Alternative Strategies for Control of Sulfur Dioxide Emissions

Achievement of air quality goals now more than ever requires careful consideration of alternative control strategies in view of national concerns with energy and the economy. Three strategies which might be used by coal-fired steam electric plants to achieve ambient air quality standards for sulfur dioxide have been compared, and the analysis shows that the desired objective can be achieved using the intermittent control strategy with substantially less impact on the environment, less consumption of energy, and at a much lower economic cost than using either stack gas scrubbing or low-sulfur coal.     

Nashville Sulfur Dioxide Emission Inventory and the Relationship of Emission to Measured Sulfur Dioxide

A detailed inventory of sulfur dioxide emissions was prepared as part of the Nashville Community Air Pollution Study conducted by the Public Health Service during 1958–59. The primary purpose of the inventory was to provide data for a study of the relationship between the emission of sulfur dioxide and measured ambient levels. The development of the inventory, data collection methods, and calculations are described. Ambient levels of sulfur dioxide were related to average emissions of sulfur dioxide in such a way (correlation coefficient = 0.81) that mean seasonal concentrations of atmospheric sulfur dioxide in square-mile areas could be predicted with fairly good confidence from a knowledge of sulfur dioxide emissions. For these long-period {average) predictions meteorological variables can be disregarded. On a square-mile basis, on the average, one ton of sulfur dioxide emitted per day produced a mean atmospheric sulfur dioxide concentration of 0.022 ppm, and 10 tons of sulfur dioxide per day produced a concentration of 0.067 ppm.     

Modeling of Sulfur Dioxide Emissions and Acidic Precipitation at Mesoscale Distances

A steady state mesoscale model developed to predict primary SO₂ concentrations from a single point source is presented. The model was validated with data from the Midwest Interstate Sulfur Transport and Transformation (MISTT) project, with root mean square errors of 9.69 μg m^?3 and 0.42 μg m^?3 for SO₂ and SO₄ respectively. Wet deposition (washout and rainout), eddy dispersivity, dry deposition of SO₂ and mean wind speed were found to be the most important factors controlling sulfur dioxide and sulfate concentrations. Estimation of precipitation acidity was then carried out using scavenging theory. The greatest potential acidification occurred approximately 200 km from the source along plume centerllne, which indicates a rather local effect as opposed to a long distance effect. The cross-plume influence was up to 60 km in width at a distance of 400 km from the source.     

Impact of Free Calcium Oxide Content of Fly Ash on Dust and Sulfur Dioxide Emissions in a Lignite-Fired Power Plant

Abstract

Emitted pollutants from the Agios Dimitrios lignite-fired power plant in northern Greece show a very strong linear correlation with the free calcium oxide content of the lignite ash. Dust (fly ash) emissions are positively correlated to free calcium oxide content, whereas sulfur dioxide (SO₂) emissions are negatively correlated. As a result, at present, the Agios Dimitrios Power Plant operates very strictly within the legislative limits on atmospheric particulate emission. In the present study, the factors to be considered in assessing the impact of lignite combustion on the environment are presented and evaluated statistically. The ash appears to have a remarkable SO₂ natural dry scrubbing capability when the free calcium oxide content ranges between 4 and 7%. Precipitator operating problems attributable to high ash resistivity can be overcome by injecting sulfur trioxide to reduce the ash resistivity, with, of course, a probable increase in operating costs.     

The Lead Dioxide Estimation Of Sulfur Dioxide Pollution

A new system of measuring sulfation is presented. Because of its simplicity, operation of large sulfation networks can be accomplished at extremely nominal costs. Because of increased sensitivity, present 1 -month sampling time intervals may be shortened to approximately 1 day. Use of this system will permit more definitive investigations of the relationship of sulfation to sulfur dioxide concentration.     

Sulfur Dioxide Emissions and Market Effects under the Clean Air Act Acid Rain Program

ABSTRACT

The Clean Air Act Amendments of 1990 (CAAA90) established a national program to control sulfur dioxide (SO₂) emissions from electricity generation. CAAA90's market-based approach includes trading and banking of Soumissions allowances. We analyzed data describing electric utility SO₂ emissions in 1995, the first year of the program's Phase I, and market effects over the 1990-1995 period. Fuel switching and flue-gas desulfurization were the dominant means used in 1995 by targeted generators to reduce emissions to 51% of 1990 levels. Flue-gas desulfur-ization costs, emissions allowance prices, low-sulfur coal prices, and average sulfur contents of coals shipped to electric utilities declined over the 1990-1995 period. Projections indicate that 13-15 million allowances will have been banked during the program's Phase I, which ends in 1999, a quantity expected to last through the first decade of the program's stricter Phase II controls. In 1995, both allowance prices and SO₂ emissions were below pre-CAAA90 expectations. The reduction of SO₂ emissions beyond pre-CAAA90 expectations, combined with lower-than-expected allowance prices and declining compliance costs, can be viewed as a success for market-based environmental controls.     

