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Continuous digester process safety improvements • Stress corrosion cracking and overpressure protection lessons learned and opportunities, TAPPI Journal October 2024

ABSTRACT: Georgia-Pacific has recent experience with continuous digester stress corrosion cracking (SCC) repairs where the extent of SCC was more than previous spot inspections had predicted (one digester had anodic protection, one did not). This paper offers case studies of reviewed and improved digester inspections by use of “boat” samples to quantify the depth of cracking mechanism. Boat sample test data is used to support repair recommendations based on hardness testing. Georgia-Pacific also reviewed overpressure protection systems and corrected gaps found in these systems. These included updating to the latest original equipment manufacturer (OEM) designs and formalizing functional testing procedures and practices. This review of digester inspection, testing, and repairs since 2020 provides: (1) a basis for including a 3rd party corrosion expert to be a part of inspections; (2) removes the use of power-wire brushes; (3) enhances digester inspection with 100% phased-array ultrasonic testing to detect SCC; and (4) ensures overpressure protection design and testing is aligned with corporate needs and the site-specific challenges.

Taking the Guesswork Out of Decarbonizing Pulp and Paper Mills, Paper360º September/October 2024

TAPPI Journal Summaries, Paper360º September/October 2024

Optimizing OCC refining with defloccing, TAPPI Journal April 2025

ABSTRACT: Subjecting pulp to a high shear zone immediately after refining results in more efficient refining. This phenomenon was originally observed to benefit softwood pulp refining. It was attributed to floc reduction based on floc measurements in mill refiners and the observation of reduced headbox plugging. Hence, this phenomenon has been termed “defloccing.” The present work shows this technology also benefits refining of North American old corrugated containers (OCC). The combined results of several mill trials with OCC defloccing demonstrate the interactions between OCC refining intensity, defloccing technology, and other state-of-the-art refining improvements. At the same refining intensity, defloccing OCC on 100% recycled machines increases OCC refining efficiency by 15%, with greater efficiency improvement on machines that use softwood as well as OCC. Furthermore, it is shown that the benefits of defloccing are additive to refining improvements made in the refining zone of a refiner plate. Most OCC refiner plate designs can therefore benefit from the addition of a defloccing feature.

Summaries from TAPPI Journal April 2025 and May 2025 Issues, Paper360º July/August 2025

Gap mechanics in pulp refiners, TAPPI Journal June 2025

ABSTRACT: Studies of pulp refining have shown that a single bar impact on pulp has only a 1%•5% probability of producing a successful refining effect. This study has explored the reason why. An analysis of refining kinetics suggested that small segments of a fiber length, about a fiber diameter in size, are treated during each impact. Measurements of localized swelling along fiber lengths caused by refining supported this finding. Based on these findings, it was postulated that force transmittal through fiber networks occurred primarily at fiber crossings. The small size of fiber diameters relative to fiber lengths accounts for the low probability of a successful refining event at each impact. This probability, and the probability of fibers being captured and impacted during passage through a refiner, account for the need for multiple bar crossings to refine pulps.

Boiler retrofit improves efficiency and increases biomass firing rates, TAPPI Journal March 2021

ABSTRACT: Domtar’s fluff pulp mill in Plymouth, NC, USA, operates two biomass/hog fuel fired boilers (HFBs). For energy consolidation and reliability improvement, Domtar wanted to decommission the No. 1 HFB and refurbish/retrofit the No. 2 HFB. The No. 2 HFB was designed to burn pulverized coal and/or biomass on a traveling grate. The steaming capacity was 500,000 lb/h from coal and 400,000 lb/h from biomass. However, it had never sustained this design biomass steaming rate. As the sole power boiler, the No. 2 HFB would need to sustain 400,000 lb/h of biomass steam during peak loads. An extensive evaluation by a combustion and boiler technologies supplier was undertaken. The evaluation involved field testing, analysis, and computational fluid dynamics (CFD) modeling, and it identified several bottle-necks and deficiencies to achieving the No. 2 HFB’s biomass steam goal. These bottlenecks included an inadequate combustion system; insufficient heat capture; excessive combustion air temperature; inadequate sweetwater con-denser (SWC) capacity; and limited induced draft fan capacity.To address the identified deficiencies, various upgrades were engineered and implemented. These upgrades included modern pneumatic fuel distributors; a modern sidewall, interlaced overfire air (OFA) system; a new, larger economizer; modified feedwater piping to increase SWC capacity; replacement of the scrubber with a dry electrostatic precipitator; and upgraded boiler controls.With the deployment of these upgrades, the No. 2 HFB achieved the targeted biomass steaming rate of 400,000 lb/h, along with lowered stack gas and combustion air temperatures. All mandated emissions limit tests at 500,000 lb/h of steam with 400,000 lb/h of biomass steam were passed, and Domtar reports a 10% reduction in fuel firing rates, which represents significant fuel savings. In addition, the mill was able to decommission the No. 1 HFB, which has substantially lowered operating and maintenance costs.

Introduction to Low Pressue Laminates and Foils, 1996 Plastic Laminates Symposium Proceedings

Introduction to Low Pressue Laminates and Foils, 1996 Plastic Laminates Symposium Proceedings

Development of Separation Release Paper for HP Laminate Production with Modern Environment-Friendly Products, 1996 Plastic Laminates Symposium Proceedings

Development of Separation Release Paper for HP Laminate Production with Modern Environment-Friendly Products, 1996 Plastic Laminates Symposium Proceedings

Preventing, Mitigating, and Venting Steam-Driven Explosions, 1996 Plastic Laminates Symposium Proceedings

Preventing, Mitigating, and Venting Steam-Driven Explosions, 1996 Plastic Laminates Symposium Proceedings