Anhydrous Ammonia Control for Nitrogen Oxides Reduction
As a technique to reduce the level of Nitrogen Oxides (NOx) in boiler or furnace exhaust gases, Selective Catalytic Reduction (SCR) has been around for years. SCR is a technology which converts Nitrogen Oxides (NOx) with the aid of a catalyst into diatomic Nitrogen (N2) and Water (H2O). A reductant agent is injected into the exhaust stream through a special catalyst. A typical reductant used here is Anhydrous Ammonia (NH3).
A customer of Bronkhorst, who has been selling and servicing boilers and pumps for commercial and industrial applications for over 50 years, had been using a mass flow controller (MFC) which was not reliable and robust enough for the application and thus their customers were suffering from poor ammonia measurement and control.
Why use mass flow measurement in Ammonia Control?
Some NOx reduction systems are liquid ammonia based, and others are gas based ammonia. Whatever the state of the ammonia in the NOx reduction system Bronkhorst can offer accurate ammonia measurement and control. Systems in the field today are using the MASS-STREAM (gas), IN-FLOW (gas) and Mini CORI-FLOW (liquid) to accurately control the ammonia being injected into the exhaust gas stream so that proper reaction takes place without ammonia slip. Ammonia slip is when too much ammonia is added to the process and it is exhausted, un-reacted, from the system; effectively sending money out the exhaust stack.
There are very strict federal and state air quality regulations that specify the allowable level of NOx which can be released into the atmosphere and there can be very heavy fines if those levels are exceeded. The company needs to provide their customers with a reliable and robust solution. The application demands a robust and repeatable mass flow controller that is at home in industrial environments.
What kind of Mass Flow Meter or Controller can be used here?
In the NOx reduction system serviced by our customer the mass flow controllers are used to control the flow of anhydrous ammonia (ammonia in gas state) into the exhaust gas of a boiler or furnace where it is adsorbed onto a catalyst. The exhaust gas reacts with the catalyst and ammonia which converts the Nitrogen Oxides into Nitrogen and Water.
Bronkhorst recommended a mass flow controller – from the MASS-STREAM series - using the CTA (Constant Temperature Anemometer) technology which is ideal to avoid clogging in potentially polluted industrial gas applications.
Let me explain a bit about the working principle of this kind of mass flow controller and why it is suitable for an application like this.
The CTA (Constant Temperature Anemometer) principle is essentially a straight tube with only two stainless steel probes (a heater and a temperature sensor) in the gas flow path. A constant temperature difference between the two probes is maintained with the power required to do so being proportional to the mass flow of the gas. This means the MASS-STREAM is less sensitive to dirt, humidity, or other contaminants in the gas, as compared to a by-pass type flow meter that relies on a perfect flow split between two paths. The thru-flow nature of the CTA technology is ideal to avoid clogging in potentially polluted industrial gas applications. The straight flow path and highly repeatable measurement and control capability, combined with the robust IP65 housing, allows the MASS-STREAM to thrive in tough applications.
Watch our video animation, explaining the functions and features of the Bronkhorst Mass Flow Meters and Controllers for gases using the CTA principle.
Check out the top 5 reasons why to use mass flow controllers with CTA measurement.
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Traditionally, and in most cases we see, dosing- or metering pumps are believed to be accurate because the theory is that a known pump head displacement will move a known volume over a known time giving a known delivered volume. In practice however it will never achieve a high level of accuracy with deviations of 10-15% being normal. Inaccuracies like this are caused by many changing process conditions, such as:
Wear of components
These factors can each be the cause of an inaccuracy in the expected volume of displacement from a pump head movement. If you then multiple each of those factors you can realise quite large measuring errors that create both inaccuracy and inconsistency.
Please refer to our earlier blog about ‘High Accuracy’.
What can be done to improve the accuracy?
Option 1) Add a flow meter between the pump and the process
By adding a flow meter between the pump and the process, you can take information from the flow meter to adjust the speed of the pump. Traditionally, this would be managed with an analogue output signal, 4….20 mA or similar, from the flow meter into a separate PID controller that compares the real flow signal to the desired flow. Subsequently, the electronic controller can then adjust the speed of the pump to achieve the desired dose or flow.
