Location: Charlevoix, Michigan
Owner/Operator: St Marys Cement Group
St Marys Cement is a leading manufacturer of cement and related construction products in the United States and Canada. One of the company’s operations is a Portland cement manufacturing facility on the shores of Lake Michigan in Charlevoix County, Michigan, which has been in operation since 1966. The total area of the site, including the quarry, is approximately 1,370 acres.
The Cement Kiln
The plant operates on dry process rotary kiln, which typically operates 24 hours per day, 7 days a week. The kiln is rated at 6,000 tons of clinker per day or 1.927 million tons per year. The kiln uses a combination of coal, petroleum coke, alternative fuels and propane as fuel. The majority of raw materials needed to produce the final product are obtained from onsite quarrying operations and offsite materials, which are brought to the site by trucks and ships/barges.
Kiln Stack Modifications
The company identified a need for improved air dispersion from the kiln stack. Extending the discharge height of the 300’ stack to accomplish this was not possible given the proximity of the facility to the Charlevoix Municipal Airport. Instead, the decision was made to increase the exit velocity of stack emissions by replacing the upper 80’ portion of the stack with a stepped reducer, which would decrease the diameter of the stack discharge by approximately 30%.
Environmental Noise Study
HGC Engineering was engaged by St. Marys Cement to assess the acoustical significance of any change in sound emissions resulting from the kiln stack modification in the neighboring vicinity. We had already completed noise studies for the St. Marys Cement plants in St. Marys and Bowmanville, Ontario. In fact, in support of a noise study for the Bowmanville plant, HGC Engineering had already visited the Charlevoix plant in 2016, so we were already familiar with the Michigan based operations.
Assessing the Pre and Post Modification Sound Levels of the Plant
Because the kiln stack is just one of many sound sources at the site, assessing the risk of increased sound from the stack following modification first required some understanding of the existing acoustic environment in the vicinity. We therefore measured the sound levels of the plant in the neighboring community and the sound emission levels of the kiln stack itself, prior to the modification. This allowed us to determine the relative contribution of sound from the kiln stack to the facility-total sound levels in the community and, further, to assess the significance of increased stack sound emissions, post-modification.
Acoustic Measurements and Analysis Conclusions
The results of the measurements and analysis indicated that the kiln stack is a relatively significant contributor to the sound levels of the facility in the community to the east of the site. Sound generated by the induced draft (“ID”) fan that discharges up the kiln stack is the dominant component of the total sound emissions from the stack outlet. Detailed analysis concluded that sound generated by flow within and at the stack outlet is secondary, both pre- and post-modification. Working with site personnel, it was established that the operating conditions of the ID fan would remain essentially unchanged after the stack modification. On that basis, it was concluded that the total sound emissions from the stack outlet would not be expected to materially change following the stack modification, nor would the sound levels of the kiln stack in the surrounding community. After the stack modifications were completed, St. Marys Cement personnel indicated that there was indeed no discernable difference in sound emissions from the kiln stack, nor any related noise concerns raised by neighboring residents.
Acoustical Engineering Services Included:
- Comprehensive onsite and offsite acoustical measurements
- Predictions of flow/discharge noise generation
- 3-Dimensional computational acoustical modelling