ECONOMICALLY EFFECTIVE METHOD OF SULFATE VARIATION WITH USE OF POLYSULPHIDE CREAM Russian patent published in 2018 - IPC D21C1/06 D21C3/02 

FIELD: pulp industry.

SUBSTANCE: invention relates to process for producing sulfate cellulose (kraft pulp) with increased yield of cellulose from lignin-containing cellulosic material using polysulfide cooking liquor. Method for producing sulfate cellulose with increased yield of cellulose from lignin-containing cellulosic material using polysulfide cooking liquor involves supply of pre-impregnated lignin-containing cellulosic material first to upper zone of first vertical tank operating under pressure created in tank upper zone, not exceeding 0.2 bar, and providing, in the first upper tank, lignin-containing cellulosic material; loading at least 80 % of total charge of alkaline cooking liquor in form of polysulfide liquor into the first reservoir and providing downstream liquor level below said upper level, before addition of polysulfide liquor, said polysulfide liquor is heated to temperature above boiling point, which allows water to be evaporated from polysulfide liquor, wherein vapor is retained in volume of lignin-containing cellulosic material located above downstream liquor level; maintaining suspended lignin-containing cellulosic material in the first reservoir for time required to achieve H-factor of at least 1; feeding suspended lignin-containing material from lower region of first reservoir to upper zone of second vertical tank, where lignin-containing cellulosic material is cooked at maximum cooking temperature in range of 130–160 °C to finite number of Kappa below 40, as any remaining alkaline cooking liquor is added, during feed to second tank or cooking in second tank.

EFFECT: implementation of invention makes it possible to obtain economically efficient system, including in aspects related to investment, as well as in aspects related to heat savings in operation of method.

13 cl, 1 dwg