Finding new energy sources is a hot topic in today’s society. In Switzerland, I love the scenery we have with beautiful mountains everywhere you look. Wouldn’t it be great if we could use these mountains in a way they can help us creating our own clean energy?
In fact, the Swiss Grimsel Rock Laboratory (owned by NAGRA, ETH Zürich) investigates the possibilities to use the earth’s heat as a energy source, Geothermal energy.
Using Geothermal energy to warm up your power plant?
Electricity production in Switzerland today can be divided in 3 main sources:
- Hydropower plants
- Nuclear power plants
- Conventional thermal power plants and other plants
About 30% of the electricity production comes from nuclear power plants. How nice would it be to reduce this even more into a more clean energy?
Geothermal energy seems to be a good replacement for a part of the currently used nuclear energy here. The idea itself is quite simple: pump cold water into the earth’s crust, allow it to be heated by earth heat, and pump up the hot water to exploit its heat, for example in a power plant.
However, there is catch. At a depth of 4 to 5 kilometres, when the injected water is heated up to 200 °C, it will expand inside the porous rocks. The permeability of the rock is low and need to be enhanced through high pressure fluid injections. This pressure increase can cause induced seismic events.
At the Grimsel Rock Laboratory it is investigated under which conditions such induced earthquakes occur and how the magnitude of such earthquakes can be reduced to be not felt at the earth surface.
Why use Mass flow controllers?
Bronkhorst mass flow controllers are used in their experiments to simulate the geothermal energy generation process by controlled supply of water flows into the subterranean rocks.
Mass flow controllers are required to accurately inject the desired amounts of water into the rocks, at the right pressure. To investigate which water flow rate will induce a certain activity inside the rocks, the devices should be able to cover a large range of water flow rates.
A series of hydraulic tests such as:
- pulse injection
- constant rate
- constant head
- cyclic water injections are conducted to determine the hydraulic properties of the rock mass and to monitor its influence (i.e. the pressure response) within boreholes in close vicinity to the injection point.
As rocks with low permeability are part of the investigation, very small amounts of water at very small rates have to be injected over very long times.
Which mass flow controllers were used?
The Bronkhorst solution consists of three different Coriolis mass flow controllers mounted on a flow board, including control and monitoring equipment. The mass flow controllers (MFC’s) were used to control pure water.
- MFC for 2 to 100 g/h (mini CORI-FLOW M12)
- MFC for 20 to 1000 g/h (mini CORI-FLOW M13)
- MFC for 0,8 to 40 kg/h (mini CORI-FLOW M15)
To investigate the influence of the low flow rate, many different flow rates of pure water have to be used as input parameter, with only a small number of devices.
With the used flow board, each of the three devices can be selected for the appropriate flow rate. Coriolis instruments are used here because of their high accuracy, and because they are able to directly supply a certain mass of water regardless of process conditions, such as ambient temperature and pressure.
Furthermore, water properties such as its temperature and density can be read in real-time. The maximum temperature of the water used at the Grimsel Rock Laboratory, which is located at a depth of 400 to 500 meters, is 40°C (only during the thermal tests).
This setup is a robust, reliable, flexible, compact and easy-to-use way to control the water supply. To track their experiments, the researchers from ETH Zürich use Bronkhorst software, including FlowPlot to make a plot of the entire experiment.
Furthermore, they have the possibility using TeamViewer to control, view and monitor the setup at Grimsel from a remote location, so they do not have to be at the test site the entire period of time.
• Download the application story ‘Reducing earthquakes when exploiting geothermal energy’
In today’s blog I would like to take you with me into the world of thermodynamics and explain how the ideal gas law helped us creating a software tool called Fluidat on the Net.
As an R&D Engineer at Bronkhorst High-Tech calculating pressure drops of an instrument and using physical properties in gas conversion models of thermal mass flow instruments are frequently recurring activities.
At Bronkhorst, these physical properties are used to design and select flow devices, and to calibrate the flow devices during the production process on the customers’ requirements.
Therefore an application was developed which can easily generate the physical fluid properties based on theoretical calculation methods.
The application is called Fluidat on the Net, which can also be accesed through the Bronkhorst website.
