Monthly Archives: July 2017

Select the Right NOx Control Technology

Most major industrialized urban areas in the U.S. are unable to meet the National Ambient Air Quality Standards (NAAQS) for ozone. Atmospheric studies have shown that ozone formation is the result of a complex set of chemical reactions involving volatile organic compounds (VOCs) and nitrogen oxides (NOx). Those studies indicate that many urban areas with VOC/NOx ratios greater tan 15:1 can reduce ambient ozone levels only by reducing NOx emissions. Many states, therefore, are implementing NOx control regulations for combustion devices in order to achieve compliance with the NAAQS ozone standard.

This article discusses the characterization of NOx emissions from industrial combustion devices. It then provides guidance on how to evaluate the applicable NOx control technologies and select an appropriate control method.

Characterizing Emissions

Most industrial combustion devices have not been tested to establish their baseline NOx emission levels. Rather, the NOx emissions from these units have been simply estimated using various factors. In light of recent regulations, however, it is mandatory that the NOx emissions from affected units now be known with certainty. This will establish each unit’s present compliance status and allow definition of fee applicable control technologies for those units that will require modification to achieve compliance.

It is, therefore, important to test each combustion device to verify its NOx emissions characteristics. The testing process should be streamlined to provide timely and necessary information for making decisions regarding the applicability of NOx control technologies.

The basic approach is to select one device from a class of units (that is, of same design and size) for characterization testing (NOx, CO2, and 02). Testing is conducted at three load points that represent the normal operating range of the unit, with excess oxygen variation testing conducted at each load point. Figure 1 illustrates the typical characterization test results. The remaining units in the class are tested at only one load point, at or near full load.

The operational data obtained during testing, in conjunction with the NOx and CO data, are used to define the compliance status of each unit, as well as the applicable NOx control technologies for those devices that must be modified. In most instances, this approach will allow multiple units to be tested in one day and provide the necessary operational data the engineer needs to properly evaluate the potential NOx control technologies.

Fundamental Concepts

Reasonably available control technology (RACT) standards for NOx emissions are defined in terms of an emission limit, such as 0.2 lb NOx/MMBtu, rather than mandating Specific NOx control technologies. Depending on the fuel fired and the design of the combustion device, a myriad of control technologies may be viable options. Before selecting RACT for a particular combustion device, it is necessary to understand how NOx emissions are formed so that the appropriate control strategy may be formulated.

NOx emissions formed during the combustion process are a function of the fuel composition, the operating mode, and the basic design of the boiler and combustion equipment. Each of these parameters can play a significant role in the final level of NOx emissions.

NOx formation is attributed to three distinct mechanisms:

1. Thermal NOx Formation;

2. Prompt (i.e.. rapidly forming) NO formation; and

3. Fuel NOx formation.

Each of these mechanisms is driven by three basic parameters – temperature of combustion, time above threshold temperatures in an oxidizing or reducing atmosphere, and turbulence during initial combustion.

Thermal NOx formation in gas-, oil-. and coal-fired devices results from thermal fixation of atmospheric nitrogen in the combustion air. Early investigations of NOx formation were based upon kinetic analyses for gaseous fuel combustion. These analyses by Zeldovich yielded an Arrhenius-type equation showing the relative importance of time, temperature, and oxygen and nitrogen concentrations on NOx formation in a pre-mixed flame (that is, the reactants are thoroughly mixed before combustion).

While thermal NOx formation in combustion devices cannot actually be determined using the Zeldovich relationship, it does illustrate the importance of the major factors that Influence thermal NOx formation, and that NOx formation increases exponentially with combustion temperatures above 2.800°F.

