Pulp Viscosity Research Articles

Use of Additive Technologies to Optimize Design of Classifying Devices

The article considers perspectives of the use of additive technologies to optimize the design of classifying devices. A brief overview of the solutions developed using 3D printing of for mining industry is given. It is stated that creation of models is impossible without knowledge of the laws of distribution of flows and expressions describing them. For this purpose, the influence of the pulp viscosity on classification in a hydrocyclone on an experimental unit has been studied. A modified Plitt model was proposed to predict the separation grain. The proposed model takes into account the pulp viscosity and predicts the size of the boundary grain more accurately.

Using Oxone and TAED activator in non-chlorine bleaching of soda bagasse pulp

Abstract Bagasse fiber has been used in the production of bleached chemical pulp by the Pars Paper Company. In this company, a conventional three-stage sequence of hypochlorite, alkaline extraction and second hypochlorite (HEH) is applied in pulp bleaching. Pulp bleaching is one of the most important environmental pollutant stages in the pulp and paper industry. In this research, the bleaching of soda bagasse pulp by applying Oxone and TAED-activator in non-chlorine bleaching sequences has been investigated. The unbleached pulp, with kappa number of 20, 955 ml/g viscosity and 37 % brightness, was prepared from Pars Paper Company. Results indicated that, the TAED at the first and second stages were more effective than in the Oxone stages. Moreover, the sequences, which contained TAED- and Oxone-second-stage, could reach the minimum level of kappa (1.7), but the highest brightness (80 %) was attained by using only TAED with a comparatively high level of pulp viscosity (752).

Recovery of sphalerite from a high zinc grade tailing

In this work, the flotation recovery of sphalerite and pyrite from an old high zinc grade tailing was studied. In particular, the effect of different flotation reagents such as collector, auxiliary collector, depressant, activators, and frother on the flotation performance were investigated. The synergic effect of the collector blends, as well as frother blends were also studied. In addition, the effect of the pre-conditioning of flotation pulp with scrubbing or ultrasonic on the selective separation of sphalerite and pyrite minerals were studied. More than 73% of the sphalerite was recovered from the accumulated tailings in the rougher stage. The pulp viscosity was considerably increased by increasing the pH from 5.5 to 10.5. As a result, sphalerite recovery and Zn selective separation were both considerably dropped. It was also found that frothers (MIBC and A65) have a synergic effect, and their mixture showed better metallurgical results than when each frother were solely used. The pre-conditioning with scrubbing or ultrasonic resulted in a major increase in the sphalerite floatability.

Improvement in selectivity of ozone bleaching using DTPA as carbohydrate protector for wheat straw pulp

Abstract Effect of using diethylenetriamine pentaaceticacid (DTPA) as carbohydrate protector in ozone stage on delignification efficiency, bleaching efficiency, selectivity, metal ions, strength, morphological properties and effluent properties of wheat straw pulp was studied. Using DTPA during ozone treatment viscosity of pulp was improved by 1.1 units, delignification efficiency improved by 13.8 % and pulp brightness improved by 2.5 units compared to that of control. Most importantly the selectivity of ozone treatment was improved by 124 %. Ozone treatment along with DTPA reduced the Fe, Cu and Mn content in the pulp by 52 %, 27 % and 70 %, respectively. Use of DTPA in ozone stage improved the bleached pulp viscosity by 9 %, post colour number by 27 % and reduced the pulp shrinkage by 5 % compared to control pulp. DTPA treated and control pulps have comparable physical strength and morphological properties.

