US3883406A - Process for recovering electrolytically produced alkali metal chlorates - Google Patents

Process for recovering electrolytically produced alkali metal chlorates Download PDF

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Publication number
US3883406A
US3883406A US376978A US37697873A US3883406A US 3883406 A US3883406 A US 3883406A US 376978 A US376978 A US 376978A US 37697873 A US37697873 A US 37697873A US 3883406 A US3883406 A US 3883406A
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United States
Prior art keywords
chlorate
alkali metal
sodium
liquor
cell
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Expired - Lifetime
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US376978A
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English (en)
Inventor
Thomas Francis O'brien
Jimmie Ray Hodges
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Arkema Inc
Pennwalt Corp
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Pennwalt Corp
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Priority to US376978A priority Critical patent/US3883406A/en
Priority to CA201,835A priority patent/CA1024933A/en
Priority to AU70020/74A priority patent/AU7002074A/en
Priority to GB2628974A priority patent/GB1456874A/en
Priority to JP49075081A priority patent/JPS5038698A/ja
Priority to FR7423496A priority patent/FR2235874B1/fr
Priority to DE2432416A priority patent/DE2432416A1/de
Priority to SE7408897A priority patent/SE401815B/sv
Application granted granted Critical
Publication of US3883406A publication Critical patent/US3883406A/en
Assigned to PENNWALT CORPORATION, A PA CORP. reassignment PENNWALT CORPORATION, A PA CORP. MERGER (SEE DOCUMENT FOR DETAILS). Assignors: PEN-OLIN CHEMICAL COMPANY A DE CORP.
Assigned to ATOCHEM NORTH AMERICA, INC., A PA CORP. reassignment ATOCHEM NORTH AMERICA, INC., A PA CORP. MERGER AND CHANGE OF NAME EFFECTIVE ON DECEMBER 31, 1989, IN PENNSYLVANIA Assignors: ATOCHEM INC., A DE CORP. (MERGED INTO), M&T CHEMICALS INC., A DE CORP. (MERGED INTO), PENNWALT CORPORATION, A PA CORP. (CHANGED TO)
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    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B1/00—Electrolytic production of inorganic compounds or non-metals
    • C25B1/01—Products
    • C25B1/24—Halogens or compounds thereof
    • C25B1/26—Chlorine; Compounds thereof
    • C25B1/265—Chlorates
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B11/00—Oxides or oxyacids of halogens; Salts thereof
    • C01B11/12—Chloric acid
    • C01B11/14—Chlorates

