• Energy Research

The technique of proton transfer reaction mass spectrometry (PTR-MS) couples a proton transfer reagent, usually H3O+, with a drift tube and mass spectrometer to determine concentrations of volatile organic compounds. Proton transfer reaction-mass spectrometry (PTR-MS) has successfully been applied to a wide variety of matrices to identify and to investigate on the behavior of trace compounds; among the possible field of applications we can find: food, air, energy, etc. Natural gas is considered as a fuel for high energy efficiencies applications such as SOFC generators. The ability to distinguish several isobaric aldehydes, ketones, isoprenoids and other compounds is impossible using PTR-MS instrument. In the present research work, PTR-ToF-MS was coupled to a prototype FastGC system allowing for a rapid (90 s) chromatographic separation of the sample headspace prior to PTR-MS analysis. The system was tested on natural gas trace compounds to individuate the major elements and to identify possible issues for the SOFC generators. In comparison to the results obtained by direct injection, FastGC provided additional information, thanks to a less drastic dilution of the sample and due to the chromatographic separation of isomers. This was achieved without increasing duration and complexity of the analysis.

The removal of trace compounds contained in a biogas from the dry anaerobic digestion of organic waste was accomplished. The resulting data were monitored online with a direct injection mass spectrometry technique. Biochar from the pyrolysis of recovered wood waste was used as sorbent material. This material was selected to demonstrate the usefulness of recovered waste for the energy production purposes. Biochar withstands the removal of 2-butanone (158.8 mg/g), toluene (140.1 mg/g) and limonene (64 mg/g) better compared to sulfur (H2S 1.05 mg/g) and siloxane (D3, 1.28 mg/g) compounds. Hydrogen sulfide was the most abundant sulfur compound with the average concentration about 24 ppm(v). The tested sorbent material was able to withstand the H2S and siloxane concentration for almost 30 h with the biogas pilot plant conditions before toachieve the limit value for SOFC applications, 1 ppm(v) and 150 ppb(v) respectively. The performance achieved with this material are comparable to some commercial carbons, even if some more optimized and selective materials show better results especially for the removal of sulfur compounds.

A practical and feasible solution to reduce the global impacts from fossil fuels is represented by the locally distributed micro-cogeneration systems with high temperature solid oxide fuel cells (SOFC) fed by biogenous fuel coupled in an energy distributed system. One of the main drawback is the low tolerability towards certain fuel impurities, mostly sulfur, chlorine and siloxane compounds. The opportunity to predict the breakthrough time of a gas cleaning section with a high precision level is mandatory to meet SOFC requirements. The reaction kinetic equation called the Wheeler-Jonas equation is adopted to estimate this breakthrough time. Two different commercial activated carbons were studied estimating the breakthrough time varying the operating temperature, the pollutant concentration (single and multiple effects) and the relative humidity. Results showed how relative humidity content affects inversely the removal performance for both sorbents. The Carbox sample, below RH 20% showed interesting results due to its metals content and microstructure. Here, relative humidity promoted the best condition to remove organic vapors from the biogas stream. Multiple contaminant conditions for both sorbent materials decreased the removal performance (tb). This decreasing for the Carbox sample ranged from a minimum of 44% to a maximum of 50% for H2S, and 70% for HCl with wet and dry conditions respectively.

Abstract Since the Kyoto Protocol (1997), the European Union has fought against climate change adopting European, national and regional policies to decarbonise the economy. Moreover, the Paris Agreement (2015) calls 2050 solutions between −80% and −100% of greenhouse gas emissions compared with 1990. Regions have an important role in curbing CO2 emissions, and tailor-made strategies considering local energy demands, savings potentials and renewables must be elaborated factoring in the social and economic context. An “optimized smart energy system” approach is proposed, considering: (I) integration of electricity, thermal and transport sectors, (II) hourly variability of productions and demands, (III) coupling the EnergyPLAN software, to develop integrated and dynamic scenarios, with a multi-objective evolutionary algorithm, to identify solutions optimized both in terms of CO2 emissions and costs, including decision variables for all the three energy sectors simultaneously. The methodology is tested at the regional scale for the Province of Trento (Italy) analyzing a total of 30,000 scenarios. Compared to the Baseline 2016, it is identified: (I) the strategic role of sector coupling among large hydroelectric production and electrification of thermal and transport demands (heat pumps, electric mobility), (II) slight increases in total annual cost, +14% for a −90% of CO2 emissions in 2050.

