1,721,047 research outputs found
Biogas from anaerobic digestion of biomass (Organic Fraction of Municipal Solid Waste and sewage sludge): trace compounds characterization through an innovative technique (PTR-MS) and detrimental effects on SOFC energy generators, from single cells to short stacks
No full textThe use of biofuels instead of conventional fossil derived fuels is becoming an increasingly crucial topic for future energy systems where environmental issues are also taken into account. Biomass exploitation, including biowaste, appears as a promising means for the energy production and also it contributes to the carbon dioxide emissions reduction. Among the different techniques for biomass exploitation, interesting aspects are covered by the dry anaerobic fermentation of organic waste (OFMSW). In addition also interesting aspects can be achieved by the anaerobic digestion of sewage sludge in waste water treatment plants (WWTPs). Organic waste collection from local municipal areas or from sewage sludge exploitation with subsequent energy valorization through CHP systems allows to reduce the amount of waste disposed into landfills and the pollutant emissions into the atmosphere. Solid Oxide Fuel Cell (SOFC) systems are among the most promising energy generator respect to traditional power generating systems due to their higher electrical conversion values, even at partial loads. This is due to the direct conversion of chemical energy to electrical energy. Hence, fuel cells are very appealing from both energy and environmental point of view. In this work, the main goal was to demonstrate the real feasibility of a SOFC stack system fed by real biogas. This main goal has to be achieved considering three main sub-goals. The first one related to the biogas aspects, mainly on trace compounds investigation followed by the VOCs cleaning for SOFC requirements and then testing the main and the most dangerous VOCs on single cells and on short stacks. These information have been fundamentals for the SOFC generator directly fed by biogas. A 500 We SOFC stack by SOFCpower (Italy) was operated for more than 400 hrs in conjunction with a biogas feeding syste
BEV, electric vehicles safety issues - thermal runaway and abuse testing in confined spaces
No full textUse of sewage sludges for CO2 removal
No full textSewage sludge from the Turin water purification system (SMAT; TO) is first anaerobically digested for biogas production and then used as filter material. Filter material for the purification of biogas produced by anaerobic digestion. The digested sludge must be appropriately treated. The case study was focused on the technical feasibility of the process. These samples were adopted for the removal of carbon dioxide from a biogas mixture. A sensitivity analysis was performed considering the main process parameters (temperature, residence time, activation agent, heating rate and activation flow rate). The sludge is characterised by its irregular shape and size, ranging from 1 mm to approximately 2 cm in equivalent diameter. Activation of the ground sludge was carried out in a tubular stainless steel reactor 57 cm long and 3.4 cm in outside diameter. A cylindrical electric furnace was adopted for the pyrogasification process, using N2, CO2 or air as the activating agent. A temperature control regulator, ranging from 200 to 600 °C, was adopted. These lower values compared to the literature are related to the coupling of SOFC discharges as possible agents for char production. Temperature and residence time are the most relevant parameters for char production with the pyrogasification process from sewage sludge. Temperature is the parameter that most influences the char production value. The biogas mixture (CH4/CO2=1.5) was considered. The untreated material shows an adsorption capacity of 4 mg/g, while the physically activated material shows a maximum value of about 102.5 mg/g. Future work will focus on the chemical activation of this sludge to investigate its gas-cleaning potential
Direct injection mass spectrometry technique for the odorant losses at ppb(v) level from nalophanTM sampling bags
No full textTrace compound stability is crucial for real time gas analysis and for high efficiency energy generators, where part per billion concentrations have a high impact. In this context, the container type chosen for the gas analysis becomes important. Several types of containers, such as stainless-steel canisters, glass bulbs, gas tight syringes and sampling bags can be adopted for sampling and storing such samples. Sampling bags are cheap and easy to manage, for these reasons other solutions are rarely used. Literature studies have showed how nalophanTM bags represent the best choice for the collection of samples due to the extremely low cost, the good sample stability and the low background interaction. No studies have considered the biogas trace constituents, especially at an ultra-low concentration level. Most of the studies relating to trace compound detection, use a GC–MS