Stefan von Kann
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A control valve is used to control a flow by varying the size of the flow passage as directed by a signal from a controller, such as an on-board PID controller in a flow meter. It is one of the most used accessories in flow control.

An accessory for mass flow controllers

Control valves can be furnished as an intergral part of mass flow controllers and pressure controllers or as a separate component used in combination with a flow- or pressure meter. Together with a feedback loop from the mass flow controller or pressure controller, the valve controls the amount of flow passing through to go to an imposed flow- or pressure setpoint.

Depending on the application it is often clear whether your mass flow controller needs a shut-off (open-close) valve or a control valve, or whether one needs a normally opened or normally closed valve. Within the group of control valves, there are a number of different valves available, each having their own parameter ranges, advantages, and disadvantages.

In this blog I will highlight some valves and focus on how to cope with higher absolute and differential pressures, and how to get higher flowrates at low differential pressures.

The direct control valve

A direct control valve consists of an orifice for controlling the flow and a controlled surface that determines the size of the opening that flow can pass through, and thus determines the amount of flow passing through the valve.

• Advantage: such a valve is relatively fast, cheap, and uses only little power to control the flow. • The disadvantage here is that it can only handle limited pressures and flows.

Let’s take an electromagnetic valve as an example:

For a valve, the force (F) needed to overcome to open the valve is determined by the orifice diameter size (d) and the pressure difference (Δp) over the valve , (F ~ Δp * ¼ d2). When either the pressure differential or the orifice diameter gets higher, the direct control valve will not open adequately due to this pressure force, which can be > 15 N for a 200 bar differential pressure over a 1mm orifice, pushing the valve shut.

An electromagnetic valve can only exert a force of ca. 5N on its plunger. It could be a possibility to use a stronger coil, delivering a larger magnetic force. However, mass flow controllers often have a limited power supply and the amount of heat that is produced can become a problem as well. Resulting in a limited maximum flow, proportional to pressure and the diameter squared.

In summary, most direct control valves are not suitable for high flows, or to handle high differential pressures or absolute pressures due to these restrictions. The direct control valves could be used for low flows from 1mln/min up to approximately 50ln/min.

What alternatives do we have?

  • Redesign the direct valve for higher pressures
  • Using a 2-phase valve, an indirect control valve
  • Using a pressure compensated valve, to reach high flows at low pressures

  • High pressure direct control valve

The easiest solution to cope with higher pressures is a redesign of the direct control valve. As the orifice size is limited, it can be used for relatively small flows (up to 20ln/min) . To handle the larger pressure differences, up to 200 bar differential pressure (bard), the valve and mass flow controller body have to be more robust. Most valves can not handle a burst of 200 bard; either the sealing material can rupture, or mechanical parts can not handle the sudden force bursts that are possible at 200 bard.

The dimensions of the valve are only slighty larger than for a common valve, and thus the entire mass flow controller. On the other side, low flows are often limited due to leakage through the valve at high pressure differences.

  • Indirect control valve, a 2-phase valve

To go to even higher pressures and more flow, up to 200ln/min, we have to take a larger step in changing our mass flow controller. With a so called indirect control valve (figure 1) higher flows and higher absolute and differential pressures can be reached.
[Figure 1 – Indirect control valve]

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An indirect control valve (or 2-phase control valve) consists of:

  • a direct controlled pilot valve (A), with the behavior as described before, and without needing any extra power.
  • an additional valve in the body; a pressure compensation part (B) to maintain a constant pressure difference (P1 -P2) of only a few bars across the pilot valve (A). By doing so, both the inlet and outlet pressure may change without having any impact on the valve’s function. The pressure force over the pressure compensated part keeps the valve closed. Only when the top valve opens, the pressure force is brought back to a small enough value to open the valve and control the flow.

So, the indirect control valve consists of two valves in series (A+B), where both the pressure drop and the orifice size together determine the resulting flow.

