Mathematical Modeling of Coal Gasification Processes in a Well-Stirred Reactor: Effects of Devolatilization and Moisture Content

2012 ◽  
Vol 26 (9) ◽  
pp. 5759-5768 ◽  
Author(s):  
Jian Xu ◽  
Li Qiao
Keyword(s):  
Mathematical Modeling ◽  
Moisture Content ◽  
Coal Gasification ◽  
Stirred Reactor

Exergy and Energy Analysis, Drying Kinetics and Mathematical Modeling of White Mulberry Drying Process

2014 ◽  
Vol 10 (2) ◽  
pp. 269-280 ◽  
Author(s):  
Hosain Darvishi ◽  
Mohammad Zarein ◽  
Saied Minaei ◽  
Hamid Khafajeh
Keyword(s):  
Mathematical Modeling ◽  
Energy Efficiency ◽  
Energy Consumption ◽  
Moisture Content ◽  
Specific Energy ◽  
Microwave Power ◽  
Specific Energy Consumption ◽  
Drying Kinetics ◽  
Improvement Potential ◽  
White Mulberry

Abstract The energy and exergy analysis, drying characteristics and mathematical modeling of the thin-layer drying kinetics of white mulberry using microwave drying were investigated. Results indicated that values of exergy efficiency (33.63–57.08%) were higher than energy efficiency (31.85–55.56%). Specific energy consumption increased with increasing microwave power while improvement potential decreased. The specific energy consumption and improvement potential varied from 3.97 to 6.73 MJ/kg water and 0.71 to 2.97 MJ/kg water, respectively. Also, energy efficiency decreased with decrease in moisture content and microwave power level. The best exergy and energy aspect was obtained by drying at 100 W microwave power. Drying took place mainly in warming up, constant rate and falling rate periods. The Page model showed the best fit to experimental drying data. Effective diffusivity increased with decreasing moisture content and increasing microwave power. It varied from 1.06 × 10−8 to 3.45 × 10−8 m2/s, with an energy activation of 3.986 W/g.

Experimental Investigations of Lean Stability Limits of a Prototype Syngas Burner for Low Calorific Value Gases

2011 ◽  
Author(s):  
Ivan R. Sigfrid ◽  
Ronald Whiddon ◽  
Marcus Alde´n ◽  
Jens Klingmann
Keyword(s):  
Equivalence Ratio ◽  
Coal Gasification ◽  
Stability Limit ◽  
Calorific Value ◽  
Kinetic Mechanism ◽  
Experimental Investigations ◽  
Stirred Reactor ◽  
Wobbe Index ◽  
The Stability ◽  
Experimental Values

The lean stability limit of a prototype syngas burner is investigated. The burner is a three sector system, consisting of a separate igniter, stabilizer and Main burner. The ignition sector, Rich-Pilot-Lean (RPL), can be operated with both rich or lean equivalence values, and serves to ignite the Pilot sector which stabilizes the Main combustion sector. The RPL and Main sectors are fully premixed, while the Pilot sector is partially premixed. The complexity of this burner design, especially the ability to vary equivalence ratios in all three sectors, allows for the burner to be adapted to various gases and achieve optimal combustion. The gases examined are methane and a high H2 model syngas (10% CH4, 22.5% CO, 67.5% H2). Both gases are combusted at their original compositions and the syngas was also diluted with N2 to a low calorific value fuel with a Wobbe index of 15 MJ/m3. The syngas is a typical product of gasification of biomass or coal. Gasification of biomass can be considered to be CO2 neutral. The lean stability limit is localized by lowering the equivalence ratio from stable combustion until the limit is reached. To get a comparable blowout definition the CO emissions is measured using a non-dispersive infrared sensor analyzer. The stability limit is defined when the measured CO emissions exceed 200 ppm. The stability limit is measured for the 3 gas mixtures at atmospheric pressure. The RPL equivalence ratio is varied to investigate how this affected the lean blowout limit. A small decrease in stability limit can be observed when increasing the RPL equivalence ratio. The experimental values are compared with values from a perfectly stirred reactor modeled (PSR), under burner conditions, using the GRI 3.0 kinetic mechanism for methane and the San Diego mechanism for the syngas fuels.

