The Idaho Department of Environmental Quality (IDEQ) has received a request from Agrium’s Nu-West Conda Phosphate Operations near Soda Springs to modify its air quality permit. The modification would allow Agrium, which operates the complex as Nu-West Industries Inc., to replace its No. 2 absorbing tower at its east sulfuric acid plant with newer technology and install a cesium catalyst in a fourth converter bed, which is considered a best available control technology. It would use vanadium and potassium salts on a silica substrate. That sulfuric acid plant can produce up to 1,550 tons of 100 percent sulfuric acid per day, or 565,750 tons per year. Emissions would remain within legal limits, IDEQ officials said.
The brick-lined tower would be replaced with a new high silicon stainless steel tower, and the absorbing tower acid pumps and cooling system would be upgraded. To complete the project, the existing tower exhaust stack would need to be removed and reinstalled after the new tower is installed.
Agrium withdrew a prevention of significant deterioration application after company and IDEQ officials met several times in 2009 to discuss the project. Agrium officials decided a minor permit to construct application was appropriate. The modification, which is designed to reduce sulfur dioxide emissions by nearly 100 percent, is planned for this June, when the complex’s turnaround is scheduled.
Because it has insufficient capacity onsite to meet its needs, the company must routinely buy sulfuric acid from outside sources to meet production needs. Nu-West operates its east sulfuric acid plant to maximize yield and minimize product loss in the form of atmospheric emissions.
The operation or overall production capacity of downstream process units ?Çô such as the SPA plant, the phosphoric acid plant, fertilizer product storage, or load-out equipment – are not expected to be affected by the modifications.
Exhaust gases from the sulfuric acid plant are collected and emitted from a single, common exhaust stack. The plant’s emission limits include four pounds of sulfur dioxide per ton of sulfuric acid production. The complex’s existing operating permit imposes sulfur dioxide emission rate limits of 258 pounds per hour and 945 tons per any consecutive 12 months.
Nitrous oxide and particulate emissions are not expected to increase as a result of the proposed modifications.