The ideal gas law
The origin of Fluidat is directly related to the ideal gas law - the combination of Boyle, Gay-Lussac, Charles, and Avogadro Law - resulting in the following equation of state and thermodynamic law of a hypothetical ideal gas:
- P is the pressure of the gas;
- V is the volume of the gas;
- n is the amount of gas (molecules);
- R is the universal gas constant;
- T is the absolute temperature of the gas.
Equations of state like the ideal gas law are thermodynamic equations relating state variables, like pressure and temperature, and are useful in describing properties of fluids, either gas or liquid. For example, if in closed volume the pressure is increased by moving a piston, one is able to calculate the resulting temperature.
However, the ideal gas law is based on an ideal model, but in practice I have experience that real gases do not behave in this way. Molecules are not point particles, but do have volume and can also interact with each other. The first adaption to the ideal gas law was performed by Johannes Diderik van der Waals, a famous Dutch theoretical physicist:
- a is the interaction energy between molecules;
- b is the occupied volume by the molecules.
This equation gives a much better prediction of real gas behavior in practice. Each gas (or mixture) has different a en b coefficient. When the molecules do not interact (a=0) and do not occupy space (b=0), the result is again the ideal gas law.
The equation of state used in Fluidat is based on a more advanced virial equation of state (an expression of a system derived from statistical mechanics, usually describing a system in equilibrium as a power series of particle interactions). It is called the Benedict-Webb-Rubin equation, named after the three researchers (M. Benedict, G.B. Webb and L.C. Rubin) working at the research laboratory of M. W. Kellogg Limited who determined the model.
From this equation of state the non-ideal behavior of fluids can be derived, a required input for the calculation of physical properties like:
- heat capacity
- thermal conduction
- and vapor pressure
The Benedict-Webb-Rubin equations are calculated using intrinsic properties, like molar mass, critical properties, polarity, accentric factor and other parameters. These intrinsic properties characterize the fluid, taken into account effects like compressibility, variable specific heat capacity, and Van der Waals forces. These properties will influence the physical properties of a fluid.
For example the accentric factor (the shape of the molecule) will influence the viscosity for large hydrocarbon molecules. And the critical properties are most important to calculate the reduced (or normalized) properties; all calculations perfomed in the Benedict-Webb-Rubin equations are based on reduced properties, thus resulting in a universal gas model . The reduced properties are calculated by deviding the actual state properties by the critical properties (for example P_r=P/P_c, where P_r is the reduced pressure and P_c is the critical pressure).
Basically, the Benedict-Webb-Rubin equation is a model to derive the compressibility factor (the deviation from ideality) of fluids:
Generalized compressibility factor Z diagram. The compressibility factor is required for property calculations and can be found in this graph by looking up the value for a certain reduced temperature T_r=T/T_c and reduced pressure p_r=p/p_c (solid lines).
The total non-ideal behavior of fluids is summarized in the compressibility factor Z:
where Z=1 for an ideal gas. Under normal operating conditions, usually the compressibility factor is Z<1 for common gases, except Hydrogen and Helium for which under normal circumstances the compressibility factor is Z>1 resulting in different behavior compared to other gases, for example the Joule-Thomson effect when a real gas is throttled through a valve or porous plug.
When the compressibility factor is known, the physical properties like density, specific heat capacity, thermal conductivity, and viscosity can be calculated using specific calculation methods. These physical properties can be used in other calculations.
It is important to include real gas behavior in a mass flow controller (MFC), because the ideal gas law can differ significantly from the real gas behavior, especially near the critical point and vapour pressure line. Some important gases, like CO2 and SF6 are at critical tempeture at room temperature, thus real gas compensation is important to achieve high accuracy for these gases.
The physical properties are also required for calibration and gas conversion, thus an accurate fluid database is necessary te deliver customer requirements. Without the Fluidat database, for me as an engineer it would be impossible to accurately predict the behavior of mass flow controllers, because you require highly accurate property calculations, for example for conversion model for thermal instruments.
In conclusion, Fluidat is a valuable fluid database when it comes to mass flow meters, both for our internal use and to our customers, either indirect during the calibration process or directly on our website.
Do you already benefit from Fluidat?
