Pilot-Scale NOx and SOx Aftertreatment Using a Two-Phase Ozone and Chemical Injection in Glass-Melting-Furnace Exhaust Gas

As NO
_x
and SO
_x
have significant environmental impacts, advanced treatments are required to remove them from the exhaust gas of a glass melting furnace. Here, we investigate a plasma-chemical hybrid process (PCHP) for this purpose. A pilot-scale experiment of the simultaneous removal of NO
_x
and SO
_x
using a PCHP combined with the existing semi-dry type desulfurization reactor is conducted on actual high-temperature exhaust gas from a glass melting furnace. NO (the majority of NO
_x
exist as NO) in the exhaust gas is oxidized to NO
₂
using active oxygen (ozone: O
₃
) generated by a plasma ozonizer. The exhaust gas must be cooled to less than 150 °C in order to suppress the thermal decomposition of O
₃
, while the gas temperature at the outlet of the semi-dry reactor must be kept at 200-;250 °C to protect the dry-type electrostatic precipitator. Therefore, it is important to form a local cooling area for NO oxidation in the reactor. In this article, we use the three-fluid nozzles of O
₃
, water, and air to form the local cooling area and effectively oxidize NO to NO
₂
. In addition, we spray NaOH aqueous solution for SO
₂
absorption downstream of the NO oxidation area to allow sufficient time for NO oxidation. The SO
₂
reacts with NaOH to produce Na
₂
SO
₃
, a powerful reducing agent. Subsequently, NO
₂
reacts with Na
₂
SO
₃
and is reduced to N
₂
, and the Na
₂
SO
₄
generated in this reaction is reused as a clarifier of the raw materials for glass manufacturing. As a result, the ratio of the amount of removed NO and NO
_x
to the amount of injected O
₃
(de-NO/O
₃
and de-NO
_x
/O
₃
) is 64% and 78%, respectively; therefore, high efficiency is obtained. This article includes actual examples of the treatment of exhaust gas in a glass melting furnace, using PCHP de-SO
_x
and de-NO
_x
technologies along with results from pilot-scale experiments.