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Co-gasification tests were carried out in a pilot scale bubbling fluidized bed gasifier, large enough to exclude any scale-up effect, and able to treat up to 100 kg/h of plastics and biomass mixtures. It was operated under chemical and thermal steady-state, with equivalence ratios varying from 0.19 to 0.28, and plastics/biomass blending ratios from mono gasification of plastics to that of biomass. The results are reported in terms of main process performance parameters and axial profiles of syngas composition and reactor temperature. They indicate that plastics/biomass ratio and equivalence ratio remarkably affect the gasifier performances, even though the obtained syngas was always of rather good quality, with a low heating value between 7 and 10 MJ/m3N. The axial syngas compositions showed a monotonic reduction of carbon dioxide concentration (of about 20–30%) and a corresponding increase of hydrogen concentration (of about 90–110%), highlighting the key role of water gas shift, and steam and dry reforming reactions. The overall set of results provides information about the feasibility of co-gasification of plastics waste and biomass at a demonstration scale and supports the optimisation of design or operating criteria as well as the implementation of reliable numerical models of bubbling fluidized bed gasifiers.

One of the critical energy challenges, which our planet is confronting today, is how to curtail the reliance on fossil fuels for a sustainable environment. Biomass is a promising source of renewable energy for sustainable power generation compared to the conventional coal. However, they are hard to mill to finer size due to their fibrous nature. In this study, the size dependency on the flame propagation and burning characteristics of pulverized biomass is examined compared to coals. Modified Hartmann and 1-m3 explosion vessels were used to perform flame speed and explosion tests. Fine-sized particles propagated the flame with a flame velocity of 2.5 m/s for non-spherical-shaped particles compared to round-shaped lycopodium and corn flour. For coarse size particles, the flame speeds were measured to be around 1 m/s. The minimum explosion concentration was measured to be 0.2–0.4 equivalence ratio for a size range of 40–200 μm and higher for larger particle sizes. Reactivity data showed functional correlations for selected biomass and coal samples. SEM images of post-explosion residues showed incomplete combustion of bigger particles and formation of the cenosphere because of siliceous contents. The study findings concluded that the fine-sized particles of biomass had higher fire/explosion risk due to greater burning characteristics and it could only be replaced with conventional coal after assessing their combustion data by reliable methods.

CO2-derived methanol and dimethyl ether can play a very important role as fuels, energy carriers, and bulk chemicals. Methanol production from CO2 and renewable hydrogen is considered to be one of the most promising pathways to alleviate global warming. In turn, methanol could be subsequently dehydrated into DME, alternatively, one-step CO2 conversion to DME can be obtained by hydrogenation on bifunctional catalysts. In this light, four oxide catalysts with the same Cu and Zn content (Cu/Zn molar ratio = 2) were synthesized by calcining the corresponding CuZnAl LDH systems modified with Zr and/or Ce. The fresh ex-LDH catalysts were characterized in terms of composition, texture, structure, surface acidity and basicity, and reducibility. Structural and acid–base properties were also studied on H2-treated samples, on which specific metal surface area and dispersion of metallic Cu were determined as well. After in situ H2 treatment, the ex-LDH systems were tested as catalysts for the hydrogenation of CO2 to methanol at 250 °C and 3.0 MPa. In the same experimental conditions, CO2 conversion into dimethyl ether was studied on bifunctional catalysts obtained by physically mixing the exLDH hydrogenation catalysts with acid ferrierite or ZSM-5 zeolites. For both processes, the effect of the Al/Zr/Ce ratio on the products distribution was investigated.

This work reports the results of an experimental campaign aiming at the characterization of the CO2 absorption performance for different aqueous solutions of potassium lysinate (LysK). The solvent stands out as a promising amino acid for post-combustion CO2 capture from combustion flue gas and it has been selected based on the high values of the overall kinetic constant (kov) and CO2 absorption flow reported in the literature. Three different LysK concentrations (8.9, 17.4 and 32.9 %w/w) have been compared and benchmarked against aqueous MEA solution (30% w/w), via closed-cycle absorption tests conducted on a bench-scale column (D = 80 mm, Packed Height = 900 mm). Liquid to gas ratios (1.39 mol/mol) and synthetic flue gas conditions (4% CO2 concentration on a molar basis, the remainder being N2) target the solvent application of CO2 capture in natural gas combined cycles, and are consistent with previous tests conducted on MEA and Potassium prolinate (ProK) solutions. Results highlight that LysK attains faster loading increase rates compared to ProK and higher CO2 loadings at saturation (between 0.82 and 0.98 molCO2/molAlk depending on the test case) with respect to MEA (0.52 molCO2/molAlk) and ProK. Finally, according to the capacity trend measured in this work, an aqueous solution with 43.7% w/w LysK has been identified as a promising option to be further investigated, verifying potential savings in the absorber packing requirements (i.e. lower packing height in a full-scale application, due to the better kinetics of LysK) while ensuring the same absorption capacity level of 30% MEA.

The solar absorption efficiency of water as a base-fluid can be significantly improved by suspending nanoparticles of various materials in it. This experimental work presents the photo thermal performance of water-based nano-fluids of graphene oxide (GO), zinc oxide (ZnO), copper oxide (CuO), and their hybrids under natural solar flux for the first time. Nanofluid samples were prepared by the two-step method and the photothermal performance of these nanofluid samples was conducted under natural solar flux in a particle concentration range from 0.0004 wt % to 0.0012 wt %. The photothermal efficiency of water-based 0.0012 wt % GO nanofluid was 46.6% greater than that of the other nanofluids used. This increased photothermal performance of GO nanofluid was associated with its good stability, high absorptivity, and high thermal conductivity. Thus, pure graphene oxide (GO) based nanofluid is a potential candidate for direct absorption solar collection to be used in different solar thermal energy conversion applications.

