The recent social media complaints about a smell in Peace River on March 6 from the Mercer Peace River pulp mill were largely due to an issue stemming from the extreme cold, according to Mercer mill manager Shawn Elliott.
“In preparing for a planned outage on March 6, the chip bin (a vessel where wood chips enter the mill and are steamed to raise the chip temperature and expel entrapped air from the wood chips) was being emptied of chips and the steam supply to the chip bin was shut off,” Elliott explains.
“When the chip bin level had dropped to approximately one third full, the automatic temperature control re-opened the steam valve which caused the Chip Bin Pressure Protection System to open to safely relieve pressure in the chip bin vent.”
The Mercer team immediately investigated and reviewed the shutdown procedures, and Elliott says they identified that the existing procedure needed to be modified to accommodate extremely cold wood chips, resulting from the long streak of abnormally cold weather in the Peace region.
When the chip bin was shut down again on March 7, the new procedures successfully prevented any further release of a smell.
None of the vented gases are dangerous to the public, Elliott says.
“When process steam contacts wood chips or is recovered from our cooking process, it will contain malodourous sulphurous gases. These sulphurous gases are very foul smelling and normally are collected, concentrated, and incinerated in either our boiler or lime kiln. These sulphurous gases are very objectionable and are detectable by our noses at concentration as low as 2 PPB (Parts Per Billion).”
Elliott says the Mercer Peace River mill has an air monitoring station in the town of Peace River which recorded a maximum hourly reading on March 6 of 10 PPB TRS (Total Reduced Sulphur).
Occupational Health and Safety has determined a safe 8-hour exposure limit for Sulphurous compounds can range from 500 PPB for Methyl Mercaptan to 10,000 PPB for Dimethyl Sulfide.
“At Mercer Peace River, we consider the reduction of odour a significant environmental focus for our operation,” Elliott says. “We have a target of zero odour complaints and we did achieve this target in 2017. We are disappointed that we will not be able to achieve this target again in 2019, but we will continue to work toward this goal.”