Development of an Odor Panel for Evaluation of Odor Control Equipment

The odor panel using the syringe dilution technique has been successfully used to judge the effectiveness of control equipment in eliminating industrial odor problems by monitoring stack emissions. Data is presented using this odor panel method for efficiency tests of direct-flame fume incinerators performed in a large variety of industrial process applications, including pulp and paper mills, rubber processing plants, food processing plants, wire enameling plants, glass fiber manufacturing plants, paint bake ovens, brake manufacturing plants, caster manufacturing plants, rendering plants, and chemical plants. Test data shows that this method of measuring odor using the syringe dilution technique is a useful and practical tool in analyzing odor problems and determining the effectiveness of control equipment by monitoring stack emissions.     

The Odor Impact Model

Abstract

This paper presents the simulation and field evaluation results of two approaches to localize pollutant emission sources with open-path Fourier transform infrared (OPFTIR) spectroscopy. The first approach combined the plume’s peak location information reconstructed from the Smooth Basis Function Minimization (SBFM) algorithm and the wind direction data to calculate source projection lines. In the second approach, the plume’s peak location was determined with the Monte Carlo methodology by randomly sampling within the beam segment having the largest path-integrated concentration. We first conducted a series of simulation studies to investigate the sensitivity of using different basis functions in the SBFM algorithm. It was found that fitting with the beta and Weibull basis functions generally gave better estimates of the peak locations than with the normal basis function when the plumes were mainly within the OP-FTIR’s monitoring line. However, for plumes that were symmetric to the peak position or spread over the OP-FTIR, fitting with the normal basis function gave better performance. In the field experiment, two tracer gases were released simultaneously from two locations and the OP-FTIR collected data downwind from the sources with a maximum beam path length of 97 m. For the first approach, the release locations were within the 0.25- to 0.5-probability area only after the uncertainty of the peak locations was included in the calculation process. The second approach was easy to implement and still performed as satisfactorily as the first approach. The distances from the sources to the best-fit lines (i.e., the regression lines) of the estimated locations were smaller than 10 m.     

The Odor Threshold of Phosphine

In the literature for odor threshold, values of phosphine are given which vary between 3 ppm^1,2 and 0.02 ppm.³ According to another paper phosphine is odorless even in concentrations up to 200 ppm.⁴ Since phosphine prepared from metal phosphides is used as a fumigant for foods, feeds, and processed food products, we carried out new investigations to clarify the discrepancy.     

Odor Control In Los Angeles County

Abstract

Concentrations of 38 gas-phase organic air toxics were measured over a 2-yr period at four different sites in and around Pittsburgh, PA, to investigate spatial variations in health risks from chronic exposure. The sites were chosen to represent different exposure regimes: a downtown site with substantial mobile source emissions; two residential sites adjacent to one of the most heavily industrialized zones in Pittsburgh; and a regional background site. Lifetime cancer risks and non-cancer hazard quotients were estimated using a traditional and interactive risk models. Although study average concentrations of specific air toxics varied by as a much as a factor of 26 between the sites, the additive cancer risks of the gas-phase organic air toxics varied by less than a factor of 2, ranging from 6.1 × 10^-5 to 9.5 × 10^-5. The modest variation in risks reflects the fact that two regionally distributed toxics, formalde-hyde and carbon tetrachloride (CCl₄), contributed more than half of the cancer risk at all four sites. Benzene contributed substantial cancer risks at all sites, whereas trichloroethene and 1,4-dichlorobenzene only contributed substantial cancer risks at the downtown site. Only acrolein posed a non-cancer risk. Diesel particulate matter is estimated to pose a much greater cancer risk in Pittsburgh than other classes of air toxics including gas-phase organic, metals, polycyclic aromatic hydrocarbons, and coke oven emissions. Health risks of air toxics in Pittsburgh are comparable with those in other urban areas in the United States.     

Odor Control in Cattle Feed Yards

Commercial cattle-feeding is a large industry in the United States. In California, for instance, there are more than 500 commercial feedlots. Each of these lots handles from less than 500 to more than 50,000 head of cattle at one time. With the urban and suburban explosion, feedlots that were at one time many miles from residential centers are now “just across the street.” Naturally the high odor level from improperly operated yards gives rise to considerable complaint and citizen indignation.

