•Integration performance of MEA-Methanol was studied comparing with aqueous MEA.•Effects of three parameters on Qreg were tested at a constant CO2 removal rate of 90%.•Under the optimum conditions, Qreg of MEA-Methanol was obviously lower than that of MEA.The present work reported tests of a new solvent 30 wt% MEA-Methanol compared to aqueous 30 wt% MEA solvent in a pilot-plant test bed, which comprises the complete absorption/desorption. The two solvents were studied in the same way in the test bed and detailed results were reported for both solvents. The measurements were carried out at a constant CO2 removal rate of 90% by an adjustment of the regeneration energy in the desorber for systematically varied L/G ratios, flue gas flow rate and absorber height. Results from these studies indicated that MEA-Methanol solvent had a faster CO2 absorption rate and a lower regeneration energy consumption compared to aqueous MEA solvent. Regeneration heat duty (Qreg) of MEA-Methanol solvent at optimum operating conditions was obviously lower than that of aqueous MEA solvent (3.22 MJ/kg CO2 and 4.04 MJ/kg CO2, respectively), which showed that MEA-Methanol had a potential to replace aqueous MEA solvent in industrial CO2 pilot plant.

•Effects of several absorber parameters on CO2 absorption performance were studied.•kGav and CO2 capture efficiency were sensitive to the parameters studied in this work.•Absorption performance under Sulzer BX500 packing was the best.Effects of different operating conditions on the CO2 capture and mass transfer performance of the absorption of CO2 into a hybrid solvent MEA-Methanol were studied in a pilot-plant absorber packed with three different packing consist of Sulzer BX500, Mellapale Y500 and Pall rings 16 × 16. The results showed that the structured packing had an obvious advantage in the mass transfer performance. And Sulzer BX500 was better than Mellapale Y500 for it had a more uniform gas–liquid distribution on the packing surface. In addition, CO2 lean loading, lean solvent temperature, lean solvent flow rate and flue gas flow rate all had great effects on the absorption performance of the MEA-Methanol absorption system.

Nowadays, the ammonia-based wet flue gas desulfurization is gaining more popularity. In this study, the ammonia-based wet flue gas desulfurization obtained ammonia resource from urea hydrolysis instead of anhydrous ammonia and aqueous ammonia, which was beneficial for the development of circular economy. An electric-heating reactor was employed as the hydrolysis reactor instead of traditional ones using hot air or water vapor as the heat carrier. The effects of temperature, pressure, urea solution concentration, and time on urea hydrolysis were investigated, and the optimum hydrolysis condition was estimated to be 30 (wt, %) urea solution hydrolyzing for 4 h at 140 °C, 0.4 MPa. The desulfurization experiment was conducted in a bubbling reactor. The effects of SO2 concentration and liquid–gas ratio on desulfurization were investigated. The ammonia-based absorbent for desulfurization was prepared by the ammonia produced from the 30 (wt, %) urea solution hydrolyzing for 4 h at 140 °C, 0.4 MPa. The experimental results showed that all desulfurization efficiencies at different SO2 concentrations exceeded 99%, and a higher liquid–gas ratio could raise the desulfurization efficiency. The suitable pH range for this ammonia-based absorbent is 6.5–7.5. It was also found that higher SO2 concentration and lower liquid–gas ratio could promote the generation of high added-value ammonium sulfate.

Exhaust flue gas from fossil fuel combustion usually contains a large quantity of SO2 and NO. In this paper, a process of simultaneous removal of NO and SO2 by ozone oxidation combined with NaOH absorption was chosen. The main investigations involved O3 decomposition, factors affecting NO oxidation (O3 dosage, reaction temperature, NO initial concentration, and presence of SO2), and NaOH absorption. The results indicated O3 decomposition rate increased as temperature rose and was less affected by initial concentration of O3. The optimal temperature for NO oxidation was 150 °C. NO oxidation efficiency increased with the increase of O3 dosage at a fixed temperature. NO initial concentration and the presence of SO2 had a slight effect on NO oxidation. The NO oxidation efficiency remained above 90% when nO3/nNO was 1. Absorption by NaOH solution resulted in the final removal of above 99% NO, 90% NO2, and nearly 100% SO2 at pH above 11.

