US3623967A - Electrolytic apparatus for the production of alkali metal chlorate with grounding means - Google Patents

Electrolytic apparatus for the production of alkali metal chlorate with grounding means Download PDF

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Publication number
US3623967A
US3623967A US875257A US3623967DA US3623967A US 3623967 A US3623967 A US 3623967A US 875257 A US875257 A US 875257A US 3623967D A US3623967D A US 3623967DA US 3623967 A US3623967 A US 3623967A
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cell
cells
liquor
volts
tank
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US875257A
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English (en)
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Richard M O Maunsell
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Electric Reduction Company of Canada Ltd
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Electric Reduction Company of Canada Ltd
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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
    • C25B9/00—Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
    • C25B9/60—Constructional parts of cells
    • C25B9/65—Means for supplying current; Electrode connections; Electric inter-cell connections

Definitions

  • Electrolytic apparatus includes a power supply. at least two bipolar cells and at least one cell tank so arranged that the liquor in the cell tank is at ground potential, thereby avoiding the necessity and expense of insulating the cell tank 7 from ground and also protecting certain components against corrosion.
  • This invention relates to electrolytic apparatus for the production of an alkali metal chlorate and to power supplies therefor.
  • the production of sodium chlorate and the production of caustic/chlorine commonly is carried out by electrolysis of aqueous solutions of sodium chloride.
  • monopolar diaphragm or mercury cells are used almost universally, the total power supplied to each cell being relatively small, and the voltage applied across each cell being of the order of 4 or 5 volts. It is common practice to connect of the order of 150 such cells 'in series electrically, thereby permitting the use of an economical rectifier set having a DC voltage output of the order of 600 volts.
  • the end cells of the line will be at potentials of +300 volts and 300 volts with respect to ground potential, and, in order to avoid current leakage between cells, it is common practice to mount the cells on porcelain insulators. This is not a difficult task because of the relatively small size and weight of such cells.
  • each chlorate cell and its associated cell tank are relatively large and may weight 200 tons or more.
  • Such a cell generally requires about 120 volts and 1,500 kilowatts or more. It is common practice to connect six such cells in series electrically and supply the same from a single power producing 720 volts, the end cells of the line being 'at potentials of +360 volts and 360 volts with respect to ground.
  • the large cell tanks associated with the cells are difficult and expensive to insulate from ground either by means of porcelain insulators or by constructing the cell tanks themselves of insulating material.
  • a virtual ground In a line of six such cells there will be established what is referred to as a virtual ground. In a balanced system the virtual ground will be between the third and fourth cells in the line. However, if ground leakage increases in any cell, it is possible for the position of the virtual ground to shift. In an extreme case this could result in about 660 volts (liquor potential) to ground on one end cell and an intolerable increase in (l) the voltage stress applied to the cell and its components, (2) the current leakage and (3) excessive local heat evolution and destruction of the cell tank.
  • the foregoing problems are eliminated by providing a system including a power supply, a cell and a cell tank wherein the potential of the liquor in the cell tank is ground potential.
  • FIG. I is a schematic representation of the prior art system for electrolyzing an aqueous solution of sodium chloride to produce an aqueous solution of sodium chloride and sodium chlorate;
  • FIG. 2 is a schematic representation of one embodiment useful in explaining the instant invention.
  • FIG. 3 is a schematic representation of a preferred embodi ment of the instant invention.
  • each cell is of conventional construction and includes a plurality of bipolar electrodes 16, liquor inlet tubes (not shown) and liquor outlet tubes (not shown).
  • a DC power supply 17 has its positive terminal connected to one end electrode in cell 10 and its negative terminal connected to one end electrode in cell 15. If the cells are 120 volt cells, power supply 17 may be rated at, say, 760 volts, the voltage in excess of 720 volts being to compensate for wearing of the graphite electrodes as electrolysis proceeds.
  • the end electrodes in the different cells are connected together as shown in FIG. 1 to thereby connect the cells in series electrically.
  • Cells 10-15 may be immersed in the liquor in cell tanks 20-25 respectively or may be outside of the cell tanks. In this event circulating pumps will be required to pump liquor from the cell tanks into the respective cells.
  • the sodium chloride solution may be introduced into cell tank 20 and flow through the other cells and cell tanks in series (cascade operation), or the cells may operate in parallel as far as liquor flow is concerned, or they may be batch operated.
  • cells 10 and 15 will be at potentials of +3 and 380 volts, and a virtual ground will be established between the third and fourth cells as shown at 18.
  • the position of this ground can shift depending upon the operation of the various cells. Thus, for example, if cell 10 became grounded, the virtual ground would shift to cell 10, and the full voltage of the power supply would be applied between cell 15 and ground.
  • the cells are within their respective cell tanks, it will be necessary to insulate the cell tanks from ground. If they are outside the cell tanks, both the cells and the cell tanks will have to be insulated from ground.
  • a 120 volt DC power supply a bipolar chlorate cell containing bipolar electrodes 116 and a cell tank 200.
  • the power supply is of a three-phase type and includes the secondary windings (Y connected) 101, 102 and 103 of a transformer and power rectifiers 104.
