Indrek Aarna - Academia.edu (original) (raw)
Papers by Indrek Aarna
Portions of this document may be illegible in electronic image products. Images are produced from... more Portions of this document may be illegible in electronic image products. Images are produced from the best available original document.
Oil Shale, 2013
The oil shale industry has slowly but steadily increased its reach in the global energy sphere. T... more The oil shale industry has slowly but steadily increased its reach in the global energy sphere. The sharing of experience between experts plays an important part in education in the energy field, and the the latest International Oil Shale Symposium, which took place from 10 to 11 June 2013 at Tallinn University of Technology, in the capital of Estonia, once again provided a great opportunity for that. All who took part in the summary discussion of the Symposium came to the conclusion that the oil shale community is a small and very interdependent one, which makes cooperation in this sector extremely important. Although more than 400 experts from the energy field participated in the Symposium, yet many were unable to attend because there were not enough places available. It is those people in particular to whom I want to give an overview of this important event in the oil shale field. The first speakers of the opening day concentrated on the broader trends in the energy field, their speeches and presentations relating to the history of the oil shale industry, as well as to oil shale deposits around the world. Besides the experiences in the field of oil shale processing, environmental and socioeconomic impacts were also considered. Environmental topics were the focus of a separate session on the second day of the Symposium. The Symposium was opened by Sandor Liive, Chairman of the Management Board of Eesti Energia, according to whom the interest in non-traditional energy sources keeps growing around the world. Oil shale is a very slowly changing type of energy whose locations, quality, and accessibility have been studied thoroughly. "Although the accurate forecasting of the future is difficult, the valuations conducted by the International Energy Agency and others show that oil prices should remain constant-and on the level that makes oil shale profitable," Liive said. The oil shale reserves of the US are significantly greater than Estonia's, but the latter has the most experience in oil shale processing. Jeffrey D. Levine, the United States Ambassador to Estonia, pointed out that for the US both security and affordable prices are important in the
This report was prepared as an account of work sponsored by an agency of the United States Govern... more This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process. or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect thosc of the DOE / pc94218-4
Limited availability of conventional petroleum resources and the world’s growing demand for fuel ... more Limited availability of conventional petroleum resources and the world’s growing demand for fuel and energy sources have brought about the need for development of efficient techniques to make use of fuel resources other than crude oil within the past decades. One of these resources is oil shale. With the aim of developing an energy-efficient and economically viable oil shale processing solution, Outotec and Eesti Energia have combined their competences in the fields of fluidized bed technology and solid heat carrier based oil winning. The developments achieved in the framework of this collaboration led to the Enefit280 oil winning plant, which is now operating in the eastern Estonian region of Auvere. The presented work provides a detailed overview of the Enefit280 process and the interdependence of its individual components. Special attention is paid to the multi-functional role of a circulating fluidized bed incinerator, which is operated at a solids feed rate of up to 840 tons pe...
Progress in Thermochemical Biomass Conversion, 2001
Energy & Environment, 2011
... oil hydrotreater unit can use process concepts, hardware components, and catalysts commercial... more ... oil hydrotreater unit can use process concepts, hardware components, and catalysts commercially proven ... to our development work, OT has comprehensive expertise and R&D support, proven scale ... and auxiliary systems such as pumps, tanks and boiler feed water preparation. ...
This report conveys recent progress on two issues. The first concerns the prediction on char-NO r... more This report conveys recent progress on two issues. The first concerns the prediction on char-NO reactivity in general. The work has been performed upon a literature review, supplemented by our own recent results. The second part has to do with more detailed issues related to the mechanism of the reaction. Specifically, it is concerned with how oxide desorption can affect
The emission of nitrogen oxides from combustion of coal remains a problem of considerable interes... more The emission of nitrogen oxides from combustion of coal remains a problem of considerable interest, whether the concern is with acid rain, stratospheric ozone chemistry, or {open_quotes}greenhouse{close_quotes} gases. Whereas earlier the concern was focused mainly on NO (as a primary combustion product) and to a lesser extent NOâ, in recent years the emissions of NâO have also captured considerable attention, particularly in the context of fluidized bed combustion, in which the problem appears to be most acute. The research community has only recently begun to take solid hold on the NâO problem. This is in part because earlier estimates of the importance of NâO in combustion processes were clouded by artifacts in sampling which have now been resolved. This project is concerned with the mechanism of reduction of both NO and NâO by carbons.
Fuel, 1997
The literature on the kinetics of the NO-carbon reaction is reviewed. Data are examined both from... more The literature on the kinetics of the NO-carbon reaction is reviewed. Data are examined both from studies in which catalysis played no role and from studies in which catalysts were present as a result of addition or as natural inclusions (i.e. in coals). It is concluded that there generally exist three distinct reaction regimes, defined in terms of reaction temperatures. There is a near-ambient-temperature chemisorption regime, in which steady gasification is not possible. In this regime, both reversible and irreversible chemisorption processes are observed. A low-temperature gasification regime is observed at temperatures above ~ 500 K, but below ~ 1000 K. A hightemperature gasification regime is observed above this transition temperature. The low-temperature gasification regime is characterized by low activation energies, and the high-temperature regime by high activation energies. These two distinct gasification regimes however are not observed in all cases, and there is as yet no clear understanding of what determines this. In the reaction of pure NO with carbons, the order of reaction with respect to NO appears to be near unity in the gasification regimes and two in the low-temperature chemisorption regime. The apparent order in gasification is strongly influenced by the presence of CO in the reactant gas stream, and in certain reaction configurations the CO may be self-generated. In the presence of CO, the apparent order with respect to NO decreases, and there are several reports of apparent fractional order. Other oxidizing gases (e.g. O2, H20) can also influence the kinetics and course of the NO-carbon reaction. The thermal history of the carbon can have a significant effect on its reactivity in NO. It appears however that the annealing of carbons towards NO cannot be reliably predicted from the annealing behaviour of the carbons towards other oxidizing gases (i.e. 02). Reaction rates of NO with carbon can also be influenced by the presence of mineral matter. There is no general agreement on the quantitative importance of mineral catalysis in the reaction of carbons with NO.
The goal of this research was to investigate the pore development of a non-softening coal char in... more The goal of this research was to investigate the pore development of a non-softening coal char in different oxidizing gas environments. Char prepared from the Pittsburgh No. 8 coal in the Argonne Premium Sample Bank was chosen as representative of a char from a softening coal. The activation pattern of a coal char from softening coal follows a similar pattern in CO 2 , oxygen and H 2 O gas environments, under Zone 1 conditions. During the first step of the gasification the pores smaller then 10Å are opened, followed by larger micropore, mesopore and macropore growth. After a critical level of burn off level the first pores to collapse or disappear are meso-and macropores followed by the micropores.
Symposium (International) on Combustion, 1998
ABSTRACT
Proceedings of the Combustion Institute, 2002
A detailed study has been conducted on the nature of porosity developed during the combustion of ... more A detailed study has been conducted on the nature of porosity developed during the combustion of coal chars. This information is used to provide information on the mode of char combustion in full-scale pulverized coal boilers. Both laboratory-prepared and actual commercial boiler chars have been examined. The characterization of porosity involved the use of nitrogen and carbon dioxide adsorption. Porosity development in the laboratory chars, in air under zone I reaction conditions, followed a trend dictated by rank. Porosity generally increases with decreasing rank. The development of porosity under zone II conditions was also explored and found to follow a different course than that under zone I burning: significantly less microporosity was developed under these conditions. It can be inferred from the development of porosity in commercial chars, when burned under laboratory zone I conditions, that the utility boilers were operating under zone II conditions. Comparison of the laboratory chars with the commercial chars also supports this conclusion. The conclusion that nitrogen is a better general probe of commercial (high burnoff) char than carbon dioxide receives further support. A hypothesis is advanced regarding the origin of the very steep increase in apparent nitrogen-accessible porosity at low burnoffs.
Symposium (International) on Combustion, 1998
ABSTRACT
Fuel, 2009
The oxidation behavior of tire-derived fuel (TDF) char has recently been studied by several group... more The oxidation behavior of tire-derived fuel (TDF) char has recently been studied by several groups. In the present study, TDF char oxidation has been examined between 670 and 825K, at oxygen partial pressures ranging from 2 to 19.8kPa. The order of reaction with respect to oxygen varied with burnoff, and was in the range 0.72–0.86. The activation energy of reaction
Energy & Fuels, 1999
... Casa-Lillo, MA; Linares-Solano, A. Langmuir1998, 14, 4589−4596. [ACS Full Text ACS Full Text ... more ... Casa-Lillo, MA; Linares-Solano, A. Langmuir1998, 14, 4589−4596. [ACS Full Text ACS Full Text ]. (6) DeGroot, WF; Richards, GN Carbon1991, 29, 179. ... Agustín Bueno-López, José Antonio Caballero, and Avelina García-García. Energy & Fuels 2002 16 (6), 1425-1428. ...
