W. Jozewicz et Bk. Gullett, STRUCTURAL TRANSFORMATIONS IN CA-BASED SORBENTS USED FOR SO2 EMISSIONCONTROL, ZKG international. Edition B, 47(1), 1994, pp. 31-38
Economizer temperature injection of Ca-based sorbents is an option for
dry control of SO2-Emissions from coal-fired boilers. Their reactivit
y with SO2 was found to be a function of their specific surface areas.
In the course of this work, Ca(OH)2 sorbents with specific surface ar
eas from 2 to 79 m2/g and porosities from 0.02 to 0.48 were produced f
rom a number of commercial sources in a laboratory-scale hydrator by '
'single'' or ''double'' hydration. Single hydration produced Ca(OH)2 f
rom CaCO3-derived CaO with specific surface areas up to 17.3 m2/g and
porosities up to 0.29. Double hydration produced Ca(OH)z from Ca(OH)z-
derived CaO with specific surface areas up to 23 M2/g and porosities u
p to 0.33. In both types of hydration, a significant correlation was o
bserved between the measured specific surface area and porosity of the
CaO and its hydration product. Ca(OH)2. Ca(OH)2 sorbents were calcine
d in a flow reactor operated at 550-degrees-C and 1 s residence time t
o simulate conditions encountered by the solids during economizer inje
ction and to investigate their response to economizer temperature. A c
orrelation could be found between structural properties of Ca(OH)2 and
the product of its calcination in the flow reactor. Calcination of hi
gher specific surface area/porosity Ca(OH)2 resulted in higher specifi
c surface area/porosity CaO. Similar pore size distributions were meas
ured for CaO produced from calcination of Ca(OH)2 with similar specifi
c surface area, regardless of the source of Ca(OH)2. Based on the stru
ctural response of Ca(OH)2 following 550-degrees-C and 1 s exposure in
the flow reactor. Ca(OH)2 with a high specific surface area (55-60 m2
/g) and high porosity (approximately 0.40) is recommended for economiz
er injection application.