초록 ▼

A process of producing cooking liquor for addition to a digester for enhancement of the yield derived from kraft pulping of wood chips in which a portion of the black liquor is treated with lime under certain conditions and then reused as cooking liquor. The causticizing of the black liquor results

A process of producing cooking liquor for addition to a digester for enhancement of the yield derived from kraft pulping of wood chips in which a portion of the black liquor is treated with lime under certain conditions and then reused as cooking liquor. The causticizing of the black liquor results in the generation of polysulfide ions and allows, through the formation of calcium-organo complexes, for the carryover of soluble calcium with the black liquor. The presence of calcium ions synergistically enhances the effectiveness of polysulfide such that the use of the new cooking liquor results in pulp yield increases of several percentage points for the same lignin content when compared to conventional kraft pulping.

대표청구항 ▼

In the process of producing kraft cooking liquor for addition to a digester for enhancement of the yield derived from kraft pulping of wood chips in which black liquor obtained from washing digested pulp is concentrated and burned, the resulting smelt is dissolved in water and the resulting green li

In the process of producing kraft cooking liquor for addition to a digester for enhancement of the yield derived from kraft pulping of wood chips in which black liquor obtained from washing digested pulp is concentrated and burned, the resulting smelt is dissolved in water and the resulting green liquor is causticized with a calcium salt to produce a white liquor for use in digestion, the steps of treating at least a part of the black liquor by the direct addition thereto of a calcium salt or base in the presence of air to generate solublized calcium ions and, polysulfide ions in an amount sufficient to increase the pulp yield, and returning the treated black liquor to the digester. An improved kraft cooking liquor for digestion of wood chips which comprises a mixture of a white pulping liquor and a black liquor treated according to the method of claim 1 to provide polysulfide and calcium ions.