engines were (in decreasing order of importance) the fuel system, rings/piston ring grooves, cylinder coatings and exhaust valves/seats.

To some extent, the use of bitumen water emulsions and slurries in diesel engines provides a good analogue for MRC. Over the last 20 years there have been a number of initiatives to produce bitumen water fuels to replace heavy fuel oil in boilers, and these fuels have also been used in diesel engines. Such fuels include Orimulsion produced from natural bitumen, and MSAR (multiphase superfine atomised residue) produced from refinery residue (an extremely heavy tar, which is solid at room temperature). MSAR was developed as an Orimulsion replacement, and is really a bitumen-MRC (solid bitumen particles in water). While it is a very difficult fuel, giving both poor atomisation and ignition, and contains highly abrasive catalyst fines, it has been used in adapted large engines.

Although the list of changes for modern engines remains to be defined (and will be an outcome of the upcoming 1 MW engine tests by MAN), based on past experience, the modifications could include:

    • a corrosion resistant fuel system - conventional steels will rust with MRC (as can be the case for some bio oils)
    • ability to flush the fuel system for shut down
    • dual fuel system to allow starting and low load operation with the assistance of lighter fuels
    • low intensity agitation of storage tanks (current commercial systems for CWF should be appropriate)
    • different fuel preconditioning system to enable viscosity trim control by additives or water, and for fuel straining at ~250µm
    • seal oil protected, hydraulically actuated fuel pump plungers (similar to the latest HEUI type atomisers), to avoid needing to meter MRC directly
    • ceramic cut off valve/seat
    • ceramic nozzle block with nozzles optimised for MRC's unusual high shear flow characteristics
    • ceramic coated rings and lower ring grooves
    • revised lamp black/grunge oil drainage system (cross head engines)
    • upgraded lub oil filtration system (4-stroke engines)
    • lubricants optimised for solid carbon fuels (probably with lower base number, but higher detergency than for heavy fuel oils)
    • degritting separator upstream of the turbo expander
    • grit removal system for the exhaust ducting
    • heat recovery boiler designed for coal
    • NOx, SOx and particulate removal system designed for coal

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What reductions in CO2 are possible with DICE?

DICE provides a higher efficiency coal-based generation technology, with a step reduction in CO2 emissions of 20-35% for black coals, and 30-50% for brown coals (these ranges refer to new DICE versus new supercritical pf coal, and new DICE versus old pf coal). This benefit can be doubled if bio-chars are blended with coal (coal is needed to improve the combustion characteristics of the char-coal blend).

How would NOx, SOx and particulates be controlled?

It is assumed that DICE would employ the same technology as for current large diesel engines for stationary power generation. These use conventional SCR, FGD and either precipitators or fabric filters for control of these emissions. As it is expected that MRC will produce significantly lower NOx and SOx than heavy fuel oil, it is likely that these control measures may not be required for some smaller installations.

What about the chemical additives used to produce the fuel?

Only small amounts of relatively benign additives are required:  PSSNa and CMC are used in medicines, eye drops and personal lubricants).  Diesel and MIBC are the current industry standards for flotation.  These additives contain predominantly C, H, O, S and Na and in terms of combustion should be no different to coal.

Compared to conventional coal cleaning, MRC production from black coal uses only small amount of chemical additives, which amount to less than 5% of the cost of production.  Nominal values for black coal MRC are as follows:



Rate kg/t dry coal

Cost $/GJ






Amount required depends on coal hydrophobicity and extent of micronising





Low because micronising increases froth stability





Cost based on production data for a 10,000 tpa plant






Total cost of additives



* of active ingredient (added in aqueous solution)

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How is MRC transported?

MRC has similar rheological properties to coal water mixtures for boilers, and it is therefore assumed that it can be reliably stored and shipped. Like all slurries, some settling will occur given sufficient time, and therefore all tanks are required to be equipped with low intensity tank agitators (for example, as used for heavy fuel oil storage).

It is envisaged that MRC would be mostly transported as slurry; however, it would also be possible to transport the fuel as a cake or briquette. To produce MRC from cake, only a small addition of water and dispersant is required in a mixer. Briquettes would also require remilling.

