Method for producing acetate grade dissolving pulp from poplar residual slabs

Abstract

The disclosure relates to the technical field of dissolving pulp preparation, and particularly relates to a method for producing acetate grade dissolving pulp utilizing poplar residual slabs. The method comprises the following steps: adding an auxiliary agent for prehydrolysis, performing a Soda/AQ cooking I segment, performing a Soda/AQ cooking II segment, performing OpDQEPP bleaching and performing enzyme coprocessing, thereby preparing high-purity high-reactivity poplar residual slab acetate grade dissolving pulp. In the method, used chemicals are clean and environmental friendly, and production process is clean.

What is claimed is: 
     
         1 . A method for producing acetate grade dissolving pulp utilizing poplar residual slabs, comprising:
 (1) adding an auxiliary agent for prehydrolysis: a liquid ratio is 1:(4˜10), the addition amount of a hydrolysis auxiliary agent is 0.1˜2.0% of the mass of oven dry poplar residual slab, a hydrolysis temperature is 80˜170° C., preservation time is 10˜180 minutes, the hydrolysis auxiliary agent is a mixture obtained by mixing sodium borate, magnesium sulfate, nonylphenol polyoxyethylene ether phosphate and tetrasodium iminodisuccinate in a mass ratio of 1:1:1:1;   (2) performing a Soda/AQ cooking I segment;   (3) performing a Soda/AQ cooking II segment;   (4) performing O p D Q E P P bleaching; and   (5) performing enzyme coprocessing: the concentration of pulp is 2˜10%, the temperature is 30˜50° C., treatment time is 60 min, pH=4.0˜7.0, the amount of polyaspartic acid is 0.01%˜1.0% of the mass of oven dry pulp, the amount of OP-13 is 0.001˜0.01% of the mass of oven dry pulp, the amount of OP-15 is 0.001˜0.01% of the mass of oven dry pulp, the amount of endoglucanase is 0.1˜0.6 IU/gpulp, the amount of xylanase is 2˜4 XU/gpulp, and the amount of pectase is 0.1˜10 IU/gpulp.   
     
     
         2 . The method according to  claim 1 , wherein, the process conditions of the Soda/AQ cooking I segment are as follows: the amount of alkali is 5˜15% of the mass of oven dry pulp based on Na 2 O, a liquid ratio is 1:(3˜8), the amount of magnesium hydroxide is 0.5% of the mass of oven dry pulp, the amount of sodium sulfite is 1.0˜10.0% of the mass of oven dry pulp, the amount of AQ is 0.05% of the mass of oven dry pulp, the temperature is 80˜120° C., and preservation time is 10˜180 minutes. 
     
     
         3 . The method according to  claim 1 , wherein, the process conditions of the Soda/AQ cooking II segment are as follows: the amount of alkali is 5˜25% of the mass of oven dry pulp based on Na 2 O, the amount of magnesium hydroxide is 0.5% of the mass of oven dry pulp, the amount of sodium sulfite is 1.0˜10.0% of the mass of oven dry pulp, a liquid ratio is 1:(3˜10), the amount of AQ is 0.05% of the mass of oven dry pulp, the temperature is 140˜180° C., and preservation time is 10˜240 minutes. 
     
     
         4 . The method according to  claim 1 , wherein, the process conditions of O p D Q E P P bleaching are as follows: the oxygen pressure of O p  bleaching is 0.4˜0.6 Mpa, the concentration of pulp is 10%, the amount of MgSO 4  is 0.6% of the mass of oven dry pulp, the amount of NaOH is 1.0˜3.0% of the mass of oven dry pulp, the amount of H 2 O 2  is 0.5˜3.0% of the mass of oven dry pulp, the temperature is 70˜110° C., and preservation time is 60 min. 
     
     
         5 . The method according to  claim 1 , wherein, the process conditions of O p D Q E P P bleaching are as follows: the reaction time of Q D  bleaching process is 10˜120 minutes, T=30±2° C., the concentration of pulp is 2˜8%, pH=1˜3, the amount of sodium chlorite is 0.2˜6.0% of the mass of oven dry pulp, and the amount of IDS is 0.01˜1.0% of the mass of oven dry pulp. 
     
