Hydrogen recovery from On Site Electro Chlorination system.

The production of hypochlorite can occur through the process of electrolysis of a saline solution with a hydrogen production that is usually discarded. The main objective of the study was to assess, in practice, whether it is possible to recover the hydrogen produced during the electrolysis of a saline solution in order to use one or more fuel cells. The energy produced by such cells can be used to reduce the energy consumption of the production of sodium hypochlorite or other purposes. We first made an evaluation of the producibility of hydrogen from the electrolysis process for a OSEC (On Site Electro Chlorination) system, called MK4, working in batch mode. We then verified experimentally the ability to collect hydrogen and to use it in one or more fuel cells. The methodology involved the following steps: • Change of the original system to collect the gas, • Whatever purification of chlorine gas, • Measure of the flow of gas produced, • Analysis of the purity of the gas produced by gas chromatograph. Once purified from chlorine, the gas has been placed in different configurations of fuel cells stacks. The power obtained from the fuel cell was assumed to be about 24 W, so the efficiency is about 25 %, that is not very high for a fuel cell. It was evaluated that energy recovery is around 8-10%, considering the input power of the OSEC and the output power from the fuel cell. But the gas produced contains about 85% hydrogen and 15% oxygen. The presence of oxygen could reduce the proportion of hydrogen involved in the electrochemical reaction, lowering the efficiency of the fuel cell. If the presence of oxygen in the anode gas is limited, we may obtain an efficiency of the fuel cell of about 40%. So the energy recovery would be 14%.