ACERC
Abstracts - 1991 |
ACERC
Abstracts - 1991 |
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Thrust Area 3: Pollutant Formation/Control and Waste Incineration |
Larsen, F.S.; McClennen,
W.H.; Deng, X.-X.; Silcox, G.D. and Allison, K.
Combustion Science and Technology, 1991 (in press). Funded by Weyerhaeuser
Corp. and ACERC.
Hydrocarbon and formaldehyde emissions from the combustion of pulverized wood waste were measured in 100 kW, cylindrical combustion chamber measuring 0.61 by 0.61 m. The wood was pneumatically conveyed to the burner and natural gas was used as an auxiliary fuel. The wood was screened prior to feeding so that its size distribution was representative of the suspension phase of a stoker boiler. Chamber wall and gas temperatures ranged from 920 to 1200 K and oxygen concentrations ranged from 2 to 9 percent, dry. Two types of waste were studied, plain wood and wood that was impregnated with a phenol-formaldehyde resin. The latter was a by-product of particleboard production. In general, the emissions of products of incomplete combustion (PICs) from the resinated waste were higher than those produced by plain wood. This may have been due to three factors: 1) the resinated wood was slightly wetter than the plain wood (6-9 percent by weight vs. 3 percent), 2) there was a difference in particle size distribution between the two materials as received, the resinated wood being larger, and 3) the resin may have had an effect on the emissions. Ultimate analyses of the two wastes showed no significant differences, other than moisture, in composition. At temperatures above 1200 K, total hydrocarbon emissions were roughly 10 to 29 ppm and formaldehyde emissions were less than the detection limit of 1 ppm. Typical waste wood boiler temperatures are roughly 1600 K. Hence, unless there are cool, poorly mixed regions in the full-scale facility, hydrocarbon and formaldehyde emissions should not be significant. However, the emissions from burning the two different types of wood would probably be different if all operating parameters in the wood-fired boiler are held constant.
McClennen, W.H.; Sheya,
S.A.N.; Arnold, N.S.; Meuzelaar, H.L.C.; Deng, X.-X.; Larsen, F.S. and Silcox,
G.D.
Combustion Science and Technology, 1991 (in press). Funded by ACERC.
This paper describes a method for on-line gas chromatography/mass spectrometry (GC/MS) of formaldehyde in combustion gases. The method uses a recently developed vapor-sampling inlet to monitor the concentration of formaldehyde and other products of incomplete combustion (PICs) from the burning of plain and phenol-formaldehyde resin treated wood chips. Other PICs that were simultaneously monitored included ketene, propylene, propyne and acetaldehyde. The direct analysis method has detection limits of less than 1 ppm for the reactive formaldehyde and excellent selectivity for determinations in the complex mixtures of combustion products. The rapid sampling technique allows monitoring of transient events of only a few minutes or less duration. Examples of the technique include the detection of sample line problems and the comparison of PIC concentrations from different points in the combustion exhaust stream.
Lindgren, E.R.; Pershing,
D.W.; Kirchgessner, D.A. and Drehmel, D.C.
Environmental Science and Technology, 1991 (in press). Funded by Environmental
Protection Agency.
A refractory-lined, natural gas furnace was used to study the fuel rich sulfur capture reactions of calcium sorbents under typical combustion conditions. The fuel rich sulfur species hydrogen sulfide (H2S) and carbonyl sulfide (COS) were monitored in a nearly continuous fashion using a gas chromatograph equipped with a flame photometric detector and an automatic sampling system which sampled every 30 seconds. Below the fuel rich zone, 25 percent excess air was added, and the ultimate fuel lean capture was simultaneously measured using a continuous sulfur dioxide (SO2) monitor. Under fuel rich conditions high levels of sulfur capture were obtained, and calcium utilization increased with sulfur concentration. The ultimate lean capture was found to be weakly dependent on sulfur concentration and independent of the sulfur capture level obtained in the fuel rich zone.
Lester, T.W.; Cundy, V.A.;
Sterling, A.M.; Montestruc, A.N.; Jakway, A.J.; Lu, C.; Leger, C.B.; Pershing
D.W.; Lighty, J.S.; Silcox, G.D. and Owens, W.D.
Environmental Science Technology, 25:1142-1152, 1991. Funded by Environmental
Protection Agency, Louisiana State University/Hazardous Waste Research Center
and ACERC.
