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On the diagnosis of a fouling condition in a kraft recovery boiler: combining process knowledge and data-based insights, TAPPI Journal March 2023
ABSTRACT: Fouling is still a major challenge for the operation of kraft recovery boilers. This problem is caused by accumulation of ash deposits on the surfaces of heat exchangers in the upper part of the boiler over time. The first consequence is the reduction of steam production due to loss of heat transfer and, finally, the shutdown of the boiler due to clogging. The present work investigated the operational condition of a modern kraft boiler under a critical fouling condition. This boiler had even faced a manual cleaning due to a clogging event. This analysis combined process knowledge, plant team experience, and a data-driven approach, given the complexity of the process. In this sense, historical data covering this critical period of operation were collected. After a cleaning procedure, they were used to obtain a predictive neural network model for the flue gas pressure drop in the boiler bank, which is an indirect measure of ash deposit accumulation. Once validated, it was used for sensitivity analysis, with the aim of quantifying the effects of the model inputs. Five variables out of eighteen accounted for nearly 60% of the total effect on pressure drop. Namely, primary air temperature (21.6% of the total effect) and flow rate (11.1%), black liquor flow rate (9.9%) and temperature (8.4%), and white liquor sulfidity (8.6%). The analysis of these results mainly suggested an excess of carryover, which composes the ash deposits. Recommended actions to mitigate the fouling condition involved adjustments to the primary air system before the more drastic solution of reducing the boiler load.
Journal articles
Magazine articles
Improving the efficiency of hydrogen peroxide bleaching of c
Improving the efficiency of hydrogen peroxide bleaching of chemimechanical pulp by continuous replenishment of bleaching chemicals, TAPPI JOURNAL June 2017
Journal articles
Magazine articles
Investigation of the Cellulose-Water Relationship by the Pressure Plate Method, TAPPI Journal July 2022
ABSTRACT: The swelling and water retention properties of pulp fibers are of basic importance in papermaking.
Journal articles
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A review of green liquor scale formation, TAPPI Journal October 2018
A review of green liquor scale formation, TAPPI Journal October 2018
Journal articles
Magazine articles
Editorial: 2018 TAPPI Journal features diverse content, TAPPI Journal November 2018
Editorial: 2018 TAPPI Journal features diverse content, TAPPI Journal November 2018
Journal articles
Magazine articles
Ultrastructural Behavior of Cell Wall Polysaxxharides, TAPPI Journal April 2022
ABSTRACT: Considerable information on the ultrastructural organization of the plant cell wall and the supermolecular arragement of the cell wall components, in particular of cellulose, has been obtained with the electron microscope.
Journal articles
Magazine articles
Mill experience of calcium carbonate scale formation in green liquor pipelines, TAPPI Journal August 2020
ABSTRACT: Experience of hard calcite (CaCO3) scale formation in green liquor pipelines at four kraft pulp mills was systematically investigated to determine if there is any correlation between the severity of the scaling problem at each mill and the design and operating conditions of its causticizing plant. The results show that the high degree of supersaturation of calcium ions (Ca2+) in the liquor is the main contributing factor. Mills that operate at a lower green liquor total titratable alkali (TTA), higher causticity, and a larger liquor temperature drop are more likely to produce a green liquor that is supersaturated with Ca2+, and thus experience more severe scaling problems. In order to minimize CaCO3 scaling, the green liquor handling equipment should be operated as steady as possible to avoid conditions that allow Ca2+ to be supersaturated. The strategies include minimizing variations in liquor TTA, insulating the green liquor pipelines to reduce temperature gradients, and adding lime mud to weak wash to provide seeds for precipitation to occur on mud particles instead of on metal substrate.
Journal articles
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A hundred years of corrosion in the pulp and paper industry, TAPPI JOURNAL May 2018
A hundred years of corrosion in the pulp and paper industry, TAPPI JOURNAL May 2018
Journal articles
Magazine articles
Tetraethyl orthosilicate-containing dispersion coating — water vapor and liquid water barrier properties, TAPPI Journal September 2021
ABSTRACT: An aqueous styrene-butadiene latex dispersion coating containing in-situ processed tetraethyl orthosilicate (TEOS) applied on paperboard demonstrated improved water barrier performance. Coatings containing TEOS equivalent to 0.8% silicon dioxide (SiO2; dry basis) exhibited water vapor performance of < 25 g/m2/day (23°C, 50% relative humidity [RH]) and liquid water barrier performance Cobb 1800 s of < 6 g/m2, when applied as a single-layer 18 g/m2 coating. Cobb 1800 s barrier performance was still good (< 11 g/m2) at coat weights of 7•10 g/m2. The use of filler materials such as kaolin improved the vapor barrier properties of the coating, but this was not critical to the liquid water barrier properties.
Journal articles
Magazine articles
Pulping and bleaching of Malaysian oil palm empty fruit bunc
Pulping and bleaching of Malaysian oil palm empty fruit bunches, TAPPI JOURNAL June 2017