[en] Pulverized coal combustion in tangentially fired furnaces with fuel rich/lean burners was investigated for three low volatile coals. The burners were operated under the conditions with varied value N_d, which means the ratio of coal concentration of the fuel rich stream to that of the fuel lean stream. The wall temperature distributions in various positions were measured and analyzed. The carbon content in the char and NO_x emission were detected under various conditions. The new burners with fuel rich/lean streams were utilized in a thermal power station to burn low volatile coal. The results show that the N_d value has significant influences on the distributions of temperature and char burnout. There exists an optimal N_d value under which the carbon content in the char and the NO_x emission is relatively low. The coal ignition and NO_x emission in the utilized power station are improved after retrofitting the burners

[en] Highlights: • Compare three models of heat recovery and power generation for industrial waste gas. • Pinch method is used in thermodynamic analysis. • Parameter optimization increases power generation by 15% for single-pressure systems. • Parameter optimization increases power generation by 17% for dual-pressure systems. • Energy integration doubles the improving effect of power generation with fuel saving. - Abstract: A large quantity of waste gas from industrial processes can be used for steam and power generation. Thus, it is of great interest to define a strategy for these power generation systems to get improved performances and efficiency. Three detailed thermodynamic models of heat recovery and power generation from industrial waste gas specified as single-pressure, dual-pressure, and energy integration systems are presented; Meanwhile, impact factors such as steam parameters, pinch temperature difference, and fluctuation of waste gas source on power generating capacity and total site efficiency are comparable analyzed by adopting a thermodynamic analysis combined with pinch method. Also, a case study of energy integration which doubles the improving effect of power generation accompanied with considerable energy saving is performed on basis of fuel efficiency and exergy calculation. In particular, the hierarchical strategy of energy integration of the total site is proposed and exampled.

[en] Highlights: • A supported model of (MnO₂)₃ cluster on γ-Al₂O₃(1 1 0) surface was established. • The interaction between the γ-Al₂O₃ carrier and (MnO₂)₃ cluster was explored. • Adsorption and co-adsorption of NO/O₂ on the (MnO₂)₃/γ-Al₂O₃ surface were calculated. Based on first-principles density functional theory (DFT), the adsorption performance of MnO₂(1 1 0) surface for NO and O₂ was calculated, and the deposition of (MnO₂)₃cluster on the γ-Al₂O₃(1 1 0) surface was studied. In addition, the adsorption and co-adsorption of NO and O₂ on the surface of (MnO₂)₃/Al₂O₃ were further calculated. The results showed that NO was more inclined to adsorb on the four-coordinated Mn(Ⅳ) sites on the MnO₂(1 1 0) surface (the maximum E_ads was −75.35KJ·mol⁻¹). There were very few O₂ adsorption sites on the MnO₂(1 1 0) surface, and only the vacancies between adjacent Mn(IV) could adsorb O₂ stably. PDOS analysis showed that the hybridization between Mn 3d orbital and N 2p (or O 2p) orbital was the main reason for Mn-N bonds (or Mn-O bonds). The (MnO₂)₃ cluster tended to load on Al₂O₃(1 1 0) surface in a flat six-membered ring structure. There are abundant active oxygen sites on the (MnO₂)₃/Al₂O₃ surface, which had an excellent ability to adsorb NO (the maximum E_ads was −278.24 KJ·mol⁻¹). NO molecules interacted with surface-active oxygen to generate nitroso, and NO₂ was easily desorbed from the (MnO₂)₃/Al₂O₃ surface. The co-adsorption of NO and O₂ on the (MnO₂)₃/Al₂O₃ surface formed an ONOO* structure, which could decompose to form adsorbed NO₂* and O*. Compared with single-phase manganese oxide crystals, manganese oxide clustered on γ-Al₂O₃ had superior NO adsorption performance and may have excellent catalytic oxidation properties.