The disadvantages of this valve are its size and the relative high costs. Besides that, a minimal pressure difference is needed to close the pressure compensation part of the valve. Also, the orifices are still limited in size, thus to get to 200 ln/min a minimal inlet pressure of > 150 bara is needed. To get such flows at lower pressures, a whole different kind of valve is needed, like a pressure compensated valve, a bellow valve.

  • Pressure compensated valve

It is possible to use larger orifices and reach higher flows with a direct control valve, but to do that, the pressure force in the valve has to be reduced. This can be done with a pressure compensated bellow valve, where the effective orifice for the pressure force has been reduced significantly (figure 2). With a bellow valve, flows of several hundreds of liters per minute can be reached with a minimum pressure difference. However, the absolute pressure is limited due to the design and the valve is much larger and more expensive than a common direct control valve.

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Conclusion: Depending on the pressure that you want to put over your mass flow controller and the outlet flow needed, you can either use:

  • a direct controlled high pressure valve (up to 200 bara and 20 ln/min), or
  • an indirect pressure compensated valve (up to 700 bara or 400 bard and 200 ln/min).

To reach high flows at low pressures, a pressure compensated valve will be the best solution.

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Have a look at the control valves we often use in combination with our flow meters or pressure meters.

Michaela Aufderheide
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Prof. Aufderheide has been working for more than 30 years in the field of cell-based alternative methods with a focus on inhalation toxicology, which studies the effect of airborne substances on the epithelial cells of the respiratory tract. For this research, she has developed special equipment together with colleagues: the patented CULTEX RFS module, which makes it possible to treat the cultivated cells with these active substances directly. Increasing pollution of the environment and workplaces demands new testing methods to predict the level of risk presented by such substances. The high sensitivity of biological testing systems requires a stable and precise technological set-up to test of such atmospheres where, in addition to the CULTEX technology, mass flow controllers are of vital importance in adjusting and controlling the aerosol flows over the cells.

The e-cigarette

The history of humankind is characterised by its receptiveness to stimulants. Since the beginning of time, these substances have included intoxicants such as alcohol, as well as smoking. Although we are all aware of the health risks, 'most people only give up their vices when they cause them discomfort' (William Somerset Maugham).

This adage is particularly true of smoking. It is widely known that excessive smoking increases the risk of cardiovascular diseases and lung cancer, yet we still yield to the temptation of the 'nicotine fix'. Epidemiological studies have repeatedly shown the harmful effects of this addictive pleasure, but attempts to quit smoking often fail, despite the certain knowledge that every cigarette can be one too many.

In response, the cigarette industry is propagating the e-cigarette as an alternative. Combustion of tobacco releases thousands of harmful substances that are of course inhaled by smokers as well. In contrast, the e-cigarette lets you inhale a vapour that does not contain any products which present a risk to your health; at least, it is claimed. This 'vapour' is created from an aromatic liquid (main ingredients include propylene glycol, glycerine, ethanol, various flavourings and nicotine, as required) using a vaporiser.

Accordingly, the electronic cigarette is marketed by the cigarette industry as a 'healthier' alternative to traditional cigarettes or a means to help people quit smoking. A lot of money is being invested to prove scientifically that e-cigarette products are less harmful than tobacco products. This statement is essentially true. However, it does not really answer the question about the effects of the 'vapour'. Epidemiological studies, such as those for cigarette smoking, are not available and no one can therefore rule out that excessive or long-term consumption could cause harm to users’ health.

Figure 1: A. CULTEX®RFS Compact with 6 transwell positions that are exposed separately to the test atmosphere. B. The test atmosphere is sucked centrally via the mass flow controllers into the module in a controlled manner, distributed radially to the cell culture vessels and drawn continually across the cells. Image description

In vitro studies

So how can I now approach this question? The only remaining option is to carry out in vitro studies. To do so, we use living cell cultures as an alternative to animal experiments.

