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Predicting strength characteristics of paper in real time using process parameters, TAPPI Journal March 2022
ABSTRACT: Online paper strength testing methods are currently unavailable, and papermakers have to wait for manufacture of a complete reel to assess quality. The current methodology is to test a very small sample of data (less than 0.005%) of the reel to confirm that the paper meets the specifications. This paper attempts to predict paper properties on a running paper machine so that papermakers can see the test values predicted in real time while changing various process parameters. This study was conducted at a recycled containerboard mill in Chicago using the multivariate analysis method. The program provided by Braincube was used to identify all parameters that affect strength characteristics. Nearly 1600 parameters were analyzed using a regression model to identify the major parameters that can help to predict sheet strength characteristics. The coefficients from the regression model were used with real-time data to predict sheet strength characteristics. Comparing the prediction with test results showed good correlation (95% in some cases). The process parameters identified related well to the papermaking process, thereby validating the model. If this method is used, it may be possible to predict various elastic moduli (E11, E12, E22, etc.) in the future as the next step, rather than the traditional single number “strength” tests used in the containerboard industry, such as ring crush test (RCT), corrugating medium test (CMT), and short-span compression strength test.
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Enhancing tissue wet pressing performance and dry end material efficiency for cost savings, TAPPI Journal May 2024
ABSTRACT: The steadily growing global tissue paper demand lays a foundation for new technologies targeting tissue production optimization, as well as improved material and time efficiency. Tissue making is an especially energy-intensive field of paper industry, creating unique demands for performance in wet pressing and drying processes to cut energy usage. Intelligent roll solutions offer new tools for tissue making to achieve these goals. These tools aim at improving press nip, moisture, and tension profiles; reeling nip and parent roll hardness profiles; rewinder runnability; and end product web handling characteristics in converting. Intelligent rolls can be utilized in all the main processes and positions on tissue production lines. With these tools, production cost reductions and energy savings can be obtained by optimizing the press nip-to-Yankee cylinder contact, avoiding moisture profile errors requiring overdrying with the Yankee hood and reducing reeling/winding broke under low nip load conditions typical to tissue windups. The intelligent roll system consists of a helically mounted force or temperature sensors, roll covers, measurement electronics, digital radio transmission, and a receiver system connected to a user interface or the mill automation system. What distinguishes these implementations is that no layout changes or added external measurement devices are required, helping to fit into compact tissue machine environments, regardless of the equipment type • traditional, hybrid, or through-air drying (TAD) concept. In tissue processing equipment, the optimal positions for these rolls are press nip rollers, reeling cylinders, rewinder or converting line paper lead rolls, or rewinder winding drums. In addition to these, temperature profile measurements are utilized, with the main application being the sheet temperature profile detection after Yankee drying for moisture profile and drying process optimization.
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A true green cover for industrial waste landfills, TAPPI Journal April 2024
ABSTRACT: Greenhouse gas (GHG) emissions in the United States totaled 5,981 million metric tons of carbon dioxide equivalent (MMT CO2eq) in 2020. Of that, GHG emissions by the pulp and paper sector amounted to 35 MMT CO2eq direct emissions and those by industrial waste landfills summed to 7.4 MMT CO2eq direct emissions. Loss of GHG sinks due to change in land use further contributes to the net GHG emissions. Industrial waste landfills are typically required to comply with certain federal and state regulations, including meeting requirements for final cover systems. Conventional final cover systems have included use of soil covers and/or soil-geosynthetic composite covers. An engineered turf cover provides for an excellent “green” alternative final cover system for industrial waste landfills.This paper discusses various sustainability aspects pertaining to use of an engineered turf final cover, including: (i)significantly low carbon footprint associated with the construction of an engineered turf alternative final coverwhen compared to closure using a traditional or prescriptive cover system; (ii) saving valuable soil and land resourc-es; (iii) saving water resources by reduction in its use during and after construction; (iv) reducing impacts associated with borrow areas; and (v) reducing overall carbon footprint. Further, when using an engineered turf cover, opportunities exist for beneficial reuse of land, including development of solar energy. A brief discussion on the potential fordevelopment of solar energy is included.
