Sulfur Dioxide and Nitrogen Oxides Emissions from U.S. Pulp and Paper Mills, 1980–2005

Abstract

Comprehensive surveys conducted at 5-yr intervals were used to estimate sulfur dioxide (SO₂) and nitrogen oxides (NO_x) emissions from U.S. pulp and paper mills for 1980, 1985, 1990, 1995, 2000, and 2005. Over the 25-yr period, paper production increased by 50%, whereas total SO₂ emissions declined by 60% to 340,000 short tons (t) and total NO_x emissions decreased approximately 15% to 230,000 t. The downward emission trends resulted from a combination of factors, including reductions in oil and coal use, steadily declining fuel sulfur content, lower pulp and paper production in recent years, increased use of flue gas desulfurization systems on boilers, growing use of combustion modifications and add-on control systems to reduce boiler and gas turbine NO_x emissions, and improvements in kraft recovery furnace operations.     

Gaseous Sulfur Pollutants from Urban and Natural Sources

Major aspects of the circulation through the atmospheric environment of sulfur pollutants have been estimated, including source magnitudes, residual atmospheric concentrations, and scavenging processes. The compounds considered include SO₂ and H₂S, as well as sulfates. One-third of the sulfur reaching the atmosphere comes from pollutant sources, mainly as SO₂. Within the atmosphere there is a net transfer of sulfur from land to ocean areas. Pollutant sources annually amount to 73 × 10⁶ tons as sulfur while natural sources amount to 142 × 10⁶ tons, mainly as H₂S and sulfate sea spray. More than two thirds of the natural and pollutant sulfur emissions occur in the northern hemisphere. When only pollutant emissions are considered, 93 per cent occur in the northern hemisphere.     

The South Karelia Air Pollution Study: Relationship of Outdoor and Indoor Concentrations of Malodorous Sulfur Compounds Released by Pulp Mills

We studied the indoor penetration of ambient air malodorous sulfur compounds released by pulp mills. The indoor and outdoor concentrations were simultaneously measured with automatic SO₂ analyzers. The filtering effect of three different materials connected to a gaseous filter unit was tested during six study periods. The tested materials were Sorbixofil® based on gypsum impregnated by KMnO₄ Purafil® based on Al₂O₃, both absorbing sulfur compounds by oxidation, and carbonized tissue. The periods lasted from 14 to 88 days. The results indicated that malodorous sulfur air pollutants penetrated indoors effectively, but after some delay because the dilution was slow. In a comparison of different filter materials, Purafil® was the most effective, producing low indoor concentrations. The study concludes that people living near pulp mills are exposed to substantial amounts of malodorous air pollutants, both indoors and outdoors. This exposure can be reduced by using gaseous sulfur sensitive filter materials connected to a controlled ventilation system.     

Effect of Oxidizing and Reducing Conditions on the Reaction of Water with Sulfur Bearing Blast Furnace Slags

The evolution of H₂S and SO₂ from hot blast furnace slags by reaction with H₂O has been found to be dependent upon the presence of O₂ or H₂ in the reaction zone as well as on the temperature. H₂ has been found to produce a small increase in H₂S and a small decrease in SO₂ emission, while O₂ has been found to produce a very great inhibiting effect on H₂S emission and only a small increase in SO₂ emission. The total emission of sulfur bearing gases is much less when H₂O + air is blown at the slag than when H₂O + Ar is blown at the slag, particularly at 1200°C and above. These effects may be useful in attempts to design systems for slag quenching which will produce less pollution.     

A comparison of hourly with annual air pollutant emissions: Implications for estimating acute exposure and public health risk

Health risks from air pollutants are evaluated by comparing chronic (i.e., an average over 1 yr or greater) or acute (typically 1-hr) exposure estimates with chemical- and duration-specific reference values or standards. When estimating long-term pollutant concentrations via exposure modeling, facility-level annual average emission rates are readily available as model inputs for most air pollutants. In contrast, there are far fewer facility-level hour-by-hour emission rates available for many of these same pollutants. In this report, we first analyze hour-by-hour emission rates for total reduced sulfur (TRS) compounds from eight kraft pulp mill operations. This data set is used to demonstrate discrepancies between estimating exposure based on a single TRS emission rate that has been calculated as the mean of all operating hours of the year, as opposed to reported hourly emission rates. A similar analysis is then performed using reported hourly emission rates for sulfur dioxide (SO₂) and oxides of nitrogen (NO_x) from three power generating units from a U.S. power plant. Results demonstrate greater variability at kraft pulp mill operations, with ratios of reported hourly to average hourly TRS emissions ranging from less than 1 to greater than 160 during routine facility operations. Thus, if fluctuations in hourly emission rates are not accounted for, over- or underestimates of hourly exposure, and thus acute health risk, may occur. In addition to this analysis, we also demonstrate an additional challenge when assessing health risk based on hourly exposures: the lack of human health reference values based on 1-hr exposures.

