Development of a High-Temperature Subtractive Analyzer for Hydrocarbons

This paper discusses the development of a high-temperature subtractive analyzer for separating the hydrocarbons present in gaseous mixtures into two categories— reactive hydrocarbons and unreactive hydrocarbons. The analyzer utilizes the ability of selected substances to absorb certain groups of hydrocarbons and their derivatives from a gas mixture and is designed for operation with a flame ion-ization detector. The body of information presented in this paper is directed to individuals concerned with the analysis of the exhaust gases of gas turbine engines or other combustion sources as stationary power plants. The analyzer grew out of an investigation of a previously reported subtractive analyzer system which operates at ambient temperature. Current state-of-the-art requirements for the accurate determination of total hydrocarbons at the concentrations present in turbine exhaust gases necessitate that sampling and measurements be conducted at elevated temperatures (325-375°F), rather than ambient temperature, to reduce or eliminate condensation and wall adsorption sampling errors. To fulfill this requirement, the sampling lines and flame ionization detector must be heated. After tests determined that the previously reported scrubber system would not remove the same hydrocarbons at elevated temperature levels as it did at ambient temperatures, an investigation of the effectiveness of various absorbents at elevated temperatures was conducted. This led to the development and test of the high-temperature subtractive analyzer concept discussed in this report. In its final form, one path of this unit contains no absorbent, the second contains a column of concentrated H₂SO₄ on Ultraport and a column containing PdSO₄ and H₂SO₄ on Ultraport. The two columns are connected in series. The absorbents remove olefins, aromatics, acetylene, and oxygenated hydrocarbons but pass paraffins. As the final step in this program, a comparison of the two subtractive analyzers was made using the exhaust from a gas turbine combustion system.     

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.     

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.     

Balance Corrections for Buoyancy

This paper describes a versatile experimental facility for evaluating the collection of high resistivity fly ash by advanced electrostatic precipitator designs at near full scale. The unit will operate on a slipstream of up to 424 m³/min (15,000 acfm) from a boiler firing pulverized low sulfur Western coal with an ash resistivity of 10¹³ ohm-cm at 149°C (300°F). The test unit is designed so that if can be configured as either a single-stage or a two-stage unit and allows for easy installation of different charger and collector components for evaluation. A dampered heat exchanger provides control over the gas temperature from 93°C (200°F) to 370°C (700°F) so that tests can be run at either hot-side or cold-side conditions. Support equipment includes a gas circulating fan, venturi meter for measurement and control of the flow, an instrumentation trailer housing a computerized system for data collection and control of the ESP, and a gas analysis trailer and particulate sampling station for a comprehensive evaluation of the system.     

A System for Control of Aluminum Chloride Fumes

During primary aluminum processing the molten aluminum is periodically fluxed with chlorine to separate impurities from the metal. The gaseous effluent from the chlorination process contains submicron particulates and gaseous vapors which produce a dense, white plume. The plume is acidic with hydrogen chloride and chlorine vapors, which cause a variety of corrosion problems. Since the stack discharge temperature can range as low as 200°F-and aluminum chloride sublimates at about 360°F, blockage of ductwork can also occur. For effective removal of both the particulates and chloride gases in the effluent, a sodium hydroxide solution is recommended. However, such a scrubbing liquor produces a flocculent precipitate. Therefore, a nonplugging type of scrubber is required. The solution UOP advanced was a “mobile packing” type of scrubber, utilizing a bed of polypropylene spheres in random, turbulent motion. The motion of the packing prevents plugging. The paper describes the design for such a system, describing the optimum use of ductwork, scrubber placement, gas saturation, and recirculation equipment. Instrumentation requirements, both minimum and optimum are discussed.     

