Reactor Exit Research Articles

Simulation analysis of gas-solid two-phase flow and reaction in a novel catalytic cracking reactor

A gas-solid two-phase flow reaction model was developed to evaluate the performance of a novel catalytic cracking reactor in the residue-to-chemicals (RTC) process. Coupled TFM, EMMS drag, and 12-lump kinetic models were employed to simulate the flow reaction process. The reaction temperature and product yields at the reactor exit aligned well with real industrial RTC reactor test results, indicating the reliability and effectiveness of the coupling model. Catalyst particles formed an internal circulation structure in the reactor, increasing the instantaneous catalyst-to-oil ratio. The reactor exhibited low axial and radial temperature gradients with higher reaction temperatures, accelerating the catalytic cracking rate and enhancing the selectivity for high-value products. The effects of the catalyst-to-oil ratio, catalyst inlet temperature, and feedstock mass flow rate on the flow reaction process were optimized. Results showed that both the catalyst-to-oil ratio and catalyst inlet temperature influenced the overall catalyst velocity distribution. Within the limit range, increasing the catalyst-to-oil ratio increased feedstock conversion, gasoline, LPG, dry gas, and coke yields, but decreased diesel yield. Conversely, increasing the feedstock mass flow rate showed opposite trends. Different trends in product yields were observed with varying inlet catalyst temperatures, with optimal product distribution at 973.15 K.

Predicting nickel catalyst deactivation in biogas steam and dry reforming for hydrogen production using machine learning

This study employs Random Forests (RF) and Artificial Neural Networks (ANN) to model the transient behavior of Ni catalyst deactivation during steam and dry reforming of model biogas containing H2S, with a focus on hydrogen production. Deactivation, induced by carbon deposition and sulfur poisoning, is a complex and transient phenomenon demanding precise kinetic mechanisms for accurately predicting Ni catalyst behavior in biogas reforming. Black-box machine learning (ML) models are developed, incorporating catalyst properties, biogas composition, and operating conditions. Encompassing both dry and steam reforming, the ML models aim to predict catalyst behavior, expressed in terms of packed bed reactor exit mole fractions (H2, CO, CH4, and CO2) and conversions (CH4 and CO2). The ML models are trained and tested across a temperature range of 700–900 C with 0–145 ppm of H2S in model biogas (CH4/CO2 ratio varying from 1.0 to 2.0). RF outperforms the ANN across all performance metrics, including overall R2 and root mean squared error (RMSE). The RF achieves a mean overall R2 of 0.979, with training and testing RMSE equal to 6.7×10−3 and 1.47×10−2 respectively. In contrast, the ANN achieves a mean overall R2 of 0.939, with training and testing RMSE equal to 2.6×10−2 and 2.55×10−2 respectively. Moreover, pre-trained RF models are validated with unseen data of dry reforming of biogas containing 30 ppm of H2S (25 data points). It is suggested that 35 % of this unseen experimental data is required to train the RF model for it to predict catalyst deactivation, achieving a validation R sufficiently2> 0.9. The mean overall R2 values attained by the RF fine-tuned on 35 % of the unseen experiment data for both CH4 and CO2 conversions, as well as for all mole fraction predictions, are 0.952 and 0.948, respectively.

A multi-index evaluation method of supercritical CO2 Brayton cycle for nuclear power plants design

ABSTRACT This paper investigated four different S-CO2 Brayton cycle layouts for nuclear energy conversion: simple recuperation cycle (SR), recompression cycle (RC), re-heating cycle (RH), and intercooling cycle (IC). We compared these S-CO2 Brayton cycle schemes for nuclear energy conversion using the G1+TOPSIS multi-index evaluation method. The evaluation results of different schemes based on their safety, thermodynamics, techno-economic and compactness are given. The results show that for Generation IV reactors with the same designed thermal power, the thermodynamic performance of the S-CO2 system is better for higher reactor exit temperature. Among the schemes, the gas-cooled fast reactor (GFR)+RC scheme has the highest thermal efficiency (47.4%) and exergy efficiency (56.48%). The GFR+IC scheme has the lowest specific cost (1861.3$/W) and the internal rate of return (24.8%). The re-heating cycle (RH) has worse indexes, but it requires the lowest initial investment cost. The intercooling cycle (IC) has the lowest levelized cost of electricity (0.0134 $/KW•h) coupling to GFR. Considering all indexes of four aspects, the reactor’s performance ranking is MSR>LFR>SFR>GFR, and the S-CO2 system's performance ranking is RC>SR>IC>RH. For Generation IV nuclear energy conversion technologies, the molten salt reactor (MSR)+RC scheme should be given priority, while GFR+RH schemes should be carefully considered.

