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Eboh, F. C., Andersson, B.-Å. & Richards, T. (2019). Economic evaluation of improvements in a waste-to-energy combined heat and power plant. Waste Management
Open this publication in new window or tab >>Economic evaluation of improvements in a waste-to-energy combined heat and power plant
2019 (English)In: Waste Management, ISSN 0956-053X, E-ISSN 1879-2456Article in journal (Refereed) Published
Abstract [en]

Improving the efficiency of waste-to-energy combined heat and power plants increases their production of both electricity and heat. Economic evaluation of such improvements enables adequate decisions to be made between the various alternatives with respect to economic viability of the plant. In this study, the cost and profitability of different modifications to improve efficiency in a waste-to-energy plant are considered: these include the re-arrangement of air heaters, the introduction of a reheater, flue gas condensation (FGC) and an integrated gasification-combustion process. The base case and the modifications are evaluated and compared when operating either as a combined heat and power plant or as a power plant. Modelling, simulation and cost estimations were performed with the Aspen Plus software. Although the integrated gasification-combustion technology with FGC has the highest exergy efficiency, its higher capital cost is greater than all of the other alternatives. Modification 6, which involves both re-arrangement and changing the air heating medium has the lowest capital cost with respect to enhancing exergy efficiency. Modifications 1 and 7, involving FGC, are the best alternatives for the capital cost per total unit of revenue generated. These modifications not only provides the highest heat production but also the highest net present value (NPV). The base case and the modifications investigated all have positive NPV, indicating that a waste-to-energy combined heat and power plant is an attractive investment. However, an increase of about 122% in the gate fees would be required for a system with only electricity production to be profitable.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Waste-to-energy plant, Efficiency improvement, Economic viability, Cost of improvement
National Category
Engineering and Technology
Identifiers
urn:nbn:se:hb:diva-21730 (URN)10.1016/j.wasman.2019.09.008 (DOI)
Available from: 2019-09-14 Created: 2019-09-14 Last updated: 2019-10-07Bibliographically approved
Eboh, F. C., Ahlström, P. & Richards, T. (2019). Evaluating improvements in a waste-to-energy combined heat and power plant. Case Studies in Thermal Engineering
Open this publication in new window or tab >>Evaluating improvements in a waste-to-energy combined heat and power plant
2019 (English)In: Case Studies in Thermal Engineering, ISSN 2214-157XArticle in journal (Refereed) Published
Abstract [en]

Evaluation of different alternatives for enhancement in a waste combustion process enables adequate decisions to be made for improving its efficiency. Exergy analysis has been shown be an effective tool in assessing the overall efficiency of a system. However, the conventional exergy method does not provide information of the improvements possible in a real process. The purpose of this paper is to evaluate state-of-the art techniques applied in a municipal solid-waste fired heat and power plant. The base case plant is evaluated first; the results are then used to decide upon which technical modifications should be introduced and they are thereafter evaluated. A modified exergy-based method is used to discover the improvement potential of both the individual components and the overall base case plant. The results indicate that 64% of exergy destruction in the overall process can theoretically be improved. The various modifications selected involve changing the bed material, using a gasifier followed by a gas boiler and incorporating a more durable material into the boiler walls. In addition, changing the heating medium of the incoming air (from steam to flue gas) along with a reduction in the stack temperature and the integration of flue gas condensation were considered for utilizing the exergy in the flue gases. The modification involving gasifier, gas boiler and flue gas condensation proved to be the best option, with the highest exergy efficiency increment of 21%.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Theoretical process, Exergy efficiency, Flue gas condensation, Municipal solid-waste fired plant, Improvement potential, Gasification-combustion process
National Category
Engineering and Technology
Identifiers
urn:nbn:se:hb:diva-21729 (URN)10.1016/j.csite.2019.100476 (DOI)2-s2.0-85067188415 (Scopus ID)
Available from: 2019-09-14 Created: 2019-09-14 Last updated: 2019-10-07Bibliographically approved
Chandolias, K., Richards, T. & Taherzadeh, M. J. (2018). Combined gasification-fermentation process in waste biorefinery. In: Waste Biorefinery: Potential and Perspectives. Elsevier
Open this publication in new window or tab >>Combined gasification-fermentation process in waste biorefinery
2018 (English)In: Waste Biorefinery: Potential and Perspectives, Elsevier, 2018Chapter in book (Refereed)
Abstract [en]

