Bio-ethylene Production: from Reaction Kinetics to Plant Scale

Ethylene production from renewable bio-ethanol has been recently proposed as sustainable alternative to fossil sources. The possibility to exploit diluted bioethanol as less expensive feedstock was studied both experimentally, using different catalysts at lab-level, and through preliminary process design. In this work, a full-scale plant simulation is presented, built on a detailed reaction kinetics. Rate equations for the primary and side reactions are revised and implemented with a process simulation package, using a range of thermodynamic methods as best suited to the different process stages. The catalyst loading within the reactor can be effectively distributed according to the underlying kinetic, and the overall plant layout let foresee the best routes for the material recycles. The detailed reaction modeling and the choice of the thermodynamic models are essential to obtain reliable predictions. Setting a target yield of 105 t/year of polymer-grade ethylene, the reactive section must be fed with 76 t/h of diluted ethanol and operated at 400 \ub0C. 85% of the fed carbon mass is found as ethylene, 12% remains as ethanol and a 2% as longer olefins. Considering also the recycle of ethanol the carbon conversion and recovery increases to the value of 97.6%. The global ethylene recovery is 90.7%: most of the loss takes place in the last stage due to the non-condensable purification and to the adopted strategy of having low reflux ratio \u2013 and then a closed cryogenic balance \u2013 in the last purification column. Full heat integration of the process with upstream bioethanol production and purification sections allows process intensification and consistent energy savings. This newly designed process sets the sustainable ethylene production on a detailed and reassessed computational basis and has been assessed as for Capital and Operational Expenditures and Total Investment costs

Performance assessment of drop tube reactor for biomass fast pyrolysis using process simulator

Biomass pyrolysis process from a drop tube reactor was modelled in a plug flow reactor using Aspen Plus process simulation software. A kinetic mechanism for pyrolysis was developed considering the recent improvements and updated kinetic schemes to account for different content of cellulose, hemicellulose, and lignin. In this regard, oak, beechwood, rice straw, and cassava stalk biomasses were analyzed. The main phenomena governing the pyrolysis process are identified in terms of the characteristic times. Pyrolysis process was found to be reaction rate controlled. Effects of pyrolysis temperature on bio-oil, gases, and char yields were evaluated. At optimum pyrolysis conditions (i.e., 500?), a bio-oil yield of 67.3, 64, 43, and 52 wt.% were obtained from oak, beechwood, rice straw, and cassava stalk, respectively. Oak and beechwood were found to give high yields of bio-oil, while rice straw produced high gas and char yields compared to other biomasses. Although temperature is the main factor that plays a key role in the distribution of pyrolysis products, the composition of cellulose, hemicellulose, and lignin in the feedstock also determines the yield behaviour and composition of products. With the rise in pyrolysis temperature, further decomposition of intermediate components was initiated favouring the formation of lighter fractions. Comparably, species belonging to the aldehyde chemical family had the highest share of bio-oil components in all the investigated feedstocks. Overall, the present study shows a good agreement with the experimental study reported in the literature, confirming its validity as a predictive tool for the biomass pyrolysis process

Syngas Production, Storage, Compression and Use in Gas Turbines

This chapter analyses syngas production through pyrolysis and gasification, its compression and its use in gas turbines. Syngas compression can be performed during or after thermal treatment processes. Important points are discussed related to syngas ignition, syngas explosion limit at high temperatures and high pressures and syngas combustion kinetics. Kinetic aspects influence ignition and final emissions which are obtained at the completion of the combustion process. The chapter is organized into four subsections, dealing with (1) innovative syngas production plants, (2) syngas compressors and compression process, (3) syngas ignition in both heterogeneous and homogeneous systems and (4) syngas combustion kinetics and experimental methods. Particular attention is given to ignition regions that affect the kinetics, namely systems that operate at temperatures higher than 1000 K can have strong ignition, whereas those operating at lower temperatures have weak ignition. Keywords: Pyrogas Pyrolysis Ignition Syngas Compression GasificationacceptedVersio

Hydrogen Production by Steam Reforming of Bioethanol: Catalytic Tests and Process Design

