Assessment of control strategies for reducing volatile organic compound emissions from the polyvinyl chloride wallpaper production industry in Taiwan

This study attempts to assess the effectiveness of control strategies for reducing volatile organic compound (VOC) emission from the polyvinyl chloride (PVC) wallpaper production industry. In Taiwan, methyl ethyl ketone, TOL, and cyclohexanone have comprised the major content of solvents, accounting for approximately 113,000 t/yr to avoid excessive viscosity of plasticizer dioctyl phthalate (DOP) and to increase facility in working. Emissions of these VOCs from solvents have caused serious odor and worse air quality problems. In this study, 80 stacks in five factories were tested to evaluate emission characteristics at each VOC source. After examining the VOC concentrations in the flue gases and contents, the VOC emission rate before treatment and from fugitive sources was 93,000 and 800 t/yr, respectively. In this study, the semiwet electrostatic precipitator is recommended for use as cost-effective control equipment.     

Determination of VOC Emission Rates and Compositions for Offset Printing

Abstract

The release rates of volatile organic compounds (VOC) as fugitive emissions from offset printing are difficult to quantify, and the compositions are usually not known. Tests were conducted at three offset printing shops that varied in size and by process. In each case, the building shell served as the test “enclosure,” and air flow and concentration measurements were made at each air entry and exit point. Emission rates and VOC composition were determined during production for (1) a small shop containing three sheetfed presses and two spirit duplicators (36,700 sheets, 47,240 envelopes and letterheads), (2) a medium-size industrial in-house shop with two webfed and three sheetfed presses, and one spirit duplicator (315,130 total sheets), and (3) one print room of a large commercial concern containing three webfed, heatset operations (1.16 x 106 ft) served by catalytic air pollution control devices. Each test consisted of 12 one-hour periods over two days. Air samples were collected simultaneously during each period at 7-14 specified locations within each space. The samples were analyzed by gas chromatography (GC) for total VOC and for 13-19 individual organics. Samples of solvents used at each shop were also analyzed by GC. Average VOC emission rates were 4.7-6.1 kg/day for the small sheetfed printing shop, 0.4-0.9 kg/day for the industrial shop, and 79-82 kg/day for the commercial print room. Emission compositions were similar and included benzene, toluene, xylenes, ethylbenzene, and hexane. Comparison of the emission rates with mass balance estimates based on solvent usage and composition were quite consistent. The average compositions of emissions from these tests were much more detailed than has been previously available, but they agreed well with previous chemical fingerprint values for toluene and o-xylene, which have been successfully applied to source-receptor modeling for graphic arts.     

Formaldehyde Concentrations Inside Private Residences: A Mail-Out Approach to Indoor Air Monitoring

Abstract

The main objective of this study was to monitor the volatile organic compounds (VOCs) in the stack gas released from organic chemical industrial plants to determine emission factors. Samples from 52 stacks, with or without air pollution control devices (APCDs), from seven industrial processes were taken and VOCs measured using U.S. Environmental Protection Agency (EPA) Method 18. These 7 processes, including 26 plants, were the manufacturers of acrylonitrile–butadiene–styrene (ABS), polyvinyl chloride (PVC), polystyrene (PS), acrylic resin (ACR), vinyl chloride (VC), para–terephthalic acid (PTA), and synthetic fiber (SYF). The results clearly indicate significant variations of emission factors among the various industrial processes, particularly emission factors for those without APCDs. As expected, those with APCDs yield much less emission factors. Regardless of those with or without APCDs, the order of manufacturing processes with regard to VOC emission factors is SYF > ABS > PS > ACR > PTA > PVC > VC. The emission factors for some processes also differ from those in EPA–42 data file. The VOC profiles further indicate that some VOCs are not listed in the U.S. VOC/Particulate Matter Speciation Data System (SPECIATE). The potential O₃ formation is determined from the total amount of VOC emitted for each of seven processes. The resultant O₃ yield varied from 0.22 (ACR) to 2.33 g O₃ g^–1 VOC (PTA). The significance of this O₃ yield is discussed.     

