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Methanol production via black liquor co-gasification with expanded raw material base: Techno-economic assessment
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.ORCID iD: 0000-0002-2314-8097
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.ORCID iD: 0000-0002-4597-4082
RISE Bioeconomy.
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2018 (English)In: Article in journal, Editorial material (Refereed) Submitted
Abstract [en]

Entrained flow gasification of black liquor combined with downstream-gas-derived synthesis of biofuels in Kraft pulp mills has shown advantages regarding energy efficiency and economic performance when compared to combustion in a recovery boiler. To further increase the operation flexibility and the profitability of the biofuel plant while at the same time increase biofuel production, black liquor can be co-gasified with a secondary feedstock (blend-in feedstock). This work has evaluated the prospects of producing biofuels via co-gasification of black liquor and different blend-in feedstocks (crude glycerol, fermentation residues, pyrolysis liquids) at different blend ratios. Process modelling tools were used, in combination with techno-economic assessment methods. Two methanol grades, crude and grade AA methanol, were investigated. The results showed that the co-gasification concepts resulted in significant increases in methanol production volumes, as well as in improved conversion efficiencies, when compared with black liquor gasification; 5-11 and 4-10 percentage point in terms of cold gas efficiency and methanol conversion efficiency, respectively. The economic analysis showed that required methanol selling prices ranging from 55-101 €/MWh for crude methanol and 58-104 €/MWh for grade AA methanol were obtained for an IRR of 15%. Blend-in led to positive economies-of-scale effects and subsequently decreased required methanol selling prices, in particular for low cost blend-in feedstocks (prices below approximately 20 €/MWh). The co-gasification concepts showed economic competitiveness to other biofuel production routes. When compared with fossil fuels, the resulting crude methanol selling prices were above maritime gas oil prices. Nonetheless, for fossil derived methanol prices higher than 80 €/MWh, crude methanol from co-gasification could be an economically competitive option. Grade AA methanol could also compete with taxed gasoline. Crude glycerol turned out as the most attractive blend-in feedstock, from an economic perspective. When mixed with black liquor in a ratio of 50/50, grade AA methanol could even be cost competitive with untaxed gasoline.

Place, publisher, year, edition, pages
2018.
Keyword [en]
Bio-methanol, Gasification, Black liquor, Pyrolysis liquid, Crude Glycerol, Fermentation residues
National Category
Energy Systems Energy Engineering
Research subject
Energy Engineering
Identifiers
URN: urn:nbn:se:ltu:diva-68207OAI: oai:DiVA.org:ltu-68207DiVA, id: diva2:1195565
Available from: 2018-04-05 Created: 2018-04-05 Last updated: 2018-04-06
In thesis
1. Opportunities to broaden biomass feedstocks in thermochemical conversion technologies
Open this publication in new window or tab >>Opportunities to broaden biomass feedstocks in thermochemical conversion technologies
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Möjligheter till utökad bioråvarubas förtermokemiska konverteringstekniker
Abstract [en]

Global environmental concerns are motivating a growing interest in broadening the biomass feedstock base in several energy sectors, including (i) the domestic heating sector, presently dominated by stem wood combustion, and (ii) biofuel production, presently dominated by edible crops. The objective of this thesis is to investigate new opportunities to broaden the biomass feedstock in thermochemical conversion technologies. The performance of different feedstocks was therefore investigated for (i) heat production in small-scale combustion systems and (ii) biofuel production in large-scale gasification-based plants. The selected feedstocks were agricultural residues, forest wood, pyrolysis liquid and industrial by-products, such as lignin, black liquor, crude glycerol and fermentation residues.

The alkali metals content in biomass has an important role in combustion and gasification. Alkali metals can cause ash-related problems in small-scale combustion systems, while they can catalyse gasification reactions thus increasing conversion efficiency. Keeping this effect in mind, the present investigation was based on combustion tests with pelletised agricultural residues (non-woody feedstocks with ash contents of 3-8 wt% on a dry basis) to evaluate their combustion feasibility in several small-scale appliances. Moreover, the potential techno-economic benefits of alkali addition in gasification-based biofuel plants were investigated in two different systems: (i) stand-alone biofuel plant operated with wet-alkali-impregnated forest residues and alkali-rich lignin as well as (ii) biofuel plant integrated with a Kraft pulp mill operated with black liquor (an inherently alkali-rich feedstock) mixed with different blend ratios of pyrolysis liquid, crude glycerol or fermentation residues (co-gasification concept). The techno-economic analysis in large-scale entrained-flow-gasification-based biofuel plants was made with the help of simulation tools.

The combustion tests have shown that high alkali feedstocks lead to problems with ash accumulation and slag formation in small-scale appliances. The results indicated that non-woody feedstocks can only be burned in appliances adapted to manage high ash content feedstocks. Effective ash cleaning and enhanced combustion controlling mechanisms are relevant characteristics to have in appliances when using these feedstocks. It has been shown that four out of the seven selected feedstocks can be burned in small-scale appliances, while fulfilling the legal European requirements (EN 303-5:2012) in terms of combustion efficiency and emissions. The nitrogen content and ash composition were shown to be important parameters to evaluate whether a feedstock can be utilised in small-scale combustion appliances.

The techno-economic investigations of the gasification-based biofuel plants have shown that alkali impregnation is an attractive option to increase energy performance and downstream biofuel production. The economic assessment has indicated that alkali impregnation does not significantly increase biofuel production costs, while it allows the application of a new syngas cleaning system that can significantly reduce biofuel production costs. The present study has shown that the vi co-gasification concept has also techno-economic benefits as a result of the (i) alkali content in black liquor and (ii) economy-of-scale effects. These benefits can be enhanced by choosing energy-rich and low-cost blend-in feedstocks. The gasification-based biofuel production routes hereby investigated exhibit a good economic performance since biofuel required selling prices were economically competitive with other biofuel production routes as well as with taxed gasoline.

Place, publisher, year, edition, pages
Luleå: Luleå University of Technology, 2018. p. 150
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
Keyword
Non-woody biomass, Combustion, Gasification, Biofuels, Techno-economic analysis
National Category
Energy Systems Energy Engineering
Research subject
Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-68200 (URN)978-91-7790-088-7 (ISBN)978-91-7790-089-4 (ISBN)
Public defence
2018-05-28, E632, Luleå tekniska universitet, Luleå, 10:00 (English)
Opponent
Supervisors
Available from: 2018-04-06 Created: 2018-04-05 Last updated: 2018-05-15Bibliographically approved

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