Mathematical modeling of alternating injection of oxygen and steam in underground coal gasification

2015 ◽  
Vol 150-151 ◽  
pp. 154-165 ◽  
Author(s):  
Ali Akbar Eftekhari ◽  
Karl Heinz Wolf ◽  
Jan Rogut ◽  
Hans Bruining
Keyword(s):  
Mathematical Modeling ◽  
Coal Gasification ◽  
Underground Coal Gasification

Mathematical Modeling of the Stream Method of Underground Coal Gasification

1975 ◽  
Vol 15 (05) ◽  
pp. 425-436 ◽  
Author(s):  
C.F. Magnani ◽  
S.M. Farouq Ali
Keyword(s):  
Mathematical Modeling ◽  
Carbon Dioxide ◽  
Coal Seam ◽  
Coal Gasification ◽  
Underground Coal Gasification ◽  
Hydrocarbon Gases ◽  
Underground Gasification ◽  
Performance Curves ◽  
Synthetic Gas

Abstract This investigation focuses on mathematical modeling of the process of underground gasification of coal by the stream method. A one-dimensional, steady-state model consisting of five coupled differential equations was formulated, and the solution, extracted analytically, was used to develop closed-form expressions for the parameters influencing coal gasification. The model then was used for interpreting field performance curves, predicting the results of The performance curves, predicting the results of The field tests, and ascertaining the over-all process sensitivity to the input variables. The usefulness of the model was shown by establishing the parameters influencing the success or failure of parameters influencing the success or failure of an underground gasification project. Introduction One method of eliminating many of the technological and environmental difficulties encountered during the production of synthetic gas through aboveground coal gasification involves gasifying cod in situ. This process, known as underground coal gasification, was first proposed in 1868 by Sir William Siemens and is based on the controlled combustion of coal in situ. This in-situ combustion results in the production of an artificial or synthetic gas that is rich in carbon dioxide, carbon monoxide, hydrogen, and hydrocarbon gases. Despite the fact that reaction stoichiometry is a moot element of underground coal gasification, it is nonetheless believed thatcarbon dioxide is formed by the partial oxidation of coal,carbon monoxide is generated by the subsequent reduction of carbon dioxide, andthe hydrogen and hydrocarbon gases result from the water-gas reaction and carbonization of coal, respectively. To effect the controlled combustion of coal in situ, the coal seam first must be ignited and a means must be provided for supporting combustion (through injection of a suitable gasification agent) and producing the gases generated underground. Fig. 1 presents a schematic diagram of an underground gasification system that complies with these requirements. This approach to gasifying coal is known as the stream or channel method and necessitates drilling two parallel galleries, one serving as an injection gas inlet and the other as a producer gas outlet. These wells are then linked by a borehole drilled horizontally through the coal seam. Ignition occurs in the coal seam at the gas inlet and proceeds in the direction of flow. The combustion front thus generated moves essentially perpendicular to the direction of gas flow. perpendicular to the direction of gas flow.Since the technological inception of underground gasification, over 1,500 publications have appeared in the literature that bear testimony to the absence of a complete, legitimate, theoretical analysis of the underground gasification process. Given this observation, it is the basis of this paper that progress in underground coal-gasification research progress in underground coal-gasification research has suffered from the absence of "interpretative theory"; that is, it has suffered from a lack of logical, physical, and mathematical analysis of the governing and underlying aerothermochemical principles. The difficulties in formulating a principles. The difficulties in formulating a mathematical model adequately describing the numerous phenomena involved during coal gasification are indeed formidable. SPEJ P. 425

scholarly journals Effect of Lignite Properties on Its Suitability for the Implementation of Underground Coal Gasification (UCG) in Selected Deposits

Energies ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5816
Author(s):  
Krzysztof Kapusta
Keyword(s):  
Moisture Content ◽  
Coal Gasification ◽  
Calorific Value ◽  
Process Efficiency ◽  
Average Moisture Content ◽  
Underground Coal Gasification ◽  
Gasification Process ◽  
Laboratory Setup ◽  
Large Bulk

