Rob ten Haaft
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It might surprise you but already since the Middle Ages, people are interested in the smell of a person’s breath. In those days it must have been quite a challenge to investigate but as early as those days diseases like diabetes (associated with a sweet, acetone odor) and liver failure ( a fish-like smell) were diagnosed upon one’s breath. I will not discuss the treatments during those years; let’s say that much has improved since the Middle Ages. For example, nowadays, we use Ion Mobility Spectrometers (IMS) to measure Volatile Organic Compound (VOC).

At the beginning of the 21st century, research studies show that dogs are able to detect cancer by smell. The dogs are trained to detect different kinds of cancer in exhaled breath of human patients, as they can smell with a sensitivity of parts per trillion (ppt). To give an example: the scent of one cc of blood, diluted in 20 Olympic sized swimming pools can still be detected by the dog.

It was concluded that dogs are probably discriminating between breath samples based on a specific breath odor but it is still unknown what odor or mix of compounds dogs detect. The detection of cancer by trained dogs seems to be obvious when you think about it, but it requires a lot of training of the dogs and it is still unknown why not all cases of cancer are detected.

Volatile Organic Compound (VOC)

This is the reason that researchers have started to develop analyzers that can do the dog’s job. In the last few years it was discovered that Volatile Organic Compounds (VOC) can be distinctive biomarkers in the diagnosis of human diseases. Volatility is the tendency of a substance to evaporate, therefore Volatile Organic Compounds are organic compounds that will easily evaporate or sublimate at room temperature.

The exhaled human breath contains a few thousand volatile organic compounds and the composition of the VOCs is used in breath biopsy to serve as a biomarker to test for diseases such as lung cancer.

An increasingly popular analytical technique to measure VOC’s is Ion Mobility Spectrometry (IMS). This technique is ideal for analysis in medical applications since the analysis is fast, not affected by humidity, highly sensitive, and operates at ambient pressures. This makes the technique very suitable for portable or Point of Care application.

Ion Mobility Spectrometry (IMS)

The Ion Mobility Spectrometer operating principle is based on the drift, or time-of-flight, of ions that are formed in the reactant section. The ions travel, supported by an electric field, through the drift tube where they encounter a drift gas (N2 or Air). The shape and the charge number of the ion will make it easier or harder to flow through the drift gas which will cause a separation of the ions in the sample and after detection give an IMS-spectrum as shown in Figure 1.

Image description Figure 1 : Ion Mobility Spectrometer with spectrum

Mass Flow Controllers

To deliver the gases to the drift tube, Bronkhorst has the knowledge and experience to supply the right products. Our products address the specifications that are important for controlling the gases in Ion Mobility Spectrometry such as:

  • cleanliness,
  • small instrument size
  • fast response
  • good reliability
  • low power and
  • low cost of ownership. Our MEMS (Micro Electro Mechanical Systems) based instruments, such as the IQ+FLOW thermal flow meters, are very suitable for Ion Mobility Spectrometry.

Image description IQ+FLOW thermal flow meter

  • Are you interested to read more about mass spectrometry (MS) and how mass flow controllers and evaporation is used for Electrospray Ion source, check our blog ‘A closer Ion them’.
  • Check our success story using IQ+ gas flow meters and pressure controllers for a gas chromatography application.
  • If you have questions or ideas on Ion Mobility Spectrometry other analytical applications that involve controlling of gas or liquid, feel free to contact us.!
Chris King
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You would think that measurements of mass flow would be expressed in units of mass, such as grams/hour, milligrams/second etc. Most users, however, think and work in units of volume. That’s OK, at least when we are talking about the same reference conditions. Let me start with an example:

Mass versus Volume

Imagine you have a cylinder of 1 liter, which is closed by means of a moveable piston of negligible weight. This cylinder contains 1 liter of air at ambient pressure, approximately 1 bar. The weight of this volume of air at 0°C is 1.293 g, this is the mass.

