Part of the $940 million upgrades at LG&E’s Mill Creek power plant. Two of the baghouses, which filter fine particles, mercury and other substances, can be seen in the center, with gray walls. | Photo courtesy of LG&E.
A $940 million, four-year construction project to reduce pollution at a local power plant is nearing completion.
At its peak, the project, which should reduce emissions of some toxic pollutants at the Mill Creek power plant by more than 80 percent, required 1,600 construction workers on a site that normally employs about 200.
Louisville Gas & Electric Company and Kentucky Utilities Company (LG&E KU) made the upgrades to comply with the federal pollution rules.
The coal-fired power plant, which sits on the Ohio River in the southwestern part of the county, generates nearly 1,500 megawatts of power, or enough to power about 1.5 million homes.
It is by far the largest emitter of toxic pollutants in Jefferson County. Its releases in 2014, of nearly 5 million pounds of pollutants, primarily sulfur dioxide, accounted for about 52 percent of the total emissions released by 58 facilities.
LG&E installed two primary pollution control devices: a baghouse, or massive warehouses full of thousands of bags that filter small particles that can cause health problems; and scrubbers, which remove sulfur dioxide, a greenhouse gas that contributes to climate change.
Scott Straight, LG&E’s director of project engineering, told IL that if the new pollution controls had been in place in 2014, emissions of fine particles would have been 82 percent lower, while emissions of sulfur dioxide would have been reduced by 86 percent.
Pollution control
LG&E is adding four baghouses to the site, which has four power generation units. Think of a baghouse as a warehouse that holds about 17,000 upright, high-tech vacuum cleaner bags that measure 8 inches in diameter and 60 feet in height.
The burning of coal creates byproducts including sulfur dioxide, mercury and very fine particles, much thinner than a human hair. The plant mixes the combustion exhaust gas containing those substances with carbon and lime, and sucks it into the baghouse.
The fine particles, the carbon — which binds the mercury — and the lime — which binds acid aerosols — cannot go through the tight mesh of the bags and, because of the negative pressure in the baghouse, begin sticking to the bags’ exterior.
When too many of the particles stick to the bags’ exterior, a pulse of air knocks the particles into hoppers below the bags, from where the particles are sent to silos or landfills.
Meanwhile, the remaining exhaust gas, which contains sulfur dioxide, flows through the bags and is blown into scrubbers, which are large, cylindrical towers into which LG&E sprays a wet slurry of limestone. Calcium carbonate in the limestone reacts with the sulfur dioxide to make sulfate. LG&E blows air into the sulfate to convert it into gypsum crystal, which the company markets to businesses that use it for products including drywall.
Straight said the old particulate filtering system removed about 95 percent of the fine particles. The new baghouses will remove about 99.97 percent. The old scrubbers, which dated to the late 1970s, removed 88 to 90 percent of the sulfur dioxide, while the new ones will remove 98 percent or more.
Logistical difficulties
The Mill Creek plant now has six baghouses, including the four new ones. The site’s space constraints required ingenuity, Straight said. Some structures had to be built upon existing ones to make them all fit. And smaller warehouses had to be razed to make room for the new pollution control equipment.
“This is all being built while the plant’s making power,” he said.
A drawing of LG&E’s Mill Creek power plant after $940 million of upgrades. The drawing shows original structures in gray. Everything in color has been added (or will be added) since late 2012. | Courtesy of LG&E.
The company this month obtained a building permit for a 32,000-square-foot warehouse to replace some of the buildings that have been demolished. Straight said the facility will hold mechanical and electrical equipment, cables, gaskets, rags and spare bags for the baghouses. The bags are replaced every two to four years.
Crews have essentially completed the installation of three of the four baghouses, Straight said, and he hopes the last one will be finished in June. Cleanup and road paving on the property likely will continue until asphalt plants shut down for the winter.
As the upgrades are required by the federal government and approved by the Kentucky Public Service Commission, the company gets to recover the infrastructure and maintenance costs from consumers, who can find an Environmental Cost Recovery on their monthly bills.
LG&E said that during 2016 project costs would increase the monthly bill of a consumer who use 1,000 kilowatt hours per month by $16.33.
Health benefits
The EPA said the new rules that prompted the Mill Creek upgrades will annually avert, nationwide, 11,000 premature deaths, 4,700 heart attacks and 130,000 asthma attacks. The value of the air quality improvements for people’s health totals between $37 billion and $90 billion annually, or about $3 to $9 for each American. The rules also will eliminate 540,000 sick days each year, which will enhance productivity.
Straight said the Mill Creek project has exceeded expectations in many aspects, from safety and lack of power interruptions to the share of local labor that was hired by the San Antonio, Texas-based contractor.
“It’s one of our star projects,” Straight said.