Reducing Aerosol Emissions by Decoupled Parameter Management during the CO2 Capture Process in a Multi-stage Circulation Absorber.

Aerosol emissions from the CO2 capture process have a significant impact in terms of solvent loss and environmental pollution. Here, we propose a novel approach with multi-stage circulation for CO2 capture and synergistic aerosol reduction, which divides the absorption section into three circulation stages and reduces aerosol emissions through decoupled operation of the three absorption sections and the management of solvent CO2 loadings. Experimental results show that with the decoupled management of the liquid-gas ratio and solvent temperature in absorption sections, the aerosol mass concentration at the outlet of the 3rd absorption section can be reduced by 25.6% to a minimum of 349.7 mg/m3 at a liquid-gas ratio of 43.2 L/m3 and a solvent temperature of 303 K. Furthermore, aerosol removal is performed by setting up a water wash section after the absorption section. The aerosol mass concentration at the outlet of the absorber is reduced to 168.6 mg/m3 with the regulation of the wash water temperature and flow rate. In addition, improvements are proposed for the combination of the utilization of recovered solvents and the co-removal of SO2. This study provides innovative insights into the design of the CO2 capture system and the reduction of aerosol emissions, which are of great significance for the mitigation of global warming and the control of environmental pollution.

Applied phosphorus is maintained in labile and moderately occluded fractions in a typical meadow steppe with the addition of multiple nutrients.

Phosphorus (P) is a limiting nutrient second only to nitrogen (N) in the drylands of the world. Most previous studies have focused on N transformation processes in grassland ecosystems, particularly under artificial fertilization with N and atmospheric N deposition. However, P cycling processes under natural conditions and when P is applied as an inorganic P fertilizer have been understudied. Therefore, it is essential to examine the fate of applied P in grassland ecosystems that have experienced long-term grazing and, under certain circumstances, continuous hay harvest. We conducted a 3-year field experiment with the addition of multiple nutrient elements in a typical meadow steppe to investigate the fate of the applied P in various fractions of P pools in the top soil. We found that the addition of multiple nutrients significantly increased P concentrations in the labile inorganic P (Lab-Pi) and moderately occluded inorganic P (Mod-Pi) fractions but not in the recalcitrant inorganic P (Rec-Pi) fraction. An increase in the concentration of total inorganic P was found only when P and N were applied together. However, the addition of other nutrients did not change P concentrations in any fraction of the mineral soil. The addition of P and N significantly increased the total amount of P taken up by the aboveground plants but had no effect on the levels of organic and microbial P in the soil. Together, our results indicate that the P applied in this grassland ecosystem is taken up by plants, leaving most of the unutilized P as Lab-Pi and Mod-Pi rather than being immobilized in Rec-Pi or by microbial biomass. This implies that the grassland ecosystem that we studied has a relatively low P adsorption capacity, and the application of inorganic P to replenish soil P deficiency in degraded grasslands due to long-term grazing of livestock or continuous harvest of forage in the region could be a practical management strategy to maintain soil P fertility.

Preventing Aerosol Emissions in a CO2 Capture System: Combining Aerosol Formation Inhibition and Wet Electrostatic Precipitation.

Aerosol emission from the CO2 capture system has raised great concern for causing solvent loss and serious environmental issues. Here, we propose a comprehensive method for reducing aerosol emissions in a CO2 capture system under the synergy of aerosol formation inhibition and wet electrostatic precipitation. The gas-solvent temperature difference plays a vital role in aerosol formation, with aerosol emissions of 740.80 mg/m3 at 50 K and 119.36 mg/m3 at 0 K. Different effects of SO2 and SO3 on aerosol formation are also found in this research; the aerosol mass concentration could reach 2341.25 mg/m3 at 20 ppm SO3 and 681.01 mg/m3 at 50 ppm SO2 with different aerosol size distributions. After the CO2 capture process, an aerosol removal efficiency of 98% can be realized by electrostatic precipitation under different CO2 concentrations. Due to the high concentration of aerosols and aerosol space charge generated by SO2 and SO3, the removal performance of the wet electrostatic precipitator decreases, resulting in a high aerosol emission concentration (up to 130.26 mg/m3). Thus, a heat exchanger is installed before the electrostatic precipitation section to enhance aerosol growth and increase aerosol removal efficiency. Under the synergy of aerosol formation inhibition and electrostatic precipitation, an aerosol removal efficiency of 99% and emission concentrations lower than 5 mg/m3 are achieved, contributing to global warming mitigation and environmental protection.

Co-Benefits of Pollutant Removal, Water, and Heat Recovery from Flue Gas through Phase Transition Enhanced by Corona Discharge.

Pollutant removal and resource recovery from high-humidity flue gas after desulfurization in a thermal power plant are crucial for improving air quality and saving energy. This study developed a flue gas treatment method involving phase transition enhanced by corona discharge based on laboratory research and established a field-scale unit for demonstration. The results indicate that an adequate increase in size will improve the ease of particle capture. A wet electrostatic precipitator is applied before the condensing heat exchangers to enhance the particle growth and capture processes. This results in an increase of 58% in the particle median diameter in the heat exchanger and an emission concentration below 1 mg/m3. Other pollutants, such as SO3 and Hg, can also be removed with emission concentrations of 0.13 mg/m3 and 1.10 µg/m3, respectively. Under the condensation enhancement of the method, it is possible to recover up to 3.26 t/h of water from 200 000 m3/h saturated flue gas (323 K), and the quality of the recovered water meets the standards stipulated in China. Additionally, charge-induced condensation is shown to improve heat recovery, resulting in the recovery of more than 43.34 kJ/h·m3 of heat from the flue gas. This method is expected to save 2628 t of standard coal and reduce carbon dioxide emission by 2% annually, contributing to environmental protection and global-warming mitigation.

Reducing aerosol and ammonia emission in post-combustion CO2 capture: Additives as key solutions.

Advancement of the absorbent for CO2 capture is essential in optimizing the performance and reducing the negative environmental effects associated with this technology. Despite ammonia's promise as an absorbent, the volatility limits its practical application and creates potential environmental pollution. Therein, we assess various additives (amino acids, carbonates, and alkanolamines) for ammonia-based solvents using multi-stage circulation absorber from the viewpoints of aerosol emission, ammonia emission, and CO2 capture efficiency. Experimental findings reveal that ammonia volatilization can be inhibited by the protonation of free ammonia by carboxyl groups and the formation of hydrogen bonding between amino/hydroxyl groups and ammonia, with ammonia emission reduced by 21.7 %, aerosol emission reduced by 26.5 %, and CO2 capture efficiency increased to a maximum of 87.8 % under the condition of adding histidine. Moreover, the experiment highlights a positive correlation between total ammonia emission and aerosol concentration/diameter. Additionally, tests combining source abatement with water wash exhibit up to 50.5 % aerosol removal efficiency and up to 76.6 % ammonia removal efficiency. To further mitigate emissions, a comprehensive approach is proposed, achieving an 84.4 % reduction in ammonia emission and a 61.9 % reduction in aerosol emission. Finally, a method for recycling ammonia for desulfurization is suggested.