Inhaled active substances first reach the epithelial tissues lining the lungs. These tissues are made up of a multitude of cells that serve to defend against or inactivate the inhaled substances based on their special functions. We find mucus-producing cells here whose secretions 'capture' harmful substances, as well as cilia-bearing cells that can transport the mucus away. Other cells have a detoxifying effect, while we have sufficient replacement cells in an intact body which can replace the function of damaged or dead cells. In the field of cell-based research, we can make these human cell populations available for research (see Figure 2A). These cells are cultivated in so-called transwells on microporous membranes, where they are fed nutrients from the underside of the membrane while the apical (outer) part of the culture can react with the surrounding atmosphere.

Figure 2: Cross-section of cell culture insert membranes with HE (Hematoxylin and Eosin) stained immortalized NHBE cells (CL-1548). After 21 days of cultivation at the air-liquid interface, the cells were exposed repeatedly (daily for five days and after a recovery phase of two days again on three subsequent days, maximum exposure cycle: 8 smoke exposure repetitions) to clean air (CA), mainstream cigarette smoke (CS; 4x K3R4F cigarettes per run according to ISO 3308, University of Kentucky, Lexington, KY, USA) and e-liquid vapor (EC) without nicotine (Tennessee Cured, Johnsons Creek, Hartland, WI, USA). K3R4F cigarettes were smoked by a smoking robot and operated as follows: 24 puffs with a volume of 35 mL in 2 s, a blowout time of 7 s and an inter-puff interval of 10s. The electronic cigarette type InSmoke Reevo Mini (InSmoke Shop, Switzerland) was handled in a comparable manner: 50 puffs (volume 35 mL, puff duration 2 seconds, low-out time of 7 seconds) with an inter-puff interval of 10 s.

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Mass Flow Controller – the guardians of cell exposure

Over a number of years, we have developed efficient cell exposure systems: the CULTEX®RFS module, which allows for a direct, stable and reproducible exposure of lung cells at the air-liquid interface ([ALI); see Figure 1A). Their stability in particular guarantees significant results, due to the aerophysically adjusted design of the CULTEX®RFS module on the one hand and the use of the computer-guided mass flow controller on the other (Bronkhorst IQ+FLOW series and EL-FLOW Select series), the control and design of which have been adapted to cell-based exposure. The flow control ensures a precise and reproducible atmosphere for the exposure of the cells to the test gases. It is primarily the robustness of the experimental design which delivers results that allow us to draw conclusions about the effect of the respective test atmospheres. In this case, the various cells were exposed in an unpressurised atmosphere to the e-cigarette vapour (50 puffs per run) and compared with normal cigarette smoke (24 puffs per run); the cells were exposed to the respective doses for 8 days. A control was provided in the form of cells exposed to clean air.

The remarkable results are summarised in Figure 2. Comparing histological preparations of cells treated with smoke and e-cigarette vapour to the clean air control confirms the expectation that cigarette smoke causes a clear reduction in mucus production as well as the number and occurrence of cilia. A comparable – albeit less pronounced – effect could also be observed for the e-liquid aerosol after this treatment period, however. Compared with the cells exposed to clean air, we observed a significant effect that certainly should give us pause for thought. The statement that the 'vapour is less harmful than smoke' must not be confused with the conclusion that the vapour is not harmful at all. In the future, this problem will have to be addressed in order to tackle long-term harm through preventive means.

Products used in this research are IQ+FLOW mass flow controller and EL-FLOW Select thermal mass flow controller.

Dirk Jan Boudeling
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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.

Umicore project with Bronkhorst flow meters

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.

Test bench for ageing simulation with flow meters

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:

1.Reduction of nitrogen oxides to nitrogen and oxygen: 2NOx → xO2 + N2

2.Oxidation of carbon monoxide to carbon dioxide: 2CO + O2 → 2CO2

3.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.

Mr Yang Umicore

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.”