VOC Recovery through Microwave Regeneration of Adsorbents: Comparative Economic Feasibility Studies

ABSTRACT

Microwave regeneration of adsorbents facilitates the recovery of volatile organic compounds (VOCs) by decoupling the bed heating from the stripping gas. This makes possible the creation of a highly-concentrated regeneration effluent from which the VOCs can be recovered by condensation at near-ambient temperatures. The economic feasibility of two novel microwave-regenerated adsorption systems was evaluated by systematically comparing the capital and operating costs of the proposed systems with 10 conventional VOC control technologies. The microwave systems were found to have similar capital and operating costs to conventional steam regeneration systems and, therefore, may present an attractive alternative for recovering water-miscible solvents. In general, the cost of the microwave subsystem is a relatively small component of the overall system costs, and the microwave power requirements are within the range of commercially available generators, even for large emission streams.     

Emission Characteristics of Volatile Organic Compounds from Semiconductor Manufacturing

Abstract

A huge amount of volatile organic compounds (VOCs) is produced and emitted with waste gases from semiconductor manufacturing processes, such as cleaning, etching, and developing. VOC emissions from semiconductor factories located at Science-Based Industrial Park, Hsin-chu, Taiwan, were measured and characterized in this study. A total of nine typical semiconductor fabricators (fabs) were monitored over a 12-month period (October 2000-September 2001). A flame ionization analyzer was employed to measure the VOC emission rate continuously in a real-time fashion. The amount of chemical use was adopted from the data that were reported to the Environmental Protection Bureau in Hsin-chu County as per the regulation of the Taiwan Environmental Protection Administration. The VOC emission factor, defined as the emission rate (kg/month) divided by the amount of chemical use (L/month), was determined to be 0.038 ± 0.016 kg/L. A linear regression equation is proposed to fit the data with the correlation coefficient (R²) = 0.863. The emission profiles of VOCs, which were drawn using the gas chromatograph/mass spectrometer analysis method, show that isopropyl alcohol is the dominant compound in most of the fabs.     

Nonvolatile,semivolatile, or volatile: Redefining volatile for volatile organic compounds

Although widely used in air quality regulatory frameworks, the term “volatile organic compound” (VOC) is poorly defined. Numerous standardized tests are currently used in regulations to determine VOC content (and thus volatility), but in many cases the tests do not agree with each other, nor do they always accurately represent actual evaporation rates under ambient conditions. The parameters (time, temperature, reference material, column polarity, etc.) used in the definitions and the associated test methods were created without a significant evaluation of volatilization characteristics in real world settings. Not only do these differences lead to varying VOC content results, but occasionally they conflict with one another. An ambient evaporation study of selected compounds and a few formulated products was conducted and the results were compared to several current VOC test methodologies: SCAQMD Method 313 (M313), ASTM Standard Test Method E 1868-10 (E1868), and U.S. EPA Reference Method 24 (M24). The ambient evaporation study showed a definite distinction between nonvolatile, semivolatile, and volatile compounds. Some low vapor pressure (LVP) solvents, currently considered exempt as VOCs by some methods, volatilize at ambient conditions nearly as rapidly as the traditional high-volatility solvents they are meant to replace. Conversely, bio-based and heavy hydrocarbons did not readily volatilize, though they often are calculated as VOCs in some traditional test methods. The study suggests that regulatory standards should be reevaluated to more accurately reflect real-world emission from the use of VOC containing products.

Implications:The definition of VOC in current test methods may lead to regulations that exclude otherwise viable alternatives or allow substitutions of chemicals that may limit the environmental benefits sought in the regulation. A study was conducted to examine volatility of several compounds and a few formulated products under several current VOC test methodologies and ambient evaporation. This paper provides ample evidence to warrant a reevaluation of regulatory standards and provides a framework for progressive developments based on reasonable and scientifically justifiable definitions of VOCs.     

Receptor Model Evaluation of the Southeast Michigan Ozone Study Ambient NMOC Measurements

Abstract

Large-scale studies like the Southeast Michigan Ozone Study (SEMOS) have focused attention on quantifying and spedating inventories for volatile organic compounds (VOCs). One approach for evaluating the accuracy of a VOC emission inventory is the development of a chemical mass balance (CMB) receptor model for ambient non-methane organic compound (NMOC) measurements. CMB evaluations of ambient hydrocarbon data provide a sample-specific allocation of emissions to individual source categories. This study summarizes the results of an application of the CMB model to the NMOC data from the SEMOS study. Comparison of CMB results with emission inventory values for the Detroit area show that vehicle emissions are well represented by the inventory, as are architectural coatings and coke ovens. Estimated emissions from petroleum refineries and graphic arts industries are much lower in the inventory than determined from the receptor allocation. Under-reporting of fugitive VOC emissions from petroleum refineries is an ongoing problem. Emissions from graphic arts industries are underestimated in the inventory partly because of the broad characterization of the emission factor (i.e., mass emitted/capita), which may be less useful when specific locations and days are under consideration. This study also demonstrates the effectiveness of the CMB approach when used prospectively to track the implementation of emission control strategies. While vehicle emission concentrations were unchanged from 1988 to 1993, measurement-based CMB results suggest a decrease in evaporative emissions during this time period resulting from Reid vapor pressure (RVP) reductions (from 11.0 psi in 1988 to 8.6 psi in 1993) and fleet turnover. Changes in emissions from coke plants and petroleum refineries were also seen in the CMB allocations for these sources.     

Predicting the Performance of VOC Condensers

Volatile organic compounds (VOC) are commonly released from process vents and equipment leaks. These discharges are a threat to the environment, and cost manufacturers millions of dollars in added raw material costs. For these reasons, one may be confronted with the task of evaluating alternatives for reducing VOC emissions from a process plant.

There are two basic approaches for reducing VOC emissions: a) changing the process, or b) installing control equipment.

Methods for changing the process include replacing highly volatile solvents with less volatile ones, making piping changes to reduce the number of vents, tightening the process to eliminate open tanks and leaks, altering process temperature and pressure conditions, etc. Equipment that is applicable to VOC emission control includes incineration, carbon adsorption, scrubbing and condensation.

This article addresses the application of condensers to process vents. A computer spreadsheet model is described, providing a quick screening which indicates whether a vent condenser might be a viable option for controlling emissions. The template provides, for each of a range of condensing temperatures, estimates for the amount of VOC that will be condensed, the condenser size and the tons of refrigeration required.     

An Estimate of Biogenic Emissions of Volatile Organic Compounds during Summertime in China (7 pp)

Background and Aim An accurate estimation of biogenic emissions of VOC (volatile organic compounds) is necessary for better understanding a series of current environmental problems such as summertime smong and global climate change. However, very limited studies have been reported on such emissions in China. The aim of this paper is to present an estimate of biogenic VOC emissions during summertime in China, and discuss its uncertainties and potential areas for further investigations. Materials and Methods This study was mainly based on field data and related research available so far in China and abroad, including distributions of land use and vegetations, biomass densities and emission potentials. VOC were grouped into isoprene, monoterpenes and other VOC (OVOC). Emission potentials of forests were determined for 22 genera or species, and then assigned to 33 forest ecosystems. The NCEP/NCAR reanalysis database was used as standard environmental conditions. A typical summertime of July 1999 was chosen for detailed calculations. Results and Discussion The biogenic VOC emissions in China in July were estimated to be 2.3×10¹²gC, with 42% as isoprene, 19% as monoterpenes and 39% as OVOC. About 77.3% of the emissions are generated-from forests and woodlands. The averaged emission intensity was 4.11 mgC m⁻² hr⁻¹ for forests and 1.12 mgC m⁻² hr⁻¹ for all types of vegetations in China during the summertime. The uncertainty in the results arose from both the data and the assumptions used in the extrapolations. Generally, uncertainty in the field measurements is relatively small. A large part of the uncertainty mainly comes from the taxonomic method to assign emission potentials to unmeasured species, while the ARGR method serves to estimate leaf biomass and the emission algorithms to describe light and temperature dependence. Conclusions This study describes a picture of the biogenic VOC emissions during summertime in China. Due to the uneven spatial and temporal distributions, biogenic VOC emissions may play an important role in the tropospheric chemistry during summertime. Recommendations and Perspectives Further investigations are needed to reduce uncertainties involved in the related factors such as emission potentials, leaf biomass, species distribution as well as the mechanisms of the emission activities. Besides ground measurements, attention should also be placed on other techniques such as remotesensing and dynamic modeling. These new approaches, combined with ground measurements as basic database for calibration and evaluation, can hopefully provide more comprehensive information in the research of this field. Submission Editor: Prof. Dr. Gerhard Lammel (lammel@recetox.muni.cz)     

