Instrumenting Light Aircraft for Air Pollution Research

Light aircraft and helicopters have been occasionally used to conduct aerial traverses for a single pollutant or atmospheric tracer. The continuous analyzer or sample collector is temporarily tied down with a seat belt or hand held. Flight variables are visually observed and written on the recorder chart, a notebook or possibly voice-recorded on a portable tape recorder. The versatile airborne instrumentation package described can measure and record up to 27 pollutant and flight variables from a Cessna Skymaster center-line thrust, light twin. Real-time analysis instrumentation include non-dispersive infrared analyzers for CO₂, CO, and hydrocarbons, conductivity and coulometric analyzers for sulfur dioxide and sulfur-containing gases, and Charlson-Ahlquist visual range nephelometer. A Battelle “bulk sampler” is used to collect particulates for weighing and microscopic examination. Indicated air speed, altitude, rate of climb, magnetic heading, temperature, and relative humidity are continuously measured. All variables are sequentially recorded on a 7-track, 200 bit per second, 27-channel, magnetic tape data logging system. Measured variables are recorded once each 0.3 to 0.8 sec—equivalent to 33-100 ft of traversedepending upon the number of variables recorded (i.e., between 9 and 27) when flying at 90 mph. Tape data are reduced directly by IBM 360 computer to a digital print-out or from tape to an X-Y analog plot.     

The Removal of Particulate Matter from Fluid Bed Catalytic Cracking Unit Stack Gases

The application of a high-efficiency centrifugal type of separator to fluid bed catalytic cracking units is described in which most of the catalyst particles often lost to the atmosphere are concentrated into a small part of the stack gas (2%). A further separation can then be made on this small stream by an auxiliary separator which further concentrates the catalyst particle into 0.1% of the initia stream. Performance of the main and auxiliary separators are such as to reduce the loss of catalyst particles in the stack gas from 800 ppm to less than 60 ppm in a typical unit. Large amounts of power can be recovered by application of expander turbines to catalytic cracking plants employing this system of separation.     

The Effect of Fuel Composition on Atmospheric Aerosol Due to Auto Exhaust

Aerosols attributable to automobile exhaust can be classified as two types—primary aerosol (initially present in the exhaust) and secondary aerosol (generated photochemically from hydrocarbons and nitrogen oxides in the exhaust). In this study, investigation was made of possible effects of motor-fuel composition on the formation of these aerosols. Secondary aerosol, of principal interest in this work, was produced by irradiating auto exhaust in Battelle-Columbus’ 610 ft³ environmental chamber. A limited number of determinations of primary aerosol in diluted auto exhaust was made at the exit of a 36 ft dilution runnel. Determination of both primary and secondary aerosol was based on light-scattering measurements.

Exhaust was generated with seven full-boiling motor gasolines, both leaded and nonleaded, in a 1967 Chevrolet which was not equipped with exhaust-emission control devices. Changes in fuel composition produced a maximum factor of three difference in light scattering due to primary aerosol. Aerosol yields, for consecutive driving cycles on the same fuel, vary considerably; as a result, ranking the fuels on the basis of average primary aerosol yield was not very meaningful. In addition to fuel composition, the more important independent variables are initial SO₂ concentration, relative humidity and initial hydrocarbon concentration. Statistical analysis of the data indicates that the seven test fuels can be divided into two arbitrary groups with regard to secondary aerosol-forming potential. The fuels in the lower light-scattering group had aromatic contents of 15 and 21%, while those in the higher light-scattering group had aromatic contents of 25, 48, and 55%. Although the fuels can be grouped on the basis of a compositional factor, the grouping of fuels with aromatic content ranging from 25 to 55% indicates that this compositional factor cannot be equated simply with aromatic content. In an associated study of the aerosol-forming potential of individual hydrocarbons prominent in auto exhaust, it was observed that aromatics produce substantially more photochemical aerosol than olefins and paraffins. However, experiments with binar/hydrocarbon mixtures containing aromatjcs, as well as in these exhaust experiments, a strong dependence of aerosol yield on the aromatic components is is not observed. Thus, the data indicate that the dependence of secondary aerosol formation on fuel factors is a complex one and cannot be predicted solely on the basis of a sirigle hydrocarbon component reactivity scale.

The two types of automobile aerosol did not have the same dependence on fuel, composition. The variation in total light scattering attributable to primary plus secondary aerosol was less than that due to either component alone. It therefore was concluded that the light scattering due to automobile exhaust emissions in these experiments was not significantly affected by changing fuel composition.     

New Approaches to the Design of Afterburners for Varnish Cookers

The best method of controlling varnish kettle emissions is by thermal incineration. Two new approaches have been developed; these utilize the integral-blower burner and the non-powered raw gas burner. Both of these new approaches offer significant advantages over conventional methods of incineration. Installation, operating, and maintenance costs are substantially reduced when either approach is utilized.

When compared to conventional methods, the new approaches achieve an increase of 100% in mixing velocity or turbulence. This results in a reduction of 20% in fuel consumption. Residence time is reduced by 29% via the non-powered raw gas burner approach. An average reduction of 65% is obtained in the length to diameter ratio. Choice of which approach depends upon several factors, primarily the type of fuel available and the minimum oxygen concentration in the fume stream.     

Modifications to an H2S Tape Sampler for Increasing Sensitivity and Accuracy in H2S Sampling

The tape samplers using lead acetate impregnated paper tapes for continuous hydrogen sulfide sampling are subject to a number of errors which can throw considerable doubt on the accuracy of H₂S concentrations being measured. Some of the errors have been minimized with a change in the humidification system and a reduction of the lamp intensity in the optical system.     

Emissions from Slash Burning and the Influence of Flame Retardant Chemicals

Pollutants sampled during the burning of 30 lb ponderosa pine fuel beds yielded emission factors for CO, hydrocarbon gases, and par-ticulate matter of 146, 8.4, and 9.1 lb/ton of fuel, respectively. When similar beds were treated with diammonium phosphate flame retardant, these factors increased to 166, 11.7, and 19.3 lb/ton of fuel, respectively.

Gas chromatographic analysis of hydrocarbon gases showed that 15-40% of this material was composed of methane and eth-ylene. Ethane and acetylene were the next most abundant materials, with photochemically important materials constituting minor portions of this gaseous component. Fuel beds treated with flame retardant produced more oiefins, and this production lasted throughout the smoldering phase of burning.

These tests showed that the smoldering phase of combustion is of major importance to air pollutant production during slash burning. The initial 80% of the fuel burned accounted for only 20-30% of HC and CO emissions. This suggests that a rapid mop-up of slash burns could substantially reduce air pollutant production.     

Stack Sampling of Hygroscopic Particulates In an Entrained Water Environment

Reference methods for the determination of mercury emissions from stationary sources typically include collection of mercury by solutions which are acidic and oxidizing. In the presence of high levels of SO₂ the oxidizing capacity of these absorbing solutions will be degraded and the collection efficiency for mercury compromised. This seriously limits the usefulness of the reference methods as they apply to the mining and smelting industries. In the present work peroxide is used to remove SO₂ and acidic permanganate is used to collect mercury. At a mean sampling rate of 10 L/min concentrations of at least 12 mg/m³ mercury can be satisfactorily collected in the presence of up to 20,000 ppm SO₂.