Tissue Paper Production Research Articles

EC treatment for reuse of tissue paper wastewater: Aspects that affect energy consumption

The need for more rational use of water also calls for more efficient usage. An example is the production of tissue paper, where large amounts of water are discharged into the drain because its turbidity does not allow for recirculation. While this is a serious problem, even worse is the fact that the quality of such wastewater makes it difficult not only to recirculate but also to discharge due to environmental law restrictions. In this paper, electrocoagulation is proposed as a suitable technology to meet standards of water discharge, and even better, as a treatment option for removal of turbidity. Since energy consumption has been a drawback for EC applications, relevant aspects that contribute to increase it such as cell voltage and current density have been reviewed. For this purpose a systematic micro-electrolysis study combined with macro-electrolysis experiments have provided evidence that shows it is possible to achieve a turbidity removal of 92% with an energy consumption of 0.68 kWh/m 3. Thus, the results presented in this paper support the use of EC to obtain water of acceptable quality for reuse in the tissue paper industry.

Influence of pulp refining on tissue paper properties

We investigated the influence of refining conditions (refiner tackle type and specific edge load) on bulk softness, absorbency, tensile strength, and wet tensile strength of bleached pulp. Commercial elemental chlorine free (ECF) and totally chlorine free (TCF) bleached sulfite and kraft spruce, birch, and eucalypt pulps were used in this investigation. We found that refiner tackle type and specific edge load had a significant influence on the evaluated properties. Higher specific edge load when using a universal tackle increases softness and absorbency of hard-wood kraft pulps. The highest tensile index of bleached hardwood kraft and spruce sulfite pulps was achieved by fibrillation refining at low specific edge load (under 0.70 J/m). The wet tensile strength index of the tested pulps beaten to 30°SR increased 3-4 times. Pulp refining increases wet tensile index and reduces water absorbency of paper. Hardwood kraft pulps are suitable for production of tissue paper with high softness and absorbency. Spruce sulfite pulps are suitable to achieve high bulk softness and low tissue paper absorbency. Birch kraft pulp is a good choice if a higher tensile strength is required in addition to softness and absorbency. To manufacture tissue papers with deep embossing, softwood kraft pulp is required because of its high strength properties.

Modeling Drying and Energy Performance of Industrial Through-Dryers

A model of an industrial through-dryer for production of tissue paper was developed. The model can be used to predict the performance of a dryer section of an industrial through-drying machine consisting of one or more through-drying rolls separated by free draw sections. Roll diameters, wrap angles, machine speed, basis weight, initial paper moisture ratio, operating pressure differentials, drying air temperatures, and drying air humidity are input parameters to the model. Based on the input information, the model predicts paper drying rate, paper moisture ratio, paper temperature, exhaust air humidity, exhaust air temperature, and air flow rate as a function of time, which at a given machine speed is equivalent to a certain position in the machine direction of the dryer. The model also includes a description of the fabric and along with the paper properties the model also predicts fabric drying rate, fabric moisture ratio, fabric temperature, and fabric air humidity as a function of time (or position). Air, vapor, and enthalpy fluxes were integrated over the residence time of each through-drying roll in order to retrieve the average flow rate and air properties of the air leaving each roll. These data were then used in a steady-state description of the air system of each roll, which means that, for given drying conditions, natural gas consumption in the burners and the fan power associated with each roll can be predicted. The model was used to study how the different operating conditions affect the energy demand and economics of the through-drying process. The simulation results indicate small differences in total drying cost for different operating conditions. Reduction of fabric water was shown to have a relatively large impact on overall drying cost. Reducing the initial fabric moisture ratio from 0.019 to 0.012 kg water/kg dry solids reduced total operating costs by approximately 3.3%.