  • the common terminal of the Y connected secondary windings is grounded, and the positive and negative terminals 105 and 106 respectively of the power supply are conventionally connected to monopolar electrodes 107 in cell 100.
  • Cell tank 200 also is grounded.
  • terminals 105 and 106 may be at +60 volts and -60 volts respectively. Since the liquor in cell 100 and cell tank 200 will assume a potential midway between +60 volts and 60 volts, i.e., 0 volts or ground potential, insulation of the cell and cell tank from ground is not necessary, and, indeed, the liquor in cell tank 200 can be grounded by grounding the cell tank, although this is not essential.
  • the grounding of the common terminal of Y connected secondary windings 101-103 also is not essential, although it is preferred. It has the effect of minimizing small potential differences of the order of 1 volt which occur in cell tank 200 due to the submerged cell 100 and which aggravate corrosion of cooling coils in the cell tank liquor and other equipment.
  • FIG. 2 The advantages of a system of the type shown in FIG. 2 are numerous.
  • the problem of insulating the cell and/or the cell tank from ground is solved, because such insulation is not required. Malfunctioning of any one system will not change the voltage applied to the cell of any other system, it being understood that six systems of the type shown in FIG. 2 would replace the system of FIG. 1.
  • a relatively inexpensive concrete-lined mild steel vessel can be employed for cell tank 200, since the vessel can be cathodically protected. Current leakage is no more of a problem than it is with any one of the cells of FIG. I when operating normally. Corrosion and deterioration of piping, pumps, cooling coils, cell tanks and cell boxes is materially reduced.
  • a disadvantage of the system of FIG. 2 is the cost of six lowvoltage power supplies (6 X volts X 12,000 amps) as compared with the cost of one 760 volt X 12,000 amps power supply.
  • 6 X volts X 12,000 amps 6 X volts X 12,000 amps
  • three 760 volts X 4,000 amps power supplies have been found to cost no more than a conventional single power supply having the same total capacity, particularly as there is a considerable saving in copper bus bars, as is the case with the system of FIG. 3.
  • 760 volts cannot be applied across a single bipolar chlorate cell without creating intolerable current leakage and voltage stress problems. Any attempt to solve the current leakage problem necessarily will reduce the rate of natural gas lift liquor circulation in the cell and hence reduce current efficiency and increase cell voltage, thus providing a lower output at a higher power cost.
  • FIG. 3 there is provided a power supply like the power supply of FIG. 2 but rated at, say, 760 volts and 4,000 amps rather than 120 volts and 4,000 amps.
  • the cell itself is divided into two sections 100a and 1001), and each section is insulated from ground by porcelain or other insulators 108. This creates no great problem, since each cell section would weight of the order of tons rather than of the order of 200-300 tons, the weight of both a cell and a cell tank.
  • Each cell section contains monopolar and bipolar (not shown) electrodes 107 and 116 respectively arranged as shown in FIG. 2, and the cell sections are connected in series electrically by bus bar 109. Across each half cell section is a potential of 380 volts, the electrode 107 of half cell section 100a to which the power supply is connected being at +380 volts and the electrode 107 of half cell section 1001) to which the power supply is connected being at 380 volts.
  • each half cell section Associated with each half cell section is an inlet manifold 130 to which cell liquor is supplied from common cell tank 200 for distribution to the various unit cells. Also associated with each cell section is an outlet manifold 131 to which liquor from the various unit cells is supplied and which delivers this liquor to cell tank 200.
  • Cell tank liquor is supplied to manifolds 130 by a pump 132 and pipes 133 and 134, the liquor first passing through a cooler 135 or heat exchanger.
  • the liquor is returned to cell tank 200 from manifolds 131 via pipes 136 and 137 and a gas separator 138 from which hydrogen is withdrawn via a pipe 139. It will be seen that the liquor flow paths to and from the two cell sections are in parallel with each other.
  • components designated 132, 135 and 138 can be duplicated, if desired, and a separate cell tank for each half cell section employed in the interest of more cient use of the graphite or other electrodes in cascade operation when a small number of the cells are required.
  • each half cell section While one end of each half cell section is at a potential 380 volts different from ground potential, the half cell sections are insulated by insulators 108. Provided that insulators 108 are kept clean, the maximum potential stress over the surface of or through the material of each half cell section is 3 volts per inch as compared with 240 volts per inch for presently used cells and 2,500 volts per inch for presently used cell tanks. Obviously, the potential stress in cell tank 200 is zero.
  • Electrolytic apparatus for electrolyzing an alkali metal chloride to produce an alkali metal chlorate comprising: a DC power supply having positive and negative terminals relative to ground potential; first and second electrolytic cells each including a housing and, within said housing, first and second monopolar electrodes and a plurality of bipolar electrodes located between said monopolar electrodes; means electrically connecting said positive terminal to said first monopolar electrode of said first cell; means electrically connecting said negative terminal to said second monopolar electrode of said second cell; means electrically grounding said second monopolar electrode of said first cell and said first monopolar electrode of said second cell to maintain said second monopolar electrode of said first cell and said first monopolar electrode of said second cell at ground potential; means insulating said cells from ground; at least one cell tank adapted to contain liquor to be electrolyzed; at least one inlet manifold for supplying liquor from said cell tank to said cells; at least one outlet manifold for receiving liquor from said cells; means for delivering liquor from said cell tank to said inlet manifold; means for delivering liquor from said cell

