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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.

Preparation of regenerated cellulose from rice straw lignocellulosic waste and its use for reinforced paper products, TAPPI Journal July 2021

ABSTRACT: Rice straw waste is a lignocellulosic waste produced by farmers in large quantities. In this study, regenerated cellulose (RC) from rice straw was prepared by dissolving rice straw holocellulose (HC) in NaOH/Urea/Thio-urea/Water solution by the freeze-thawing process. The crystallinity index of RC was calculated at 31%, which is out of the crystallinity range of 39%•69% that has been previously suggested.The study indicated that the RC is amorphous with a low degree of polymerization (638) and higher hydroxyl group content as compared to HC. The fiber length of RC was found to be 26.7% shorter; however, the width of RC was 21.2% higher as compared to HC. Reduced kinked fiber content was observed in the fraction of RC (18.3%) as compared with HC (39.1%), and a higher curl index of fiber was observed more so in HC (10.5%) than RC (5.6%). Because of the regeneration process, the fiber length was reduced and a fines element content of about 96% was observed in RC compared to the initial fines content of HC (56.9%). Irrespective of the high fines element content of RC, the composite paper of rice straw bleached pulp and RC fibers was developed with an increase in the tensile index from 41.4 N.m/g to 71.2 N.m/g and an increase in the burst index from 4.7 kPa.m2/g to 5.3 kPa.m2/g with the addition of 5% and 15% RC, respectively. However, enhanced tear index of paper was observed up to 5% and then it declined upon further addition of RC. The study revealed that regenerated cellulose can be used as a strength additive to overcome the shortcomings of low mechanical properties in paper products.

Life Cycle Assessment of Construction-grade Thermoplastics from Organosolv Lignin, 2021 PEERS Conference (21PEE03)

Life Cycle Assessment of Construction-grade Thermoplastics from Organosolv Lignin, 2021 PEERS Conference (21PEE03)

LIME MUD DRYERS & CYCLONES, 2022PEERS/IBBC Conference (22PEE/22IBB)

Lime Mud Filter (LMF) Optimization, 2023 PEERS Conference

Continuous Digester Rapid Thinning, 2023 PEERS Conference

Bioproducts Development by Phosphorylation of Lignocellulosic Materials, 2022PEERS/IBBC Conference (22PEE/22IBB)

The Knowledge Trail, Paper360º, July/August 2017

The Knowledge Trail, Paper360º, July/August 2017

Experimental Validation of a Recovery Boiler Superheater Reg

Experimental Validation of a Recovery Boiler Superheater Region CFD Model, 2016 PEERS

The Future of Sustainability at Pulp and Paper Mills, Paper360º November/December 2021

The Future of Sustainability at Pulp and Paper Mills, Paper360º November/December 2021