Spelling suggestions: "subject:"bisulphate pulping process."" "subject:"disulphate pulping process.""
1 |
Measurement of delignification diversity within kraft pulping processesBoyer, Brian S. 05 1900 (has links)
Institute of Paper Science and Technology / Thesis (Ph. D) -- Institute of Paper Science and Technology, 1998.
|
2 |
Reduction of sulfur release through indigester oxidation in kraft pulpingBakke, Bruce W. 05 1900 (has links)
No description available.
|
3 |
Kinetic and equilibrium analysis of metal ion adsorption onto bleached and unbleached kraft pulpsYantasee, Wassana 01 May 2001 (has links)
Most metal ions have negative impacts on pulp mill operations. The
concentrations of metal ions on pulp fibers and in washwaters rise significantly with
increased wastewater recycling. The development of technology to remove these metal
ions requires an understanding of how metal ions are bound to pulp components. It is
also desirable to predict distribution of metal ions between the pulp fibers and the
washwaters.
The adsorption isotherms for eight metal ions (Ca, Ba, Mn, Zn, Pb, Cd, Ni, Na)
were measured on bleached and unbleached (brownstock) kraft pulps at neutral pH and
temperatures ranging from 25 to 75��C. On bleached pulps, the metal ion adsorption
increased rapidly with increasing metal ion concentration in solution and then leveled off.
At neutral pH, the adsorption on bleached pulp was stoichiometric to the carboxylate
sites, whereas the adsorption on unbleached pulp was not, especially at high metal ion
concentration in solution and low temperature.
The pH isotherms specify the adsorption isotherms of sodium and calcium on
wood pulps as pH ranging from 2.5 to 11.0. The pH isotherms on bleached pulp with
only COOH functional groups (pK[subscript a] of 3.77) were saturated at pH 4 and above, whereas
those on brownstock pulp with both COOH and PhOH (pK[subscript a] of 10) functional groups
increased in two steps, at pH 4 and 8.
The brownstock pulp is heterogeneous material. Therefore, only the empirical
Freundlich model was applied to the data. To predict the metal ion adsorption on
bleached pulps, two fundamental equilibrium models were developed: the multi-component
ion exchange and the Donnan equilibrium models. The ion-exchange model
better predicts the metal adsorption at neutral pH, whereas the Donnan equilibrium model
more accurately predicts the pH isotherms.
The adsorption kinetics of Ba����� and Ni����� were measured on wood pulps as a
function of mixing speed, initial metal ion concentration, and temperature. The adsorption
of metal ions reached equilibrium rapidly. The intraparticle diffusion model, based on first
principle with a linear relationship assumption between adsorbed and free metal ion
concentration, satisfactorily predicted the adsorption kinetics at low metal ion
concentration in solution. / Graduation date: 2001
|
4 |
Nucleation in bulk solutions and crystal growth on heat-transfer surfaces during evaporative crystallization of salts composed of NaCO and NaSOEuhus, Daniel D. 01 December 2003 (has links)
No description available.
|
5 |
A dynamic model of kraft-anthraquinone pulpingBurazin, Mark Alan 01 January 1986 (has links)
No description available.
|
6 |
Determination of the optical constants of ash samples from kraft recovery boilersSamretvanich, Artit 24 April 1997 (has links)
Graduation date: 1997
|
7 |
Sintering of fume deposits in kraft recovery boilersTechakijkajorn, Udom 04 October 1995 (has links)
Fume, sub-micron aerosal particles in the combustion gases, have been identified
as a cause of extensive plugging and fouling in the heat transfer section of a kraft
recovery boiler in kraft pulp mills. After the deposition on the heat transfer surface,
fume deposits will undergo the sintering process which causes densification and
hardening, making them hard to remove. There has been relatively little information
available on the kinetics of the sintering of fume particles, and no information on the
modeling of the sintering process of this particular material. No conclusion about the
effect of chloride species on the sintering of fume particles has been made.
A series of sintering tests in air at various temperatures were conducted using
dense pellets made from a specific fume dust which contains a low amount of chlorides.
Each pellet was heated at a constant temperature, ranging from 300��C to 550��C, for a
different time interval. By the study of the microstructural change of each sintered
specimen, the initial stage, intermediate stage, and final stage of sintering were
identified. By the presence of an empirical constant K���, the relative linear shrinkage data
in the initial stage sintering fit well with the model proposed by Kingery and Berg��� when
volume diffusion is the controlling mechanism. By the presence of an empirical constant
K2 and the application of grain growth data, the porosity-time data in the intermediate
stage sintering fit well with the model proposed by Coble����� when volume diffusion is the
controlling mechanism. The apparent activation energy obtained from the initial stage
sintering is equal to 54.5 �� 27.7 kcal/mol which is in good agreement with the apparent
activation energy obtained from the intermediate stage sintering which is equal to
56.0 �� 31.3 kcal/mol. A semi-empirical model for the sintering process of this particular
well-packed fume dust was formulated. The model does not apply well to the loosely packed
fume dust due to some unidentified factors
The same experiment was carried out for the other fume dust which contains a
high amount of chloride. By the use of the fractional density, the qualitative comparison
of the sintering of the low chloride and high chloride dusts was made. At low
temperatures, the sintering rate of the high chloride fume dust is lower than that of the
low chloride fume dust. At high temperatures, both dusts have the same sintering rate
and can sinter close to the theoretical density. It is postulated here that the retarded
grain growth rate for the high chloride dust can improve the densification process in the
intermediate stage sintering. / Graduation date: 1996
|
8 |
Inorganic aerosol formation during black liquor drop combustionVerrill, Christopher Lee 01 January 1992 (has links)
No description available.
|
9 |
Comparative refining characteristics of northern and southern hemisphere bleached softwood Kraft species.Palmer, B. January 2009 (has links)
An experiment was designed to test the hypothesis that each softwood pulp is unique and
requires a specific, well defined mechanical treatment to derive its maximum strength potential.
