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Journal articles
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Lignin-based resins for kraft paper applications, TAPPI Journal November 2019
ABSTRACT: We investigated miscanthus (MS) and willow (W) lignin-furfural based resins as potential reinforce-ment agents on softwood and hardwood kraft paper. These resins might be sustainable alternatives to the commercial phenolformaldehyde (PF) resins. Phenol is a petrochemical product and formaldehyde has been classified as a carcinogen by the U.S. Environmental Protection Agency. The lignin used in this study was derived from hot water extraction (160ºC, 2 h) of MS and W biomass, and may be considered sulfur-free. These biorefinery lignins were characterized for their chemical composition and inherent properties via wet chemistry and instrumental techniques. The resin blends (MS-resin and W-resin) were characterized for their molecular weight, thermal behavior, and mechanical properties. Mechanical properties were measured by the resin’s ability to reinforce softwood and hard-wood kraft papers. The effect of adding hexamethylenetetramine (HMTA), a curing agent, to the resin was also examined. Mixtures of PF and lignin-based resins were investigated to further explore ways to reduce use of non-renewables, phenol, and carcinogenic formaldehyde. The results show that lignin-based resins have the potential to replace PF resins in kraft paper applications. For softwood paper, the highest strength was achieved using W-resin, without HMTA (2.5 times greater than PF with HMTA). For hardwood paper, MS-resin with HMTA gave the highest strength (2.3 times higher than PF with HMTA). The lignin-based resins, without HMTA, also yielded mechanical properties comparable to PF with HMTA.
Journal articles
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Black liquor evaporator upgrades— life cycle cost analysis, TAPPI Journal March 2021
ABSTRACT: Black liquor evaporation is generally the most energy intensive unit operation in a pulp and paper manufacturing facility. The black liquor evaporators can represent a third or more of the total mill steam usage, followed by the paper machine and digester. Evaporator steam economy is defined as the unit mass of steam required to evaporate a unit mass of water from black liquor (i.e., lb/lb or kg/kg.) The economy is determined by the number of effects in an evaporator train and the system configuration. Older systems use four to six effects, most of which are the long tube vertical rising film type. Newer systems may be designed with seven or even eight effects using falling film and forced circulation crystallization technology for high product solids. The median age of all North American evaporator systems is 44 years. Roughly 25% of the current North American operating systems are 54 years or older. Older systems require more periodic maintenance and have a higher risk of unplanned downtime. Also, older systems have chronic issues with persistent liquor and vapor leaks, shell wall thinning, corrosion, and plugged tubes. Often these issues worsen to the point of requiring rebuild or replacement. When considering the age, technology, and lower efficiency of older systems, a major rebuild or new system may be warranted. The intent of this paper is to review the current state of black liquor evaporator systems in North America and present a basic method for determining whether a major rebuild or new installation is warrant-ed using total life cycle cost analysis (LCCA).
Journal articles
Magazine articles
Can carbon capture be a new revenue opportunity for the pulp and paper sector?, TAPPI Journal August 2021
ABSTRACT: Transition towards carbon neutrality will require application of negative carbon emission technologies (NETs). This creates a new opportunity for the industry in the near future. The pulp and paper industry already utilizes vast amounts of biomass and produces large amounts of biogenic carbon dioxide. The industry is well poised for the use of bioenergy with carbon capture and storage (BECCS), which is considered as one of the key NETs. If the captured carbon dioxide can be used to manufacture green fuels to replace fossil ones, then this will generate a huge additional market where pulp and paper mills are on the front line. The objective of this study is to evaluate future trends and policies affecting the pulp and paper industry and to describe how a carbon neutral or carbon negative pulp and paper production process can be viable. Such policies include, as examples, price of carbon dioxide allowances or support for green fuel production and BECCS implementation. It is known that profitability differs depending on mill type, performance, energy efficiency, or carbon dioxide intensity. The results give fresh understanding on the potential for investing in negative emission technologies. Carbon capture or green fuel production can be economical with an emission trade system, depending on electricity price, green fuel price, negative emission credit, and a mill’s emission profile. However, feasibility does not seem to evidently correlate with the performance, technical age, or the measured efficiency of the mill.
