Dr. Jens Rother
Cover Image

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. Image description

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.

Image description

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.

Image description

Chris King
Cover Image

The measurement of fluid flow is critical to not only the proper functioning of pipes and tubes, but their role and use within the wider application. Meters are a necessary component because they measure the rate and flow of fluids, an indication of the successful performance of the wider application. There are many meters to choose from, all of which should be selected based on their specific use value. Below we will outline the main types of meters, as well as the benefits associated with each.

1. Mass Flow Meter

Importantly, mass flow meters do not measure volume per unit of time, but rather mass per unit of time. This type of meter is used in mining, waste, and pharmaceutical industries.

Thermal mass flow meters and Coriolis flow meters fall under this category. Thermal mass flow meters measure the heat of a flow stream after a heat source is detected by a temperature sensor, and operate apart from viscosity, pressure, and density. However, their accuracy depends on these components functioning optimally within the larger application, as well as temperature and flow rate. Advantageously, thermal mass flow meters have no moving parts, and often have an unobstructed flow path.

Coriolis flow meters offer direct mass measurements that are not affected by temperature, pressure, viscosity, or density alterations. They measure fluid using a sensor tube that vibrates in an angular harmonic oscillation with the force of the fluid creating a shift in that harmonic oscillation which is directly related to the mass of the fluid Coriolis flow meters are also universal meters in that they are capable of measuring liquids, gases, and slurries. They produce incredibly accurate results with a wide turndown.

2. Velocity Flow Meters

Velocity flow meters measure the velocity of the flowing stream of liquid to determine the volumetric flow. They are able to calculate this by measuring the speed in an isolated point of the flow, and then integrating the flow speed throughout the entire flow area. Velocity meters become less sensitive when the Reynolds number is above 10,000. Types of velocity meters include turbine, paddlewheel, vortex shedding, ultrasonic, and magnetic. These meters are useful because they give a reading of one of the most common characteristics of fluid flow - velocity. However, they can be sensitive to the process conditions within the wider application.

3. Positive Displacement Flow Meters

Positive displacement flow meters are the only meter to directly measure the volume of the fluid flowing through the tube. This is accomplished by repeatedly entrapping the fluid to most accurately measure its flow. Entrapment occurs through rotating parts that form moving seals between each part, as well as the tube. Without tight tolerance of the rotating parts, these seals cannot prevent fluid from flowing freely without being measured. To ensure this tightness, bearings are often used to support the rotating parts of the positive displacement flow meter. The speed of the flow occurs in proportion to the amount of fluid flowing in the tube.

Due to their accuracy, positive displacement flow meters are used in applications that require extreme sanitization and cleanliness, such as water, food, and some gases. They are advantageous in smaller line sizes, high viscosity, and low flow rates. They are long-lasting, especially in oil-based applications. The disadvantages of positive displacement meters include the eventual wearing of their moving parts and the corresponding maintenance, risk for impurity, and the fact that their design is not always as updated as frequently as similar technologies.

4. Differential Pressure Flow Meters

Differential pressure flow meters calculate the flow of liquid in a pipe by measuring the pressure drop through obstructions that are inserted in the flow. With the increase of flow comes a greater pressure drop, which is picked up by the transmitter. First the differential pressure flow meters produce a change in kinetic energy by using elements such as pitot tubes, orifice plates, segmental wedges, flow nozzles, or venturi flow meters depending on the measurement needed. Then they measure the differential pressure and provide the signal to the greater application.

Differential pressure flow meters make up around 20% of the flow meters around the world. They are used in the oil and gas, water, pharmaceutical, paper, marine, and mining industries. Advantages of differential pressure flow meters include fairly low cost, recognition and reliability within a large amount of applications, their customizable designs, and their compatibility with external pressure and temperature sensors to provide mass flow for gases. Disadvantages include potential limited range and inaccuracy that results from extended use and the resulting wear and clogging within the tube.