Experimentally measured NOx formation rates near the flame zone are higher than those predicted by the Zeldovich relationship. This rapidly forming NO is referred to as prompt NO. The discrepancy between the predicted and measured thermal NOx values is attributed to the simplifying assumptions used in the derivation of the Zeldovich equation, such as the equilibrium assumption that O = ½ 02. Near the hydrocarbon-air flame zone, the concentration of the formed radicals, such as O and OH, can exceed the equilibrium values, which enhances the rate of NOx formation. However, the importance of prompt NO in NOx emissions is negligible in comparison to thermal and fuel NOx.

When nitrogen is introduced with the fuel, completely different characteristics are observed. The NOx formed from the reaction of the fuel nitrogen with oxygen is termed fuel NOx. The most common form of fuel nitrogen is organically bound nitrogen present in liquid or solid fuels where individual nitrogen atoms are bonded to carbon or other atoms. These bonds break more easily than the diatomic N2 bonds so that fuel NOx formation rates can be much higher than those of thermal NOx. In addition, any nitrogen compounds (e.g., ammonia) introduced into the furnace react in much the same way.

Fuel NOx is much more sensitive to stoichiometry than to thermal conditions. For this reason, traditional thermal treatments, such as flue gas recirculation and water injection, do not effectively reduce NOx emissions from liquid and solid fuel combustion.

NOx emissions can be controlled either during the combustion process or after combustion is complete. Combustion control technologies rely on air or fuel staging techniques to take advantage of the kinetics of NOx formation or introducing inerts that inhibit the formation of NOx during combustion, or both. Post-combustion control technologies rely on introducing reactants in specified temperature regimes that destroy NOx either with or without the use of catalyst to promote the destruction.

Conbustion Control

The simplest of the combustion control technologies is low-excess-air operation–that is, reducing the excess air level to the point of some constraint, such as carbon monoxide formation, flame length, flame stability, and so on. Unfortunately, low-excess-air operation has proven to yield only moderate NOx reductions, if any.

Three technologies that have demonstrated their effectiveness in controlling NOx emissions are off-stoichiometric combustion. low-NOx burners, and combustion temperature reduction. The first two are applicable to all fuels, while the third is applicable only to natural gas and low-nitro-gen-content fuel oils.

Off-stoichiometric, or staged, combustion is achieved by modifying the primary combustion zone stoichiometry – that is, the air/fuel ratio. This may be accomplished operationally or by equipment modifications.

An operational technique known us burners-out-of-service (BOOS) involves terminating the fuel flow to selected burners while leaving the air registers open. The remaining burners operate fuel-rich, thereby limiting oxygen availability, lowering peak flame temperatures, and reducing NOx formation. The unreacted products combine with the air from the terminated-fuel burners to complete burnout before exiting the furnace. Figure 2 illustrates the effectiveness of this technique applied to electric utility boilers. Staged combustion can also be achieved by installing air-only ports, referred to as overfire air (OFA) ports, above the burner zone. redirecting a portion of the air from the burners to the OFA ports. A variation of this concept, lance air, consists of installing air tubes around the periphery of each burner to supply staged air.

BOOS, overfire air, and lance air achieve similar results. These techniques are generally applicable only to larger, multiple-burner, combustion devices.

Low-NOx burners are designed to achieve the staging effect internally. The air and fuel flow fields are partitioned and controlled to achieve the desired air/fuel ratio, which reduces NOx formation and results in complete burnout within the furnace. Low-NOx burners are applicable lo practically all combustion devices with circular burner designs.

Combustion temperature reduction is effective at reducing thermal N0x but not fuel NOx. One way to reduce the combustion temperature is to introduce a diluent. Flue gas recirculation (FGR) is one such technique.

FGR recirculates a portion of the flue gas leaving the combustion process back into the windbox. The recirculated flue gas, usually on the order of 10-20% of the combustion air provides sufficient dilution to decrease NOx emission. Figure 3 correlates the degree of emission reduction with the amount of flue gas recirculated.

On gas-fired units, emissions arc reduced well beyond the levels normally achievable with staged combustion control. In fact, FGR is probably the most effective and least troublesome system for NOx reduction for gas-fired combustors.