The kinetics of sulfite oxidation in the magnesium-based wet flue gas desulfurization (FGD) process were investigated in a stirred bubbling reactor by varying the concentrations of MgSO3 and MgSO4, pH, air flow and temperature. The reaction was found to be 0.88 order with respect to magnesium sulfite and the oxidation could reach the maximum rate when the pH value was close to 6.5. The mechanism of the oxidation was discussed, and it was concluded that the oxidation is controlled by diffusion of oxygen. These results would be useful for the design or process optimization of the magnesium-based wet FGD system.

Quaternary ammonium modified resins for emulsified oily wastewater treatment were synthesized from polystyrene resin through ion exchange reaction between sulfonic acid groups and three quaternary ammonium surfactants. The base resin and modified resins were characterized by infrared spectra, zeta potential measurement and capillary rise test (the Washburn method) to evaluate the effect of modification with quaternary ammonium on the surface characteristics of the resin. The surface electrostatic and hydrophobic characteristics of the resin were significantly altered due to grafting hexadecyltrimethylammonium bromide (HTAB), hexadecylpyridinium bromide (HPB) and tetrabutylammonium bromide (TBAB) onto the resin surface. The grafted quaternary ammonium surfactants made the resin more effective for removing oil droplets by coalescence-filtration because of a less negative-charged and more hydrophobic resin surface. In addition, incorporation of a longer alkyl group on resin surface had a more positive effect on its oil removal capability. The resin modified by HTAB demonstrated a better oil removal capability than other modified resins.Graphical abstractResearch highlights▶ Various quaternary ammonium surfactants had different effects on the polystyrene resin surface characteristics. ▶ A capillary rise test was conducted to evaluate the wettability of modified resin. ▶ A less negative-charged and more hydrophobic resin surface benefits the oil removal process. ▶ Incorporation of a longer alkyl group on resin surface had a more positive effect on its oil removal capability.

The application of modified resin as a filter medium treating the anionic surfactant stabilized oil-in-water emulsion was investigated. In this study, emulsion breaking was accelerated by the grafting cetyltrimethylammonium bromide on polystyrene resin, so the need for expensive specific chemicals was eliminated. The results indicated that, as a new type of coalescence material, the modified resin has incomparable advantages over polypropylene, ceramic, and activated carbon. A series of experiments were performed to evaluate the effect of flow velocity, bed height, oil concentration, temperature, and pH value on the oil removal performance of the modified resin coalescer. More than 80% of emulsified oil was removed under optimal operating conditions: flow velocity 60−180 mL/h, bed height 20−40 cm, temperature 20−60 °C, and pH value 2−10. The results further indicated that modified resin bed coalescer is feasible to be used in the treatment of oil-in-water emulsion due to integration of both advantages of chemical demulsification and coalescence process.

The treatment of emulsified oily wastewater containing n-octane (used as simulated wastewater) was investigated by various packing materials and a hybrid system of modified resin and activated carbon. Cetyltrimethyl-ammonium bromide-modified polystyrene resin (R-CTAB) was synthesized and its oil removal performance was compared with granular-activated carbon (GAC) and polypropylene granular (pp). The effect of operation conditions was studied and attentions should be paid on volumetric flow and influent oil concentration because they are two crucial factors for oily wastewater treatment performance. The results indicated that R-CTAB has the most stable oil removal performance in various operation conditions due to hydrogen bond formation between hydrocarbon molecules and the free hydrophilic part of the fixed surfactant. The application of hybrid system of R-CTAB + GAC can remove most of the oil from the oily wastewater, which resulted in higher than 90% reduction of oil content in the treated effluent.