WO1997000225A1 - Procede de production d'acide caro - Google Patents

Procede de production d'acide caro Download PDF

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Publication number
WO1997000225A1
WO1997000225A1 PCT/US1996/010475 US9610475W WO9700225A1 WO 1997000225 A1 WO1997000225 A1 WO 1997000225A1 US 9610475 W US9610475 W US 9610475W WO 9700225 A1 WO9700225 A1 WO 9700225A1
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WO
WIPO (PCT)
Prior art keywords
acid
caro
water
hydrogen peroxide
mixture
Prior art date
Application number
PCT/US1996/010475
Other languages
English (en)
Inventor
Harry Marcus Castrantas
James Lawrence Manganaro
Ralph Joseph Mikida
William Ramsey Johnson
Original Assignee
Fmc Corporation
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Fmc Corporation filed Critical Fmc Corporation
Priority to AU62824/96A priority Critical patent/AU700876B2/en
Priority to BR9608341A priority patent/BR9608341A/pt
Publication of WO1997000225A1 publication Critical patent/WO1997000225A1/fr

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B15/00—Peroxides; Peroxyhydrates; Peroxyacids or salts thereof; Superoxides; Ozonides
    • C01B15/055—Peroxyhydrates; Peroxyacids or salts thereof
    • C01B15/06—Peroxyhydrates; Peroxyacids or salts thereof containing sulfur