Journal articles
Effects of silica on chemical recovery in the direct caustic
Effects of silica on chemical recovery in the direct causticization of wheat straw black liquor, TAPPI JOURNAL August 2016
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Dynamic CFD modeling of calcination in a rotary lime kiln with an external dryer, TAPPI Journal August 2023
ABSTRACT: Mid-kiln ring formation is a problem in lime kilns that may be related to fluctuations in the start location of calcination. To calculate fluctuations in bed and gas temperature profiles within a lime kiln with an external dryer, a dynamic two-dimensional (2D) axisymmetric computational fluid dynamics (CFD) gas model with a methane burner implemented in ANSYS Fluent, coupled by mass and heat balances to a one-dimensional (1D) bed model, was developed. The dynamic model was used to calculate changes in the location where calcination starts with fluctuations in operational conditions using pulp mill data. This model simulates radiative, convective, and conductive heat transfer between the gas, wall, and bed to determine the axial bed temperature in the kiln. The calcination reaction is described using a shrinking core model that allows for the prediction of the location at which calcination begins and the degree of calcination achieved. The solid motion within the kiln is modeled using Kramer’s equation modified for transient response. Steady-state and dynamic simulation results were compared to data from an industrial dry lime kiln, and good agreement was found. A sensitivity analysis was also performed to provide insight on how operating conditions and model variables impact the calcination location and degree of calcination. Of the variables examined, the fuel rate and the feed temperature had the largest impact on both the calcination location and degree of calcination in the kiln. Model predictions of a period of ring formation in the industrial kiln showed that the start location of calcination fluctuated by more than 2 m on either side of the mean of regular operation, warranting further investigation of the importance of these fluctuations on mid-kiln ring formation.
Journal articles
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Advanced real-time digital microscopy of foaming processes, TAPPI Journal January 2023
ABSTRACT: The properties of aqueous foams play a major role in foam forming and foam coating. Inline real-time foam measurements provide highly desired opportunities for optimization and control of foaming processes. This paper presents inline digital microscopy measurements of aqueous foams in foaming processes. It presents methods for providing detailed information on foam quality parameters, such as foam density and foam homogeneity in real time from the process. In addition, this study evaluates the performance of transillumination and front-light illumination in imaging of foams. The tests show very good results for the transillumination approach. Limitations of the image-based optical technique are discussed, and the precision of bubble size distribution measurement is assessed with a certificated reference substance. The measured foam densities are compared against the reference foam densities in the range 100•300 g/L, providing a linear correlation with R2 value of 0.99. In the case of heterogenous foams with a wide bubble size distribution, the bubble size-dependent dimensionless depth of field must be taken into account to obtain accurate estimates of foam density. Bubble-scale foam homogeneity is described by the standard deviation of bubble size distribution in foam.
Journal articles
Magazine articles
Pareto-based design of experiments for identifying and comparing optimum sealing parameters of heat sealing applications in packaging machines, TAPPI Journal June 2023
ABSTRACT: Sealing is one of the most important process steps in industrial packaging, because the sealed seam is the most sensitive section of a package in terms of quality. For this reason, a major focus in flexible packaging is the sealing process, and among this, heat sealing is the most frequently used technology. In detail, applications of heat sealing processes are confronted with four conflicting objectives: increasing seam quality, reducing dwell time, reducing sealing temperature, and increasing process robustness towards varying conditions. Typical problems, such as identification of the optimum process parameters or selection of the most appropriate packaging film, are subject to these conflicting objectives.This paper presents a recently published design of experiments for characterizing and comparing heat sealing properties of packaging films based on a multi-objective optimization algorithm. The approach provides easy-to-read charts showing all optimum sealing parameters with regard to the four essential objectives of heat sealing: seam quality, dwell time, sealing temperature, and process robustness. Three case studies show exemplary applications of the new approach: 1) analyzing transport damages of beverage powder packages; 2) identifying and comparing optimum sealing parameter of a standard, mono-material, and fiber based packaging film regarding tightness and visual properties of the produced sachets; and 3) analyzing the effect of additional aluminum layers on sealing characteristics regarding hot-tack.The new design of experiments may provide the basis of a standard test method for the identification of optimal sealing parameters in the heat sealing processes.
