In recent years, steam systems have increasingly been branded as inefficient and a problem to maintain. Some sites are decommissioning steam and switching to hot water or other means of energy transfer, expecting it to be more efficient. This is a real pity as steam is still the quickest and most effective way to transport heat energy around a plant. In fact the problem isn’t that steam systems are not effective, it is that most people have no idea that they can optimize their existing system by recovering any wasted energy.
There is an effective way to permanently increase the efficiency of such systems to over 80%. On average only 55% of the fuel Input to a steam system is used as useful heat output. Of the 45% wasted energy the biggest losses are the 15-25% that goes up the stack as exhaust gasses and 10% that is lost through leaking steam straps. Both these losses can be easily recovered by implementing two simple projects bringing the efficiency of your steam system to at least 83%.
Technology 1 – Direct Contact Condensing Economizer
We all know about traditional boiler economizers. They fit on to the back of your boiler and can usually collect about 2-4% of the wasted energy. This system however has application limitations and can only recover the sensible heat from the waste gas. A Direct Contact Condensing heat recovery system, such as FLU-ACE, can recover the full 18% stack losses providing fantastic returns. The system can reduce the boiler exhaust gas temperature below the exhaust dew point as far as 25°C. Cooling beyond the dew point releases all the latent energy in the exhaust by condensing all the moisture inside a separate stack. For a natural gas boiler, this latent energy will be around 18% of energy in the fuel. By the time boiler and distribution losses have been accounted for, they can typically save 20% of the fuel bill.
FLU-ACE can recover the waste heat from the exhausts on boilers, CHP plants, dryers and other industrial heat sources. The recovered energy can be used for example, to pre-heat makeup water, heat Domestic Hot Water (DHW), or be used for heating systems etc. In addition, this also reduces greenhouse gases and helps work towards energy reduction targets. The control panels on the heat recovery units can also contain data loggers that continually record the energy being recovered and provide fault warnings if any issues arise. The system is very low maintenance, stand alone and payback on a typical project is usually 2-3 years and the units have a predicted lifespan of 20-30 years.
Technology 2 – Venturi Orifice Steam Traps
On average, 10% of mechanical steam traps fail annually. These steam traps can either fail open or closed. When they fail open they leak live steam which is inefficient, wasteful and can pressurise condensate recovery lines. When they fail closed, the condensate can back up causing waterhammer and if not detected quickly, can be catastrophic causing pipework to erode, and at times explode.
It is the moving parts in mechanical traps that cause them to fail. Low maintenance steam traps like our venturi orifice GEM traps can provide an ultimate permanent solution. These steam traps do not contain any moving parts and therefore remove the possibility of a trap failing. When correctly implemented, they are sized to ensure that no live steam can ever pass through. This makes them energy saving and maintence free.
Venturi steam traps functions on a principal of flash steam. Following the orifice there is a cleverly configured staged throat that is individually sized for the application to accommodate its varying condensate loads. The staged throat is designed to create a variable back pressure at the orifice as the load changes self-regulating their capacity across a range suitable for the vast majority of industrial applications.
Combining these two proven technologies can recover 28% of the energy wasted. Making this more cost effective and more efficient then decommission or changing your heat source. Not only is this more efficient but it also involves less time hassle and money as there is no need to redesign and implement an entirely new system. So next time you think of decommissioning steam, don’t. Contact us instead.
A large amount of the heat supplied by most fuel-fired heating equipment is wasted as exhaust or flue gases. In furnaces, air and fuel are mixed and burned to generate heat, some of which is transferred to the heating device and its load. When the heat transfer reaches its practical limit, the spent combustion gases are removed from the furnace via a flue or stack. At this point, these gases still hold considerable thermal energy. In many systems, this is the greatest single heat loss. The energy efficiency can often be increased by using waste heat gas recovery systems to capture and use some of the energy in the flue gas.
Heat Recovery 101: Exhaust gas loss or waste heat depends on flue gas temperature and its mass flow, or in practical terms, excess air resulting from combustion air supply and air leakage into the furnace. The excess air can be estimated by measuring oxygen percentage in the flue gases.
Waste Heat Recovery
Heat losses must be minimized before waste heat recovery is investigated. The most commonly used waste heat recovery methods are preheating combustion air, steam generation and water heating, and load preheating.
