Page 186 - CW E-Magazine (16-4-2024)

Special Report

other considerations for batch to ing of intrinsic chemistry. This prefer- is to validate the model on which the
flow transitions ably involves the use of mathematical techno-economic analysis was based.
Note that difficult transitions to flow, modelling and non-linear regression It is recommended that during pilot-
including processes involving viscous to determine rates of the primary and ing, the exact configuration of the reac-
slurries, abrasive solids, dry powders, side reactions and temperature effects. tors be used as in the final commercial
long residence times, and molten mate- Thermic effects and thermal and hydro- system, except for smaller volumes
rials, are still possible and often very much dynamic properties of the reaction or smaller numbers. For example, if
worthwhile. They present more difficult mass should be obtained or reasonably 1-inch diameter tubular reactors are to
engineering challenges and have a estimated at this stage. be used in the commercial system, use
longer lead time to commercialisation. 1-inch diameter tubes in the pilot – but
During this time, one of the above processes Design and simulation with shorter lengths.
would have successfully transitioned and Once all the kinetic and property
started yielding revenue. parameters are in hand, it is necessary The following statement goes against
to invest time and effort in developing the accepted industry wisdom – but we
An essential concern for fine chemi- mathematical models of the process in would like to lay it out anyway: there is
cal manufacturers is the seasonal demand its putative flow reactor. The scaling really no need to demonstrate the same
for chemicals. In this case, the strategic relationship governing hydrodynamics of performance as in the commercial
transition team should identify two or the flow reactors, i.e., pressure drops, reactor, i.e., it is not necessary to demon-
more processes, with anticipated cam- residence time distributions, heat trans- strate in the pilot the same conversions
paign durations of at least three months, fer coefficients, and mass-transfer as in the commercial reactor. Instead,
for transitioning to flow and design flow coefficients (in the case of multi-phase check if the model predicts the obtained
equipment that can be rapidly repurposed systems), are already abstracted into conversions. If they are, further scale-up
for one or the other of these. A multi- correlations by the manufacturer of the can be achieved with great confidence.
product flow system can be devised if reactors. Combined with the intrinsic If they are not, retrain the model on the
one can envisage demand for multiple system behaviour, these can be incor- pilot data and scale-up with confidence.
products. Intense manual involvement porated into a reliable mathematical Manufacturers of flow reactors will offer
is only required during the transition model of the system, which can be vali- assistance in piloting – from helping with
between campaigns. This is operating in dated using small-scale experiments. modelling to building the full pilot skids.
a continuous campaign mode. Another round of techno-economic and
First techno-economic analysis financial analysis can happen at this stage
The roadmap to flow Based on the simulations, validated at if necessary.
The roadmap to flow, as presented small scales, but extrapolated to commer-
here, presupposes access to the afore- cial scales using the scaling relationships, Commercial plant
mentioned interdisciplinary teams. a techno-economic evaluation of the Once piloting is completed, the com-
Suppose such a team still needs to be commercial plant should be conducted mercial plant’s plans should be drawn up.
assembled. In that case, it is recom- in silico. This should involve all capital, Much of the work is already done dur-
mended to get the assistance of flow raw material, utility, and other anticipated ing the techno-economic evaluation. The
solutions providers such as Amar Equip- expenses and should be the input to a manufacturers of the flow reactors will
ment Pvt. Ltd., which has such teams financial model whose results are trusted often provide hand-holding and some-
and offers services at every stage of the by the decision-makers. The capital times a guarantee on the performance of
batch-to-flow transition, from concept expense includes reactors and ancillar- their reactors. The plant can be set up by
to commercialisation. ies like pumps (typically among the most one of several EPC contractors available
oversized sinks of capital), valve pressure on the market, in close coordination with
The roadmap to flow has several regulators, control and monitoring sys- the flow reactor manufacturer, since the
waystations, from understanding the tems, etc. The financial analysis should EPC contractor will need details of the
chemistry to full commercialisation. be conducted before these decision- engineering aspects of the non-standard
makers make a go-no-go decision. components forming the flow reactors.
Quantitative understanding of intrinsic
system behaviour Piloting conclusIon
The very first way to do this is by In case of a go decision, the next In conclusion, flow operation offers
developing a thorough understand- step is piloting. The purpose of piloting many advantages over the business-as-

186 Chemical Weekly April 16, 2024

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