Development of Federal Air Standards to Reduce Sulfur Dioxide Emissions from New Industrial Boilers

Federal new source performance standards to control air emissions of sulfur dioxide from new industrial boilers were proposed by EPA on June 19, 1986. These standards would require boiler owners to reduce SO₂ emissions by 90 percent and meet an emission limit of 1.2 lb/MM Btu of heat input for coal-fired boilers and 0.8 lb/MM Btu for oil-fired boilers. In developing these standards, several regulatory options were considered, from standards that could be met by firing low sulfur fuels to standards that would necessitate flue gas treatment. The environmental, economic, and cost impacts of each option were analyzed. National impacts were estimated by a computer model that projects the population of new boilers over the 5-year period following proposal, predicts the compliance strategy that will be used to comply with the particular option (always assuming that the lowest cost method of compliance will be selected), and estimates the resulting emission reductions and costs. Impacts on specific industries and on model boilers were also analyzed. This paper focuses on these analyses and their results. The Agency's conclusions from these analyses, which led to the decision to establish percent reduction standards, are provided, and the proposed SO₂ standards are summarized. The proposed standards also include an emission limit for particulate matter from oil-fired boilers (0.1 lb/MM Btu). However, this article focuses only on the SO₂ standards.     

Supply Curves for Using Powder River Basin Coal to Reduce Sulfur Emissions

Abstract

Supply curves were prepared for coal-fired power plants in the contiguous United States switching to Wyoming's Powder River Basin (PRB) low-sulfur coal. Up to 625 plants, representing ～44% of the nameplate capacity of all coal-fired plants, could switch. If all switched, more than $8.8 billion additional capital would be required and the cost of electricity would increase by up to $5.9 billion per year, depending on levels of plant derating. Coal switching would result in sulfur dioxide (SO₂) emissions reduction of 4.5 million t/yr. Increase in cost of electricity would be in the range of 0.31-0.73 cents per kilowatt-hour. Average cost of S emissions reduction could be as high as $1298 per t of SO₂. Up to 367 plants, or 59% of selected plants with 32% of 44% nameplate capacity, could have marginal cost in excess of $1000 per t of SO₂. Up to 73 plants would appear to benefit from both a lowering of the annual cost and a lowering of SO₂ emissions by switching to the PRB coal.     

Photo-Oxidation of Sulfur Dioxide

SO₂/O₂ mixtures were photolyzed at 3130 Å and in the range 2500–4000 Å at room temperature. The only product of photolysis was SO₃. Attempts to estimate ф(S0₃) using mass spectrometry, l.R. spectroscopy and pressure change measurements were unsuccessful, because it was not possible to obtain reproducible quantitative estimates of SO₃. ф(SO₂) values were determined by monitoring the 3130 Å absorption for its concentration measurements. ф(SO₂) was independent of SO₂ (11.6 to 50.4 torr) and O₂ (50.0 to 390.6 torr) pressures. At 3130 Å, ф(SO₂) varied between 1.5 × 10^?2 and 2.2 X 10^?2. Over the integrated range 2500–4000 Å ф(SO₂) values of 2.1 X 10^?3 to 2.9 X 10^?3 were obtained. The differences in ф(SO₂) values are explained in terms of wavelength dependence of the rate constants for the two primary reactions: ¹SO₂ + SO₂ → 2SO₂(1) and ¹SO₂ + SO₂ → ³SO₂ + SO₂(2); (k₂/k₁) _{3130 Å} ≈ 10(k₂/k₁)_{2500–4000 Å}.     

Relating Summer Ambient Particulate Sulfur,Sulfur Dioxide,and Light Scattering to Gaseous Tracer Emissions from the MOHAVE Power Project

ABSTRACT

Project MOHAVE was initiated in 1992 to examine the role of emissions from the 1580 MW coal-fired MOHAVE Power Project (MPP) on haze at the Grand Canyon National Park (GCNP), located about 130 km north-northeast of the power plant. Statistical relationships were analyzed between summertime ambient concentrations of a gaseous perfluorocarbon tracer released from MPP and ambient SO₂, particulate sulfur, and light scattering to evaluate whether MPP's emissions could be transported to the GCNP and then impact haze levels there. Spatial analyses indicated that particulate sulfur levels were strongly correlated across the monitoring network, regardless of whether the monitoring stations were upwind or downwind of MPP. This indicates that particulate sulfur levels in this region were influenced by distant regional emission sources. A significant particulate sulfur contribution from a point source such as MPP would result in a non-uniform pattern downwind. There was no suggestion of this in the data.