An advantage of FGR is that it can be used with most other combustion control methods. Many industrial low-NOx burner systems on the market today incorporate induced FGR. In these designs, a duct is installed between the stack and forced-draft inlet (suction). Flue gas products are recirculated through the forced-draft fan, thus eliminating the need for a separate fan.

Water injection is another method that works on the principle of combustion dilution, very similar to FGR. In addition to dilution, it reduces the combustion air temperature by absorbing the latent heat of vaporization of the water before the combustion air reaches the primary combustion zone.

Few full-scale retrofit or test trials of water injection have been performed. Until recently, water injection has not been used as a primary NOx control method on any combustion devices other than gas turbines because of the efficiency penalty resulting from the absorption of usable energy to evaporate the water. In some cases, water injection represents a viable option to consider when moderate NOx reductions are required to achieve compliance.

Reduction of the air preheat temperature is another viable technique for culling NOx emissions. This lowers peak flame temperatures, thereby reducing NOx formation. The efficiency penalty, however, may be substantial. A rule of thumb is a 1% efficiency loss for each 40º F reduction in preheat. In some cases this may be offset by adding or enlarging the existing economizer.

Post-Combustion Control

There are two technologies for controlling NOx emissions after formation in the combustion process – selective catalytic reduction (SCR) and selective noncatalytic reduction (SNCR). Both of these processes have seen very limited application in the U.S. for external combustion devices. In selective catalytic reduction, a gas mixture of ammonia with a carrier gas (typically compressed air) is injected upstream of a catalytic reactor operating at temperatures between 450º F and 750º F. NOx control efficiencies are typically in the 70-90% percent range, depending on the type of catalyst, the amount of ammonia injected, the initial NOx level, and the age of the catalyst.

The retrofit of SCR on existing combustion devices can be complex and costly. Apart from the ammonia storage, preparation, and control monitoring requirements, significant modifications to the convective pass ducts may be necessary.

In selective noncatalytic reduction, ammonia- or urea-based reagents are injected into the furnace exit region, where the flue gas is in the range of 1,700-2,000º F. The efficiency of this process depends on the temperature of the gas, the reagent mixing with the gas, the residence time within the temperature window, and the amount of reagent injected relative to the concentration of NOx present. The optimum gas temperature for die reaction is about 1,750°F; deviations from this temperature result in a lower NOx reduction efficiency. Application of SNCR, therefore, must be carefully assessed, as its effectiveness is very dependent on combustion device design and operation.

Technology Selection

As noted previously, selection of applicable NOx control technologies depends on a number of fuel, design, and operational factors. After identifying the applicable control technologies, an economic evaluation must be conducted to rank the technologies according to their cost effectiveness. Management can then select the optimum NOx control technology for the specific unit.

It should be noted that the efficiencies of NOx control technologies are not additive, but rather multiplicative. Efficiencies for existing combustion devices have been demonstrated in terms of percent reduction from baseline emissions level. This must be taken into account when considering combinations of technology.

Consider, for example, the following hypothetical case. Assume a baseline NOx emissions level of 100 ppmv and control technology efficiencies as follows: low-excess-air operation (LEA), 10%; low-NOx burners (LNB), 40%; and flue gas recirculation (FGR). 60%. The three controls are installed in the progressive order of LEA-LNB-FGR.

It should also he noted that combining same-principle technologies (for example, two types of staged combustion) would not provide a further significant NOx reduction than either of the combination, since they operate on the same principle.

It must be emphasized that virtually all of the available control technologies have the potential for adversely affecting the performance and/or operation of the unit. The operation data obtained during the NOx characterization testing, therefore, must be carefully evaluated in light of such potential impacts before selecting applicable control technologies. Operational limitations such as flame envelope, furnace pressure, forced-draft fan capacity, and the like must he identified for each potential technology and their corresponding impacts quantified. (Reference (4), for example, discusses these items, in detail.)

