I represent the whole shale oil process as a combination of variable difficulty pseudo-random "puzzle" based around the real industrial process, actually rather better than my original "Ria" simulation.
The product flow is as follows:
Coke and shale are loaded offstage into tubs and placed on the flats. These are taken to the retort-house and loaded into the appropriate part. Waste is discharged from the retort house into empty tubs to be taken to the tailings whilst product, in small barrels, is loaded onto flats to be take to be loaded onto the barge.
The "puzzle" comes as follows:
The "coke/waste" tubs are loose filled, whereas the "shale" tubs are permanently loaded and disappear into the retort (they could in fact be some other type of container). On average, an operator reversing the flats into the loading area will receive one tub of each type, but sometimes two of one or two of the other. The retort-house takes equal quantities and disgorges one waste and one product in return. Shale tubs disappear into the retort house leaving a flat space for carrying barrels. Coke tubs are emptied and can be re-used for disposing of waste. The operator can return one, two or zero empty tubs in return for a new load.
Everything should be balanced, and there is space opposite the retort-house for storing the spare tubs (probably four), but. the degree of difficulty can be controlled by:
The game ends when the operator is expected to make a waste run and has no empty tub available, or when the operator runs out of storage space including the flat cars and either the operator is outside the acceptable "mix" in the retort house or has to make a "product" run next.