Author(s): Wei Yan, S. Kent Hoekman
ABSTRACT
An increasing number of countries and areas in the world suffer from either natural or anthropogenic dust, which results in a serious hazard with respect to the environment and to personal health and safety. This paper reviews and summa- rizes open literature involving the use of glycerin in dust control applications. Glycerin, a by-product from biodiesel manufacturing, has been evaluated for dust suppressant performance when applied alone as aqueous solutions, or in combinations with surfactants, polymers, or other chemicals. There are reports indicating that glycerin is effective in some dust suppression applications, although details about its use and performance metrics are generally lacking. Re- cent growth of the biodiesel industry has significantly increased the supply of crude glycerin, making it an economically attractive material for use in dust suppression. This paper also highlights several environmental accidents caused by irresponsible discharges of crude glycerin, and points out the need to understand environmental consequences of gly- cerin and its impurities when used in dust suppression applications.
1. Introduction
Sources of dust, including tephra, occur globally, but the major source regions lie in and around the extremely arid to semi-arid dryland of the world. The largest of these stretches over 10,000 km, from the western Sahara in North Africa, through the Middle East, to central and eastern Asia [1,2].
Sources of erodible natural dust are found in wadis, salt pans, and alluvial deposits, as well as in ephemeral, saline, and dry lakes through North Africa, the Middle East, the northwestern Indian subcontinent, central Asia, and northwestern China. The extent to which particles are taken up from the ground surface depends on several factors: the critical wind speed necessary to dislodge particles (known as the threshold velocity); the instability of the atmosphere; particle size; the degree of particle exposure; vegetation cover; and the mineralogical composition of loose dust on the ground surface [1,2].
Human activities also generate substantial amounts of dust. Anthropogenically disturbed land can become major dust sources, especially in the drought-stricken agricultural regions of Africa, Australia, China, and the U.S. Midwest. Estimates of the magnitude of anthropogenic contributions to global dust load range from less than 10 wt% to 50 wt%, a range of variation that reflects modeling uncertainties and a dearth of measured observational data. More recently, however, direct measurements with satellite-borne spectroradiometers, combined with surface land-use data, show that in regions where 5% - 25% of the land surface is disturbed, more than half the territory is potentially an anthropogenic dust source [1-3].
Mineral dust is composed of variable amounts of quartz, feldspars, micas, various clay minerals, carbonates, oxides and evaporative minerals. Minerals in dust occur as individual grains, aggregates or surface coatings—from less than 1 µm to ~30 µm in diameter. Dust entrainment by saltation and suspension processes takes place mostly when winds are strong and gusty. Freshly entrained dust may initially have a mineral composition similar to that of the surface soil. Particle segregation and deposition of coarse materials takes place over short distances, depending on the mineralogical composition and the physical properties of the dust. Fine and low-density particles remain in suspension and are lofted into the upper troposphere, where they can circle the globe. Airborne dust also carries micro fauna, including diatoms, bacteria and viruses; some of the latter remain alive despite being transported for distances of several thousand kilometers [4]. African dust outbreaks are partly responsible for exceeding the maximum particle concentrations permitted by air quality guidelines in southern Europe.
Fugitive dust from dirt surfaces, and the handling of bulk products with attendant particulate materials, can generate significant health, environmental and safety problems. In mining facilities, industrial sites and construction sites, the operations may be significantly restricted by dust cloud formation. Also health, environmental and safety problems may arise when any kind of dust is inhaled [2-4].
more: http://www.scirp.org/journal/PaperInformation.aspx?PaperID=17468
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