Performance of a Pilot-Scale Biotrickling Filter in Controlling the Volatile Organic Compound Emissions in a Furniture Manufacturing Facility

Abstract

A 0.75-m³ pilot-scale biotrickling filter was run for over 1 yr in a Spanish furniture company to evaluate its performance in the removal of volatile organic compounds (VOCs) contained in the emission of two different paint spray booths. The first one was an open front booth used to manually paint furniture, and the second focus was an automatically operated closed booth operated to paint pieces of furniture. In both cases, the VOC emissions were very irregular, with rapid and extreme fluctuations. The pilot plant was operated at an empty bed residence time (EBRT) ranging from 10 to 40 sec, and good removal efficiencies of VOCs were usually obtained. When a buffering activated carbon prefllter was installed, the system performance was improved considerably, so a much better compliance with legal constraints was reached. After different shutdowns in the factory, the period to recover the previous performance of the biotrickling reactor was minimal. A weekend dehydration strategy was developed and implemented to control the pressure drop associated with excessive biomass accumulation.     

Determination of Source Contributions to Ambient Volatile Organic Compound Concentrations in Berlin

ABSTRACT

During three measuring campaigns in June, July, and August 1996, volatile organic compound (VOC) concentrations were measured at a rural background site, a city residential site, and a street site in Berlin. In addition, samples were taken near relevant sources of VOCs. The meaurements covered the volatile hydrocarbons in the range C₁-C₁₄ and included aldehydes and ketones. Samples were taken at four characteristic periods of 2 hr/day: during the night, during the early morning rush hour, at midday, and during the evening rush hour. An assessment of the contribution of emission categories to the observed concentrations was made with the chemical mass balance (CMB) modelling technique.

The VOC concentrations at the residential area and at the street site in the inner city were, respectively, a factor of 3 and 7 above the background concentration. Traffic exhaust contributed approximately 80-90% of the non-methane hydrocarbon (NMHC) concentration in the inner city and approximately 60% at the background area. Evaporative losses of motor fuel are estimated to account for approximately 7% at all sites. Natural gas leakage also contributed significantly to the observed VOC concentrations: in the inner city approximately 510% and at the background area approximately 30%. The measurements also showed a contribution of smaller sources, such as dry cleaning, use of solvents, and bio-genic emissions. However, the contribution of these sources to the total observed concentrations at the sites is estimated to be very small.     

The Effect of Reformulated Gasoline on Ambient Carbon Monoxide Concentrations in Southeastern Wisconsin

Abstract

Reformulated gasoline (RFG) contains oxygen additives such as methyl tertiary butyl ether or ethanol. The additives enable vehicles to burn fuel with a higher air/fuel ratio, thereby lowering the emission of carbon monoxide (CO) and volatile organic compounds (VOCs). Because VOCs react with sunlight to form ozone (O₃), the Clean Air Act requires severe O₃ nonattainment areas such as southeastern Wisconsin to use RFG. On July 17, 2001, the U.S. Environmental Protection Agency (EPA) granted Milwaukee, WI, and Chicago, IL, a waiver from the VOC reduction requirement of Phase II RFG. The VOC reduction requirement was lowered from 27.4% of the 1990 baseline fuel to 25.4%. The assumption was that ethanol-blended RFG would lower summertime CO concentrations sufficiently to offset the increased VOC emissions. The waiver is estimated to increase VOC emissions by ～0.8%, or 0.4 t of VOC on a hot summer weekday. This study evaluates whether RFG has been effective in lowering southeastern Wisconsin ambient CO concentrations. Three years of ambient CO data before RFG was introduced were compared with the first three years of ambient CO data after RFG was introduced. This paper also evaluates how the meteorology, vehicle inspection/maintenance program, vehicle miles traveled, and stationary source emissions influence CO concentrations. The winter decrease in ambient CO concentrations was found to be statistically significant, while the summer data showed no statistically significant change, indicating that RFG is most effective lowering ambient CO concentrations in cold weather.     

