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Using multistage models to evaluate how pulp washing after the first extraction stage impacts elemental chlorine-free bleach demand, TAPPI Journal November 2018
Using multistage models to evaluate how pulp washing after the first extraction stage impacts elemental chlorine-free bleach demand, TAPPI Journal November 2018
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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.
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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.
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Model development for real oxygen delignification processes, TAPPI Journal October 2024
ABSTRACT: Previous extensive work has been done on modeling the oxygen delignification process, based on how the basic parameters, i.e., temperature, kappa number, concentration of alkali, and concentration of oxygen, affect the delignification rate. However, these models are not used extensively to evaluate the performance of real processes, primarily because they have not been able to properly consider all the essential issues affecting delignification in practice. Such issues include the mass transfer and consumption of oxygen, which defines the concentration of dissolved oxygen in the process, and the effect of that concentration on the delignification rate. In this paper, a new way to model the oxygen delignification process is used in which these parameters, among other smaller matters, are taken into account. The basic model and its parameters were defined by the information obtained from the literature, delignification made in the laboratory tests, and mill processes and mill tests. An essential aspect of these studies was the information obtained from the oxygen concentration measured in the residual gas obtained from the top of the reactor. With the aid of this measurement, it was possible to define more accurately the consumption of oxygen and partial pressure of oxygen that define the concentration of dissolved oxygen in the reactor. Using mill experiments, a model was formed that predicts the operation of the oxygen delignification process. The model was used to show how much the process could be improved by optimizing the charge of the oxygen. The mill experiments also confirmed that mass transfer of oxygen is modeled correctly enough, except when the charge of oxygen is very low and/or the mixing is not efficient enough. In that case, there is variation in the concentration of oxygen in the process that should be taken into account in the modeling.
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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).
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Preparing prehydrolyzed kraft dissolving pulp via phosphotungstic acid prehydrolysis from grape branches, TAPPI Journal January 2022
ABSTRACT: Dissolving pulp was successful prepared via phosphotungstic acid (PTA) prehydrolysis kraft (PHK) cooking followed by an elementary chlorine-free (ECF) bleaching process from grape branches. The effects of prehydrolysis temperature, reaction time, and PTA concentration that potentially affect the quality of dissolving pulp product on chemical components of pulp were studied via an orthogonal experiment. The structure of lignin was activated during the PTA prehydrolysis phase, and lignin was easily removed during the following cooking process. Thus, relatively mild conditions (140°C, 100 min) can be used in the cooking process. During the prehydrolysis phase, temperature exhibited the most significant influence on the cellulose purity of the obtained pulp fiber, followed by reaction time and PTA concentration. The optimized prehydrolysis conditions were as follows: prehydrolysis temperature, 145°C; reaction time, 75 min; and PTA concentration, 1 wt%. Whether the excessively high prehydrolysis temperature or prolonging the reaction time did not favor the retention of long chain cellulose, the delignification selectivity for the cooking process could not be further improved by excessive PTA loading. Under these prehydrolysis conditions, 94.1% and 29.0% for a-cellulose content and total yield could be achieved after the given cooking and bleaching conditions, respectively. Moreover, the chemical structure and crystal form of cellulose were scarcely changed after PTA prehydrolysis, which could be confirmed by results from Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD). PTA prehydrolysis could be considered as an alternative method for preparing PHK dissolving pulp under relatively mild cooking conditions.
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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.
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Production of antimicrobial paper using nanosilver, nanocellulose, and chitosan from a coronavirus perspective, TAPPI Journal July 2021
ABSTRACT: The pulp and paper industry has an opportunity to play a vital role in breaking the spread of the COVID-19 pandemic through production that supports widespread use of antimicrobial paper. This paper provides a brief review of paper and paper-related industries, such as those producing relevant additives, and R&D organizations that are actively engaged in developing antimicrobial papers. The focus here is on the potential of three nano-additives for use in production of antimicrobial papers that combat coronavirus: nanosilver, nanocellulose, and chitosan. Various recent developments in relevant areas and concepts underlining the fight against coronavirus are also covered, as are related terms and concepts.
Journal articles
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Boiler retrofit improves efficiency and increases biomass firing rates, TAPPI Journal March 2021
ABSTRACT: Domtar’s fluff pulp mill in Plymouth, NC, USA, operates two biomass/hog fuel fired boilers (HFBs). For energy consolidation and reliability improvement, Domtar wanted to decommission the No. 1 HFB and refurbish/retrofit the No. 2 HFB. The No. 2 HFB was designed to burn pulverized coal and/or biomass on a traveling grate. The steaming capacity was 500,000 lb/h from coal and 400,000 lb/h from biomass. However, it had never sustained this design biomass steaming rate. As the sole power boiler, the No. 2 HFB would need to sustain 400,000 lb/h of biomass steam during peak loads. An extensive evaluation by a combustion and boiler technologies supplier was undertaken. The evaluation involved field testing, analysis, and computational fluid dynamics (CFD) modeling, and it identified several bottle-necks and deficiencies to achieving the No. 2 HFB’s biomass steam goal. These bottlenecks included an inadequate combustion system; insufficient heat capture; excessive combustion air temperature; inadequate sweetwater con-denser (SWC) capacity; and limited induced draft fan capacity.To address the identified deficiencies, various upgrades were engineered and implemented. These upgrades included modern pneumatic fuel distributors; a modern sidewall, interlaced overfire air (OFA) system; a new, larger economizer; modified feedwater piping to increase SWC capacity; replacement of the scrubber with a dry electrostatic precipitator; and upgraded boiler controls.With the deployment of these upgrades, the No. 2 HFB achieved the targeted biomass steaming rate of 400,000 lb/h, along with lowered stack gas and combustion air temperatures. All mandated emissions limit tests at 500,000 lb/h of steam with 400,000 lb/h of biomass steam were passed, and Domtar reports a 10% reduction in fuel firing rates, which represents significant fuel savings. In addition, the mill was able to decommission the No. 1 HFB, which has substantially lowered operating and maintenance costs.
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Commercially relevant water vapor barrier properties of high amylose starch acetates: Fact or fiction?, TAPPI Journal September 2021
ABSTRACT: Starches have recently regained attention as ecofriendly barrier materials due to the increased demand for sustainable packaging. They are easily processable by conventional plastics processing equipment and have been utilized for oil and grease barrier applications. While starches have excellent oxygen barrier properties and decent water barrier properties at low relative humidity (RH), they are moisture sensitive, as demonstrated by the deterioration of the barrier properties at higher RH values. Starch esters are chemically modified starches where the hydroxyl group of the starch has been substituted by other moieties such as acetates. This imparts hydrophobicity to starches and has been claimed as a good way of retaining water vapor barrier properties of starches, even at high RH conditions. We studied the water vapor barrier properties of one class of starch esters, i.e., high amylose starch acetates that were assumed to have good water vapor barrier properties. Our investigations found that with a high degree of substitution of hydroxyl groups, the modified starches did indeed show improvements in water vapor response as compared to pure high amylose starch films; however, the barrier properties were orders of magnitude lower than commercially used water vapor barriers like polyethylene. Even though these materials had improved water vapor barrier response, high amylose starch acetates are likely unsuitable as water vapor barriers by themselves, as implied by previous literature studies and patents.