A survey of the continuous reactor market will throw up a daunting variety of shapes and types of machine.
Beneath this variation however lies a relatively small number of key design features which determine the capabilities of the reactor.
In many cases, the physical structure and fabrication techniques for micro reactors make cleaning and unblocking very difficult to achieve.
In extreme cases, poor temperature control can lead to severe over pressure which can be destructive on the equipment and potentially dangerous.
From a user’s perspective, this approach is only suitable for processes where the effects of hot/cold spots do not compromise safety, quality or yield.
Micro reactors can be tube or plates and have the key feature of small diameter flow channels (typically less than <1 mm).
Although micro reactors are efficient heat transfer devices, the narrow channels can result in high pressure drops, limited flow capacity and a tendency to block.
Within each stage the ideal heat transfer conditions can be achieved by varying the surface to volume ratio or the cooling/heating flux.
By tackling the problem as a series of stages, extreme cooling/heating conditions to be employed at the hot/cold spots without suffering overheating or overcooling elsewhere.
Larger flow channels are generally desirable as they permit higher rate, lower pressure drop and a reduced tendency to block.
If the fluid velocity is sufficiently high, turbulent flow conditions exist (which promotes mixing).
Static mixers can be effective but still require relatively long flow channels and generate relatively high pressure drops.
The oscillatory baffled reactor is specialised form of static mixer where the direction of process flow is cycled.
Whilst this adds complexity to the reactor design, it offers significant advantages in terms of versatility and performance.
This problem can be managed by breaking up the reactor into a series of mixed stages separated by small plug flow channels.