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Method for Sequestering Carbon Dioxide and Sulfur Dioxide Utilizing a Plurality of Waste Streams

Date Posted
USPN 7,922,792


The Department of Energy’s National Energy Technology Laboratory is seeking licensing partners interested in implementing United States Patent Number 7,922,792 titled "Method for Sequestering Carbon Dioxide and Sulfur Dioxide Utilizing a Plurality of Waste Streams."

Disclosed in this patent is the invention of a neutralization/sequestration method that concomitantly treats bauxite residues from aluminum production processes, as well as brine wastewater from oil and gas production processes. The method uses an integrated approach that coincidentally treats multiple industrial waste by-product streams. The end results include neutralizing caustic by-products, reducing costly treatment of by-product brines, and directly using COand SO2 from flue gas to neutralize bauxite residue/brine mixtures. Another added benefit is the sequestration of both CO2 and SO2 via the bauxite residue/brine mixtures.


Researchers estimate that approximately 200 million tons of bauxite residues exist worldwide, and the overwhelming majority is stored in tailing ponds. Of that total, more than 70 million tons is generated annually when aluminum is extracted from the principal ore called bauxite. And, in the oil and gas industry, 20-30 billion barrels of saline wastewater are produced annually in the United States as a by-product of enhanced oil and gas recovery.

A number of methods have been tried to mitigate the potential environmental impacts of the stored bauxite residue, including seawater washing and land application. Despite these attempts, no solutions have been found that can deal with the high-volume of residues in an economically viable way. The caustic nature of the by-product presents long-term environmental concerns because leakage of the alkaline liquid from impoundments into groundwater aquifers can result in the movement of several elements, including iron, aluminum, and hydroxide ion.

This invention discovered that mixtures of oil/gas wastewater brine and bauxite residue can effectively sequester acid gases through a combination of solubility and long-term mineral trapping. The bauxite residue/brine mixture has a high alkalinity that can be used to neutralize acid gases as well as acid waste material. Unexpectedly, the invention found that mixing the bauxite residue and brine alone would not effectively neutralize bauxite residue, but the reactions with CO2 and SO2 resulted in complete neutralization. It also found that the mixture was just as effective in simultaneously removing both CO2 and SO2 from industrial flue gas streams. The invention has generated significant industry interest, particularly in the aluminum sector.


This neutralization/sequestration invention has the following advantages:

  • Neutralizes caustic by-product residues
  • Decreases the need for costly treatment of by-product brines
  • Reduces the need for costly separation of CO2 from industrial by-product gas steams
  • Simultaneously removes both CO2 and SO2 from industrial flue gas streams
  • Can be applied under a variety of pressure and temperature conditions
  • Generates a low volume of brine wastewater
  • Reduces the potential impact of caustic by-products to the environment

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