Journal articles
Magazine articles
Comparative analysis and benchmarking of commercial and emerging fast pyrolysis technologies, TAPPI Journal May 2023
ABSTRACT: It is well established that producing sustainable fuels and replacing the fossil-based ones is one of the key solutions to achieving net-zero emissions goals. One of the most advanced commercial-scale pathways to biofuels available today is fast pyrolysis. However, due to the need for a supportive regulatory environment and mitigation strategies for uncertainties related to costs and feedstock quality, fast pyrolysis is not yet being widely implemented. In this case study, three fast pyrolysis technologies with a technology readiness level (TRL) of 6 and above have been compared to distinguish between them and identify the conditions under which they are economically viable. The circulating fluidized bed (CFB), rotating cone (RC), and mechanically assisted fluidized bed (MFB) fast pyrolysis technologies were considered. First, the flow diagram and a mass and energy balance comparison were addressed. It was revealed that the RC configuration has better bio-oil yields because it can handle smaller particles. The MFB configuration has a progressive condensation unit at the end of the process, which produces a nearly dry oil having a higher energy content. Four implementation scenarios were studied. The first was the fast pyrolysis standalone process, where all options had marginal economic attractiveness, and the RC configuration economically outperformed the other two. Integration of a fast pyrolysis plant into a sawmill in the second scenario was found to bring significant improvements in revenues and internal rate of return (IRR). Realization of the full value of bio-oil (the third scenario) brought significantly more revenues for the MFB. Finally, the fourth scenario involved adding a progressive condensation unit, which increased the capital expenditure (CAPEX) by 3%•4% while increasing revenues by 32%•35%. A sensitivity analysis highlighted the importance of financial support towards capital cost and the full valuation of bio-oil for the economic viability of fast pyrolysis processes. Progressive condensation leading to more added-value bio-oil makes the standalone fast pyrolysis process more profitable.
Journal articles
Magazine articles
Formic acid pulping process of rice straw for manufacturing of cellulosic fibers with silica, TAPPI Journal August 2021
ABSTRACT: Emerging technology has the potential to develop entirely new approaches for producing cellulose fiber-based materials along with fuels and chemical raw materials like lignin and furfural. Rice straw is a rich source of cellulosic fibers and inorganic micronic-sized particles termed as ash. They can prove helpful in development of new or enhanced agricultural residue-based materials and products that offer cost effective substitutes for nonrenewable materials used in different domestic and industrial applications. Lignocellulose is an abundant material that is submicronic at the basic level. Rice straw is a fibrous lignocellulosic material obtained as agricultural residue, but it differs from most crop residues in its high content of silicon dioxide (SiO2). Ash content on a dry weight basis ranges from 13% to 20%, varying according to the state of conservation of the straw after harvest. The ash in rice straw has nearly 75% SiO2. The particle size analysis shows variation from a few microns to hundreds of microns for inorganic residues left after burning at high temperatures above 550°C. Proximate analysis of rice straw shows that it contains 54% to 56% holocellulose and 15% to 18% lignin, both of which are natural biopolymers. The compound analysis shows the different compounds present in rice straw ash.Rice straw is available in hundreds of million tons in India and other Asian countries, so suitable technologies are required to convert rice straw from a biomass waste to useful bioproducts like pulp, paper, and paperboard. This research paper is intended to obtain pulp with fibers having inherent silica present in it to give high opacity paper and better bonding between fibers.
Journal articles
Magazine articles
Understanding wet tear strength at varying moisture content in handsheets, TAPPI Journal January 2021
ABSTRACT: A laboratory study was conducted looking at the effects of moisture content on wet tear strength in handsheets. Three different wetting techniques were used to generate the wet tear (Elmendorf-type) data at varying moisture levels, from TAPPI standard conditions (dry) to over 60% moisture content (saturated). Unbleached hardwood and softwood fiber from full-scale kraft pulp production were used. The softwood fiber was refined using a Valley beater to reduce freeness. Handsheets were made with a blend of hardwood and softwood and with refined softwood, without the addition of wet-end chemistry. The resulting grams-force tear data obtained from the test was indexed with basis weight and plotted versus both moisture content and dryness. As moisture content levels in the handsheets increased, the wet tear strength also increased, reaching a critical maximum point. This marked a transition point on the graph where, beyond a critical moisture content level, the tear strength began to decline linearly as moisture increased. This pattern was repeated in handsheets made from a blend of hardwood and softwood and from 100% refined softwood.