This paper presents the experimental development at demonstration scale of an integrated gasification system fed with wood chips. The unit is based on a fixed-bed, updraft and air-blown gasifier—with a nominal capacity of 5 MWth—equipped with a wet scrubber for syngas clean-up and an integrated chemical and physical wastewater management system. Gasification performance, syngas composition and temperature profile are presented for the optimal operating conditions and with reference to two kinds of biomass used as primary fuels, i.e., stone pine and eucalyptus from local forests (combined heat and power generation from this kind of fuel represents a good opportunity to exploit distributed generation systems that can be part of a new energy paradigm in the framework of the circular economy). The gasification unit is characterised by a high efficiency (about 79–80%) and an operation stability during each test. Particular attention has been paid to the optimisation of an integrated double stage wastewater management system—which includes an oil skimmer and an activated carbon adsorption filter—designed to minimise both liquid residues and water make-up. The possibility to recycle part of the separated oil and used activated carbon to the gasifier has been also evaluated.

In this study, we prepared and characterized composite films formed by amorphous poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) and particles of the size-selective Zeolitic Imidazolate Framework 8 (ZIF-8). The aim was to increase the permselectivity properties of pure PPO using readily available materials to enable the possibility to scale-up the technology developed in this work. The preparation protocol established allowed robust membranes with filler loadings as high as 45 wt% to be obtained. The thermal, morphological, and structural properties of the membranes were analyzed via DSC, SEM, TGA, and densitometry. The gas permeability and diffusivity of He, CO2, CH4, and N2 were measured at 35, 50, and 65 &deg, C. The inclusion of ZIF-8 led to a remarkable increase of the gas permeability for all gases, and to a significant decrease of the activation energy of diffusion and permeation. The permeability increased up to +800% at 45 wt% of filler, reaching values of 621 Barrer for He and 449 for CO2 at 35 &deg, C. The ideal size selectivity of the PPO membrane also increased, albeit to a lower extent, and the maximum was reached at a filler loading of 35 wt% (1.5 for He/CO2, 18 for CO2/N2, 17 for CO2/CH4, 27 for He/N2, and 24 for He/CH4). The density of the composite materials followed an additive behavior based on the pure values of PPO and ZIF-8, which indicates good adhesion between the two phases. The permeability and He/CO2 selectivity increased with temperature, which indicates that applications at higher temperatures than those inspected should be encouraged.

Global warming is one of most severe environmental concerns that our planet is facing today. One of its causes is the previous generation of refrigerants that, upon release, remain in the atmosphere for longer periods and contribute towards global warming. This issue could potentially be solved by replacing the previous generation’s high global warming potential (GWP) refrigerants with environmentally friendly refrigerants. This scenario requires an analysis of new refrigerants for a comparison of the thermodynamic properties of the previously used refrigerants. In the present research, a numerical study was conducted to analyze the thermodynamic performance of specifically low GWP hydrofluoroolefens (HFO) refrigerants for an actual vapor compression refrigeration cycle (VCRC) with a constant degree of 3 K superheat. The output parameters included the refrigeration effect, compressor work input, the coefficient of performance (COP), and the volumetric refrigeration capacity (VRC), all of which were calculated by varying the condenser pressure from 6 to 12 bars and vapor pressure from 0.7 to 1.9 bars. Results showed that R1234ze(Z) clearly possessed the desired thermodynamic performance. The drop in refrigeration effect for R1234ze(Z) was merely 14.6% less than that of R134a at a 12 bar condenser pressure; this was minimum drop among candidate refrigerants. The drop in the COP was the minimum for R1234ze(Z)—5.1% less than that of R134a at a 9 bar condenser pressure and 4.7% less than that of R134a at a 1.9 bar evaporator pressure, whereas the COP values of the other refrigerants dropped more drastically at higher condenser pressures. R1234ze(Z) possessed favorable thermodynamic characteristics, with a GWP of 7, and it can serve as an alternative refrigerant for refrigeration systems for a sustainable environment.

The present research work provides a quantitative evaluation of the CO2 absorption performance of potassium prolinate by setting a reliable and cost-effective approach for solvent screening, based on both experimental activities and data analysis. Potassium prolinate has been chosen as a promising green solvent to be tested at two different concentrations (30% and 43.38% w/w ProK aqueous solutions). The applied methodology involves direct comparison of the alternative solvent against a reference case, such as 30% w/w MEA solution. The test has been carried out on a bench-scale facility composed of a glass column with internal random packing located at Sotacarbo Research Center (Sardinia); the facility has been run in open and closed cycle mode, assessing the performance in terms of CO2 removal from NGCC synthetic flue gases (e.g.: 4% mol/mol CO2 concentration). The outcome of this work provides new information based on experimental data on removal, maximum achievable loading, loading increment rate and solvent capacity, and it constitutes a novel contribution to the literature. Moreover, it represents a tangible effort in delivering an insight on non-precipitating amino acid viability for flue gas decarbonization in CCS technologies.