Bronkhorst Global Sales Office

• Learn more about another application in this market: Simulation of exhaust gas to test lambda probes. • Do you want to stay up-to-date with our new applications? Subscribe for our newsletter

Gerhard Bauhuis
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The temperatures are sky high! All winter you've thought about going camping, travelling with your caravan and planning precious family trips. Finally now it’s the time to leave everything behind, and for a moment, forget the busy daily live and struggling at home. However, everywhere you go, Bronkhorst is travelling with you. Bronkhorst plays a role in many more applications than you think, also when you go camping. Let me guide you through some mainstream products you often see at a camping site, and the involvement of mass flow controllers.

Surface treatment

If you are travelling to your holiday destination by car, you will constantly look at some Bronkhorst solutions. Let’s start with the dashboard of your car. Many cars have a leather dashboard; at least, it looks like leather. A major company manufactures ‘skin’ that covers a car's dashboard, to give it this ‘leather look’. The skin is produced by spraying liquid, coloured polyurethane into a nickel mould. A Coriolis mass flow controller combined with a valve forms the basis of this solution to accurately supply external release agent to the nickel mould surface.

Coating of a dashboard But also the foam within the dashboard is manufactured by using Bronkhorst products. To create foam, a gas is added to a mixture, containing acrylonitrile-butadiene-styrene (ABS) or polyvinyl chloride (PVC), to give it the right volume. Too much gas will make the foam unstable, too little and you’ll get a heavy solid block. Therefore, it is utterly important that the correct amount of gas is added with an accurate gas flow controller.

Glass coating

If you look beyond your dashboard, you’ll look through the front window of your car. To control the light transmittance of glass, but also to make glass water repellent, protect it from mechanical and chemical stress, increase the scratch resistance and shatter protection, thermal mass flow controllers are used for the coating process. By controlling individually process gas flows, film thickness uniformity improvements are achieved.

Coating on headlights

When polycarbonate was introduced as a replacement for headlights glass in the early 1980s, new problems arised. Headlights are subject to a harsh environment. Due to the position in the front of a car, critical parameters for lifetime and performance are weather ability, scratches and abrasion. To protect headlights from these factors, scratch and abrasion coatings have been developed that are sprayed on the headlights with the help of robots in which Coriolis mass flow controllers control the flow to the spraying nozzles.

Hydrophobic coating

However, surface treatment is not only applicable for glass and dashboards. If you have experience with camping, you will be familiar with how fierce the summer weather sometimes can be. The awning of your caravan needs to be water repellent - this also applies to your raincoat - to sustain the heavy rainfall now and then. To make fabrics and textiles hydrophobic, Empa - a research institute of the ETH Domain, applies plasma polymerisation to deposit thin, nanoscale layers on top of fabrics and fibers. For this, they are using a Controlled Evaporation and Mixing system, in short a CEM system. In one of our previous blogs ‘Hydrophobic coating, the answer to exercising in the rain’ you can read about this application.

Image description Mass flow controllers are used to make awnings hydrophobic

Odoration

Bronkhorst is also involved with many smaller attributes you will encounter on a campingsite. Most people still enjoy the comfort of gas for heating or cooking on the stove. But also with gas we are able to fire up the barbecue in no time at all, in comparison with the old-fashioned briquettes that are sometimes hard to ignite. When gas escapes from a pressurized cylinder, you’ll recognize this from its penetrating scent. However, like Sandra Wassink stated in her blog “How mass flow controllers make our gas smell”, natural gas is odorless. By controlled supply of odorants like Tetrahydrothiophene (THT) or Mecaptan with a mass flow controller, the scent is added to the natural gas on purpose.

Barbecue

Let’s stay with the topic scent for a moment. For when we want to decrease the amount of mosquitos in our surroundings, we often enlight a citronella candle when we are getting tired of using the flyswatter. With the CORI-FILL dosing technology, Bronkhorst offers an easy-to-use setup to dose fragrances, like citronella, in candles. The addition of fragrance to a candle should be carefully monitored to ensure the candle burns cleanly and safely. To read in more detail about the production of scented candles, please read the blog of Graham Todd.

