| 1. |
- Alevanau, Aliaksandr, 1965-, et al.
(författare)
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Applicability of Scaling Approach for Analysis of Pyrolysis and Gasification of Porous Structures Composed of Solid Fuel Particles
- 2012
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Ingår i: ISRN Mechanical Engineering. - : Hindawi Publishing Corporation. - 2090-5122 .- 2090-5130.
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Tidskriftsartikel (refereegranskat)abstract
- Experimental research on the pyrolysis and gasification of randomly packed straw pellets was conducted with an emphasis on the reactive properties of the shrinking porous structure of the pellets. The apparent kinetics of such pyrolysis was approximated by the random pore, grain, and volumetric models. The best approximation results were obtained with the grain and random pore models. The self-organized oscillations of the pellet conversion rate during pyrolysis were observed. Two complementary explanations of the phenomenon are proposed.
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| 2. |
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| 3. |
- Alevanau, Aliaksandr, et al.
(författare)
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Parameters of high temperature steam gasification of original and pulverised wood pellets
- 2011
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Ingår i: Fuel processing technology. - : Elsevier BV. - 0378-3820 .- 1873-7188. ; 92:10, s. 2068-2074
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Tidskriftsartikel (refereegranskat)abstract
- Experiments on gasification of chars obtained from original and pulverised wood pellets were conducted in atmosphere of water steam and nitrogen under temperatures of 800, 900 and 950 degrees C. Molar flow rates of carbon containing product gases were measured and approximated using different models with respect to extents of carbon conversion in char of the pellets. Comparison of the random pore, grain and volumetric models revealed the best applicability for approximations of the random pore model. Apparent activation energies obtained as a result of application of the models to the data from experiments with char of original pellets were higher in comparison to those of pulverised pellets, except for a grain model. Approximations under 800 degrees C showed relatively big deviations from experimental data on the beginning of char gasification. This is attributed to catalytic effects from alkali metals in the pellets.
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| 4. |
- Alevanau, Aliaksandr, et al.
(författare)
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Prospective side effects of the heat and mass transfers in micro-porous structure of char during intermediate and final stages of the high-temperature pyrolysis
- 2013
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Ingår i: Nonlinear Phenomena in Complex Systems. - 1561-4085 .- 1817-2458. ; 16:3, s. 287-301
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Tidskriftsartikel (refereegranskat)abstract
- The general problem of a decrease of activation energy for reactions of thermal decomposition in ligno-cellulosic materials in the end of the high-temperature pyrolysis has been discussed. Experiments emphasizing the differences between the starting, intermediate and final stages of the process were conducted. A hypothesis to solve the problem from the point of view of a fundamental fractal theory was formulated. The conclusions of the discussions related to the hypothesis gave a description of new experiments to prove the fundamental theory on diffusion processes with naturally or artificially created conditions for self-organization.
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| 5. |
- Alevanau, Aliaksandr, 1965-
(författare)
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Study of the Apparent Kinetics of Biomass Gasification Using High-Temperature Steam
- 2010
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Among the latest achievements in gasification technology, one may list the development of a method to preheat gasification agents using switched ceramic honey combs. The best output from this technology is achieved with use of water steam as a gasification agent, which is heated up to 1600 °C. The application of these temperatures with steam as a gasification agent provides a cleaner syngas (no nitrogen from air, cracked tars) and the ash melts into easily utilised glass-like sludge. High hydrogen content in output gas is also favourable for end-user applications.Among the other advantages of this technology is the presumable application of fixed-bed-type reactors fed by separately produced and preheated steam. This construction assumes relatively high steam flow rates to deliver the heat needed for endothermic reactions involving biomass. The biomass is to be heated uniformly and evenly in the volume of the whole reactor, providing easier and simpler control and operation in comparison to other types of reactors. To provide potential constructors and exploiters of these reactors with the kinetic data needed for the calculations of vital parameters for both reactor construction and exploitation, basic experimental research of high-temperature steam gasification of four types of industrially produced biomass has been conducted.Kinetic data have been obtained for straw and wood pellets, wood-chip charcoal and compressed charcoal of mixed origin. Experiments were conducted using two experimental facilities at the Energy and Furnace Division of the Department of Material Science and Engineering (MSE) at the School of Industrial Engineering and Management (ITM) of the Royal Institute of Technology (KTH) and at the Combustion Laboratory of the Mechanical Engineering Department of the University of Maryland (UMD), USA.The experimental facility at the Energy and Furnace Division has been improved with the addition of several constructive elements, providing better possibilities for thermo-gravimetric measurements.The obtained thermo-gravimetric data were analysed and approximated using several models described in the literature. In addition, appropriate software based on the Scilab package was developed. The implementation of the isothermal method based on optimisation algorithms has been developed and tested on the data obtained under the conditions of a slow decrease of temperature in experiments with the char gasification in small-scale experimental facilities in the Energy and Furnace Division.The composition of the gases generated during the gasification of straw and wood pellets by high-temperature steam has been recorded and analysed for different experimental conditions.
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| 6. |
- Alevanau, Aliaksandr, et al.
(författare)
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Study of the effects of gaseous micro-expansion on the efficiency of convective heat transfer during pyrolysis
- 2013
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Ingår i: Fuel processing technology. - : Elsevier BV. - 0378-3820 .- 1873-7188. ; 106, s. 253-261
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Tidskriftsartikel (refereegranskat)abstract
- Measurements of temperature in the proximity of wood pellets (8 mm diameter) and thin wooden stick slices (5 cm diameter and 5 mm thickness) were conducted to estimate the effects of mixing between the evolving volatiles and hot steam (T > 700°C) flowing around the particles. Measurements of mass loss of the slices were conducted to estimate the apparent kinetic parameters of their pyrolysis. A simple kinetic model of the process (type II by Pyle and Zaror (1984) [20]) was investigated. The experiments showed a plateau-like part in the graphs of temperature measured in the proximity to the samples. The existence of this plateau-like part agrees with the general data of calorimetric measurements of pyrolysis, which show extensive energy consumption in the beginning of an active production of volatiles. A hypothesis regarding feedback on the process due to the micro-expansion and mixing of volatiles in the convective boundary layer is discussed.
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| 7. |
- Biswas, Amit, et al.
(författare)
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Change of pyrolysis characteristics and structure of woody biomass due to steam explosion pretreatment
- 2011
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Ingår i: Fuel processing technology. - : Elsevier BV. - 0378-3820 .- 1873-7188. ; 92:10, s. 1849-1854
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Tidskriftsartikel (refereegranskat)abstract
- Steam explosion (SE) pretreatment has been implemented for the production of wood pellet. This paper investigated changes in biomass structure due to implication of steam explosion process by its pyrolysis behavior/ characteristics. Salix wood chip was treated by SE at different pretreatment conditions, and then pyrolysis characteristic was examined by thermogravimetric analyzer (TGA) at heating rate of 10 K/min. Both pyrolysis characteristics and structure of biomass were altered due to SE pretreatment. Hemicellulose decomposition region shifted to low temperature range due to the depolymerization caused by SE pretreatment. The peak intensities of cellulose decreased at mild pretreatment condition while they increased at severe conditions. Lignin reactivity also increased due to SE pretreatment. However, severe pretreatment condition resulted in reduction of lignin reactivity due to condensation and re-polymerization reaction. In summary, higher pretreatment temperature provided more active biomass compared with milder pretreatment conditions. © 2011 Elsevier B.V. All rights reserved.