Have a look at our previous blog to find out what Fluidat can do for you: Software to access the world of properties for mass flow meter or controller
Register for a FREE account of Fluidat today!
I’ve worked at Bronkhorst France since 10 years now and I must confess, the instrumentation career brings me to discover new applications in various markets even today. Markets like the chemical industry, environmental industry, research applications and so on, for which flow control and measurement solutions are often essential. The applications in which supercritical fluids are used, are often complex because of the fluids state.
It was during one of my visits that I met Jérémy Lagrue, director and founder of SFE Process. I discussed with him the use of Coriolis flow meters) in supercritical CO2 processes.
What do we call "supercritical fluid"?
As an example, supercritical carbon dioxide refers to carbon dioxide that is in a fluid state while also being at or above both its critical temperate and pressure, yielding rather uncommon properties.
The density, viscosity and diffusivity of the fluid are then intermediate between those of the liquid phase and those of the gaseous phase.
Supercritical CO2 in extraction processes
Supercritical CO2 is, I believe, the most known supercritical. It is an important commercial and industrial solvent due to its role in chemical extraction in addition to its low toxicity and environmental impact.
Supercritical CO2 can be found in extraction processes, such as algae, oils, flavors and active principles. It is also used in splitting processes, such as drinks fermentation, deodorization of fatty substances in the field of cosmetics and purification processes for polymers.
This inert fluid is interesting because it reaches its supercritical phase at a relatively low pressure (73.8 bara) and a low temperature (31.1 °C.). The relatively low temperature of the process and the stability of CO2 also allows most compounds to be extracted with little damage or denaturing.
Carbon dioxide usually behaves as a gas at standard temperature and pressure (STP) or as a solid called dry ice when frozen. If the temperature and pressure are both increased from STP to be at or above the critical point for carbon dioxide, it can adopt properties midway between a gas and a liquid.
More specifically, it behaves as a supercritical fluid above its critical temperature (31.1°C) and critical pressure expanding to fill its container like a gas but with a density like that of a liquid.
Besides, CO2 offers the advantage of being odorless, non-toxic and non-flammable. It does not alter the product to be extracted or purified.
For environmental reasons, more and more industries tend to use supercritical CO2 in their process because it is positioned as an alternative to organic solvents. Indeed, unlike solvents that are produced from petroleum, CO2 is naturally available and abundant, it is therefore less expensive. However, there are very few solutions to implement it because installations remain expensive.
What is SFE Process?
Jérémy Lagrue, director and founder of SFE Process
Jérémy Lagrue: “At SFE Process, we’re dealing with applications in high pressure equipment and accessories. The specialty of SFE Process, is the production of special machines or devices for supercritical fluids (like CO2). We supply also consulting, metrology advice, maintenance, and training. SFE has developed an innovative design of high pressure pumps for processes with supercritical fluids, used either to compress liquid CO2 up to 1000 bar or for supercritical recirculation.”
Coriolis flow meter and SFE Process pump
Which problem did SFE want to solve?
“Our customers that are active in the chemical market, such as bio technology or pharmaceutical market, want to inject CO2 into a process of molecule separation or fraction. The goal here is separation of the molecules. To realize this separation, special equipment is necessary. SFE Process manufactures this type of equipment, moreover, they manufacture the pump to generate the flow of this particular fluid. The most important requirements of these pumps are stability, repeatability and accuracy.”
Which solution did SFE Process choose?
“I wanted to offer my customers the possibility to establish their mass balance in these chemical processes. Since I’ve worked a long time with many industries and laboratories, I know the importance of the flow parameter in order to determine the efficiency of the process, its production cost, its yield and to make the transition from laboratory scale to industrial scale.”
SFE Process has good experience in supercritical CO2 but they needed to prove the reliability of the equipment and also guaranty that CO2 injection is highly accurate and repeatable.
“The problem was to find an accurate and reliable flow meter capable of guaranteeing the veracity of the results and of course that lends itself perfectly to the use of supercritical CO2. I chose the Coriolis flow meter) offered by Bronkhorst. In addition to its design, the reputation of this flow meter and the 3 year manufacturer warranty had influenced my decision making and the tests carried out with this flow meter met my expectations.”