LED lighting

However a candle can bring much light to your surroundings, you won’t take a candle with you when you haste to the camping toilets at night. Instead you will use a flashlight of course. The working principle of the LED (Light Emitting Diode) inside this flashlight is a technology where Bronkhorst plays its part. LED works via the phenomenon called electroluminescence, which is the emission of light from a semiconductor (diode) under the influence of an electric field. By applying a semiconducting material like Gallium arsenide phosphide for instance, the manufacturing of red, orange and yellow light emitting diodes is possible.

Flashlight

I already told you so much, but frankly, just a tiny bit of all the camping applications we are involved at. Hopefully you got some more insights on the importance of Bronkhorst in many industries, also when you go camping.

If you want more information concerning the discussed applications, please contact us.

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Marlies
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The automotive industry is the biggest industry in the world. Some quick facts: • Approximately 99 million motor vehicles are produced per year (source: European Automobile Manufacturers Association). • The world’s largest car-producing countries are China, Japan, Germany, India and South Korea (2017). • There is a large discrepancy in the average annual distance travelled by car between countries. In the US, this figure is around 21,500 km/year. In Europe, the average is 12,000 km/year (source: Odyssee). • On average, a car has 30,000 parts (source: Netstar). A lot of people go to their work and on holiday by car. I do as well. I use my car every day, but while driving to Ruurlo, I had never realised that the flow meters which we develop have been used to produce my car. Did you? Inspired by that realisation, I discovered that our flow meters play a role in a lot of applications in the automotive industry; probably not in all 30,000 parts, but for sure in some of them. I have therefore collected three interesting applications of flow meters in the automotive industry to share with you.

1. Accurate dosing of release agent

In its automotive department, a major company manufactures ‘skin’ that covers a car's dashboard to give it a ‘leather look’. This skin is produced by spraying liquid, coloured polyurethane into a nickel mould. To allow easy skin release from the mould without any damage, an external release agent has to be applied onto the mould surface prior to spraying the polyurethane. Bronkhorst was requested to supply a [suitable mass flow controller](http://www.bronkhorst.com/int/markets/miscellaneous-applications/application-note-a075-gp03-accurate-dosing-of-release-agent/ ) in order to dose this release agent.

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2. Valve seat testing

Valve manufacturers check any metal-to-metal valve seats using pressure degradation methods. Since the new generation of car engines are running on higher pressures, the manufacturers are in need of new methods for leak testing to keep up with customer needs. Recently, Bronkhorst has been successfully involved with manufacturers of [valves and valve seat testing machines](http://www.bronkhorst.com/int/markets/miscellaneous-applications/application-note-a056-gp03-valve-seat-testing/ ) to implement low-flow measurement as an alternative method for a better performance.

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3. Simulation of exhaust gas to test lambda probe

Each modern car with a combustion engine has a self-controlling way to optimise engine performance. A lambda probe, a sensor positioned in the exhaust section of the car, measures the oxygen content of the car exhaust gases. This oxygen content, the ‘lambda value’, is a measure for the effectiveness of the combustion process in a car’s engine. The research department of a car producer needs to test the performance of these lambda probes with several exhaust gas compositions. To this end, they built an artificial exhaust line in which they do not use real exhaust gas but simulate the composition of car exhaust gases. They asked Bronkhorst to deliver [mass flow controllers](http://www.bronkhorst.com/int/markets/miscellaneous-applications/application-note-a069-gp03-simulation-of-exhaust-gas-to-test-lambda-probe/ ) for this purpose.

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Renewable energy in the automotive industry

Next to these applications at car manufacturers (or suppliers to the automotive industry), Bronkhorst instruments are also used by universities that join competitions or are doing research into renewable fuel sources for the automotive industry. For example, Green Team Twente is trying to build the most efficient hydrogen car. In this blog, they tell more about their research.

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In addition, Solar Team Twente participates in the World Solar Challenge every two years. Participating teams are challenged to design a car that drives 3,000 kilometers from North to South Australia in a maximum of six days, purely on solar energy. Bronkhorst sponsors this team. Read more in our news article.

