Autothermal Operation of a Biomass Torrefaction Plant

2018 ◽  
Author(s):  
Yousef Haseli
Keyword(s):  
Moisture Content ◽  
Residence Time ◽  
Thermal Energy ◽  
Carbon Dioxide Emissions ◽  
Process Model ◽  
Energy Content ◽  
Operating Temperature ◽  
Heat Requirement ◽  
Autothermal Operation ◽  
Main Operating

Biomass torrefaction is a thermal pretreatment which takes place at a temperature between 200–300 °C in a non-oxidative environment. The process requires thermal energy for drying and torrefying the raw biomass. The amount of the required heat may vary depending on the biomass moisture content, operating temperature and residence time. The volatiles released during the torrefaction are usually burnt in a combustor to meet the heat requirement of the process. If the energy content of the volatiles is less than the thermal energy required for the process, the operation of the torrefaction unit is below the autothermal mode so an auxiliary fuel such as natural gas is burnt together with the volatiles. This paper investigates autothermal operation of a torrefaction unit which consists of a dryer, a torrefaction reactor, a combustor, and two heat exchangers. An experimentally validated process model is employed to identify a relation between the moisture content, torrefaction temperature, and residence time at autothermal operation. The model is capable of predicting the composition of volatiles and torrefied biomass, mass and energy yields, process heat requirement, and CO2 emissions. The results are graphically presented allowing one to determine whether a torrefaction unit operates below or above the autothermal mode at given torrefaction temperature, residence time and moisture content. Furthermore, the effect of the main operating parameters on the carbon dioxide emissions of the torrefaction unit is discussed.

Autothermal biodrying of municipal solid waste with high moisture content

2010 ◽  
Vol 64 (2) ◽  
Author(s):  
Agnieszka Zawadzka ◽  
Liliana Krzystek ◽  
Stanisław Ledakowicz
Keyword(s):  
Moisture Content ◽  
Municipal Solid Waste ◽  
Solid Waste ◽  
Energy Content ◽  
Plastic Material ◽  
Initial Moisture Content ◽  
Tubular Reactor ◽  
Calorific Value ◽  
High Energy ◽  
Total Capacity

AbstractTo carry out autothermal drying processes during the composting of biomass, a horizontal tubular reactor was designed and tested. A biodrying tunnel of the total capacity of 240 dm3 was made of plastic material and insulated with polyurethane foam to prevent heat losses. Municipal solid waste and structural plant material were used as the input substrate. As a result of autothermal drying processes, moisture content decreased by 50 % of the initial moisture content of organic waste of about 800 g kg−1. In the tested cycles, high temperatures of biodried waste mass were achieved (54–56°C). An appropriate quantity of air was supplied to maintain a satisfactory level of temperature and moisture removal in the biodried mass and high energy content in the final product. The heat of combustion of dried waste and its calorific value were determined in a calorimeter. Examinations of pyrolysis and gasification of dried waste confirmed their usefulness as biofuel of satisfactory energy content.

NUMERICAL ESTIMATION OF MOISTURE CONTENT IN SPRAY DRIED JUICE POWDER

2016 ◽  
Vol 78 (8-3) ◽  
Author(s):  
Aliyu Bello A. ◽  
Arshad Ahmad ◽  
Adnan Ripin ◽  
Olagoke Oladokun
Keyword(s):  
Experimental Data ◽  
Moisture Content ◽  
Diffusion Model ◽  
Process Model ◽  
Small Error ◽  
Operating Conditions ◽  
Balance Model ◽  
Pineapple Juice ◽  
Droplet Drying ◽  
Spray Dried

The moisture contents of powders is an important parameter that affects the quality and commercial value of spray dried products. The utility of predicted moisture content values from two droplet drying models were compared with experimental data for spray dried pineapple juice, using the Ranz-Marshal and its modified variants for the heat and mass transfer correlations. The droplet Diffusion model, using the Zhifu correlation, gave estimates with errors of about 8% at 165 oC, 9% at 171 oC, 26% at 179 oC and 2% at 185 oC. The Ranz-Marshal correlation also gave comparable results with this model while results using the Downing and modified Ranz-Marshall correlations widely diverged. The Energy balance model predicted completely dried juice particles, and short drying times, in contrast to the experimental data. The small error sizes of the Diffusion model improves on the wide error sizes of an earlier process model, making is useful as a first approximation choice, for spray drier design and simulation, especially for juices under comparable operating conditions.

