US-12623185-B2 - Apparatus and method for exhaust gas pollution reduction

US12623185B2US 12623185 B2US12623185 B2US 12623185B2US-12623185-B2

Abstract

A method for reducing pollution in exhaust gases and a system for treating exhaust gas are provided. The method includes the step of treating an exhaust gas stream with a treating fluid. In one application, the treating fluid is injected by spraying droplets into the exhaust gas stream. A system for treating exhaust gas includes a reagent, and a nozzle to spray the reagent into the exhaust gas stream.

Inventors

Norman Divers
John Gage

Assignees

MERCURY CAPTURE INTELLECTUAL PROPERTY, LLC

Dates

Publication Date: 20260512
Application Date: 20230124

Claims (4)

1 . A system for treating exhaust gas streams from an industrial process, the system comprising: a treating fluid comprising a reagent comprising one or more chelating agents, the chelating agents comprising a mixture of ethylenediaminetetraacetic acid and amino tris (methylene phosphonic acid); at least one nozzle configured to communicate with an exhaust gas stream; a particulate collection system; wherein said at least one nozzle injects said treating fluid into said exhaust gas stream to form a combined stream before entering the particulate collection system, the one or more chelating agents interacting with one or more heavy metals in the exhaust gas stream through chelation or physical binding, to form one or more particulates; wherein the nozzle produces droplets of the treating fluid having a size to maintain sufficient residence time for effective interaction with the one or more heavy metals in the exhaust gas stream; and wherein the particulate collection system separates the one or more particulates comprising at least a portion of the one or more heavy metals from the combined stream by forming a particulate residue containing the one or more heavy metals in non-leachable form.
2 . The system of claim 1 , wherein said treating fluid further comprises at least one selected from the group of a surfactant, a dispersant, and a hyperdispersant to enhance dispersion of the chelating agents within droplet phase and facilitate interaction with gas-phase of the one or more heavy metals.
3 . The system of claim 1 , wherein the treating fluid further comprises a solvent comprising propylene glycol wherein the solvent maintains droplet stability and promotes residence time of the treating fluid in the exhaust gas stream.
4 . A method for treating exhaust gas streams from an industrial process, the method comprising: providing an exhaust gas stream; providing a reagent comprising one or more chelating agents, the one or more chelating agents comprising a mixture of ethylenediaminetetraacetic acid and amino tris (methylene phosphonic acid); providing at least one nozzle configured to communicate with an exhaust gas stream, wherein the nozzle produces droplets of the treating fluid having a size to maintain sufficient residence time for effective interaction with one or more heavy metals in the exhaust gas stream; providing a particulate collection system; injecting the treating fluid into the exhaust gas stream through the nozzle to form a combined stream before entering the particulate collection system, the one or more chelating agents interacting with the one or more heavy metals in the exhaust gas stream through chelation or physical binding, to form one or more particulates; and separating the one or more particulates in the particulate collection system comprising at least a portion of the one or more heavy metals from the combined stream by forming a particulate residue containing the one or more heavy metals in non-leachable form.

Description

FIELD OF THE INVENTION The present disclosure relates to particulate matter pollution reduction in exhaust gases. BACKGROUND OF THE INVENTION Industrial exhaust gases vary significantly and typically contain volatile heavy metals, such as mercury, which are generally volatilized from the raw materials and fuels and carried into the atmosphere. For instance, cement kiln exhaust gases typically contain oxides of carbon, sulfur, nitrogen, alkalis, excess chlorides and volatile heavy metals such as mercury. Mercury in both its elemental and ionic form are generally continually emitted through the exhaust stack in varying concentrations dependent upon the operation of the kiln, in-line raw mill and raw material or fuel inputs. These gases may also be re-used for drying and heating within the inline raw mill and then exit the process as cement kiln exhaust gas. The heavy metals within the gases may then be released to the atmosphere after they pass through a kiln baghouse electrostatic precipitator, or other particulate collection apparatus. Typical mercury concentrations in cement kiln exhaust gases may vary significantly and are highly dependent on the raw materials, process conditions, and fuels burned in the clinkering process at each site. Previous attempts to capture and contain mercury from cement kiln exhaust gas in both its elemental and its oxide form have generally had mixed results. These processes may also be expensive. These processes include activated carbon injection, flue gas desulphurization scrubbers, and sorbent technology. Furthermore, the treatment fluid used in these process may cause the creation of undesirable chemical byproducts. Treatment processes for power plants such as those disclosed in Hurley U.S. Pat. Nos. 7,407,602, 7,771,683, and 7,776,294 are likewise inapplicable or inappropriate to the environment of the cement kiln for a variety of reasons. SUMMARY OF THE INVENTION In an illustrative embodiment, a method for treating industrial exhaust gas is disclosed. The method includes providing an exhaust gas stream from an industrial process; providing a reagent; combining the exhaust gas stream with the reagent to create a combined stream; and removing at least a portion of one heavy metal, such as mercury, from the combined stream. The method may further include passing the combined stream through a particulate collection system and recycling the collected particulate for use as raw material. In combining the exhaust gas stream with the reagent, the method may include spraying the reagent into the exhaust gas stream. The method may include combining the reagent with one or more solvents to create a reagent solution prior to combining the exhaust gas stream with the reagent. Factors affecting the amount of reagent used or its ratio to solvent may include the exhaust's particulate load, dispersion, exhaust gas velocity, presence and amount of metals other than mercury, and any number of other environmental or processing parameters. It is often desirable to use as little of the reagent as needed to achieve the desired amount of heavy metal reduction. The method may also include providing at least one of a surfactant, a dispersant, and a hyperdispersant, and combining the reagent and solvent with the at least one of the surfactant, the dispersant, and the hyperdispersant prior to combining the exhaust gas stream with the reagent. The reagent solution may further comprise one or more chelating agents. In an exemplary embodiment, the reagent solution may include a mixture of ethylenediaminetetraacetic acid (“EDTA”) and amino tris(methylene phosphonic acid) (“ATMP”) and/or their corresponding salts. In some embodiments, the solvent may include a diol such as propylene glycol. Accordingly, the solvent may include a water dilution of propylene glycol. In an illustrative embodiment, a method for reducing pollution in an industrial environment is disclosed. In this embodiment, the method includes treating an exhaust gas stream with a treating fluid. The treating fluid may comprise one or more chelating agents (e.g., EDTA and ATMP), a solvent such as propylene glycol, and at least one of a surfactant and a hyperdispersant. Injecting the treating fluid may include spraying droplets of the treating fluid into the exhaust gas stream. The treating fluid may be injected into the exhaust gas stream at a point where the exhaust gas stream has a temperature of about 350 degrees Fahrenheit. The treating fluid may be injected into the exhaust gas stream subsequent to a first particulate collection system and prior to a second particulate collection system. The treating fluid may also be injected into a gas resonance chamber or a duct carrying the exhaust gas stream. The treating fluid may also contain water and at least one of a surfactant and a hyperdispersant. The system and method may be adapted so that the droplets have a size which allows the droplets to have a minimum residence time of about 1 to a