Imaging wet granules with different flow patterns by electrical capacitance tomography and microwave tomography

Nowadays, the optimization of energy consumption and resources is one of the most urgent topics in worldwide industry. The energy consumption monitoring and control in various multiphase flow industrial applications, where a proper flow characteristic and an optimal phase mixture control is crucial, is hard to perform due to the physical and chemical complexity of the processes. The Electrical Capacitance Tomography (ECT) is one of the relatively cheap non-invasive measurement methods that can help in the monitoring and control of optimal energy and resources dozing in industrial processes. ECT diagnostics systems use unique sensors that can non-intrusively detect spatial capacitance changes caused by spatial changes in the electrical permittivity of industrial process components. One of the latest ECT extensions is a three-dimensional measurement strategy that uses a multilayer structure of the capacitance sensor. In this paper, the authors propose a novel approach to the 3D ECT sensors fabrication process that uses 3D computer modelling and 3D printing to easily get any sensor shape, electrode layout, scale and shielding strategy. This study compares the measurement abilities of a 3D ECT sensor fabricated using a traditional hand-made technique with the 3D printed device. The results have proven the potential of the new 3D print-based sensor regarding its significant fabrication time reduction as well as the improvement of the overall 3D ECT sensor measurement accuracy and stability.

While fluidized beds are commonly used in the pharmaceutical industry, the understanding of the fluidization processes is limited because no efficient tool is available for real-time online monitoring and measurement. In recent years, electrical capacitance tomography (ECT) has been used to investigate granulation, drying and coating processes in pharmaceutical fluidized beds. For measuring drying and granulation processes, a novel online calibration method was proposed and implemented to deal with continuous change in the moisture content of solids. Experiments were carried out using various fluidized beds of different scale, and good results were obtained. For monitoring the coating process in a Wurster fluidized bed, a unique ECT sensor is designed with three sets of electrodes. By this electrode combination, all regions of the Wurster fluidized bed can be monitored. Based on the work done so far, it is concluded that ECT is a very useful tool for monitoring and measurement of pharmaceutical fluidized beds.

Flow regime identification in the subsea jumper based on electrical capacitance tomography and convolution neural network

Electrical capacitance tomography (ECT) technique has been developed due to its inherent simplicity and low cost. The tomographic images are obtained based on the permittivity differences between the investigated materials and background material (air, in most cases). The dynamic range of capacitance measurements in ECT could be 40 dB or higher. Simultaneously, the changes in the measured capacitances take up only 5% of the full measurement range. Therefore, the capacitance measuring circuit should be of high dynamic range as well as high precision, which constitutes one of the greatest challenges in ECT system design. The standing capacitances in ECT measurements may be canceled by differential measurement. In this paper, a recently developed differential ECT scheme has been presented. An active screen is employed as the differential electrode in the sensor, which is placed between the measuring electrode array and outer screen. Accordingly, a transmitter channel is implemented to accommodate the active screen, which enables the active screen to deliver multi-level AC signal. Simulation and experimental results show that the differential ECT system has a signal-to-noise ratio of 16 dB higher than the previous design, i.e. the non-differential system.

Measurement techniques are vital for the control and operation of multiphase oil–water flow in pipes. The development of such techniques depends on laboratory experiments involving flow visualization, liquid fraction (‘hold-up’), phase slip and pressure drop measurements. They provide valuable information by revealing the physics, spatial and temporal structures of complex multiphase flow phenomena.This paper presents the hold-up measurement of oil–water flow in pipelines using gamma densitometry and electrical capacitance tomography (ECT) sensors. The experiments were carried out with different pipe inclinations from −5° to +6° for selected mixture velocities (0.2–1.5 m s−1), and at selected watercuts (0.05–0.95). Mineral oil (Exxsol D60) and water were used as test fluids. Nine flow patterns were identified including a new pattern called stratified wavy and mixed interface flow. As a third direct method, visual observations and high-speed videos were used for the flow regime and interface identification.ECT and gamma densitometry hold-up measurements show similar trends for changes in pipeline inclinations. Changing the pipe inclination affected the flow mostly at lower mixture velocities and caused a change of flow patterns, allowing the highest change of hold-up. ECT hold-up measurements overpredict the gamma densitometry measurements at higher input water cuts and underpredict at intermediate water cuts. Gamma hold-up results showed good agreement with the literature results, having a maximum deviation of 6%, while it was as high as 22% for ECT in comparison to gamma densitometry.Uncertainty analysis of the measurement techniques was carried out with single-phase oil flow. This shows that the measurement error associated with gamma densitometry is approximately 3.2%, which includes 1.3% statistical error and 2.9% error identified as electromagnetically induced noise in electronics. Thus, gamma densitometry can predict hold-up with a higher accuracy in comparison to ECT when applied to oil–water systems at minimized electromagnetic noise.

The solid volume fraction and volume composition ratio of different solid particles in a silo are important parameters indicating the character of granular mixtures. In this paper, measurement of the two parameters is studied by utilizing Electrical Capacitance Tomography (ECT). This preliminary work focuses on comparing normalized permittivity changes from ECT with those predicted by the Maxwell Garnett formula (MGF) relating to solid volume fraction and volume composition ratio. Experimental results show that normalized permittivity changes from the two methods have a strong linear correlation in gas-solid two- and three-phase systems. This work demonstrates that ECT is a promising technique for monitoring solid volume fraction of single solid particles and the volume composition ratio of mixtures of two different solid particles in a silo.

