Performance and Design of Paper Stock Mixers

Authors:

J.Y. Oldshue

A.T. Gretton

The document discusses the fundamentals and advancements in paper stock mixing within the pulp and paper industry, emphasizing how mixer design, impeller type, and tank configuration influence uniformity and efficiency. It explores quantitative definitions of mixing performance, detailing experimental results, flow behavior, and the impact of operational parameters such as impeller position, power input, and chest geometry. Overall, the study provides a comprehensive analysis of industrial mixing processes, offering insights into optimizing blending performance, energy efficiency, and consistency control in large-scale paper stock systems.

Key Learnings

• Effective paper stock mixing is essential for maintaining uniform consistency and product quality in pulp and paper operations.
• Impeller type, position, and tank geometry significantly influence mixing efficiency, flow patterns, and power requirements.
• Achieving complete uniformity throughout the stock chest is often impractical; instead, focus is placed on adequate motion near the pump suction and within key volume zones.
• Quantitative definitions of mixing performance help evaluate and compare the effectiveness of different mixer configurations.
• Top-entering and side-entering mixers each have unique advantages depending on chest design and process needs.
• Off-center impeller placement and draft tubes can improve flow circulation and minimize stagnant zones.
• Proper impeller clearance and speed selection enhance turbulence and blending without excessive energy use.
• Tracer and flow visualization tests are valuable for studying mixing behavior and verifying uniformity in experimental and industrial settings.
• Power draw and pumping capacity are critical performance measures for optimizing mechanical agitation systems.
• Laboratory and pilot-scale tests provide insights that support scaling up to industrial-size stock chests.
• Efficient mixing contributes to energy savings, reduced process variability, and improved product uniformity.
• The research underscores the importance of process control and equipment design optimization for achieving consistent, cost-effective stock mixing performance.