Mathematical Modeling of the Process of Operation of the Drying Chamber of a Tower Grain Dryer With a Suction Air Flow

2020 ◽  
pp. 114-121
Author(s):  
Viktor Shvidia ◽  
◽  
Serhii Stepanenko ◽  
Keyword(s):  
Moisture Content ◽  
Air Flow ◽  
Initial Moisture Content ◽  
Material Balance ◽  
Operating Parameters ◽  
Conservation Of Energy ◽  
Grain Moisture ◽  
Optimal Mode ◽  
Drying Chamber ◽  
Main Operating

In the article, a drying scheme in a tower grain dryer has been developed, equations for the conservation of energy and material balance for grain, equations for mass transfer and heat transfer between the drying agent and grain have been drawn up. On their basis, analytical dependences of changes in the temperature and moisture content of grain, moisture content and temperature of the drying agent along and in the width of the drying channel were obtained, depending on the operating parameters (the value of rarefaction in the drying channel, the speed of grain movement along the drying channel, the speed of movement of the drying agent, the initial temperatures of the grain and drying agent, initial moisture content of grain, as well as initial moisture content of drying agent). Their analysis facilitates the work in choosing the optimal mode. The developed analytical dependences of changes in the main drying parameters (moisture and temperature of grain, moisture content and temperature of the drying agent) along the length and width of the drying channel in tower dryers with suction air flow make it possible to link the main operating parameters, which facilitate the choice of rational drying modes.

Simulation of Sugarcane Residues Co-Gasification (Vinasse-Straw-Bagasse) for Different Equivalence Ratios and Gasifying Agents

2021 ◽  
Vol 15 (1) ◽  
pp. 50-60
Author(s):  
Cláudia C. Santos ◽  
Janaine dos A. Oliveira ◽  
Igor de A. Barbieri ◽  
Filipe A. E Monhol
Keyword(s):  
Return On Investment ◽  
Energy Content ◽  
Operating Temperature ◽  
Energy Potential ◽  
Fuel Gas ◽  
Gasification Process ◽  
Thermoelectric Plant ◽  
Thermodynamic Equilibrium Model ◽  
Sugarcane Industry

This study evaluates the co-gasification of the main residues of the sugarcane industry (vinasse, bagasse and straw), in order to recover their energy and give an appropriate destination, making them suitable for use as fuel gas (syngas). To verify the feasibility of energy conversion through gasification, thermodynamic equilibrium model for gasification process was carried out and verified by literature available data. The gasification parameters for different gasification agents and equivalence ratio values were then obtained, such as: syngas composition and energy content, operating temperature, production rate and conversion efficiency. For equivalence ratios (ER) between 0.35 and 0.4 and temperatures around 750 °C, the quality of the syngas obtained is better, but a higher energy content is obtained in ER values of 0.2. There is a high H2/CO ratio for the gasifying agent formed by air and steam, and when using oxygen-enriched air, there is a change in the ER value that generates better syngas quality (to 0.3–0.35) and an increase in its energy content. There is also a possible better return on investment in a thermoelectric plant for the lowest ER values, which can increase gains by up to 21.4% and decrease the installation’s payback. The results indicate that the co-gasification of the waste is feasible, allowing a better use of its energy potential.

scholarly journals Evaporative cooling of icy interstellar grains

2020 ◽  
Vol 633 ◽  
pp. A97 ◽  
Author(s):  
Juris Kalvāns ◽  
Juris Roberts Kalnin
Keyword(s):  
Thermal Desorption ◽  
Thermal Energy ◽  
Energy Content ◽  
Cosmic Ray ◽  
Numerical Code ◽  
Radiative Cooling ◽  
Volatile Species ◽  
Interstellar Clouds ◽  
Ice Surface ◽  
Interstellar Grains