Implications: Largely due to the lack of reported hourly emission rate data for many air pollutants, an hourly average emission rate (calculated from an annual emission rate) is often used when modeling the potential for acute health risk. We calculated ratios between reported hourly and hourly average emission rates from pulp and paper mills and a U.S. power plant to demonstrate that if not considered, hourly fluctuations in emissions could result in an over- or underestimation of exposure and risk. We also demonstrate the lack of 1-hr human health reference values meant to be protective of the general population, including children.     

Removal of SO2 From Flue Gases Using Carbon at Elevated Temperatures

The interaction of a typical flue gas with active charcoal and bituminous coal char at temperatures between 600 and 800°C and atmospheric pressure has been studied. The SO₂ in the flue gas interacts with the carbon to form primarily H₂S, COS, and a carbon-sulfur surface complex. H₂S and COS break through the carbon bed much in advance of SO₂. At 800°C, sulfur retention on the bed exceeds at least 11% before SO₂ breakthrough occurs. The reaction of H₂S and COS with O₂ over active charcoal at 100–140°C to produce sulfur, which deposits on the carbon, has also been studied and found to be feasible. As a result of this study, a new process is outlined for the removal of SO₂ from flue gas, with the ultimate conversion     

Photochemical oxidation and dispersion of gaseous sulfur compounds from natural and anthropogenic sources around a coastal location

The photochemical oxidation and dispersion of reduced sulfur compounds (RSCs: H₂S, CH₃SH, DMS, CS₂, and DMDS) emitted from anthropogenic (A) and natural (N) sources were evaluated based on a numerical modeling approach. The anthropogenic emission concentrations of RSCs were measured from several sampling sites at the Donghae landfill (D-LF) (i.e., source type A) in South Korea during a series of field campaigns (May through December 2004). The emissions of natural RSCs in a coastal study area near the D-LF (i.e., source type N) were estimated from sea surface DMS concentrations and transfer velocity during the same study period. These emission data were then used as input to the CALPUFF dispersion model, revised with 34 chemical reactions for RSCs. A significant fraction of sulfur dioxide (SO₂) was produced photochemically during the summer (about 34% of total SO₂ concentrations) followed by fall (21%), spring (15%), and winter (5%). Photochemical production of SO₂ was dominated by H₂S (about 55% of total contributions) and DMS (24%). The largest impact of RSCs from source type A on SO₂ concentrations occurred around the D-LF during summer. The total SO₂ concentrations produced from source type N around the D-LF during the summer (a mean SO₂ concentration of 7.4 ppbv) were significantly higher than those (≤0.3 ppbv) during the other seasons. This may be because of the high RSC and SO₂ emissions and their photochemistry along with the wind convergence.     

Stainless Steel Anti-Smog Mufflers—Cut Air Pollution

An automatic process gas chromatograph has been developed for use on the recovery furnace stack of a Kraft pulp mill. The instrument analyzes for widely varying concentrations of H₂S, SO₂, CH₃SH and higher order sulfur compounds. It is insensitive to the fixed gases and water vapor, and performs its analysis in approximately ten minutes. The instrument features a microcoulometric detector giving it sensitivity to H₂S as low as 0.1 ppm, and SO₂ and CH₃SH as low as 0.5 ppm. The major limit to even higher sensitivity at this stage of development lies with two problems: the background noise level in the detector and the sulfur compound absorption in the Porapak Q chromatograph column. At the reported sensitivity, a 40-ml gas sample was used. The instrument also contains a data analysis system supplementary to the usual strip chart recorder. This system is made up of a digital voltmeter, a digital translator, and a teletype and hence allows the transfer of the output data to a digital computer for processing. The processed data are usually presented in the form of ppm quantities of the component gases in the stack gas. The instrument has worked successfully on small furnace effluent for periods of 25 hr but has not been tried on recovery furnace stacks. It has also run on prepared samples for periods of up to seven days with no maintenance or attendance necessary.     

Removal of SO2 from Simulated Flue Gases Using Non-Thermal Plasma-Based Microgap Discharge

Abstract

The removal of sulfur dioxide (SO₂) from simulated flue gases streams (N₂/O₂/H₂O/SO₂) was experimentally investigated using microgap discharge. In the experiment, the thinner dielectric layers of aluminum oxide (Al₂O₃) were used to form the microgap discharge. With this physical method, a high concentration of hydroxyl (OH·) radicals were produced using the ionization of O₂ and H₂O to further the conversion of SO₂ into sulfuric acid (H₂SO₄) at 120° C in the absence of any catalysts and absorbents, which were captured with the electrostatic precipitator (ESP). As a result, the increase of discharge power and concentrations of O₂ and H₂O increased the production of OH· radicals resulting in enhanced removal of SO₂ from gas streams. With the test and analysis, a number of H₂SO₄ droplets were produced in experiment. Therefore, a new method for removal of SO₂ in semidry method without ammonia (NH₃) additive was found.     

Influence of ozone, relative humidity, and flow rate on the deposition and oxidation of sulfur dioxide on yellow sand

To evaluate the influences of O₃, relative humidity (RH), and flow rate on the reaction between yellow sand and SO₂, the SO₂ deposition velocity and the oxidation state of sulfur were investigated by means of exposure experiments in a cylindrical flow reactor. Early in the reaction, the deposition velocity was not influenced by the RH or the presence of O₃; as the reaction progressed, however, the deposition velocity increased in the presence of O₃ and at high humidity. The oxidation of sulfur from S(IV) to S(VI) was also enhanced under these conditions. The amount of sulfur oxidation was positively correlated with the amount of deposited O₃. Furthermore, the SO₂ deposition velocity increased with increasing flow rate. However, changes in the flow rate had no noticeable effect on the amount of SO₂ oxidation.     

A Study of Primary Sulfate Emissions From a Coal-Fired Boiler with FGD

A study was carried out to investigate the emissions of SO₂ and primary sulfate materials (H₂SO₄ and inorganic particulate matter) from a boiler burning fossil fuel and using a wet-limestone scrubber for SO₂ removal. Experiments were designed to assess the scrubbing efficiency for SO₂ and sulfate, as well as the potential for scrubber liquor reentrainment. The boiler studied was an 820 MW cyclone-fired unit equipped with a wet, limestone scrubber, consisting of eight two-stage venturi-absorber modules designed to treat a flue gas flow rate of 2,760,000 acfm. The boiler fuel was a low-grade sub-bituminous coal with ash and sulfur contents of 25 and 5%, respectively. Multiple-sampling methods were employed concurrently on the inlet and outlet of a candidate absorber module to measure SO₂, total water-soluble sulfate, and free H₂SO₄. Samples were collected during three field experiments from September 1977 through April 1978. The average SO₂ scrubbing efficiency was 76% and was observed to decrease over the 5 day operation/maintenance cycle of the module. The total water-soluble sulfate input to the scrubber amounted to approximately 1% of the total sulfur oxides and was composed of a 5:1 ratio of H₂SO₄ to particulate sulfate. The total sulfate scrubbing efficiency, averaging about 29%, was invariant with respect to SO₂ removal. The sulfate emissions measured in the scrubber exit gas consisted of about 85 % H₂SO₄ as a fine aerosol. Mass emissions of acid and particulate sulfate were calculated as 1730 Ib/hr and 305 Ib/hr, respectively.     

Studies on the Removal of Sulfur Dioxide from Hot Flue Gases to Prevent Air Pollution

The pollution of the atmosphere by sulfur dioxide is one of the gravest of all in public nuisance problems, especially in the industrial regions. A practically applicable method in industry for the removal of sulfur dioxide has been studied. The Kiyoura-T .I .T. process utilizes the oxidation method to convert S0₂ of the flue gas to S0₃ in the presence of vanadium oxide. A limited amount of water vapor present in the flue gas reacts with S0₃ to form H₂SO₄. Ammonia is then introduced to the gaseous mixture, which is now at the suitable temperature, to form ammonium sulfate. Conditions are controlled to produce ammonium sulfate of the right size to produce aggregate that may be removed by a dry cyclone separator.     

