Continuous Flow Monitoring

Challenge: Continuous flow reactors require fast, multipoint measurements to determine the status of a process along the length of the reactor, thereby allowing informed process control. Current analytical techniques which can technically determine the status of a reaction are either too slow or not suitable for cost effective multipoint monitoring, making controlling the highly dynamic nature of continuous flow reactions difficult.

Solution: The SpectroSens optical microchip sensor technology is small, robust and easy to network, meaning it can be fitted at multiple points along the reaction zone to accurately monitor process evolution in real-time.

Stratophase Advantages:

• Real-time process status indication
• Multipoint inline tracking of process evolution along reaction zone
• Easy to interpret comparison of realtime data against historical model
• Direct monitoring of concentration for systems with a low number of chemical variables
• Overview of changes in chemical composition from complex mixtures
• Range of pipe-fittings and flow-cells to monitor temperature compensated refractive index
• Armoured optical fibre network allowing 8 probes to connect to a single readout unit

Challenges in Continuous Flow Monitoring:

Although many production processes take place within large reaction tanks, some types of manufacture are not well suited to this approach. For example, some processes are not economical when carried out in large volumes, as it is not always efficient to make and store large amounts of product. In addition, achieving rapid changes in reaction conditions, such as altering the temperature or working at high pressure, can be challenging when working with large volumes.

Where these scenarios arise, companies have turned to continuous flow production processes, as is recently the case for pharmaceutical and fine chemical manufacture. Using this method, the reaction proceeds along a pipeline or similar flow-channel and is often split into discrete sections at which different reaction conditions are applied. The strength of this approach is that rapid changes in conditions can be enforced upon the reaction mixture and higher temperatures and pressures can be achieved along the pipeline. In addition, should a problem occur which cannot be corrected in realtime, the process can be stopped, thereby minimising wastage compared with errors in large batch production. In order to take advantage of these benefits, continuous flow production requires accurate real-time monitoring, rather than the off-line sampling traditionally used to assess reaction status, as the latter is too slow for facilitating rapid changes in the reactor.

The Stratophase Solution

The SpectroSens monitoring system provides a powerful solution for the in-line, real-time monitoring of continuous flow processes. The proprietary optical microchip technology devised by Stratophase is capable of accurately tracking the refractive index (RI) of any liquid passing across the chip surface, independently of any confounding temperature changes. The sensors can be engineered to fit seamlessly into a multitude of different environments, from the ends of probes to the surfaces of flow pipes, making them flexible enough to successfully integrate into a diverse range of systems.

After calibration, the SpectroSens system can scrutinise the reaction mixture for changes in RI, and the subsequent data used to infer the current status of the reaction. This allows the process operator to monitor the reactor in real-time, facilitating the fine adjustment of input materials to maximise yield, as well as providing an early warning system for detecting reaction failure. In a closed system employing a relatively few number of chemical species, the SpectroSens technology is powerful enough to measure absolute concentration. Where, complex reaction mixtures exist, an 'idealised' process RI profile can be defined and used to ensure the reaction stays within optimal operation parameters.

SpectroSens sensors can be networked to a SpectroSens control unit via readily available and easy-to-deploy armoured fibre optical cable. This allows up to eight independent sensors, each monitoring a separate stage of the continuous flow pathway, to be connected to one control unit. Here, the data can be integrated, analysed and interpreted. Multiple control units can also be networked together, or can be connected to common process management systems via standard industrial data networking protocols.