High Pulp Viscosity Research Articles

Three-phase froth stability in hematite flotation using DDA as a collector

The effect of hematite and quartz with different particle sizes on the three-phase froth stability using dodecylamine (DDA) as a collector was investigated, and the mechanism of how quartz improves froth stability was explored. Microflotation experiment, three-phase froth stability experiment, froth morphology photography, pulp viscosity measurement, contact angle measurement, zeta potential measurement, time-of-flight secondary ion mass spectrometry analysis, and molecular dynamics simulation were conducted in this investigation. Results showed that flotation performance and froth stability were obviously different for minerals with different particle sizes. The froth half-life was remarkably higher in the presence of quartz particles compared with hematite particles, forming stickier froth, especially for quartz particle sizes below −18 μm. Fine quartz was found to be a key factor in improving the froth stability in hematite flotation using DDA as a collector. The high pulp viscosity, damping coefficient, and maximum capillary pressure resulting from quartz with low density, small size, and high concentration hindered liquid drainage and reduced the desorption probability of particles from the bubble surface, thereby preventing the coalescence of two adjacent bubbles. DDA was found to be more readily adsorbed on the quartz surface, leading to a higher adsorption capacity, better hydrophobicity, and increased distribution of counter ions at the interface. This condition reinforced the mutual repulsion force between liquid film surfaces and prevented further thinning of the liquid film, ultimately strengthening froth stability.

New perceptions into the detrimental influences of serpentine on Cu-Ni sulfide flotation through rheology studies and improved the separation by applying garnet

The flotation separation between sulfides and fine serpentine has always been a difficult problem due to their hetero-coagulation. To acquire a better understanding on the adverse effect of fine serpentine on Cu-Ni sulfide flotation, rheology measurements and flotation tests on Cu-Ni sulfide/serpentine system were explored under different conditions in this study. Rheology results revealed that in the aqueous solution at pH 9.5–10, serpentine particles could partially aggregate in pulp, whereas Cu-Ni sulfide particles did not aggregate. In the mixed Cu-Ni sulfide/serpentine system, the higher the total solid concentration was, the greater the influence of serpentine proportion on pulp rheology was. When pulp solid concentration was higher than 10 %, pulp viscosity increased obviously as serpentine proportion increased no matter in the absence or presence of potassium butyl xanthate (PBX). However, with the increase of serpentine proportion, pulp yield stress gradually increased in aqueous solution, indicating the hetero-coagulation between sulfide and serpentine occurred, while in the presence of PBX, the pulp yield stress increased first and then decreased. The deterioration of the flotation performance of Cu-Ni sulfide suggested that the hetero-coagulation was not the only factor affecting the flotation of Cu-Ni sulfide containing serpentine, high pulp viscosity could also worsen that. However, with the addition of coarse garnet particles (-104 + 44 μm), the pulp yield stress decreased remarkably, illustrating that the hetero-coagulation between sulfide and serpentine was limited. Furthermore, pulp viscosity also decreased obviously, and the synthetic actions improved Cu-Ni sulfide flotation. Micro-flotation and batch flotation results verified that the Ni recovery in concentrate increased significantly with a remarkable decrease in SiO2 content after adding garnet (-104 + 44 μm). This study offered some new insights into the adverse effect of serpentine on sulfide flotation, and the employment of stir medium such as garnet, might be a potential way to improve the flotation separation of sulfides from serpentine.

Fundamental understanding of distracted oxygen delignification efficiency by dissolved lignin during biorefinery process of eucalyptus

In this work, a fundamental understanding of oxygen delignification distracted by dissolved lignin was investigated. In the new biorefinery model of shortening kraft pulping integrated with extended oxygen delignification process, increasing content of residual lignin in the original pulp could result in enhanced delignification efficiency, higher pulp viscosity and less carbonyl groups. However, the invalid oxygen consumption by dissolved lignin could be increased with the increase of process temperature and alkali dosage. The normalized ultraviolet absorbance (divided by absorbance at 280 nm) also showed that the content of chromophoric group in dissolved lignin decreased with oxygen delignification proceeded, both of which indicated that dissolved lignin could enhance the invalid oxygen consumption. Therefore, a conclusion that replacement of the liquor at the initial phase of oxygen delignification process would balance the enhancement of delignification efficiency and invalid oxygen consumption was achieved.

Application of response surface method of optimization in flocculant assisted filtration of uranium bearing alkaline leach slurry of limestone origin

Leach slurries of alkaline nature often show very low rate of filtration due to high pulp viscosity contributed by dissolved solutes in solution and very fine grained nature of the unleached solids. Maximisation of filtration performance generally needs exhaustive experimentation involving various parameters which influence the solid–liquid separation process. The study reported in this paper pertains to optimisation of parameters in vacuum filtration of uranium bearing alkaline leach slurry generated from a brecciated limestone ore using response surface methodology. The d80 size of solids in the leach slurry is 60 μm and the pH of the pulp is 9·5–10. Initial screening of various commercial flocculants of anionic, cationic and non-ionic nature was carried out using the capillary suction time (CST) as basis. Minimum CST was achieved using a combination of anionic and non-ionic flocculant namely the Indfloc (IF) 477 and Guargum. The dosages of the flocculant combination and the slurry temperature were optimised to achieve maximum rate of filtration with optimal cake moisture under vacuum filtration conditions.

