Reactor Zone Research Articles

Characteristics and kinetics of in-situ catalytic cracking of biomass tar in a micro dual bed reactor

This research introduces a novel micro dual bed reactor, combining rapid pyrolysis in a top-down with a fluidized bed for biomass tar catalytic cracking assessment. The study initially examines the impact of reactor zones on biomass pyrolysis, followed by an exploration of thermal and catalytic cracking behaviors of in-situ biomass tars using three fluidizing media. It delves into the generation of cracking gas and tar cracking reaction kinetics, based on the evolutionary trends of the gas. The process involves two distinct stages (S1 and S2). In S1, olivine shows the highest tar conversion rates at 650 °C and 750 °C, while char peaks at 850 °C. In S2, char leads in conversion rate and reaction time, with a preference for CO and H2. Tar conversion rates at high temperatures follow the order char > olivine > sand, and reaction times vary as olivine > sand > char. Temperature affects tar cracking rates due to thermal and catalytic effects interplay. This study applies an integral method to solve the kinetics under varying conditions, providing insights into tar behaviors during both thermal and catalytic cracking. These findings support designing and optimizing tar removal units in biomass gasification, potentially reducing tar production and enhancing gas quality.

Syngas Purpose Pyrolysis-Gasification of Organic Fractions of MSW over Metal-Loaded Y-Zeolite Catalysts

The increasing environmental consideration and the growth of instability of the energy market call for methods that can process the organic fraction of municipal solid waste (OFMSW) into fuel instead of disposal. Due to the pyrolysis and gasification that are efficient procedures to achieve valuable products, gasification of OFMSW with different particle sizes and compositions was carried out in the presence of Ni and Ni-Ce-loaded Y-zeolite in a multizone tubular kiln reactor. During the experiments, 500°C was applied in the first reactor zone, while the 2nd zone was at an elevated temperature of 600°C or 900°C in the presence of steam. The combined pyrolysis and gasification experiments were also carried out without a catalyst with the same operating conditions. The feedstock was collected from the organic fraction of a Hungarian mechanical-biological treatment (MBT) plant and was separated into four different fractions based on particle size: <1 cm dry biomass and fine particles, 1-2 cm paper-rich, 2-6 cm paper and plastic-rich feedstocks, and <6 cm mixture of these fractions. During the experimental work, product yields; gaseous product composition; the ratio of H2/CO, CO2/CO, and CH4/CO; and lower heating value were determined in the function of feedstock composition, the applied temperature, and catalysts. It was found that the hydrogen content and H2/CO ratio of gaseous products were increased due to catalyst application and temperature elevation in the 2nd reactor zone. The addition of Ce to the Ni/Y-zeolite catalyst was advantageous in the case of hydrogen formation at a lower temperature (600°C). The hydrogen and methane content of products obtained from the catalytic pyrolysis-gasification of paper and plastic-rich OFMSWs on elevated temperatures were higher, which increased the lower heating value of those products. Based on the elemental analysis of the obtained solid residues, it was found that paper/plastic-rich feedstock released hydrogen and carbon with a higher extent. 1-2 cm feedstock-related solid residues had the highest H/C ratio which caused a 12.5-12.8 MJ/kg gross heating value. As a result, combined pyrolysis and gasification appear to be an efficient method to attain valuable outputs from OFMSW not only in gas but also in solid products.

Continuous Flow‐By Electrochemical Reactor Design for Direct Lithium Extraction from Brines

AbstractThe demand for lithium is expected to increase significantly in the next few years, mainly due to the energy transition in the mobility sector. To electrify the entire global transportation system, it is necessary to have access to a wide variety of lithium deposits to ensure resource sovereignty and sufficient supply to meet demand. For this reason, much effort has recently been invested in developing technologies for direct lithium extraction (DLE) from brines. In this work, a membrane‐based continuous flow‐by reactor for the electrochemical extraction of lithium from brine with a LiMn2O4/λ‐MnO2 system has been studied. A zoned reactor was proposed in which the current density and electrode mass loading gradually decrease along with the depletion of lithium in the brine, obtaining an average electrode capacity of 80 mAh/g throughout three different reactor sections. The limiting Reynolds number was determined for the dilute lithium segment of the reactor to avoid mass transport limitations, with brine concentration equal to Li 3 mM and Na 1.3 M. A homogeneous cycle time was achieved for the three reactor zones and their associated average energy consumption was determined, ranging from 3.9 Wh/mol Li to 9.5 Wh/mol Li.

