Why does a high current density lead to increased power consumption?

As the current increases, the slot voltage rises; according to the power consumption formula, power consumption also increases.

The electrolysis process requires a large amount of electrical energy. The theoretical formula for calculating the energy consumption is: W = 1000v/kη, where W represents the electrical energy consumed per ton of 100% caustic soda, in kWh； V—slot voltage, (V) ； k—electrochemical equivalent of caustic soda, g/Ah, (1.4923 g/Ah) ； η—efficiency (%). The relationship between the operating voltage and current density in an ion-exchange membrane cell is nonlinear, as certain components of the cell voltage, particularly the cathode overvoltage, do not increase linearly with the current density. However, when the current density exceeds 1 kA/m2, the relationship between the operating slot voltage and current density is linear: U = U0 + ki ； Here, U0 is not the theoretical decomposition voltage; U0 and the k value depend on different cell parameters and electrolysis conditions. If the electrolyzer operates at a high current density, the cell voltage of the electrolyzer increases according to the formula U = U0 + ki ； As per the formula W=1000v/kη, it can be seen that an increase in the cell voltage of the electrolyzer leads to higher power consumption ； Therefore, why can a high current density lead to increased power consumption.

But one thing is for sure: running in this manner over the long term does increase production capacity

But today’s good electrolyzers all operate at high current densities; only electrolyzers with high current densities and zero electrode spacing can save energy consumption

It is normal for the cell voltage to be high when operating at high current densities, but this does not necessarily mean an increase in power consumption. You need to calculate the increase in cell voltage caused by the rise in current density and the amount of caustic soda produced as a result of the increased current, in order to properly determine whether high current densities lead to higher power consumption.

In copper smelting, after high current densities are applied, to avoid concentration polarization, the solution concentration is increased; this leads to an increase in resistance and thus higher electricity consumption.

This post was last edited by sunjl1981 on 2013-12-27 09:43. As the electrical density increases, the overpotentials for chlorine evolution, hydrogen evolution, membrane voltage drop, and liquid voltage drop all increase, resulting in higher energy consumption per ton of alkali produced. But equipment investment has decreased, and that is why high electric density is being adopted now.

Can you drive a car? Increasing the throttle to raise the speed will definitely lead to higher fuel consumption

Power consumption formula: W = 1000v/kη. W represents the electrical energy consumed per ton of 100% caustic soda, in kWh； V—slot voltage, (V) ； k—electrochemical equivalent of caustic soda, g/Ah, (1.4923 g/Ah) ； η—current efficiency (%). At 13KA, the voltage of the unit frame is 2.95 V and the current efficiency is 95%; thus, W = 1000*2.95/1.492*95% = 2081 KWh/T. At 17KA, the voltage of the unit frame is 3.09 V with the same current efficiency of 95%, giving W = 1000*3.09/1.492*95% = 2180 KWh/T, which represents an increase of 100 KWh/T.

To be precise, this is the case when the current efficiency remains constant. However, as the electrical density increases, the current efficiency should decrease; therefore, power consumption definitely increases.