CO2CRC TESTS CAPTURE SOLVENT THAT USES SO2, NOX TO PRODUCE SELLABLE FERTILIZER

Tamar Hallerman
GHG Monitor
05/25/12

Cooperative Research Center for Greenhouse Gas Technologies (CO2CRC) and University of Melbourne researchers began trialing a post-combustion capture technology this week that utilizes fossil-plant byproducts to produce sellable fertilizer. CO2CRC’s Chief Technologist Barry Hooper told GHG Monitor that researchers are kicking off two years of lab-scale testing of a precipitating potassium carbonate technology, known as UNO MK3, with similar properties to baking soda. Researchers will capture hundred pounds of CO2 per day for the solvent testing, during which the potassium carbonate will react with the sulfur dioxide (SO2) and nitrogen oxide (NOx) produced from burning fossil fuels to form potassium sulfate and nitrate fertilizers that could provide a revenue stream for future project developers. “The whole process has a sort of holistic approach to looking at this capture problem, from the inputs through to the outputs and how it actually fits within the potassium feedstock. You’re removing impurities while also creating a sellable product,” Hooper said.

In addition to a revenue stream from the fertilizer, Hooper said the post-combustion capture technology could lead to significant cost savings for developers due to the nature of its carbonate-bicarbonate capture mechanism. “You’re cycling between carbonate and bicarbonate. Because the potassium carbonate itself is non-volatile, you don’t have the emissions concerns or environmental issues [of many other post-combustion capture systems],” Hooper said. “It’s a fairly benign material in itself since it is effectively baking soda. It tends to have a low toxicity, low environmental impact, as well as having a fundamentally low energy profile.” That lower energy profile could lead to cost reductions of 15 to 20 percent compared to traditional post-combustion capture systems, according to Hooper. “We think it has a very strong position to reduce costs,” he said.

Adapting the Carbonate-Bicarbonate System

Potassium carbonates have been used for solvent absorption processes in the chemical industry for years, but challenges have arisen while applying the solvent to carbon capture and storage systems. In particular, the need for the carbonate to work under lower pressures has been a challenge for researchers, according to Hooper. “Potassium carbonate-bicarbonate systems already exist, but they are in a different space at a higher pressure, and they’ve never been applied in this post-combustion environment,” he said. “We’re looking to do this in the context of CCS, stand back and look at how this can really be a wise approach to utilization of potassium carbonate scrubbing.” 

In particular, Hooper said UNO MK3 could be an ideal technology for systems processing flue gases with a high oxygen content, conditions found in natural gas combined cycle generation systems. Hooper said the solvent’s low volatility is more compatible to NGCC systems compared to other post-combustion capture technologies. “It’s oxygen tolerant and in those sorts of environments it doesn’t degrade or have the issues of some other organic solvents,” he said. Hooper added that UNO MK3 can also work for pre-combustion capture systems for new-build coal and gas plants.

Hooper said that while researchers at the University of Melbourne proceed with the bench-scale UNO MK3 research, CO2CRC staff will also simultaneously move forward on plans to trial the solvent on pilot- and plant-scale. The lab-scale work will be able to inform researchers as they design the larger-scale trials, Hooper said, as well as help validate their project models.