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| 8. |
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| 9. |
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| 10. |
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| 11. |
- Biswas, Amit Kumar, et al.
(författare)
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Steam pretreatment of Salix to upgrade biomass fuel for wood pellet production
- 2011
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Ingår i: Fuel processing technology. - : Elsevier BV. - 0378-3820 .- 1873-7188. ; 92:9, s. 1711-1717
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Tidskriftsartikel (refereegranskat)abstract
- Steam explosion (SE) pretreatment is served to separate the main components of woody biomass. In general there is a noticeable gap in literature in terms of application of steam explosion process to upgrade biomass fuel for wood pellet production. In order to study the influence of steam explosion pretreatment on biomass fuel, Salix wood chips was used as raw material. Four different SE experiments were performed by varying two key process factors; time and temperature. Elementary quality and ash properties of the pretreated residue were investigated. Moreover, physical and thermochemical properties of the pellet, produced from the residue, were also investigated. Reduction in ash content especially in alkali metals was observed in steam treated residue. Pretreatment of biomass also enhanced carbon content and reduced oxygen amount in the fuel which enhanced the heating value of the fuel. Moreover, pretreatment enhanced pellet density, impact resistance, and abrasive resistance of pellet. However, small degradation in ash fusion characteristics and char reactivity was also observed as the severity of the process increased.
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| 12. |
- Biswas, Amit Kumar, 1984-
(författare)
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Thermochemical behavior of pretreated biomass
- 2011
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Mankind has to provide a sustainable alternative to its energy related problems. Bioenergy is considered as one of the potential renewable energy resources and as a result bioenergy market is also expected to grow dramatically in future. However, logistic issues are of serious concern while considering biomass as an alternative to fossil fuel. It can be improved by introducing pretreated wood pellet. The main objective of this thesis is to address thermochemical behaviour of steam exploded pretreated biomass. Additionally, process aspects of torrefaction were also considered in this thesis. Steam explosion (SE) was performed in a laboratory scale reactor using Salix wood chips. Afterwards, fuel and thermochemical aspects of SE residue were investigated. It was found that Steam explosion pretreatment improved both fuel and pellet quality. Pyrolysis of SE residue reveals that alerted biomass composition significantly affects its pyrolysis behaviour. Contribution from depolymerized components (hemicellulose, cellulose and lignin) of biomass was observed explicitly during pyrolysis. When devolatilization experiment was performed on pellet produced from SE residue, effect of those altered components was observed. In summary, pretreated biomass fuel characteristics is significantly different in comparison with untreated biomass. On the other hand, Process efficiency of torrefaction was found to be governed by the choice of appropriate operating conditions and the type of biomass.
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| 13. |
- Blasiak, Wlodzimierz, et al.
(författare)
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Evaluation of new combustion technologies for CO2 and NOX reduction in steel industries
- 2004
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Ingår i: AIR POLLUTION XII. - 1853127221 ; , s. 761-771
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Konferensbidrag (refereegranskat)abstract
- The paper presents state-of-the-art combustion technologies for heating applications in the steel industry. Two types of burners that exhibit dilution combustion were evaluated in this study carried out in a semi-industrial furnace. These were regenerative air-fuel burner and oxy-fuel burner. The tests with regenerative air-fuel were carried out applying operation both with and without oxygen-enrichment. The main parameters studied for the different types of burners and operations include heat flux, thermal efficiency, and NOX at different levels of in-leakage of air. The in-flame parameters were measured including temperature, gas composition, total and radiative heat fluxes. All the studied burners provide a high efficiency of fuel utilization, a large 'flame' with uniform temperature and heat flux profiles. The results also clearly indicate that NOX emissions can be maintained at low or even very low levels well (less than 100 mg/MJ of fuel) meeting the restrictions at industrial-scale operation.
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| 14. |
- Blasiak, Wlodzimierz, et al.
(författare)
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"Flameless" oxyfuel combustion development for process improvement, emission reduction in furnaces and incinerators
- 2006
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Ingår i: Waste Management and the Environment III. - ASHURST, SOUTHAMPTON : WIT PRESS/COMPUTATIONAL MECHANICS PUBLICATIONS. - 1845641736 ; , s. 247-256
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Konferensbidrag (refereegranskat)abstract
- In recent years, the focus for the development of combustion technology focus has been set on the following main aims: fuel consumption reduction, nitrogen oxides emission reduction, increased productivity and product quality. Fuel consumption reduction has been reduced by as much as 30-40%, and also CO2 emission reduction was achieved by replacing combustion air with oxygen. To achieve very low emission of nitrogen oxides (NOx) the new combustion technology is characterised by: lower temperature of flame, more uniform temperature distribution and reduced concentration of oxygen as well as nitrogen inside the combustion chamber. As in this combustion technique a flame is replaced by a large chemical reaction zone and thus is often not visible the process was named as "flameless" combustion. "Flameless" combustion process that use oxygen, so called oxyfuel combustion, as well as its technical application is the subject of this work. The work presents a description and main features of the "flameless" oxyfuel combustion, results of laboratory tests of a new type of burner, REBOX (R), as well as examples of industrial applications including waste incineration are included.
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| 15. |
- Blasiak, Wlodzimierz
(författare)
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Modern technologies of biomass combustion and pre-treatment for more efficient electricity production : Review and case analysis
- 2013
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Ingår i: Climate Change Management. - Berlin, Heidelberg : Springer. - 1610-2002. ; , s. 269-282
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Tidskriftsartikel (refereegranskat)abstract
- Biomass combustion and biomass–coal cofiring represents a near-term, low-risk, low-cost, sustainable, renewable energy option that offers reduction in effective CO2 emissions, reduction in SOx and NOx emissions. However, untreated, woody biomass has a relatively low energy density, low bulk density, high moisture content and is difficult to comminute into small particles. As a matter of fact, these properties make biomass preparation and conversion to electricity expensive. Moreover, biomass can absorb moisture during storage and may rot as well. These properties have negative impacts during energy conversion such as lower combustion and electricity generation efficiencies. Therefore, enhancement of biomass properties is advisable not only to improve its inferior characteristics, but also to make it a suitable alternative to fossil fuels. In order to address these problems, biomass is required to be pretreated to improve its quality.
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| 16. |
- Blasiak, Włodzimierz, et al.
(författare)
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Oxyfuel flameless combustion for fuel consumption and nitrogen oxides emissions reductions and productivity increase
- 2006
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Ingår i: A and WM, Annual International Conference on Incineration and Thermal Treatment Technologies. - 0923204849 - 9780923204846 ; , s. 668-685
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Konferensbidrag (refereegranskat)abstract
- During last years development of combustion technology focussed the following main aims: fuel consumption reduction, nitrogen oxides emission reduction, increase of productivity and product quality. Fuel savings up to 50%, thus also CO 2 emission reduction, was achieved by replacing combustion air with oxygen. To achieve very low emission of nitrogen oxides (NOx) the new combustion technology is characterised by: lower temperature of flame, more uniform temperature distribution and low concentration of oxygen as well as nitrogen inside combustion chamber. Because in such combustion a flame is replaced by a large chemical reaction zone and thus often is not visible the process was named as flameless combustion. Flameless combustion process with use of oxygen, so called oxyfuel combustion, as well as its technical application is subject of this work. This work presents description and main features of the flameless oxyfuel combustion, results of laboratory tests of new type of flameless oxyfuel burner, as well as examples of industrial applications. This newly developed and applied combustion technology guarantees fuel consumption reduction (thus CO 2 reduction), increase of productivity as well as drastic reduction of nitrogen oxides emission when applied for example to thermal treatment processes of wastes, and a recovery of zinc-bearing feed in a rotary kiln.
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| 17. |
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| 18. |
- Blasiak, Wlodzimierz, et al.
(författare)
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Reforming Of Biomass Wastes Into Fuel Gas With High Temperature Air And Steam
- 2005
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The presented work aims to provide information on solid biomass conversion into fuel gas as a result of air and steam gasification process. In contrary to the conventional gasification in this work highly preheated air and steam is used as a gasifying agent. Preheat of air and steam is realised by means of the high-cycle regenerative air/steam preheater. Use of highly preheated gasifying media provides additional energy into the gasification process that enhances the thermal decomposition of the gasified solids. The objective of this work is to provide information on the process of biomass wastes reforming to fuel gas using high temperature air and steam gasification.High Temperature Air/Steam Gasification of biomass wastes has very clear economical and environmental benefits. It will increase consumption of biomass thus decreases CO2 emissions. Apart from CO2 reduction possibility, the new process, High Temperature Gasification has the following advantages:- Clean fuel gas for production of heat or electricity,- No need to treat ashes from gasification since there is no ash or at least no carbon in the ash produced,- No need to landfill since the produced slag can be used for example as a building material.In this work high temperature air and steam gasification of charcoal and wood pellets in a fixed bed updraft gasifier is tested. The following conclusions were found out:• For both charcoal and wood pellets gasification cases it was seen that an increase of steam molar fraction in the feed gas decreases the temperature of the gasification, the gasification rate, the mass yield of the fuel and molar fraction of carbon monoxide but increases molar fraction of hydrogen,• An increase of the feed gas temperature reduces production of tars, soot and char residue as well as increases calorific value of the fuel gas produced,• Preheating of the feed gas obtains a higher gasification efficiency and a higher gasification rate,• High temperature air and mixture of air and steam used as feed gas in a fixed bed gasifier shows the capability of this technology of maximising the gaseous product yield,• High lower heating value of fuel gas and high molar fraction of hydrogen and hydrocarbons obtained by using high temperature air and steam gasification technology increase the technical possibility of the application of fuel gas produced.
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| 19. |
- Donaj, Pawel
(författare)
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Conversion of biomass and waste using highly preheated agents for materials and energy recovery
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- One of the greatest challenges of human today is to provide the continuous and sustainable energy supply to the worldwide society. This shall be done while minimizing all the negative consequences of the operation(s) to the environment and its living habitants including human beings, taking from the whole life cycle perspective. In this thesis work new solutions for treatment biomass and waste are analyzed. Based on the fundamental research on the conversion of various materials (biomass: straw pellets, wood pellets; and waste: plastic waste, ASR residues after pyrolysis), converted by means of different systems (pyrolysis in a fluidized bed reactor, gasification in a fixed-bed reactor using highly preheated agents) it is recommended to classify materials against their charring properties under pyrolysis, in order to find the best destination for a given type of fuel. Based on phenomenological research it was found that one of the important effects, affecting performance of downdraft gasifiers, is the pressure drop through the bed and grate. It affects, directly, the velocity profile, temperature distribution and of the height of the bed, especially for the grate with restricted passage surface, although it was not investigated in literature. The lower grate porosity, the higher conversion of fuel and heating value of gas is produced. However, the stability of the process is disturbed; therefore reducing the grate porosity below 20% is not recommended, unless the system is designed to overtake the consequences of the rising pressure inside the reactor. This work proposed the method for prediction of a total pressure drop through the fixed-bed downdraft gasifier equipped with a grate of certain porosity with an uncertainty of prediction ±7.10. Three systems have been proposed; one for the treatment of automotive shredder residue (ASR), one for the treatment of plastic waste (polyolefins) and one for biomass (wood/straw pellets). Pyrolysis is an attractive mean of conversion of non-charring materials (like plastic waste) into valuable hydrocarbons feedstock. It gives directly 15-30% gaseous olefins while the residue consisting of naphtha-like feedstock has to be reformed/upgraded to olefins or other chemicals (e.g. gasoline generation) using available petrochemical technologies. Pyrolysis of complex waste mixture such as ASR is an attractive waste pretreatment method before applying any further treatments, whereby useful products are generated (gaseous and liquid fuel) and char, rich in precious metals. The solid residues are meant for further treatment for energy and metals recovery. Gasification is a complementary method for handling pyrolysis residues. However, metals can be removed before gasification. Pyrolysis of charring materials, like biomass, is a very important step in thermo-chemical conversion. However, the char being approximately 25%wt. contains still very high caloric value of about 30MJ/kg. This in connection with the High Temperature Steam Gasification process is a very promising technology for biomass treatment, especially, above 900oC. This enhances the heat transfer towards the sample and accelerates kinetics of the gasification. This, in turn, improves the conversion of carbon to gas, increases the yield of the producer gas and reduces tar content. At higher steam to fuel ratio the process increases the yield of hydrogen, making it suitable for second-generation biofuels synthesis, whereas at lower steam to fuel ratio (S/F<2) the generated gas is of high calorific value making it suitable for power generation in a combined cycle.
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| 20. |
- Donaj, Pawel, et al.
(författare)
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Conversion of microwave pyrolysed ASR's char using high temperature agents
- 2011
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Ingår i: Journal of Hazardous Materials. - : Elsevier BV. - 0304-3894 .- 1873-3336. ; 185:1, s. 472-481
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Tidskriftsartikel (refereegranskat)abstract
- Pyrolysis enables to recover metals and organic feedstock from waste conglomerates such as: automotive shredder residue (ASR). ASR as well as its pyrolysis solid products, is a morphologically and chemically varied mixture, containing mineral materials, including hazardous heavy metals. The aim of the work is to generate fundamental knowledge on the conversion of the organic residues of the solid products after ASR's microwave pyrolysis, treated at various temperatures and with two different types of gasifying agent: pure steam or 3% (v/v) of oxygen. The research is conducted using a lab-scale, plug-flow gasifier, with an integrated scale for analysing mass loss changes over time of experiment, serving as macro TG at 950, 850 and 760 degrees C. The reaction rate of char decomposition was investigated, based on carbon conversion during gasification and pyrolysis stage. It was found in both fractions that char conversion rate decreases with the rise of external gas temperature, regardless of the gasifying agent. No significant differences between the reaction rates undergoing with steam and oxygen for char decomposition has been observed. This abnormal char behaviour might have been caused by the inhibiting effects of ash, especially alkali metals on char activity or due to deformation of char structure during microwave heating.
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| 21. |
- Donaj, Pawel, et al.
