NOVELTY - Reacting compounds, comprises: directing a liquid into a helical constrained flow (37) having an outer circumferential flow surface, the liquid containing at least one of a catalyst and a reactant; sparging a fluid reactant into the helical constrained flow from the outer circumferential flow surface to form a fluid product; and removing the fluid product.    USE - The method is useful for: reacting compounds to form fluid product e.g. methanol and dimethyl ether (all claimed); and reactions including refining and/or treatment of heavy petroleum residues, bio-oils, tar sands, coal-derived liquids and shale oil.    ADVANTAGE - The method carried out in the fluid-sparged helical channel reactor: provides excellent dispersion of gaseous reactants with a catalyst slurry; requires short residence time and small consumption of catalysts; enables reduction in capital and operational costs of syngas processes; can readily sized and scaled up; suppresses unwanted side reactions; and provides high syngas conversion and excellent process heat transfer management.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for a fluid-sparged helical channel reactor (10), comprising: a constrained-flow unit located within a reactor body (12), the unit having an inner wall and an outer wall configured to produce a helical constrained flow along an enclosed helical flow path around an axial interior volume, where at least part of the outer wall comprises a sparging portion to allow fluid reactant to be sparged into the helical constrained flow; a liquid inlet (32) fluidly connected to the reactor body and configured to allow addition of a liquid into the enclosed helical flow path; a sparging fluid inlet fluidly connected to the reactor body for supply of a sparging fluid to the sparging portion of the constrained-flow unit; a liquid outlet fluidly connected to the reactor body to allow removal of liquid from the constrained-flow unit; and a gas outlet fluidly associated with the enclosed helical flow path to allow removal of gases from the enclosed helical flow path.    DESCRIPTION OF DRAWING(S) - The figure shows a cross-sectional view of a fluid-sparged helical channel reactor for gas feed and product applications.    Fluid-sparged helical channel reactor (10)    Reactor body (12)    Plenum chamber (26)    Liquid inlet (32)    Helical constrained flow (37)