Steady-state Reactor Model Research Articles

Fischer–Tropsch Synthesis as the Key for Decentralized Sustainable Kerosene Production

Synthetic fuels play an important role in the defossilization of future aviation transport. To reduce the ecological impact of remote airports due to the long-range transportation of kerosene, decentralized on-site production of synthetic paraffinic kerosene is applicable, preferably as a near-drop-in fuel or, alternatively, as a blend. One possible solution for such a production of synthetic kerosene is the power-to-liquid process. We describe the basic development of a simplified plant layout addressing the specific challenges of decentralized kerosene production that differs from most of the current approaches for infrastructural well-connected regions. The decisive influence of the Fischer–Tropsch synthesis on the power-to-liquid (PtL) process is shown by means of a steady-state reactor model, which was developed in Python and serves as a basis for the further development of a modular environment able to represent entire process chains. The reactor model is based on reaction kinetics according to the current literature. The effects of adjustments of the main operation parameters on the reactor behavior were evaluated, and the impacts on the up- and downstream processes are described. The results prove the governing influence of the Fischer–Tropsch reactor on the PtL process and show its flexibility regarding the desired product fraction output, which makes it an appropriate solution for decentralized kerosene production.

Real-Time Application of pH Control in a Carbon Dioxide Bubble Column Reactor by Input/Output Linearizing Control Coupled with pH Target Optimizer

A new strategy for the control application to enhance the CO2 absorption efficiency of the bench-scale bubble column reactor by combining the pH target optimizer with an I/O linearizing controller is presented. A lumped parameter approach using two-film theory is introduced to develop the reactor model. The target pH set point is obtained by solving an optimization problem to maximize the absorption efficiency based on the steady state reactor model, while the I/O linearizing controller enforces the pH to track the target. Real-time control performance of the proposed method with a bench-scale bubble column reactor is investigated. The experimental results show that the I/O linearizing controller successfully enforces the reactor pH with less fluctuation in control action compared with a PI controller. The pH target optimizer provides the optimal use of the sodium hydroxide flow to enhance the CO2 removal efficiency in the reactor.

Optimization of ethylene oxychlorination fluidized-bed reactor using Differential Evolution (DE) method

The present work aims to employ Di erential Evolution (DE) algorithm to optimize ethylene oxychlorination process to produce 1,2-dichloroethane in a fluidized bed reactor as a feedstock of PVC production. A steady-state reactor model, based on twophase theory of fluidization, was developed to investigate the e ffects of various parameters on C2H4 and HCl conversions. The model's results were compared favorably with theindustrial data obtained from a pilot plant working in Italy. The feed temperature, pressure, HCl and O2 molar ow rates, and cooling medium temperature were selected as decision variables to minimize the objective function subject to the environmental constraints. The highest performance was found at HCl/C2H4 and O2/C2H4 molar ratios of 2 and 0.55, respectively; feed and cooling medium temperatures of 440 and 360 K, respectively; pressure of 367.6 kPa. The results show a decrease of 20C in the feed temperature, which leads to saving energy and reducing the size of the pre-heater.

Solar carbothermal reduction of aerosolized ZnO particles under vacuum: Modeling, experimentation, and characterization of a drop-tube reactor

A vacuum aerosol particle reactor was tested for the carbothermal reduction of zinc oxide using concentrated solar power as a heat source. A steady state reactor model was developed to investigate the effect of pressure dependent particle residence time and radiative input power on the zinc production rate. Radiative heat transfer to the particle cloud is solved by Monte Carlo ray tracing, accounting for spectral and directional optical properties and temperature dependent chemical kinetics. Experiments with the solar drop-tube reactor were conducted to ascertain the reaction capacity of the system at pressures between 1 and 960mbar by varying the reactant feed rate between 4 and 56g·min−1. Experiments show that the zinc production rate is maximal at around 100mbar and significantly diminishes under high vacuum. Model and experimental results indicate that the reaction at 1mbar is inhibited due to insufficient residence time and heat up of the particles in the reaction zone. Maximum experimental zinc production rate was 51.4mmol·min−1, while feeding 56g·min−1 of solid reactants and operating the reactor at 100mbar with 9.8kW of radiative input power. Extrapolation to higher feed rates with the reactor model predicts a peak zinc production capacity of 52.1mmol·min−1 at a feed rate of 68g·min−1, achieving a net thermal efficiency of 3.2%.

