Iomcube
Chemical
- Dec 11, 2015
- 187
Question entails a background of NaOH production via Brine membrane electrolysis
See below figures for element internals, in a nutshell membrane(DuPONT) is sandwiched b/w anode(titanium made) & cathode(Nickel made). Anode fabrication is much more robust when compared with nickel cathode, although both best can be described as mesh structures
ours is Generation3
anode/cathode chambers are sandwiched, but are segregated entirely by inbetween membrane, or otherwise H2/Cl2 mixture may cause explosion!
stack of multiple elements is referred as electolyser
Elements are connected in series with respect to applied potential, current(~13kA) is same for every element, though voltage varies depending on its health
Brine(~300g/L) is fed at anode while caustic(~30wt%) at cathode, thus both chambers are flooded with respective electrolyte ..for rest see the flash animation
After about 2months of dormant period & by that i mean that all of Elements of Electrolyser are drained ..there is long procedure for that. But during that period according to manufacturer ambient temperature must not get below 10celsius or membrane can get dehydrated plus you have keep them humid by flooding anolyte/catholyte headers with demin water as shown below
we did that all
After that dormant period we checked all the elements for membrane leakage, we refer to it as bubble test. Its fairly simple, pressurise catholyte side with ~40mbar of N2 & check whether you get any bubble at the outlet hose of anolyte. If membrane is compromised of that element ..well we see lot of bubbles. although we did found many membranes compromised but we saw something else too:
Unknown corrosion type at anode side (titanium perforated ribs, with SECRET oxide layer)
Compare above anode fabrication with that of cathode below. The welding is dislocated & had punctured our membranes
Corrosion observed at anode cannot be classified as any type of corrosion as far as i know. The scorched metal points with simultaneous exposure of fresh metal isn't any type of corrosion but appears to be some sort of spark assisted deformation (Electrolyser during operation suffers ~13kA load).
Question is what do you think cause these localised (i will not refer to them as pitting) scorches. Has anyone experienced such metal blisters especially on Titanium
See below figures for element internals, in a nutshell membrane(DuPONT) is sandwiched b/w anode(titanium made) & cathode(Nickel made). Anode fabrication is much more robust when compared with nickel cathode, although both best can be described as mesh structures
ours is Generation3
anode/cathode chambers are sandwiched, but are segregated entirely by inbetween membrane, or otherwise H2/Cl2 mixture may cause explosion!
stack of multiple elements is referred as electolyser
Elements are connected in series with respect to applied potential, current(~13kA) is same for every element, though voltage varies depending on its health
Brine(~300g/L) is fed at anode while caustic(~30wt%) at cathode, thus both chambers are flooded with respective electrolyte ..for rest see the flash animation
After about 2months of dormant period & by that i mean that all of Elements of Electrolyser are drained ..there is long procedure for that. But during that period according to manufacturer ambient temperature must not get below 10celsius or membrane can get dehydrated plus you have keep them humid by flooding anolyte/catholyte headers with demin water as shown below
we did that all
After that dormant period we checked all the elements for membrane leakage, we refer to it as bubble test. Its fairly simple, pressurise catholyte side with ~40mbar of N2 & check whether you get any bubble at the outlet hose of anolyte. If membrane is compromised of that element ..well we see lot of bubbles. although we did found many membranes compromised but we saw something else too:
Unknown corrosion type at anode side (titanium perforated ribs, with SECRET oxide layer)
Compare above anode fabrication with that of cathode below. The welding is dislocated & had punctured our membranes
Corrosion observed at anode cannot be classified as any type of corrosion as far as i know. The scorched metal points with simultaneous exposure of fresh metal isn't any type of corrosion but appears to be some sort of spark assisted deformation (Electrolyser during operation suffers ~13kA load).
Question is what do you think cause these localised (i will not refer to them as pitting) scorches. Has anyone experienced such metal blisters especially on Titanium
