Pulp Production: Stock Preparation Innovation

Innovating Locally: How Mercer Celgar Reduced Fiber Losses by Around 80%

Mercer Celgar’s dual-pulp-machine setup is a unique configuration in the pulp industry. This design stems from integrating Pulp Machine 1, part of the original 1960s mill, into a modern kraft line built during Celgar’s 1990s modernization. While this setup provides exceptional production flexibility—allowing outputs between 650 and 1,850 metric tonnes per day—it also introduces challenges.

The shared stock preparation system removes impurities like sand, small rocks, and plastics and must handle significant flow fluctuations as production rates change. These variations caused inefficiencies in the five-stage hydrocyclone cleaning system, which separates unwanted materials from the pulp. As a result, Mercer Celgar faced excessive fiber losses of approximately 4.2 tonnes per day, significantly higher than typical losses for a mill of this size. 

Given the increasing costs of fiber and chemicals since the pandemic, these losses were particularly concerning because the fiber had already undergone the entire pulping process. Addressing this inefficiency became a key priority in optimizing fiber utilization.

What improvement or innovation did you introduce?

To resolve the inefficiency, we decoupled the stock preparation system from the production rates of the two pulp machines. This was achieved by stabilizing the system’s flow rate at a fixed level slightly above the maximum combined demand of the machines. The solution included installing recirculation stock lines from the machine chest back to the blend chest, allowing unused stock to loop back into the system rather than adjusting throughput to match production.

This adjustment ensured the hydrocyclone cleaning system operated consistently at optimal flow rates. To support this novel approach, the project also involved significant upgrades to automation and process control systems. With the stock preparation system stabilized, we fine-tuned the cleaning process, reducing fiber losses and enhancing overall system performance. Partnering with Andritz, our parts supplier, we leveraged their process expertise to align the operation with modern industry standards.

How did you identify this opportunity for improvement?

This opportunity emerged during a time when Mercer Celgar prioritized fiber utilization, driven by the rising costs of chip procurement as sawmill operations slowed during the pandemic. The idea originated in the machine room control room during a conversation with veteran papermakers Bob Shaw and Garry Ingham.

We discussed various efforts to improve fiber utilization, from optimizing chip delivery to reevaluating the acceptance of pins and fines and increasing kappa in the digester to produce more pulp with less fiber. The conversation shifted to fiber losses in the stock preparation system—losses involving high-value fiber that had already been cooked and bleached.

Bob and Garry observed, “It sure would be nice if we didn’t swing stock prep around with the machines.” That simple yet insightful remark sparked deeper discussions. 

“Could we decouple stock preparation from the machines, stabilize their flow, and optimize the cleaning system?”

What began as an offhand comment quickly evolved into months of planning, brainstorming, and development. A dedicated team of operators, engineers, and operations staff worked together to turn the idea into reality. The success of this project is a testament to the value of listening to those who run the plant daily. Practical insights and deep operational experience from our machine room operators were crucial in identifying and implementing this unconventional but highly effective solution.

What measurable outcomes resulted from your efforts?

Once the project was implemented and the cleaning system optimized, fiber losses were reduced by an impressive 79%, resulting in annual savings of approximately $500,000. Beyond financial benefits, the changes reduced wear on cleaner components, increasing lifespan and minimizing maintenance needs.

The process has become far more stable, with fewer variations in stock consistency and tank levels. This stability has reduced process upsets, enabling operators to focus on proactive improvements rather than responding to unexpected issues.

How has this improvement impacted your team and the broader operation at Mercer Celgar?

This project brought our team closer together. While we had previously worked on smaller initiatives, this was a large-scale effort that required close collaboration across disciplines. Despite the pandemic’s challenges, we successfully implemented this complex project and achieved our goals, adding value to the organization.

Bob and Garry have since retired, but their contributions and insights were instrumental in driving this project forward. The team they helped inspire remains intact and is now working on another operator-driven initiative. This project reflects the lasting impact of fostering teamwork and listening to the people who know the plant best, paving the way for future successes.