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Application of spruce wood flour as a cellulosic-based wood additive for recycled paper applications— A pilot paper machine study, TAPPI Journal October 2021
ABSTRACT: This study gives a first insight into the use of wood flour as a plant-based and cellulosic-based alter-native additive for newsprint and paperboard production using 100% recycled fibers as a raw material. The study compares four varieties of a spruce wood flour product serving as cellulosic-based additives at addition rates of 2%, 4%, and 6% during operation of a 12-in. laboratory pilot paper machine. Strength properties of the produced news-print and linerboard products were analyzed. Results suggested that spruce wood flour as a cellulosic-based additive represents a promising approach for improving physical properties of paper and linerboard products made from 100% recycled fiber content. This study shows that wood flour pretreated with a plant-based polysaccharide and untreated spruce wood flour product with a particle size range of 20 μm to 40 μm and 40 μm to 70 μm can increase the bulk and tensile properties in newsprint and linerboard applications.
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Corrosion damage and in-service inspection of retractable sootblower lances in recovery boilers, TAPPI Journal October 2021
ABSTRACT: Several reports of accidents involving serious mechanical failures of sootblower lances in chemical recovery boilers are known in the pulp and paper industry. These accidents mainly consisted of detachment and ejection of the lance tip, or even of the entire lance, to the inside of the furnace, towards the opposite wall. At least one of these cases known to the author resulted in a smelt-water explosion in the boiler.In other events, appreciable damage or near-miss conditions have already been experienced. The risk of catastrophic consequences of the eventual detachment of the lance tip or the complete lance of a recovery boiler soot-blower has caught the attention of manufacturers, who have adjusted their quality procedures, but this risk also needs to be carefully considered by the technical staff at pulp mills and in industry committees.This paper briefly describes the failure mechanisms that prevailed in past accidents, while recommending inspection and quality control policies to be applied in order to prevent further occurrences of these dangerous and costly component failures. Digital radiography, in conjunction with other well known inspection techniques, appears to be an effective means to ensure the integrity of sootblower lances in chemical recovery boilers used in the pulp and paper industry.
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Comparative study of guar gum and its cationic derivatives as pre-flocculating polymers for PCC fillers in papermaking applications, TAPPI Journal April 2022
ABSTRACT: In this work, gums from guar seeds were evaluated as a potential precipitated calcium carbonate (PCC) filler pre-flocculant to induce functional filler in papermaking applications. In recent years, guar has been conidered one of the promising wet-end additives due to its abundance, rich source of hemicellulose content, and bio-degradability. However, application of guar gum in filler pretreatment methods for producing high ash paper has scarcely been reported. In this paper, the flocculating ability of three types of guar gum was established with charge analysis and turbidity (NTU) of the system at 1% and 5% for each gum: native gum (NG) having a degree of substitution (DS) of 0, and cationic gums having a DS value of 0.07 (CL) and 0.15 (CH). It was interesting to observe that even at a 5% dose of G, the charge density of PCC did not deviate much from the initial values. The system carried a weak negativeharge, resulting in an unstable colloidal suspension that led to PCC-PCC particle bridging. On the other hand, the operative mechanism of CL and CH during adsorption and PCC flocculation was predicted to be charge neutralization and electrostatic-patch formation, accompanied by particle bridging. Note that CL, with a maximum 47.5% eduction in residual turbidity of PCC at a 1% dose, was much more efficient in doing so than the other two gums; NG had a 40% maximum reduction in residual turbidity at a 5% dose and CH had a maximum 30% reduction at a 1% ose. Later on, floc formation and structure were correlated with optical and field emission scanning electron microscopy (FE-SEM) images. In the next set of trials, paper properties were determined by varying the different gum dosages from 0.2% to 5% at a constant dose of 20% filler. It is also noteworthy to mention that with 1% CL (low DS) dose, PCC retention increased by 39%, which also enhanced the tensile, tear, burst, and opacity properties by 11%, 19%, 5%, and 4.4%, respectively, without significantly affecting the bulk properties. Further, wide-angle X-ray diffraction (XRD) analysis nd Fourier transform infrared (FTIR) analysis revealed that pre-flocculating PCC with a 1% gum dose did not induce any change in crystalline transformation. Based on observation, it was found that cationic gums with low DS values re a better choice for maximizing the strength of paper while maintaining bulk and high opacity when pre-flocculaion is adopted to increase the filler retention in paper.
