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Title: Modeling of activated carbon production from lignite

Abstract

In the current work, a model has been successfully developed to describe the production of activated carbons from lignite char by physical activation. The mathematical model is based on the random pore model for the partial gasification undergone in a solid composed of spherical char particles placed in a fixed bed. To provide the necessary experimental input to test the model, three sets of samples have been produced by activation with carbon dioxide at different temperatures and a sequence of times. Data for the adsorption of nitrogen were obtained and analyzed to study the experimental development of the solid porosity in different ranges of pore size. With the initial textural characteristics of the char and only one previously fitted parameter from thermogravimetric analysis, the kinetic constant, the model predicts accurately not only the conversion rate but also the porosity development of the solid to an extent of 60% activation. 16 refs., 3 figs., 2 tabs.

Authors:
; ; ; ; ;  [1]
  1. Instituto de Carboquimica, CSIC, Zaragoza (Spain)
Publication Date:
OSTI Identifier:
20838267
Resource Type:
Journal Article
Resource Relation:
Journal Name: Energy and Fuels; Journal Volume: 20; Journal Issue: 6; Other Information: amastral@carbon.icb.csic.es
Country of Publication:
United States
Language:
English
Subject:
01 COAL, LIGNITE, AND PEAT; ACTIVATED CARBON; LIGNITE; MATHEMATICAL MODELS; CARBON DIOXIDE; COAL GASIFICATION; PRODUCTION

