Volume 36, Issue 4

Rotary kilns are large-scale unit operations that are critical to many industrial processes such as cement production, pyrometallurgy, and kraft pulping. As expensive, energy-intensive units, it is imperative from both an economic and environmental perspective to ensure efficient operation of the rotary kiln. To provide additional insights for operation and maintenance, rotary kilns are increasingly outfitted with more advanced sensing technology. Leveraging this supplementary data requires strategies and active efforts towards storage, processing, and visualization. In this work we provide a visualization strategy for industrial thermal camera data that is measured along the shell profile of a rotary lime kiln. The proposed strategy assists specifically with the visualization of ring formation at different timescales, but it also serves more generally as a useful tool for operations management. This paper describes the visualization strategy, provides a demonstration with industrial data, and offers open-source resources for interested users to implement it themselves.

Bangladesh is very much successful in coastal afforestation programmes, which protects from frequent cyclones. Casuarina equisetifolia has showed a climate resilient and promising species. No study has been done on industrial application of C. equisetifolia in Bangladesh. In this study, C. equisetifolia was characterized in terms of chemical, morphological and anatomical properties. It is characterized with higher α-cellulose, similar hemicelluloses and lignin as compared to other hardwood species grown in Bangladesh. The C. equisetifolia lignin contained mainly of syringyl unit followed by guaiacyl unit. The fiber of C. equisetifolia was shorter in length with very thick cell wall and narrow lumen, consequently the wood density and runkel ratio were very high (2.89). The C. equisetifolia was also fractionated by formic acid (FA) at atmospheric pressure to pulp, dissolved lignin and hemicelluloses. Pulp yield was 50 % with kappa number of 40 at the conditions of 3 h treatment with 90 % FA followed by 2 h peroxyformic acid treatment. But in the kraft process, C. equisetifolia produced pulp yield of 44 % with kappa number 17. Both pulps showed good bleachability. The papermaking properties were in acceptable range. Finally, it can be said that C. equisetifolia is promising species for pulping.

Polysulfide pulping is a method to increase the pulp yield in a kraft pulp mill. Higher production is in the core of pulp mill process development, but modifications in cooking raise questions on their effects on the other parts of the process. This study focuses on the impacts of polysulfide pulping on the energy use and production of kraft pulp mills. The impacts are estimated by calculating and analyzing the steam and electricity balances of reference softwood and hardwood mills. Energy generation using residual biomass is an essential part of the operation of a kraft pulp mill, and often a notable source of income. The results show that implementation of polysulfide cooking affects both energy consumption and production. Higher hemicelluloses content of pulp cooked using polysulfide liquor means that less organic material ends up in the black liquor. Subsequently, the recovery boiler energy production suffers. The reduced steam production together with increased steam consumption decreased electricity production, corresponding to a decline in sellable electricity of 22.4 % in the hardwood mill and 28.4 % in the softwood mill. The study shows that increasing the pulp production by investing in polysulfide cooking in stand-alone kraft pulp mills can be economically feasible.

Bleachability is evaluated as how easily a pulp sample is bleached and it depends on the structure of residual lignin and carbohydrates. Also, the bleachability varies depending on the bleaching sequence. ECF light sequences have been improved significantly in the recent years. However, we still don’t fully understand how ECF light bleach plants are optimally run. This work studies the bleachability of softwood kraft pulp in an ECF light bleaching sequence, (OO)Q(OP)D(PO). Three pulp samples with brown stock kappa number 27, 32 and 35 were bleached and studied for residual lignin, hexenuronic acid and carbohydrate content. It was found that in the bleaching stages that are highly delignifying, it is beneficial with a higher kappa number for the delignifying bleachability. However, in the bleaching stages where the objective is brightness increase, the brightness gain bleachability is improved by a lower kappa number. We also intended to determine which of the three samples had the best suited kappa number for this particular bleaching sequence. According to our results, the bleaching was most effective with kappa number around 32. Although an even higher kappa number resulted in higher yield after cooking, it seemed that this bleaching sequence cannot preserve the yield gain.

