scholarly journals Thermochemical Heat Storage in a Lab-Scale Indirectly Operated CaO/Ca(OH)2 Reactor—Numerical Modeling and Model Validation through Inverse Parameter Estimation

2021 ◽  
Vol 11 (2) ◽  
pp. 682
Author(s):  
Gabriele Seitz ◽  
Farid Mohammadi ◽  
Holger Class
Keyword(s):  
Numerical Model ◽  
Gas Flow ◽  
Reaction Rate ◽  
Heat Storage ◽  
Bulk Material ◽  
Fixed Bed ◽  
Experimental Results ◽  
Fixed Bed Reactor ◽  
Thermochemical Heat Storage ◽  
Speed Up

Calcium oxide/Calcium hydroxide can be utilized as a reaction system for thermochemical heat storage. It features a high storage capacity, is cheap, and does not involve major environmental concerns. Operationally, different fixed-bed reactor concepts can be distinguished; direct reactor are characterized by gas flow through the reactive bulk material, while in indirect reactors, the heat-carrying gas flow is separated from the bulk material. This study puts a focus on the indirectly operated fixed-bed reactor setup. The fluxes of the reaction fluid and the heat-carrying flow are decoupled in order to overcome limitations due to heat conduction in the reactive bulk material. The fixed bed represents a porous medium where Darcy-type flow conditions can be assumed. Here, a numerical model for such a reactor concept is presented, which has been implemented in the software DuMux. An attempt to calibrate and validate it with experimental results from the literature is discussed in detail. This allows for the identification of a deficient insulation of the experimental setup. Accordingly, heat-loss mechanisms are included in the model. However, it can be shown that heat losses alone are not sufficient to explain the experimental results. It is evident that another effect plays a role here. Using Bayesian inference, this effect is identified as the reaction rate decreasing with progressing conversion of reactive material. The calibrated model reveals that more heat is lost over the reactor surface than transported in the heat transfer channel, which causes a considerable speed-up of the discharge reaction. An observed deceleration of the reaction rate at progressed conversion is attributed to the presence of agglomerates of the bulk material in the fixed bed. This retardation is represented phenomenologically by mofifying the reaction kinetics. After the calibration, the model is validated with a second set of experimental results. To speed up the calculations for the calibration, the numerical model is replaced by a surrogate model based on Polynomial Chaos Expansion and Principal Component Analysis.

scholarly journals Effects of the Limestone Particle Size on the Sulfation Reactivity at Low SO2 Concentrations Using a LC-TGA

Materials ◽  
2019 ◽  
Vol 12 (9) ◽  
pp. 1496 ◽  
Author(s):  
Runxia Cai ◽  
Yiqun Huang ◽  
Yiran Li ◽  
Yuxin Wu ◽  
Hai Zhang ◽  
...  
Keyword(s):  
Particle Size ◽  
Reaction Rate ◽  
Fixed Bed ◽  
Sulfur Removal ◽  
Experimental Results ◽  
Fixed Bed Reactor ◽  
Model Parameters ◽  
Particle Sizes ◽  
Fluidized Bed Combustion ◽  
Wide Range

Limestone particle size has a crucial influence on SO2 capture efficiency, however there are few studies on the sulfation reactivity, which covers a broad range of particle sizes at low SO2 concentrations. In this paper, a large-capacity thermogravimetric analyzer (LC-TGA) was developed to obtain the sulfur removal reaction rate under a wide range of particle sizes (3 μm–600 μm) and SO2 concentrations (250 ppm–2000 ppm), and then compared with the results of a traditional fixed bed reactor and a commercial TGA. The experimental results showed that the LC-TGA can well eliminate the external mass transfer and obtain a better measurement performance. Both the final conversion and the reaction rate reduced with the decreasing of SO2 concentration, but ultrafine limestone particles still showed the good sulfation reactivity even at 250 ppm SO2. An empirical sulfation model was established based on the experimental results, which can well predict the sulfation process of different limestone particle sizes at low SO2 concentrations. The model parameters have a strong negative correlation against the particle size, and the fit of the reaction order of SO2 was found to be about 0.6. The model form is very simple to incorporate it into available fluidized bed combustion models to predict SO2 emission.

Application of Biofilm Kinetics to Anaerobic Fixed Bed Reactors

1991 ◽  
Vol 23 (7-9) ◽  
pp. 1319-1326 ◽  
Author(s):  
I. E. Gönenç ◽  
D. Orhon ◽  
B. Beler Baykal
Keyword(s):  
Removal Rate ◽  
Fixed Bed ◽  
Experimental Studies ◽  
Pilot Scale ◽  
Cod Removal ◽  
Experimental Results ◽  
Fixed Bed Reactor ◽  
Removal Mechanism ◽  
Term Operation ◽  
Fixed Bed Reactors