(författare)
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High temperature agent gasification of microwave pyrolysed chars from Automotive Shredder Residue
- 2010
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Ingår i: International Conference on Thermal Treatment Technologies and Hazardous Waste Combustors 2010. - 9781617386633 ; , s. 459-469
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Konferensbidrag (refereegranskat)abstract
- Presently, there is a growing need for handling Automobile Shredder Residues - ASR or "car fluff". One of the most promising methods of treatment ASR is pyrolysis. Apart of obvious benefits of pyrolysis: energy and metals recovery, there is serious concern about residues generated from that process which need to be recycled. Unfortunately, not much work has been reported providing solutions for handling pyrolysis waste's streams. The raw light fraction of ASR, containing mainly foam, textiles and light plastics was gravimetrically separated from the rest of ASR, and treated via microwave pyrolysis to generate 11% of gaseous, 30% of liquid and 59% of solid products, respectively. The resulting char has been characterized and gasified with either a pure steam or 3%vol. oxygen at temperatures between 950-750 °C, respectively, in a lab scale, fixed-bed reactor. The external temperature of gas and the mass loss of sample were continuously recorded. The activity of chars was investigated basing on carbon (ash free basis) conversion during gasification and pyrolysis stage. It was found the char activity decreases with the rise of external gas temperature and with the time of the process. No significant differences between the reactions undergoing with steam and oxygen. This abnormal char behaviour might have been caused the by the inhibiting effect of ash, especially alkali metals on char activity or due to deformation of char structure during microwave heating.
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| 22. |
- Donaj, Pawel J., et al.
(författare)
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Conversion of Industrially Processed Biomass Waste into Value-added Products Using High Temperature Agents
- 2011
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Ingår i: International Conference on Thermal Treatment Technologies and Hazardous Waste Combustors.
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Konferensbidrag (refereegranskat)abstract
- Biomass can be utilized for energy and chemicals generation, gradually replacing the significance of fossil fuels. In this work the conversion of an industrially processed biomass waste (straw pellets) has been studied by means of High Temperature Steam Gasification (HTSG) and High Temperature Pyrolysis (HTP) at T=750-950oC and at three levels of steam to fuel ratio (S/F): 3.2; 1.875 and 0. The primary objectives are focused on a parametric study in which the emphasis is put on the influence of temperature and S/F on the reaction rate, conversion of carbon to gas, as well as yields, composition and heating value of generated Syngas. The results show the increasing trend in the reaction rate, hydrogen yield and tar cracking with an increase in agent temperature and S/F. However, this growth is significantly increased for the temperatures around 950oC. The yield of gas varied from 1.2 to 1.5 Nm3/kg for HTP to 1.5 to 2.5 Nm3/kg for HTSG and the LHV ranged between 8-13MJ/Nm3. At highest S/F the reduction of CO and hydrocarbons is observed even at 850oC yielding amount of hydrogen by 100% up to 38% compared with a lower S/F. Pyrolysis and lower S/F generated gas suitable for energetic purpose, whereas higher S/F for chemical synthesis.
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| 23. |
- Donaj, Pawel J., et al.
(författare)
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Effect of Pressure Drop Due to Grate-Bed Resistance on the Performance of a Downdraft Gasifier
- 2011
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 25:11, s. 5366-5377
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Tidskriftsartikel (refereegranskat)abstract
- The grate-bed resistance coefficient appears to be an important operating parameter having a strong influence on the overall performance during downdraft fixed-bed gasification- it affects, directly, the velocity profile, temperature distribution, and height of the bed. To date no information on the pressure drop due to the grate-bed resistance has been found. The objective of this paper is to propose a correlation that can predict the total effectof pressure drop (caused by bed resistance and grate-bed resistance), through a grate of a certain surface porosity (open area/total area) covered by the porous bed. The term related to the grate-bed resistance is based on the effective grate porosity, which combined surface bed porosity with geometrical criteria of the grate. Based on this a new term has been integrated into the Ergun’s equation. The prediction has been validated within the experimental work conducted on a 0.7MW downdraft fixed-bed gasifier fueled with wood pellets. In this study, three grates of different porosities and thicknesses have been tested using various operating conditions. The predicted values of pressure drop showed a good agreement within the experimental results with ±7.10% of uncertainty. Although, the lower grate porosity, the higher conversion of fuel and heating value of gas is produced, the stability of the process is disturbed; therefore the grate porosity reduction below 20% is not recommended.
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| 24. |
- Donaj, Pawel, et al.
(författare)
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Kinetic study of decomposition of ASR residues after pyrolysis in inert and oxidative atmosphere
- 2009
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Ingår i: International Thermal Treatment Technologies (IT3) & Hazardous Waste Combustors (HWC) Joint Conference 2009. - 9781615671830 ; , s. 465-483
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Konferensbidrag (refereegranskat)abstract
- The kinetic studies on solid residues after pyrolysis from ASR (Automobile Shredder Residue) originated from STENA Metall AB have been performed with the use of thermogravimetry analysis TGA. The char after microwave pyrolysis has been pyrolyzed and combusted in the presence of helium and air respectively. The TG experiments have been performed with heating rate of 10, 20, 40, 60 and 100deg/min. The influence of heating rate for decomposition rate and the char reactivity was also analyzed. Three different decomposition peaks have been identified for pyrolysis process in the range of temperatures 230-430, 400-500 and 680-850°C, respectively. The activation energy (E act) and pre-exponential (frequency) factor (A) were calculated from the DTG curves using Coats and Redfern (C&R) method and Doyle's (D), based on the assumption of an independent, parallel first order Arrhenius-type global kinetic model. The kinetic data were also obtained for small lab scale gasification process of ASR pyrolysis residues. The mass loss and the heating of sample are recorded. It was proved, that the char's heating rate plays a significant role in the conversion rate as well in the char reactivity. The relatively high ignition temperature of 630°C would require the steam temperature to be well above 800°C. Thus, reasonable would be to use high temperature steam gasification for treating ASR residues after microwave pyrolysis.
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| 25. |
- Donaj, Pawel, et al.
(författare)
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Recycling of automobile shredder residue with a microwave pyrolysis combined with high temperature steam gasification
- 2010
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Ingår i: Journal of Hazardous Materials. - : Elsevier BV. - 0304-3894 .- 1873-3336. ; 182:1-3, s. 80-89
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Tidskriftsartikel (refereegranskat)abstract
- Presently, there is a growing need for handling automobile shredder residues - ASR or "car fluff". One of the most promising methods of treatment ASR is pyrolysis. Apart of obvious benefits of pyrolysis: energy and metals recovery, there is serious concern about the residues generated from that process needing to be recycled. Unfortunately, not much work has been reported providing a solution for treatment the wastes after pyrolysis. This work proposes a new system based on a two-staged process. The ASR was primarily treated by microwave pyrolysis and later the liquid and solid products become the feedstock for the high temperature gasification process. The system development is supported within experimental results conducted in a lab-scale, batch-type reactor at the Royal Institute of Technology (KTH). The heating rate, mass loss, gas composition, LHV and gas yield of producer gas vs. residence time are reported for the steam temperature of 1173K. The sample input was 10 g and the steam flow rate was 0.65 kg/h. The conversion reached 99% for liquids and 45-55% for solids, dependently from the fraction. The H-2:CO mol/mol ratio varied from 1.72 solids and 1.4 for liquid, respectively. The average LHV of generated gas was 15.8 MJ/N m(3) for liquids and 15 MJ/N m(3) for solids fuels.