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)
US875257A 1968-11-08 1969-11-10 Electrolytic apparatus for the production of alkali metal chlorate with grounding means Expired - Lifetime US3623967A (en)

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2491091A1 (fr) * 1980-09-26 1982-04-02 Mironescu Nicolae Dan Systeme d'alimentation en courant continu des installations d'electrolyse industrielle
FR2871479A1 (fr) * 2004-06-10 2005-12-16 Solvay Sa Sa Belge Circuit electrique d'un electrolyseur a electrodes bipolaires et installation d'electrolyse a electrodes bipolaires
CN104591347A (zh) * 2015-01-07 2015-05-06 成都邦研科技有限公司 酸性氧化电位水生成器绝缘系统
EP4074863A1 (de) * 2021-04-14 2022-10-19 Siemens Energy Global GmbH & Co. KG Elektrolyseeinrichtung

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2432013A (en) * 1942-04-16 1947-12-02 Du Pont Measurement of leakage resistance in electrolytic cell systems
US2435973A (en) * 1941-08-19 1948-02-17 Rusta Restor Corp Method of and means for providing cathodic protection of metallic structures
CA741311A (en) * 1966-08-23 E. Colman John Electrolytic apparatus and processes for making the same

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA741311A (en) * 1966-08-23 E. Colman John Electrolytic apparatus and processes for making the same
US2435973A (en) * 1941-08-19 1948-02-17 Rusta Restor Corp Method of and means for providing cathodic protection of metallic structures
US2432013A (en) * 1942-04-16 1947-12-02 Du Pont Measurement of leakage resistance in electrolytic cell systems

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2491091A1 (fr) * 1980-09-26 1982-04-02 Mironescu Nicolae Dan Systeme d'alimentation en courant continu des installations d'electrolyse industrielle
FR2871479A1 (fr) * 2004-06-10 2005-12-16 Solvay Sa Sa Belge Circuit electrique d'un electrolyseur a electrodes bipolaires et installation d'electrolyse a electrodes bipolaires
WO2005121410A2 (en) * 2004-06-10 2005-12-22 Solvay (Societe Anonyme) Electric circuit of an electrolyzer with bipolar electrodes and electrolysis installation with bipolar electrodes
WO2005121410A3 (en) * 2004-06-10 2007-03-08 Solvay Electric circuit of an electrolyzer with bipolar electrodes and electrolysis installation with bipolar electrodes
US20070205110A1 (en) * 2004-06-10 2007-09-06 Solvay (Societe Anonyme) Electric Circuit Of An Electrolyzer With Bipolar Electrodes And Electrolysis Installation With Bipolar Electrodes
EA011603B1 (ru) * 2004-06-10 2009-04-28 Солвей (Сосьете Аноним) Электрическая цепь электролизера с биполярными электродами и электролизная установка с биполярными электродами
CN104591347A (zh) * 2015-01-07 2015-05-06 成都邦研科技有限公司 酸性氧化电位水生成器绝缘系统
CN104591347B (zh) * 2015-01-07 2016-05-04 成都邦研科技有限公司 酸性氧化电位水生成器绝缘系统
EP4074863A1 (de) * 2021-04-14 2022-10-19 Siemens Energy Global GmbH & Co. KG Elektrolyseeinrichtung
WO2022218582A1 (de) * 2021-04-14 2022-10-20 Siemens Energy Global GmbH & Co. KG Elektrolyseeinrichtung

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