Structure and reactivity of cellulose from bleached kraft pulps of different Eucalyptus species upgraded to dissolving pulp

Bleached kraft pulps from Eucalyptus benthamii, E. globulus, E. nitens and E. nitens × E. globulus hybrid were prepared in laboratory scale and upgraded to dissolving-grade via cold caustic extraction (CCE) and dilute acid hydrolysis. The CCE reduced the alkali solubility (S18) of bleached kraft pulps from 11.8–16.4% to 4.5–6.3% after extraction with 5% (w/v) NaOH, and to 0.9–1.7% after extraction with 10% (w/v) NaOH. The dilute acid hydrolysis with 3% H2SO4 reduced the intrinsic viscosity of CCE-treated kraft pulps from 800–900 to 110–450 ml/g. E. nitens and E. benthamii displayed the most contrasting values for S18 and intrinsic viscosity after CCE and acid hydrolysis treatments. The X-ray diffraction results showed that the crystallinity index of bleached kraft pulps followed the order: E. benthamii > E. globulus > En × Eg > E. nitens. Regarding cellulose reactivity, the Fock reactivity of the bleached kraft pulps was in the range of 34.7–41.3%. After CCE, the pulps reactivity was reduced to 13.7–25.4%, whereas after acid hydrolysis it was increased to 40.7–87.5%. E. benthamii and E. nitens pulps showed to be the less reactive pulps after pulp activation via acid hydrolysis, whereas E. globulus and the hybrid showed to be the most reactive pulps towards xanthation. It was observed that different Eucalyptus species can lead to kraft pulps with different requirements towards xanthation, and that the inherent features of wood and how they are processed are of outmost importance for the final use of kraft-based dissolving pulp from a given wood species.

An application of integrated EPC–SPC methodology for simultaneously monitoring multiple output characteristics

Purpose The purpose of this paper is to develop an integrated engineering process control (EPC)–statistical process control (SPC) methodology for simultaneously monitoring and controlling autocorrelated multiple responses, namely, brightness and viscosity of the pulp bleaching process. Design/methodology/approach The pulp bleaching is a process of separating cellulose from impurities present in cooked wood chips through chemical treatment. More chemical dosage or process adjustments may result in better brightness but adversely affect viscosity. Hence, the optimum chemical dosage that would simultaneously minimize the deviation of pulp brightness and viscosity from their respective targets needs to be determined. Since the responses are autocorrelated, dynamic regression is used to model the responses. Then, the optimum chemical dosage that would simultaneously optimize the pulp brightness and viscosity is determined by fuzzy optimization methodology. Findings The suggested methodology is validated in 12 cases. The validation results showed that the optimum dosage simultaneously minimized the variation in brightness and viscosity around their respective targets. Moreover, suggested solution has been found to be superior to the one obtained by optimizing the responses independently. Practical implications This study provides valuable information on how to identify the optimum process adjustments to simultaneously ensure autocorrelated multiple responses on or close to their respective targets. Originality/value To the best of the authors’ knowledge, this paper is the first to provide application of the integrated EPC–SPC methodology for simultaneously monitoring multiple responses. The study also demonstrates the application of dynamic regression to model autocorrelated responses.

Особенности процесса нейтрализации технической серной кислоты природным известняком

The work was devoted to the solution of the environmental problem associated with the disposal of sulfur dioxide emissions from metallurgical production at the Nadezhda Metallurgical Plant (Norilsk, Norilsk Nickel PJSC). For utilization of sulfur dioxide it is planned to build a sulfuric acid plant. Concentrated sulfuric acid produced at plant is planned to be neutralized with natural limestone. This work presents the results of the study on the neutralization of concentrated sulfuric acid with limestone pulp from the Mokulay deposit (Norilsk). The influence of the following parameters was investigated: limestone consumption, acid dosing rate, limestone pulp density. It is established that the process is limited by the internal diffusion of acid through the layer of gypsum. In order to eliminate internal diffusion process it is advisable to carry out neutralization in a periodic mode by introducing a strictly measured amount of acid into an excess amount of limestone pulp. This process allows one to speed up the process of neutralization in 3-3.5 times and achieve a higher value of the final pH of the pulp comparing with continuous process. Carrying out the process in the periodic way also makes it possible to achieve the complete absence of the release of acidic off-gas during neutralization. The optimal values of neutralization parameters were determined as the following: limestone pulp density was 11-12%, acid delivery time was 40 minutes, neutralization time was 20 minutes, and final pH value was at least 6.5, while the limestone feeding was an excessive by 22-28% from stoichiometry. It was shown that an increase in the limestone pulp density is impractical because it will lead to an increase in the duration of neutralization, as well as to a sharp increase in the viscosity of the gypsum pulp. That, in its turn, makes gypsum pulp difficult to flow from the neutralization apparatus. It was recommended to filter the resulting pulp in order to obtain a gypsum cake with a moisture content of about 55%. It was recommended to store cake on a special site. A flowsheet has been developed and process schedules have been implemented for the design of a neutralization plant with a capacity of up to 2 million tons technical sulfuric acid per year.