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Application of ATR-IR measurements to predict the deinking efficiency of UV-cured inks, TAPPI Journal January 2022
ABSTRACT: In recent years, ultraviolet (UV)-curable ink has been developed and widely used in various printing applications. However, using UV-printed products (UV prints) in recovered paper recycling causes end-product dirt specks and quality issues. A new method was developed that can distinguish UV prints from other prints by means of attenuated total reflectance infrared (ATR-IR) spectroscopy. Application of this method could allow more efficient use of UV prints as raw materials for paper recycling.First, a mill trial was performed using UV prints alone as raw materials in a deinked pulp (DIP) process. Second, test prints were made with four types of UV inks: a conventional UV ink and three different highly-sensitive UV inks. Each print sample had four levels of four-color ink coverage patterns (100%, 75%, 50%, and 25%). Next, deinkability of all prints was evaluated by laboratory experiments. Finally, each print was measured using the ATR-IR method, and the relationship between the IR spectra and deinkability was investigated. Mill trial results showed that UV prints caused more than 20 times as many dirt specks as those printed with conventional oil-based ink. There were variations in recycling performance among UV prints taken from bales used for the mill trial. Lab tests clearly revealed that not all UV-printed products lead to dirt specks. In order to clarify the factors that affected deinkability of UV prints, the print samples were investigated by lab experiments. Key findings from lab experiments include: œ The number of dirt specks larger than 250 µm in diameter increased as the ink coverage increased. œ Higher ink coverage area showed stronger intensity of ATR-IR spectral bands associated with inks. These results indicate that deinkability of UV prints could be predicted by analysis of ATR-IR spectra. œ Finally, the method was applied for assessment of recovered paper from commercial printing presses. It was confirmed that this method made it possible to distinguish easily deinkable UV prints from other UV prints. Based on these findings, we concluded that the ATR-IR method is applicable for inspection of incoming recovered paper.
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Economic and competitive potential of lignin-based thermoplastics using a multicriteria decision-making method, TAPPI Journal September 2022
ABSTRACT: As a result of new lignin extraction plants hatching and increasing volumes of technical lignin becoming available, a variety of lignin derivatives, including phenolic resins and polyurethane (PU) foams, are reaching the marketplace or being used as intermediate products in many industrial applications. In the spectrum of possible lignin derivatives, thermoplastics appear particularly attractive due to a symbiosis of market, policy, and technology drivers. To assess the preferredness for lignin-based thermoplastics, this paper adapted a risk-oriented methodology formerly applied to assess lignin usage in various applications (phenol-formaldehyde [PF] resins, PU foams, and carbon fiber applications) to the case of lignin-based thermoplastics using hydroxypropylated lignin (HPL) and miscible blends of lignin and polyethylene oxide (PEO). The HPL is considered for garbage bags and agricultural films applications, while lignin-PEO blends are used as replacement for acrylonitrile butadiene styrene (ABS) in applications such as automotive parts. In the methodology, two phased-implementation strategies were defined for each thermoplastic derivative, considering perspectives for profit maximization (90 metric tons/day integrated units) and revenue growth (350 metric tons/day overall capacity), which were considered for implementation within a softwood kraft pulping mill. A set of six criteria representative of the main economic and market competitiveness issues were employed, and their respective importance weights were obtained in a multicriteria decision-making (MCDM) panel.Early-stage techno-economic estimates were done as a basis for the calculation of decision criteria. Compared to product derivatives previously assessed, capital investment for thermoplastic strategies appeared marginally higher due to the required lignin modification steps (on average 30% higher at similar capacity, and 6% for higher-scale revenue diversification strategies). Higher operating costs were also observed due to increased chemical expenses for all thermoplastic strategies, which are ultimately balanced by revenues associated with targeted thermoplastic products, leading to greater annual margins and cash flow generation over the project lifetime for thermoplastic strategies compared to other product applications (58% to 66% higher on average, at similar scale). Benefits of improved economics were reflected in economic criteria, internal rate of return (IRR), and cash flow on capital employed (CFCE), as well as in the price competitiveness criterion, CPC. Overall, the combination of relatively high lignin content in the plastic formulation and the less costly modification method contributed to lignin-PEO strategies, gaining the top two rankings. Based on their overall scores, both strategies defined for HPL would also integrate the group of “preferred” strategies, but are outranked by strategies that consider lignin positioning on PU foam applications.