Definitions

  • This invention relates to a method for producing alkali metal chlorates, and more particularly relates to a process for direct crystallization of alkali metal chlorates from an aqueous solution containing alkali metal chlorates and chlorides.
  • Alkali metal chlorates are commonly produced by electrolysis of an aqueous solution of alkali metal chloride under conditions which produce a cell effluent containing both the chlorate and the chloride.
  • the electrolysis is normally conducted commercially in diaphragmless electrolytic cells in which chlorine is produced at the anode while alkali metal hydroxide is formed at the cathode.
  • the chlorine and hydroxyl ions are thus free to react chemically to form alkali metal hypochlorite as per the following equation.
  • the instant process consists essentially of (l) evaporation of water from the cell liquor, preferably under relatively high vacuum, until substantial amounts of solid alkali metal chlorate but no or little solid alkali metal chloride is formed, (2) mechanically separating the solids from the liquid such as by filtration or centrifugation, (3) washing of the solid chlorate crystals with cold water to remove occluded liquor and some solid impurities, and (4) recycling the liquid from the separation step back to the electrolytic cells along with fresh feed.
  • the washings from step (3) may also be sent back to the operating cells.
  • the advantages attendant to crystallization of the alkali metal chlorate directly from the cell liquor include l) its great simplicity, (2) the ability to utilize conventional materials of construction, such as steel, in contradistinction to exotic materials, such as titanium, and especially (3) the greatly reduced evaporative load.
  • the only water which is added is that which is necessary to dissolve fresh salt for feed as compared to the conventional process in which water must be added to redissolve salt dropping out during the first crystallization step in addition to the fresh salt feed.
  • the instant process is conducive to considerable steam economy, a significantly large cost factor in a chlorate process.
  • FIG. 1 is a flow diagram illustrating the process of the present invention.
  • FIG. 2 is an equilibrium phase diagram showing graphically the parameters of the present invention.
  • sodium chlorate may be produced by electrolysis of sodium chloride in electrolytic cells utilizing coated titanium anodes for example.
  • the cells may be operated individually or in groups employing either series or parallel flow of the liquor therethrough so that the final cell liquor product contains at least 30 grams sodium chloride per liter of solution, and preferably at least 40 grams NaCl per liter.
  • the weight ratio of sodium chlorate to sodium chloride should be at least 5 to l and preferably at least 7 to l. Concentrations of other materials such as dichromate, sodium hypochlorite, chlorine, etc., and cell operating conditions need only be consistent with sound practices.
  • the effluent from the cells is then subjected to vacuum evaporation in a crystallizer operating at a vacuum of at least 26 inches of mercury.
  • the degree of evaporation is such that substantial amounts of sodium chlo rate are removed from the solution but little or none of the chloride is crystallized out. That is, the evaporation is performed below the solid phase NaClO -NaCl equilibrium curve of the phase diagram.
  • the evaporation can be performed in a single vessel, or in a multiple effect evaporative system. However, it is preferable for reasons of steam economy to operate in a two-step evaporation system with vapor produced in the first vessel used as the source of heat in the second. In the latter instance, the initial step of evaporation is run at any convenient pressure level and in such a way that no solids would be produced.
  • the slurry produced in the crystallizer is then separated into solid and liquid fractions by mechanical means and the liquid fraction is returned to the cells for further electrolysis.
  • the solids are washed with cold 5 water to provide clean, wet crystals of sodium chlorate which are then dried to yield the final product.
  • FIG. 1 a process in which sodium chlorate may be recovered directly from an electrolytic solution of sodium chlorate and chloride without first crystallizing out solid salt.
  • graph A represents a typical course pursued by a process of prior commercial practice using graphite anodes.
  • a cell liquor having a sodium chloride concentration of about 125 grams per liter (16 grams NaCl per 100 grams H and about 420 grams per liter of sodium chlorate (54 grams NaClO per 100 grams H O) would be subjected to evaporation (along line A1) until point Z (92 C) was reached, where saturation of sodium chloride would occur. Salt would then drop out of solution with further removal of water.
  • point Y represents the liquor concentration within the evaporator.
  • a cooling crystallizer operating at about 45 C would cause the process to follow horizontal line A3 to point X and chlorate crystallizing from solution would be removed.
  • the cell By inspection of the coordinates of point T it can be determined that the ratio of the sodium chlorate to sodium chloride in the cell liquor must be at least :1 in order to produce solid chlorate under the chosen conditions. Therefore, the cell must operate to the right of RT. For good efficiency and voltage characteristic in addition to avoiding formation of undesirable perchlorate, the cell should operate with at least 30 gpl. sodium chloride.
  • the dashed line RS at the lower portion of FIG. 2 is the straight line approximation for this minimum 30 gpl. NaCl limitation, the line RS being slightly inclined to designate the corresponding NaCl and Na- ClO concentrations in grams per 100 grams of water. i.e., corrected for density.
  • Point S itself is determined by the anticipated temperature of the cell room in the event of a power failure, for example. That is, if the cells were operating at a cell liquor concentration of 4.5 grams NaCl per l grams H 0 and l23 grams NaClO per I00 grams H O, chlorate would not drop out in the cells themselves unless the temperature were to fall below 50 C (122 F). Thus, the line TS represents outer limits of concentrations which would avoid crystallization of chlorate within the cells themselves should a shutdown occur. Therefore, the maximum chlorate-towhloride ratio would be represented by the slope of the line OS which passes through the origin, i.e., l23/4.5 or about 27:1.
  • the smaller dashed triangle QNP designates a set of conditions which are more restrictive but preferred.
  • the line QN designates a minimum sodium chloride concentration of 40 grams per liter which would offer slightly improved voltage and current efficiency characteristics while providing some margin of safety for fluctuations and process shutdowns.
  • point N 98 grams NaClO per I00 grams H 0 and 5.8 grams NaCl per 100 grams H O, represents a temperature at 30 C (86 F) which would allow the cell room to drop to such a temperature without crystallizing out the chlorate of the designated concentration.
  • the chlo rate concentration at point N is approximately 700 grams per liter and the slope of the line ON is 98/58 or a chlorate to chloride ratio of l6: 1.
  • the slope of the line OP is approximately 7:1 which permits a more reasonable amount (e.g., over 25%) of chlorate to be recovered in each pass through the crystallizer.
  • EXAMPLE A cell was operated at about 600 gpl. NaClO and 50 gpl NaCl.
  • the cell liquor contained gpl NaOCl and 5 gpl Na Cr O
  • Anodic current density was 306 amps/ft. and the temperature of the cell was 90 F.
  • the anode was titanium coated with platinum. Current eff"- ciency was 92%. Chlorine was added to the recirculating liquor periodically to maintain pH below 7.0.
  • the chlorate crystals was washed and dried giving a recovery of more than 60 percent of the chlorate in the sample with quality equivalent to normal commercial product.
  • a method for electrolytically producing alkali metal chlorate from an alkali metal chloride comprising the steps of:

