Production of highly superheated steam by cyclic detonations of propane- and methane-steam mixtures with oxygen for waste gasification

Highlights: • We study pulsed detonations of ternary C3H8/CH4–O2–steam mixtures at 0.1 MPa. • Maximum steam dilution in initial mixtures is 60% for C3H8 and 40% for CH4. • Maximum steam content in the detonation products expanded to 0.1 MPa attains 80%. • Steam temperature in expanded detonation products exceeds 2250 K. • Steam produced by pulse detonations can be used for clean waste gasification to syngas. It is proposed to produce highly superheated steam (HSS) for environmentally friendly steam assisted gasification of organic municipal and industrial wastes using cyclic detonations of ternary propane/methane–oxygen–steam mixtures. Systematic experiments to determine the detonation limits of such mixtures in terms of steam dilution have been conducted. The experiments are performed in an innovative pulse-detonation steam superheater (PDSSH) with cyclic detonations of ternary mixtures at variation of fuel-to-oxygen equivalence ratio (from 0.14 to 1.77 in propane mixtures and from 0.3 to 1.84 in methane mixtures) and steam volume fraction (from 0 to 0.7) at normal atmospheric pressure. The experiments are supplemented by thermodynamic calculations. Cyclic detonations of ternary propane/methane–oxygen–steam mixtures are proved to generate HSS with temperature exceeding 2250 K, when expanded to the atmospheric pressure. The detonation products of stoichiometric ternary mixtures under consideration can contain up to 80% HSS and up to 17% CO₂ with trace amounts of CO, O₂ and H₂. As a result of deep processing (gasification) of organic wastes by such products a gaseous mixture of CO and H₂ is obtained, which can be further used as a fuel gas for PDSSH operation, heat/electricity production, and as a raw material for production of methanol and synthetic motor fuels. Due to periodic filling of the PDSSH with the cool ternary gas mixture, the temperature of PDSSH walls and inner elements increases insignificantly, so that conventional (not heat-resistant) construction materials can be used for its production.