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A feasibility study of using the organic Rankine cycle for power generation from the flue gases of recovery boilers, TAPPI Journal August 2022
ABSTRACT: Almost 415 tons/h of flue gases with a temperature of 160°C are released to the atmosphere from the recovery boiler of a pulp mill with capacity of 1000 air dried (a.d.) metric tons of pulp per day. This is a large waste heat stream that can be used to generate power, to decrease the operating costs of a pulp mill, and to save carbon dioxide (CO2) emissions. In this work, the feasibility of using an organic Rankine cycle (ORC) with ammonia as the working fluid to generate power from the flue gases of recovery boilers is studied. CHEMCAD and Taguchi methods are used for simulation of the process and for optimization of operating conditions, respectively. The temperature of the ammonia and flue gases at the exit of evaporator, exit pressure of the pump and turbine, and the degree of subcooling of ammonia at the exit of the condenser are five operating parameters that are manipulated to optimize the process. Three different scenarios are defined: minimizing the net power cost, maximizing the ORC efficiency, and maximizing the net profit. Different aspects of these scenarios, such as net power generation, cost, efficiency, and CO2 emission savings are discussed, and optimum operating conditions are reported.
Journal articles
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Utilization of kraft pulp mill residuals, TAPPI Journal February 2022
ABSTRACT: Kraft pulp mills produce on average about 100 kg of solid residuals per metric ton of pulp produced. The main types of mill waste are sludge from wastewater treatment plants, ash from hog fuel boilers, dregs, grits, and lime mud from causticizing plants and lime dust from lime kilns. Of these, about half is disposed of in landfills, which highlights the need and potential for waste recycling and utilization. Sludge is either incinerated in hog fuel boilers to generate steam and power or used in various forms of land application, including land spreading, composting, or as an additive for landfill or mine waste covers. The majority of hog fuel boiler ash and causticizing plant residues is landfilled. Alkaline residuals can be conditioned for use in land application, manufacture of construction materials, and production of aggregates for road work. This technical review summarizes residuals utilization methods that have been applied in pulp and paper mills at demonstration- or full-scale, and therefore may act as a guide for mill managers and operators whose goal is to diminish the costs and the environmental impact of waste management.
Journal articles
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Review of coating cracking and barrier integrity on paperboard substrates, TAPPI Journal November 2022
ABSTRACT: Barrier packaging formats are major growth areas for the pulp and paper industry. It is technically challenging to maintain barrier properties during converting and end-use applications. Improved manufacturing capabilities and coating formulation knowledge will help maintain barrier integrity and enable growth of barrier products in challenging applications. These improvements will accelerate product development and commercialization, and allow faster response to product performance issues such as cracking. The literature on coating cracking provides knowledge mostly on the effects of coating formulations and to a lesser extent on substrate effects. Despite a large number of publications dedicated to coating failures, the approach to improve coating cracking remains empirical, and the transferability between studies and to real life applications has not been well established. Model development that successfully predicts commercial performance is in its infancy. However, some of these simplified models do a fairly good job predicting experimental data. The current work reviews the state of understanding as regards coating and barrier cracking and highlights the need for more research on cracking and barrier integrity.
Journal articles
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Utilization of palm fiber as papermaking materials: Microscopic structure and chemical pulping, TAPPI Journal October 2022
ABSTRACT: The microscopic structure and pulping properties of palm fiber were explored. Soda cooking and sulfate cooking were conducted and compared in terms of physical strength of the obtained pulps. Sulfate pulp showed better performance than soda pulp, as indicated by the 23% higher tensile index, 49% higher tear index, and 36% higher burst index. To further elevate physical strength, long fibered pulp (LFP), namely commercial softwood sulfate pulp, was mixed with sulfate pulp of palm fiber at levels from 20% to 50%. At the blend level of 50%, tensile index of 52.13 Nœm/g, tear index of 15.63 mNœm2/g, and burst index of 3.42 kPaœm2/g were attained. The lignin in spent liquor from pulping was isolated and characterized. Soda lignin of palm fiber was mainly composed of guaiacyl and syringyl units, and showed weight-average molecular weight of 3616 g/mol.
