Abstract: A centrifugal compressor is provided with means to centrifugally accelerate a gas stream and to simultaneously centrifugally accelerate a stream of dense small solid particles and discharging both streams into a vane free radial diffuser to form a composite flow in which kinetic energy from the particles is absorbed by the gas molecules while the heat of compression of the gas is absorbed by the solid particles, the composite flow then entering a centrifugal particle separator to give a clean high pressure gas for subsequent utilization.