Using this solution will mitigate the issues in the original solution, however it introduces more:
Slow flow signal due to signal filtering in the PID controller
Slow pump response due to extra control relay
Increased complexity with extra components
Time to achieve stable flow can be long
Additional price of meter and PID controller
Option 2) Direct mass flow measurement with a flow meter with built in PID control
Now we need to discuss the next possible solution, using a direct Mass Flow measurement device with built in PID control
that can drive a pump to achieve the desired dose or flow.
With this solution you do not need to include the pump in the control system, just give a set point demand to the mass flow meter and it will drive the pump to achieve the desired dose or flow. This solution will give you several advantages, such as:
Direct mass flow control of the flow
Mass flow dosing is independent of temperature and pressure, in contrast to the volumetric dosing when only a pump is used;
Accurate delivery mitigating normal pump issues
Alarm functionality of low flow
Preventative maintenance based on pump performance over time
Consistent flow measurement based on actual not assumed numbers
Coriolis mass flow meter in modular dosing system
These advantages can be utilised in many different industries:
Anywhere that liquid is dispensed into a container that will require quality assurance, and commonly the quality control test is carried out on a small percentage of the vials to ensure general compliance. If you use a mass flow meter to control the dose you can achieve 100% QC checking of your product with reduced human input.
If you need to dose additives, performance chemicals or mix liquids then the ability to control the flow of the additive and know what that flow is can be a huge advantage to the outcome of the application.
Pump control can offer accurate dosing solutions for house hold chemicals like detergents and cleaning products.
Within the medical arena there is increased pressure on budgets and financial accountability, with a significant trend for the sector to look again at how resources are used and where savings can be made.
One of the largest expenditures in most hospitals is the cost of purchasing or producing the various medical gases needed, such as Medical Air, Nitrogen, Oxygen and Nitrous Oxide. Often the usage and consumption of these gases is neither monitored nor measured or, whenever it is done, it is often a crude estimation, inaccurate and recorded only by pen and paper.
Most hospitals rely on the rate at which the cylinders (in which the gas is supplied) empty to determine the amount and rate of gas used. There are of course many issues associated with this method, such as:
The amount of gas in a particular sized cylinder can vary greatly, even when directly delivered by the gas supplier
Total gas consumption and peak times of consumption cannot be accurately determined
Leaks can go undetected
Specific point of use consumption is impossible to determine
This makes it very difficult to manage costs overall and to assign invoicing costs to individual departments and sections.
A company specialising in the design, installation and maintenance of gas systems was asked to install the medical gas network in a new hospital. An approach was made to Bronkhorst UK Ltd for the supply of gas meters which could then be communication-linked to the building maintenance system.
Thermal mass flow Instruments with integrated multi-functional displays were offered to fulfil both the accuracy and reliability requirements . As a result of their through-flow measurement (Constant Temperature Anemometry - CTA technology) the thermal mass flow instruments offered the additional benefits of no risk of clogging, no wear as there are no moving parts, minimal obstruction to the flow of the gas and hence ultra-low pressure drop, all based upon the fact that the instrument body is essentially a straight length of tube.
In addition to the local integrated displays both 4…20 mA and RS232 output signals were available ensuring integration with the Building Management System (BMS). This gave the end user real time continuous data logging and remote alarming should the gas supply enter low- or high-flow status for any given event. As a double failsafe the instrument offers both on-board flow totalization and further hi/lo alarms.
The installation of the mass flow instruments for this hospital application provided the following benefits to the client:
1. On primary networks:
Separated invoicing for hospital/clinic/laboratory departments sharing the same source of medical gas
Monitoring and acquisition of consumption data
Leak detection within gas line, safety vent and medical gas source
2. On secondary networks:
Independent gas consumption invoicing between the health institution departments
Monitoring and acquisition of consumption data
Leak detection within gas line
Subsequent installations across Europe have followed the trend of increased accountability by installing a Mass Flow Meter for the incoming bulk delivery, obtaining a totalized flow reading and cross matching this to the bulk invoice. This could be useful in the event of inadvertent errors or typos when a bulk delivery invoice is being raised.
Why using a Controlled Evaporation and Mixing system can decrease food waste
We are all aware that the current level of food waste cannot be sustained if we have a hope of reducing food poverty across the world. This is not just a Western issue; globally food is lost or wasted at different points in the supply chain. Today’s technologies, such as sterilization, can help reduce this spoilage. However, the strict compliance requirements will ask for continuous improvement of this technology.
