Chemical process simulation is software that works out how materials will move, heat and react as they pass through a refinery or chemical plant. Engineers use it to design the plant, and later to tune it to run better. It lets them test a plant on a computer, where a wrong design costs nothing.
The engineer draws the plant as a diagram: tanks, pumps, heaters, reactors and columns, joined by pipes. She enters what goes in, such as the amount and temperature of each material. The software then calculates, for every item, what comes out. It uses the known properties of each chemical, for instance the temperature at which it boils. The two basic checks are the mass balance, which says that everything that goes in must come out somewhere, and the heat balance, which says the same for energy.
Say a company near Vadodara wants to recover acetone, a common solvent, from a waste stream that is 30% acetone and 70% water. The stream is 10,000 kg an hour, and the company wants acetone that is 99% pure. The engineer places a distillation column in the diagram. A distillation column is a tall vessel that separates liquids by their boiling points. Acetone boils at 56 °C and water at 100 °C, so the acetone rises to the top as vapour. She enters the feed and the purity she wants. The software shows how many trays the column needs and how much heat its boiler must supply. She then changes one setting, such as how much liquid is sent back down the column, and sees at once how the heat needed changes. She can repeat this a hundred times in an afternoon.
Simulation also warns when a separation will not work. Ethanol and water, for example, form an azeotrope, a mixture whose vapour has the same composition as its liquid. At about 95.6% ethanol, a plain distillation column can go no further. Plants that need stronger ethanol use another step after the column. The software knows such limits for many chemicals, so the engineer finds them on screen, not on site.
The result goes on to other tools. Plant design software uses the vessel sizes to lay out the plant. The distributed control system (DCS) needs the settings. A plant digital twin starts from the same model, and an operator training simulator uses it to let new operators practise on a virtual plant.