discharge of under calcined trona ore the steam and carbon dioxide evolved in reactor 18 is passed to waste a heat boiler not shown via line 21 where the bulk of the steam is condensed along with a small quantity of carrier liquid vaporized in reactor 18 low pressure steam from the waste heat boiler can be utilized for heating purposes condensed steam is vented from reactor 18 via line 22 and conveyed to generator 23 via line 22 where the water is used to generate steam from introduction into reactor 18 via line 19 as described above the hot slurry of sodium carbonate and carrier liquid is conveyed to settler 24 via line 25 where the coarser particles of sodium carbonate settle out leaving behind a slurry of finer particles of sodium carbonate and liquid carrier the coarser particles are conveyed directly to dissolver 26 via lines 27 and 30 by passing interchanger 28 the hot slurry of fine particles and carrier liquid is conveyed to interchanger 28 via line 29 where the slurry is cooled and the cooled slurry is passed from interchanger 28 to dissolver 26 via line 30 water or weak aqueous sodium carbonate solution is introduced.