Search

[Display omitted] • Comprehensive mechanism explorations on plasma-based dry reforming by detailed kinetic modeling and in-situ OES measurements. • A CH 4 conversion as high as 44.76 % was achieved without catalyst at 300 °C. • Plasma kinetic model with incorporation of dynamic electron filed and thermal effects. • The formation of C 2 hydrocarbons followed a pathway of CH 4 ↔ CH 3 /CH → C 2 H 6 ↔ C 2 H 5 ↔ C 2 H 4 → C 2 H 2. Plasma-based dry reforming in an atmospheric dielectric barrier discharge (DBD) reactor has been thoroughly studied by combination of experiments and detailed kinetics simulation. With the assistances of in-situ optical emission spectroscopy (OES) measurements and reaction pathway analysis based on plasma kinetic simulation considering non-constant electric field and thermal effects, this study provided deep insights into the reaction mechanism of plasma-based dry reforming under varied feeding gas composition, gas residence time and operation temperature. A CH 4 conversion as high as 44.76 % could be achieved without catalyst at 300 °C, with an SEI of 78 J/cm3 and feeding CH 4 ratio of 50 %. Increase of feeding CH 4 proportions were found to enhance the generation of C 2 and C 3 hydrocarbons. Consistently, the OES analysis showed that the relative intensities of spectra bands induced by deexcitation of CH, CO, and C 2 also increased monotonically. With the same increment in SEI, increasing gas residence time led to larger promotions in CH 4 and CO 2 conversion, as being compared to increase of input power. The reason could be explained as that CH 4 and CO 2 molecules experienced more successive micro-discharges with a longer gas residence time, so more energy would be devoted into CH 4 /CO 2 conversion, whereas more energy was dissipated into heat as rudely increased the discharge power due to the limit of reaction time. CO 2 conversion continuously decreased with increasing gas temperature, owing to the recombination of CO and O enhanced at higher gas temperatures. Reaction pathway analysis showed that CH 4 conversion was mainly induced by electronic dissociation and ionization at the discharge stage, while CO 2 was mainly converted by recombination reaction CO 2 + CH 2 → CH 2 O + CO and also electron collision vibrational reaction e + CO 2 → e + CO 2 (v n). The formation of C 2 hydrocarbon products was supposed to follow the path of CH 4 ↔ CH 3 /CH → C 2 H 6 ↔ C 2 H 5 ↔ C 2 H 4 → C 2 H 2. [ABSTRACT FROM AUTHOR]

Steel slag-derived CaO (CaO(SS)) was applied in cyclic sorption enhanced steam reforming of coke oven gas process (cyclic SE-SRCOG) for high-purity hydrogen production. Effects of leaching acid concentration on the cyclic CO 2 capture capacity of CaO(SS) were investigated. Using 1 mol/L acetic acid solution as leaching solution, the prepared CaO-based sorbent showed a stable CO 2 capture capacity of 0.27 g CO2 /g CaO after 35 sorption-desorption cycles. Impacts of operating modes (with different particles contents and loading patterns), operating procedure, and leaching residue (LR) blending on cyclic SE-SRCOG performance were experimentally investigated in detail. Combined catalyst-sorbent by adhesively tableting exhibited the worst stability due to loss of Ni active sites, caused by severe sintering and coverage by CaCO 3. With a reforming temperature of 600 °C, cyclic SE-SRCOG with layered packing catalyst-sorbent particles could achieve H 2 purity of 95% and CH 4 conversion of 87% at the 5th cycle, and they were still maintained to be 87% and 65% at the 10th cycle, respectively. In operating mode using layered packed catalyst-sorbent particles, integration of LR into the sorbent facilitated further improvements of CH 4 conversion to 86% at the 10th cycle, mainly due to that LR could act as catalytic promoters of SRCOG and sintering-resistance spacers of CaO(SS). [Display omitted] [ABSTRACT FROM AUTHOR]

• Multiple field parameters investigation of plasm-enhanced CO 2 spliting. • A combination analysis of optical emission spectrum and multiphysics simulation of plasma process. • Trade-off effects of plasma power and gas flow on conversion and energy efficiency. • A reduced plasma chemistry set for CO 2 dissociation. • Dissociation reactions of neutrals and electron impact reactions dominated CO 2 splitting. CO 2 dissociation in DBD plasma was thoroughly studied by combining dissociation experiments, multi-physics coupling simulation and in-situ emission spectroscopy measurements. Evolution of spatial–temporal distributions of key field parameters such as discharge mode, electron density (N e), electron temperature (T e), intermediate concentration and reaction rates were analyzed in depth, to uncover the underlying reaction mechanism. The specific energy input (SEI) had a large impact on CO 2 conversion and energy efficiency, and there was a trade-off between plasma power and gas flow rate. The highest CO 2 conversion was achieved a maximum of 15.5% at SEI = 177 J·cm−3 in this work. Meanwhile, the spectrum shows that there was a large amount of CO 2 +, CO, O, and O 2 in the plasma. In addition, we proposed and validated a reduced CO 2 splitting plasma chemistry set to explore the field parameter and key reactin rates distributions. According to the multiphysics modelling, the discharge gap greatly affected the discharge form of DBD, which will subsequently influence CO 2 splitting. In discharge gap > 1.75 mm formation of discharge channels remarkably decreased, and an over small discharge gap (δ g < 1.25 mm) would restrain the electric field range, causing shorter motion path of charged particles and less free electrons, both of which hindered the conversion of CO 2. A thinner dielectric layer can promote CO 2 conversion, due to the reduction in breakdown field strength and increase of high-energy electrons. Electron impact reactions (e + CO 2 → CO + O−, e− + CO 2 → CO + O + e−), reactions of the excited CO 2 * (CO 2 + CO 2 * → CO 2 + CO + O, CO 2 *+O → CO + O 2) mainly contributed to the CO 2 dissociation. [ABSTRACT FROM AUTHOR]