Modeling and Parameter Tuning for Continuous Catalytic Reforming of Naphtha in an Industrial Reactor System

A two-dimensional mathematical model was developed to simulate naphtha reforming in a series of three industrial continuous catalytic regeneration (CCR) reactors. Discretization of the resulting partial differential equations (PDEs) in the vertical direction and a coordinate transformation in the radial direction were performed to make the model solvable using Aspen Custom Modeler. A sensitivity-based parameter subset selection method was employed to identify the most influential parameters within the model. Tuning of 8 out of 180 parameters was used to ensure that model predictions match experimental data from one steady-state run. The updated parameter values improved the model fit to the data, reducing the weighted least-squares objective function for parameter estimation by 73%. The proposed model was used to predict reactor temperatures, catalyst coke weight fraction at the exit of the third reactor, and benzene flowrate from the outlet of the third reactor. The simulation results demonstrated a good agreement between the simulated values and the industrial measurements. Finally, the reactor model was utilized to explore the effects of changes in inlet temperatures and inlet level of catalyst deactivation, providing valuable insights for identifying desirable operational conditions that will improve the overall efficiency of the CCR process.

A computational-fluid-dynamics model for particle-size evolution in the presence of turbulent mixing

A computational model for the simulation of the particle-size evolution of nanoparticles in mixing-controlled processes is presented. This model accounts for the effect of molecular mixing on particle-size evolution when mixing time scales are smaller than the phase-space time scales. The approach is formulated by deriving evolution equations for the moments of joint mixture fraction-size moments PDF, and closing such moment equations using the conditional quadrature method of moments. A test case consisting of a mixing-dependent aggregation problem in a multi-inlet vortex reactor is considered. The results accounting for the correlation between mixture fraction and size moments are compared against those computed neglecting such correlation to demonstrate its impact on the model predictions. The average particle volumes are different in the order of 104mm3 at the reactor exit under the studied conditions.

Ammonia generation in Ns pulse and Ns pulse/RF discharges over a catalytic surface

Plasma-catalytic ammonia synthesis in a ns pulse discharge and a ‘hybrid’ ns pulse/RF discharge in plane-to-plane geometry is studied by Fourier Transform infrared absorption spectroscopy. The data are taken in a preheated H2–N2 mixture, with and without Ni/γ-Al2O3 or Co/γ-Al2O3 catalyst placed in the discharge section. The measurement results are taken using two different approaches. The first is a ‘single-stage’ process, where a ns pulse discharge in the H2–N2 mixture is sustained continuously. In this case, the ammonia yield increases slowly, over a period of tens of minutes. The second is a ‘two-stage’ process, where the catalyst is first activated by the ns pulse discharge sustained in pure nitrogen, and then the activated catalyst is exposed to the H2–N2 flow, with or without the discharge. In this case, a strong overshoot of the NH3 number density at the reactor exit is detected, by over a factor of two compared to the single-stage process. After the initial overshoot, the ammonia yield gradually decreases to the ‘single stage’ value (with the discharge on), or to near zero (with the discharge off). The results demonstrate that the ammonia yield in the plasma-catalytic reactor is controlled by the N atom accumulation on the catalyst surface, which reacts with H atoms thermally dissociated on the catalyst or generated in the plasma. The results also show that the plasma-catalytic ammonia yield is significantly higher compared to that in the ns pulse discharge without the catalyst. The accumulation of H atoms on the catalyst, with their subsequent reactions with N atoms generated in the plasma, is of relatively minor importance at the present conditions. An additional series of measurements was made with a sub-breakdown RF waveform overlapped with the ns pulse discharge train, to enhance the vibrational excitation of nitrogen. The ammonia yield measured with the RF waveform added is approximately 20% higher compared to that at the baseline ns pulse discharge conditions, both with and without the catalyst. This effect is weaker compared to that of the catalyst activation by N atoms. Additional data are necessary to isolate the possible effect of the vibrationally excited N2 molecules on the ammonia synthesis in the plasma catalytic reactions.