An analysis from the Food and Agriculture organization of the United Nations highlights some discrepancies;
• In developing countries food waste and losses occur mainly at early stages of the food value chain and can be traced back to financial, managerial and technical constraints in harvesting techniques as well as storage and cooling facilities.
• In medium- and high-income countries food is wasted and lost mainly at later stages in the supply chain. Differing from the situation in developing countries, the behavior of consumers plays an important role in industrialized countries.
So, where can we make a difference?
Looking at the graph of food losses below, and the statements above, we can see that it is worthwhile to invest in production techniques, potentially to increase the shelf life of packaged food. This would have a positive impact on the waste of food in developed countries.
One of the ways to improve these figures is to improve the sterilization of the packaging that food is placed in, to reduce spoilage and increase shelf life. This is the point where Controlled Evaporation Mixing (CEM) systems come in the picture.
Bronkhorst share in extension of the shelf life
Sterilisation of packaging to extend shelf life is not something new, it already has been done for years. I believe the first aseptic filling plant for milk was already presented in 1961.
However, it is a technology which has been improved tremendously throughout the years and still is improving. Bronkhorst has an extended range of instruments which can support you in this process.
An ingenious development in this area is a Controlled Evaporation and Mixing system (also called a CEM), as one compact solution for industrial processes such as sterilization. The compact solutions consist of various type of instruments, such as liquid and gas flow meters and an evaporator.
Using Controlled Evaporation Mixing (CEM) systems for sterilisation
The challenge given to Bronkhorst via a customer that was using a Hydrogen Peroxide (H2O2) mix (containing 35% of H2O2 and water) to decontaminate carton and plastic packaging for liquid and cream filling. Using a mix of H2O2 is an excellent way to do this, because it is great at killing bacteria and can be easily evaporated. Bronkhorst is an experienced supplier of this kind of solutions.
To get the best production with minimal waste you need to:
Dose the correct amount of H2O2 mixture
Too much and the final product is spoiled
Too little and the residual bacteria is too high
Avoid de-gassing of the H2O2 mix
Have a controlled flow that condenses on the inside of the package
Limit the flow. If it’s too high it will increase drying time at the end of sterilisation
The best result for this application was given by vapour generation combined with a Coriolis mass flow meter. Because H2O2 mixtures are not particularly stable this results in changing physical properties. Adding a Coriolis mass flow meter to the CEM made the measurement of mass flow medium properties independent. Furthermore as the Coriolis instrument is capable of measuring medium density, it can be used to monitor the concentration and thus watch over quality of H2O2.
Using a CEM system has some real advantages:
Stable temperature of vapour
Stable concentration of condensation because of a controlled dew point of the mixture
All of the above is possible because the gas, liquid and mixing temperature are controlled
Benefits as perceived by the customer
Stable liquid mass flow, even if physical properties vary
Monitoring the concentration and quality of the H2O2
Monitoring and traceability of the sterilisation process
Mass flow control of liquid
Mass flow control of gas
Direct control of dew point through control of gas and air mixture
In this week’s blog we will have a look at the growing Chocolate Confectionery industry and the trends in using flavors. Who else can do this better than a woman you should think… as 75% of the women against 68% of the men report that they indulge in chocolate.
Chocolate…a growing worldwide market of $100 billion once started with a simple choice between Milk, Dark or White chocolate. Nowadays the choice in variations is tremendous due to flavorings.
Chocolate as a seasonal gift is very popular. Around the holidays we tend to buy more chocolate. The top selling season for chocolate is not Valentine’s Day, as you might think, but Easter.
In addition to treating oneself, mood enhancement is also a popular reason for the rising sales, especially for young adults. The majority of the chocolate buyers (particularly in the US) are looking for options with mix-ins as opposed to the plain/unflavored varieties.
The global chocolate market has seen considerable innovation in flavor and texture. New product development continues to be imaginative, with more exploration of flavors and textures in addition to the traditional sweetness. However the consumer base tends to be rather conservative as the most popular flavors currently are Hazelnut, Caramel, Almond, and Orange.
Older consumers tend to have a lower engagement with chocolate. The lack of interest reflects their desire to eat healthy. To regain this group of adult customers, companies have turned to tactics such as using alcohol flavors, organic ingredients, and premium positioning such as dark chocolate with Limoncello or chocolates filled with sweet liqueur.