Effect of clay minerals on pulp rheology and the flotation of copper and gold minerals

In this study, the effect of bentonite and kaolinite minerals with low and high crystallinity on pulp rheology and the flotation of copper and gold minerals was investigated. It was found that clay minerals modified the pulp rheology depending on the type of clay minerals present. Bentonite, a 2:1 structured clay mineral increased pulp viscosity more significantly than kaolinite, a 1:1 structured clay mineral, and poorly crystallized kaolinite increased pulp viscosity more than well crystallized kaolinite. It was also found that pulp rheology modified by clay minerals was strongly correlated with copper and gold flotation. The higher pulp viscosity corresponded to the lower copper recovery. While high pulp viscosity was related to the decreased gold flotation, slightly increased pulp viscosity by clay minerals enhanced gold flotation.

High-Consistency Electrochemical Delignification of Poplar Kraft Pulp

The electrochemically mediated delignification of pulp fibers is one of the promising bleaching methods, which can give the delignified pulp with good subsequent bleachability and high pulp viscosity. Our previous work has shown that the poplar kraft pulp can be delignified to 45% delignification ratio with less than 10% pulp viscosity loss at the condition of 1% pulp consistency which limits the application of this method in pulp industry. The high-consistency electrochemical delignification of poplar kraft pulp was investigated in this paper. The delignification ratio, pulp viscosity loss and brightness were measured as well as the delignification conditions, such as pulp consistency, voltage of electrolysis cell, temperature, circulation of electrolysis liquor and time, were discussed. The results showed that at the 10% pulp consistency, the circulation of electrolysis liquor between pulp cell and electrolysis cell can efficiently improve the delignification ratio, and the pulp viscosity loss is less than 10%. The subsequent bleachability for H2O2 is similar as that of 1% consistency delignified pulp. The pulp also can be bleached to higher than 80% ISO with following EP stage at 2.5% H2O2 dosage.

Alternative pulping process for producing dissolving pulp from jute

Dissolving pulps are the raw materials of cellulose derivatives and of many other cellulosic products. Jute is a very good source of cellulose and worthy of consideration for the production of dissolving pulp. In this investigation jute fiber, jute cuttings, and jute caddis were used as raw materials to prepare dissolving pulp by a formic acid process. A very high bleached pulp yield (49 to 59%) was obtained in this process. The alpha-cellulose content was 93 to 98%, with a high pulp viscosity. Also a good brightness (81 to 87%) was achieved in totally chlorine free bleaching. Jute fiber showed the best and jute caddis showed lowest performance in producing dissolving pulp via the formic acid process. R18-R10 values were much lower than for conventional dissolving pulp.

Impact of Kraft Process Modifications on Eucalyptus globulus Pulping Performance and Polysaccharide Retention

The impact of effective alkali (EA) splitting and anthraquinone (AQ) addition on Eucalyptus globulus kraft pulping yield and pulp quality was investigated. AQ addition to kraft pulping enhances the rate of delignification, leading to alkali saving and reducing time at maximum temperature. A 1.9% total yield increase was observed, assigned to the enhancement of both cellulose and xylan retention but also due an increase of rejects content. Contrary to results described in the literature for other woods, the use of an even effective alkali concentration profile throughout the cook of E. globulus did not affect pulp yield or carbohydrate composition of screened pulp. However, EA profiling resulted in a higher pulp viscosity, indicating a lower degradation of cellulose chains along the pulping. Such results were interpreted taking into account the peculiar chemical structure of E. globulus wood components.

Assessment of potential approaches to improve Eucalyptus globulus kraft pulping yield

AbstractThe main goal of this work is to study the potential approaches to improve polysaccharides retention during Eucalyptus globulus kraft pulping. The addition of anthraquinone to kraft pulping leads to the highest pulp yield while the addition of urea promotes lower depolymerization of polysaccharides (higher pulp viscosity), but does not have a significant effect on yield. The early interruption of kraft cooking followed by oxygen delignification is a reliable approach to increase pulp yield, particularly when pulping is interrupted at the end of the faster and more selective kinetic regime (bulk phase). Yield loss during oxygen delignification is considerably lower than that incurred in the last phase of kraft pulping. Pulping with OH−/HS− charge profiling, carried out with liquor injection in three different phases leads to a yield increase. However, this increase results from a lower total alkali charge applied when profiling pulping is compared to standard pulping conditions, rather than to alkali profiling. Standard kraft pulping with different active alkali (AA) charges demonstrated that this operational variable is determinant for pulp yield and viscosity. Pulping experiences with lower AA (14%) resulted in a higher and almost constant pulp viscosity and in a higher pulp yield, assigned to improved retention of both cellulose and xylan. During the last stage of pulping, cellulose content decreases, this being mainly responsible for the decrease of pulp yield, while xylan content is almost constant, a feature attributed to the peculiar structure of this E. globulus's hemicellulose. Copyright © 2007 Society of Chemical Industry

