Desulfurization and denitrification experiments in SDA system: A new high-efficient semi-dry process by NaClO2

Optimization of Injection Source Settings for SNCR Numerical Simulation of Low-Water Content Biomass Boilers with Blending

In order to control NOx emissions and meet China's ultralow emission standards, a numerical simulation based on the computational fluid dynamics (CFD) approach is performed for the optimization of the reductant injection volume, number of injection sources, distribution, and injection direction for the flue gas denitrification process of a circulating fluidized bed boiler (CFB) blended with low-water content biomass in a 168 MW unit of a thermal power plant. Using the target power plant boiler entity as a template, a simplified geometric model is established, 1:1, and the mass fractions of each flue gas component set by the inlet boundary conditions are O22, H2O11.6, CO216.2%, and NO0.05%(about 134 ppm), and the reduction reactions under different optimized conditions are numerically simulated using the SNCR model in ANSYS Fluent 2021 R1. The simulation results under each condition were analyzed. The results show that the optimal ammonia-to-nitrogen ratio should be taken as NSR = 1.25, the denitrification efficiencies of 81.00, 81.63, and 82.74% at the three outlets are high, and the ammonia escapes of 1.76, 2.08, and 9.42 mg/s are within a reasonable range; increasing the number of injection sources can significantly reduce the disturbance of the flue gas flow field by reductant injection; the direction of injection is parallel to the direction of the flue gas flow, and the line of the injection source is orthogonal to the direction of the flue gas flow, which is conducive to the mixing of the reductant and flue gas; the optimized boiler denitrification efficiency reaches 74.2%, meeting the ultralow emission requirements of nitrogen oxides and ammonia escape.

Intensification Effect of a Multi-Jet Structure on a Multiphase Flow and Desulfurization Process in a Fluidized Bed

The introduction of a multi-jet structure at the bottom and middle of a fluidized bed can intensify the interphase mixing and improve desulfurization efficiency. The computational fluid dynamics were used to study the gas-liquid-solid flow in a bottom multi-jet fluidized bed and middle multi-jet fluidized bed (BMJFB and MMJFB). It was found that for the gas-liquid-solid interphase mixing, the intensification effect of introducing the multi-jet structure in the middle of the bed is more obvious than that in the bottom. The effect of the water spray volume flow rate on the MMJFB was examined under the same conditions. The results showed that with the increase of the water flow rate, the gas-liquid-solid interphase mixing and desulfurization process are promoted in the MMJFB, and its desulfurization efficiency reaches 68.2%. The effects of the width and number of multi-jet structures on the MMJFB were also investigated. The results show that when the jet width is 20 mm and the number of jets is four, the gas-liquid-solid three-phase is uniformly mixed and the desulfurization efficiency of the MMJFB equals 69.3%, which is 18.5% higher than that of the conventional fluidized bed.

Advances in air pollution control for key industries in China during the 13th five-year plan

Industrial development is an essential foundation of the national economy, but the industry is also the largest source of air pollution, of which power plants, iron and steel, building materials, and other industries emit large amounts of pollutants. Therefore, the Chinese government has promulgated a series of stringent emission regulations, and it is against this backdrop that research into air pollution control technologies for key industrial sectors is in full swing. In particular, during the 13th Five-Year Plan, breakthroughs have been made in pollution control technology for key industrial sectors. A multi-pollutant treatment technology system of desulfurization, denitrification, and dust collection, which applies to key industries such as power plants, steel, and building materials, has been developed. High-performance materials for the treatment of different pollutants, such as denitrification catalysts and desulfurization absorbers, were developed. At the same time, multi-pollutant synergistic removal technologies for flue gas in various industries have also become a hot research topic, with important breakthroughs in the synergistic removal of NO_x, SO_x, and Hg. Due to the increasingly stringent emission standards and regulations in China, there is still a need to work on the development of multi-pollutant synergistic technologies and further research and development of synergistic abatement technologies for CO₂ to meet the requirements of ultra-low emissions in industrial sectors.

Graphene oxide promotes V-Cu-Ce-ZSM-5 to catalyze SO2 and NO at low temperature: performance and mechanism

A catalyst (V-Cu-Ce-ZSM-5) was explored to simultaneously remove the SO₂ and NO_x from flue gas by use of the ZSM-5 molecular sieve as the carrier, V and Cu as the active components, and Ce as the additive in low temperature of 150 °C. The performance of V-Cu-Ce-ZSM-5 was evaluated for the oxidation of NO and SO₂ before and after the addition of graphene oxide (GO). The results showed that V-Cu-Ce-ZSM-5@GO0.5 had the best performance at a reaction temperature of 150 °C, and the oxidation efficiency of SO₂ and NO was 94.60% and 83.64%, respectively. The multiple structural characterizations (BET, SEM, Raman, XRD, and XPS) revealed that the loading of V and Cu with the additive Ce expanded the specific surface area and pore volume of ZSM-5, provided more adsorption sites for SO₂ and NO, and had good desulfurization and denitration activity. The addition of GO further improved the dispersibility of active components and auxiliaries, increased the number of active sites in the reaction process, and significantly improved catalytic activity.

