AES Greenidge turns to biomass burning

Aug 25, 2009 at 02:59 pm by Observer-Review


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AES Greenidge turns to biomass burning

DRESDEN—Starting in August, AES Greenidge has increased the amount of energy it produces from wood biomass.
Doug Roll, plant  manager, said the plant started Aug. 1 with commercial operations.  AES Greenidge is contracted to provide New York State Energy and Research Development Authority (NYSERDA) with 28,500 megawatts-hour for the next three years.  He said that each ton of biomass (wood chipped down to very small pieces) provides one MW of energy.  Roll said AES can sell whatever else is produced over the amount of energy  required by NYSERDA.  He explained biomass energy now provides 10 percent of the energy produced.  The rest is still coal powered.
Roll said that AES bid for the contract last year and won.  Because the plant is paid for each MW of power generated, he said it was now cost effective to improve the system for biomass burning.  The facilities are almost complete, with just the receiving building under construction.  Roll said that should be complete by the end of this week.  However, AES has been able to produce energy from wood.  Roll said the new facilities are designed to process 240 tons a day.
The plant now ships in wood, from places like sawmills, within a 50 mile radius.  He explained that any farther away and it is no longer cost effective to transport the raw material.  Roll explained that a broker, Mesa Reduction Engineering and Processing in Auburn, handles finding the wood for AES.  People who have wood they want to sell can call Mesa at 315-704-0004.
Once at the plant, the wood has to be chipped down to small pieces.  After the receiving building is complete, wood will be brought into it and dumped onto a moving floor.  Roll explained that segments in the floor shift, moving the wood in the desired direction.
From the receiving building, the wood chips go to the next step of its journey, which involves three different magnets.  Roll explained that the wood can not have anything else in it to be used for energy.  Two of the magnets are traditional ones, but the third is used for nonferrous metals.  He explained that magnet detects anything that is not wood and takes it out.
Once all of the metals are gone, the wood is then taken by moving floors to a sifter.  If any pieces are bigger than two by two inches, it is dumped out into a bin.  Those pieces will then be chipped down to smaller sizes and sent through the process again.  The pieces that do make it through go to the hammer mill, which can handle 12 tons per hour.
Roll explained that because the process would create a lot of dust, the “bag house” collects all the dust.  It is a large white storage unit with several pipes.  By now the wood has been hammered so much that it is almost fluffy in consistency.  Roll said that samples of this are taken every day so AES can prove the fuel they are producing is clean.
From here, the biomass goes into a metering bin.  He explained that once it is full enough, it goes to the boiler through four different pipes.  Roll said that the biomass is delivered into the center of the fire from four separate corners.
Before the new facilities were built, AES did produce some energy from wood, but at the time it was only a little.  Roll explained that starting in 1995 AES burned willow trees for energy.  He said the trees were fast growing and bushier than regular willow trees.  However, the willows did not splinter very well because of the high amount of moisture in the wood.
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