Study On Preparation For PCC Of Lime Mud

Due to higher silicon content in lime mud produced straw black liquor,so the recovery and recycling of lime mud becomes more difficult,at present the key treatment of lime mud is landfilled,which cause many problems such as secondary pollution.Therefore,straw lime mud resource utilization is becoming value and significant research direction.But the silicon,sulfur and other elements in the green liquor will affect the recovery of the lime mud quality.In this paper,straw PCC preparation has been studied to provide an effective way for the straw lime mud resource utilization.This paper focuses on the effects of green liquid caustic reaction conditions and the green liquor pretreatment conditions on the quality of PCC.The research results are summarized as follows :(1)The optimum technology conditions of laboratory straw pulp alkali recovery preparation of PCC: temperature 110?,time 120 mins,the usage of lime 20 g.The whiteness of lime mud is 92.33%ISO.Ca CO3 takes 95.82%,sedimentation volume 2.8g.ml-1.105?volatile content 0.085%,HCl insoluble 0.22%.(2)Further study of the causticization show that adding different qualities of lime to increase the pre-causticizing stage and after causticization with carbon dioxide or whiteness control agents are added PCC performance will have some impact.after added AR lime,the whiteness of lime mud is 91.07%ISO;added industrial lime its whiteness is 73.92% ISO;two caustic caustic better than some,two analytical grade lime causticizing lime mud whiteness and calcium carbonate content increased by 1.22% ISO and 1.2%,but industrial lime two caustic increased by 4.14% and 4.06%ISO.After the causticization with carbon dioxide,resulting lime mud whiteness and calcium carbonate content will be increased,the use of analytical grade two indicators increased by 0.85%ISO and 1.4%,when the use of industrial-grade lime increased 1.40%ISO and 1.85%;after the end of the causticization without washing lime mud added whiteness control agents,industrial lime resulting lime mud whiteness can be increased 4.48%ISO,reached 80.14%ISO.(3)The condition of green liquor pretreatment have an impact on the PCC quality.The green liquor is treated by Casi O3,Na Al O2 and Ca O can remove the water insoluble matter effectively,And the treatment effect of Ca O,only 20 min can achieve complete settlement.(4)Acid titration of green liquid discovery that,the the beginning p H of green liquor is12.76 and no floccules in it;when the p H dropped to 10.42,white flocculation is appeared in the green liquor.With HCl being added continually,the content of floccules is increased.When the p H is 1.16,the floccules disappeared rapidly.Adding HCl contunually,when the p H dropped under 0.52,the floccules appeared again.