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Understanding the pulping and bleaching performances of eucalyptus woods affected by physiological disturbance, TAPPI Journal November 2018
Understanding the pulping and bleaching performances of eucalyptus woods affected by physiological disturbance, TAPPI Journal November 2018
Journal articles
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Multifunctional barrier coating systems created by multilayer curtain coating, TAPPI Journal November 2020
ABSTRACT: Functional coatings are applied to paper and paperboard substrates to provide resistance, or a barrier, against media such as oil and grease (OGR), water, water vapor as measured by moisture vapor transmission rate (MVTR), and oxygen, for applications such as food packaging, food service, and other non-food packaging. Typical functional barrier coatings can be created by applying a solid coating or extruded film, a solvent based-coating, or a water-based coating to the paper substrate using various means of coating applicators.This paper focuses on water-based barrier coatings (WBBC) for OGR, water, MVTR, and oxygen barriers. The main goal was to create coated systems that can achieve more than one barrier property using multilayer curtain coating (MLCC). Curtain coating has emerged as the premier low-impact application me thod for coated paper and paperboard. This paper provides examples using MLCC to create coating structures that provide multiple barrier properties in a single coating step. Barrier polymer systems studied include styrene butadiene, styrene acrylate, vinyl acrylic, and natural materials, as well as proprietary additives where required to give desired performance. The paper also shows how the specific coating layers can be optimized to produce the desired property profile, without concern for blocking, as the addition of a non-blocking top layer can be applied in the MLCC structure as well. Experiments on base sheet types also shows the importance of applying the multilayer structure on a pre-coated surface in order to improve coating thickness consistency and potentially allow for the reduction of more expensive layer components.
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The use of hollow sphere pigments as strength additives in paper and paperboard coatings—Part 1: The predictive nature of packing models on coating properties, TAPPI Journal November 2020
ABSTRACT: Hollow sphere pigments (HSPs) are widely used at low levels in coated paper to increase coating bulk and to provide gloss to the final sheet. However, HSPs also provide an ideal system through which one can examine the effect of pigment size and particle packing within a coating due to their unimodal and tunable particle sizes. The work presented in Part 1 and Part 2 of this study will discuss the use of blends of traditional inorganic pigments and HSPs in coating formulations across a variety of applications for improved coating strength. Part 1 of this study focuses on the theory of bimodal spherical packing and demonstrates the predictive nature of packing models on the properties of coating systems containing HSPs of two different sizes. This study also examines conditions where the model fails by examining the effect of particle size on coating strength in sytems like thermal paper basecoats where the non-HSP component has a broad particle size distribution, and how these surprising trends can be used to generate better-than-expected thermal printing performance in systems with low HSP/clay ratios. Part 2 of this study focuses on the incorporation of HSPs of different particle sizes into paperboard formulations to affect coating strength and opacity.
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Crossflow filtration of green liquor for increased pulp production, improved green liquor quality, and energy savings, TAPPI JOURNAL October 2020
ABSTRACT: A new green liquor filtration system has been installed and commissioned at the Ence pulp mill in Pontevedra, Spain. The filtration system is based on microfiltration and was developed in collaboration with the KTH Royal Institute of Technology in Stockholm, Sweden. The patented method for efficient purification of green liquor decreases the non-process element (NPE) content by providing more efficient solids/liquid separation, reducing energy and chemical consumption in pulp mills and increasing production capacity by eliminating certain capacity bottlenecks. The process has been continuously tested at the Aspa Bruk Mill outside Askersund, Sweden, since 2013. The technology has proven to create nearly particulate-free green liquor during the purification process. The technology can also be used to polish white liquor to provide higher pulp quality.To provide for a simple and cost-effective installation, the system was designed as a skid-mounted unit that is pre-piped, instrumented, and tested before shipment. The system is modular and allows for easy expansion of capacity. This paper discusses the process design, process integration, and startup of the new system, along with experiences from the first months of operation.