Simultaneous mechanical refining and phosphotungstic acid catalysis for improving the reactivity of kraft-based dissolving pulp

Improvements on reactivity and viscosity control of the prehydrolysis kraft (PHK) dissolving pulp in an efficient and sustainable way is of both fundamental and practical interest. In this study, we proposed a novel concept of using a simultaneous treatment consisting of mechanical refining (R) and phosphotungstic acid (PTA) catalysis (defined as R-PTAsim) for this purpose. Results showed that the simultaneous process (R- PTAsim) was more effective in improving Fock reactivity, from 47.2 to 83.5%, while the sequential process (initial refining, followed by PTA catalysis, defined as R-PTAseq) increased from 47.2 to 77.2%. The viscosity of resultant pulps was 411 mL/g and 428 mL/g for the R- PTAsim and the R-PTAseq, respectively. The explanations are: (1) the PTA catalysis induces cellulose depolymerization and morphological changes of fibers, and improves the mechanical refining efficiency, (2) mechanical refining facilitates the diffusion/adsorption of PTA into cellulose fibers and further enhances the PTA catalysis, (3) an enhanced synergistic effect occurs in simultaneous treatment. It was demonstrated that PTA has a high chemical stability and recyclability/reusability. This concept can offer a new pathway for sustainable manufacturing high- quality dissolving pulp.

An investigation of the effect of clay type on coal flotation along with DLVO theoretical analyses

ABSTRACTCoals generally exist with clay minerals, which are very fine-sized minerals, and adversely affect the flotation of coal. For instance, they make the coal surface hydrophilic by coating coal surfaces and therefore, they inhibit bubble-particle attachment. Clay minerals can also cause over-consumption of reagents due to their high surface area. Additionally, clay minerals can transfer into the concentrate during the flotation process by entrainment because of their low weight and small particle size, and thus, increase pulp viscosity and changing froth stability. In this study, the influence of various clay minerals (kaolinite, illite, and bentonite) on the flotation behavior of coal sample was studied in detail by conventional flotation tests. In addition, the values obtained from flotation tests were correlated with theoretical energy barrier values established with classical DLVO theory based on zeta potential values of coal and clay samples measured at different pH values. According to the results of this study, no significant effect of clay minerals was observed on coal flotation. This was probably because of the high floatability of the coal used for this study. Both the results obtained from the experiments and theoretical analysis, DLVO calculations, showed that the type of clay mineral is the main indicator parameter for coal flotation.

Balancing the effect of pretreatment severity on hemicellulose extraction and pulping performance during auto-hydrolysis prior to kraft pulping of acacia wood.

When using a combination of pre-extraction and chemical pulping, a high yield of sugar recovery and minimal negative effect on the subsequent pulping step are expected. In this work, the P factor was utilized to investigate the effect of auto-hydrolysis severity on sugar recovery, removal of the main component, and impact on the kraft pulping of acacia wood chips. Using a P factor of 235, 84.34% of the polysaccharides in 14.05 g L-1 of dissolved sugars could be obtained. In addition, the soluble sugars were easily separated with a recovery yield of 3.54 g ·L-1 and Mw of 4,690 g mol-1 by direct precipitation using organic solvents. However, a maximum of 22.14 g L-1 of dissolved sugars was obtained with approximately 72.53% polysaccharides and Mw of 2,198 g mol-1 for a P factor of 601. Moreover, nearly 50% of the degraded carbohydrates remained in the auto-hydrolyzed wood chips. The decrease in the mass of pentosan, holocellulose, and klason lignin was 62, 30, and 8.76%, respectively. With intensifying severity, the screened yield and viscosity of pulps decreased markedly, whileas the Kappa number increased. No significant differences were observed in the morphology of the resultant fibers. Moreover, there was a decrease in the physical strength of the pulps due to the loss of the intrinsic strength of the pulp fibers, which in turn resulted from the cellulose damage. The combustion performance of the resultant pulping black liquor is improved due to the higher lignin content.