Assessing the feasibility of a downstream heterogeneous Fenton process for the oxidative degradation of biologically treated ranitidine, diclofenac, and simvastatin

This work assesses the feasibility of coupling the heterogeneous Fenton process to biologically treated domestic sewage to remove diclofenac, ranitidine, and simvastatin (50 µg L−1 each). The catalyst was a purified natural zeolite, which was impregnated with iron (2Fe4A). First, batch tests (10 g L−1 catalyst, 2 g L−1 H2O2, and pH 7) were performed to gather information about the performance of the process. Simvastatin could not be significantly removed as its molecular dimensions were larger than the zeolite pores. Drugs removal by adsorption and mineralization were not observed. After five cycles of 30 h each, leached iron was approximately 2%, with no significant change in the drugs removal performance. Second, a fixed-bed reactor packed with 2Fe4A was placed after the exit of the biological reactor, with hydraulic retention time of 12 min. 98 and 82% of diclofenac and ranitidine, respectively, were removed, as well as 93% of the added hydrogen peroxide. The coupled system was stable for, at least, 10 days. The operating cost of the heterogeneous Fenton process combined to the biological one was estimated and, although diclofenac and ranitidine could be significantly removed in a short period of time, it was concluded that it is a relatively expensive process that has the disadvantages of high hydrogen peroxide consumption and size exclusion effects.

Experimental investigation of CaO/Ca(OH)2 for thermochemical energy storage – commissioning of a 0.5 kWh experimental setup

Thermochemical energy storage using the material system CaO/Ca(OH)2 and fluidized bed technology is currently becoming more interesting for applications at 400 °C - 600 °C. This work presents a new, unique setup for examining the material and process characteristics in a size relevant for a scale-up. It is specifically designed to enable time-efficient, high-throughput experiments into the long-term cyclisation of CaO/Ca(OH)2 and its production reaction from CaCO3 at precisely adjustable reaction conditions over the entire cyclisation process. The cylindrical reactor has a fluidized bed volume of 1.8 L (9.5 L total volume) with a height to diameter ratio of up to 4. This enables batch sizes of up to 1 kg Ca(OH)2, equal to a storage capacity of 0.5 kWh. Nitrogen or steam are used as fluidizing medium, enabling fluidization velocities of up to 0.3 m/s. Process conditions of up to 800 °C and 4 bar are possible in the reaction zone. To extend the range of analytics on the setup, a system is installed to allow measurements of the differential pressures between the windbox, reaction zone, freeboard and reactor exit and numerous temperatures in the reactor. A blowback system is installed to the off-gas filtration system. First experimental investigations using CaCO3 with a particle size of 250 µm - 400 µm as initial material show promising results in terms of performing the calcination reaction at 700 °C - 750 °C and successive cyclisation of the produced CaO in a pure steam atmosphere. Up to 40.5 storage cycles were achieved with no detectable loss in fluidization quality. The development of the particle size distribution throughout the storage cycles shows a discontinuous but steady increase of fines within the fluidized bed that is accompanied by entrainment of the fines.

Modeling and estimating kinetic parameters for CO2 methanation from fixed bed reactor experiments

AbstractCO2 methanation, which converts CO2 and hydrogen into methane as fuel, is one of the promising candidates for the development of CO2 utilization technologies. Recently, a highly active catalyst made of Ni/ZrO2 for methanation has been developed, and is currently investigated as a potential use in a high‐performance reactor. However, design of reactor must be carried out carefully, since this reaction is highly exothermic, which may cause reactor runaway and deterioration of catalysts. For this problem, a mathematical model that can predict the behavior inside the reactor is necessary. In this work, we consider the methanation reaction of CO2 in a reactor model and estimate the kinetic parameters in the reaction rate model from experimental data. In the parameter estimation using literature values and Tikhonov regularization, eight kinetic parameters in the rate equations were identified from 64 data points with a wide range of conditions. We confirm that molar fractions at the reactor exit predicted by this reactor model are in good agreement with the experimental results. Furthermore, the developed model was validated to predict the compositions and temperature that were not used in the estimation. We expect the developed model will be a powerful tool for the reactor design.

