In 1983 the BLP added emission control equipment to Sims Unit III to further reduce particulate and SO2. The cost to install this equipment was approximately one-third the total construction cost of Unit III.
The air or “flue gas” from the generation process contains by-products referred to as bottom ash and fly ash. The heavier ash, or bottom ash, falls into a water filled collection hopper at the bottom of the furnace. This ash is transported and dispersed into one of two ash ponds on the island where it settles and eventually is scooped out for landfill delivery.
Fly ash is sent through the Precipitator, which filters the particulate out of the flue gas. This process begins by giving the particulate a negative charge by emitting electrons from vertical wires energized at 50,000 volts. These charges cause the ash particles in the flue gas to stick to plates within the Precipitator. Small hammers tap the plates every couple of seconds to knock the fly ash off and into a series of hoppers for disposal. This process removes 99.2% of particulate from the flue gas. The remaining particulate passes through the wet lime scrubber, reducing the particulate even further.
Flue Gas Desulfurization Unit (FGD)
Installed as original equipment to Unit III in 1983, the FGD or scrubber unit was added to remove SO2 from the flue gas. At that time, the BLP was the second scrubber unit installed in the State of Michigan. Today, there are still less than a half dozen scrubbers in Michigan. The scrubber utilizes a wet lime slurry mixture to remove the SO2 from the flue gas.
In 2005, we began blending low sulfur Western coal with Pennsylvania and West Virginal coal. When these coals were combined, we were able to reduce SO2 emissions even further from the original 90% design.
In 2006, when Sims 3 was upgraded an additional 10% capacity per megawatt gross output, we further reduced our sulfur emissions output by one- third, agreeing to keep our rate below .315pounds per million btu’s as part of the BLP’s permit application with the DEQ.
By Products of the Generation Process
A Gypsum by-product is created through the scrubber process, which is currently marketed to local farmers for land fertilization. This product was formerly marketed to Georgia Pacific in Grand Rapids to product drywall board.
Last year, we marketed and sold approximately 10% of our fly ash to the asphalt market. We also provide our fly ash as a stabilizer for others who have environmental spills or remedial cleanups from old sites.