20 30 40 50 60 70 80 90 100

Figure 2.15 Minor species concentrations vs. oxidant (O2 + N2) composition, for an adiabatic equilibrium stoichiometric CH4 flame. (From Ref. 27. Courtesy of CRC Press.) The actual flame temperature is lower than the adiabatic equilibrium flame temperature due to imperfect combustion and radiation from the flame. The actual flame temperature is determined by how well the flame radiates its heat and how well the combustion system, including the load and the refractory walls, absorbs that...

1326 Forging

Forging is a metal-working process used to change the shape of a metal part by using compressive forces, often with the use of a die to obtain the desired shape. This can be done in either a batch or continuous process, depending on the original and final part shapes, the material temperature, and the material composition. Forging may be done when the part is hot or cold. Hot parts may require energy to heat them up if they started cold, but require lower compressive forces to do the shaping....

723 Regulations

Figure 7.7 shows CO emissions in the United States since 1970 for some of the applications considered in this book 4 . Eisinger et al. 5 note the dramatic reduction in CO ambient concentrations over the past few decades as a result of increased regulations. They believe this trend will continue into the future. Since controlling CO is generally relatively inexpensive, there is not a compelling reason to Figure 7.7 CO emissions in the United States since 1970 by application type. (From Ref. 4.)...

14211 Unit Melter

Figure 14.6 shows a schematic of a typical unit melter. The term unit melter'' is generally given to any fuel-fired glass-melting furnace that has no heat recovery device. Typically, the air fuel-fired unit melters are relatively small in size and are fired with two to 16 burners. Furnaces range in production from as large as 40 tons (36 metric tons) of glass per day to as small as 500 lb (230 kg) of glass per day. Larger air fuel unit melters are found in areas where fuel is extremely cheap....

2978

Source Ref. 23. (Courtesy of CRC Press.) Source Ref. 23. (Courtesy of CRC Press.) Figure 2.25 Adiabatic equilibrium flame temperature vs. fuel blend composition for stoichiometric air fuel flames at different air preheat temperatures. (From Ref. 27. Courtesy of CRC Press.) Figure 2.25 Adiabatic equilibrium flame temperature vs. fuel blend composition for stoichiometric air fuel flames at different air preheat temperatures. (From Ref. 27. Courtesy of CRC Press.) Figure 2.26 is a similar plot of...

153 Emissions

The Western States Petroleum Association (WSPA) and the American Petroleum Institute (API) worked with the California Air Resources Board (CARB) to develop air toxics emission factors for the petroleum industry 65 . Source data were provided Figure 15.33 Typical installation of multiple enclosed flares. (From Ref. 63. Courtesy of John Zink Co. LLC.) Figure 15.33 Typical installation of multiple enclosed flares. (From Ref. 63. Courtesy of John Zink Co. LLC.) Figure 15.34 Combination of enclosed...

932Environmental Damage

Another environmental concern of particulates is deposition. This can reduce the aesthetic appeal of structures and monuments. This can lead to frequent cleaning or painting, depending on how severe the deposition. If the particles are corrosive, or become corrosive on contact with water (e.g., rain) then further damage can result, including reducing the structural integrity of infrastructure like roads and bridges. Particles can damage vegetation and waterways if they are in high...

742 Environmental Concerns

There are a number of potential environmental problems with VOCs, which are somewhat dependent on the specific VOC. As described above, the main concern is Table 7.3 Types of VOCs Emitted from Fuel Oil and Gaseous Fuels Aromatic hydrocarbons Benzene Toluene o-Xylene m-Xylene p-Xylene Ethylbenzene Other VOCs Ketones, not specified VOCs, not specified the participation of VOCs in photochemical smog formation. Another concern is that some VOCs like benzene are carcinogenic while others may be...

1145 Measurement Techniques

EPA Method 23 discusses how to measure the emissions of dioxins and furans from stationary sources 93 . A sample is withdrawn isokinetically and collected on a glass fiber filter. The sample is then separated using high-resolution gas chromatography and measured by high-resolution mass spectrometry. A schematic of an approved gas-sampling train is shown in Fig. 5.42. The condenser and adsorbent trap must be specially designed for this application. Specific filters, reagents, adsorbents, and...

N

Figure 16.8 Oxygen-enhanced combustion overcomes mass-transfer limitations to increase solid waste and ash burnout left-hand figure is for air fuel combustion, right-hand figure is for oxy fuel combustion. CO spikes. In a fixed rotary kiln incinerator, pure O2 was injected at the firing end of the kiln. This virtually eliminated the CO spikes, which increased the processing rates by 25-40 , depending on the waste composition. Because of higher temperatures and more chemical reactivity, OEC can...

01

Figure 2.2 High-luminosity oil flame. (From Ref. 27. Courtesy of John Zink Co.) Figure 2.2 High-luminosity oil flame. (From Ref. 27. Courtesy of John Zink Co.) One of the advantages of liquid fuel oils is that they often make the flames much more luminous. Figure 2.2 shows an example of a high-luminosity oil flame from a burner used in the petrochemical industry. The higher luminosity is caused by the high solid carbon content which produces infrared radiation when heated. This can...

5413 Calculation

This is a simple and straightforward method for calculating the average exhaust gas flow rate, which is often of sufficient accuracy for many situations. As will be shown, this method uses a combination of measurements, assumptions, and calculations to determine the gas flow rate. There are also some variations of the technique as will be shown. However, in general, the technique involves calculating the gas flow rate based on either the measured input flow rates, on the measured stack gas...

131 Air Pollution Control

Crawford 33 has written an extensive work on the theory of the common techniques used to control air pollution 33 . Because of the rapid changes in this field, the book is somewhat out of date. The focus is more on controlling pollutants after they have been formed and not on minimizing their formation. Wark and Warner 34 have written a general-purpose book on air pollution that discusses the control of pollutants of interest here including particulates, carbon monoxide, SOx, and NOx.This book...

11 Industrial Combustion

Combustion has been the foundation of worldwide industrial development for the past 200 years 1 . Industry relies heavily on the combustion process as shown in Table 1.1. The major uses for combustion in industry are shown in Table 1.2. Hewitt et al. 2 have listed some of the common heating applications used in industry, as shown in Table 1.3. Typical industrial combustion applications can also be characterized by their temperature ranges, as shown in Fig. 1.1. As can be seen in Fig. 1.2, the...

152 Unburned Combustibles

A principle unburned combustible is CO, which is formed by the incomplete combustion of carbon-containing fuels. CO is a colorless, odorless gas that can cause asphyxiation and death in high enough concentrations. Formation of CO is normally easily prevented by proper control of the combustion process and is not typically a problem for the vast majority of industrial combustion applications. Over three-quarters of the ambient CO in the atmosphere comes from automobile emissions and only a small...

4434 Multiple Phases

In some combustion systems, multiple phases are present. The most notable involve the combustion of liquid and solid fuels. In the case of a liquid fuel, the fuel is atomized or vaporized into a fine spray which can then be combusted. In the case of a solid fuel, the fuel normally must be finely ground so that complete combustion can be achieved. In both cases, the modeling effort is significantly complicated. In the United States, the vast majority of industrial combustion processes use...

400850

Hydroprocessing Remove contaminating metals, sulfur, and nitrogen from the feedstock Hydrogen is added and reacted over a catalyst Less severe than hydrodesulfurization Removes metals, nitrogen, and sulfur from lighter feedstocks Hydrogen is added and reacted over a catalyst Combination of two hydrocarbons to produce a higher molecular weight hydrocarbon Heater used on the fractionator Low-octane naphthas are converted to high-octane, aromatic naphthas Feedstock is contacted with hydrogen over...

9644 Filters

Filters are a mechanical separation device used to remove particles from gas streams. The principle behind filters is simple the holes in the filter are large enough for gas to pass through but too small for particles to go through (although as discussed below sometimes even the particles could pass through the holes) hence, the particles get trapped on the surface of the filter. The filter is composed of any suitable porous material including granular or fibrous materials. The filter material...

74 Volatile Organic Compounds

Volatile organic compounds (VOCs) are liquids or solids that vaporize easily and contain organic carbon bonded to carbon, hydrogen, nitrogen, or sulfur but do not include carbonate carbon (e.g., CaCO3) nor carbide carbon (e.g., CaC2, CO, or CO2). VOCs are generally low molecular weight aliphatic and aromatic hydrocarbons like alcohols, ketones, esters, and aldehydes 11 . The U.S. EPA defines a volatile organic compound as ''any organic compound which participates in atmospheric photochemical...

4443Symmetry

There are many problems having some type of symmetry which can be used to reduce the number of computations needed to simulate a combustion system. One type of symmetry is where, for example, the left half of a furnace is a mirror image of the right half. In that case, only one of the halves needs to be modeled, with a symmetry boundary condition along the axis of symmetry in the middle of the furnace. Another type of symmetry is slice symmetry where only a single slice of a furnace is modeled...

8000

Figure 10.1 Threshold of hearing compared to the threshold of pain in humans. (From Ref. 42. Courtesy of John Zink Co., Tulsa, OK.) Figure 10.1 Threshold of hearing compared to the threshold of pain in humans. (From Ref. 42. Courtesy of John Zink Co., Tulsa, OK.) of hearing and pain for humans as a function of frequency and sound pressure level. These two curves nearly intersect at the lowest and highest frequencies. The threshold of pain is relatively flat at about 120 dB. Noise is a common...

5412 Direct Measurement

EPA Method 2A discusses the direct measurement of the gas volume flow rate through pipes and small ducts. These devices include, for example, positive displacement meters and turbine meters. This is a much simpler and faster technique than measuring multiple traverse points in the exhaust gas stack and then computing the flow rate based on several different types of measurements (pressure difference, gas temperature, barometric conditions, and moisture in the stack gases). Direct measuring...

Info

Because it is the function of the incinerator itself, rather than being an auxiliary process to control emissions. Pretreating the incoming waste materials generally involves removing chemicals that may be hazardous or difficult to burn without generating pollutants that may be more difficult to remove prior to exhausting into the atmosphere. One example is removing automotive batteries that contain lead, which is not destroyed during incineration but can be carried with the exhaust products...

103 Vibration

Harris 17 defines vibration as an oscillation wherein the quantity is a parameter that defines the motion of a mechanical system.'' Vibrations caused by combustion Figure 10.28 Ear muffs designed to be used with hard hats. Figure 10.28 Ear muffs designed to be used with hard hats. processes have been given many names including combustion-driven oscillations, combustion resonance, pulsations, and combustion hum to name a few. These combustion-induced vibrations can be even more difficult to...

425 Time Dependence

Another critical aspect of combustion modeling is whether or not the solution is time dependent. Nearly all industrial combustion processes are time dependent at small length scales due to turbulence. However, these processes are normally modeled as steady-state systems because of the limitations of the turbulent submodels, the large increase in computer time required to simulate transient combustion, and the lack of need for such detailed information in most industrial combustion systems.