Note On The Collection of Lint Fly by Wet Impingement

A combined water scrubber-impinger was used to control lint cleaner effluent from machine-stripped short staple (11/16-13/16 in.) cotton because of its high efficiency and low pressure drop. The 8 × 4 × 4 ft rectangular scrubber could handle a maximum of 8000 CFM entering air at 80°F, 20% relative humidity and 0.7 g particulates/m³ with a 1-sec residence time at a maximum pressure drop of 0.5 in. of water across the chamber. Water to the chamber’s 6 doublespray and 2 single-spray nozzle taps was supplied from recycle and makeup sources at pressures of 7.5–30 psig with total flows of 21.8–31.1 gpm depending on number of nozzle taps in use. These sprays effectively wetted the particulate- laden air and provided enough water to wash the collected particulate matter down the chamber walls. The four WR-10 nozzles used at the base of the scrubbing chamber provided fine conical spray patterns co-current with the air flow. The two sets of four F-20 nozzles used in the center portion of the chamber provided coarse flat sheet sprays perpendicular to the air flow path. Two large TR-50 nozzles at the top of the chamber provided the necessary coarse conical sprays to wash the collected particulates down the chamber wall to the trash-water separator below. Water flows through the nozzles were determined from pressure readings at each tap. Chamber pressure drop was determined by 15° inclined manometer readings taken across the chamber at the locations where the air inlet and outlet mean square velocities occurred.     

The Effect of Ethanol Fuel on the Emissions of Vehicles over a Wide Range of Temperatures

ABSTRACT

The emissions from a fleet of 11 vehicles, including three from the State of Alaska, were tested at 75, 0, and -20 °F with base gasolines and E10 gasolines, that is, gasolines with 10% by volume ethanol added. The data for the changes in emissions for the test run at 75 °F are included, since most other studies on the effects of E10 gasoline on emissions were run at that temperature. The three Alaskan vehicles were also tested at 20 °F. The testing followed the Federal Test Procedure, and regulated emissions—CO, total hydrocarbons (THC), and nitrogen oxides (NO_x)—CO₂, speciated organics, and fuel economy were measured. A total of 490 FTP tests were run. The data obtained indicated that with most vehicles, at the temperatures tested, improvements in both CO and THC emissions were obtained with the use of E10 fuel. At the lowest temperature used, -20 °F, most vehicles had an increase in NO emissions with the use of E10 fuel. At the other temperatures, however, more vehicles showed a decrease in NO_x emissions with the use of E10. With all vehicles at all temperatures tested, the emissions of acetaldehyde increased significantly when E10 fuel was used. The highest increase was about 8 to 1. Benzene, formaldehyde, and 1,3 butadiene showed both increases and decreases in the emissions when using E10 fuel. Unexpected results were obtained with the fuel economy, with about half of the tests showing an increase in fuel economy with the use of E10 fuel.     

Laboratory Evaluations of the Thermal Degradation Properties of Toxic Organic Materials in Sewage Sludge

Laboratory thermal decomposition studies were performed to evaluate potential emissions from sewage sludge incinerators. Precisely controlled thermal decomposition experiments were conducted on sludge spiked with mixtures of hazardous organic compounds, on mixtures of pure compounds without sludge, and on unspiked sludge. Experiments were conducted in nitrogen and air atmospheres with gas phase reaction times of 2.0 seconds over the temperature range 300°C-1000°C.

It was found that sludge inhibited the decomposition of moderately stable spiked contaminants but accelerated the decomposition of the most stable components. This effect was attributed to radical scavengers produced by the sludge matrix at lower temperatures which then decomposed at higher temperatures. A multiple hearth simulation study suggested that most of the organic material present In the sludge matrix is vaporized within the upper hearths that are held at lower temperatures and may consequently escape from such incinerators undestroyed. A number of stable byproducts resulted from the sludge decomposition that may be of environmental concern.     

Feasibility Demonstration of Electrostatic Precipitation at 1700°F

An experimental high-temperature, high-pressure electrostatic precipitator module has been designed, fabricated and then evaluated in a gaseous environment having the characteristics anticipated for the combustion chamber of a system for generating electric power from the incineration of municipal solid wastes.

Stable positive and negative corona discharges were established in combustion gases from the burning of methanol and air (temperature and pressure approximately 1700°F and 100 psig, respectively) without any apparent deleterious effects due to thermal ionization and/or emission. At gas conditions of about 1700°F and 50 psig, positive polarity energization of the discharge electrode appeared superior to that of negative polarity in terms of voltage level that could be applied and electrical stability.

However, precipitator performance on removal of alumina dust injected under controlled conditions with the methanol fuel, showed negative polarity to be superior to positive polarity at the selected conditions of 1650°F and 100 psig which closely correspond to those required for optimum operation of the gas turbine presently under consideration. Removal efficiencies ranging from 25% for positive polarity to as high as 87% with negative polarity were measured.

