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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
Energy reduction at a kraft mill: examining the effects of process integration, benchmarking, and water reduction, TAPPI JOURNAL & Solutions! March 2005, Vol. 4(3)
Energy reduction at a kraft mill: examining the effects of process integration, benchmarking, and water reduction, TAPPI JOURNAL & Solutions! March 2005, Vol. 4(3)
Journal articles
Response of bagasse and wheat straw recycled pulps to refining, Solutions! & TAPPI JOURNAL, October 2004, Vol. 3(10) (349KB)
Response of bagasse and wheat straw recycled pulps to refining, Solutions! & TAPPI JOURNAL, October 2004, Vol. 3(10) (349KB)
Journal articles
Accelerated light exposure of wood-containing pulps. part I: effects of wavelength and intensity, Solutions! & TAPPI JOURNAL, October 2004, Vol. 3(10) (726KB)
Accelerated light exposure of wood-containing pulps. part I: effects of wavelength and intensity, Solutions! & TAPPI JOURNAL, October 2004, Vol. 3(10) (726KB)
Journal articles
The role of evaporative dewatering in impulse pressing, TAPPI JOURNAL, March 2003, Vol. 2(3) (185KB)
The role of evaporative dewatering in impulse pressing, TAPPI JOURNAL, March 2003, Vol. 2(3) (185KB)
Journal articles
Laboratory- and mill-scale study of surfactant spray flotation deinking, TAPPI JOURNAL, October 2005, Vol. 4(10) (216 KB)
Laboratory- and mill-scale study of surfactant spray flotation deinking, TAPPI JOURNAL, October 2005, Vol. 4(10) (216 KB)
Journal articles
PET Recyclable Polymer for Making Paper Washbowls, TAPPI JOURNAL May 2008
PET Recyclable Polymer for Making Paper Washbowls, TAPPI JOURNAL May 2008
Journal articles
Effect of Eucalyptus Globulus Wood Density on Papermaking Potential, TAPPI JOURNAL May 2008
Effect of Eucalyptus Globulus Wood Density on Papermaking Potential, TAPPI JOURNAL May 2008
Magazine articles
Setting a limit, TAPPI JOURNAL, July 2002, Vol. 1(5) (52KB)
Setting a limit, TAPPI JOURNAL, July 2002, Vol. 1(5) (52KB)