Optimised liquid outflow from membrane electrolysers

Abstract

A method comprising operating an electrolysis apparatus comprising a plurality of electrolyzers is provided. Each electrolyzer on the anode side has at least one liquid drain and at least one gas outlet, and separately therefrom on the cathode side has at least one liquid drain and at least one gas outlet. The anode spaces of these electrolyzers are connected to one another and separately therefrom the cathode spaces of these electrolyzers are connected to one another, in each case at least via a liquid feed, a gas discharge and a liquid discharge. The liquid drains from the anode spaces and/or the cathode spaces of the electrolyzers are effected, per electrolyzer, via a pipeline siphon into the pipeline system of the liquid discharge. An electrolysis apparatus and a method comprising decoupling an operating pressure on a liquid drain side of an electrolyzer are also provided.

1 . A method comprising operating an electrolysis apparatus, the electrolysis apparatus comprising a plurality of electrolyzers selected from membrane electrolyzers, wherein at least each electrolyzer on the anode side has at least one liquid drain and in each case at least one gas outlet, and separately therefrom on the cathode side has at least one liquid drain and in each case at least one gas outlet, and the anode spaces of these electrolyzers are connected to one another and separately therefrom the cathode spaces of these electrolyzers are connected to one another, in each case at least via a liquid feed, a gas discharge and a liquid discharge, wherein the operating pressure of at least one liquid discharge is set lower than the operating pressure of the electrolyzers, and wherein:
 (a) the liquid drains from the anode spaces or the cathode spaces or from both of these spaces of the electrolyzers are effected, per electrolyzer, via a pipeline siphon into a pipeline system of the liquid discharge, as a result of which on the liquid drain side the operating pressure of the electrolyzers is decoupled by means of each pipeline siphon from the lower operating pressure of the adjoining pipeline system of the liquid discharge ( 2 . 5 ), and   (b) each gas outlet of the electrolyzers decoupled by means of pipeline siphon is effected individually for each electrolyzer via an individual control valve per electrolyzer into a common gas discharge.   
     
     
         2 . The method as claimed in  claim 1 , wherein the electrolysis apparatus operated contains a plurality of electrolyzers selected from membrane electrolyzers with gas diffusion electrode, these electrolyzers being connected to one another at least via a gas-diffusion-electrode-side gas feed, via a gas-diffusion-electrode-side liquid feed as liquid feed, a gas-diffusion-electrode-side residual gas discharge as gas discharge, and a gas-diffusion-electrode-side liquid discharge as liquid discharge. 
     
     
         3 . The method as claimed in  claim 1 , wherein the membrane electrolyzers are selected from alkali metal chloride membrane electrolyzers. 
     
     
         4 . The method as claimed in  claim 3 , wherein the alkali metal chloride used is selected from lithium chloride, sodium chloride, potassium chloride, or mixtures thereof. 
     
     
         5 . The method as claimed in  claim 2 , wherein the electrolyzers are selected from membrane electrolyzers with oxygen-depolarized cathode as gas diffusion electrode, the gas-diffusion-electrode-side gas feed of which is connected to a source for an oxygen gas-containing gas stream. 
     
     
         6 . The method as claimed in  claim 2 , wherein the electrolyzers are selected from membrane electrolyzers with gas diffusion electrode, the gas-diffusion-electrode-side gas feed of which is connected to a source for a carbon dioxide-containing gas stream. 
     
     
         7 . The method as claimed in  claim 1 , wherein the operating pressure of the electrolyzers is between atmospheric pressure and 1 bar positive pressure. 
     
     
         8 . The method as claimed in  claim 1 , wherein the operating pressure on the drain side of the pipeline siphon is lower than the operating pressure on the inlet side. 
     
     
         9 . The method as claimed in  claim 1 , wherein
 (i) a gas, selected from product gas, residual gas, or a mixture of product gas and residual gas, and   (ii) a liquid   
       of each individual electrolyzer are first guided out as a mixture in a drain manifold of each individual electrolyzer and this mixture is then subjected to a gas-liquid separation, where after separation has been effected the gas is caused via the gas outlet according to step (b) and the liquid via the liquid drain according to step (a). 
     
     
         10 . The method as claimed in  claim 1 , wherein the liquid discharge is effected according to step (a) in every operating mode of the electrolysis apparatus. 
     
     
         11 . An electrolysis apparatus, containing a plurality of electrolyzers selected from membrane electrolyzers, wherein at least each electrolyzer on the anode side has at least one liquid drain and at least one gas outlet, and separately therefrom on the cathode side has at least one liquid drain and at least one gas outlet, and the anode spaces of these electrolyzers are connected to one another and separately the cathode spaces of these electrolyzers are connected to one another, in each case at least via a liquid feed, a gas discharge and a liquid discharge, wherein:
 (a) for decoupling, on the liquid drain side, the operating pressure of the electrolyzers from the operating pressure of a pipeline system of at least one of the liquid discharges, the liquid drains from the anode spaces or the cathode spaces or from both of these spaces of the electrolyzers, per electrolyzer, are in fluid connection with the pipeline system of the liquid discharge via a pipeline siphon, and   (b) the gas outlet of all electrolyzers that are equipped with the pipeline siphon is in fluid connection with a corresponding common gas discharge via an individual control valve per electrolyzer.   
     
     
         12 . The electrolysis apparatus as claimed in  claim 11 , wherein the electrolyzers contain gas diffusion electrodes, the electrolyzers being additionally connected to one another at least via a gas feed on the gas diffusion electrode side. 
     
     
         13 . A method comprising decoupling an operating pressure on a liquid drain side of an electrolyzer of an electrolysis apparatus from an operating pressure of an adjoining pipeline system of a liquid discharge with a pipeline siphon at a liquid drain of the electrolyzer, the electrolysis apparatus containing a plurality of membrane electrolyzers, the electrolyzers being connected to one another at least via a liquid feed, a gas discharge and the liquid discharge. 
     
     
         14 . The method as claimed in  claim 2 , wherein the gas diffusion electrode comprises an oxygen-depolarized cathode. 
     
     
         15 . The method as claimed in  claim 6 , wherein the gas-diffusion-electrode-side gas feed is connected to a gas stream of carbon dioxide. 
     
     
         16 . The method as claimed in  claim 7 , wherein the operating pressure of the electrolyzers is in a range of from 100 to 500 mbar positive pressure. 
     
     
         17 . The method as claimed in  claim 8 , wherein the operating pressure on the drain side of the pipeline siphon is between atmospheric pressure and 100 mbar positive pressure. 
     
     
         18 . The method as claimed in  claim 1 , wherein the liquid discharge is effected according to step (a) when starting up, shutting down and during operation of the electrolysis apparatus. 
     
     
         19 . A method comprising producing chlorine with the electrolysis apparatus as claimed in  claim 11 . 
     
     
         20 . The electrolysis apparatus as claimed in  claim 12 , wherein the electrolyzers contain gas diffusion electrodes on the cathode side.