US4080428A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Process for the purification of flue and other waste gas
Assignee: Individual
•
Filing: 1975-08-22
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Granted: 1978-03-21
•
Expires: 1995-08-22
Abstract
Abstract The invention is concerned with improved process and apparatus for the removal of sulphur dioxide from flue gas or other waste gas of the kind in which the waste gas is scrubbed by a circulating wash liquid containing lime suspensions, i.e. suspensions of calcium oxide, hydroxide or carbonate, the calcium/sulphur compounds so formed being oxidized and removed from the circulation, the improvements of the present invention comprising primarily the freeing of the wash liquid from solid matter before contact with the waste gas and then the control of pH values of the wash liquid at different stages of the circulation to facilitate, for example, the oxidation of the particular calcium/sulphur compound, formed in the scrubbing process, to calcium sulphate, the apparatus also being designed to improve the oxidation step.
Inventors
- 👤 Heinz Holter
- 👤 Heinz Gresch
- 👤 Heinrich Igelbuscher
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 15:10
CPC Classifications
B; B01; B01D; B01D53/00; B01D53/14; B01D53/1456; B01D53/34; B01D53/46; B01D53/48; B01D53/50; B01D53/501; C; C01; C01F; C01F11/00; C01F11/46; C01F11/464; C05; C05C; C05C3/00
Claims Analysis
Total Claims: 27
Claim 1
Independent Claim
151 words
A process for purifying sulphur-dioxide-containing waste gas comprising: a. contacting the gas with circulating calcium-ion containing wash liquid, the wash liquid being only clarified wash liquid having a pH from a maximum initial pH of 12 to a minimum subsequent pH in the weakly-acid zone, b. adding to the gas-contacted circulating wash liquid acid or salt ingredient means to increase the degree of calcium-ion dissociation therein, c. oxidizing calcium bisulphite in the ingredient-means-containing circulating wash liquid to calcium sulphate at a pH of at least 4.5, d. adding to the thus-oxidized circulating wash liquid a sufficient amount of a substance selected from the group consisting of calcium carbonate, calcium oxide and calcium hydroxide to form calcium-sulphur compounds from components in the circulating wash liquid and to provide said circulating wash liquid with calcium ions for step (a), and e. clarifying the circulating wash liquid before contacting the sulphur-dioxide-containing waste gas therewith.
Claim 2
Dependent Claim
151 words
A process for purifying sulphur-dioxide-containing waste gas comprising: a. contacting the gas with circulating calcium-ion containing wash liquid, the wash liquid being only clarified wash liquid having a pH from a maximum initial pH of 12 to a minimum subsequent pH in the weakly-acid zone, b. adding to the gas-contacted circulating wash liquid acid or salt ingredient means to increase the degree of calcium-ion dissociation therein, c. oxidizing calcium bisulphite in the ingredient-means-containing circulating wash liquid to calcium sulphate at a pH of at least 4.5, d. adding to the thus-oxidized circulating wash liquid a sufficient amount of a substance selected from the group consisting of calcium carbonate, calcium oxide and calcium hydroxide to form calcium-sulphur compounds from components in the circulating wash liquid and to provide said circulating wash liquid with calcium ions for step (a), and e. clarifying the circulating wash liquid before contacting the sulphur-dioxide-containing waste gas therewith.
Claim 3
Dependent Claim
33 words
A process according to claim 1 wherein the weakly-acid zone of step (a) has a minimum pH of 4.5 and which further comprises separating solids from the clarified wash liquid of step (e).
Claim 4
Dependent Claim
45 words
A process according to claim 1 wherein the waste gas is flue gas and which comprises regulating the pH value of the wash liquid so that said pH value in contact with the flue gas is in the acid range but is not below 4.5.
Claim 5
Dependent Claim
32 words
A process according to claim 3 which comprises adjusting the pH value of the wash liquid to a basic value which does not exceed 12 before contacting it with the flue gas.
Claim 6
Dependent Claim
77 words
A process according to claim 1 wherein the ingredient means added to increase the degree of discoloration of calcium is an acid selected from the group consisting of halogen, nitrogen and phosphorous acids or a salt thereof, the anion of which forms, with calcium ions, water-soluble compounds which, in the presence of sulphurous acid, permit exchange in neutral or weakly-acid medium, with the acid residue of sulphurous acid and, in an alkaline medium reform water-soluble calcium compounds.