Investigation of regeneration cycles with different catalysts on steam gasification of biomass

In this work, agricultural biomass waste was gasified in a two-zone tubular reactor in the presence of steam. Firstly, during preliminary experiments the effect of temperature in the 1st and 2nd reactor zone, as well as the influence of catalysts and steam/raw material ratio was investigated, then the reusability of catalysts was also studied during ten regeneration cycles. Based on the preliminary results, in the 1st reactor zone a lower temperature was used (400 °C), where the yield of carbon dioxide was ∼55 %, which has a positive effect on numerous reactions, also it can be converted to carbon monoxide with proper catalysts with in-situ process. Regarding the temperature, it is important to be mentioned that a significant difference was observed in the yield of synthesis gas at 700 °C thus, the experiments were carried out using 700 °C in the 2nd reactor zone. A natural (Clinoptilolite) and a synthetic zeolite (ZSM-5), a mesoporous alumina (Al2O3) and a carbon dioxide capturing carrier (CaO) were selected and impregnated with nickel for further use and for enhancing the yield of synthesis gas and hydrogen during the gasification process. The utilization of catalysts helped the in-situ reduction of carbon dioxide while their performance in the gasification process during the regeneration cycles was also investigated. Henceforward, the tested Ni/ZSM-5, Ni/Al2O3 and Ni/Clinoptilolite, reduced the amount of carbon monoxide from the 5th regeneration cycles, while the amount carbon dioxide with the four mentioned catalysts was decreased by 15–35 mmol/g raw material, compared to the results obtained during thermal degradation.

Harnessing Fermentation May Enhance the Performance of Biological Sulfate-Reducing Bioreactors.

Biological sulfate reduction (BSR) represents a promising strategy for bioremediation of sulfate-rich waste streams, yet the impact of metabolic interactions on performance is largely unexplored. Here, genome-resolved metagenomics was used to characterize 17 microbial communities in reactors treating synthetic sulfate-contaminated solutions. Reactors were supplemented with lactate or acetate and a small amount of fermentable substrate. Of the 163 genomes representing all the abundant bacteria, 130 encode 321 NiFe and FeFe hydrogenases and all genomes of the 22 sulfate-reducing microorganisms (SRM) encode genes for H2 uptake. We observed lactate oxidation solely in the first packed bed reactor zone, with propionate and acetate oxidation in the middle and predominantly acetate oxidation in the effluent zone. The energetics of these reactions are very different, yet sulfate reduction kinetics were unaffected by the type of electron donor available. We hypothesize that the comparable rates, despite the typically slow growth of SRM on acetate, are a result of the consumption of H2 generated by fermentation. This is supported by the sustained performance of a predominantly acetate-supplemented stirred tank reactor dominated by diverse fermentative bacteria encoding FeFe hydrogenase genes and SRM capable of acetate and hydrogen consumption and CO2 assimilation. Thus, addition of fermentable substrates to stimulate syntrophic relationships may improve the performance of BSR reactors supplemented with inexpensive acetate.

Effect of Inserting Baffles on the Solid Particle Segregation Behavior in Fluidized Bed Reactor: A Computational Study

In multi-solid, particle-size fluidized bed reactor systems, segregation is commonly observed. When segregation occurred, small solid particles were entrained to the top of the bed and escaped from the reactor. During the combustion process, the small solid particles that escaped from the boiler were burned and subjected to damage around the cyclone separator. This study then employed a computational fluid dynamics approach to investigate solid particle behavior in the reactor using three different sizes of solid particles. The effects of baffle insertion, baffle angle, stage number, and its arrangement were examined. The percentage of segregation was calculated to compare behavior among different reactor systems. The insertion of 45-degree baffles resulted in reduced segregation behavior compared to cases without baffles and with 90-degree baffles, attributed to solid hindering and collision phenomena. Additionally, a double-stage baffle with any arrangement could reduce segregation behavior. The best arrangement was “above-arrangement” due to particles hindering, swirling, and accumulating between the baffle stages. Therefore, to diminish segregation behavior and enhance combustion chemical reactions, the insertion of baffles in the reactor zone is recommended.