A comparison is made, for the first time, between the evolution of hydrocarbons from clay sorbent beds in a field-scale rotary kiln incinerator and in a pilot-scale rotary kiln simulator. To relate the data from the different sized units, due allowance is made for bed dynamical similitude, bed geometrical factors, and bed heat-up. To minimize the effects of disturbances caused by foreign matter in the field scale bed and differences in loading techniques, the rate of evolution is characterized by an "evolution interval" defined as the time required for the middle 80% of the ultimate containment evolution to occur. A comparison of evolution intervals with reciprocal bed temperature reveals that the data are consistent with an analysis that assumes a uniform bed temperature (at any instant of time) and desorption controlled evolution rate. Furthermore, the evolution intervals scale inversely with a modified Froude Number, which characterizes bed dynamics. The success in comparing field and simulator results indicates that pilot scale rotary kilns may be used to simulate certain features of industrial-scale units if dynamical, geometrical and thermal parameters are matched appropriately.
Owens, W.D.; Silcox, G.D.;
Lighty, J.S.; Deng, X.-X.; Pershing D.W.; Cundy, V.A.; Leger, C.B. and Jakway,
A.J.
Combustion and Flame, 86:101-114, 1991. Funded by Gas Research Institute,
ACERC and Louisiana State University/Hazardous Waste Research Center.
A comprehensive heat-transfer model and associated simplified scaling laws are developed and verified using a pilot-scale, directly fired rotary kiln with a slumping bed of dry or wet, 6-mm clay sorbent particles. The kiln operating conditions examined include: rotation rate (0.1 to 0.9 rpm), percent fill fraction (3-8), feed moisture content (0-20 wt.%), and inner-wall temperature (190º to 790ºC). The model is used to determine the relative importance of several heat-transfer mechanisms including radiation, gas-to-solid convection, and wall-to-solid convection. Simple scaling laws are also developed for water vaporization. Generally good agreement is obtained between theory and experiment without adjusting any model parameters. Further, the simplified scaling laws provide a reasonable estimate of the pilot scale performance. The key conclusions of this study for kilns at the conditions examined are (1) water exerts a profound effect on the solids thermal profile, (2) simple geometrical scaling is not sufficient, (3) the assumption of a well mixed (radially isothermal) solids bed for the heat transfer analysis is appropriate, (4) a dimensionless group, which is a function of temperature, can be defined giving the relative importance of radiative and convective modes of heat transfer, and (5) moisture vaporization rates can be roughly approximated by assuming that the water vaporizes at the boiling point at a rate controlled by the rate of heat transfer to the bed. The implications of the scaling laws for scale-up and kiln design are also examined.
Arnold, N.S.; McClennen,
W.H. and Meuzelaar, H.L.C.
Analytical Chemistry, 63:299-304, 1991. Funded by ACERC.
A number of methods are currently used for atmospheric vapor and gas sampling with mass spectrometric detection and identification. Direct mass spectrometry (MS) sample introduction methods include fixed molecular tasks, atmospheric pressure ionization, trap and desorb, and membrane separation, while gas chromatography/mass spectrometry (GC/MS) methods employ trap and desorb, direct bubbler solvent injection, sample loops, and pressurized gas plug introduction. Approaches vary depending upon whether MS, tandem MS, or GC/MS analyses are desired. Direct MS and tandem MS analyses typically give quick response times and high repetition rates but are often sensitive to interferents, including atmospheric constituents, while GC/MS analyses offer greater specificity but with typically lower results.
Meuzelaar, H.L.C.; Kim,
M.-G.; Arnold, N.S.; Kalousek, P. and Snyder, A.P.
US Army Research Office Workshop on Spectrometry and Spectroscopy for Biologicals,
Cashiers, NC, 1991. Funded by US Army/Chemical Research Development and Engineering
Center and US Department of Defense/Army Research Office.
The capabilities of ion mobility spectrometry (IMS) with regard to the detection and identification of chemical warfare agents are widely recognized. Tens of thousands of IMS based CAM® (Chemical Agent Monitor) systems manufactured by Graseby Ionics (Watford, U.K.) are currently in use by NATO forces, including US Army Marine Corps.
The hand-held, battery powered CAM draws approx. 500 ml. min-1 of ambient air over a heated silicone rubber membrane covering the entrance to the ionization chamber (a Ni-63 source) and the IMS drift tube region both of which are being operated slightly below ambient pressure. A Faraday cup detector registers the arrival time of mobile ion species traversing the drift tube at different velocities after being admitted into the drift tube region by gating pulses at 20 msec intervals. Typical drift times ("mobilities") of ion species representing volatile organic compounds are in the 5-10 msec range. The CAM can be operated in either positive or negative ion detection mode (switch selectable).