Hydrogen production via solid waste gasification with subsequent amine-based carbon dioxide removal using Aspen Plus

This simulation study presents the municipal solid waste gasification, along with a detailed design of CO2 capturing unit using monoethanolamine (solvent). The gasifier's operational parameters, such as pressure, temperature, and equivalence ratio, are chosen to optimize the gasified H2-enriched product stream. At optimal operational parameters, such as temperature (800 °C), pressure (1 bar), and equivalence ratio (0.2), a maximum H2 content of 27.9% could be attained. Following that, 39.5% H2 is found at the high-temperature shift reactor's exit, followed by 42.1% at the low-temperature shift reactor's output. It is observed that the absorber (16.5 m) and stripper (6 m) packing heights are required to capture 95% CO2 from the product effluent obtained after shift reactors, along with column diameters of 2.70 and 3.61 m, respectively. Hence, the proposed model can give vital information for large-scale gasifier and CO2 capture unit design, operation, and optimization with respect to different flue gases.

Removal of brilliant green tannery dye by electrocoagulation

• Bright green dye (BG) removal from tannery wastewater by electrocoagulation (EC). • Continuous up-flow parallel plate EC reactor with 1018 steel plates as electrodes. • Decolorization and COD removal reached values up to 100% and 96%, respectively. • Best conditions were 6 mA cm −2 and 0.69 cm s −1 giving overall cost of 0.193 USD m −3 . • The removal of BG occurs by adsorption on iron oxyhydroxides flocs. This paper deals with the removal of brilliant green (BG) tannery dye from synthetically prepared water (chemical oxygen demand 660 ≤ COD ≤ 2065 mg L −1 , in 6000 mg L −1 C l - at pH 6.0) by electrocoagulation (EC) using a continuous up-flow parallel plate EC reactor. The reactor employed two 1018 steel plates as sacrificial electrodes. The influence of flocculation time (15 ≤ τ f ≤ 35 min) on the dye removal efficiency was examined, using a jar test coupled to the exit of the EC reactor. The effect of hydrodynamics, in terms of mean linear flow rate and Reynolds number (0.69 ≤ u ≤ 3.47 cm s −1 and 72 ≤ Re ≤ 362), and current density, applied to the EC reactor, and the initial BG dye concentration on the elimination of color and COD was systematically analyzed. The range of Reynolds numbers studied in the EC reactor obeys a laminar flow, Re <2100. Laminar flow pattern allows the initial floc growth to occur orderly within the EC reactor. The decolorization and COD removal reached values up to 100% and 86%, respectively, at j = 6 mA cm −2 and u = 0.69 cm s −1 ( Re = 72), giving electrolytic energy consumption and overall operating cost of 0.077 kWh m −3 (0.134 kWh (kg COD) −1 ) and of 0.193 USD m −3 (0.34 USD (kg COD) −1 ), respectively. XRD, XRF-EDS, SEM, FTIR, and OEA analysis of the dried flocs indicated the removal of BG by adsorption on iron oxyhydroxides flocs.

A continuum model for heat and mass transfer in moving-bed reactors for thermochemical energy storage