Context. While radiative cooling of interstellar grains is a well-known process, little detail is known about the cooling of grains with an icy mantle that contains volatile adsorbed molecules. Aims. We explore basic details for the cooling process of an icy grain with properties relevant to dark interstellar clouds. Methods. Grain cooling was described with the help of a numerical code considering a grain with an icy mantle that is structured in monolayers and containing several volatile species in proportions consistent with interstellar ice. Evaporation was treated as first-order decay. Diffusion and subsequent thermal desorption of bulk-ice species was included. Temperature decrease from initial temperatures of 100, 90, 80, 70, 60, 50, 40, 30, and 20 K was studied, and we also followed the composition of ice and evaporated matter. Results. We find that grain cooling occurs by partially successive and partially overlapping evaporation of different species. The most volatile molecules (such as N2) first evaporate at the greatest rate and are most rapidly depleted from the outer ice monolayers. The most important coolant is CO, but evaporation of more refractory species, such as CH4 and even CO2, is possible when the former volatiles are not available. Cooling of high-temperature grains takes longer because volatile molecules are depleted faster and the grain has to switch to slow radiative cooling at a higher temperature. For grain temperatures above 40 K, most of the thermal energy is carried away by evaporation. Evaporation of the nonpolar volatile species induces a complete change of the ice surface, as the refractory polar molecules (H2O) are left behind. Conclusions. The effectiveness of thermal desorption from heated icy grains (e.g., the yield of cosmic-ray-induced desorption) is primarily controlled by the thermal energy content of the grain and the number and availability of volatile molecules.

Evaluation of the predictive capacity of dead fuel moisture models for Eastern Australia grasslands

2016 ◽  
Vol 25 (9) ◽  
pp. 995 ◽  
Author(s):  
Miguel G. Cruz ◽  
Susan Kidnie ◽  
Stuart Matthews ◽  
Richard J. Hurley ◽  
Alen Slijepcevic ◽  
...  
Keyword(s):  
Moisture Content ◽  
Process Model ◽  
Prediction Models ◽  
Percentage Error ◽  
Fuel Moisture ◽  
Fire Behaviour ◽  
Predictive Capacity ◽  
Eastern Australia ◽  
Physically Based ◽  
Community Information

The moisture content of dead grass fuels is an important input to grassland fire behaviour prediction models. We used standing dead grass moisture observations collected within a large latitudinal spectrum in Eastern Australia to evaluate the predictive capacity of six different fuel moisture prediction models. The best-performing models, which ranged from a simple empirical formulation to a physically based process model, yield mean absolute errors of 2.0% moisture content, corresponding to a 25–30% mean absolute percentage error. These models tended to slightly underpredict the moisture content observations. The results have important implications for the authenticity of fire danger rating and operational fire behaviour prediction, which form the basis of community information and warnings, such as evacuation notices, in Australia.

Thermal Balance Calculation for Sludge Drying-Incineration System Based on Spreadsheet Software

2012 ◽  
Vol 516-517 ◽  
pp. 124-128 ◽  
Author(s):  
Wen Yi Deng ◽  
Xiao Lei Wang ◽  
Ya Xin Su ◽  
Xiao Dong Li ◽  
Jian Hua Yan
Keyword(s):  
Energy Consumption ◽  
Moisture Content ◽  
Process Model ◽  
Thermal Balance ◽  
Total Energy Consumption ◽  
Balance Calculation ◽  
High Efficient ◽  
Sludge Drying ◽  
User Friendly ◽  
Spreadsheet Software

In this study, a process model for thermal balance calculation of sludge drying-incineration system was constructed by spreadsheet software. Auxiliary fuel and total energy consumption of sludge drying-incineration and sludge direct incineration was calculated respectively. The result indicated that sludge moisture content of 60 wt.% was recommended for incineration, and that sludge drying-incineration consumed much less energy than sludge direct incineration when sludge moisture content was higher than 60 wt.%. The process model was proved to be high efficient, convenient and user-friendly in this study.

Moisture content and residence time distributions in mixed-flow grain dryers

2011 ◽  
Vol 109 (4) ◽  
pp. 297-307 ◽  
Author(s):  
J. Mellmann ◽  
K.L. Iroba ◽  
T. Metzger ◽  
E. Tsotsas ◽  
C. Mészáros ◽  
...  
Keyword(s):  
Moisture Content ◽  
Residence Time ◽  
Mixed Flow ◽  
Residence Time Distributions
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