Cathodic Protection Performance Of Typical Sacrificial Anodes In Sulfur Recovery Catalysts

The corrosion of sulfur recovery unit(SRU)of natural gas liquefaction systems working in open-sea is very serious,due to the corrosive catalyst.Moreover,it is difficult and costly to maintain the SRU equipment for it is far away from continent.So it is necessary to take effective measures to protect the sulfur recovery device from corrosion in the whole life.The cathodic protection method of sacrificial anode is a widely used and effective corrosion protection technology,and has the feasibility of being applied to the corrosion protection of the sulfur recovery device.Sulfur recovery catalyst solution shows strongly alkalinity.And sacrificial anode performance has been widely studied in neutral or acidic environment but rarely reported in strong alkaline solution.Therefore,the electrochemical performances of six kinds of common sacrificial anode were tested in sulfur recovery catalyst solution in this paper,which evaluated the applicability of different sacrificial anode and provided a basis for sacrificial anode protection design and material selection of sulfur recovery unit.In this paper,the electrochemical performances of six kinds of specially selected sacrificial anode materials were tested at 20°C,40°C and 60°C by galvanostatic experiments in sulfur recovery catalyst solutions through comparing and analyzing the open circuit potentials,working potentials,surface dissolution appearances,actual capacitances,theoretical capacitances and current efficiencys of six sacrificial anodes.The results shows that the high-silicon cast iron sacrificial anode behaves the best overall performance which appeared in stable open circuit potential,working potential,uniform dissolution appearance and high current efficiency especially reached 89.7%at 60?.What's more,the dissolved production is Fe²⁺which will avoid contaminating the catalyst.Therefore,the high-silicon cast iron is an ideal sacrificial anode material for sulfur recovery unit protection by preliminary judgementThen the six kinds of sacrificial anodes were studied more depth by testing potentiodynamic polarization curves and electrochemical impedance spectroscopy in sulfur recovery catalyst,which analyzed anode dissolution mechanism and explained the anomalous phenomenon of aluminum alloy sacrificial anode in galvanostatic experiments.Finally,the cathodic protection performance of high-silicon cast iron sacrificial anode was verified by self-discharge test and adding different content of element S to desulfurization catalyst.The results turn out that the high-silicon cast iron sacrificial anode shows great performance in sulfur recovery catalyst solution but became variation when adding element S.Based on above research,the paper carried out theoretically and numerically simulates of high-silicon sacrificial anode protection scheme on the inner wall of the sulfur recovery unit reactor.For the volume of?3×10 m'sulfur recovery reactor,in 15 a'protection period,needs8 pieces of size 200×150×600 mm'high-silicon cast iron sacrificial anode.A simulation model was established by the finite element software Comsol Multiphysics^?R to verify the protective results of the protection scheme.The results show that the corrosion potential of sulfur recovery unit inner wall was negative shifted 360 m V and the corrosion current density of the inner wall was infinitesimally,which indicated that high-silicon cast iron sacrificial anode has significant protective effect on the inner wall of the sulfur recovery reactor.