Definitions

  • the invention is in the field of producing Caro's acid by reaction of hydrogen peroxide and sulfuric acid in a controlled and effective manner.
  • Caro's acid which is peroxymonosulfuric acid, is a strong oxidizing compound which has been suggested for use in any applications including purification of cyanide-containing effluents by conversion of their cyanides into non-toxic derivatives.
  • Caro's acid is usually produced by reacting together concentrated sulfuric acid (85% to 98% by weight H 2 S0 4 ) with concentrated hydrogen peroxide (50% to 90% by weight H 2 0 2 ) to produce an equilibrium mixture of Caro's acid containing peroxymonosulfuric acid (H 2 S0 5 ), sulfuric acid and hydrogen peroxide.
  • the Caro's acid is not stable for long periods it must be made and immediately used on site or quickly cooled and stored at refrigerated temperatures. In general, the Caro's acid is manufactured on site as needed and in just the amounts required for the specified application without the necessity of having to store any excess amounts.
  • the first problem is the protection of a large amount of hydrogen peroxide in storage tanks, used to feed the Caro's acid producing generator, from possible contamination.
  • the need to prevent contamination of this large hydrogen peroxide source from either Caro's acid, sulfuric acid, or other such impurities is critical to the safe containment and use of the hydrogen peroxide.
  • the second problem is to control the Caro's acid reaction so that the Caro's acid is formed efficiently with maximum use of the hydrogen peroxide reagent and without having the hot reaction mixture formed during the reaction go out of control and overflow or rupture the reaction chamber.
  • the second problem arises because the reaction of sulfuric acid and hydrogen peroxide is an exothermic reaction and some hydrogen peroxide decomposes to form large amounts of gas which may cause pressure build up capable of rupturing the reactor or causing the reagents to overflow. This may cause the hot reaction mixture to go out of control with the waste of both sulfuric acid and hydrogen peroxide and further, if no break tank is used, may become a possible source of contamination of the hydrogen peroxide storage tank if it backs up into the hydrogen peroxide line connecting the hydrogen peroxide storage tank to the Caro's acid reactor.
  • This process for producing Caro's acid is carried out by reacting sulfuric acid having an concentration of at least about 85% by weight and hydrogen peroxide having a concentration of at least about 50% by weight, wherein the hydrogen peroxide is introduced through a first feed line and the sulfuric acid is introduced through a second feed line into a tunneling zone open to the atmosphere, the first feed line and second feed line having air gaps between their ends and the tunneling zone, passing said hydrogen peroxide and sulfuric acid by gravity flow from said tunneling zone into one end of a reaction zone that has been sized to permit a pressure drop therein which is at least 8 times the theoretical pressure drop for liquids flowing through such reaction zone and removing a mixture containing Caro's acid from an exit end of the reaction zone.
  • the Caro's acid that issues from the end of the reactor open to the atmosphere is quite hot because of the exothermic reaction between the sulfuric acid and hydrogen peroxide and tends to form an undesired Caro's acid mist.
  • the Caro's acid mist is an irritant to the mucus membranes of workers who are in the vicinity of the outlet of the Caro's acid reactor.
  • the mist is especially objectionable when the reactor is inside a building where the mist can collect and build up in concentration to a point where protective gear and/or special exhaust provisions are required. Even outdoors the mist is noticeable and most objectionable to any workmen who may be downwind from the Caro's acid reactor.
  • the Caro's acid when used to treat tailing slurries to reduce their cyanide concentrations, the mixing of the Caro's acid with the tailing slurries is not instantaneous due to the syrupy nature of the concentrated Caro's acid that issues from the Caro's acid generator and the high density of the tailing slurries (35% to 40% solids). This is undesired because it allows time for the Caro's acid to decompose before reacting with the cyanide in the tailing slurry. It has now been found that the Caro's acid mist, that forms when
  • Caro's acid is produced by reaction of sulfuric acid and hydrogen peroxide in a reaction zone and the hot Caro's acid mixture is released from the end of the reaction zone, can be reduced or eliminated by quenching the hot Caro's acid mixture with water to both cool and dilute the Caro's acid.
  • the Caro's acid is produced by reacting sulfuric acid and hydrogen peroxide together, preferably in a continuous manner and in accordance with the process set forth in our copending U.S. Application SN 08/351,987 filed December 8, 1994 (now Patent No. 5,470,564) in the names of James L. Manganaro et. al.
  • While other processes may also be employed for producing the Caro's acid, this is the preferred method because the Caro's acid is formed efficiently with maximum use of hydrogen peroxide reagent and without having the hot reaction mixture formed during the reaction go out of control and overflow or rupture the reaction chamber.