In this study, the effect of process- and online analyser configuration on pulp quality control is explored. The following parameters were included: analyser sampling interval, time delay, measurement error magnitude, and latency chest residence time. Using different values of parameters in a process model, a range of configurations were constructed. For each configuration, the achievable control performance was evaluated using an optimization approach. PI controller settings were chosen based on minimization of the integrated absolute error ( IAE ) in pulp quality after an input step disturbance. The results show that reducing the sampling interval improves performance also when the interval is smaller than the chest residence time or the analyser delay. Moreover, reducing the chest residence time can reduce the IAE by up to 40 %. However, reducing the residence time to lower than 1/3 of the sampling interval does not improve performance. Further improvement is possible if the analyser delay is reduced. The compromise between reducing the IAE and avoiding creating variation by acting on measurement error has a strong influence on the results. In conclusion, pulp quality control performance can be improved significantly by making changes to the studied configuration parameters.

Seven copolymers of maleic anhydride were hydrolyzed and impregnated into sheets of bleached softwood kraft pulps to enhance market pulp properties. Drying the impregnated pulps at 120 °C for 10 minutes, attached to the fiber surfaces up 0.16 meq of carboxyl groups per gram of dry pulp. Heating the impregnated pulps regenerates succinic anhydride moieties which can then form stable ester linkages with cellulosic hydroxyls. The pH of the impregnation solution is important. Impregnation with solutions at pH 8 gave polymer contents without repulping issues. By contrast, impregnation at pH 4 gave dried pulp sheets that were too strong to enable repulping in a paper mill. Although most of the seven copolymers were fixed to cellulose, poly(ethylene-alt-maleic anhydride) gave the highest density of carboxyl groups. The simplicity of waterborne polymers and mild drying temperatures suggests maleic anhydride copolymer treatment could be implemented in a conventional market pulp mill.

Coated paper with enhanced barrier properties was prepared via a simple layered self-assembly method using hemicellulose and starch as biobased coatings. Effect of the coating on properties of cellulose paper was investigated. Barrier properties of the paper was increasingly strengthened as the coating amount of hemicellulose rose. When the paper was coated with starch (10.7±0.3  g / m 2 \text{g}/{\text{m}^{2}}) and hemicellulose (6.9±0.2  g / m 2 \text{g}/{\text{m}^{2}}) successively, the oil resistance of the paper was increased from 0 to grade 7. Air permeability and water vapor transmittance was decreased by 93.8 % and 39.7 %, respectively. The water contact angle of the coated paper reached 91.7° when the amount of hemicellulose was 1.5±0.2  g / m 2 \text{g}/{\text{m}^{2}}. The hydrophobicity of the coated paper was superior to the original paper although it was negatively influenced by the increasing amount of hemicellulose. The improvement of barrier properties of the coated paper was mainly ascribed to the formation of a thin polymer network on paper surface through intermolecular interaction via hydrogen bonds as demonstrated in SEM and FTIR-ATR results. Moreover, tensile strength and rupture resistance of the coated paper was improved. The results offered an environmentally friendly and economical strategy for preparation of food packaging paper with good barrier properties using biobased coating materials.

In this paper, white pixel percentage (WPP) value, as an overall measure of fold crack damages, has been analysed with respect to selected parameters of sample preparation and digitalization process, as well as the results of residual tensile strength. The WPP values were derived by an automated image processing algorithm, developed earlier, based on extensive comparative analysis of the existing computer-aided methods. Results indicate that WPP values correlate well with the extent of fold cracks on the coated samples, as far as the used parameters of sample preparation and digitalization are concerned. In the case of correlation with residual tensile strength, results for samples folded in cross direction revealed that the extent of the visually registered fold cracks agree well with the actual damage, while for samples folded in machine direction, the overall strength losses weren’t alarming, although the fold cracks were detected correctly. In addition, results pointed out that the simplest sample placement position (inner angle of 180°) is not applicable for realistic sample representation. Furthermore, scanners could provide a superior image quality in lab conditions, but for industry application, a camera-based solution would be more purposeful, while micrographs are more suitable for traditional visual analysis.