It is difficult to know the details of material distribution in a fluidised bed. Electrical capacitance tomography (ECT) technology has been developed for imaging industrial processes containing dielectric materials. This paper discusses the principles of ECT and presents the first experimental results of using ECT to measure gas/solids distribution in square circulating fluidised beds (CFB). A wide range of fluidisation conditions was tested, from bubbling to circulating fluidisation. It has been shown that over the range, ECT can provide solids concentration and voids distribution instantaneously. Different fluidisation regimes could also be identified from the reconstructed images.

Dielectric properties of garlic ( Allium sativum L.) at 2450 MHz as function of temperature and moisture content

Two means can be used to improve the data acquisition rate of the electrical capacitance tomography (ECT) system with a fixed excitation frequency, i.e., improving the capacitance measurement speed or changing the capacitance measurement mode from serial to parallel. This paper presents a newly developed high-speed ECT system by combing digital recursive demodulation and parallel-mode capacitance measurement methods. By using the digital recursive demodulator, the time-cost for one time of capacitance measurement can be one period of the excitation sinusoid or less. By using the parallel-mode capacitance measuring unit, capacitances between the exciting electrode and all other measuring electrodes can be measured simultaneously. The data acquisition rate of the parallel-mode ECT system with a sensor of N electrodes is N-1 times of a traditional serial-mode ECT system with the same excitation frequency. When the excitation frequency is 100 kHz and 0.6 periods of data are used for signal demodulation, the data acquisition rate can reach up to 15 150 frames/s. The developed system together with a heat-resisting circular ECT sensor with 12 electrodes was used to monitor the ignition process of a cylindrical flame generated by a Bunsen burner. Experimental results show that the ECT system can locate the position and capture the dynamic process of the flame with a high temporal resolution.

Electrical Capacitance Tomography (ECT) is a method to determine the material distribution within the interior of a closed object by measuring the capacitance values across externally mounted electrodes. Traditionally, an AC excitation pulse is applied to a pair of electrodes that form a capacitor during each measurement step, in order to determine the capacitance from the output current measured. This paper investigates how the speed of inter-electrode capacitance measurement can be improved by comparatively studying three methods that affect the way electrodes are excited and signals are received: 1) multiple-excitation-single-receiving, 2) single-excitation-multiple-receiving, and 3) multiple-excitation-multiple-receiving. A PSPICE circuit model was built to simulate the bandwidth and interference between the simultaneously sampled measurement channels. Simulations using ECT sensors with 8 and 12-electrodes have shown that measurement speed can be increased by up to 3 ∼ 30 times as compared to the traditional mode of capacitance measurement. Such new capability opens up new possibilities for ECT as an effective tool for online, real-time monitoring of a wide range of dynamical processes in the industry.

Investigation of wetting and drying process in a gas-solid fluidized bed by electrical capacitance tomography and pressure measurement

Electrical Capacitance Tomography (ECT) determines the dielectric permittivity of the interior object depending on the measurements of exterior capacitance. Generally, the electrodes are placed outside the PVC cylinder where the medium to be imaged is present; but in ECT using inter-electrode capacitance measurements can be achieved by placing inside of the dielectric medium. In the proposed ECT system, the ECT sensor is modeled using ANSYS software and the model is implemented in real ECT system. For each step of measurement, a stable AC signal is applied to a pair of electrodes that form a capacitor. The novel system is to measure the capacitance range variation in picofarad and the corresponding voltage ranges from 1 volt to 4 volts. The switching speed of all combinational electrodes is implemented using embedded system to achieve higher speed performance of AC ECT system which eliminates the drift and stray capacitance error. This is yielding the original image of unknown multiphase medium inside the electrodes using Lab VIEW. This paper investigates several advantages such as improved overall system performance; simple structure, avoids stray capacitance effect, reduces the drift problem and achieves high signal to noise ratio.

The physiological performance of wheat seeds may be influenced by the harvest season and storage system. This study aimed at evaluating the physiological performance of wheat seeds as a function of different moisture contents at harvest, with later storage under hermetic and conventional systems. Harvest was performed when the seeds reached moisture contents of 28.6 %, 18.5 % and 12.9 %. Subsequently, they were stored for 240 days, in both systems, at room temperature. The evaluation of seed physiological performance was carried out by germination and vigor tests, shoot length and dry matter of seedlings. The germination of wheat seeds stored under the hermetic system increased up to 180 days of storage, due to the seed dormancy breaking, with a subsequent decrease of the values, while those stored under the conventional system showed a linear decrease of germination throughout the storage. The hermetic system provided an increase in seed vigor up to 120 days of storage and, after this period, there was a reduction of the values. The conventional system promoted a linear reduction of seed vigor throughout the storage, except for the results obtained in the tests of first germination count and germination speed index, which showed an increase up to 60 days of storage. Harvest delay negatively influenced seed germination and vigor, regardless of time and storage system. The combination of harvest anticipation and hermetic storage improves the physiological performance of seeds over time.

In this study, the validity of moisture measurement by an IR sensor was investigated in fluidized bed granulation. The effects of operating variables on the relationship between granule moisture content and the absorbance of IR spectra were examined experimentally. It was found that the air flow rate of purge air used for preventing powder adhesion, fluidizing air velocity, agitator rotational speed and spray mist size had no effect on the relationship. However, if the dampening speed was extremely low, the effects of fluidization air temperature and liquid flow rate on the relationship could be recognized. This was because the surface drying due to the extremely low dampening speed caused water to transfer from the inside to the surface. As a result, it can be concluded that the measurement of moisture content by an IR moisture sensor can be conducted with high accuracy, free of operating conditions, unless the granulation is conducted under an extremely low dampening speed.

Visualization of flow pattern in thermosyphon by ECT