US5198201A — Removal of sulphur and nitrogen oxides from flue …

Claim 1

Independent Claim 160 words

A method for removing pollutants from boiler plant flue gas, comprising: indirectly cooling the flue gas with a first fluid to cool the flue gas to a first temperature below the condensation point of sulfuric acid but above the condensation point of water and to combine substantially all SO 3 in the flue gas with H 2 O to form sulfuric acid; removing the sulfuric acid from the flue gas as a first condensate; collecting the first condensate; continuously introducing at least a part of the first condensate into flue gas prior to the first indirect heat exchange step to improve removal of pollutants and heat exchange in the flue gas; and indirectly exchanging heat between the flue gas and a second fluid to cool the flue gas to a second temperature heat exchange step to condense H 2 O from the flue gas as a second condensate while dissolving SO 2 in the flue gas in the second condensate.

Claim 2

Independent Claim 160 words

A method for removing pollutants from boiler plant flue gas, comprising: indirectly cooling the flue gas with a first fluid to cool the flue gas to a first temperature below the condensation point of sulfuric acid but above the condensation point of water and to combine substantially all SO 3 in the flue gas with H 2 O to form sulfuric acid; removing the sulfuric acid from the flue gas as a first condensate; collecting the first condensate; continuously introducing at least a part of the first condensate into flue gas prior to the first indirect heat exchange step to improve removal of pollutants and heat exchange in the flue gas; and indirectly exchanging heat between the flue gas and a second fluid to cool the flue gas to a second temperature heat exchange step to condense H 2 O from the flue gas as a second condensate while dissolving SO 2 in the flue gas in the second condensate.

Claim 3

Dependent Claim 21 words

The method of claim 1, which further comprises: collecting the second condensate; and extracting the SO 2 from the second condensate.

Claim 4

Dependent Claim 81 words

The method of claim 2, wherein the extracting step comprises: circulating the second condensate to a reservoir; applying vacuum pressure to the reservoir above the second condensate; combining at least part of the extracted SO 3 with metallic iron to produce ferrous sulfite; and introducing at least part of the ferrous sulfite produced in said combining step to flue gas that has undergone the first indirect heat exchange step but that has not yet undergone the second temperature heat exchange step.

Claim 5

Dependent Claim 24 words

The method of claim 2, which further comprises providing ferrous sulfite to the second condensate to decompose oxides of nitrogen in the second condensate.

Claim 6

Dependent Claim 28 words

The method of claim 4, which further comprises producing the ferrous sulfite by reacting metallic iron with a sulphurous acid and collecting ferrous sulfite formed by the reaction.

Claim 7

Dependent Claim 31 words

The method of claim 5, wherein said ferrous sulfite producing step includes producing at least part of the sulphurous acid from the sulphur dioxide extracted during said sulphur dioxide extracting step.

Claim 8

Dependent Claim 85 words

The method of claim 2, wherein the first indirect heat exchange step and the first condensate collecting step are performed over a first vertical flue gas flue path, the second temperature heat exchange step and the second condensate collecting step are performed over a second vertical flue gas flow path, and which further comprises effecting at least one directional change between the first and second vertical flue gas flow paths to prevent the first condensate from passing directly into the second temperature heat exchange step.

Claim 9

Dependent Claim 45 words

The method of claim 7, which further comprises adding ammonia to the flue gas that has undergone the second indirect heat exchange step in an amount sufficient to react with substantially all remaining oxides of nitrogen in the flue gas to produce nitrogen and water.

Claim 10

Dependent Claim 67 words

The method of claim 2, which further comprises indirectly exchanging heat between the flue gas and a third fluid, to cool the flue gas to a third indirect, after the second temperature heat exchange step, to condense H 2 O from the flue gas as a third condensate and to further dissolve SO 2 in the flue gas in the third condensate; and collecting the third condensate.

Claim 11

Dependent Claim 44 words

The method of claim 9, which further comprises the step of introducing at least a part of the third condensate to flue gas that has undergone the second indirect heat exchange step but that has not yet undergone the third indirect heat exchange step.

Claim 12

Dependent Claim 137 words

The method of claim 9, wherein the first indirect heat exchange step and the first condensate collecting step are performed over a first vertical flue gas flow path, the second indirect heat exchange step and the second condensate collecting step are performed over a second vertical flue gas flow path, the third indirect heat exchange step and the third condensate collecting step are performed over a third vertical flue gas flow path, and which further comprises effecting at least one directional change between the first and second vertical flue gas flow paths to prevent the first condensate from passing directly into the second indirect heat exchange step, and effecting at least one directional change between the second and third vertical flue gas flow paths to prevent the second condensate from passing directly into the third cooling step.

Claim 13

Dependent Claim 26 words

The method of claim 2, which further comprises removing particulate material including fly ash from the flue gas prior to the first temperature heat exchange step.

Claim 14

Dependent Claim 45 words

The method of claim 12, which further comprises introducing ammonia to the flue gas after the second temperature heat exchange step, and passing the flue gas through a bag house while reacting residual oxides of nitrogen and sulphur in the flue gas with the ammonia.

Claim 15

Independent Claim 187 words

A method for removing pollutants from boiler plant flue gas, comprising: indirectly cooling the flue gas with a first fluid to cool the flue gas to a first temperature and combine substantially all SO 3 in the flue gas with H 2 O; condensing the SO 3 and H 2 O from the flue gas as a first condensate to form sulfuric acid; collecting the first condensate; indirectly cooling the flue gas with a second fluid to cool the flue gas to a second temperature, after the first indirect heat exchange step, to condense H 2 O from the flue gas as a second condensate and dissolve SO 2 in the flue gas in the second condensate to form sulfurous acid; collecting the second condensate; extracting the SO 2 from the second condensate; collecting the SO 2 extracted from the second condensate; reacting at least a portion of the extracted SO 2 with water and oxygen to form sulfuric acid; and adding ammonium hydroxide to at least a portion of the sulfuric acid produced during said combining step to produce (NH 4 ) 2 SO 4 .

Claim 16

Independent Claim 187 words

A method for removing pollutants from boiler plant flue gas, comprising: indirectly cooling the flue gas with a first fluid to cool the flue gas to a first temperature and combine substantially all SO 3 in the flue gas with H 2 O; condensing the SO 3 and H 2 O from the flue gas as a first condensate to form sulfuric acid; collecting the first condensate; indirectly cooling the flue gas with a second fluid to cool the flue gas to a second temperature, after the first indirect heat exchange step, to condense H 2 O from the flue gas as a second condensate and dissolve SO 2 in the flue gas in the second condensate to form sulfurous acid; collecting the second condensate; extracting the SO 2 from the second condensate; collecting the SO 2 extracted from the second condensate; reacting at least a portion of the extracted SO 2 with water and oxygen to form sulfuric acid; and adding ammonium hydroxide to at least a portion of the sulfuric acid produced during said combining step to produce (NH 4 ) 2 SO 4 .

Claim 17

Dependent Claim 30 words

The method of claim 14, which further comprises adding oxygen to at least a portion of the extracted SO 2 to oxidize said extracted SO 2 to SO 3 .

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1996-03-29	1996-09-28	1997-03-30	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	2000-03-29	2000-09-28	2001-03-30	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2004-03-29	2004-09-28	2005-03-30	$7700.00	Window Closed / Lapsed

Removal of sulphur and nitrogen oxides from flue gases

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