  • the reactants are added into a tunneling zone, or other type of feeding zone, open to the atmosphere and then the hydrogen peroxide and sulfuric acid flow from the tunneling zone by gravity into one end of a reaction zone where the reaction takes place.
  • the reaction zone which is Iocated downstream from the tunneling zone is preferably a pipe-like or tube reactor, whose diameter may be variable or constant, which may be either vertically oriented or horizontally oriented or any skew angle intermediate these two extremes and is fed by gravity from the tunneling zone. Further, it is preferred that the reaction zone have a size which permits a pressure drop in the reaction zone which is at least eight times the theoretical pressure drop for liquids passing through such reaction zone.
  • Such reaction zones are normally static reactors containing several mixing elements which ensure a complete mixing and reaction of the two reagents.
  • the sulfuric acid employed in the reaction can be of any concentration from about 85% by weight to about 98% by weight H 2 S0 4 with about 93% by weight sulfuric acid being preferred because of its ready availability and workability.
  • the hydrogen peroxide employed can be of any concentration from about 50% by weight H 2 0 2 to about 90% by weight H 2 0 2 with 70% by weight hydrogen peroxide being preferred because of safety considerations and availability.
  • the mole ratios of sulfuric acid to hydrogen peroxide (H 2 S0 4 /H 2 0 2 ) can range from about 1/1 to about 4/1 with about 2/1 to about 3/1 being preferred.
  • the reaction results in Caro's acid being foimed in a solution which is an equilibrium mixture of hydrogen peroxide, sulfuric acid, Caro's acid and water.
  • H 2 S0 4 + H 2 0 2 ⁇ H 2 SO s + H 2 O
  • a typical composition prepared from a 2.5/1 mole ratio of 93 weight percent sulfuric acid and 70 weight percent hydrogen peroxide is as follows: Caro's Acid (peroxymonosulfuric acid) 25 weight percent; sulfuric acid 57 weight percent; hydrogen peroxide 3.5 weight percent; and water 14.5 weight percent.
  • Caro's Acid peroxymonosulfuric acid
  • hydrogen peroxide 3.5 weight percent and water 14.5 weight percent.
  • a considerable amount of heat is released as a result of mixing the hydrogen peroxide with sulfuric acid. The amount of heat released depends on the concentration of the starting reagents and the mole ratios of sulfuric acid to hydrogen peroxide.
  • Caro's acid mist is generated as the hot Caro's acid mixture exits the reactor unit.
  • Caro's acid is added directly from the reactor to the tailings slurry.
  • the Caro's acid mist is released as the Caro's acid mixture free falls between the end of the Caro's acid reactor and the surface of the tailings slurry. Further, mist is released as the Caro's acid spreads out onto the surface of the slurry before it mixes with the tailings slurry. The higher the Caro's acid temperature, the more acid mist is generated.
  • the acid mist has a sharp odor which can cause irritation of the mucus membranes.
  • the acid mist is also corrosive to equipment and instruments used in precious metal recovery sites. Where the injection point for Caro's acid to a tailings pond is Iocated outdoors, the Caro's acid mist is extremely objectionable to anyone downwind from the site where the mist is generated.
  • the Caro's acid mist can be substantially reduced or even eliminated by quenching the hot Caro's acid mixture with water to both cool and dilute the mixture as it exits the Caro's acid reactor.
  • the above quenching of the above hot Caro's acid mixture can take place in a number of ways.
  • One way is to direct water sprays at the base of the pipe where the Caro's acid mixture exits.
  • the water sprays simultaneously emit water streams directly into the Caro's acid mixture and also form a curtain of water droplets that surround the end of the pipe from which the Caro's acid mixture exits.
  • a second method for carrying out the above quenching of the Caro's acid mixture is to introduce dilution water into an annular tube surrounding the outside of the pipe from which the Caro's acid mixture exits resulting in a ring of water flowing co-currently with the Caro's acid contained within the water ring.
  • the Caro's acid and water intimately mix as they fall from the exit pipe of the Caro's acid reactor and the ring of water prevents any release of the Caro's acid mist before it is scrubbed and reacts with the water to quench and dilute the Caro's acid.
  • Another system for quenching the Caro's acid mixture is to attach a water aspirator to the pipe from which the Caro's acid mixture exits.
  • the instant mixing of the water and Caro's acid assures immediate dilution and cooling of the Caro's acid before it exits from the static mixer into the tailings sump.
  • the simplest and most economic way of carrying out the quenching of the Caro's acid mixture is to place the exit tube of the Caro's acid reactor into a container in which a continuous water stream is directed with the exit tube being below the level of the water that is present in the container. In other words the exit tube is placed into a container full of water, below the water level, and into which a continuous water stream is directed and overflows the container.
