Modular or Filterpress Electrolysers

Learn the difference between modular and filterpess designs of electrolyser, and why modular electrolysers are more efficient for chlor-alkali applications.

Modular or filterpress electrolyser for chlor-alkali? How to choose.

Electrolyser Capital Cost

Due to the nature of their construction, filterpress electrolyser designs are marginally cheaper to manufacture than modular technology designs. This is because they can be made of thinner material as the anode and cathode are mutually supporting, with smaller flanges and no need for bolt holes (less metal and less membrane required).

Power Consumption

There has been much debate about which design of electrolyser has the lowest power consumption. In reality, it is not the style of electrolyser that determines the power consumption, but a combination of the internal structure, electrode coatings and membrane choice. INEOS BICHLOR Electrolysers, a modular and inherently safer technology, offer the lowest power consumption.


Over many years, it has been observed that filterpress electrolyser designs average twenty years of life before the operational economics dictate that the electrolysers should be replaced. There are several reasons for this relatively short operational life, compared to modular electrolyser designs.

  • Anodes can only be replaced by removing each mesh, repairing the structure and re-welding a new mesh on. This can only be done a finite number of times before the integrity of the structure becomes compromised and further repairs are uneconomic
  • Filterpress electrolyser elements are made from thinner materials than modular electrolyser designs, so they are more easily distorted and holed, resulting in a higher attrition rate as they age
  • Filterpress element gaskets are glued in place, and flange coatings are damaged when removing the glue

Modular electrolyser designs have an operational life of up to 40 years because:

  • Each module is built of thicker material and so is more robust
  • Electrodes are re-coated without removal of each mesh (in-pan coating) so there is no damage done to the structure during refurbishment and can be re-coated indefinitely
  • As each anode and cathode on a modular electrolyser are separate structures, any irreparable damage to either does not mean scrapping a full structure
  • Gaskets are not glued, removing the risk of flange coating or surface damage from glue removal
Ability To Economically Repair

Only modular electrolyser designs allow complete access to all areas of the structure, enabling weld repairs during refurbishment. Filterpress electrolysers suffer from premature and higher scrap rates due to the difficulty of refurbishment.

Electrode Recoating

Due to the bimetallic nature of their construction, filterpress electrolyser structures can not be re-coated without removing the mesh, due to the risk of structure distortion. This adds significant cost to refurbishment, as new meshes are required each time as well as considerable labour to remove and re-attach the electrodes. Additionally, the removal and reattachment of meshes further reduce the overall lifetime of the structure.

Modular technology designs feature an anode made from titanium and a cathode from nickel so it can be recoated without removing the meshes, saving considerable expense and effort. 

Safety, Health & Environment (SHE)

Filter press technologies have a number of design aspects that present SHE challenges, such as :

  • To remove a filterpress structure the seals have to be broken, which releases any entrained electrolytes which fall to the cellroom floor creating hazards to the operators
  • To re-membrane the operators have to stand on top of the filterpress electrolyser, presenting a fall hazard 
  • All maintenance work is done in the filterpress cellroom, next to potentially live equipment which is particularly dangerous as liquids are also present

Modular electrolyser technology eliminates all of these SHE hazards, with cells opened horizontally, away from the cellroom and work is carried out without having to climb the electrolyser structure.

Summary Comparison Table:

Electrolyser Performance Attribute Modular Filterpress

Electrolyser capital cost

  Marginally cheaper

Power consumption

                    Not determined by electrolyser type


Up to 40 years    20 years

Ability to repair economically

Totally repairable Some scrappage

Cost of recoating

Significantly cheaper  

Safety, Health & Environment (SHE)

Highest SHE Standard