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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.
Journal articles
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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
ABSTRACT: This study investigates the impact of pulp screening on oxygen delignification of high lignin content kraft pulps from spruce wood. An alternative process is proposed: terminating kraft cooking at higher kappa numbers and applying oxygen deligni
ABSTRACT: This study investigates the impact of pulp screening on oxygen delignification of high lignin content kraft pulps from spruce wood. An alternative process is proposed: terminating kraft cooking at higher kappa numbers and applying oxygen delignification directly to unscreened and non-defibrated pulp. The objective is to evaluate whether this non-standard approach can maintain delignification efficiency while improving yield and reducing energy input. The findings demonstrate that screening prior to oxygen delignification is not essential for effective lignin removal or pulp quality. Similar delignification degrees and ISO brightness levels were obtained after oxygen delignification, whether it was performed on screened or unscreened pulps. Notably, the delignification rate in the oxygen stage was the same for the non-standard procedure as for pulp from the standard procedure with the reject fractionremoved prior to the oxygen stage. No significant differences were seen in fiber morphology, brightness level, orbrightness stability. The amount of total fiber charges in pulps not screened before oxygen delignification was slightly higher than in screened pulps.
Journal articles
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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.
Journal articles
Magazine articles
Decision-making process for the identification of preferred
Decision-making process for the identification of preferred lignin-based biorefinery strategies, TAPPI JOURNAL April 2017
Journal articles
Corrosion Monitoring and Root Cause Identification in High Solids Concentrators
Black liquor high solids (about 80%) concentrators have often been found to suffer from aggressive corrosion. In particular, the first and second effect bodies are susceptible to corrosion attacks resulting in tube leaks and wall thinning, which limit the availability and lifetime of evaporator lines. Corrosion dynamics and construction materials have been studied extensively within the pulp and paper industry to understand the corrosion process. However, it has been challenging to identify root causes for corrosion, which has limited proactive measures to minimize corrosion damage. Corrosion of the first phase concentrator was studied by defining the potential regions for passive area, stress corrosion cracking, pitting corrosion, and general corrosion. This was achieved by using a technique called polarization scan that reveals ranges for the passive area in which the equipment is naturally protected against corrosion. The open circuit potential, also known as corrosion potential, and linear polarization resistance of the metal were monitored online, which allowed for definition of corrosion risks for stainless steel 304L and duplex stainless steels 2205 and SAF 2906. An online temperature measurement added insight to the analysis. A process diagnostics tool was used to identify root causes of the corrosion attacks. Many of the root causes were related to process conditions triggering corrosion. Once the metal surface was activated, it was difficult to repassivate the metal naturally unless a sufficient potential range was reached.
Journal articles
Magazine articles
Rethinking the paper cup — beginning with extrusion process optimization for compostability and recyclability, TAPPI Journal June 2021
ABSTRACT: More than 50 billion disposable paper cups used for cold and hot beverages are sold within the United States each year. Most of the cups are coated with a thin layer of plastic — low density polyethylene (LDPE) — to prevent leaking and staining. While the paper in these cups is both recyclable and compostable, the LDPE coat-ing is neither. In recycling a paper cup, the paper is separated from the plastic lining. The paper is sent to be recycled and the plastic lining is typically sent to landfill. In an industrial composting environment, the paper and lining can be composted together if the lining is made from compostable materials. Coating paper cups with a compostable performance material uniquely allows for used cups to be processed by either recycling or composting, thus creating multiple pathways for these products to flow through a circular economy.A segment of the paper converting industry frequently uses an extrusion grade of polylactic acid (PLA) for zero-waste venues and for municipalities with ordinances for local composting and food service items. The results among these early adopters reveal process inefficiencies that elevate manufacturing costs while increasing scrap and generally lowering output when using PLA for extrusion coating. NatureWorks and Sung An Machinery (SAM) North America researched the extrusion coating process utilizing the incumbent polymer (LDPE) and PLA. The trademarked Ingeo 1102 is a new, compostable, and bio-based PLA grade that is specifically designed for the extrusion coating process. The research team identified the optimum process parameters for new, dedicated PLA extrusion coating lines. The team also identified changes to existing LDPE extrusion lines that processors can make today to improve output.The key finding is that LDPE and PLA are significantly different polymers and that processing them on the same equipment without modification of systems and/or setpoints can be the root cause of inefficiencies. These polymers each have unique processing requirements with inverse responses. Fine tuning existing systems may improve over-all output for the biopolymer without capital investment, and this study showed an increase in line speed of 130% by making these adjustments. However, the researchers found that highest productivity can be achieved by specifying new systems for PLA. A line speed increase to more than 180% and a reduction in coat weight to 8.6 µm (10.6 g/m2 or 6.5 lb/3000 ft2) was achieved in this study. These results show that Ingeo 1102 could be used as a paper coating beyond cups.
Journal articles
Magazine articles
Experiments and visualization of sprays from beer can and turbo liquor nozzles, TAPPI Journal February 2022
ABSTRACT: Industrial scale swirl-type black liquor nozzles were studied using water as the test fluid. Simple water spraying experiments were found to be very beneficial for studying and comparing nozzles for black liquor spraying. These kinds of experiments are important for finding better nozzle designs. Three nozzle designs were investigated to understand the functional differences between these nozzles. The pressure loss of nozzle 1 (“tangential swirl”) and nozzle 3 (“turbo”) were 97% and 38% higher compared to nozzle 2 (“tan-gential swirl”). Spray opening angles were 75°, 60°, and 35° for nozzles 1, 2, and 3, respectively. Video imaging showed that the nozzles produced sprays that were inclined a few degrees from the nozzle centerline. Spray patter-nation showed all the sprays to be asymmetric, while nozzle 2 was the most symmetric. Laser-Doppler measure-ments showed large differences in spray velocities between nozzles. The spray velocity for nozzle 1 increased from 9 m/s to 15 m/s when the flow rate was increased from 1.5 L/s to 2.5 L/s. The resulting velocity increase for nozzle 2 was from 7 m/s to 11 m/s, and for nozzle 3, it was from 8 m/s to 13 m/s. Tangential flow (swirl) directed the spray 6°–12° away from the vertical plane. Liquid sheet breakup mechanisms and lengths were estimated by analyzing high speed video images. The liquid sheet breakup mechanism for nozzle 1 was estimated to be wave formation, and the sheet length was estimated to be about 10 cm. Sheet breakup mechanisms for nozzle 2 were wave formation and sheet perforation, and the sheet length was about 20 cm. Nozzle 3 was not supposed to form a liquid sheet. Nozzle geometry was found to greatly affect spray characteristics.
Journal articles
Magazine articles
The influence of strain rate and pulp properties on the stre
The influence of strain rate and pulp properties on the stress relaxation of wet paper — modeling of relaxation, November 2016 TAPPI JOURNAL