Experimental Study of Silver Cathode for Electrochemical Deoxygenation of Seawater for Enhanced Oil Recovery

Abstract

Seawater injection into reservoirs is a common method to enhance oil recovery. In order to avoid corrosion in pipes, the oxygen has to be removed from the seawater. This study focuses on the use of silver cathodes in electrochemical cells for oxygen removal, and the physical parameters that affect the efficiency of this process. Three electrochemical cells have been constructed and tested with packed bed cathodes made up of pure silver particles and silver plated brass spheres. Experimental results showed that silver was a suitable cathode material for oxygen removal. The most important parameter for optimizing cell performance was the depth of the cathode chamber. In addition, the thickness of the silver plating is also an important parameter to adjust since a too-thin layer results in erosion giving rise to galvanic corrosion between brass and silver, which reduces the efficiency of the cell.

The Effects of Acidic, Alkaline, and Neutral Anolytes on Electrochemical Seawater Deoxygenation

“…This method avoids the use of additional chemicals and utilizes only seawater as an electrolyte. The electrochemical system with a silver cathode for oxygen removal works efficiently on both the laboratory scale and the industrial scale, as previously reported by Dotel et al [1,2].…”

“…The catholyte for the tests was 0.5 M NaCl (pH range 6-7); however, during stabilization before experiments, the acidic anolyte made the stagnant catholyte acidic (pH 5), and the alkaline anolyte made the catholyte slightly alkaline (pH 9). In our previous study [1], the pH of the anolyte that was stagnant decreased significantly from pH 8.00 to pH 2.16. Thus, for an industrial-scale deoxygenation cell, it is recommended to avoid keeping the anolyte stagnant.…”

Electrochemical Oxygen Removal from Seawater in Industrial Scale Using Silver Cathode

“…The design of the electrochemical cell is based on experiences from the lab scale setup in our previous work . The cell was designed in such a way that a uniform flow of water was ensured throughout the cathode section.…”

“…The use of an electrochemical process for the removal of oxygen from seawater is an alternative method that avoids the disadvantages described for the other methods. − The oxidation of water to yield hydroxium ion and oxygen, and the reduction of oxygen to water are the basis for deoxygenation of water. The main reactions at the two electrodes are two opposite directed reactions:…”

“…The cation exchange membrane (CEM) allows the passage of cation from the anode compartment to the cathode compartment. In our recent study, the effect of salt concentration, flow rate, and voltage was examined with respect to oxygen removal in a laboratory scale cell (L: 51 cm, D: 3 cm, W: 31 cm) . Different electrode materials, such as copper, graphite, and nickel, have been tested in laboratory scale as the cathode material for oxygen reduction; however, associated problems, such as corrosion and hydrogen peroxide production, limit their use for oxygen removal .…”