A third renewable energy source being researched is formic acid (Hydrozine). In her blog, Lotte Pleging of Team FAST explains why they believe in formic acid (HCOOH) as a suitable candidate to replace fossil fuels and what the role of the Bronkhorst thermal mass flow meters is in the process of generating this renewable fuel. Read more below.

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Sources used:

http://www.odyssee-mure.eu/publications/efficiency-by-sector/transport/distance-travelled-by-car.html https://ceoworld.biz/2018/11/20/worlds-top-20-largest-passenger-car-producing-countries-in-2017-million-units/

Erwin Broekman (Br-NL)
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Why do we all (at least most of us) like candy, soda, cookies and cake? All these products contain sugar which makes it taste real good. But where does this sugar come from? All green plants make sugar through photosynthesis. Of all plants, sugar beets and sugar cane contain the greatest quantities of sugar; that’s why we usually use these two plants to extract sugar. In this blog we focus on the processing of sugar beets and the role that Bronkhorst flow meters have in this process.

Convergence Industry B.V. is a supplier of customized measurement and control systems for liquids and gases. In the process of getting sugar from sugar beets one of the customers of Convergence discovered that by using membrane filtration, it was possible to extract more components out of the sugar beet than sugar alone. For this a customized lab scale system for nano filtration was used.

Membrane filtration

Membrane filtrations is a high-quality purification process using sophisticated techniques. How does this work? A simple explanation of membrane filtration is comparing it with making coffee. If you pour water in a coffee filter filled with coffee beans, you want coffee as a result without the shell of the coffee bean. That’s what the filter is for. On another level this is similar to water filtration where you want to filter the ions so you can make drinking water out of seawater. As simple as that!

Collaboration with Convergence for membrane filtration

For the membrane filtration a ‘Convergence inspector Colossus’can be used. This is a fully automated customized lab scale system for nano filtration which makes it interesting. Felix Broens (Chief Technology Officer of Convergence Industry B.V.) explains how this system works:

”The nanofiltration system is fed with water in which a phosphatefree anti scalant is dosed. Using a high pressure pump the system is pressurized, causing a part of the water to pass to the membrane (permeate). The part of the water that cannot pass through the membrane (retentate) is led back to where the water has been fed. An extra pump in the recirculation conduit causes a higher velocity across the surface of the membrane, which reduces pollution on the membrane itself. The permeate can eventually be used as clean water for different applications.”

“The anti scalant is used to prevent scaling on the membrane, by forming a complex of metal-containing ions, which keeps them in the retentate stream so that they can be led out of the system. Because of using a phosphate free and biodegradable anti scalant, it doesn’t have any harmful effects on the environment.”

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Bronkhorst flow meters in membrane filtration

The heart of the nanofiltration system is a Bronkhorst Coriolis mass flow meter for controlling the process. It uses a Coriolis flow meter because it can measure density as well, which is important in case of sugary solutions. The flow meter is placed at the ‘clean’ side of the process, so behind the membrane where the permeate flow takes place (the purified product flow). The degree of separation of the membrane can be influenced by both flow speed and pressure. And thus a Coriolis flow meter with a wide range is the best option to cover a large test range.

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This Convergence system has made it possible for their customer to improve their process enormously. Before using the Convergence system it was a manual process that was rather time consuming and not always accurate. Nowadays the whole process is automated using client-specific Convergence software which makes it possible to accurately control the Coriolis mass flow meter with the pump and therefore, the permeate flow can now be controlled accurately and fast. This results in a good reproducibility, reliability, datalogging and shorter lead times for the experiment compared to as it was before. This customized lab scale system makes it possible to generate a sufficient amount of residue for testing purposes without making it necessary to upscale the process to a pilot plant.

Check out the Coriolis flow meters available for this application: https://www.bronkhorst.com/int/products/liquid-flow/mini-cori-flow/

Contact Convergence for more information about membrane filtration https://www.con-vergence.com/