Acid Orange 7 degradation using methane as the sole carbon source and electron donor

• AO7 degradation was coupled with anaerobic methane oxidation. • Higher concentration of AO7 inhibited the degradation. • The maximum removal rate of AO7 reached 280 mg/(L·d) in HfMBR. • ANME-2d dominated the microbial community in both batch reactor and HfMBR. • ANME-2d alone or synergistic with the partner bacteria played a significant role. Azo dyes are widely applied in the textile industry but are not entirely consumed during the dyeing process and can thus be discharged to the environment in wastewater. However, azo dyes can be degraded using various electron donors, and in this paper, Acid Orange 7 (AO7) degradation performance is investigated using methane (CH₄) as the sole electron donor. Methane has multiple sources and is readily available and inexpensive. Experiments using ¹³C-labeled isotopes showed that AO7 degradation was coupled with anaerobic oxidation of methane (AOM) and, subsequently, affected by the initial concentrations of AO7. Higher concentrations of AO7 could inhibit the activity of microorganisms, which was confirmed by the long-term performance of AO7 degradation, with maximum removal rates of 8.94 mg/(L·d) in a batch reactor and 280 mg/(L·d) in a hollow fiber membrane bioreactor (HfMBR). High-throughput sequencing using 16S rRNA genes showed that Candidatus Methanoperedens, affiliated to ANME-2d, dominated the microbial community in the batch reactor and HfMBR. Additionally, the relative abundance of Proteobacteria bacteria (Phenylobacterium, Pseudomonas, and Geothermobacter) improved after AO7 degradation. This outcome suggested that ANME-2d alone, or acting synergistically with partner bacteria, played a key role in the process of AO7 degradation coupled with AOM.     

可编程序控制器（PC）在环境工程自动控制系统中的应用

介绍可编程序控制器（ＰＣ）的由来，发展，特点及其在环境工程自动控制系统中的应用前景与应用实例。     

Analysis of reduction stage of chemical looping packed bed reactor based on the reaction front distribution

Traditional combustion of syngas derived from biomass has incurred numerous environmental problems, and syngas chemical looping combustion is environmentally friendly for syngas energy conversion. As a key part of chemical looping combustion, reactor configuration is noticeable. The dynamically operated packed bed reactor is an emerging conception applied to chemical looping combustion. Our attention is paid to the conversion of the oxygen carrier in the packed bed as the limited maximum conversion of the oxygen carrier in a packed bed is unclear. In this paper, the reaction front distribution during iron oxide reduced by CO is firstly proposed on the basis of chemical equilibrium and then validated by the effluent gas profile. Based on the reaction front distribution, the detail of the reduction stage in iron-based chemical looping combustion is analyzed to obtain the characteristics of reaction fronts. The reaction rates of reduction from Fe₂O₃ to Fe₃O₄, Fe₃O₄ to Fe_0.947O and Fe_0.947O to Fe are 5.280, 3.329 and 4.379 mol m^?3 s^?1, respectively. And the velocities of reaction front I, II, III are 0.605, 0.326, 0.044 cm min^?1, respectively, which demonstrate the reaction front distribution. The methodology established in this paper can be used to study multiple reaction front system in the packed bed reactor.     

Performance and kinetics of iron-based oxygen carriers reduced by carbon monoxide for chemical looping combustion

Chemical looping combustion is a promising technology for energy conversion due to its low-carbon, high-efficiency, and environmental-friendly feature. A vital issue for CLC process is the development of oxygen carrier, since it must have sufficient reactivity. The mechanism and kinetics of CO reduction on iron-based oxygen carriers namely pure Fe₂O₃ and Fe₂O₃ supported by alumina (Fe₂O₃/Al₂O₃) were investigated using thermo-gravimetric analysis. Fe₂O₃/Al₂O₃ showed better reactivity over bare Fe₂O₃ toward CO reduction. This was well supported by the observed higher rate constant for Fe₂O₃/Al₂O₃ over pure Fe₂O₃ with respective activation energy of 41.1±2.0 and 33.3±0.8 kJ·mol⁻¹. The proposed models were compared via statistical approach comprising Akaike information criterion with correction coupled with F-test. The phase-boundary reaction and diffusion control models approximated to 95% confidence level along with scanning electron microscopy results; revealed the promising reduction reactions of pure Fe₂O₃ and Fe₂O₃/Al₂O₃. The boosting recital of iron-based oxygen carrier support toward efficient chemical looping combustion could be explained accurately through the present study.     

Chemical looping combustion: A new low-dioxin energy conversion technology

Dioxin production is a worldwide concern because of its persistence and carcinogenic, teratogenic, and mutagenic effects. The pyrolysis-chemical looping combustion process of disposing solid waste is an alternative to traditional solid waste incineration developed to reduce the dioxin production. Based on the equilibrium composition of the Deacon reaction, pyrolysis gas oxidized by seven common oxygen carriers, namely, CuO, NiO, CaSO₄, CoO, Fe₂O₃, Mn₃O₄, and FeTiO₃, is studied and compared with the pyrolysis gas directly combusted by air. The result shows that the activity of the Deacon reaction for oxygen carriers is lower than that for air. For four typical oxygen carriers (CuO, NiO, Fe₂O₃, and FeTiO₃), the influences of temperature, pressure, gas composition, and tar on the Deacon reaction are discussed in detail. According to these simulation results, the dioxin production in China, Europe, the United States, and Japan is predicted for solid waste disposal by the pyrolysis-chemical looping combustion process. Thermodynamic analysis results in this paper show that chemical looping combustion can reduce dioxin production in the disposal of solid waste.     

Stepwise reduction kinetics of iron-based oxygen carriers by CO/CO2 mixture gases for chemical looping hydrogen generation

Journal of Material Cycles and Waste Management - Chemical looping hydrogen generation using iron oxides as oxygen carriers is a novel technology to convert carbonaceous substances into hydrogen....     

Chemical looping combustion: A new low-dioxin energy conversion technology

Dioxin production is a worldwide concern because of its persistence and carcinogenic, teratogenic, and mutagenic effects. The pyrolysis-chemical looping combustion process of disposing solid waste is an alternative to traditional solid waste incineration developed to reduce the dioxin production. Based on the equilibrium composition of the Deacon reaction, pyrolysis gas oxidized by seven common oxygen carriers, namely, CuO, NiO, CaSO₄, CoO, Fe₂O₃, Mn₃O₄, and FeTiO₃, is studied and compared with the pyrolysis gas directly combusted by air. The result shows that the activity of the Deacon reaction for oxygen carriers is lower than that for air. For four typical oxygen carriers (CuO, NiO, Fe₂O₃, and FeTiO₃), the influences of temperature, pressure, gas composition, and tar on the Deacon reaction are discussed in detail. According to these simulation results, the dioxin production in China, Europe, the United States, and Japan is predicted for solid waste disposal by the pyrolysis-chemical looping combustion process. Thermodynamic analysis results in this paper show that chemical looping combustion can reduce dioxin production in the disposal of solid waste.