3322 Heating Type

As described above for burners, combustors are often classified as operating by indirect or direct heating. An important consideration for the choice of the type of oven or dryer for the specific application depends on whether direct or indirect heating is needed 17 . In indirect heating, there is some type of intermediate heat-transfer medium between the flames and the load which keeps the combustion products separate from the load (see Fig. 3.33). One example is a muffle furnace where there...

3313Heat Recovery

When heat recovery is used in an industrial combustion process, it is an integral part of the system. The two most popular methods are regenerative and recuperative, which are discussed briefly below. The heat-recovery system is important in the design of the combustor as it determines the thermal efficiency of the process and the flame temperatures in the system. It also influences the heat-transfer modes as it may increase the both the radiation and convection because of higher flame...

4212 Vortex Methods

Most numerical approaches for solving fluid-flow problems use a Eulerian scheme with a fixed coordinate system that is discretized into small parts. One problem with this approach is that there may often be areas in the flow where the gradients are very high and require very fine discretization, while in nearby areas the gradients may be much lower and need much less discretization. To complicate this disparity further, these areas may be moving. Finite difference solution convergence problems...

6836 Reburning

Reburning is a technique similar to fuel staging but uses a different strategy. An example is methane reburn where some methane is injected into the exhaust gases, usually well after the primary combustion zone, where the gases are at a lower temperature. As previously shown in Fig. 6.28, fuel-rich conditions are not favorable to NOx. As the exhaust gases from the combustion process flow through this fuel-rich reducing zone, NOx is reduced back to N2. Any CO and other unburned fuels in the...

Example

Given Circular 5 ft external diameter duct with 6 in. of insulation inside the duct, located 30 ft downstream of the nearest disturbance and 10 ft upstream of the nearest disturbance no particulates in the gas stream. Table 5.1 Recommended Measurement Layout for Rectangular Cross-Sectional Area Ducts Table 5.1 Recommended Measurement Layout for Rectangular Cross-Sectional Area Ducts

1423 Emissions

Glass production is a significant source of emissions because of a variety of factors. The EPA estimates that approximately 99 of the total emissions from a glass plant come from the melting furnaces 4 . The materials used to produce glass are a major source of particulate emissions because of the fine nature of the sand and other batch materials. The raw materials can also be a source of lead emissions, for example, in the production of leaded glass. The incoming batch often contains niter,...

20 30 40 5 0 60 70 30 90 100

Figure 11.11 Available heat as a function of the oxygen content in the oxidizer where exhaust gases are at 2400 F (1600 K). convection through openings in the combustor. Ideally, these heat losses are minimized to maximize the thermal efficiency of the system. The available heat is a convenient way of showing trends related to thermal efficiency. Figure 11.11 shows how removing nitrogen from the combustion air can significantly increase the available heat in a combustion system. As the oxygen...

O

Temperature Decrease combustion intensity Boilers, furnaces. IC, gas turbines Boilers, furnaces flame zone furnaces cooling reduce residence time Direct suppression of thermal NOx mechanism Increased flame zone cooling yields lower peak temp. Increased flame zone cooling yields lower peak temp. Reduced air Water preheat injection, FGR Enlarged firebox, increased burner spacing Redesign heat transfer surfaces, firebox aerodynamics Ammonia injection Redesign possible on some units convective...

56 Continuous Monitoring

Depending on regulations and the size of the emission source, some industrial combustion processes may be required to have a continuous emissions monitoring system. For example, some air permits may be written in such a way as to limit emissions over some time interval, such as a 24-hr rolling average. Another common limit is that emissions of a particular pollutant may not exceed a given concentration at any time. There are many other variations as well. In order to determine whether a plant...

10262 Sound Transmission Mitigation

This technique involves mitigating the transmission of the sound from the source to the receiver. This can be done in a variety of ways. One rather simple but not always practical method is simply to increase the distance between the source and the receiver, which reduces the sound levels at the receiver. Another strategy is to put some type of barrier between the source and the receiver. For example, a concrete wall could be built around the source. People commonly plant trees and shrubs on...

4452 Finite Volume

The finite volume technique is probably the most popular in commercial codes, possibly because it has been used since the earliest days of commercial CFD codes. Figure 4.10 shows a typical two-dimensional grid for the finite volume method. This technique developed from a modification of the finite difference technique, in order to solve more complicated flow geometries 23 . In this method, finite volumes are used around each grid point to calculate the discretized fluid-flow equations, along...

134 Heat Treating

Heat treating involves the thermal treatment of metal to produce some type of enhanced performance characteristic. Typical material improvements include surface hardening, strengthening the part, relieving stresses, and improving ductility. Typical thermal treatments include annealing, brazing, carburizing, normalizing, sintering, and tempering. Annealing is a heat treatment used to remove internal stresses and to make a material less brittle by heating a part and then cooling it. This may be...

95 Measurement Techniques

EPA Method 5 is used to determine particulate emissions from stationary sources 13 . Method 5B refers to the determination of nonsulfuric acid particulate matter emissions from stationary sources. Method 5D concerns determining particulate matter emissions from positive pressure fabric filters, also known as baghouses, where this method has particular emphasis on the sample location. Method 5E describes the procedure for determining particulate emissions from fiberglass wool manufacturing....

References

Modeling Atmospheric Dispersion of Pollutants. In PN Cheremisinoff (ed.). Air Pollution Control and Design for Industry. New York Marcel Dekker, 1993. 2. EPA. 40 CFR 60 Standards of Performance for New Stationary Sources. Washington, DC U.S. Environmental Protection Agency, 2001. 4. AJ Wheeler, AR Ganji. Introduction to Engineering Experimentation. New York Prentice Hall, 1995. 5. GW Cobb. Introduction to Design and Analysis of Experiments. New York SpringerVerlag, 1998. 6. JP Holman....