In this work, the co-pyrolysis and co-gasification of Nannochloropsis sp. microalgae (NM) and Colombian bituminous coal (CC) were performed in order to evaluate potential synergistic effects and the kinetic parameters, which are essential for advancing the co-utilization. The effect of the share of feedstock, microalgae and coal, on the co-pyrolysis and co-gasification behavior was studied under different heating rates and temperatures. There were synergistic effects between the two fuels during their co-pyrolysis process, especially for that mixture containing 50 wt% of microalgae. At conversion levels

Among the carbon capture and storage (CCS) technologies suitable for power generation plants, partial oxy-combustion coupled with post combustion CO2 capture is gaining interest, since such a hybrid configuration could allow to reduce the size and enhance the performance of post-combustion CO2 capture by operating combustion with air enriched with oxygen and reducing the dilution of flue gas. Moreover, partial oxy-combustion is a potential candidate for the retrofit of existing steam plants because it could be based on an almost conventional boiler and requires a smaller CO2 capture section. This work presents the results of a comparative techno-economic analysis of a 1000 MWth partial oxy-combustion plant based on an ultra-supercritical pulverized coal combustion power plant integrated with a post-combustion CO2 capture system and geological storage in saline aquifer. In particular, plant performance is assessed by using simulation models implemented through Aspen Plus 7.3 and Gate Cycle 5.40 commercial tools, whereas economic performance are evaluated on the basis of the expected annual cash flow. The analysis shows that, for new plants, this hybrid approach is not feasible from the economic point of view and full oxy-combustion potentially remains the most profitable technology even if, in the short-term period, the lack of commercial experience will continue to involve a high financial risk.

This paper reports on the results of air-blown combustion and oxy-combustion kinetic characterization (comparing two different isoconversional methods: Flynn-Wall-Ozawa and Kissinger-Akahira-Sunose) of different kinds of coal (from Italy, South Africa and Hungary) and biomass (pine and eucalyptus chips) by thermogravimetric analysis (TGA) and differential scanning calorimeter (DSC) together with the assessment of different characteristic combustion parameters. It can be observed that the burning rate of fuels can be improved by the oxy-combustion process, shortening the burning time (a mean reduction of the burnout time of 14% and 22% can be observed for coal and biomass samples, respectively). Moreover, biomass shows better ignition performance than coal and enhances combustibility indexes ( S and H f ), especially in oxy-combustion conditions. For example, the S index, which reflects combustion properties, increases by an order of magnitude for biomass combustion and oxy-combustion with respect to coal values, thus indicating a higher combustion activity for biomass; an opposite trend can be observed for the H f index, which describes the rate and intensity of the process and is lower for biomass than for coal, thus indicating better performance for wood chips combustion. Kinetic analysis shows that the activation energy E a varies with conversion values, reflecting the kinetic complexity in both the processes. Moreover, with the same range of heating rates (10 ≤ β ≤ 50 °C/min) and for the overall range of conversion (0.1 ≤ α ≤ 0.9), both of the models used fit the experimental data in combustion regime, whereas the increase of the oxygen concentration makes the results reliable for coal samples and more sensitive to weight loss for biomass samples.

The burning of fossil fuels in power sectors for energy generating purposes and in agricultural country like Pakistan the residues of crops on large area of land are burnt every year that results in continuous addition of CO2 in environment. CO2 capture through solid based adsorbents is one of the best valued, echo friendly and techno-economic processes. The present research involves the development of activated carbons using five different waste biomass materials through single step chemical activation for effective CO2 adsorption, study of isosteric heat of adsorption and change in these values with a change in level of CO2 adsorbed. Chemical activation with single-step method was carried out to prepare the adsorbents. The samples were characterized and compared for the textural properties by recording isotherms of nitrogen adsorption at temperature of 77 K while CO2 adsorption curves at 273 K then at 298 K. SEM was brought into use to investigate morphological characters, surface morphology of activated carbons that confirms the presence of random micro-pores. Nonlinear density functional theory (NDLFT) strengthen the fact that CO2 adsorption depends upon the volume of pores. Samples have pore volume ranging from 0.11 cm3 to 0.44 cm3, whereas BET surface area values were observed from 439 m2/g up to 979 m2/g. Among the prepared activated carbons, the sample with date seeds as base material showed the uppermost uptake of 5.8 mmol/g at 273 K. Linear fitting of the curve between CO2 adsorbed and pore volume at a temperature of 273 K and 298 K with R2 values greater than 0.9 demonstrate the strong relation between pore volume, temperature and CO2 adsorbed. Isosteric heat of adsorption (IHA) values were found to be in the assortment of 44 KJ/mol with minimum value of 14.3 KJ/mol that decreases with increase of CO2 adsorption. High isosteric heat means strong interaction of CO2 molecules and prepared adsorbents. Obtained results confer base to use waste biomass materials for development of solid based adsorbents and use of these adsorbents in effective carbon capture applications to reduce the carbon footprints in the environment and avoid the waste burning of biomass residues. © 2021 Elsevier Ltd

This paper presents the results of a combined experimental and computational characterization of a biomass gasification process as a carbon neutral technology for power generation and/or green hydrogen production. With the aim to set and validate a computational fluid dynamic (CFD) multiphase flow simulation model based on the MFiX suite – as a support for the design and optimization of advanced reactors for energy purposes – a wide experimental campaign has been carried out with cypress (Cupressus sempervirens) wood chips in a lab-scale bubbling fluidized-bed gasification unit in different operation modes: pyrolysis, air-blown gasification as well as steam gasification of char. In addition, pyrolysis kinetics have been experimentally assessed by thermogravimetric analysis (TGA). This study shows that biomass pyrolysis is characterized by a syngas yield of 0.65–0.66, whereas its gasification allows the production of a syngas (1.73–1.77 Nm3 per kilogram of fuel) characterized by a lower heating value of about 5 MJ/Nm3, with a hydrogen concentration between 11.4 and 14.3% by volume (depending on the equivalence ratio). In addition, model used is a good predictive tool that can successfully simulate the process and predict syngas composition with good accuracy, in particular for CO, H2 and CH4.

The increasing attention toward climate changes and the recent strategic policies to stabilize and reduce CO2 emission is promoting research in the field of carbon capture, storage and more recently utilization technologies, whereby CO2 is captured from industrial flue gas, reused if possible or permanently stored in geological formations, such as depleted oil or gas fields and saline aquifers. In this scenario, Sotacarbo is leading the “Centre of Excellence on Clean Energy” research project, funded by the Regional Government of Sardinia, which aims to develop technologies for low emission power generation and for CO2 capture, utilization and storage. Among these technologies, CO2 utilization by hydrogenation and photoelectrochemical reduction are experimentally studied in the Sotacarbo laboratories. This work presents a general overview of the researches (carried out in close cooperation with the University of Cagliari) on CO2 utilization by conversion into liquid fuels, with a description of the research facilities and a hint on preliminary experimental results.