Evidence of fast neutron operating in Oklo.

Since the discovery of the first reactor zone (RZ) at the Oklo uranium deposit in 1972, many isotopic studies have been performed to understand the mechanism of the operation as fission reactors and to trace the migration behaviors of fissiogenic isotopes produced in the Oklo RZs. As the representative parameters to characterize the operating conditions of RZs, neutron fluence generated in RZ, duration of RZ operation, restitution factor of 235U from α decay of 239Pu produced by neutron capture of 238U and the proportion of fission events due to 235U, 238U and 239Pu are compiled and compared with individual RZs. In particular, one of the Oklo RZs, RZ 13, shows several specific features in the view point of isotopic and nuclear characteristics. By comparison of the data between RZ13 and other RZs, fission contribution of 238U for RZ13 is found to be significantly higher than those of other RZs.

A Review of Top-Submerged Lance (TSL) Processing—Part I: Plant and Reactor Engineering

Part I of this series of papers focuses on plant and reactor engineering aspects of the TSL reactor technology. A general flowsheet is presented, while emphasis is given to the definition of different reactor zones in terms of fluid dynamics and occurring reactions. Then, the technical advantages of TSL processing, such as feed flexibility and high conversion rates (due to induced turbulence), low dust generation, and low fugitive emissions, are explained. In addition, the reactor is analyzed part by part, also taking into account patent literature, focusing on furnace design, settling furnaces for molten phase disengagement, feeding systems regarding input material streams such as concentrates and fuels, vessel cooling arrangements, off-gas system, and aspects associated with the refractory lining. Furthermore, specific focus is given to the centerpiece of the TSL reactor, i.e., the reactor lance. Associated developments have focused on establishing a slag coating to hinder lance wear, i.e., the development of cooling mechanisms (e.g., use of fluid-cooled lance and shroud arrangements), the increment of O2 enrichment within the incoming air stream, and influencing of fluid dynamics (e.g., O2 conversion at the lance tip, bubble formation, and bath splashing). Finally, comprehensive tables concerning process developments and commissioned TSL plants are provided thus concluding Part I of the review.

Soil organic pollution and ecological risk assessment in brownfield soil from Northwest China: an integrated analysis of man-land interrelations

In general, chemical plants are accompanied by a variety of secondary production in the production process, which may have different degrees of impact on the environment. At the same time, in order to ensure the environmental safety of new urban construction land, it is necessary to conduct pollution investigation and further environmental risk assessment on potentially polluting abandoned chemical plants. This paper takes a chemical plant producing food grade fumaric acid in Northwest China as an example to investigate the pollution of organic matter in the soil in accordance with relevant standards, then analyzes the vertical pollution degree of key pollution areas. The calculation results of single factor pollution index and Nemerow pollution index show that there are 17 kinds of organic pollutants that exceed the screening value in land of Class I. Among them, benzene, 1,2,3-trichloropropane and 1,1,2,2-tetrachloroethane are most serious, and the highest exceeded the standard by 11,311 times. Moreover, the distillation zone and the reactor zone have reached the level of V pollution, and the maximum pollution depth can reach more than 6 m. The results of HERA software analysis showed that there were 18 and 10 kinds of organic pollutants with carcinogenic risk values exceeding 10−6 in the reactor and distillation area, respectively, and 25 and 11 kinds of organic pollutants with hazard quotients exceeding 1, respectively. According to relevant regulations, the contaminated areas with unacceptable regional risks must be properly repaired.

