Heat exchange reactor with reduced metal dusting

A process for converting a first gas feed comprising CO2 and H2 to a synthesis gas stream, via a CO2 shift reaction of said first gas feed in a heat exchange reactor, HER, said HER comprising

• at least one process side and at least one heating side, wherein the process side of the HER comprises a process side inlet and a process side outlet,
• wherein the process side of the HER comprises a first reaction zone disposed closest to the process side inlet, and
• wherein process side of the HER comprises a second reaction zone disposed closest to the process side outlet,
• wherein the heating side of the HER comprises a heating side inlet and—optionally—a heating side outlet,
• said at least one process side and said at least one heating side, being arranged such that heat transfer from heating side to at least a part of said process side is possible,
• said process comprising the steps of:
• supplying the first gas feed to the process side of the HER via said process side inlet;
• supplying a heating fluid to the heating side of the HER via said heating side inlet, and allowing heat transfer from said heating fluid to the process side of the HER;
• carrying out an overall exothermic reaction of said first gas feed in the first reaction zone, wherein the overall exothermic reaction comprises at least the following reactions, which have a net progress from left to right:
• carrying out an overall endothermic reaction of gas from said first reaction zone in the second reaction zone, wherein the overall endothermic reaction comprises at least the following reactions, which have a net progress from left to right:
• outletting the synthesis gas stream from the process side via the process side outlet;
• optionally in admixture with a cooled fluid, and
• optionally outletting a cooled fluid from said heating side, via the heating side outlet.