Absorption and Reaction Kinetics of Amines and Ammonia Solutions with Carbon Dioxide in Flue Gas

Abstract

The removal system for the absorption of CO₂ with amines and NH₃ is an advanced air pollution control device to reduce greenhouse gas emissions. Absorption of CO₂ by amines and NH₃ solutions was performed in this study to derive the reaction kinetics. The absorption of CO₂ as encountered in flue gases into aqueous solutions of monoethanolamine (MEA), diethanolamine (DEA), and NH₃ was carried out using a stirred vessel with a plane gas-liquid interface at 50 °C. Various operating parameters were tested to determine the effect of these variables on the absorption kinetics of the reactants in both gas and liquid phases and the effect of competitions between various reactants on the mass-transfer rate.

The observed absorption rate increases with increasing gas-liquid concentration, solvent concentration, temperature, and gas flow rate, but changes with the O₂ concentration and pH value. The absorption efficiency of MEA is better than that of NH₃ and DEA, but the absorption capacity of NH₃ is the best. The active energies of the MEA and NH₃ with CO₂ are 33.19 and 40.09 kJ/mol, respectively.     

Total SO2 emission control strategies for the management of air pollution in ulsan industrial complex

Since emission regulations in Korea concentrate mainly on the limitation of pollutant concentration in the stack gas, it is difficult to achieve a desirable air quality in a heavily industralized city like Ulsan. To ensure a suitable air quality in the future, a total emission control method is proposed with a stack height formula of H = 10.6 q^0.5, where H is the stack height (m) and q is the SO₂ emission rate (m³ h⁻¹ reduced to 0°C). The total emission permitted can be allocated to industries

• 1.(1) at an uniform reduction rate,
• 2.(2) by the formula Q = aQ_o^0.925, where Q is the emission allowed (g s⁻¹), a is a constant, and Q_o is the emission before control (g s⁻¹), or
• 3.(3) by using a linear programming technique.

The above three approaches were evaluated using the TCM 2 air quality model. In order to achieve the air quality goal set for the area, the first approach requires 38.7 % reduction of SO₂ emission from industries, the second 53.3 %, and the third 4.3 %. The linear programming method is found to be very economical, but there are some administrative difficulties in enforcement.     

Vegetation: A Sink for Atmospheric Pollutants

The possibility of vegetation being an important sink for gaseous air pollutants was investigated. Plant pollutant uptake measurements were made utilizing a typical vegetation canopy and chambers that were designed specifically for gaseous exchange studies. The data indicate that an alfalfa canopy removed gases from the atmosphere in the following order: hydrogen fluoride (HF) > sulfur dioxide (SO₂) > chlorine (Cl₂) > nitrogen dioxide (NO₂) > ozone (O₃) > peroxyacetyl nitrate (PAN) > nitric oxide (NO) > carbon monoxide (CO). The absorption rate of NO was low, and no absorption of CO could be detected with the methods used. In the typical ambient concentration range uptake increased linearly with increasing concentration except for O₃ and Cl₂ which caused partial stomatal closure at the higher concentrations. Wind velocity above the plants, height of the canopy, and light intensity were shown to affect the pollutant removal rate. A relationship between the absorption rate and solubility of the pollutant in water was also shown. It was concluded that vegetation may be an important sink for many gaseous air pollutants.     

Development of a 24-Hour Method for Analysis of SO2 and CO2 from Electric Utility Units Equipped with Flue Gas Desulfurization Scrubbers

A procedure was developed for the 24-h determination of SO₂ and CO₂ in effluent gas from fossil fuel combustion sources. Laboratory experiments were conducted to test absorption of SO₂ in hydrogen peroxide solution and absorption of CO₂ by sodium hydroxide on an inert substrate at expected ambient temperatures of 15 to 45°C. Isopropyl alcohol cannot be used to trap sulfuric acid and particulates because it permeates the sampling train and prevents complete absorption of CO₂. Elemental analysis of stack particulates revealed that at least 31 elements were present. Iron and other elements interfered with SO₂ analysis. These particulates were completely removed by a heated borosilicate glass filter. Both laboratory and field experiments showed that molecular sieves are a promising alternative for CO₂ absorption. Statistical evaluation of data collected at three units equipped with flue gas desulfurization scrubbers proved that the new procedure is accurate and precise.     