Математическое моделирование процесса полимеризации этилена в автоклавном реакторе с мешалкой

Building a mathematical model of the polymerization reactor is necessary to determine the dependencies between the input variables, the technological mode and the output variables of the ethylene polymerization process in an autoclave reactor with a stirrer, as well as to analyze the effect of the reactor design parameters on efficiency. A deterministic mathematical model developed on the basis of analysis of the physico-chemical regularities of the ethylene polymerization process is proposed to solve these problems. There is shown a schematic diagram of ethylene polymerization indicating the flows of substances and energy, a description of the process, the mechanism of chemical kinetics of ethylene polymerization, a system of assumptions simplifying the construction of a mathematical model, equations of a mathematical model of an ethylene polymerization reactor in an autoclave reactor with a stirrer. The autoclave ethylene polymerization reactor is presented as a cascade of ideal mixing apparatus to describe each of the reactor zones. The rates of chemical reactions of initiation, growth and chain breakage are expressed in accordance with the law of acting masses. The mathematical model in its final form is a system of ordinary differential equations for describing each of the reactor zones. The initial numerical values of variables and parameters for modeling ethylene polymerization in the autoclave reactor are given. The results of numerical experiments are shown, and the influence of various factors on the output variables of the ethylene polymerization process is investigated. The proposed mathematical model can be used to optimize the technological regime of the ethylene polymerization process in an autoclave reactor with a stirrer, as well as to analyze the influence of the design parameters of the reactor on its efficiency.

Elemental sulphur recovery from a sulphate-rich aqueous stream in a single hybrid linear flow channel reactor is mediated through microbial community dynamics and adaptation to reactor zones.

The coupled application of biological sulphate reduction (BSR) and partial sulphide oxidation to treat sulphate-rich wastewater is an effective strategy to mitigate pollution and recover elemental sulphur for repurposing. The recent development of the hybrid linear flow channel reactor (LFCR) achieves simultaneous BSR and partial sulphide oxidation with biosulphur recovery via a floating sulphur biofilm (FSB). Here, we explore the microbial community zoning and dynamics facilitating the process. A total of three continuous LFCRs were used to evaluate the effect of reactor zones, hydraulic residence time (HRT), carbon source, namely lactate and acetate, as well as reactor geometry and scale on process performance and microbial community dynamics. Community composition of sessile and planktonic microbial consortia were resolved at a 5- and 2-day HRT through 16S rRNA amplicon sequencing. Preferential attachment and prevalence of specific phylotypes within the sessile and planktonic communities revealed clear adaptation of key microorganisms to different microenvironments. Key microbial taxa affiliated with sulphate reduction and sulphide oxidation as well as those implicated in fermentation and syntrophic metabolism, fluctuated in response to changes in HRT and process performance. Through understanding the relationship between microbial community dynamics and process performance, this research will inform better process design and optimization of the hybrid LFCR.

Characterization and Assessment of Organic Pollution at a Fumaric Acid Chemical Brownfield Site in Northwestern China

Large-scale fumaric acid chemical brownfield sites have posed a significant obstacle to environmental safety, public safety, and the redevelopment of brownfield sites. A comprehensive study was conducted to determine the main pollution indicators, soil pollution characteristics, and the multiple potential risks to the environment and the ecosystem of a fumaric acid brownfield site in northwestern China. The results showed that 1,2,3-trichloropropane(1,2,3-TCP) was the primary pollutant at the fumaric acid brownfield site. The atmospheric volatile organic compounds (VOCs) in this brownfield site did not exceed the Chinese standard limits. The soil contamination was more severe within the site, with a total of about 30 VOCs detected, including the uncommon brominated pollutants. The level of longitudinal soil contamination decreased with increasing soil depth. The distillation area was more contaminated with a maximum exceedance multiple of 11,291.8. The longitudinal contamination depths in the distillation and reactor zones were 10.0 m and 4.0 m, respectively. Soil texture and production processes are considered to be one of the influencing factors for the depth of vertical soil contamination. Our findings heighten the awareness of brownfield site soil contamination and provide a reference for contamination controls and the comprehensive management of fumaric acid brownfield sites.

Pyrolysis-gasification of biomass using nickel modified catalysts: The effect of the catalyst regeneration on the product properties