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)
US376978A 1973-07-06 1973-07-06 Process for recovering electrolytically produced alkali metal chlorates Expired - Lifetime US3883406A (en)

Priority Applications (8)

Application Number Priority Date Filing Date Title
US376978A US3883406A (en) 1973-07-06 1973-07-06 Process for recovering electrolytically produced alkali metal chlorates
CA201,835A CA1024933A (en) 1973-07-06 1974-06-06 Process for recovering electrolytically produced alkali metal chlorates
AU70020/74A AU7002074A (en) 1973-07-06 1974-06-12 Alkali metals
GB2628974A GB1456874A (en) 1973-07-06 1974-06-13 Electrolytic process for the production of sodium chlorate
JP49075081A JPS5038698A (sv) 1973-07-06 1974-07-02
FR7423496A FR2235874B1 (sv) 1973-07-06 1974-07-05
DE2432416A DE2432416A1 (de) 1973-07-06 1974-07-05 Verfahren zur gewinnung von elektrolytisch hergestellten alkalichloraten
SE7408897A SE401815B (sv) 1973-07-06 1974-07-05 Forfarande for kristallisation av natriumklorat ur en celleffluentlosning

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US376978A US3883406A (en) 1973-07-06 1973-07-06 Process for recovering electrolytically produced alkali metal chlorates

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US3883406A true US3883406A (en) 1975-05-13

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US (1) US3883406A (sv)
JP (1) JPS5038698A (sv)
AU (1) AU7002074A (sv)
CA (1) CA1024933A (sv)
DE (1) DE2432416A1 (sv)
FR (1) FR2235874B1 (sv)
GB (1) GB1456874A (sv)
SE (1) SE401815B (sv)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4339312A (en) * 1980-09-10 1982-07-13 Pennwalt Corporation Continuous process for the direct conversion of potassium chloride to potassium chlorate by electrolysis
US4551219A (en) * 1984-05-21 1985-11-05 Pfizer Inc. Flush edge protected metal laminates
US4702805A (en) * 1986-03-27 1987-10-27 C-I-L Inc. Production of sodium chlorate
US5087334A (en) * 1988-04-22 1992-02-11 Krebs & Cie Continuous process for the manufacture of potassium chlorate by coupling with a sodium chlorate production plant
US6949376B2 (en) 1997-05-02 2005-09-27 Biomerieux, Inc. Nucleic acid amplification reaction station for disposable test devices
WO2006124196A1 (en) * 2005-05-11 2006-11-23 Tronox Llc Perchlorate removal from sodium chlorate process
EP2217744A2 (en) * 2007-11-16 2010-08-18 Akzo Nobel N.V. Electrode
CN107840309A (zh) * 2017-11-16 2018-03-27 四川岷江雪盐化有限公司 一种三段连续低温真空蒸发结晶生产不同粒径氯酸盐的方法

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4606238A (en) * 1980-08-20 1986-08-19 Toyota Jidosha Kogyo Kabushiki Kaisha Mounting construction of shift lever retainer casing in change-speed gearing unit
SE463626B (sv) * 1988-12-28 1990-12-17 Eka Nobel Ab Foerfarande foer reducering av halten perklorat i elektrolyter foer kloratframstaellning

