Systematic equipment performance analysis of a Kraft process through new and adapted key performance indicators

摘要

The Canadian pulp and paper sector is an important key player in the country's economic growth and gross domestic product [1], providing over 320, 000 direct and indirect employment opportunities for Canadians [4].;Pulp and paper industry in Canada is one of the largest energy-consumer amongst all industries in Canada, consuming approximately 30% of the industrial energy [2]. However, during the last two decades, the pulp and paper sector has been facing an unprecedented crisis due to competition from emerging economies like India and China, stringent environmental regulations and high energy prices. Because energy is a significant production-cost component (about 25% of the total production cost), in order to remain competitive, the sector has made efforts towards identifying ways to improve the energy efficiency through implementing energy recovery systems. The sector has also reduced its energy use by an average of 1% annually since 1990 [3]. Despite these improvements, the pulp and paper industry still seeks ways to identify inefficiencies and improve its overall energy and water utilization. Many process integration (PI) techniques have been developed and gave encouraging results. These techniques use both conceptual and mathematical approaches. However, these techniques consider that the unit operations in place function efficiently, which is often not the case in real operating pulp mills. Therefore, analysing the performance of unit operations is an important step prior to any process integration technique. In fact, equipment with poor performance could increase the energy and water demand of the overall process and discredit the results of energy and utility enhancement procedures.;The objective of this thesis is to develop, apply and validate a methodology for Kraft process equipment performance analysis in terms of energy, water and chemical utilization by means of new and adapted key performance indicators.;The core of the methodology consists in four successive stages through which the unit operations are examined to evaluate how their energy, water and chemical requirements can be reduced by increasing their own performance. The steps comprise: (i) the computation of key performance indicators for each piece of equipment, (ii) the identification of significant deviations from the target performance, and therefore the location of poor performance unit operation and, (iii) diagnosis of the causes of inefficiencies and the proposal of remedial actions.;The existing techniques for the evaluation of equipment performance include either energy or water utilization efficiency. The current study considers water, energy and chemical utilization in the process. It also takes into account the interactions between unit operations and uses more than one KPI to evaluate the performance of the process operations.;At first, data reconciliation and gross error detection are performed to produce a reliable model of the process studied and obtain reliable results when performing performance evaluation. Initially, data reconciliation and gross error detection are used to locate and identify process leaks and biases. A strong measurement adjustment is considered in this study as a first key performance indicator (KPI). An exergy efficiency analysis is performed to identify poor energy efficiency unit operations. Exergy efficiency is the KPI for energy utilization. Once these two analyses have been performed, a list of unit operations suspected to have poor performance is constructed. These unit operations are further evaluated by means of KPIs developed based on a dimensional analysis and enhancement measures and improvement projects are proposed according to the diagnoses established.;The interest of this methodology is demonstrated in the case of an operating Kraft pulp located in Eastern Canada. The mill produces an average of 280 adt/d of pulp from which newsprint is made. The methodology has been demonstrated to be able to improve the overall efficiency of the process in terms of energy, water and chemical utilization through an adequate evaluation of its equipment.;This thesis provides mill engineers with a systematic and strategic way to evaluate the performance of their unit operations by means of new KPIs.