Thermal processes of wastes lead to production of energy in form of electricity and/or heat. However, if the goal is to produce materials, thermochemical processes can be applied. These processes via e.g. gasification produce raw syngas that is a mixture of principally H2, CO and CO2, with some impurities. This raw syngas is traditionally cleaned and catalytically treated via chemical processes such as Fischer-Tropsch. However, as there is a variety of microorganisms that can assimilate syngas, this gas can be used as a substrate to produce different chemicals via biochemical routes. This chapter is dedicated to describe an efficient thermochemical-biochemical route of waste treatment. The gasification process, the design and the factors that affect the syngas composition are firstly described. Thereafter, the microbiology, biochemical reactions, metabolic pathways and process conditions toward production of several metabolic products from syngas such as carboxylic acids, ethanol, butanol, 2,3-butanediol, methane and biopolymers are presented. 

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
Gasification, Fermentation, Biofuels, Valuable chemicals
National Category
Engineering and Technology
Identifiers
urn:nbn:se:hb:diva-14190 (URN)9780444639929 (ISBN)
Funder
Swedish Research Council
Available from: 2018-05-16 Created: 2018-05-16 Last updated: 2018-06-21Bibliographically approved
Richards, T., Erikson, M. G., Eriksson, A., Nagy, A. & Johnson, E. (2017). A conceptual model of how research can influence student development. In: : . Paper presented at Connecting Higher Education: International perspectives on research-based education, London, 26-28 June, 2017.
Open this publication in new window or tab >>A conceptual model of how research can influence student development
Show others...
2017 (English)Conference paper, Oral presentation only (Refereed)
National Category
Educational Sciences
Identifiers
urn:nbn:se:hb:diva-12581 (URN)
Conference
Connecting Higher Education: International perspectives on research-based education, London, 26-28 June, 2017
Available from: 2017-09-18 Created: 2017-09-18 Last updated: 2017-09-19Bibliographically approved
Eboh, F. C., Ahlström, P. & Richards, T. (2017). Exergy Analysis of Solid Fuel-Fired Heat and Power Plants: A Review. Energies
Open this publication in new window or tab >>Exergy Analysis of Solid Fuel-Fired Heat and Power Plants: A Review
2017 (English)In: Energies, ISSN 1996-1073, E-ISSN 1996-1073Article in journal (Refereed) Published
Abstract [en]

The growing demand for energy is particularly important to engineers with respect to how the energy produced by heat and power plants can be used efficiently. Formerly, performance evaluation of thermal power plants was done through energy analysis. However, the energy method does not account for irreversibilities within the system. An effective method to measure and improve efficiency of thermal power plant is exergy analysis. Exergy analysis is used to evaluate the performance of a system and its main advantage is enhancement of the energy conversion process. It helps identify the main points of exergy destruction, the quantity and causes of this destruction, as well as show which areas in the system and components have potential for improvements. The current study is a comprehensive review of exergy analyses applied in the solid fuels heat and power sector, which includes coal, biomass and a combination of these feedstocks as fuels. The methods for the evaluation of the exergy efficiency and the exergy destruction are surveyed in each part of the plant. The current review is expected to advance understanding of exergy analysis and its usefulness in the energy and power sectors: it will assist in the performance assessment, analysis, optimization and cost effectiveness of the design of heat and power plant systems in these sectors.

Place, publisher, year, edition, pages
Basel, Switzerland: MDPI, 2017
Keywords
exergy, heat and power, solid fuels, system efficiencies
National Category
Engineering and Technology Energy Engineering
Research subject
Resource Recovery
Identifiers
urn:nbn:se:hb:diva-11885 (URN)10.3390/en10020165 (DOI)000395469200019 ()2-s2.0-85014124644 (Scopus ID)
Available from: 2017-02-02 Created: 2017-02-02 Last updated: 2018-11-29Bibliographically approved
Megwai, G. & Richards, T. (2016). A Techno-Economic Analysis of Biomass Power Systems Using Aspen Plus. International Journal of Power and Renewable Energy Systems (IJPRES), 31(2), 25-36
Open this publication in new window or tab >>A Techno-Economic Analysis of Biomass Power Systems Using Aspen Plus
2016 (English)In: International Journal of Power and Renewable Energy Systems (IJPRES), ISSN 2374-3751, Vol. 31, no 2, p. 25-36Article in journal (Refereed) Published
Abstract [en]

This paper provides an analysis of biomass‐based power technologies in terms of electric performance, environmentalindicators and economic evaluations. Several power generation processes are analyzed: gas turbines, steam turbines, micro gasturbines, Stirling engines and internal combustion engines. Furthermore, the potential of nitrogen oxide (NOx) produced ineach process model is used as a measure of the environmental impact made. The parameters considered for economic feasibilitywere fixed capital cost, working capital cost and total capital investment. It was found that a higher electric efficiency wasachieved when biomass gasification technology was integrated with gas‐based power systems; the Stirling engine power systemalso indicated a good potential when its process model was optimized. Moreover, the internal combustion engine process emitsmore nitrogen oxides than other technologies, thus indicating a need of more gas cleaning. The economic studies showed thatthe internal combustion engine and Stirling engine power system prove to be economically feasible, especially in small‐scalepower production. Higher total capital investment costs were indicated for both the steam turbine and the gas turbine powersystems, illustrating the reason for their being employed mainly in medium/large‐scale biomass power generation systems.

Keywords
Biomass, Power Systems, Gasification, Process Simulation
National Category
Chemical Engineering
Research subject
Resource Recovery
Identifiers
urn:nbn:se:hb:diva-11455 (URN)
Available from: 2016-12-14 Created: 2016-12-14 Last updated: 2017-01-24Bibliographically approved
Mohsenzadeh, A., Richards, T. & Bolton, K. (2016). DFT study of the water gas shift reaction on Ni (111), Ni (100) and Ni (110) surfaces. Surface Science, 644, 53-63
Open this publication in new window or tab >>DFT study of the water gas shift reaction on Ni (111), Ni (100) and Ni (110) surfaces
2016 (English)In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 644, p. 53-63Article in journal (Refereed) Published
Abstract [en]

Density functional theory (DFT) calculations were used to study the water gas shift (WGS) reaction on Ni(111), Ni(100) and Ni(110) surfaces. The adsorption energy for ten species involved in thereaction together with activation barriers and reaction energies for the nine most important elementary steps were determined using the same model and DFT methods. The results reveal that these energies are sensitive to the surface structure. In spite of this, the WGS reaction occurs mainly via the direct (also referred to as redox) pathway with the CO + O → CO2 reaction as the rate determining step on all three surfaces. The activation barrier obtained for this rate limiting step decreases in the order Ni(110) > Ni(111) > Ni(100). Therefore, if O species are present on the surfaces then the WGSreaction is fastest on the Ni(100) surface. However, the barrier for desorption of H2O (which is the source of the O species) is lower than its dissociation reaction on the Ni(111) and Ni(100) surfaces, but not on the Ni(110) surface. Hence, at low H2O(g) pressures, the direct pathway on the Ni(110) surface will dominate and will be the rate limiting step. The calculations also show that the reason that the WGS reaction does not primarily occur via the formate pathway is that this species is a stable intermediate on all surfaces. The reactions studied here support the Brønsted-Evans-Polanyi (BEP) principles with an R2 value of 0.99. © 2015 Elsevier B.V. All rights reserved.

Keywords
DFT, Ni(100), Ni(110), Ni(111), Nickel, Water gas shift reaction
National Category
Other Chemical Engineering
Research subject
Resource Recovery
Identifiers
urn:nbn:se:hb:diva-10790 (URN)10.1016/j.susc.2015.09.014 (DOI)000367489000009 ()2-s2.0-84943566189 (Scopus ID)
Available from: 2016-09-28 Created: 2016-09-28 Last updated: 2017-12-15Bibliographically approved
Eboh, F. C., Ahlström, P. & Richards, T. (2016). Estimating the specific chemical exergy of municipal solid waste. Energy Science & Engineering, 4(3), 217-231
Open this publication in new window or tab >>Estimating the specific chemical exergy of municipal solid waste
2016 (English)In: Energy Science & Engineering, ISSN 2050-0505, Vol. 4, no 3, p. 217-231Article in journal (Refereed) Published
National Category
Energy Engineering
Identifiers
urn:nbn:se:hb:diva-10793 (URN)10.1002/ese3.121 (DOI)000377213700005 ()2-s2.0-85014098626 (Scopus ID)
Available from: 2016-09-28 Created: 2016-09-28 Last updated: 2018-11-29Bibliographically approved
Eboh, F. C., Ahlström, P. & Richards, T. (2016). Estimating the specific exergy of municipal solid waste. Energy Science & Engineering, 4(3), 217-231
Open this publication in new window or tab >>Estimating the specific exergy of municipal solid waste
2016 (English)In: Energy Science & Engineering, ISSN 2050-0505, Vol. 4, no 3, p. 217-231Article in journal (Refereed) Published
Abstract [en]

