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Sefidari, Hamid
Publications (9 of 9) Show all publications
Sefidari, H., Wiinikka, H., Lindblom, B., Nordin, L. O., Wu, G., Yazhenskikh, E., . . . Öhman, M. (2019). Comparison of high-rank coals with respect to slagging/deposition tendency at the transfer-chute of iron-ore pelletizing grate-kiln plants: A pilot-scale experimental study accompanied by thermochemical equilibrium modeling and viscosity estimations. Fuel processing technology, 193, 244-262
Open this publication in new window or tab >>Comparison of high-rank coals with respect to slagging/deposition tendency at the transfer-chute of iron-ore pelletizing grate-kiln plants: A pilot-scale experimental study accompanied by thermochemical equilibrium modeling and viscosity estimations
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2019 (English)In: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 193, p. 244-262Article in journal (Refereed) Published
Abstract [en]

Iron-ore pelletizing plants use high-rank coals to supply the heat necessary to process ores. Ash material from coal, in combination with iron-ore dust originating from the disintegration of the pellets, can cause deposition/slagging which often leads to severe production losses and damage. Deposition/slagging is most prominent in the hot areas of the grate-kiln setup and is more severe at the inlet of the rotary-kiln, i.e., the transfer-chute. Following on from our previous work, high-rank bituminous coals with potential for use in the pelletizing process were combusted in a pilot-scale (0.4 MW) pulverized-coal fired experimental combustion furnace (ECF). The fly-ash particles and short-term deposits were characterized to shed light on the observed difference in slagging/deposition tendencies of the coals. Global thermodynamic equilibrium modeling, in combination with viscosity estimates, was used to interpret the experimental findings and investigate the effect of the coal-ash composition upon deposition/slagging. This approach was carried out with and without the presence of Fe2O3-rich pellet-dust under oxidizing conditions within the temperature range at the transfer-chute of iron-ore pelletizing rotary-kilns. Based on the findings, a Qualitative Slagging Indicator (QSI) was proposed that can help pre-screen new solid fuels for potential slagging issues. The proposed QSI highlights the following: (1) an inverse relationship between viscosity and slagging/deposition tendency of the coals was observed (2) as viscosity decreases (either with increasing temperature or due to the change in the coal-ash composition), stronger deposits will form that will complicate the mechanical removal of the deposited layer. It was therefore inferred that low viscosity molten phases facilitate deposition/slagging, which is exacerbated by the presence of fluxing agents (e.g., CaO, MgO, K2O, Na2O, and Fe2O3) in the deposits. The low viscosity coal-ash-induced molten phases are also more likely to interact with the Fe2O3-rich pellet-dust that results in further decreases in viscosity, thereby intensifying depositions. The results from this work complement the on-going research by our group to elucidate and alleviate ash-related problems in industrial grate kilns.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Iron-ore pelletizing, Coal-ash, Pellet-dust, Deposition (slagging), Thermochemical equilibrium calculations, Viscosity estimations
National Category
Energy Engineering
Research subject
Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-74064 (URN)10.1016/j.fuproc.2019.05.026 (DOI)000473842100026 ()2-s2.0-85066109318 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-06-10 (oliekm)

Available from: 2019-05-28 Created: 2019-05-28 Last updated: 2019-08-15Bibliographically approved
Sefidari, H., Lindholm, B., Wiinikka, H., Nordin, L. O., Mouzon, J., Bhuiyan, I. U. & Öhman, M. (2018). The effect of disintegrated iron-ore pellet dust on deposit formation in a pilot-scale pulverized coal combustion furnace: Part I: Characterization of process gas particles and deposits. Fuel processing technology, 177, 283-298
Open this publication in new window or tab >>The effect of disintegrated iron-ore pellet dust on deposit formation in a pilot-scale pulverized coal combustion furnace: Part I: Characterization of process gas particles and deposits
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2018 (English)In: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 177, p. 283-298Article in journal (Refereed) Published
Abstract [en]

