Methods for removing contaminants from exhaust gases

Abstract

A method for removing contaminants from a gas stream by feeding the gas stream into a scrubber that can use seawater as the scrubbing medium. The gas stream is first scrubbed with the seawater and then mixed with ozone to remove the contaminants. Nitrogen oxides that are present in the gas stream are converted to nitric acid / nitrates and these are recovered via condensate or coalesced mist for neutralization. The treated gas stream is then exhausted to the atmosphere.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This application claims priority from U.S. provisional application Ser. No. 61 / 640,128, filed Apr. 20, 2012.BACKGROUND OF THE INVENTION[0002]The invention provides for methods for removing contaminants selected from the group consisting of nitrogen oxides, sulfur oxides, particulates, heavy metals and acid gases from gas streams. More particularly, the invention provides for the removal of contaminants from gas streams arising from engines and other combustion devices on board ships and on land where seawater is used for scrubbing of the combustion gas streams.[0003]The invention can also treat exhaust gas streams from chemical, metallurgical, partial and full combustion processes by the removal of contaminants such as nitrogen oxide, sulfur oxides, hydrochloric acid and particulate materials when co-scrubbing of nitrogen oxides would generate nitrates that are objectionable by-products.[0004]The nitrogen oxides captured are separated fro...

AI Technical Summary

Benefits of technology

The patent describes a method for removing contaminants from a gas stream using a combination of a scrubber, seawater, and ozone. The gas stream containing contaminants is first contacted with seawater, then exposed to ozone. The resulting gas stream is then either recovered or treated further. The method can be used to remove a variety of contaminants from flue gas or other gas streams, and the method has been found to be effective in reducing emissions from ship processes and other operations. The use of ozone and seawater in the method helps to oxidize the contaminants and produce byproducts that can be further utilized or treated. The method may also include the use of a droplet separator and other devices to help condense and recover the reaction products of the oxidation process.

Problems solved by technology

Combustion and chemical processes generally result in gas streams containing contaminants that need to be cleaned up before the gas stream is exhausted to the atmosphere.

Large ocean freighters, ferries, ocean liners and navy vessels use low cost hydrocarbon fuels that contain sulphur, chlorine, nitrogen and metal compounds in hydrocarbons which results in exhaust gases with contaminants such as acid gases, particulate matter and heavy metals.

Coal, solid fuels, heavy oils and other carbon feed stocks when combusted form exhaust gas streams that contain particulate matter and other objectionable contaminants such as heavy metals like mercury which may or may not be effectively scrubbed by aqueous scrubbing operations.

This all adds to the expense of treating for the nitrogen oxides.

This generates a large quantity of liquid discharge from the wet scrubber.

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