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Recovery boiler back-end heat recovery, TAPPI Journal March 2023
ABSTRACT: Sustainability and efficient use of resources are becoming increasingly important aspects in the operation of all industries. Recently, some biomass-fired boilers have been equipped with increasingly complex condensing back-end heat recovery solutions, sometimes also using heat pumps to upgrade the low-grade heat. In kraft recovery boilers, however, scrubbers are still mainly for gas cleaning, with only simple heat recovery solutions. In this paper, we use process simulation software to study the potential to improve the power generation and energy efficiency by applying condensing back-end heat recovery on a recovery boiler. Different configurations are considered, including heat pumps. Potential streams to serve as heat sinks are considered and evaluated. Lowering the recovery boiler flue gas temperature to approximately 65°C significantly decreases the flue gas losses. The heat can be recovered as hot water, which is used to partially replace low-pressure (LP) steam, making more steam available for the condensing steam turbine portion for increased power generation. The results indicate that in a simple condensing plant, some 1%•4% additional electricity could be generated. In a Nordic mill that provides district heating, even more additional electricity generation, up to 6%, could be achieved. Provided the availability of sufficient low-temperature heat sinks to use the recovered heat, as well as sufficient condensing turbine swallowing capacity to utilize the LP steam, the use of scrubbing and possibly upgrading the heat using heat pumps appears potentially useful.
Journal articles
Magazine articles
Non-process elements in the recovery cycle of six Finnish kraft pulp mills, TAPPI Journal March 2023
ABSTRACT: In this work, the aim was to study the distribution and accumulation of the non-process elements (NPEs) in the recovery cycle of Finnish pulp mills and look at whether the geographical location (North vs. South) correlates with the current Finnish NPE levels. In addition, a comparison to older similar Finnish measurements was made with an attempt to analyze the reasons behind differences in the most typical non-process elements, aluminum (Al), silicon (Si), calcium (Ca), phosphorus (P), magnesium (Mg), manganese (Mn), chlorine (Cl), and potassium (K), taking into account the main elements in the white liquor, sodium (Na) and sulfur (S). The extensive laboratory results gained in this study are from seven sampling points at six pulp mills and present analytical data of metal concentrations. The data obtained presents an update to previous NPE studies. The levels found did not statistically differ between North and South Finland. The NPE levels, apart from phosphorus, found in Finnish pulp mills today have not changed considerably compared to the levels in earlier investigations in the 1990s. In the newest data, the phosphorus concentration was consistently higher in the as fired black liquor, electrostatic precipitator (ESP) ash, lime mud, and green liquor than in the previous results. In addition, the levels of Al, Si, Ca, P, and Mg in recovery boiler ESP ash were consistently higher compared to the older results. As the mills start to close their systems more, a stronger accumulation of NPEs can be expected, increasing the likelihood of more operational problems in the process. Further understanding of where the NPEs accumulate and how they can be most effectively removed will be valuable knowledge in the future.
Journal articles
Preparation of a vegan leather from mycelium with papermaking method, TAPPI Journal June 2026
ABSTRACT: With growing concern over the environmental impacts of both natural leather and conventional synthetic leathers, the development of sustainable and eco-friendly leather alternatives has become an urgent research priority. In this study, an innovative wet papermaking strategy is proposed to fabricate continuous, homogeneous mycelial sheets from chitin-rich fungal mycelium, mimicking the matrix structure of genuine leather. These mycelial sheets were chemically modified to meet the performance requirements of leather foam layers. Subsequently, the modified mycelial sheets were combined with a substrate fabric to produce a novel mycelium-based leather composite (myco-paper leather) that achieves an excellent balance of mechanical properties and tactile qualities. Experimental results demonstrate that the mycelium-sheet-based leather substitute exhibits remarkable mechanical performance, with a tensile strength of approximately 45 MPa and an elongation at break of about 10.5%. After lamination with the substrate fabric, the composite material shows a tear strength of approximately 16 N, along with a desirable hand feel and surface texture. Following tannic acid tanning, the mycelial sheets also exhibit significant antimicrobial and antifungal properties, forming an inhibition zone of approximately 2 mm against Staphylococcus aureus. Through reinforcement with plant fibers, the developed material attains both strength and flexibility, indicating that the wet papermaking of mycelial sheets is a feasible and scalable approach for producing sustainable leather alternatives. This work not only employs a simple and mature papermaking process to process fungal mycelium but also provides a new conceptual and practical foundation for the large-scale production of bio-based leather substitutes. The findings have significant implications for advancing a low-carbon, sustainable leather industry.
