Cape Girardeau plant’s successful completion of a new process baghouse replacement in April 2018 was a joint cooperative effort of plant and project personnel. The original process baghouse system, constructed 1981, had 32 reverse air filtration modules located on top of the raw feed blend silos, and operated with a two-fan system (Kiln ID and Raw Mill ID) at 45 to 50 inches of negative pressure.  Low operating temperatures also made the modules susceptible to acid attack and internal corrosion that was accelerated beginning in 1992 with the initiation of a robust alternate fuel program. Escalating corrosion quickly lead to major annual maintenance and replacement of ductwork, modules and components, resulting in significant maintenance costs.

In 2016, engineering commenced for the conceptual development of a pulse-jet bag filter installed at ground level with a cone valve gas control system and conversion to a three fan system. The design objectives were to improve operating control, optimize production, lower operating pressure, and reduce the risk of acid attack. The project was approved in 2016 and final engineering was started February 2017, with the goal of completing replacement on an aggressive one-year schedule. To make the project even more challenging, the scope was increased to include replacement of the old raw mill cyclones together with installation of Stage II Vortex Finder modifications.

Physical space constraints were a big challenge, due to the site configuration. The foot print for the bag filter, ID Fan, cone valve and stack limited crane accessibility and the ability to preassembly and erect the components. This made coordination between the primary contractors critical. Lee Mechanical Contractors, of Park Hills, Missouri, was hired to perform the mechanical, structural and electrical construction for everything except the baghouse itself. The supply and erection of the baghouse was awarded to Boldrocchi S.r.L of Biassono, Italy. The site seismic and soil conditions required to meet building codes impacted cost of foundations and structural design. Foundation construction started in May 2017, underground utilities were relocated and pilings were installed by July 2017, with foundation placements completed by October 2017. Timely delivery of major equipment (bag filter, cone valve, dust handling, and ID fan) from overseas was critical.

The general contract for steel, ductwork and equipment installation was awarded in August 2017.  By early September 2017 the contractor had mobilized, and steel and ductwork deliveries started.  A 330-ton LR 1300 crane with 400 feet of boom was needed to reach over the existing baghouse for demolition and construction. The bag filter erection, the cone valve assembly and ductwork erection were done concurrently.  Both the bag filter erector and general contractor worked closely together in the limited space.

Winter conditions, freezing temperatures and ice during January 2018 impeded progress.  Due to limited space for pre-assembly, the bag filter casing and plenum were assembled on the ground, and set with one crane. A larger Terex CC 2800 (660 tons) crane was then needed for the bag filter and ductwork installation.  Cone valves and dust handling equipment were assembled prior to the outage.

Since the existing baghouse and ID fans continued to operate through all but the very end of construction, only 50% of ductwork and support structures could be erected prior to the outage. The ductwork and supports were preassembled and transported to the site for installation.  Setting of the bag filter casing and penthouse controlled the crane usage.  The outage commenced February 16, 2018 after setting the bag filter.  The Terex CC 2800 was reconfigured for extended lifts, demolition of cyclones, structures and ductwork.  Contractors worked 12 hours a day 7 days a week for nearly two months to meet the schedule, successfully achieving start-up of the new system on April 4, 2018.