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Rice straw-based sustainable food packaging material with improved strength and barrier properties: Development and characterization, TAPPI Journal October 2023
ABSTRACT: Sustainable food packaging paper with high barrier and strength properties was developed with rice straw nanocellulose materials. Pulping and bleaching of rice straw were performed using an organosolv pulping and DED (D: chlorine dioxide bleaching; E: sodium hydroxide extraction) bleaching sequence. Bleached rice straw pulp was refined to 90°SR using a laboratory Valley beater. The laboratory handsheets were prepared using pulp slurry at 40°SR and 90°SR. The handsheets of cellulose nanofibrils (CNFs) made of highly refined pulp (90°SR) were surface sized using alkyl ketene dimer (AKD) wax to increase the barrier properties of paper for selective food packaging applications. The paper samples were tested for mechanical, optical, surface, and barrier properties, including tensile index, burst index, tearing index, bending stiffness, elongation, porosity, apparent density, opacity, Cobb value, water vapor transmission rate (WVTR), oil and grease resistance, and contact angle. The refined pulp (90°SR) was analyzed using field-emission scanning electron microscopy (FE-SEM), and it was observed that the morphology of the developed fibers changes to the nanoscale (<100 nm) for at least one dimension. The particle size distribution of the refined pulp using DLS analyzer also confirmed the cellulose fibers to near nanoscale. It was concluded that nanofibers were formed by a high degree of the mechanical pulp refining process and found to be much more economical than alternative processes in this direction. The sample handsheets of CNFs showed good strength and barrier properties. The barrier properties further increased when surface sizing was done using low-cost, nontoxic, and biodegradable AKD wax.
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Using bleaching stage models for benchmarking hardwood ECF bleach plants, TAPPI Journal October 2023
ABSTRACT: Steady-state models estimated the performance of the D0(EOP)D1 bleach sequence at two mixed hardwood bleach plants in the southern United States. At Mill 1, the full sequence’s chlorine dioxide charge that brightens the pulp to ~84% ISO was monitored for two weeks. Mill 2 considered the partial sequence that brightens the pulp to ~86% ISO for nearly four weeks. Elevated levels of chlorine dioxide were linked to increased washer carryover in brownstock and extraction areas. For Mills 1 and 2, an extra 0.24% and 0.33% chlorine dioxide was consumed in the D0 stage. This extra bleach demand was equivalent to an additional 4.8 and 5.5 kappa load to the brownstock, respectively. Some differences were observed for the D1 stage. Mill 1 had extraction carryover that averaged 1.1 units higher than was measured, contributing to use of an extra 0.22% of chlorine dioxide. Mill 2 had extraction carryover that averaged between 0 and 0.7 kappa units and consumed up to 0.13% more chlorine dioxide. Another data set from Mill 2 showed high brownstock and extraction carryover, leading to ~0.90% more total chlorine dioxide usage to brighten to 84% ISO. Overall, this investigation illustrated that the models could be employed as benchmarks.
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In-process detection of fiber cutting in low consistency ref
In-process detection of fiber cutting in low consistency refining based on measurement of forces on refiner bars, TAPPI JOURNAL April 2017
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Low consistency refining of mechanical pulp — system design
Low consistency refining of mechanical pulp — system design, TAPPI JOURNAL July 2017
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A novel unit operation to remove hydrophobic contaminants, TAPPI Journal April 2020
ABSTRACT: For mills making paper with recovered fiber, removal of hydrophobic contaminants is essential for trouble-free operation of paper machines. Significant cost savings on paper machine operation can be achieved by reducing deposits, which results in better quality, reduced downtime, increased fiber yield, and reduced energy consumption. Bubble nucleation separation (BNS) is a relatively new process for removing hydrophobic particles. When vacuum is applied to a slurry, dissolved gas bubbles nucleate on hydrophobic particles and drag them to the surface for easy removal. We constructed a 16-L batch unit to evaluate the effect of operating parameters on removal of hydrophobic particles, using statistical design of experiments. These results were used to guide our design of a 16-L continuous unit. We tested this unit on laboratory and mill samples. The removal of 60%•80% of hydrophobic particles was achieved with a low reject rate of < 2%.Following on this success, we built a 200-L pilot unit and tested it in our pilot plant. With promising results there, we installed the pilot unit at a commercial paper recycling mill. Over the course of several mill trials, we showed that it was possible to remove a considerable amount of suspended solids from paper machine white water with less than 2% rejects. Unfortunately, due to the unit only treating 50 L/min and the mill flow being 12000 L/min, we were not able treat a sufficient portion of the white water to know whether a large-scale implementation of BNS would improve paper machine runnability.
Journal articles
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Regulatory and sustainability initiatives lead to improved polyaminopolyamide-epichlorohydrin (PAE) wet-strength resins and paper products, TAPPI JOURNAL September 2018
Regulatory and sustainability initiatives lead to improved polyaminopolyamide-epichlorohydrin (PAE) wet-strength resins and paper products, TAPPI JOURNAL September 2018