The deep aquifer located at a depth of about 1000-1500 m within fractured carbonate in the Sulcis coal basin (South-West Sardinia, Italy) constitutes a potential reservoir to develop a pilot-scale CO2 storage site. The site is well known in terms of stratigraphy and structural settings, due to the data available from the coal mining activity. On the basis of these data, a potential deep reservoir and the caprock can be recognized; more in detail, in the southern sector of the basin, the top of the potential reservoir reaches a suitable depth for storage. At the same time, the already existing infrastructures (the Sotacarbo Research Centre on carbon capture, utilization and storage), coupled with some peculiar features (as the low natural seismicity, the hydrogeological system, etc.) makes the Sulcis area a potential experimental site capable to further develop CO2 storage technologies, such as low-cost drilling, site monitoring, and experimental studies on CO2 diffusion and leakage. In this context, Sotacarbo (in cooperation with ENEA, the Universities of Cagliari and Rome “La Sapienza”, OGS, INGV and RSE) is leading a very ambitious research program, funded by both the Italian and the Sardinian Regional Governments within two different and complementary projects, to characterize the Sulcis coal basin as a potential site for the development of CO2 geological storage technologies. The research activities are structured in two different phases: (i) site characterization, including the construction of an underground and a fault laboratories and (ii) the installation of a test site for small-scale injection of CO2. In particular, the underground laboratory will host geochemical and geophysical experiments on rocks, taking advantages of the buried environment and the very well confined conditions in the galleries; in parallel, the fault laboratory will be constructed to study CO2 leakage phenomena in a selected fault. Overall, the project, which is currently ongoing, will allow to characterize the Sulcis basin and to develop a permanent infrastructure (know-how, equipment, laboratories, etc.) for advanced international studies on CO2 storage. This work describes the whole Sulcis CO2 storage project, highlighting its current status, some of the preliminary results of site characterization phase, planned activities and the links with the research activities on carbon capture and utilization.

Since coal will be widely used in the next decades, mainly in the developing countries such as China and India, carbon capture and storage (CCS) technologies will have a key role in the containment of global warming. This paper presents a techno-economic comparison between the most promising power generation technologies for a CO2-free power generation in a short-term future. In particular, three different power generation technologies have been considered in their conventional (without CCS) and CO2-free configurations: (a) ultra supercritical (USC) pulverized coal combustion, (b) oxy-coal combustion (OCC) and (c) integrated gasification combined cycle (IGCC). Process simulation, based on Aspen Plus and Gate Cycle commercial tools, allows to calculate plant performance, including the energy penalty due to the CCS system (10.9% points for USC and 8.7% points for IGCC). In parallel, a detailed economic assessment shows that, among the commercial-ready technologies, USC could be the most convenient solution for power generation without CCS (presenting a levelized cost of electricity – LCOE – of 38.6 €/MW h, significantly lower than 43.7 €/MW h of IGCC), whereas IGCC becomes competitive for CO2-free systems (with a LCOE of 59.6 €/MW h, to be compared with 63.4 €/MW h of USC). Moreover, oxy-coal combustion, which is currently not mature enough for commercial-scale applications, promises to become strongly competitive for CCS applications due to its relatively low levelized cost of electricity (62.8 €/MW h). This kind of analysis typically presents strong uncertainties, due to the variability of several key parameters (e.g. fuel and CCS prices, determined by the fluctuation of the international markets, or an improvement of the technologies). Therefore, a sensitivity analysis has been done to determine the effects of these potential fluctuation or the improvement on the economic performance of the plant.

In recent times, the methanol was employed in numerous innovative applications and is a key compound widely used as a building block or intermediate for producing synthetic hydrocarbons, solvents, energy storage medium and fuel. It is a source of clean, sustainable energy that can be produced from traditional and renewable sources: natural gas, coal, biomass, landfill gas and power plant or industrial emissions. An innovative methanol production process from coal gasification is proposed in this work. A suitable comparison between the traditional coal to methanol process and the novel one is provided and deeply discussed. The most important features, with respect to the traditional ones, are the lower carbon dioxide emissions (about 0.3%) and the higher methanol production (about 0.5%) without any addition of primary sources. Moreover, it is demonstrated that a coal feed/fuel with a high sulfur content allows higher reductions of carbon dioxide emissions. The key idea is to convert hydrogen sulfide and carbon dioxide into syngas (a mixture of hydrogen and carbon monoxide) by means of a regenerative thermal reactor. This is the Acid Gas to Syngas technology, a completely new and effective route of processing acid gases. The main concept is to feed an optimal ratio of hydrogen sulphide and carbon monoxide and to preheat the inlet acid gas before the combustion. The reactor is simulated using a detailed kinetic scheme.

The paper deals with the application of the novel Acid Gas To Syngas (AG2S™) technology to the gasification of solid fuels. The AG2S technology is a completely new effective route of processing acid gases: H2S and CO2 are converted into syngas (CO and H2) by means of a regenerative thermal reactor. To show the application of the AG2S technology, modeling and simulation advances for gasification systems are initially discussed. The multi-scale, multi-phase, and multi-component coal gasification system is described by means of detailed kinetic mechanisms for coal pyrolysis, char heterogeneous reactions and for successive gas-phase reactions. These kinetic mechanisms are then coupled with transport resistances resulting in first-principles dynamic modeling of non-ideal reactors of different types (e.g., downdraft, updraft, traveling grate), also including the catalytic effect of ashes. The generalized approach pursued in developing the model allows characterizing the main phenomena involved in the coal gasification process, including the formation of secondary species (e.g., COS, CS2). This tool is here further validated on literature data and, then, adopted to demonstrate the AG2S effectiveness, where H2S and CO2 emissions are reduced with an increase of syngas production. The resulting process solution is more economically appealing with respect to the traditional Claus process and finds several application areas.