A NOVEL BIOTECHNOLOGICAL APPROACH TO MODIFY THE VISCOSITY OF TOMATO FRUIT PULP: RIBOZYMES ACTIVE AGAINST ENDO-1,4-β-GLUCANASE MRNAS

The endo-1,4-β-glucanases (EGases, cellulases) are enzymes active in virtually all phases of plant development where a modification of the cell wall occurs, such as cell expansion and differentiation, fruit ripening and abscission. Tomato genes coding for EGases (tcels) constitute a gene family with at least eight members. Two of these genes, tcell and tcel2, exhibit increased transcription during fruit ripening, but the suppression of mRNA accumulation of tcell alone or tcel2 alone did not detectably alter fruit softening or pulp viscosity. We therefore decided to explore the possibility of down regulating the expression in planta of several EGases using the ribozyme strategy. Specifically we constructed two ribozymes: the first one with a catalytic activity against the mRNA of the tcel3, tcel5, and tcel8 genes, and the second one active against tcell, tcel2, tcel4, tcel7 gene transcripts. Tomato cotyledons were transformed with both ribozymes cloned in two different transgenes under the control of 35S promoter. TO transgenic plants detected by Southern analysis were self-fertilised and T1 seeds were planted in soil inside a greenhouse. Fruits were harvested at the red ripe stage and were used to determine rheological (viscosity and firmness) and chemical parameters (acidity, pH, Brix degrees, reducing sugars). These determinations were conducted on fruits from 85 different transgenic plants. Analysis of viscosity measurement permitted the identification of 9 plants with a very high pulp viscosity, derived from five different T0 transgenic genotypes. The average viscosity of this group was 236.7 cPoise significantly higher than 57.7 cPoise which was the mean of the remaining 76 plants. Interestingly, the high viscosity was not correlated to the glucose and fructose content, as it was instead shown for the pulp with normal viscosity. Additional investigations are undertaken on these 9 transgenic plants to explain the transgene effects.

Combination treatment of kenaf bast fiber for high viscosity pulp

The viscosity of kenaf bast fiber has been found to be highly sensitive and variable with different pulping methods; therefore, it is important to choose proper chemicals and conditions for pulping and bleaching of kenaf bast fiber. From several pulping experiments, a nonconventional pulping method with a combination of ammonium oxalate pretreatment followed by soda pulping at normal pressure and then acidic chlorite delignification was developed to obtain high-viscosity pulp (162 centipoise). The optimum level of alkali dosage of soda pulping for high-viscosity pulp was found to be 15% (on pulp as NaOH). Pulps showed linear relations between viscosity and xylose or glucose contents, but the combination pulping method gave extremely high pulp viscosity, beyond the relations. The highest viscosity pulp from kenaf bast fiber demonstrated a tear index about twofold and a folding endurance 6.2-fold higher than those of Manila hemp pulp with comparable tensile and burst indexes. The high-viscosity pulp could be used in the production of high-quality currency paper or longevity paper for special uses.

Reinforcement of Alkaline Pulping Processes with Organic Solvents. Part II. Screening of Suitable Solvents

The effects on the delignification process by adding different organic solvents to soda, soda-anthraquinone and kraft processes were studied. Eleven solvents were selected via a principal component analysis of 103 solvents and 9 solvent descriptors, to cover a wide range of physical properties of the solvents. The results show that many of the added solvents have a positive effect on the pulping selectivity i.e give a high pulp viscosity at a given lignin content. The most promising solvents were found in a rather narrow polarity range. The effect of adding a solvent, with regard to both delignification and carbohydrate degradation, is similar in the three alkaline pulping processes studied.

Extended Delignification Kraft Pulping of Softwoods - Effect of Treatments on Chips and Pulp with Sulfide-Containing Liquors

Abstract Pretreatment of softwood chips with Na2 S liquors at moderately-elevated temperatures prior to a kraft stage delignification resulted in higher pulp viscosity at a given kappa number as compared to that of a conventionally-cooked reference kraft pulp. Final pulp yields were equivalent to, or slightly better than for conventional kraft pulps. The high viscosity is due to the lower alkali requirement during the kraft stage as a result of the pretreatment. The decreased alkali requirement is due to the extraction and removal of hemicelluloses during pretreatment which normally produce sugar acids via peeling reactions. The presence of sulfide in the pretreatment promotes lignin degradation and also enhances polysaccharide stability during the subsequent kraft stage. When kraft pulps, pretreated with sulfide-contaim'ng liquors, were further delignified in an oxygen stage, lower kappa numbers at equivalent viscosity were obtained versus conventional kraft-0? treatment. This enhanced polysaccharide stability toward an oxygen stage can also be achieved by treating a conventional kraft pulp with sulfide-containing liquors, including green liquor and black liquor, but a lesser effect is achieved compared with chip pretreatment.