Abstract 2nd generation bioethanol was considered as raw material for the sustainable hydrogen production by catalytic steam reforming. An experimental kinetic investigation has been carried out selecting different catalysts synthesized by Flame Spray Pyrolysis, a one step high temperature synthesis able to impart strong metal-support interaction, besides high thermal resistance [1]. Ethanol conversion, selectivity to the main possible byproducts and the CO/CO2 ratio, as a measure of the contribution of the water gas shift reaction, were correlated to the temperature, water/ethanol ratio and space velocity in a central composite experimental design [2]. Two different bioethanol samples, 50 and 90 vol%, produced and supplied by a company (Mossi&Ghisolfi), have been used for at each temperature. Attention was paid to the catalyst resistance towards deactivation by coking. The kinetic expression was implemented in a software simulation (Aspen Plus), designing a high pressure reactor. A successive process design was investigated considering the hydrogen purification section as well and evaluating the economic feasibility of different plant configurations and operative conditions. Net plant efficiencies and total capital investment will be estimated as well as internal rate of return and payback period. [1] M. Compagnoni, J. Lasso, A. Di Michele, I Rossetti*, Cat. Sci. & Tech, 6 (2016) 6247 [1] M. Compagnoni, A. Tripodi, I. Rossetti*, App. Cat. B:Environ., 203 (2017) 899\u201390

Explosion characteristics of methane-air mixtures in a spherical vessel connected with a duct

With the aim of exploring explosion characteristics of methane-air explosive mixtures in a ducted vessel, a 20 l spherical vessel connected with a 2813 mm long duct was employed. The experimental setup was comprised of a wafer check valve, which kept the methane-air mixture initially confined and opened at the time of explosion. The system introduced turbulence to the gas mixture during operation and pyrotechnic igniters were employed in the investigation. This approach assisted to obtain data that can be correlated with real world ducted explosion accidents where the explosion initiates in the presence of strong ignition energies and in turbulent states of methane-air mixtures. This study shows that the explosion severity can be very high in the turbulent field of methane-air mixture and in the presence of strong ignition energies. The pressure rise in the vessel and the flame speed along the length of the duct were found to be higher in the present study when compared to data obtained with quiescent methane-air mixtures and low ignition energies. The impact of the duct length and pyrotechnic igniters' energy on reduced peak explosion pressure was characterised. The rate of pressure rise, a parameter linked to the burning rate, increased from the ducted to the vented configurations of the explosion test units

Bio-ethyelene production: from reaction kinetics to plant scale

Ethylene production from renewable bio-ethanol has been recently proposed as sustainable alternative to fossil sources. The possibility to exploit diluted bioethanol as less expensive feedstock was studied both experimentally, using different catalysts at lab-level, and through preliminary process design. In this work, a full-scale plant simulation is presented, built on a detailed reaction kinetics. Rate equations for the primary and side reactions are revised and implemented with a process simulation package, using a range of thermodynamic methods as best suited to the different process stages. The catalyst loading within the reactor can be effectively distributed according to the underlying kinetic, and the overall plant layout let foresee the best routes for the material recycles. The detailed reaction modeling and the choice of the thermodynamic models are essential to obtain reliable predictions. Setting a target yield of 105 t/year of polymer-grade ethylene, the reactive section must be fed with 76 t/h of diluted ethanol and operated at 400 \ub0C. 85% of the fed carbon mass is found as ethylene, 12% remains as ethanol and a 2% as longer olefins. Considering also the recycle of ethanol the carbon conversion and recovery increases to the value of 97.6%. The global ethylene recovery is 90.7%: most of the loss takes place in the last stage due to the non-condensable purification and to the adopted strategy of having low reflux ratio \u2013 and then a closed cryogenic balance \u2013 in the last purification column. Full heat integration of the process with upstream bioethanol production and purification sections allows process intensification and consistent energy savings. This newly designed process sets the sustainable ethylene production on a detailed and reassessed computational basis and has been assessed as for Capital and Operational Expenditures and Total Investment costs

Hydrogen production by steam reforming of bio-ethanol: Process design and economic assessment

Hydrogen production from bioethanol steam reforming was techno-economically assessed, considering different bioethanol sources. In particular, 1stgeneration and 2ndgeneration bioethanol have been compared with purity degree. The advantages of using bioethanol with different cost and water/impurities content are discussed. The steam reforming plant was sized based on industrial technologies commercial available and on previous studies on the use of second generation bioethanol, for a total production of 889 kg/h of H2(7.8 kton/year) considering a feed stream of 40 kton of bioethanol per year. The minimum hydrogen selling price and internal rate of return (IRR) of the investment were chosen as criteria of evaluation and comparison with the literature reports. The results revealed that the process is a cost-competitive option for the current state of technology, with a minimum selling price of hydrogen (including 10% rate of return) of 2.39 \ue2\u82\uac/kg. Cash flow diagrams are also presented in order to better analyse the economic viability and compatibility