Influences On BCTMP Pulp Properties By White-water Recycle And Reduction Of DCS Contents In Pulps

In this paper, the DCS properties of the recycled water were analyzed, the compounds of DCS were clarified by GC-MS; Secondly, the influences brought by the recycled water to the bleaching properties of the pulp were studied; then the influences brought by the recycled water to the DCS of both unbleached and bleached pulp were studied; finally, the techniques of treating DCS with alu minium sulfate, pectinase and CPAM were discussed.The result shows that the total DCS in recycled water DCS is about 12g/L, of which about 95% are contributed by dissolved substances(DS); the ash content of the DCS is about 4.2 g/L, of which 96% are contributed by DS. The turbidity of the DCS water is mainly contributed by Colloidal substances (CS); the cationic demand (CD) and COD of the DCS water are mainly contributed by DS; almost all the conductivity is contributed by DS. The composes of DCS were clarified by GC-MS, after ethanolysis, six compounds i.e. galactose, mannose, xylose, arabinose, glucuronic acid and galacturonic acid were clarified. By MTBE extraction, 15compounds including fatty acids, alcohols, Esters were clarified.By Simulation Experiment, the influences of the recycled water on the bleaching properties of the pulp have been studied. Results show the applying of the recycled water almost has no influences on the brightness gain and the strength properties of the bleached pulp.The influences on the DCS of both unbleached and bleached pulp brought by the recycled water have been studied. Results show, by the applying of recycled water, the total DCS of unbleached pulp have been increased from 0.22 g/L to 0.85g/L; the total DCS of bleached pulp have been increased from 3.43 g/L to 4.21 g/L; the CD of the unbleached pulp DCS water has been increased from 36.32μeq/L to 124.89μeq/L; the CD of the bleached pulp DCS water has been increased from 873μeq/L to 998μeq/L. There are more DCS released out from the pulp during the hydrogen peroxide bleaching comparing to the refineing process, compared to the hydrogen peroxide bleaching, The influences on the bleached pulp DCS brought by the recycled water are much slighter. Both of the compounds of the unbleached and bleached pulp DCS water were studied. For unbleached pulp DCS, after ethanolysis,5 carbohydrates had been found , 9 extractives had been found in the MTBE extractives ; for bleached pulp DCS, after ethanolysis,7 carbohydrates had been found ,13 extractives had been found in the MTBE extractives.The cationic demand can be decreased by pectinase treatment in a certain extent. By the Pectinase treatment, when the treatment time is one hour and the dosage of the pectinase is 100U?L, the cationic demand of the DCS water of HuaTai group BCTMP has been decreased by 22%. Also, the alu minium sulphate and CPAM are used to treat the DCS water. When the dosage of alu minium sulphate is 0.7g/L, the CD has almost been decreased to almost zero, when the dosage of CPAM is 50mg/L, the CD has been decreased by 9%.