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Pilot scale black liquor concentration using pressure driven membrane separation, TAPPI Journal April 2023
ABSTRACT: Black liquor concentration using pressure driven membrane separation has long been proposed as a means of achieving energy savings and breaking production bottlenecks. To date, limitations in membrane performance and stability under black liquor process conditions have prevented those promises from being realized out-side of tightly controlled laboratory settings. In this work, we describe the first successful pilot scale field deployments of a membrane system for black liquor concentration. Using a purpose-built system and commercial sized, spiral wound graphene oxide membrane elements, we have logged nearly 6000 h of runtime across deployments to multiple mill sites. We demonstrate concentration of black liquor from 14% to >20% total solids, while generating permeate water comparable in quality to that of evaporator condensate and an 81% reduction in energy consumption relative to evaporation. At a commercial scale, these results translate to $2 M/year in net energy savings for a typical mill, as well as an opportunity to support production increases or mill expansions. These results represent a significant leap forward in the ability of membrane systems to deliver substantial value via black liquor concentration.
Journal articles
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Evaluation of soap recovery efficiency from black liquor — analytical tools, TAPPI Journal April 2023
ABSTRACT: Soap skimmings (“soap”) are typically recovered from black liquor in kraft mills that process a high percentage of softwood. In many mills, the recovery of soap is inefficient, negatively impacting performance of evaporators and recovery boilers and resulting in loss of potential revenue. A thorough evaluation of soap recovery performance in a kraft mill requires measurement of soap content in black liquor at various sampling locations, especially around the soap skimmer.The standard laboratory method for evaluating soap content in black liquor is a complex, multi-step process that relies on solvent extraction and titration; most mills send these samples to an outside laboratory for this analysis. In this study, 100 black liquor samples, with a wide range of soap concentrations, were tested by the standard solvent extraction method. After additional dilution, each sample was also tested for surface tension with a bubble pressure tensiometer. The results were found to correlate very closely with the solvent extraction tests results. This alternate method, using surface tension measurements of diluted black liquor samples, produces rapid results and can be easily implemented in most kraft mills, which would facilitate much more frequent in-house evaluations of soap recovery performance.
Journal articles
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Advantages of lean duplex stainless steels in the pulp and paper industry, TAPPI Journal April 2023
ABSTRACT: The performance of lean duplex stainless steels has been utilized by the pulp and paper industry since their introduction to the market almost 20 years ago. Experience has shown that this group of stainless steels has exceptional performance in, for example, alkaline environments towards typical deterioration mechanisms, i.e., uniform corrosion and stress corrosion cracking. The chemistry of the “lean” duplex steels is designed so that the content of volatile and expensive elements like nickel and molybdenum can be reduced to an absolute minimum without sacrificing the technical performance. This reduces the raw material cost and most importantly provides predictability of the steel price, which is often challenging with conventional austenitic and duplex stainless steels.Thanks to a dual phase microstructure and high nitrogen content, lean duplex steels have at least two times higher strength compared to standard austenitic stainless steels. This is often a preferred feature in pulp and paper construction, as it enables lighter structures and less material to be utilized. Today, lean duplex steels are widely available in various dimensions, from thin cold rolled sheets up to thick hot rolled plates. Lean duplex steels are also fully recyclable after the decommissioning stage of the equipment, thereby contributing to the circular economy.
