The Roles of Sulfur-Containing Species in the Selective Catalytic Reduction of NO with NH3 over Activated Carbon

Enhanced adsorption of NO onto activated carbon by gas pre-magnetization

The NO removal efficiency was relatively low in the traditional activated carbon adsorption process. In this work, a gas pre-magnetization and activated carbon adsorption process was developed to enhance the adsorption of NO onto activated carbon. In this innovative and green process, the mixed gas was magnetized in the external magnetic field and then absorbed by activated carbon. The results indicated that the maximal removal rate of NO could be increased from 75.0% to 89.5%, and the NO adsorption capacity of commercial activated carbon in one hour elevated from 2.28 to 2.60 mg/g when the magnetic induction intensity of external magnetic field increased from 0 T to 2 T. The strengthening mechanism of the gas pre-magnetization was investigated. It was found that magnetic field could elevate the oxidation rate of NO by 11.4% and thus promote the physical adsorption of NO onto activated carbon. External magnetic field could increase the reaction activity of NO and promote the chemical reaction between NO and some functional groups (CO, CO and COOH) on the activated carbon and thus promote the chemisorption process of NO.

Coupling mechanism of activated carbon mixed with dust for flue gas desulfurization and denitrification

To clarify the effect of coking dust, sintering dust and fly ash on the activity of activated carbon for various industrial flue gas desulfurization and denitrification, the coupling mechanism of the mixed activated carbon and dust was investigated to provide theoretical reference for the stable operation. The results show that coking dust had 34% desulfurization efficiency and 10% denitrification efficiency; correspondingly, sintering dust and fly ash had no obvious desulfurization and denitrification activities. For the mixture of activated carbon and dust, the coking dust reduced the desulfurization and denitrification efficiencies by blocking the pores of activated carbon, and its inhibiting effect on activated carbon was larger than its own desulfurization and denitrification activity. The sintering dust also reduced the desulfurization efficiency on the activated carbon while enhancing the denitrification efficiency. Fly ash blocked the pores of activated carbon and reduced its reaction activity. The reaction activity of coking dust mainly came from the surface functional groups, similar to that of activated carbon. The reaction activity of sintering dust mainly came from the oxidative property of Fe₂O₃, which oxidized NO to NO₂ and promoted the fast selectively catalytic reduction (SCR) of NO to form N₂. Sintering dust was activated by the joint action of activated carbon, and both had a coupling function. Sintering dust enhanced the adsorption and oxidation of NO, and activated carbon further promoted the reduction of NO_x by NH₃; thus, the denitrification efficiency increased by 5%-7% on the activated carbon.

DeNOx of Nano-Catalyst of Selective Catalytic Reduction Using Active Carbon Loading MnOx-Cu at Low Temperature

With the improvement of environmental protection standards, selective catalytic reduction (SCR) has become the mainstream technology of flue gas deNOx. Especially, the low-temperature SCR nano-catalyst has attracted more and more attention at home and abroad because of its potential performance and economy in industrial applications. In this paper, low-temperature SCR catalysts were prepared using the activated carbon loading MnOx-Cu. Then, the catalysts were packed into the fiedbed stainless steel micro-reactor to evaluate the selective catalytic reduction of NO performance. The influence of reaction conditions was investigated on the catalytic reaction, including the MnOx-Cu loading amount, calcination and reaction temperature, etc. The experimental results indicate that SCR catalysts show the highest catalytic activity for NO conversion when the calcination temperature is 350 °C, MnOx loading amount is 5%, Cu loading amount is 3%, and reaction temperature is 200 °C. Under such conditions, the NO conversion arrives at 96.82% and the selectivity to N2 is almost 99%. It is of great significance to investigate the influence of reaction conditions in order to provide references for industrial application.

Carbon consumption mechanism of activated coke in the presence of water vapor

To reduce chemical carbon consumption in activated coke technology used for flue gas purification, the carbon consumption mechanism of commercial activated coke in the presence of water vapor was studied. A fixed-bed reactor and a Fourier transform infrared (FTIR) spectrometer were combined to study the amount of carbon consumption. Temperature-programmed desorption (TPD) coupled with in situ diffuse reflectance infrared Fourier transform (in situ DRIFT) spectra were used to investigate functional group changes of activated coke. The sources and factors influencing carbon consumption in various adsorption atmospheres and in the N₂ regeneration atmosphere were compared. Carbon consumption during the adsorption and regeneration process was mainly due to the release of C-O and C=C groups. The addition of H₂O increased the formation of carbonates and carboxylic acids during the adsorption process, which decomposed during the regeneration process, thereby increasing carbon consumption. Carbon consumption was reduced during regeneration in an H₂O-SO₂ adsorption atmosphere, mainly because of the formation of C-S bonds, which reduced the formation of CO₂. The C-N bonds generated in an H₂O-NO adsorption atmosphere were decomposed during the regeneration process, thereby increasing carbon consumption. In a complex atmosphere of SO₂, NO, NH₃, and H₂O, SO₂ was absorbed by NH₃, and the amount of carbon consumption was consistent with that in the NO atmosphere during the regeneration process. The total carbon consumption in various adsorption atmospheres ranged from 85.4 to 125.2 μmol/g. Compared with an anhydrous atmosphere, chemical carbon consumption increased by 6.5-14.3% in the presence of H₂O. Chemical carbon consumption was reduced by decreasing the H₂O concentrations, which provides a reference concept for reducing the operating cost of the activated coke process in industry.

NO x reduction by CO over ASC catalysts in a simulated rotary reactor: effect of CO2, H2O and SO2

The influence of CO₂, H₂O and SO₂ on the NO reduction by CO over Fe/Co activated semi-coke catalyst was investigated in a simulated rotary reactor. The results showed that, in the simulated rotary reactor, the influence of CO₂ and H₂O on the NO adsorption was significant at low temperatures, and the inhibition became weak when increasing the temperature. However, the NO adsorption efficiency could not be improved by increasing temperature after catalyst sulfur poisoning. The heavily inhibited NO adsorption process, which was due to the competitive adsorption and formation of the sulfate, resulted in a low NO reduction efficiency in the presence of CO₂, H₂O or SO₂. The in situ DRIFT study showed that the dominant effect of CO₂, H₂O and SO₂ on the NO adsorption was the inhibition of the free nitrate ions formation. In addition, the introduction of CO₂, H₂O and SO₂ could not change the route of NO reduction, but just reduced the degree of the NO + CO reduction.

The influence of CO₂, H₂O and SO₂ on the NO reduction by CO over Fe/Co activated semi-coke catalyst was investigated in a simulated rotary reactor.