Two basic phenomena, reactor hydraulics and mass transport through biofilm coupled with kinetic expressions for substrate transformations were accounted for in order to describe the soluble COD removal mechanism in anaerobic fixed bed reactors. To provide necessary verification, experimental results from the long term operation of the pilot scale anaerobic reactor treating molasses wastewater were used. Theoretical evaluations verified by these experimental studies showed that a bulk zero-order removal rate expression modified by diffusional resistance leading to bulk half-order and first-order rates together with the particular hydraulic conditions could adequately define the overall soluble COD removal mechanism in an anaerobic fixed bed reactor. The experimental results were also used to determine the kinetic constants for practical application. In view of the complexity of the phenomena involved it is found remarkable that a simple simulation model based on biofilm kinetics is a powerful tool for design and operation of anaerobic fixed bed reactors.

scholarly journals ADSORPTION OF FLUORIDE FROM INDUSTRIAL WASTEWATER IN FIXED BED COLUMN USING JAVA PLUM (SYZYGIUM CUMINI)

2016 ◽  
Vol 9 (9) ◽  
pp. 320 ◽  
Author(s):  
Tej Pratap Singh ◽  
Sanjay Ghosh ◽  
Majumder Cb
Keyword(s):  
Residence Time ◽  
Industrial Wastewater ◽  
Fluoride Concentration ◽  
Fixed Bed ◽  
Experimental Results ◽  
Fixed Bed Reactor ◽  
Thomas Model ◽  
Fixed Bed Column ◽  
Empty Bed Residence Time

ABSTRACTObjective: The quality of drinking water is important for public safety and quality of life. Thus, providing every person on earth safe drinking waterseems to be the biggest challenge in front of mankind. For this purpose, here we have investigated the fluoride removal capacity of java plum.Methods: In this study, removal of fluoride from industrial wastewater using fixed-bed reactor adsorption techniques by java plum seed (Syzygiumcumini) was investigated. Fixed-bed column experiments were carried out for different bed depths, influent fluoride concentrations, and various flowrates. The Thomas model and bed depth service time model were applied to the experimental results. Both model predictions verify the experimentaldata for all the process parameters studied, indicating that the models were suitable for java plum (S. cumini) seeds (Biosorbent) fix-bed columndesign.Results: The empty bed residence time (EBRT) model optimizes the EBRT, and the Thomas model showed that the adsorption capacity is stronglydependent on the flow rate, initial fluoride concentration, and bed depth and is greater under conditions of a lower concentration of fluoride, lowerflow rate, and higher bed depth.Conclusion: The experimental results were encouraging and indicate that java plum (S. cumini) seed is a feasible option to use as a biosorbent toremove fluoride in a fixed bed adsorption process.Keywords: Adsorption, Column experiment, Thomas model, Empty bed residence time, Java plum.

scholarly journals Solution Combustion Synthesis of Fe2O3-Based Catalyst for Ammonia Synthesis

Catalysts ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1027
Author(s):  
Binxiang Cai ◽  
Huazhang Liu ◽  
Wenfeng Han
Keyword(s):  
Combustion Synthesis ◽  
Reaction Rate ◽  
Ammonia Synthesis ◽  
Fixed Bed ◽  
Solution Combustion Synthesis ◽  
Fixed Bed Reactor ◽  
High Dispersion ◽  
Synthesis Reaction ◽  
Solution Combustion ◽  
Metal Nitrates

Fe2O3-based catalysts were prepared by solution combustion synthesis (SCS) with metal nitrates (Fe, K, Al, Ca) as the precursors and glycine as the fuel. The activities of catalysts were evaluated in terms of ammonia synthesis reaction rate in a fixed bed reactor similar to the industrial reactors. The results indicate that the precursor of catalyst prepared by SCS is Fe2O3 which facilitates the high dispersion of promoters to provide high activity. The catalysts exhibit higher activity for ammonia synthesis than that of traditional catalysts, and the reaction rate reaches 138.5 mmol g−1 h−1. Fe2O3 prepared by SCS could be favorable precursor for ammonia synthesis catalyst. The present study provides a pathway to prepare catalyst for ammonia synthesis.

Bio-oil production from fast pyrolysis of maple fruit (acer platanoides samaras): product yields

2017 ◽  
Vol 14 (1) ◽  
pp. 55-59 ◽  
Author(s):  
Ali Bahadir ◽  
Turgay Kar ◽  
Sedat Keles ◽  
Kamil Kaygusuz
Keyword(s):  
Gas Flow ◽  
Fast Pyrolysis ◽  
Fixed Bed ◽  
Pyrolysis Product ◽  
Fixed Bed Reactor ◽  
Energy Sources ◽  
Potential Candidate ◽  
Content Type ◽  
Product Yields ◽  
Bio Oil

Purpose The purpose of this paper is to investigate fast pyrolysis of maple fruit as an energy sources. This could serve as a solution to the energy sources problem. Design/methodology/approach Fast pyrolysis of maple fruit (samara) was achieved in a fixed bed reactor. The pyrolysis experiments have been conducted on the sample of maple seeds to particularly determine the effects of pyrolysis temperature, particle size and sweep gas flow rate on the pyrolysis product yields. Findings The oil of maple fruit from fast pyrolysis has good properties to be a potential candidate as a biofuel or as a source of chemicals. In addition to being environmentally desirable, it can reduce the energy cost, e.g. that Turkey imports a majority of its energy. Originality/value The use of maple fruit for fast pyrolysis and pyrolysis conditions impact on the yields of pyrolysis liquid can be considered as novel aspects of this paper.