Totally chlorine-free bleaching of prehydrolysis soda pulp from plantation hardwoods consisting of various lignin structures

The process of prehydrolysis followed by soda-anthraquinone (AQ) cooking and totally chlorine-free (TCF) bleaching with peroxymonosulfuric acid (Psa) was investigated to develop a biorefinery process. Eucalyptus globulus, showing a high syringaldehyde (Sa) to vanillin (Va) molar ratio after nitrobenzene oxidation, was utilized. Xylooligosaccharide yield in the prehydrolysate (PHL) obtained at 150 °C for 2.5 h reached 7.2% of wood weight, indicating 47% extraction of xylan. Furfural yields increased with acid catalytic dehydration of the PHL to 1.0–1.8% of wood weight; adding an earlier acid post-hydrolysis of the PHL to generate monomeric xylose enhanced furfural production to 4.0%. Soda-AQ cooking, a non-sulfur process affording simpler alkali lignin isolation than kraft cooking, was utilized. Active alkali dosage increment decreased both Sa to Va molar ratio (S/V ratio) and Sa and Va yields of dissolved lignin. Gel permeation chromatography indicated decreased or increased purified lignin weight-average molecular weight (Mw) upon increased active alkali dosage or prehydrolysis temperature, respectively (e.g., 150 to 170 °C at 18% alkali increased Mw 1653 to 2050). Chlorine dioxide (0.083% and 0.042% as active chlorine) inclusion during the 1st and 2nd Psa stages with Psa (0.2% and 0.1% as H2SO5 weight, respectively) improved final bleached pulp viscosity from 6.0 to 7.2 mPa s.

Ultraviolet resonance Raman spectroscopy analysis of carbonyl groups present after different bleaching stages for various bleach sequences

Different bleaching reagents have different efficiencies of removing chromophore groups from chemical pulps. The objective of this work was to evaluate the effect of different bleaching sequences on the removal of chromophore groups, especially carbonyls, which are suspected to cause brightness reversion. The bleaching sequences analyzed comprise the stages: chlorine dioxide, acid hydrolysis at high temperature, alkaline extraction with hydrogen peroxide, pressurized hydrogen peroxide, and hydrogen peroxide. After bleaching an oxygen-delignified eucalypt kraft pulp with these sequences, the pulps were analyzed for their final brightness, brightness reversion, and pulp viscosity; the bleached pulps were also analyzed using ultraviolet resonance Raman spectroscopy in the infrared region. The infrared analysis indicated that bleaching stages that used hydrogen peroxide, such as pressurized hydrogen peroxide or hydrogen peroxide, in the terminal position reduced the amount of carbonyl groups in the bleached pulp as measured by the absorption band intensity. This study observed that the inclusion of a hot acid hydrolysis stage in the bleach sequence improved the final brightness and brightness stability of the bleached eucalyptus pulp. The replacement of a chlorine dioxide brightening stage by a hydrogen peroxide stage at the end of a bleach sequence yielded higher pulp brightness, and less brightness reversion. The use of pressurized hydrogen peroxide with oxygen resulted in less brightness reversion.