Two experimental simulations of underground coal gasification (UCG) processes, using large bulk samples of lignites, were conducted in a surface laboratory setup. Two different lignite samples were used for the oxygen-blown experiments, i.e., “Velenje” meta-lignite (Slovenia) and “Oltenia” ortho-lignite (Romania). The average moisture content of the samples was 31.6wt.% and 45.6wt.% for the Velenje and Oltenia samples, respectively. The main aim of the study was to assess the suitability of the tested lignites for the underground coal gasification process. The gas composition and its production rates, as well as the temperatures in the artificial seams, were continuously monitored during the experiments. The average calorific value of gas produced during the Velenje lignite experiment (6.4 MJ/Nm3) was much higher compared to the result obtained for the experiment with Oltenia lignite (4.8 MJ/Nm3). The Velenje lignite test was also characterized by significantly higher energy efficiency, i.e., 44.6%, compared to the gasification of Oltenia lignite (33.4%). The gasification experiments carried out showed that the physicochemical properties of the lignite used considerably affect the in situ gasification process. Research also indicates that UCG can be considered as a viable option for the extraction of lignite deposits; however, lignites with a lower moisture content and higher energy density are preferred, due to their much higher process efficiency.

Thin-Layer Mathematical Modeling of Turmeric in Indirect Natural Conventional Solar Dryer

2020 ◽  
Vol 142 (4) ◽  
Author(s):  
Masnaji R. Nukulwar ◽  
Vinod B. Tungikar
Keyword(s):  
Mathematical Modeling ◽  
Moisture Content ◽  
Thin Layer ◽  
Air Velocity ◽  
Drying Time ◽  
Sun Drying ◽  
Solar Dryer ◽  
Air Temperatures ◽  
Drying Efficiency ◽  
Kinetics Of

Abstract The objective of this study is to find an optimized thin-layer mathematical model suitable for drying kinetics of turmeric. Turmeric has a high moisture content which necessitates effective drying. A 10 kg, sample batch, of turmeric was dried in a solar dryer. Drying air temperatures and air velocity were observed in the range of 55 °C–68 °C and 0.7 m/s–1.4 m/s, respectively, in the drying experiments. It is seen that the moisture content of the turmeric is reduced from 77% to 11.93% in 22 h when compared with open sun drying, which required 60 h for the same reduction in the moisture content. Scheffler dish was used to generate steam for the dryer. Seven thin-layer mathematical models, cited in the literature, had been used for the study. These models were applied for different trays placed in the dryer. The result of the research and experimentation showed that the Page model fits best for drying in the steam-based dryer and open sun drying. Experimental results showed 63.33% saving in drying time, and the drying efficiency was found as 29.85%. Uncertainty in the drying efficiency was observed as 0.67%. Experimental investigation and the findings from the mathematical modeling are presented in this paper.

scholarly journals Conveyor-Belt Dryers with Tangential Flow for Food Drying: Mathematical Modeling and Design Guidelines for Final Moisture Content Higher Than the Critical Value

Inventions ◽  
2020 ◽  
Vol 5 (2) ◽  
pp. 22
Author(s):  
Dario Friso
Keyword(s):  
Mathematical Modeling ◽  
Moisture Content ◽  
Rational Design ◽  
Conveyor Belt ◽  
Design Guidelines ◽  
Final Moisture Content ◽  
Temperature Sensitive ◽  
Optimized Design ◽  
Tangential Flow ◽  
Product Flow

The mathematical modeling presented in this work concerns the conveyor-belt dryer with the tangential flow of air with respect to food. This dryer, if operating in co-current, has the advantage of well preserving the organoleptic and nutritional qualities of the dried product. In fact, it has a low air temperature in the final stretch where the product has low moisture content and is therefore more temperature sensitive. It is a bulkier dryer than the continuous through-circulation conveyor dryer with a perforated belt. The latter is therefore more frequently used and has received greater study attention from researchers and designers of the industry. With the aim to propose guidelines for a rational design of the conveyor-belt dryer with tangential flow, a mathematical model was developed here through the differentiation of the drying rate equation followed by its integration performed along the dryer belt. Consequently, and with the assumption that the final moisture content XF of the product is higher than the critical moisture content XC, the relationships between the intensive quantities (temperatures, humidity and enthalpies), the extensive quantities (air and product flow rates) and the dimensional ones (length and width of the belt), were obtained. Finally, on the basis of these relationships, the rules for an optimized design for XF > XC were obtained and experimentally evaluated.

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