When we move the piston half way to the bottom of the cylinder, then the contained volume of air is only ½ liter, the pressure is approximately 2 bar, but the mass hasn’t been changed, 1.293 g; nothing has been added, or left out.

According to this example, mass flow should actually be expressed in units of weight such as g/h and mg/s. Many users, however, think and work in units of volume. This not a problem, provided conditions under which the mass is converted to volume are agreed upon.

Using density in converting mass flow to volume flow

In order to use density in converting mass flow to volumetric flow, we must pick a set of specific pressure and temperature conditions at which we use the density value for the gas.

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The conditions that are agreed upon contain various references, normal reference and standard reference, available in European or American style. What is de difference?

Normal reference, European style

Following the ‘European’ definition, a temperature of 0°C and a pressure of 1,013 bar are selected as ‘normal’ reference conditions, indicated by the underlying letter “n” in the unit of volume used (mln/min or m3n/h). The direct thermal mass flow measurement method is always based on these reference conditions unless otherwise requested.

An example conversion to volumetric units using Normal reference conditions: The mass flow meter indicates 100 g/h of Air flow. • Density Air (@ 0°C) = 1.293 kg/m3 • X ln/m Air = 100 g/h / (60 minutes x 1.293 kg/m3) • Flow = 1.29 ln/m Air

Standard reference, European style

Alternatively, a temperature of 20°C and a pressure of 1,013 bar are used to refer to ‘standard’ reference conditions, indicated by the underlying letter ‘s’ in the unit of volume used (mls/min or m3s/h).

An example conversion to volumetric units using Standard conditions: The mass flow meter indicates 100 g/h Air flow. • Density Air (@ 20°C): 1.205 kg/m3 • X ls/m Air = 100 g/h / (60 minutes x 1.205 kg/m3) • Flow = 1.38 ls/m Air

If the prefix ‘s’ has been used, it refers to the American style.

Standard reference, American style

According to the ‘American’ definition the prefix ‘s’ in sccm, slm or scfh refers to ‘standard’ conditions, 101.325 kPa absolute (14.6959 psia) and temperature of 0°C (32°F).

Please be aware of the reference conditions when ordering an instrument. ‘Normal’ and ‘Standard’ can be relative to each customer.

Why is this important? Because mixing up these reference conditions causes an offset in what the customer expects to see by greater than 7%!

Learn more about the technologies of Bronkhorst and read more about the Mass Flow Theory

Table with the normal- and standard references, divided into European- and American style

Normal vs standard conditions

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.

Harry Bosvelt
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Maintenance represents a key issue for many organisations due to the ongoing digitisation of production processes. Maintenance can be broadly defined as all aspects relating to the effective performance of mass flow meters and controllers. Maintenance may consist of corrective maintenance – maintenance conducted when needed, e.g. after contamination – or preventive maintenance, where instruments are periodically returned for servicing or calibration. Today's instruments are increasingly future-proof and 'intelligent'. In addition to the rise of condition-based maintenance, we are also seeing a shift towards predictive maintenance, which helps reduce unscheduled downtime and wastage. Regulations are also having a growing impact on maintenance, with numerous markets introducing more and more instrument maintenance requirements.

The importance of effective maintenance

The maintenance of mass flow instruments is of crucial importance to Bronkhorst customers. Bronkhorst mass flow instruments have a highly robust design and are resistant to wear under normal circumstances. Instruments are increasingly being utilised under extreme process conditions. Effective maintenance can reduce the likelihood of sudden failures under such circumstances. Unexpected downtime triggers direct costs in terms of the extra hours that staff need to check and recommission the instrument. Moreover, this downtime also has a negative impact in terms of short-term yields or production quality and potential long-term reputational damage.

The aspect of maintenance plays a considerable role in Industry 4.0. Following the invention of the steam engine, mass production driven by electric engines and far-reaching automation, we are currently in the midst of the fourth industrial revolution. The current revolution is characterised by the application and exchange of data through high-speed network connections, yielding more efficient and intelligent production techniques. This development is also referred to as 'smart industry'. Among other motivating factors, Industry 4.0 is driven by the desire to reduce the cost of ownership. The associated digital technologies can be applied to cut maintenance costs by 30% or more and reduce unscheduled downtime by over 70%. *1) Given these high figures, there is certainly much room for improvement.

