The choice of reactor technology is critical to follow the desired kinetic pathway in pyrolysis. The emphasis of this section will be on selected reactor technologies that have been successfully demonstrated at large scale with a pilot-scale or larger unit. Several reactor concepts have been demonstrated in the scientific literature at small-scales, but they will not be considered.

The mass and energy balances are the main fundamental and semi-empirical tools to design reactors when coupled to reaction kinetics. These balances involve heat and mass transfer equations, which are dependent on the system gas/solid hydrodynam­ics. Several handbooks are dedicated to reactor design with various hydrodynamics models to represent these equipments. However, the objective of this section is not to review these models in details. Considering that heat transfer is the limiting step in pyrolysis reactors, the emphasis is put on heat transfer parameters evaluation.