A variety of methods to reduce odor to an acceptable level have been tried with varying results. A highly satisfactory procedure is based on “good housekeeping” practices, frequent removal of fecal material, and abatement of residual odor by spraying the lots at designated intervals with a solution of potassium permanganate. Details of the method are discussed.     

Some Chemical Aspects Of Kraft Odor Control

The principal sources of odor in the kraft pulping process are the digester, the direct evaporator, and the recovery furnace. Control of odor from the digester requires the confinement of the noncondensable gases and their destruction by chlorination, burning, or by some other means. Control of odor from the direc’ evaporator depends on efficient black liquor oxidation. The recovery furnace, which potentially can be the worst source of air pollution, must be operated properly within its rated capacity. The chemistry of various control measures is discussed.     

Nature of Odor Components in Diesel Exhaust

Offensive exhaust odors are characteristic of diesel engines. One problem in control and reduction of odor is lack of understanding of odorant sources and mode of formation. The solution of this problem depends on identification of the odorants so that study of their formation and control can be undertaken. A human panel performed odor assessments in studying raw and modified diesel exhaust and synthetic blends representing portions of diesel exhaust. Their assessments were used in determining odorant identity and quantitative contribution to exhaust odor. Low molecular weight aldehydes appear to contribute little to diesel odors. The sulfur and nitrogen oxides have been examined as odorants but of these apparently only nitrogen dioxide is a potential odor contributor.     

Odor Determination Techniques for Air Pollution Control

Abstract

An airborne lidar was used to study the smoke plume from the burning of a controlled oil spill on the ocean. The ratio of the amount of light (at a wavelength, λ, of 0.532 u.m) backscattered by the smoke to the amount of light extinguished by the smoke was determined by measuring the strength of a laser beam after it had passed through the smoke plume, been reflected from the ocean, and passed through the smoke plume again, and comparing this to the strength of the laser beam reflected directly from the ocean. The optical depth of the smoke (at λ = 0.532 µm) was typically between 0.2 and 0.5. The mass fluxes of smoke particles that passed through four vertical cross sections of the (nonsteady state) smoke plume were estimated from lidar measurements to be 142, 175, 423, and 414 g ^s-1, compared to an average smoke mass production rate of ~770 g s^-1. The spatial distribution of smoke mass along the long axis of the plume was also estimated from the lidar measurements; derived smoke mass concentrations were generally <300 µg ^m-3, with a few isolated values up to ~800 µg ^m-3.     

Measurement of Odor Intensity by an Electronic Nose

ABSTRACT

The possibility of using electronic noses (ENs) to measure odor intensity was investigated in this study. Two commercially available ENs, an Aromascan A32S with conducting polymer sensors and an Alpha M.O.S. Fox 3000 with metal oxide sensors, as well as an experimental EN made of Taguchi-type tin oxide sensors, were used in the experiments. Odor intensity measurement by sensory analysis and EN sensor response were obtained for samples of odorous compounds (n-butanol, CH₃COCH₃, and C₂H₅SH) and for binary mixtures of odorous compounds (n-butanol and CH₃COCH₃). Linear regression analysis and artificial neural networks (ANN) were used to establish a relationship between odor intensity and EN sensor responses.

The results suggest that large differences in sensor response to samples of equivalent odor intensity exist and that sensitivity to odorous compounds varies according to the type of sensors. A linear relationship between odor intensity and averaged sensor response was found to be appropriate for the EN based on conducting polymer sensors with a correlation coefficient (r) of 0.94 between calculated and measured odor intensity. However, the linear regression approach was shown to be inadequate for both ENs, which included metal oxide-type sensors. Very strong correlation (r = 0.99) between measured odor intensity and calculated odor intensity using the ANN developed were obtained for both commercial ENs. A weaker correlation (r = 0.84) was found for the experimental instrument, suggesting an insufficient number of sensors and/or not enough diversity in sensor responses. The results demonstrated the ability of ENs to measure odor intensity associated with simple mixtures of odorous compounds and suggest that ANN are appropriate to model the relationship between odor intensity measurement and EN sensor response.