Effect of hydrocarbon fractions, N₂ and CO₂ in feed gas on hydrogen production using sorption enhanced steam reforming: Thermodynamic analysis

H₂ yield and purity from sorption enhanced steam reforming (SE-SR) are determined by temperature, S:C ratio in use, and feed gas composition in hydrocarbons, N₂ and CO₂. Gases with high hydrocarbons composition had the highest H₂ yield and purity. The magnitude of sorption enhancement effects compared to conventional steam reforming (C-SR), i.e. increases in H₂ yield and purity, and drop in CH₄ yield were remarkably insensitive to alkane (C1-C3) and CO₂ content (0.1-10 vol%), with only N₂ content (0.4-70 vol%) having a minor effect. Although the presence of inert (N₂) decreases the partial pressure of the reactants which is beneficial in steam reforming, high inert contents increase the energetic cost of operating the reforming plants. The aim of the study is to investigate and demonstrate the effect of actual shale gas composition in the SE-SR process, with varied hydrocarbon fractions, CO₂ and N₂ in the feedstock

Chemical equilibrium analysis of hydrogen production from shale gas using sorption enhanced chemical looping steam reforming

Detailed chemical equilibrium analysis based on minimisation of Gibbs Energy is conducted to illustrate the benefits of integrating sorption enhancement (SE) and chemical looping (CL) together with the conventional catalytic steam reforming (C-SR) process for hydrogen production from a typical shale gas feedstock. CaO(S) was chosen as the CO2 sorbent and Ni/NiO is the oxygen transfer material (OTM) doubling as steam reforming catalyst. Up to 49 % and 52 % rise in H2 yield and purity respectively were achieved with SE-CLSR with a lower enthalpy change compared to C-SR at S:C 3 and 800 K. A minimum energy of 159 kJ was required to produce 1 mole of H2 at S:C 3 and 800 K in C-SR process, this significantly dropped to 34 kJ/mol of produced H2 in the CaO(S) /NiO system at same operating condition without regeneration of the sorbent, when the energy of regenerating the sorbent at 1170 K was included, the enthalpy rose to 92 kJ/mol H2, i.e., significantly lower than the Ca-free system. The presence of inert bed materials in the reactor bed such as catalyst support or degraded CO2 sorbent introduced a very substantial heating burden to bring these materials from reforming temperature to sorbent regeneration temperature or to Ni oxidation temperature. The choice of S:C ratio in conditions of excess steam represents a compromise between the higher H2 yield and purity and lower risk of coking, balanced by the increased enthalpy cost of raising excess steam

Steam reforming of shale gas with nickel and calcium looping

High purity H₂ production from shale gas using sorption enhanced chemical looping steam reforming (SE-CLSR) was investigated at 1 bar, GHSV 0.498 h⁻¹, feed molar steam to carbon ratio of 3 and 650 °C for 20 reduction-oxidation-calcination cycles using CaO and 18 wt% NiO on Al₂O₃ as sorbent and catalyst/oxygen carrier (OC) respectively. The shale gas feedstock was able to cyclically reduce the oxygen carrier and subsequently reform with high H₂ yield and purity. For example H₂ yield of 31 wt% of fuel feed and purity of 92% were obtained in the 4th cycle during the pre-breakthrough period (prior to cycles with low sorbent capacity). This was equivalent to 80 and 43% enhancement compared to the conventional steam reforming process respectively

Steam reforming of shale gas in a packed bed reactor with and without chemical looping using nickel based oxygen carrier

The catalytic steam reforming of shale gas was examined over NiO on Al₂O₃ and NiO on CaO/Al₂O₃ in the double role of catalysts and oxygen carrier (OC) when operating in chemical looping in a packed bed reactor at 1 bar pressure and S:C 3. The effects of gas hourly space velocity GHSV (h⁻¹), reforming temperatures (600–750 °C) and catalyst type on conventional steam reforming (C-SR) was first evaluated. The feasibility of chemical looping steam reforming (CL-SR) of shale gas at 750 °C with NiO on CaO/Al₂O₃ was then assessed and demonstrated a significant deterioration after about 9 successive reduction-oxidation cycles. But, fuel conversion was high over 80% approximately prior to deterioration of the catalyst/OC, that can be strongly attributed to the high operating temperature in favour of the steam reforming process

Phytochemical, nutritional and antimicrobial properties of the leaves of Nigerian Ziziphus Spina – Christi (l.) Willd

Z. spina found in the tropical regions of the world is a small tree capable of resisting heat and drought. Traditionally, the leaves of the plant are preserved as feed for animals during intense drought as well as used to treat external wounds, swellings, diarrhea, and intestinal spasm among others. Phytochemical screening was performed using standard procedures, while the nutritional and antibacterial studies were conducted using the Association of Analytical Chemist (AOAC) and agar well diffusion methods respectively. The result of the phytochemical screening confirmed the presence of flavonoids, tannins, saponins, reducing sugars, among others. Moisture content (27.24 ± 1.19 %), total ash (29.11 ± 0.66 %), acid insoluble ash (1.43 ± 0.06 %), alcohol-soluble extractive (0.26 ± 0.14 %) and water-soluble extractive (0.72 ± 0.12 %) values were obtained from the quantitative proximate analysis. The mineral analysis revealed 14 ± 0.09, 135 ± 1.29 and 1.05 ± 0.19 mg/100 g dry weight as the sodium, potassium and phosphorus compositions respectively. Escherichia coli was found to be the most susceptible bacteria to the extract with an MIC value of 0.25 mg/ml while Staphylococcus aureus was the most resistant strain with an MIC value of 1.00 mg/ml. Conclusively, the leaves of the plant may find use in food formulation operations as well as explored further for the treatment of microbial infections. Keyword: Antimicrobial, Extract, MIC, Nutritional, Ziziphus spin