(223c) A Novel Sensing Technology for Online Detecting Reaction State and Fluid Mixing Using Electrical Resistance Tomography

It is crucial to accurately determine the endpoints of reactions in the process industry, which directly influence the final product quality or downstream separation processes. At present, in most cases quality control relies on offline sample testing. However, due to this kind of offline testing being a single time point and a single location, confidence in the outcome needs to be gained through repeated testing using multiple locations. It is needed to develop a novel technology for online detecting reaction state and fluid mixing in the process industry. Electrical resistance tomography (ERT) has been applied in a wide range of scientific and engineering fields, such as geophysical study, clinical diagnosis, chemical or mineral process measurement, and process optimization. ERT is usually used to collect data on the processes in vessels and pipes. It can do online real-time measurements and without the need to draw samples from the reaction vessel that makes the data collection much easier compared to existing technologies.

In this research, ERT uses an array of 16 electrodes located equidistant in a layer around the inside of the vessel. As fluids flow past the measurement plane, conductivity is measured in the 2D plane. The information on the state of the reaction and the fluid mixing can be extracted from the data of ERT measurements. Our ERT system can collect more than 1000 datasets per second with 104 data points per dataset. Multiple test cases over a range of vessels, volumes, and chemical concentrations have been done. From 0.05 M to 4 M HCl and H₂SO₄ titrated with 0.1 M to 5 M NaOH. Figure 1 shows online real-time ERT measurements to detect the titration reaction's endpoints for (a) 0.25M HCl titrated with 1M NaOH, (b) 0.25M H₂SO₄ titrated with 1M NaOH. When compared to other methods to find the endpoints of the reactions, it can be seen that the start of the upward trend after the dip matches up closely to those measured endpoints. Additionally, more accurate time points can be obtained by the ERT system comparing to other methods. Another significant benefit of the 2D planar measuring is the ability to monitor the fluid mixing. Figure 2 reveals a location with slower mixing relative to the rest of the vessel. Knowing where these spots exist allows for monitoring the products for any potential defects due to this imperfect mixing. This novel technology can be potentially used in large reactors where visibility, testing access, or conditions restrict access to the vessel, such as higher pressure and temperatures.