Journal of The Energy Institute最新文献

Calcium has a definite catalytic effect in char gasification and affects the distribution and composition of gasification products. Therefore, a deep understanding of the reaction properties and mechanism of calcium in gasification is of great significance for the gasification process. Reactive Force Field Molecular Dynamics (ReaxFF MD), an approach for exploring complex chemical reactions, has provided an indispensable aid to the insightful study of the reaction properties of calcium in coal gasification processes. In this work, ReaxFF MD was adopted to construct gasification reactions with different conditions, and the effect of calcium on the products during the gasification was investigated by counting the distribution of the gasification products as well as the changes of calcium species in different conditions. At the same time, the catalytic mechanism of calcium in char during gasification was further investigated by calculating the charge and electrostatic potential of the gasification agent and the gasification agent after calcium binding, as well as the radial distribution function between different atoms. Research has shown that during gasification, the release of calcium from char combined with oxygen atoms in the gasifying agent leads to a decrease in the O–H or C=O bond energy, which promotes the cracking of the gasifying agent. It is worth noting that in comparison to CO₂, Ca can easily form ionic bonds with O in the H₂O molecule during the gasification process, which leads to easier breaking of the O–H bonds.

In the present study, we have investigated the impact of introducing different amounts of hydrogen peroxide into the air on the co-combustion behavior of propane and ammonia. Various combustion criteria including flame speed, ignition delay, heat release, NO emission, and reaction pathways have been explored within different compositions of propane/ammonia/air/hydrogen peroxide. This investigation has been performed through the kinetic study applying a detailed mechanism compromising 188 species and 1604 reactions. According to the findings, air replacement by hydrogen peroxide might improve the laminar burning velocity, heat release rate, flame temperature. The substantial reactivity of hydrogen peroxide leads to a significant increase in OH and H radicals, consequently accelerating the reaction rates as the hydrogen peroxide content in the oxidizer increases. The reaction H + O₂↔O + OH (R906) plays the most significant role in enhancing flame propagation in a fuel/air mixture. However, as the hydrogen peroxide content in the mixture increases, the influence of this reaction diminishes, and the reaction H₂O₂(+M)↔2OH(+M) (R929) becomes more dominant. Initially, NO levels increase with the addition of hydrogen peroxide, but they start to decline at higher proportions of hydrogen peroxide. The initial increase may be attributed to the higher flame temperature, while the subsequent decrease could be linked to a substantial reduction in atmospheric nitrogen levels in the oxidizer. In situations where, pure hydrogen peroxide is used as the oxidizer, there is no production of NO_x in pure propane combustion due to the lack of nitrogen. When compared to pure ammonia combustion, cofiring results in approximately half the amount of NO_x emissions.

Auto-ignition triggering plays an important role in the study of knock, accurate and generalized calculation methods are of great significance. In this study, a brand new calculation method of end-mixture auto-ignition timing based on heat release rate (HRR) is proposed based on several sets of data with different knock intensities of a small turbocharged gasoline engine. The calculation method effectively eliminates the effect of fluctuations in the actual HRR data by setting the search range and the auto-ignition threshold, and also eliminates the calculation delay caused by the second-order derivatives of HRR in the regular calculation method. Under this calculation method, the auto-ignition and knock characteristics present a good fit. The effects of combustion parameters on auto-ignition are significantly different. The changes in engine coolant and inlet air temperature as well as the over-rich mixture significantly affected the auto-ignition trigger pressure, while the ignition timing and the over-lean mixture had no effect on it. The effects of methanol on auto-ignition trigger pressure were also significantly different under various injection timings. The calculation of auto-ignition timing provides a vital prerequisite for the study of auto-ignition triggering, which is of obvious significance for the study of knock.

Pyrolysis is a thermo-chemical conversion method for harmless and resource utilization of sewage sludge, which gives carbon-containing products with high added value and benefits for GHG reduction towards “carbon peaking and carbon neutrality” goals. In this work, co-pyrolysis of sewage sludge and poplar wood was studied to investigate the effects of the wood blend ratio and the volatile-char interactions on the pyrolysis product characteristics. It was found that the synergistic effect during co-pyrolysis could enhance the production of aromatic hydrocarbons but inhibit the formation of nitrogen-containing and phenolic compounds. Meanwhile, the aromaticity of the char increased with increasing the wood blend ratio, resulting in an enhanced quality of the char. The volatile-char interactions could facilitate the cracking of large molecules in volatiles into small-molecule gases, leading to an increase in the gas yield of 0.6–14.6 %, and especially the H₂ yield of 16.2–53.8 %, as compared to the case without interaction in the experiment. The char yields hold fairly constant but the physicochemical structure of the char changed significantly with the interactions. Specifically, the O-containing functional groups on the char surface decreased significantly with increasing aromaticity and stability. More importantly, the total phosphorus content of char was increased by 11.3–33.6 %, as compared to the case without interaction, with the enhanced conversion of non-hydroxyapatite phosphorus to hydroxyapatite phosphorus. The interaction can increase bio-availability of the phosphorus and make biochar to be a better organic fertilizer in application.

As a renewable energy with zero carbon emission, the utilization of biomass has attracted widely studied. One of the most effective methods is to gasify the biomass into high-quality gas fuel. In the recent years, the majority of research on biomass gasification is conducted in the laboratory. However, it lacks the research in engineering application scale. In this work, a biomass gasification-combustion plant was designed and built to provide the industrial steam with a rate of 30 t/h for a food industrial park. The agricultural and forestry waste biomass was gasified in a gasifier, and then the product gas combusted in a boiler to supply the steam. The characteristics of the product gas from the gasifier were studied. The corrosion and pollutants in the combustion process were investigated. In the gasification process, the main components of the product gas are CO, H₂ and CH₄. CO and H₂ account for 29.55 vol%-30.56 vol% and 11.65 vol%-15.35 vol%, respectively. The calorific value of the product gas is 5.88–6.29 MJ/m³. The tar concentration is 110.58–155.07 g/Nm³. At the outlet of the boiler, the concentration of the filterable particulate matter is 300.25 mg/Nm³, and the particle size is concentrated at 1.00–2.50 μm. The concentration of the condensable particulate matter (CPM) is 157.14 mg/Nm³, and the proportion of water-soluble ions in CPM is 86.36 wt%. The concentration of Cl⁻, SO₄^2-, NH₄⁺ and Na⁺ in CPM is relatively high, with the values of 28.83 mg/Nm³, 10.29 mg/Nm³, 7.46 mg/Nm³, and 5.06 mg/Nm³, respectively. During the half-year running, the ash deposition and corrosion were detected in the boiler heating surface and the economizer. The ash deposit in the boiler is mainly composed of the sulfate and silicate, such as CaSO₄, Zn₂SO₄, Na₂SO₄ and K₃Na(SO₄)₂. The ash deposit in the economizer is primarily composed of the sulfate and a small amount of alkali metal chloride. The flue gas reaches the emission requirement after passing through the pollution control devices and can be discharged into the atmosphere.

With the combination of stepwise dechlorination and co-pyrolysis techniques, this study conducted polyvinyl chloride (PVC) dechlorination experiments and co-pyrolysis experiments of poplar wood (PW) with dechlorinated polyvinyl chloride (DPVC) by thermogravimetric analysis and a fixed bed reactor. Stepwise pyrolysis effectively removed Cl from PVC with a dechlorination efficiency of 99.84 % at 360 °C for 30 min. Thermogravimetric tests and thermokinetic variables were employed to describe the co-pyrolysis process's thermodynamic behavior, where co-pyrolysis significantly diminished the activation energy of the initial pyrolysis stage (9.65–21.62 kJ/mol) and increased the reaction rate (0.02–0.09 %/°C). The synergistic effect of co-pyrolysis enhanced the yield and quality of liquid oil and reduced the solid residue rate, with the maximum change in solid residue rate (−2.36 wt%) occurring at PW:DPVC = 3:7. The optimal conditions for the synergistic effect are a raw material ratio of 3:7 at 500 °C. Co-pyrolysis efficiently reduced the content of oxygen-containing compounds of phenols, ketones, and acids in oil, and elevated the selectivity of aromatics. The research methods avoid the drawbacks of bio-oil and plastic oil and improve the quality of pyrolysis oil in a concise and efficient manner, which provides some new ideas for the resource and clean utilization of municipal waste.

Acetic acid dry reforming (ADR) is a promising route for sustainable H₂ generation. However, coke inhibition during ADR is the main challenge and not resolved by using suitable promoted catalysts. In this work, Ce promotion on 10%Ni/Al₂O₃ catalysts with 1-5 wt%Ce was evaluated for ADR at varied temperatures of 923–998 K and stoichiometric feed in a fixed-bed rig. CeO₂ addition of 1–3% enhanced metal dispersion, and surface area whilst basic CeO₂ character significantly boosted the concentration and density of basic sites on catalysts. Particularly, the CO₂ uptake of promoted catalysts was about 2.49–3.73 times greater than that of counterpart sample. CH₃COOH and CO₂ conversions were enhanced with rising Ce loading and the highest reactant conversions were observed at 3 wt%Ce. The improved adsorption of acidic CH₃COOH and CO₂ molecules due to increasing amount of basic sites as well as redox attributes of CeO₂ promoter could be responsible for the enhancement in ADR activity and yield of H₂ and CO. The mechanistic two-step pathway for coke suppression induced by CeO₂ promotion was elaborated in this work. Generally, carbonaceous species formation on 3%Ce–10%Ni/Al₂O₃ was considerably reduced about 1.6–2.0 times. H₂/CO ratio varied from 0.59 to 0.65 relying on ADR temperature over 3%Ce–10%Ni/Al₂O₃. These H₂/CO values, two times higher than theoretical H₂/CO ratio in ADR, are compatible for downstream gas-to-liquid processes to selectively yield high molecular weight olefins. Water formation rate increased from 8.67 × 10⁻⁶ to 4.71 × 10⁻⁵ ${\text{mol}}_{H_{2}O}$ g_cat⁻¹ s⁻¹ with rising temperature within 923–998 K on 3%Ce–10%Ni/Al₂O₃.

This research delves into the field of fast hydropyrolysis of mixed municipal solid waste (MSW), with the goal of understanding product distribution and interactions in a hydrogen-rich condition. Through experimental investigations on MSW and its components, this study thoroughly examines the impact of pyrolysis temperature and gasification atmosphere (30 % H₂+30 % CO+20 % CO₂+20 % H₂O) on the yields and distribution of the three-phase products. As the temperature increases, the gas yield gradually increases, while the yields of tar and char gradually decrease. The introduction of a hydrogen source increases the methane content in the combustible gas, which generally reaches its maximum at 850 °C, and promotes aromatic formation in tar, making aromatics the main component of pyrolysis oil. Notably, aromatics have the highest-octane number in gasoline. This study highlights gasification as a promising technology for converting organic waste into valuable fuel, advancing waste management and energy recovery.