scholarly journals Penentuan Temperatur Optimal Pembakaran Boiler untuk Karbonisasi Hidrotermal Sampah Organik Melalui Model Semi-Analitik Perpindahan Panas

2019 ◽  
Vol 20 (2) ◽  
pp. 291
Author(s):  
Dian Purwitasari Dewanti ◽  
Albert Sulaiman
Keyword(s):  
Organic Waste ◽  
Combustion Process ◽  
Hydrothermal Carbonization ◽  
Two Dimensions ◽  
Air Emissions ◽  
Thermal Displacement ◽  
Carbonization Process ◽  
Water Tube ◽  
Runge Kutta ◽  
Rayleigh Benard

ABSTRACTBoiler is the one of the importance main equipment in the hydrothermal carbonization process. Steam produced from boiler is used to hydrothermal carbonization of organic waste in the reactor. This steam is produced due to the thermal displacement resulting from fuel combustion. The effectiveness of thermal displacement affects the amount of the fuel consumed and the air emissions produced by the combustion process. The study of the thermal transfer in a water tube typed boiler through Rayleigh-Benard convection semi-analytic modeling was carried out in this study. The boiler is modeled as a cylinder of two-dimensions with degrees of freedom of radius and height of the cylinder. Semi-analytic solutions are obtained by applying the Galerkin method where ordinary nonlinear differential equation systems are solved using the 4th order Runge-Kutta method. The results show that the amplitude that is function of the stream and thermal dispersion will oscillate sharply at the start of the heating process and then periodically oscillate with small variability as quasi patterns. Simulation shows that the rolling condition starts with a large rolling radius and then shrinks that is followed by uniformly distributed rolling and thermal spread throughout the boiler. The simulation results show the optimal temperature is around 300 oC. At this temperature, steam meets the conditions needed during the hydrothermal carbonization process of organic waste and fuel consumption can be adjusted to reduce air emissions resulting from combustion.Key words: boiler, convective, heat transfer, hydrothermal carbonization, Rayleigh-Benard.ABSTRAKBoiler atau ketel uap merupakan salah satu peralatan utama yang sangat penting pada proses karbonisasi hidrotermal. Uap air (steam) yang dihasilkan dari boiler dibutuhkan untuk proses karbonisasi hidrotermal sampah organik dalam reaktor. Produksi uap disebabkan oleh perpindahan panas yang dihasilkan dari pembakaran bahan bakar. Efektifitas perpindahan panas mempengaruhi jumlah bahan bakar yang dibutuhkan dan emisi udara yang dihasilkan oleh proses pembakaran tersebut. Kajian perpindahan panas dalam boiler bertipe water tube melalui pemodelan semi analitik konveksi Rayleigh-Benard dilakukan dalam penelitian ini. Boiler dimodelkan sebagai silinder dua dimensi dengan derajat kebebasan jari jari dan tinggi silinder. Solusi semi analitik diperoleh dengan menerapkan metode Galerkin dimana sistem persamaan diferensial biasa nonlinier model dipecahkan menggunaan metode Runge-Kutta orde 4. Hasilnya menunjukkan bahwa amplitude yang merupakan fungsi aliran (stream) dan dispersi panas akan berosilasi secara tajam pada awal waktu proses pemanasan dan kemudian secara periodik berosilasi dengan variabilitas yang kecil mengikuti pola kuasi. Simulasi menunjukkan bahwa kondisi rolling dimulai dengan jari jari rolling yang besar dan kemudian mengempis yang diikuti dengan tersebar meratanya rolling dan panas secara seragam di seluruh boiler. Hasil simulasi menunjukkan suhu optimal adalah sekitar 300oC. Pada suhu tersebut, steam memenuhi kondisi yang dibutuhkan selama proses karbonisasi hidrotermal sampah organik dan konsumsi bahan bakar bisa diatur untuk mengurangi emisi udara yang dihasilkan dari pembakaran.Kata kunci: boiler, karbonisasi hidrotermal, konvektif, perpindahan panas, Rayleigh-Benard.

scholarly journals Valorization of tree leaves waste using microwave‐assisted hydrothermal carbonization process

GCB Bioenergy ◽  
2021 ◽  
Author(s):  
Kang Kang ◽  
Tianle Zhang ◽  
Guotao Sun ◽  
Mingqiang Zhu ◽  
Kankan Li ◽  
...  
Keyword(s):  
Hydrothermal Carbonization ◽  
Tree Leaves ◽  
Carbonization Process ◽  
Microwave Assisted

Direct numerical simulations of Rayleigh–Bénard convection in water with non-Oberbeck–Boussinesq effects

2019 ◽  
Vol 881 ◽  
pp. 1073-1096 ◽  
Author(s):  
Andreas D. Demou ◽  
Dimokratis G. E. Grigoriadis
Keyword(s):  
Numerical Simulations ◽  
Two Dimensions ◽  
Direct Numerical Simulations ◽  
Wall Region ◽  
Number Range ◽  
Bénard Convection ◽  
Benard Convection ◽  
Rayleigh Benard Convection ◽  
Rayleigh Benard ◽  
Near Wall

