Page 24 - CW E-Magazine (Oct-Nov-2023)

Flow Chemistry

obtained using different process sis have utmost importance in the plug leaks (which are imperative with
simulators, viz. Aspen Plus. Selec- process for a success chemical pro- so many connections), (iv) selection
tion of appropriate thermodynamic cess. These need to be taken seri- of the right components for building
models are necessary step for sepa- ously at the lab scale as the scale a set-up, (v) developing an operating
ration of components in the chemi- of hazards increases exponentially protocol (viz. for CSTRs in series be-
cal processes. Non-ideal behaviour as the scale of operation increases. fore starting the pumps all CSTRs must
of the gas-liquid phases should be This is quite essential for a con- have a solvent and one must be patient
taken into account with residual tinuous operation as it directly dic- enough to collect it as waste while the
properties/activity coefficients for tates the control and interlocks. It system reaches steady state), (vi) devel-
gas and liquid phases. This exercise is necessary to have a quantitative oping troubleshoot procedure (viz. for
avoids back and forth random ex- HAZOP done and verified through clogging, handling of solids, evaporat-
periments to save time. an independent safety team. ing gases, sticky materials etc.), (vii)
* Detailed process flow diagram flow distribution in large number of
(PFD): It is essential to describe a Classification of challenges and pos- parallel reactors, (viii) absence of SOP
chemical synthesis in the block flow sible solutions of integrated system, (ix) having stand-
diagram (BFD) initially, as it helps Once such an approach is devel- by and spare items for components with
to visualize the unit operations in- oped internally by any flow synthesis moving parts as they need more main-
volved in process development. team, many of the other challenges can tenance, (x) double check on control
Then, the complete process flow be addressed subsequently. These can and monitoring of measurable param-
diagram (PFD) can be established, be classified into design challenges, op- eters, and finally (xi) having an in-line
depending on the techno-economic erational challenges and personal/orga- analysis. The general perception that a
feasibility studies. nizational challenges/barriers. flow synthesis system cannot be used
* Piping & Instrumentation Diagram for multiple reactions is incorrect and
(P&ID): P&ID describes the details Design challenges a properly designed system can be used
of the process with automation for Among many important design re- for variety of reactions.
the smooth operation of the com- lated challenges, a few pose significant
plete process plant. The process challenges while transforming batch Organizational mind-set related chal-
parameters (pressure, temperature, process to continuous. These include: lenges
rotational speed, etc.) are set using (i) Selection of right components, (ii) This aspect is quite important in In-
instrumentation tools. A programme expertise in designing an experimental dia. When it comes to implementing an
can be set by an instrumentation en- set-up, (iii) can designing a flow reac- advanced technology that is still in the
gineer for plant operation in a dis- tor be as easy as a stirred tank reactor, pipeline, often we harbour the attitude
tributed control system (DCS) or (iv) what will be the guarantee that the of “let someone try it first”; thereby no
other relevant control options. set-up will perform as per the expecta- one wants to be 1 , and no one wants
st
* Process control strategy & inter- tions, (v) consistency in fabrication and to be too late by becoming 3 . Such
rd
locks: The processes designed for inherent tolerances is quite critical, (vi) “Neither 1 nor 3 syndrome” affects
rd
st
a specific product with desired pu- choice and clarity of the design basis, the overall organizational mindset and
rity can be operated continuously etc. kills creativity. The present hurry in
for several hours without manual picking up ready-to-use trained man-
intervention using control systems A smart team can easily address power in flow chemistry at higher and
& interlocks. The process control these issues and such examples do ex- higher salaries clearly indicates this
systems are designed for safe-oper- ist in many of the industries mentioned approach.
ation of the plant in order to avoid earlier.
deviations from the hazards occur- Similarly, every new technology
ring in the plant using interlock sys- Operational challenges needs some new investment to be made
tems. Further, the control systems Operational issues while executing and often hesitation is seen even if
are advancing towards artificial any batch protocol into a continuous the laboratory scale flow synthesis re-
intelligence-based technologies that protocol are seen in the following: (i) sults are far more promising than the
reduces human efforts. Having trained manpower, (ii) estab- conventional routes that are used for
* HAZOP and What-if analysis: lishing a flow lab with minimal neces- decades. Economics does play a role,
HAZOP studies and What-If analy- sary facilities, (iii) ability to foresee and but having a better process cannot beat

20 Chemical Weekly October / November 2023