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Biomass Thermogravimetric Analysis: Uncertainty Determination Methodology and Sampling Maps Generation

The objective of this study was to develop a methodology for the determination of the maximum sampling error and confidence intervals of thermal properties obtained from thermogravimetric analysis (TG), including moisture, volatile matter, fixed carbon and ash content. The sampling procedure of the TG analysis was of particular interest and was conducted with care. The results of the present study were compared to those of a prompt analysis, and a correlation between the mean values and maximum sampling errors of the methods were not observed. In general, low and acceptable levels of uncertainty and error were obtained, demonstrating that the properties evaluated by TG analysis were representative of the overall fuel composition. The accurate determination of the thermal properties of biomass with precise confidence intervals is of particular interest in energetic biomass applications.

A Refrigerated Web Camera for Photogrammetric Video Measurement inside Biomass Boilers and Combustion Analysis

This paper describes a prototype instrumentation system for photogrammetric measuring of bed and ash layers, as well as for flying particle detection and pursuit using a single device (CCD) web camera. The system was designed to obtain images of the combustion process in the interior of a domestic boiler. It includes a cooling system, needed because of the high temperatures in the combustion chamber of the boiler. The cooling system was designed using CFD simulations to ensure effectiveness. This method allows more complete and real-time monitoring of the combustion process taking place inside a boiler. The information gained from this system may facilitate the optimisation of boiler processes.

Uncertainty Determination Methodology, Sampling Maps Generation and Trend Studies with Biomass Thermogravimetric Analysis

This paper investigates a method for the determination of the maximum sampling error and confidence intervals of thermal properties obtained from thermogravimetric analysis (TG analysis) for several lignocellulosic materials (ground olive stone, almond shell, pine pellets and oak pellets), completing previous work of the same authors. A comparison has been made between results of TG analysis and prompt analysis. Levels of uncertainty and errors were obtained, demonstrating that properties evaluated by TG analysis were representative of the overall fuel composition, and no correlation between prompt and TG analysis exists. Additionally, a study of trends and time correlations is indicated. These results are particularly interesting for biomass energy applications.

Single‐Image Rectification Technique in Forensic Science

Many researchers have been working in Spain to document the communal graves of those assassinated during the Spanish Civil War. This article shows the results obtained with two low‐cost photogrammetric techniques for the basic documentation of forensic studies. These low‐cost techniques are based on single‐image rectification and the correction of the original photo displacement due to the projection and perspective distortions introduced by the lens of the camera. The capability of image rectification is tested in an excavation in the village of Loma de Montija (Burgos, Spain). The results of both techniques are compared with the more accurate data obtained from a laser scanner system RIEGL LMS‐Z390i to evaluate the error in the lengths. The first technique uses a camera situated on a triangle‐shaped pole at a height of 5 m and the second positions the camera over the grave using a linearly actuated device. The first technique shows measurement errors less than 6%, whereas the second shows greater errors (between 8% and 14%) owing to the positioning of the carbon‐fiber cross on an uneven surface.

Experimental analysis of several biomass fuels: The effect of the devolatilization rate on packed bed combustion

An experimental analysis of the ignition front propagation of eight biomass fuels in a one-dimensional fixed-bed combustor (batch reactor) is carried out and these biomass materials are also researched by thermogravimetry to study their thermal behaviour during devolatilization. The analysis of the thermogravimetric data has been centered on the results obtained for 50 °C · min−1 (maximun heating rate of the thermogravimetric (TG) equipment), taking into consideration that it is the nearest heating rate value to the one at which the heating process is carried out in the batch reactor. The influence of the TG-determined devolatilization rate in the burning behaviour of biomass in situations of packed bed combustion is analyzed. This study reveals that the biomass fuels with higher devolatilization rates during pyrolysis are the ones with a higher velocity of propagation of the ignition front during combustion processes in the fixed-bed combustor. The thermal decomposition characteristics during devolatiliz...

Parameter identification of a Round-Robin test box model using a deterministic and probabilistic methodology

In this paper, two different methodologies are applied to the parameter estimation problem of a computational model of a Round-Robin test box. The numerical model is developed using TRNSYS. A global sensitivity analysis is carried out to determine the most important parameters that should be considered in the subsequent calibration procedure. Using the Bayesian (probabilistic) approach, the posterior distribution of the unknown input parameters is estimated via simulation techniques. Using the deterministic approach, executed in GenOpt, the calibration is performed by the minimization of an objective function that measures the differences between model predictions and real measured data. Parameter estimation results obtained with both methodologies are then compared and discussed. A reduction of the Coefficient of Variation of the Root Mean Square Error (CV (RMSE)) after calibration over 40% with both methods has been obtained, being the CV (RMSE) for calibration and validation periods on average 3.21% an...

Combined Heat and Mass Transfer by Natural Convection from a Semi-Infinite Plate Submitted to a Magnetic Field with Hall Currents

Abstract: The present work is concerned with the MHD unsteady free convection flow from a vertical semi-infinite plate of an incompressible electrically conducting fluid. The effects of the viscous dissipation and the Hall currents are analyzed. The unsteady governing equations are reduced to a system of ordinary differential non-dimensional equations and the resulting equation system is solved numerically by using the Network Simulation Method. This numerical method is based on the electrical analogy, where only previous spatial discretization is necessary to obtain a stable and convergent solution with very low computational times. To solve the system of algebraic equations with time as continuous function, an electric circuit simulator is used. Numerical results for velocities, temperature, concentration and current terms are illustrated graphically. We have observed that the Grashof number for heat transfer (Gr) and mass transfer (G*) accelerate the velocity of the flow field at all points. But the increase in velocity of the flow field is more significant in presence of mass transfer. The effect of Schmidt number Sc on mass transfer process is a decrease of concentration distribution as a result of decrease of the concentration boundary layer thickness.