Method of producing kraft pulp using an acid prehydrolysis and pre-extraction
First Claim
1. A method of producing carbohydrate material and kraft pulp from a liquid slurry of comminuted cellulosic fiber material comprising the steps of continuously:
- (a) subjecting the liquid slurry of comminuted cellulosic fiber material to mild acid prehydrolysis, by subjecting said material to an acid concentration of, or equivalent to, about 0.2-0.5 percent H2 SO4, and a temperature of about 120°
C. or less;
(b) subjecting the slurry of prehydrolized comminuted cellulosic fiber material to mild caustic pre-extraction, by subjecting said material to a caustic concentration of, or equivalent to, about 0.5-4.0 percent NaOH, and at a temperature of about 60°
-90°
C.;
(c) removing hydrolysate, having carbohydrate material, released during the practice of steps (a) and (b) from the comminuted cellulosic material while continuously practicing steps (a) and (b); and
(d) effecting kraft cooking of the prehydrolized, pre-extracted comminuted cellulosic fiber material to produce kraft pulp.
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Accused Products
Abstract
A method for produce both kraft pulp and alcohol from hardwood chips or the like. The chips are subjected to mild acid prehydrolysis following by mild caustic pre-extraction. The withdrawn hydrolysate has insufficient furfural to inhibit microorganism growth, and both the hexose and pentose sugars in the hydrolysate are fermented to ultimately produce ethanol, butanol, or the like. The chips - after caustic pre-extraction - are subjected to a sulphate cook, and wash, and the resultant pulp is kraft pulp and even has viscosity and tear strength characteristics more desirable than that of conventional kraft pulp. The pulp can be subjected to oxygen delignification, and achieve a higher K number in fewer subsequent bleaching stages than conventional kraft pulp.
119 Citations
20 Claims
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1. A method of producing carbohydrate material and kraft pulp from a liquid slurry of comminuted cellulosic fiber material comprising the steps of continuously:
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(a) subjecting the liquid slurry of comminuted cellulosic fiber material to mild acid prehydrolysis, by subjecting said material to an acid concentration of, or equivalent to, about 0.2-0.5 percent H2 SO4, and a temperature of about 120°
C. or less;(b) subjecting the slurry of prehydrolized comminuted cellulosic fiber material to mild caustic pre-extraction, by subjecting said material to a caustic concentration of, or equivalent to, about 0.5-4.0 percent NaOH, and at a temperature of about 60°
-90°
C.;(c) removing hydrolysate, having carbohydrate material, released during the practice of steps (a) and (b) from the comminuted cellulosic material while continuously practicing steps (a) and (b); and (d) effecting kraft cooking of the prehydrolized, pre-extracted comminuted cellulosic fiber material to produce kraft pulp. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method of treating cellulosic fiber material utilizing a first vessel and a separate second vessel, said method comprising the steps of continuously:
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(a) feeding comminuted cellulosic fiber material entrained in treatment liquid to a top portion of the first vessel; (b) effecting mild acid prehydrolysis in an upper portion of the first vessel, by subjecting the material to an acid concentration of, or equivalent to, about 0.2-0.5 percent H2 SO4, and a temperature of about 120°
C. or less;(c) effecting mild caustic pre-extraction in a lower portion of the first vessel, by subjecting the material to a caustic concentration of, or equivalent to, about 0.5-4.0 percent NaOH, and at a temperature of about 60°
-90°
C.;(d) withdrawing hydrolysate from a screen of the first vessel; (e) withdrawing liquid from a top portion of the first vessel to feed it back to entrain further feed comminuted cellulosic fiber material; (f) withdrawing prehydrolized and pre-extracted fiber material from the bottom of the first vessel; (g) feeding the material withdrawn from the bottom of the first vessel to the top of the second vessel; (h) effecting sulfate digestion of the fiber material in the second vessel; (i) withdrawing liquid from the top portion of the second vessel and returning it to the bottom of the first vessel; and (j) withdrawing pulp from the bottom of the second vessel. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification