Reactor Process Research Articles

The quest for down scale representativeness: how to exploit CFD to design a shear study for vaccines

In this work, we exploit computational fluid dynamics (CFD) to evaluate stirred tank reactor (STR) process engineer parameters (PEP) and design a scale-down system (SDS) to be representative of the formulation and filling process steps for an Aluminum adjuvanted vaccine drug product (DP). To study the shear history in the SDS we used the concept of number of passages, combined with an appropriate stirring speed down scale strategy comprising of either (i) tip speed equivalence, widely used as a scale-up criterion for a shear-sensitive product, or (ii) rotating shear, a shear metric introduced by Metz and Otto in 1957 but never used as scaling criterion. The outcome of the CFD simulations shows that the tip equivalence generates a worst-case SDS in terms of shear, whereas the rotating shear scaling approach could be used to design a more representative SDS. We monitored the trend over time for “In Vitro Relative Potency” as DP Critical Quality Attribute for both scaling approaches, which highlighted the crucial role of choosing the appropriate scaling-down approach to be representative of the manufacturing scale during process characterization studies.

Cultivation of phosphate-accumulating biofilm: Study of the effects of acyl-homoserine lactones (AHLs) and cyclic dimeric guanosine monophosphate (c-di-GMP) on the formation of biofilm and the enhancement of phosphate metabolism capacity

This study investigated the mechanisms of microbial growth and metabolism during biofilm cultivation in the biofilm sequencing batch reactor (BSBR) process for phosphate (P) enrichment. The results showed that the sludge discharge was key to biofilm growth, as it terminated the competition for carbon (C) source between the nascent biofilm and the activated sludge. For the tested reactor, after the sludge discharge on 18 d, P metabolism and C source utilization improved significantly, and the biofilm grew rapidly. The P concentration of the recovery liquid reached up to 157.08 mg/L, which was sufficient for further P recovery via mineralization. Meta-omics methods were used to analyze metabolic pathways and functional genes in microbial growth during biofilm cultivation. It appeared that the sludge discharge activated the key genes of P metabolism and inhibited the key genes of C metabolism, which strengthened the polyphosphate-accumulating metabolism (PAM) as a result. The sludge discharge not only changed the types of polyphosphate-accumulating organisms (PAOs) but also promoted the growth of dominant PAOs. Before the sludge discharge, the necessary metabolic abilities that were spread among different microorganisms gradually concentrated into a small number of PAOs, and after the sludge discharge, they further concentrated into Candidatus_Contendobacter (P3) and Candidatus_Accumulibacter (P17). The messenger molecule C-di-GMP, produced mostly by P3 and P17, facilitated P enrichment by regulating cellular P and C metabolism. The glycogen-accumulating organism (GAO) Candidatus_Competibacter secreted N-Acyl homoserine lactones (AHLs), which stimulated the secretion of protein in extracellular polymeric substances (EPS), thus promoting the adhesion of microorganisms to biofilm and improving P metabolism via EPS-based P adsorption. Under the combined action of the dominant GAOs and PAOs, AHLs and C-di-GMP mediated QS to promote biofilm development and P enrichment. The research provides theoretical support for the cultivation of biofilm and its wider application.

Mass yields of products and composition of syngas from pyrolysis of Brazilian plastic solid wastes: Combustion simulation and burner design to minimize COx and CxHy emissions

For the first time, the mass yields of products and the composition of synthesis gas (syngas) from pyrolysis of Brazilian plastic solid waste were evaluated for a reactor processing 20 g of plastic at 800 °C. Combustion of the syngas was simulated, evaluating the levels of COx and CxHy emissions, and a burner was designed to minimize emissions during combustion. The main findings highlighted the importance of performing thermogravimetric analyses of waste materials. Higher thermal degradation temperatures (530–900 °C) were obtained for all the plastics, compared to values reported in the literature (300–600 °C). Between 46.7 and 98.0 wt% of syngas was produced, with lower heating values ranging from 10390 to 45684 kJ kg−1, due to differences between the plastics in the fractions of inorganic and hydrocarbon gases produced. The maximum temperatures for syngas combustion, simulated using ANSYS software, were 2000 and 800 °C inside the burner and combustion chamber, respectively. In the burner, higher COx and CxHy levels were related to the syngas composition and incomplete chemical reactions in the flame zone. The CO and CxHy levels decreased towards the combustion chamber, where CO2 was less than 8 wt%, in compliance with the CONAMA 316/2002 regulation.

A Numerical Case Study of Particle Flow and Solar Radiation Transfer in a Compound Parabolic Concentrator (CPC) Photocatalytic Reactor for Hydrogen Production

Compound parabolic concentrator (CPC) photocatalytic reactors are commonly used for photocatalytic water splitting in hydrogen production. This study aimed to gain a better understanding of the physical processes in CPC photocatalytic reactors and provide theoretical support for their design, optimization, and operation. The analysis involved the ray tracing approach, Euler–Euler two-fluid model, and discrete ordinates method (DOM) to study solar radiation transfer and particle flow in the reactor. The distribution of solar radiation on the receiving tube’s surface after CPC concentration was obtained by conducting the ray tracing approach. This solar radiation distribution was then coupled into the Euler–Euler two-fluid model to solve for the natural convection flow field, the temperature field, and particle phase volume fraction distribution inside the receiving tube over a period of 120 s. Lastly, the discrete ordinates method (DOM) was used to analyze the transfer of radiation inside the receiving tube at different times, obtaining the distribution of local volume radiative power absorption (LVRPA) and the total radiative power absorption (TRPA) inside the tube. The results showed that the TRPA reached its maximum at 120 s, accounting for 66.61% of the incident solar UV radiation. According to the above results, it could be suggested that adopting an intermittent operation mode in CPC photocatalytic reactors is reasonable and efficient.

REACTOR SECTION PRESSURE CONTROL AT DIESEL HYDROTREATING UNIT

Diesel Hydrotreating Units (DHUs) are essential components within petroleum refineries, playing a critical role in the production of clean and high-quality diesel fuel. This abstract provides a comprehensive overview of the mechanisms, necessity, and operational significance of DHUs in the refining process. Firstly, the abstract discusses the fundamental principles underlying the operation of DHUs. The catalytic hydrotreating process is elucidated, highlighting the role of hydrogenation reactions in the removal of sulfur, nitrogen, and aromatic compounds from diesel feedstocks. The synergy between catalysts and hydrogen gas in promoting desulfurization, denitrification, and hydrodenitrogenation reactions is examined, emphasizing the pivotal role of DHUs in enhancing the environmental and performance attributes of diesel fuel. Furthermore, the abstract addresses the imperative need for Diesel Hydrotreating Units. The detrimental impacts of sulfur-containing compounds, such as sulfur oxides (SOx), on air quality and human health are discussed, underscoring the regulatory mandates aimed at reducing sulfur emissions from diesel fuel. DHUs emerge as indispensable tools for compliance with stringent environmental regulations, ensuring the production of low-sulfur diesel fuel that meets or exceeds regulatory standards. Moreover, the abstract emphasizes the operational significance of DHUs within petroleum refineries. Through the integration of advanced reactor designs, catalyst technologies, and process optimization strategies, DHUs enable refineries to achieve efficient desulfurization and meet production targets while minimizing energy consumption and operational costs. The adaptability of DHUs to varying feedstock compositions and processing conditions further underscores their versatility and importance in the refining industry. In conclusion, this abstract provides a comprehensive overview of Diesel Hydrotreating Units, elucidating their mechanisms, necessity, and operational significance in the production of clean and high-quality diesel fuel. By facilitating the removal of sulfur and other impurities from diesel feedstocks. Keywords: Diesel Hydrotreatment Unit, Control Systems, Petrochemical Industry, Efficiency, Safety.

Anammox process in anaerobic baffled biofilm reactors with columnar packings: Characteristics of flow field and microbial community

The enrichment of anammox bacteria is a key issue in the application of anammox processes. A new type of reactor － anaerobic baffle biofilm reactor (ABBR) developed from anaerobic baffle reactor (ABR) was filled with columnar packings and established for effective enrichment of anammox bacteria. The flow field analysis showed that, compared with ABR, ABBR narrowed the dead zone so as to improve the substrate transferring performances. Two ABBRs with different types of columnar packings (Packings 1 and Packings 2) were constructed to culture anammox biofilms. Packings 1 consisted of the single-form honeycomb carriers while Packings 2 was modular composite packings consisting of non-woven fabric and honeycomb carriers. The effects of different types of columnar packings on microbial community and nitrogen removal were studied. The ABBR filled with Packings 2 had a higher retention rate of biomass than the ABBR filled with Packings 1, making the anammox start-up period be shortened by 21.28%. The enrichment of anammox bacteria were achieved and the dominant anammox bacteria were Candidatus Brocadia in both R1 and R2. However, there were four genera of anammox bacteria in R2 and one genus of anammox bacteria in R1, and the cell density of anammox bacteria in R2 was 95% higher than that in R1. R2 has the advantage of maintaining excellent and stable nitrogen removal performance at high nitrogen loading rate. The results revealed that the packings composed of two types of carriers may have a better enrichment effect on anammox bacteria. This study is of great significance for the rapid enrichment of anammox bacteria and the technical promotion of anammox process.

Гетерофазные явления при фракционировании трития в водных системах

Tritium is the only one of the radioactive isotopes that a filtering system is unable to neutralize. It is produced by collateral fission processes in nuclear reactors and displays itself in radioactive wastes and effluents in different forms of tritium oxides. Thus the development and application of nuclear energy entails a challenging problem of treating tritium-containing radioactive wastewater. The paper deals with tritium water isotopologues, namely, with prototritium water and deuterotritium water. Various approaches to the problem of tritium separation have been outlined. The choice of the appropriate process of water detritiation depends, first of all, on whether the detritiated water is recycled back to the reactor system or is discharged to the environment and on whether molecular tritium is to be extracted for further application. Special attention is paid to the process of electrosonochemical water detritiation which is shown to be the preferential one due to its ability to provide molecular tritium. Tritiated water decomposition should be preceded by its concentrating, the latter being two-stage and including water conditioning followed by providing concentrated tritiated water. Reverse-osmosis conditioning and salt rectification are considered as preferential techniques.

The transformative role of Computational Fluid Dynamics (CFD) in chemical engineering

Chemical engineering is a discipline intrinsically linked to fluid behavior. From reaction kinetics to reactor design, understanding how fluids flow, mix, and transfer heat is paramount. Traditionally, this relied heavily on experimentation, a time-consuming and resource-intensive process. The emergence of Computational Fluid Dynamics (CFD) has revolutionized the field, offering a powerful in-silico approach to analyze fluid dynamics in chemical engineering processes. This review paper explores the transformative role of CFD, examining its impact on various aspects of chemical engineering, including reactor design, optimization, process intensification, scale-up, and safety analysis. The paper also discusses the challenges associated with CFD simulations, ongoing advancements in the field, and potential future directions.

CFD simulation and water model experiments with overflow-type supergravity reactor set up for continuously removing inclusions from aluminum melt

In this work, an overflow-type supergravity reactor has been tested for removal of inclusions from aluminum melt. A combination of numerical and physical simulations was employed to investigate the continuous separation process of recycled aluminum melt and inclusions, with a focus on evaluating the effects of reactor structures, process parameters, and inclusion characteristics on the inclusion separation efficiency. The results of numerical simulation indicate that the inclusion separation efficiency is positively related to overflow pipe length (L), overflow pipe installation height (H), gravity coefficient (G), inclusion density (ρ) and inclusion diameter (d), and negatively related to overflow pipe diameter (Φ) and melt inflow rate (Q). The overflow-type supergravity reactor exhibited excellent performance in separating inclusions from recycled aluminum melt. Under the conditions of L = 40 mm, H = 108 mm, Φ = 10 mm, G = 500, and Q = 0.5 kg/s, the separation efficiency of 18 μm Al2O3 inclusions reached nearly 100 %. The high consistency between the results of numerical and physical simulations provided full verification of the reliability and accuracy of the numerical simulation.

Improving the rigor and reproducibility of catalyst testing and evaluation in the laboratory

Experimental testing and evaluation of catalysts in reactors is a central feature of fundamental catalysis science and reaction engineering. Measurements must be reproducible and interpretable to provide evidence for mechanistic studies or structure–function relationships, or to yield robust and intrinsically meaningful parameters to enable reactor scale-up and process development. Consequently, catalysis practitioners should seek to plan and perform catalyst testing in a manner that distinguishes between the intrinsic chemical kinetics governed by the catalyst and hydrodynamic, transport, and deactivation processes introduced by the form of the catalyst, the reactor vessel, and the nature of the contacting fluid. We highlight the importance of clear testing procedures for both the individual practitioner and the catalysis community and then discuss the sources and methods to address key sources of artifacts in catalyst testing. We organize sections in the form of questions practitioners should ask themselves when planning a catalyst testing campaign. This article references the original literature but also recasts the catalyst testing procedure in the form of a workflow diagram and illustrated depictions of the control experiments implemented within our laboratories to minimize the occurrence of artifacts. The content reflects our collective knowledge in the design, set up, and use of laboratory scale reactors for catalyst testing.

OXIDATION OF CO WITH THE PARTICIPATION OF ALUMINUM-COPPER-CHROME OXIDE CATALYSTS IN A BED REACTOR

Bed reactors are critical components widely used in industrial processes. Because these reactors often operate under heavy workloads, they face high power and durability requirements.re However, heavy workloads and continuous use can lead to deterioration of the material properties of the reactor. The most important of these problems is the accumulation of carbon monoxide (CO) in the structural components of the reducer. CO is a toxic gas released into the atmosphere as a byproduct of industrial processes. Controlling this gas is important for both environmental and occupational health and safety. In this context, ensuring CO oxidation in fluidized bed reactors is an important area of research to both increase energy efficiency and reduce environmental impacts. This work aims to investigate the catalytic effects of aluminum, copper and chromium to enhance CO oxidation in hot bed reactors. Understanding the effect of incorporating catalytic materials on CO oxidation kinetics will be an important step towards improving reactor stability and performance. The research aims to contribute to a more sustainable and efficient use of fluidized bed reactors in industrial processes. A unique aspect of the study is to systematically investigate the effect of aluminum, copper and chromium on the CO oxidation process in reactors. It should be noted that the results obtained for this purpose are important in terms of their use and potential effects in industrial applications. This research aims to help make industrial processes more sustainable and environmentally friendly by filling the knowledge gaps related to CO control and oxidation in fluidized bed reactors. Keywords: hot-bed reactor, carbon monoxide, oxidation, copper, chromium, aluminum, catalytic effects.

The anaerobic exposure time (AET) as a novel process parameter in the anaerobic side-stream reactor (ASSR)-based process for excess sludge minimization

Minimization of excess sludge produced by wastewater treatment plants has become a topical theme nowadays. One of the most used approaches to achieve this aim is the anaerobic side-stream reactor (ASSR) process. This is considered affected by the hydraulic retention time (HRT) of the anaerobic reactor, the anaerobic sludge loading rate (ASLR) and the sludge interchange ratio (SIR), although, studies available in the literature did not reflect a clear relationship with the sludge minimization yields.To overcome this, a novel parameter namely anaerobic exposure time (AET) was defined and related to reduction of the observed yield coefficient (Yobs) in a lab-scale plant implementing the ASSR process. Furthermore, the AET was validated by performing a detailed and thorough review of previous literature. Excess sludge production was successfully reduced (10–60 %) with the increase of the AET (7.9–13 h/d), although maintaining the same HRT in the ASSR and a constant sludge interchange ratio (SIR) (100 %). A strong correlation (Pearson = 0.763) was found between the AET, and the Yobs reduction reported in previous studies, also indicating a linear relationship (R2 = 0.92) between these parameters. Contrarily, the correlation between the Yobs with the ASLR and the ASSR-HRT resulted moderate (Pearson = 0.186) or weak (Pearson=−0.346), respectively. Overall, while operating at low AET (< 6 h), maintenance and uncoupling metabolism were found the main sludge reduction mechanisms. Increasing the AET (>8 h) favoured the occurrence of extracellular polymeric substances (EPS) hydrolysis and endogenous decay mechanisms, which improved excess sludge reduction. To conclude, the AET could be considered a reliable parameter to be used for design or control purposes for the ASSR-based process.

Research on plasma modified fly ash denitration

The effects of reactor parameters and process parameters on the denitration rate of modified fly ash in different gas atmospheres were studied by using a dielectric barrier plasma reactor and using orthogonal experiments. The characteristics of modified fly ash were analyzed using scanning electron microscope, specific surface area analyzer, X-ray diffraction, Boehm titration and Fourier transform infrared spectroscopy. The experimental data were processed by variance analysis and linear regression to induce the denitration mechanism. R2 of the linear regression analysis model is 0.789, which means that the adsorption pore size, acid groups and basic group can explain 78.9% of the change in denitration rate. The basic group will have a significant positive impact on the denitration rate, and the adsorption pore size and acidic group will have a significant negative impact on the denitration rate. Through variance analysis of the experimental data, it was found that the input power and discharge gap have a significant effect on the denitration rate, but the ionization time and discharge length have no significant effect. The input power affects the denitration rate by impacting the basic group, and the discharge gap affects the denitration rate by influencing the adsorption pore size. There are three denitration mechanisms on the surface of fly ash: physical adsorption, chemical adsorption and absorption process. Among them, chemical adsorption is the main mechanism of action, accounting for approximately 60.86%.

Field-Scale Testing of a High-Efficiency Membrane Reactor (MR)-Adsorptive Reactor (AR) Process for H2 Generation and Pre-Combustion CO2 Capture.

The study objective was to field-validate the technical feasibility of a membrane- and adsorption-enhanced water gas shift reaction process employing a carbon molecular sieve membrane (CMSM)-based membrane reactor (MR) followed by an adsorptive reactor (AR) for pre-combustion CO2 capture. The project was carried out in two different phases. In Phase I, the field-scale experimental MR-AR system was designed and constructed, the membranes, and adsorbents were prepared, and the unit was tested with simulated syngas to validate functionality. In Phase II, the unit was installed at the test site, field-tested using real syngas, and a technoeconomic analysis (TEA) of the technology was completed. All project milestones were met. Specifically, (i) high-performance CMSMs were prepared meeting the target H2 permeance (>1 m3/(m2.hbar) and H2/CO selectivity of >80 at temperatures of up to 300 °C and pressures of up to 25 bar with a <10% performance decline over the testing period; (ii) pelletized adsorbents were prepared for use in relevant conditions (250 °C < T < 450 °C, pressures up to 25 bar) with a working capacity of >2.5 wt.% and an attrition rate of <0.2; (iii) TEA showed that the MR-AR technology met the CO2 capture goals of 95% CO2 purity at a cost of electricity (COE) 30% less than baseline approaches.

Enhancing disinfection and microcontaminant removal by coupling LED driven UVC and UVA/photo-Fenton processes in continuous flow reactors

For the first time, the sequential combination of UVC-LED (276 nm) and photo-Fenton/UVA-LED (376 nm) process has been assessed in continuous flow mode for wastewater reclamation according to the new European Regulation for reuse in agricultural irrigation (EU 2020/741). The results show that it is possible to obtain water quality class B (Escherichia coli ≤ 100 CFU/100 mL) by UVC-LED irradiation alone, operating the system with a hydraulic residence time (HRT) of 6.5 min and liquid depth of 5 cm in the case of secondary effluents with low Escherichia coli load (8.102–3.1.103 CFU/100 mL). As for high bacteria concentrations (1.2–4.2.104 CFU/100 mL), HRTs longer than 30 min are required. The bacterial load has not influenced decontamination, removing 18 ± 4 % of microcontaminants. Coupling the UVC (30-min HRT and 5.0 cm liquid depth) and the UVA/photo-Fenton (60-min and 15-cm liquid depth) systems allows 58 ± 4 % of real organic microcontaminants to be removed, in addition to achieving water quality class B.

Core-shell equivalent reactor network model to bridging CFD and process simulations of a fluidized bed reactor

Equivalent reactor network (ERN) is expected to narrow the gap between the computational fluid dynamics (CFD) and process simulations of a fluidized bed reactor (FBR). In view of this, a novel CFD-based core–shell ERN framework is proposed, where the core compartment is represented by a variable cross-section PFR (vPFR) and shell zones are simulated by CSTRs. The CFD simulation indicates that the gas phase flow in a propane dehydrogenation (PDH) FBR deviates significantly from the ideal plug-flow. The developed core–shell ERN is reliable to reproduce the non-ideal flow. With the process model integrating the core–shell ERN, the PDH reactor performance and process efficiency are evaluated. Process defects are found mainly in the heat exchange section because of the largest lost work (i.e., 45.34 %) and lowest second-law efficiency (i.e., 20.75 %). Overall, the core–shell ERN is capable of bridging CFD and process simulations of an FBR and detecting process weakness.

Dislocations/Defects analysis in III-V nitrides - a cost effective MOCVD epitaxy solution

In present paper an innovative technique to reproduce the epitaxial growth results through lateral flow metal organic chemical vapor deposition (MOCVD) reactor process at atomistic scale is reported. It includes the equivalent MOCVD reactor geometry architecture of AIXTRON 200/4 RF-S horizontal flow reactor. The gas- and surface phase chemical reaction kinetics and thermodynamics are given due consideration in the present study without use of any continuum or fluid dynamics models. The optimum conditions are extracted by running design of experiments over TNL-EpiGrow simulator to achieve high crystalline quality aluminum nitride (AlN) films over Si (111) substrate. The impact of variation in precursor NH3 flow rates and carrier gas N2 pressure are used to predict the conditions to optimize the improved morphology and quality of the AlN films. The defects densities are characterized in terms of vacancies and dislocation densities. The roughness and lattice parameters are extracted. The growth rates obtained in present studies are compared against reported the similar experiments. The excellent agreement is observed between experimental and simulated results. The dislocation densities in grown samples are also found in good agreement with the similar experimental reported densities in each sample.

Simulation assisted process simplification and energy recovery from a cryptic biological nutrient removal plant

In this study, simulation-based analysis is conducted for nitrogen removal mechanism in a biological nutrient removal plant designed in an encrypted manner. In the first phase, the simulation study elucidates how nitrogen removal occurs in a complex design using a series of 4 carousel bioreactors with additional nitrate recycle. It is demonstrated that pre-anoxic volume fed with limited internal recirculation only would not be sufficient to meet the discharge Total Nitrogen (TN) limit of 10 mg N/L. However, the addition of simultaneous nitrification-denitrification (SND) processes in aerobic reactors enables compliance with TN discharge limits. In the second phase, the configuration is simplified by means of process simulation, where the complex design is streamlined by eliminating internal recycle while achieving nitrogen removal through the SND process. Plant data confirmed that the simplified configuration can achieve nitrogen removal providing the same discharge quality. The simulations resulted that TN concentration achieved at the plant effluent is comparable, while effluent total phosphorus concentration is decreased by approximately 50 % due to increased activity of Phosphorus Accumulating Organisms (PAOs) under reduced sludge retention time (SRT). In the third phase, the application of the SND process in the field using a simplified and new activated sludge configuration yields similar results to the simulation. According to plant records, 28 % energy savings and an equivalent chemical cost reduction of €945,000 per year were achieved with the new process configuration.

Development of automated metabolite control using mid-infrared probe for bioprocesses and vaccine manufacturing.

Intelligent digital control systems using continuous in-line metabolite data enabled end-to-end automation of fed-batch processes in stirred-tank reactors.

Essential aspects of the CFD software modelling of biomass gasification processes in downdraft reactors.

Mathematical modelling and simulation of gasification processes are increasingly used in the scientific field. This review explores the application of computational fluid dynamics (CFD) in modeling biomass gasification processes in downdraft gasifiers. It discusses the different types of gasification agents used, the composition of syngas, and key operational parameters influencing the process. The review then delves into the aspects of CFD modeling, focusing on the implementation of sub-models within ANSYS fluent software. The limitations of the existing literature are addressed, and strategies for enhancing downdraft gasifier performance are proposed to facilitate successful commercialization.