5. Open Channel Flow Meters

Open channel flow meters measure open liquids that flow in a free surface. This is seen in applications such as streams, rivers, canals, irrigation systems, and sewers. To measure the liquid in open channels, v-notch, weirs, and flumes are used. These dam-adjacent elements allow for a concentrated flow of liquid depending on the shape, width, and depth of the structure. Due to the size and scope of these sites, the implementation of the open channel flow meters must involve experienced professionals familiar with the specifications of the corresponding wider application.

Which flow meter performs the best?

There is no concrete answer to the question of the ‘greatest’ device, as each flow meter is designed and used across differing applications. To single out one flow meter would be disregarding the functionality of the others in serving the required application. To select the required flow meter, you must understand the specifics of the application for which the meter is being used. This includes awareness of the gas or liquid properties and their temperature and viscosity, flow rates and pressure limits of the design, and application location and potential exposure to the elements.

Meters are priced on their capabilities and potential to serve the most extreme applications, so it is best to consider the meters’ potential service to the application rather than the price. Usually, meters that are low in price quickly lose appeal in use because they fail to live up to the demands set forth in their application. By choosing a low-price meter for use in critical conditions, you risk damage to the flow process and danger to the people on or around the site. Consider the advantages of the value provided by the meter first, and then select the correct device accordingly.

For more information about selecting the right flow meter for your application, contact the Bronkhorst USA team at sales@bronkhorstusa.com.

Chris King

Image description

In the past contact lenses manufacturers manually prepared 17,000 liter batches of PVP (Polyvinylpyrrolidone) diluted into a saline solution. The solution then had to be refrigerated, and due to bacterial generation had a shelf life of just 20 hours. As a result the manufacturing process had to be halted while freshly prepared batches were reinstalled.

Thanks to the Bronkhorst® continuous proportional dosing system a major contact lens manufacturer has considerably increased production output and reduced manufacturing costs.

The Bronkhorst Coriolis Mass Flow Controller primary function is the proportional dosing of PVP into a saline solution using a Master / Slave principle. As a result of a variable main flow measured by the Master instrument, the Slave instrument responds to the changed Master output signal to dose the PVP in exact ratio to the main flow. By communicating, in this case, directly via DeviceNet™ with the supervisory automation and control system the Master CORI-FLOW™ instrument is provided with the precise dosing requirements.

The compact design of the Bronkhorst solution, where the Coriolis meter and controlling micro-annular pump are mounted in one compact unit, was a key factor in selecting the Bronkhorst solution.

The advantages this customer saw with using the Bronkhorst continuous dosing solution were increased production time, reduced floor space needed for two 17,000 liter vessels, and reduced PVP wastage due to the highly accurate Coriolis measurement principle.

Image description Image description

Many applications ask for compact, accurate measurement and control of additives to be proportionally dosed into a main flow. By using mini CORI-FLOW™ instruments it is easy to set up compact autonomous working systems that offer this functionality without the need of external computer hardware and software.

Chris King
Cover Image

Introducing BronkU.com, a new resource for the University research community.

BronkU.com is a fresh new resource designed specifically for the university community. It is the brainchild of Bronkhorst USA, a leader and trusted expert in mass flow measurement and control solutions. We've always supported universities and BronkU.com is our way of advancing our commitment to future scientists.

In celebration of launching BronkU.com, we are awarding a $500 grant to assist future scientists in pursuing their research.

Visit BronkU.com

Chris King
Cover Image

Quality Control has a very high value. The value comes from the security it provides. Air and Liquid tightness can be of critical importance, also on a small scale. It is our mission to support the development of tools that can help achieve this goal. Leaks can lead to unstable process conditions which in turn can create potentially dangerous results. An example is the Bhopal disaster : a gas leak incident in India which is considered as the world’s worst industrial disaster. Over 500,000 people were exposed to methyl isocyanate gas and other chemicals.

There are three major solutions that we have provided to demonstrate leak integrity:

  • Valve seat leak testing
  • Fabric permeability testing
  • Ventilation and Air conditioning systems (HVAC)

Each of the challenges has different demands and requires an independent approach.

