Power Cost Reduction Through Advanced Quality Control and Refiner Segment Change at Tembec Pine Falls

摘要

In late 2004 the Tembec Pine Falls mill, teamed up with Metso's Paper and Automation divisions to achieve optimal refining performance by consistently producing high quality pulp with minimal power costs. These objectives required the implementation of advanced controls and real time optimization technologies combined with refiner segment configuration changes on the mainline refiners to prove the concept and measure the savings contribution of the segments and controls independently. As significant energy savings and a large reduction in pulp quality variability were accomplished and sustained, the mill decided to proceed with a permanent installation of the main line system and extended the controls and optimization to incorporate screening and reject refining. A mill peak power control and optimization module was also implemented to optimize operations by managing total mill power and peak load. Four key mechanisms for energy cost reduction were utilized during the project: 1. Specific energy reduction through: 1.1 freeness target shift (possible due to variability reduction), 1.2 optimization of refiner operation (accomplished through advanced control), 1.3 refiner segment changes, 2. Power cost reduction by lowering mill peak power. The advanced quality control component was configured to minimize pulp quality variability while achieving the energy reduction objectives. The results from the project were very positive. Initially, there was a reduction in specific energy in main line refining in excess of 4% attributable to refiner segment changes. This was increased to a 7% reduction in specific energy when the advanced control was implemented on the mainline refiners. After final optimization of the mainline control system and implementation of advanced control on the screens and reject refiner the energy reduction was increased to more than 10%. Monthly peak power load at the mill was reduced from 80 MW to less than 75MW. This also resulted in a significant reduction in power costs. In addition to energy cost reduction, the project achieved the desired reduction in pulp quality variability. The freeness variance on mainline refiners was reduced by 31%. After reject and screen implementation, variance of reject refiner freeness was reduced 10% compared to the level it reached with only mainline control. The quality improvement was not limited to the TMP mill. A measurable increase in MD Tensile and CD Tear occurred on both paper machines during the same time period. Since completion of the project in November of 2005 the system has sustained energy cost savings for the Pine Falls mill.