NOx Reduction in a Gas Fired Utility Boiler by Combustion Modifications

Data on the effect of several combustion modifications on the formation of nitrogen oxides and on boiler efficiency were acquired and analyzed for a 110 MW gas fired utility boiler. The results from the study showed that decreasing the oxygen in the flue gas from 2.2% to 0.6% reduced the NO_x formation by 33% and also gave better boiler efficiencies. Flue gas recirculation through the bottom of the firebox was found to be ineffective. Staged combustion was found to reduce the NO_x emissions by as much as 55 % while decreasing the efficiency by about 5%. Adjustment of the burner air registers reduced the NO_x formation by about 20 ppm. The lowest NO_x emissions of 42 ppm (at about 3% O₂) in the stack was obtained for air only to one top burner and 0.5% oxygen in the flue gas.     

A laboratory study of microalgae-based ammonia gas mitigation with potential application for improving air quality in animal production operations

Ammonia gas emission is a major concern in concentrated animal production operations. It not only reduces the manure value as fertilizer due to nitrogen loss, but also has considerable environmental consequences for both animals and ecosystem. In this work, a microalgae culture system was developed as an ammonia gas bioscrubber to reduce ammonia gas emission. The green algae Scenedesmus dimorphus was grown in a flat-panel photobioreactor aerated with ammonia-laden air. A continuous culture was performed at different operational conditions including dilution rate (D = 0.05, 0.1, 0.2, and 0.3 day^?1), ammonia gas loading rate (9.4, 19.3, 28.9, 39.9, 55.6 mg/L-day), and medium pH (5, 6, 7, and 8). The alga culture at 0.1 day^?1 dilution rate, 39.9 mg/L-day ammonia gas loading rate, and pH 7 resulted in the highest cell density and biomass productivity. In order to provide a wide spectrum evaluation of the algae-based ammonia mitigation system, four parameters were determined, including ammonia removal rate, overall ammonia gas removal efficiency, cellular ammonia consumption rate, and cell yield based on ammonia input. Depending on the operational conditions used, the maximum values of those four evaluative parameters were 50.92 ± 2.91 mg/L-day of ammonia removal rate, 94.90 ± 1.87% of ammonia removal efficiency, 0.0597 ± 0.0024 g NH₃/g cell-day of cellular ammonia consumption rate, and 19.40 ± 2.52 g cell/g NH₃ of cell yield based on ammonia. It was also found that the majority of nitrogen in the ammonia gas was assimilated by the algal cells. At D = 0.1 day^?1, 39.9 mg/L-day of ammonia gas loading rate and pH 7, algal biomass assimilated 98.6% of nitrogen contained in the ammonia gas input, with less than 5% of inlet ammonia gas was exhausted after the algal treatment.

Implications: This study demonstrated the effectiveness of using microalgae for mitigating ammonia gas emission from animal production operations. The results enabled us to better understand the mechanisms of ammonia assimilation by microalgae, the engineering design parameters for the process scale up, and the economic viability of the system. Eventually, it will lead to a novel, alternative method for mitigating ammonia gas emission from concentrated animal operations while producing biomass as high-quality feed ingredient.     

Nitrogen Dioxide Absorption and Sulfide Oxidation in Aqueous Sulfide

ABSTRACT

Rates of nitrogen dioxide (NO₂) absorption and sulfide oxidation were measured in a highly characterized stirred cell contactor at 55 °C, with O₂ present in the gas phase. The rate constant of the reaction between NO₂ and sul-fide at 55 °C was determined to be 26.4 x10⁵ M^-1sec^-1. A reaction mechanism was proposed that is consistent with the kinetic data. NO₂ absorption initiates sulfide oxidation in the presence of oxygen. The rate of sulfide oxidation increased with sulfide and oxygen concentration and with the rate of NO₂ absorption. Furthermore, thiosulfate was an effective inhibitor of sulfide oxidation.     

Simulation of Stack Plume Opacity

ABSTRACT

The visual impact of primary particles emitted from stacks is regulated according to stack opacity criteria. In-stack monitoring of the flue gas opacity allows plant operators to ensure that the plant meets U.S. Environmental Protection Agency opacity regulations. However, the emission of condensable gases such as SO₃ (that hydrolyzes to H₂SO₄), HCl, and NH₃, which may lead to particle formation after their release from the stack, makes the prediction of stack plume opacity more difficult.

