Coal-fired technologies back in the spotlight

Paul Boughton

Overcoming the environmental and technical challenges of electricity from coal is a major challenge. Sean Ottewell looks at new technologies that could help.

New technologies aimed at burning both high-grade and low-grade coal to generate electricity are now capable of competing with natural gas as a fuel. In the US, for example, FutureGen 2.0, a US$1.68billion (EUR1.21billion) clean coal project jointly sponsored by the US Department of Energy (DOE) and a group of international energy-sector companies, has won a favourable record of decision (ROD) from the DOE. This means that the department is now in a position to provide about US$1billion (EUR720million) of financial assistance through cooperative agreements with the FutureGen Alliance, which includes Alpha Natural Resources, Anglo American, Joy Global, Peabody Energy and Xstrata Coal.

FutureGen 2.0 is a first-of-its-kind, near-zero emissions coal-fuelled power plant. In cooperation with the DOE, the FutureGen 2.0 project partners will upgrade a power plant in Meredosia, Illinois, with oxy-combustion technology to capture approximately 1.1million tons of carbon dioxide each year - more than 90per cent of the plant's carbon emissions.

Integrated carbon capture

In a statement, Ken Humphreys, chief executive officer of the FutureGen Alliance, said: "The US Department of Energy's approval of a favourable ROD advances the project another step forward. Issuance of the ROD is an important milestone and a boost to demonstrating fully integrated carbon capture and storage technology at commercial-scale coal-fuelled power plant."

In another boost to the project, the FutureGen Alliance has also got the go-ahead from state regulators for a 30-mile underground pipeline that would carry carbon dioxide to an experimental, deep-earth storage site in northeast Morgan County.

The 10- to 12-inch diameter pipeline would be buried at depths of at least four feet in the corridor that passes just north of Jacksonville on its way from Meredosia to the storage site. A depth of at least five feet would be required beneath farm ground.

FutureGen proposes to store one million metric tons of carbon annually for 30 years at depths of about 4,500 feet - that's 90 per cent of the plant's carbon emissions.

Integrated gasification

Meanwhile Southern believes that the power it will produce from its coal-fired integrated gasification combined cycle plant in Kemper County, Mississippi, USA, will be cheaper than that from competitor natural gas-fired plants.

For over 15 years the company has been developing its transport integrated gasification (TRIG) technology which uses circulating fluidised bed technology to turn low-grade, inexpensive coal such as lignite into a gas used to generate power while eliminating about 65per cent of the carbon dioxide emissions that would usually come with burning this fuel.

A key feature of TRIG technology is the high-efficiency design that sends lignite not converted to gas in the initial process back for a second round of gasification.

This allows a high rate of lignite-to-gas conversion to take place at a lower temperature - and thus lower cost - than is possible with other available gasification technologies.

The company also hopes to access the European and Asian markets with TRIG because natural gas prices there are higher than those in the USA.

In Europe, Siemens has commissioned what it says is the cleanest and most efficient hard-coal-fired plant in Europe (Fig. 1). Owned by Trianel Kohlkraftwerk Lünen, and with an electrical efficiency of nearly 46per cent, the 750MW Lünen plant was built as a turnkey unit under a consortium arrangement between Siemens and IHI Corporation.

With 7000 full-load operating hours predicted for this year the Lünen plant can provide electricity for around 1.5 million households. It also supplies the city of Lünen with district heating and will save up to a million tonnes of carbon dioxide emissions each year.

The core feature of the plant comprises a model SST5-6000 steam turbine and a model SGen5-3000W generator.

Responsive ramping

The SST5-6000 high-performance steam turbine guarantees not only highly efficient operation in base load, but thanks to its design characteristics it is also ideally suited for highly responsive ramping. These properties are crucial to meeting changing demands due to the increasing importance of power from renewable resources.

"Despite difficulties arising from the special licensing situation for coal-fired power plants in Germany, we have managed to build a plant to the highest technical standards that by far surpasses the contractually agreed performance values for output and efficiency," stressed Rainer Hauenschild, cheif executive officer of the energy solutions business unit at Siemens Energy.

"The high-efficiency coal-fired power plant in Lünen is a mainstay of the energy mix in the state of North-Rhine Westphalia. The power from this plant is in demand," said Manfred Ungethüm, managing director of the Trianel power provider.

House blocks proposed EPA rukes for coal-fired plant

By a margin of 229 votes to 183, the US House of Representatives has approved a bill to block proposed regulations from the US Environmental Protection Agency (EPA) setting stricter emissions limits on new and existing fossil-fuelled power plants.

Bill HR 3826, the Electricity Security and Affordability Act, was created in response to pending regulations published by EPA, which would establish national limits on greenhouse gas (GHG) emissions from new power plants fuelled by coal or natural gas.

HR 3826 seeks the establishment of standards it says are better aligned with existing technologies for environmental controls and requires Congress to set an effective date for EPA regulations affecting existing power stations.

EPA's proposed rule for GHG emissions from new coal-fired power plants would set the requirement to install carbon capture and sequestration technology, a move opponents of the rule have said would effectively ban coal power in the US.

Ahead of the House vote, the White House issued a statement saying the president would veto HR 3826 because it "threatens the health and economic welfare of future generations by blocking important standards to reduce carbon pollution from the power sector".

"Our bill will base emissions standards for new plants on the best performing technologies actually in use today. For existing plants, Congress will weigh in to ensure that states are accorded the proper role intended for them under the Clean Air Act, and that consumers are not subject to skyrocketing costs.

"Far from barring EPA from controlling greenhouse gas emissions, by insisting on standards based on proven technologies our approach will actually work," said the bill's authors in a Huffington Post interview.

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