In spite of the successful development and application of the CAM for detecting chemical warfare agents, several remaining shortcomings inherent to IMS based detection devices (e.g., limited ability to distinguish between individual components in complex mixtures as well as low dynamic range and lack of linear response), seriously hamper its application as a quantitative detection tool. Moreover, only organic species that readily pass through the silicone rubber membrane can be detected. This prevents the use of the CAM for detection of nonvolatile materials such as most biological warfare agents.
Arnold, N.S.; Meuzelaar,
H.L.C.; Dworzanski, J.P.; Cole, P.C. and Snyder, A.P.
US Army Chemical Research Development and Engineering Center Scientific Conference
on Chemical Defense Research, Arberdeen Proving Grounds, MD, November 1991.
Funded by US Department of Defense/Army Research Office.
The feasibility of telemetry based, drone-portable IMS (ion mobility spectrometry) and GC/IMS (gas chromatography/-ion mobility spectrometry) for real-time detection and monitoring of atmospheric concentrations of target vapors in otherwise inaccessible locations has been demonstrated using primarily "off the shelf" technology. The test configuration involved a Graseby Ionics CAM (Chemical Agent Monitor) with an ASP type PC interface, a Compaq 386 mother-board with 1 Mbyte RAM, two H-Cubed Corp. and Tekk Corp. digital radio transmitter and receiver sets, CoSession (Triton Technology) communications software and a remote, 386 level computer workstation. On-board system components weigh <15 lbs and use <30W of battery power. Preliminary test results indicate the feasibility of transmitting ion mobility data at up to 9600 baud, corresponding to approximately 20 spectra per minute. Typical range of the tested transceiver system is 1-2 miles. Potential applications include military or law enforcement operations as well as environmental and industrial screening or monitoring.
Arnold, N.S.; Urban, D.T.;
Watteyne, R.L.; Cole, P.C. and Meuzelaar, H.L.C.
Proceedings of the 39th Annual ASMS Conference on Mass Spectrometry and Allied
Topics, 671-672, Nashville, TN, May 1991. Funded by US Department of Defense
and ACERC.
In order to protect and inform personnel involved in monitoring, containment and remediation of hazardous volatiles materials, it is important that exposure to such materials be limited and that personnel working in such environments have sensitive and easily handled tools that do not limit mobility or vision. In order to meet these requirements a man-portable GC/MS system described previously has been modified to meet four objectives: (1) to allow remote instrument operation via a serial data transfer protocol compatible with broadband radio telemetry; (2) to reduce system size for placement in a single backpack or in a small, unmanned reconnaissance plane (drone); (3) to reduce system weight under 50 lbs for worker mobility in man-portable mode and to meet payload requirements for drone aircraft; (4) to increase pumping speed for greater sample throughput and lower detection limits.
Eddings, E.G. and Lighty,
J.S.
Western States Section/The Combustion Institute, Los Angeles, CA, October
1991. Funded by National Science Foundation.
Metal vaporization experiments were carried out in a bench-scale, Differential-Bed Reactor to identify possible inconsistencies between experimental behavior and predictions based on equilibrium considerations. It was found that, under the conditions investigated, the equilibrium model accurately reflected the behavior of Cr, Ni, and Zn, but there was disagreement between the model and the experimental behavior of Pb and Cu. Pb predictions were improved by including information about elements associated with the particular species of Pb present on the waste and by omitting volatile PbCl4 from the calculations.
Detailed experiments of Pb behavior exhibited a strong binding effect of the solid substrate at low concentrations of PbCl2 preventing volatile behavior at temperatures expected to promote vaporization. A surface effect was also noted with experiments involving Cu; however, the effect was to actually enhance the vaporization of CuSO4 at low concentrations in the solid substrate relative to its behavior at high concentrations. The combined effects resulted in overprediction of Pb volatility and underprediction of Cu volatility by the equilibrium model.
Boardman, R.D.; Eatough,
C.N.; Germane, G.J. and Smoot, L.D.
First International Conference on Combustion Technologies For a Clean Environment,
Vilamoura, Portugal, September 1991. Funded by Morgantown Energy Technology
Center through subcontract from Advanced Fuel Research Co.
A combined thermal and fuel nitric oxide submodel has recently been added to a generalized, 2-dimensional pulverized coal gasification and combustion model (PCGC-2). This model is applicable to reacting and non-reacting gaseous and particle-laden flows. The thermal NO model is based on the extended Zel'dovich mechanism. To perform an evaluation of the NOx submodel, combustion measurements of gas velocities, temperatures, and species concentrations were made in a laboratory-scale, experimental reactor with a 150 kW natural gas flame at an equivalence ratio of 1.05 and a secondary-air swirl number of 1.5. Combustion measurements of velocities and major species concentrations show generally good agreement with predicted values. Gas temperature measurements closely match predictions in the recovery region but fail to show predicted high temperature in the annular region. This study provides an evaluation of a comprehensive combustion model and the NOx submodel that can be useful as a design tool to provide pollutant formation trends in applied systems as combustion parameters are varied.
