Wet pressing of wheat straw pulp - correlations between dewatering parameters

The paper presents test results on wet pressing of paper sheets containing various proportions of different and modified non-wood pulps. The kraft eucalyptus pulp used in the paper sheets was partly substituted by various amounts of non-wood pulps, while the kraft pine pulp content was kept constant at 20% in the sheets. The dewatering test results were clearly dependent on the amount of non-wood pulp in the paper sheet. The CSF value, SR number, drainage time in a sheet mould as well as WRV were measured for the pulps. The dry solids content was determined for different stages of pressing. The WRV value correlated best with the dry solids content during wet pressing. WRV seems to be a fairly good indicator to predict the behavior of pulp furnishes containing non-wood pulp during wet pressing. Laborious experimental work can be reduced by concentrating on the WRV value. The drying of the pulp sample, cooking method and fines removal had strong effects on the dewatering properties during wet pressing of furnishes containing non-wood pulp. Dried non-wood pulp prepared with an acidic cooking process behaved the same way during wet pressing as the reference kraft eucalyptus/pine pulp.