The naturally fractured carbonates have a great potential for Carbon Capture and Storage (CCS) purpose because they could offer the possibility for CO2 storage in areas where no suitable sandy reservoirs are available, as for example in the Mediterranean area, where most of the stratigraphic succession is composed by carbonate rocks. The Sulcis basin, located in the south-western part of Sardinia island (Italy), is an ideal site for technology development. Although the site is not feasible for commercial-scale geological storage (mainly due to the lack of stationary CO2 sources), it represents an optimal location for pilot-scale experiments. Thanks to data available from several national and international projects, as well as from the mining activities, it has been possible to recognize a potential reservoir-caprock system, suitable for pilot-scale CCS development. A sequence of well bedded, about 50 m thick, mudstones and grainstones (“Miliolitico Fm.”) has been identified as a potential reservoir; the caprock is represented by a thick succession of siltstones, sandstones and conglomerates (“Cixerri Fm.”) and up to 900 m of OligoMiocene volcanic rock, ranging from basaltic to rhyolitic composition. In this work we present the results of several geophysical and geological surveys, including reflection seismic profiles, and geo-structural analysis. All the data were combined in a 3D model, defining the volumes of each formation. The evaluation of the storage capacity and the existence of a thick and impermeable caprock are essential to consider the site suitable for the experimental tests. With this aim, we measured primary porosity and permeability, whereas the fracture network was studied using scan lines and scan areas techniques on outcropping analogue of reservoir and seals. The measured linear parameters were used to build several Discrete Fracture Model (DFN) both of reservoir and caprock formations. In particular, DFN were constructed varying length and aperture values to evaluate their influence on the total secondary porosity.

Air gasification tests have been carried out in a pilot scale bubbling fluidized bed gasifier, able to treat up to 100 kg/h of Eucalyptus wood chips, and operated, under chemical and thermal steady-state conditions, at different values of equivalence ratio. The results are reported in terms of the main process performance parameters and transfer coefficients, which indicate the fate of carbon in the different output streams (syngas, fines, tars). The results can be transferred to commercial scale reactors and confirm the technical feasibility of the air gasification of the biomass in the range 0.25–0.34 of equivalence ratio, yielding a good quality syngas, with a low heating value between 5000 and 6000 kJ/m3N,syngas. The measured axial syngas composition profiles along the reactor indicate a monotonic reduction of methane and carbon dioxide concentrations and an increase of that of hydrogen. This suggests that water gas shift and steam and dry reforming reactions play a significant role, together with a limited contribution of tar cracking reactions, probably enhanced by alkali and alkaline earth metallic species contained in the inorganic fraction of elutriated fines. Results can support the implementation of reliable numerical models of bubbling fluidized bed gasifiers and the optimisation of design/operating criteria.

This paper reports the results of a complete kinetic study, based on thermogravimetric characterisation, to compare the performance of Nannochloropsis sp. and Tetraselmis sp. microalgae during pyrolysis and combustion with air, enriched air and oxygen. The analysis has been carried out including both the single- and multi-step approach studying the effect of different model-free methods and heating rates. In addition, the study brings together the pseudo-components (obtained by peaks deconvolution) model and master plot methodology to discriminate the kinetic model followed by the different processes with the aim to determine the kinetic triplet (activation energy, reaction order and pre-exponential factor). It results that the thermal decomposition of the microalgae cannot be represented by a single reaction mechanism for the whole conversion range, but several parallel decomposition reactions have been taken into account, and the kinetics have been assessed from each decomposition kinetic of the pseudo-components. The kinetic profiles can be interpreted as the combined effects of reaction-order (F), nucleation (A), exponential nucleation (P) and geometrical contraction (R) mechanisms.

Small-scale coal gasification technology, coupled to a reciprocating engine generator, has the potential for making coal a cost competitive resource for meeting the flexible energy needs and resiliency requirements of utilities across the United States. To maintain grid stability and reliability, electrical generation must be regulated to match the load at the proper voltage and frequency. With the expansion of intermittent sources into the grid, such as wind and solar, frequency and voltage regulation become increasingly important and challenging. This work presents the results of a Front End Engineering Design (FEED) effort to detail the engineering and preliminary economics of a small-scale, air blown, fixed-bed gasification process, operating at near-atmospheric pressure, with gas cleanup to provide syngas and pyrolysis liquid fuels for use in reciprocating engine generators for combined heat and power at the University of Alaska Fairbanks. A very detailed assessment of capital and operating costs allows the evaluation of a levelized cost of electricity of 208.06 $/MWh, which can be reduced through the selling of by-products (steam for heating purposes and pyrolysis liquids to be used for power generation in an existing diesel engine). A combined sensitivity analysis, based on the Monte Carlo approach, has been carried out to evaluate the effects of the uncertainties (capital and operating costs and plant annual availability) on the LCOE.

