EP0148023B1 - Procédé de purification de mercure - Google Patents

Procédé de purification de mercure Download PDF

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Publication number
EP0148023B1
EP0148023B1 EP84309076A EP84309076A EP0148023B1 EP 0148023 B1 EP0148023 B1 EP 0148023B1 EP 84309076 A EP84309076 A EP 84309076A EP 84309076 A EP84309076 A EP 84309076A EP 0148023 B1 EP0148023 B1 EP 0148023B1
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EP
European Patent Office
Prior art keywords
mercury
reactor
gas
purification
aqueous solution
Prior art date
Legal status (The legal status 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 status listed.)
Expired
Application number
EP84309076A
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German (de)
English (en)
Other versions
EP0148023A2 (fr
EP0148023A3 (en
Inventor
Giorgio Gavelli
Marino Gramondo
Gianni Donati
Giuseppe Faita
Gian Lorenzo Marziano
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Montedipe SpA
Original Assignee
Montedipe SpA
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Filing date
Publication date
Application filed by Montedipe SpA filed Critical Montedipe SpA
Publication of EP0148023A2 publication Critical patent/EP0148023A2/fr
Publication of EP0148023A3 publication Critical patent/EP0148023A3/en
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Classifications

    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B43/00—Obtaining mercury

Definitions

  • the present invention relates to a process for the purification of mercury, coming from a NaCI or KCI electrolysis plant, and more particularly to the purification of the mercury of electrolytic cells of chlorine-sodium hydroxide and chlorine-potassium hydroxide plants.
  • the impurities present in the mercury also have other adverse effects on the electrolytic process. There may, for instance, form an amalgam foam (called “mercury butter”) which disturbs the regular flow of the mercury, as a result of which the cell voltage rises and there may occur short-circuits which will damage the anodes.
  • amalgam foam called "mercury butter”
  • the accumulation of impurities in the mercury also causes unbalances in the distribution of the current in the various longitudinal sections as well as cross sections of the cell.
  • the brine In order to limit the introduction of impurities in the mercury, the brine, before its conveyance to the cells, is subjected to a costly process of chemical and physical purifications. Since there remain, however, possible accidental pollutions of the brine, the mercury tends nonetheless to grow rich in impurities, as a result of which it is necessary to frequently carry out periodical washings of the cells and purification of the mercury itself, by means of distillation.
  • US ⁇ A ⁇ 3895938 discloses a process for the purification of mercury wherein mercury flowing out from an amalgam decomposer is turbulently admixed by a rotor with an aqueous acid solution. In such a process the mercury will be dispersed in the aqueous phase in the form of minute droplets and will be intensively mixed with the aqueous phase, whereby the impurities contained in the mercury will pass into the aqueous phase.
  • One aim of the present invention is to provide a simple, cheap and effective process for the purification of mercury from the metal impurities contained in it.
  • the present invention provides a process for the purification of mercury, coming from a NACI or KCI electrolysis plant and containing metal impurities, wherein the impure mercury is brought into contact downstream of the disamalgamation step with an aqueous solution containing an inorganic acid inside a purification reactor (1), whereby a liquid dispersion isformed therein, a gas being present in the upper portion (2) of said reactor, characterized in that a stream of said liquid dispersion is taken from the bottom of said reactor and recycled to said upper portion through a pump (11) and through an ejector (3, 4), from which ejector said stream is so ejected as to suck in said gas and redisperse mercury together with said gas in the form of very small droplets in the liquid dispersion contained in the reactor, whereby said metal impurities are transferred into said aqueous phase without addition from outside of any mercury salt.
  • the drawing shows a reactor 1 which contains in its upper part 2 a gas. Fixed to the upper end of this reactor is arranged a nozzle 3. Furthermore there is present a converging-diverging tube 4 which is so arranged with respect to the nozzle 3 as to form with this latter a liquid-gas ejector.
  • the converging-diverging tube 4 is maintained in the reactor 1 in the most suitable position with respect to the nozzle by means of any mechanical device suited for this purpose, for instance by means of fixing spokes fixed to the nozzle itself.
  • the mechanical device is chosen in such a way as not to hinder the passage of the gas from the upper part 2 of the reactor to the inside of the converging-diverging tube 4 itself.
