1,721,026 research outputs found
Fuzzy control of a biomass-fired and solar-powered fluidized bed prototype as a residential cogeneration System
No full textA fuzzy PI controller is proposed as an alternative to a PI traditional controller for regulation and control of a small-scale fluidized bed cogeneration system driven by two renewable energy sources: direct solar and biomass combustion. The design of the fuzzy logic controller, with Sugeno inference method, was based on the knowledge of the more relevant continuity diagrams of the process model, characterized by nonlinearity and parameter variability. The simulation results show that the PI fuzzy logic controller delivers a higher performance, in terms of robustness and response speed, compared with the traditional PI controller. It is proved that the use of PI fuzzy controllers can be a good choice for the control of nonlinear processes with parameters varying in tim
Distillation Control: type-1 and type-2 fuzzy control
No full textTwo advanced controllers were developed in this paper, i.e., a type-1 and a type-2 fuzzy
logic controller and their performances compared in simulation for a case study, i.e., a binary
distillation column, which is characterized by high nonlinearities and parameter uncertainties in the
underlying mathematical model. Priority was given to the type-2 fuzzy controller, with special
attention to input fuzzy sets and type-2 Gaussian membership functions. All the simulation results
confirmed the robustness and the effectiveness of the fuzzy control action, with evident advantages for
the type-2 fuzzy controller
Effect of system pressure on char combustion in Fluidized Beds. Model predictions
No full textAlthough Pressurized Fluidized Bed Combustion is already at the demonstration stage, fundamental studies on the effect of system pressure on the many aspects of the process are still under way. In this paper the effect of system pressure on fluidized bed char combustion is considered from a theoretical standpoint. Char combustion in bubbling fluidized bed is controlled by the oxygen transfer from bubbles to emulsion phase and from this latter to char particle surface, oxygen diffusion in the pore network and char intrinsic reactivity. According to previous indications this study confirms that the actual influence of system pressure on char combustion can only be deduced by means of a comprehensive mathematical model which accounts for the controlling steps altogether. The extention of a model previously developed by the authors to a pressure higher than atmospheric is finalized to this objective. This model is based on a char particle population balance and considers particle combustion, attrition and elutriation under simple bed fluid dynamics. With reference to a pre-pilot combustor, from which experimental data at atmospheric pressure were available, bed carbon loading, specific carbon combustion rate, characteristics resistances of the combustion mechanism and combustion efficiency have been calculated at a pressure of 12 bar and compared with results at 1 bar. In model evaluations, the excess air has been considered the main parametric variable. Different assumptions concerning bed fluid dynamics as well as combustion kinetics have been tested. Model results clearly indicate that bed carbon loading increases with pressure even though char combustion rate is faster due to higher oxygen partial pressure
Thinking, Modeling and Assessing Costs of Extracting Added-value Components from Tomato Industrial By-products on a Regional Basis
Full text linkThis contribution is a piece of work within a more comprehensive research program dedicated to a thorough exploitation of industrial tomato by-products, which should be technically feasible, economically convenient and environmentally friendly. In this respect, the proposed paper focuses three aspects of newer and broader interest: lycopene extraction, cutin separation and compost production. The investigated case study refers to the tomato industry in the Campania region (IT).
The lycopene extraction from peels is usually carried out by a solvent- or supercritical CO2-assisted operation; the separation of cutin is performed in two process steps: alkaline hydrolysis and acidification. The solid residual, after cutin separation, is proposed to be used as feedstock for composting, not alone, but mixed with other suitable biomass to adjust both the final moisture content and C/N ratio. To this end, two scenarios according to the “biorefinery cascade approach” were developed that differ in the extraction technology for lycopene, i.e., 1) an optimized organic solvent; 2) CO2 as a supercritical fluid. The proposed process block diagram takes into account the upstream separation of peels from seeds and the downstream composting of seeds and residual solids (i.e., after lycopene and cutin extraction) in both scenarios, which were set up and quantitatively evaluated, under both viewpoints of process feasibility and economic sustainability. The mass and energy balances were written for all the involved process steps; the balance equations and the mathematical calculations were implemented and solved in MS EXCEL®
An Aspen Plus® tool for simulation of lignocellulosic biomass pyrolysis via equilibrium and ranking of the main process variables
No full textPyrolysis of non-fossil fuels is raising a growing interest in the nowadays scenario for the alternative supply of energy, fuels and chemicals. Biomass is among the most widely available and technologically promising candidate feedstocks. For simulation purposes and process design goals, kinetic-based models promise to be quite accurate in literature; however, they are computationally intensive and, more importantly, applicable only when kinetic data are available for the specific feedstock and pyrolysis equipment. Here, a different modeling approach is followed by considering that the pyrolysis reactor is under the thermodynamic equilibrium; then, the authors take advantage of the capabilities provided by the Aspen Plus® software. Therefore, this work is focused on the development of an input-output reactor model to simulate pyrolysis of a lignocellulosic biomass and to predict the effects of the main process variables. The trends of the predicted results as a function of the process operating variables are generally in accordance with those that are experimentally evident and published in literature. A limited comparison is provided against the experimental results of Honus [25]. It has to be noted that the Aspen code could not predict the composition of the liquid residue, i.e., tar
Biodiesel production from tomato seed by transesterification with Alkaline and ‘Green’ catalysts: Simulation and discussion
No full textThe aim of this work is to model a more environmental-friendly production of biodiesel from tomato seed oil to assess the feasibility of using an alternative catalyst. The AspenPlus® software is used to this end. Different cases are evaluated and compared, by changing the catalyst and by considering the additional production of high purity glycerol and potassium phosphate. Tomato seed oil obtained from tomato pomace coming from local industries, methanol and catalyst are considered as raw materials. Based on literature data, a methyl-esters yield formulation is developed and the catalytic transesterification reaction implemented in a simulated reactor, while methanol is recovered by distillation and recycled to the reactor. The necessary distillation towers are designed. All the mass and energy balances were set up for the whole process. The energy return of investment (EROI) was determined by considering the energy for harvesting and that for producing biodiesel. Results show that tomato seed oil can be a feasible alternative for biodiesel production
Continuity diagram analysis at open loop and closed loop to improve the operability of a bioreactor
No full textThe paper analyzes the dynamics of a simple biochemical reactor model with a substrate inhibition
kinetics under open as well as closed loop configuration and discusses the system continuity diagram in both
cases. The controller chosen for closed loop system is a traditional proportional integral controller. Attention is
focused on the effects that open loop and closed loop models have on dynamics of the same system and how
the nature of the continuity diagram changes when moving just from an open system to a controlled system.