Cu/ZnO@SBA-15 and Cu/ZnO/ZrO2@SBA-15 nanocomposites have been synthesized by an innovative impregnation-sol-gel autocombustion combined strategy and tested as catalysts for carbon dioxide hydrogenation to methanol. The composites, differing as to the active phase loading (20 and 35 wt.%) and Cu/Zn molar ratio (1.0-2.5 mol mol−1), have been characterized in terms of chemical, morphological, structural and textural features by a multi-technique approach. Characterization techniques revealed that the active phase is highly dispersed into/over the well-ordered mesoporous channels especially at low loading and low Cu/Zn molar ratio. In all the composites, the mesostructure of the support is retained together with a high surface area, large pore volume and uniform pore size. Catalytic results showed that the supported catalyst with the lowest Cu/Zn molar ratio (1.0 mol mol−1) exhibits the best catalytic performance with a space-time-yield of methanol of 376 mgCH3OH h-1 gcat-1, much more efficient than the unsupported catalyst (10 mgCH3OH h-1 gcat-1). The confinement of the active phase in the SBA-15 structure enhances its ability to interact with H2 and CO2, which results in improved performance. Moreover, the results show the influence of the active phase loading and the Cu/Zn molar ratio that lead to differences in the morphology and dispersion of the active phase, which in turn cause the composite to catalyse the reaction differently.

It was previously proven that small loadings of few-layer graphene (G) and monolayer graphene oxide (GO) adjust the permselectivity and reduce the ageing of thick poly(trimethyl silyl propyne) (PTMSP) membranes, which currently inhibits their application in real separations. In this work, we extend the analysis to thin film composite membranes with top layers of PTMSP/G and PTMSP/GO between 1 and 7 µm. The good quality of the films, obtained by spin coating the polymer solution on porous flat supports, indicates that graphenic sheets are aligned parallel to the film surface, without defects, and that the large-scale production of such composite films is feasible. The addition of G and GO to PTMSP can improve the gas permeability and selectivity, and even change the behaviour from CO2-selective to He-selective. GO produces more repeatable effects than graphene, and it generally enhances the PTMSP permeability. The ageing was studied by tracking permeability of 4 gases with time: thin films age faster than thick ones, because ageing is due to free volume diffusion across the film. Incorporation of 1 wt% of G and GO visibly reduces the ageing of thin PTMSP films, and the effect is repeated on many different samples. The ageing can be correlated, with a single power law, to the ratio between time and squared film thickness. The exponent of such function, that quantifies the ageing rate, decreases when G and GO are added to PTMSP thin films, by factors as high as 40%. The temperature effect was studied, up to 60 °C, on annealed samples: the membranes, CO2-selective at room temperature, can become easily He-selective by raising the temperature. The He/CO2 selectivity increases with temperature: such effect could be exploited syngas purification and pre-combustion capture processes.

Membranes obtained by adding small amounts (1 wt %) of nanoplatelets of graphene (G) and graphene oxide (GO) to poly(1-trimethylsilyl-1-propyne) (PTMSP) were fabricated with a simple route, and their gas permeability was measured at 30 °C over 9 months. In most cases, variations of PTMSP permeability due to the addition of filler are limited, while the ideal selectivity of CO2/He, CH4/He, and CH4/N2 is slightly enhanced by addition of filler. Specific measurements indicate that the CO2 and CH4 diffusivity are more strongly affected by addition of graphene than their solubility: such behavior indicates that the filler modifies mainly the microstructure of the polymer rather than its interactions with the gas, as it is reasonable. The most significant quantitative effect observed after filler incorporation is the reduction of PTMSP aging, that was monitored by studying gas permeability after 9 months of aging at room temperature and after annealing at 200 °C. The reduction of aging observed after adding graphene is more significant than that obtained with large amounts (up to 20 vol %) of other inorganic fillers, like MgO and TiO2, even though the amount of filler added in this work is small (

Small-scale fixed-bed coal and biomass gasifiers represent an attractive option for distributed combined heat and power generation. As known, gasification phenomena are very complex, involving drying, devolatilization, pyrolysis, heterogeneous and homogenous reactions, with a large number of intermediate and final products. Gasification processes are also influenced by reaction kinetics and fluid-dynamical effects, such as temperature and concentration gradients. For this reason, simulation models are able to predict gasifiers performance under the assumption of thermodynamic equilibrium only if the gasification process takes place at a known temperature and the reaction time is lower than the reactants residence time. As a consequence, for fixed-bed gasifiers equilibrium models must consider drying and devolatilization taking place at lower temperature in the heat transfer zone, where solid feed is heated by syngas. Therefore, moisture and volatiles are not involved in the gasification reactions since they are released before reaching the reaction zone. Several models based on steady-state and one-dimensional representations have been developed to reproduce gasification processes in fixed-bed reactors. These models have been found adequate to provide information for engineering design and process optimization. In this framework a steady-state simulation model has been developed at the Department of Mechanical Chemical and Materials Engineering (DIMCM) of the University of Cagliari by using the Aspen Plus computer code for predicting performance of small-scale up-draft fixed-bed coal gasifiers. The model can be used to evaluate the mass and energy balance in each zone of the gasifier and the main characteristics of the syngas produced by the gasification process (composition, mass flow, temperature, heating value, etc.). This paper describes the model and presents the main results of a parametric analysis, which shows how the gasification process is influenced by the main operating parameters. Moreover, the results of the model have been compared with the experimental results of an up-draft gasifier fed with an lignite from Alaska. The above-mentioned gasifier is part of a pilot gasification and gas treatment plant built at the Sotacarbo Research Centre in Sardinia, Italy. The comparison shows that the model well represents the performance of the pilot-scale unit.