A new model for predicting the specific chemical exergy of municipal solid waste (MSW) is presented; the model is based on the content of carbon, hydrogen, oxygen, nitrogen, sulfur, and chlorine on a dry ash-free basis (daf). The proposed model was obtained from estimations of the higher heating value (HHV) and standard entropy of MSW using statistical analysis. The ultimate analysis of 56 different parts of MSW was used for the derivation of the HHV expression. In addition, 30 extra parts were used for validation. One hundred and seventeen relevant organic substances that represented the main constituents in MSW were used for derivation of the standard entropy of solid waste. The substances were divided into different waste fractions, and the standard entropies of each waste fraction and for the complete mixture were calculated. The specific chemical exergy of inorganic matter in the waste was also investigated by considering the inorganic compounds in the ash. However, as a result of the extremely low value calculated, the exergy of inorganic matter was ignored. The results obtained from the HHV model show a good correlation with the measured values and are comparable with other recent and previous models. The correlation of the standard entropy of the complete waste mixture is less accurate than the correlations of each individual waste fraction. However, the correlations give similar results for the specific chemical exergy, indicating that HHV has a greater impact when estimating the specific exergy of solid waste than entropy.

Place, publisher, year, edition, pages
John Wiley & Sons, 2016
National Category
Energy Engineering
Research subject
Resource Recovery
Identifiers
urn:nbn:se:hb:diva-11085 (URN)10.1002/ese3.121 (DOI)000377213700005 ()2-s2.0-85014098626 (Scopus ID)
Available from: 2016-10-26 Created: 2016-10-26 Last updated: 2018-11-29Bibliographically approved
Oluoti, K., Pettersson, A. & Richards, T. (2016). Investigating the morphology and reactivity of chars from Triplochiton scleroxylon pyrolysed under varied conditions. Bioresource technology, 208, 94-99
Open this publication in new window or tab >>Investigating the morphology and reactivity of chars from Triplochiton scleroxylon pyrolysed under varied conditions
2016 (English)In: Bioresource technology, E-ISSN 3736-3751, Vol. 208, p. 94-99Article in journal (Refereed) Published
Abstract [en]

The astronomical increase in global energy demand makes locating energy sources other than fossil fuels worthwhile. The use of tropical biomass wood waste as a renewable energy source was investigated in this study. The thermal conversion analysis of Albizia gummifera (ayinre) was carried out in a thermobalance reactor via steam gasification under varying temperature (700 to 1000 °C) and steam partial pressure (0.020 to 0.050 MPa). The experimental data was evaluated using three gas-solid reaction models. The modified volume reaction model (mVRM) gave the overall highest coefficient of determination (0.9993) and thereby the best conversion prediction. The observed char activation constant rates (from paired reaction conditions) indicated, on average, an increase in reactivity as the parameters increased. The results showed that the activation energy of the mVRM gave the lowest value (32.54 kJ/mpI) compared with those of the shrinking core model (SCM) and the volume reaction model (VRM) (49.29 and 49.89 kJ/mol, respectively).

Keywords
Albizia gummifera, Gas-solid reaction models, Kinetic parameters, Steam gasification, Tropical biomass
National Category
Energy Engineering
Identifiers
urn:nbn:se:hb:diva-10791 (URN)10.15376/biores.11.2.3736-3751 (DOI)000371930900014 ()2-s2.0-84965177737 (Scopus ID)
Available from: 2016-09-28 Created: 2016-09-28 Last updated: 2017-05-04Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-0037-3555

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