We have expertise with contamination issues related to both air and water. Our forte is to add key phenomenology to classical methods to enable solution to real-life problems (such as incorporation of chemical reactions into classical atmospheric dispersion models; and addition of agglomerate structure characterization capability to standard light scattering based particle sizing methods). Our clients in this domain include government agencies (Air Force, DTRA, Army, Navy, DOE, EPA), national labs, environmental services companies, and chemical companies. We provide software, hardware/instrumentation, specialized testing, training and expert witness services. We have assisted companies with safety assessment and preparation of Risk Management Plans (RMP).
- Atmospheric Dispersion of Reactive Agents (ADORA)
- Fate and transport of chemical/biological contaminants in drinking water distribution networks (H2OFate)
- Toxic releases from various types of fires and explosions
- Material properties of various hazardous chemicals (PC-Chris)
- Reaction kinetics databases
- Case Studies
- Hazard contours due to release of boron trichloride
- Emission due to combustion of toxic waste (Teflon-oil)
- Incineration of Volatile Organic Compounds
- Dust Emission and Deposition from a Cement Plant
- Smoke Emission from Cotton Seed Processing Plant
- Numerical Simulation of Turbulent Buoyant/Heavy Cloud Motion
- Evaluation of Afterburner
- Catalyst of NO-CO Reaction in Exhaust
- Warehouse Fire of Magnesium/Teflon/Fuel Oil Mixture
- Air pollution control
- Odor Control
- Explosion Hazards of Petrochemical Plants
- Explosions of Accidentally Released Fuels TNT Yields
- Modeling of deflagration of Unconfined Propane For an Oil Co.
- Near-source model for chemically reacting radionuclides
- Off-site Consequence Analysis (OCA) for chemical process industry
- Kinetics of Water Vapor Reactions with Hazardous Chemical
- UF6 Dispersion Modeling
- PSD and NAAQS Modeling Analysis
- Vulnerability Assessment of Drinking Water Systems
Halogenated inorganic chemicals such as boron trichloride and titanium tetrachloride have a strong tendency to react with moisture.Other models neglect such reactions and therefore predict unrealistic hazard distances. ADORA, on the other hand, accounts for such chemical reactions with the entrained moisture during atmospheric dispersion.
Boron trichloride is initially heavier than air at ambient temperatures. In the absence of chemical reactions with ambient moisture, the BCl3 cloud hugs the ground over large distances. Chemical reactions with moisture result in the formation of hydrogen chloride (HCl) and the heat released due to chemical reactions lifts the cloud off the ground reducing the ground level hazard.
(a) No reaction: Contour of Reactant BCl3
(b) With reaction: Contour of Reactant HCl
Concentration contours (mg/m3) for BCl3 releases
The following table shows the effect of accounting for chemical reactions with ambient moisture for four chemicals.
1. Reactant equivalent TLV calculated based on the product TLV.
2. Downwind hazard distances are computed at ground-level.
# Cloud lifts off
In summary, ADORA solves for the exothermic reactions between the released chemical and ambient moisture for the release of moisture-reactive chemicals. If the heat release from the reaction is significant enough, it predicts the lift-off of the initially dense ground-hovering clouds.
The failure of an incinerator in handling the Volatile Organic Compounds (VOC) emitted by a fuel conditioning process was investigated. It was determined that the emission was cyclical in nature, which was overlooked in the design of the existing incinerator. Catalytic and thermal incinerators were surveyed and a high thermal inertia system was selected suitable for handling the time-varying VOC load.
Fuel Condition System
Close-Up of Damaged Incinerator
Dispersion calculation was carried out by one of our staff for a cement plant in Egypt under the auspices of the Supreme Council of Universities. A complete set of meteorological measurements were collected and analyzed. The deposition rates of cement dust were calculated and the options for the pollution control were provided.
Currently working on a project for Delta-Pine cotton-seed processing plant to devise engineering ways of reducing smoke emissions. The project involved developing a detailed process flow sheet of the plant, collecting particle emissions from different locations, carrying-out a detailed mass and energy balance, data analysis, and suggesting ways to reduce the emissions.
For the National Institute of Standards and Technology, a multi-dimensional numerical code for the rise and dispersion of massive fire plumes was developed based on vortex and transport element methods. Various buoyant plume phenomena, such as: plume bifurcation, plume penetration of inversion layer, detailed entrainment and mixing patterns, and dense smoke cloud spreading in complex terrain, are quantified. The model has been used for the study and prediction of the dispersion of the Kuwaiti fire plumes. Lately, the model has been extended to the simulation of puff lift-off from the ground. The puff stem formation, puff lift-off, and vortex ring formation, as well as the detailed entrainment process are described and compared well with field experiments. Modifications of the code (MARS) to simulate practical mixing and reaction problems are in progress. The code simulates the time-dependent high-Reynolds number turbulent mixing and transition without using conventional turbulent modeling procedures. For two-dimensional problems, this computational code can be executed on a PC Pentium
For a cogeneration plant, we evaluated the effectiveness of an afterburner to destroy the benzene emitted by a 42 MW diesel engine set. We correlated kinetic data published for various pressures, temperatures and compositions. Based on this correlation, we identified air preheat and excess air settings that would minimize emission
For a chemical company, we investigated the use of a proprietary metalloceene to catalyze the NO-CO reaction in car exhaust. The catalyst was sublimated in a fluidized bed heater and injected hot at various locations in the exhaust line. Recommendations were made on the suitability of this catalyst to automotive applications.
We performed an analysis of a warehouse fire involving magnesium, Teflon and fuel oil. We calculated the cloud temperature and concentrations of product species versus time until the end of chemical reactions and cloud rise. After the first one second, the concentration variation is dominated by the entrainment of ambient air into the cloud.
For a number of petrochemical companies in the US, the North Sea, and the Middle East, BlazeTech modeled the accidental releases of chemicals from oil and gas operations such as liquid spills, atmospheric dispersion, explosions, and fires including vapor fires, pool/dike/trench fires and fireballs.
Reducing of odors from manholes was investigated. An innovative system was suggested for use in wastewater pumping stations. The system involved stripping of Hydrogen sulfide from the wastewater gases with liquid hypo-chloride.
We assessed explosion hazards associated with the operations of several petrochemical plants. The overpressure field was calculated based on a TNT equivalent analysis, and on the assumption of a Chapman-Jouget detonation followed by gas expansion. We translated these estimates into hazard zones using damage criteria for building collapse and window breakage. We identified means of mitigating the hazards.
For NASA, we compiled TNT yields reported for major explosions of accidentally released fuels such as propane and ethelyne oxide. To interpret a large scatter in the data, we delineated two factors: the fraction of chemical energy released in the explosion; and the fraction of released energy transmitted to the blast. The later factor varied little and placed a theoretical upper limit on yield (which was consistent with the data). The former factor was accident specific and varied significantly, thus contributing to the scatter in the data.
We modeled the fast deflagration of unconfined propane vapor clouds of pancake shape. We used linear acoustic theory and a Taylor-type constant-velocity flame-piston formulation to estimate bounds on the overpressure. We showed that the results differ significantly from those obtained with the assumption of a spherically symmetric cloud or with a standard TNT analysis.
Developed a model to predict the atmospheric dispersion of chemicals that undergo complex interactions with atmosphere. Examples include uranium hexafluoride hydrogen fluoride. When released into the atmosphere, these chemicals react with ambient humidity to form hazardous compounds. This model solves the simultaneous chemical reactions, thermodynamic transformations, and cloud motion to determine the evolution and spread of the cloud formed from different types of releases into atmosphere. The predictions of the model were realistic and compared well with accident data from literature.
For several chemical plants, he modeled a number of accident scenarios, including the spills of reactive chemicals such as chlorine trichloride, boron trichloride and titanium tetrachloride in the atmosphere including the effect of reaction with water vapor in the air and plume lift-off from the ground. The results were used to prepare Risk Management Plans for EPA under the 112r rule.
For USAF, a detailed chemical kinetic model for the degradation of a halogen based agent in a humid atmosphere is being investigated for the purposes of determining the environmental hazards associated with a spill. The model is currently being refined, with the aid of a comparison against experimental data from actual controlled releases of agent into a humid environment, in order to more accurately model certain key environmentally hazardous byproducts. From the basic model, a stripped-down version will eventually be extracted for inclusion in our atmospheric dispersion model (ADORA).
For Martin Marietta Energy Systems, a complex chemistry and thermodynamics module for Uranium Hexafluoride releases in the atmosphere was developed. The technical issues addressed include mixing-limited chemical reaction, flash and sublimation, HF thermodynamics, plume descend, lift-off, and rise. The module was implemented in various HGSYSTEM dispersion models. These extended models have been used for estimating the environmental effects of accidental releases of UF6 at gaseous diffusion plants in Paducah, KY, and Portsmouth, OH
For a number of companies, PSD and NAAQS modeling analyses were conducted. These studies include ISC2 and BLP modeling of plant sources and background sources. Technical issues addressed include building downwash effects and line source dispersion. We also investigated the air pollution problem resulting from the cement industry. The deposition rates of cement dust were evaluated and options for pollutant control were provided.
For the Department of Defense, we evaluated the adequacy of various existing VA methodologies for vulnerability assessment of drinking water distribution networks with particular focus on terrorist attacks. Based on the findings, we developed the framework for an alternative vulnerability assessment method tailored to this application.