  • the amount of water employed for water dilution and quenching is not critical and can vary widely. For example we have found that from 1/1 to 200/1 weight dilution of water to Caro's acid is effective. Obviously, larger amounts of water can be used without deleterious affects.
  • the dilution water can be at any temperature which will cool the Caro's acid mixture. Temperatures from about 5 s to about 45 S C are useful with ambient temperatures being preferred because they are the most economical. Since the temperature of the Caro's acid mixture exiting from the Caro's acid reactor is normally from about 52 Q C to 98 9 C, any temperature below 52 e C will usually be effective.
  • the testing was carried out with a tailing slurry recovered from a gold extraction using sodium cyanide as the extracting agent.
  • the Caro's acid is employed to reduce the cyanide levels in the tailings slurry.
  • the Caro's acid was added to the tailing slurry without any water to quench the Caro's acid mixture.
  • the tailing slurry in contact with undiluted Caro's acid turned green. It is believed that the green color was due to some component of the ore slurry such as a heavy metal changing color under oxidation and/or acid conditions. Once the Caro's acid mixed with the slurry the green color disappeared.
  • the green color provided a unique visual opportunity to observe mixing patterns of Caro's acid with the slurry and to observe any unreacted Caro's acid which was green in color and which floated on top of the tailing slurry.
  • Caro's acid for detoxification of cyanides (CN ) and WAD (Weekly Acid Dissociable) CN in gold mine tailings slurries
  • the invention can also be used in any other application where Caro's acid is prepared on site and injected into a substrate to destroy, deodorize, decolor, or alter a chemical composition.
  • Caro's acid is prepared on site and injected into a substrate to destroy, deodorize, decolor, or alter a chemical composition.
  • the syrupy Caro's acid mixture exiting from the Caro's acid reactor forms many large pools on the surface of the tailing slurry and these pools can be seen to be bubbling indicating that the hot Caro's acid is decomposing. This is wasteful of oxidizing potential of the Caro's acid and of course, diminishes the effectiveness of the Caro's acid in reducing the cyanide concentration in the tailing slurry.
  • Example 1 Generation and Use of Caro's Acid Without Water Quenchin ⁇ -Prior Art A Caro's acid generator, consisting of a tunneling zone attached to a static tubular reactor installed in a vertical position beneath the tunneling zone and containing four (4) mixing elements was placed over a sump filled with tailing slurry that contained residual cyanide values. The tunneling zone was open to the atmosphere as was the outlet of the static reactor. Sulfuric acid in the amount of 0.85 gallons per minute of 93% by weight H 2 SO 4 and 0.20 gallons per minute of 70 weight percent of H 2 0 2 was added to the tunneling zone and produced from the bottom of the reactor a mixture containing 27% Caro's acid on a continuous basis.
  • the Caro's acid mixture was passed directly into the sump to treat a stream of 840 gallons per minute of the tailing slurry containing 1.3 lbs. per minute of cyanide (CN ). This equated to a Caro's acid/cyanide mole ratio of 0.71/1 and resulted in a 43.3% destruction of WAD cyanide (CN ).
  • the hot Caro's acid exiting from the Caro's acid generator was not treated in any way before it fell into the sump containing the tailing slurry. Caro's acid mist was prevalent in the vicinity of the Caro's acid addition point.
  • the water was at ambient temperature and the amount of water used was estimated to be in excess of a weight ratio of water to Caro's acid of 10:1. There was no detectable Caro's acid mist present in the vicinity of the Caro's acid outlet pipe. For a brief time during the trial the water that was being sprayed on the outlet pipe was shut off and shortly thereafter the acid mist returned immediately. When the water was tumed on again, allowing the water spray to impinge upon the outlet of the Caro's acid pipe, the acid mist quickly disappeared.
  • Example 2 Another run was made using the same Caro's acid generator and reagents as in Example 1 , except that the 840 gallons per minute of tailing slurry contained 1.8 lbs/minute of cyanide values (CN ) and was treated with Caro's acid prepared from 1.0 gallons per minute of 93% by weight H 2 S0 4 and 0.25 gallons per minute of 70% by weight H 2 0 2 . This equated to a Caro's acid/cyanide mole ratio of 0.64/1 and resulted in a 50% destruction of WAD cyanide (CN ). During this run a large plastic bucket was positioned under the Caro's acid outlet pipe and a stream of water was continually added to the bucket.
  • CN WAD cyanide
  • the level of the Caro's acid outlet pipe was below the water level in the bucket and the Caro's acid and water mixture in the bucket overflowed into the tailings slurry contained below it. No Caro's acid mist was present and no bubbling of any pockets of Caro's acid pools floating on top of the slurry were observable in the vicinity of the Caro's acid injection point. Also no green streaks were evident on the surface of the tailings slurry in the slurry pipe outlet 12 feet downstream from the Caro's acid injection point.

