ELECTROLYZERS ACID CLEANING (GENERAL)

April 15, 2019 at 10:07 AMadmin

It is well known that the generators of active chlorine by electrolysis of seawater are fouled by precipitation on the cathodes of hydroxides and carbonates cations, such as magnesium and calcium, present in the feed solution.

·         The fouling rate mainly depends on:

·         Material and surface finishing of the cathodes

·         Cathodic current density;

·         Seawater chemical composition, temperature and flow-rate through the electrolyzers.

·         low current density together with low seawater flow-rate favouring the fouling of the electrolyzers.

If acid cleaning is unduly delayed or its time (duration) and/or acid concentration are not sufficient, salt deposits will lead to hard scaling problems of electrodes. Therefore subsequent cleaning cycles could be not effective if path between adjacent electrodes is completely blocked. Lead to an increase of power consumption, quick damage of anodic coating and even short circuits between anodes and cathodes

ACID CLEANING PROCESS

The cleaning cycle for the generators is carried out after shutting off the electric current and draining the seawater from the electrolyzers.

During acid washing, the operator should determine the concentration of the circulating acid every 10-15 minutes by chemical titrimetric analysis and make sure concentration remains 5~6% HCL (w/w) if not maintain the concentration by adding concentrated acid. Three consecutive identical concentration reading (not decreasing anymore) will indicate that all the precipitates have been removed and the circulation can be stopped.

At the end of the cleaning cycle, the acid solution is recovered again in a tank. Before re-starting operation, generating module is flushed with seawater (shutting off the electric current) for a few minutes to remove any remaining traces of HCL that may still be left un-drained in the system.

HYDROCHLORIC ACID- SPECIFICATION

Sp. Gr. (20°C)

1.16 g/ml

Appearance

clear

Conc.

30-33% w/w

Iron (Fe)

5-10 ppm (max)

Lead (Pb)

< 2 ppm

Copper (Cu)

< 1 ppm

Ca + Mg

< 1 ppm

SiO2

< 1 ppm

Free chlorine

< 1 ppm

Fluoride

nil

 

Remark: It is strongly recommended using hydrochloric acid free of fluorides. If acid washing is performed with commercial acid with fluoride content, this will cause the decay of coating in electrodes and affect warranty.

Posted in: Electrochlorinator | General | Titanium Electrolyzer

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