In this work, agricultural biomass waste (maize) was used as raw material in a pyrolysis-gasification process with the presence of nickel-loaded zeolites, CaO and Al2O3. Henceforward, the reusability and the deteriorating effect of the catalysts are important to be analysed, therefore the catalysts were reused for ten regeneration cycles. During the measurements, the effect of temperature, catalysts and the regeneration cycles of catalysts were also investigated, as well as the components of the gaseous product. At first, the proper temperature was determined in the 1st (200–800 °C) and the 2nd (500–700°) reactor zone, where 400 °C and 700 °C, while for the regeneration 800 °C was chosen. Throughout the regeneration cycles in case of Ni/ZSM-5 lighter hydrocarbons was increased while that of the carbon monoxide and carbon dioxide was decreased. In the presence of Ni/CaO the amount of carbon dioxide decreased until the 3rd regeneration cycle, while carbon monoxide and hydrogen was decreased till the 10th cycle. Regarding the Ni/Al2O3, the amount of CO2 and CO was significantly decreased at each cycles, while in case of Ni/Clinoptilolite reduction was observed in hydrogen and carbon dioxide, however not only the amount of carbon monoxide but the syngas yield increased remarkably. Due to the mentioned results, the Ni/Clinoptilolite has an effective syngas enhancing and carbon dioxide capturing effect, even with low pyrolysis temperature.

Reduced order modeling and large-scale validation for non-catalytic partial oxidation of natural gas

• Reduced order modeling of non-catalytic partial oxidation of natural gas. • Low computational effort through a physics-based and compact model. • Validation against semi-industrial test plant experiments and CFD. • Demonstrated exibility and reliability of the model for a broad spectrum of operating parameters. • Analysis of conversion processes in different reactor zones. A reduced order model (ROM) for the non-catalytic partial oxidation (POX) of natural gas was developed and validated against large-scale numerical and experimental results. The ROM utilizes a network of perfectly stirred reactors, each describing a distinctive reactor zone and corresponding conversion processes. The zone definition is based on the CFD calculation of reactive flow, resulting in a compact, physics-based model that is valid for a broad range of POX reactors. The ROM is capable of predicting global reactor characteristics and flow field pattern within a short period of time, enabling the optimization of reactor geometry and the boundary and operating conditions. Additionally, the ROM can be used to evaluate detailed chemical reactions mechanisms. The ROM is validated against semi-industrial process data, and used to analyze the influence of each reactor zone on the overall species conversion. A new correlation between the fuel slip from the burner to the downstream reactor zones, the steam injection, and the λ value is built.

Study of Gas Holdup Distribution in Cylindrical Split Airlift Reactor by Using Gamma-Ray Densitometry (GRD)

The local gas holdup details and behaviors in the cylindrical split airlift column by using an unconventional gamma-ray densitometry (GRD) measurement in non-invasive manner technique was investigated for the first time in this work for such kind of airlift column. With different gas velocities, 1, 2, and 3 cm/s, at three various axial planes (different levels) in z = 3, 60, and 110 cm were studied for local distribution in radial gas holdup profiles. The distribution in gas–liquid phases (air-water system) in the entire split reactor column, in the rising and descending sides, including their behavior in the upper and lower zones of the split plate, were investigated as well. The results of this study showed that approximately all reactor zones had exemplary gas–liquid phases and that there was a large magnitude over both the dividing ring and the top sections. The results further indicated that the distribution of which flow variable in the implementation of the cylindrical split reactor can have an important impact on its behavior, especially for cultivating applications of microorganisms. These data can be used as benchmarks results for CFD simulations and validation.

Ecuaciones de diseño de un reactor electroquímico tubular con electrodos concéntricos de mallas expandidas a través de un análisis teórico del micro/macromezclado de curvas de DTR

In the present work, the liquid flow pattern in a Tubular Electrochemical Reactor (TC-ECR) with concentric cylindrical expanded meshes as electrodes and inlet/outlet distributors of shower‑sprinkler type was evaluated. It was found that the CFD theoretical results describe the experimental F(t)-curves obtained with the methodology of “step-signal input”. Later, the F(t)-curves estimated with CFD for each reactor zone were adequately approximated with global parametric models for the development of the TER design equations. The Stagnant Zone Model with mass exchange with the anodic zone turns out to be adequate for the reactor shell zone. However, for the cathode and anode meshes, the Axial Dispersion Model with mass exchange between them proves to be appropriate. For all liquid flow rates (0.37 to 4.0 L min-1), the dispersion numbers (Nd) are in a magnitude order of small dispersion. This confirms that the incorporation of inlet/outlet distributors in a T-ECR improve considerably the liquid flow pattern behaviour. This experimental methodology, coupled with micro/macromixing theoretical analysis of RTD curves with CFD, can be a good alternative for the reactor design.

The perspective of using the «open biological conveyor» method for purifying landfill filtrates

The concept of an open-type biological conveyor has been developed that can be used to treat contaminated wastewater. Unlike the closed biological conveyor method, it is characterized by the organized periodic selection of biomass used for biogas production. The typical scheme of an open-type bioconveyor consisting of an anaerobic bioreactor zone, an aerobic bioreactor zone, a biogas reactor zone and a phyto reactor zone is presented. The rational scheme of the biological conveyor of the open type setup for landfill filtrate purification is introduced. Laboratory studies have been conducted to determine the effectiveness of the use of nozzles for the immobilization of microbiocenosis in aerated lagoons used for landfill leachate purification.

Intensification of Gas Hydrate Formation Processes by Renewal of Interfacial Area between Phases

This paper presents the analysis of the main reasons for a significant decrease in the intensity of diffusion processes during the formation of gas hydrates; solutions to this problem are proposed in a new process flow diagram for the continuous synthesis of gas hydrates. The physical processes, occurring at the corresponding stages of the process flow, have been described in detail. In the proposed device, gas hydrate is formed at the boundary of gas bubbles immersed in cooled water. The dynamic effects arising at the bubble boundary contribute to the destruction of a forming gas hydrate structure, making it possible to renew the contact surface and ensure efficient heat removal from the reaction zone. The article proposes an assessment technique for the main process parameters in the synthesis of hydrates based on the criterion of thermodynamic parameters optimization. The optimization criterion determines the relationship of intensity of heat and mass transfer processes at the phase contact interface of reacting phases, correlating with the maximum GH synthesis rate, and makes it possible to determine optimum thermodynamic parameters in the reactor zone.

Satisfactory catalyst stability in SNG production using real biogas despite sulfur poisoning evidences at different reactor zones

The performance of a nickel-ceria micro-catalyst in biogas methanation was evaluated in a complete pilot plant during 1,000 h. The core of the exothermic methanation process consisted in two micro-reactors using a decreasing temperature profile, intermediate water removal and moderate pressure. The obtained gas quality and the reactors temperature profile remained constant during operation, indicating no signs of catalyst deactivation. After the experimental campaign, catalyst samples from different reactors sections were withdrawn, collected and independently characterized. It has been demonstrated that the different reaction conditions, in which the catalyst operated, played a significant role on the different level of degradation of the catalyst samples. On one hand, various characterization techniques agreed that sintering of nickel and ceria nanoparticles (+10–30%) and loss of surface area (−20%) was restricted to the initial reactor zones, which is attributed to the higher operation temperatures. On the other hand, despite the cautions undertaken for biogas cleaning and gas monitoring, sulfur was detected along the entire reactor longitudinal profile (0.25–0.91%). Accordingly, a progressive diffuse flow poisoning mechanism is expected from very long operation times. In particular, higher amount of sulfur was detected in the latest reactor zones, which operated at lower temperatures and under more oxidizing conditions. Beneficially, sulfur was predominantly detected as Ce2O2S phase, confirming thereby the crucial sacrificial role of CeO2 that allows for maintaining the catalytic activity of nickel active sites. The overall outcome of this work is very promising and reveals a sufficient catalyst lifespan for industrial application.

The Places of Products Localization and the Influence of this Factor on the Technological Characteristics

The search for optimal conditions for the method of synthesis of copper (II) salts to create a unified one-step method for obtaining salts from natural raw materials was the purpose of this work. During the process of salt production, it is desirable that the product accumulates in the solid phase and is easily separated by phase separation methods. The study of the direct interaction of copper (II) oxide with acids in organic liquid media using a bead mill as a reactor and grinding agent of different nature showed that besides the usual places of localization of product that take place in practice, we can meet unusual places of localization of product, such as the surface of a foreign solid phase in the reactor zone, for example, the surface of the grinding agent, reactor elements, etc. It was found that in some cases, localization on a solid surface could be a favorable localization option in terms of the speed of the process. But it happens not always, because it requires specific methods of separation of film from surface, which can be very expensive. Often, the localization of the product on the solid surfaces is an extremely unfavorable localization option. It was found that different variants of product localization of interaction CuO with acids which were implemented in different proportions, prevented the creation of a unified method for producing salts in such systems