Refined coal

Summary

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Refined coal is the product of the coal-upgrading technology that removes moisture and certain pollutants from lower-rank coals such as sub-bituminous and lignite (brown) coals, raising their calorific values.^[1] Coal refining or upgrading technologies are typically pre-combustion treatments and processes that alter the characteristics of coal before it is burned. Pre-combustion coal-upgrading technologies aim to increase efficiency and reduce emissions when coal is burned. Depending on the situation, pre-combustion technology can be used in place of or as a supplement to post-combustion technologies to control emissions from coal-fueled boilers.^[2]

A primary benefit of refined coal is the capacity to reduce the net volume of carbon emissions that is currently emitted from power generators and would reduce the number of emissions that is proposed to be managed via emerging carbon sequestration methodologies. Refined coal technologies have primarily been developed in the United States. Several similar technologies have been researched, developed, and tested in Victoria, Australia, such as the Densified coal technology (Coldry Process) developed to alter the chemical bonds of brown coal to create a product that is cleaner, stable (not prone to spontaneous combustion), exportable and of sufficiently high calorific value to be a black coal equivalent.

Coal-upgrading technology edit

Coal-upgrading technology refers to a class of technologies developed to remove moisture, and certain pollutants from low rank coals such as sub-bituminous coal and lignite (brown coal) and raise their calorific values. Companies in Australia, Germany, and the United States are the principal drivers of this research, development, and commercialization.^{[citation needed]}

Environmental rationale edit

Around 30 nations collectively operate more than 1,400 brown coal-fired power stations worldwide. Brown coal power stations that cannot economically dewater brown coal are inefficient and cause high levels of carbon emissions. High-emitting power stations, notably the Hazelwood power station in Australia, attract environmental criticism. Many modern economies, including Greece and Victoria (Australia), are highly dependent on brown coal for electricity. Improved environmental performance and the need for stable economic environment provide incentives for investment to substantially reduce the negative environmental impact of burning raw ('as mined') brown coal.

Economic rationale edit

Coal-upgrading technologies remove moisture from 'as mined' brown coal and transform the calorific performance of brown coal to a 'cleaner' burning status relatively equivalent to high calorific value black coal. Some coal-upgrading processes result in a densified coal product that is considered to be a Black coal equivalent product suitable for burning in black coal boilers.

Victorian brown coal, with a characteristic moisture content of 60% by weight, is regarded as the world's moistest brown coal. The high moisture content is the key reason the state's three major power stations are collectively regarded as the dirtiest carbon emitters in the world. Studies undertaken by the University of Melbourne and Monash University confirm that when moisture is removed from Victorian brown coal, naturally low levels of ash, sulfur, and other elements rank it as being one of the cleanest coals in the world. When de-watered, upgraded brown coal can compete in the export market at comparable prices to black coal.

With significant brown coal mining occurring worldwide and mining levels increasing, the need for coal-upgrading technologies has become more apparent. The technologies will help to address the global environmental concern of rising emissions from the burning of brown coal and provide alternative fuel options to rapidly emerging economies such as Vietnam, that face difficulty competing for black coal with China, India, Japan, and other nations.

Lignite mined in millions of metric tons^{[citation needed]}

Country	1970	1980	1990	2000	2001
Germany	369.3	388.0	356.5	167.7	175.4
Russia	127.0	141.0	137.3	86.4	83.2
United States	5.4	42.3	82.6	83.5	80.5
Australia	24.2	32.9	46.0	65.0	67.8
Greece	8.1	23.2	51.7	63.3	67.0
Poland	32.8	36.9	67.6	61.3	59.5
Turkey	4.4	15.0	43.8	63.0	57.2
Czech Republic	67.0	87.0	71.0	50.1	50.7
People's Republic of China	13.0	22.0	38.0	40.0	47.0
SFR Yugoslavia	26.0	43.0	60.0	-	-
Serbia and Montenegro	-	-	-	35.5	35.5
Romania	14.1	27.1	33.5	17.9	29.8
North Korea	5.7	10.0	10.0	26.0	26.5
Total	804.0	1,028.0	1,214.0	877.4	894.8

Technology comparison edit

Because of inherent high moisture content, all lignites need to be dried prior to combustion. Depending on the technology, drying is achieved either via a discrete operation or part of a process. The comparison chart identifies different drying methods that are in development in different countries and provides a qualitative comparison.

