Process comprising exothermal catalytic reaction of a synthesis gas and related plant

A synthesis process, comprising:

• steam reforming a gaseous hydrocarbon feedstock, thereby obtaining a synthesis gas;
• exothermically reacting said synthesis gas in the presence of a catalyst, thereby obtaining a synthesis product;
• removing heat from said exothermal reaction by producing steam, wherein at least part of said steam provides a heat input to the reforming of said hydrocarbon feedstock;
• wherein the steam reforming of the hydrocarbon feedstock includes:
• a) forming a mixture containing steam and hydrocarbons by at least a step of adding a first stream of water to the hydrocarbon feedstock in a saturating tower, said stream of water being pre-heated by indirect heat exchange, prior to admission into said tower, with at least a portion of the steam produced by removing heat from the exothermal synthesis reaction;
• b) heating said mixture by indirect heat exchange with at least part of said synthesis gas;
• and
• c) reforming said mixture after said heating step b).