- Milton R. Young Units 1 & 2
Burns & McDonnell is providing preliminary engineering, detailed design, field engineering support and startup services for the flue gas desulfurization (FGD), selective non-catalytic reduction (SNCR) and overfire air (OFA) retrofit projects at the Milton R. Young Station, Units 1 and 2, near Center, N.D.
- Preliminary engineering
- Technology assessment
- Detailed engineering
- Field engineering support
- Startup assistance
The Milton R. Young air quality control system will be installed on Units 1 and 2 to meet the requirements of Minnkota Power’s consent decree with the U.S. Environmental Protection Agency. The project includes the addition of an FGD system on Unit 1, upgrades to an FGD system on Unit 2, the addition of lime receiving and preparation systems for both units, and the addition of SNCR and OFA systems to both units.
Burns & McDonnell performed a technology assessment to investigate available proven technologies that could meet the criteria of the consent decree for both sulfur dioxide (SO2) and nitrous oxide (NOx) emissions.
The technology selected for SO2 reduction on Unit 1 was a wet lime FGD system because it could provide the removal required by the consent decree at the most effective cost. The existing electrostatic precipitator performs well, saving the cost of a fabric filter required by dry technologies. Also, the owner was already familiar with wet lime technology since the existing Unit 2 FGD system uses wet lime technology.
Two new lime unloading, storage and preparation systems will be provided. Each system is capable of providing 100 percent of the slurry necessary for both units. The system includes two new lime storage silos. Vertical ball mill slakers will be enclosed underneath each silo.
The existing Unit 2 FGD system uses flue gas bypass around the FGD absorbers to reheat the flue gas above saturation. The consent decree will no longer allow flue gas bypass. Also, the existing Unit 1 chimney is not suitable for wet flue gas operation. A new chimney with a FRP liner will be built for Unit 2. The existing Unit 2 chimney will be converted to wet flue gas operation for Unit 1. This will include wall papering the liner with alloy to resist corrosion and adding a drain system to collect the condensate.
Modifications to the existing Unit 2 FGD system will be implemented to eliminate the flue gas bypass and improve the SO2 removal efficiency. The exit cones of the absorber modules will also be modified to interface with the new chimney and handle the increased flue gas flow resulting from no bypass.
The technology selected for NOx reduction on both units was OFA with SNCR. OFA systems were designed for both units. The existing lignite drying systems were modified to provide room necessary to accommodate the OFA ductwork. Urea solution was selected as the reagent for the SNCR. Four 60,000-gallon urea storage tanks in an enclosed building were designed to store, prepare and deliver the urea solution to the boiler injection ports.
The project is being performed under a multiple contract approach with Burns & McDonnell providing the detailed design for the balance of plant systems and integrating the various subsystems. Several contracts were used to procure equipment for the project including the FGD system and the SNCR system. Multiple construction contracts were created to complete the on-site work for the project.
Burns & McDonnell is providing a field engineering staff on-site during the project construction and is assisting the owner with startup.
Anticipated removal efficiencies for SO2 emissions will be 95 percent on Unit 1 and 90 percent on Unit 2. NOx emissions will be reduced in two phases. The first phase will reduce NOx emissions using OFA by 37 percent on Unit 1 and by 40 percent on Unit 2. Phase two will reduce NOx using SNCR systems on both units.
The project is being constructed in multiple phases to comply with the consent decree dates and coordinate with planned outages. Construction began in spring 2007 and will be completed by summer 2011.
- Wet lime FGD system on Unit 1
- Upgrade existing wet lime FGD system on Unit 2
- Lime receiving and preparation systems for Units 1 and 2
- SNCR systems for Units 1 and 2
- OFA systems for Units 1 and 2