Preheating Combustion Air
A recuperator is the most widely used heat recovery device. It is a gas-to-gas heat exchanger placed on the stack of the furnace that preheats incoming air with exhaust gas. Designs rely on tubes or plates to transfer heat from the exhaust gas to the combustion air and keep the streams from mixing
Another way to preheat combustion air is with a regenerator, which is an insulated container filled with metal or ceramic shapes that can absorb and store significant thermal energy. It acts as a rechargeable storage battery for heat. Incoming cold combustion air is passed through the regenerator. At least two regenerators and their associated burners are required for an uninterrupted process: one provides energy to the combustion air while the other recharges.
Steam Generation and Water Heating
These systems are similar to conventional boilers but are larger because the exhaust gas temperature is lower than the flame temperature used in conventional systems. Waste heat boilers can be used on most furnace applications, and special designs and materials are available for systems with corrosive waste gases. Plants that need a source of steam or hot water can use waste heat boilers, which may also work for plants that want to add steam capacity. However, the waste boiler generates steam only when the fuel-fired process is operating.
If exhaust gases leaving the high temperature portion of the process can be brought into contact with a relatively cool incoming load (the material being heated), energy will be transferred to the load, preheating it and reducing the energy consumption. Load preheating has the highest potential efficiency of any system that uses waste gases. Load preheating systems can be difficult to retrofit and are best suited for continuous rather than batch furnaces.
Waste heat recovery should generally be considered if the exhaust temperature is higher than 1,000°F, or if the flue gas mass flow is very large. Contact us today to learn more about how a FLU-ACE direct contact condensing heat recovery system can help your business lower its fuel costs and reduce its carbon emissions.
Heat recovery technologies have wide applications in the food and beverage industry. From breweries and bottling operations, to food processing, packaging, and other food and beverage operations, heat recovery technologies can help companies reduce their energy costs while lowering their greenhouse gas emissions. Here is a case study that looks at one of our FLU-ACE heat recovery systems installed at one of a leading cereal manufacturer's plants.
Thermal Energy International implemented a FLU-ACE Condensing Heat Recovery System on the plant’s boiler exhaust. The system was designed to recover up to 5 MMBtu/h of waste heat energy that would otherwise be exhausted to the atmosphere.
The recovered heat, in the form of water at 60°C, is used to heat and preheat:
This project was implemented on a turn-key basis, and was completed on budget and on schedule.
FLU-ACE uses direct contact gas-to-liquid mass transfer and heat exchange. It condenses almost all of the water vapour (steam) from the exhaust, and this latent heat is the source of the bulk of the waste heat available in a boiler flue gas.
“Sensible” heat refers to energy that can be released through a temperature change. Heating water from 32°F to 212°F (0°C to 100°C) is a change in “sensible” heat. “Latent” heat refers to energy stored or released in a phase change, such as the heating that is done when steam changes from vapor to water, without any temperature change. As it turns out, the energy released when a pound of steam turns into a pound of water, all happening at 212°F (100°C) (no temperature change, so this is latent heat) is some five times the energy released when that same pound of water is cooled from 212°F to 32°F (100°C to 0°C). All this to say there is a lot of energy released in the phase change from water vapor to liquid water.
Therefore, condensing heat recovery technology, which can capture latent heat, is much more efficient than the typical feedwater economizer, which can only capture sensible heat. When it comes to overall boiler plant efficiency, FLU-ACE is able to provide a 10% to 15% improvement, while a typical feedwater economizer provides an improvement of 2% to 4%.
Steam traps are an essential part of a steam system. Unfortunately, conventional mechanical traps are often wasteful and laborious to maintain. As such, there has been much discussion on the energy that can be recovered by properly monitoring and maintaining steam traps. It is considered best practice for sites to have an annual steam trap survey to determine failures and replace any failed traps. More recently there has been the encouraged use of wireless monitoring to keep on top of maintenance and ensure that a failed trap is located quickly and then repaired. Wireless monitoring is a great step forward, and when paired with low maintenance steam traps, could be the optimum solution for steam users.
