Typical Applications
EIT can be applied off-line to monitor the performance of stand-alone equipment, or used for on-line measurement, control and analysis of industrial processes [1]. It can therefore be used in its own right to monitor mixing, separation, flow and reactor dynamics (time-evolving concentration fields and implementation of velocity fields) of both single and multiphase processes [2, 3, 4], which despite years of investigative research are still not fully understood. A schema was proposed to facilitate the use of IPT based upon the boundary conditions of a process [5]. Three types of boundary condition were identified to aid in the determination of tomographic layout: I). Volume restricted A (forced movement of a dominant phase, e.g. stirrer agitation/introduction of secondary phase causing movement) requiring multiple planes to image the mixing/reaction process; II). Volume restricted B (similar to type I, although the moving phase passes through a structured medium phase), commonly requiring multiple planes for detailed process observation; and III). Boundary limitations (phase(s) move principally in one direction) necessitating only a single plane array to image concentration profile in cross-section confined flow. These are summarised in Table 1 for a range of industrial applications.
Table 1 . Comparision of EIT applications, key attributes and their relative industrial users
Application |
Method (Boundary Cond.) |
Derivative [Example Reference] |
Key Attributes of EIT |
Industrial Impact |
Separation |
Fluidised Beds (III) |
Solid/Gas/Liquid [6, ,7] |
Used to qualify/quantify 3D multiphase flow system dynamics |
Chemical, Pharmaceutical |
Hydrocyclones (I) |
Fine slurry treatment, Refining of china clay [8] |
Fault detection, measurement of air-core size (for different operational conditions), calculation of solids concentration. |
Mineral Processing |
|
Filtration (III) |
Solid-Liquid pressure filtration [9, 10, 11, 12] |
Identify malformation, performance of filter cakes, monitor liquid level, provide real-time info on end point of filtration and drying |
Chemical, Pharmaceutical |
|
Mixing |
Stirred Vessels – Batch/Continuous Feed (I) |
Solid-Liquid [13,14,15] |
Improved understanding and quantifying of mixing phenomena, improved process control and equipment design |
Pharmaceutical, Fine Chemical |
Liquid-Liquid 16,17,18] |
Understand how evolving concentration fields influence chemical selectivity as a function of mixing dynamics |
Chemical, Fine Chemical |
||
Gas-Liquid [19,20,21] |
Identify gas hold-up, mixing processes at plant scale, impeller performance |
Fine Chemical |
||
Gas-Solid [14] |
Identify gas-solid distributions, gas hold-up in stirred tanks |
Chemical |
||
Transport. & Flow Charactn. |
Hydraulic Conveying (III) |
Solid-Liquid flows [22, 23, 24] |
Monitor suspension/distribution of solid particulates (inc. slurry transportation) |
Mineral Proc., Nuclear Reproc., Dredging |
Liquid-Liquid flows [25, 26] |
Measurement of volume fraction and flow velocity distribution |
Oil Field Pipelines |
||
Pneumatic Conveying (III) |
Gas-Solid flows[27,28] |
Demonstrate 3D flow patterns in horizontal and vertical pipes, inc. identification of slugs/plugs. |
Chemical |
|
Gas-Liquid [29] |
Imaging of slug/plug/stratified flow, flow velocity in horizontal/vertical pipes |
Oil Field Pipelines |
||
Packed Beds (II) |
Column/Heap leaching [30, 31] |
Monitor flow of leachate through packed beds, map hydraulic flow characteristics to optimise mineral recovery/reduce residence times |
Mineral Processing |
|
Reactors |
Bubble Column Reactor (I) |
Gas-Liquid chemical reaction [32,33] |
Permit improved process control of bubble column reactor - minimise gas hold-up and increase gas interfacial area |
Chemical |
Crystallisation (I) |
Crystallisation from ethanol [34] |
Monitor gas hold-up, on-set and progression of crystallisation. |
Chemical, Pharmaceutical |
|
Stirred Vessel Reactor (I) |
Hydrolysis of ethyl acetate [35] |
Investigate progress of chemical reaction of Active Pharmaceutical Ingredients within a stirred process vessel |
Pharmaceutical |
|
Condensation Reaction (I) |
Polymerisation of nylon [36] |
Monitor rate of polymer chain growth, provide a means to effectively control/improve process efficiency |
Chemical |
|
Precipitation Reactors (II) |
Precipitation of nitric acid [37] |
Optimise feed positions and minimise peak concentrations of reactants |
Chemical, Pharmaceutical |
References