Paper is an environmentally friendly, recyclable material whose main material is cellulose, which can be obtained from all kinds of trees and plants, used as writing, printing and packaging material. Due to its structural properties, papers are not resistant to temperature and humidity, as well as problems with ink transfer with its porous structure and experienced negative printability properties. In recent years, especially the growth of the packaging industry has increased the demand for papers with improved printability properties. In order to obtain better printability properties from papers, some processes can be performed in paper production, as well as some surface treatments after production. These processes are paper coating, sizing and calendering. Paper coatings are generally water-dispersed coating solutions with one or more pigments, binders and certain additives to improve the desired properties. With these processes, by filling the gaps between the pores of the paper, a shapely and smooth surface is obtained and good printability is obtained together with the optical and physical properties of the papers. In this study, the interactions and printability properties of different types of pigments with xanthan gum binder were investigated by preparing paper coating formulations using calcium carbonate, barite and talc pigments and xanthan gum as binder. As a result, xanthan is a good coating binder and CaCO 3 {\mathrm{CaCO}_{3}} from the compared pigments is the most suitable compared to the other 2 pigments, considering all the studied areas.

In this work, we studied the multilayer adsorption of cellulose nanocrystals and cellulose nanofibers with other polysaccharides such as xyloglucan and chitosan. We showed that the specific interactions between these biopolymers can be exploited to prepare three-dimensional functional materials. Quartz crystal microbalance studies showed that both biopolymers were adsorbed irreversibly on the nanocellulose surfaces. In aqueous media, the maximum amount of adsorbed polymer was higher for the smaller and more crystalline cellulose nanocrystals, compared to cellulose nanofibers. For both nanocelluloses employed, the amount of xyloglucan of the first bilayer was larger than the amount of chitosan adsorbed. Ellipsometry showed that both xyloglucan and chitosan were adsorbed on nanocellulose surfaces. However, at the second layer no mass change was detected by quartz crystal microbalance when xyloglucan was added, while for addition of successive layers of chitosan a decrease of frequency was detected. The water uptake of multilayers was higher for cellulose nanocrystals than for nanofibers, which was ascribed the presence of voids in the nanocrystal layer. Finally, we demonstrated that multilayer adsorption of these biopolymers can be performed on calcium carbonate sacrificial templates, which can then be removed to yield hollow polysaccharide microcapsules.

Superhydrophobic surfaces have high potential in self-cleaning and oil-water separation applications. We developed a three-step method for the preparation of superhydrophobic filter paper. It involved citric acid (CA) pretreatment to activate cellulose fibers, coating with cellulose nanofibrils/functionalized silica (CNFs/ m -SiO 2 ) slurry to increase surface roughness, and grafting of hexadecyltrimethoxysilane (HDTMS) to enhance water resistance. The water contact angle (WCA) and siding angle (SA) of the prepared filter paper reached 151.5° and 7.5°, respectively. The results showed that, compared to the coated filter paper without the added CNFs, the coated paper with CNFs had higher retention of m -SiO 2 , thus roughness required for superhydrophobic surface was achieved. Further test under frequent abrasion and acid or alkali conditions showed that CA pretreatment improved the durability of superhydrophobic filter paper due to chemical crosslinking between the modified substrate and m -SiO 2 . Besides, the prepared superhydrophobic filter paper had outstanding self-cleaning property and high oil-water separation efficiency for various oil-water mixtures. Therefore, it is expected to be used for the treatment of oily wastewater.

