US3547791A - Manufacture of chlorine and caustic alkali in diaphragm cells - Google Patents

Manufacture of chlorine and caustic alkali in diaphragm cells Download PDF

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Publication number
US3547791A
US3547791A US709391A US3547791DA US3547791A US 3547791 A US3547791 A US 3547791A US 709391 A US709391 A US 709391A US 3547791D A US3547791D A US 3547791DA US 3547791 A US3547791 A US 3547791A
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United States
Prior art keywords
diaphragm
current density
pressure
rate
cell
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Expired - Lifetime
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US709391A
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English (en)
Inventor
Stuart Frederick Mellish
Robert Joseph Roach
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Imperial Chemical Industries Ltd
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Imperial Chemical Industries 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
    • C25B1/00—Electrolytic production of inorganic compounds or non-metals
    • C25B1/01—Products
    • C25B1/34—Simultaneous production of alkali metal hydroxides and chlorine, oxyacids or salts of chlorine, e.g. by chlor-alkali electrolysis
    • C25B1/46—Simultaneous production of alkali metal hydroxides and chlorine, oxyacids or salts of chlorine, e.g. by chlor-alkali electrolysis in diaphragm cells
    • 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
    • C25B15/00—Operating or servicing cells
    • C25B15/02—Process control or regulation

Definitions

  • Varying electrical loads may be handled during the continuous operation of a chlor-alkali cell which has a percolating asbestos diaphragm by rapidly making changes in the rate of flow of electrolyte through the diaphragm by altering the gas pressure on the anode compartment or cathode compartment each time the current density across the diaphragm is changed.
  • the rate of electrolyte flow is always approximately proportional to the current density.
  • the present invention relates to the manufacture of chlorine and caustic alkali in diaphragm cells. More particularly it relates to a method of operating cells with percolating asbestos diaphragms under varying electrical load conditions.
  • 1 represents the outer casing of a unit cell which is divided by asbestos diaphragm 2 into an anode compartment 3 and a cathode compartment 4.
  • the anode is indicated as 5 and the foraminate cathode 6 is set close to the diaphragm.
  • Brine is fed to the anode compartment at a steady rate through pipe 7 to maintain a level of brine as shown in the head tank 8.
  • 9 is an outlet for chlorine liberated in the anode compartment and 10 is an outlet for hydrogen produced in the cathode compartment.
  • the outlet for caustic liquor from the cathode compartment is connected towards the bottom of the compartment as shown at 11 and the caustic liquor is delivered by way of a swan-neck 12 and a lute 13 to the delivery pipe at 14.
  • the swan-neck 12 is connected by a flexible pipe 15 to the hydrogen outlet 10 and the connection at 11 is also made flexible so that the whole swan-neck and accompanying lute can be raised and lowered when desired.
  • This arrangement is most useful when it is desired to have the facility for lowering the liquor level in the cathode compartment gradually during the life of the diaphragm to compensate for the normal slow decrease in diaphragm permeability with age, since these small adjustments of cathode liquor level can be made from time to time as appropriate by lowering the whole swan-neck and accompanying lute.
  • a pressure-control valve 18 is inserted in the hydrogen delivery pipe. On closing this valve to the required extent the gas pressure on top of the cathode compartment is increased and the level of liquor in the inner limb of the lute 13 is depressed, thus giving an indication of the amount of pressure applied to the cathode compartment.
  • FIG. 2 The arrangement of FIG. 2 is suitable when it is not desired to be able to change the level of liquor in the cathode compartment.
  • the lute 13 is connected directly to the hydrogen line as shown at 16 and also to the cathode compartment at the normal liquor level as shown at 17.
  • the feed of brine to the head tank 8 must also be adjusted to match the new current density or overflow means must be provided so that the head of liquor in tank 8 remains at approximately the same level when the current density and the back-pressure on the cathode compartment are altered.
  • the diaphragm when it is desired to operate a cell with very severe load-shedding, e.g., 90% reduction in electrical load, it is preferred to arrange for the diaphragm to be completely submerged in the catholyte and in fact to have a few centimetres head of caustic liquor above the top edge of the diaphragm, rather than to have part of the diaphragm exposed as in the schematic arrangements of the drawings.
  • the necessary substantial increase in back pressure can then be applied to the cathode compartment without any danger of forcing hydrogen through the diaphragm from the gas space above the catholyte into the anode compartment.
  • Very accurate control of the rate of flow of liquor through the cell diaphragm can be achieved if desired by metering the caustic liquor delivery rate or its alkalinity and adjusting the back-pressure on the cathode compartment to bring the delivery rate to the new value or to maintain the alkalinity substantially constant each time the current density is changed.
  • the electrolyte flow rate is not then exactly proportional to current density at all times, the error introduced by working in this way is generally acceptable.
  • the back-pressure on the cathode compartment may be controlled automatically when the current density is changed.
  • This can be achieved by operating the control valve by a servo-motor which is fed with a voltage proportional to the electrolyzing current and with an opposing voltage related to the position of the control valve so that whenever there is an error between these two voltages the control valve is moved to a new position until the error is brought to zero.
  • the control valve servo-system may be calibrated to operate on the principle of maintaining the differential pressure across the diaphragm proportional to current density or, if desired, it may be operated in terms of the more accurate parameter of electrolyte flow rate by continuously metering the caustic liquor flow rate by automatic means and feeding this metered data to the servo-system which controls the valve in the hydrogen line.
  • Another alternative is to have the pressure-control valve automatically operated by a servo-system which is responsive to changes in the alkalinity of the caustic liquor produced in the cell, so as to maintain this alkalinity substantially constant. With this arrangement, a slow change or a stepwise change in the alkalinity reference point can be built in to allow for the normal changes in diaphragm percolation rate with ageing.
  • the invention is further illustrated by the following experimental data obtained on a laboratory-scale cell fitted with a chrysotile asbestos diaphragm and continuously electrolysing a feed brine containing 315 g.p.l. sodium chloride at approximately C.
  • the full-load current was 2 ka./m. of diaphragm area.
  • the cell was operated with the electrical load reduced to 34% (66% load-shedding) for 4.5 hours a day on five consecutive days each week up to the twenty-second day shown in the table and thereafter with loadshedding for 4.5 hours a day.
  • Load-shedding was carried out in the manner of the invention by rapidly applying additional back-pressure to the cathode compartment by adjusting a control valve on the hydrogen outlet to show the required depression in a lute connected to the cathode compartment, as in FIG. 1 of the drawings accompanying the Provisional Specification, when the current density was reduced, while keeping a constant head of brine on the anode compartment.
  • a method for the operation under conditions of varying electrical load of a chlor-alkali cell which incorporates a percolating asbestos diaphragm which is characterised by rapidly making such change in the rate of flow of electrolyte through the diaphragm by altering the gas pressure on at least one of the anode compartment and the cathode compartment of the cell each time the current density across the diaphragm is changed that the rate of electrolyte flow is always approximately proportional to the current density.