What did the maintenance of mass flow instruments look like in the past, what does it look like in the present and what – according to Bronkhorst – will it look like in the future? And what will be the role of Industry 4.0?

Maintenance through the years

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Maintenance-ladder

Corrective maintenance

In Bronkhorst's early days, corrective maintenance was still the industry standard. Most mass flow meters and controllers were still analogue and did not have any diagnostic parameters. Any instruments in need of maintenance were either shipped to Bronkhorst or serviced by a visiting technician. This method was extremely costly and time-consuming due to the lengthy downtimes involved. The company's worldwide service network was later restructured, and currently comprises 20 GSOs (Global Service Offices, authorised service departments around the world) and a 24/7 help desk. Spare parts were kept in stock in order to ensure rapid service.

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After-sales field support

Preventive maintenance

The digital age – which started after the turn of the century and is currently still more or less ongoing – marked the rise of preventive maintenance. Customers periodically returned their instruments to a Bronkhorst service department for maintenance and calibration. Although this still required a great deal of planning and time, the necessary downtime was more or less planned. Despite reducing the likelihood of unscheduled downtime, this form of maintenance offered no guarantees: things could still break down.

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Service department

Since 2004, instruments can be read remotely through a service we call 'Remote Support'. Working remotely, our support staff can observe the on-site situation and identify instabilities in the customer's process or other issues. The customer connects the instrument to a PC or laptop with online connectivity. The instrument's status can be read on the basis of internal diagnostic parameters. We then use the status indication or findings to identify appropriate measures in consultation with the customer. For example, we can adjust the control setting (PID values) if a process is not being regulated effectively.

A recent case in point: a Canadian customer recently called our Worldwide Support Line. He informed us that an analyser connected to his Bronkhorst vapour flow control (Controlled Evaporation Mixing, or CEM) system application was failing to detect water. Our Remote Support staff used Bronkhorst software to determine that the customer had incorrectly configured a specific control setting: the Bronkhorst liquid flow regulator was not receiving the correct setpoint value, causing the water supply control valve to stay closed. The solution? We worked with the customer to find the appropriate settings for the process, instantly resolving the issue. As a result, there was no need to ship the instrument to our service department or schedule a visit from our technician, saving valuable time and resources.

Ready for the future

As part of efforts to improve our Remote Support, we will soon be introducing an additional service in the form of Bronkhorst Expert Eye. Expert Eye is a smartphone app with video support. The app enables customers to connect with Bronkhorst service staff directly to receive live support. The video and audio connection allows us to provide immediate advice.

In the future, we aim to upgrade the intelligence of our instruments in order to service our customers more effectively. The data applied by our existing instruments contain valuable information on the instrument's condition or process quality of the mass flow controller's overarching system. We aim to apply these data towards more effective preventive maintenance, process monitoring and process optimisation.

We look forward to improving the app further in collaboration with our customers. Please feel free to contact us for further details on specific data solutions for mass flow controllers and condition-based and preventive maintenance.

Source: Driving Unconventional Growth through the Industrial Internet of Things (2015)

Jean-François Lamonier
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Jean-François Lamonier, a lecturer/researcher at the University of Lille, is an expert in the catalytic treatment of volatile organic compounds (VOCs). He leads the 'Remediation and Catalytic Materials' (REMCAT) research team in the Laboratory of Catalysis and Solid State Chemistry (UCCS), which specialises in the catalytic removal of atmospheric pollutants emitted by both fixed and mobile sources (such as factories and vehicles, respectively). In this blog post, he tells us about his research and explains how his team uses measuring instruments and flow controllers.