Three bleached softwood Kraft pulps and respective wood samples were sourced from both the
Northern and Southern Hemispheres. The raw fibre characteristics of P. patula (Southern
Hemisphere), P. menziesii (Northern Hemisphere) and P. mariana (Northern Hemisphere) were
measured and compared. The raw pulp sheets were refined at different energies and intensities
under controlled laboratory conditions using a 12” single disc pilot refiner. Results were
assessed to determine the raw fibre characteristics, optimum refining conditions and the relative
refined strength potential for each of the three samples.
Results from anatomy measurements on the three wood samples differed significantly. P. patula
exhibited a relatively high proportion of springwood growth in the early growing years. As the
P. patula aged and formed mature wood there was a significant increase in the frequency of
latewood formation. This was characterized by an abrupt and significant increase in the wall
thickness, beyond that of the two Northern softwood samples. When the cell wall thickness
increased, the lumen width and fibre diameter of the P. patula decreased significantly, yielding
extremely coarse, stiff fibres.
The Northern P .mariana and P. menziesii samples were characterized by a relatively consistent
transition between high and low densities from the pith to the bark of the tree. The Southern P.
patula had a unique density trend with an increasing frequency of high density peaks indicative
of an increased latewood formation from the pith to the bark.
The slower growing Northern P. menziesii and P. mariana samples did not have as clear a
differentiation in fibre characteristics between juvenile and mature wood formation. The
Northern samples did however contain a significantly higher proportion of juvenile latewood
growth than the P. patula. However, the difference in fibre characteristics between earlywood
and latewood formation was not as significant as that noted with the Southern P. patula
Fibre morphology measurements on the unrefined bleached Kraft pulps also revealed significant
differences between the three samples. The average MORFI LAB01 results on the P. patula
defined fibres with a high coarseness and relatively low number of fibres per gram of pulp. The
extremely coarse latewood fibres formed during mature wood growth being the most likely
source. However, P. patula was also characterized with a high fibre flexibility and large lumen,
characteristics consistent with earlywood fibres. The Pulmac Z-Span 3000 was used to define
the individual fibre strength, when due consideration was given to the number of fibres per
gram, the corrected Pulmac results suggested P. patula had the strongest fibres.
When refined, using a standard disc refining programme, P. patula exhibited a fast freeness
development. Conventional thinking would suggest that this was an indication of a weaker fibre.
However, this species had a robust morphology compared to the Northern Hemisphere woods.
The theory developed in this dissertation suggests that the effect of coarseness and the
concomitant number of fibres per gram plays a significant role. These two parameters are not
included in the “traditional” refining calculations. The applied refining load and intensity was
calculated on the flow of the pulp passing through the refiner. The calculation did not consider
the actual number of fibres present in that specific volume. The implication is that when a fixed
refining load is applied to a pulp with coarse fibres there may be a higher effective load on those
fewer fibres (resulting in fibre cutting and fines generation). In this case, the Northern samples
have a comparatively low coarseness and more fibres per gram with each receiving a smaller
portion of the total load and intensity.
In terms of refined pulp properties, P. patula developed a relatively high bulk and tear index
consistent with coarse, rigid fibres. The Northern P. mariana and P. menziesii samples produced
a pulp with good tensile properties, consistent with a greater number of finer, collapsible fibres
with a higher relative bonding area.
P. patula fibres were extremely heterogeneous in nature containing the smallest relative lumen
width during latewood formation and the largest lumen width during earlywood growth. As a
result, P. patula contains extremes of both fine and coarse fibres in the same blend. It may be
more beneficial for this species than the others to improve both the tear and tensile properties
through fibre fractionation with appropriate development of the separate accepts and rejects
streams.
In terms of fibre development, low intensity refining parameters maximized the tensile strength
of the Southern P. patula. The Northern P. mariana and P. menziesii samples had a greater
number of fibres per gram of pulp requiring both a higher refining energy and intensity to
develop the pulp to its maximum potential. To develop optimum tear results, high intensity
refining, with a relatively low specific energy provided optimum results for all 3 samples.
Results confirmed that there were significant differences in the fibre morphology both between
the three different species and between the two Hemispheres. There was strong evidence that the
fibre characteristics dictate the manner in which a fibre responds to refining which in turn
determines the relative contribution to specific refined pulp properties. It may be possible to use
fibre characteristics to determine the appropriate refining parameters for optimal fibre
development which will enhance the value of the end product.
To derive the maximum strength potential from P. patula pulp samples, it is recommended that
further studies investigate Hydracyclone fractionation and the concomitant benefits of refining
the separate streams. Furthermore, a separate study on fibre morphology and refining
characteristics of the same species grown in both the Northern and Southern Hemisphere would
provide valuable insight. / Thesis (M.Sc.Eng)-University of KwaZulu-Natal, Durban, 2009.
|
10 |
SO��� capture and HCl release at Kraft recovery boiler conditionsBoonsongsup, Lerssak 03 September 1993 (has links)
Graduation date: 1994
|
Page generated in 0.0754 seconds