Base case process development for energy efficiency improvement, application to a Kraft pulping mill. Part I: Definition and characterization

The development of a base-case process is a fundamental step in an energy efficiency study to obtain reliable results. However, this step is often overlooked and there are no clear guidelines for the systematic development of the base-case. A methodology has been proposed to properly define and evaluate the complete process for a subsequent in-depth energy analysis. It consists of two stages: definition and characterization of the process, and benchmarking analysis. In this paper, the first stage is presented. The base-case should encompass the process and the utilities systems, i.e., steam and water, as they are the driving forces of the chemical transformations. A four-pronged procedure is proposed to properly define and characterize a process and its utilities: data gathering, master diagram construction, utilities systems analysis, and simulation. The main objective is to build a computer simulation model to provide detailed information on production, distribution, utilization and post-utilization treatment of steam and water. Process inefficiencies are also identified, such as the low condensate recovery or the presence of non-isothermal mixing points. The procedure has been applied to an operating Kraft pulping mill in Eastern Canada.