We present here a computer simulation model that calculates the opacity due to both primary particles emitted from the stack and secondary particles formed in the atmosphere after the release of condensable gases from the stack. A comprehensive treatment of the plume rise due to buoyancy and momentum is used to calculate the location at which the condensed water plume has evaporated (i.e., where opacity regulations apply).

Conversion of H₂SO₄ to particulate sulfate occurs through nucleation and condensation on primary particles. A thermodynamic aerosol equilibrium model is used to calculate the amount of ammonium, chloride, and water present in the particulate phase with the condensed sulfate. The model calculates the stack plume opacity due to both primary and secondary particles. Examples of model simulations are presented for three scenarios that differ by the emission control equipment installed at the power plant: (1) electrostatic precipitators (ESP), (2) ESP and flue gas desulfurization, and (3) ESP and selective catalytic reduction. The calculated opacity is most sensitive to the primary particulate emissions. For the conditions considered here, SO₃ emissions showed only a small effect, except if one assumes that most H₂SO₄ condenses on primary particles. Condensation of NH₄Cl occurs only at high NH₃ emission rates (about 25 ppm stack concentration).     

Opacity of monodisperse sulfuric acid aerosols

The plume opacity and droplet diameters of a monodisperse sulfuric acid aerosol were calculated as a function of the initial H₂SO₄ concentration, initial H₂O concentration and final gas temperature after cooling from an original stack gas temperature of 300°C. Calculation assumptions include heterogeneous heteromolecular condensation of H₂SO₄ and H₂O onto monodisperse nuclei of 0.05 μm dia., three aerosol particle nuclei concentrations of 10⁶, 10⁷ and 10⁸ cm⁻³ (at 300°C and 760 mm Hg); and a stack or plume diameter of 6 m. The calculated results show that for the conditions considered and with the stack temperatures in excess of 125°C, initial H₂SO₄ stack gas concentrations of 10ppm or less will result in calculated opacities of less than 20 % for a plume diameter of 6 m. The results show that the calculated opacity is significantly affected by the initial H₂SO₄ and initial H₂O concentrations and the final gas temperature. The increases in the calculated opacities upon cooling of the stack gases are similar in general to the increases in the measured opacities between instack and outstack reported by Nader and Conner (1978) for an oil-fired boiler.     

Probabilistic assessment of the potential indoor air impacts of vent-free gas heating appliances in energy-efficient homes in the United States

Use of vent-free gas heating appliances for supplemental heating in U.S. homes is increasing. However, there is currently a lack of information on the potential impact of these appliances on indoor air quality for homes constructed according to energy-efficient and green building standards. A probabilistic analysis was conducted to estimate the impact of vent-free gas heating appliances on indoor air concentrations of carbon monoxide (CO), nitrogen dioxide (NO₂), carbon dioxide (CO₂), water vapor, and oxygen in “tight” energy-efficient homes in the United States. A total of 20,000 simulations were conducted for each Department of Energy (DOE) heating region to capture a wide range of home sizes, appliance features, and conditions, by varying a number of parameters, e.g., room volume, house volume, outdoor humidity, air exchange rates, appliance input rates (Btu/hr), and house heat loss factors. Predicted airborne levels of CO were below the U.S. Environmental Protection Agency (EPA) standard of 9 ppm for all modeled cases. The airborne concentrations of NO₂ were below the U.S. Consumer Product Safety Commission (CPSC) guideline of 0.3 ppm and the Health Canada benchmark of 0.25 ppm in all cases and were below the World Health Organization (WHO) standard of 0.11 ppm in 99–100% of all cases. Predicted levels of CO₂ were below the Health Canada standard of 3500 ppm for all simulated cases. Oxygen levels in the room of vent-free heating appliance use were not significantly reduced. The great majority of cases in all DOE regions were associated with relative humidity (RH) levels from all indoor water vapor sources that were less than the EPA-recommended 70% RH maximum to avoid active mold and mildew growth. The conclusion of this investigation is that when installed in accordance with the manufacturer’s instructions, vent-free gas heating appliances maintain acceptable indoor air quality in tight energy-efficient homes, as defined by the standards referenced in this report.

