Remodeling Effects and Operating Experience of Kraft Pulp Production

Hashimoto Kentaro

doi:10.2524/jtappij.71.51

Fiber lines in Mishima mill have been modified and extended step by step along with new installations of paper machines. The total energy cost was pushed up due to increased number of equipment and distance of pulp traffic line.Most recently, with a change of the production structure after the Lehman shock, two of softwood fiber lines were unified to one. Hardwood fiber line was also retrofitted to get more production and to reduce energy. We decided to modify our softwood fiber line to get more production and energy efficiency improvement, making the most of equipment that had been idle after the retrofit of hardwood fiber line to reduce capital investment.The concepts of the remodeling are as follows.1. Upsizing the equipment by using larger one that had been idle2. Operational improvement by modifying the existing cooking system3. Chemical reduction with the washing and screening capacity upgrade4. Improvement of energy efficiency by heat recovery flow changeTo increase the production rate, continuous digester has been modified to the Compact Cooking G1^TM, which could accelerate the downflow of the chip column in the digester, and the capacity of screening and bleaching process has been upgraded.At the startup, we have experienced quality fluctuations and increase of chemical consumption due to the digester operation which was not stable, but we stabilized the operation by adjusting multi charges feeding ratio of white liquor, liquor-to-wood ratioand chip compaction in digester. After this modification, the softwood production has been increased from 650 t/day to 1,000 t/day with the most highly capacity in Japan.

Remodeling Effects and Operating Experience of Kraft Pulp Production

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