Fewer than one in a hundred chemical plant designs ever gets built
Before a new chemical plant rises, engineers sketch dozens of alternatives, and typically under 1 percent of design ideas reach commercial use. Cost studies kill most of them early. The survivors usually begin as a small pilot plant, because a reaction that behaves nicely in a laboratory flask can misbehave badly at industrial scale.
A chemical plant turns raw feedstocks into more valuable materials through chemical or biological change and separation. Its core is a set of units, large vessels where individual steps called unit operations happen, linked by pipes carrying gases, liquids, slurries or solids. One plant's product is often another's feedstock: refinery outputs feed petrochemical plants, which in turn supply pharmaceutical makers. For that reason petrochemical works usually sit beside refineries, while smaller specialty chemical plants can go almost anywhere.
Plants run in two basic modes. Continuous operation keeps feed flowing in and product flowing out at the same time, ideally in a steady state where temperatures, pressures and flow rates hold constant; it suits huge commodity producers like oil refineries. Batch operation charges a vessel, runs the reaction, empties it and repeats, which gives flexibility and traceability for pharmaceuticals and fine chemicals. Engineers typically assume plants handling fluids run about 90 percent of the time, and those handling solids about 80 percent.
Inside, vessels are often cylinders with rounded ends, a shape that copes with high pressure or vacuum. Reactors may be stirred tanks or beds packed with solid catalysts that must periodically be regenerated when deposits such as coke poison their surfaces. Separation relies on filtration, distillation, crystallisation, reverse osmosis, drying and adsorption, with heat exchangers doing much of the heating and cooling. Clusters of storage tanks are called tank farms, and designers map everything in flow diagrams built on material and energy balances.
For a long time many plants were thrown together haphazardly, before chemical engineering existed as a discipline. That changed in 1887, when George E. Davis gave twelve lectures on industrial chemical practice at the University of Manchester, the first chemical engineering course, earning him the title of the world's first chemical engineer. Today chemists typically work out reactions at small scale, and chemical engineers scale them up, joined later by mechanical, electrical and structural specialists.
Source: Chemical plant