12341 Recuperative Burners

Recuperative burners have an internal heat exchanger of some type where the exhaust gases from the combustion process are pulled through the burner to heat typically the incoming combustion air. An example of a recuperative burner is shown in Fig. 3.35. Unlike regenerative burners, recuperative burners are in continuous operation rather than cycling between heating and cooling. While the burner design is complicated by both the internal heat exchanger and by the temperature differences of the...

10223 Combustion Roar

Another source of noise in a combustion system comes from the burner and is sometimes referred to as combustion roar'' 27 . This noise is a combination of the gas flow through the burner nozzles and also from the combustion process itself. It is broadband noise (noise distributed over a wide range of frequencies with no pronounced peaks) generated by the combustion processes in the flame and can be a Figure 10.9 Shock vs. mixing noise. (Courtesy of John Zink Co., Tulsa, OK.) Figure 10.9 Shock...

20

Figure 11.1 Adiabatic equilibrium CO2 (wet basis) as a function of the hydrogen content in CH4 H2 or C3H8 H2 blends combusted with ambient air at an equivalence ratio of one. Figure 11.2 Adiabatic equilibrium CO2 (wet basis) as a function of the fuel preheat temperature for the combustion of CH4 or C3H8 with ambient air at an equivalence ratio of one. Figure 11.2 Adiabatic equilibrium CO2 (wet basis) as a function of the fuel preheat temperature for the combustion of CH4 or C3H8 with ambient...

1825Sensors and Analyzers

Advanced fast-reacting flame scanning may be necessary to adjust rapidly to changing operating conditions while minimizing emissions 3 . Robust emission sensors will be required to monitor quickly and reliably the effluents from combustion systems. Ruao et al. 10 describe a new technique for making in-flame NO measurements using a spectral ultraviolet visible imaging device. The device was tested in a small-scale laboratory furnace using a propane- or ethylene-fired swirl burner. Besides NOx,...

543 Particulates

EPA Method 5 is used to determine particulate emissions from stationary sources. Method 5B refers to the determination of nonsulfuric acid particulate matter emissions from stationary sources. Method 5D concerns determining particulate matter emissions from positive pressure fabric filters, also known as baghouses, where this method has particular emphasis on the sample location. Method 5E Figure 5.41 EPA Method 25 sampling train schematic for measuring volatile organic compounds. (From Ref....

14221 Container Glass

This segment includes glass used to make bottles, jars, and other similar containers used in packaging. Figure 14.16 shows a photograph of glass bottle making. Bottle glass plants are sometimes located directly on the site of the beverage (e.g., soda, wine, or beer) production. This segment has received a great deal of pressure from the plastics and aluminum industries. Increased emphasis on reducing pollution emissions has put on further pressure. The main quality concern in bottle production...

1844 Post Treatment Equipment

In most cases, it is preferable to prevent pollutant formation rather than clean up emissions after they have already been formed. Some pollution control technologies (e.g., scrubbers) may generate another, although more benign, pollutant themselves (sludge in some cases) that must also be treated. As with nearly all technologies, there is always a demand for cheaper, more efficient, smaller, easier-to-operate, lower maintenance, more durable, more flexible, retrofittable, more robust, etc.,...

Raph

Staged combustion, creating fuel-rich and fuel-lean zones Low operating cost, no capital requirement required for BOOS Provides internal staged cumbustion, thus reducing peak flame temperature and oxygen availability Up to 20-30 of the flue gas recirculated and mixed with the combustion air, thus decreasing peak flame temperatures. Injection of steam or water at the burner, which decreases flame temperature Air preheater modification to reduce preheat, thereby reducing flame temperature Low...

10321 Thermoacoustic Instability

Cammarata et al. 56 experimentally studied combustion instabilities in a lean premixed combustion system. These systems have the promise of low NOx emissions, but are more susceptible to instabilities because of constraints like preventing flashback and autoignition. While other studies have examined this phenomenon intrusively, the goal of their study was to study it nonintrusively with external microphones. The measurement technique may be applicable for controlling instabilities in...

3311Load Handling

A primary consideration for any combustor is the type of material that will be processed. One obvious factor of importance in handling the load and transporting it through the combustor is its physical state, whether it is a solid, liquid, or gas. Another factor is the transport properties of the load. For example, the solid may be granular or it might be in the form of a sheet (web) as shown in Fig. 3.31. Related to that is how the solid will be fed into the combustor. A granular solid could...

Stratification Layer

Figure 17.1 Continuous airless dryer. (From Ref. 2. Courtesy of Marcel Dekker.) elevation view of a Fourdrinier paper machine commonly used to make paper. The steam-heated cylinders in the drying section can be seen in more detail. Figure 17.4 shows a schematic of the Kraft process for handling the pulp and bark used to make the paper, including the treatment of the chemicals in the various reactors, which are considered in more detail below. Figure 17.5 shows pollution emissions from pulp and...

Other Industries

There are some lower temperature drying applications employing industrial combustion that are briefly considered in this chapter. These include the paper industry, printing and publishing, textile manufacturing, and food processing. Drying is defined as a process in which a wet solid is heated or contacted with a hot gas stream, causing some or all of the liquid wetting the solid to evaporate'' 1 . Kudra and Mujumdar have written a new book 2 on advanced drying technologies that cover a wide...