Effects of Zn on Steam Gasification Characteristics of Shenhua Lignite Char

2014 ◽  
Vol 1008-1009 ◽  
pp. 252-256
Author(s):  
Wipawan Sangsanga ◽  
Jin Xiao Dou ◽  
Zhe Lei Tong ◽  
Jiang Long Yu
Keyword(s):  
Gas Chromatography ◽  
Catalytic Activity ◽  
Fixed Bed ◽  
Steam Gasification ◽  
Experimental Results ◽  
Fixed Bed Reactor ◽  
Gas Composition ◽  
Gaseous Products ◽  
Lignite Char ◽  
Catalytic Effects

The catalytic effects of Zn on the yield of the gaseous products during steam gasification of lignite char were investigated by using a fixed-bed reactor. The gas composition was measured using a gas chromatography (GC). The experimental results show that Zn has catalytic effects on steam gasification and increased the yield of H2. There was an optimum content of Zn implanted into the coal above which zinc does not show further catalytic activity.

scholarly journals Numerical Model of Radical Photopolymerization Based on Interdiffusion

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Shuhei Yoshida ◽  
Yosuke Takahata ◽  
Shuma Horiuchi ◽  
Hiroyuki Kurata ◽  
Manabu Yamamoto
Keyword(s):  
Diffusion Coefficient ◽  
Numerical Model ◽  
Reaction Rate ◽  
Beam Propagation Method ◽  
Reaction Model ◽  
Experimental Results ◽  
Hologram Recording ◽  
Elementary Reactions ◽  
Proposed Model ◽  
And Diffusion

An accurate reaction model is required to analyze the characteristics of photopolymers. For this purpose, we propose a numerical model for radical photopolymerization. In the proposed model, elementary reactions such as initiation, propagation, and termination are considered, and we assume interdiffusion for each component in the material. We analyzed the diffraction characteristics of a radical photopolymer based on the proposed interdiffusion model with the beam propagation method. Moreover, we also performed hologram-recording experiments and evaluated the diffraction characteristics of the photopolymer medium. By comparing the numerical and experimental results, medium parameters such as reaction rate and diffusion coefficient can be estimated. We confirmed that the interdiffusion model can reproduce the experimental results and showed that the medium parameters affect the diffraction characteristics.

Comparative study of catalytic conversion of glycerol, a by-product of transesterification, to cyclic hydrocarbons using MCM-22, ZSM-5 and alumina

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Sandeep Kumar ◽  
Dinesh Kumar ◽  
Neeru Anand ◽  
Vinay Shah
Keyword(s):  
Rate Constant ◽  
Reaction Rate ◽  
Fixed Bed ◽  
Liquid Product ◽  
Value Added ◽  
Fixed Bed Reactor ◽  
High Yield ◽  
Esterification Reaction ◽  
Glycerol Conversion ◽  
Ms Analysis

Abstract Recently chemical consumption has increased due to the growth of human population and industrialization. Depleting fuel reserves and increase in chemicals rise has led and researcher to focus on alternative bio based chemicals. Glycerol which is produced as a major byproduct from the trans-esterification reaction of fatty acids for producing biodiesel has been used in this work for conversion to value added products. Conversion of glycerol in presence of alumina, MCM-22 (pure silica based mesoporous catalyst) and ZSM-5 (Si-Al based catalyst) is investigated at different temperature and catalyst weight in a fixed bed reactor. The conversion of glycerol was found to be maximum in presence of alumina whereas maximum liquid products were obtained with ZSM-5. GC/MS analysis confirmed the production of Furan compounds in higher fraction with both alumina as well as ZSM-5 showing the importance of acid sites for the glycerol conversion to higher hydrocarbons. The GC/MS analysis of liquid product obtained in presence of catalyst was also observed with high area% of unconverted glycerol. The order is as follow 54% (MCM-22) > 44% (ZSM-5) > 42.2% (Alumina). For the investigation of the conversion for varying catalyst weight (0–3 g with 0.5 g weight difference), reaction temperature were varied between 450 and 550 °C. Different values of n = 0, 1, 2 etc. were used for the fitting of the respective plot. A change in reaction rate and the rate constant indicated that with the change of temperature, reaction rate was increased. The rate constant value obtained between 0.09 and 0.12 h−1. In all cases 450 °C and catalyst weight of 2.5 g was obtained as optimum for higher liquid yield. TGA analysis of spent catalyst also showed that alumina give high yield (∼50% by weight) of coke as compared to ZSM-5 and MCM-22.

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