As anyone familiar with combustion processes knows, one technology does not fit all. Careful consideration must he used to select the appropriate, compatible control technology or technologies to ensure compliance at least cost with minimal impact on performance, operation, and capacity.

To evaluate if IFGR technology is suitable for your needs, or if you need additional information on ETEC, IFGR, Slip-Stream FGR and other NOx reduction technologies, please: visit us at http://www.etecinc.net or contact us at (281) 807-7007 or by email at: mailto:info@etecinc.net.

About Entropy Technology & Environmental Consultants (ETEC):
ETEC has pioneered advancements in Flue Gas Recirculation and offers turnkey installation for its IFGR and Slip Stream FGR Technologies. ETEC engineers have designed/installed over 30 FGR based systems. ETEC specializes in providing technical consulting services in the energy and environmental fields. ETEC engineers have experience in working with over 80 clients including, Reliant Energy, Entergy, LCRA, ExxonMobil, Lyondell-Citgo Refinery, BASF, etc.

History of Wireless Technologies

The development of Wireless technology owes it all to Michael Faraday – for discovering the principle of electromagnetic induction, to James Maxwell – for the Maxwell’s equations and to Guglielmo Marconi – for transmitting a wireless signal over one and a half miles. The sole purpose of Wi-Fi technology is wireless communication, through which information can be transferred between two or more points that are not connected by electrical conductors.

Wireless technologies were in use since the advent of radios, which use electromagnetic transmissions. Eventually, consumer electronics manufacturers started thinking about the possibilities of automating domestic microcontroller based devices. Timely and reliable relay of sensor data and controller commands were soon achieved, which led to the discovery of Wireless communications that we see everywhere now.

History

With the radios being used for wireless communications in the World war era, scientists and inventors started focusing on means to developing wireless phones. The radio soon became available for consumers and by mid 1980s, wireless phones or mobile phones started to appear. In the late 1990s, mobile phones gained huge prominence with over 50 million users worldwide. Then the concept of wireless internet and its possibilities were taken into account. Eventually, the wireless internet technology came into existence. This gave a boost to the growth of wireless technology, which comes in many forms at present.

Applications of Wireless Technology

The rapid progress of wireless technology led to the invention of mobile phones which uses radio waves to enable communication from different locations around the world. The application of wireless tech now ranges from wireless data communications in various fields including medicine, military etc to wireless energy transfers and wireless interface of computer peripherals. Point to point, point to multipoint, broadcasting etc are all possible and easy now with the use of wireless.

The most widely used Wi-Fi tech is the Bluetooth, which uses short wavelength radio transmissions to connect and communicate with other compatible electronic devices. This technology has grown to a phase where wireless keyboards, mouse and other peripherals can be connected to a computer. Wireless technologies are used:

· While traveling

· In Hotels

· In Business

· In Mobile and voice communication

· In Home networking

· In Navigation systems

· In Video game consoles

· In quality control systems

The greatest benefit of Wireless like Wi-Fi is the portability. For distances between devices where cabling isn’t an option, technologies like Wi-Fi can be used. Wi-fi communications can also provide as a backup communications link in case of network failures. One can even use wireless technologies to use data services even if he’s stuck in the middle of the ocean. However, Wireless still have slower response times compared to wired communications and interfaces. But this gap is getting narrower with each passing year.

Progress of Wireless technology

Wireless data communications now come in technologies namely Wi-Fi (a wireless local area network), cellular data services such as GPRS, EDGE and 3G, and mobile satellite communications. Point-to-point communication was a big deal decades ago. But now, point-to-multipoint and wireless data streaming to multiple wirelessly connected devices are possible. Personal network of computers can now be created using Wi-Fi, which also allows data services to be shared by multiple systems connected to the network.