The Pioneers

Abstract

This study surveyed emissions from 2- and 4-stroke new and in-use motorcycles. Emission tests were carried out on a dynamometer following the designated test procedure of the Economic Commission for Europe (ECE). Samples were derived during various driving stages, which included idle, acceleration, 30 km/hr cruise, 50 km/hr cruise, and deceleration. All test motorcycles (10 new and 15 in-use) complied with Taiwan Environmental Protection Administration’s Phase III Motorcycle Emission Standards. The dominant volatile organic carbon (VOC) species were isopentane (53 and 295 mg/km, 2- and 4-stroke, respectively), 2-methylpentane (75 and 83 mg/km), 3-methylpentane (34 and 66 mg/km), and toluene (30 and 100 mg/km). The VOC emission factors for the 2-/4-stroke motorcycles were 311/344 (new) and 1479/433 (inuse) mg/km, respectively. In addition, the dominant carbonyl species for the new and in-use motorcycles were formaldehyde (0.4 and 0.7 mg/km, respectively), acetaldehyde (0.6 and 1.2 mg/km), and acetone (0.5 and 0.7 mg/km). The carbonyl compound emission factors for the 2- and 4-stroke motorcycles were 3.2/3.1 (new) and 5.3/4.6 (in-use) mg/km, respectively. The ozone formation potentials, based on an ECE test cycle, show that the values from the in-use motorcycles were higher than those from the new motorcycles. The dominant VOC species for the ozone formation potential were propylene (65 and 502 mg-O₃ /km, respectively), isopentane (98 and 501 mg-O₃ /km), 2-methylpentane (152 and 167 mg-O₃ /km), 3-methylpentane (79 and 253 mg-O₃ /km), and toluene (127 and 398 mg-O₃ /km). Further, the dominant carbonyl species were formaldehyde (4.1 and 6.2 mg-O₃ /km, new and in-use, respectively) and acetaldehyde (4.8 and 9 mg-O₃ /km).     

Use of Subsampled Traffic Data to Estimate Roadway Emissions,Including Conversion to MOBILE6 Vehicle Classifications

Abstract

Air quality is degraded by many factors, among which the emissions from on‐road vehicles play a significant role. Timely and accurate estimate of such emissions becomes very important for policy‐making and effective control measures. However, lack of traffic data and outdated emission software make this task difficult. This research has demonstrated a new method that facilitates the vehicular emission inventories at the local level by using shorter-time Highway Performance Monitoring System (HPMS) traffic data along with the latest U.S. Environment Protection Agency (EPA) emission modeling software, MOBILE6. The conversion methodology was developed for converting readily available HPMS traffic volume data into EPA MOBILE-based traffic classifications, and a corresponding software program was written for automating the process. EPA MOBILE6 model was used to obtain emissions of nitrogen oxides (NO_x), volatile organic compound (VOC), and cabon monoxide (CO) emitted by the parent traffic and subsampled traffic data, and these emissions were additionally compared. The case study has shown that the difference of the magnitude between the emission estimates produced by certain subsampled and parent traffic data are minor, indicating that subsampled HPMS data can be used for reporting parent traffic emissions. It was also observed that traffic emissions follow a Weibull distribution, and NO_x emissions were more sensitive to the traffic data composition than VOC and CO. Lastly, use of average emission values of 20 or 30 consecutive minutes appears to be valid for representing hourly emissions.     

