GB1387794A - Electrolytic cell comprising bipolar elements - Google Patents

Abstract

1387794 Electrolytic diaphragm cell SOLVAY ET CIE SA 12 April 1973 [12 April 1972] 17614/73 Heading C7B An electrolytic diaphragm cell (e.g. for electrolyzing an aqueous solution of NaCI) comprises a stack of horizontal bipolar elements, each having the form of a flat box with upper and lower foraminous metal sheet walls 2 and 6 which are electrically connected together by struts 21, 22, Fig.3 (not shown). In use, the walls 2 and 6 form cathode and anode surfaces respectively. There are surrounding sides 3 to the box and a fluid tight partition 7 dividing the box into cathode and anode compartments 8 and 9, each compartment having means for introducing or removing electrolyte therefrom. A horizontal diaphragm (not shown) is located either directly in contact with the cathode surface 2 or spaced therefrom by an interposed foraminous structure (not shown), e.g. of polypropylene. Brine can be introduced to anode compartment 9 through a reservoir 11 by a pipe 13 and C12 can be removed through the same reservoir by a pipe 12. Caustic brine and H 2 can be removed from cathode compartment 8 by a pipe 14. A stack of bipolar elements, one above the other, with unipolar elements at each end and interposed diaphragms and electrically insulating elastomeric sealing between elements is held together by means of rods 15, Fig.4 (not shown) and cross beams (16). At the top and bottom of the stack are current lead-in and extraction bars (19, 20). The cathode surfaces may be of steel. The anode may be of one of the film-forming metals Ti, Zr, Nb, Ta, W or an alloy based on one of these carrying a coating. The coating may comprise one or more metals of the Pt group and/or their oxides, titanium nitride; or the borides, phosphides or silicides of metals of the Pt group. The coating may also contain oxides of film forming metals such as Ti. Other specified anode coating materials are RuO 2 ; tellurium oxide; tellurate, tungstate and molybdate of Rh; and compounds of formula A 2 BO 6 , A 2 BO 6 .MO 2 , and A 2 BO 6 .M<SP>1</SP>M<SP>1</SP><SP>1</SP>O 4 where A represents Co, Cr, Fe, Mn, Al, Ga, Ir, Rh and/or V in the trivalent state; B represents Te, W, Mo and/or Re in the hexavalent state; M represents Ir, Mn, Os, Rh, Ru, Sn and/or Ti in the tetravalent state; M<SP>1</SP> represents Al, Cr, Fe, Ga and/or Rh in the trivalent state, and M<SP>1</SP><SP>1</SP> represents Nb, Sb, Ta and/or V in the pentavalent state. Other specified materials for various parts are:- A surrounding side 3 of concrete or steel optionally coated on its inside with rubber, ebonite or Ti. A partition- 7 of Ti, of steel coated with Ti on the anode side or of synthetic resin. A diaphragm of asbestos or polytetrafluoroethylene. The anode-cathode distance may be not more than 4 mm. thereby enabling a current density of 4.5 kA/m<SP>2</SP> with a voltage of 3.4V.