  • the lower part of the tube 4 is immersed in the liquid phases present in the reactor.
  • Into the upper part 2 of the reactor are fed in the mercury to be purified via a line 5, and the aqueous solution via a line 6.
  • a recirculation line 8 ⁇ 9 ⁇ 10 which leads first to a pump 11 and thereafter to an optional heat exchanger 12 and returns back to the reactor, entering the nozzle 3.
  • the gas produced by the purification reaction flows out through a line 13.
  • the pump 11 ensures the circulation of the two liquid phases (the mercury and the aqueous solution) in the reactor and in the external recirculation line.
  • the nozzle 3 causes an agitation (or stirring-up) of the liquid phases and the consequential dispersion of the mercury in the aqueous solution, in the form of droplets of small diameter.
  • the liquid-gas ejector sucks gas from the top of the reactor, still further increasing in this way the turbulence in the jet and in the reactor, and dispersing gas into the system.
  • This dispersed gas reduces the coalescence of the mercury particles and provides an extensive exchange surface for the removal of the gas produced by the reaction.
  • the aqueous solution is a mineral acid solution, for example a sulphuric acid solution containing from 0.5% to 10% by weight of H 2 S0 4 .
  • a mineral acid solution for example a sulphuric acid solution containing from 0.5% to 10% by weight of H 2 S0 4 .
  • the impurity dissolving reaction proves to be faster.
  • the chemical reaction that takes place is, for instance in the case of iron:
  • an oxidizer for instance H 2 0 2 .
  • the gas present in the reactor may be at atmospheric pressure; however, it may instead be at a reduced pressure; that is, the process may be operated under a vacuum, as a result the only gas present being the gas freed by the reaction (H 2 ).
  • H 2 the reaction
  • the pressure of the gaseous phase is for example from about 10 mmHg to about 5 atmospheres absolute.
  • the nature of the gas present in the reactor is not critical; there may be used various types of gases, for example air or nitrogen.
  • gases for example air or nitrogen.
  • air is convenient in as much as it may help to dissolve the impurities because the oxygen contained in the air acts as an oxidiser.
  • the ratio between the volume of liquid phases sent back into the reactor each hour and the volume of the reactor itself is in general at least 10, more preferably from 50:1 to 150:1.
  • the delivery pressure of the pump is in general at least 0.3 atmospheres, more preferably from 0.7 to 3 atmospheres.
  • the temperature at which the purification reaction takes place is usually from 20°C to the boiling temperature of the aqueous solution.
  • the purification reaction obviously proceeds faster when the temperature increases, but at high temperatures, in an acid medium, there may arise problems of corrosion of the equipment.
  • Pumps suitable for ensuring an effective dispersion of the liquid phases in each other are for example gear pumps and rotary pumps as well as particular types of centrifugal pumps.
  • the liquid phases may be discharged through the valve 15 which leads, for instance, to a tank where the purified mercury and the exhausted aqueous solution are separated by decanting.
  • the mercury When purifying the mercury of electrolytic cells, the mercury is subjected to the purifying process after its dis-amalgamation.
  • the mercury purification system in which the process of the present invention is carried out may be coupled to the conventional purification of the brine, or the latter purification may be dispensed with, as a result of which the only purification carried out is that in accordance with the invention.
  • the whole flow of mercury which flows out of the dis-amalgamator passes into the purification apparatus shown in the drawing, during all the time of operation of the electrolytic cell or at suitable time intervals.
  • the mercury is separated by decanting from the aqueous phase and then flows back into the cell.
  • the purification apparatus is provided with a circulating pump of its own.
  • the plant will have two pumps, one for the circulation of the mercury in the cell, and one for the purification apparatus.
  • the purification process of the present invention may also be used for purifying the mercury butters gathered during the washing of the cells.
  • the total volume of the reactor and of the recirculation circuit was about 5 litres.
  • the process was conducted discontinuously, at room temperature.
  • the mercury to be treated came from end boxes (examples 4 and 5) and from feed boxes of electrolytic cells of a chlorine-sodium hydroxide plant.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Removal Of Specific Substances (AREA)
  • Treating Waste Gases (AREA)
  • Manufacture And Refinement Of Metals (AREA)

Claims (7)

