Search

Improving the power generation efficiency of coal-fired units is an effective measure to achieve energy conservation and carbon reduction. The engineering application of 700 ℃ ultra-supercritical coal-fired power generation is hindered by the high price of superalloy materials; therefore, it is necessary to explore new layouts and structures to shorten the high-temperature steam pipelines and reduce the engineering costs. By taking the phase III expansion project—the world’s first demonstration project of high-level layout—of the Jinjie coal-fired power plant as an example, this study introduces the engineering innovation practice of the high-level layout technology for an air-cooled ultra-supercritical steam-turbine generator unit. The results indicate that the reinforced concrete frame and shear wall structure can effectively lower the overall center of gravity and improve the seismic performance of the main power house,thereby ensuring the safety of the main power house structure, high-temperature steam pipelines, and steam turbine generator unit through technological breakthroughs. Compared with those of the conventional layout (its operating floor level being 12.6‒17 m), the main steam and reheat steam pipelines of the high-level layout (its operating floor level being 65 m) can save 34.2% and 20.9% of raw materials,respectively; and exhaust steam pipes of the air-cooled island can save 93% of raw materials. Furthermore, the power supply coal consumption can be reduced by 4.5‒5.1 g/(kW·h) compared with the design value, and the overall economical efficiency is significantly improved. The monitoring data after operation show that all parameters in the real-time on-line monitoring system of the main power house structure are within the safety threshold, and the plant structure and critical equipment are both in a safe state. Therefore, we propose to promote clean and efficient coal-fired power generation technologies and apply the high-level layout technology to the advanced air-cooled coal-fired power units in northeast, north, and northwest China as these regions are rich in coal but short of water. This can provide practical experience for the construction of economical high-temperature steam pipelines for 700 ℃ ultra-supercritical coal-fired power units.

Fly ash carbonation is an effective method to achieve carbon reduction and stabilize the heavy metals. Supercritical CO2 can facilitate the carbonation process due to its strong diffusivity, but the effect of parameters on the stabilisation characteristics under supercritical conditions is unclear. In this paper, the heavy metal leaching characteristics of carbonized fly ash under supercritical CO2 conditions were comprehensively investigated. The experimental results showed that, increasing the pressure, applying mechanical force, increasing the rotational speed, raising the temperature, increasing the liquid-to-solid ratio, and adding calcium oxide all reduced the heavy metals leaching concentration. Compared with the original ash, Pb decreased by 38.65%, Cd by 31.66%, Hg by 47.06%, and As by 4.91% under supercritical conditions. After the fly ash carbonation, the influence of environmental factors such as the acid–base value, temperature, moisture, reaction time, and additives on the release characteristics were investigated. It was found that carbonized fly ash had good stability. At 30 °C, that leaching rate of Ni, Cr, Cd, Pb, Hg, and As after carbonation were 28.80%, 8.62%, 26.60%, 22.19%, 100.00% and 17.47%, respectively, lower than those of the original sample. The leaching rate of heavy metals increased with increasing temperature, and moisture aggravated the precipitation of heavy metals, which also increased with the reaction time. The addition of gypsum decreased the heavy metals leaching. The extraction experiments showed that after carbonation the heavy metals changed from active forms to stable residue states, except for Hg and As. Supercritical CO2 carbonation has a good effect on the stabilization of heavy metals. [ABSTRACT FROM AUTHOR]

Heavy metals in flue gas desulfurization (FGD) gypsum from coal-fired power plants are at risk of releaching during the processes of stockpiling and resource utilization. In this study, the effects of organosulfur chelators dithiocarbamate (DTC) and trisodium trithiocyanate-15 (TMT-15) on the solidification characteristics of heavy metals in desulphurized gypsum under different mass fractions, pH values, water contents and reaction times were investigated. The chemical composition and morphology were analyzed by inductively coupled plasma atomic emission spectrometer (ICP-AES) and scanning electron microscope (SEM). The experiments showed that both DTC and TMT-15 were effective at stabilizing the heavy metals in the FGD gypsum, with more than a 50% curing effect for all the heavy metals except Pb. DTC showed a better stabilization for Pb, Hg, Cu, Zn, and Cr, and TMT-15 showed a better curing effect for Cd. The solidified gypsum had good heavy metal stability in low-water-content environments. Increasing the mass fraction, reaction time, and pH decreased the heavy metal leaching, and the mass fraction had the greatest effect on the total heavy metal leaching concentration, followed by the reaction time and pH value. [ABSTRACT FROM AUTHOR]

In light of the current situation where the utilization of calcium carbide slag yields low profits but holds significant potential for reducing carbon emissions, ammonium acetate was employed to leach calcium carbide slag. It also played a crucial role in regulating the products of indirect carbon dioxide carbonation when mixed with glycine and lye. Ammonium acetate's significance underscores its dual role in both the leaching and carbonation processes. This process yielded calcium carbonate with particle sizes smaller than 100 nm, with a purity of 98% and a single vaterite phase. The calcium carbide residue demonstrated an impressive CO2 uptake rate of 23.5%. Ammonium acetate exhibited an efficiency of 79.2% as a leaching agent. The ammonium acetate method demonstrated enhanced environmental friendliness and facilitated a more efficient carbon uptake rate of 23.5% compared to conventional indirect methods. Furthermore, the addition of lye, glycine, and ammonium acetate effectively extended the nucleation time of the calcium carbonate crystals and induced the formation of more vaterite intermediates with smaller particle sizes. The influence mechanism of compound additives on the carbonation reaction was revealed through kinetic analysis and molecular dynamics. This innovative approach offers a promising avenue for simultaneously treating solid waste and reducing CO2 emission. © 2023 Society of Chemical Industry and John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Cu-based catalysts for efficient C2+ production from CO2 electrocatalytic reduction reaction (CO2ERR) exhibit significant promise, but still suffer from ambiguous mechanisms due to the intrinsic structure instability during electroreduction. Herein, we report an oxide-derived copper nanowire bundle (OD-Cu NWB) for efficient CO2ERR to C2+ products. OD-Cu NWBs with a well-preserved nanowire bundle morphology lead to promoted multi-carbon production compared to commercial copper powders. The formation of OD-Cu NWBs shows a great dependence on the precipitation/calcination temperatures and per-reduction potentials, which further influence the ultimate CO2ERR performance correspondingly. The optimized preparation parameters for the formation of a well-ordered nanowire bundle morphology are found, leading to a preferred C2+ production ability. Besides the nanowire bundle morphology, the oxide-derived Cu essence of OD-Cu NWBs with stabilized Cu+ species from per-reduction also promotes the CO2ERR activity and facilitates the C-C coupling of key intermediates for C2+ production. This work provides a facile strategy and inspiration for CO2ERR catalyst developments targeting high-valued multi-carbon products. [ABSTRACT FROM AUTHOR]