Method of producing pulp and burning waste liquor obtained thereby
OwnerAnders Vegebyinventor
Life of this patent
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Abstract
Environmental regulations tend to restrict the emissions from pulping platns, which increase the amount of sulphur and chlorine in the cooking liquor to undesirable amounts. This is detrimental to the process and increases the risk of corrosion upon the furnace walls. According to the invention certain metals, preferably iron and/or aluminum are burned together with the waste liquor, and will form compounds with the sulphur and the chlorine, respectively, which are easily separated from the chemicals taking part in the normal process cycle.
Claims6
In a process for producing pulp, in which a cellulose feed stock is cooked in an aqueous liquor containing sulphur, and the resulting waste liquor is burnt in a furnace in order to recover chemicals which are used for preparing cooking liquor to be recycled in the process, the steps of:
- a. introducing an iron compound into the furnace, together with, or in parallel to the waste liquor;
- b. reacting said iron compound within the furnace with the sulphur constituent in the burning waste liquor to form a smelt containing an insoluble iron sulphide;
- c. removing said smelt from the furnace and dissolving said smelt in an aqueous solution to form a weak liquor for recycling in the process;
- d. separating said insoluble sulphide from said solution;
- e. reacting said separated iron sulfide with sulphuric acid to produce FeSO.sub.4 and H.sub.2 S, and separating said FeSO.sub.4 and H.sub.2 S;
- and reacting the FeSO.sub.4 with NH.sub.4 OH to obtain ammonium sulfate, (NH.sub.4).sub.2 SO.sub.4, and iron hydroxide, Fe(OH).sub.2, and recycling the latter as the iron compound to be introduced into the furnace.
In a process for producing pulp, in which a cellulose feed stock is cooked in an aqueous liquor containing chlorine, and the resulting waste liquor is burnt in a furnace in order to recover chemicals which are used for preparing cooking liquor to be recycled in the process, the steps of:
- a. introducing an aluminum compound into the furnace together with, or in parallel to the waste liquor;
- b. reacting said aluminum compound within the furnace with the chlorine constituent of the burning waste liquor to form combustion gases carrying returnable process chemicals and aluminum chloride, said aluminum chloride being volatile at the elevated temperature prevailing in the furnace;
- c. removing said combustion gases from the furnace and separating off said returnable process chemicals from the combustion gases while the same still are at an elevated temperature;
- and thereafter
- d. removing said aluminum chloride from the combustion gases at a lower temperature.
In a process for producing pulp in which a cellulose feed stock is cooked in an aqueous liquor containing sulphur and chlorine, and the resulting waste liquor is burnt in a furnace in order to recover chemicals which are used for preparing cooking liquor to be recycled in the process, the steps of:
- a. introducing an iron compound and an aluminum compound into the furnace together with, or in parallel to the waste liquor;
- b. reacting said iron compound with the sulphur constituent in the burning waste liquor, and said aluminum compound with the chlorine constituent of the burning waste liquor, within the furnace to form a smelt containing an insoluble iron sulphide and combustion gases carrying returnable process chemicals and aluminum chloride, respectively, said aluminum chloride being volatile at the elevated temperature prevailing in the furnace;
- c. removing said smelt from the furnace and dissolving said smelt in an aqueous solution to form a weak liquor for recycling in the process;
- d. separating said insoluble sulphide from said solution;
- e. removing said combustion gases from the furnace and separating off said returnable process chemicals from the combustion gases while the same still are at an elevated temperature;
- and thereafter
- f. removing said aluminum chloride from the combustion gases at a lower temperature.
Dependencies are inferred from the claim text.