Implications: Probabilistic modeling of indoor air concentrations of carbon monoxide (CO), nitrogen dioxide (NO₂), carbon dioxide (CO₂), water vapor, and oxygen associated with use of vent-free gas heating appliances provides new data indicating that uses of these devices are consistent with acceptable indoor air quality in “tight” energy-efficient homes in the United States. This study will provide authoritative bodies such as the International Code Council with definitive information that will assist in the development of future versions of national building codes, and will provide evaluation of the performance of unvented gas heating products in energy conservation homes.     

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.     

Improvement of Air Quality in a Small Indoor Ice Arena by Effective Emission Control in Ice Resurfacers

ABSTRACT

The effectiveness of a new emission control system in the ice resurfacer was tested in an exhaust gas emission laboratory, and the improvement of the air quality in a small, enclosed ice arena was demonstrated in a 4.5-month follow-up study. The emission control system consisted of a lambda sensor-controlled fuel supply and a three-way metallic catalyst that were applied to a propane-fueled resurfacer. In the laboratory tests, the engine emissions of carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NO ) reduced simultaneously by 91, 90, and 96%, respectively. During the air quality follow-up the median 1-hour average nitrogen dioxide (N0₂) concentration inside the ice arena decreased from 430 ug/m³ (230ppb) to 58 ug/m³ (31 ppb), and that of CO decreased from 4.4 mg/m³ (3.8 ppm) to 1.5 mg/m³ (1.3 ppm). The new emission control system proved to be a feasible, reliable, and effective means to improve the indoor air quality in the ice arena. However, continuous mechanical ventilation was necessary during all business hours in order to achieve and maintain a fully acceptable air quality with this technology.     

Opacity Reduction Using Dry Hydrated Lime Injection

Abstract

This investigation studied the effects of injecting dry hydrated lime into flue gas to reduce sulfur trioxide, (SO₃) concentrations and consequently stack opacity at the University of Missouri-Columbia power plant. The opacity was due to sulf uric acid mist forming at the stack from high SO₃ concentrations. As a result of light scattering by the mist, a visible plume leaves the stack. Therefore, reducing high concentrations of SO₃ reduces the sulfuric acid mist and consequently the opacity. To reduce SO₃ concentrations, dry hydrated lime is periodically injected into the flue gas upstream of a baghouse and downstream of an induced draft fan. The hydrated lime is transported downstream by the flue gas and deposited on the filter bags in the baghouse forming a filter cake. The reaction between the SO₃ and the hydrated lime takes place on the filter bags. The hydrated lime injection system has resulted in at least 95% reduction in the SO₃ concentration and has reduced the opacity to acceptable limits. Low capital equipment requirements, low operating cost, and increased bag life make the system very attractive to industries with similar problems.     

Evaluation of the Iron-o-Phenanthroline Procedure For Determining S02 in Turbine Exhaust Gases

Several wet chemical methods have been used or suggested for the determination of SO₂ concentrations in air pollution work. These include the iron-O-phenanthroline procedure reported by Stephens and Lindstrom, the Scaringelli-modified West-Gaeke method and the Schulze method. This paper describes a laboratory study to evaluate the usefulness of the iron-o-phenanthroline procedure and is directed to individuals concerned with the analysis of gases from the exhaust of gas turbine engines and other combustion processes, including stationary power plants. The variables considered were: range of usefulness in terms of concentration of SO₂, efficiency of collection, effect of contaminants, specifically oxides of nitrogen, olefin and aldehyde and effect of storage prior to spectrophctometric measurement. The Stephens-Lindstrom method was found to be suitable for measuring higher levels of SO₂ concentrations. It can accurately measure amounts totalling 6000 µl of SO₂ and above whereas the other mentioned methods are generally used for lower levels. Collection efficiency was satisfactory. Contaminants, particularly oxides of nitrogen, are a problem only at low levels of SO₂. NO₂ interference may be eliminated by absorption of the NO₂ on Ultraport S impregnated with ANEDA/H₂SO₄ solution. Temperature control during SO₂ addition is necessary. Storage of exposed reagents prior to measurement produce only small errors if stored at 0°C or at room temperature.     