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Convolutional neural networks enhance pyrolysis gas chromatography mass spectrometry identification of coated papers, TAPPI Journal August 2024
ABSTRACT: In the evolving paper industry, accurate identification of coated paper components is essential for sustainability and recycling efforts. This study employed pyrolysis-gas chromatography mass spectrometry (Py-GCMS) to examine six types of coated paper. A key finding was the minimal interference of the paper substrate with the pyrolysis products of the coatings, ensuring reliable analysis. A one-dimensional convolutional neural network (1D-CNN) was employed to process the extracted ion chromatograms directly, simplifying the workflow and achieving a predictive accuracy of 95.2% in identifying different coating compositions. Additionally, the study high-lighted the importance of selecting an optimal pyrolysis temperature for effective feature extraction in machine learning models. Specific markers for coated papers, including polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polybutylene succinate (PBS), polylactic acid (PLA), and waterborne polyacrylates (WP), were identified. This research demonstrates a novel approach to coated paper identification by combining Py-GCMS with machine learning, offering a foundation for further studies in product quality and environmental impact.
Journal articles
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Effect of high sulfate content on viscosity of recovery boiler molten smelt, TAPPI Journal March 2024
ABSTRACT: A systematic study was conducted to examine the effect of high sulfate content on the freezing temperature of molten smelt and how this may contribute to the formation of viscous jellyroll smelt in recovery boilers. The results show that even for recovery boilers with a smelt reduction as low as 70%, the sulfate content in smelt has no or little effect on smelt freezing temperature, and hence, on molten smelt fluidity. The perceived adverse effect of high sulfate content on smelt fluidity and on jellyroll smelt formation comes from the high sulfate content in deposits that have fallen from the upper furnace. Fallen deposits may or may not form jellyroll smelt, depending on whether or not they can melt and be well-mixed with molten smelt by the time they reach the smelt spouts. It is not the high sulfate content in smelt resulting from the low smelt reduction efficiency that makes molten smelt viscous and forms jellyroll smelt, but rather, it is the incomplete melting of fallen deposits that results in one of the proposed mechanisms for jellyroll smelt formation.
Journal articles
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Functionalization of wood/plant-based natural celluslose fibers with nanomaterials: a review, TAPPI JOURNAL February 2018
Functionalization of wood/plant-based natural celluslose fibers with nanomaterials: a review, TAPPI JOURNAL February 2018
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Print quality of flexographic printed paperboard related to coating composition and structure, TAPPI Journal January 2018
Print quality of flexographic printed paperboard related to coating composition and structure, TAPPI Journal January 2018
Journal articles
Magazine articles
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
Magazine articles
Three-dimensional visualization and characterization of paper machine felts and their relationship to their properties and dewatering performance, TAPPI Journal July 2021
ABSTRACT: Polymeric felts are commonly used in the papermaking process on the paper machine wet end, in the press section, and in the dryer section. They provide an important function during paper manufacturing, including as a carrier or support; as a filter media assisting with water removal on the paper machine; in retention of fibers, fines, and fillers; and in some applications, such as tissue and towel, to impart key structural features to the web. These felts can have highly interwoven complex internal structures comprised of machine direction and cross-machine direction yarns of varying sizes and chemical compositions. Here, we present a non-intrusive three-dimensional (3D) image visualization method using advanced X-ray computed tomography (XRCT). This method was used to characterize the complex 3D felt structure and determine the water removal characteristics of some commonly used paper machine felts. The structural features analyzed include porosity; specific pore-yarn interfacial surface area; 3D pore size distribution; 3D fiber or yarn-size distribution; and their variations through the thickness direction. The top, middle, and bottom layers of the felt have very different structures to assist with water removal and impart paper properties. The size distribution of the yarns, as well as the pores in the different layers of the felt, are also inherently different. These structural features were non-intrusively quantified. In addition, variation in the structural characteristics through the thickness of the felts and its potential role in papermaking is explored. In addition to the 3D structural characteristics, permeability characteristics and water removal characteristics, including rewetting of select felt samples, have also been experimentally determined. It is interesting to observe the relationship between key structural features and permeability and water removal characteristics. These relationships can provide additional insights into press felt design, as well as ways to improve product properties and the dewatering efficiency and productivity of the paper machine.