Effect of steam injection on syngas composition in coal and waste plastics mixed gasification

Central Research Institute of Electric Power Industry (CRIEPI) is developing the basic technologies for a poly-generation system with CO2 capture utilizing various fuels such as coal, waste plastics and biomass. The system uses an O2/CO2/H2O blown gasifier to produce syngas. The composition of syngas can be adjusted by controlling the amount of H2O supplied to the gasifier. For chemical synthesis from syngas, it is necessary to adjust the H2/CO ratio of syngas to achieve the appropriate balance required for the synthesis process. Although the use of waste plastics as a fuel is considered a promising approach for achieving decarbonization, the high content of volatile matter raises concerns regarding the formation of tar. Excessive tar generation can impede the stable operation of the equipment. Therefore, it is necessary to implement measures to suppress tar formation. We investigated experimentally the influence of mixing waste plastics with coal on gasification performance using 3t/d coal research gasifier. The gasifier is a two-stage entrained-flow type, which enables the separate supply of fuel to the combustor and the reductor sections. The gasification tests were conducted by feeding coal and RPF (Refuse-derived paper and plastics densified fuel) at the same time and changing CO2 and H2O concentrations of gas fed into the gasifier. It was found that the supply of waste plastics to the combustor section effectively suppresses the formation of tar. By adjusting the composition of the inlet gas, it was shown that the H2/CO ratio can be adjusted for chemical synthesis.