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| 26. |
- Dor, L., et al.
(författare)
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Paper #IT3-12 Presented at the 37th International Conference on Thermal Treat-ment Technologies & Hazardous Waste Combustors, October 2-3, 2019, League City, TX
- 2019
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Ingår i: IT3/HWC 2019 - 37th International Conference on Thermal Treatment Technologies and Hazardous Waste Combustors. - : Air and Waste Management Association.
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Konferensbidrag (refereegranskat)abstract
- Today the long-kept secret is out. Everyone now knows that waste is a major problem and it is not going away! This issue is going to grow more and more severe following the economic growth and urbanization happening in Africa and Asia over the past few decades. This means unprecedented prosperity growth for people which will result in more waste and more need for energy. According to the World Bank,70% of world's waste today is dumped, burned or landfilled without energy recovery - wasting energy from 1.4 billion tons of waste every year1. The energy potential in that waste that is squandered wasted corresponds to >500GW nameplate of solar PV, which is close to the nameplate capacity of all Solar PV installed on the planet. IEA puts global cumulated installations of PV at 580GW up until 2018. Incineration, today's 'go to solution', is unable to close this gap of untreated waste. Being large-scale and mostly about aggregating and concentrating waste into toxic ash; it fails on lifecycle accountability (every 1000 tons of waste after all means some 200-300 tons of toxic ash for treatment and deposit). Globally, incineration is also confined to a power-only model, as there is largely no large-scale thermal grid infrastructure available outside parts of Europe. The power produced is also high-voltage power requiring capital intensive transmission infrastructure. Adding the waste transportation on top is a major contributor to urban congestion and pollution. This stresses growing cities of all sizes and means. Done right, waste is actually one of few 'fuels' produced everywhere, and perhaps surpris-ingly, very suitable for the production of, for instance, sustainable greenhouse-gas-free thermal cooling in increasingly hot cities. There is a next generation of game-changing 'first-mile' solutions for better-cleaner-cheaper thermal treatment of mixed waste that can also treat medical and hazardous waste. 'First-mile' solutions for waste is the next generation of clean and circular small-scale waste-to-energy solutions. Waste should literally not have to travel more than a mile. These local solutions can completely change the way waste is man-aged and turn waste into a sustainable fuel that contributes to sustainable urban autonomy and resilience. Smart waste treatment for smart cities. Small-scale allows for being close to both producers of waste and end-users of power and heat or thermal cooling - so 'Swedish levels' of final energy efficiency can be achieved without heavy infrastructure investments. Vitrified slag can be used as a construction material in the city, rather than having to treat or deposit large amounts of ash. Shortening and simplifying waste supply chains also reduce leakage of already collected waste and plastic into rivers and oceans. All together, these solutions have the potential to be better-cleaner-cheaper than today's large-scale solutions.
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| 27. |
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| 28. |
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| 29. |
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| 30. |
- Flamme, Michael, et al.
(författare)
-
Radiant Tube Burners
- 2010
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Ingår i: Industrial Combustion Testing. - : Taylor & Francis Group. ; , s. 487-504
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 31. |
- Gunarathne, Duleeka, 1984-
(författare)
-
Advanced Gasification of Biomass/Waste for Substitution of Fossil Fuels in Steel Industry Heat Treatment Furnaces
- 2016
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- With the current trend of CO2 mitigation in process industries, the primary goal of this thesis is to promote biomass as an energy and reduction agent source to substitute fossil sources in the steel industry. The criteria for this substitution are that the steel process retains the same function and the integrated energy efficiency is as high as possible.This work focuses on advanced gasification of biomass and waste for substitution of fossil fuels in steel industry heat treatment furnaces. To achieve this, two approaches are included in this work. The first investigates the gasification performance of pretreated biomass and waste experimentally using thermogravimetric analysis (TGA) and a pilot plant gasifier. The second assesses the integration of the advanced gasification system with a steel heat treatment furnace.First, the pyrolysis and char gasification characteristics of several pretreated biomass and waste types (unpretreated biomass, steam-exploded biomass, and hydrothermal carbonized biomass) were analyzed with TGA. The important aspects of pyrolysis and char gasification of pretreated biomass were identified.Then, with the objective of studying the gasification performance of pretreated biomass, unpretreated biomass pellets (gray pellets), steam-exploded biomass pellets (black pellets), and two types of hydrothermal carbonized biomass pellets (spent grain biocoal and horse manure biocoal) were gasified in a fixed bed updraft gasifier with high-temperature air/steam as the gasifying agent. The gasification performance was analyzed in terms of syngas composition, lower heating value (LHV), gas yield, cold gas efficiency (CGE), tar content and composition, and particle content and size distribution. Moreover, the effects on the reactions occurring in the gasifier were identified with the aid of temperature profiles and gas ratios.Further, the interaction between fuel residence time in the bed (bed height), conversion, conversion rate/specific gasification rate, and superficial velocity (hearth load) was revealed. Due to the effect of bed height on the gasification performance, the bed pressure drop is an important parameter related to the operation of a fixed bed gasifier. Considering the limited studies on this relationship, an available pressure drop prediction correlation for turbulent flow in a bed with cylindrical pellets was extended to a gasifier bed with shrinking cylindrical pellets under any flow condition. Moreover, simplified graphical representations based on the developed correlation, which could be used as an effective guide for selecting a suitable pellet size and designing a grate, were introduced.Then, with the identified positive effects of pretreated biomass on the gasification performance, the possibility of fuel switching in a steel industry heat treatment furnace was evaluated by effective integration with a multi-stage gasification system. The performance was evaluated in terms of gasifier system efficiency, furnace efficiency, and overall system efficiency with various heat integration options. The heat integration performance was identified based on pinch analysis. Finally, the efficiency of the co-production of bio-coke and bio-H2 was analyzed to increase the added value of the whole process.It was found that 1) the steam gasification of pretreated biomass is more beneficial in terms of the energy value of the syngas, 2) diluting the gasifying agent and/or lowering the agent temperature compensates for the ash slagging problem in biocoal gasification, 3) the furnace efficiency can be improved by switching the fuel from natural gas (NG) to syngas, 4) the gasifier system efficiency can be improved by recovering the furnace flue gas heat for the pretreatment, and 5) the co-production of bio-coke and bio-H2 significantly improves the system efficiency.
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| 32. |
- Gunarathne, Duleeka, 1984-, et al.
