Successful technology upgrade reduces thermo-mechanical pulp mill energy footprint

This paper is a case study outlining the successful implementation of a wood chip pretreatment and interstage screening project at North Pacific Paper Company (NORPAC) in Longview, Washington USA. The paper will review the process changes inspired by a business wide energy efficiency initiative with focus on the thermo-mechanical pulp (TMP) mill and improved performance as a result of the pre-treatment and interstage screening initiatives. A discussion of the mill's alignment with the local utility service provider in leveraging energy credits to help fund the project will be reviewed. The paper will discuss process improvements included in the system upgrade and electrical system design considerations. One area of focus will include the selection and installation of ten (10) medium-voltage adjustable frequency AC drives used for process industrial motor speed control and unique performance requirements for these drives to assure efficient operation of the process loads across the require operating speed range. Project metrics and results as identified by the company corporate engineering staff, the mill site project team and major equipment suppliers after installation and commissioning of this successful project will be reviewed.