On average, 10% of mechanical steam traps fail annually. These steam traps can either fail open or closed. When they fail open they leak live steam which is inefficient, wasteful and can pressurise condensate recovery lines. When they fail closed, the condensate can back up causing waterhammer and if not detected quickly, can be catastrophic as it causes pipework to erode, and at times, the implosion of pipework.
What is the solution?
It is the moving parts in mechanical traps that cause them to fail in either the open or closed position. Low maintenance steam traps like our venturi orifice GEM steam traps can provide the ultimate solution. GEM steam traps do not contain any moving parts and therefore removes the possibility of a trap failing.
How does it work?
Unlike most mechanical steam traps, a venturi orifice steam trap continuously removes condensate from a system. It allows any condensate present in the steam line to pass into the condensate return system the moment it is formed. The operation of the trap is based on the difference in density between water and steam. At low pressures, the density of condensate is about 1,000 times greater than that of steam. When both media are present, the much denser condensate will be preferentially discharged and stop the steam from passing through the orifice. The size of the orifice of each trap should be determined by the specific pressure and condensate flow through that trap. Each trap should be engineered to ensure a small plug of condensate is present at the orifice at all times. This means that no live steam can leak through the trap and it protects the orifice from any erosion by live steam.
As condensate is forced through the orifice it passes from the area of high pressure into a lower pressure region in the throat of the trap. Water’s capacity to contain energy reduces as pressure reduces and so any excess energy in the condensate, which can no longer be contained due to the pressure drop, instantly evaporates once in the throat of the trap. This evaporation is known as flashing, and the instantaneous expansion of the flash steam creates a localised back pressure on the orifice.
It is not just the orifice that should be sized specifically for the application the steam trap serves; the throat is also specifically configured. The throat contains a number of different stages of varying diameters. At lower flow rates the condensate flashes close to the orifice in a smaller diameter stage whereas at higher load conditions it flashes further down the throat in a larger stage. The flash point moves up and down the throat under variable loads.
The pressure on the orifice applied by the flashing therefore depends on the flowrate, meaning venturi orifice traps can self-regulate their capacity and work effectively across a range suitable for industrial applications. The GEM steam trap is a venturi orifice type trap. The engineers at Thermal Energy International take full responsibility for accurately sizing the internal configuration of each and every trap, using their extensive experience to ensure GEM traps work effectively across variable loads, and do not pass live steam, maximizing potential energy savings.
Low maintenance solutions
As venturi orifice traps contain no moving parts that can wear, seize and fail, they require less maintenance than mechanical steam traps. They eliminate the need for the traditional cycle of ‘trap failure - identification of failed trap -replacement of failed trap’.
With any steam trap, it is best practice to clean the strainer baskets once a year, and rather than identifying and replacing a failed mechanical trap, a smaller orifice on a venturi orifice trap may simply require a poke to remove any small debris that may have collected over the year.
Combining wireless monitoring systems with traps that use venturi orifice technology is the ultimate low maintenance, low cost solution for any site. No more spare parts, hours fixing and determining problems or wastage of precious live steam. The ultimate solution.
Heat Recovery 101: What’s the difference between a direct-contact and an indirect-contact economizer?
Condensing heat recovery can be applied in two ways: direct-contact and indirect-contact systems. An indirect-contact system is simply a standard heat exchanger: water passes through tubes and the hot exhaust passes outside the tubes. Sensible heat and latent heat are transferred through the tube walls from the hot side to the cold side. By contrast, direct contact systems bring the cold water medium in direct contact with the hot gas in an open spray tower or packed spray tower to recover the heat directly by heating the water.
Neither of these technologies is a "one size fits all" solution," so it’s best to take a look at the pros and cons of each type before making the right choice for your facility.
Some advantages and disadvantages of the two types of systems include:
Direct Contact Economizer
Indirect Contact Economizer
Clearly the selection of either direct contact or indirect contact is dependent upon the specific process heating application, both on the characteristics of the heat source and the heat sink.
For more on this topic see our white paper entitled Condensing Heat Recovery – The Final Step towards the 95% Efficient Boiler Plant, as published in Process Heating, Volume 22, Number 2.
We are pleased to announce that we have achieved Carbon Trust Accredited Supplier status, the prestigious accreditation for high quality energy efficient equipment and renewable energy technology suppliers.
