846 research outputs found
An empirical correlation for the electric energy consumption of household refrigerator-freezers
No full textAnalysis of aerosol emissions from a rubber vulcanization process
No full textPaper G11-04 Vulcanization is a non-reversible chemical process, which greatly improves the useful properties of natural rubber gum or certain synthetic polymers. The vulcanization process generates a complex mixture of gaseous substances in the exhaust gases that must be removed before discharging them outdoors.
We monitored and analyzed the emission control systems of some post-curing ovens, serving a production unit manufacturing small parts containing rubber for the automotive industry. Concentrations and size distributions of particles in the exhaust streams were measured using optical particle spectrometers (size ranges from 300 nm to 10000 nm) and electric particle mobility analyzers (mobility diameter between 10 nm and 420 nm).
We measured the emissions exhausted by two different types of ovens: in-line and batch ones. Each emission control unit was equipped with a heat exchanger cooling the exhaust gases to a value suitable for the operation of the downstream two-stage electrostatic precipitator. Each single exhaust treatment unit collects the gases exhausted by 3 to 5 ovens, treating a flow rate of less than 1000 m3/h at a duct velocity of about 3.8 m/s.
The goals in performing the measurements were:
To assess the performance of the exhaust fume purifying unit, with emphasis on the electrostatic precipitator performance and its assessment;
To evaluate the adequacy and efficacy of the current maintenance schedule, whose time interval may significantly influence the performance of the electrostatic precipitators;
To develop a robust measurement protocol to evaluate the reliability of innovative solutions for removing the pollutants
Reversible Solid Oxide Cell (ReSOC) as flexible polygeneration plant integrated with CO2 capture and reuse
No full textThis work presents the concept of a Reversible Solid Oxide Cell (ReSOC) system localized in an urban residential district. The system is operated as a polygeneration plant that acts as interface between the electricity grid and the local micro-grid of the district. The ReSOC plant produces hydrogen via electrolysis during periods of low electricity demand (i.e., low-priced electricity). Hydrogen is used for multiple city needs: public mobility (H2 bus fleet), electricity production delivered to the micro-grid during peak-demand hours, and heat (accumulated in a storage) provided to the local district heating (DH) network. An additional option analyzed is the use of part of the H2 to produce DME using CO2 captured from biogas obtained from municipal solid wastes. The DME is used for fueling a fleet of trucks for the garbage collection in the residential district. A traditional CO2 removal process based on liquid MEA thermally integrated with the ReSOC system is studied. A time-resolved model interfaces the steady-state operating points with the thermal storage and the loads (electrical, H2 buses, DME trucks, heat), implementing constraints of thermal and H2 self-sufficiency on the system. Neglecting the DME option, the average daily roundtrip electric efficiency is about 38%, while the annual efficiency, which includes H2 mobility and thermal energy to DH, reaches 68%. When the DME option is considered, the thermal demand for CO2 removal and conversion process reduces the heat availability for DH, while the need for additional H2 for DME synthesis increases the electricity consumption for water electrolysis: both these phenomena imply a reduction of system efficiency (-9%) proportional to DME demand
CO2 from direct air capture as carbon feedstock for Fischer-Tropsch chemicals and fuels: Energy and economic analysis
No full textThe investigated plant concept integrates the direct air capture technology with the Fischer-Tropsch synthesis. 250 kt/h of air, with a CO2 concentration of 400 ppm, are used as feedstock to produce the synthetic hydrocarbons. The direct air capture is modelled as a high-temperature calcium recovery loop process. An alkaline electrolyser and a reverse water-gas shift reactor produce the required syngas. The Fischer-Tropsch products distribution is described by a carbide model developed for a Co-Pt/ɣAl2O3 catalyst for alkanes and alkenes of carbon number C1-C70. Five integration scenarios are analysed. In the base case, the energy demand of the direct air capture process is supplied with natural gas from the distribution grid. In improved configurations, the effect of Fischer-Tropsch off-gas recirculation to the reverse water-gas shift and/or the direct air capture units is explored, excluding the need of fossil fuel. An electrified direct air capture solution is also included. In the analysed scenarios, the highest system efficiency corresponds to 36.3 %, while the maximum carbon dioxide conversion is of 68.3 %. The maximum waxes production corresponds to 8.7 t/h. Lastly, capital and operating plant costs are allocated in an economic investigation, considering different market electricity costs and financial risk values. In a medium financial risk scenario (interest rate: 7.5 %), the minimum Fischer-Tropsch waxes production cost corresponds to 6.3 €/kgwax, reaching 5.05 €/kgwax at an interest rate of 0%. Lastly, the effect of learning curves over the production cost at the year 2030 and 2050 is included
Methanol synthesis through CO2 capture and hydrogenation: Thermal integration, energy performance and techno-economic assessment
No full textThis work assesses the opportunity of using “green” methanol (MeOH) produced from renewable electricity as a
vector for the decarbonization of chemical process industry. We developed a comprehensive process model to
