Time filter

Source Type

Calcium carbonate scaling is a critical problem in papermills. It often has been observed that scaling occurs in aerated sections of the process, where CO 2 stripping from the solution is responsible for the saturation increase with respect to CaCO 3. To better cope with scaling problems, it is important to be able to predict both supersaturation levels after aeration and the rate at which the system becomes supersaturated. In this study, trials are performed on a bubble column. Air is bubbled to strip out the dissolved CO 2 from a CaCO 3-CO 2-H 2O system. The saturation kinetics with respect to CaCO 3 are followed by recording pH, and analyzed by speciation calculations. Aeration conditions are determined through gas hold-up and bubble size measurements. A general kinetic model is proposed to estimate how fast a solution will become saturated with respect to calcium carbonate during aeration. The model is applied to water quality and aeration conditions typically encountered in some unit operations of the papermaking process. Knowing the rate of change of calcium carbonate saturation will help papermakers to better estimate scaling risk in their process, and will help equipment suppliers to either minimize scaling problems in aerated sections of the process or design aeration units for calcium carbonate removal by controlled precipitation. © 2011 American Chemical Society.

French National Center for Scientific Research and Center Technique Du Papier | Date: 2013-12-30

Film having liquid-water, grease, gas and water-vapour barrier properties, comprising a PVA film grafted on the surface with a fatty acid.

Center Nationale Of La Recherche Scientique and Center Technique Du Papier | Date: 2013-02-04

A process for treating a solid substrate coupled to a polyol, wherein said polyol bears free hydroxyl groups, comprising the grafting of at least one fatty acid having an aliphatic chain comprising at least 12 carbon atoms onto said solid substrate coupled to a polyol by esterification of at least one free hydroxyl group of said polyol.

Huber P.,Center Technique du Papier | Rousset X.,Center Technique du Papier | Zeno E.,Center Technique du Papier
Industrial and Engineering Chemistry Research | Year: 2011

There is a need to monitor flotation deinking operations, in order to better control their efficiency, reduce losses, and save fiber resources. The objective of this work is to understand the variations of ink removal efficiency and flotation yield at industrial scale. A preflotation bank has been instrumented with air probes, and parameters relevant to flotation operations (chemicals dosages, brightness, effective residual ink content (ERIC), pH, temperature, water levels in cells, rejects flows, consistencies) have been exported from the mill data logging system. Then, relationships among flotation parameters are investigated. Air content in preflotation primary cells is found to vary considerably over time. On the other hand, air content in secondary cells is much higher, but rather stable. Ink removal is enhanced by a higher air content in primary cells. High air content is also found to impair the flotation yield. Most air content variations are explained by opposite variations of pulp concentration. It is proposed that pulp concentration lowers air content, by causing stronger pulp flocculation. These results suggest that deinking flotation yield may be maximized by running the flotation bank at the highest possible pulp concentration, while maintaining the target on the effective residual ink content. © 2011 American Chemical Society.

Ketep S.F.,Center Technique du Papier | Ketep S.F.,National Polytechnic Institute of Toulouse | Fourest E.,Center Technique du Papier | Bergel A.,National Polytechnic Institute of Toulouse
Bioresource Technology | Year: 2013

Microbial bioanodes were formed in pulp and paper effluent on graphite plate electrodes under constant polarization at -0.3V/SCE, without any addition of nutriment or substrate. The bioanodes were characterized in 3-electrode set-ups, in continuous mode, with hydraulic retention times from 6 to 48h and inlet COD from 500 to 5200mg/L. Current densities around 4A/m2 were obtained and voltammetry curves indicated that 6A/m2 could be reached at +0.1V/SCE. A theoretical model was designed, which allowed the effects of HRT and COD to be distinguished in the complex experimental data obtained with concomitant variations of the two parameters. COD removal due to the electrochemical process was proportional to the hydraulic retention time and obeyed a Michaelis-Menten law with respect to the COD of the outlet flow, with a Michaelis constant KCOD of 400mg/L. An inhibition effect occurred above inlet COD of around 3000mg/L. © 2013 Elsevier Ltd.

Discover hidden collaborations