Claim 7
Dependent Claim
25 words
A process according to claim 1 comprising additionally adding a carboxylic acid buffer to the wash liquid before contacting the latter with the waste gas.
Claim 8
Dependent Claim
33 words
A process according to claim 6 wherein the calcium-sulphur-compound forming substance added to the circulating wash liquid is calcium carbonate and the means to increase the degree of calcium-ion dissociation comprises hydrochloric acid.
Claim 9
Dependent Claim
33 words
A process according to claim 6 wherein the calcium-sulphur-compound forming substance added to the circulating wash liquid is calcium oxide and the means to increase the degree of calcium-ion dissociation comprises hydrochloric acid.
Claim 10
Dependent Claim
33 words
A process according to claim 6 wherein the calcium-sulphur-compound forming substance added to the circulating wash liquid is calcium hydroxide and the means to increase the degree of calcium-ion dissociation comprises hydrochloric acid.
Claim 11
Dependent Claim
37 words
A process according to claim 1 wheren the wash liquid contains 0.25% of hydrochloric acid and about 1% of formic acid when the flue gas has a sulphur-dioxide concentration of from 2,000 to 3,000 mg/Nm 3 .
Claim 12
Dependent Claim
65 words
A process according to claim 1 wherein the ingredient means to increase the degree of dissociation of calcium is an organic acid or salt thereof, radicals of which form, with calcium ions, water-soluble compounds which, in the presence of sulphurous acid, permit exchange in neutral or weakly acid media with the acid residue of sulphurous acid and, in an alkaline media reform water-soluble calcium compounds.
Claim 13
Dependent Claim
13 words
A process according to claim 11 wherein the ingredient means is formic acid.
Claim 14
Dependent Claim
13 words
A process according to claim 11 wherein the ingredient means is ammonium formate.
Claim 15
Dependent Claim
25 words
A process according to claim 1 which comprises oxidizing calcium bisulphite, formed during washing of the flue gas, to calcium sulphate at an acid pH.
Claim 16
Dependent Claim
15 words
A process according to claim 4 wherein the acid pH is between 4.5 and 6.5.
Claim 17
Dependent Claim
41 words
A process according to claim 1 which comprises adding the substance selected from the group consisting of a calcium carbonate, calcium oxide and calcium hydroxide after oxidizing the calcium bisulphite and before clarifying the circulating wash liquid at a basic pH.
Claim 18
Dependent Claim
25 words
A process according to claim 16 which comprises maintaining the wash liquid for a dwell time of at least 15 minutes before separating solids therefrom.
Claim 19
Dependent Claim
18 words
A process according to claim 1 wherein oxidizing the calcium-bisulphite is effected catalytically with elemental iron as catalyst.
Claim 20
Dependent Claim
19 words
A process according to claim 18 wherein the elemental iron catalyst is in refined-sheet form or in copper-alloy-steel form.
Claim 21
Dependent Claim
22 words
A process according to claim 1 wherein oxidizing the calcium-bisulphite to calcium sulphate is effected with wash liquid containing an alkaline salt.
Claim 22
Dependent Claim
16 words
A process according to claim 20 wherein the alkaline salt is iron chloride or iron sulphate.
Claim 23
Dependent Claim
25 words
A process according to claim 1 which comprising washing sludge from solid materials freed from said wash liquid for at least half-an-hour with sulfuric acid.
Claim 24
Dependent Claim
30 words
A process according to claim 22 which comprises blowing air into the sludge while washing it with sulphuric acid and recirculating entrained sulphur dioxide to the waste gas being purified.
Claim 25
Dependent Claim
30 words
A process according to claim 1 which comprises alternately feeding flue gas and wash liquid which dissolves calcium sulphate to two separate drip tanks of wash apparatus connected in parallel.
Claim 26
Dependent Claim
41 words
A process according to claim 24 which comprises leading the wash liquid which dissolves calcium sulphate through a separate tank into circulating wash liquid, the wash liquid which dissolves calcium sulphate containing hydrochloric acid and having a pH value below 4.5.
Claim 27
Dependent Claim
19 words
A process according to claim 24 wherein the wash liquid which dissolves calcium sulphate is an ammonium sulphate solution.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1981-03-20 | 1981-09-19 | 1982-03-21 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1985-03-20 | 1985-09-19 | 1986-03-21 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1989-03-20 | 1989-09-19 | 1990-03-21 | $7700.00 | Window Closed / Lapsed |