Влияние импульсного электрического поля на реологию масличного материала

Treatment with pulse electric field is a promising method of preliminary preparation of oil-bearing material before further treatment. Experimental data was obtained in Kuban State Technological University (“Food and Chemical Technologies Research Center”) (Krasnodar). The author studied oil-bearing material rheological properties and assessed the influence of preliminary treatment with pulse electric field. Using mathematical tools and an experiment the author found out that plastic viscosity of pulp corresponds to oil viscosity which confirms the assumption about Bingham rheology made in the paper. Experimental works have shown that there is structure formation in the material that enters conveyor auger feeder. The author determined that there is an effect after treatment with pulse electric field as the structure of the material changed and critical shear stress decreased from 24.36 to 22.89 Pa for the samples which were treated with field having field intensity E = 8 kV/cm and number of pulses n = 300 during three seconds. Critical shear stress decrease due to the treatment with pulse electric field allows to use less energy for oil-bearing material transportation and crushing in case of pressing process. That factor is a positive complement to the existing effect of oil yield increase after preliminary preparation. The obtained parameters of the engineering model make it possible to forecast rheology of viscoplastic flow in wide range of shear strain rates in conveyor auger feeder as well as during treatment with pulse electric field.

Process Parameters Optimization of Casuarina equisetifolia for Enhanced Production of Bleachable Grade Kraft Pulp through RSM

Casuarina equisetifolia (beach sheoak), a fast-growing deciduous tropical hardwood tree, was utilized to assess its suitability for pulp and paper production. Response surface methodology (RSM) based on central composite design (CCD) was used to optimize the kraft pulping process by varying the alkali doses, reaction temperature, and time. Using the best optimum pulping conditions with alkali charge 17.9%, temperature 170.2 °C, and pulping time 82.1 min, a high screened pulp yield of 52.4% with low kappa number of 18.1 and pulp viscosity of 974.5 cm3/g could be achieved. The laboratory handsheets prepared with kraft pulp under optimum conditions showed good mechanical strength properties at an optimum beating level of 45 °SR.

Effect of sodium alginate on reverse flotation of hematite and its mechanism

Given the gradual increase in the chlorite content of hematite ores, pulp properties seriously deteriorate during flotation. The traditional anion reverse flotation of hematite cannot effectively eliminate the effects of chlorite, leading to a significant decrease in the total Fe (TFe) grade of the concentrate. In this work, the effect of sodium alginate on the reverse flotation of hematite was systematically investigated. Flotation tests of artificially mixed ores were conducted, and the results showed that sodium alginate can significantly improve the removal rates of quartz and chlorite. The adsorption measurements, infrared spectroscopy, and contact angle tests demonstrated that sodium alginate adsorbs on the quartz surface by chelating with calcium ions, thereby weakening the steric hindrance of oleate ions and increasing the adsorption capacity of sodium oleate to ultimately improve the removal rate of quartz. Furthermore, owing to its lower density and fine particle size, chlorite is easily entrained into the foam layer. Sodium alginate dramatically increases the liquid-to-gas ratio of the foam layer by increasing pulp viscosity, thereby increasing the entrainment rate of chlorite and finally improving its removal rate. The core content of this thesis bears significance in improving the Fe grade in the reverse flotation of chlorite-containing hematite.

Modelling and optimization of the last two stages of an environmentally-compatible TCF bleaching sequence

A totally chlorine free (TCF) bleaching sequence was studied for an acid sulfite pulp mill that produces dissolving pulps. Laboratory analyses of the last two bleaching stages, an oxidant-reinforced alkaline extraction stage (EOP), and a subsequent pressurized peroxide with oxygen stage (PO), were performed on a eucalypt pulp that had been delignified by an ozone (Z) stage in the pulp mill. The goal was to predict the optimal costs and operational conditions for the (EOP)(PO) partial bleach sequence for three different specialty pulp products. Four independent variables affecting the pulp quality properties were examined for each stage (i.e., reaction temperature, reaction time, NaOH dosage and H2O2 dosage). The dependent variables were various pulp properties, such as intrinsic pulp viscosity, alpha-cellulose content, kappa number, and GE brightness. Three scenarios were considered to optimize the bleaching process, which related to a regenerated cellulose product (viscose) that is widely commercialized, and to two novel products (nanocrystalline cellulose (NCC) and nanofibrillated cellulose (NFC). Statistical response surface models indicated that the bleaching behavior of the ozone-treated pulp could be represented by second-order polynomial equations. These non-linear optimization models predict cost savings of 62.2%, 73.4%, and 63.3% for producing viscose, NCC, and NFC pulp grades, respectively.