(författare)
-
BIOMASS PRETREATMENT FOR LARGE PERCENTAGE BIOMASS CO-FIRING
- 2014
-
Konferensbidrag (refereegranskat)abstract
- With the target of reducing net GHG emissions from coal fired power plants, biomass co-firing in such plants is becoming more and more attractive option among other thermal applications of biomass such as combustion, gasification and pyrolysis. Not only CO2, but effective reduction of SOx and NOx emissions can also be expected with this low cost, sustainable and renewable energy option. However, the economic feasibility of such process largely depends on the cost of biomass acquisition and transportation. Therefore, local availability of large quantities of biomass is important for more economic co-firing. Since always this is not the case, pretreatment of biomass to increase energy density is another way to make biomass economical for long distance transportation. Pretreatment also broaden the usage of biomass sources (eg. wet and waste biomass), reduce the moisture content make it hydrophobic reducing drying energy demand, ease to comminute into small particles creating it more economical source for co-firing. Further, as a result of pretreatment, combustion and electricity generation efficiencies will be improved due to increased heating value of pretreated biomass. Therefore, enhancement of biomass properties is advisable not only to improve its inferior characteristics as well as to make it as suitable alternative for fossil fuels. In this paper, the technologies of biomass pretreatment for thermal application, such as physical and thermochemical pretreatments were reviewed. The upgrading processes of biomass including steam explosion, torrefaction and hydrothermal carbonization-HTC were described based on the HHV, adiabatic flame temperature, fouling tendency and emissions. Furthermore, a case study using severely torrified biomass for large percentage co-firing with coal is discussed.
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| 33. |
- Gunarathne, Duleeka, 1984-, et al.
(författare)
-
Performance of High Temperature Air/Steam Gasification of Hydrothermal Carbonized Biomass
- 2014
-
Ingår i: 22nd European Biomass Conference and Exhibition. - 9788889407523 ; , s. 626-631
-
Konferensbidrag (refereegranskat)abstract
- In order to effectively use the biomass resources for thermal applications, use of biomass pretreatment technologies like hydrothermal carbonization are emerging. With the aim of studying the gasification performance of hydrothermal carbonized biomass (biocoal) in high temperature air/steam medium, gasification of two types of biocoal pellets produced from spent grain and horse manure, was carried out in a fixed bed updraft gasifier. Steam gasification gave syngas having 10-11 MJ/Nm3 of LHV with both types of biocoal. The syngas yield and thus cold gas efficiency was higher with gasification of spent grain biocoal, but syngas purity in terms of tar and particulates was better with gasification of horse manure biocoal.
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| 34. |
- Gunarathne, Duleeka Sandamali, et al.
(författare)
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Gasification Characteristics of Hydrothermal Carbonized Biomass in an Updraft Pilot-Scale Gasifier
- 2014
-
Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 28:3, s. 1992-2002
-
Tidskriftsartikel (refereegranskat)abstract
- Biocoal pellets were gasified in an updraft high-temperature agent gasification (HTAG) unit with preheated air at 900 degrees C to study the performance of the air gasification of hydrothermal carbonized biomass. In comparison to raw biomass, hydrothermal carbonization increased the carbon content from 46 to 66% and decreased the oxygen content from 38 to 16%. As a result, the heating value of biomass on a dry basis was increased from 19 to 29 MJ/kg after hydrothermal carbonization. Thermogravimetric analysis (TGA) of biocoal featured early decomposition of hemicellulose and a shoulder attached to the cellulose peak corresponding to lignin decomposition. Char gasification demonstrated a peak near conversion of 0.2. Syngas with 7.9 MJ Nm(-3) lower heating value (LHV) was obtained from gasification experiments performed in the pilot-scale gasifier. The maximum cold gas efficiency was 80% at the lowest equivalence ratio (ER) and also resulted in high-purity syngas. The LHV and cold gas efficiency were higher than that of the previously studied unpretreated biomass pellets. The fuel conversion positively correlated with the fuel residence time in the bed, and almost 99% conversion could be achieved for a residence time of 2 h. The superficial velocity (or hearth load) and specific gasification rate were higher than the reported values of updraft gasifiers because of the high-temperature operation and specific fuel used.
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| 35. |
- Gunarathne, Duleeka Sandamali, et al.
(författare)
-
Gasification characteristics of steam exploded biomass in an updraft pilot scale gasifier
- 2014
-
Ingår i: Energy. - : Elsevier BV. - 0360-5442 .- 1873-6785. ; 71, s. 496-506
-
Tidskriftsartikel (refereegranskat)abstract
- Pretreatment of biomass becomes more and more important due to the large scale application of biomass having low energy density. In this paper, steam exploded biomass pellets (Black pellets) and unpretreated biomass pellets (Gray pellets) were gasified with air and steam at an updraft HTAG (High Temperature Agent Gasification) unit. Decomposition characteristics of pellets were first analyzed with TGA (thermo gravimetric analysis). Early decomposition of hemicellulose and cellulose were seen with Black pellets around 241 degrees C and 367 degrees C respectively. Introducing CO2 led comparatively high mass loss rate with Black pellets. Gasification of Black pellets resulted in syngas with high CO and hydrocarbon contents while Gasification of Gray pellets resulted in high H-2 content of syngas. LHV (lower heating value) of syngas was high around 7.3 MJ/Nm(3) and 10.6 MJ/Nm(3) with air gasification and steam gasification respectively. Even with significantly low syngas temperature with gasification of Black pellets, only slightly high total tar content was seen compared to that of Gray pellets gasification. Phenolic compounds dominated the tar composition. In general, steam gasification of Black pellets seems to be more feasible if syngas with high energy value is desired. If higher H-2 yield is preferred, gasification of unpretreated pellets likely to be more attractive.
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| 36. |
- Kantarelis, Efthymios, PhD, 1982-, et al.
(författare)
-
Biomass pyrolysis for energy and fuel production
- 2013
-
Ingår i: Technologies for Converting Biomass to Useful Energy: Combustion, Gasification, Pyrolysis, Torrefaction and Fermentation. - : CRC Press. ; , s. 245-278
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Pyrolysis is the thermochemical decomposition of organic matter in the absence of oxygen and produces a wide range of useful products. The word is coined from the Greek-derived elements pyr "ρ-fire” and lysis "λUsσς-breakdown/separation” emphasizing the disintegration of matter due to heat. It is a standalone process or one of several reaction steps in gasification and combustion processes1 and is considered as the basic thermochemical process to produce valuable fuels and energy from biomass. Pyrolysis is also known as thermolysis, thermal cracking, dry distillation, destructive distillation, etc.; however, there are differences in those terms. During pyrolysis, complex macromolecules of biomass break down into relatively smaller molecules producing 3 major products which can be classified as follows: •a solid residue (which mainly consists of carbon and ash) known as char•gases (mainly CO, CO2, CH4, H2 and other light hydrocarbons)•Vapors/liquids known as bio-oil or bio-crude (mainly oxygenates, aromatics, water, products of low degree of polymerization, tars, etc.)
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| 37. |
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| 38. |
- Kantarelis, Efthymios, et al.
(författare)
-
Effect of zeolite to binder ratio on product yields and composition during catalytic steam pyrolysis of biomass over transition metal modified HZSM5
- 2014
-
Ingår i: Fuel. - : Elsevier BV. - 0016-2361 .- 1873-7153. ; 122, s. 119-125
-
Tidskriftsartikel (refereegranskat)abstract
- Catalytic pyrolysis of biomass over metal modified zeolites (multifunctional catalysts) is a very promising route for production of hydrocarbons and less oxygenated liquid feedstock suitable for fuels and/or chemicals. In this work the effect of zeolite to binder ratio (Z/B) of a metal modified HZSM5, on products yields and composition during steam pyrolysis of biomass has been investigated. Increased zeolite content resulted in lower liquid yield and increased coke formation; however, more deoxygenated liquids obtained at higher zeolite loadings. Char yield is not significantly affected by the zeolite content. Declining catalytic activity is observed at longer time on stream because of coke deposition. While acidic function of the catalyst deoxygenates carboxylic acids and carbonyls, metal functions seem to selectively convert phenols and methoxy phenols. Competitive steam adsorption on the acid sites of the zeolite seems to lower the conversion to aromatics. The high availability of acid sites, at higher zeolite loading, increases aromatics concentration exponentially. Increased yields of hydrogenated products have been obtained indicating that the Ni-V/HZSM5 catalyst exhibits some hydrogenation activity.