683 Combustion Modification

The second strategy for reducing NOx is known as combustion modification. Combustion modification prevents NOx from forming by changing the combustion process. There are numerous methods that have been used to modify the combustion process for low NOx. A popular method is low NOx burner design where specially designed burners generate less NOx than generated by previous burner technologies. Low NOx burners may incorporate a number of techniques for minimizing NOx including flue gas...

442 Potential Problems of CFD

As with most things, CFD modeling is not a panacea which can be used to solve all problems. As the saying goes, garbage in garbage out,'' or the results are only as good as the input data. It is incumbent on the user to input the relevant geometry and boundary conditions into the simulation and to select the appropriate submodels for a given problem. Because of the ease of use of the codes available today, it is possible for someone with little or no training in fluid dynamics, heat transfer,...

0 400 Soo 1200 1600 2000 2400 2800 3200 3600 4000

Figure 11.10 Equilibrium CO2 concentration (wet basis) as a function of the exhaust gas temperature for the combustion of CH4 or C3H8 with ambient air at an equivalence ratio of one. (1300 C), but then significantly decline for higher temperatures due to dissociation. Since the thermal efficiency declines as the exhaust gas temperature increases, most combustion systems operate at exhaust gas temperatures below 2400 F (1300 C) for the combustion of fuels like methane or propane with ambient air...

12342 Regenerative Burners

Regenerative burners incorporate some type of thermal storage medium inside the burner to increase the system fuel efficiency and in some cases the flame temperature for higher temperature applications. These burners differ from recuperative burners because they cycle between heating and cooling. For the first part of the cycle, half of the burners are firing while the other half of the burners are off. The exhaust gases from the first set of burners flow through the second set of burners. The...

153 Sulfur Oxides

Sulfur dioxide is a pollutant emission formed in industrial combustion applications during the firing of fuels, like heavy oil, that contain sulfur. Under typical combustion conditions, essentially all of the sulfur in the fuel is converted into SO2. The primary environmental concern with SOx emissions is the generation of acid rain when SO2 reacts with water in the atmosphere to form sulfuric acid. SOx emissions also contribute to particulate matter formation and can cause respiratory problems...

123 Effects On Pollution

There are a variety of factors that affect the emissions produced by burners. Some of the more important parameters are considered next including the fuel type, mixing effects, oxidizer, and heat recuperation. Figure 12.14 shows an example of a liquid fuel-fired flame. Figure 12.15 shows emissions from industrial combustion processes (not including power generation) firing fuel oil 14 . Figure 12.16 shows the effect of the nitrogen content in oil fuels on NOx emissions 15 . As can be seen, NOx...

725 Abatement Strategies

De Wit et al. 7 discuss the use of an oxidation catalyst (rhodium) for destroying CO emissions from exhaust gases, particularly in very fuel-lean combustion systems where the gas temperatures are low. The efficiency of the catalytic oxidation increases above 200 C (400 F) and typically operates in flue gas streams at temperatures between 400 and 500 C (750 -930 F). The higher the temperature, the higher the destruction efficiency. If the temperature is high enough, then no catalyst is needed....

444 Boundary and Initial Conditions

There are several types of boundary condition that may be applicable to a particular problem, depending on the specific conditions. For the sake of argument, a two-dimensional rectangular coordinate system (x, y) will be used for illustration purposes. A boundary condition of the first kind is where a variable is specified as a function along a given boundary where 0 is the variable and r is time. Examples include a constant-temperature wall t(x,y 0, r) 2000 F or a constant inlet velocity u(x...

Cooling Air

Figure 16.17 Schematic of a multiple-hearth sludge incinerator. (From Ref. 20.) cylinders where waste is fed into the bottom and both ash and flue gases exit at the top, as shown in Fig. 16.18. Fluidizing air is injected through the floor to enhance heat transfer, mass transfer, and combustion processes. A schematic of a sludge incineration process is shown in Fig. 16.19. The greatest challenge in sludge incineration is the large amount of energy required to evaporate the large quantity of...

163 Waste Materials

The waste fed into incinerators is generally classified into seven categories as shown in Table 16.1 18 . Theodore and Reynolds 19 recommend that the following data be collected to characterize properly the waste materials to be incinerated 19 Concentrations of carbon, hydrogen, oxygen, nitrogen, sulfur, halogens, phosphorus, ash, metals, salts, and moisture in the waste. Special characteristics such as toxicity, corrosiveness, thermal stability, and chemical stability. The U.S. EPA classifies...

Hf

Product of aluminium smelting causes reactive flurosis in cattle toxic pollutants. Common greenhouse gases of interest to industrial combustion processes include carbon dioxide, water vapor (H2O), and nitrous oxide (N2O) 9 . The issue of global warming is broad and diverse and covers a variety of topics including environmental, economics, political, regulatory legal, technology, and a host of scientific areas. Geyer 10 , a geophysicist, has edited a book that attempts to look at global warming...

33 Combustors

This section briefly introduces the combustors that are commonly used in industrial heating and melting applications. Dryers (see Fig. 3.30 for examples of continuous dryers) are commonly used in lower temperature applications. Heaters are used in Figure 3.29 Examples of porous ceramic and wire-mesh radiant burners. (From Ref. 15. Courtesy of Solaronics, Rochester, MI.) Figure 3.29 Examples of porous ceramic and wire-mesh radiant burners. (From Ref. 15. Courtesy of Solaronics, Rochester, MI.)...

10

As expected, the biased standard deviation is slightly less than the unbiased because of the larger denominator. Many calculators and spreadsheet software packages have standard deviation functions, although one must be careful to know which one is being used or how to get the desired standard deviation if both forms are available. For example, in Microsoft EXCEL , both functions are available. The n 1 or unbiased function is STDEV and the n or biased function is STDEVP. The unbiased standard...