What are the results of this solution?
“The improvement that I experience is that final customers can be sure of the quantity of the fluid they put in their process. SFE Process can justify the good accuracy and repeatability of the pump by way of flow measurement of the Coriolis flow meter. So accuracy has improved.
I’ve integrated the Coriolis flow meter into all the equipment that I offer to users with the fundamental need to build up their mass balance and refer to a reliable flow value.”
Today I would like to share an application story with you using mass flow meters in an application at Umicore in Suzhou (China).
Umicore is one of the world’s leading producers of catalysts used in automotive emission systems. The company develops and manufactures high performing catalysts for, among other things, gasoline and diesel engines to transform pollutants into harmless gases, resulting in cleaner air.
Umicore’s production location in Suzhou ‘Umicore Technical Materials’ is using Bronkhorst Mass Flow Controllers and Vapour Systems for research and testing of automotive emission catalyst materials. Newly developed catalytically active materials of Umicore consist of oxides and precious metals, such as platinum and palladium, incorporated into a porous structure which allows intimate contact with the exhaust gas.
What catalyst materials does Umicore test?
Umicore in Suzhou uses various test benches in which newly developed catalytic materials are tested on performance (read: low output of toxic emissions). “Umicore develops new catalysts directly with top-tier automobile manufacturers in China. We are testing new formulations of materials and shapes of the catalysts on performance” explains Mr. Yang Jinliang.
How are the mass flow meters and controllers applied for identical testing and simulation?
The Bronkhorst mass flow meters and controllers are used to accurately deliver the right amount of several gases in a mixture that simulates the exhaust of an engine in different circumstances. “To really compare the performance of newly developed formulations, we have to be sure that the operational conditions of our tests are identical.” Mr. Yang explains that this requires the use of high performance mass flow controllers to accurately mix the simulated exhaust gas.
“We need flow control equipment which is reliable and has excellent repeatability during our simulation runs. Therefore Umicore developed the test equipment together with the Bronkhorst flow specialists.” Umicore runs various simulations. “We simulate exhaust gases of engines under various life cycle simulations and operating conditions. For example, the exhaust gas of the car is different if the engine is still cold or if the engine has a high number of revolutions.”
Test bench for ageing simulation
One special test bench of Umicore simulates the ageing of the catalyst materials. This has been achieved by heating the ambient temperature of the Catalyst up to 800° Celsius for a couple of hours up to 24 hours in a test run while adding the simulated exhaust gas. “Here the Bronkhorst instruments prove high stability under the harsh testing conditions,” says Mr. Yang.
Exhaust gas simulation recipe
In order to simulate engine exhaust gas, Umicore mixes multiple gases. In general the following reactions take place in the catalytic converter:
- Reduction of nitrogen oxides to nitrogen and oxygen: 2NOx → xO2 + N2
- Oxidation of carbon monoxide to carbon dioxide: 2CO + O2 → 2CO2
- Oxidation of unburnt hydrocarbons (HC) to carbon dioxide and water: CxH2x+2 + [(3x+1)/2]O2 → xCO2 + (x+1)H2O
To mix these gases, EL-FLOW Select digital mass flow controllers are being used. In order to maintain the gas mix under the same pressure, an EL-PRESS pressure controller instrument is used to control the pressure simultaneously with the flow.
Exhaust gases of engines also contain evaporated H2O. For this purpose the Bronkhorst ‘Controlled Evaporation Mixer’ (CEM) is used. All digital mass flow controllers, pressure controller and the CEM are connected with a computer that runs a software program to control the instruments.
In the ageing simulation test-bench of Umicore, high-temperature mass flow controllers of Bronkhorst are applied. The Bronkhorst EL-FLOW Select controllers have remote electronics to resist gas temperatures as high as 110° Celsius and still control the gases with high accuracy and excellentrepeatability.
How do you like the support of Bronkhorst products in China?
When asked about Bronkhorst support and service in China, Mr. Yang is very enthusiastic: “All Bronkhorst experts in China are very professional and have quick response. Especially during the start-up phase of our project, when we needed it most, my contacts were determined to support us. The system runs smoothly, but it’s comfortable to know that Bronkhorst is having one of its Global Service Offices in Shanghai if we need calibration or service.”
