Search Results (4)

This article presents advancements in using Micro-Electro-Mechanical Systemsbased (MEMS-based) devices for measuring the calorific value and hydrogen content in hydrogenated gaseous fuels, such as natural gas. As hydrogen emerges as a pivotal clean energy source, blending it with natural gas becomes essential for a sustainable energy transition. However, precise monitoring of hydrogen concentrations in gas distribution networks is crucial to ensure safety and reliability. Traditional methods like gas chromatography and mass spectrometry, while accurate, are often too complex and costly for real-time applications. In contrast, MEMS technology offers innovative, cost-effective alternatives that exhibit miniaturization, ease of installation, and rapid measurement capabilities. The article discusses the development of a novel MEMS thermal conductivity detector (TCD) and a new ionization spectrometer with an optical readout, both of which enable accurate assessment of hydrogen content and calorific values in natural gas. The TCD has demonstrated a 3% uncertainty in calorific value measurement and an impressive accuracy in determining hydrogen concentrations ranging from 2% to 25%. The research detailed in this article highlights the feasibility of integrating these MEMS devices into existing infrastructure, paving the way for efficient hydrogen monitoring in real-world applications. Moreover, preliminary findings reveal the potential for robust online process control, positioning MEMS technology as a transformative solution in the future of energy measurement. The ongoing innovations could significantly impact residential heating, industrial processes, and broader energy management strategies, facilitating a sustainable transition to hydrogen-enriched energy systems. Full article

Global gas markets are changing as natural gas (NG) is replaced by biomethane. Biomethane is produced by upgrading biogas, which can have a molar concentration of methane to over 98%. This renewable energy has been injected into the pipeline networks of NG, which offers the possibility to increase its usage in industrial and residential applications. However, the expectation of the increase in biomethane proportion on the NG grids could increase the fluctuations on the composition of the NG–biomethane mixture in amplitude and frequency. In this context, the injection of biomethane into the existing network of NG raises a discussion about the extent to which variations in gas quality will occur and what permissible limits should exist, as variations in combustion characteristics can affect the operation of the combustion processes, with consequences for consumers, distributors and gas producers. This study describes a gas quality analysis with regard to the use of biomethane in industrial equipment, mixed or not mixed with NG, taking into account the indicators for gas interchangeability and provides a discussion on the necessary gas quality level to be achieved or maintained for efficient combustion in equipment originally designed to operate with NG. NG and biomethane real data collected for 92 consecutive days in 2022 and provided by two different companies in Brazil were used for this study. It is shown that the maximum deviation of the Wobbe Index (WI) of 5%, which is allowed for industrial plants, does not work for the operation of furnaces at temperatures of 1200 °C or more. In addition, it is shown that the WI, as defined in relation to the calorific value of the fuel, may allow inappropriate substitution of fuel gases, which is likely to reduce the range of blending of biomethane in NG pipelines. The results can be assessed to analyze how the addition of biomethane to NG grids will impact the WI and the equipment operation parameters such as the air-to-gas ratio, products-to-gas ratio, adiabatic flame temperature and furnace temperature. Full article

Micro gas turbines fit perfectly with the energy roadmap to 2050: on-site, small scale power generation, combined with heat recovery from exhaust gas, offers an opportunity to deploy primary energy saving and pollutant emission reduction. Moreover, their flexibility enables fuel switching from natural gas (NG) to carbon-free fuels such as hydrogen and ammonia. This study aims to explore the potential of direct combustion of ammonia in a micro gas turbine (MGT), from a thermodynamic point of view. A modeling procedure was developed to simulate the behavior of a 100 kW MGT operating at full and part-load. After validation with NG as fuel, an increasing fraction of ammonia was fed to the combustor to predict performance variations in terms of electric, thermal and total efficiency, as well as exhaust gas composition, for a load range between 40% and 100%. Additional relevant details, related to the interaction between compressor and turbine in the single-shaft arrangement, were discussed through performance maps. Full replacement of NG with ammonia was found to reduce electric efficiency by about 0.5 percentage points (pp), whatever the power output, with a consequent improvement in exhaust gas heat recovery. Thus, total efficiency is maintained at a high level, with values ranging from 74.5% to 79.1% over the investigated load range. The benefit of zero CO₂ emissions can be achieved provided that compressor–turbine matching is adjusted to compensate for the reduction in fuel calorific value: at rated power, when the largest fuel input is required, flow rates of air and flue gas decrease by 4.3% and 2.8%, respectively, with an increase in Brayton cycle pressure ratio of 2%. Full article

The calorific value of household refuse (HR) is greatly improved after classification, which includes the implementation of sufficient pyrolysis conditions. Therefore, a better pyrolysis effect can be achieved by co-pyrolysis with industrial solid waste (ISW) with high calorific value. In this work, HR and ISW were used as raw materials for co-pyrolysis experiments. The influence on the distribution of three-phase products after co-pyrolysis, the concentration of heavy metals and dioxins in the flue gas, and the distribution of PCDD/Fs isomers were studied. The results showed that, at a temperature of 600 °C and H/C = 1.3, of the formed material, the quantity of pyrolysis gas was approximately 27 wt.%, and the quantity of pyrolysis oil was approximately 40.75 wt.%, which mainly contained alkanes, olefins, and aromatic hydrocarbons. When S/C = 0.008, pyrolysis gas accounted for 25.95 wt.% of the formed material, and pyrolysis oil for 41.95 wt.% of the formed material. The ignition loss rate of pyrolysis coke was approximately 20%, and the maximal calorific value was 14,217 KJ/kg. According to the thermogravimetric experiment, the co-pyrolysis of HR and ISW can promote the positive reaction of pyrolysis, and the weight loss reached 62% at 550 °C. The emission of gaseous heavy metals was relatively stable, and the concentration of heavy metals slightly decreased. The main heavy metals in the ash were Cu, Fe, and Zn. The emission of dioxins could be effectively reduced by the pyrolysis of HR with ISW, and the produced dioxins were mainly synthesized from de novo synthesis. After pyrolysis, the toxic equivalent of dioxins in the flue gas was reduced from 0.69 to 0.29 ng I-TEQ/Nm³, and the distribution of dioxin isomers in the flue gas had little influence. The experimental results provide a theoretical basis for the application of co-pyrolysis technology with HR and ISW. Full article