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Mild Wet Torrefaction and Characterization of Woody Biomass from Mozambique for Thermal Applications
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Energy and Furnace Technology.
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Mozambique has vast forestry resources and also considerable biomass waste material such as bagasse, rice husks, sawdust, coconut husks and shells, cashew nut shell and lump charcoal waste. The potential of the total residues from the agricultural sector and the forest industry is estimated to be approximately 13 PJ. This amount of energy covers totally the production of charcoal which amounted to approximately 12.7 PJ in 2006. Although biomass is an attractive renewable source of energy, it is generally difficult to handle, transport, storage and use due to its lower homogeneity, its lower energy density and the presence of non-combustible inorganic constituents, which leads to different problems in energy conversion units such as deposition, sintering, agglomeration, fouling and corrosion. Therefore, a pretreatment of the biomass to solve these problems could lead to a change of current biomass utilization situation. The aim of this study is to convert Mozambican woody biomass residue into a solid biochar that resembles low-grade coal.

In this work the current energy situation in Mozambique has been reviewed, and the available and potential renewable sources including residues from agricultural crops and forest industry as energy have been assessed. It was found that the country is endowed with great potential for biofuel, solar, hydro and wind energy production. However, the production today is still far from fulfilling the energy needs of the country, and the majority of people are still not benefiting from these resources. Charcoal and firewood are still the main sources of energy and will continue to play a very important role in the near future. Additionally, enormous amounts of energy resources are wasted, especially in the agricultural sector. These residues are not visible on national energy statistics. The chemical composition and the fuelwood value index (FVI) showed that by failing to efficiently utilise residues from Afzelia quanzensis, Millettia stuhlmannii and Pterocarpus angolensis, an opportunity to reduce some of the energy related problems is missed. An evaluation of effect of a mild wet torrefaction pretreatment showed that the chemical composition of the biochar is substantially different than the feedstock. The use of diluted acid as catalysts improves the biochar quality, namely in terms of the energy density and ash characteristics; however, the increment of the S content in the final product should be considered for market acceptance (because the fuels have a maximum allowance for S concentration). The thermal behaviour of the untreated and treated biomass was also investigated. The pyrolytic products of umbila and spruce were affected by the treatment and catalyst in terms of yield and composition of the vapours.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2015. , v, 71 p.
Keyword [en]
Biomass, Wet torrefaction, Fast Pyrolysis, kinetics, Catalyst
National Category
Engineering and Technology Chemical Process Engineering
Identifiers
URN: urn:nbn:se:kth:diva-159476ISBN: 978-91-7595-429-5 (print)OAI: oai:DiVA.org:kth-159476DiVA: diva2:785099
Public defence
2015-02-20, Sal F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20150202

Available from: 2015-02-02 Created: 2015-02-02 Last updated: 2015-02-02Bibliographically approved
List of papers
1. Energy situation in Mozambique: A review
Open this publication in new window or tab >>Energy situation in Mozambique: A review
2010 (English)In: Renewable & sustainable energy reviews, ISSN 1364-0321, E-ISSN 1879-0690, Vol. 14, no 7, 2139-2146 p.Article, review/survey (Refereed) Published
Abstract [en]

The need to increase energy security and promote development, especially in rural areas has forced many developing countries in southern Africa, like Mozambique to take several actions toward development of several infrastructures and legislations for production and use of liquid biofuels. The main objective of this study is to present the energy situation in Mozambique and assess the potential for energy generation from widely available renewable sources including residues from agricultural crops and forest industry. The country is endowed with great potential for biofuels, solar, hydro and wind energy production. The energy production today is, however, far from fulfilling energy needs of the country, and the majority of people are still not benefiting from these resources. The potential of total residues from agricultural sector and forest industry is estimated to be around 128 PJ. This amount of energy covers almost half of the combined production of charcoal and firewood which amounted to approximately 298 PJ in 2006. However, such amount of energy resources is wasted and is not visible on national energy statistics.

Keyword
Energy, Biomass, Fuelwood, Forest residues, Agricultural residues, Biofuels, Mozambique
National Category
Bioenergy
Identifiers
urn:nbn:se:kth:diva-159479 (URN)10.1016/j.rser.2010.02.002 (DOI)000279258000038 ()2-s2.0-77956070756 (Scopus ID)
Funder
Sida - Swedish International Development Cooperation Agency
Note

QC 20150202

Available from: 2015-02-02 Created: 2015-02-02 Last updated: 2017-12-05Bibliographically approved
2. The Characterization of Wood Species from Mozambique as a Fuel
Open this publication in new window or tab >>The Characterization of Wood Species from Mozambique as a Fuel
2014 (English)In: Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, ISSN 1556-7036, E-ISSN 1556-7230, Vol. 36, no 8, 851-857 p.Article in journal (Refereed) Published
Abstract [en]

The efficient utilization of fuelwood as a source of energy is strongly dependent on the properties of the biomass. This study characterizes common hardwood species from Mozambique and evaluates their quality as a fuel. Disc samples, taken at breast height, from Afzelia quanzensis Welwn, Millettia stuhlmannii Taub, Pterocarpus angolensis DC, Sterculia appendiculata K. Schum, Pericopsis angolensis Meeuwen, Acacia nigrescens Oliv., Pseudolachostylis maprounaefolia Pax, and Icuria dunensis Wieringa, were collected from three provinces in Mozambique. Chemical and physical properties were analyzed. The raking of the species as fuel was performed using fuelwood value index. The higher heating value varied between 19.38 and 21.50 MJ/kg dry weight. The concentration of lignin ranged from 21.96 up to 36.69% weight dry basis (wt% d.b.), and ash free. All studied species showed very low concentrations of Si, S, and Cl. Ash content varied between 0.76-3.71 wt% (d.b.), while the basic density ranged from 536 to 1,111 k gm(-3). Heavy metals were also determined and their concentrations were below the values reported in the literature. The species Acacia nigrescens had the highest fuelwood value index and it was closely followed by Icuria dunensis and Millettia stuhlmannii. The worst ranked was Sterculia appendiculata.