The mechanical pulp of mulberry branches was evaluated as a raw material for the production of cellulose II and its subsequent conversion to nanocellulose via high-pressure homogenization, 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-oxidation, and sulfuric acid hydrolysis. The morphology, chemical structure, crystallinity, and thermal stability of the nanocellulose samples prepared by each method were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, field-emission scanning electron microscopy, atomic force microscopy, and thermogravimetric analysis. The results showed that nanocellulose prepared by high-pressure homogenization exhibited higher aspect ratio (>100), and the weight loss peak in the DTG chart was 361 °C, with the best thermal stability, whereas that prepared by sulfuric acid hydrolysis featured shorter fiber length (96±31 nm) and a higher crystallinity (78.2 %).The TEMPO oxidized nanocellulose (TOCN) had smaller width (5.5±1.6 nm) and high carboxyl content (1.5 mmol/g). In addition, we have further studied the application of TOCN in the wet end of papermaking, replacing the colloidal SiO 2 in CPAM/ colloidal SiO 2 /APAM retention system with the same amount (3600 ppm) of TOCN. The study found that the strength of the paper obtained by adding TOCN instead of the traditional wet end additives is similar, and the water drainage and retention properties of the pulp are improved.

Nonwovens are increasing in demand due to their versatility which enables use in a broad range of applications. Most nonwovens are still produced from fossil-based resources and there is thus a need to develop competitive materials from renewable feedstock. In this work, nonwovens are produced from cellulose via a direct solution blowing method. Cellulose was dissolved using the ionic liquid 1-ethyl-3-methylimidazolium acetate (EMIMAc) and was regenerated into nonwovens by coagulation in water. The properties of such nonwovens were previously rather stiff and papery-like and the aim of this work was to improve the softness and feel of the materials by simple adjustments of the post-processing steps, i. e. washing and drying. It was shown that by primarily changing the drying method, it was possible to create a much softer and bulkier material using the same solution blowing parameters.

Increased tensile strength of paper is a primary objective of low consistency refining. Although refining is typically controlled by Specific Refining Energy and Specific Edge Load, these parameters are not independent because both depend directly on power. To overcome this shortcoming, we derived simplified expressions for the number and intensity of impacts on pulp. The number of impacts reflects the capacity of the refiner to impose loading cycles on pulp. The intensity, combined with a response parameter, reflects the probability of a successful refining event at each impact. Based on these parameters, we employed an equation based on cumulative probability to predict tensile strength of pulp after refining. Non-linear fits of this equation to data from the literature for a wide range of pulps refined by various refiners gave response parameters that were remarkably similar ranging from 1.6 – 3.3 × 10 − 6 1.6\text{--}3.3\times {10^{-6}} kg/J. The resulting probability of successful refining events at each impact was found to be quite small, about 1–3 %. We postulated that this is likely due to most force being imposed at fibre crossings in the pulp network. Consequently, multiple cycles are required to expose other parts of fibres and new fibres to loadings. In summary, this new approach to characterizing refining reflects the stochastic nature of the process and enables a direct quantitative link between refiner operation and fibre development.

Paper mill effluent has been characterized as recalcitrant because of containing lignin and its derivatives. Since biofilm system exhibits a notable potential for the removal of recalcitrant contaminants, a sequencing batch biofilm reactor (SBBR) was employed to treat coagulated recycled paper mill effluent in this study. The results indicated that the SBBR removed 91.3 % of chemical oxygen demand (COD), whilst total suspended solid (TSS) and color removal reached 83.1 % and 71.0 %, respectively. The microbial analysis suggested that three typical heterotrophic phyla, Proteobacteria , Bacteroidetes and Acidobacteria are dominant bacteria and reflected the removal of recalcitrant contaminants. The COD removal rate of SBBR is evidently superior to conventional activated sludge process due to high sludge concentration as well as long sludge retention time (SRT). Whilst the problem of sludge bulking can be successfully avoided, the blockage of reactor caused by TSS accumulation and microbial growth deserve further investigation.

Refiners develop pulp properties by applying forces on fibres during bar crossings. The size of these forces is critical in developing fibre properties while avoiding fibre shortening. This study has shown that bar force calculated from Specific Edge load (SEL) gives the same result as vector-based derivations of average bar force. Predicted forces agree reasonably well with ones measured by a novel piezo-electric sensor in refiner bars and forces estimated from measurements of fibre shortening.