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  • Chemical & Material Sciences (AREA)
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  • Inorganic Chemistry (AREA)
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Abstract

Procédé servant à diminuer ou à éliminer la brume d'acide Caro qui est créée quand on prépare un mélange chaud contenant de l'acide Caro par réaction d'acide sulfurique et de peroxyde d'hydrogène, et consistant à refroidir rapidement le mélange chaud d'acide Caro avec de l'eau, afin de refroidir et, à la fois, de diluer l'acide Caro.
PCT/US1996/010475 1995-06-16 1996-06-17 Procede de production d'acide caro WO1997000225A1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
AU62824/96A AU700876B2 (en) 1995-06-16 1996-06-17 Method for producing Caro's acid
BR9608341A BR9608341A (pt) 1995-06-16 1996-06-17 Processo de produzir ácido de caro por reação de ácido dulfúrico e peróxido de hidrogénio

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US49143995A 1995-06-16 1995-06-16
US08/491,439 1995-06-16

Publications (1)

Publication Number Publication Date
WO1997000225A1 true WO1997000225A1 (fr) 1997-01-03

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Application Number Title Priority Date Filing Date
PCT/US1996/010475 WO1997000225A1 (fr) 1995-06-16 1996-06-17 Procede de production d'acide caro

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AU (1) AU700876B2 (fr)
BR (1) BR9608341A (fr)
CA (1) CA2224016A1 (fr)
WO (1) WO1997000225A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2008047864A1 (fr) 2006-10-18 2008-04-24 Mitsubishi Gas Chemical Company, Inc. Procédé de production d'acide monopersulfurique et appareil de production continue d'acide monopersulfurique

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB738407A (en) * 1953-01-16 1955-10-12 Stevensons Dyers Ltd A process for the manufacture of permonosulphuric acid
WO1992007791A1 (fr) * 1990-10-27 1992-05-14 Solvay Interox Limited Production de peroxoacide
WO1995004002A1 (fr) * 1993-08-03 1995-02-09 Fmc Corporation Traitement d'effluents renfermant des cyanures au moyen de l'acide de caro
US5470564A (en) * 1994-08-01 1995-11-28 Fmc Corporation Method for producing caro's acid

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2789954A (en) * 1953-12-14 1957-04-23 Stevensons Dyers Ltd Process for making peroxymonosulphuric acid

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB738407A (en) * 1953-01-16 1955-10-12 Stevensons Dyers Ltd A process for the manufacture of permonosulphuric acid
WO1992007791A1 (fr) * 1990-10-27 1992-05-14 Solvay Interox Limited Production de peroxoacide
WO1995004002A1 (fr) * 1993-08-03 1995-02-09 Fmc Corporation Traitement d'effluents renfermant des cyanures au moyen de l'acide de caro
US5470564A (en) * 1994-08-01 1995-11-28 Fmc Corporation Method for producing caro's acid

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2008047864A1 (fr) 2006-10-18 2008-04-24 Mitsubishi Gas Chemical Company, Inc. Procédé de production d'acide monopersulfurique et appareil de production continue d'acide monopersulfurique
EP2075230A1 (fr) * 2006-10-18 2009-07-01 Mitsubishi Gas Chemical Company, Inc. Procédé de production d'acide monopersulfurique et appareil de production continue d'acide monopersulfurique
EP2075230A4 (fr) * 2006-10-18 2011-12-14 Mitsubishi Gas Chemical Co Procédé de production d'acide monopersulfurique et appareil de production continue d'acide monopersulfurique
US9181094B2 (en) 2006-10-18 2015-11-10 Mitsubishi Gas Chemical Company, Inc. Method for producing peroxymonosulfuric acid and apparatus for continuously producing peroxymonosulfuric acid
US9988269B2 (en) 2006-10-18 2018-06-05 Mitsubishi Gas Chemical Co., Inc. Method for producing peroxymonosulfuric acid and apparatus for continuously producing peroxymonosulfuric acid

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BR9608341A (pt) 1999-01-05
AU6282496A (en) 1997-01-15
AU700876B2 (en) 1999-01-14
CA2224016A1 (fr) 1997-01-03

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