     
         6 . The method according to  claim 1 , wherein, the process conditions of O p D Q E P P bleaching are as follows: the reaction time of the E p  extraction process is 30˜180 min, the amount of MgSO 4 is 1.0˜5.0% of the mass of oven dry pulp, the amount of NaOH is 0.5˜5.0% of the mass of oven dry pulp, the amount of H 2 O 2  is 1.0˜5.0% of the mass of oven dry pulp, the amount of IDS is 0.01˜1.0% of the mass of oven dry pulp, the concentration of pulp is 8%, and the temperature is 70˜95° C. 
     
     
         7 . The method according to  claim 1 , wherein, the process conditions of O p D Q E P P bleaching are as follows: the reaction time of P bleaching is 60˜180 min, the amount of MgSO 4  is 0.5% of the mass of oven dry pulp, the amount of NaOH is 0.4% of the mass of oven dry pulp, the amount of NaAC is 0.4% of the mass of oven dry pulp, the amount of H 2 O 2  is 1.0˜5.0% of the mass of oven dry pulp, the concentration of pulp is 10%, and the temperature is 80˜95° C. 
     
     
         8 . The method according to  claim 1 , comprising the following steps:
 (1) adding an auxiliary agent for prehydrolysis: a liquid ratio is 1:6, the addition amount of the auxiliary agent is 0.4% of the mass of oven dry pulp, the temperature is 160° C., preservation time is 60 minutes;   (2) performing a Soda/AQ cooking I segment: the amount of alkali is 5% of the mass of oven dry pulp, a liquid ratio is 1:4, the amount of magnesium hydroxide is 0.5% of the mass of absolutely dry pulp, the amount of sodium sulfite is 5.0% of the mass of oven dry pulp, the amount of AQ is 0.05% of the mass of oven dry pulp, T max =100° C.±2° C., and preservation time is 60 minutes;   (3) performing a Soda/AQ cooking II segment: the amount of alkali is 18% of the mass of oven dry pulp, the amount of magnesium hydroxide is 0.5% of the mass of oven dry pulp, the amount of sodium sulfite is 3.0% of the mass of oven dry pulp, a liquid ratio is 1:7, the amount of AQ is 0.05% of the mass of oven dry pulp, the maximum temperature is 160° C., and preservation time is 120 minutes;   (4) performing O p D Q E P P bleaching: the oxygen pressure of O P  bleaching is 0.5 Mpa, the concentration of pulp is 10%, the amount of MgSO 4  is 0.6% of the mass of oven dry pulp, the amount of NaOH is 2.0% of the mass of oven dry pulp, the amount of H 2 O 2  is 1.0% of the mass of oven dry pulp, the temperature is 95° C., and preservation time is 60 min; the reaction time of the Q D  bleaching process is 60 minutes, T=30±2° C., the concentration of pulp is 4.0%, pH=1.5, the amount of sodium chlorite is 3.0% of the mass of oven dry pulp, and the amount of IDS is 0.05% of the mass of oven dry pulp; the reaction time of the E p  extraction process is 90 min, the amount of MgSO 4  is 0.5% of the mass of oven dry pulp, the amount of NaOH is 3.0% of the mass of oven dry pulp, the amount of H 2 O 2  is 2.0% of the mass of oven dry pulp, the amount of IDS is 0.05% of the mass of oven dry pulp, the concentration of pulp is 8%, and the temperature is 85° C.; the reaction time of P bleaching is 120 min, the amount of MgSO 4  is 0.5% of the mass of oven dry pulp, the amount of NaOH is 0.4% of the mass of oven dry pulp, the amount of NaAC is 0.4% of the mass of oven dry pulp, the amount of H 2 O 2  is 3.0% of the mass of oven dry pulp, the concentration of pulp is 10%, and the temperature is 90° C.; and   (5) performing enzyme coprocessing: the concentration of pulp is 5%, the temperature is 40° C., treatment time is 60 min, pH=5.0, the amount of polyaspartic acid is 0.05% of the mass of oven dry pulp, the amount of OP-13 is 0.005% of the mass of oven dry pulp, the amount of OP-15 is 0.005% of the mass of oven dry pulp, the amount of endoglucanase is 0.2 IU/gpulp, the amount of xylanase is 3 XU/gpulp, and the amount of pectase is 3 IU/gpulp.   
     
     
         9 . The method according to  claim 1 , wherein, in the step (1), the used poplar residual slab is 10˜30 mm in length, the content of pentosan is 22.3˜24.3%, and the content of α-cellulose is 43.0˜45.0%.