instrument and focus on few compounds of interest. In this paper, one of the most rapid and reliable direct injection mass spectrometry techniques was used. PTR-QMS was adopted to investigate the real biogas mixture stability. The concentration losses were studied continuously during 24 h from the sampling. These losses may be related to the wall adsorption and/or through the wall diffusion phenomena. The most stable compounds detected were acetone, methanol and formaldehyde with a concentration loss below 5%. Terpenes and sulphur compounds had a concentration loss of around 50%, while hydrocarbons and aromatic compounds showed concentration losses around 60%. The stability of the compounds monitored with acceptable losses (below 5%), was achieved within the first 3 h after the sampling was carried out
High temperature materials for CSP receivers: Experimental insights and material selection challenges
No full textMultiphysical model to assess the temperature and state-of-charge dependence of the OCV of a LIB cell
No full textLithium-ion batteries (LIBs) have shown rapid growth in both the stationary and vehicle electric storage sectors. This is due to their high energy density, low weight, low memory effect, and low maintenance requirements. The performance of LIBs is greatly influenced by the temperature of the
environment and the cell itself. At extreme temperatures, whether cold or hot, phenomena are triggered that damage the capacity and durability of the battery and can lead to the riskiest cases to the cell exploding. In recent years, many researchers have investigated these issues to find solutions that could make batteries more efficient and safer in these operating conditions by improving the battery management system (BMS). The OCV open circuit voltage) behaviour of LFP batteries at different states of charge (SOC), placed in a temperature range from -20°C to 60°C, is analyzed. A multiphysics model was developed to simulate the trend of the experimental results. The results showed that the OCV curves generally maintain a fairly constant trend throughout the experiment, demonstrating the fact of thermal stability of the LFP type. Only in the case of full charge, 100%
SOC, is a slightly more variable behaviour noticeable, due to the presence of more active material. To bridge these differences, it would therefore be advisable to conduct tests on the batteries to obtain more certain and reliable data on entropic coefficient values to update the model
Thermal gradients - evaluations for the receiver of a disc solar concentrator
Full text linkThe receiver of a disc solar concentrator is not only stressed by the high solar radiation concentrated in a limited volume; it must also cope with thermal fluctuations. The resulting thermal gradient has a catastrophic effect on the mechanical characteristics of the receiver. As the thermal gradient increases, the thermal stress on the selected materials increases. If the creep limit is exceeded, the material begins to deform plastically to the point of fracture. The outputs of the problem are the spatial trend of the temperature at the end of the transient and the temporal trend of the most
stressed section, which turns out to be the output section. In addition, the thermal stress induced by the temperature gradient was evaluated at the end of the transient, which turns out to be the most extreme working condition. The following materials were studied: Alloy 625, Alloy 800H, Haynes
230, Inconel 740H, Alloy 316H. The best material is Inconel 740H, which has a high yield strength and the lowest ΔT of all the materials analyzed. It is also the only one that could withstand the induced thermal shock even under extreme working conditions
SOFC single cells fed by biogas: Experimental tests with trace contaminants
No full textBiogas from biological treatments and from the waste degradation in landfills generally contains a wide range of trace impurities (e.g., sulphur compounds, siloxanes, halogens, tar compounds, etc.). This paper describes an experimental analysis performed with SOFC single cells fed by a synthetic gas polluted by H2S, HCl, D4 and a mixture of H2S + C2Cl4. The aim is to detect the threshold tolerance limit on different cell performance parameters. Results show how: hydrogen sulphide has a strong impact on the polarization losses due to the nickel sulphide formation on the electrode that causes a mass transfer resistance. Hydrogen chloride particularly limited the electrochemical processes. Octamethylcyclotetrasiloxane (D4) showed a high impact on SOFC performance even at ultra-low level (78–178 ppb(v)) as a consequence of the formation of silicon dioxide covering the anode porous sites. Sulphur added to C2Cl4, accelerated the deterioration of SOFC performance. In addition, current density variations and operating temperature are studied during sulphur poisoning. An opposite behaviour on SOFC performance was revealed by operating temperature and current density
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