Portions of this document may be illegible in electronic image products. Images are produced from... more Portions of this document may be illegible in electronic image products. Images are produced from the best available original document.
Oil Shale, 2013
The oil shale industry has slowly but steadily increased its reach in the global energy sphere. T... more The oil shale industry has slowly but steadily increased its reach in the global energy sphere. The sharing of experience between experts plays an important part in education in the energy field, and the the latest International Oil Shale Symposium, which took place from 10 to 11 June 2013 at Tallinn University of Technology, in the capital of Estonia, once again provided a great opportunity for that. All who took part in the summary discussion of the Symposium came to the conclusion that the oil shale community is a small and very interdependent one, which makes cooperation in this sector extremely important. Although more than 400 experts from the energy field participated in the Symposium, yet many were unable to attend because there were not enough places available. It is those people in particular to whom I want to give an overview of this important event in the oil shale field. The first speakers of the opening day concentrated on the broader trends in the energy field, their speeches and presentations relating to the history of the oil shale industry, as well as to oil shale deposits around the world. Besides the experiences in the field of oil shale processing, environmental and socioeconomic impacts were also considered. Environmental topics were the focus of a separate session on the second day of the Symposium. The Symposium was opened by Sandor Liive, Chairman of the Management Board of Eesti Energia, according to whom the interest in non-traditional energy sources keeps growing around the world. Oil shale is a very slowly changing type of energy whose locations, quality, and accessibility have been studied thoroughly. "Although the accurate forecasting of the future is difficult, the valuations conducted by the International Energy Agency and others show that oil prices should remain constant-and on the level that makes oil shale profitable," Liive said. The oil shale reserves of the US are significantly greater than Estonia's, but the latter has the most experience in oil shale processing. Jeffrey D. Levine, the United States Ambassador to Estonia, pointed out that for the US both security and affordable prices are important in the
This report was prepared as an account of work sponsored by an agency of the United States Govern... more This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process. or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect thosc of the DOE / pc94218-4
Limited availability of conventional petroleum resources and the world’s growing demand for fuel ... more Limited availability of conventional petroleum resources and the world’s growing demand for fuel and energy sources have brought about the need for development of efficient techniques to make use of fuel resources other than crude oil within the past decades. One of these resources is oil shale. With the aim of developing an energy-efficient and economically viable oil shale processing solution, Outotec and Eesti Energia have combined their competences in the fields of fluidized bed technology and solid heat carrier based oil winning. The developments achieved in the framework of this collaboration led to the Enefit280 oil winning plant, which is now operating in the eastern Estonian region of Auvere. The presented work provides a detailed overview of the Enefit280 process and the interdependence of its individual components. Special attention is paid to the multi-functional role of a circulating fluidized bed incinerator, which is operated at a solids feed rate of up to 840 tons pe...
Progress in Thermochemical Biomass Conversion, 2001
Energy & Environment, 2011
... oil hydrotreater unit can use process concepts, hardware components, and catalysts commercial... more ... oil hydrotreater unit can use process concepts, hardware components, and catalysts commercially proven ... to our development work, OT has comprehensive expertise and R&D support, proven scale ... and auxiliary systems such as pumps, tanks and boiler feed water preparation. ...
This report conveys recent progress on two issues. The first concerns the prediction on char-NO r... more This report conveys recent progress on two issues. The first concerns the prediction on char-NO reactivity in general. The work has been performed upon a literature review, supplemented by our own recent results. The second part has to do with more detailed issues related to the mechanism of the reaction. Specifically, it is concerned with how oxide desorption can affect
The emission of nitrogen oxides from combustion of coal remains a problem of considerable interes... more The emission of nitrogen oxides from combustion of coal remains a problem of considerable interest, whether the concern is with acid rain, stratospheric ozone chemistry, or {open_quotes}greenhouse{close_quotes} gases. Whereas earlier the concern was focused mainly on NO (as a primary combustion product) and to a lesser extent NOâ, in recent years the emissions of NâO have also captured considerable attention, particularly in the context of fluidized bed combustion, in which the problem appears to be most acute. The research community has only recently begun to take solid hold on the NâO problem. This is in part because earlier estimates of the importance of NâO in combustion processes were clouded by artifacts in sampling which have now been resolved. This project is concerned with the mechanism of reduction of both NO and NâO by carbons.