Focus areas for the REMCAT research team

REMCAT (Remediation and Catalytic Materials) research team of the Laboratory of Catalysis and Solid State Chemistry (UCCS)

The REMCAT team comprises six lecturer/researchers. Our work is focused on catalytic after-treatment of atmospheric pollutants, primarily nitrogen oxides (NOx and N2O) and volatile organic compounds (VOCs). Our team possesses broad knowledge in the field of heterogeneous catalysis: from catalyst synthesis to characterisation of new catalytic formulations, evaluation of their performance through comprehensive testing, advanced characterisation of catalysts using operando infrared spectroscopy, reaction kinetics and reactor modelling.

Air pollution treated efficiently by combining non-thermal plasma with catalysis

This set of skills in environmental catalysis allows us to develop original processes that involve combining different technologies to devise a cheaper, more effective and more environmentally-friendly method of treating air pollution. In this context, we collaborate with various national and international research groups, such as the 'Research Unit Plasma Technology' (RUPT) at the University of Ghent. This research unit specialises in developing plasma reactors; we lend them our expertise in heterogeneous catalysis to help develop processes to couple non-thermal plasma with catalysis. This research is being conducted in an International Associated Laboratory on 'Plasma-Catalysis', which we recently created under the auspices of the European INTERREG V 'DepollutAir' project, which is currently funding our research.

Using adsorption functionality in plasma-catalytic transformation processes

Traditional plasma-catalytic processes to remove volatile organic compounds (VOCs), which are present in industrial waste gases, require a continuous energy supply. Our approach is to insert an earlier step in the plasma-catalytic transformation process involving adsorption of the pollutant. This enables the plasma to work sequentially to remove the volatile organic compounds and means the adsorbent is regenerated, resulting in substantial energy savings. Our team is lending its expertise to the development of new adsorbent/catalyst materials and to the advanced characterisation of these materials.

Using flow meters and flow controllers in the catalytic treatment of volatile organic compounds (VOCs)

In our research, we need to generate mixtures of VOCs to simulate industrial waste gases. As these waste gases are different for each type of industry and we need to be as representative as possible of industrial realities, we have to be able to generate gas flows with highly variable VOC levels, containing VOCs of many different types, such as formaldehyde, toluene, chlorobenzene, trichloroethylene and butanol.

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Dilution system with Coriolis flow meter

To this end, we use a dilution system supplied by Bronkhorst, which comprises a Coriolis flow meter, a pressure regulator (overflow valve) and a number of mass flow controllers. We needed a device that would enable us to achieve low concentrations of VOCs, because increasingly restrictive standards have resulted in a decrease in atmospheric VOC levels. We also needed the system to be as flexible as possible, so it could adapt both to the nature of the various liquids injected into the system to be transformed into gases and to the VOC levels in the waste gases, which can range from 10 to 1000 ppmv.

Catalytic formulations

The relative humidity of the waste gases is an important parameter to take into consideration when developing catalytic formulations. As you might imagine, the presence of steam can have a positive or negative effect on the performance of the catalytic process. Consequently, the system for generating the gases must also be able to generate a variable relative humidity in the gas mixture.

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Furthermore, to develop a catalytic formulation suitable for industrial applications, we not only need to verify that the catalyst is both active and selective (in other words, that the catalyst can produce the desired products), but also that it is stable over time. It’s hard to imagine a catalyst that only works for a single day and has to be replaced the next day.

That’s why we need to reproduce an industrial waste gas stream that remains constant for several days. If we’re performing a catalytic test over the course of a single day, we might consider using a bubbler system. However, when we need to check the stability of the catalysts over time, we conduct long-term tests to see if the catalyst is capable of maintaining its activity over several days. It would be more complicated to conduct tests over time using a traditional system, but the Bronkhorst system generates a constant, continuous, smooth flow of VOCs into the air. This is a distinct advantage that enables us to validate our process.

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To find out more about Bronkhorst’s dilution solutions Click here for more information about the research of Jean-François Lamonier and the REMCAT team from the Laboratory of Catalysis and Solid State Chemistry.

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