Imaging of mixing of two miscible liquids using electrical impedance tomography and linear impedance sensor

The objective of this study was to determine whether electrical impedance tomography (EIT) can be used to image the mixing of two miscible liquids in a turbulent flow, using the Trumpjet mixing system of papermaking chemicals and additives. Trumpjet is a jet injection mixer developed and produced by Wetend Technologies Ltd. An EIT system and a linear impedance sensor, developed at the Department of Physics, University of Kuopio, were used as a monitoring system. In EIT, a difference reconstruction approach was used to produce two- and three-dimensional images of the conductivity distribution with a frame rate about of 40 frames/s. In the linear impedance sensor, 8 impedance values can be measured with a speed of 4 s−1. In order to make changes in the conductivity distribution a saline solution was used as chemical. In order to evaluate the quality of the mixing, a mixing index was calculated based on the reconstructed images. Laboratory tests were carried out in a pilot plant. The efficiency of the mixing of the chemical into the main flow using Trumpjet technology and using the conventional chemical injection system was compared. It was found that the Trumpjet technology is more efficient, and that EIT and a linear sensor can be used in mixing studies.