Transformations,Lifetimes, and Sources of NO2, HONO,and HNO3 in Indoor Environments

Recent research has demonstrated that nitrogen oxides are transformed to nitrogen acids in indoor environments, and that significant concentrations of nitrous acid are present in indoor air. The purpose of the study reported in this paper has been to investigate the sources, chemical transformations and lifetimes of nitrogen oxides and nitrogen acids under the conditions existing in buildings. An unoccupied single family residence was instrumented for monitoring of NO, NO₂, NO_y, MONO, HNO₃, CO, temperature, relative humidity, and air exchange rate. For some experiments, NO₂ and HONO were injected into the house to determine their removal rates and lifetimes. Other experiments investigated the emissions and transformations of nitrogen species from unvented natural gas appliances. We determined that HONO is formed by both direct emissions from combustion processes and reaction of NO₂ with surfaces present indoors. Equilibrium considerations influence the relative contributions of these two sources to the indoor burden of HONO. We determined that the lifetimes of trace nitrogen species varied in the order NO ~ HONO > NO₂ >HNO₃. The lifetimes with respect to reactive processes are on the order of hours for NO and HONO, about an hour for NO₂, and 30 minutes or less for HNO3. The rapid removal of NO₂ and long lifetime of HONO suggest that HONO may represent a significant fraction of the oxidized nitrogen burden in indoor air.     

The Effect of Water Vapor on Ozone Synthesis in the Photo-oxidation of Alpha-pinene

A study of the effect of water vapor on the photochemical system NO₂ + alphapinene + hv was conducted. A Hotpack Environmental Room was used as a constant temperature chamber, a bank of ultraviolet and fluorescent lamps as a source of simulated solar radiation, and a 150-liter FEP Teflon bag as a reaction vessel. Representative concentrations of 10 pphm NO₂ and 50 pphm alphapinene were used in a 3 × 2 × 2 factorial design where absolute humidities of 0.0000, 0.0090, 0.01 80 g H₂O/g dry air were varied.

Matheson zero air was passed through a clean air train and used as the diluent. Nitrogen dioxide was added to the reaction mixture by a permeation tube, and water and alpha-pinene by evaporation techniques.

Variables measured as a function of time over a 2-hour irradiation period were total oxidants (Mast Ozone Meter), condensation nuclei (General Electric Small Particle Detector), ozone (Regener Chemiluminescent Ozone Meter), nitrogen dioxide and nitric oxide (Technicon Autoanalyzer), and alpha-pinene (Perkin- Elmer Model 800 gas chromatograph).

Upon irradiation, systems containing nitrogen dioxide and alpha-pinene formed oxidants, ozone, condensation nuclei, and nitric oxide. Based on the differences between simultaneous oxidant and ozone measurements, the formation of peroxide- like compounds may be inferred. During the course of the irradiation, nitrogen dioxide and alpha-pinene were consumed. The concentration-time profiles of all variables were characteristic of those exhibited by typical photochemical smog systems.

An effect of water vapor on the systems studied was demonstrated. Increasing humidity decreased net mean/time oxidant and ozone production and net maximum condensation nuclei production. These effects were significant at a 0.05 confidence level. Effects of water on average mean/time NO₂, NO, and alphapinene concentrations were insignificant at this level. The oxidant to ozone ratio was found to decrease with increasing humidity.

The significant decreases in net oxidant and ozone production and NO₂ consumption with increasing water vapor concentration in systems of nitrogen dioxide alone, suggests that water manifests an effect on pertinent inorganic reactions, and the data also suggest additional water participation in the organic reactions.     

The Cost of Stack Gas Cleaning in New York State

A cost estimating methodology has been applied to an emission point inventory to estimate the capital and operating costs of stack gas cleaning in the manufacturing sector of New York State. The study represents the first major attempt to estimate control costs on a source by source basis for a large region. The various control cost components are presented for each of the twenty manufacturing industry groups and the usefulness of the estimates for an abatement planning model is outlined.

In recent years a number of heroic efforts have been made to estimate the cost of air pollution abatement on a national or regional basis. Unfortunately, these studies have relied almost entirely upon emission factors, cost engineering functions, pilot plant operations, and average or ideal firms, because of the paucity of primary data.^1-6

In the estimates of capital and operating costs presented below, an attempt has been made to improve on previous research by making extensive use of primary data. The data were taken from an emission inventory of over 20,000 sources of air contamination in New York State. A cost estimating methodology was applied to engineering parameters of existing control operations on a source by source basis. The results have been aggregated to the two-digit SIC level.     

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.