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Nowadays, reactor runaway is still a crucial phenomen from the safety viewpoint. About 120 scientific journal articles are published every year in the last decade in which thermal runaway is a keyword. The possible cause and consequences of reactor runaway are adressed where the worst case is the explosion of the reactor. Prevention steps to avoid the development of thermal runaway include the appropriate design of the reactor, the operation strategy and an early warning detection system. The available assessment methods for thermal risk analysis are addressed in detail. Reactor runaway criteria can indicate early the thermal runaway, which criteria are addressed in this review in detail under three classes: geometry-, sensitivity-, and stability-based runaway criteria. Operation strategy of semi-batch reactors can be designed by calculating Westerterp-diagram whose evolution is cleary presented. Significant works on the field of the reactor design, operation and reactor safety are collected and evaluated. Finally possible further research areas are suggested to improve our knowledge about thermal safety, such as investigating parameter uncertainty in runaway indication or optimize the safety actions to moderate the consequences of runaway.

The correct answer regarding which nonlinear optimization algorithm should we use for a given problem is that “it depends.” In this paper, we would like to add that “it depends, but use multiple programs whenever possible.” Here we consider 23 algorithms, implemented in MATLAB, evaluating their performance both on a lumped kinetic model for vacuum gas oil hydrocracking and a few-step kinetic model for ethane pyrolysis; the former particularly raised our interest as the kinetic parameters have no reference values in such models. We can use the results of such a study to estimate model variance; moreover, the statistical analysis of the identified minimum values can also quantify the parameter uncertainty. We can also identify key operating conditions where the applied kinetic model shows the highest sensitivity to the identified parameters, opening up the possibility to further reduce the uncertainty by targeting additional experimental work or by refining the identification problem.

Sonochemistry in combination with a combustion procedure was used to prepare superparamagnetic iron oxide nanoparticles. Two different iron precursors, ferrocene and iron(II)-acetate were dispersed...

It has been generally accepted for long that water molecules are integral parts of layered double hydroxides (LDHs). It is even thought that in the absence of water molecules, there is no LDH structure. It is shown in this contribution that via the solvolysis of Mg- or Ca-alkoxides and Al-alkoxide with methanol or propanol and co-precipitated in methanolic methoxide, water-free LDH-like structures could be constructed. These novel LDH-like materials proved to be more active and selective catalysts in a Knoevenagel condensation than the corresponding ‘classical’ LDHs.

Safe operation of thermally sensitive chemical reactors remains a crucial engineering issue. Thermal runaway occurs mainly due to loss of temperature control, and many chemical accidents initiated by thermal runaway can be foreseen by an appropriate analysis of thermal process data. Thermal runaway criteria can be applied to determine the onset of runaway phenomena and safety boundary diagrams can be constructed. However, several runaway criteria exist, which define the runaway-and safe zones differently. In this work nine commonly applied thermal runaway criteria were analyzed and compared based on their critical curves. As a result of this analysis, two new criteria were developed. Reliability of the derived criteria were investigated, where the occurrence of real runaway was determined based on the number of indications applying different criteria. The two new criteria were tested in three general reaction systems and in case a complex problem, where feeding trajectory of fed-batch reactor was optimized applying new criteria as non-linear constraint. One of the new criteria shows the highest reliability in indication of runaway development from all investigated runaway criteria.

With improving industrial chemical technologies Hazard and Operability Analysis (HAZOP) becomes more difficult to perform, because the technologies become more integrated and complex. It is more difficult to explore all hazard events due to the more frequent operating point transition. Therefore the experts’ work becomes more and more complicated, it takes a long time to analyze thoroughly a chemical technology with respect to process safety. Applying dynamic HAZOP can help the experts to explore all hazard situations in a technology based on dynamic process simulation, therefore a framework for exploring hazard events is suggested in this work. The proposed framework works via OPC (Open Platform Communication) connection between MATLAB and Aspen HYSYS dynamic process simulator. Based on the OPC connection data from Aspen HYSYS can be efficiently analyzed, moreover process optimization can be performed with a wide range of algorithms implemented in MATLAB. Applying the proposed framework different malfunctions can be preprogrammed and the effects of malfunctions can be analyzed automatically, hence the spending time of HAZOP can be shortened. Concentration of cumene-hydroperoxide (CHP) in vacuum distillation column is chosen as a case study to show how the framework can be applied to analyze process safety related situations. The malfunctions are generated through controller failures with significant changes in setpoints.

A green and facile method has been developed for the preparation of in situ immobilized gold nanoparticles (AuNPs) using agarose as a reducing and stabilizing agent. The size of the synthesized AuNPs ranges between 10 and 100 nm, and their average size can be controlled by the concentrations of the agarose and gold salt. The agarose matrix as a mild and green reaction medium can provide a good dispersion environment for forming AuNPs, and the hydrogel can be well homogenized with polyacrylic macroporous microbeads as well, which can adsorb and stabilize the particles leading to the simultaneous synthesis and immobilization of AuNPs avoiding harmful inorganic compounds or organic solvents. The supported gold nanocatalyst was successfully applied as a catalyst in packed bed reactors for efficient NaBH4-mediated reduction of p-nitrophenol in continuous-flow mode.

Biomass is of growing interest as a secondary energy source and can be converted to fuels with higher energy density especially by pyrolysis or gasification. Understanding the mechanism and the kinetics of biomass pyrolysis (thermal decomposition) and gasification (conversion of organic material to gases) could be the key to the design of industrial devices capable of processing vast amounts of biomass feedstock. In our work real product components obtained in pyrolysis were took into consideration as well as char and oil as lumped components, and the kinetic constants for a biomass model compound (cellulose) pyrolysis and gasification were identified based on a proposed simplified reaction mechanism within a compartment model structure. A laboratory scale reactor was used for the physical experiments containing consecutive fast pyrolysis and gasification stages using alkali metal (K) containing feedstock, which has a significant effect on the cellulose pyrolysis and gasification. The detailed model was implemented in MATLAB/Simulink environment, and the unknown kinetic parameters were identified based on experimental data. The model was validated based on measurement data, and a good agreement was found. Based on the validated first principle model the optimal parameters were determined as 0.15 mL/min steam flow rate, and 4% K content.

The biocomponent ratio in liquid fuels as well as the usage of renewable resources for fuel consumption in the transport sector needs to be increased as a result of EU directive 2003/30/EC. Based on radiocarbon (14C) measurements, it should be relatively simple and fast to measure the weight percentage of the fossil and biological sources by accelerator mass spectrometry (AMS) as recommended in the ASTM D 6866-12 and EN 16640 standards. In this study, a relatively easy and fast sample preparation and measurement method based on AMS measurements was developed at the Hertelendi Laboratory of Environmental Studies (HEKAL) using reference samples from the Hungarian MOL Nyrt. oil company. Considering the recent EU regulation for mixing rates of liquid fuels in the transport sector (0.7–2% biofuel content) and the projected higher rates (2–10% biofuel content), the method is applicable to determine fatty acid methyl ester (FAME) and/or hydrotreated vegetable oil (HVO) derived proportions of fuel blends with a 1σ uncertainty better than±0.3% m/m.

Pyrolysis of waste polymers looks an attractive way for their recycling as valuable hydrocarbons are produced that can be utilized as cleaner energy carriers or petrochemical feedstock. The lumping approach is often used to study the reaction kinetics of such complex systems as the high number of individual chemical species formed during pyrolysis and the several reactions that take place between them make the detailed kinetic modeling of the process often not feasible. Here we propose a two-step identification strategy, which requires no a priori knowledge regarding fast and slow reactions or the temperature dependence of the rate coefficients, to determine the kinetic parameters of pyrolysis and estimate product composition with the required precision using the discrete lumping method. Pyrolysis of a shredded real waste HDPE/PP/LDPE mixture was carried out previously in a laboratory scale two-stage reactor operated in batch mode. The process was investigated at different temperatures; both thermal and thermo-catalytic pyrolysis were studied, the latter on different types of zeolite-based catalysts. Our results indicate that with the suggested lumped model and kinetic identification strategy not only the experimental results can be reproduced but also the essential behavior of different catalysts can be explained. Furthermore, the two stages of the pyrolysis process have also been able to be differentiated. It can be stated that with the proper selection of pseudocomponents, the lumping approach is appropriate for catalyst evaluation and comparison as well, leading to a better understanding of the previous experimental results and the overall pyrolysis process. Hence, the results might also be used during process design or scale-up.

Nitrogen‐doped, bamboo‐like carbon nanotubes (BCNTs) were synthesized from butylamine by catalytic chemical vapor deposition (CCVD method). The nanotubes were oxidized by H2SO4/HNO3 treatment and used to prepare calcium alginate gelled BCNT spheres. These beads were first carbonized and then Pd, Rh and Ni nanoparticles were anchored on the surface of the spheres. These systems were then applied as catalysts in CO2 hydrogenation. The BCNT support was examined by Raman spectroscopy, dynamic light scattering (DLS) and X‐ray photoelectron spectroscopy (XPS). The prepared catalysts were characterized by HRTEM and SEM. The oxidation pretreatment of BCNTs was successful, with the electrokinetic potential of the water‐based dispersion of BCNTs measuring −59.9 mV, meaning the nanotube dispersion is stable. Pyridinic and graphitic types of incorporated nitrogen centers were identified in the structure of the nanotubes, according to the XPS measurements. The Pd‐containing BCNT sphere catalyst was the most efficient in the catalytic studies. The highest conversion was reached on the Pd catalyst at 723 K, as well as at 873 K. The difference in the formation rate of CO was much less at 873 K between the Pd and Rh compared to the 723 K values. Accordingly, the application of Pd‐containing BCNT/carbon‐supported catalyst favored the generation of CO. However, the Ni‐BCNT/carbon catalyst leads to the formation of CH4 as the major product.

In this work, we focus on the most crucial units in a chemical technology, the chemical reactors. Using a commercially available CFD software package, COMSOL Multiphysics, 3D mathematical models of a batch reactor with different impeller geometries have been investigated. The reasonable agreement between the experimental and simulation results indicates the validity of the developed CFD model. The effect of the impeller design, e. g. number of blades on the mixing efficiency is evaluated based on the simulation studies. The proposed measure to determine the energy efficiency of mixing (i. e. mixing index) is based on the calculated velocity field and energy usage. The information about the homogeneity of the mixed phase in the system can be extracted from the developed velocity field. Hence, we proposed histograms of velocity fluctuations on a logarithmic scale as an efficient tool to measure the achieved homogeneity of the phase in case of different impellers and rotational speeds.

Chlorine-free Platinum/nitrogen-doped graphene oxygen reduction reaction catalysts were synthesized by a one step method of annealing a mixture of platinum acetylacetonate and graphene oxide under ammonia atmosphere. Nanoparticles with close to the ideal particle size for oxygen reduction reaction (ORR) were formed, i.e., with diameter of 3–4 nm (500 and 600 °C) and 6 nm (700 °C). X-ray photoelectron spectroscopy confirmed the successful introduction of both pyridinic and pyrrolic type nitrogen moieties into the graphene layers, which indicates a strong interaction between the nanoparticles and the graphene layers. The electrocatalytic activity of glassy carbon electrodes (GCE) modified with the synthesized Pt/NG samples for oxygen reduction was compared to that of a platinum/carbon black catalyst modified electrode in acidic and alkaline media. Based on the measured limiting current densities and calculated electron transfer number, the highest activity was measured in acidic and alkaline media on the samples annealed at 600 and 700 °C, respectively.

Four Pd-Cu-based (2:1 wt.%) catalysts for water denitration, differing in physico-chemical characteristics and structural quality, were prepared, using carbon nanotubes (CNTs) as supports. The extent of lattice defects in the pristine CNTs turned out to govern resulting varieties of Pd nanoparticle size and the composition of the bimetallic (Pd:Cu) entities in the catalysts, playing an important role in nitrate reduction. Catalyst samples characterized by close proximity of Pd and Cu, as in an alloy, displayed the highest degree of nitrate conversion. At the same time, the size of the Pd particles, alone, or decorated to different extents with Cu atoms, was found to be critical for the second step of denitration reaction, directing the formed nitrite to either N2 or NH3. Water denitration is a structure sensitive reaction related to Pd particle size, and this effect is further emphasized in the decoration of the particle by the incorporation of Cu atoms into Pd particle corners and edges.

Alternative methods, including green synthetic approaches for the preparation of various types of nanoparticles are important to maintain sustainable development. Extracellular or intracellular extracts of fungi are perfect candidates for the synthesis of metal nanoparticles due to the scalability and cost efficiency of fungal growth even on industrial scale. There are several methods and techniques that use fungi-originated fractions for synthesis of gold nanoparticles. However, there is less knowledge about the drawbacks and limitations of these techniques. Additionally, identification of components that play key roles in the synthesis is challenging. Here we show and compare the results of three different approaches for the synthesis of gold nanoparticles using either the extracellular fraction, the autolysate of the fungi or the intracellular fraction of 29 thermophilic fungi. We observed the formation of nanoparticles with different sizes (ranging between 6 nm and 40 nm) and size distributions (with standard deviations ranging between 30% and 70%) depending on the fungi strain and experimental conditions. We found by using ultracentrifugal filtration technique that the size of reducing agents is less than 3 kDa and the size of molecules that can efficiently stabilize nanoparticles is greater than 3 kDa.

In the search for stable, visible light active photoelectrodes, hydrothermally synthesized tungsten oxide nanowires were modified via nitrogen incorporation into their structure. To this end, nanowires were heat-treated in ammonia/nitrogen atmosphere at different temperatures. This procedure caused transitions in their structure that were investigated along with the photoelectrochemical properties of the samples. Results were subsequently compared to the reference samples treated in inert nitrogen atmosphere. Morphological changes and structural transitions were followed by transmission and scanning electron microscopy and X-ray diffraction. Bandgap energies were determined from the UV–vis spectra of the materials, while photoelectrochemical properties were tested by linear sweep photovoltammetry and electrochemical impedance spectroscopy. Pristine tungsten oxide nanowires were first transformed into tungsten oxynitride and then tungsten nitride during high-temperature calcination in ammonia atmosphere. Electron microscopic investigation revealed that, along with phase transition, the initial fibrous morphology gradually converted into nanosheets. Simultaneously, bandgap energies significantly decreased in the calcination process, too. Photoelectrochemical measurements demonstrated that photoactivity in the treated samples was not improved by the decrease of the bandgap. This behavior might be explained with the deterioration of charge carrier transport properties of the materials due to the increased number of structural defects (acting as trap states), and current ongoing work aims to verify this notion.

The so-called “lumping approach” is widely used to study complex processes such as hydrocracking of vacuum residue. In order to describe the composition changes in such systems, not only must the kinetic parameters be determined, but the lumped reactions that occur should also be identified. In this study, the modeling of catalytic hydrocracking of vacuum gas oil has been carried out using six component lumps. Three different identification strategies have been developed to determine the reaction subnetwork containing a given number of reaction pathways that provides the data fit. The strategies were compared according to their tendency to provide increasingly better results, as a function of the number of reactions present. Although, in this way, 40% of the original reaction superstructure was eliminated from the system, the kinetic parameters of the remaining reactions still could not be identified with complete certainty. Hence, the linearized state-space model representations of the reaction networks ...

Scrubbing of hydrocarbon-based gases such as natural gas or biogas is essential prior to its use. These gas mixtures when contaminated with hydrogen sulfide cause safety, environmental, and corrosion problems in pipelines. There are several methods of reducing the content of hydrogen sulfide in sour gases, but few of these are selective as well. Selectivity is important to avoid unnecessary chemical usage. Chemisorption in sodium hydroxide solution by applying a special spray technique appears to be an efficient and selective method for hydrogen sulfide removal. This study aims to determine the characteristic of system and thereby facilitating the design of gas-cleaning parameters. The studied parameters include the contact time, concentration of sodium hydroxide, absorbent volumetric flow rate, and gas composition. Model gas mixtures of hydrogen sulfide, carbon dioxide, and nitrogen were used for experiments. To define the optimal experiment setup, the Box–Behnken design (BBD) method was applied. Based o...

Heterocatalytic oxidation of HCl into Cl2 (HCl conversion process) over a CeO2–CuO catalyst in a fixed-bed reactor has been optimized using four different objective functions and three different methods. For a given residence time, the HCl conversion could be maximized in various reactor configurations, namely with the application of a graded catalyst bed, with partitioning the reactor shell and using multistage temperature control, or with the combination of both methods. However, as the obtained temperature profiles differed considerably from each other, we considered three objective functions in order to smooth the reactor temperature profile. These implement a nonconventional approach since the proposed objective functions aim to deal directly with the temperature changes and HCl conversion is only taken into consideration as a nonlinear constraint. The different results from each method and objective function were compared using the apparent temperature gradients along the length of the reactor. The ...

Boron doped titanate nanoparticles were prepared from protonated (H-form) titanate nanotubes (TiONT) and nanowires (TiONW). The chemical nature and morphology of boron were monitored by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and transmission electron microscopy (TEM). XPS proved that significant part of the boron incorporated into interstitial position (Ti O B) of titanate nanotubes and nanowires, while a smaller part of the boron formed boron titanates via ion-exchange process. In the case of titanate nanotubes the presence of boron induced morphological (tubular to rod-like) and structural (trititanate to anatase) changes. These effects were not so pronounced on titanate nanowires.

Surface modification of the halloysite-10 A mineral with tubular morphology can be achieved by slightly modified procedures developed for the delamination of kaolinite minerals. The resulting delaminated halloysite nanoparticles have unexpected surface/morphological properties that display, new potentials in catalyst development. In this work, a four-step intercalation/delamination procedure is described for the preparation of thin-walled nanoscrolls from the multi-layered hydrated halloysite mineral that consists of (1) intercalation of halloysite with potassium acetate, (2) replacement intercalation with ethylene glycol, (3) replacement intercalation with hexylamine, and (4) delamination with toluene. The intercalation steps were followed by X-ray diffraction, transmission electron microscopy, N 2 adsorption-desorption, thermogravimetry, and infrared spectroscopy. Delamination eliminated the crystalline order and the crystallite size along the ‘ c ’-axis, increased the specific surface area, greatly decreased the thickness of the mineral tubes to a monolayer, and shifted the pore diameter toward the micropore region. Unexpectedly, the removal of residual organics from intercalation steps adsorbed at the nanoscroll surface with a peroxide treatment resulted in partial recovery of crystallinity and increase of crystallite size along the ‘ c ’-crystal direction. The d(001) value showed a diffuse pattern at 7.4–7.7 A due to the rearrangement of the thin-walled nanoscrolls toward the initial tubular morphology of the dehydrated halloysite-7 A mineral.

Process engineers and operators should understand reactor runaway phenomenon to avoid hazard situations and accidents. Reactor runaway occurs when an exothermic reaction takes place in a reactor with insufficient heat transfer area. The reaction rate increases due to the temperature rise, causing a further increase in reaction rate and temperature. Without any safety action, only the reactant consumption limits the maximum temperature. One of the safety actions can be the application of runaway criteria to characterize the safe operating regimes where the optimal operating conditions can be found. This paper presents runaway criteria and the application of these in case of the feeding trajectory optimization of a fed-batch reactor model. The most important runaway criteria and the relations between them are presented, and critical curves of criteria are calculated using a simple dimensionless tubular reactor. The optimal feeding trajectory is determined in case a pilot plant fed-batch reactor using different runaway criteria as a non-linear constraint based on particle swarm optimization and sequential quadratic programming. Designers need to know how they can choose the right criterion, and the results can help with it. Selectivity and profit can be decreased if runaway occurs in a fed-batch reactor, therefore it is important to deal with this problem.

Recently, there has been an increasing interest in the application of nanotubular structures for drug delivery. There are several promising results with carbon nanotubes, however, in light of some toxicity issues, the search for alternative materials has come into focus. The objective of the present study was to investigate the influence of the applied solvent on the composite formation of titanate nanotubes (TNTs) with various drugs in order to improve their pharmacokinetics, such as solubility, stability, and bioavailability. Composites were formed by the dissolution of atenolol (ATN) and hydrochlorothiazide (HCT) in ethanol, methanol, 0.01 M hydrochloric acid or in ethanol, 1M sodium hydroxide, dimethylformamide (DMF), dimethyl sulfoxide (DMSO), respectively, and then they were mixed with a suspension of TNTs under sonication for 30 min and vacuum-dried for 24 h. The structural properties of composites were characterized by SEM, TEM, FT-IR, differential scanning calorimetry (DSC), thermogravimetric (TG) analysis, and optical contact angle (OCA) measurements. Drug release was determined from the fast disintegrating tablets using a dissolution tester coupled with a UV&ndash, Vis spectrometer. The results revealed that not only the good solubility of the drug in the applied solvent, but also the high volatility of the solvent, is necessary for an optimal composite-formation process.

Catalytic systems prepared by controlled processes play an important role in the utilization of CO2 via catalytic hydrogenation to produce useful C1 chemicals (such as CO, CH4 and CH3OH), which will be vital for forthcoming applications in energy conversion and storage. Size controlled Pt nanoparticles were prepared by a polyol method and deposited on H-ZSM-5 (SiO2/Al2O3 = 30, 50, 80 and 280) zeolite supports. The prepared catalysts were tested for the CO2 hydrogenation in the temperature range of T = 473–873 K and ambient pressure, with CO2/H2 = 1:4. Size-controlled Pt nanoparticles boosted the catalytic activity of the pure H-ZSM-5 zeolites resulted in ~16 times higher CO2 consumption rate. The activity were ~4 times higher and CH4 selectivity at 873 K was ~12 times higher over 0.5 % Pt/ H-ZSM-5 (SiO2/Al2O3 = 30) compared to 0.5 % Pt/H-ZSM-5 (SiO2/Al2O3 = 280). In situ DRIFTS studies assuming the presence of a surface comlex in which the CO is perturbed by hydrogen and adsorbes via C-end on Pt but the oxygen tilts to the protons of the zeolite support.

The current article aims to study the influence of pH, temperature, and oxidant concentrations on the dissolution process of metals from liquid crystal display (LCD) boards in a Na2S2O8 environment...

Extremely high specific surface area mesoporous carbon-supported Pd nanoparticle catalysts were prepared with both impregnation and polyol-based sol methods. The silica template used for the synthesis of mesoporous carbon was removed by both NaOH and HF etching. Pd/mesoporous carbon catalysts synthesized with the impregnation method has as high specific surface area as 2250 m 2 /g. In case of NaOH-etched impregnated samples, the turnover frequency of cyclohexene hydrogenation to cyclohexane at 313 K was obtained ~ 14 molecules ∙ site − 1 ∙ s − 1 . The specific surface area of HF-etched samples was higher compared to NaOH-etched samples. However, catalytic activity was ~ 3–6 times higher on NaOH-etched samples compared to HF-etched samples, which can be attributed to the presence of sodium and surface hydroxylgroups of the catalysts etched with NaOH solution.

In this work, the mixing efficiency is studied in case of different multibore nozzle constructions in a pretreatment part of a continuous reactor. Computational Fluid Dynamics (CFD) is used to model the multijet mixer, and design of the nozzle is carried out by simulation studies. The simulation model is validated by residence time experiments performed in a laboratory device with the same spatial scale as in the industrial case. The aim of the study is to find the most effective nozzle design out of some limited number of physically realizable constructions considering predefined mixing metrics. Poincare maps are prepared by a particle tracking study, and the derived mixing maps are introduced to give a first impression about the quality of mixing. According to the quantified results, the nozzle with 6 bores angled at 23 degrees is proposed as the optimal construction, which reduces the volume of the dead zones and increases the mixing efficiency, providing a proper pretreatment of the inlet stream for the consequent reactor unit.

Fossil materials are widely used raw materials in polymerization processes, hence, in many cases, the primary goal of green and sustainable technologies is to replace them with renewables. An exciting and promising technology from this aspect is the isocyanate-free polyurethane production using vegetable oil as a raw material. Functional compounds can be formed by the epoxidation of vegetable oils in three reaction steps: epoxidation, carbonation, and aminolysis. In the case of vegetable oil carbonation, the material properties vary strongly, with the composition affecting the solubility of CO2 in the reaction mixture. Many attempts have been made to model these interactions, but they generally do not account for the changes in the material properties in terms of spatial coordinates. A 2D CFD model based on the combination of the k-&epsilon, turbulence model and component mass balances considering the spatial inhomogeneities on the performance of the reactor was created. After the evaluation of the mesh independence study, the simulator was used to calculate the carbonation reaction in a transient analysis with spatial coordinate-dependent density and viscosity changes. The model parameters (height-dependent mass transfer parameters and boundary flux parameters) were identified based on one physical experiment, and a set of 15 experiments were used for model validation. With the validated model, the optimal operating temperature, pressure, and catalyst concentration was proposed.

