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81.
H. E. Friedrich 《Journal of the Air & Waste Management Association (1995)》2013,63(12):924-928
Hot-mix asphalt paving plant operations and the associated air pollution control problems are presented. Field observations and test data are included for full scale installations. Comparisons are made for various types of control equipment and their effectiveness. The dry cyclonic units offer the least cost expenditures, lowest space requirements, and can collect the fines in a usable condition. Wear can often be a problem, and their efficiency capabilities limit their use as total collection devices. They no longer are suitable as total collection units in many localities. Their role is being relegated to that of primary and secondary collectors. Wet collectors of several types, particularly the more sophisticated and high energy units, are capable of satisfying higher efficiency requirements. They offer space advantages and are in the medium cost range. Wear is generally no problem, however, corrosion can be a problem depending on the amount of sulphur in the rotary dryer burner fuel. Settling tanks, ponus, or pits are necessary for settling of the collected dust. The dust, as collected, is not readily reusable as mineral filler in the mix. Fabric collectors are capable of satisfying the most stringent codes. They offer the greatest cost advantage for material recovery to be used as mineral filler. First cost and space requirements of fabric filters are highest of the three classes of equipment discussed. 相似文献
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Passive vapor monitoring of underground storage tanks (USTs) containing volatile hydrocarbons at locations external to the tank (an external system) is touted as a fast and effective method of leak detection. However, major gaps remain in our knowledge of the physical processes that relate a measured vapor concentration to the leak rate, thus making network design according to a quantitative design criterion nearly impossible, and differentiation between surface spills and a leaking UST requires certain levels of sophistication in the leak detection system and in the analysis that are not usually available. Heavier-than-air vapors from the constituents of stored hydrocarbons could result in a density-driven convective propagation component that complicates the design of leak detection systems, and finally, detection times are highly sensitive to concentration detection threshold levels set by the system. The use of inadequate systems and analyses can lead to either wasted efforts or excessive subsurface contamination. This paper discusses the physical processes involved, explores the above aspects of external passive vapor leak detection design, and suggests some alternatives as they pertain to gasoline service stations. 相似文献
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The investigation of 5547 prenatal diagnoses showed 31 unexpected structural chromosome rearrangements. These included 3 Robertsonian translocations, 14 reciprocal translocations and 14 inversions. A11 were balanced, including 5 de novo rearrangements. In 3 of these cases an induced abortion was performed and in 2 cases children without detectable malformations were delivered. 相似文献
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