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Synergistic combination of pyrolysis, anaerobic digestion, and CHP plants.
Mälardalen University, School of Business, Society and Engineering, Future Energy Center.ORCID iD: 0000-0002-4932-7368
Mälardalen University, School of Business, Society and Engineering, Future Energy Center.ORCID iD: 0000-0002-5014-3275
Karlstad University, Sweden.
Mälardalen University, School of Business, Society and Engineering, Future Energy Center.ORCID iD: 0000-0002-3485-5440
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2019 (English)In: Energy Procedia, Elsevier Ltd , 2019, Vol. 158, p. 1323-1329Conference paper, Published paper (Refereed)
Abstract [en]

The anaerobic digestion of biodegradable fraction of municipal solid waste (MSW) is a widely used process for biogas production. However, the biodegradable fraction of MSW also contains lignocellulosic waste which hinders the biogas production if added to the digester in higher quantity. So it needs to be separated from biodegradable waste and sent for alternate treatment, e.g., incineration, landfilling or compositing. Pyrolysis of lignocellulosic waste to produce biochar, syngas, and bio oil is an alternate treatment to consider. Furthermore, there is a reported correlation between the addition of biochar in the digester and higher biogas production. Previously, we coupled the pyrolysis of lignocellulosic waste with anaerobic digestion plant. Pyrolysis produces the biochar and vapors. Biochar was added in the digester to enhance the biomethane production. The vapors produced in the pyrolysis process were converted to biomethane through the catalytic methanation process. The combination gives the overall efficiency of 67%. In this work, we modified the process concept to increase the integration level of these processes. The main issue with the pyrolysis process is its heat required to operate, while some of its downstream processes also generate excess heat. In this study, the pyrolysis of lignocellulosic waste is integrated with an operating combined heat and power (CHP) plant, by using its existing infrastructure for heat transport among different pyrolysis operations. The combustor of the CHP plant provides the heat for drying and pyrolysis while the excess heat is transferred back to the combustor. The biochar produced from pyrolysis is transported back to the digester as an adsorbent. The process simulation results show that the combined efficiency of pyrolysis with CHP plant reached 80%. If the biochar is sent back to the anaerobic digester, the synergetic efficiency of all three processes, i.e., pyrolysis-CHP and anaerobic digestion was obtained at 79.7% as compared with the 67% efficiency when the pyrolysis was only integrated with the anaerobic digestion process.

Place, publisher, year, edition, pages
Elsevier Ltd , 2019. Vol. 158, p. 1323-1329
Keywords [en]
Heat integration, Lignocellulosic waste, Municipal solid waste, Biogas, Cogeneration plants, Combustors, Power generation, Pyrolysis, Waste incineration, Anaerobic digestion process, Biodegradable fraction, Biodegradable wastes, Combined heat and power, Lignocellulosic wastes, Municipal solid waste (MSW), Synergistic combinations, Anaerobic digestion
National Category
Energy Engineering
Identifiers
URN: urn:nbn:se:mdh:diva-43183DOI: 10.1016/j.egypro.2019.01.326ISI: 000471031701106Scopus ID: 2-s2.0-85063896503OAI: oai:DiVA.org:mdh-43183DiVA, id: diva2:1307161
Conference
10th International Conference on Applied Energy, ICAE 2018, 22 August 2018 through 25 August 2018
Available from: 2019-04-26 Created: 2019-04-26 Last updated: 2020-09-04Bibliographically approved
In thesis
1. Waste-integrated biorefineries: A path towards efficient utilization of waste
Open this publication in new window or tab >>Waste-integrated biorefineries: A path towards efficient utilization of waste
2020 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Waste-management systems have progressed from landfilling and dumping to waste prevention, recycling and resource recovery. In state-of-the-art waste-management industries, waste is separated into various fractions and treated with suitable processes. The non-recyclable organic fraction of waste can be incinerated for combined heat and power (CHP) production, while biodegradable waste can be converted to biomethane through the anaerobic digestion (AD) process. Thermochemical processes such as gasification and pyrolysis provide alternative methods for treating various fractions of waste. This thesis aims to design energy-efficient and cost-effective waste-integrated biorefineries by integrating thermochemical processing of waste with existing WtE technologies.

A system analysis of five process-integration case studies have been performed. The first case assesses the limitations and operational limits of thermochemical processes retrofitted in an existing waste-based CHP plant. The second and third case studies evaluate the feasibility of the current waste-based CHP plant to shift from cogeneration to polygeneration of biofuels, heat and power. In the fourth case study, a new process configuration is presented that couples AD of biodegradable waste with pyrolysis of lignocellulosic waste. The last case deals with the handling of digested sludge from WWTPs by the integration of thermochemical processes.

The findings suggest that waste-integrated biorefineries can utilize infrastructure and products from existing waste industries through process integration and improve the overall process efficiencies and economics. Existing waste-based CHP plants can provide excess heat for integrated thermochemical processes; however, the modifications required are different for different gasifiers and pyrolyzers. Similarly, refuse-derived fuel (RDF) — processed from municipal solid waste (MSW) — can be utilized for production of various biofuels alongside heat and power without disturbing the operation of the CHP. But biomethane and dimethyl ether (DME) showed higher process feasibility than methanol and drop-in biofuels.

The integration of pyrolysis with the AD process can almost double biomethane production compared with a standalone AD process, increasing efficiency to 67% from 52%. The integration is an attractive investment when off-site — rather than on-site — integration of pyrolysis and AD is considered.

Drying of sludge digestate from wastewater treatment plants (WWTPs) is a bottleneck for its post-processing by thermochemical processes. However, waste heat from the existing CHP plant can be utilized for drying of sludge, which can also replace some of the boiler feed through co-incineration with waste biomass.

The economic performance of waste-integrated biorefineries will depend on the volatility of market conditions. Finally, assessment of the effects of uncertainty of input data and process parameters on metrics of technical and economic performance is vital for evaluation of overall system performance.

Place, publisher, year, edition, pages
Västerås: Mälardalen University, 2020
Series
Mälardalen University Press Dissertations, ISSN 1651-4238 ; 322
Keywords
Gasification; Pyrolysis; Anaerobic digestion; Process integration; Aspen Plus; Ebsilon; Techno-economic analysis
National Category
Energy Engineering
Research subject
Energy- and Environmental Engineering
Identifiers
urn:nbn:se:mdh:diva-49878 (URN)978-91-7485-476-3 (ISBN)
Public defence
2020-10-23, Beta + (Online, Zoom), Mälardalens högskola, Västerås, 09:00 (English)
Opponent
Supervisors
Available from: 2020-09-04 Created: 2020-09-03 Last updated: 2020-09-23Bibliographically approved

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Salman, Chaudhary AwaisSchwede, SebastianThorin, EvaYan, Jinyue

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