Block flow diagrams were introduced early in the chemical engineering curriculum. In the first course in
material and energy balances, often an initial step was to convert a word problem into a simple block
diagram. This diagram consisted of a series of blocks representing different equipment or unit operations
that were connected by input and output streams. Important information such as operating temperatures,
pressures, conversions, and yield was included on the diagram along with flowrates and some chemical
compositions. However, the diagram did not include any details of equipment within any of the blocks.