Microalgae present promising green economy applications in the energy and biorefinery sectors. The work concerns a pilot study on the integration of anaerobic digestion with microalgae cultivation for managing at the same time emissions and digestate from the dry anaerobic treatment of organic waste. Biogas produced was used to feed Solid Oxide Fuel Cell after a filtering step for removing toxic compounds. The exhausts and digestate were used for providing carbon and nutrients for microalgae growth. The experimental workflow includes the characterization of both for defining their suitability in the microalgal growth (Chlorella vulgaris) tests. The exhausts of Solid Oxide Fuel Cells showed relatively stable concentration of CH4 (4–7%) and CO2 (93–96%) and low concentrations (sub ppm(v)) of sulphur, carbonyl and carboxyl, and aromatic compounds and terpenes, making it particularly suited for algae growing as compared with internal combustion engines. The challenging growing conditions are a compromise between carbon recovery and use of digestate. A good microalgae growth has been obtained (22.31 mm3 mL−1 of biovolume corresponding to 151 dry mg L−1 day−1) exploiting ammonia and phosphate from dilute digestate (removal efficiency 94% and 30% respectively) as well as a good carbon recovering (310 mg CO2 L−1 day−1). Based on our data, the integration of microalgae growth and anaerobic digestion process seems a viable solution to achieve (i) reduced emissions due to carbon recovery; (ii) optimum integrated management of anaerobic digestion waste and (iii) biomass production by low-cost nutrients and carbon.

Abstract The research efforts for SOFC plants fed by biogas moved from the prototypal research to the feasibility of pilot plants up to achieve industrial size plants. Siloxanes among the other trace compounds contained in biogas appear to be the most detrimental for the fuel cell performance. Siloxanes are difficult to be detected and monitored continuously in the gas matrix. A direct injection mass spectrometry technique (PTRMS) was adopted for the monitoring of siloxane removal. Commercial and waste derived sorbent materials are experimentally tested for the removal of siloxanes. Waste derived material was selected to implement the circular recovery purposes. A simple parametric investigation study was developed. It was considered the influence of gas velocity and sulphur compounds, as co-vapors. Physical and chemical characteristics were correlated to the adsorption capacity. Results show three separated groups. Group I shows the best performance in terms of siloxane removal. There is a direct and strong relation between active surface area and microporous volume with the adsorption capacity. This direct correlation is not verified for some elements such as Fe and S, while it is respected for Cu and K. Higher performance are registered for not all the commercial carbons. In fact, the physical structure and impregnating agents are crucial for the siloxane removal.

Abstract Organic waste collection from local municipal areas with subsequent energy valorization through CHP systems allows for a reduction of waste disposal in landfill. Pollutant emissions released into the atmosphere are also reduced in this way. Solid oxide fuel cell (SOFC) systems are among the most promising energy generators, due to their high electrical efficiency (>50%), even at part loads. In this work, the local organic fraction of municipal solid waste has been digested in a dry anaerobic digester pilot plant and a biogas stream with methane and carbon dioxide concentrations ranging from 60–70 and 30–40% vol., respectively, has been obtained. Trace compounds from the digester and after the gas clean-up section have been detected by means of a new technique that exploits the protonation reactions between the volatile compounds of interest and the ion source. Sulfur, chlorine and siloxane compounds have been removed from as-produced biogas through the use of commercial sorbent materials, such as activated carbons impregnated with metals. A buffer gas cylinder tank has been inserted downstream from the filtering section to compensate for the biogas fluctuations from the digester. The technical feasibility of the dry anaerobic process of the organic fraction of municipal solid waste, coupled with a gas cleaning section and an SOFC system, has been proved experimentally with an electrical efficiency ranging from 32 to 36% for 400 h under POx conditions.