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Aldo Steinfeld - One of the best experts on this subject based on the ideXlab platform.

  • thermal dissociation of ch4 using a particle flow Chemical Reactor exposed to concentrated solar radiation
    Volume 8: Energy Systems: Analysis Thermodynamics and Sustainability; Sustainable Products and Processes, 2008
    Co-Authors: Gilles Maag, Wojciech Lipinski, Francisco J Gutierrez, Aldo Steinfeld
    Abstract:

    The performance of a 5 kW particle-flow Chemical Reactor for the co-production of H-2 and C by thermal decomposition of CH4 is investigated using concentrated solar radiation as the energy source of hi-h-temperature process heat. The solar Reactor features a directly-irradiated flow of CH4 laden with carbonaceous particles that serve the functions of radiant absorbers and nucleation sites for the heterogeneous cracking reaction. Main operational parameters are the solar power input, CH4 mass flow rate, and solid phase volume fraction. Their effect on the Chemical conversion and solid products' characteristics are examined for active carbon and carbon black laden particles. Higher particle volume fraction resulted in hi-her radiative absorption and enhanced kinetics.

  • band approximated radiative heat transfer analysis of a solar Chemical Reactor for the thermal dissociation of zinc oxide
    Solar Energy, 2007
    Co-Authors: Reto Muller, Aldo Steinfeld
    Abstract:

    Abstract A solar Chemical Reactor for the thermal dissociation of ZnO is modeled by means of a detailed heat transfer analysis that couples radiative transport to the reaction kinetics. An extended band-approximated radiosity method enables the analysis of directional and wavelength depended radiation exchange. Boundary conditions included the incident concentrated solar radiation, determined by the Monte Carlo ray-tracing technique, and the hemispherical and band-approximated optical properties derived for the quartz window. Validation was accomplished by comparing the numerically modeled and experimentally measured window temperatures, reaction rates, and energy conversion efficiencies. The experimentally measured solar-to-Chemical energy conversion efficiency increased with temperature, peaked at 14% for a Reactor temperature of 1900 K and ZnO dissociation rate of 12 g/min, and decreased as the Reactor approached its stagnation temperature. The conditions for which this efficiency can be augmented are discussed.

  • steam gasification of coal in a fluidized bed packed bed Reactor exposed to concentrated thermal radiation modeling and experimental validation
    Industrial & Engineering Chemistry Research, 2005
    Co-Authors: Peter Von Zedtwitz, Aldo Steinfeld
    Abstract:

    The steam-gasification of coal in a fluidized-bed or a packed-bed Chemical Reactor is considered using an external source of concentrated thermal radiation for high-temperature process heat. The en...

  • radiative transfer in a solar Chemical Reactor for the co production of hydrogen and carbon by thermal decomposition of methane
    Chemical Engineering Science, 2004
    Co-Authors: David Hirsch, Aldo Steinfeld
    Abstract:

    Abstract Radiation heat transfer in a solar Chemical Reactor for the co-production of hydrogen and carbon by thermal decomposition of CH 4 is analyzed by the Monte Carlo ray-tracing method. The solar Chemical Reactor features a vortex flow of CH 4 confined to a cavity and laden with carbon particles that serve simultaneously as radiant absorbers and nucleation sites for the heterogeneous decomposition reaction. The Reactor is treated as a 3D non-isothermal non-gray absorbing–emitting–scattering gas/particle suspension directly exposed to concentrated solar irradiation. The analysis includes coupling to conduction/convection heat transfer and Chemical kinetics. Calculated temperature distribution and Chemical conversion are compared with the experimentally measured values obtained with a 5 kW prototype Reactor tested in a solar furnace.

  • solar hydrogen production by thermal decomposition of natural gas using a vortex flow Reactor
    International Journal of Hydrogen Energy, 2004
    Co-Authors: David Hirsch, Aldo Steinfeld
    Abstract:

    Abstract The endothermic decomposition of natural gas is experimentally investigated using concentrated solar radiation as the source of high-temperature process heat. The solar Chemical Reactor features a vortex flow of CH4 confined to a cavity-receiver and laden with carbon particles that serve simultaneously as radiant absorbers and nucleation sites for the heterogeneous decomposition reaction. A 5 kW Reactor prototype was fabricated and tested in a high-flux solar furnace with power flux intensities exceeding 3500 kW / m 2 . The Chemical Reactor engineering, experimental setup, and test results are described. Maximum Chemical conversion of CH4 to H2 and C(gr) was 67% at 1600 K and 1 bar . Carbon formed was of nano-filamentary nature. The proposed solar hybrid Chemical process conserves natural gas, reduces CO2 emissions, and provides a transition path to solar hydrogen.