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2511516A (en) * 1945-10-31 1950-06-13 Western Electrochemical Compan Process for making sodium chlorate
US3043757A (en) * 1959-07-08 1962-07-10 Olin Mathieson Electrolytic production of sodium chlorate
US3511619A (en) * 1965-11-30 1970-05-12 Hooker Chemical Corp Crystallization of alkali metal chlorate from an alkali metal chloratealkali metal chloride solution
US3690845A (en) * 1969-12-22 1972-09-12 Hooker Chemical Corp Crystallization of a metal chlorate from a chlorate-chloride containing solution

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2511516A (en) * 1945-10-31 1950-06-13 Western Electrochemical Compan Process for making sodium chlorate
US3043757A (en) * 1959-07-08 1962-07-10 Olin Mathieson Electrolytic production of sodium chlorate
US3511619A (en) * 1965-11-30 1970-05-12 Hooker Chemical Corp Crystallization of alkali metal chlorate from an alkali metal chloratealkali metal chloride solution
US3690845A (en) * 1969-12-22 1972-09-12 Hooker Chemical Corp Crystallization of a metal chlorate from a chlorate-chloride containing solution

Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4339312A (en) * 1980-09-10 1982-07-13 Pennwalt Corporation Continuous process for the direct conversion of potassium chloride to potassium chlorate by electrolysis
US4551219A (en) * 1984-05-21 1985-11-05 Pfizer Inc. Flush edge protected metal laminates
US4702805A (en) * 1986-03-27 1987-10-27 C-I-L Inc. Production of sodium chlorate
AU600258B2 (en) * 1986-03-27 1990-08-09 Chemetics International Company Limited Production of sodium chlorate
US5087334A (en) * 1988-04-22 1992-02-11 Krebs & Cie Continuous process for the manufacture of potassium chlorate by coupling with a sodium chlorate production plant
US20050244887A1 (en) * 1997-05-02 2005-11-03 Biomerieux, Inc. Nucleic acid amplification reaction station for disposable test devices
US6949376B2 (en) 1997-05-02 2005-09-27 Biomerieux, Inc. Nucleic acid amplification reaction station for disposable test devices
US20060263871A1 (en) * 1997-05-02 2006-11-23 Biomerieux, Inc. Nucleic acid applification reaction station for disposable test devices
US20110020921A1 (en) * 1997-05-02 2011-01-27 Biomerieux, Inc. Nucleic acid amplification reaction station for disposable test devices
WO2006124196A1 (en) * 2005-05-11 2006-11-23 Tronox Llc Perchlorate removal from sodium chlorate process
EP2217744A2 (en) * 2007-11-16 2010-08-18 Akzo Nobel N.V. Electrode
US20100236937A1 (en) * 2007-11-16 2010-09-23 Akzo Nobel N.V. Electrode
US8764963B2 (en) * 2007-11-16 2014-07-01 Akzo Nobel N.V. Electrode
CN107840309A (zh) * 2017-11-16 2018-03-27 四川岷江雪盐化有限公司 一种三段连续低温真空蒸发结晶生产不同粒径氯酸盐的方法
CN107840309B (zh) * 2017-11-16 2020-07-28 四川岷江雪盐化有限公司 一种三段连续低温真空蒸发结晶生产不同粒径氯酸盐的方法

Also Published As

Publication number Publication date
GB1456874A (en) 1976-12-01
AU7002074A (en) 1975-12-18
DE2432416A1 (de) 1975-01-30
SE401815B (sv) 1978-05-29
FR2235874A1 (sv) 1975-01-31
SE7408897L (sv) 1975-01-07
CA1024933A (en) 1978-01-24
JPS5038698A (sv) 1975-04-10
FR2235874B1 (sv) 1979-03-16

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Owner name: PENNWALT CORPORATION, A PA CORP.

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Free format text: MERGER AND CHANGE OF NAME EFFECTIVE ON DECEMBER 31, 1989, IN PENNSYLVANIA;ASSIGNORS:ATOCHEM INC., A DE CORP. (MERGED INTO);M&T CHEMICALS INC., A DE CORP. (MERGED INTO);PENNWALT CORPORATION, A PA CORP. (CHANGED TO);REEL/FRAME:005496/0003

Effective date: 19891231