Experimental investigation on the production of hydrogen from discarded circuit boards in supercritical water

Circuit boards are indispensable components of electronic products. They are difficult to burn as they capture active free radicals, therefore the traditional disposal methods for discarded circuit boards are inefficient and polluting. In this work, discarded circuit boards were gasified in supercritical water. The operating conditions employed were as follows: temperature 500–750 °C; reaction time 1–30 min; feedstock concentration 1–10 wt%; and pressure 23 MPa. Analysis of the components in the gasification products showed that the increase of the reaction temperature and reaction time improved the gasification performance. Furthermore, the reduction in the feedstock concentration could also significantly enhance the conversion rates of both the carbon and hydrogen. It can be concluded that the efficient and economical working condition were as follows: temperature 700 °C; reaction time 10 min; feedstock concentration 5% and the addition of a catalyst. The conversion efficiencies for both carbon and hydrogen were 84.67% and 146.77% under these conditions, representing an increased efficiency with reduced costs. Finally, the conversion process of the bromine atoms in the tetrabromobisphenol A epoxy resin was examined and the bromine atoms in the raw material were converted into the gas phase product, hydrogen bromide, the solid phase products copper bromide and other bromides, and the liquid phase products bromide ions and bromine-containing organic molecules.