Pulping kinetics

Willis JM, Jagannathan NR, Herring FG (1986) The potential of l3C CP/MAS NMR in the study of kraft pulping kinetics. J Wood Chem Technol 6 249-267... 

Flotation process kinetics determine the residence time, the average time a given particle stays in the flotation pulp from the instant it enters the ceU until it exits. One way to study flotation kinetics is to record flotation recoveries as a function of time under a given set of conditions such as pulp pH, coUector concentration, particle size, etc. The data allow the derivation of an expression that describes the rate of the process. 

The stoichiometric relationship between chlorine dioxide added and color removed during bleaching is nonlinear, but it is independent of temperature, pH, and pulp concentration under conditions normally used. Models used to explain the kinetics and stoichiometry show a strong dependence on chromophore concentration that probably results from differences in the reaction rates of the various chromophores present in the pulps (80). 

Sharma, S.K. and Le Maguer, M., Kinetics of lycopene degradation in tomato pulp solids under different processing and storage conditions. Food Res. Int, 29,309, 1996. 

Gierer, J. Ljunggren, S. The reactions of lignin during sulfate pulping. Part 17. Kinetic treatment of the formation and competing reactions of quinone methide intermediates. Sven. Papperstidn. 1979, 82, 503-512. 

Sojo MM, Nunez-Delicado E, Sanchez-Ferrer A and Garcia-Carmona F. 2000. Oxidation of salsolinol by banana pulp polyphenol oxidase and its kinetic synergism with dopamine. J Agric Food Chem 48(11) 5543-5547. 

In pulp and paper processing, anthraquinone (AQ) accelerates the delignification of wood and improves liquor selectivity. The kinetics of the liquid-phase oxidation of anthracene (AN) to AQ with NO2 in acetic acid as solvent has been studied by Rodriguez and Tijero (1989) in a semibatch reactor (batch with respect to the liquid phase), under conditions such that the kinetics of the overall gas-liquid process is controlled by the rate of the liquid-phase reaction. This reaction proceeds through the formation of the intermediate compound anthrone (ANT) ... 

Involved in extensive study of SCWO processes Investigated SCWO process for pulp mill sludges Explored kinetics of SCWO of phenol Explored supercritical water reactor Investigated the unique features of supercritical water in terms of density, dielectric constant, viscosity, diffusivity, electric conductance, and solvating ability Explored multistep kinetic model of phenol in SCWO Involved in extensive SCWO study of priority pollutants... 

Figure 9. Kinetics of irradiation of peroxide-bleached chemimechanical pulp (CMPB) at selected wavelengths analyzed by measuring the reflectance at 457 nm.

The kinetics of the delignification are of importance especially when considering the control of the pulping process. Since kraft pulping follows simpler kinetics than the sulfite processes, more applications have been adopted for this case. Because of the heterogenity of the system, however, pulping reactions are complicated and can therefore not be treated in the same fashion as homogeneous reactions in solution. 

The overall rate of the bulk delignification in kraft pulping, during which the variations in hydroxyl and hydrosulfide ion concentrations are moderate, follows pseudo-first-order kinetics, approximately in conformity with the following equation ... 

Figures 4A-D show that most of the pulps have initial kinetics approaching zero order. Pulps FB, SBS, BBC, and BRK all show two-component curves with a minor peak indicated between 0.05 and 0.1 conversion, possibly corresponding to the hemicellulose fraction as discussed earlier. The maximum rate of weight loss occurs for all pulps at about 60-65% loss of initial weight. This corresponds to plots of theoretical rate of weight loss vs. conversion plots of reaction order Vi to 1(14).

Cui, Y., Puthson, R, Chen, C. L., Gratzl, J. S., and Kirkman, A. G., Kinetic study on delignification of kralt-AQ pine pulp with hydrogen peroxide catalyzed by Mn(IV)-Me4DTNE. Holzforschung 2000, 54 (4), 413-419. 

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