Keyword
mineral content, calorific value, lignin, fuelwood value index, ash content, wood fuel, hardwood
National Category
Energy Engineering Environmental Sciences
Identifiers
urn:nbn:se:kth:diva-159481 (URN)10.1080/15567036.2011.582601 (DOI)000331601300006 ()2-s2.0-84894590809 (Scopus ID)
Funder
Sida - Swedish International Development Cooperation Agency
Note

QC 20150202

Available from: 2015-02-02 Created: 2015-02-02 Last updated: 2017-12-05Bibliographically approved
3. Spruce pretreatment for thermal application: Water, alkaline, and diluted acid hydrolysis
Open this publication in new window or tab >>Spruce pretreatment for thermal application: Water, alkaline, and diluted acid hydrolysis
2012 (English)In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 26, no 10, 6426-6431 p.Article in journal (Refereed) Published
Abstract [en]

Hydrolysis a process that involves a separation of the main components of lignocellulosic material (LCM) primarily developed for ethanol production was applied in this work to upgrade biomass for thermal application. The purpose of the pretreatment was to remove hemicellulose and alkali metals and consequently increase the energy content of the biomass and improve the fuel properties. Freshly chopped (2-10 mm) spruce (Picea abies) samples were hydrolyzed (liquid/solid ratio of 800 mL/80 g), using water, diluted acid, and sodium hydroxide in a rotating autoclave at 180 2 ̊C for 150 and 350 min. Several analyses, such as proximate and ultimate analyses, ash composition and fusibility characteristics, and thermogravimetric analysis under pure nitrogen, were performed. Despite the reduction of mass and energy yields with increment of the severity factor, a significant increment of the higher heating value and ash quality was achieved, revealing that hydrolysis using water or diluted acid is a promising method to upgrade biomass as fuel. For alkaline treatment, a huge degradation on the quality of the ash was observed.

Keyword
Acid hydrolysis, Alkaline treatment, Ash composition, Energy content, Energy yields, Ethanol production, Fuel properties, Higher heating value, Lignocellulosic material, Picea abies, Pre-Treatment, Severity factor, Sodium hydroxides, Thermal applications, Ultimate analysis
National Category
Energy Systems
Identifiers
urn:nbn:se:kth:diva-105426 (URN)10.1021/ef301167v (DOI)000309902200040 ()2-s2.0-84867650070 (Scopus ID)
Note

QC 20121121

Available from: 2012-11-21 Created: 2012-11-21 Last updated: 2017-12-07Bibliographically approved
4. The Impact of a Mild Sub-Critical Hydrothermal Carbonization of Pretreatment on Umbila Wood: A Mass and Energy Balance Perspective
Open this publication in new window or tab >>The Impact of a Mild Sub-Critical Hydrothermal Carbonization of Pretreatment on Umbila Wood: A Mass and Energy Balance Perspective
2015 (English)In: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 8, no 3, 2165-2175 p.Article in journal (Refereed) Published
Abstract [en]

Over the last years, the pretreatment of biomass as a source of energy has become one of the most important steps of biomass conversion. In this work the effect of a mild subcritical hydrothermal carbonization of a tropical woody biomass was studied. Results indicate considerable change in carbon content from 52.78% to 65.1%, reduction of oxygen content from 41.14% to 28.72% and ash slagging and fouling potential. Even though decarboxylation, decarbonylation and dehydration reactions take place, dehydration is the one that prevails. The mass and energy balance was affected by the treatment conditions than the severity of the treatment.

National Category
Energy Engineering
Identifiers
urn:nbn:se:kth:diva-159483 (URN)10.3390/en8032165 (DOI)000351942000035 ()2-s2.0-84927157788 (Scopus ID)
Funder
Sida - Swedish International Development Cooperation Agency
Note

Updated from Manuscript to Article. QC 20150422

Available from: 2015-02-02 Created: 2015-02-02 Last updated: 2017-12-05Bibliographically approved
5. Effect of mild hydrothermal pretreatment on biomass pyrolysis characteristics and vapors: A Mass and Energy Balance Perspective
Open this publication in new window or tab >>Effect of mild hydrothermal pretreatment on biomass pyrolysis characteristics and vapors: A Mass and Energy Balance Perspective
Show others...
(English)Manuscript (preprint) (Other academic)
Identifiers
urn:nbn:se:kth:diva-159485 (URN)
Note

QS 2015

Available from: 2015-02-02 Created: 2015-02-02 Last updated: 2015-02-02Bibliographically approved
6. Effect of zeolite on product yield and composition during pyrolysis of hydrothermally pretreated Spruce
Open this publication in new window or tab >>Effect of zeolite on product yield and composition during pyrolysis of hydrothermally pretreated Spruce
Show others...
(English)Manuscript (preprint) (Other academic)
Identifiers
urn:nbn:se:kth:diva-159486 (URN)
Note

QS 2015

Available from: 2015-02-02 Created: 2015-02-02 Last updated: 2015-02-02Bibliographically approved

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