Assessment of the effects of process water recirculation on the surface chemistry and morphology of hydrochar

Arauzo, Pablo J.; Olszewski, Maciej P.; Wang, Xia; Pfersich, Jens; Sebastián, Víctor; Manyà, Joan J.; Hedin, Niklas; Kruse, Andrea

doi:10.1016/j.renene.2020.04.050

Cited by 43 publications

(31 citation statements)

References 50 publications

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“…Higher reaction temperatures and longer reaction times lead to hydrochars with properties similar to sub-bituminous coal, which can be used as a co-fuel [ 9 , 45 ]. By considering the results in literature [ 46 , 47 , 48 ], the obtained H/C and O/C ratios in Figure 3 were close to that of other solid fuels like coal, lignite and peat, thus showing their possibility to be used as co-fuels.…”

Section: Resultssupporting

confidence: 90%

Hydrothermal Conversion of Spent Sugar Beets into High-Value Platform Molecules

et al. 2020

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The growing importance of bio-based products, combined with the desire to decrease the production of wastes, boosts the necessity to use wastes as raw materials for bio-based products. A waste material with a large potential is spent sugar beets, which are mainly used as animal feeds or fertilizers. After hydrothermal treatment, the produced chars exhibited an H/C ratio of 1.2 and a higher heating value of 22.7 MJ/kg, which were similar to that of subbituminous coal and higher than that of lignite. Moreover, the treatment of 25 g/L of glucose and 22 g/L of fructose by heating up to 160 °C led to a possible application of spent sugar beets for the production of 5-hydroxymethylfurfural. In the present study, the maximum concentration of 5-hydroxymethylfurfural was 3.4 g/L after heating up to 200 °C.

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Section: Resultssupporting

confidence: 90%

Hydrothermal Conversion of Spent Sugar Beets into High-Value Platform Molecules

et al. 2020

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“…After recirculation steps, as it can be observed, the hydrogen (H) and nitrogen (N) contents remained almost unchanged, as commonly observed during HTC of lignocellulosic waste biomass [59]. Differently, carbon (C) and fixed carbon (FC) contents increased while oxygen (O) and volatile matter (VM) contents decreased [46,66,67,73]. These findings confirm that the hydrochars are further converted into solid fuel by HTC with recirculated PW.…”

Section: Effect On Chemical Compositionsupporting

confidence: 77%

“…The increase in solid microparticles polymerized from the organic matter of PW leads to an increase in the carbon content of hydrochars and thus their energy content. In other studies [66,68,75], HHV remained almost unchanged or slightly decreased. Organic acids and some sugars produced during the hydrothermal process are oxygenated and have lower HHV than deoxygenated biocarbon [68]; thus, any deposition of these substances on the hydrochar surface could balance the increase in carbon content, leading to hydrochars showing unchanged or decreased HHV.…”

Section: Effect On Hhv and Energy Yieldmentioning

confidence: 71%

“…Sugars derived from the hydrolysis of hemicellulose and cellulose are dehydrated into intermediates such as HMF which are further dehydrated and decarboxylated, producing H 2 O and CO 2 [78]. Besides, during condensation and polymerization of furfurals, further water is eliminated, causing a remarkable reduction of the oxygen content in the solid products [66]. As well reported in the literature, hydrochars often exhibit lower ash content than raw feedstock [34,79,80].…”

Section: Effect On Chemical Compositionmentioning

confidence: 90%

“…Most of the microspheres precipitate on hydrochar surface contributing to its mass growth, while the remaining amount is suspended in the aqueous medium [46]. Thus, the organic acids in the liquid phase formed during the HTC process, if recirculated, could act as a catalyst and promote dehydration reactions which significantly boost the carbonization process, contributing to hydrochar production through condensation and back-polymerization reactions [46,66,67]. Moreover, organic acids could also directly participate in the formation of hydrochars through condensation reactions and the subsequent precipitation on hydrochar matrix.…”

Section: Effect Of Pw Recirculation On Hydrochar Properties 21 Effect On the Mass Yieldmentioning

confidence: 99%

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Process Water Recirculation during Hydrothermal Carbonization of Waste Biomass: Current Knowledge and Challenges

2021

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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

Wüst

Pablo

Habicht³

et al. 2021

Waste Biomass Valor

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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 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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Assessment of the effects of process water recirculation on the surface chemistry and morphology of hydrochar

Cited by 43 publications

References 50 publications

Hydrothermal Conversion of Spent Sugar Beets into High-Value Platform Molecules

Hydrothermal Conversion of Spent Sugar Beets into High-Value Platform Molecules

Process Water Recirculation during Hydrothermal Carbonization of Waste Biomass: Current Knowledge and Challenges

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

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