Evaluation of Ohio fly ash/hydrated lime slurries and Type 1 cement sorbent slurries in the U.C. Pilot spray dryer facility. Final report, September 1, 1993--August 31, 1994
in electronic image produced from the document. illegible Portions of this document may be products. Images are best available original EXECUTIVE SUMMARY Objectives. The objectives of this year's work included an evaluation of the performance of fly ashhydrated lime as well as hydrated cement sorbents for spray drying absorption (SDA) o SO, from a simulated high-sulfur flue gas. These sorbents were evaluated for several different hydration methods, and under different SDA operating conditions.
... n addition, the physical properties of surface area and porosity of the sorbents was determined. temp Conclusions. The most reactive fly ashhydrated lime sorbent studied was prepared at room rature with milled fly ash. Milling fly ash prior to hydration with lime did have beneficial effect on calcium utilization. No benefit in utilization was experienced either by hydrating the slurries at a temperature of 90°C as compared to hydration at room temperature, or by increasing hydration time. While the surface areas varied greatly from sorbent to sorbent, the pore size distributions indicated "ink bottle" pores with surface porosity on the order of 0.5 microns. No correlation could be drawn between the surface area of the sorbents and calcium utilization. These results suggest that the composition of the resulting sorbent might be more important than its surface area T i e most effecnve sorbent studied this year was produced by hydrating cement for 3 days at room temperature. This sorbent provided a removal efficiency and a calcium utilization over 25 percent higher than baseline results at an approach to saturation 11 . temperature of 30°F and a stoichiometric ratio of 0.9. A maximum SO, removal efficiency of about 90 percent was experienced with this sorbent at an approach to saturation temperature of 20°F. The hydrated cement studies indicate a clear benefit in milling the cement slurry during hydration, As in the fly ashhydrated lime studes, no clear relationship between surface area and reactivity was exhibited. The pore size distribution of the reactive sorbent indicates a bimodal pore size on the oider of 1 mixon and 0.1-0.2 microns. The larger surface pore size may contribute to the enhanced reactivity. Future Objectives. In the following year the performance of hydrated cement in the spray dryer will be more fully investigated. .Bench scale experiments at elevated temperatures will be performed. .Sorbent. reactivity wiIl be related to spray -ilryer:aperating parameters, as well as to ball mill )-hydration ,conditions. Surface area and porosity will continue to be evaluated. Also, the effect of additives such as fumed silica and diatomacious earth will be determined. A wet chemistry procedure for determining the caicium content of cement will be evaluated. The procedure, from ASTM C 114, consists of removing siIicon, aluminum, iron, titanium, phosphorus, and manganese from a sample of cement through a series of precipitations and filtrations. Calcium is then precipitated as an oxalate. After filtering, the oxalate is redissolved and titrated with potassium pernaganate (KMnO,).