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 3,143 tonnes of NOx and 13,211 tonnes of SOx. This is an absolute reduction of 2 percent in NOx emissions and 28 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. The US$7,700,000 Selective Catalytic Reduction (SCR) unit installed last year (2017) at our Louisiana, Missouri (LOMO) nitric acid plant reduced potential NOx emissions at the site by 98 percent during 2018.

As a result, IPL exceeded its 2018 intensity target of a 30 percent reduction in NOx emissions per tonne of nitric acid produced against our 2015 baseline. With the installation of SCR at LOMO, 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 2018 on the design of a new wet scrubber system for the acid tanks with consultants developing several alternative designs. The project requires permit approval and the application has been submitted to state authorities for review. It is planned that the scrubber will recycle vent fumes from both nitric and sulphuric acid tanks, combining them with water to create a weak acid stream. This stream will then be sent for distillation to separate nitric and sulphuric acid products for use in product manufacture.

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 last year (2017). 

This new catalyst improved the conversion of sulphur dioxide (SO2to make sulphuric acid, reducing SOx emissions at the site by 32 percent against 2016 SOx emissions.