I study chemical engineering. This is a link from my department website which explains clearly what chemical engineering is: http://www3.imperial.ac.uk/portal/page?_pageid=100,372291&_dad=portallive&_schema=PORTALLIVE
This simulation exercise involves an evaporator plant whereby potassium nitrate (KNO3) solution is concentrated. Concentrating a beaker of solution in the laboratory involves mild heating with a
burnsen burner to evaporate the solvent. The solute remains in the solvent throughout the process and the evaporated solvent is discharged into the environment.
However, the same process cannot be emulated in an industrial chemical plant. An industrial chemical plant would need to concentrate tonnes and tonnes of solution, thus a lot of heat will be needed for the process. An efficient and economic mean of transferring heat to the solution is therefore important. Moreover, tonnes and tonnes of the evaporated solvent will be produced and cannot be discharged into the environment for two reasons. Firstly, the discharged solvent maybe reused and thus contributing to bringing down the cost of production. Secondly, the evaporated solvent maybe harmful to environment, therefore cannot be discharged beyond a legally restricted concentration.
In order to meet all this criteria, the process to concentrate the potassium nitrate solution is broken down into 4 unit operations: stirring, heat exchange, evaporation and condensation.
Stirring ensures uniform concentration of the feedstock.
Heat exchangers, unlike the burnsen burner, does not produce soot while heating the feedstock and at the same time facilitate energy integration.
Evaporation is carried out in a container to prevent unnecessary harmful discharge into the environment.
Condensation recovers the evaporated solvent and facilitate re-use or allow further chemical treatment to the solvent before discharging it into the environment.
The above quote came from my pilot plant report. It should give you an idea of what chemical engineers study and do. The technical nature of chemical engineering is best characterised by the unit operations, such as stirring, heat transfer, etc.
Chemical engineers seldom deal with high level chemistry, except chemical kinetics and catalysis. Even the so-called industrial chemistry modules which i take essentially cover chemical kinetics and reaction engineering, ie. design and troubleshooting reactors.
I attached a picture (from my dept website) to show what the typical study themes that run through a chemical engineering undergraduate degree. it involves some chemistry, but essentially it's all physics and mathematics. however, strictly speaking, engineering still differs alot from physics. Engineers use models that produce results that agree with experimental data, although the model maybe fundementally wrong. eg. using perfect gas assumption on a liquid fluid. Physicists, on the hand, seek to explain the natural phenomena emperically.
Hope my description of chemical engineering proves helpful to you.