Each industrial process starts on laboratory scale to define the important parameters efficiently. These parameters might be pressure, temperature, flow but also cost efficiency and standing times. The process with the highest yield is not automatically the most efficient one. For example in catalysis or exhaust/raw gas purification it is very important to find the economically best materials and parameters. From the laboratory beaker to bulk is the process which starts at a microscale and ends with a fully operating industrial process. In between often a pilot stage is included.
Biogas Purification Testing
In Pressure Swing Adsorption systems (PSA), adsorption processes are used for the purification of bio- or natural gas. Thereby, the preferred adsorption of CO2 by zeolites or carbon-based sorbents is used to generate highly pure methane. This methane can be used for heat and power generation, offering an alternative to fossil fuels. Particularly in case of pressure swing adsorption systems, new materials are continuously being developed and evaluated, promising optimized efficiency caused by better sorptive separation properties.
Laboratory scale studies are of special interest as the potential of new materials as well as the associated economics of corresponding industrial processes can be assessed in advance.
Breakthrough Measurements on Laboratory Scale
The Rubolab GmbH has been a spin-off from Rubotherm GmbH, Germany and the Ruhr-University in Bochum, Germany. Rubolab offers a broad versified portfolio of different adsorption measurement instruments. As Managing Director of Rubolab, I developed the worldwide first manometric high pressure adsorption screening instrument in 2012. During the last years, dynamic adsorption measurement instruments, so called Breakthough Analyzers, have gained increasing importance. In this context, Rubolab offers costumized instruments for the evaluation of novel sorbents in smallest amounts (MiniBTC series).
High pressure resistant vessels are filled with the materials which have to be analyzed. Afterwards this adsorber bed is pressurized using defined gas flows. A corresponding flow sheet of the instrument is shown in the following figure.
In the example above, the sorptive separation of CO2 and CH4 is investigated. In this case, CO2 is adsorbed by the material while the gas is flowing through the fixed bed. A high-purity methane stream is recovered at the top end of the adsorber column.
Three temperature sensors are positioned at different heights within the adsorber column. Due to the exothermic adsorption process, a temperature change within the adsorber bed can be detected, indicating the so-called Mass Transfer Zone (MTZ) going through the fixed bed. When this zone reaches the adsorber head, a corresponding breakthrough can be observed by using downstream gas analysis. Thereby the measured CO2 concentration in the product stream approaches the CO2 concentration of the feed stream. In larger industrial systems the adsorber should be regenerated at this time. This kind of experimental data provides information about adsorption capacities of the substances being investigated.
Mass Flow Controller and pressure regulation valves
For the highly accurate controlling of mass flows and downstream pressures these instruments are equipped with Bronkhorst mass flow controller and pressure regulation valves. In particular devices of the newest generation of mass flow controllers, the Bronkhorst EL-FLOW Prestige series, are used in corresponding laboratory instruments for high end accuracy and versatility. In other devices where the size is of high importance, the Bronkhorst IQ+FLOW series is used to take advantage of it’s very compact size and the possibility to set up small manifolds.
Mass Flow Controller of the EL-FLOW Prestige Series
EL-FLOW Prestige mass flow controllers and meters are highly versatile instruments with their onboard database for gases and mixtures. So it is easy to react on changing customer needs without the necessity to purchase another instrument, when the test gas changes. The Prestige guarantees highly accurate and reproducible gas flow due to an automatic temperature correction, newly designed sensor and valve technology.
Mass Flow Controller of the IQ+FLOW Series
The IQ+FLOW series consists of ultra compact mass flow meters, controllers and also pressure controllers, which are designed for analytical instruments with limited space. The integrated chip technology enables fast measurement and control down to smallest ammounts. 3-Channel devices designed for customer’s application are also available.
To get familiar with this mass flow controller series, please download the white paper for more in-depth information.
You will receive the white paper when you fill out your email in the form above.
Check our instruments used in this application:
How does it compare to conventional CTA (Constant Temperature Anemometer) measurement technologies?
