George J. Newton

Use of a Jet Mill for Dispersing Dry Powder for Inhalation Studies

Compressed air-powered jet mills are used in the chemical and food industries for grinding and classifying powders. We adapted one type of these fluid energy mills as a powder generator for inhalation experiments. The generating system included a jet mill and a screw feeder, the jet mill consisting of an elongated channel, a feeding jet to deliver the material into the channel, and two high-speed air jets. High speed air circulating in the channel created turbulence and centrifugal forces to disperse powder. The jet mill used can be operated from 25 to 100 psig at flow rates of 300 to 900 L/min. Two test materials--a solvent yellow dye and a dye mixture of solvent green and solvent yellow--were used. Both dyes were soft and sticky and could not be dispersed with several other powder generators tested at the concentrations required for toxicity studies. Aerosol concentrations ranging from 10 to 1500 mg/m3 at a flow rate of 400 L/min were obtained by adjusting the feed rate to the jet mill. Stability of aerosol concentration during six-hour continuous generation was 15 to 20%. Comparisons of several generators for producing sticky organic powders are also discussed.

Respirable aerosols from fluidized bed coal combustion. 3. Elemental composition of fly ash

Trace element constituents in fly ash from an experimental atmospheric fluidized bed combustor (AFBC) are reported and compared with pulverized coal combustor (PCC) data and those from other fluidized bed combustors. Bulk and size-separated particles were collected and analyzed using spark source mass spectrometry. Fluidized bed combustion ash was similar to PCC ash in minor and trace element composition, but AFBC ash showed less size dependence of elemental composition. Bulk particle elemental composition varied with sampling position within the effluent stream. Penetration of elements through each cleanup stage and elemental enrichment were a function of the cleanup stage and the element under consideration.

High-temperature-high-pressure cascade impactor design, performance, and data analysis methods

Abstract A high-temperature-high-pressure, seven-stage cascade impactor has been designed, built, calibrated, and used to obtain size-classified samples of entrained fly ash from process streams of a pressurized low Btu coal gasifler. The cascade impactor was designed for an effective cutoff diameter (ECD) range of 12 μm down to about 0.5 μm aerodynamic diameter. Methods for calculating gas mixture viscosity, density, and mean free path have been developed and used to calculate impactor stage characteristics at operating temperatures and pressures for the gas mixture sampled. Process stream conditions were 400–700°C and 900–1370 kPa. The measured size distribution at stream conditions indicated a mass median aerodynamic diameter (MMAD) of 2.88 ± 0.47 μm with a geometric standard deviation (σg) of 2.35 ± 0.35.

Nonideal collection characteristics of a cascade impactor with various collection substrates.

A series of collection substrates was used to evaluate the dependence of collection efficiency on substrate type on one stage of a seven-stage cascade impactor. Data obtained were used to determine which substrates yielded the best collection characteristics for cascade impactors. Stainless steel, silver membrane filters, and cellulose acetate membrane filters as cascade impactor collection substrates showed stage collection characteristics that closely fit theoretical predictions. Fiber-type substrates showed the most deviation from the theoretical efficiency curve.

Low Btu Coal Gas Combustion Emission Characteristics

Information presented in this paper is directed to individuals concerned with the emission characterization and control of process streams. Emissions from burning low Btu gas from an experimental gasifier were sampled and characterized. Both particulate and vapor samples were collected. Transmission electron micrographs showed that the particles were single droplets less than 1 μm in diameter. Size distributions of aerosols as measured by the electrical aerosol analyzer showed a bimodal distribution. Energy dispersive X-ray analysis and ion chromatography analyses indicated that SO4 -2 was the major component of the aerosol. This suggested that the combustion aerosol from low Btu gas may be sulfuric acid droplets or other sulfates produced from oxidation of H2S in the combustion process. Particulate mass loadings were estimated to be 0.1 and 0.0024 lb/106 Btu for H2S levels of 3600 and 500 ppm respectively. Some reduction of organic vapors in the combustion products was observed when the H2S level was red...

Physical and chemical characterization of the process stream for a commercial-scale fluidized-bed combustion boiler.

Analyse des effluents gazeux et cendres volantes issus de la combustion en lit fluidise. Identification des composes aromatiques polycycliques (naphtalene, phenanthrene, pyrene, chrysene, benzopyrene)

Characterization of selected epa priority pollutant elements in process and potential waste streams of an experimental low-btu gasifier

Abstract To aid in assessment of potential environmental consequences of coal gasification, process streams of an experimental, fixed-bed Wellman—Galusha gasifier were analyzed. Selected Environmental Protection Agency priority pollutant elements were analyzed by atomic absorption spectroscopy. These analyses were intended to aid in the evaluation of the effectiveness of product gas clean-up devices and provide data for improved human health risk estimates. We analyzed samples of Venturi scrubber water, tars from the humidifier and tar trap, dust from the cyclone, and raw and cleaned samples of process gas. Lead, chromium, and arsenic in the Venturi scrubber outlet water were present at 100, 40, and 26 times the limit of the primary drinking water standard (0.05 ppm) for these elements. Significantly higher concentrations of sodium and potassium were observed in the smaller particles than in the larger particles collected by a high-temperature high-pressure cascade impactor from the raw process gas. Enrichment of chromium and nickel in process stream particles during passage through the clean-up system may indicate some erosion of the gas producer.