US EPA

2168908 

Journal Article 

Seasonality in the "grasshopping'' and atmospheric residence times of persistent organic pollutants over the oceans 

Jurado, E; Dachs, J 

2008 

Yes 

Geophysical Research Letters
ISSN: 0094-8276
EISSN: 1944-8007 

35 

17 

10.1029/2008GL034698 

WOS:000258999800003 

Petrographic techniques have been used to examine bed materials from fluidized bed combustion experiments that utilized wood and rice straw fuel blends. The experiments were conducted using a laboratory-scale combustor with mullite sand beds, firing temperatures of 840 to 1030 degrees C, and run durations of 5.5 h. A narrow continuous zone borders virtually all bed particles. The highest concentrations of potassium are found in this surface zone that also is enriched in appreciable amounts of other elements. Thin discontinuous films of adhesive cement, formed preferentially on surfaces and contact areas between bed particles, ultimately led to bed agglomeration. The interfaces and the presence of gas bubbles in the cement suggest a bonding material with a high surface tension and a liquid state. The cement films originate by filling of irregularities on individual and partially agglomerated bed particle surfaces by accumulation of liquid droplets preferentially in areas sheltered from turbulence and mechanical interaction. The composition of the film suggests melting of locally accumulated dust or aerosol mixture of ash particles and mullite. The film only locally enlarged bed particles. Large straw ash particles appear to have mostly been passively incorporated into the adhesive melt without melting or reaction. (c) 2010 Elsevier B.V. All rights reserved.