The Reversible Removal of SO2 by Amino Functionalized ZIF8 with 5-Aminotetrazole via Post-Synthesis Modification

The post-synthesis modification is a highly efficient method for the modification of Metal-organic framework (MOF) materials, which has been used to synthesize MOF materials purposefully that cannot be prepared by direct synthesis and impregnation method. In this work, amino modified ZIF8 with 5-aminotetrazole was prepared by the post synthesis modification method and was employed to reversibly remove SO2 from flue gas. Based on the characterization and analysis of X-ray diffraction (XRD), Scanning Electron Microscope (SEM), and Brunner Emmet Teller (BET), it was found that the functionalized ZIF8 (Zn(5-ATZ)1.5) was a microporous material with a two-dimensional nano-layered structure. According to the SO2 adsorption experiments, the adsorption capacity of SO2 at the concentration of 1.6% vol can reach to 122 mg/g under the optimal conditions (25 °C, 2865 h−1). Five successive adsorption-desorption experiments exhibited that Zn(5-ATZ)1.5 had excellent regeneration performance. The characterization results of Raman Spectra (Raman) and X-ray photoelectron spectroscopy (XPS) as well as the DFT simulation calculations revealed that SO2 mainly interacted with Zn(5-ATZ)1.5 by hydrogen bonds between O of SO2 and amino H in the Zn(5-ATZ)1.5, and the interaction of SO2 with amino N and 5-aminotetrazole N by forming a non-covalent charge transfer complex. This work suggested that Zn(5-ATZ)1.5 is an excellent potential sorbent for SO2 removal.

O3 oxidation combined with semi-dry method for simultaneous desulfurization and denitrification of sintering/pelletizing flue gas

With the vigorous development of China's iron and steel industry and the introduction of ultra-low emission policies, the emission of pollutants such as SO₂ and NO_x has received unprecedented attention. Considering the increase of the proportion of semi-dry desulfurization technology in the desulfurization process, several semi-dry desulphurization technologies such as flue gas circulating fluidized bed (CFB), dense flow absorber (DFA) and spray drying absorption (SDA) are briefly summarized. Moreover, a method for simultaneous treatment of SO₂ and NO_x in sintering/pelletizing flue gas by O₃ oxidation combined with semi-dry method is introduced. Meantime, the effects of key parameters such as O₃/NO molar ratio, CaSO₃, SO₂, reaction temperature, Ca/(S+2N) molar ratio, droplet size and approach to adiabatic saturation temperature (AAST) on denitrification and desulfurization are analyzed. Furthermore, the reaction mechanism of denitrification and desulfurization is further elucidated. Finally, the advantages and development prospects of the new technology are proposed.

Sulfur dioxide removal: An overview of regenerative flue gas desulfurization and factors affecting desulfurization capacity and sorbent regeneration

Numerous mitigation techniques have been incorporated to capture or remove SO₂ with flue gas desulfurization (FGD) being the most common method. Regenerative FGD method is advantageous over other methods due to high desulfurization efficiency, sorbent regenerability, and reduction in waste handling. The capital costs of regenerative methods are higher than those of commonly used once-through methods simply due to the inclusion of sorbent regeneration while operational and management costs depend on the operating hours and fuel composition. Regenerable sorbents like ionic liquids, deep eutectic solvents, ammonium halide solutions, alkyl-aniline solutions, amino acid solutions, activated carbons, mesoporous silica, zeolite, and metal-organic frameworks have been reported to successfully achieve high SO₂ removal. The presence of other gases in flue gas, e.g., O₂, CO₂, NOx, and water vapor, and the reaction temperature critically affect the sorption capacity and sorbent regenerability. To obtain optimal SO₂ removal performance, other parameters such as pH, inlet SO₂ concentration, and additives need to be adequately governed. Due to its high removal capacity, easy preparation, non-toxicity, and low regeneration temperature, the use of deep eutectic solvents is highly feasible for upscale utilization. Metal-organic frameworks demonstrated highest reported SO₂ removal capacity; however, it is not yet applicable at industrial level due to its high price, weak stability, and robust formulation.

Simultaneous Desulfurization and Denitrification Using La-Ce-V-Cu-ZSM-5 Catalysts in an Electrostatic Precipitator

Different catalysts were loaded onto the collecting plate of an electrostatic precipitator to achieve the simultaneous removal of multiple pollutants from coal-fired gas. The synergistic desulfurization and denitrification effect of the catalyst and the effect of corona discharge on the activity of the catalyst were studied. The La(6%)-Ce(8%)-V(7%)-Cu(8%)-ZSM-5 catalyst prepared by successive impregnation methods had the optimum simultaneous desulfurization and denitrification efficiency at a roasting temperature of 600 °C. The desulfurization and denitrification rates reached 97.09 and 83.30%, respectively. BET and SEM characterization results showed that the loading of active components and additives improved the pore structure of the molecular sieve, which contributed to the high stability of the catalyst's internal structure and large surface area, as well as better desulfurization and denitrification efficiency. Corona discharge can significantly improve the catalytic effect.