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Multi-component Removal in Flue gas by Aqua Ammonia

National Energy Technology Laboratory

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Technology Marketing Summary

The Department of Energy’s National Energy Technology Laboratory is seeking licensing partners interested in implementing United States Patent Number 7,255,842, titled "Multi-component Removal in Flue Gas by Aqua Ammonia."

This patent discloses a method for the removal of potential environmental-impacting compounds from flue gas streams. The method oxidizes some or all of the acid precursors such as sulfur dioxide (SO2) and nitric oxides (NOx) into sulfur trioxide and nitrogen dioxide, respectively. Following this step, the gas stream is then treated with aqua ammonia or ammonium hydroxide to capture the compounds via chemical absorption through acid-base or neutralization reactions where a fertilizer is formed. Carbon dioxide is also captured by the aqueous ammonia-containing solution and is produced for sequestration purposes by thermally regenerating the spent solution.

Acid rain-related air pollution problems have long been caused by uncontrolled acid anhydride gases, such as SO2 and NOx, in flue gas produced by the combustion of fossil fuels. This combustion also causes the emission of another acid anhydride, CO2, which can result in the global climate change called the greenhouse effect. Currently, researchers propose to apply amine-based CO2 absorption technology to prevent carbon dioxide from entering the atmosphere. Sulfur dioxide and nitric oxides are removed, respectively, from power generation facilities by lime/limestone wet scrubbing and selective catalytic reduction. However, these technologies are highly complex and very costly, especially when each acid gas is removed by a different combination of technologies. Therefore, neither one is wholly effective for simultaneously removing gaseous acid anhydrides from combustion flue gases.
As a result, a need exists in the post-combustion flue gas cleanup area for removal of all environmentally impacting gases from combustion emissions without producing any harmful by-products. This patented aqueous-based ammonia scrubbing method facilitates the removal of gaseous acid anhydrides from flue gases while requiring low energy use to minimize costs. The overall process cools the flue gases, removes particulate matter from the gases, oxidizes the anhydrides, converts the oxidized anhydrides to ammonia salts, captures the carbon dioxide, and thermally regenerates the carbonated solution with respect to carbon dioxide capture. The products derived from the reactions with the acid precursors SO2 and NOx can be collected as slurries, or dewatered and dried for use as fertilizers. Regarding the carbon dioxide capture, the ammonium bicarbonate product can be regenerated to the hydroxide or carbonate by a thermal swing technique.

This aqua ammonia method has the following advantages:

  • Removes virtually all environmentally impacting compounds, including CO2, from flue gases    
  • Produces no harmful by-products
  • Produces useful slurry products, such as fertilizers
  • Reduces energy costs by lowering the regenerative heat duty
  • Offers a simpler and less costly alternative to existing technologies
More Information

U.S Patent No. 7,255,842, issued August 14, 2007, titled "Heat Recirculating Cooler for Fluid Stream Pollution Removal.”

Inventors: James Yeh and Henry Pennline

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To: Jessica Lamp<>