Wireless technologies with faster speeds at 5 ghz and transmission capabilities were quite expensive when they were invented. But now, almost all mobile handsets and mini computers come with technologies like Wi-Fi and Bluetooth, although with variable data transfer speeds. Wireless have grown to such a level, where even mobile handsets can act as Wi-Fi hotspots, enabling other handsets or computers connected to a particular Wi-Fi hotspot enabled handset, can share cellular data services and other information. Streaming audio and video data wirelessly from the cell phone to a TV or computer is a walk in the park now.

Wireless Technology today, are robust, easy to use, and are portable as there are no cables involved. Apart from local area networks, even Metropolitan Area networks have started using Wi-fi tech (WMAN) and Customer Premises Equipment ( CPE ). Aviation, Transportation and the Military use wireless technologies in the form of Satellite communications. Without using interconnecting wires, wireless technologies are also used in transferring energy from a power source to a load, given that the load doesn’t have a built-in power source.

However, the fact that ‘nothing comes without a drawback’ or ‘nothing is perfect’ also applies to Wi-fi technology. Wireless technologies still have limitations, but scientists are currently working on it to remove the drawbacks and add to the benefits. The main limitation is that Wireless technologies such as Bluetooth and Wi-Fi can only be used in a limited area. The wireless signals can be broadcasted only to a particular distance. Devices outside of this range won’t be able to use Wi-Fi or Bluetooth. But the distance limitation is becoming reduced every year. There are also a few security limitations which hackers can exploit to cause harm in a wireless network. But Wireless technologies with better security features have started to come out. So this is not going to be a problem for long.

Speaking of progress, Wi-Fi technology is not limited to powerful computers and mobile handsets. The technology has progressed enough that Wi-Fi enabled TVs and microwaves have started appearing in the markets. The latest and the most talked-about wireless technology is the NFC or Near Field Communication, which lets users exchange data by tapping their devices together. Using wireless technologies are not as expensive as it used to be in the last decade. With each passing year, newer and better wireless technologies arrive with greater benefits.

Using Technology Lesson Plans In The Classroom

With technology becoming so much more accessible and important in the world, many teachers are turning to technology lesson plans to help in teaching their students. Whether using technology to introduce a new concept, review past material, or teach students to use the machines themselves, teachers are using technology more and more in the classroom.

Keeping up on technological advancements can be time consuming and difficult. Teachers do have resources that can help them, however. The internet has dozens of websites that offer teachers free help in preparing lessons. Some websites allow teachers to submit their own technology lesson plans. They can also find specific plans created by other teachers. These plans give details on which programs or software to use as well as how to present the information to students.

Teachers can use technology to teach any subject. From teaching students to read graphs to virtually visiting the sites of the Revolutionary War, teachers are finding ways to use technology to increase their students’ knowledge. Technology allows teachers to use a computer as a telescope to study the universe. The technological possibilities are constantly changing and improving to provide students with better learning situations.

Staying up-to-date on the latest trends in technology can be done by attending workshops. There are also online seminars available to give teachers the most current information. Many schools have a technology expert who is available to help teachers keep up with technology. These experts can also help teachers in forming their technology lesson plans.

Students generally enjoy using technology in the classroom. Teachers can capitalize on their students’ interest by giving them a variety of opportunities and mediums to use electronics for learning. This helps students stay engaged and involved in their own learning.

Teaching about technology in school has evolved from just teaching word processing and computer navigation skills. Teachers now use many forms of technology. Webcams, digital cameras, and online video presentations aid teachers in their teaching. Students can get involved as well. Group or individual projects can involve using technology to present what they have learned.

Technology gives students unmatched opportunities for learning and growth. From their own classrooms students can learn about the world virtually. Students can use webcams to communicate with students and professionals around the globe. Teachers can give students the opportunity to shadow a professional in a career of their choice all through technology.

As technology continues to change and improve, the use of technology in the classroom grows. Teachers can find help in making technology lesson plans which can improve the quality of their teaching.