Option	Drycol	ZEMAG[note 1]	Coldry Process[note 2]	RWE-WTA[note 3]	HTFG[note 4]	WEC-BCB[note 5]	UBC[note 6]	Exergen CHTD[note 7]	MTE[note 8]	Kfuel[note 9]	LCP[note 10][3]
Country of origin	United States	Germany	Australia	Germany	China	Australia	Indonesia/Japan	Australia	Australia	United States	China
Process Description	Drycol Microwave Drying	indirect contact drying in tubular dryers	exothermic reaction. natural evaporation. accelerated drying at 25-30 °C	fluidised bed stream drying	High temp flue gas fluidised bed drying	flash dry coal fines. use pressure to form briquettes	mixing crushed coal with oil, heating the mixture to 130-160 °C under 19-19.5 Bar pressure, separating the slurry cake from the oil by a centrifuge and then drying and briquetting it	Continuous Hydrothermal Dewatering decarboxylation reaction in the slurry form at 300 degC and 100 Bar, followed by gas/liquid/solid separation and press drying	heat and squeeze at 250 °C and 125 Bar, express water from coal	heat and squeeze at 200 °C and 100 Bar	pyrolytic process that employs heat and pressure in an oxygen-free environment to continue the coalification process that occurs naturally in the earth
Drying Description	Microwave Drying while keeping coal below 90 deg C	drying achieved using low pressure steam of max. 180 °C, 4 bar	drying achieved using low-temperature waste heat to provide evaporative drying	drying achieved using >100 °C low pressure steam	drying achieved using >900 °C flue gas to dry 0–50 mm raw coal with 2-4% system O2 concentration under slight positive pressure	drying achieved via exposure to high pressure combustion stream (flash drying)	drying achieved by exposure to 130-160 °C under 19-19.5 Bar pressure in oil slurry	drying achieved by exposure to high pressure and temperature in a vertical autoclave, followed by a flashing step	drying achieved via high pressure and temperature compression	drying achieved via high pressure and temperature compression	The process employs no additives and extracts both surface and inherent moisture.
Grade of heat used for drying	Very Low	Low	Low	Medium	Low	High	Medium	Medium	High	High	Medium
Alternative uses for energy consumed in drying	None	power generation	none	power generation	coal sales (fines used for combustion	coal sales (fines used for combustion	n/a	electrical energy	electrical energy	electrical energy	power generation
Pretreatment requirement	Sizing for material handling	crushing/screening (normal)	(normal) plus mechanical mastication and extrusion	(normal)	crushing/screening to 50 mm	(normal)	crushing and mixing wit
CO2 exposures	n/a	n/a	Up to 40% reduction in CO2. Net beneficial CO2 position due to low heat and low pressure	Up to 30-40% CO2 reduction from the boiler. (Lost steam energy utilised in fluid bed dryer not accounted for)	Up to 25-35% CO2 reduction from the boiler	zero net improvement due to energy source for drying is coal combustion	n/a	Up to 40% reduction in CO2	~15% CO2 reduction in combustion (detailed analysis not available). Zero net improvement due to energy used for heating and compression	~15% CO2 reduction in combustion (detailed analysis unavailable). Utilises energy for heating and compression	n/a
Waste streams generated from drying	clean water	none	none	none	none	none	waste water stream	none	waste water stream	waste water stream	none
Byproduct streams possible	none	none	demineralised water	none	none	none	n/a	demineralised water	none	none	tar product
Coal output stream description	Direct use	for briquetting/exporting or power generation	coal pellets for use and export	input coal for power generation only	coal for sale or power generation	coal briquettes for use and export	coal briquettes for use and export	coal for use and export	input coal for power generation only	input coal for power generation only	exportable coal for power generation
Coal output moisture level	10 - 30%	5-20%	12-14%	12-14%	6-30%	10-15%	n/a	5-10%	~18%	~20%	1-15%
Coal output - transportable or exportable	long-distance transport	long-distance transport	non-pyrophoric	direct to boiler only	short-distance transport	non-pyrophoric	non-pyrophoric	non-pyrophoric	pyrophoric	pyrophoric	hydrophobic, transportable & exportable
Industrial maturity	Technology in food industry 35 years	well established and proven technology, industrial plants of up to 3 MTPA capacity running in Germany and the Czech Republic	pilot plant operational for 7 years; extensive database of global testing; commencing feasibility for full-scale commercial operation by 2014	commercial operations in several locations	It was used for coking drying since 1955 for over 200 wash plants	one commercial scale plant, operations have not exceeded 30% of nameplate capacity	pilot plant operational, demonstration plant 2008-2011	Pilot Plant 2002 - 2008, ready for commercialisation. Tested on Victorian and Indonesian coals	pilot plant abandoned	pilot plant operational	1MTPA plant in Inner Mongolia fully operational since 2012