Fuel, 1997
The literature on the kinetics of the NO-carbon reaction is reviewed. Data are examined both from... more The literature on the kinetics of the NO-carbon reaction is reviewed. Data are examined both from studies in which catalysis played no role and from studies in which catalysts were present as a result of addition or as natural inclusions (i.e. in coals). It is concluded that there generally exist three distinct reaction regimes, defined in terms of reaction temperatures. There is a near-ambient-temperature chemisorption regime, in which steady gasification is not possible. In this regime, both reversible and irreversible chemisorption processes are observed. A low-temperature gasification regime is observed at temperatures above ~ 500 K, but below ~ 1000 K. A hightemperature gasification regime is observed above this transition temperature. The low-temperature gasification regime is characterized by low activation energies, and the high-temperature regime by high activation energies. These two distinct gasification regimes however are not observed in all cases, and there is as yet no clear understanding of what determines this. In the reaction of pure NO with carbons, the order of reaction with respect to NO appears to be near unity in the gasification regimes and two in the low-temperature chemisorption regime. The apparent order in gasification is strongly influenced by the presence of CO in the reactant gas stream, and in certain reaction configurations the CO may be self-generated. In the presence of CO, the apparent order with respect to NO decreases, and there are several reports of apparent fractional order. Other oxidizing gases (e.g. O2, H20) can also influence the kinetics and course of the NO-carbon reaction. The thermal history of the carbon can have a significant effect on its reactivity in NO. It appears however that the annealing of carbons towards NO cannot be reliably predicted from the annealing behaviour of the carbons towards other oxidizing gases (i.e. 02). Reaction rates of NO with carbon can also be influenced by the presence of mineral matter. There is no general agreement on the quantitative importance of mineral catalysis in the reaction of carbons with NO.
The goal of this research was to investigate the pore development of a non-softening coal char in... more The goal of this research was to investigate the pore development of a non-softening coal char in different oxidizing gas environments. Char prepared from the Pittsburgh No. 8 coal in the Argonne Premium Sample Bank was chosen as representative of a char from a softening coal. The activation pattern of a coal char from softening coal follows a similar pattern in CO 2 , oxygen and H 2 O gas environments, under Zone 1 conditions. During the first step of the gasification the pores smaller then 10Å are opened, followed by larger micropore, mesopore and macropore growth. After a critical level of burn off level the first pores to collapse or disappear are meso-and macropores followed by the micropores.
Symposium (International) on Combustion, 1998
ABSTRACT
Proceedings of the Combustion Institute, 2002
A detailed study has been conducted on the nature of porosity developed during the combustion of ... more A detailed study has been conducted on the nature of porosity developed during the combustion of coal chars. This information is used to provide information on the mode of char combustion in full-scale pulverized coal boilers. Both laboratory-prepared and actual commercial boiler chars have been examined. The characterization of porosity involved the use of nitrogen and carbon dioxide adsorption. Porosity development in the laboratory chars, in air under zone I reaction conditions, followed a trend dictated by rank. Porosity generally increases with decreasing rank. The development of porosity under zone II conditions was also explored and found to follow a different course than that under zone I burning: significantly less microporosity was developed under these conditions. It can be inferred from the development of porosity in commercial chars, when burned under laboratory zone I conditions, that the utility boilers were operating under zone II conditions. Comparison of the laboratory chars with the commercial chars also supports this conclusion. The conclusion that nitrogen is a better general probe of commercial (high burnoff) char than carbon dioxide receives further support. A hypothesis is advanced regarding the origin of the very steep increase in apparent nitrogen-accessible porosity at low burnoffs.
Symposium (International) on Combustion, 1998
ABSTRACT
Fuel, 2009
The oxidation behavior of tire-derived fuel (TDF) char has recently been studied by several group... more The oxidation behavior of tire-derived fuel (TDF) char has recently been studied by several groups. In the present study, TDF char oxidation has been examined between 670 and 825K, at oxygen partial pressures ranging from 2 to 19.8kPa. The order of reaction with respect to oxygen varied with burnoff, and was in the range 0.72–0.86. The activation energy of reaction
Energy & Fuels, 1999
... Casa-Lillo, MA; Linares-Solano, A. Langmuir1998, 14, 4589−4596. [ACS Full Text ACS Full Text ... more ... Casa-Lillo, MA; Linares-Solano, A. Langmuir1998, 14, 4589−4596. [ACS Full Text ACS Full Text ]. (6) DeGroot, WF; Richards, GN Carbon1991, 29, 179. ... Agustín Bueno-López, José Antonio Caballero, and Avelina García-García. Energy & Fuels 2002 16 (6), 1425-1428. ...