Rayleigh–Bénard convection in water is studied by means of direct numerical simulations, taking into account the variation of properties. The simulations considered a three-dimensional (3-D) cavity with a square cross-section and its two-dimensional (2-D) equivalent, covering a Rayleigh number range of $10^{6}\leqslant Ra\leqslant 10^{9}$ and using temperature differences up to 60 K. The main objectives of this study are (i) to investigate and report differences obtained by 2-D and 3-D simulations and (ii) to provide a first appreciation of the non-Oberbeck–Boussinesq (NOB) effects on the near-wall time-averaged and root-mean-squared (r.m.s.) temperature fields. The Nusselt number and the thermal boundary layer thickness exhibit the most pronounced differences when calculated in two dimensions and three dimensions, even though the $Ra$ scaling exponents are similar. These differences are closely related to the modification of the large-scale circulation pattern and become less pronounced when the NOB values are normalised with the respective Oberbeck–Boussinesq (OB) values. It is also demonstrated that NOB effects modify the near-wall temperature statistics, promoting the breaking of the top–bottom symmetry which characterises the OB approximation. The most prominent NOB effect in the near-wall region is the modification of the maximum r.m.s. values of temperature, which are found to increase at the top and decrease at the bottom of the cavity.

scholarly journals Hydrothermal Carbonization of Organic Waste and Biomass: A Review on Process, Reactor, and Plant Modeling

2020 ◽  
Author(s):  
Giulia Ischia ◽  
Luca Fiori
Keyword(s):  
Organic Waste ◽  
Review Paper ◽  
Recent Literature ◽  
State Of The Art ◽  
Hydrothermal Carbonization ◽  
Residual Biomass ◽  
Current State ◽  
Potential Applications ◽  
Intrinsic Complexity ◽  
Context Models

Abstract Hydrothermal carbonization (HTC) is an emerging path to give a new life to organic waste and residual biomass. Fulfilling the principles of the circular economy, through HTC “unpleasant” organics can be transformed into useful materials and possibly energy carriers. The potential applications of HTC are tremendous and the recent literature is full of investigations. In this context, models capable to predict, simulate and optimize the HTC process, reactors, and plants are engineering tools that can significantly shift HTC research towards innovation by boosting the development of novel enterprises based on HTC technology. This review paper addresses such key-issue: where do we stand regarding the development of these tools? The literature presents many and simplified models to describe the reaction kinetics, some dealing with the process simulation, while few focused on the heart of an HTC system, the reactor. Statistical investigations and some life cycle assessment analyses also appear in the current state of the art. This work examines and analyzes these predicting tools, highlighting their potentialities and limits. Overall, the current models suffer from many aspects, from the lack of data to the intrinsic complexity of HTC reactions and HTC systems. Therefore, the emphasis is given to what is still necessary to make the HTC process duly simulated and therefore implementable on an industrial scale with sufficient predictive margins. Graphic Abstract

Modeling and simulation of a continuous biomass hydrothermal carbonization process

2019 ◽  
Vol 207 (6) ◽  
pp. 751-768 ◽  
Author(s):  
Jaime Gómez ◽  
Giancarlo Corsi ◽  
Ernesto Pino-Cortés ◽  
Luis A. Díaz-Robles ◽  
Valeria Campos ◽  
...  
Keyword(s):  
Modeling And Simulation ◽  
Hydrothermal Carbonization ◽  
Carbonization Process

Removal of copper and cadmium from aqueous solution using switchgrass biochar produced via hydrothermal carbonization process

2012 ◽  
Vol 109 ◽  
pp. 61-69 ◽  
Author(s):  
Pusker Regmi ◽  
Jose Luis Garcia Moscoso ◽  
Sandeep Kumar ◽  
Xiaoyan Cao ◽  
Jingdong Mao ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Hydrothermal Carbonization ◽  
Carbonization Process

Boundary layers and wind in cylindrical Rayleigh–Bénard cells

2012 ◽  
Vol 697 ◽  
pp. 336-366 ◽  
Author(s):  
Sebastian Wagner ◽  
Olga Shishkina ◽  
Claus Wagner
Keyword(s):  
Boundary Layer ◽  
Boundary Layers ◽  
Large Scale ◽  
Linear Increase ◽  
Two Dimensions ◽  
Local Analysis ◽  
Bottom Plate ◽  
Special Focus ◽  
Layer Region ◽  
Rayleigh Benard

AbstractWe analyse the wind and boundary layer properties of turbulent Rayleigh–Bénard convection in a cylindrical container with aspect ratio one for Prandtl number $\mathit{Pr}= 0. 786$ and Rayleigh numbers ($\mathit{Ra}$) up to $1{0}^{9} $ by means of highly resolved direct numerical simulations. We identify time periods in which the orientation of the large-scale circulation (LSC) is nearly constant in order to perform a statistical analysis of the LSC. The analysis is then reduced to two dimensions by considering only the plane of the LSC. Within this plane the LSC is treated as a wind with thermal and viscous boundary layers developing close to the horizontal plates. Special focus is on the spatial development of the wind magnitude and the boundary layer thicknesses along the bottom plate. A method for the local analysis of the instantaneous boundary layer thicknesses is introduced which shows a dramatically changing wind magnitude along the wind path. Furthermore a linear increase of the viscous and thermal boundary layer thickness along the wind direction is observed for all $\mathit{Ra}$ considered while their ratio is spatially constant but depends weakly on $\mathit{Ra}$. A possible explanation is a strong spatial variation of the wind magnitude and fluctuations in the boundary layer region.

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