Process Monitoring of Antisolvent Based Crystallization in Low Conductivity Solutions Using Electrical Impedance Spectroscopy and 2-D Electrical Resistance Tomography

Abstract

Industrial process monitoring is an important field of research where different chemical processes are monitored and controlled. In this work, electrical impedance spectroscopy (EIS) was used to analyze antisolvent based crystallization of sucrose solutions. The impedance and phase spectra were recorded for four known sucrose concentrations in water, and for each case, four predetermined amounts of ethanol were added. As a result, sixteen different solutions involving sucrose solutions of different concentrations and ethanol to water ratios were analyzed. Significant differences were observed in the magnitude and phase spectra of the solutions in the frequency range of 50 kHz to 300 kHz. The experimentally obtained data from the EIS were converted into frequency response models. Three continuous-time transfer function models of the first-order, second-order, and a second-order with a zero were estimated and compared. In addition, a 2-D electrical resistance tomography (ERT) system with a low conductivity sensor unit was designed and tested with demineralized water, tap water and industrial food grade saturated sucrose solution. Non-conducting phantom and sugar crystals were observed within the saturated sucrose solution using the Bayesian reconstruction algorithm. These demonstrations have the potential to be developed into a multi-frequency ERT systems for monitoring the distribution of the crystals in the reactor. The EIS modality can be a complementary process analytical technology (PAT) tool indicating supersaturation status and provide quality assurance.

Quantitative Evaluations with 2d Electrical Resistance Tomography in the Low-Conductivity Solutions Using 3d-Printed Phantoms and Sucrose Crystal Agglomerate Assessments

“…These applications involve different spatial sizes of the target region of interest and varied conductivity profiles. Even though it is challenging to do ERT imaging in low-conductivity environments [ 22 ], many applications have been demonstrated, such as imaging composite structures [ 23 ] and bone cement [ 24 ].…”

“…The main challenge to utilize ERT in the antisolvent crystallization process is the low conductivity of the solutions involved [ 41 ]. It affects the ability to perform quantitative evaluations and to implement the control system in the nonionic solutions [ 22 , 36 ]. The objective of this work was to test the accuracy of the newly developed sensor of the ERT system for the accurate representation of nonconductive objects in the low-conductivity solutions.…”

Ultrasonic Time-of-Flight Computed Tomography for Investigation of Batch Crystallisation Processes

“…Ultrasonic measurements have proven to offer solutions in fermentation, solidification and crystallisation processes in the food or pharmaceutical industry [ 16 , 17 , 18 ]. Many recent studies have been focused on tomography’s potential in the monitoring of crystallisation and stirred tanks’ functionality [ 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 ]. This is the first study that investigates the application of USCT travel-time tomography results for the crystallisation process in stirred tanks.…”

Quantitative Evaluations with 2D Electrical Resistance Tomography in the Low Conductivity Solutions Using 3D Printed Phantoms for Crystallization Process Monitoring

“…These applications involved different spatial sizes of the target region of interest and varied conductivity profiles. Even though it is challenging to do ERT imaging in low conductivity environments [22], many applications have been demonstrated such as imaging composite structures [23] and bone cement [24].…”

“…The main challenge to utilize ERT in the anti-solvent crystallization process is the low conductivity of the solutions involved [41]. It affects the ability to perform quantitative evaluations and to implement the control system in the non-ionic solutions [22,36]. The objective of this work was to test the accuracy of the newly developed sensor of the ERT system for the accurate representation of non-conductive objects in the low conductivity solutions.…”