In order to check whether materials having a low ionization potential would thermally ionize to such an extent that the voltage-corona current characteristics of the precipitator would be impaired, rendering it ineffective, potassium chloride salt in solution was injected with the fuel. Results indicated that amounts of approximately one part by weight of potassium ion in 2500 to 3000 parts by weight of gas at 1700°F tripled the current measured for a given voltage when compared to non-injection.

Although a limited test program was conducted, sufficient data were obtained to allow preliminary design and sizing of larger scale units.     

Metallic elements in particulates released during incense-burning at Tzu Yun Yen temple, Taichung, Taiwan

Concentrations of ambient suspended particulates were measured at Tzu Yun Yen temple (120°, 34′ 10”E; 24°, 16′, 12”N), using a Universal sampler and dry deposition plates. The temple is a characteristic incense-burning and semi-open sampling site. PM_2.5 concentrations for Period 1 (average 901μg/m3) were higher than those for Period 2 (average 701μg/m3). Results for average PM_2.5-10concentrations showed equal distributions in Period 1 and Period 2. Average ratios of PM_2.5/ PM₁₀ were higher in Period 1 (74%) than Period 2 (71%). In addition, the suspended particulate (PM₁₀) elements concentrations during Zhong Yuan Jie, and the first and 15th days of nong li for each month (Chinese lunar calendar) were all higher than during non-Zhong Yuan Jie and non-first and non-15th days. Furthermore, the dry deposition velocities of manganese in fine particulates (PM_2.5) and suspended particulates (PM₁₀) were 1.43 and 0.751cm/s, respectively, and the dry deposition velocities of cadmium in fine particulates (PM_2.5) and suspended particulates (PM₁₀) were 1.86 and 0.991cm/s, respectively.     

Effect of temperature and particle size on the thermal desorption of PCBs from contaminated soil

Thermal desorption is widely used for remediation of soil contaminated with volatiles, such as solvents and distillates. In this study, a soil contaminated with semivolatile polychlorinated biphenyls (PCBs) was sampled at an interim storage point for waste PCB transformers and heated to temperatures from 300 to 600 °C in a flow of nitrogen to investigate the effect of temperature and particle size on thermal desorption. Two size fractions were tested: coarse soil of 420–841 μm and fine soil with particles <250 μm. A PCB removal efficiency of 98.0 % was attained after 1 h of thermal treatment at 600 °C. The residual amount of PCBs in this soil decreased with rising thermal treatment temperature while the amount transferred to the gas phase increased up to 550 °C; at 600 °C, destruction of PCBs became more obvious. At low temperature, the thermally treated soil still had a similar PCB homologue distribution as raw soil, indicating thermal desorption as a main mechanism in removal. Dechlorination and decomposition increasingly occurred at high temperature, since shifts in average chlorination level were observed, from 3.34 in the raw soil to 2.75 in soil treated at 600 °C. Fine soil particles showed higher removal efficiency and destruction efficiency than coarse particles, suggesting that desorption from coarse particles is influenced by mass transfer.     

Development of a standard reference material containing 22 chlorinated hydrocarbon gases at 1 μmol/mol in nitrogen

A gas standard mixture containing 22 chlorinated hydrocarbons in high purity nitrogen was prepared using a two-step weighing method and a gasifying apparatus developed in-house. The concentration of each component was determined using a gas chromatograph with flame ionization detection (GC/FID). Linear regression analysis of every component was performed using the gas standard mixture with concentrations ranging from 1 to 10 μmol/mol, showing the complete gasification of volatile organic compound (VOCs) species in a selected cylinder. Repeatability was also examined to ensure the reliability of the preparation method. In addition, no significant difference was observed between domestic treated and imported treated cylinders, which were conducive to reduction of the cost of raw materials. Moreover, the results of stability testing at different pressures and long-term stability tests indicated that the gas standard at 1 μmol/mol level with relative expanded uncertainties of 5% was stable above 2 MPa for a minimum of 12 months. Finally, a quantity comparison was conducted between the gas standard and a commercial gas standard from Scott Specialty Gases (now Air Liquide America Specialty Gases). The excellent agreement of every species suggested the favorable accuracy of our gas standard. Therefore, this reference material can be applied to routine observation of VOCs and for other purposes.     

