Development of Pollution Control Technology During Coal Combustion - Simultaneous Multi-Pollutants Removal in Flue Gas by Ozone - page 19

comparison with a conventional multi-pollutants removal technology, here the two
types on the one side, do not reduce the amount of devices required, on the other
side, are uneconomical to collect the generated diluted sulfuric acid for an efficient
utilization.
Activated carbon adsorption combined with SCR/SNCR [76-78] . The basic
principles of this type are that in a desulfurization tower, SO 2 is absorbed by
activated carbon and then catalytically oxidized into an adsorbed sulfuric acid
phase at gas temperatures ranging from 100 - 200 °C. The activated carbon is
thereafter injected into separation columns to be regenerated at 350 °C. High
concentrations of SO 2 are released accordingly. Then the flue gas enters into a
denitration tower where the contained NO x is reduced into N 2 by the sprayed NH 3 ,
with activated carbon as the catalyst. The desulfurization and denitrification
efficiencies reach high levels of above 90% and 70%, respectively. The key factor
of this technology is the preparation of activated carbon itself and the loaded
active substances. However, this technology turns out unfeasible for large-scale
commercial applications because of the high capital cost for the activated carbon
preparation. If the cost can be cut down or some alternative can be found, the
multi-pollutants removal method will be competitive.
1.3.2.2 Metal-Based Absorbent Multi-Pollutants Removal Technology
This category uses high-efficient metal-based absorbents (integrating metal
carriers such as Ca, Na, and Al with various additives) to achieve deSO x and
deNO x simultaneously. Generally, a high deSO 2 efficiency and only a moderate
deNO x level can be achieved, accompanied by high cost in preparing these
high-efficient metal-based absorbents. Introductory material about several typical
technique cases belonging to this category are listed as below.
Ca-based adsorbent based multi-pollutants removal technology . This type
is developed from the advanced silicate (ADVACATE) semi-dry FGD technology.
With fly ash, CaSO 3 , NaOH, Na 2 SO 3 and other additives added into Ca(OH) 2 and
then undergone a hydrated drying process, a highly active adsorbent can be
prepared. In fixed beds or pipelines, both SO 2 and NO x can be removed by
injecting the aforementioned adsorbent at temperatures ranging from 60 - 125 °C.
As the key point of this multi-pollutants removal technology, the preparation of
this highly active absorbent necessitates a comprehensive consideration in the
material share, additive types, hydration conditions, and other factors. The