1. Un procédé de purification de mercure provenant d'une installation d'électrolyse de NaCI ou KCI et contenant des impuretés métalliques, dans lequel le mercure impur, en aval de l'étape de désamalgame, est mis au contact d'une solution aqueuse contenant un acide minéral dans un réacteur de purification (1) pour que s'y forme une dispersion liquide, un gaz étant présent dans la partie supérieur (2) dudit réacteur, ce procédé étant caractérisé en ce qu'un courant de ladite dispersion liquide, soutiré en cuve dudit réacteur est recyclé dans ladite partie supérieure à l'aide d'une pompe (11) et d'une tuyère (3, 4), le courant étant éjecté de ladite tuyère de façon à produire l'aspiration dudit gas et la dispersion du mercure et dudit gaz sous forme de très petites gouttes dans la dispersion liquide contenue dans le réacteur et que lesdites impuretés soient transférées dans la phase aqueuse sans que cela ne requiert l'addition se sel de mercure d'origine extérieure.
2. Un procédé tel que revendiqué dans la revendication 1, caractérisé en ce que ledit gaz est un gaz oxydant, de préférence de l'air.
3. Un procédé tel que revendiqué dans la revendication 1 ou 2, caractérisée en ce que la solution aqueuse contient un agent oxydant, de préférence du peroxyde d'hydrogène.
4. Un procédé tel que revendiqué dans une quelconque des revendications 1 à 3, caractérisé en ce que la vitesse spatiale du liquide recyclé est d'au moins 10m3/h par m3 de réacteur, et en ce que la pression d'alimentation de ladite pompe est d'au moins 0,3 atmosphères, et de préférence comprise entre 0,7 et 3 atmosphères.
5. Un procédé tel que revendiqué dans la revendication 4, caractérisé en ce que la vitesse spatiale est comprise entre 50 et 150 h- (m3/h per m3).
6. Un procédé tel que revendiqué dans une quelconque des revendications 1 à 5, caractérisé en ce que la température de purification est comprise entre 20°C et la température d'ébullition de ladite solution aqueuse.
7. Un procédé tel que revendiqué dans une quelconque des revendications 1 à 6, caractérisé en ce que l'acide minéral est une solution aqueuse d'acide sulfurique dont la concentration est comprise entre 0,5 et 10% en poids.
EP84309076A 1983-12-30 1984-12-21 Procédé de purification de mercure Expired EP0148023B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
IT2443983 1983-12-30
IT24439/83A IT1170081B (it) 1983-12-30 1983-12-30 Procedimento per la depurazione del mercurio

Publications (3)

Publication Number Publication Date
EP0148023A2 EP0148023A2 (fr) 1985-07-10
EP0148023A3 EP0148023A3 (en) 1985-11-21
EP0148023B1 true EP0148023B1 (fr) 1989-03-15

Family

ID=11213524

Family Applications (1)

Application Number Title Priority Date Filing Date
EP84309076A Expired EP0148023B1 (fr) 1983-12-30 1984-12-21 Procédé de purification de mercure

Country Status (4)

Country Link
EP (1) EP0148023B1 (fr)
DE (1) DE3477205D1 (fr)
ES (1) ES8707568A1 (fr)
IT (1) IT1170081B (fr)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
IL122374A0 (en) * 1997-12-01 1998-06-15 Verdeco Technologies Ltd Improved voltammetric apparatus with mercury recycling device
AU2002222451A1 (en) * 2000-12-05 2002-06-18 Ionguard Ltd. Recycling and purification of dropping mercury electrode

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1721188A (en) * 1921-04-18 1929-07-16 Canadian Electro Prod Co Manufacture of mercury salts
FR735855A (fr) * 1931-04-30 1932-11-16 Procédé de purification du mercure utilisé comme cathode dans les procédés d'électrolyse
GB772226A (en) * 1954-10-26 1957-04-10 Olin Mathieson Process for recovering purified mercury from impure mercury containing alloying metal impurities
GB941136A (en) * 1960-08-12 1963-11-06 Nandor Heim Process and apparatus for cleaning mercury
GB1048147A (en) * 1964-10-21 1966-11-09 John Norman Castle Mercury cleaning apparatus
DE2304063A1 (de) * 1973-01-27 1974-08-01 Bayer Ag Verfahren zur reinigung von quecksilber

Also Published As

Publication number Publication date
ES539137A0 (es) 1987-08-01
IT8324439A0 (it) 1983-12-30
DE3477205D1 (en) 1989-04-20
EP0148023A2 (fr) 1985-07-10
ES8707568A1 (es) 1987-08-01
IT1170081B (it) 1987-06-03
EP0148023A3 (en) 1985-11-21

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