Two of these solutions required a flow pressure combination and one was a Coriolis solution. The valve seat leak test required a Coriolis sensor to meet the specific demands of that industry. Both the fabric and ventilation systems required a Thermal Mass Flow meter and Pressure instrument and that is what we are talking about this week.

Fabric permeability testing

The fabric test was completed by using a closed loop flow-pressure control solution. A chamber with an outlet, Digital Electronic Pressure Meter (DEPM) to control the internal pressure and an inlet, Mass Flow Controller (MFC) to control the inlet flow was built with a custom made fabric clamp on top of the chamber for the fabric.

This system allows the end user to clamp in a chosen fabric sample, always a consistent size, give set-point to the pressure meter, which via a closed loop control cable then controls the valve on the mass flow controller to allow the addition of air into the chamber until the pressure set-point is reached and then maintain it. Once reached the flow controller records the flow of AiR required to maintain the set-point giving a value to the permeability of the fabric. This process provides data acquisition for the test.

Ventilation and air conditioning system

The ventilation leak test system requires a more industrial approach. Also, with larger volumes to fill and potentially several devices under test (DUT) the system is controlled by a Digital Electronic Pressure Controller (DEPC). A Mass Flow Meter (MFM) is used in series to meter the flow of AiR required to maintain the set pressure. With an MFM and DEPC in-series you can set a pressure on the DUT via the DEPC and fill with AiR, the DEPC then controls the pressure while the MFM records the amount of AiR required to maintain the pre-determined pressure. This will then give a reading on the leakage rate of the DUT.

Image description

There are a few key factors to making sure that you get repeatable and consistent test data:

Firstly, if the test volume would require a long fill time, or secondly, a small leak rate might be measured then a safe by-pass would be required to achieve a quick fill and stabilisation time.

The third and most important parameter that can affect the result of the test is temperature. The gas and components must be allowed to equalise before testing begins, for example a 2 Deg C shift in temperature can result in a 0.7% change in volume measured due to gas expansion. Any leaks smaller than this volume would not be measured and the integrity and repeatability of the test would be under question.

To help counter some of the issues discussed we have developed a new flow controller that will provide your process with cutting edge performance, click here for more information.

Chris King
Cover Image

An often heard assumption about a Coriolis meter is that it is easily and regularly affected by external vibrations, and for that reason is not a reliable flow measurement technology. I’m here to tell you, that it is just not true.

A simple explanation of the working principle of a Coriolis meter is that a tube is made to vibrate at a specific frequency and when the fluid flows through the tube the frequency of vibration will change. This change in frequency is directly related to the mass of the fluid going through the tube and thus the mass flow measurement is made. The important bit here is that there is an induced vibration frequency of the tube.

Coriolis meters are regularly installed in pipelines where they are subject to external vibrations, and they perform extremely well; very accurate, very fast response. The key is that most external vibration is not at, or even very close to, the induced vibration frequency. If, and this very, very rarely occurs, the external vibration frequency matches the induced vibration frequency then measurement errors can occur. As long as those two vibration frequencies are not very close the Coriolis measurement will be stable.

Maybe you have seen the video of the Tacoma Narrows Bridge that broke apart in 1940; the wind started the bridge flexing, then really undulating and eventually it broke apart. The wind provided an external frequency that matched the bridge’s natural structural frequency. Wind had blown in that area before that fateful day, but had not damaged the bridge because the wind frequency was different than that of the bridge. The same concept applies in a Coriolis meter. Not that a meter will fall apart, but if an external vibration matches the internal induced vibration the measurement can be off. But, just as it was an incredibly rare occurrence with the wind and the bridge, so it is with external vibration in a plant or lab and the induced vibration of a Coriolis meter; if the two are not close, no problem.

Don’t be put off by the Myth of Vibration. If you are looking for an accurate, stable, responsive mass flow meter that is adaptable to your process you really ought to give a Coriolis meter a try.

See for yourself:

Image description