IGCC is the Best Way to Burn Solid Fuels for Energy
IGCC: What it is, and Why IGCC is the Best Biomass Technology for the Future

IGCC is the combination of gasification with a combined-cycle turbine system to generate electricity. Don't let the complexity of the technological terms put you off reading this!

Unfortunately, this technology is not easy for the ordinary public to understand, but that does not mean that it should be ignored or dismissed, in fact it is all the more important to persevere until you do understand. It is important that as many people as possible appreciate how this could help a world desperately in need of low cost energy produced in the most environmentally responsible way.

The typical Integrated Gasification Combined Cycle power plant consists of four major operating components:

1. an air separation unit (ASU) to provide pure oxygen;
2. a gasification plant where heat is generated;
3. a gas clean-up system;
4. and a combined-cycle power plant (which by “combined cycle” simply means that the energy from both the high pressure gas produced by gasification, and the the steam from gas combustion has passed through the turbine).

Fig. 1: Block Diagram of the IGCC Plant built with EU Funding Assistance in Puertollano/Spain (Courtesy: IChemE and W. Schellberg, Krupp Uhde GmbH, from their paper; "Commercial Operation of the Puertollano IGCC Plant")

The gasification process takes place at extremely high pressure and temperature which very effectively almost totally destroys all of the residual toxic and polluting chemicals which traditional coal fired power station combustion leaves behind.

IGCC is the cleanest technology available so far for the conversion of solid fuel into electricity. The emissions expected and achieved from these plants when compared to standard coal plants (and that includes even the newest proposed throughout the world today) are far lower.

Another great feature of IGCC is that it is the only thermal power option, excluding new nuclear plants, that effectively mitigates fuel price volatility while addressing current and future environmental concerns. An IGCC project’s fuel cost hedging capability stems from its ability to gasify any combination of natural gas, coal, and waste-products such as petroleum coke.

As we have already indicated, but wish to stress is that the power is generated from both the gas and steam turbines, resulting within this combined cycle, a much higher efficiency. This is even after the loading placed upon the turbine as it simultaneously compresses the feed reactants, as it turns.

That IGCC using coal for power generation is currently the cleanest coal technology available is being demonstrated to the US House of Representatives, committee on Energy and Commerce, Subcommittee on Energy and Air Quality in an programme commenced in 2003, at four plants that are currently operating.

Perhaps the principal obstacle to the development of IGCC projects is their capital cost compared to conventional steam/electric options. The capital cost of a new IGCC facility is around 20 to 30% higher than the cost of a new conventional pulverized-coal-fired plant.

Implementing IGCC is a long term strategy for hedging against oil price rises. As the oil and gas prices rise the argument for IGCC just keeps getting stronger. Until now, although many in the US have recommended that an accelerated shift toward coal use by gasification would put a long-term ceiling on the price of oil a stronger lobby has pointed out that the United States would benefit more financially from simply scaling up extraction of offshore oil and natural gas.

For the present, especially in the US, coal-fired plants are still competitive while IGCC technology is being implemented in a few plants, and is getting its chance to prove commercial viability.

But, the final benefit from IGCC of easy and simple carbon capture within the process when you gasify like this, is likely to be the winning feature ultimately driving this new technology forward into mainstream generating capacity. Carbon separation and long term capture, before its emission (as Carbon Dioxide) to the atmosphere from the flue gases is also called “carbon sequestration” in the US.

Carbon sequestration has yet to be proven but could become a large factor in reducing climate change from carbon emissions. The idea is that you produce carbon dioxide, but don't emit it to the atmosphere. By not emitting it, all worry about climate change would be arrested in its tracks!

There are two types of sinks which could be used and are highly unlikely to be needed for any other use. These are deep un-mineable coal seems and deep saline aquifers. Carbon capture is under way at several sites in Europe and the United States. Sequestration tests need to find out if the CO2 stays put and won't leak up into drinking aquifers or out into the atmosphere.

The proof of the technology to capture and sequester the carbon dioxide and other pollutants is still five to 10 years off, at best. Also, there are no legal mandates yet requiring that new coal plants be made compatible with carbon sequestration technologies when they become ready for deployment.

Nevertheless, coal burnt by conventional combustion is in serious trouble. Coal-fired power plants are the leading source of mercury in air in many US states. Even looking nationwide, these plants are responsible for over 40% of the mercury that enters the air each year. The widespread adoption of IGCC would immediately remedy this problem.

IGCC is a clean coal technology that combines two technologies, coal gasification and combined cycle, with the low cost associated with coal. Coal IGCC works, GEC has proven it, and arguably so have a handful of EU funded working scale pilot plant demonstration projects. It is known technology and can be built today. There are no real technical barriers, and compatibility with any sequestration requirements in the future is excellent.

by Steve Last - 3 August 2008

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