In this work, a continuum heat and mass transfer model coupling transport phenomena and high-temperature thermochemical reactions is developed for stationary packed-bed and counter-flow moving-bed reactors. After presenting the general modeling framework, we focus on the 2D axisymmetric version of the model for which validation is conducted with experimental results for a packed-bed reactor in the literature for manganese-iron oxide reduction/oxidation and an in-house counter-flow moving-bed reactor for magnesium-manganese oxide reduction up to 1450 °C. Transient simulation results including the local distributions of gas/solid temperatures, oxygen concentration and the extent of reaction, as well as the various energy flow components and energy conversion efficiencies are reported. The results based on the 2D axisymmetric model are also compared with those obtained from a previous 1D model. The comparison shows that capturing the radial variation is critical in reactor modeling and the 2D results demonstrate improved agreement with experiments. Specifically, large temperature variations along the radial direction are observed especially in the reaction zone; this non-uniform radial temperature distribution has a significant effect on the chemical reaction extent due to its strong dependence on temperature; and the overall oxygen concentration at the reactor exit and the predicted system efficiency are slightly lower in the 2D model compared to the 1D model. The present heat and mass transfer model can provide valuable insights into reactor design, scale-up, and operating conditions selection to maximize system energy storage efficiency.

A PRELIMINARY EXPERIMENTAL INVESTIGATION INTO AMMONIA OXIDATION IN A FIXED-BED

This paper reports the findings of a preliminary experimental investigation into NH3 oxidation in a quartz fixed-bed reactor. The reactor was filled with quartz sand of a size fraction of 1.0 ~ 2.0 mm to a bed height of 430 mm. NH3 and O2 were diluted with Ar, mixed and passed through the reactor at a constant total gas flowrate of 818 mL·min-1. The experiments were carried out at various reaction temperatures between 700 and 1450 K, corresponding to residence times ranging from 0.68 to 2.07 s and equivalence ratios of 0.5, 1.0, and 1.5. The reactor exit stream was sampled and analysed using a gas chromatograph (Shimadzu 2014) and an electrochemical analyser (Testo 340) for the concentrations of N2, O2, NO, and NO2. A set of comparative experiments without bed material (considered as an ‘empty bed reactor’) at identical residence times were also performed in order to appreciate the effect of quartz surface on NH3 oxidation and NOx formation. It was revealed that the lowest temperature to initiate noticeable NH3 oxidation was reduced from 1300-1350 K in the empty bed reactor, to 1050-1350 K in the quartz sand filled fixed-bed reactor. The presence of quartz sand significantly reduced NOx formation during NH3 oxidation. Additionally, the peak NO concentrations and the temperature to reach the peak were reduced from 578 to 191 ppm and ~1350 to ~1050 K, respectively. It is speculated that the active radicals such as NH* produced from the heterogeneous decomposition reaction of NH3 on the quartz surface may have promoted NH3 oxidation and NOx reduction.

Nickel-based alumina supported catalysts for dry reforming of biogas in the absence and the presence of H2S: Effect of manganese incorporation

In this study, the effects of manganese incorporation on the activity of nickel-based sol-gel alumina-supported catalysts in the dry reforming of biogas were investigated in the absence and the presence of H2S. This article presents new information on reactions using gas mixtures of H2S, CO2, and CH4. Characterization studies were performed to explain catalyst performance during activity tests using XRD, N2 adsorption/desorption, XPS, DRIFTS, TGA/DTA, and SEM/EDX techniques. N2 adsorption/desorption and XRD studies showed that synthesized catalysts have a mesoporous structure with metallic nickel and γ-Al2O3 phases. Activity tests of the catalysts were performed in a tubular reactor at 750 °C and 1 atm in the absence and the presence of H2S (2 ppm and 50 ppm). Alumina-supported Ni, and Ni-Mn catalysts showed stable activity during dry reforming of biogas reaction in the absence of H2S. Mn incorporation decreased the activity of Ni-based catalysts in terms of CH4 conversion; however, it increased its activity in terms of CO2 conversion due to enhancement of reverse water gas shift reaction. In the catalytic activity tests performed in the presence of 2 ppm H2S, the activity of mono and bimetallic catalysts decreased slightly with reaction time. In order to explain the effect of H2S in the feed stream on the catalytic activity for dry reforming, reaction tests were performed with different gas mixtures, namely: H2S + He, H2S + CO2 + He, and H2S + CO2 + CH4 + He. In that case, the reactor exit stream was analyzed by an online FTIR spectrometer. In reaction tests, different sulfur components, such as H2S, COS, S, SO2, and H2O were observed by FTIR analyses. In the case of the presence of H2S in the feed stream, the formation of COS and H2O were predominantly observed. Mn incorporation did not enhance the sulfur resistance of Ni catalyst due to the formation of sulfate on the catalyst surface.

