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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
Open Access
Z-direction chemical analysis for new application methods, TAPPI Journal January 2023

ABSTRACT: In conventional wet-end chemical addition during paper production, chemical distribution through the z-direction of the sheet is usually not considered an important characteristic. With a nontraditional chemical dosing approach, such as foam-assisted additive addition, the chemistry can appear at different concentrations throughout the sheet, typically in a z-direction gradient. To fully understand the strength properties of the sheet, it is helpful to view or quantify the chemical distribution through the sheet in the z-direction. One qualitative method uses a dye technique along with confocal laser scanning microscopy to generate an image where the relative chemical concentration can be observed. A quantitative method involves compiling nitrogen analyses of layered subsections of the sheet into a composite graph of relative chemical concentration vs. the z-direction of the sheet. Chemical distribution analysis can be paired with traditional z-direction strength tests, such as Scott bond and z-direction tensile, to help one understand and improve the chemical addition process and its effects.

Journal articles
Magazine articles
Open Access
The Mechanism of Bonding, TAPPI Journal September 2022

ABSTRACT: Three factors are involved in cellulose bonding--available area, contact, and hydrogen bonding.

Journal articles
Open Access
Impulse drying: heterogeneous press-roll surfaces offer new product opportunities, TAPPI JOURNAL, May 1992, Vol. 75(5)

Impulse drying: heterogeneous press-roll surfaces offer new product opportunities, TAPPI JOURNAL, May 1992, Vol. 75(5)

Journal articles
Open Access
Lignin functionalization and the alkaline delignification rate, TAPPI JOURNAL, May 1992, Vol. 75(5)

Lignin functionalization and the alkaline delignification rate, TAPPI JOURNAL, May 1992, Vol. 75(5)

Journal articles
Open Access
Printing and finishing among hot roundtable topics, TAPPI JOURNAL, April 1992, Vol. 75(4)

Printing and finishing among hot roundtable topics, TAPPI JOURNAL, April 1992, Vol. 75(4)

Journal articles
Open Access
Heavy metal analysis of inks: a survey, TAPPI JOURNAL, April 1992, Vol. 75(4)

Heavy metal analysis of inks: a survey, TAPPI JOURNAL, April 1992, Vol. 75(4)

Magazine articles
Open Access
Alkaline filler addition and retention, TAPPI JOURNAL, April 1992, Vol. 75(4)

Alkaline filler addition and retention, TAPPI JOURNAL, April 1992, Vol. 75(4)

Magazine articles
Open Access
Controlling anaerobic bacteria to improve product quality and mill safety, TAPPI JOURNAL, February 1991, Vol. 74(2)

Controlling anaerobic bacteria to improve product quality and mill safety, TAPPI JOURNAL, February 1991, Vol. 74(2)

Journal articles
Open Access
Principles of hydrodynamic instability: application in coating systems, TAPPI JOURNAL, February 1991, Vol. 74(2)

Principles of hydrodynamic instability: application in coating systems, TAPPI JOURNAL, February 1991, Vol. 74(2)

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