Abstract
Process system engineering applying the system thinking approach leads to a tremendously improved process design that considers many conflicting objectives. These conflicting objectives lead to interesting trade-offs that could hardly have been predicted since the processes are operating under many complex interactions taking place between their subsystems. Studying these interactions can reveal new insights into and rules for better process design. An example of such insight was proposed by Lang et al. (1988), showing that performing heat integration simultaneously with process optimisation leads not only to a reduction of utility consumption but also to decreased raw material usage due to higher overall conversion. This observation was made for processes with recycling steps performing heat integration within the recycle loops. However, the processes generally consist of several steps: the raw material preparation step, the central reaction/separation step with or without recycling, and the final product purification, conditioning step. Different synergistic effects are expected when the integration is performed only partly within a recycle. Moreover, different types of integration can lead to diverse solutions. In this study, the following scenarios were studied: i) no integration, ii) heat integration, iii) power (shaft work) integration, and iv) heat and electricity (shaft work) integration. The solutions obtained enable us to provide some valuable insights about exploiting the synergistic effects of various types of integration, their effects on the design, conversion, and selectivity of the processes and, nevertheless, also the effects among different processes via Mass Integration.
