Ventilation systems not only clear the air in underground mines, they can also provide power for up to 20,000 homes.
BHP Billiton Illawarra Coal is reducing greenhouse gas emissions by converting discarded mine exhaust into fuel for a sophisticated power plant.
West Cliff mine Ventilation Air Methane Project (WestVAMP) is a new type of power plant that will use extremely dilute methane from West Cliff mine ventilation air to generate electricity.
The project is said to be the first demonstration of commercial power generation solely from mine ventilation air.
“It is the first plan of its kind in the world, and the first plant in the world capable of taking very low concentrations of methane in ventilation air and applying that to electricity generation,” Illawarra Coal general manager projects Allan Dann told Australian Mining.
Rolled out with the support of a $6 million Australian Greenhouse Office (AGO) contribution through the Greenhouse Gas Abatement Program, WestVAMP is capable of mitigating a significant portion of greenhouse gas emissions from operations, generating electricity at the same time.
“There has been a couple of enablers of this project for us, and it is important to say that some of these enablers spent around six million dollars, like the AGO. Also our technology partners MEGTEC Systems AB were important in the success of the project,” Dann said.
The company has a history of successfully using waste coal mine methane gas for power generation.
For almost two decades Illawarra Coal has been capturing and using the methane gas, which is drained from coal seams prior to mining for safety reasons.
The gas has been piped to gas engine power plants near the townships of Appin and Douglas Park since 1995, reducing the company’s annual greenhouse gas emissions by 2.5 million tonnes, and producing enough energy to power around 60,000 homes each year.
However, not all the methane in coal seam is able to be drained and small percentages of methane are present in ventilation air which is exhausted from the underground operations.
To address this, BHP Billiton Illawarra Coal, in partnership with international emission control specialist MEGTEC Systems AB, established a pilot plant at its Appin site to trial the use of VOCSIDIZER technology.
The success of this pilot led to the establishment of WestVAMP.
WestVAMP is a new type of power plant that will use the extremely dilute methane in the ventilation air from West Cliff mine to generate electricity. It will use up to 20% of the mine ventilation air to achieve a further reduction in greenhouse gas emissions, said to be up to 250,000 tonnes of CO2 equivalent every year.
The amount of CO2 to be saved is the same as taking 45,000 cars off the road each year, or producing enough electricity for 20,000 homes.
A cow emits 50 kg to100 kg of methane each year, while a coal mine shaft in comparison can emit some 50,000 tonnes of methane.
Methane concentrations in mine ventilation air are typically less than 1.25% by volume, which is not freely combustible with conventional combustion systems.
Dann said the technology will benefit more than just the local community
“Greenhouse gas emissions are more than a local community issue. The two biggest advantages are the reduction of greenhouse gas emission of around 250,000 tonnes of CO2 equivalent per year and the generation of electricity,” Dann said.
“The technology will allow mine managers to reduce greenhouse emissions with ventilation air that has traditionally been extracted into the atmosphere,” he said.
The technology works by merging emission control technology and a steam cycle power plant developed by Swedish emission control specialist MEGTEC Systems AB.
The boiler process is based on flameless, single bed, regenerative oxidation in a unit called the VOCSIDIZER.
High efficiency heat exchangers recover large levels of thermal energy released to produce high quality steam.
This steam is used to drive a conventional steam turbine.
By reducing greenhouse gas emissions by about 2.5 million tonnes of CO2 equivalent each year during the past five years, Illawarra Coal provides the largest single contribution to greenhouse gas emission reduction in NSW.
There is a lot of interest in the technology, according to Dann.
“This is a technology that should be looked at in every underground mining operation that vents air from underground coal seams into the atmosphere.
New South Wales Premier Morris Iemma officially opened the company’s West Cliff Ventilation Air Methane Project.
Premier Iemma congratulated BHP Billiton on its commitment to greenhouse gas abatement.
“This facility will make a significant contribution to greenhouse gas reduction in New South Wales, and I applaud the ingenuity of BHP Billiton and its technology providers MEGTEC Systems AB,” he said.
“The NSW Government’s forward thinking Greenhouse Gas Abatement Scheme has provided the fiscal conditions to make this innovative investment possible,” BHP Billiton Illawarra Coal president Colin Bloomfield said
Bloomfield added the support of the Australian Government’s Greenhouse Gas Abatement Program with a $6 million contribution has also been critical to the commercial viability of the investment.
BHP Billiton Illawarra Coal
General manager, projects