Material and Energy Balance

Scheduled in the second year of the program, this course is possibly the most important course in the chemical engineering curriculum. The title of course is generally Material and Energy Balance, but it may sometimes be called Chemical Engineering PrinciplesIntroduction to Chemical Processes, or a variation thereof. Simply put, the course is aimed at teaching the students the techniques to conduct the material and energy audits on the process. Material balance involves accounting for quantities of materials flowing in and out of a process unit, a sequence of units, and the entire plant. Energy balance is, similarly, the quantification of energy flows in and out of the system for which this analysis is conducted. In essence, the course teaches students how to apply the principles of conservation of mass and conservation of energy to units in chemical processes. These units may involve reacting or nonreacting systems, as well as single-phase and multiphase systems. Figure 3.13 presents an overview of this course.

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Figure 3.13 Overview of the Material and Energy Balance course.

Typically, the course starts with the concept of material balances and application of this concept to a single step in a simple, nonreacting system. Subsequent topics include complex combinations of nonreacting units, a single unit involving reaction(s), a combination of reacting and nonreacting units, energy effects not involving reaction, and energy effects in reacting systems [12].

A student, after successful completion of the course, should be able to determine accurately the mass, volume, temperature, and composition of each material stream flowing into and out of a process unit. The process occurring within this unit may be simple mixing, a physical separation, or a complex reaction. The process streams may be solid, liquid, gaseous, or any combination thereof. Similarly, the student should be able to determine accurately the energy flows into and out of the units.

Quantifying the material and energy streams connected to a process unit is a prerequisite to designing that unit. These design principles and techniques are taught in the advanced chemical engineering courses previously described. It is clear that unless the student acquires competence in tackling the material and energy balances, he/she will not be in a position to learn the advanced topics in chemical engineering. The Material and Energy Balance course provides an indicator of the ability of a student to be a chemical engineer, often serving as a “gate” for continuation in the chemical engineering program.


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