The accreditation was awarded in recognition of our capability to deliver well-engineered energy efficiency solutions and the track records of both our GEM steam trap and FLU-ACE heat recovery systems. This independent validation of quality is a valuable differentiator in the fast-growing energy efficiency marketplace.
With Carbon Trust Accredited Supplier status we are also able to access low-cost financing on behalf of our customers for energy efficiency projects in both the public and private sector. Through their partnership with Siemens there is £550m of Energy Efficiency Financing available. In Northern Ireland and Wales the Carbon trust also offers 0% interest loans to businesses seeking to invest in green technology.
The Carbon Trust is an independent, global organization that measures and certifies the environmental footprint of organizations, supply chains and products against a trusted quality standard.
Steam has been a valuable source of power since the industrial revolution. Contrary to what people believe steam is still one of the most efficient and convenient ways of distributing high quality heat energy; however, if systems are not maintained properly they can be wasteful, inefficient and dangerous. With the never-ending cycle of steam wastage most companies fail to realize that proper steam trap testing and maintenance can reduce their fuel bills by 10-30%.
As steam travels through pipework and industrial applications it loses energy to surfaces and condenses. This condensate must be removed without leakage of live steam to keep the system at full efficiency. A steam trap must remove condensate from a system as quickly as possible without leaking precious live steam. As well as keeping the system efficient the steam trap helps to prevent water hammer.
If you are familiar with steam traps then you know that they can be a pain to manage and maintain. Around 10% of steam traps fail each year due to wear of mechanical parts. Oversized traps can also allow steam to escape which can cause further damage by wiredraw as steam takes the fastest path to escape to a lower pressure area cutting a path as it flows. This amounts to an average of 15% energy wasted through failed traps and condensate/flash loss.
In order to get maximum efficiency from the system, steam traps need to be tested properly and regularly. These methods need to be easy to use as traps are often in confined locations and hard to access. The two most common forms of testing are thermography and ultrasonic. Both can be conducted on site with compact lightweight tools and the results can be analysed immediately. This allows problems to be identified and investigated fully to give a better understanding of the entire system and all its inefficiencies.
Ultrasonic measurements are usually more accurate but can be more time consuming. Ultrasonic frequencies in the trap are converted into the audible range by a probe for analysis by ear. In general steam traps work in a cycle. They contain a valve that is closed when steam is present in the trap and open when condensate is present. The duration of the cycle varies by trap and load. By listening for the distinctive cycles of a low volume period as the trap is filling with condensate and a louder rushing sound as condensate discharges we can check that the trap is working correctly.
For thermodynamic and inverted bucket steam traps there is a very clear on/off cycle that can be heard under almost all loads. Other types of trap including float, thermostatic and bimetallic all cycle between a higher and lower volume but do not have a distinct on and off. At low loads such as line drainage on insulated lines this cycle can be even less distinct. They sound like a dribble on light load and modulate on higher loads. Bimetallic traps respond even slower than the other traps making it even harder to distinguish between the cycles.
Venturi-orifice traps operate on a completely continuous principle with no cycle. Therefore these traps cannot be tested with ultrasonic measurements as there is no distinction to be heard. The orifice in these traps is smaller than in other types and so the same quantity of condensate discharges at a faster speed. The sound level in these traps is higher due to the speed of condensate and restriction of flash expansion in the throat. When ultrasonic testing is used on such traps they can incorrectly be identified as failed open. However, the performance of venturi-orifice traps can be verified using thermography as described below.
In order to use thermography efficiently you need to collect vital information about steam pressure including local variations, reductions and back pressure from lifts and flash heat recovery. The temperature upstream and downstream of the trap must be taken and compared with the values on the steam tables for the given pressures. If temperatures upstream are lower than expected it could be because the trap is blocked and is backing up condensate. If however temperatures are higher downstream than expected it indicates that the condensate return line is pressurized. This could result from passing steam, undersized condensate lines or an obstruction.
