Pulverized coal: The smart energy choice for Big Stone II
Why is supercritical pulverized coal technology the best Big Stone II option?
After much study, a supercritical pulverized coal-fired boiler was determined to be the best technology option for Big Stone II. The fuel combustion technology of choice among coal-using utilities, this process involves pulverizing coal into a fine dust, which is mixed with hot air and injected into a boiler where it is burned. Water circulates through tubes lining the boiler and becomes steam. The steam propels a turbine generator that produces electricity. “Supercritical” refers to the higher pressure and temperature developed in this advanced generation process.
- This is proven, efficient coal technology. It will extract 20% more energy from each ton of low-sulfur, western coal used.
- Choosing this technology is an environmentally responsible decision. The new plant will emit 20% less carbon dioxide than the average existing coal-fired units in the region. While more than doubling the combined plants’ generation capacity, the emissions of sulfur dioxide, nitrogen oxides and mercury from the two plants will be less than or equal to emissions from the existing plant.
- Coal is abundant and available. Enormous reserves of lignite and access to the sub-bituminous supplies of Wyoming and Montana make coal the logical choice of generation fuel for regional electricity suppliers. Three-fourths of the electricity used in the Midwest originates with energy from coal.
- Abundant and affordable, coal is a critical resource in helping to reduce our nation’s dependence on imported energy.
Why not generate electricity with wind or natural gas?
Renewable energy, such as wind, is a critical component in the resource mix and can help meet energy needs. In fact, the Big Stone II participants plan to add large quantities of wind energy. But wind energy cannot replace the need for baseload power that will be provided by Big Stone II. Wind is not reliable and must be backed up by another source, usually natural gas or coal. Natural gas prices are highly volatile and annual natural gas production by the U.S. and Canada is either flat or falling. Coal is an important part of the electricity generation mix in terms of reliability, cost and energy independence.
Why not use IGCC technology at Big Stone II?
Another coal-conversion technology gaining interest among utilities is the integrated gasification combined cycle (IGCC) technology, which creates a synthetic gas from either oil or coal by heating the fuel stock to high temperatures. The energy produced to run turbine generators is both chemical and steam energy — hence the term “Combined Cycle.” This technology holds promise for future electricity generation. But IGCC is not an option for Big Stone II, for the following reasons:
- IGCC is a developing technology — one not yet proven for commercial power production. The Big Stone II participants and the consumers they serve would be exposed to an enormous financial risk by relying on IGCC technology that has not been satisfactorily proven.
- IGCC applications to date have used higher-grade bituminous coals. Those coals are found in the eastern United States. Several Big Stone participants are helping fund a lower grade coal demonstration project, but the completion date of the project is unknown.
- IGCC technology would not allow the Big Stone II participants to simultaneously control and reduce sulfur dioxide, nitrogen oxides and mercury emissions from the existing Big Stone Plant. A common scrubber would not be an option if Big Stone II were to be built as an IGCC plant.
For more information, contact:
Dan Sharp, Manager, Communications . 701-426-3650
Steve Schultz, Manager, External Affairs . 218-770-9111
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