For over 35 years Bronkhorst High-Tech has brought a revolutionary flow technology to the market, and in today’s blog I would like to discuss one such example, called MASS-STREAM™. This device leverages Constant Temperature Anemometer (CTA) thermal mass flow technology, though differently than conventional meters in this category. I will describe what CTA thermal mass flow meters are, the conventional type and their applications, and what makes MASS-STREAM™ technology different.
What is a conventional Constant Temperature Anemometer (CTA) thermal mass flow meter?
The CTA thermal mass flow meter works with a sensor with probes, which are inserted into the gas stream in order to directly contact the flowing gas. One of the two sensors is designed as a heater, and the other one is designed as a temperature probe.
When the instrument is powered up a constant difference in temperature (ΔT) is created between the two sensor probes. The heater energy required to maintain this ΔT is dependent on the mass flow. The working principle is based on King’s Law of the ratio between the mass flow and heater energy. What that means is the higher the flow, the more energy is required to maintain the chosen.
A conventional CTA thermal mass flow meter is installed by inserting the long probes through the pipe wall and into the gas stream. The probes are passed through an insertion port (hole) in the pipe. The “head” of the instrument is above the outer wall of the pipe.
Common characteristics of CTA thermal mass flow meters are having no moving parts, a low pressure drop across the instrument, and no need for additional temperature or pressure compensation.
Where are conventional Constant Temperature Anemometer (CTA) thermal mass flow meters used?
As you might imagine, processes where gas flows in pipes are places one will find CTA thermal mass flow meters. The rugged nature, no moving parts, and low pressure drop are beneficial for measuring gas flow in industries like midstream Oil & Gas, upstream Oil & Gas, Wastewater treatment, and Steel.
The types of applications where these flow meters are used include applications with gases such as methane, propane, argon, compressed air, coal emissions, carbon dioxide, ammonia, and others as well.
Typically a CTA thermal mass flow meter is a good choice when the gas has the potential to be dirty or includes some moisture as the through flow nature of the technology can be more forgiving to contamination than other flow meter technologies.
MASS-STREAM™ Mass Flow Meters
Also based on CTA thermal mass flow technology, the MASS-STREAM™ flow meter/controller differentiates itself from conventional CTA flow meters on several points.
The MASS-STREAM™ flow meter/controller is not installed using an insertion port through the wall of a pipe. Rather, the MASS-STREAM™ is an in-line flow instrument. That means that the instrument itself is connected between two ends of the tube or small pipe and effectively becomes part of it.
Unlike the conventional CTA thermal mass flow meter, the MASS-STREAM™ is a compact instrument where the main circuit board housing and sensor sit on top of the flow body through which the sensor probes project.
An inline instrument allows for the use of CTA technology in applications using tubes and small pipes.
2. Flow Rate
As mentioned earlier the MASS-STREAM™ flow meter/controller is an instrument which is mounted in the line of the tube or small pipe, and applications which use tubes for flowing gas are ones where the flow rate is low.
Of course “low” is a subjective term, so as an example the MASS-STREAM™ lowest flow range is 10 -200 mln/min, but the flow meter family can go as high as 5000 ln/min.
Perhaps the most important difference between the MASS-STREAM™ and the conventional CTA thermal mass flow technology is that the MASS-STREAM™ is available as a meter (as are all the others) or as a thermal mass flow controller.
The MASS-STREAM™ thermal mass flow controller is a complete control loop. It measures the gas flow, it has an onboard PID algorithm, and it provides a control signal to an electrically and mechanically connected control valve. All it needs is a setpoint signal and it will precisely control of the gas flow.
It is a complete control loop that can easily fit in one’s hand.
While other Constant Temperature Anemometer (CTA) thermal mass flow meters well serve the applications for which they are best suited, none are designed for low flows or as a complete control loop like the MASS-STREAM™. This meter serves applications ranging from process industries to food and beverage to pharmaceuticals to medical and chemical and beyond. MASS-STREAM™ technology is usable for virtually any kind of gas or gas mix, provides precise control, and is very compact and robust.
In our blog ‘How mass flow meters can help hospitals save on medical gases’ an application of MASS-STREAM technology used in the medical industry has been explained.
Check our video of the principle of operation of MASS-STREAM.
To learn more about MASS-STREAM™, and whether it’s the right meter for your application, please contact our office.