NOVELTY - A solid feed system (12), comprises: a supersonic nozzle (44); an isolated injection section (46) positioned downstream from the supersonic nozzle, having a port (52) for injection of solid feedstock; and a supersonic diffuser (54) positioned downstream from the isolated injection section.    USE - As a solid feed system used in gasification system for reacting a solid feedstock under pressure (Claimed) in application e.g. coal and biomass gasification plant.    ADVANTAGE - Use of a converging/diverging diffuser having a variable geometry, such as the supersonic diffuser, any region of the supersonic diffuser that may experience significant impingement of fluid flow, such as regions that protrude into the flow stream, may be positioned away from a region of the flow stream that may have the highest solid feedstock concentration. This avoids impingement of solid feedstock particles against the walls of the supersonic diffuser and thus avoids erosion of the supersonic diffuser, as observed with existing solid pumping systems, like the Stamet pump. The solid feed system is improved and suitable for use in elevated pressure processes, such as coal and biomass gasification plants.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following    (1) a gasification system, comprising: a fluid inlet port (20); a solid feed system, comprising: a plenum operably associated with the fluid inlet port; the supersonic nozzle downstream from the plenum; an isolated injection section positioned downstream from the supersonic nozzle and having a port for injection of solid feedstock; and a supersonic diffuser positioned downstream from the isolated injection section; and a reaction chamber () downstream of the solid feed system; and    (2) a method of reacting a solid feedstock under pressure, involving: directing a fluid flow through a supersonic nozzle to provide a supersonic flow stream; directing the supersonic flow stream through an isolated injection section at a static pressure at least 50% lower than an operating pressure within a reaction chamber; feeding a solid feedstock from an ambient pressure environment into the isolated injection section; converting fluid dynamic pressure of the supersonic flow stream to fluid static pressure with a supersonic diffuser to provide a pressurized fluid flow; and directing the pressurized fluid flow and solid feedstock into the reaction chamber.    DESCRIPTION OF DRAWING(S) - The figure shows a longitudinal cross-sectional view of the solid feed system.    Solid feed system (12)    Fluid inlet port (20)    Supersonic nozzle (44)    Isolated injection section (46)    Port for injection of solid feedstock (52)    Supersonic diffuser (54)