History of chemical engineering
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Chemical engineering as a discipline is a little over a hundred years old. It grew out of mechanical engineering in the last part of the 19th century, because of a need for chemical processers. Before the industrial revolution (18th century), industrial chemicals were mainly produced through batch processing. Batch processing is simlair to cooking. Individuals would mix ingredients into a vessel, heat or pressurize the mixture, test it, and purify it to get a salable product. Batch processes are still performed today on expensive products, such as prefumes, or pure maple syrups, where one can still turn a profit, despite batch methods being slow and inefficient. Most chemical today are produced through a continuous "assembly line" chemical process. The industrial revolution was when this shift from batch to continuos processing occurred.
The industrial revolution led to an unprecedented escalation in demand, both with regard to quantity and quality, for bulk chemicals such as sulfuric acid and soda ash. This meant two things: one, the size of the activity and the efficiency of operation had to be enlarged, and two, serious alternatives to batch processing, such as continuous operation, had to be examined. This created the need for an engineer who was not only conversant with how machines behaved, but also understood chemical reactions and transport phenomena (how substances came together to react, how the required conditions could be achieved, etc), and the influence the equipment had on how these processes operated on the large scale. Thus, chemical engineering was born as a distinct discipline; distinct from both mechanical engineering on one hand and industrial chemistry on the other.
The set of 12 lectures that George Davis presented at the Manchester Technical School in 1887 can be regarded as the forerunner of chemical engineering syllabi as a separate discipline. This organisation of course material came to be the hallmark of chemical engineering. Shortly thereafter, the Chemistry department of the Massachusetts Institute of Technology started the first four-year program in chemical engineering called Course X (ten). Other programs soon followed.
These early programs married industrial chemistry with mechanical engineering, with the emphasis most decidedly on engineering. But chemical engineers still needed to clearly define their activity as something more than a mishmash of chemistry and engineering. To emphasize their identity and thus help the growth of their profession, chemical engineers formed the American Institute of Chemical Engineers in 1908. For the other established branches of engineering, there were ready associations in the mind of the common man: mechanical engineering meant machines, electrical engineering meant circuitry, and civil engineering meant structures. So what symbolized chemical engineering? The answer, provided by Arthur D. Little to the President of AIChE, was to emphasize the approach chemical engineers took to the design and analysis of processes rather than a process or a product. The concept of Unit operations was developed to emphasise the underlying unity among seemingly different operations. For example, the principles are the same whether one is concerned about separating alcohol from water in a fermenter, or separating gasoline from diesel in a refinery, as long as the basis of separation is generation of a vapor of a different composition from the liquid. Therefore such separation processes can be studied together as a unit operation (in this case called distillation). The concept has stood the profession in good stead in its phase of growth, and has even been used to understand the way the human body functions.
In the early part of the last century, a parallel concept called Unit Processes was used to classify reactive processes. Thus oxidations, reductions, alkylations etc. formed separate unit processes and were studied as such. This was natural considering the close affinity of chemical engineering to industrial chemistry at its inception. Gradually however, the subject of chemical reaction engineering has largely replaced the unit process concept. This subject looks at the entire body of chemical reactions as having a personality of its own, independent of the particular chemical species or chemical bonds involved. The latter does contribute to this personality in no small measure, but to design and operate chemical reactors, a knowledge of characteristics such as rate behaviour, thermodynamics, single or multiphase nature, etc. are more important. The emergence of chemical reaction engineering as a discipline truly signaled the severance of the umbilical cord connecting chemical engineering to industrial chemistry, and served to cement the truly unique character of this discipline.