Journal articles
Magazine articles
Investigation of the influencing factors in odor emission from wet-end white water, TAPPI Journal October 2020
ABSTRACT: Emission of malodorous gases, such as volatile organic compounds (VOCs), hydrogen sulfide (H2S), and ammonia (NH3) during pulping and papermaking has caused certain harm to the air environment and human health. This paper investigated the influencing factors of odor emission from wet-end white water during the production of bobbin paper in a papermaking mill using old corrugated containers (OCC) as raw material. The concentration of malodorous gases emitted from wet-end white water was determined with pump-suction gas detectors. The results indicated that low temperature could limit the release of malodorous gases from white water. Specifically, no total volatile organic compounds (TVOC), H2S, and NH3 was detected at a temperature of 15°C. The concentrations of malodorous gases were slightly increased when temperature increased to 25°C. When temperature was 55°C, the released concentrations of TVOC, H2S, and NH3 were 22.3 mg/m3, 5.91 mg/m3, and 2.78 mg/m3, respectively. Therefore, the content of malodorous gases significantly increased with the temperature increase. The stirring of white water accelerated the release of malodorous gases, and the release rate sped up as the stirring speed increased. However, the total amount of malodorous gases released were basically the same as the static state. Furthermore, the higher the concentration of white water, the greater the amount of malodorous gases released. The pH had little influence on the TVOC release, whereas it significantly affected the release of H2S and NH3. With the increase of pH value, the released amount of H2S and NH3 gradually decreased. When pH reached 9.0, the release amount of H2S and NH3 was almost zero, proving that an alkaline condition inhibits the release of H2S and NH3.
Journal articles
Magazine articles
Control of malodorous gases emission from wet-end white water with hydrogen peroxide, TAPPI Journal October 2021
ABSTRACT: White water is highly recycled in the papermaking process so that its quality is easily deteriorated, thus producing lots of malodorous gases that are extremely harmful to human health and the environment. In this paper, the effect of hydrogen peroxide (H2O2) on the control of malodorous gases released from white water was investigated. The results showed that the released amount of total volatile organic compounds (TVOC) decreased gradually with the increase of H2O2 dosage. Specifically, the TVOC emission reached the minimum as the H2O2 dosage was 1.5 mmol/L, and meanwhile, the hydrogen sulfide (H2S) and ammonia (NH3) were almost completely removed. It was also found that pH had little effect on the release of TVOC as H2O2 was added, but it evidently affect-ed the release of H2S and NH3. When the pH value of the white water was changed to 4.0 or 9.0, the emission of TVOC decreased slightly, while both H2S and NH3 were completely removed in both cases. The ferrous ions (Fe2+) and the copper ions (Cu2+) were found to promote the generation of hydroxyl radicals (HOœ) out of H2O2, enhancing its inhibition on the release of malodorous gases from white water. The Fe2+/H2O2 system and Cu2+/H2O2 system exhibited similar efficiency in inhibiting the TVOC releasing, whereas the Cu2+/H2O2 system showed better perfor-mance in removing H2S and NH3.
Journal articles
Magazine articles
The role of hornification in the deterioration mechanism of physical properties of unrefined eucalyptus fibers during paper recycling, TAPPI Journal February 2024
ABSTRACT: Physical properties of cellulosic paper deteriorate significantly during paper recycling, which hinders the sustainable development of the paper industry. This work investigates the property deterioration mechanism and the role of hornification in the recycling process of unrefined eucalyptus fibers. The results showed that during the recycling process, the hornification gradually deepened, the fiber width gradually decreased, and the physical properties of the paper also gradually decreased. After five cycles of reuse, the relative bonding area decreased by 17.6%, while the relative bonding force decreased by 1.8%. Further results indicated that the physical property deterioration of the paper was closely related to the decrease of fiber bonding area. The fiber bonding area decreased linearly with the reduction of re-swollen fiber width during paper recycling. Re-swollen fiber width was closely related to the hornification. Hornification mainly reduces the bonding area of unrefined eucalyptus fiber rather than the bonding force. The work elucidates the role of hornification in the recycling process of unrefined eucalyptus fibers and the deterioration mechanism of paper physical properties, which will be helpful to control the property deterioration of paper and achieve a longer life cycle.