Sotacarbo is currently developing several research projects to optimize a coal and biomass gasification process for small- and medium-scale power generation and hydrogen production. To achieve this goal, between 2007 and 2008, Sotacarbo built a flexible pilot platform in its Research Centre in the Serbariu former coal mine (Sardinia, Italy), which is still very much into operation. The platform includes a demonstration and a pilot air-blown fixed-bed gasifiers, the latter tested for more than 2200 h and equipped with a flexible syngas treatment line for combined power generation and CO 2 -free hydrogen production. This paper reports the characterization of several kinds of fuels in terms of pyrolysis and gasification performance. In particular, a number of different coal and biomass samples have been tested, including South African bituminous coal, Sardinian high sulphur Sulcis sub-bituminous coal, lignites from Alaska and Hungary and stone pine wood chips. An improved understanding of coal and biomass pyrolysis may be useful to predict the reactor performance in a gasification process and also to optimize the experimental campaigns in the pilot plant. Therefore, before the tests in the pilot-scale gasification unit, fuels are typically characterized by a thermogravimetric analysis to evaluate the pyrolysis behavior. Among all the tested coals, Usibelli lignite from Alaska is the most reactive one. Its derivative thermogravimetric (DTG) profile presents a clear pyrolysis peak at 478 °C. The pilot-scale experimental results show that the gasification of 24 kg/h of Usibelli lignite allows the production of 79.67 kg/h of raw syngas, characterized by a lower heating value of 5.14 MJ/kg. An opposite behavior is shown by the South African bituminous coal, which does not present a peak in the DTG curve, as a consequence of the low volatile content in the fuel structure. This is confirmed by the gasification tests in the atmospheric fixed-bed plant, which show a low coal consumption and, as a consequence, a low syngas production (46.83 kg/h). Wood chips presents a very significant peak in the DTG profile at the temperature of 318 °C but, due to the low energy density, its gasification involves a low syngas production (23.31 kg/h).

Sotacarbo is currently developing several research projects to optimize a coal-to-hydrogen process configuration within the field of hydrogen production through coal gasification for distributed power generation. To achieve this goal, between 2007 and 2008, Sotacarbo built a flexible pilot platform within its Research Centre in the Serbariu former coal mine (Sardinia, Italy), which is still very much into operation. The platform includes a demonstration plant and a pilot air-blown fixed-bed gasifier, the latter equipped with a flexible syngas treatment line for combined power generation and CO2-free hydrogen production. This paper aims to give a brief description of the whole experimental equipment and to summarize the main results obtained during more than 1700 h of experimental tests in the pilot unit. It is also reported the gasification performance under different operating conditions. A number of different fuels and fuel blends were tested, including South African sub bituminous coal, Sardinian high sulfur coal, lignite from Alaska and wood chips from local forests. Alaska's lignite reached the best gasification performance due to the high reactivity. There is also a quick examination of the syngas cleaning process's main performance. Finally, the very high efficiency of sulfur compounds removal through a zinc oxide-based hot gas desulphurization process suggested to evaluate the possibility to integrate the plant with a fuel cell system for a high efficiency combined heat and power (CHP) generation. The main results of this theoretical assessment, reached through a properly developed simulation model, are also reported in this work.

Differently from the conventional combustion and entrained flow gasification technologies, fixed-bed up-draft gasification process tested in pilot scale appears very suitable for the “multipurpose transformation” of Hungarian low-rank and high sulfur brown coal (for the production of electrical energy, heat and eventually gaseous or liquid fuels). This paper presents the positive results of the wide-range analysis (led jointly by Sotacarbo in Italy and by Ormosszen in Hungary) on the possibility to use the Hungarian coal from the North-East basins for energy purposes. At this stage, there is no scientific literature on this subject (the energetic use of this fuel, which is very complex in conventional power generation plants), whereas there are several studies on the geological properties of the Hungarian brown coal and on the energetic exploitation of the Mecsek basin's high-rank coal. In addition to the conventional characterization (proximate, ultimate and thermal analyses), a series of bench-scale experimental tests were carried out to preliminary assess the combustion performance of Hungarian brown coal and to set a pilot-scale experimentation in the Sotacarbo gasification pilot plant. As results from the experimental tests, the air-blown up-draft gasification of about 11 kg/h of Hungarian brown coal allows to produce about 24–25 kg/h of raw syngas, characterized by a lower heating value of 3.55 MJ/kg. The high sulfur content in primary fuel is one of the main problems when that coal is used. As a matter of fact, conventional cold gas desulfurization processes are typically not sufficient for an efficient syngas desulfurization. But a very high H 2 S and COS removal efficiency has been experimentally obtained treating syngas with a zinc oxide-based hot gas desulfurization system. This process allowed to obtain a final H 2 S and COS global concentration lower than 20 ppm (by volume), operating at about 400 °C.

Worldwide energy production requirements could not be fully satisfied by nuclear and renewables sources. Therefore a sustainable use of fossil fuels (coal in particular) will be required for several decades. In this scenario, carbon capture and storage (CCS) represents a key solution to control the global warming reducing carbon dioxide emissions. The integration between CCS technologies and power generation plants currently needs a demonstration at commercial scale to reduce both technological risks and high capital and operating cost. This paper compares, from the technical and economic points of view, the performance of three coal-fired power generation technologies: (i) ultra-supercritical (USC) plant equipped with a conventional flue gas treatment (CGT) process, (ii) USC plant equipped with SNOX technology for a combined removal of sulphur and nitrogen oxides and (iii) integrated gasification combined cycle (IGCC) plant based on a slurry-feed entrained-flow gasifier. Each technology was analysed in its configurations without and with CO 2 capture, referring to a commercial-scale of 1000 MW th . Technical assessment was carried out by using simulation models implemented through Aspen Plus and Gate-Cycle tools, whereas economic assessment was performed through a properly developed simulation model. USC equipped with CGT systems shows an overall efficiency (43.7%) comparable to IGCC (43.9%), whereas introduction of SNOX technology increases USC efficiency up to 44.8%. Being the CCS energy penalties significantly higher for USC (about 10.5% points vs. about 8.5 for IGCC), the IGCC with CCS is more efficient (35.3%) than the corresponding CO 2 -free USC (34.2% for the SNOX-based configuration). Whereas, for the case study, USC is most profitable than IGCC (with a net present value, NPV, of 190 M€ vs. 54 M€) for a conventional configuration, CO 2 -free IGCC shows a higher NPV (−673 M€) than USC (−711 M€). In any cases, the NPV of all the CO 2 -free configurations is strongly negative: this means that, with the current market conditions, the introduction of a CCS system cannot be economically justified without a significant incentive.

