The J.R. Simplot Co. has filed an air quality permit request with the Idaho Department of Environmental Quality (IDEQ) to modify a sulfuric acid plant at its integrated fertilizer complex west of Pocatello, Idaho. The permit to construct asks for a production increase, but a decrease in allowable sulfur dioxide emissions from the Power County plant, which produces phosphate, nitrogen, and sulfate commercial fertilizer.
Simplot operates two sulfuric acid plants, an ammonium sulfate plant, a wet process phosphoric acid plant, a super phosphoric acid plant, three granulated fertilizer plants, and several natural gas-fired steam generators at the site.
Simplot is discussing with the U.S. Environmental Protection Agency settlement of Clean Air Act liabilities related to its two sulfuric acid plants. If an agreement is reached, it could significantly reduce sulfur dioxide emissions.
To meet targets, Simplot must implement changes to the No. 400 plant beginning this June. Other changes are planned for scheduled plant turnarounds in 2014 and 2016. Once they are completed, allowable SO2 emissions are expected to drop from four pounds per ton to 1.7 pounds per ton.
Production capability at the No. 400 plant is expected to increase to an average 2,500 tons per day. Allowable SO2 emissions are expected to be reduced nearly 700 tons annually, and actual emissions by more than 200 tons a year. Simplot proposes to cut plant emissions in two steps the next four years.
The No. 400 plant uses a double absorption contact process to produce sulfuric acid from elemental sulfur, which is burned in a furnace to produce an SO2 gas stream, which is then cooled in a waste heat boiler before it is routed to a multi-pass, four-bed catalytic converter. There, it reacts with oxygen to form sulfur trioxide.
After a third catalyst bed, the SO3 gas stream is cooled and sent to an intermediate absorbing tower, where exhaust gas is reheated and returned to the catalytic converter, where it passes through a fourth and final catalyst bed.
The gas exits the converter, cools, and then routes to the final absorbing tower, where virtually all of the remaining gas is absorbed into a concentrated sulfuric acid solution.
The exiting gas, which contains nitrogen, oxygen, unreacted So2, and NOx, then passes through a set of mist eliminators and the No. 400 plant stack.
Planned 2012 changes include replacing the final absorbing tower and mist eliminators, installing a new final absorber acid feed cooler, upgrading the capacity of the final absorber acid feed and product pumps, replacing the product dilution cooler with a larger unit, installing a new cooling tower, installing a cesium promoted catalyst in the converter, and making various improvements to infrastructure, electrical, and instrumentation systems. Virtually all of the planned changes during the next four years modify the No. 400 plant. Only the new cooling tower represents construction of a new emissions unit.
If all the planned changes are made, Simplot anticipates the No. 400 sulfuric acid plant’s production capability will increase by about 9 percent on an annual basis. While some of the additional sulfuric acid may be used in producing fertilizer at the Don Plant, some may also be exported to customers.
Historically, the plant has imported raw sulfuric acid when demand outstripped supply. Conversely, the Don Plant also has exported sulfuric acid when production exceeded internal demands. The maximum sulfuric acid imported in the last 10 years was in 2008, when more than 25,000 tons of sulfuric acid were imported. Maximum exports totaled more than 57,000 tons in 2007.
A public comment period will be provided on the proposed permit if a written request is submitted to IDEQ by Friday, Jan. 27.