Introduction

The modular approach to teaching chemical engineering often raises an important question: do students understand and appreciate the contributions of these modules in the context of designing and operating a chemical process on an industrial scale? Many chemical engineering curricula around the world have a compulsory capstone plant design project in the final year where students get an opportunity to apply their design knowledge acquired from different modules to complete a comprehensive process/plant design project. Such projects are important in the training of a chemical engineer. Perhaps a strong complementary approach will be to expose the students to the interconnectedness of content knowledge and how the process units interact with each other from an early stage in the curriculum.

We would like to present how interactive process simulation and visualisation software can be used as a common platform to integrate modular teaching. We hypothesise that such an integrated approach will help students to better appreciate the interconnectedness of knowledge acquired in different modules, which in turn will also stimulate their interest in the modules.

The software

We have created a simple process flowsheet in collaboration with the Centre for Instructional Technology (CIT) that simulates a methanol production process. The flowsheet comprises a reactor, flash separator, distillation column and absorber as main units (Figure 1). It shows the individual and overall mass balances and allows students to study the impact of operating variables on various units in a limited way. Design of different units will be emphasised in different modules and the flowsheet will act as a common storyboard for students to appreciate the connection between various modules and their importance in the context of a chemical process. This tool rides on the capabilities of FLASH—a software platform that enables multimedia content to be built into webpages thereby facilitating an interactive e-learning experience for students. The software may be accessed for academic use at: http://courses.nus.edu.sg/course/chels/integrated/cn.htm.

Figure 1. Screenshot of the interactive visualisation software for a
representative chemical process

As the MATLAB platform overcomes the computational limitations of FLASH, the possibility of using MATLAB as the computational backbone and its GUI development tools for visualisation have also been explored in the form of a final year research project.

An example of how the tool is used

The tool is currently used in CN 2123 “Equilibrium Stage Separations”—one of the beginning process design modules in chemical and biomolecular engineering curriculum. It serves to show the interaction among the various primary separation process units (i.e. flash, distillation and absorption) which are core learning objectives for the module. Students are asked to use the software to think through a set of questions for further discussion during the first tutorial. Some representative questions are given below.

• Verify if the software achieves mass balance closure for all the components.
  
  
• Prepare a short description of the process based on what you see on the screen.
  
  
• What is the role of the flash separator?
  
  
• Set the reactor temperature to 400 K and pressure to 150 atm. Now observe the effects of changing temperature and pressure of the flash separator. Choose a few temperatures and pressures and note down the corresponding results. Can you draw a general conclusion based on the trends observed?
  
  
• How does the change in the pressure or temperature of the flash separator affect the absorber and the distillation column?
  
  
• What is the role of the absorber? How is the exit CO₂ concentration from the absorber related to the L/G ratio? For the default operating conditions in the reactor, what % of CO₂ fed to the absorber is coming from the distillation column?
  
  
• Due to changing market conditions, you have been asked to reduce the fraction of methanol in the distillate stream to 0.97. Explore a few ways of achieving this. Start with the default conditions. Do you think all the possibilities you have come up with are equally justifiable in a real plant? Discuss and rank the options in the order of merit.

Conclusions

The idea of integrated teaching of chemical engineering modules by interactive process visualisation presented here provides a supporting pedagogical approach to actively engage students in the learning process. Though the software presented in this paper has limited capabilities, it allows instructors of different modules to take students beyond the scope of textbook problems, help students explore a wide range of operating conditions and inculcate a deeper understanding of principles of the process.