Electrolyser unit comprising a plurality of individual electrolyser stacks and method for connecting electrolyser stacks to form units

An electrolyser unit comprising:

• a plurality of individual electrolyser stacks, wherein each individual electrolyser stack has a series of cell circumferential cell frames configured for being urged against each other between an interconnection endplate and an opposed distal endplate, wherein each cell includes:
• a diaphragm spanning the cell frame;
• electrodes;
• a catholyte flow channel;
• an anolyte flow channel;
• a catholyte and hydrogen evacuation channel;
• and
• an anolyte and oxygen evacuation channel;
• wherein the cell frames are configured for securing the alkaline electrolyte and gasses within the cell under elevated pressure when pressed against adjacent circumferential cell frames;
• wherein the interconnection endplate of each individual cell stack includes:
• an axially through-going hydrogen gas and electrolyte connection which is in fluid communication with a hydrogen separation vessel and an axially through-going oxygen gas and electrolyte connection which is in fluid communication with an oxygen separation vessel;
• and
• axially through-going electrolyte flow channels which are in fluid communication with electrolyte pumps;
• wherein at least a pair of electrolyser stacks are provided and arranged pairwise adjacent each other;
• wherein in each pair of stacks, first current injection electrodes provided at each interconnection endplate are electrically interconnected and connected to a common electrical zero potential and second current injection electrodes, at each of the distal endplates, are connected to electric power supply at potentials equally higher and lower than the electrical zero potential realised at the electrodes at the interconnection endplates, and in that stack pairs are further connected to common hydrogen and oxygen separation vessels and electrolyte supply pumps through their interconnection endplates.

A method for supplying pairs of electrolyser stacks with alkaline electrolyte, electric current and gas drain piping, comprising, for each pair of electrolyser stacks:

• supplying, through interconnection endplates, alkaline electrolyte at elevated pressure through common electrolyte supply pipes;
• draining off, through the interconnection endplate, oxygen gas containing electrolyte, and hydrogen gas containing electrolyte, to common gas separation vessels for oxygen and hydrogen respectively;
• pulling first electrically interconnected current injection electrodes at interconnection endplates to zero electrical potential, through ground connection leads;
• and
• supplying second current injection electrodes belonging to stack pairs and placed at distal endplates of each stack with electric current at potentials equally higher and lower respectively than the zero potential at the first current injection electrodes.