Electrochemical importance of Anode and Cathode Coating in a Membrane Cell in Chlor Alkali Industry

August 9, 2018 at 2:35 PMadmin

 Electrochemical importance of Anode and Cathode Coating in a Membrane Cell in

Chlor Alkali Industry

Abstract

Membrane Cell operation for the production of Caustic and Chlorine is the latest environment and energy friendly process for a Chlor-Alkali Plant. The membrane cell consists of Cathode (Nickel), Anode (Titanium) and a floro carbonated membrane. By the continuous process and process requirement in energy point of view in a normal running Chlor-Alkali Plant, Anode and Cathode coating is required in order to increase more lifetime and more productivity for a cell. This anode and cathode coating not only increase the total productivity of a Chlor-Alkali Unit but also can decrease the fixed cost for a unit by increasing process reliability. A study has been done to understand the electrochemical importance of anode and cathode coating and the thrust zone for more research in this area to increase the productivity as well as increasing the depreciation time for the Cell.

Introduction:

Chlor Alkali Industry is a special and separate zone of chemical Engineering process and design which meets the need of tones of caustic for textile, pulp and paper, pharmaceutical industries and chlorine for PVC, water purification, and bleaching industries. In industry, from the last century caustic and chlorine is produced by Electrolysis of saturated Brine (320gpl of NaCl in H2O) by diaphragm or mercury or Membrane cell operation. But for operational and cost Excellence Membrane cell electrolysis process In Chlor-Alkali Industry dominates over the other two processes from the last four to five decades. In Membrane cell Electrolysis process, the membrane is set between a Cathode (Ni) and Anode (Ti) and the electrolysis takes place in both Cathode and anode side by high current. Saturated Brine comes in anode side and depleted into Na+ and Cl- ions. 26% caustic comes in Cathode side where depletion of water into H+ and OH- ion takes place.   Membrane is a very thin perfluroted substance with carboxylic coating in Cathode side and sulphonic coating in anode side which only allows Na+ ion in cathode side from anode side. NaOH forms in cathode side with H2 as a byproduct, and Cl2 forms in the anode side with lean brine recycle after dechlorination process. Membrane structure and selectivity is a separate zone of research and is not the scope of present study. The Membrane cell dominates over other two electrochemical manufacturing process of Chlor-Alkali Industry due to the following reasons.

The power requirement is very high in Chlor-Alkali industry. Applications of Membrane cell technology decrease the power consumption over the other two processes. But reduction of power is still a thrust zone of research because Chlor-Alkali Industry is still the largest consumer of power. It is tried to reduce the voltage from the root i.e. one single cell voltage to reduce power requirement in the Electrolysis process. The cathode and anode ageing is another problem and replacement cost is also very high. Reminding both causes i.e. increasing cathode and anode life and decreasing cell voltage; anode side and cathode side coating is generally done. In presents the need, factors affecting and methods for applying cathode and anode coating is highlight with latest development in this zone. It is expected that the study will help to understand the anode and cathode coating in details manner in Chlor-Alkali Industry and modification needed in this zone. The objective of the study is given below:

1. To see the various causes of the failure of electrode coatings.

2. To discuss the effective coating process.

3. A one shop stop for the knowledge of anode coating.

Anode and Cathode Coating:

The key components of all electrochemical processes are the electrodes and, in some cases, the separators. The last century has seen many developments in both for the electrode materials and ion permeable membranes and allows successful implementation of many novel concepts. Where optimum performance of electrode material is needed, electrodes made from noble metals or noble metal oxides are the components of choice. The common features of the materials of electrodes are

a)        The use of the platinum group and there oxides as coatings on inert substances.

b)        The minimization of platinum metal loading.

c)        Minimization of inter electrode gaps and having high energy efficiency by abrication of membrane or the electrodes.

d)        To increase electrode stability by the use of platinum group metal alloys that also helps to minimize over potentials.

 Conclusions:

Electrochemical technology is the cleanest technology considered today. The Membrane cell technology is the most environment friendly technology and energy efficient technology. All this technology depends on stable electrode materials and frequently only platinum group metal materials fulfill this requirement. The objective of the electrode and coating catalyst design is often therefore to place the noble metal in a stable matrix and to achieve the required performance with a minimum noble metal loading. In today research is going on further reduction of over potential of both sides of electrodes to reduce energy consumption and also to increase its operating life and this is the challenge for the Chlor alkali industries in the 21st century.

Request you to go through the above and please feel free to contact us for further clarifications / queries on repair, refurbishment and recoating of anode and cathode elements or visit our website www.chloralkalianodes.com

 

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