simulate all the relevant sections for the conversion of 1.25 t/h of captured CO2 from a coal-fired power plant to
methanol, using “green” hydrogen via water electrolysis. We applied the pinch analysis methodology for an
improved thermal management of the integrated carbon capture, electrolysis and methanol synthesis plant. A
network of recovery heat exchangers was designed with the pinch analysis methodology, allowing a thermal
energy saving of 4.59 MW, with a net reduction of heating and cooling demands by 81 % and 47 %, respectively,
and an improvement of the global efficiency of the plant from 26.74 % to 37.22. We followed a bottom-up
approach for the techno-economic assessment, defining a confidence range for the main indicators of system
economic viability. We assessed their sensitivity to the cost of electricity from seven renewable energy sources
and to the option of selling oxygen produced by water electrolysis, in three different cost scenarios (1-optimistic,
2-realistic, 3-pessimistic). The estimated values of the cost of methanol (COM) span from a maximum range of
2624–2706 €/t (in the case of concentrated solar power) to a minimum of 565–647 €/t (hydropower with highest
valorization of electrolytic oxygen), hence resulting in line with the future trends of methanol market price
(400–800 €/t) in five of the considered configurations. We have finally estimated the levelized cost of methanol
(LCOM) ensuring an internal rate of return ranging from 0 to 10 % for each of the techno-economic scenarios
identified. Assuming 10 % as the target, LCOM in case of hydropower as renewable energy source spans from 874
to 1356 €/t, hence close to the future market price of MeOH with margin of improvement (655–1135 €/t) in case
of lower costs of electric energy
In-service performance assessment of electrostatic precipitators serving a rubber vulcanization process
No full textWe examined two emission abatement systems of some vulcanization ovens, serving a unit producing small rubber-based parts for automotive application. Each emission control unit treats the gases exhausted by three to five ovens. A heat exchanger cools down the fumes to a temperature suitable for the correct operation of a couple of two-stage electrostatic precipitators in series. We performed quantitative analysis of concentrations and size distributions in these rubber fumes using aerosol technology instrumentation, namely optical particle spectrometers and electrical mobility particle sizers. The size of sampled particles was mainly between 100 nm and 1000 nm. We evaluated the performance of the exhaust fume abatement units, with focus on the electrostatic precipitator. Concerning batch ovens, the quantitative trend of the emissions follows the thermal cycle of the post-curing process. Time interval since the last maintenance operation causes a gradual reduction in the removal efficiency. The measured data demonstrate the reliability and the adequacy of aerosol instrumentation for the characterization of the emissions from rubber vulcanization ovens. The pair of electrostatic precipitators was shown to be effective in removing most of the particles detected in the fumes stream. The measurement protocol developed in this study allows assessing the influence of the maintenance schedule on the performance of the emission control units. New technologies for treating organic vapors can be evaluated in a reliable and effective way
Fine morphology of the myrmecophilous larva of Paussus kannegieteri (Coleoptera: Carabidae: Paussinae: Paussini). Corresponding author
No full textFIGURES 13–18. Paussus kannegieteri third instar larva: 13, thorax, left lateral view; 14, thorax, dorsal view; 15, mesothoracic spiracle; 16, metathoracic spiracle-like structure; 17, mesothoracic leg, anterolateral view; 18, apex of metathoracic leg with lanceolate setae, posterolateral view. CO = coxa, ls = lanceolate setae, m = membrane, ME = mesonotum, MT = metanotum, pe = peritreme, PR = pronotum, un = claw. Scale bars: Figs. 13–14 = 500 µm; Fig. 15 = 10 µm; Fig. 16 = 20 µm; Fig. 17 = 200 µm; Fig. 18 = 50 µm.Published as part of Giulio, Andrea Di, 2008, Fine morphology of the myrmecophilous larva of Paussus kannegieteri (Coleoptera: Carabidae: Paussinae: Paussini), pp. 37-50 in Zootaxa 1741 on page 44, DOI: 10.5281/zenodo.18152
Power-to-X and power-to-power routes
No full textThe increasing dependence on a worldwide scale of the power generation sector on non-dispatchable renewable sources, such as wind or solar, is posing challenges to the electricity infrastructures that require flexibility solutions to keep the balance between power supply and demand. Flexible generation, energy storage, demand side response are among the several strategies pursued to increase the flexibility of electricity management in the presence of a large share of RES generation, but flexibility can also derive by the conversion of electricity to other energy commodities. Among the secondary energy carriers, electricity can be stored in the form of chemical potential following the so-called “Power-to-X” scheme. In this route, electricity is converted in energy carriers, such as hydrogen, that can be exploited not only for time-shifted power delivery (“X-to-Power” reverse scheme), but also employed to cover nonelectrical demand in different sectors, such as transportation, heating, and industry. This chapter provides a detailed description of the different routes in the Power-to-X scheme, highlighting the technologies, the benefits and services provided to the energy system, the strengths and criticality points, the possible applications of the output streams, and the lessons learned from projects and demonstrations worldwide
- …