1031 Sources

The primary sources of vibration related to industrial combustion systems are due to instability and thermoacoustic coupling of the combustion processes with the furnace. Here, it is assumed that vibration caused by, for example, combustion air blowers can be easily mitigated with proper vibration-dampening mounts and is, therefore, not considered here. Blevins 51 has written a book on flow-induced vibrations that could be present in the auxiliary equipment in a combustion system. Some of the...

342 Moving Substrate

In some applications, heaters and burners are used to heat or dry moving substrates or webs. An example is shown in Fig. 3.31. One common application is the use of gas-fired infrared (IR) burners to remove moisture from paper during the forming process 18 . These paper webs can travel at speeds over 300m sec (1000 ft sec) and are normally dried by traveling over and contacting steam-heated cylinders. IR heaters are often used selectively to dry certain portions of the web that may be wetter...

62 Formation Mechanisms

There are three generally accepted mechanisms for NOx production thermal, prompt, and fuel. These are discussed next. Hill and Smoot 11 have written a detailed article on modeling the chemistry of the formation and destruction of NOx Figure 6.2 Stationary sources of NOx emissions. (From Ref. 10.) Figure 6.2 Stationary sources of NOx emissions. (From Ref. 10.) in combustion systems, which includes information on formation mechanisms and simplifications used in modeling. Thermal NOx is formed by...

So 70 60 So 40 30 20 10

Figure 11.6 Equilibrium CO2 concentration (dry basis) as a function of the oxygen content in the oxidizer for the combustion of CH4 or C3H8 with the oxidizer in ambient conditions for a gas temperature of 2400 F (1300 C) at an equivalence ratio of one. Figure 11.6 Equilibrium CO2 concentration (dry basis) as a function of the oxygen content in the oxidizer for the combustion of CH4 or C3H8 with the oxidizer in ambient conditions for a gas temperature of 2400 F (1300 C) at an equivalence ratio...

Ic

High NOx pockets in the flame Flame cooling and dilution during delayed mix reduces peak temp. Reduces local hot stoichiometric regions in over all fuel lean combustion Flame cooling in low-O2, low-temp. primary zone reduces peak temp. Reduces exposure of fuel nitrogen intermediaries to O2 Volatile fuel N reduces to N2 to the absence of oxygen Volatile fuel N reduces to N2 in the absence of oxygen Burners out of Overfire service biased air ports, stratified burner firing charge Burner firebox...

14341 Dust Control

All cement and lime kilns are equipped with some type of particulate collection system to remove cement kiln dust. Baghouses are commonly used to control dust emissions in glass manufacturing processes 28 . Bandhu and Garg 56 have written a short book on pollution emissions and control in the cement industry. Much is devoted to the discussion of dust, which is one of the largest air pollution problems in the cement industry. Most of the dust, is generated prior to the actual calcination process...

81 Introduction

Elemental sulfur is relatively inert and harmless to human beings and in fact is needed in some quantity for life. It occurs naturally in the environment, mostly in the form of sulfates like CaSO4. However, sulfur oxides are recognized pollutants that are harmful to the environment. Sulfur oxides, usually referred to as SOx, include SO, S2O, SnO, SO2, SO3, and SO4 of which SO2 and SO3 are of particular importance in combustion processes 1 . Sulfur dioxide (SO2) tends to be preferred at higher...

5411 Pitot Tube

EPA Method 2 discusses how to determine the volumetric stack gas flow rate using an S-Type Pitot tube that includes a temperature sensor (see Fig. 5.14). The method only applies to flows that are not swirling or cyclonic. This method combines measurements and calculations to determine the gas flow rate. Specific guidelines are given for what materials should be used and what dimensions are critical. Each pitot probe must be calibrated with a known coefficient that should be engraved on the...

341 Process Tubes

In petrochemical production processes, process heaters are used to heat petroleum products up to operating temperatures. The fluids are transported through the process heaters in process tubes. These heaters often have a radiant section and a convection section. In the radiant section, radiation from burners heats the process tubes. In the convection section, the combustion products heat the tubes by flowing over the tubes. The design of the radiant section is especially important as flame...

1522 Reformers

As the name indicates, reformers are used to reformulate a material into another product. For example, a hydrogen reformer takes natural gas and reformulates it into hydrogen in a catalytic chemical process that involves a significant amount of heat. A sample set of reactions are given below for converting propane into hydrogen 49 C3H8 C2H4 + CH4 C2H4 + 2H2O 2CO + 4H2 CH4 + H2O CO + 3H2 CO + H2O CO2 + H2 The reformer is a direct-fired combustor containing numerous tubes, filled with catalyst,...

14214 Forehearth Furnace

Multiple forehearth furnaces (see Fig. 14.15) are located after the melting furnaces to prepare the glass for further processing. Many small burners line both sides of the forehearth to homogenize the temperature ofquantities ofglass much smaller than those of the upstream melting furnace. At the exit of the forehearth, the glass is ready to be formed into the desired shapes. Temperature uniformity is important to making good quality glass products. Nonuniformities can cause defects in the...