Modelling and Dynamic Simulation of One-Dimensional Isothermal Axial Dispersion Tubular Reactors with Power Law and Langmuir-Hinshelwood-Hougen Watson Kinetics

In this paper, the modelling, numerical lumping and simulation of the dynamics of one-dimensional, isothermal axial dispersion tubular reactors for single, irreversible reactions with Power Law (PL) and Langmuir-Hinshelwood-Hougen-Watson (LHHW)-type kinetics are presented. For the PL-type kinetics, first-order and second-order reactions are considered, while Michaelis-Menten and ethylene hydrogenation or enzyme substrate-inhibited reactions are considered for the LHHW-type kinetics. The partial differential equations (PDEs) developed for the one-dimensional, isothermal axial dispersion tubular reactors with both the PL and LHHW-type kinetics are lumped to ordinary differential equations (ODEs) using the global orthogonal collocation technique. For the nominal design/operating parameters considered, using only 3 or 4 collocation points, are found to adequately simulate the dynamic response of the systems. On the other hand, simulations over a range of the design/operating parameters require between 5 to 7 collocations points for better results, especially as the Peclet number for mass transfer is increased from the nominal value to 100. The orthogonal collocation models are used to carry out parametric studies of the dynamic response behaviours of the one-dimensional, isothermal axial dispersion tubular reactors for the four reaction kinetics. For each of the four types of reaction kinetics considered, graphical plots are presented to show the effects of the inlet feed concentration, Peclet number for mass transfer and the Damköhler number on the reactor exit concentration dynamics to step-change in the inlet feed concentration. The internal dynamics of the linear (or linearized) systems are examined by computing the eigenvalues of the linear (or linearized) lumped orthogonal collocation models. The relatively small order of the lumped orthogonal collocation dynamic models make them attractive and useful for dynamic resilience analysis and control system analysis/design studies.

Synthesis of freestanding few-layer graphene in microwave plasma: The role of oxygen

We systematically studied the role of oxygen in gas-phase synthesis of graphene in atmospheric hydrocarbon-fed microwave plasmas. Oxygen is introduced through the use of alcohols, and mixtures of ethylene and water. These reactants were contrasted with oxygen-free hydrocarbon reactants, including ethylene and toluene. Solid materials were collected at the plasma reactor exit and characterized. Gas-phase temperature and key species concentrations were measured using in situ Fourier-transform infrared absorption and emission spectroscopy inside the reactors. Ethanol resulted in pure few-layer graphene formation, in agreement with previous studies. In contrast, ethylene fed at the same flow rate produced a mixture of carbon allotropes. A shift towards graphene formation is observed when water is added to ethylene, or when the flow rate of ethylene is cut to half. Simulations suggest that reactants undergo rapid chemical reactions in the plasma front and the mixture composition in and immediately after the plasma is in chemical equilibrium. The primary factor that controls graphene growth appears to be the total amount of carbon available in the growth region. Oxygen, through CO formation, modulates the amount of acetylene and other growth species, while other factors require further study.

Reactor Model of Counter-Current Continuous Catalyst-Regenerative Reforming Process toward Real Time Optimization

A new kinetic model involving 44 lumped pseudocomponents and 70 reactions for catalytic reforming was developed to satisfy real-time optimization of the commercial counter-current continuous catalyst-regenerative reforming units. The reaction kinetic model was constructed with the equation oriented method, using the orthogonal collocation method to transform the differential equations of the kinetic model into algebraic equations with variables. The sequential quadratic programming method is used to solve the equation oriented model in this study. The validation results showed that the good agreement of material compositions and catalyst coke content at the exit of the fourth reactor, as well as the temperature and pressure at the exit of each reactor, was obtained between simulated values and industrial values. Moreover, the reactor kinetic model is also used to predict the influence of process parameters which is consistent with the trend in actual industrial production. The model makes it possible to find optimal conditions in real-time optimization.