Citation Formats

M.V. Navarro, R. Murillo, J.M. Lopez, T. Garcia, M.S. Callen, and A.M. Mastral. Modeling of activated carbon production from lignite. United States: N. p., 2006. Web. doi:10.1021/ef060103o.
M.V. Navarro, R. Murillo, J.M. Lopez, T. Garcia, M.S. Callen, & A.M. Mastral. Modeling of activated carbon production from lignite. United States. doi:10.1021/ef060103o.
M.V. Navarro, R. Murillo, J.M. Lopez, T. Garcia, M.S. Callen, and A.M. Mastral. Fri . "Modeling of activated carbon production from lignite". United States. doi:10.1021/ef060103o.
@article{osti_20838267,
title = {Modeling of activated carbon production from lignite},
author = {M.V. Navarro and R. Murillo and J.M. Lopez and T. Garcia and M.S. Callen and A.M. Mastral},
abstractNote = {In the current work, a model has been successfully developed to describe the production of activated carbons from lignite char by physical activation. The mathematical model is based on the random pore model for the partial gasification undergone in a solid composed of spherical char particles placed in a fixed bed. To provide the necessary experimental input to test the model, three sets of samples have been produced by activation with carbon dioxide at different temperatures and a sequence of times. Data for the adsorption of nitrogen were obtained and analyzed to study the experimental development of the solid porosity in different ranges of pore size. With the initial textural characteristics of the char and only one previously fitted parameter from thermogravimetric analysis, the kinetic constant, the model predicts accurately not only the conversion rate but also the porosity development of the solid to an extent of 60% activation. 16 refs., 3 figs., 2 tabs.},
doi = {10.1021/ef060103o},
journal = {Energy and Fuels},
number = 6,
volume = 20,
place = {United States},
year = {Fri Dec 15 00:00:00 EST 2006},
month = {Fri Dec 15 00:00:00 EST 2006}
}
  • The Energy & Environmental Research Center (EERC) has pursued a research program for producing activated carbon from North Dakota lignite that can be competitive with commercial-grade activated carbon. As part of this effort, small-scale production of activated carbon was produced from Fort Union lignite. A conceptual design of a commercial activated carbon production plant was drawn, and a market assessment was performed to determine likely revenue streams for the produced carbon. Activated carbon was produced from lignite coal in both laboratory-scale fixed-bed reactors and in a small pilot-scale rotary kiln. The EERC was successfully able to upgrade the laboratory-scale activatedmore » carbon production system to a pilot-scale rotary kiln system. The activated carbon produced from North Dakota lignite was superior to commercial grade DARCO{reg_sign} FGD and Rheinbraun's HOK activated coke product with respect to iodine number. The iodine number of North Dakota lignite-derived activated carbon was between 600 and 800 mg I{sub 2}/g, whereas the iodine number of DARCO FGD was between 500 and 600 mg I{sub 2}/g, and the iodine number of Rheinbraun's HOK activated coke product was around 275 mg I{sub 2}/g. The EERC performed both bench-scale and pilot-scale mercury capture tests using the activated carbon made under various optimization process conditions. For comparison, the mercury capture capability of commercial DARCO FGD was also tested. The lab-scale apparatus is a thin fixed-bed mercury-screening system, which has been used by the EERC for many mercury capture screen tests. The pilot-scale systems included two combustion units, both equipped with an electrostatic precipitator (ESP). Activated carbons were also tested in a slipstream baghouse at a Texas power plant. The results indicated that the activated carbon produced from North Dakota lignite coal is capable of removing mercury from flue gas. The tests showed that activated carbon with the greatest iodine number was superior to commercial DARCO FGD for mercury capture. The results of the activated carbon market assessment indicate an existing market for water treatment and an emerging application for mercury control. That market will involve both existing and new coal-fired plants. It is expected that 20% of the existing coal-fired plants will implement activated carbon injection by 2015, representing about 200,000 tons of annual demand. The potential annual demand by new plants is even greater. In the mercury control market, two characteristics are going to dominate the customer's buying habit-performance and price. As continued demonstration testing of activated carbon injection at the various coal-fired power plants progresses, the importance of fuel type and plant configuration on the type of activated carbon best suited is being identified.« less
  • Activated carbon is produced from coconut shell char using steam or carbon dioxide as the reacting gas in a 100 mm diameter fluidized bed reactor. The effect of process parameters such as reaction time, fluidizing velocity, particle size, static bed height, temperature of activation, fluidizing medium, and solid raw material on activation is studied. The product is characterized by determination of iodine number and BET surface area. The product obtained in the fluidized bed reactor is much superior in quality to the activated carbons produced by conventional processes. Based on the experimental observations, the optimum values of process parameters aremore » identified.« less
  • A series of micro- and mesoporous activated carbons were produced from paper mill sludge using a modified carbonization methodology. N{sub 2}-adsorption isotherm data and mathematical models such as the D-R equation, {alpha}{sub s}-plot, and MP and BJH methods were used to characterize the surface properties of the produced carbons. Results of the surface analysis showed that paper mill sludge can be economically and successfully converted to micro- and mesoporous activated carbons with surface areas higher than 1000 m{sup 2}/g. Activated carbons with a prescribed micro- or mesoporous structure were produced by controlling the amount of zinc chloride (ZnCl{sub 2}) usedmore » during chemical activation. Pore evolvement was shown to be most affected by the incremental addition of ZnCl{sub 2}. Increasing the ZnCl{sub 2} to sludge ratio from 0.75 to 2.5 resulted in a 600% increase in the mesopore volume. ZnCl{sub 2} to sludge ratios less than 1 and greater than 1.5 resulted in the production of micro- and mesoporous carbons, respectively. At a ZnCl{sub 2} to sludge ratio of 3.5, an activated carbon with a predominantly (80%) mesoporous structure was produced. The calculated D-R micropore volumes for activated carbons with the suggested microporous structure were in good agreement with those obtained from the {alpha}{sub s} method, while estimated micropore volumes from the {alpha}{sub s} method deviated markedly from those obtained from the D-R equation for carbons with a predominantly mesoporous structure.« less
  • The EERC is undertaking a research and development program on carbon development, part of which is directed towards investigating the key parameters in the preparation of activated carbons from low-rank coals indigenous to North Dakota. Carbons have been prepared and characterized for potential sorption applications in flue gas and waste liquid streams. Lignite, owing to its wide occurrence and variability in properties, has received significant attention as a precursor of active carbon manufacture. Mineral matter content and its alkaline nature are two highly variable properties that can have important consequences on the production of suitable activated carbons. Other factors affectingmore » the production include carbonizing conditions, the activation agents, activation temperature, and activation time. However, as previously noted, the relationship between the above factors and the sorption activity is particularly complex. Part of the difficulty is that sorption activity encompasses at least three parameters, namely, surface area, pore distribution, and surface acidity/basicity. The presence of mineral matter in the coal can affect not only carbonization but also the activation and subsequent sorption and desorption processes. This paper presents results of an investigation of demineralization, carbonization temperature, activation temperature, and activation time for one lignite and leonardite from North Dakota.« less