1. ^ ZEMAG Clean Energy Technology, Germany
2. ^ Coldry Process, ECT Limited, Australia
3. ^ RWE-WTE = RWE (Rhenish-Westphalian Electric) WTE technology
4. ^ HTFG = Delta Drying Technology Ltd
5. ^ WEC-BCB = White Energy Company, Binderless Coal Briquetting
6. ^ UBC = Upgraded Brown Coal Process, Japan Coal Energy Center & Kobe Steel Ltd.
7. ^ Exergen company, Continuous Hydrothermal Dewatering technology
8. ^ MTE = Mechanical Thermal Expression, develop|ed by the CRC for Clean Power
9. ^ KFuel = Koppelman Fuel, Evergreen Energy, Denver, Colorado, USA
10. ^ LCP = LiMaxTM Coal Process Technology, developed by GB Clean Energy

History and advantages edit

United States edit

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The best known producer of refined coal is a company based in Denver, Colorado called Evergreen Energy Inc. The company is publicly traded and is listed on the NYSE Arca exchange. According to the company's website and its Form 10-K on file with the U.S. Securities and Exchange Commission, it was founded in 1984 to commercialize a coal-upgrading technology first developed in a Stanford University laboratory by Edward Koppelman. Taking the "K" from Koppelman's name, Evergreen, formerly KFx Inc., branded its refined coal product as "K-Fuel."^{[citation needed]}

Much of the coal in the western United States is known as "lower-rank" coal that falls under the categories of "sub-bituminous" and "lignite" coals. These coals have high moisture levels and can be 20% to 30% water. This relatively high moisture content compared to "higher rank" coals like bituminous and anthracite coals make lower-rank coals less efficient. The average heat content of sub-bituminous coal consumed in the United States is approximately 8,500 British thermal units (Btu) per pound. The K-Fuel(R) process uses heat and pressure to remove approximately 30 percent of the moisture from raw, low-rank coal and raises its thermal content to approximately 11,000 Btu per pound.^[1] In addition to raising the coal's heat value, a significant amount, up to 70 percent, of the elemental mercury in the coal is removed and, because of its higher efficiency, lower chloride and nitrogen oxides emissions are achieved on a per kilowatt hour generated basis.^[4]

The advantages of the refined coal process are more efficient transportation and the ability of utilities to switch to a fuel made of 100 percent refined coal or a blend of raw and refined coals in order to achieve lower emissions and greater efficiency.^[5] A disadvantage is that the industry requires significant subsidies. An examination of government figures show that in 2007, for every megawatt-hour generated, refined coal received $29.81 in federal support, solar power received $24.34, wind power received $23.37, and nuclear power received $1.59.^[6]

Australia edit

The producer of densified coal in Australia is a company based in Melbourne, Victoria called Environmental Clean Technologies Limited (ECT Limited)^[7] The company is publicly traded and listed on the Australian Stock Exchange (ASX). The company was listed in 2005 with the primary purpose of commercialising the Coldry Process coal-upgrading methodology first developed in the Chemical Laboratory of Melbourne University by Dr B. A. John in the 1980s. The name of the process derived from the Calleja Group, which acquired the technology in 1994 and developed the technology to pilot demonstration at Maddingley Mine, Bacchus Marsh, Victoria in 2004 before licensing the technology to ECT Limited for further commercialisation in 2005.

The State of Victoria contains approximately 25% of the world's known reserves of brown coal (lignite). This coal is also amongst the world's 'wettest' coal, with a typical moisture content of 60 per cent water by weight. High moisture content makes Victorian brown coal an inefficient fuel source and is the primary reason why the Hazelwood power station in the Latrobe Valley is regarded as the world's dirtiest coal-fired power station. The Coldry Process uses low-pressure mechanical shear to create a natural exothermic reaction within the coal that then naturally expels 80 per cent of the moisture content. Expelled moisture is then captured and recovered as distilled water. Victorian brown coal transformed by the Coldry Process has a raised thermal content of 5874 kcal/kg, which is comparable to most export-grade Australian black coal.

The advantage of the Coldry Process is its ability to allow power generators to switch to a blend of raw as mined brown coal and Coldry pellets to achieve lower emissions in existing inefficient boilers, or achieve substantially less emissions by introducing black coal boilers and using 100 per cent Coldry refined coal pellets as a black coal equivalent. The Coldry Process provides the added advantage of creating new revenue streams for power generators through the production of a product that can be exported to other countries as a replacement for black coal. Unlike other refined coal processes, the Coldry Process is a commercial methodology that does not require subsidy.

Commercial development edit

See also edit

References edit