Journal articles
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Energy saving potential of interstage screen fractionation for production of board grade BCTMP, TAPPI Journal August 2023
ABSTRACT: Over the last few decades, the continuing decline in mechanical pulp-based grades has led pulp producers to modify operations and implement measures to reduce production costs in order to stay competitive. In spite of a considerable effort to reduce energy consumption, the latter is still a major portion of production costs in the process of making bleached chemithermomechanical pulp (BCTMP). In this study, we evaluated the impact of interstage screening fractionation (ISSF) and secondary refining strategy for producing BCTMP with the objective of reducing refining energy consumption while maintaining or improving bulk and strength properties. In the first step and to establish a baseline for a mill’s existing configuration, the collected primary refined pulp and reject streams from the ISSF were refined in a high consistency (HC) refiner to target freeness levels. The accepts and refined rejects streams were recombined, and their properties were compared to those of the refined primary pulp. The results showed that, at a given freeness of 400 mL and compared to the control case (without fractionation), the ISSF using an 0.070 in. basket followed by rejects refining could lead to about 25% energy saving in the second stage HC refining. Handsheet properties showed that utilization of ISSF could produce BCTMP with higher bulk and similar average fiber length and tear index. However, a slight reduction in tensile strength was observed. In the second set of trials, the primary refined pulp and the rejects from the ISSF using the 0.070 in. basket were refined by a low-consistency (LC) refiner. The results showed that, at the same freeness of 400 mL and compared to refined primary pulp, the ISSF saved about 26% in net LC refining energy. At a specific edge load (SEL) of 0.4 J/m, the produced pulp had similar bulk and strength properties compared to those of the control sample. A higher SEL of 0.6 J/m in LC refining could further decrease net refining energy consumption; however, it also led to reduction in fiber length, bulk, and strength properties.
Journal articles
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The use of minerals in fiber-based packaging and pulp molding, TAPPI Journal January 2024
ABSTRACT: Minerals are widely used in the pulp and paper industry for aiding the processing, economics, and final quality of fiber-based products. Among these, calcium carbonate, talc, and kaolin are widely used as fillers, and these can have varying brightness, particle size distributions, and aspect ratios. For the molded fiber area, these minerals can raise the solids content of the pulp mixture and improve throughput and lower energy requirements for drying. Talc is also widely used as a process control agent, picking up pitch and stickies and improving productivity by lowering machine cleaning time.The replacement of single use plastic with fiber-based replacements is a global trend; however, it does come with some significant challenges, such as grease and moisture proofing. Previously, per- and polyfluoroalkyl substances (PFAS) have been used to provide functions such as water and grease repellency, but regulatory demands have seen its demise in the packaging industry. Therefore, water holdout is now generally achieved by addition of alkyl ketene dimer (AKD) sizing. Wax additives are being developed and tested as PFAS replacements for oil and grease resistance. Rather than strongly repelling lipids from the fiber surface, these PFAS alternatives restrict flow pathways and react with food oils to alter their flow characteristics to prevent penetration through the substrate. During studies incorporating both PFAS substitutes and minerals, no detrimental interactions were observed. This paper addresses the different needs of the molded fiber market by including mineral fillers in molded fiber articles and will be presented as a series of different case studies. In all studies, we show that the trends observed when mineral filler is added to molded fiber are broadly similar to those seen in conventional paper and paperboard applications. Mineral addition in all studies gave improvements in productivity and optical appearance. With its organophilic surface, hydrophobic talc had the additional advantage of pitch and sticky control, and although a small decrease in strength was always observed when filler was added, the final articles still retained sufficient strength for their particular application. This small strength reduction should be balanced against the productivity gains.