Initiative Promises Better Sensors

A U.K. consortium aims to develop optical sensors that can monitor multiple complementary parameters of liquid streams, with the goal of using such sensors to increase the efficiency of producing high-value materials. The about-$1.8-million Advanced Process and Production Light Enabled Sensors (APPLES) project, which will run for two years, will strive to produce an integrated sensor head that can provide in-line real-time monitoring and to validate the sensor system.

The project brings together international pharmaceutical giant GlaxoSmithKline (GSK), Brentford, U.K.; Green Biologics, Abingdon, U.K., a biotech company involved in advanced fermentation processes to convert biomass into fuel and chemicals; Stratophase, a sensor developer based in Romsey, U.K.; and the Centre for Process Innovation (CPI), Wilton, U.K. The U.K. government-sponsored Technology Strategy Board, Swindon, U.K., is assisting with the funding.

The consortium will build upon Stratophase's intrinsically safe microchip sensors that use so-called SpectroSens technology. The currently available systems measure refractive index and temperature using optically integrated chips (Figure 1), notes Sam Watts, the firm's business development and commercial officer, and now are being trialed at select end users.

"At this stage, the consortium has not fully defined all of the parameters which will be investigated and/or implemented," he explains. "However, simultaneously monitoring the following is of interest: temperature, refractive index, turbidity (additional particle content information can also be derived through monitoring both refractive index and turbidity), optical absorption, pressure and viscosity."

"It is anticipated that the use of multiple complementary parameters, measured at a single point, will allow much greater process model fidelity than if individual parameters were used in isolation — the whole is greater than the sum of its parts," he adds.

Optical Sensor

Figure 1. Microchip measures change in refractive index of a liquid with a precision exceeding 1 ppm. Source: Stratophase.

"The ultimate aim of the project is to allow the refinement of existing processes and the development of novel processes, through the use of a multi-parameter, real-time, in-line monitoring tool based on a development of the Stratophase system."

"At GSK the sensor system will be used to monitor different unit operations, such as reactions and distillations, in continuous processes producing a variety of different APIs [active pharmaceutical ingredients] or associated intermediates. It is intended to validate the capabilities of the sensor system at both laboratory and pilot-plant scale."

"GSK's use of the sensor system is focused on chemical process monitoring. We anticipate being able to use the data to confirm, and potentially control, the concentration of dissolved solid components in a wide range of solvent systems." Applications may include checking that concentrations in feed and product streams are correct, and that reactions have gone to the expected degree of completion, says Watts.

"Applications within bioprocesses, such as fermentation associated with biofuels production, will use the monitoring techniques to profile the status of the process and allow for optimization of biological growth and resultant product evolution." This should enable real-time comparisons to the process ideal or "golden batch," he explains.

Ultimately, the goal is to use such readings for process control. "Tighter process control allows improved yield, minimized waste and better overall production efficiency," Watts notes.

"Stratophase expects the monitoring technology developed during the project to directly influence its product line," he adds.