Mitigating the negative effects of clay minerals on gold flotation by a lignosulfonate-based biopolymer

The objective of this study was to identify various mechanisms responsible for the poor flotation of a high-clay-content gold ore and then develop a remedial solution. Compared to the flotation of a clean gold ore with a low clay content, obtained from the same flotation plant, the flotation of the high-clay-content gold ore produced much lower gold grade and gold recovery. The degree of entrainment (ENT) was calculated and it was found that a high mechanical entrainment of gangue minerals occurred in the flotation of the high-clay-content gold ore, contributing to the low gold grade in flotation. Electrochemical impedance spectroscopic (EIS) measurements were conducted to detect a possible clay slime coating on gold surface during flotation. It was observed that a clay slime coating did not occur on gold surface in the flotation of the high-clay-content gold ore, and therefore slime coating was not the reason for the poor gold flotation performance. Rheological measurements show that the high-clay-content gold ore slurry exhibited a non-Newtonian behaviour with a high apparent viscosity, contributing to the low gold recovery in flotation. Based on the previous studies, a lignosulfonate-based biopolymer (DP-1777) was used to mitigate the negative effects of clay minerals in the flotation of the high-clay-content gold ore. It was found that DP-1777 improved both gold grade and gold recovery significantly through the reduction of mechanical entrainment and pulp viscosity, respectively.

Utilization of grinding aids in oil shale milling

ABSTRACTGrinding aids (GAs) effectively reduce the energy requirements of the grinding process and improve grinding productivity. Two GAs (sodium silicate and triethanolamine (TEA)) were selected and their mechanisms of action were explored. The effect of the different grinding parameters on oil shale grinding efficiency was determined. The adsorption characteristics of the GAs were investigated using scanning electron microscopy (SEM), pulp viscosity, surface potential, and Fourier transform infra-red spectroscopy (FTIR). The results indicate that compared to grinding without GAs, the addition of sodium silicate and triethanolamine (TEA), increases the yield of −0.075 mm particles by −2.97% and 14.05%, respectively. The optimal grinding parameters were determined for a pulp concentration 40%, a steel ball weight ratio of Φ32 mm: Φ25 mm: Φ22 mm: Φ18 mm (50:24:17:9), and a grinding time of 20 min. The flotation test results indicate that compared to sodium silicate, TEA is the more suitable GA. The addition of sodium silicate reduced the sharp edges of the particles, increased the pulp viscosity and reduced the surface potential. It was not conducive to pulp dispersion. Conversely, TEA reduced the pulp viscosity and increased the surface potential, which enhanced the repulsive force between the particles, increasing the particle spacing, and the dispersion of the pulp. Sodium silicate and TEA both formed hydrogen bonds or chemical bonds on the surface of the mineral particles, strengthened the steric-hinderance effect, and enhanced the repulsive force between the particles.

The enhanced flotation of coal by nanosilica particles

ABSTRACT It is well known that the stability of hydration film on the particle surface affected the particle-bubble attachment in a flotation process. In this paper, the effect of attached nanosilica particles on the stability of liquid film around the coal particles was investigated by measurements of viscosity of the coal pulp and the bubble attachment time for coal particles. The interaction energy between a nanosilica particle and a coal particle was calculated using the EDLVO theory. Results showed that the nanosilica-coal attachment was driven by hydration attraction. And the stability of liquid film was weakened with the attachment of nanosilica particles, which is probably due to the change of surface roughness. In this case, the bubble-particle attachment time was reduced and further improved the flotation recovery of coal.

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.