Fast-ion transport in qmin>2, high-β steady-state scenarios on DIII-D

Results from experiments on DIII-D [J. L. Luxon, Fusion Sci. Technol. 48, 828 (2005)] aimed at developing high β steady-state operating scenarios with high-qmin confirm that fast-ion transport is a critical issue for advanced tokamak development using neutral beam injection current drive. In DIII-D, greater than 11 MW of neutral beam heating power is applied with the intent of maximizing βN and the noninductive current drive. However, in scenarios with qmin>2 that target the typical range of q95= 5–7 used in next-step steady-state reactor models, Alfvén eigenmodes cause greater fast-ion transport than classical models predict. This enhanced transport reduces the absorbed neutral beam heating power and current drive and limits the achievable βN. In contrast, similar plasmas except with qmin just above 1 have approximately classical fast-ion transport. Experiments that take qmin>3 plasmas to higher βP with q95= 11–12 for testing long pulse operation exhibit regimes of better than expected thermal confinement. Compared to the standard high-qmin scenario, the high βP cases have shorter slowing-down time and lower ∇βfast, and this reduces the drive for Alfvénic modes, yielding nearly classical fast-ion transport, high values of normalized confinement, βN, and noninductive current fraction. These results suggest DIII-D might obtain better performance in lower-q95, high-qmin plasmas using broader neutral beam heating profiles and increased direct electron heating power to lower the drive for Alfvén eigenmodes.

Modeling and simulation of a small-scale trickle bed reactor for sugar hydrogenation

Laboratory-scale trickle bed reactor was modeled and simulated, taking into account axial dispersion, gas–liquid, liquid–solid and internal mass transfer as well as catalyst deactivation under isothermal conditions. For catalyst particles dynamic and steady state models were developed, including both mass and heat balances. Catalyst deactivation was included in the model by using the final activity concept for the catalyst particles. A well-working numerical algorithm (method of lines) was applied for solving the reactor model with Matlab 7.1 and the results followed experimental trends very well. The steady-state reactor model was based on simultaneous solution of mass balances. The aim was to illustrate how these parabolic partial differential equations could be solved with a step-by-step calculation for a selected geometry. The final model verification was done against experimental data from the hydrogenation of arabinose to arabitol on a ruthenium catalyst.

Mechanistic and kinetic studies of NO x storage and reduction on Pt/BaO/Al 2O 3

NO x storage and NO oxidation experiments have been carried out on a model Pt/BaO/Al 2O 3 catalyst powder in order to elucidate kinetic and thermodynamic limitations. Uptake of NO on a pre-oxidized catalyst reveals the existence of multiple regimes. The short-term storage is a sensitive function of storage time, but is nearly independent of temperature whereas the long-time storage has much slower kinetics and is a non-monotonic function of temperature. A simple steady-state reactor model is developed that predicts NO oxidation conversion and the limiting NO x storage. The model predicts that full barium utilization is thermodynamically feasible even under kinetically limiting conditions of incomplete NO oxidation. However, apparent NO x diffusion limitations prevent complete utilization. Storage and reduction (with propylene) experiments indicate that less than 10% of the barium is needed to achieve high NO x conversion (>85%) at moderate space velocity. At higher temperature both NO oxidation and barium nitrate formation are thermodynamically limited, both of which adversely impact the NO x reduction. Thermogravimetric measurements corroborate a physical picture in which only a small fraction of barium is utilized during lean/rich cycling protocols giving high NO x conversion.

Catalytic combustion in a reactor with periodic flow reversal. Part 2. Steady-state reactor model

Analysis of the reverse-flow reactor and comparison to a conventional adiabatic fixed bed reactor with external heat exchanger has shown that both systems are closely related. The required additional system parameter is the center of gravity of energy release caused by exothermic chemical reaction, which can also be rationalized as the mean fraction of the reverse-flow reactor acting as a regenerative heat exchanger. A simple steady-state countercurrent reactor model that is capable of describing the influence of adiabatic temperature rise and heat transfer properties of the fixed bed of catalyst on mean reactant conversion and temperature profile in cycle steady state is proposed. Generally, the agreement between calculated and experimentally determined parameters is satisfying. While discrepancies occur in the case of carbon monoxide oxidation, reactant conversion and maximum temperature as well as the minimum concentration for stable operation in cycle steady state are accurately predicted for the oxidation of propane.

97/03986 Catalytic combustion in a reactor with periodic flow reversal Part 2. Steady-state reactor model

97/03986 Catalytic combustion in a reactor with periodic flow reversal Part 2. Steady-state reactor model

Modelling and simulation of a deep well reactor for the wet air oxidation of sewage sludge

Mathematical models for simulating the VERTECH deep well reactor under steady-state and non-steady-state conditions are presented. The basic assumptions of the model involve parallel chemical reactions and multiphase heat and mass-transfer problems over the whole reactor length on the basis of a non-equilibrium thermodynamic state. After selecting the required model parameters from the literature, a steady-state reactor model has been constructed and the resulting differential equations solved by means of a special numerical iteration scheme. The simulation runs carried out demonstrate the feasibility of the process. Under steady-state conditions, COD can be reduced up to ca. 65%–90% at a bottom temperature of nearly 280 °C. The dynamic model has been developed in two steps of increasing accuracy. To investigate safety aspects, a failure of the jacket cooling system has been simulated successfully by means of a dynamic reaction zone model. As an extension, a more sophisticated dynamic model for the whole deep well reactor has been developed, based on the model assumptions of the steady-state reactor but for non-steady-state conditions. As an example of the reaction engineering power of this computer code, a reactor start-up phase realized in several consecutive steps has been simulated.