Biochemical and Physiological Detection of Sulfur Dioxide Injury to Pea Plants (Pisum sativum)

Biochemical and physiological experiments were conducted on pea plants (Pisum sativum) continuously exposed in growth chambers to SO₂ gas for 18 days. S0₂ gas concentrations were 0.1, 0.15, and 0.25 ppm. In plants exposed to 0.1 and 0.15 ppm it was clearly demonstrated that there was a greater accumulation of inorganic sulfur, a reduced buffer capacity of the cells relative to H-ions, and a stimulation of glutamate dehydrogenase activity. The only macroscopic symptom seen was slight chlorosis of the older leaves. There was only a slight decrease in fresh and dry weights of these plants compared to the control plants whereas in the group of plants exposed to 0.25 ppm SO₂ foliage necrosis was considerable. In addition, there was a marked reduction in the fresh and dry weights of the latter plants. However, the relationship among accumulated inorganic sulfur, reduced buffer capacity, and increased glutamate dehydrogenase activity as seen for the lower S0₂ concentrations was close. Accordingly, if might be possible to use these three parameters to diagnose S0₂ injury before any significant symptoms appear. In the case of severe SO₂ injury there was a marked increase in glutamine and ammonia concentrations suggesting that these factors in addition to the above could be used in diagnosing severe SO₂ injury. There was no significant difference between plants treated with 0.1 or 0.15 ppm SO₂ and control plants in the contents of K, Ca, P, and N fractions. Therefore, these factors would not be useful in the early detection of SO₂ injury.     

Sulfate Emissions from Vehicles on the Road

Experiments have been conducted to measure vehicle sulfate emissions, by vehicle type, at two tunnels on the Pennsylvania Turnpike. A satisfactory balance between estimated fuel sulfur consumption and observed emissions of sulfur compounds corrected for ambient-air contributions was obtained. This work started in 1974 before the introduction of catalyst-equipped automobiles and continued into 1976. The sulfate contributed by vehicles even in the tunnels was found to be generally modest relative to rural ambient sulfate levels. Average sulfate emission rates were found to be ~30 mg/km (50 mg/mi) from heavy-duty Diesel trucks, <15 mg/km from catalyst-equipped cars (probably in the range 4 to 7 mg/km), and probably <1 mg/km from non-catalyst cars. The overall SO₂ —* SO₄ ^-2 conversion of the vehicle emissions was 2 %.     

Monitoring of atmospheric reduced sulfur compounds and their oxidation in two coastal landfill areas

In this study, the distribution characteristics of reduced sulfur compounds (RSCs) in ambient air were investigated in two coastal landfill (LF) facilities and their surrounding areas. The photochemical conversion of RSCs to sulfur dioxide (SO₂) was also evaluated using a photochemical box model (PCBM). Measurements of RSCs were carried out from both in and around areas of two coastal LFs in Gunsan (G) and Donghae (D) city, Korea during several field campaigns (May through December 2004). The dominant RSCs at the Gunsan landfill (G-LF) were found to be DMS and H₂S, whereas those at the Donghae landfill (D-LF) were H₂S and DMDS. The concentrations of DMS at these study sites were likely to be affected not only by LF processes but also by an oceanic source, while such a pattern was more prominent at the D-LF. The chemical species of RSCs that can exert significant influences on the photochemical production of SO₂ in the LF environment were identified to be H₂S, DMS, or DMDS.     

Anthropogenic emissions of SO2 and NOx in Asia: Emission inventories

The anthropogenic emissions of SO₂ and NO_x for 25 Asian countries east of Afghanistan and Pakistan have been calculated for 1975, 1980, 1985, 1986 and 1987 based on fuel consumption, sulfur content in fuels and emission factors for used fuels in each emission category. The provincial- and regional-based calculations have also been made for China and India. The total SO₂ emissions in these parts of Asia have been calculated to be 18.3 and 29.1 Tg in 1975 and 1987, respectively. The calculated total NO_x emissions were 9.4 and 15.5 Tg in 1975 and 1987, respectively. The SO₂ and NO_x emissions in East Asia (China, Japan, South Korea, North Korea and Taiwan) were 23.4 and 10.7 Tg in 1975 and 1987, respectively.Keyword: Emission inventories, sulfur dioxide emissions, nitrogen oxide emissions, Asian emissions, anthropogenic emissions.     

