Abstract
A new two-stage refiner mechanical pulping system utilizing the well-known reduction of energy to rupture in the wood structure at elevated temperature well above the softening point of lignin has been offered by Sunds Defibrator AB, with the new process name Thermopulp®, in the production of mechanical pulp for printing grades. In this paper, a summary of mill scale trials of Thermopulp® concept carried out on Scandinavian spruce at Ortviken, SCA is presented ; about 20% of refining energy consumption was reduced with equivalent pulp qualities except a small reduction in brightness and tear index compared to the referenced conventional TMP system for news quality pulp. Application of the same concept to TMP reject pulp refining has also been proven with acceptable result. Extending the raw material reference base, some pilot plant trials have also been carried out on Pines with encouraging results. Totally 4, 500 t/d of printing grade pulp plants designed on Thermopulp® process have been installed in Sweden, Canada and Chile and under operation with great success. Now a users group has been formed in North America and started realistic activities to exchange and divide all experience and requirement on research and optimization of the new process, with the common goal of 40% energy saving in the near future. An interstage bleaching in the new process is also one technology shall be chased and developed.
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