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‘Total Active Chlorine (TAC) = (ClO2*2.63 + H202*2.09 + O3*2.5); “Includes yield loss across O/O stage.

Table 4 ‘Total Active Chlorine (TAC) = (ClO2*2.63 + H202*2.09 + O3*2.5); “Includes yield loss across O/O stage.

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Table 1. General oxygen delignification and bleaching conditions RESULTS AND DISCUSSION
Table 1. General oxygen delignification and bleaching conditions RESULTS AND DISCUSSION
Oxygen Delignification Results ee Ee ee ae ae Sa eee ae: ee Eee ee ee The main factors affecting eucalyptus kraft pulp oxygen delignification efficiency are kappa number, HexAs content, and carryover to the bleach plant. The overall oxygen delignification efficiency, as measured by the kappa drop across the O/O stage, increased with increasing kappa number, but the efficiency based only on the “true lignin kappa number” tended to decrease (Table 3). “True lignin kappa number” is the one derived only from lignin, after subtraction of the kappa number due to hexenuronic acids, considering the ratio 10 mmol/kg HexA equals to 1 kappa number unit. The lignins from higher kappa pulps tend to contain less free phenolic hydroxyl groups (Gellerstedt 1996), which are the main sites for oxygen reactions, and this may explain the slightly lower efficiency based solely on lignin. However, the higher kappa pulps contained, proportionally, more lignin available for reaction than the lower kappa ones because of their similar or lower HexAs contents. Therefore, the higher kappa pulps produced higher overall oxygen delignification efficiency than the lower kappa ones, given that HexAs do not react with oxygen (Vuorinen et al. 1996). In this work, the influence of HexAs on kappa number was calculated assuming that 10 mmol/kg pulp of HexAs is equivalent to 1 kappa unit (Vuorinen et al. 1996). This ratio has been somewhat questioned in a later work by Li and Gellerstedt, 1997 who claim a ratio of 11.6-11.9 mmol/kg pulp of HexAs per kappa unit. were observed at kappa 14. The aforementioned results confirmed the very well known concept that higher kappa pulps present higher yield and viscosity. The question which remains is: Is the wood savings derived from this improved yield sufficient to pay for the additional chemicals cost required to bleach the higher kappa pulps, considering the low cost of eucalyptus wood in Brazil?
Oxygen Delignification Results ee Ee ee ae ae Sa eee ae: ee Eee ee ee The main factors affecting eucalyptus kraft pulp oxygen delignification efficiency are kappa number, HexAs content, and carryover to the bleach plant. The overall oxygen delignification efficiency, as measured by the kappa drop across the O/O stage, increased with increasing kappa number, but the efficiency based only on the “true lignin kappa number” tended to decrease (Table 3). “True lignin kappa number” is the one derived only from lignin, after subtraction of the kappa number due to hexenuronic acids, considering the ratio 10 mmol/kg HexA equals to 1 kappa number unit. The lignins from higher kappa pulps tend to contain less free phenolic hydroxyl groups (Gellerstedt 1996), which are the main sites for oxygen reactions, and this may explain the slightly lower efficiency based solely on lignin. However, the higher kappa pulps contained, proportionally, more lignin available for reaction than the lower kappa ones because of their similar or lower HexAs contents. Therefore, the higher kappa pulps produced higher overall oxygen delignification efficiency than the lower kappa ones, given that HexAs do not react with oxygen (Vuorinen et al. 1996). In this work, the influence of HexAs on kappa number was calculated assuming that 10 mmol/kg pulp of HexAs is equivalent to 1 kappa unit (Vuorinen et al. 1996). This ratio has been somewhat questioned in a later work by Li and Gellerstedt, 1997 who claim a ratio of 11.6-11.9 mmol/kg pulp of HexAs per kappa unit. were observed at kappa 14. The aforementioned results confirmed the very well known concept that higher kappa pulps present higher yield and viscosity. The question which remains is: Is the wood savings derived from this improved yield sufficient to pay for the additional chemicals cost required to bleach the higher kappa pulps, considering the low cost of eucalyptus wood in Brazil?
Bleaching Results
Bleaching Results
"Vege A ate ce PL ee i RAGS TRIPS EA BO! 1 11 a ER ORO 6 oR EO OE Total Active Chlorine (TAC) = (ClO2*2.63 + H202*2.09 + O3*2.5); “Includes yield loss across O/O stage.
"Vege A ate ce PL ee i RAGS TRIPS EA BO! 1 11 a ER ORO 6 oR EO OE Total Active Chlorine (TAC) = (ClO2*2.63 + H202*2.09 + O3*2.5); “Includes yield loss across O/O stage.
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