Development of Pollution Control Technology During Coal Combustion - Simultaneous Multi-Pollutants Removal in Flue Gas by Ozone - page 16

1.3.1.2 Low-NO x Burner Combined with Ca-Based Sorbent
Steward et al . [58] studied a low-NO x burner combined with Ca-based sorbent
technique for deNO x and deSO x at same time. A desulfurization efficiency of over
50% was achieved at a Ca:S ratio of 2.5 - 3.0. In addition, NO x emissions were
reduced by about 50% by utilizing air-staging conditions. This technique is a
typical simple combination of sole methods. The desulfurization and
denitrification efficiencies are both relatively low, thus resulting in a poor
application in real furnaces.
1.3.1.3 Limestone/Urea Injection in Furnace
Studies on the limestone/urea combined injection technique have been reported
widely for deNO x and deSO x at same time [59-61] . In this technique, desulfurization
is achieved by the limestone injection, while denitrification is obtained by the urea
injection based SNCR. Defluorination and dechlorination can also be achieved
through an additional Ca-based sorbent. As reported in the literature [61] , both
desulfurization and denitrification efficiencies reached approximately 80% with
Ca/S=2 and NH 3 /NO=1. Lu [62] concluded that over 90% of SO 2 and 80% of NO
could be removed by injecting limestone and urea in an entrained-flow reactor at
800 - 1200 °C, with Ca/S=2 and NH 3 /NO=2.
1.3.1.4 Multi-Pollutants Removal with Organic Calcium Injection
Xiao [63] focused on using organic calcium injection to control SO x and NO x
simultaneously. The realization of this strategy needs a relatively simple process.
The common organic calcium is mainly Ca-Mg acetate (CMA) and calcium
acetate. The main principle is that the added organic calcium is decomposed into
organic fragments CH x and CaO. The former can reduce NO directly and the latter
can promote heterogeneous reductions of NO by char. CaO itself can remove SO 2
in the furnace. Organic calcium develops a high porous structure during its
calcinations process at high temperatures, which is helpful to adsorb SO 2 , HF, HCl,
and so on. Therefore, defluorination and dechlorination efficiencies are enhanced
accordingly. Xiao [63] found that at the stoichiometric ratio of 1.0 and gas
temperature of 1200 °C, denitrification and desulfurization efficiencies reached
73% and 50%, respectively. Results from Nimmo et al . [64,65] suggested that using