A compact sulfur recovery system is disclosed which comprises a primary structure including a catalytic partial oxidation reaction zone, a first temperature-control zone, a first Claus catalytic reaction zone, a second temperature-control zone, a first liquid sulfur outlet, and a first effluent gas outlet. In some embodiments, a secondary structure follows the primary structure and comprises a second Claus catalytic reaction zone, a third temperature-control zone, a second liquid sulfur outlet, and a second effluent gas outlet. One or more components of the system employ heat transfer enhancement material in the temperature-control zones, and one or more components deter accumulation of liquid sulfur in the Claus catalytic reaction zones. A process for recovering elemental sulfur from hydrogen sulfide-containing gas streams comprises regulating the temperature of certain components to favor the partial oxidation reaction, and the Claus reaction, as appropriate, and deters pooling of liquid sulfur on the Claus catalyst(s).