Thermal And Thermodynamic Properties

Thermal conductivity, Btu hr ft deg F Boiling point (sat 14.7 psia), deg F deg C (1 atm) Latent heat of fusion, Btu lb Latent heat of fusion, J kg Critical temperature, deg F Critical temperature, deg C Critical pressure, psia Critical pressure, MN m2 Critical volume, ft3 lb Critical volume, m3 kg Flammable (yes or no) Heat of combustion, Btu ft3 Heat of combustion, Btu lb Heat of combustion, kJ kg

E

3 -(------- -20 30 40 50 60 70 80 90 100 Figure 2.41 Normalized flue gas volume vs. oxidizer composition, for a stoichiometric CH4 flame. (From Ref. 23. Courtesy of CRC Press.) the oxidizer. A major change compared to air fuel combustion is the reduction in the flue gas volume. Figure 2.41 shows the exhaust gas flow rate, normalized to the fuel flow rate at standard temperature and pressure conditions (e.g., standard cubic feet per hour or SCFH), for the stoichiometric combustion of CH4 where...

40

Source Ref. 9. (Courtesy of CRC Press.) Source Ref. 9. (Courtesy of CRC Press.) The problem with the stoichiometry definition commonly used in industry (S2) is that the stoichiometry must be recalculated whenever the oxidizer composition changes and stoichiometric conditions change for each oxidizer composition. This is not a concern if air is always used as the oxidizer, which is the case for the vast majority of combustion processes. For example, consider the reaction of methane and pure...

Cd

Fundamental understanding Regulation instrumentation Theoretical limits of process efficiency Lack of selective process sensors Fuel efficiency and adaptability Inefficient heat recovery Modeling inadequeacies for combustion High cost of oxygen production for oxy-fuel firing Production of by products and contamination Broader compositional range Lack of cost-effective water treatment technology Technologies to control CO2 emissions Lack of measurement technology for emissions (low cost) Current...

45 Industrial Combustion Examples

The two major parts of industrial combustion problems include the burners and the combustors. Often these are modeled separately for a variety of reasons as previously discussed. Examples of modeling different types of burners and combus-tors are given next. There have been numerous papers on modeling industrial burners. A sampling of references are given for modeling such burners Radiant tube burners 246-248 Pulse combustion burner 252 Porous radiant burners 253-258 Industrial hydrogen sulfide...

90

Substituting oil coke for coal in a cement kiln can both reduce pollutant emissions, particularly SOx. The three predominant strategies used to minimize NOx emissions in these types of processes are process modifications, combustion modifications, and post-treatment. The first two minimize NOx formation while the third removes the NOx that has been formed. Depending on how much reduction is required, these strategies may all be used. Table 14.11 shows a comparison of typical NOx reductions for...

014 037 0068 0274

Based on tests using crude propylene containing 80 propylene and 20 propane. aMeasured as methane equivalent. bSoot in concentration values nonsmoking flares, 0 micrograms per liter (mg L) lightly smoking flares, 40 mg L average smoking, 177 mg L and heavily smoking flares, 274 mg L. Source Ref. 77. API 535 discusses CO emissions from refinery burners 16 . The point where the CO concentration in the exhaust gases approaches an asymptote is referred to as the CO breakpoint or CO breakthrough....

163 Variable Emission Regulations

Many approaches are being used to address the dynamic nature of pollutionemission regulations. The most common approach is simply to continue to rewrite the regulations as new technologies are developed to reduce emissions significantly compared to previous technologies. This process to rewrite the regulations can be expensive, tedious, lengthy, and fraught with problems. Regulators work in conjunction with users to determine what new levels make sense in the light of economics and technology....

11263 Combustion Modification

A major objective in combustion modification is to increase the overall thermal efficiency so that less fuel will need to be burned for a given level of production. Reducing fuel consumption simultaneously reduces CO2 emissions. The U.S. Department of Energy has funded major research projects designed to mitigate CO2 generation by combustion modification processes 24 . Most of the research is targeted at power generation, which produce the largest portion of CO2 emissions. One common method for...

11221 Fuel Composition and Temperature

There are many factors that affect the amount of CO2 produced during the combustion of fossil fuels in industrial processes. The global simplified reaction of a hydrocarbon with air can be written as follows CxHy + a(O2 + 3.76N2) xCO2 + 0.5yH2O + bO2 + 3.76aN2 + minor species where x and y are determined by the fuel, and the minimum a for complete combustion can be calculated from an O atom balance where b 0 In reality, there will be some excess O2 (b > 0) to ensure complete combustion. For...

1842 Combustion Modification

EPA has sponsored much research on reducing NOx 20 and SOx 21 emissions, which has led to a number of combustion modification technologies that have been applied in industry. One example of a new yet-to-be commercialized research and development project is a demonstration of the use of pulse combustion in waste incineration to reduce pollutant emissions 22 . The technology was applied in the Environmental Protection Agency's Incineration Research Facility rotary kiln system. The...

13311 Furnaces Used in Aluminum Melting

The general method for secondary aluminum production includes the following processes charging, melting, fluxing, demagging, degassing, alloying, skimming, and pouring. Charging involves adding pretreated scrap (to remove impurities, shredding, etc.) and flux to a small pool (referred to as a heel) of molten aluminum left behind from the previous heat. The flux materials combine with contaminants and cause them to float so that they can be easily skimmed off and removed. The materials floating...

1989

A spectral line-based weighted-sum-of-gray-gases model for arbitrary RTE solvers. J. Heat Transfer, Vol. 115, pp. 1004-1012, 1993. RG Siddall, N Selcuk. The Application of Flux Methods to Prediction of the Behavior of a Process Gas Heater. In Heat Transfer in Flames, ed. NH Afgan, JM Beer. Washington, DC Scripta Book Company, Chap. 11, pp. 191-200, 1974. LD Cloutman, L Brookshaw. Numerical Simulation of Radiative Heat Loss in an Experimental Burner. Lawrence Livermore...