Igor Novosselov - One of the best experts on this subject based on the ideXlab platform.

  • prevention of lean flame blowout using a predictive Chemical Reactor network control
    Fuel, 2019
    Co-Authors: Saurabh Gupta, Philip C Malte, Steven L Brunton, Igor Novosselov
    Abstract:

    Abstract Optimization of efficiency and pollution control for gaseous species and particulate matter are common to any combustion system. Combustor lean blowout (LBO) is a concern for aircraft safety and for land-based gas turbines designed to operate at lean equivalence ratios to achieve better fuel efficiency and to limit NOx emissions. This paper provides an experimental demonstration of model-based control applied to a laboratory jet-stirred Reactor (JSR) approaching LBO. The approach uses (1) combustor temperature measurements, coupled with (2) the calculation of free radical concentrations in the Reactor using a real-time Chemical Reactor network (RT-CRN) model as the Reactor approaches LBO, which in turn (3) are used by a predictive control algorithm to achieve stable combustion. The RT-CRN represents the combustor as three perfectly stirred Reactors (PSRs) in series with a recirculation pathway; the model inputs include real-time measurements of temperature and mass flow rates of fuel and air. In a series of experiments, the combustor is operated on a premixed methane-air mixture; after achieving stable combustion, the air flow rate is increased beyond the stable air-fuel ratio either as a step function or by ramping up linearly. The predictive RT-CRN control algorithm calculates the distribution of hydroxyl (OH) radicals in the free jet, impinging jet, and recirculation regions of the JSR in near real-time (∼1 s delay), and determines the leanest stable state based on the OH uniformity in the combustor. As the OH shifts towards the recirculation region, the Reactor approaches LBO, if this condition is detected the control algorithm injects additional fuel; Reactor stabilization is achieved within a 5–15 s time frame. Although this proof-of-concept demonstration is performed for LBO control in a JSR with ceramic walls, the control methodology is applicable to other types of high-intensity recirculation stabilized combustors.

  • real time prediction of lean blowout using Chemical Reactor network
    Fuel, 2018
    Co-Authors: Abhishek Kaluri, Philip C Malte, Igor Novosselov
    Abstract:

    Abstract Lean blowout (LBO) of combustion systems is a concern that can cause costly and time-intensive reignition of land-based gas turbines and can affect the rate of descent for aircraft and the maneuverability of military jets. This work explores the feasibility of model-based combustor monitoring and real-time prediction of combustion system proximity to LBO. The approach makes use of (1) real-time temperature measurements, coupled with (2) the use of a real-time Chemical Reactor network (CRN) model to interpret the data as it is collected. The approach is tested using a laboratory jet-stirred Reactor (JSR), operating premixed on methane at near atmospheric pressure. The CRN represents the combustion Reactor as three perfectly stirred Reactors (PSRs) in series with a recirculation pathway; the model inputs include real-time temperature measurements and mass flow rates of fuel and air. The goal of the CRN is to provide a computationally fast means of interpreting measurements in real time regarding proximity to LBO. The CRN-predicted free radical concentrations and their trends and ratios are studied in each combustion zone. The results indicate that the hydroxyl radical maximum concentration moves downstream as the combustion Reactor approaches LBO. The ratio of hydroxyl radical concentrations in the flame zone versus the recirculation zone is proposed as a criterion for the LBO proximity. The model-based process monitoring approach sheds insight into combustion processes in aerodynamically stabilized combustors as they approach LBO.

  • model based approach for combustion monitoring using real time Chemical Reactor network
    Journal of Combustion, 2018
    Co-Authors: Pieter Depape, Igor Novosselov
    Abstract:

