Gabriele Calì’s scientific contributions

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 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.

Coal gasification is a thermo-chemical process aiming at the production of high heating value syngas. The coal charges present, typically, a low quantity of sulfur compounds for prevent the formation of a large amount of sulfuric acid (H2S), that is a pollutant and a poison for catalysts, in syngas stream. However, in the world there are a lot of coals that cannot be used for gasification because of their high sulfur content (e.g. Sulcis Italian coal or Inner Mongolia Chinese coal). The interest on these types of coal is increasing due to a novel technology that allows to convert H2S and CO2 into syngas (AG2S TM). The aim of this work is to propose a predictive kinetic model of the release of sulfur compounds (e.g H2S) from coal. This kinetic scheme is implement into GASDS, a package that includes a gasifier mathematical model, which accurately describes the inter-phase mass and heat transfer. The first complexity relies in the characterization of the coal, in particular the relative amount of the different forms of sulfur components (e.g. inorganic such as pyritic and sulfates, and organic sulfur such as aliphatic, aromatic and thiophenic) and their pyrolysis and devolatilization process. The kinetic model, with the related rate parameters, is validated through comparison with experimental data from the literature and obtained during several experimental campaigns at the Sotacarbo S.p.A. pilot platform. Finally, different operating conditions of gasification are analyzed in order to obtain the best yield in the downstream process, with special reference to the novel Acid Gas to Syngas (AG2S TM) process.

In the field of coal and biomass gasification for distributed power generation, ENEA and Sotacarbo are developing several activities on demonstration plant scale in order to test gasification technologies for combined production of synthesis gas and electric power in medium and small-scale industrial plants. The Sotacarbo pilot platform has been built up to test different plant solutions at different operating conditions; therefore, a very flexible and simple layout has been designed and constructed. Both demonstration and pilot plants are based on an up-draft, air-blown and fixed-bed gasification process, suitable to be fed with both coal and wood chips. In particular, the demonstration unit of the plant platform includes a 5 MWth gasifier equipped with a wet scrubber for syngas clean up in equicurrent conditions and a flare. This presentation reports some results of the experimental activities related to the start-up of coal and biomass gasification carried out on a demonstration plant at Sotacarbo Research Centre in the South-West of Sardinia (Italy). The aim is to assess the system behaviour and to evaluate the gasification performance. The experimental activity was carried out in order to check the operability of all components and to improve the knowledge of gasifier operation in the different phase of start-up, run and shut down. A characterization of the process was performed and the modalities and key parameters to achieve standard operating conditions were identified. The ultimate aim is to provide useful data so as to improve the system efficiency and to make electricity generation suitable by an internal combustion engine fed by clean syngas. In particular, during the experimental tests different types of fuel were tested: wood chips, Colombian coal, blends of Colombian coal and wood chips. A steady-state simulation model of the gasification process has been developed in the Aspen Plus v.8 simulation environment. The experimental data were used for a first tuning of the model. The validating activity is still going on with newer experimental data. The aim is to realise a model of the plant able to predicts syngas composition, heating value, cold gas efficiency (CGE) and performance at different operating conditions. The model will be a useful tool for future experimental activities.

The removing CO2 from fossil fuel based power plants has got increased interest due to environmental reasons. CO2 absorption by chemical solvents is an attractive and commercial applicable CO2 capture technology.In that field ENEA, together with Sotacarbo, is developing different activities on their pilot plants to test the use of gasification technologies for the combined production of hydrogen and electric power in medium and small scale commercial plants and to test CO2 absorption and regeneration technologies. This paper reports the first results achieved during preliminary experimentations carried out to assess the CO2 absorption performance with monoethanolamine. Different plant operating conditions have been tested. The absorption CO2 efficiency has been evaluated and the main parameters of the regeneration process are discussed.

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.