Journal articles
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Kraft pulp viscosity as a predictor of paper strength: Its uses and abuses, TAPPI Journal October 2023
ABSTRACT: For bleached kraft pulps, two factors govern paper strength: the individual fiber strength, and the bond strength that adheres the individual fibers together in the paper matrix. Inherent fiber strength is related to the length of the carbohydrate polymers, also known as the degree of polymerization (DP). Average DP (DP) is inferred by performing pulp viscosity measurements. Under certain circumstances during kraft pulping and bleaching, the average polymer lengths can be shortened, resulting in lower pulp viscosity, and may indicate fiber damage. Fiber damage typically manifests itself as a reduction in tear strength for well-bonded handsheets.This paper will review the literature on how pulp viscosity can predict paper/fiber strength and how it can be used as a diagnostic tool. It can be a means to monitor pulp quality during pulping and bleaching, as well as to alert when such operations approach a critical threshold. However, viscosity losses must be carefully and judiciously analyzed. Like most diagnostic tools, viscosity measurements can be misused and abused, which can lead to incorrect inferences about intrinsic fiber strength. This review will also cover these misuses. The overall goal is to provide the papermaker a better understanding of what pulp viscosity is, how it correlates to potential sheet strength, and what its limitations are. It will be illustrated that when pulp viscosity drops below a critical value, it will indicate an appreciable deterioration in the paper’s tear and tensile strength.
Journal articles
Magazine articles
Control of malodorous gases emission from wet-end white water with hydrogen peroxide, TAPPI Journal October 2021
ABSTRACT: White water is highly recycled in the papermaking process so that its quality is easily deteriorated, thus producing lots of malodorous gases that are extremely harmful to human health and the environment. In this paper, the effect of hydrogen peroxide (H2O2) on the control of malodorous gases released from white water was investigated. The results showed that the released amount of total volatile organic compounds (TVOC) decreased gradually with the increase of H2O2 dosage. Specifically, the TVOC emission reached the minimum as the H2O2 dosage was 1.5 mmol/L, and meanwhile, the hydrogen sulfide (H2S) and ammonia (NH3) were almost completely removed. It was also found that pH had little effect on the release of TVOC as H2O2 was added, but it evidently affect-ed the release of H2S and NH3. When the pH value of the white water was changed to 4.0 or 9.0, the emission of TVOC decreased slightly, while both H2S and NH3 were completely removed in both cases. The ferrous ions (Fe2+) and the copper ions (Cu2+) were found to promote the generation of hydroxyl radicals (HO•) out of H2O2, enhancing its inhibition on the release of malodorous gases from white water. The Fe2+/H2O2 system and Cu2+/H2O2 system exhibited similar efficiency in inhibiting the TVOC releasing, whereas the Cu2+/H2O2 system showed better perfor-mance in removing H2S and NH3.
Journal articles
Magazine articles
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
Magazine articles
Value creation by converting pulp mill flue gas streams to green fuels, TAPPI Journal March 2023
ABSTRACT: Climate change mitigation induces strong growth in renewable electricity production, partly driven by shifts in environmental policies and regulation. Intermittent renewable electricity requires supporting systems in the form of sustainable hydrocarbon chemicals such as transportation fuels. Bulk chemical production fits well into a pulp mill environment, given their large volumes, stable operation, and ample supply of biomass-based carbon feed-stock in the form of flue gases. Until now, the utilization of the flue gases from conventional operation of a pulp mill has received little attention. Harnessing these flue gases into usable products could offer additional value to mill operators, while also diversifying their product portfolio. However, electricity-based fuels and products require extra energy in the conversion step and may not be commercially competitive with current fossil products under the current regulation. There might also be uncertainties about future commodity prices. Thus, the objective of this study is to estimate the economic competitiveness and the added value of selected side products that could be produced alongside conventional pulp and paper products. A typical modern pulp mill is modeled in different product configurations and operational environments, which allows testing of various development paths. This illustrates how the overall energy and mass balance of a pulp mill would react to changes in different final products and other parameters. The focus of the study is in synthetic methanol, which is produced from flue gases and excess resources from the mill, with minimal interference to the pulping process. The results aid in assessing the necessity and magnitude of a premium payment for subsidizing green alter-natives to replace current fossil fuels and chemicals. Additionally, the results function as an indicator of the development state of the pulp and paper industry in the turmoil of climate change regulation. The results indicate that power-to-X systems offer one more viable pathway alternative for broadening the product portfolio of the pulp and paper sector, as well as opening new flexibility measures and services to grid stabilization. Market conditions were found to have a significant impact on the perceived profitability.