Thermal behavior of hydrochar from co-hydrothermal carbonization of swine manure and sawdust: effect of process water recirculation

Hydrothermal carbonization (HTC) is considered as an efficient and constantly expanding eco-friendly methodology for thermochemical processing of high moisture waste biomass into solid biofuels and valuable carbonaceous materials. However, during HTC, a considerable amount of organics, initially present in the feedstock, are found in the process water (PW). PW recirculation is attracting an increasing interest in the hydrothermal process field as it offers the potential to increase the carbon recovery yield while increasing hydrochar energy density. PW recirculation can be considered as a viable method for the valorization and reuse of the HTC aqueous phase, both by reducing the amount of additional water used for the process and maximizing energy recovery from the HTC liquid residual fraction. In this work, the effects of PW recirculation, for different starting waste biomasses, on the properties of hydrochars and liquid phase products are reviewed. The mechanism of production and evolution of hydrochar during recirculation steps are discussed, highlighting the possible pathways which could enhance energy and carbon recovery. Challenges of PW recirculation are presented and research opportunities proposed, showing how PW recirculation could increase the economic viability of the process while contributing in mitigating environmental impacts.

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Process Water Recirculation During Hydrothermal Carbonization as a Promising Process Step Towards the Production of Nitrogen-Doped Carbonaceous Materials

Waste and Biomass Valorization ◽

10.1007/s12649-021-01603-x ◽

2021 ◽

Author(s):

Wüst Dominik ◽

Arauzo Pablo ◽

Habicht Sonja ◽

Cazaña Fernando ◽

Fiori Luca ◽

...

Keyword(s):

Hydrothermal Carbonization ◽

Added Value ◽

Process Water ◽

Carbonaceous Materials ◽

Process Step ◽

Nitrogen Doped ◽

Physico Chemical ◽

Spent Grains ◽

Liquid Products ◽

Water Recirculation

AbstractHydrothermal Carbonization (HTC) refers to the conversion of biogenic wastes into char-like solids with promising perspectives for application, but a process water (PW) results which is difficult to dispose untreated. Thus, a biorefinery approach including one or two recirculation steps with the additional objective of improving the physico-chemical characteristics of the solid was performed in this study. During HTC, constitutive molecules such as saccharides, proteins and lignin of Brewer’s Spent Grains decompose into hundreds of organic compounds, following complex reactions. To get deeper insights a combination of proximate, ultimate and structural analysis for solid products as well as liquid chromatography for liquid products were the choice. The main reactions could be identified by key compounds of low and high molecular weight resulting from hydrolysis, dehydration, decarboxylation, deamination as well as amide formation and condensation reactions. Their intensity was influenced by the feedwater pH and reaction temperature. Via reactions of Maillard character up to around 90% of the dissolved nitrogen of the recirculated process water at 200, 220 and 240 °C result in the formation of nitrogen containing heterocycles or rather Quartnernary nitrogen incorporated into the hydrochar (HC). Thus, already one recirculation step during HTC at 240 °C promises the fabrication of high added-value materials, i.e. nitrogen doped carbonaceous materials. Graphic Abstract

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Hydrothermal carbonization: Temperature influence on hydrochar and aqueous phase composition during process water recirculation

Journal of Environmental Chemical Engineering ◽

10.1016/j.jece.2018.07.053 ◽

2018 ◽

Vol 6 (4) ◽

pp. 5481-5487 ◽

Cited By ~ 22

Author(s):

Jakob Köchermann ◽

Kati Görsch ◽

Benjamin Wirth ◽

Jana Mühlenberg ◽

Marco Klemm

Keyword(s):

Phase Composition ◽

Aqueous Phase ◽

Hydrothermal Carbonization ◽

Carbonization Temperature ◽

Process Water ◽

Temperature Influence ◽

Water Recirculation

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Process Water Recirculation During Hydrothermal Carbonization as a Promising Process Step Towards the Production of N-doped Carbonaceous Materials

10.21203/rs.3.rs-232186/v1 ◽

2021 ◽

Author(s):

Dominik Wüst ◽

Pablo Arauzo ◽

Sonja Habicht ◽

Fernando Cazana ◽

Luca Fiori ◽

...

Keyword(s):

Molecular Weight ◽

Hydrothermal Carbonization ◽

Added Value ◽

Process Water ◽

Chemical Characteristics ◽

Carbonaceous Materials ◽

Process Step ◽

Physico Chemical ◽

Liquid Products ◽

Water Recirculation

Abstract Hydrothermal Carbonization (HTC) refers to the conversion of biogenic wastes into char-like solids with promising perspectives for application, but a process water (PW) results which is difficult to dispose untreated. Thus, a biorefinery approach including one or two recirculation steps with the additional objective of improving the physico-chemical characteristics of the solid was performed. During HTC, constitutive biomass molecules decompose into hundreds of organic compounds, following complex reactions. To get deeper insights a combination of proximate, ultimate and structural analysis for solid products as well as liquid chromatography for liquid products were the choice. The main reactions could be identified by key compounds of low and high molecular weight resulting from hydrolysis, dehydration, decarboxylation, deamination as well as amide formation and condensation reactions. Their intensity was influenced by the feedwater pH and reaction temperature. Reactions of Maillard character result in N-containing heterocycles incorporated into the hydrochar (HC), which promises the fabrication of high added-value materials, i.e. N-doped carbonaceous materials.

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