Journal articles
Investigation of the factors contributing to malodorous gases emission during secondary fiber reuse, TAPPI Journal June 2026
ABSTRACT: Malodorous gases are commonly produced during secondary fiber reuse, which is harmful to human health and causes environmental pollution. This paper investigated the influence of fiber type and concentration, temperature, and whitewater concentration on the malodorous gases. The results indicated that, in pulp prepared with fresh water, bleached hardwood kraft pulp (LBKP) did not produce malodorous gases after standing for five days. In contrast, the secondary fiber began to release substantial amounts of total volatile organic compounds (TVOC) on the third day and hydrogen sulfide (H2S) and ammonia (NH3) on the sixth day, and black substances began to appear in the pulp, which proved that the microorganisms began to proliferate. With the increase of the secondary fiber concentration, the release amounts of TVOC, H2S, and NH3 gradually rose, along with the black substances in the pulp. With increased temperature, the release of TVOC increased steadily, while the release of H2S and NH3 reached the maximum at about 45°C, and then began to decline. The decrease of the pulp freeness accelerated the generation of the malodorous gases, but the total release amounts of TVOC, H2S, and NH3 were basically the same. With the increase of white water concentration, the release of TVOC, H2S, and NH3 increased rapidly. When the white water/fresh water was 20 mL/80 mL, the slurry changed from pale yellow to aterrimus on the sixth day. Therefore, microorganisms in the secondary fiber caused pulp deterioration, while white water was the main reason for generating a large amount of malodorous gases.
Journal articles
Upgrading aeration system performance in secondary basins treating pulp and paper wastewater: A review, TAPPI JOURNAL June 2015
Upgrading aeration system performance in secondary basins treating pulp and paper wastewater: A review, TAPPI JOURNAL June 2015
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Magazine articles
TAPPI Journal Summaries, Paper360º May/June 2021
TAPPI Journal Summaries, Paper360º May/June 2021
Journal articles
Magazine articles
Evaluation of rice straw for purification of lovastatin, TAPPI Journal November 2021
ABSTRACT: Cholesterol synthesis in the human body can be catalyzed by the coenzyme HMG-CoA reductase, and lovastatin, a key enzyme inhibitor, can reduce hypercholesterolemia. Lovastatin can be obtained as a secondary metabolite of Aspergillus terreus ATCC 20542. In this study, rice straw of lignocellulose was used in aeration and agitation bath fermentation in a 1-L flask, and a maximal crude extraction rate of 473 mg/L lovastatin was obtained. The crude extract was treated with silica gel (230•400 mesh) column chromatography. Ethyl acetate/ethanol (95%) was used as the mobile phase, and isolation was performed through elution with various ethyl acetate/ethanol ratios. The highest production rate of 153 mg/L was achieved with ethyl acetate/ethanol in a ratio of 8:2. The lovastatin gained from the crude extract was added to 12 fractions treated with 0.001 N alkali, and acetone was then added. After 24 h of recrystallization at 4°C, the extract underwent high-performance liquid chromatography. The purity had increased from 25% to 84.6%, and the recovery rate was 65.2%.
Journal articles
Magazine articles
TAPPI Journal Summaries, Paper360º November/December 2021
TAPPI Journal Summaries, Paper360º November/December 2021
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
Application of spruce wood flour as a cellulosic-based wood additive for recycled paper applications— A pilot paper machine study, TAPPI Journal October 2021
ABSTRACT: This study gives a first insight into the use of wood flour as a plant-based and cellulosic-based alternative additive for newsprint and paperboard production using 100% recycled fibers as a raw material. The study compares four varieties of a spruce wood flour product serving as cellulosic-based additives at addition rates of 2%, 4%, and 6% during operation of a 12-in. laboratory pilot paper machine. Strength properties of the produced news-print and linerboard products were analyzed. Results suggested that spruce wood flour as a cellulosic-based additive represents a promising approach for improving physical properties of paper and linerboard products made from 100% recycled fiber content. This study shows that wood flour pretreated with a plant-based polysaccharide and untreated spruce wood flour product with a particle size range of 20 µm to 40 µm and 40 µm to 70 µm can increase the bulk and tensile properties in newsprint and linerboard applications.