Francesco Fantozzi

Biogas production from different substrates in an experimental Continuously Stirred Tank Reactor anaerobic digester.

Different mixtures were digested in a single-stage, batch, mixed, laboratory scale mesophilic anaerobic digester at the Biomass Research Centre Laboratory (University of Perugia). The yield and the composition of biogas from the different substrates were evaluated and the cumulative curves were estimated. Two experimental campaigns were carried out, the first on three mixtures (chicken, pig and bovine manures), the second on animal and vegetal biomasses (chicken and cow manure, olive husk) with different inocula (rumen fluid and digested sludge). In the first campaign pig manure mixture showed the maximum biogas production (0.35 N m(3)/kg) and energy content (1.35 kWh/kg VS); in the second one the differences in produced biogas from the different inocula were analyzed: olive husk with piggery manure anaerobically digested as inoculum showed the higher biogas (0.28 N m(3)/kg VS) and methane yield (0.11 N m(3)/kg VS), corresponding to an energetic content of 1.07 kWh/kg VS. All data obtained from the laboratory scale anaerobic digester are comparable to the values in literature for several biomass and in particular for olive husk, dairy manure and chicken manure.

Anaerobic digestion of mechanically treated OFMSW: Experimental data on biogas/methane production and residues characterization

One of the more promising processes for the energetic transformation of waste is the anaerobic digestion of the Organic Fraction of Municipal Solid Waste (OFMSW). An experimental campaign was carried out on three different samples of OFMSW from Waste Separation (WS), one as received and two obtained after mechanical treatment (squeezing): OFMSW slurry (liquid fraction) and OFMSW Waste (residual solid fraction). Anaerobic Biogasification Potential (ABP) and anaerobic digestion tests (AD) were carried out, investigating the effects of inoculum and pH. The OFMSW Waste was also examined to evaluate the possibility to dispose of it in a landfill. Results showed that OFMSW slurry must be diluted and inoculated and that pH control in the start up phase is essential, in order to have significant biogas productions. OFMSW as received did not show a significant biogas production, while OFMSW Waste showed suitable characteristics for landfill disposal, except for Dissolved Organic Carbon.

Thermogravimetric analysis of the behavior of sub-bituminous coal and cellulosic ethanol residue during co-combustion.

The influence of the addition of cellulosic ethanol residue (CER) on the combustion of Indonesian sub-bituminous coal was analyzed by non isothermal thermo-gravimetric analysis (TGA). The effect of blends ratio (5%, 10%, 15% and 20%), interaction mechanism, and heating rate (5°C/min, 10°C/min, 15°C/min, 20°C/min) on the combustion process was studied. The results show that the increase of the blending ratio allows to achieve the increase of the combustibility index from 7.49E-08 to 5.26E-07 at the blending ratio of 20%. Two types of non-isothermal kinetic analysis methods (Ozawa-Flynn-Wall and Vyazovkin) were also applied. Results indicate that the activation energy of the blends decreases with increasing the conversion rate. In particular, the blending ratio of 20% confirms to have the better combustion performance, with the average value of the activation energy equal to 41.10 kJ/mol obtained by Ozawa-Flynn-Wall model and 31.17 kJ/mol obtained by Vyazovkin model.

Rotary kiln slow pyrolysis for syngas and char production from biomass and waste -Part II Introducing product yields in the energy balance

A microscale electrically heated rotary kiln for slow pyrolysis of biomass and waste was designed and built at the University of Perugia. The reactor is connected to a wet scrubbing section, for tar removal, and to a monitored combustion chamber to evaluate the lower heating value of the syngas. The system allows the evaluation of gas, tar, and char yields for different pyrolysis temperature and residence time. The feeding screw conveyor and the kiln are rigidly connected; therefore a modification of the flow rate implies a modification of the inside solid motion and of residence time. Part I of the paper describes the theoretical and experimental evaluation of the working envelope of the reactor, that is, rotational speed as a function of feedstock density and humidity content, to obtain pyrolysis conditions inside the kiln. This paper describes the development and resolution of an energy balance of the reactor under pyrolysis conditions. Once the rotational speed n is fixed, the aim of the balance is to obtain the yield of wood biomass pyrolysis products such as syngas, tar, and char. Results can be used to choose the correct rotational speed of kiln and feeding screw before doing the real pyrolysis test.

Rotary Kiln Slow Pyrolysis for Syngas and Char Production From Biomass and Waste—Part I: Working Envelope of the Reactor

A microscale electrically heated rotary kiln for slow pyrolysis of biomass and waste was designed and built at the University of Perugia. The reactor is connected to a wet scrubbing section, for tar removal, and to a monitored combustion chamber to evaluate the lower heating value of the syngas. The system allows the evaluation of gas, tar, and char yields for different pyrolysis temperatures and residence times. The feeding screw conveyor and the kiln are rigidly connected; therefore, a modification of the flow rate implies a modification of the inside solid motion and of residence time. The paper provides the theoretical and experimental calculation of the relationships between residence time and flow rate used to determine the working envelope of the reactor as a function of the feedstock bulk density and moisture content, given the actual heat rate of the electric heaters. The methodology is extendable to any rotary kiln reactor with a rigidly connected feeding screw conveyor, given its geometric and energetic specifications. Part II of the paper will extend the energy balance, also introducing the yields of pyrolysis products.

Simulation of power plant transients with artificial neural networks: Application to an existing combined cycle

Abstract To maintain the high performance of gas-turbine-based combined cycles, transients must be properly taken into account in the design phase and efficiently monitored in the operational phase, because they are not negligible time intervals. The use of artificial intelligence techniques such as expert systems, fuzzy sets and neural networks (NNs), coupled with advanced measurement and monitoring devices, can provide a reliable and efficient monitoring system. An existing two-pressure-level combined cycle has been simulated by dividing its simplified model into blocks representative of the main elements. An NN is associated with each of these blocks. Once the training and testing of the NN are complete, using data from a simulator, the blocks are put either in a cascade arrangement or in a parallel arrangement, providing reliable systems that can predict the load-change transient behaviour of the entire plant. The parallel approach was then tested on data from the real plant. The excessive simplification introduced with the simulator required the addition of selected real cases to the training set that are able to fit the NN response to reality. The results obtained are encouraging for use in an on-line monitoring system which evaluates the difference between the measured data and the predicted data.

Gas Turbines Fired With Biomass Pyrolysis Syngas: Analysis of the Overheating of Hot Gas Path Components

Alternative resources, such as biomass, and municipal and industrial waste are being considered as a source for the production of syngas to replace natural gas as a power turbine fuel. Pyrolysis of biomass produces a syngas composed primarily of CO, CO2, CH4, and H2 with a medium-low lower heating value that is strongly dependent on the process boundary conditions such as the pyrolysis temperature and product residence time in the reactor. The issues associated with conventional gas turbines also apply to syngas turbines with the added complexity of the fuel and impurities. At present, syngas turbines are operated at firing temperatures similar to those of turbines fired on natural gas by increasing the fuel mass flow through the turbine. While this produces a higher turbine power output, the heat transferred to the hot flow-path vanes and blades is also greater. The aim of this paper is to report on the use of numerical modeling to analyze the fundamental impact of firing gas turbines with biomass pyrolysis syngas. To complete the analysis, the results have been compared with data from the literature on gas turbines fired with coal gasification syngas. The test engine used to perform this analysis is a General Electric GE10-2 gas turbine. The performance, aerodynamics and secondary flows were computed using proprietary software, while a commercial finite element software was used to perform the thermal and local creep analyses.

Integrated Pyrolysis Regenerated Plant (IPRP): An Efficient and Scalable Concept for Gas Turbine Based Energy Conversion From Biomass and Waste

A massive effort towards sustainability is necessary to prevent global warming and energy sources impoverishment: both biomass and waste to energy conversion may represent key actions to reach this goal. At the present, state of the art available technologies for biomass and waste to energy conversion are similar and include low to mid efficiency grate incineration or fluidized bed combustion with steam power cycles or mid to high efficiency gas turbine based cycles through integrated gasification technology. Nevertheless, these plants are all available from mid-to-high scale range that can be highly intrusive on protected areas and socially unacceptable. This paper proposes an innovative, low cost, high efficiency plant in which the residue is gasified in the absence of oxygen (pyrolysis), in a rotary kiln, by means of a highly regenerative gas turbine based cycle. Pyrolysis is preferred to gasification, because the syngas obtained has a higher low heating value and produces char or tar as a by-product with an interesting energy content to be re-utilized inside the cycle. Different plant configurations are proposed and discussed through principal thermodynamic variables parametric analysis. Results show that very interesting efficiencies are obtainable in the 30-40% range for every plant scale. This fact shows how IPRP technology can provide an interesting alternative to traditional technologies, especially for the small size (below 5MW). Moreover, the IPRP technology provides a unique solution for microscale (below 500 kW) power plants, opening a new and competitive possibility for distributed biomass or waste to energy conversion systems where low environmental and social impact turns into higher interest and positive dissemination effect.

CFD Simulation of Biomass Pyrolysis Syngas vs. Natural Gas in a Microturbine Annular Combustor

Biomass to energy conversion is particularly attractive on the microscale were internal combustion engines such as microturbines may be utilized coupled to an indirect gasification system. The authors have developed the IPRP technology based on rotary kiln pyrolisys and a pilot plant was built in Italy powered by an 80 kWEl microturbine fired by pyrolysis biomass syngas. This paper describes CFD numerical investigations carried out to study the combustion process occurring inside the annular rich-quick-lean combustion chamber of the given microturbine. A RANS analysis has been performed in order to simulate both natural gas and syngas combustion. A mechanisms based on two reduced and detailed chemical kinetic were taken into account and applied to carry out the CFD simulations. The numerical results obtained for NG are presented and compared with the experimental data on emission to validate the numerical assumptions. The combustion mechanism are used also in pyrolysis gas combustion case to investigate the operation of the microturbine fuelled with this biomass derived fuel.Copyright

Study of a cogeneration plant for agro-food industry

Abstract A technical and economic feasibility study for a natural gas fueled cogeneration plant was conducted in an important Italian pasta and animal feed factory. The layout analysis pointed out three main divisions; in each division electric and thermal users were pointed out and their effective energy consumption and power demand rate was monitored. A technical feasibility analysis was then carried out to determine the type and scale of the possible Combined Heat and Power (CHP) plants focusing on Internal Combustion Engines (ICEs) and gas turbine based power plants. The actual energy costs were evaluated on the base of the energy bills for the biennium 1996–97 while the detailed economic feasibility analysis was conducted on the base of the offers received from manufacturers on the market. The results obtained show the possibility to have low payback periods and appealing internal rate of returns when investing on ICEs based CHP plants covering the entire electric demand and partially fulfilling the thermal needs of the factory.