Distribution of Dissolved Iodine in the Irish Sea, a Temperate Shelf Sea

The distribution of iodine in the Irish Sea in the summer of 1977 is described in terms of iodate and total iodine, rationalized to a salinity of 35 (practical salinity scale). Both variables show a shorewards decrease, with the greatest depletions occurring in the shallower and stratified waters associated with the ledges (<50 m) that flank the sea. In the east of Liverpool Bay an interconversion of iodate without concomitant loss of total iodine is attributed to bacterial activity in the remnants of the Mersey plume. Phosphate and iodine concentrations in the more open, and deeper parts of the sea did not correlate well. Assuming the small scale of the temporal variation in the Menai Straits to be representative of the sea as a whole, it is suggested that the iodine system changes much more sluggishly than is indicated by other studies. Thus, the Irish Sea being an enclosed and 'shallow' shelf sea, is less prone to 'winter overturn' encountered on an open shelf. It thereby offers the possibility of longer periods of interaction between the iodine and biological systems. The possible future use of a steady-state reactor model is explored.

Reactor models for a series of continuous stirred tank reactors with a gas-liquid-solid leaching system: Part II. Gas-transfer control

This article is the second in a three-article series devoted to the development of comprehensive three-phase steady-state reactor models. In this article in particular, model equations are developed for the case of a leaching reactor operating under pure gas-transfer control. That is, the transfer of a gaseous reactant at the g-1 interface is considered to be the controlling step of the process rather than the particle dissolution reaction itself. For the derivation of the appropriate model equations, the gas-transfer capacity of the reactor is coupled with the particle dissolution kinetics. Two model versions are developed. In model version 1, the dissolved gas is assumed to be distributed equally among all particles. On the basis of this assumption, a gastransfer control-shrinking core model (GTC-SCM) equation is formulated which, along with the segregated flow model, helps to calculate the conversion of the solid phase. The size distribution of the particles at the exit of the reactor is computedvia a mass-particle size density (PSD) function derived with the use of the population balance model (PBM). In model version 2, the dissolved gas is assumed to be distributed among particles in proportion to their surface area. Using the PBM, equations are developed suitable for the calculation of the total specific surface area of the reacting solids and their conversion. Single as well as multiple parallel leaching reactions are considered in developing the two model versions.

Adaptive inferential control of packed-bed reactors

Three different estimators, i.e. Kalman filter, linear and nonlinear estimators, are presented to estimate the primary, unmeasured output. Control is accomplished using secondary measurements of temperature along the reactor length. Linear model estimators for product composition are found to perform poorly. Estimators based on nonlinear models of the plant are needed to accurately predict the composition. This is accomplished by a least-square curve fitting to match the observed data with the model and hence to estimate the input disturbances. Tests using some deliberately introduced plant/model mismatches indicate that the method is robust. In the second part of this paper, two distinct types of adaptive inferential control strategies for the single-input/single-output (SISO) system of the packed-bed reactor are investigated, i.e. the nonlinear inferential control, NLIC [the state feedback control (SFC) scheme] and the linear inferential control, LIC [the internal model control (IMC) scheme], to deal with the nonlinear and time-varying process control problems. The SFC scheme is developed by a nonlinear controller which is derived from the steady-state reactor model, and the IMC scheme by a linear controller which consists of an inverse of the transfer function of the process model and a filter with adjustable parameters. The basic structure of an adaptive inferential control system is coupled with a state estimator and an on-line parameter estimator. Here, we use a reduced-order, nonlinear process model to design the estimators and controller. Simulation results have shown that the performances of the SFC scheme are much better than those of the IMC scheme.

A model for a countercurrent gas—solid—solid trickle flow reactor for equilibrium reactions. The methanol synthesis

The theoretical background for a novel, countercurrent gas—solid—solid trickle flow reactor for equilibrium gas reactions is presented. A one-dimensional, steady-state reactor model is developed. The influence of the various process parameters on the reactor performance is discussed. The physical and chemical data used apply to the case of low-pressure methanol synthesis from CO and H 2 with an amorphous silica—alumina as the product adsorbent. Complete reactant conversion is attainable in a single-pass operation, so that a recycle loop for the non-converted reactants is superfluous. In the following article the installation and experiments for which this theory was developed will be described.