Partial Borate Autocausticizing Technology, 2002 Fall Technical Conference

Partial borate autocausticizing is becoming a viable technology to provide incremental recausticizing capacity to pulp mills that are recaust limited. Over six mill trials, conducted to provide 10% to 25% increase in recausticizing capacity, have shown that the technology works and there are no major side effects on any parts of the mill operations. A great advantage of the technology is that it does not require capital investment since the autocausticizing reaction occurs in the recovery boiler; however, this may make the conversion of the autocausticizing reaction sensitive to recovery boiler operations. The addition of borate to the liquor increases the black liquor solids fired in the boiler, decreases the heating value of black, and may result in a decrease in steam production especially at high levels of autocausticizing; however, the decrease in steam production and boiler fouling issues have been manageable during the mill trials. No negative effect has been found on pulp properties, equipment corrosion, digester operations, pulp washing, black liquor evaporation, lime recausticizing, and kiln operations. Partial borate autocausticizing offers cost saving and environmental benefits to kraft mills that are recaust limited.