Exothermic reactions are often performed in SBR because the generated reaction heat can be more easily kept under control in such construction. However, an unsuitable control system can lead to the development of thermal runaway, which may cause lethal damage. NMPC with implemented thermal runaway criteria is a promising tool to operate SBRs. However, engineers should always consider plant-model mismatch because uncertain predictions can cause undesirable scenarios. A novel control framework is proposed to operate SBRs and consists of NMPC with the implemented runaway criterion, extended Kalman filter and parameter identification algorithm. Both Multi-Stage NMPC and NMPC with the worst-case scenario are investigated and tested in terms of ability to handle parameter uncertainty. The former is 38 times slower than the latter with no noticeable increase in reactor performance. NMPC initialized based on the worst-case scenario with updating uncertain kinetic parameters results in a promising control structure for SBRs.

In this paper, we consider a lumped reaction network developed for studying the pyrolysis of real plastic waste carried out in a laboratory-scale two-stage batch reactor, with the primary intention of recovering valuable fuel components. Generally, the kinetic parameters of the reaction network, whether it is a lumped or detailed one, might correlate to some extent directly through the amounts of products to be formed. If the formation of two or more products has a strong correlation, we might even combine the corresponding reactions to reduce the size of the reaction network. This modeling step instinctively occurs when we have thousands of reactions, but it is usually not carried out in the case of a lumped model because of its elementary nature. Yet, in this work, we would like to show that taking the correlations between the formations of the pseudocomponents into consideration very much has its advantages. We show that these correlations can be utilized to increase the number of lumps included in the model, increasing its accuracy by applying some not so complicated structural modifications to the original model. This way, we can optimize the structure of the lumped reaction network so that we can capture the characteristics of the measurement rather efficiently without using an overcomplicated reaction model full of uncertain parameters.

International audience; Pyrolysis of waste polymers looks attractive way for their transforming into valuable hydrocarbons. Due to the high number of reactions, the detailed kinetic modeling of the pyrolysis process is often not feasible. Hence the so-called lumping technique is often used to study these complex systems. In this study, the pyrolysis reactions were modeled in a two stage laboratory scale batch reactor using five component lumps. For pyrolysis the mixtures of real plastic waste were used. Kinetic parameters were identified and the model results were compared to the experimental results. It was found that the suggested model can properly describe the dynamic behavior of the reactor under semi batch conditions.

Recycling of waste electrical and electronic equipment (WEEE) is important not only to reduce the amount of waste requiring treatment, but also to promote the recovery of valuable materials. Implementation of the European Directive on WEEE and recycling targets imposed in the European Union will require new processes to be developed and applied to recover metals from WEEE. This study aims to provide an alternative process for the dissolution of metals from WEEE which contains Cu and Zn based on our previous research. The effects of leaching parameters, such as temperature, Na2S2O8 concentration, and leaching time, were separately investigated on leaching of copper, zinc, and brass (alloy composition −35% zinc and 65% copper) in Na2S2O8 solution (0.1, 0.2 and 0.3 M). Box–Behnken experimental design (BBD) method was used to determine the number and the condition of necessary leaching experiments. Statistical analysis of variance (ANOVA) was performed to see whether process parameters such as leaching time, ...

In case of complex chemical systems in that many reactions occur between high numbers of species, it is often necessary to use some form of lumping in order to obtain a simpler kinetic model whose parameters can actually be determined from the available data. Designing a lumped reaction network, however, involves dealing with great degrees of freedom. One has to define the actual pseudocomponents, the reactions that take place in the system and finally, reliable kinetic parameters have to be identified for these reactions. This often results in high uncertainties regarding these kinetic models as well as in their limited usability in carrying out experimental design or other process engineering tasks. This point of interest is more often not get discussed than it is. The key idea of this paper is that the uncertainty of lumped kinetic models can be significantly diminished by reducing the size of the reaction network while also preserving the ability of the model to describe the observed behavior of the given system. To that end, we applied and evaluated five different global sensitivity analysis methods based on their performance, using the case studies of real plastic waste pyrolysis and vacuum gas oil hydrocracking. We point out that these tools can be effectively used to construct lumped reaction networks with fewer parameters to be estimated with narrower confidence intervals.