Abstract
H2O2 was adopted to oxidize NO in simulated flue gas at 100–500°C. The effects of the H2O2 evaporation conditions, gas temperature, initial NO concentration, H2O2 concentration, and H2O2:NO molar ratio on the oxidation efficiency of NO were investigated. The reason for the narrow NO oxidation temperature range near 500°C was determined. The NO oxidation products were analyzed. The removal of NOx using NaOH solution at a moderate oxidation ratio was studied. It was proven that rapid evaporation of the H2O2 solution was critical to increase the NO oxidation efficiency and broaden the oxidation temperature range. the NO oxidation efficiency was above 50% at 300–500°C by contacting the outlet of the syringe needle and the stainless-steel gas pipe together to spread H2O2 solution into a thin film on the surface of the stainless-steel gas pipe, which greatly accelerated the evaporation of H2O2. The NO oxidation efficiency and the NO oxidation rate increased with increasing initial NO concentration. This method was more effective for the oxidation of NO at high concentrations. H2O2 solution with a concentration higher than 15% was more efficient in oxidizing NO. High temperatures decreased the influence of the H2O2 concentration on the NO oxidation efficiency. The oxidation efficiency of NO increased with an increase in the H2O2:NO molar ratio, but the ratio of H2O2 to oxidized NO decreased. Over 80% of the NO oxidation product was NO2, which indicated that the oxidation ratio of NO did not need to be very high. An 86.7% NO removal efficiency was obtained at an oxidation ratio of only 53.8% when combined with alkali absorption.
Highlights
SO2 and NOx are two major pollutants released by coal combustion
To ensure that the H2O2 solution was fully evaporated, the H2O2 syringe needle was connected to the stainless-steel gas inlet
The general conditions of NO oxidation by H2O2 thermal decomposition were investigated in the drop-tube furnace NO oxidization experimental system
Summary
SO2 and NOx are two major pollutants released by coal combustion. Since most NOx in coalfired flue gas is NO, which is difficult to directly absorb with a liquid absorbent,[1] the removal of NOx in flue gas is more difficult than that of SO2. NOx has surpassed SO2 as the largest gaseous pollutant emission in recent years in China.[2] NOx emissions have reached twice that of SO2 in some Chinese cities.[2] China revised the emission standards for pollutants from thermal power plants in 2011, in which the NOx emission standard was changed to 100 mg/Nm3 for most pulverized-coal boilers.[3] It is imperative to develop economical and efficient NOx removal technology
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