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| 39. |
- Kantarelis, Efthymios, et al.
(författare)
-
Effects of Silica-Supported Nickel and Vanadium on Liquid Products of Catalytic Steam Pyrolysis of Biomass
- 2014
-
Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 28:1, s. 591-599
-
Tidskriftsartikel (refereegranskat)abstract
- Catalytic steam pyrolysis of biomass was performed in a bubbling fluidized-bed reactor at 450 degrees C, and the effects of silica-supported transition metals (Ni and V) on product yields and compositions have been investigated. Both metals seem to be catalytically active and altered the liquid composition. An interesting finding is the in situ reduction of the supported nickel oxide to metallic Ni during the pyrolysis reactions, which can enhance H-transfer. Vanadia-containing catalysts show higher selectivity in reduction of carboxylic acids and ketones. An increased aldehyde content, especially for the bimetallic Ni-V catalyst, suggests that selective deoxygenation can take place via the Mars van Krevelen (MvK) mechanism. Ni catalysts showed activity for aromatics formation, while both metals showed selectivity in producing phenols instead of catechols. Assessment of the catalytic performance indicates that both metals could be interesting candidates for incorporation in other support materials and evaluation of the derived modified catalysts in biomass steam pyrolysis.
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| 40. |
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| 41. |
- Kantarelis, Efthymios, et al.
(författare)
-
Production of Liquid Feedstock from Biomass via Steam Pyrolysis in a Fluidized Bed Reactor
- 2013
-
Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 27:8, s. 4748-4759
-
Tidskriftsartikel (refereegranskat)abstract
- The nature of liquids derived from biomass fast pyrolysis is far from typical oil, and thus, different approaches for bio-oil production and upgrading are needed. In this paper the steam pyrolysis of a pine and spruce wood mixture in a bubbling fluidized bed is investigated. Particularly, the effect of steam to biomass ratio and temperature in relation to products yields and composition has been studied. Products analyses indicate that steam presence affects the yields and composition of all the products (gas, char, liquid) and promotes oxygen removal from the liquid. Increased liquid yields with significantly lower amount of carboxylic acids and higher effective hydrogen index (EHI) were obtained, which makes them more suitable for further upgrading. The levoglucosan (LGA) concentration in the produced liquid is higher compared with conventional N-2 pyrolysis, which suggests that steam pyrolylsis can be regarded as an alternative for production of fermentable sugars. Polycondensation reactions are hindered by steam presence while steam seems to act as a hydrogen donor; however, increased water content is a problem that has to be considered as well.
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| 42. |
- Kantarelis, Efthymios, et al.
(författare)
-
Sustainable Valorization of Bamboo via High-Temperature Steam Pyrolysis for Energy Production and Added Value Materials
- 2010
-
Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 24, s. 6142-6150
-
Tidskriftsartikel (refereegranskat)abstract
- Bamboo is an abundant plant in many Asian countries and especially in China, it has an extremely rapid growing rate, and It can be considered as a sustainable wood resource In this paper a comparative study of pyrolysis of bamboo in the presence of high temperature steam and an inert atmosphere (N-2) as well as characterization of products has been conducted Evaluation of experimental results showed that faster devolatilization can be achieved in the presence of high-temperature steam Furthermore, the gas composition indicates interaction of steam with vapors and solid species even at low temperatures Analysis of the obtained liquid after steam pyrolysis at 797 K revealed that the H/C and O/C ratios in the liquid are 1 54 and 0 16, respectively The characteristics of the products indicate possible exploitation of derived char as an activated carbon precursor, a reducing agent in metallurgical processes, or a solid fuel for gasification and combustion processes The composition of the liquid fraction suggests further exploitation as a liquid fuel and/or chemical feedstock
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| 43. |
- Kantarelis, Efthymios, et al.
(författare)
-
Thermochemical treatment of E-waste from small household appliances using highly pre-heated nitrogen-thermogravimetric investigation and pyrolysis kinetics
- 2011
-
Ingår i: Applied Energy. - : Elsevier BV. - 0306-2619 .- 1872-9118. ; 88:3, s. 922-929
-
Tidskriftsartikel (refereegranskat)abstract
- The EU directive on waste of electrical and electronic equipment (WEEE) 2002/96/EC has set a goal of recovering 70-80% in terms of materials and energy. Nowadays, thermal cracking (pyrolysis) of such waste streams is receiving renewed attention, due to the energy and material recovery that can be achieved and therefore the sustainable waste management. However, it still lacks the kinetic background which is of great importance for a successful design of thermochemical processes. In this study the kinetic parameters of WEEE (originating from small household appliances) pyrolysis using highly pre-heated nitrogen under six different heating rates (1-2.5 K/s) have been estimated using a combination of model-free and model fitted methods. Even though WEEE is heterogeneous material, similar behavior at each of the six different heating rates applied was observed. The activation energy of the pyrolysis process determined with two different model-free methods gave comparable results. Pre-exponential factor and reaction order were determined using the Coats-Redfern method. The estimated kinetic parameters for the WEEE pyrolysis are: E = 95.54 kJ/mol, A = 1.06 x 10(8) and n = 3.38.
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| 44. |
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| 45. |
- Krishnamurthy, Narayanan, et al.
(författare)
-
Studies on low-intensity oxy-fuel burner
- 2009
-
Ingår i: PROCEEDINGS OF THE COMBUSTION INSTITUTE. - : Elsevier BV. - 1540-7489. ; 32, s. 3139-3146
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents experimental and computational results of oxy-fuel burner operating on classical flame and flameless mode for heat release rate of 26 kW/m(3). The uniqueness of the burner arises from a slight asymmetric injection of oxygen at near sonic velocities. Measurements of temperature, species, total heat flux, radiative heat flux and NOx emission were carried out inside the furnace and the flow field was computationally analyzed. The flame studies were carried Out for coaxial flow of oxygen and fuel jets with similar inlet velocities. This configuration results in slow mixing between fuel and oxygen and the flame is developed at distance away from the burner and the flame is bright/white in colour. In the flameless mode a slight asymmetric injection of the high velocity oxygen jet leads to a large asymmetric recirculation pattern with the recirculation ratio of 25 and the resulting flame is weak bluish in colour with little soot and acetylene formation. The classical flame in comparison is characterised by soot and acetylene formation, higher NOx and noise generation. The distribution of temperature and heat flux in the furnace is more uniform with flameless mode than with flame mode.
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| 46. |
- Kubik, Katarzyna, et al.