Effect of Diffusiophoresis and Thermophoresis on the Overall Particle Collection Efficiency of Spray Droplet Scrubbers

The overall particle collection efficiencies of spray scrubbers using monodisperse droplets of 100,500, and 1000 microns diameter were calculated for the cases of evaporating and condensing droplets. The properties of the gas at the inlet to the spray scrubber were maintained constant at 150°F, 100% relative humidity, and 1 atmosphere pressure. At the liquid entrance to the spray scrubber, the water droplet temperature was 50° F for the condensing case and 180° F for the evaporating case. The liquid to gas flow rate ratio for all the calculations was held constant at 4 gal/1000 acf. The gas velocity in the co-current spray tower was 1 ft/sec in the downwind direction. The calculation results show that for the particles in the 0.01 to 10 Mm diameter range, the overall spray scrubber particle collection efficiency is greater with the cooler 50°F water (condensing case) than with the warmer 180°F water (evaporating case). The effect of diffusiophoresis and thermophoresis is noticeable for all the water droplet sizes considered, but is more significant for the larger water droplets. This greater effect for the larger water droplets compared to the smaller droplets is due to the longer existence of the temperature and water vapor concentration gradients between the water droplets and the surrounding gas.     

Aircraft Release of Sulfur Hexafluoride as an Atmospheric Tracer

Abstract

The effect of temperature on polyvinylchloride (PVC) combustion using a downstream tubular furnace was investigated for the formation of polycylcic aromatic hydrocarbons (PAHs) and chlorinated compounds. As the temperature increased, higher levels of PAHs were generated. Chlorinated compounds reached a peak at 600°C, with low emissions recorded at 300 and 900°C. There was a close correlation (R² = 0.97) among polychlorinated bi-phenyls (PCBs), hexachlorobenzene, pentachloroben-zene, and polychlorinated dibenzo-p-dioxins and poly-chlorinated dibenzofurans (PCDD/Fs). PAHs at all temperatures were analyzed in the gas phase. PCDD/Fs and PCBs were emitted as a solid phase at 300 and 600°C and as a gas phase at 900°C. For some PAHs, chloroben-zenes, and PCDD/Fs, a mathematical equation between the gas and solid phase and the reciprocal temperature in semilog proportion was derived. The proposed equation, which is log (amount in gas phase/amount in solid phase) = ?A/T + B, where T is the temperature of the furnace and A and B are constants, for these species relating their gas/solid distributions showed a good relationship.     

Hydrogen Sulfide Removal From Hot Producer Gas With Sintered Absorbents

The Bureau of Mines prepared three sintered materials capable of removing H₂S from producer gas at 1000° to 1500°F. They are mixtures of ferric oxide and fly ash, ferric oxide and pumice stone, and red mud (a ferric oxide-containing residue from processing bauxite). All three absorbents were virtually completely regenerable with air. A sintered Fe₂O₃; (25%)-fly ash [75%) mixture was tested through nine H₂S absorption-air regeneration cycles without loss of absorplion capacity or attrition of the pellets. The absorbent with the greatest capacity was a red mud, absorbing 16.0% by weight of sulfur at 1000° F, 24.0% at 1250° F, and 45.1 % at 1 500° F.     

HCI Sorption by Dry NaHCO3 for Incinerator Emissions Control

The sorption of hydrochloric acid (HCI) by thermally decomposed sodium bicarbonate (NaHCO₃) was investigated using a fixed-bed reactor containing sorbent particles dispersed in a bed of spherical glass beads. The gas flow rate (68° F and 760 mm Hg) was 0.039 cfm (1.1 liter/min) and the bed had a cross-sectional area of 0.0055 sq. ft. (5.1 sq. cm). The influence of particle diameter (10, 45 and 163 μm), temperature (225, 275, 375, 455, and 550° F), superficial gas velocity (11 and 21 fpm at reactor conditions, 375° F), and Inlet HCI gas concentration (415 ppm and 760 ppm in N₂, 275 and 455° F) were studied. Results showed that HCI sorption increased strongly with increasing temperature but was only weakly dependent on particle diameter, superficial gas velocity, and HCI gas concentration.     