Furthermore, correlations between the MPP tracer and ambient particulate sulfur and light scattering at locations in the park were virtually zero for averaging times ranging from 24 hr to 1 hr. Hour-by-hour MPP tracer levels and light scattering were individually examined, and still no positive correlations were detected. Finally, agreement between tracer and particulate sulfur did not improve as a function of meteorological regime, implying that, even during cloudy monsoon days when more rapid conversion of SO₂ to par-ticulate sulfur would be expected, there was no evidence for downwind particulate sulfur impacts. Despite the fact that MPP was a large source of SO₂ and tracer, neither time series nor correlation analyses were able to detect any meaningful relationship between MPP's SO₂ and tracer emission “signals” to particulate sulfur or light scattering.     

Sulfur Dioxide and Material Damage

Whereas most estimates of material damage are based on industrial surveys, the estimates produced in this study were derived from material damage experiments and ambient air quality data. Air quality data on SO₂ were obtained from 200 or more monitoring sites primarily located in heavily populated or polluted areas. Material threshold damage function data were then compared with SO₂ levels, and an estimate of losses, as reflected in increased maintenance and replacement costs, was determined. Estimates of the total stock of various materials in use were derived from census and industry data and allocated geographically according to population. A substantial decrease in the ambient SO₂ levels, particularly in larger urban areas, has occurred during the past five years. From 1968 to 1972, the estimated amount of material damage from SO₂ in the U. S. decreased from $900 million/yr to less than $100 million. During this period, the estimated percentage of man made materials exposed to SO₂ levels exceeding the proposed secondary annual average standard (60 μg/m³) and primary annual average standard (80 μg/m³) in the U. S. fell respectively, from 20% to less than 5% and from more than 10% to less than 1%. Most of the present loss is attributed to corrosion damage of metallic surfaces that are normally exposed to the ambient environment.     

A Numerical Modeling Technique for Estimating Sulfur Dioxide Dry Deposition Due to Local Source Emissions

This paper describes a methodology for estimating the effect of local source emissions on dry deposition of sulfur dioxide in regions of complex terrain. Airflow in complex terrain is simulated by a time-dependent dynamical model for the meteorological fields. The results of the dynamical model are used to drive a semi-stochastic Lagrangian dispersion model in order to evaluate concentrations resulting from local source emissions. The Lagrangian dispersion model is coupled with a dry deposition treatment which includes the effects of both surface properties and micrometeoroiogical factors on deposition.

A sample application is discussed for a source in the Shenandoah Valley. The largest concentrations and deposition rates were obtained shortly after sunrise, during the transition from the nocturnal to the daytime flow regime. These results suggest that dry deposition may be episodic.     

Monitoring Sulfur Dioxide with Lead Peroxide Cylinders

The results of source tests to demonstrate the applicability of direct-flame incineration for the control of the effluent from a wire-enameling bake oven are presented. The tests were conducted with a portable direct-flame incinerator under actual plant conditions. The efficiency of direct-flame incineration was established at incineration temperatures of 1000F, 1200, and 1400°F. Evaluation of incineration efficiency was performed by both analysis and quantitative odor measurement using an odor panel.     

Flash Photolysis of Sulfur Dioxide

The body of information presented in this paper is directed to photochemists and air pollution scientists interested in species which result from the interaction of SO₂ and light. When SO₂ at low pressures is subjected to an intense photolysis flash, the characteristic, very structured SO₂absorption spectrum disappears immediately after the flash and is replaced by a continuous absorption. The continuous absorption gradually decays and the normal SO₂ absorption spectrum returns. The initial absorbance of the continuous absorption is proportional to the square of the SO₂ pressure and the square of the flash irradiance. From these facts we propose the formation of a metastable dimer of SO₂ formed by the collision of two excited molecules. Some properties of this dimer are: natural lifetime = 2 sec; energy above separated monomers = 4 kcal; lifetime at atmospheric pressure = 1 sec (quenching coefficients with several foreign gases = 10^-20 cm³/sec molecule); absorption of ultraviolet light results in photode-composition of the dimer into monomeric SO₂. The long lifetime of this species and its low quenching cross section may make it an important intermediate in photochemical reactions of SO₂. The relatively low excitation energy of the metastable species indicates it may also be an intermediate in thermally excited reactions and perhaps an important component of smoke stack effluent.     

