Process wherein a low CO2 content process gas generated by an ammonia-soda process unit or a refined sodium bicarbonate unit is enriched by using a Temperature Swing Adsorption CO2 concentration module into a CO2 enriched gas whose CO2 content is increased by at least +10% by volume on dry gas basis relative to the process gas, and which is subsequently recycled to the ammonia-soda process unit or optionally to the refined sodium bicarbonate unit, in order: to produce sodium carbonate, or sodium bicarbonate, or to carbonate at least part of effluent from the unit for producing sodium carbonate or bicarbonate. The TSA CO2 concentration module comprises a stator and a rotor connected to the stator and rotatable relatively to the stator about a rotational axis, the rotor comprising a plurality of sectors, each sector containing a separation device to separate at least part of the CO2 from the process gas which is led into the separation device, and each sector being fluidically connected with at least one rotary active valve.