The need to reduce CO2 emissions requires a great economical effort to optimize the processes and solve the main technical and economic problems which still limit a large-scale diffusion of this kind of carbon capture and storage (CCS) technologies. In this paper, the main results of a techno-economic comparison between ultra supercritical pulverized coal combustion (USC) and integrated gasification combined cycle (IGCC) plants are presented. The Sulcis coal basin, considered as a reference location for the plant configurations here analysed, could represent a very important site to test carbon capture and storage technologies, being representative of a lot of potential storage site in the world. For both USC and IGCC technologies, three different configurations have been compared: a configuration without CCS, a CO2-free configuration and an intermediate solution in which a demonstration CCS system is applied to only a portion of produced gas. The analysis here presented shows that USC technology is slightly more profitable than IGCC if a configuration without CCS is considered, whereas IGCC is more profitable than USC for a CO2-free configuration. Due to the high CCS costs and to the specificity of the site, the investment is not profitable if not supported by an adequate incentive.

Carbon capture and storage (CCS) represents a key solution to control the global warming reducing carbon dioxide emissions from coal-fired power plants. This study reports a comparative performance assessment of different power generation technologies, including ultrasupercritical (USC) pulverized coal combustion plant with postcombustion CO2 capture, integrated gasification combined cycle (IGCC) with precombustion CO2 capture, and oxy-coal combustion (OCC) unit. These three power plants have been studied considering traditional configuration, without CCS, and a more complex configuration with CO2 capture. These technologies (with and without CCS systems) have been compared from both the technical and economic points of view, considering a reference thermal input of 1000 MW. As for CO2 storage, the sequestration in saline aquifers has been considered. Whereas a conventional (without CCS) coal-fired USC power plant results to be more suitable than IGCC for power generation, IGCC becomes more competitive for CO2-free plants, being the precombustion CO2 capture system less expensive (from the energetic point of view) than the postcombustion one. In this scenario, oxy-coal combustion plant is currently not competitive with USC and IGCC, due to the low industrial experience, which means higher capital and operating costs and a lower plant operating reliability. But in a short-term future, a progressive diffusion of commercial-scale OCC plants will allow a reduction of capital costs and an improvement of the technology, with higher efficiency and reliability. This means that OCC promises to become competitive with USC and also with IGCC.

The increasing interest in the development of carbon capture and storage (CCS) technologies requires a great effort to reduce capital and operating costs and to demonstrate the potential application of these kind of systems on the commercial power generation plants. This paper shortly describes the main results of a technical and economical comparison between different CO2-free power generation plant configurations, with a particular reference to ultra supercritical (USC) pulverised coal combustion plant, atmospheric fluidized bed combustion (AFBC), integrated gasification combined cycle (IGCC) and a potential projection for the application of oxy-combustion technologies. The comparative analysis is based on the typical economic indicators such as net present value, internal rate of return, payback time and cost of electricity; all these parameters have been calculated on the basis of the annual cash flow during the plant operating life. Due to the impossibility to estimate with accuracy the future trend of some parameters, a sensitivity analysis has been also carried out in order to evaluate the effects of these assumptions, with a subsequent risk reduction for the potential investment. As reference case, a 660 MWe (referred to the hypothetical “basis” configuration, without CCS system) operating in close integration with the Sulcis coal mine (South–West Sardinia island, Italy) has been considered. As a matter of fact, the Sulcis sub-bituminous coal basin, in which the only Italian coal mine is located, represents a key point for the increasing of the Sardinian energy security, by raising the power generation capacity and partially releasing energy production from imported primary sources; in parallel, the economy in the Sulcis area has to be re-launched through the strengthening of the local industry.

Large-scale hydrogen production through near zero emissions gasification plants represents a reliable technology which is being seriously considered for its potential economical implications. However, the application of these technologies is currently subject to high capital and operating costs. This needs great scientific and technical effort to optimize the processes and the equipment, to reduce the hydrogen production cost. In this context, a flexible and fully equipped pilot platform has been built up in the Sotacarbo Research Centre, in order to study several integrated gasification and syngas treatment process configurations for a CO2-free combined production of hydrogen and electrical energy, to be used in medium and small-scale commercial plants. The platform includes pilot scale fixed-bed up-draft gasifiers, equipped with a flexible and complete syngas treatment line. This paper reports the main results obtained in the pilot plant during the last experimental campaign which has been carried out to improve the plant performance. In particular, a series of experimental tests has been performed in order to optimize the coal gasification process in different operating conditions. Moreover, a mention of the overall plant performance, based on the experimental results, has been presented, with particular reference to hydrogen, carbon and pollutant emissions.

Being hydrogen the most promising energy carrier for distributed power generation and being the coal-to-hydrogen technologies far from their large-scale application, mainly due to their high costs, Sotacarbo has recently built up a pilot platform for the combined production of hydrogen and electrical energy from coal. The platform includes two different units: a 5 MWth demonstrative plant and a 200 kWth pilot plant (feed with a maximum of 35 kg/h of coal). This paper, together with a detailed description of the pilot plant (which includes a fixed-bed up-draft gasifier and the whole syngas treatment line for power generation and hydrogen production), reports a critical analysis of the main results obtained in the first experimental campaigns, carried out by using a low sulphur South African coal and a high sulphur Sardinian coal (for both kinds of coal, a hot gas desulphurization system allows to reduce at about 10 ppm the H2S concentration in the clean syngas). In particular, a hydrogen production of about 1.4–1.6 kg/h (depending on the primary fuel composition and the operating conditions) has been obtained from a portion of syngas corresponding to the gasification of 7 kg/h of coal.