NOVELTY - Removing pollutants from high temperature fluid (30), involves providing two conduits (12, 22) separated by a substrate (24) which permits the transfer of heat between the conduits; passing the fluid through first conduit and into a reaction chamber (16), where heat is removed from the fluid in first conduit and the heat is transferred through substrate to second conduit; lowering the temperature of reactant fluid; removing fluid in the chamber; passing product fluid (34) through second conduit; and applying heat to product fluid as the fluid passes through second conduit.    USE - For performing an intermediate reaction process on a fluid to remove pollutants, including sulfur compounds, from reactant fluid (claimed); useful for removing other pollutants such as mercury, ammonia, COS, alkali, and particulates from fluid, such as fuel cell syngas.    ADVANTAGE - The process facilitates sulfur extraction from high temperature fluids while maintaining thermal efficiency. The process lowers the temperature of a fluid, removes sulfur, and then heats the fluid back up while losing as little thermal energy as possible to the environment. Thus, thermal energy efficiency is enhanced and overall system efficiency increased. The process efficiently removes pollutants (e.g. sulfur compounds) from high temperature fluid.    DETAILED DESCRIPTION - Removing pollutants from high temperature fluid (30) at a lower temperature, involves providing a first conduit (12) and a second conduit (22) separated by a substrate (24) which is common to both the first conduit and the second conduit and permits the transfer of heat between the first conduit and the second conduit; passing the fluid through first conduit and into a reaction chamber (16), where heat is removed from the reactant fluid as the reactant fluid passes through the first conduit and the heat is transferred through the substrate to the second conduit; lowering the temperature of the reactant fluid; performing the intermediate reaction with the reactant fluid in the reaction chamber to create a product fluid (34); passing the product fluid out of the reaction chamber and through second conduit in fluid communication with the reaction chamber; and applying heat transferred from the reactant fluid in the first conduit through the substrate to the product fluid as the product fluid passes through the second conduit.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of a heat recirculation process.    First conduit (12)    Reaction chamber (16)    Second conduit (22)    Substrate (24)    Reactant fluid (30)    Product fluid. (34)