1323 Ladle Preheating

Another major use for burners in the steel industry's melt shops is for ladle preheating, as shown schematically in Fig. 13.11 22 . Figure 13.12 23 shows a ladle that is used to transport molten metal in steel mills from the melting furnace to the casting station. Figure 13.13 shows a photograph of a ladle preheater in use. Ladles are refractory-lined cylindrical vessels closed at one end. The molten metal is poured into the top and then the ladle is usually transported via an overhead crane...

14212 Recuperative Melter

Figure 14.10 shows a schematic of a typical recuperative melter. A recuperative melter is a unit melter equipped with a recuperator. Typically, the recuperator is a metallic shell and tube style heat exchanger that preheats the combustion air to 1000 -1400 F (540 -760 C). The furnace is fired with four to 20 individual burners. These furnaces range in size from as large as 280 tons (250 metric tons) per day of glass to as small as 20 tons (18 metric tons) per day of glass. These furnaces are...

43 Simplified Models

Wilson 90 presents a new and more efficient technique for simulating the first-order dependence of a flame in a furnace. The technique is called the moving-boundary flame model. Dynamic state variables are created to keep track of the size of the flame in the furnace. The technique is claimed to be a considerable improvement over point reactor models, but is not intended to replace detailed multidimensional CFD models. Its accuracy depends on data from either experimental results or from more...

91

AReduction efficiencies for ND or MD SNCR are equal. MD mechanical draft, ND natural draft, LNB low NOx burner, ULNB ultralow NOx burner, SNCR selective noncatalytic reduction, SCR selective catalytic reduction, FCR flue gas recirculation. aReduction efficiencies for ND or MD SNCR are equal. MD mechanical draft, ND natural draft, LNB low NOx burner, ULNB ultralow NOx burner, SNCR selective noncatalytic reduction, SCR selective catalytic reduction, FCR flue gas recirculation. The fourth type of...

2400

0 200 400 600 800 1000 1200 1400 1600 1800 2000 Air Preheat Temperature ( F) Figure 2.30 Adiabatic equilibrium flame temperature vs. air preheat temperature for stoichiometric air H2, air CH4, and air C3H8 flames. (From Ref. 27. Courtesy of CRC Press.) Figure 2.31 Adiabatic equilibrium flame temperature vs. fuel preheat temperature for stoichiometric air H2, air CH4, and air C3H8 flames. (From Ref. 27. Courtesy of CRC Press.) Figure 2.31 Adiabatic equilibrium flame temperature vs. fuel preheat...

1711 Black Liquor Recovery Boilers

A flow schematic of the Kraft process is shown in Fig. 17.7 8 . It produces a strong, dark-colored fiber that is made from wood chips in either a batch or continuous digester, under pressure, in the presence of a cooking liquor 9 . The spent chemicals from the process are called black liquor, which is a highly viscous liquid waste containing inorganic cooking chemicals and organic materials such as lignin, aliphatic acids, and extractives. It is a by-product of the chemical pulping process....

452 Combustor Modeling

Numerous papers have been presented over the past few decades on modeling of industrial combustors. Some of the earliest work was done at Imperial College (U.K.) 2,268,269 . A sampling of references are given for modeling industrial combustors General combustors and boilers 270-285 Pulse combustion system 286-289 Aluminum reverberatory furnaces (see Fig. 4.15) 263,297 Metal reheat furnaces 47,298-302 Radiant tube batch furnace 303 Flash smelting furnaces 304,305 Cokeless natural gas-fired...

114 Dioxins And Furans

This class of pollutants includes the carbon-hydrogen-oxygen-halogen compounds, chemically classified as halogenated aromatic hydrocarbons, and has received considerable attention from both the general public and from regulatory agencies because of the potential health hazards associated with them. Dioxins generally refer to compounds that are structurally and chemically related to chlorinated congeners (members of the same chemical family) Polychlorinated dibenzo-para-dioxins (PCDDs)...

441 Increasing Popularity of CFD

Computational fluid dynamics is a numerical tool for simulating the complicated fluid flow, heat transfer, and chemical reactions in a combustor. This tool has been gaining in popularity in recent years because of a number of factors. One obvious change is the dramatic increase in computer power that is available at a cost that is affordable for virtually all businesses. Each new generation of computer hardware continues to have more speed and more memory at a lower cost. The personal computers...

13312 Oxygen Enhanced Aluminum Production

Conventional practice is to use air fuel burners in these rotary furnaces. The concept of using an oxygen fuel burner within an air fuel burner provides the aluminum melter with the flexibility of using either burner, or a combination of both burners (see Fig. 13.31). This innovative approach has proved to be very successful in the aluminum industry 67 . This differs considerably from both conventional oxygen-enriched techniques and the oxy fuel burners typically used for melting in the metals...

Ch

Figure 12.29 Operating regime for lean premix flames. produces low NOx emissions. Figure 12.32 shows that burner operating in a hot furnace. Figure 12.33 shows that flue furnace gas recirculation reduces NOx in premix flames. Figure 12.34 shows NOx emissions for diffusion and premix flames with and without flue furnace gas recirculation. It also shows one operating scheme where the primary combustion zone is fuel-lean premixed, the secondary zone is fuel-rich premixed, and the overall operation...

Multimode Heat Transfer And Fluid Dynamics

Figure 16.1 Fundamental processes in rotary kiln incinerators. (From Ref. 5. Courtesy of CRC Press.) recycling. For example, plastics, aluminum cans, and glass products may be selectively removed from waste materials so that they can be recycled. This is very beneficial to the incineration process because the aluminum and glass products are an additional heat load and not an additional source of fuel. Plastics can burn but they can also produce some toxic pollutants like dioxins and furans. A...