o initiate the elucidation of deposit formation during the iron-ore pelletization process, a comprehensive set of experiments was conducted in a 0.4 MW pilot-scale pulverized-coal-fired furnace where three different scenarios were considered as follows; Case 1 (reference case): Coal was combusted without the presence of pellet dust. Case 2: Natural gas was combusted together with simultaneous addition of pellet dust to the gas stream. Case 3: Coal was combusted together with the addition of pellet dust simulating the situation in the large-scale grate-kiln setup. Particles and deposits were sampled from 3 positions of different temperature via a water-cooled sampling probe. Three distinct fragmentation modes were identified based on the aerodynamic particle diameter (Dp). The fine mode: Particles with 0.03 < Dp < 0.06 μm. The first fragmentation mode: Particles with 1 < Dp < 10 μm. The second fragmentation mode: Coarse particles (cyclone particles, Dp > 10 μm). A transition from a bimodal PSD (particle size distribution) to a trimodal PSD was observed when pellet dust was added (Case 3) and consequently the elemental bulk composition of the abovementioned modes was changed. The most extensive interaction between pellet dust and coal-ash particles was observed in the coarse mode where a significant number of coal ash globules were found attached to the surface of the hematite particles. The morphology of the sharp-edged hematite particles was changed to smooth-edged round particles which proved that hematite particles must have interacted with the surrounding aluminosilicate glassy phase originating from the coal ash. The short-term deposits collected during coal combustion (Case 1) were highly porous in contrast to the high degree of sintering observed in the experiments with pellet dust addition (Case 3) which is attributed to the dissolution of hematite particles in the aluminosilicate glassy phase. The results suggest that pellet dust itself (Case 2) has low slagging tendency, independent of temperature. However, when coal-ash is present (Case 3), auxiliary phases are added such that tenacious particles are formed and slagging occurs.

Place, publisher, year, edition, pages
Elsevier, 2018
National Category
Energy Engineering Chemical Engineering Chemical Process Engineering
Research subject
Energy Engineering; Chemical Technology
Identifiers
urn:nbn:se:ltu:diva-68712 (URN)10.1016/j.fuproc.2018.05.004 (DOI)000437819600030 ()2-s2.0-85046802389 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-05-14 (andbra)

Available from: 2018-05-14 Created: 2018-05-14 Last updated: 2019-01-18Bibliographically approved
Sefidari, H., Lindblom, B., Wiinikka, H., Nordin, L. O., Lennartsson, A., Mouzon, J., . . . Öhman, M. (2018). The effect of disintegrated iron-ore pellet dust on deposit formation in a pilot-scale pulverized coal combustion furnace: Part II: Thermochemical equilibrium calculations and viscosity estimations. Fuel processing technology, 180, 189-206
Open this publication in new window or tab >>The effect of disintegrated iron-ore pellet dust on deposit formation in a pilot-scale pulverized coal combustion furnace: Part II: Thermochemical equilibrium calculations and viscosity estimations
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2018 (English)In: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 180, p. 189-206Article in journal (Refereed) Published
Abstract [en]

Fly ash particles from the combustion of solid-fuels together with disintegrated particles arising from iron-ore pellets result in accumulation of deposits on the refractory linings of the grate-kiln induration machine during the iron-ore pelletizing process. The deposits amass in the high-temperature regions of the induration furnace thus disturbing the flow of gas and pellets. Therefore, to tackle the above-mentioned issues, an understanding of deposit formation mechanism is of crucial importance. This study was conducted with the objective of addressing the effect of disintegrated iron-ore pellet dust on deposit formation and the mechanisms behind deposition (slagging) in the grate-kiln process. A comprehensive set of experiments was conducted in a 0.4 MW pilot-scale pulverized-coal- fired furnace where three different scenarios were considered as follows; Case 1 (reference case): Coal was combusted without the presence of pellet dust. Case 2: Natural gas was combusted together with simultaneous addition of pellet dust to the gas stream. Case 3: Coal was combusted together with the addition of pellet dust simulating the situation in the large-scale setup. Fly ash particles and short-term deposits were characterized and deposition was addressed in Part I of this study. In light of the experimental observations (Part I) and the thermochemical equilibrium calculations (Part II), a scheme of ash transformation during the iron-ore pelletizing process was proposed. The dissolution of hematite particles into the Ca-rich-aluminosilicate melt (from the coal-ash constituents) decreased the viscosity and resulted in the formation of stronger (heavily sintered) deposits. Overall, this pilot-scale work forms part of a wider study which aims at deepening the understanding of ash transformation phenomena during the large-scale pelletizing process.