Measuring the Organic Carbon Content of Source Emissions for Air Pollution Control

Measuring emissions of organic materials from such sources as paint bake ovens, degreas-ing operations, and printing processes is a necessy part of a control program for solvents. Over the intervening years since 1966 when Los Angeles first enacted its solvent Rule 66, a considerable number of tests have been performed and the present test method has gone through a period of experience and improvement. A sample is collected from a stack or vent in a freeze-out trap cooled with dry ice followed by an evacuated 8-liter tank. Analysis is done by a system of gas chromatography and catalytic combustion to yield the total organic carbon content. Representative industrial emission analysis results, which demonstrate the practical applicability of the system, are shown.     

The Absorption of Atmospheric Sulfur Dioxide by Water Solutions

Results of a laboratory study indicate that the rate of solution of atmospheric sulfur dioxide in distilled water, over the range of atmospheric concentrations of 0.81?8.73 mg SO₂/M³, is a function of the concentration of SO2 in the atmosphere, with saturation being reached more rapidly at the higher concentrations. This would indicate that rain water, with constantly renewed surfaces, can be very effective in the removal of atmospheric SO₂. The pH of the exposed water samples reached values of 4.0 or less, comparable to values observed in fog and cloud water near large industrial areas. Overall solubility of sulfur dioxide in distilled water did not follow the law of partial pressure. At the atmospheric concentrations used it was found that over 98.5% of the sulfite in solution was in the form of the bisulfite ion with, the remainder present as unionized sulfurous acid. Computations using the concentration of unionized sulfurous acid in the solution showed that the solubility of this portion of dissolved sulfite did follow the law of partial pressure.     

The Continuous Analysis of Sulfur Dioxide in Gaseous Samples

Sulfur dioxide is quantitatively scrubbed from atmospheric and stack gas samples through the use of a unique rotary scrubber which provides collection efficiencies in excess of 97% in the PPB through PPM range. The scrubber in addition permits the use of water as a scrubbing vehicle which, when combined with a bleached pararosanaline reagent, provides high specificity and sensitivity for the analysis. By the elimination of the tetrachloromercurate solution, cell staining is eliminated and the stability required for continuous analysis by the reagent is achieved.     

Interactions of Sulfur Dioxide with Insoluble Suspended Particulate Matter

A laboratory study was conducted of the heterogeneous catalysis of sulfur dioxide at ppm concentrations in air by insoluble particles of CaCO₂, V₂O₅, Fe₂0₃, flyash from a coal-burning power plant, MnCO₂, activated carbon, and suspended particulate matter from urban air. The investigalion was performed by utilizing a new technique for aerosol stabilization which consists of depositing the aerosol on Teflon beads in a fluidized bed. The Teflon beads with deposited aerosol particles were then packed into a flow reactor. Progress of the chemical reaction of SO₂ with deposited particles was continuously monitored by determining the SO₂ concentrations in the reactor effluent with a microcoulometer.

In this investigation, CaCOg, V₂O₅, and flyash were essentially inert to SO₂ at room temperature. Fe₂O₃, activated carbon, MnO₂, and suspended particulate matter from urban air sorbed SO₂ from air streams with up to 14.4 ppm SO₂ in air. Evidence is presented which suggests that a substantial part of the sorbed SO₂ was physically adsorbed.

Bioassay procedures which utilize pulmonary flow resistance changes in guinea pigs to monitor response to inhaled SO₂-aerosol mixtures in air have indicated the weak or non-potentiating capacity of insoluble aerosols as contrasted to soluble aerosols. Potentiating response of an aerosol appears to be strongly associated with reaction of SO₂ in a water droplet containing aerosol ions and not with physically adsorbed SO₂ on an insoluble aerosol.     

Control of Claus Plant Sulfur Compound Emissions

The body of information of this paper is directed to those individuals charged with selecting a process to control atmospheric sulfur emissions from Claus plants serving refineries, gas processing installations, and chemical plants. The TGT process developed by the French Petroleum Institute (IFP) is an extension of the Claus reaction itself in the liquid phase. Mixed H₂S and SO₂ in tail gas from Claus units is fed to a packed tower in which a solution of proprietary catalyst in a high BP polyglycol circulates countercurrent to the gas flow. The mixed gases react with the catalyst to form a complex, which in turn reacts with more gases to produce elemental sulfur. Reaction temperature keeps the sulfur above its melting point. Product accumulates in the boot of the tower and is drawn off continuously through a seal leg.

The IFP TGT process is simple in design and units have simple construction, characterized by use of low carbon steel and the use of very few pieces of equipment. Of all processes used today to take effluent sulfur values down to 1000 ppm SO₂ after incineration, the IFP TGT process requires the least capital investment and the lowest operating costs. Twenty-six full scale plants are operating or under design or construction: nine each in the U.S. and Japan, five in the U.S.S.R. and Poland, two in western Europe and one in Canada. Capacities of the Claus plants served range from 45 to 800 Lt/d sulfur.