Impact of New Technologies by 2030

According to the 2012 report, Global Trends 2030: Alternative Worlds, published the US National Intelligence Council, four technology arenas will shape global economic, social and military developments by 2030. They are information technologies, automation and manufacturing technologies, resource technologies, and health technologies.

Information technologies

Three technological developments with an IT focus have the power to change the way we will live, do business and protect ourselves before 2030.

1. Solutions for storage and processing large quantities of data, including “big data”, will provide increased opportunities for governments and commercial organizations to “know” their customers better. The technology is here but customers may object to collection of so much data. In any event, these solutions will likely herald a coming economic boom in North America.

2. Social networking technologies help individual users to form online social networks with other users. They are becoming part of the fabric of online existence, as leading services integrate social functions into everything else an individual might do online. Social networks enable useful as well as dangerous communications across diverse user groups and geopolitical boundaries.

3. Smart cities are urban environments that leverage information technology-based solutions to maximize citizens’ economic productivity and quality of life while minimizing resources consumption and environmental degradation.

Automation and manufacturing technologies

As manufacturing has gone global in the last two decades, a global ecosystem of manufacturers, suppliers, and logistics companies has formed. New manufacturing and automation technologies have the potential to change work patterns in both the developed and developing worlds.

1. Robotics is today in use in a range of civil and military applications. Over 1.2 million industrial robots are already in daily operations round the world and there are increasing applications for non-industrial robots. The US military has thousands of robots in battlefields, home robots vacuum homes and cut lawns, and hospital robots patrol corridors and distribute supplies. Their use will increase in the coming years, and with enhanced cognitive capabilities, robotics could be hugely disruptive to the current global supply chain system and the traditional job allocations along supply chains.

2. 3D printing (additive manufacturing) technologies allow a machine to build an object by adding one layer of material at a time. 3D printing is already in use to make models from plastics in sectors such as consumers products and the automobile and aerospace industries. By 2030, 3D printing could replace some conventional mass production, particularly for short production runs or where mass customization has high value.

3. Autonomous vehicles are mostly in use today in the military and for specific tasks e.g. in the mining industry. By 2030, autonomous vehicles could transform military operations, conflict resolution, transportation and geo-prospecting, while simultaneously presenting novel security risks that could be difficult to address. At the consumer level, Google has been testing for the past few years a driverless car.

Resource technologies

Technological advances will be required to accommodate increasing demand for resources owing to global population growth and economic advances in today’s underdeveloped countries. Such advances can affect the food, water and energy nexus by improving agricultural productivity through a broad range of technologies including precision farming and genetically modified crops for food and fuel. New resource technologies can also enhance water management through desalination and irrigation efficiency; and increase the availability of energy through enhanced oil and gas extraction and alternative energy sources such as solar and wind power, and bio-fuels. Widespread communication technologies will make the potential effect of these technologies on the environment, climate and health well known to the increasingly educated populations.

Health technologies

Two sets of health technologies are highlighted below.

1. Disease management will become more effective, more personalized and less costly through such new enabling technologies as diagnostic and pathogen-detection devices. For example, molecular diagnostic devices will provide rapid means of testing for both genetic and pathogenic diseases during surgeries. Readily available genetic testing will hasten disease diagnosis and help physicians decide on the optimal treatment for each patient. Advances in regenerative medicine almost certainly will parallel these developments in diagnostic and treatment protocols. Replacement organs such as kidneys and livers could be developed by 2030. These new disease management technologies will increase the longevity and quality of life of the world’s ageing populations.

2. Human augmentation technologies, ranging from implants and prosthetic and powered exoskeleton to brains enhancements, could allow civilian and military people to work more effectively, and in environments that were previously inaccessible. Elderly people may benefit from powered exoskeletons that assist wearers with simple walking and lifting activities, improving the health and quality of life for aging populations. Progress in human augmentation technologies will likely face moral and ethical challenges.