Overall logistics will depend on the feed coal and market: For example, if MRC is to be produced from tailings, it would be produced at the washery and shipped as slurry or briquette. If MRC is to be produced from an export coal, then it could be produced from normal coal products by an MRC plant that is nearby the end user - thereby avoiding the need for special logistics.

As background, it is noted that the World's first commercial trade in MRC-like fuels occurred in the 1990s, with 300,000 t/annum being produced in China, stored in a 10,000 m3 tank, and transported to Japan over 1,100 km in a modified fuel oil tanker of 5,000 DWT, followed by coastal transportation along Japan over 400 km via a fuel tanker of 700 DWT.

Another early example was by Japan COM and Joban Power. Up to 500,000 t per year were produced in Japan (including from Hunter Valley Saxonvale coal) to part fuel a 600 MWe boiler at Nakoso power station (having 12x 11 t/h burners for CWF). Transportation was via a 9 km pipeline of 350 mm diameter. The project terminated in 2003 due to low fuel oil prices. At that stage, LION Japan was producing the PSSNa dispersant from a pilot plant in Singapore.

Presently there are over 40 Mtpa of CWF being produced in China for a range of combustion and gasification applications. The fuel is transported by adapted fuel oil systems, including road, rail and pipeline.

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Why is DICE being redeveloped when development was terminated in the early 1990s?

Different drivers and philosophy:  Earlier DICE development was as a fuel oil replacement for heavy transportation.  The present development is for DICE as a clean coal technology to complete with coal, gas and fuel oil in a wide range of stationary generation applications. 

Earlier development of DICE under the USDOE (Generation 2) was in response to the global oil shocks in the 1970s - especially for heavy transportation and small scale generation using medium-high speed engines. This is a difficult application for coal, and although the technical issues were overcome, the technology became marginal when the price of diesel plummeted in the 1990s. The generations of development are shown in the figure below.


Generation 3 DICE is being developed with new environmental, economic and energy security drivers, and with technology not available to the earlier developments. For example, on the fuel production side, 2 Australian technologies (the IsaMill and J-cell) provide a step improvement in the quality of MRC and improved economics compared to what was possible during USDOE program over 1978-92. Similar step improvements have also occurred on the engine side, with electronically controlled engines, with new materials, and improved tolerance to lower grade fuels, now being available.

Together with the focus on larger and lower speed engines for stationary generation, DICE has become more economic and commercialisation technically easier to achieve.

Has coal ever been fired successfully in gas turbines?

Yes and no: There have been a number of partially successful attempts to directly fire gas turbines with coal, starting with lignite firing of very early gas turbines in Germany during WW2, work in both the USA and Victoria with lignitic/brown coals over 1965-87, and 2 notable attempts with black coals - one which fired washed coal into a gas turbine locomotive (UP 8080) and the other being a coal-fired 1978 Cadillac Eldorado.

All attempts at using lignites and brown coals resulted in extreme turbine fouling - with the hot core becoming choked with deposits within an hour or so.

The use of black coals in turbines gave better results. The extremely powerful (5.2 MW/7,000 hp) UP 8080 locomotive was trialled during 1962 over ~15,000 km but experienced severe turbine erosion - likely a combination of the relatively high ash coal (3-5%, nut product) and the char from incomplete combustion of the relatively coarse (d50~60µm) coal fired - which was milled on-board.  Development of UP 8080 ended in 1964 not long before the entire class, including the diesel fired variants, were taken out of service for noise issues.

The Cadillac also used dry coal feed (using a simple mechanical chain conveyer controlled from the accelerator pedal), but with lower ash (0.2-3.2%) and much finer grind (10-12 µm top size). The vehicle was road tested with performance matching diesel firing of the turbine. Development ended in 1983, after significant difficulties in handling dry finely ground coal, and high NOx emissions and throttle lag issues typical of small gas turbines.

All other coal-fired turbine developments ended in the 1980s in favour of the more fuel tolerant coal fired diesel engine - DICE.

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