Kinetic study and Modeling of heavy Naphtha Catalytic Reforming process in AL-Daura Refinery

In the present work, kinetics and modeling of heavy naphtha catalytic reforming process in Al-Daura refinery-Midland refineries Company were studied. A proposed reaction scheme involving (15 pseudo components) connected together by a network of 30 reactions for components in the C6-C8+ range have been modeled. In the present work, kinetics and modeling of heavy naphtha catalytic reforming process in AL-Daura refinery-Midland refineries Company were studied. A proposed reaction scheme involving (15 pseudo components) connected together by a network of 30 reactions for components in the C6-C8+ range have been modeled. The proposed model has been solved numerically using the 4th order Runge–Kutta approach. Alteration of components and temperature, with time and reactor length was evaluated. Results showed that the rate of formation of aromatics is becoming slower as the reactants proceed to the third reactor. The catalytic reaction rates in the reformer are well represented by the Hougen-Watson Langmur-Hinshelwood (HWLH) type form. The deactivation of catalyst causes the reactor behavior to continue changing over a longer period of time. This clearly seems to pay off in the scenario where coke deposition plays such a major role. It was also found that the rate of coke formation increases with the progress from first to the last bed, so keeping a decreasing inlet temperature profile from first to the last bed would lead to more uniform coke content in each bed. The production rate of reformate has a negative impact on the octane number. Temperature drop across the first reactor (~ 45oC) is larger than the temperature drops across the other two reactors (10-12oC). This could be related to the endothermic reaction rate which is faster in the first reactor. The results show that perfect agreement of temperatures, compositions, and fractions molar flow rate at the exit of the third reactor is obtained between predicted values and industrial values.This confirmed the reliability of the present model.

Structural optimization of baffle internals for fast particle pyrolysis in a downer reactor using the discrete element method

Abstract The structural optimization of baffle internals for fast pyrolysis of coal with particulate mixing and heat transfer in a downer reactor using the discrete element method (DEM) has been investigated in this research. The pyrolysis terminal temperature at the exit of the downer reactor is not only decided by the volume-feeding-rate ratio of the coal to the sand, but also is affected by the inner structural design of the baffle internals in the downer reactor. As presented in the previous publication of the author, the inhibition from the baffle internals in a downer reactor can improve the particulate-mixing degree and heat carrier, and increase the mean residence time of the coal and heat-carrier particles in the downer reactor. The structure of the baffle internals in the downer reactor mentioned in this research can be optimized by the independently developed 3D soft-sphere model of the DEM programme of a 40-mm baffle length, a 30° baffle-slope angle and at least four baffles designed in the downer reactor, which is beneficial for the process design of coal pyrolysis with a heat carrier in the downer reactor.

Using excitation-emission matrix fluorescence to evaluate the performance of water treatment plants for dissolved organic matter removal

This study is aimed at assessing the performance of water treatment plants (both wastewater and drinking water treatment plants) for dissolved organic matter (DOM) removal using excitation-emission matrix fluorescence (EEMF) as the monitoring technique.The influent from the wastewater treatment plant (WWTP) of Burgos (Spain) is characterized from the presence of protein-like peaks (T1 and T2) and humic-like peaks (A and C), T2 and A showing the highest fluorescence intensity. The percentages of total removal in the effluent were in the following order: peak T1 (65%) > peak A (45%) > peak C (34%) > peak T2 (26%). The humic-like peaks were the most removed at the primary sedimentation stage, whereas peak T1 was by far the most removed in the biological reactor. Protein-like peaks T1 and T2 experienced a slight increase in the final effluent in comparison to their fluorescence at the previous stage (the exit of the biological reactor), an increase that can be explained by the release of SMP (soluble microbial products) from the biomass in the secondary clarifier. A poor correlation was obtained between peak T2 fluorescence and COD, BOD (r2 = 0.34–0.38).The natural water from the Úzquiza reservoir in Burgos (Spain) is characterized by the only presence of humic substances: a majority peak A (fulvic-like) and a weak peak C (humic-like). The whole fluorescent DOM was removed by coagulation-flocculation but a low fluorescence peak T2 appeared at the final stage, coming from protein-like SMPs released by the biomass attached to the filters.