The closed loop configuration proves to give the advantage of greatly improving the operability of the
bioreactor around the point that is optimal with reference to substrate conversion and biomass production
Fluidized bed torrefaction of biomass pellets: A comparison between oxidative and inert atmosphere
No full textThe paper reports on an experimental study aimed at investigating the potential of performing biomass torrefaction using air instead of nitrogen as a carrier gas, which allows reducing the operating costs of upgrading biomass. Specifically, the performances of oxidative and non-oxidative torrefaction treatments were comparatively investigated by using commercial wood pellets and olive pomace pellets as a feedstock. Batch torrefaction tests at three different temperature levels (200, 230 and 250 °C) were performed in a laboratory-scale fluidized bed reactor by fixing the reaction time equal to 15 min; this allowed to investigate the impact of the torrefaction temperature and atmosphere on: a) the distribution of the main output products of the torrefaction process (torrefied solids, condensable volatiles and permanent gases); b) the properties of torrefied pellets as a fuel (i.e., proximate composition, ultimate composition and calorific values); c) the process performances in terms of mass and energy yields of the solid product; and d) the quality of torrefied pellets in terms of mass and energy densities, hardness (shore D) and non-standard durability index. Fluidized-bed torrefaction tests were also complemented by non-isothermal thermogravimetric measurements (TG/DTG/DSC) performed in both air and nitrogen atmospheres. Results show that, under the same operating conditions, the process performance of oxidative torrefaction (i.e., mass and energy yields of the solid product) are worse than that of the non-oxidative treatment, particularly in the case of olive pomace pellets. This is mostly a consequence of the higher degradation rate triggered by oxidative reactions. On the other hand, the physical properties (i.e., mass density, energy density, hardness and durability) of torrefied olive pomace pellets obtained under oxidative atmosphere are better than those obtained via non-oxidative torrefaction. A similar behavior, however, was not observed in the case of woody fir pellets. This confirms that the fluidized bed torrefaction is feedstock-sensitive process; in particular, non-woody olive pomace pellets can be torrefied in oxidative environments, whereas fir pellets are more suitable for non-oxidative torrefaction. Since the torrefaction treatment of biomass pellets in a fluidized bed reactor has not been investigated so far, findings of this work can be useful to highlight potential advantages related to use of such a technology in this specific application
Design and setup activities for the development of methane autothermal reforming in a jet fountain fluidized bed reactor
No full textIn the framework of hydrogen production and process intensification for energy applications, this work presents the design and the construction of a novel lab-scale experimental facility, which is aimed at testing and demonstrating the feasibility of the auto-thermal catalytic reforming of methane in a recently proposed reactor configuration, i.e., the jetting fountain fluidized bed (JFFBR). The proposed solution consists of a jet pipe and an annulus which are concentrical and it is designed to operate the auto-thermal reforming in two almost-distinct zones: oxidant (oxygen or air) is only fed to the jet pipe, which substantially provides methane partial oxidation and consequently heat generation; the annulus is designed to operate in a bubbling fluidized bed regime, and it is the region in which methane steam reforming essentially occurs. The two zones communicate through a pair of holes in the bottom part of the jet pipe, which determine the entrainment of solid particles and the fountain on the top of the jet pipe. The jetting fountain fluidized bed regime is expected to enhance the heat and mass transfer phenomena, while the selective fed of the oxidant to the jet pipe is expected to provide an in-situ regeneration of the catalyst. In view of starting an actual experimental program with the designed facility, a suitable catalyst has been selected and its catalytic activity has been characterized in a lab-scale fixed-bed reactor. The formulation, previously optimized, involves a ceria-silica support, which can be easily fluidized, and two active phases, namely Ni and Pt, obtaining a final catalyst 3%Pt-10%Ni/CeO2/SiO2.The catalyst performed well in terms of activity and selectivity. The activity test results from the fixed-bed reactor allowed to set-up a satisfactory kinetic model of the reacting system
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