US3954451A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method for the manufacture of mercury free sulfuric acid
Assignee: Hachinohe Smelting Co Ltd
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Filing: 1972-09-06
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Granted: 1976-05-04
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Expires: 1992-09-06
Abstract
Abstract A method of manufacturing sulfuric acid free of impurities such as mercury by the contact process, which comprises the steps: scrubbing the roasting gas coming out of a mist Cottrell with sulfuric acid having a concentration of 30 to 99% and a temperature of more than 20 DEG C within one or two mercury absorption towers (the drying tower per se may suffice) or further within an additional mercury absorption tower disposed on the outlet side of the main blower; and adding a reagent such as a sulfide, a hydrosulfide compound of alkali metal or alkaline earth metal, hydrogen sulfide, selenium compound, sulfur, etc., or a metal more active than mercury in ionization series, to the sulfuric acid used in scrubbing to thereby precipitate and separate the heavy metals - particularly mercury - contained in the sulfuric acid as solid matter such as mercury sulfide, mercury selenide, mercury metal or amalgam; thereby making it possible to utilize the resulting sulfuric acid free of impurities as the exchange acid or directly take out as an end product.
Inventors
- 👤 Hisahiro Kinoshita
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 17:49
CPC Classifications
C; C01; C01B; C01B17/00; C01B17/48; C01B17/50; C01B17/56
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
154 words
In a method of manufacturing substantially mercury-free sulfuric acid, by roasting non-ferrous metal sulfide material and then removing dust, cooling, washing and removing mist from the roasted gas to prepare a cool feed gas containing SO 2 and impurities comprising water and mercury converting the SO 2 to SO 3 and absorbing the SO 3 in dilute sulfuric acid, the improvement which comprises the steps of: continuously flowing a stream of said feed gas into and through scrubbing means and therein continuously scrubbing said feed gas with a continuously circulating stream of liquid scrubbing agent consisting essentially of sulfuric acid solution having an H 2 SO 4 concentration of from 77 to 99 wt. % and having a temperature of from 20° to 70° C, to absorb impurities comprising water and mercury present in said feed gas into said scrubbing agent and to produce a stream of purified feed gas containing SO 2 ;
Claim 2
Dependent Claim
154 words
In a method of manufacturing substantially mercury-free sulfuric acid, by roasting non-ferrous metal sulfide material and then removing dust, cooling, washing and removing mist from the roasted gas to prepare a cool feed gas containing SO 2 and impurities comprising water and mercury converting the SO 2 to SO 3 and absorbing the SO 3 in dilute sulfuric acid, the improvement which comprises the steps of: continuously flowing a stream of said feed gas into and through scrubbing means and therein continuously scrubbing said feed gas with a continuously circulating stream of liquid scrubbing agent consisting essentially of sulfuric acid solution having an H 2 SO 4 concentration of from 77 to 99 wt. % and having a temperature of from 20° to 70° C, to absorb impurities comprising water and mercury present in said feed gas into said scrubbing agent and to produce a stream of purified feed gas containing SO 2 ;
Claim 3
Dependent Claim
222 words
converting the SO 2 in said purified feed gas to SO 3 and then flowing said resultant SO 3 -containing gas through absorption tower means and therein contacting said resultant gas with dilute sulfuric acid solution to absorb the SO 3 whereby to produce concentrated sulfuric acid solution; continuously withdrawing a portion of said circulating scrubbing agent stream while continuing to circulate the balance of said scrubbing agent stream through said scrubbing means, adding to said withdrawn portion one or more precipitating agent selected from the group consisting of Na 2 S, NaSH, Na 2 S x , H 2 S, K 2 S, Na 2 SeO 4 and S, in an amount effective to precipitate the mercury present therein, together with a substance capable of making present in said withdrawn portion of said scrubbing agent silver ions or copper ions in an amount effective to accelerate the precipitation of mercury sulfide or mercury selenide in said withdrawn portion, removing the precipitated mercury sulfide or mercury selenide from said withdrawn portion of said scrubbing agent, recovering the balance of said withdrawn portion of said scrubbing agent as a purified dilute sulfuric acid solution, and utilizing at least a portion of said purified dilute sulfuric acid solution obtained from said withdrawn portion as the dilute sulfuric acid solution employed in said contacting step.
Claim 4
Dependent Claim
222 words
converting the SO 2 in said purified feed gas to SO 3 and then flowing said resultant SO 3 -containing gas through absorption tower means and therein contacting said resultant gas with dilute sulfuric acid solution to absorb the SO 3 whereby to produce concentrated sulfuric acid solution; continuously withdrawing a portion of said circulating scrubbing agent stream while continuing to circulate the balance of said scrubbing agent stream through said scrubbing means, adding to said withdrawn portion one or more precipitating agent selected from the group consisting of Na 2 S, NaSH, Na 2 S x , H 2 S, K 2 S, Na 2 SeO 4 and S, in an amount effective to precipitate the mercury present therein, together with a substance capable of making present in said withdrawn portion of said scrubbing agent silver ions or copper ions in an amount effective to accelerate the precipitation of mercury sulfide or mercury selenide in said withdrawn portion, removing the precipitated mercury sulfide or mercury selenide from said withdrawn portion of said scrubbing agent, recovering the balance of said withdrawn portion of said scrubbing agent as a purified dilute sulfuric acid solution, and utilizing at least a portion of said purified dilute sulfuric acid solution obtained from said withdrawn portion as the dilute sulfuric acid solution employed in said contacting step.