(författare)
-
Assessment of ASR treatment using pyrolysis and reforming of its residences for small scale electricity generation systems
- 2008
-
Ingår i: Air and Waste Management Association. - 9781605603797 - 9781605603797 ; , s. 717-726
-
Konferensbidrag (refereegranskat)abstract
- Due to the increased manufacturing of new vehicles, older ones the so called end-of-life vehicle's (ELV) are being disposed more frequently. The EU ELV directive (entered into force 21/10/2000) sets targets and objectives that must be obeyed by the member states. Under this directive from 01/01/2006 for all ELV, the reuse and recovery rate should be min. 85% (by weight) and min. 80% (by weight) rate of recycling. From 01/01/2015 for all ELV, the reuse and recovery rate should be min. 95% (by weight) and min. 85% (by weight) rate of recycling. Because of the lack of a cost-effective technology to recycle this waste, it is mostly land filled, smaller amounts are incinerated. In this work, basing on the reviewing of the available technological methods, a new thermal treat system for ASR is proposed: Firstly, a microwave pyrolysis of ASR is used. During this pyrolysis process, metals will be successfully recycled, and also generate by-products such as pyrolysis gas, oil, and char. These by-products will be further reformed using high-temperature steam gasification to generate high-purity synthetic gas, which will be used for a small-scale electricity generation system. Energy and mass balance of the whole system will be done. The electricity generation efficiency will be assessed.
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| 47. |
- Li, Jun, et al.
(författare)
-
CFD Approach for Unburned Carbon Reduction in Pulverized Coal Boilers
- 2012
-
Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 26:2, s. 926-937
-
Tidskriftsartikel (refereegranskat)abstract
- Low-NO, technologies are widely used in pulverized coal boilers, but they usually produce high levels of carbon in the fly ash. High levels of unburned carbon represent fuel loss, so the overall boiler efficiency is reduced. Additionally, the higher carbon content affects the suitability of fly ash for cement applications. The purpose of this paper is to provide a CFD approach for unburned carbon reduction by optimizing operating conditions. In this paper, three different boiler loads were simulated: 200 MW, 170 MW, and 140 MW. The air supply System was simulated previously for preparing as precise as possible boundary conditions. At last, the unburned carbon level of every burner was investigated, and the effects of residue residence time and the local fuel air momentum ratio are discussed in detail. According to the predicted results, operating conditions and the residence time of the coal particles affects the unburned carbon level in fly ash. Operating conditions play a more significant role during the combustion process, while the residence time affects char burnout only when the burner's location is low. Therefore, it is concluded that a cost-effective method could be developed for reducing the unburned carbon level in ash and correspondingly, the loss on ignition level. First, it is necessary to determine which burners are operating under poor conditions through CFD analysis. Then, the fuel air momentum ratios of those burners should be modified by changing the operating conditions, meanwhile increasing the residence time of coal particles to ensure complete combustion.
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| 48. |
- Li, Jun, et al.
(författare)
-
Co-firing based on biomass torrefaction in a pulverized coal boiler with aim of 100% fuel switching
- 2012
-
Ingår i: Applied Energy. - : Elsevier BV. - 0306-2619 .- 1872-9118. ; 99, s. 344-354
-
Tidskriftsartikel (refereegranskat)abstract
- Torrefied biomass has several benefits, such as higher energy density, good grindability, higher flowability and uniformity. The process of torrefaction moves the chemical and physical properties of raw biomass close to that of bituminous coal, which allows co-utilization with high substitution ratios of biomass in the existing coal-fired boilers without major modifications. In this study, a torrefaction based co-firing system was proposed and studied. Devolatilization and char oxidize kinetics of the torrefied biomass have been investigated experimentally. CFD modeling of co-firing with varying substitutions of torrefied biomass in a pulverized coal boiler have been carried out. To figure out the boiler performance when co-firing torrefied biomass, five different cases were involved and simulated, coal only, 25% biomass, 50% biomass, 75% biomass, and 100% biomass on thermal basis, respectively. The results showed torrefaction is able to provide a technical option for high substitution ratios of biomass in the co-firing system. The case-study pulverized coal boiler could be fired 100% torrefied biomass without obvious decreasing of the boiler efficiency and fluctuation of boiler load. More positively, the net CO 2 and the NO x emissions significantly reduced with increasing of biomass substitutions in the co-firing system.
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| 49. |
- Li, Jun, et al.
(författare)
-
Effects of Flue Gas Internal Recirculation on NOx and SOx Emissions in a Co-Firing Boiler
- 2013
-
Ingår i: International Journal of Clean Coal and Energy. - : Scientific Research Publishing, Inc.. - 2168-1538 .- 2168-152X. ; 2:2, s. 13-21
-
Tidskriftsartikel (refereegranskat)abstract
- Volumetric combustion has been developed to realize a high substitution ratio of biomass in co-firing boilers, which features an intensive flue gas internal recirculation inside furnace. However, the characteristics of NOx and SOx emissions in large-scale boilers with volumetric combustion were not fully clear. In this paper, an Aspen Plus model of volumetric combustion system was built up based on a co-firing boiler. In order to characterize the reductions of NOx and SOx, three biomass substitution ratios were involved, namely, 100% biomass, 45% biomass with 55% coal, and 100% coal. The effects of flue gas recirculation ratio, air preheating temperature, oxygen concentration, and fuel types on pollutants emission in the volumetric combustion system were investigated. According to the results, it was concluded the higher substitution ratio of biomass in a co-firing boiler, the lower emissions of NOx and SOx. Moreover, flue gas internal recirculation is an effective pathway for NOx reduction and an increased recirculation ratio resulted in a significant decreasing of NOx emission; however, the SOx increased slightly. The influences of air preheating temperature and O2 concentration on NOx emission were getting weak with increasing of recirculation ratio. When 10% or even higher of flue gas was recycled, it was observed that almost no NOx formed thermodynamically under all studied conditions. Finally, to reach a low emission level of NOx, less energy would be consumed during biomass combustion than coal combustion process for internal recirculation of flue gas.
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| 50. |
- Li, Jun, et al.
(författare)
-
Flame characteristics of pulverized torrefied-biomass combusted with high-temperature air
- 2013
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Ingår i: Combustion and Flame. - : Elsevier BV. - 0010-2180 .- 1556-2921. ; 160:11, s. 2585-2594
-
Tidskriftsartikel (refereegranskat)abstract
- In this work, the flame characteristics of torrefied biomass were studied numerically under high-temperature air conditions to further understand the combustion performances of biomass. Three torrefied biomasses were prepared with different torrefaction degrees after by releasing 10%, 20%, and 30% of volatile matter on a dry basis and characterized in laboratory with standard and high heating rate analyses. The effects of the torrefaction degree, oxygen concentration, transport air velocity, and particle size on the flame position, flame shape, and peak temperature are discussed based on both direct measurements in a laboratory-scale furnace and CFD simulations. The results primarily showed that the enhanced drag force on the biomass particles caused a late release of volatile matter and resulted in a delay in the ignition of the fuel-air mixture, and the maximum flame diameter was mainly affected by the volatile content of the biomass materials. Furthermore, oxidizers with lower oxygen concentrations always resulted in a larger flame volume, a lower peak flame temperature and a lower NO emission. Finally, a longer flame was found when the transport air velocity was lower, and the flame front gradually moved to the furnace exit as the particle size increased. The results could be used as references for designing a new biomass combustion chamber or switching an existing coal-fired boiler to the combustion of biomass.
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