TMP properties and refiner conditions in a CD82 chip refiner at different operation points. Part II : Comparison of the five tests

This paper is part two of a study on a CD 82 TMP chip refiner where relations between changes in the process conditions and changes in the properties of the produced pulp are investigated. Focus is on the ratio between tensile index and specific energy consumption when results from five tests are compared. Pulp properties were measured for composite pulp samples taken from the refiner blow line. Residence times and pulp consistencies were estimated by use of the extended entropy model. Clearly, an increase in specific energy does not necessarily implicate an increase in strength properties of the pulp produced. It is of high importance to have access to information about the refining zone conditions when searching for an optimal operation point in terms of the ratio between tensile index and specific energy. In these tests, this ratio had a maximum at about 55 % measured blow line consistency. Unfavourable operating conditions were identified at high pulp consistencies, especially after the FZ, where pulp consistencies well above 70 % were observed. The estimated residence time for each refining zone responded differently when applying changes in production rate, plate gaps and dilution water flow rates. In conclusion, the results associated with estimated pulp consistencies where easier to interpret compared with results for residence times, implying that additional tests are required for the latter variable. In addition to tensile index, pulp properties like freeness, Somerville shives and light scattering coefficient were included in the analysis.