Claim 5
Dependent Claim
35 words
A method according to claim 1 in which the H 2 SO 4 concentration of said withdrawn portion of said scrubbing agent is adjusted to be less than 80% before adding said precipitating agent thereto.
Claim 6
Dependent Claim
26 words
A method according to claim 1 in which said substance is selected from the group consisting of Ag, Ag 2 S, Cu and CuSO 4 .
Claim 7
Dependent Claim
28 words
A method according to claim 1 wherein said scrubbing agent has an H 2 SO 4 concentration of about 77% and a temperature of 35° to 40° C.
Claim 8
Dependent Claim
31 words
A method according to claim 1 in which the H 2 SO 4 concentration of said withdrawn portion of said scrubbing agent is more than 80% before adding precipitating agent thereto.
Claim 9
Dependent Claim
26 words
A method according to claim 5 in which said substance is selected from the group consisting of Ag, Ag 2 S, Cu and CuSO 4 .
Claim 10
Dependent Claim
363 words
In a method of manufacturing substantially mercury-free sulfuric acid, by roasting non-ferrous metal sulfide material and then removing dust, cooling, washing and removing mist from the roasted gas to prepare a cool feed gas containing SO 2 and impurities comprising water and mercury converting the SO 2 to SO 3 and absorbing the SO 3 in dilute sulfuric acid, the improvement which comprises the steps of: continuously flowing a stream of said feed gas into and through scrubbing means and therein continuously scrubbing said feed gas with a continuously circulating stream of liquid scrubbing agent consisting essentially of sulfuric acid solution having an H 2 SO 4 concentration of from more than 80 to 99 wt. % and having a temperature of from 20° to 70° C., to absorb impurities comprising water and mercury present in said feed gas into said scrubbing agent and to produce a stream of purified feed gas containing SO 2 ; converting the SO 2 in said purified feed gas to SO 3 and then flowing said resultant SO 3 -containing gas through absorption tower means and therein contacting said resultant gas with dilute sulfuric acid solution to absorb the SO 3 whereby to produce concentrated sulfuric acid solution; continuously withdrawing a portion of said circulating scrubbing agent stream having an H 2 SO 4 concentration of more than 80% while continuing to circulate the balance of said scrubbing agent stream through said scrubbing means, adding to said withdrawn portion a precipitating agent selected from the group consisting of aluminum metal, zinc metal and selenium metal in an amount effective to precipitate the mercury present therein together with a substance capable of making present in said withdrawn portion of said scrubbing agent silver ions or copper ions in an amount effective to accelerate the precipitation of mercury metal, removing the precipitated mercury metal from said withdrawn portion of said scrubbing agent, recovering the balance of said withdrawn portion of said scrubbing agent as a purified dilute sulfuric acid solution, and utilizing at least a portion of said purified dilute sulfuric acid solution obtained from said withdrawn portion as the dilute sulfuric acid solution employed in said contacting step.
Claim 11
Dependent Claim
363 words
In a method of manufacturing substantially mercury-free sulfuric acid, by roasting non-ferrous metal sulfide material and then removing dust, cooling, washing and removing mist from the roasted gas to prepare a cool feed gas containing SO 2 and impurities comprising water and mercury converting the SO 2 to SO 3 and absorbing the SO 3 in dilute sulfuric acid, the improvement which comprises the steps of: continuously flowing a stream of said feed gas into and through scrubbing means and therein continuously scrubbing said feed gas with a continuously circulating stream of liquid scrubbing agent consisting essentially of sulfuric acid solution having an H 2 SO 4 concentration of from more than 80 to 99 wt. % and having a temperature of from 20° to 70° C., to absorb impurities comprising water and mercury present in said feed gas into said scrubbing agent and to produce a stream of purified feed gas containing SO 2 ; converting the SO 2 in said purified feed gas to SO 3 and then flowing said resultant SO 3 -containing gas through absorption tower means and therein contacting said resultant gas with dilute sulfuric acid solution to absorb the SO 3 whereby to produce concentrated sulfuric acid solution; continuously withdrawing a portion of said circulating scrubbing agent stream having an H 2 SO 4 concentration of more than 80% while continuing to circulate the balance of said scrubbing agent stream through said scrubbing means, adding to said withdrawn portion a precipitating agent selected from the group consisting of aluminum metal, zinc metal and selenium metal in an amount effective to precipitate the mercury present therein together with a substance capable of making present in said withdrawn portion of said scrubbing agent silver ions or copper ions in an amount effective to accelerate the precipitation of mercury metal, removing the precipitated mercury metal from said withdrawn portion of said scrubbing agent, recovering the balance of said withdrawn portion of said scrubbing agent as a purified dilute sulfuric acid solution, and utilizing at least a portion of said purified dilute sulfuric acid solution obtained from said withdrawn portion as the dilute sulfuric acid solution employed in said contacting step.
Claim 12
Dependent Claim
26 words
A method according to claim 7 in which said substance is selected from the group consisting of Ag, Ag 2 S, Cu and CuSO 4 .
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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) | 1979-05-04 | 1979-11-03 | 1980-05-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-05-04 | 1983-11-03 | 1984-05-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-05-04 | 1987-11-03 | 1988-05-04 | $7700.00 | Window Closed / Lapsed |