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Case study: Paper mill power plant optimization—balancing steam venting with mill demand, TAPPI Journal June 2020
ABSTRACT: Most Power departments are tasked with generating steam to support mill wide operations, generate electricity, and reduce operating costs. To accomplish these tasks, power boilers generate high pressure steam that is reduced to intermediate and low pressures for process utilization in the mill by means of steam turbine generator extraction or pressure reducing valves. The most economical method to reduce steam pressure is the use of steam turbine generators, as electricity is generated from the steam when it is reduced in pressure. Electricity that is produced by these generators provides a substantial financial benefit and helps offset overall operational costs. To achieve tangible financial gains, the mill must evaluate the overall cost of steam production and the price of electricity.The current work provides a case study of power plant optimization that evaluated electricity production and steam production costs balanced with mill steam demand. Process and cost optimization led to a significant reduc-tion in low pressure steam venting, resulting in reduced fuel consumption and reduced operating cost.
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Fate of phosphorus in the recovery cycle of the kraft pulping process, TAPPI Journal March 2020
ABSTRACT: The accumulation of nonprocess elements in the recovery cycle is a common problem for kraft pulp mills trying to reduce their water closure or to utilize biofuels in their lime kiln. Nonprocess elements such as magnesium (Mg), manganese (Mn), silicon (Si), aluminum (Al), and phosphorus (P) enter the recovery cycle via wood, make-up chemicals, lime rock, biofuels, and process water. The main purge point for these elements is green liquor dregs and lime mud. If not purged, these elements can cause operational problems for the mill. Phosphorus reacts with calcium oxide (CaO) in the lime during slaking; as a result, part of the lime is unavailable for slaking reactions. The first part of this project, through laboratory work, identified rhenanite (NaCa(PO4)) as the form of P in the lime cycle and showed the negative effect of P on the availability of the lime. The second part of this project involved field studies and performing a mass balance for P at a Canadian kraft pulp mill.
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Historical perspectives of corrugated box testing for 2020, TAPPI Journal March 2020
ABSTRACT: In the age of e-commerce, corrugated packaging is experiencing a resurgence; at least, consumers are receiving more corrugated boxes today than ever before. The corrugated box has been the main package for transporting goods for over 100 years, and corrugated board and boxes have been the focus of scientific study for about as long. For the last 50 years, box compressive test strength value (BCT) has been the main focus of research and testing. That was not always the case. In addition, many of today’s boxes experience a different end-use life than their predecessors.
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Editorial: TAPPI Journal 2019 Best Research Paper runner-up focuses on persistent issue of cracking at the fold in coated papers, TAPPI Journal May 2020
ABSTRACT: TAPPI and the TAPPI Journal (TJ) Editorial Board would like congratulate the authors of the runner-up paper to the 2019 TAPPI Journal Best Research Paper Award: Seyyed Mohammad Hashemi Dajan, Douglas W. Bousfield, and Mehdi Tajvidi. Their paper: "Cracking at the fold in double layer coated paper the influence of latex and starch composition," appeared on p. 93 of the February 2019 issue. This coating research was recognized by the TJ Editorial Board for its innovation, creativity, scientific merit, and clear expression of ideas.
Journal articles
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Alternative “green” lime kiln fuels: Part I—Pulping/recovery byproducts, TAPPI Journal May 2020
ABSTRACT: This paper is the first of a two-part series on “green” lime kiln fuels. The first part of this work reviews the use of pulp mill and recovery byproducts as either full or partial replacement of oil or natural gas in the kiln. The second part reviews the use of various forms of woody biomass, bio-oils, gasification, and hydrogen as potential carbon neutral or carbon-free lime kiln fuels.
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Editorial: Ravi Challa brings tissue, nonwovens, and operational expertise to TJ Editorial Board, TAPPI Journal September 2022
ABSTRACT: TAPPI and the TAPPI JOURNAL (TJ) editorial staff would like to welcome a new member to the TJ Editorial Board, Ravi Challa, Ph.D., who is Research & Development (R&D) manager for Suominen Corporation at the company’s Bethune, SC, facility. There, his primary focus is new product development on wetlaid nonwovens paper machines, from maintaining mature technologies and innovation to discovering patterns in paper machine shutdowns and executing nonwovens product development trials.
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Development of reinforced paper and mitigation of the challenges of raw material availability by utilizing Areca nut leaf, TAPPI Journal September 2022
ABSTRACT: Paper industries are facing a raw material crisis and searching for alternate raw materials that may be able to help mitigate the issue. Many industries use agro-waste as a raw material, irrespective of it having low bleachability and poor mechanical strength. Areca nut leaf (ANL) is a nonwood-based material that may be acceptable as an alternate source of raw material that contains 61.5% holocellulose and 13.6% lignin, which is comparable to other agro-wastes and hardwood pulps. Kraft anthraquinone pulping with 20% active alkali as sodium oxide (Na2O), 25% sulfidity, and 0.05% anthraquinone produced 15 kappa pulps with about 38.5% pulping yield. The bleachability of ANL pulp was good, and 83.5% ISO brightness could be achieved using the D0(EOP)D1 bleaching sequence. The ANL fiber has 33.8% better tensile, 54.5% better tear, and 15.2% better burst index than hardwood fiber. Similarly, 60.4% better tensile, 56.5% better tear, and 21.7% better burst index were observed in ANL than in wheat straw. Thus, the study revealed that Areca nut leaf can be used as an alternative raw material for papermaking, as well as to improve the physical property of paper products by blending it with inferior quality pulp.
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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
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Fiber-based characterization of pulp refining, TAPPI Journal September 2022
ABSTRACT: Fiber development in pulp refining can be characterized by three parameters: number of impacts on pulp, N; energy per impact, I, and bar force on fibers, F. These parameters enable comparisons of radically different refining conditions; determination of intensity for hardwoods and softwoods; assessment of effect of bar width on fiber shortening; and predictions of tensile strength increases.
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.