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In This Article

  • Summary
  • Abstract
  • Introduction
  • Protocol
  • Representative Results
  • Discussion
  • Acknowledgements
  • Materials
  • References
  • Reprints and Permissions

Summary

A protocol for the emission precursor depletion from low quality biomass by low temperature microwave assisted hydrothermal carbonization treatment is presented. This protocol includes the microwave parameters and the analysis of the biocoal product and process water.

Abstract

Biomass is a sustainable fuel, as its CO2 emissions are reintegrated in biomass growth. However, the inorganic precursors in the biomass cause a negative environmental impact and slag formation. The selected short rotation coppice (SRC) willow wood has a high ash content (figure-abstract-309 = 1.96%) and, therefore, a high content of emission and slag precursors. Therefore, the reduction of minerals from SRC willow wood by low temperature microwave assisted hydrothermal carbonization (MAHC) at 150 °C, 170 °C, and 185 °C is investigated. An advantage of MAHC over conventional reactors is an even temperature conductance in the reaction medium, as microwaves penetrate the whole reactor volume. This allows a better temperature control and a faster cooldown. Therefore, a succession of depolymerization, transformation and repolymerization reactions can be analyzed effectively. In this study, the analysis of the mass loss, ash content and composition, heating values and molar O/C and H/C ratios of the treated and untreated SCR willow wood showed that the mineral content of the MAHC coal was reduced and the heating value increased. The process water showed a decreasing pH and contained furfural and 5-methylfurfural. A process temperature of 170 °C showed the best combination of energy input and ash component reduction. The MAHC allows a better understanding of the hydrothermal carbonization process, while a large-scale industrial application is unlikely because of the high investment costs.

Introduction

The application of microwaves for hydrothermal carbonization (MAHC) was used for the thermochemical transformation of biomass model compounds like fructose, glucose1,2 or cellulose3, and for organic substrates, preferably waste material4,5,6,7,8,9,10. The utilization of microwaves is advantageous as it allows an even heating of the treated biomass

Protocol

1. Preparation of sample material

  1. Harvest five year old willow, clone type “Tordes” ([Salix schwerinii x S. viminalis] x S. vim.), with a height of 12−14 m and a breast diameter of approximately 15 cm.
  2. Chip the wood and dry the chips in a kiln dryer for 24 h at 105 °C.
  3. Cut the wood chips with a cutting mill and grind with a centrifugal mill to a particle size of 0.12 mm.

2. Microwave assisted hydrothermal carbonizati.......

Representative Results

The results of the elemental analysis revealed differences between the O/C-H/C ratio of the willow wood and the MAHC biocoals (Figure 1). The raw material shows higher O/C-H/C ratios and a higher variation of the values. The MAHC treatment reduced the value variation due to homogenization in the microwave reactor. The precision of the microwave reactor allowed the differentiation of three stages of degradation. The H/C ratio was reduced at 150 °C and the.......

Discussion

The MAHC allows the differentiation of the steps of the chemical degradation by applying different intensities of thermal treatment. Therefore, it is possible to assess the interactions between the mass loss, O/C-H/C ratio, heating value, ash component reduction, pH increase of the process water and accumulation of furans in the process water. The advantage of the MAHC method over the conventional HTC reactor method is based on the thermal conduction via microwaves that penetrate the whole reactor volume and conduct the .......

Acknowledgements

The authors like to thank Christoph Warth, Michael Russ, Carola Lepski, Julian Tejada and Dr. Rainer Kirchhof for their technical support. The study was funded by the BMBF (Project BiCoLim-Bio-Combustibles Limpios) under the grant number 01DN16036.

....

Materials

NameCompanyCatalog NumberComments
5MS non-polar cloumnThermo Fisher Scientific,Waltham, USATraceGOLD SQCGCMS
9µm polyvinylalcohol particle columnMethrom AG, Filderstadt, GermanyMetrosep A Supp 4 -250/4.0Ion chromatography
argonWestfalen AG, Münster, GermanyUN 1006ICP-OES
calorimeterIKA-Werke GmbH & Co.KG, Stauffen, GermanyC6000higher and lower heating value
centrifugeAndreas Hettich GmbH & Co.KG, GermanyRotofix 32 A
centrifuge millRetsch Technology GmbH, Haan,
Germany
ZM 200
ceramic dishesCarl Roth GmbH&Co.KG, Karlsruhe, GermanyXX83.1Ash content
cutting millFritsch GmbH, Markt Einersheim, Germanypulverisette 19
D(+) GlucoseCarl Roth GmbH&Co.KG, Karlsruhe, GermanyX997.1higher and lower heating value
elemental analyzerelementar Analysesysteme GmbH, Langenselbold, GermanyvarioMACRO cubeelemental analysis
exicatorDWK Life Sciences GmbH, Wertheim, GermanyDURAN DN300Ash content
GC-MS systemThermo Fisher Scientific,Waltham, USATrace 1300GCMS
hydrochloric acidCarl Roth GmbH&Co.KG, Karlsruhe, GermanyHN53.3ICP-OES
ICP OESSpectro Analytical Instruments GmbH, Kleve, GermanySpectro Blue-EOP- TIICP-OES
Ion chromatographMethrom GmbH&Co.KG, Filderstadt, Germany833 Basic IC plusIon chromatography
kiln dryerSchellinger KG, Weingarten, Germany
kiln dryerSchellinger KG, Weingarten, GermanyAsh content
mesh filter paperCarl Roth GmbH&Co.KG, Karlsruhe, GermanyL874.1ICP-OES
microwave ovenAnton Paar GmbH, Graz, AustriaMultiwave Go
muffel furnanceCarbolite Gero GmbH &Co.KG, Neuhausen, GermanyAAF 1100Ash content
nitric acidCarl Roth GmbH&Co.KG, Karlsruhe, Germany4989.1ICP-OES
oxygenWestfalen AG, Münster, GermanyUN 1072higher and lower heating value
pH-meterylem Analytics Germany Sales GmbH & Co. KG, Weilheim,GermanypH 3310pH
sample bagIKA-Werke GmbH & Co.KG, Stauffen, GermanyC12ahigher and lower heating value
Standard Laboratory Vessels and Instruments
standard samplesBernd Kraft GmbH, Duisburg, GermanyICP-OES
sulfonamiteelementar Analysesysteme GmbH, Langenselbold, GermanySLBS4782elemental analysis
teflon reaction vesselsAnton Paar, AustriaHVT50
teflon reaction vesselsAnton Paar, AustriaHVT50ICP-OES
tin foilelementar Analysesysteme GmbH, Langenselbold, GermanyS12.01-0032elemental analysis
tungstenVIoxideelementar Analysesysteme GmbH, Langenselbold, Germany11.02-0024elemental analysis
twice deionized waterCarl Roth GmbH&Co.KG, Karlsruhe, Germany
twice deionized waterCarl Roth GmbH&Co.KG, Karlsruhe, Germanyhigher and lower heating value
twice deionized waterCarl Roth GmbH&Co.KG, Karlsruhe, GermanyICP-OES

References

  1. Li, C., Zhao, Z. K., Cai, H., Wang, A., Zhang, T. Microwave-promoted conversion of concentrated fructose into 5-hydroxymethylfurfural in ionic liquids in the absence of catalysts. Biomass and Bioenergy. 35 (5), 2013-2017 (2011).
  2. Möller, M., Harnisch, F., Schröder, U.

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