Analysis of energy systems and performance improvement of a Kraft pulping mill

An energy study was done with the objective of improving the energy efficiency of an existing Kraft pulp mill. The improvements have been achieved by developing optimized process designs for the energy systems. The first step was to develop Mass and energy models of the mill on CADSIM plus RTM software. Second, the model was validated by examining water and steam results and other major parameters. The discrepancy in total steam and water production and consumption was less than 5%. The configuration of the model has been validated directly with the mill staff.;Constraint analysis was performed on the overall mill based on a systematic and documented approach. A set of guidelines have been developed in order to customize the constraint analysis process to any pulp and paper mill. The effect of different constraint levels such as grassroot and retrofit on energy savings has been studied by examining the total savings and economic data. In terms of grassroot and retrofit approaches, it was apparent that in line A the grassroot approach savings were more by 2% while for line B the difference was insignificant. Theoretical savings based on the composite curves for line A were 22% in grassroot and 20% in retrofit. Based on the different heat exchanger network designs, it was possible to achieve 17% savings in grassroot and a maximum of 15% in retrofit. For line B, theoretical savings based on the composite curves were 24% and the potential savings based on the heat exchanger network design was 16%.;An economic analysis was carried where by the heat exchanger networks of line A, show that for the retrofit case, a simple payback period of 2.1 years is achievable while for the grassroot case a simple payback period of 3 years is achievable. This is the case when steam production and fuel consumption are reduced. Therefore, one can say that it is economically viable to design either in grassroot or retrofit constraint level for line A. For line B, the retrofit heat exchanger network was built with a simple payback period of 3.6 years if reducing the steam production is the chosen scenario. Increasing the steam production to produce more electricity was not an economically feasible scenario for both line A and line B.;The mill has been characterized and benchmarked against Canadian industry average. In addition, steam and water networks have been built and mass balances around these two systems were done. The temperature and consistency profiles of pulp and water tanks were plotted and inefficiencies due to non isothermal mixing in the process have been identified.