Tomoflow Ltd has developed a new method of measuring multiphase
flows in pipes. The Tomoflow system is completely non-intrusive
and can be used in gas/solids, gas/liquid and liquid/solids flows.
Tomoflow Ltd currently sells research versions of its
For two years, Tomoflow has been involved in a joint development exercise with a world leading multinational. The aim, successfully achieved, was to produce an industrialised, self contained, tomographic two phase flow meter. This new system represents the state of the art in electrical capacitance tomography with a custom computing element for the flow calculations yet it can be produced to a unit cost low enough to allow it to be included in standard factory installations.
The partnership is now seeking a third partner to exploit this
technology in the marketplace and in Q4 2008, we will be
presenting our technology to selected organisations.
The output of a flowmeter tells the user how much material has
passed through the meter in a certain time, either as a volume flowrate
(for example litres per second) or as a mass flowrate (for example
tonnes per hour). The measurement of flowrate may then be integrated
to give the total amount of material delivered, for example the
number of litres or tonnes. In the case of single liquids and gases
the technology to measure flow is well understood and flowmeters
are widespread, whether filling up a car on a garage forecourt or
measuring gas consumed by a household, the amount of product is
measured by a flowmeter and the indicated output of the flowmeter
is accepted by both buyer and seller as the true amount delivered.
However, many industrial processes use mixtures of products pumped
along pipes. For example, in manufacturing processes particulate
materials (plastics, grain, catalysts...) are blown along pipes
by compressed air or pumped in liquid, while in the oil business
mixtures of gas, oil and water are common in long-distance transport.
Such transport systems are very efficient, but the only way to measure
the amount delivered is to separate the components and meter them
individually or to fill some sort of tank or vessel and measure
the volume or the weight of the product in the tank. This limitation
is not inherent to the pumping mechanism, it is simply that the
technology for measuring the flowrate of mixtures of materials in
pipes by a flowmeter is not widely available. The limited flowmeter
technology for these applications adds to the cost of the operation
considerably (extra piping, valves, tanks and weighing mechanisms)
and interferes with the process flow.
The Tomoflow system uses an imaging technique analogous to medical
tomography ('scanners' - for example CAT, PET, MRI) where a cross-sectional
image of an object is produced from external sensors. Such a cross-sectional
image is known as a tomograph - hence tomography is the art of creating
such pictures. Tomoflow uses electrical fields so that the imaging
is faster and the sensor simpler than most medical scanners. Tomoflow
uses an imaging system developed by our partner company, Process
Tomography Ltd (PTL).
From the tomographic measurements of two cross sections with a
known separation, images are computed. These images are segmented
into zones. A statistical technique called correlation allows us
to calculate the velocity in each zone from a rolling history of
these images. With the sensor dimensions, we can then calculate
the volumetric flow rate per zone. By integration (summing), we
then derive volumetric flow and if the density is known, mass flow.
Figure 1. Technology overview
Multiphase flows can be measured, as long as the imaging system
can distinguish the two phases. This is not possible with other
techniques without separation.
It is non-invasive, a property of tomography making it popular
in medicine, meaning it will not disrupt the flow and can be used
where abrasive flows would destroy other devices.
Because of the lack of internal features, there is no extra pressure
drop or modification of flow pattern.
By deriving velocity in each zone across the flow cross-section,
it does not suffer from the gross errors in varying flow regimes
characteristic of multiphase flowmeters that operate with an average
Figure 2. Summary of flow measurement results in gas/solids
A summary of test results (above) for a range of flows indicates
that the Tomoflow system calculates volumetric flow, converted
here to mass flow rate, within typically a few percent of the