Resin acid markers for total resin acid content of in-mill process lines of a TMP/CTMP pulp mill

Abstract

Resin acids are a class of lipophilic extractives present in process waters of pulp and paper mills using softwoods as a furnish. These compounds cause pitch problems and adversely affect paper properties. As pulp and paper mills move toward water systems closure the concentration of these extractives are expected to increase. Therefore, it will become more important to monitor and control extractives content in the process lines of pulp and paper mills. Resin acids are traditionally analyzed by gas chromatography (GC). This method of analysis requires extracting the analytes from a sample matrix, separating by solid phase extraction and derivatizing the resin acids to increase their volatility. Although this process is tedious and expensive and cannot be used as an on-line monitoring system, it does provide quantification of the individual resin acids with a low detection limit. Finding marker compounds for the total resin acid content of an in-mill process water sample may aid in the development of a fast and reliable monitoring system. A preliminary GC analysis of 25 in-mill process water samples established abietic acid as the best single marker for total resin acid content. A correlation of 0.964 was found between the abietic acid concentration and the total resin acid content of these samples. This result led to the analysis of 167 samples from a previous audit of resin acid content of in-mill process water samples. Abietic acid was the single best marker for these samples as well with a correlation of 0.928. An improved correlation of 0.957 was obtained if a combination of isopimaric and abietic acid contents was used as the marker for total resin acid content. Dehydroabietic acid, which has been shown to be a good marker for total resin acid content of mill effluent samples, was a poor marker for in-mill samples. A correlation of only 0.664 was obtained between DHA and total resin acid content of the samples analyzed.