Vapor particulate ratio

When insufficient data are available, it may be necessary to generate test atmospheres to determine the physical state of a compound and the collection efficiency of a filter and vapor collector. The estimation of the vapor/particulate ratio may also depend on concentration and sample loading. For example, in a short sampling time, vapor may be efficiently collected on a filter, but longer term sampling may reveal saturation of the filter with vapor and eventual passage of the vapor into a backup bubbler or sorbent tube. 

This reaction is carried out in tall fluidized beds of high L/dt ratio. Pressures up to 200 kPa are used at temperatures around 300°C. The copper catalyst is deposited onto the surface of the silicon metal particles. The product is a vapor-phase material and the particulate silicon is gradually consumed. As the particle diameter decreases the minimum fluidization velocity decreases also. While the linear velocity decreases, the mass velocity of the fluid increases with conversion. Therefore, the leftover small particles with the copper catalyst and some debris leave the reactor at the top exit. 

A rough guideline was used in this program for determining if a substance exists as a vapor or particulate (or both) at levels near the OSHA standard. If the ratio of the equilibrium vapor concentration at 25°C to the standard was between Q.05 and 50, then contribution from both vapor and particulate was considered. A ratio below 0.05 indicated it would probably be vapor. Frequently,... 

If the ratio EVC/std is in the range 0.05 to 100-300, then a mixture of particulate and vapor may be present (7). A ratio above this range indicates the presence of vapor alone and below the range, particulate. The reliability of this determination depends on the accuracy of vapor pressure data. In method development and validation studies, it is often necessary to perform special tests with generated test atmospheres at different temperatures and concentrations to demonstrate the physical form of the substance. 

Preconcentration - Concentrates the explosive delivered from the sample collection subsystem. The preconcentration subsystem is a mechanical system that extracts the explosive vapor and/or particulate from the airflow of the sample collection subsystem. The preconcentration subsystem also serves as an impedance-matching device between the sample collection airflow and the detector airflow (which moves tens to hundreds of cubic centimeters of air per minute). Preconcentration in trace portals increases the concentration ratio (10-105 times) of the explosives delivered from the sample collection subsystem to the detector [8],... 

PCBs in water are transported by diffusion and currents. PCBs in surface water essentially exist in three phases dissolved, particulate, and colloid associated (Baker and Eisenreich 1990). The heavier and less soluble congeners in the water column are more likely to be associated with particulates and colloids, and do not freely exchange into the vapor phase. However, the more water soluble, lower chlorinated (and ori/io-rich) congeners are predominantly in the dissolved state in the water column and can readily partition into the vapor phase. In New Bedford Harbor, Massachusetts, Burgess et al. (1996) reported that the ratio of colloid associated PCBs to freely dissolved PCBs increased from 1.2 to 8.0 (di-CBs to octa-CBs, respectively) as the degree of chlorination increased. However, at this site, the majority of the PCBs were associated with the particulate phase regardless of solubility or chlorination. 

In combustion chambers, a small fraction of S02 is further oxidized to S03, which reacts readily with water vapor and is emitted as sulfate. Ryaboshapko (1983) estimated the direct emission of particulate sulfate to reach 12TgS/yr. This figure appears too high, however. American studies reviewed by Robinson and Homolya (1983) show that the average ratio of SOr to S02 in power-plant flue gases is close to 0.03. The corresponding global release rate of primary sulfate then is 3 Tg S/yr, a comparably minor fraction of total sulfur emissions. 

Air is ma.de up primarily of N2, O2, and Ar, which comprise 99.9% of dry air. There is a variable amount of water vapor, and many minor and trace gaseous components, as well as aerosol and particulate species. Table 26.1 lists some atmospheric gaseous components of environmental interest, along with representative concentrations in the troposphere. Typically, gaseous concentrations are expressed as mixing ratios, that is, volume/volume concentrations. A 1-ppm concentration represents 1 volume in 10 volumes of air. Such mixing ratios are independent of temperature and pressure. Environmental effects, though, may be quantitatively related to mass concentrations, and concentrations may be reported as mass per unit volume, usually mg/m of air, under specific conditions of temperature and pressure. Aerosols and particulates are reported in this way. 

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