Place, publisher, year, edition, pages
Elsevier, 2018
National Category
Energy Engineering Chemical Engineering Metallurgy and Metallic Materials Chemical Process Engineering
Research subject
Energy Engineering; Chemical Technology; Process Metallurgy
Identifiers
urn:nbn:se:ltu:diva-69019 (URN)10.1016/j.fuproc.2018.05.005 (DOI)000447580600020 ()2-s2.0-85047214684 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-11-05 (johcin) 

Available from: 2018-05-31 Created: 2018-05-31 Last updated: 2019-01-18Bibliographically approved
Razmjoo, N., Sefidari, H. & Strand, M. (2016). Measurements of temperature and gas composition within the burning bed of wet woody residues in a 4 MW moving grate boiler (ed.). Fuel processing technology, 152, 438-445
Open this publication in new window or tab >>Measurements of temperature and gas composition within the burning bed of wet woody residues in a 4 MW moving grate boiler
2016 (English)In: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 152, p. 438-445Article in journal (Refereed) Published
Abstract [en]

Moving grate firing systems are widely used for biomass combustion. The characteristics of the fuel bed combustion in moving grate boilers are of practical interest as they are directly related to the release of pollutants and affect the furnace efficiency. Measurements of temperature and gas species concentrations inside the fuel bed are necessary to improve our understanding of the highly complex processes involved in biomass combustion. There have been few experimental studies of the fuel bed of industrial scale grate furnaces. The present study measured temperature and gas species concentrations within a thick burning bed of wet woody biomass, in a 4 MW reciprocating grate boiler. Measurements were carried out under three different operating conditions through ports located in the wall of the furnace using a stainless steel probe incorporating a thermocouple. Temperatures of about 1000 °C were measured close to the grate, indicating intense combustion at the bottom of the fuel bed. The temperature distribution along the bed height showed that different stages of the combustion process take place in horizontally adjacent layers along the grate. Higher flow rates of the primary air resulted in relatively higher CO and lower CO2 and NO concentrations in the fuel bed.

National Category
Energy Engineering
Research subject
Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-4583 (URN)10.1016/j.fuproc.2016.07.011 (DOI)000381950200050 ()2-s2.0-84979696737 (Scopus ID)28d2be95-66a0-49b6-83fc-822b79247e79 (Local ID)28d2be95-66a0-49b6-83fc-822b79247e79 (Archive number)28d2be95-66a0-49b6-83fc-822b79247e79 (OAI)
Note