Organic Content of Particulate Matter In Turbine Engine Exhaust

Solid particulate matter, mainly carbon, emitted into the air from the combustion of fossil fuels contains a variety of organic species adsorbed on it. In our examination of these particulates from the combustion of kerosene type fuels in a gas turbine engine, attention was focused on polynuclear aromatic compounds, phenols, nitrosamines, and total organics. Polynuclears were determined by HPLC, GC/MS, and NMR examination. Phenols and nitrosamines were isolated and then measured by gas chromatography using a flame ionization detector and nitrogen detector. Total organics were determined by a backflush chromatographic procedure. The particulates were collected using a high capacity pumping system and 293 mm diameter teflon filters through which was passed up to 43 m³ of exhaust gas. Extraction of the organic matter was done in a Soxhlet extractor using hexane usually. The engine was operated at idle, approach, climb, and takeoff power settings with low sulfur and high sulfur (0.25%) fuels. Most of the PAH were small 3 and 4 fused ring compounds with very few, at low concentrations, of 5 and 6 fused ring species. No nitrosamines were found and except in a few cases, at low levels, no phenols. PNA and total organic levels decreased with increase in a power setting and were higher in the exhaust from low sulfur fuels. Less than 1% of the organic matter emitted by the engine was absorbed on the particulate matter. The body of information presented in the paper is directed to individuals concerned with the nature of emissions from gas turbine engines. The work was supported by a contract with the Environmental Protection Agency.     

An Analytical Method to Determine Henry’s Law Constant For Selected Volatile Organic Compounds At Concentrations And Temperatures Corresponding To Tap Water Use

Henry’s law constants (H) are needed to model human exposure to Volatile Organic Compounds (VOCs) in Indoor air resulting from the use of tap water. This paper presents an experimental method to determine Hs for several common tap water pollutants at concentrations and temperatures used in household water. For 5 VOCs Henry’s law constants were obtained simultaneously over the 25° C to 45° C temperature range, providing data on H beyond the currently available data (up to 35° C). Henry’s law constants were obtained as the ratio of equilibrium concentrations of VOCs in air and water, using simultaneous sampling from sealed bottles kept at constant temperatures. Air and water samples were concentrated by a purge-and-trap method, thermally desorbed from a Tenax trap, and analyzed with a gas chromatograph with an electron capture detector (GC-ECD). Experimental results agreed well with available literature data.     

Gasoline Evaporation–Ethanol and Nonethanol Blends

Tests were performed to compare the evaporation rate of 10 volume percent (vol%) ethanol-blended gasoline (E10) with the evaporation rate of its base gasoline. Weight loss, temperature, pressure, and humidity were monitored as lab-blended E10 and base gasolines were evaporated concurrently from glass cylinders placed on balances located side by side under an exhaust hood. The averaged results of four tests at about 70°F showed that the E10 lost more total weight to evaporation than the base fuel, but less gasoline. The increased weight was due to ethanol, which was present in the E10 evaporative emissions at concentrations of about 13 weight percent (wt%). In two-hour tests at temperatures near 70°F, during which 4.5 to 5.3 wt% of initial fuel samples were evaporated, E10 fuels lost an average of about 5% less gasoline than their base fuels. A similar result was obtained for a one-hour test, during which about 2.4 to 2.5 wt% of the initial fuel samples were evaporated. Gas chromatography (GC) component analysis indicated that the compositions of the ethanol-free emissions from the two fuels were similar. Reid vapor pressure (RVP) measurements made using a Grabner CCA-VPS according to ASTM D5191-91 indicated that E10 fuels underwent an approximate 5% greater RVP reduction than their respective base fuels.     

Pilot Study of Enclosed Thermal Soil Aeration for Removal of Volatile Organic Contamination

During the winter and spring of 1986 sandy soils contaminated with volatile organic chemicals were successfully treated during a pilot study of an enclosed thermal soil aeration process at the McKin Superfund site in Gray, Maine. Excavated soil containing up to 3310 ppm of trichloroethylene (TCE) was fed into a large rotating drum and mixed at 300°F. Aerated soil was then solidified with cement and water and returned to the on-site excavation location. Exhausted air from the enclosed aeration process was treated in a baghouse, a scrubber, and a vapor phase carbon bed prior to atmospheric release. Continuous air monitoring for organic vapors and particulates took place at the site perimeter and for organic vapors at onsite locations. Techniques to minimize uncontrolled volatilization of organic chemicals from the soil during excavation and aeration and to control dust emissions were implemented. Results of this pilot study indicate that concentrations of volatile organic contaminants routinely were reduced to nondetectable levels and achieved site-specific soil performance targets established by the U.S. Environmental Protection Agency. The pilot study was conducted by Canonie Environmental Services Corporation and funded by private companies under order from EPA.