Pershing, D.W.; Lighty,
J.S.; Silcox, G.D.; Heap, M.P. and Owens, W.D.
First International Conference on Combustion Technologies for a Clean Environment,
Vilamoura, Portugal, September 1991. Funded by the National Science Foundation,
Environmental Protection Agency, Gas Research Institute and ACERC.
Rotary kilns are used to dispose of many solid wastes and sludges and to thermally treat contaminated soils. In this communication the fates of hydrocarbon and metal species are examined with a view toward optimization of new kiln designs and maximizing existing unit throughout while minimizing pollutant emissions. Initially, process fundamentals are considered to characterize the controlling phenomena. Pilot- and large-scale data are then examined to define practical system complexities. Finally, techniques for data scale-up and performance prediction are summarized. Temperature is clearly the most important parameter with respect to the fate of both metal and hydrocarbon species; hence, heat transfer is often rate limiting. High temperatures favor hydrocarbon evolution, but can also enhance the formation of toxic metal fumes. Both the solid composition and the moisture content can significantly influence the time at temperature required for hydrocarbon destruction and metal vaporization.
Improving bed mixing helps contaminant release but can also aggravate puffing tendencies with batch charging. Full-scale performance predictions currently require a combination of small-scale data and computer modeling. Future work needs to focus on verification of large-scale predictions for complex mixtures and sludges so that expensive trial burns can be minimized.
McClennen, W.H.; Arnold,
N.S.; Meuzelaar, H.L.C.; Ludwig, E. and Lighty, J.S.
2nd International Symposium on Field Screening Methods for Hazardous Wastes
and Toxic Chemicals, Las Vegas, NV, February 1991. Funded by ACERC, Environmental
Protection Agency, Finnigan MAT Corp., US Army Chemical Research Development
and Engineering Center and Utah Power and Light.
This paper presents examples of the use of a mobile Ion Trap Mass Spectrometer (ITMS, Finnigan MAT) for on-site environmental screening and monitoring of vapors by gas chromatography/mass spectrometry (GC/MS). The instrument is built around a miniaturized ITMS system, with a novel direct vapor-sampling inlet and coupled to a high-speed transfer line GC column (short capillary column with fixed pressure drop). The column is temperature controlled inside the standard ion trap transfer line housing. This provides for high-speed analyses at 10-60 s intervals using an automated sampling system constructed with only inert materials in the sample path.
Specific laboratory and field applications exemplify key characteristics of the system including sensitivity, specificity for a broad range of compounds, ruggedness for field-testing in harsh environments, and general speed for field-testing in harsh environments, and general speed and versatility of the analytical technique. The system has been calibrated for alkylbenzenes at concentrations as low as 4 ppb in air and used to monitor these compounds in an office space. Both the MINITMASS and a simpler Ion Trap Detector (ITD) based system have been used to monitor organic vapors from acetone through 5 ring polycyclic aromatic hydrocarbons produced in laboratory scale reactors for studying the thermal desorption and incinerations of hazardous wastes. The ruggedness of the MINITMASS system has been demonstrated by vapor sampling in the Utah summer desert and at a 600 MW coal fired power plant. Finally, the analysis speed and versatility are described for vapor monitoring of volatile organic compounds at an EPA national priority list waste site.
Meuzelaar, H.L.C.; Urban,
D.T. and Arnold, N.S.
2nd International Symposium on Field Screening Methods for Hazardous Wastes
and Toxic Chemicals, Las Vegas, NV, February 1991. Funded by Environmental
Protection Agency, US Department of Defense, Finnigan MAT Corp., Utah Power
and Light, Hewlett Packard Corp. and ACERC.
In situations involving special military or law enforcement operations, as well as industrial accidents or natural disaster, mobile laboratories may be of little use because of limited site access restrictions due to contamination or terrain constraints. Under such conditions man-portable analytical instruments may offer the only acceptable means of carrying out on-site analyses. The current prototype weighs approx 70-75 lbs and uses 150-200 W of battery power. The mass spectrometer and computer are carried in front of the operator by means of a shoulder harness whereas battery pack, carrier gas supply and roughing vacuum system are carried as a backpack. Air samples can be analyzed using a special automated air-sampling inlet. The man-portable GC/MS system is supported by a vehicle transportation "docking station."
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