Mercury Control and Mercury Stability in Byproducts - Mercury Emission and its Control in Chinese Coal-Fired Power Plants - page 134

5.4.5.2 Saturated Hg 0 Adsorption Experiment by AC(MJ) in Simulated Flue
Gas

In this part of the experiment, AC(MJ) was a granular AC prepared from coal using
the steam activation method. During the experiment, the concentration of Hg 0 was
controlled at 16.9 μg/(N·m 3 ) with a total flow of 1.3 L/min. The AC(MJ) sorbent
was controlled at about 0.1 g. The heating temperature of the gas channel and the
operating temperature of the fixed adsorption bed were all kept at (130±1) °C. The
Hg 0 adsorption experiment by AC(MJ) was divided into four steps, which were
conducted continuously. The time consumed for the experiment was about 25 h.
The experimental result is shown in Fig. 5.31.
With similar Hg 0 adsorption results as those of other powder ACs produced
using steam activation, granular AC(MJ) did not have a capability for Hg 0 adsorp-
tion in an N 2 atmosphere (Fig. 5.31). AC(MJ) started to adsorb Hg 0 when simulated
flue gas components, such as NO 2 , NO and so on, were added one by one. As the
adsorption continued, Hg 2+ began to appear increasingly at the outlet of the ad-
sorption bed. Finally, the concentration of Hg 2+ was almost the same as the initial
concentration of Hg 0 . Finally, Hg 0 adsorption by AC(MJ) reached true saturation.

20

Sorbent ˖ MJ-AC

18

Hg 0

16

Hg 2+

.

14

12

10

8

6

.

4

2

0

2:13:10 4:26:30 6:39:50 8:53:10 11:06:3013:19:5015:33:1017:46:3019:59:5022:13:1024:26:30

Time (h:m:s)

Fig. 5.31 Saturated Hg 0 adsorption experiment by AC(MJ) in simulated flue gas

5.4.6 Brief Summary

The bench-scale experimental study of adsorption of Hg 0 by AC in N 2 and in the
simulated flue gas produced some important results that can help in further under-
standing the Hg adsorption mechanism by AC. The obtained results suggested that
the adsorption of Hg 0 by AC proceeded through a chemical adsorption process
either in N 2 gas or in simulated flue gas. In addition, Hg 0 was possibly oxidized to
HgCl 2 by the Cl element remaining on the carbon surface, and then adsorbed by AC
in N 2 gas. This finding indicated that chemical modification enhanced the Hg ad-
sorption capability of AC in certain flue gas environments.