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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)
  • Inorganic Chemistry (AREA)
  • Automation & Control Theory (AREA)
  • Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)
US709391A 1967-03-16 1968-02-29 Manufacture of chlorine and caustic alkali in diaphragm cells Expired - Lifetime US3547791A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB12328/67A GB1149416A (en) 1967-03-16 1967-03-16 Manufacture of chlorine and caustic alkali in diaphragm cells

Publications (1)

Publication Number Publication Date
US3547791A true US3547791A (en) 1970-12-15

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US709391A Expired - Lifetime US3547791A (en) 1967-03-16 1968-02-29 Manufacture of chlorine and caustic alkali in diaphragm cells

Country Status (10)

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US (1) US3547791A (enrdf_load_stackoverflow)
AT (1) AT277286B (enrdf_load_stackoverflow)
BE (1) BE711791A (enrdf_load_stackoverflow)
CH (1) CH476631A (enrdf_load_stackoverflow)
DE (1) DE1667804B1 (enrdf_load_stackoverflow)
ES (1) ES351705A1 (enrdf_load_stackoverflow)
FI (1) FI50802C (enrdf_load_stackoverflow)
FR (1) FR1556779A (enrdf_load_stackoverflow)
GB (1) GB1149416A (enrdf_load_stackoverflow)
NL (1) NL156758B (enrdf_load_stackoverflow)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2348889A1 (de) * 1972-10-19 1974-08-01 Du Pont Verfahren und vorrichtung zum elektrolysieren waessriger loesungen von natrium- und/oder kaliumsalzen und/oder -hydroxiden
JPS534796A (en) * 1976-07-05 1978-01-17 Asahi Chem Ind Co Ltd Electrolysis of pressurized alkali halide
US4689133A (en) * 1985-03-29 1987-08-25 The Dow Chemical Company Directly electrically coupled fuel cell-electrolysis cell system

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2426747A1 (fr) * 1978-05-26 1979-12-21 Solvay Procede d'electrolyse dans une cellule a diaphragme non mouillable

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3017338A (en) * 1958-03-03 1962-01-16 Diamond Alkali Co Electrolytic process and apparatus
US3222267A (en) * 1961-05-05 1965-12-07 Ionics Process and apparatus for electrolyzing salt solutions

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3017338A (en) * 1958-03-03 1962-01-16 Diamond Alkali Co Electrolytic process and apparatus
US3222267A (en) * 1961-05-05 1965-12-07 Ionics Process and apparatus for electrolyzing salt solutions

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2348889A1 (de) * 1972-10-19 1974-08-01 Du Pont Verfahren und vorrichtung zum elektrolysieren waessriger loesungen von natrium- und/oder kaliumsalzen und/oder -hydroxiden
US3864226A (en) * 1972-10-19 1975-02-04 Du Pont Process for electrolyzing aqueous sodium or potassium ion solutions
DK154027B (da) * 1972-10-19 1988-10-03 Du Pont Fremgangsmaade og apparat til elektrolyse af en vandig oploesning indeholdende natrium- og/eller kaliumsalte
JPS534796A (en) * 1976-07-05 1978-01-17 Asahi Chem Ind Co Ltd Electrolysis of pressurized alkali halide
US4105515A (en) * 1976-07-05 1978-08-08 Asahi Kasei Kogyo Kabushiki Kaisha Process for electrolysis of alkali halide
US4689133A (en) * 1985-03-29 1987-08-25 The Dow Chemical Company Directly electrically coupled fuel cell-electrolysis cell system

Also Published As

Publication number Publication date
BE711791A (enrdf_load_stackoverflow) 1968-09-09
NL156758B (nl) 1978-05-16
GB1149416A (en) 1969-04-23
AT277286B (de) 1969-12-29
FI50802C (fi) 1976-07-12
FR1556779A (enrdf_load_stackoverflow) 1969-02-07
DE1667804B1 (de) 1971-08-26
CH476631A (fr) 1969-08-15
NL6803661A (enrdf_load_stackoverflow) 1968-09-17
FI50802B (enrdf_load_stackoverflow) 1976-03-31
ES351705A1 (es) 1969-06-16

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