Emission projections for the U.S. Environmental Protection Agency Section 812 second prospective Clean Air Act cost/benefit analysis

Section 812 of the Clean Air Act Amendments (CAAA) of 1990 requires the U.S. Environmental Protection Agency (EPA) to perform periodic, comprehensive analyses of the total costs and total benefits of programs implemented pursuant to the CAAA. The first prospective analysis was completed in 1999. The second prospective analysis was initiated during 2005. The first step in the second prospective analysis was the development of base and projection year emission estimates that will be used to generate benefit estimates of CAAA programs. This paper describes the analysis, methods, and results of the recently completed emission projections. There are several unique features of this analysis. One is the use of consistent economic assumptions from the Department of Energy's Annual Energy Outlook 2005 (AEO 2005) projections as the basis for estimating 2010 and 2020 emissions for all sectors. Another is the analysis of the different emissions paths for both with and without CAAA scenarios. Other features of this analysis include being the first EPA analysis that uses the 2002 National Emission Inventory files as the basis for making 48-state emission projections, incorporating control factor files from the Regional Planning Organizations (RPOs) that had completed emission projections at the time the analysis was performed, and modeling the emission benefits of the expected adoption of measures to meet the 8-hr ozone National Ambient Air Quality Standards (NAAQS), the Clean Air Visibility Rule, and the PM2.5 NAAQS. This analysis shows that the 1990 CAAA have produced significant reductions in criteria pollutant emissions since 1990 and that these emission reductions are expected to continue through 2020. CAAA provisions have reduced volatile organic compound (VOC) emissions by approximately 7 million t/yr by 2000, and are estimated to produce associated VOC emission reductions of 16.7 million t by 2020. Total oxides of nitrogen (NO(x)) emission reductions attributable to the CAAA are 5, 12, and 17 million t in 2000, 2010, and 2020, respectively. Sulfur dioxide (SO2) emission benefits during the study period are dominated by electricity-generating unit (EGU) SO2 emission reductions. These EGU emission benefits go from 7.5 million t reduced in 2000 to 15 million t reduced in 2020.     

A Maximum Entropy Approach to Estimating Emissions

ABSTRACT

A maximum information entropy method of calculating probabilistic estimates of volatile organic compound (VOC) emissions by the wood furniture and fixture coating industry is presented. The maximum entropy approach is used to produce minimally biased probability distributions for number of firms, coating use, and coating emission factors from existing summary statistics. These distributions are combined to estimate VOC emissions. The maximum entropy emissions estimate provides information to support probabilistic modeling of regional air quality, probabilistic assessment of emission reduction strategies, and risk assessments. Accurate estimation of emission distributions produces more informed regulatory decisionmaking, risk comparisons, and regulatory and scientific priority setting.     

Photochemical Smog Modeling for Assessment of Potential Impacts of Different Management Strategies on Air Quality of the Bangkok Metropolitan Region,Thailand

Abstract

A photochemical smog model system, the Variable-Grid Urban Airshed Model/Systems Applications International Mesoscale Model (UAM-V/SAIMM), was used to investigate photochemical pollution in the Bangkok Metropolitan Region (BMR). The model system was first applied to simulate a historical photochemical smog episode of two days (January 13-14, 1997) using the 1997 anthropogenic emission database available at the Pollution Control Department and an estimated biogenic emission. The output 1-hr ozone (O₃) for BMR, however, did not meet the U.S. Environmental Protection Agency suggested performance criteria. The simulated minimum and maximum O₃ values in the domain were much higher than the observations. Multiple model runs with different precursor emission reduction scenarios showed that the best model performance with the simulated 1-hr O₃ meeting all the criteria was obtained when the volatile organic compound (VOC) and oxides of nitrogen (NO_x) emission from mobile source reduced by 50% and carbon monoxide by 20% from the original database. Various combinations of anthropogenic and biogenic emissions in Bangkok and surrounding provinces were simulated to assess the contribution of different sources to O₃ pollution in the city. O₃ formation in Bangkok was found to be more VOC-sensitive than NO_x-sensitive. To attain the Thailand ambient air quality standard for 1-hr O₃ of 100 ppb, VOC emission in BMR should be reduced by 50-60%. Management strategies considered in the scenario study consist of Stage I, Stage II vapor control, replacement of two-stroke by four-stroke motorcycles, 100% compressed natural gas bus, 100% natural gas-fired power plants, and replacement of methyltertiarybutylether by ethanol as an additive for gasoline.     