Simplified Models of U.S. Acid Rain Control Costs

Simplified algorithms are presented for estimating the cost of controlling sulfur dioxide (SO₂) emissions from existing coal-fired power plants on a state-by-state basis. Results are obtained using the detailed Utility Control Strategy Model (UCSM) to calculate the Impacts of emission reductions ranging from approximately 30 percent to 90 percent of projected 1995 emissions for 18 different scenarios and 36 states. Scenarios include the use of two dry SO₂ removal technologies (lime spray dryers and LIMB) as potential options for power plant retrofit, in addition to currently available emission control options including coal switching, coal cleaning and wet flue gas desulfurization (FGD). Technical assumptions relating to FGD system performance and the upgrading of existing cold-side electrostatic precipitators (ESP) for reduced sulfur levels are also analyzed, along with the effects of interest rates, coal prices, coal choice restrictions, plant lifetime, and plant operating levels. Results are summarized in the form of a 3-term polynomial equation for each state, giving total annualized SO₂ control cost as a function of the total SO₂ emissions reduction for each scenario. Excellent statistical fits to UCSM results are obtained for these generalized equations.     

Shock Wave Cleaning of Air Filters

The trends in and relationships between ambient air concentrations of sulfur dioxide and sulfate aerosols at 48 urban sites and 27 nonurban sites throughout the U.S. between 1963 and 1972 have been analyzed. The substantial decreases in ambient SO₂ concentrations measured at urban sites in the eastern and midwestern U.S. are consistent with the corresponding reductions in local SO₂ emissions, but these decreases have been accompanied by only modest decreases in ambient sulfate concentrations. Large differences in the amounts of SO₂ emitted within individual air quality control regions are associated with much smaller differences in the corresponding ambient sulfate concentrations. Substantial changes in the patterns of SO₂ emissions between air quality regions result in essentially no differences between ambient sulfate concentrations in those air quality regions. Comparisons of several air quality regions in the eastern and western U.S. with similar SO₂ emission levels and patterns of emissions clearly demonstrates the higher ambient sulfate concentration levels in eastern air quality control regions. Relationships between SO₂, sulfates, and vanadium concentrations at eastern nonurban U.S. sites cannot be explained by local emission sources. These various observed results can be best explained by long distance sulfur oxide transport with chemical conversion of SO₂ to sulfates occurring over ranges of hundreds of kilometers. This conclusion has been suggested earlier and the present analysis strongly supports previous discussions. An impact of long range transport of sulfates is to emphasize the need for Consistent strategies for reduction of sulfur oxides throughout large geographical regions. Additions of large capacities involving elevated sources in mid-continental or western regions could result in significant increases in sulfate concentrations well downwind of such sources. Some of the types of research activities required to quantitate crucial experimental parameters are discussed.     

Dissociation of Sulfur Hexafluoride Tracer Gas in the Presence of an Indoor Combustion Source

ABSTRACT

As an odorless, nontoxic, and inert compound, sulfur hexafluoride (SF₆) is one of the most widely used tracer gases in indoor air quality studies in both controlled and uncontrolled environments. This compound may be subject to reactions with water vapor under elevated temperature to form acidic inorganic compounds such as HF and H₂SO₄. Thus, in the presence of unvented combustion sources such as kerosene heaters, natural gas heaters, gas log fireplaces, candles, and lamps, the SF₆ dissociation may interfere with measurements of the emissions from these sources. Tests were conducted in a research house with a vent-free natural gas heater to investigate these potential interferences. It was observed that the heater operation caused about a 5% reduction of SF₆ concentration, which can be an error source for the ventilation rate measurement and consequently the estimated pollutant emission rates. Further analysis indicates that this error can be much greater than the observed 5% under certain test conditions because it is a function of the ventilation flow rate. Reducing the tracer gas concentration has no effect on this error. A simple theoretical model is proposed to estimate the magnitude of this error.

The second type of interference comes from the primary and secondary products of the SF₆ dissociation, mainly H₂SO₄, SO₂, HF, and fine particulate matter (PM). In the presence of ~5 ppm SF₆, the total airborne concentrations of these species increased by a factor of 4-10. The tests were performed at relatively high SF₆ concentrations, which is necessary to determine the interferences quantitatively. The second type of interference can be significantly reduced if the SF₆ concentration is kept at a low ppb level.     

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.