Simultaneous Removal of COS, H2S, and Dust in Industrial Exhaust Gas by DC Corona Discharge Plasma

Parametric investigation and RSM optimization of DBD plasma methods (direct & indirect) for H2S conversion in the air

Hydrogen sulfide (H2S) is known as a harmful pollutant for the environment and human health, and its emission control is a high priority. Non-thermal plasma is an effective technology in this field. In this study, for the first time, the performance of direct and indirect H2S plasma conversion methods was compared, optimized, and modeled with the CCD method. H2S was diluted in zero air, and the study investigated the effect of discharge power, relative humidity, total flow rate, initial H2S concentration, and their interactions. ANOVA results showed that the models for H2S conversion efficiency and energy yield were significant and efficient. The direct method achieved a maximum conversion efficiency of 56 % and energy yield of 3.43 g/kWh, while the indirect method produced 68 % conversion efficiency and 1.59 g/kWh energy yield. According to the process optimization results, the direct conversion method is more optimal than the indirect conversion method due to the presence of active species and high-energy electrons in the plasma treatment, and it is a better choice if there are suitable working conditions.

Degradation of mixed typical odour gases via non-thermal plasma catalysis

The simultaneous treatment of H₂S and NH₃ typical odours by plasma was investigated and the co-treatment of both was found to have a facilitating effect the conversion. The degradation efficiency and by-product emissions of single plasma technology and plasma co-catalytic two-stage technology were compared and the degradation mechanism was further analyzed. The results show that in the single plasma technology conversion experiment, the conversion rate of the treated odours mixture is higher than that of the treated single odours, and the by-product emissions of SO₂ and NO_x are also reduced due to the reaction of intermediate products and by-products during the reaction process. The absolute removal of the odours mixture is optimal when treating at a gas flow rate of 6 L/min, a voltage of 16 kV and a frequency of 200 Hz. The M(Ce,Cu)-Mn/13X loaded catalyst was synthesized by co-precipitation method. Under the conditions of gas flow rate of 3-7 L/min, the efficiency of H₂S and NH₃ removal and the reduction of by-product emission were ranked as: uncatalyzed > Cu-Mn/13X > Ce-Mn/13X, which proved that Ce-Mn/13X showed better catalytic activity and application value.

Novel low-temperature H2S removal technology by developing yellow phosphorus and phosphate rock slurry as absorbent

Recycling hazardous gas of H₂S is one of the most important strategies to promote sustainable development. Herein, a novel method regarding purifying H₂S is proposed by using yellow phosphorus and phosphate rock slurry as absorbent. The H₂SO₄, formed in situ by H₂S conversion, can be devoted to decompose phosphate rock, and the spent absorption slurry was applied as raw material for the production of phosphorus chemical products. According to the characterization analysis, it was found that H₂S was first oxidized to SO₂ via O₂ as well as O₃ induced by P₄. Subsequently, the generated SO₂ dissolved rapidly in water to form H₂SO₄, and then reacted with the main component of phosphate rock, CaMg(CO₃)₂. Most notably, the active substances, such as, O₃, SO₄^•- and OH•, produced in the reaction process, can oxidize H₂S and HS^- to these sulfur products. In addition, trace amounts of Fe³⁺ and Mn²⁺ that were dissolved from phosphate rock displayed a promotional effect on the formation of active substances. Consequently, as high as 85% of H₂S removal efficiency can be obtained even under acidic condition and low temperature. The proposed H₂S purification method offers a promising option for sulfur recovery and H₂S pollution control.