The Sensitivity of PM25 Source-Receptor Relationships to Atmospheric Chemistry and Transport in a Three-Dimensional Air Quality Model

ABSTRACT

Air quality model simulations constitute an effective approach to developing source-receptor relationships (so-called transfer coefficients in the risk analysis framework) because a significant fraction of particulate matter (particularly PM_2.5) is secondary (i.e., formed in the atmosphere) and, therefore, depends on the atmospheric chemistry of the airshed. In this study, we have used a comprehensive three-dimensional air quality model for PM_{2 5} (SAQM-AERO) to compare three approaches to generating episodic transfer coefficients for several source regions in the Los Angeles Basin. First, transfer coefficients were developed by conducting PM_2.5 SAQM-AERO simulations with reduced emissions of one of four precursors (i.e., primary PM, sulfur dioxide (SO₂), oxides of nitrogen (NO_x), and volatile organic compounds) from each source region. Next, we calculated transfer coefficients using two other methods: (1) a simplified chemistry for PM_2.5 formation, and (2) simplifying assumptions on transport using information limited to basin-wide emission reductions. Transfer coefficients obtained with the simplified chemistry were similar to those obtained with the comprehensive model for VOC emission changes but differed for NO and SO emission changes. The differences were due to the parameterization of the rates of secondary PM formation in the simplified chemistry. In 90% of the cases, transfer coefficients estimated using only basin-wide information were within a factor of two of those obtained with the explicit source-receptor simulations conducted with the comprehensive model. The best agreement was obtained for VOC emission changes; poor agreement was obtained for primary PM_2.5.     

Thermal and Catalytic Incinerators for the Control of VOCs

Abstract

The emission of Volatile Organic Compounds (VOCs) is attracting increasing concern both from the public and by government agencies. Among the many available control technologies for the treatment of VOC containing waste streams, incineration offers an ultimate disposal strategy rather than a means for collecting or concentrating the offending compounds. This paper describes the major, commercially available thermal and catalytic incinerator systems that are designed to treat dilute, VOC containing gas streams. Qualitative guidelines are presented whereby the technologies can be compared. In addition, an example waste stream is used to illustrate a simplified procedure for calculating the material and energy balances for each of the incinerators. The resulting parameters will be used in a companion paper to estimate the capital and operating costs associated with each design. In this manner, a first estimate can be obtained of the costs of cleaning a waste stream containing low levels of VOCs.     

Measuring Concentrations of Volatile Organic Compounds in Vinyl Flooring

ABSTRACT

The initial solid-phase concentration of volatile organic compounds (VOCs) is a key parameter influencing the emission characteristics of many indoor materials. Solid-phase measurements are typically made using solvent extraction or thermal headspace analysis. The high temperatures and chemical solvents associated with these methods can modify the physical structure of polymeric materials and, consequently, affect mass transfer characteristics.

To measure solid-phase concentrations under conditions resembling those in which the material would be installed in an indoor environment, a new technique was developed for measuring VOC concentrations in vinyl flooring (VF) and similar materials. A 0.09-m² section of new VF was punched randomly to produce ~200 0.78-cm² disks. The disks were milled to a powder at -140 °C to simultaneously homogenize the material and reduce the diffusion path length without loss of VOCs. VOCs were extracted from the VF particles at room temperature by fluidized-bed desorption (FBD) and by direct thermal desorption (DTD) at elevated temperatures. The VOCs in the extraction gas from FBD and DTD were collected on sorbent tubes and analyzed by gas chromatog-raphy/mass spectrometry (GC/MS). Seven VOCs emitted by VF were quantified. Concentration measurements by FBD ranged from 5.1 |ig/g VF for n-hexadecane to 130 |Jg/g VF for phenol. Concentrations measured by DTD were higher than concentrations measured by FBD. Differences between FBD and DTD results may be explained using free-volume and dual-mobility sorption theory, but further research is necessary to more completely characterize the complex nature of a diffusant in a polymer matrix.