Results And Discussion

1) Effect of the current density at a constant utilization of each anode and cathode reactant gases

Figure 2 shows the effect of the current density on the acid loss rate into the exhaust gases at 220°C. The acid loss rate at the anode and cathode increases with an increase of the current density and the loss into the cathode exhaust gas account for ca. 80 -85% of the total acid loss. Figure 3 shows the effect of the current density on the concentration of phosphoric acid in the exhaust gases. The concentration in the cathode exhaust gas is nearly constant in the region of 50-400 mA/cm2 but that in the anode varies with current density. Under a constant utilization of each reactant gas, the volume of reactant gases decreases with decreasing current density. So, the increase of the concentration of phosphoric acid in the anode exhaust gas in the low current density region (50-100 mA/cm2) is ascribed to the low mean linear velocity ( see Figure 4). However, it is noteworthy that a difference of the concentrations in the exhaust gases of the anode and cathode in the region of a small linear velocity even though the velocity is the same.

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