It may come as a surprise, but a healthy lifestyle, which is one of the major trends worldwide, is also responsible for a substantial growth of the chocolate market and that’s not without reason. Chocolate, specifically dark chocolate with more than 85% cocoa, offers beneficial health benefits, like:
‘Rich in Fiber, Iron, Magnesium, Copper, Manganese and other minerals’
‘Powerful source of Antioxidants’
‘Protective against cardiovascular disease’
The growing awareness of the health benefits of pure and dark chocolate is why consumption of chocolate is increasing. With the rising popularity of dark chocolate, the sales for other variations are also going up. People are seeking other ‘healthy’ variations, such as sugar-free, Gluten-Free, Kosher, or Fair Trade chocolate. Due to these ethical claims, the industry has seen a tremendous growth in variations. In order to enhance a healthy image for chocolate, functional ingredients such as fibers, protein, micronutrients, quick energy (guarana extracts), green tea extract, or chia seeds are more and more often being added to the chocolate.
The increasing demand for chocolate also has its downside. About 3 million tons of cocoa beans are consumed annually of which more than 70% is produced by four West African countries: Ivory Coast, Ghana, Nigeria and Cameroon.
Cocoa is a delicate crop and trees planted a quarter century ago have hit their production peak and the land they grown on are not as fertile as it once was. A large rehabilitation of land and trees is necessary to prevent the loss of crop production. Also climate changes are taking their toll.
This results in high costs for raw materials and unstable economic conditions in cocoa-producing nations. To prevent a supply shortage, a number of well-known chocolate producing companies have decided to invest in rehabilitation of the land and trees to make sure that cocoa will be available in the future.
This in a time that developing countries such as China, India, and Russia expect to grow their chocolate sales volume by 30%.
MASS FLOW METERS AND CHOCOLATE
Due to the tremendous growth of chocolate variations, using flavors and functional ingredients, mass flow meters and controllers find their way into the confectionery industry.
Due to their accurate and stable features, especially when they are used in combination with a pump, low flow mass flow meters and controllers using the Coriolis principle are ideal for dosing flavors and functional ingredients.
The Bronkhorst Coriolis instruments will measure direct mass flow and are independent of fluid properties which means a set point change is possible within seconds and there is no need to disassemble the pump and recalibrate the installation. This is a huge advantage which saves a lot of time, and makes the process much more flexible.
Using the Coriolis instruments for additive dosing means less downtime between batches, traceability of ingredients, and higher product consistency and quality.
At this time of year it is good to reflect on what has happened, what you have achieved and what you have enjoyed. This year I have very much enjoyed writing about our experience in Industry delivering Mass Flow Control and Metering Solutions. This week I look back at one of my first blogs, the potential possibility of switching from batch to continuous process production.
I hope you enjoy reading a second time as I enjoyed writing it.
One of the most common topics of conversation over the last few years in the chemical industry has been about the change from continuous to batch process production.
In the beginning of my involvement with the Chemical Industry I was an early advocate for switching to the batch process method. With the benefit of hindsight this was based on my perspective of the application at that time. Having worked in Operations I was heavily into data and numbers (letting the data speak), I believed they would tell you everything and provide the perfect foundation to make a decision. Develop what you have, invest in new kit or re-design an entire process.
So, the next step was to find the top 5 points that would encourage someone to discuss the change from batch to continuous production.
Quality: With greater control and automation in the production process it becomes easier to remove inconsistency in final product quality.
Waste: The better the quality and the higher the frequency of achieving that quality the less the product waste and re-work required. This has huge returns on baseline production cost.
Safety: Increasingly an important consideration in the modern workplace, reduction in contact with chemicals through increased automation and the inclusion of built in alarms can add significant safety advantages.
Space: In bulk manufacturing you have to store bulk products, both pre and post production, by moving to a lower volume continuous production method you can have smaller more frequent deliveries enabling you re-use the old storage facility for extra production lines.
Cost: In each of these improvements brings a cost incentive to the business, with extra production space, reduced waste or improved quality cost efficiency can be realised in multiple areas.
With advances made in metering and control instrumentation it would be remiss to not investigate the potential benefit an investment in continuous production could bring. The potential is there to achieve more predictable final product quality resulting in less re-works and waste product. A reduction in production space would be required; safer work environment, greater control and flexibility on supply chain operations. The ability to deliver smaller volumes to order increasing your potential customer base and reducing supply chain costs.
This has been a great topic to discuss and learn about, I would be more than happy to talk with more professionals in the field of Chemical production and expand my understanding further.