Reducing NOx and SOx

Nitrogen oxides (NO2 and NO, referred to collectively as NOx) are released when fuels are burned at high temperatures, and when nitric acid is manufactured. As of 2016, all of our nitric acid manufacturing sites have NOx abatement units installed.  Sulphur oxides (SO, SO2, SO3, referred to collectively as SOx) are emitted when fossil fuels are combusted, and in the making of sulphuric acid. This year our operations emitted 3,178 tonnes of NOx and 16,853 tonnes of SOx. This is an absolute reduction of 20 percent in NOx emissions and 14 percent in SOx emissions since last year. Although not greenhouse gases, NOx and SOx have other environmental impacts, such as air pollution. We are committed to reducing emissions of NOx and SOx across our global manufacturing sites.

During 2017 work was completed on the US$7,700,000 Selective Catalytic Reduction (SCR) unit at our Louisiana, Missouri, nitric acid plant. This unit reduced NOx emissions at the site by more than 95 percent, which enabled IPL to achieve its 2017 global target of a 30 percent reduction in NOx emissions per tonne of nitric acid produced. All of IPL’s 
nitric acid plants are now fitted with NOx reduction technology.

What is Selective Catalytic Reduction (SCR)?   
Selective catalytic reduction (SCR) is a proven active emissions control technology system that converts NOx into nitrogen (N2) and water (H2O), which are natural elements common to the air we breathe everyday. It is called selective because it injects a liquid-reductant agent, in this case, ammonia, (NH3) through a special catalyst to react specifically with NOx. SCR using ammonia as the reducing agent was patented in the United States by the Engelhard Corporation in 1957. Development of SCR technology has continued in Japan and the US with more recent research focusing on less expensive and more durable catalyst agents. The SCR process is the most efficient NOx reduction technology available because it provides the best conversion rate of NOx to environmentally friendly nitrogen and water. 

In addition to the significant reductions achieved at Louisiana, Missouri, other sites are also investing in NOx and SOx reductions. At Carthage, Missouri, work progressed during 2017 on the design of a new wet scrubber system for the acid tanks. This scrubber will receive vent fumes from both nitric and sulphuric acid tanks. The scrubber will recirculate the water, creating a weak acid stream which will then be sent for distillation to separate nitric and sulphuric acid products for use in product manufacture. During 2017, a NOx analyser was installed at St Helens, Oregon, and the evaluation of existing NOx scrubber efficiencies will continue to be assessed at other nitric acid manufacturing sites.

At Mt Isa, Australia, we invested $1,480,000 in a new high efficiency catalyst in the sulphuric acid plant converter in the first half of 2017. This new catalyst will improve the conversion of sulphur dioxide (SO2to make sulphuric acid, reducing SOx emissions at the site by up to 30% in a full year.