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Turbomachinery in Biofuel Production
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Energy Processes.
2011 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The aim for this study has been to evaluate the integration potential of turbo-machinery into the production processes of biofuels. The focus has been on bio-fuel produced via biomass gasification; mainly methanol and synthetic natural gas. The research has been divided into two parts; gas and steam turbine applications.

Steam power generation has a given role within the fuel production process due to the large amounts of excess chemical reaction heat. However, large amounts of the steam produced are used within the production process and is thus not available for power production. Therefore, this study has been focused on lowering the steam demand in the production process, in order to increase the power production. One possibility that has been evaluated is humidification of the gasification agent in order to lower the demand for high quality steam in the gasifier and replace it with waste heat. The results show that the power penalty for the gasification process could be lowered by 18-25%, in the specific cases that have been studied.

Another step in the process that requires a significant amount of steam is the CO2-removal. This step can be avoided by adding hydrogen in order to convert all carbon into biofuel. This is also a way to store hydrogen (e.g. from wind energy) together with green carbon. The results imply that a larger amount of sustainable fuels can be produced from the same quantity of biomass.

The applications for gas turbines within the biofuel production process are less obvious. There are large differences between the bio-syngas and natural gas in energy content and combustion properties which are technical problems when using high efficient modern gas turbines. This study therefore proposes the integration of a natural gas fired gas turbine; a hybrid plant. The heat from the fuel production and the heat recovery from the gas turbine flue gas are used in a joint steam cycle. Simulations of the hybrid cycle in methanol production have shown good improvements. The total electrical efficiency is increased by 1.4-2.4 percentage points, depending on the fuel mix. The electrical efficiency for the natural gas used in the hybrid plant is 56-58%, which is in the same range as in large-scale combined cycle plants. A bio-methanol plant with a hybrid power cycle is consequently a competitive production route for both biomass and natural gas.

Place, publisher, year, edition, pages
Stockholm: KTH , 2011. , iv, 39 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2011:2
Keyword [en]
Bio-Methanol, Biomass, Gasification, Humidification, Hybrid Cycle, SNG
National Category
Energy Engineering
Identifiers
URN: urn:nbn:se:kth:diva-28901ISBN: 978-91-7415-835-9 (print)OAI: oai:DiVA.org:kth-28901DiVA: diva2:390814
Presentation
2011-01-21, V3, Teknikringen 76, 2 tr, KTH, Stockholm, 13:00 (Swedish)
Opponent
Supervisors
Note
QC 20110128Available from: 2011-01-28 Created: 2011-01-24 Last updated: 2011-01-28Bibliographically approved
List of papers
1. Increased Power Generation by Humidification of Gasification Agent in Biofuel Production
Open this publication in new window or tab >>Increased Power Generation by Humidification of Gasification Agent in Biofuel Production
2010 (English)In: World Renewable Energy Congress XI, 2010Conference paper, Published paper (Refereed)
Abstract [en]

The second generation biofuels are based on gasification of waste and non-food crops. A mix of oxygen and steam is used as gasification agent. A drawback when mixing the two pure streams of oxygen and steam is that exergy is lost. The gasification process is often pressurized; which implies that both the oxygen and the steam must have higher pressure to enable feeding. The gasification process is therefore one of the main internal steam uses. However, if the steam injected can be replaced or decreased in pressure level, power generation could be significantly increased. This study shows that the power penalty can be reduced by humidification of the gasification agent compared to steam injection. The power penalty can be reduced by more than 10% when using humidification process. The power penalty is reduced by even more, 18-25%, when also using a pre-humidifier driven by latent heat recovered after the methanisation.

Keyword
Humidification, Gasification Agent, SNG
National Category
Energy Engineering
Identifiers
urn:nbn:se:kth:diva-29248 (URN)
Conference
World Renewable Energy Congress XI 25-30 September 2010, Abu Dhabi, UAE
Note
QC 20110128Available from: 2011-01-28 Created: 2011-01-28 Last updated: 2012-11-27Bibliographically approved
2. Integration of Hybrid Cycles in Bio-Methanol Production
Open this publication in new window or tab >>Integration of Hybrid Cycles in Bio-Methanol Production
(English)In: Environmental Impact of Energy SystemArticle in journal (Other academic) Submitted
Abstract [en]

In bio-based methanol production approximately 60% of the biomass energy content is converted into methanol, the remaining part can be recovered as thermal heat. Efficient utilization of the thermal heat is difficult in stand-alone methanol plants. The overall efficiency is to a large extent dependent on the further conversion of power due to the significant quantity of excess heat. Heat can be recovered in a steam cycle but due to poor steam data energy efficiency is low. This paper therefore proposes the integration of a natural gas fired gas turbine. Simulations of the hybrid cycle in methanol production have shown good improvements. The total electrical efficiency is increased by 1.4-2.4 percentage points, depending on the fuel mix. The electrical efficiency for the natural gas used in the hybrid plant is 56-58%, which is in the same range as in large-scale combined cycle plants. A bio-methanol plant with a hybrid power cycle is therefore a competitive production route for both biomass and natural gas.

Keyword
Bio-Methanol, Biomass, Gasification, Hybrid Cycles, Polygeneration
National Category
Energy Engineering
Identifiers
urn:nbn:se:kth:diva-29249 (URN)
Note
QS 20120326Available from: 2011-01-28 Created: 2011-01-28 Last updated: 2012-11-27Bibliographically approved
3. Introducing Renewable Electricity to increase Biogas Production Potential
Open this publication in new window or tab >>Introducing Renewable Electricity to increase Biogas Production Potential
2010 (English)In: International Conference on Applied Energy 2010, 2010Conference paper, Published paper (Refereed)
Abstract [en]

Facing the challenge of CO2 reduction in the transport sector, the focus on alternative fuels has been growing rapidly. Several fuels and production methods have been proposed which illustrate various aspects of how to contribute to CO2 mitigation.This paper presents how biogas production from a given amount of biomass may be increased. To enhance biogas production, process improvements for today’s digestion process and also biogas produced from biomass gasification are suggested. Both biogas production via digestion and gasification of biomass produce CO2 as a by-product. To increase the biogas production, this green CO2 could be used to produce additional methane using the well-known Sabatier reaction. The hydrogen required for the reaction is proposed to originate from electrolysis of water, where the electricity needed is preferably produced from a renewable source, e.g. wind power. Reusing carbon in such manner reduces the need for fossil methane while supplying fuel to the transport sector.In this study, a base case scenario describing plants of typical sizes and efficiencies is presented for both digestion and gasification. It is shown that, using the Sabatier process on this base case, the methane production from gasification may be increased by about 140 %. For the digestion, the increase, including process improvements, is about 74 %. By using this method more biogas may be produced, without adding new raw material to the process. This would present a great way to meet society’s increasing demand for renewable fuels, while simultaneously reusing CO2.

Keyword
biogas, digestion, gasification, synthetic fuels, Sabatier reaction
National Category
Energy Engineering
Identifiers
urn:nbn:se:kth:diva-29250 (URN)
Conference
International Conference on Applied Energy 2010
Note

QC 20110128

Available from: 2011-01-28 Created: 2011-01-28 Last updated: 2016-08-16Bibliographically approved

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