Agglomeration of High Calcium Fly Ash for Utilization II. Binding Mechanisms

Abstract

Fly ashes from the Lansing and Ottumwa power plants in Iowa were agglomerated by means of a continuous pan agglomerator, a continuous auger and a batch turbine agglomerator. In order to compare agglomeration mechanisms the following parameters were determined: (a) particle size distributions of the untreated fly ashes; (b) particle size distributions of the agglomerated fly ashes; (c) pore size distribution of agglomerates; (d) crystalline hydration products by X-ray diffraction; and (e) morphological characterization by scanning electron microscopy.In the batch system coalescence mechanisms were favoured. The agglomerates were fairly irregular in shape and had a rough surface texture. As residence time in the system increased breakage of agglomerates occurred, reducing the average agglomerate size. In the continuous systems layering of the fine feed particles onto established agglomerates was the predominant growth mechanism. The agglomerates were smooth and spherical. The layer structure was observed by scanning electron microscopy. Agglomerates of widely varying size, strength, and pore matrix can be produced in both systems. It is envisaged that while agglomerates could be produced with characteristics essential for their proposed end use by either method, continuous pan agglomeration would be the most versatile system to utilize.

Agglomeration of atmospheric fluidized bed residue and fly ash mixtures

“…Degree of coal preparation, cleaning and pulverization 4) Design, type and operation of power plant boiler unit 5) Loading and firing conditions 6) Additives to assist combustion or improve precipitator performance 7)…”

“…al. (6) have studied the variation in size and shape of the agglomerates of fly ash obtained with the rotating disc pan agglomerator, with a number of variables such as feed rate, rotation speed and water content. The effect of increase in water content is to increase the particle sizes obtained.…”

“…Escalating costs and dwindling resources of conventional aggregates are making agglomeration more and more economically feasible (6).…”