Generally for line drainage type applications this method is accurate. If however you have a low temperature process; for example an air handling unit heating air to 50°C, the steam condenses but still has enough energy as condensate to heat the air. The control valve will open and close to control the level of condensate in the process but not enough to completely drain it. In this case the trap will only ever contact steam during start-up and does nothing during normal operation. The trap will run flooded and seem to be blocked but is actually working properly. Another problem may be when several steam traps in close proximity all feed into the same condensate line. If one of these traps fails it will pressurize the condensate line with live steam. The temperature after each trap will be higher than expected due to the one failed trap and finding it may be tricky.
By using these methods in unison and understanding the processes a picture can be built up of the entire steam system. Thermography allows you to get a fast response that finds majority of failed traps. Any inconsistencies can be investigated further by an ultrasonic probe with the exception of venturi-orifice traps. This is because they discharge condensate continuously so can be tested only by thermography. Using the right equipment allows you to monitor your traps efficiently and maintain them accordingly, resulting in steam and energy savings.
"A steam trap is a device used to discharge condensate and non-condensable gases with a negligible consumption or loss of live steam. Most steam traps are nothing more than automatic valves. They open, close or modulate automatically."
The first sentence defines the function of a steam trap. All steam traps must remove condensate and non-condensable gases without losing any live steam. The second sentence explains the function of a steam trap in the simplest way. The keyword to note from this sentence is - most. This is where orifice type steam traps differ. Only mechanical type traps contain a valve. Orifice type traps do not contain any moving parts. So how do they function?
There are two main types of orifice traps, (1) fixed or plate orifice trap, and (2) venturi orifice traps. Unlike a conventional mechanical steam trap, an orifice steam trap continuously removes condensate from a system. They allow any condensate present in the steam line to pass into the condensate return system as it is formed. The operation of the trap is based on the difference in density between water and steam. At low pressures, the density of condensate is about 1,000 times greater than that of steam. In the case of a small orifice, the condensate flows with much lower velocity through the opening, than steam. If both media are present, the much denser condensate will stop the steam from passing through. This means that no live steam will leak through the trap. Although fixed and venturi traps work on the same principle, there is one key difference between them.
A fixed or plate orifice trap consists of a small orifice machined into a plate. The size of the orifice used is determined by the pressure and condensate flow through the trap. As condensate is forced through the orifice it passes from an area of high pressure into a lower pressure region. Water’s capacity to contain energy reduces as pressure reduces and so any excess energy which cannot be contained due to the pressure drop serves to instantly evaporate a proportion of the liquid water. This evaporation is known as flashing, and the instantaneous expansion of the flash steam creates a back pressure which prevents live steam from passing, and protects the orifice from erosion. However, this means that fixed orifice traps can only effectively drain condensate for a specific condensate flow condition, meaning that this type of trap cannot handle loads that are varying. If the amount of condensate which needs to be discharged reduces, the condensate plug at the orifice, created by localized back pressure from the flash expansion, will not be present. This will lead to live steam being lost. Conversely, if the condensate load exceeds the design flow for the orifice plate, then condensate will back up which may affect process temperatures or lead to waterhammer.
If you search for the definition of a steam trap Google will give you the following result:
A venturi orifice trap works on the same principle, but with is one vital difference - It is designed to handle varying loads. Following the orifice there is a cleverly configured staged throat that is individually sized for its application and varying condensate loads. The staged throat is designed to create a variable back pressure at the orifice as the load changes. At lower flow rates the condensate flashes close to the orifice whereas at higher load conditions it flashes further down the stage throat. This restricts the condensate flow through the orifice depending on the load. So venturi traps can self-regulate their capacity across a range suitable for the vast majority of industrial applications.
The GEM steam trap is a venturi orifice type trap. The engineers at Thermal Energy International ensure that our GEM traps are sized correctly; maximizing the energy saved compared to conventional mechanical traps and fixed (or plate) orifice traps. Mechanical traps tend to have much larger orifice sizes, so when failing open, or even partially open, the steam losses can be substantial. Mechanical traps can often fail closed which can have catastrophic consequences on a site due to the resulting waterhammer.
Key advantages of a venturi orifice trap:
Thermal Energy's GEM steam traps are the most efficient and reliable steam traps on the market. Our high quality product and service enables us to supply GEM steam traps with a 10-year performance guarantee. See why our customers prefer our GEM steam traps over conventional steam traps.
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