METHOD OF EXTRACTING SODIUM COMPOUNDS FROM GREEN LYE AND WASTE GASES OF SODIUM-BASE PULP PRODUCTION

摘要

The invention relates to a method for recovering sodium chemicals from green liquor by precarbonating green liquor by means of flue gases, by bringing a precarbonated solution into contact with a sodium bicarbonate solution and by stripping hydrogen sulphide from the so obtained reaction mixture by means of steam, for producing hydrogen sulphide gas and a sodium carbonate solution, which sodium carbonate solution is so pure, in relation to sodium sulphide that it can directly be led into the washing of the flue gases and into a carbonation stage, for producing the sodium bicarbonate solution. In order to save steam and sodium carbonate all precarbonated solution is not treated to the sodium sulphide free solution, which is required by a scrubber, but a part is discharged at higher sodium sulphide content by dividing the stripping into two stages which take place one above the other in the same tower, whereby a part of a solution obtained from the first stripping stage is led directly into the second stripping stage and the steams containing hydrogen sulphide, obtained from the second stripping stage are led directly into the first stripping stage.