    Flame stability and pollution control are significant problems in the design and operation of any combustion system. Real-time monitoring and analysis of these phenomena require sophisticated equipment and are often incompatible with practical applications. This work explores the feasibility of model-based combustion monitoring and real-time evaluation of proximity to lean blowout (LBO). The approach uses temperature measurements, coupled with Chemical Reactor Network (CRN) model to interpret the data in real-time. The objective is to provide a computationally fast means of interpreting measurements regarding proximity to LBO. The CRN-predicted free radical concentrations and their trends and ratios are studied in each combustion zone. Flame stability and a blowout of an atmospheric pressure laboratory combustor are investigated experimentally and via a phenomenological real-time Chemical Reactor Network (CRN). The Reactor is operated on low heating value fuel stream, i.e., methane diluted with nitrogen with N2/CH4 volume ratios of 2.25 and 3.0. The data show a stable flame-zone carbon monoxide (CO) level over the entire range of the fuel-air equivalence ratio (Φ), and a significant increase in hydrocarbon emissions approaching blowout. The CRN trends agree with the data: the calculated concentrations of hydroxide (OH), O-atom, and H-atom monotonically decrease with the reduction of Φ. The flame OH blowout threshold is 0.025% by volume for both fuel mixtures. The real-time CRN allows for augmentation of combustion temperature measurements with modeled free radical concentrations and monitoring of unmeasurable combustion characteristics such as pollution formation rates, combustion efficiency, and proximity to blowout. This model-based approach for process monitoring can be useful in applications where the combustion measurements are limited to temperature and optical methods, or continuous gas sampling is not practical.

Trond Vegard Island - One of the best experts on this subject based on the ideXlab platform.

  • the driving force distribution for minimum lost work in a Chemical Reactor close to and far from equilibrium 2 oxidation of so2
    Industrial & Engineering Chemistry Research, 1999
    Co-Authors: Signe Kjelstrup, Trond Vegard Island
    Abstract:

    Our mathematical procedure for the determination of the driving force distribution in a Chemical Reactor that has minimum entropy production for a given production rate is applied to the oxidation of SO2 to SO3. The force of reaction that gives the minimum total entropy production is much more constant through the Reactor than is a force taken from a standard textbook example. The entropy production has a peak at the entrance of the Reactor. The inverse temperature plot shows that the optimal force is nearly at equal distance from the equilibrium line in the end of the Reactor. Two practical ways that do not include changes in the apparatus are suggested to minimize the actual entropy production of the Reactor. Reductions of 5% and 21% are obtained. The ideal result suggests that there is room for further improvements, especially if the apparatus is changed.

  • the driving force distribution for minimum lost work in a Chemical Reactor far from equilibrium oxidation of so2
    Computers & Chemical Engineering, 1999
    Co-Authors: Signe Kjelstrup, Trond Vegard Island
    Abstract:

    Abstract A mathematical procedure for determination of the driving force distribution in a Chemical Reactor, that gives minimum entropy production for a given production rate, is applied to oxidation of SO 2 . The solution for the force is calculated from known reaction kinetics, and compared to the actual force. A large difference is found. Two practical ways that do not include changes the apparatus, are suggested, for moving the process towards minimum entropy production. Reductions of 5 and 21 in lost work %, and an increased production of SO 3 are obtained. The ideal results suggest that there is room for further improvements, especially if the apparatus is changed.

Yan Lin - One of the best experts on this subject based on the ideXlab platform.

  • adaptive control of nonlinear time delay systems with application to a two stage Chemical Reactor
    IEEE Transactions on Automatic Control, 2015
    Co-Authors: Xu Zhang, Yan Lin
    Abstract:

    Global adaptive regulation of general strict feedback system with unknown time-delay by state feedback is a long-standing problem. This note provides, for the first time, a solution to this problem by introducing a novel dynamic gain-based adaptive backstepping approach. A key feature of the developed approach is that the Lyapunov function and the adaptive law are chosen in a new recursive manner. With the help of appropriate Lyapunov-Krasovskii functionals, a memoryless state feedback controller is explicitly constructed. It is shown that global adaptive regulation can be achieved for the nonlinear time-delay system. Finally, we use a two-stage Chemical Reactor to demonstrate the application of the proposed scheme.

Xinping Guan - One of the best experts on this subject based on the ideXlab platform.

  • backstepping control for nonlinear systems with time delays and applications to Chemical Reactor systems
    IEEE Transactions on Industrial Electronics, 2009
    Co-Authors: Changchun Hua, Peter X Liu, Xinping Guan
    Abstract:

    The state feedback control problem is addressed for a class of nonlinear time-delay systems. The time delays appear in all state variables of the nonlinear system, which brings a challenging issue for controller design. With an introduced new Lyapunov-Krasovskii functional, we develop a novel control strategy. With the help of a backstepping method, we design a memoryless state feedback controller, which does not need the precise knowledge of time delays. It is rigorously proved that the closed-loop system is asymptotically stable. Chemical Reactor plants are typical nonlinear systems with time delays. We apply the developed method to the control design of a two-stage Chemical Reactor with delayed recycle streams, and the simulation results verify the effectiveness of the main results.