Validerad; 2016; Nivå 2; 20160805 (hamsef)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Razmjoo, N., Sefidari, H. & Strand, M. (2015). Experimental investigation of fuel bed combustion in an industrial grate boiler (ed.). Paper presented at European Conference on Industrial Furnaces and Boilers : 07/04/2015 - 10/04/2015. Paper presented at European Conference on Industrial Furnaces and Boilers : 07/04/2015 - 10/04/2015.
Open this publication in new window or tab >>Experimental investigation of fuel bed combustion in an industrial grate boiler
2015 (English)Conference paper, Oral presentation only (Refereed)
National Category
Energy Engineering
Research subject
Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-26890 (URN)0268928f-95b6-4ec0-a353-ac77eaf66477 (Local ID)0268928f-95b6-4ec0-a353-ac77eaf66477 (Archive number)0268928f-95b6-4ec0-a353-ac77eaf66477 (OAI)
Conference
European Conference on Industrial Furnaces and Boilers : 07/04/2015 - 10/04/2015
Note
Godkänd; 2015; 20150424 (hamsef)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2017-11-25Bibliographically approved
Sefidari, H., Razmjoo, N. & Strand, M. (2014). An experimental study of combustion and emissions of two types of woody biomass in a 12-MW reciprocating-grate boiler (ed.). Paper presented at . Fuel, 135, 120-129
Open this publication in new window or tab >>An experimental study of combustion and emissions of two types of woody biomass in a 12-MW reciprocating-grate boiler
2014 (English)In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 135, p. 120-129Article in journal (Refereed) Published
National Category
Energy Engineering
Research subject
Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-7116 (URN)10.1016/j.fuel.2014.06.051 (DOI)000340945400017 ()56f3d685-2281-4827-a4a6-1b082239eba3 (Local ID)56f3d685-2281-4827-a4a6-1b082239eba3 (Archive number)56f3d685-2281-4827-a4a6-1b082239eba3 (OAI)
Note
Validerad; 2014; 20140711 (hamsef)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Razmjoo, N., Sefidari, H. & Strand, M. (2014). Characterization of hot gas in a 4 MW reciprocating grate boiler (ed.). Paper presented at . Fuel processing technology, 124, 21-27
Open this publication in new window or tab >>Characterization of hot gas in a 4 MW reciprocating grate boiler
2014 (English)In: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 124, p. 21-27Article in journal (Refereed) Published
National Category
Energy Engineering
Research subject
Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-14399 (URN)10.1016/j.fuproc.2014.02.011 (DOI)dc04a27a-438c-4067-b5ff-fd48db739bf5 (Local ID)dc04a27a-438c-4067-b5ff-fd48db739bf5 (Archive number)dc04a27a-438c-4067-b5ff-fd48db739bf5 (OAI)
Note
Validerad; 2014; 20140711 (hamsef)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2017-11-24Bibliographically approved
Razmjoo, N., Sefidari, H., Strand, M. & Yang, J. (2013). Gas Measurements and Characterization of Wood Combustion in a Traveling Grate Boiler (ed.). In: (Ed.), (Ed.), Proceedings for 21st European Biomass Conference and Exhibition: . Paper presented at European Biomass Conference and Exhibition : 03/06/2013 - 07/06/2013 (pp. 591-594).
Open this publication in new window or tab >>Gas Measurements and Characterization of Wood Combustion in a Traveling Grate Boiler
2013 (English)In: Proceedings for 21st European Biomass Conference and Exhibition, 2013, p. 591-594Conference paper, Published paper (Refereed)
Abstract [en]

Experimental tests have been carried out on a moving grate boiler at a 4 MW heating plant located at a sawing mill in south of Sweden. In order to investigate the performance of the combustion chamber, the local concentrations of O2, NO and CO are determined in the region above the grate using two water-cooled stainless steel probes of different lengths and diameters. The fuel used was sawmill waste consisting of bark, sawdust and shavings. The results of the study provided valuable insights into the combustion process.

Series
European biomass conference and exhibition proceedings, ISSN 2282-5819
National Category
Energy Engineering
Research subject
Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-26918 (URN)10.5071/21stEUBCE2013-2CO.7.5 (DOI)02ffb34d-d8a8-432a-bf85-f43743cddbfa (Local ID)978-88-89407-53-0 (ISBN)02ffb34d-d8a8-432a-bf85-f43743cddbfa (Archive number)02ffb34d-d8a8-432a-bf85-f43743cddbfa (OAI)
Conference
European Biomass Conference and Exhibition : 03/06/2013 - 07/06/2013
Note
Godkänd; 2013; 20140711 (hamsef)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2017-11-25Bibliographically approved
Sefidari, H., Razmjoo, N. & Richards, T. (2011). Kinetic Analysis of Isothermal and Non-isothermal Gasification of Undigested Organic Solid Waste with CO2 from Thermogravimetric Analysis (ed.). Paper presented at International Conference of Sustainable Thermal Energy Management in the Process Industries : 25/10/2011. Paper presented at International Conference of Sustainable Thermal Energy Management in the Process Industries : 25/10/2011.
Open this publication in new window or tab >>Kinetic Analysis of Isothermal and Non-isothermal Gasification of Undigested Organic Solid Waste with CO2 from Thermogravimetric Analysis
2011 (English)Conference paper, Oral presentation only (Refereed)
National Category
Energy Engineering
Research subject
Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-39122 (URN)dbe19147-93ef-4df9-bfe8-3202bed86e4b (Local ID)dbe19147-93ef-4df9-bfe8-3202bed86e4b (Archive number)dbe19147-93ef-4df9-bfe8-3202bed86e4b (OAI)
Conference
International Conference of Sustainable Thermal Energy Management in the Process Industries : 25/10/2011
Note
Godkänd; 2011; 20140711 (hamsef)Available from: 2016-10-03 Created: 2016-10-03 Last updated: 2017-11-25Bibliographically approved
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