DIRECT PRODUCTION OF PRESSURIZED HYDROGEN FROM WASTE ALUMINUM WITHOUT GAS COMPRESSOR

An innovative environment-friendly hydrolysis process for generating high-pressure hydrogen with recycling waste Al has been proposed and experimentally validated. The effect of the concentration of NaOH solution on H2 generation rate was mainly examined. In the experiments, distilled water and Al powder were placed in the pressure-resistance reactor made of Hastelloy, and was compressed to a desired constant water pressure using a liquid pump. The NaOH solution was supplied by liquid pump with different concentrations (from 1.0 to 5.0 mol/dm) at a constant flow rate into the reactor by replacing the distilled water and the rate of H2 generated was measured simultaneously. The liquid temperature in the reactor increased due to the exothermic reaction given by Al + OH + 3H2O = 1.5H2 + Al(OH)4 – + 415.6 kJ. Therefore, a high-pressure H2 was generated at room temperature by mixing waste Al and NaOH solution. As the H2 compressor used in this process consumes less energy than the conventional one, the generation of H2 having a pressure of almost 30 MPa was experimentally validated together with Al(OH)3—a useful by-product. The energy losses in the proposed system (150.9 MJ) is 55% less than that in the conventional system (337.7 MJ) in which the gas compressor and production of Al(OH)3 consume significantly more energy.