Uncovering supercritical CO2 wood dewatering via interleaved 1H-imaging and 13C-spectroscopy with real-time reconstruction

Franich, Robert A.; Meder, Roger; Falge, Mirjam; Fuchs, Johannes; Behr, Volker C.

doi:10.1016/j.supflu.2018.10.006

Cited by 12 publications

(11 citation statements)

References 21 publications

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“…The predicted cut-off moisture content was 40.5% using the FLASH routine in the present investigation. This was higher than the expected average fibre saturation point (FSP) for wood, which is approximately 30% moisture content (Babiak and Kúdela 1995;Telkki et al 2013;Franich et al 2019). However, as the moisture content approaches the fibre saturation point, the water in the lumens has increasingly restricted mobility.…”

Section: Correlation Between Mr Image Intensity and Wood Moisture Conmentioning

confidence: 78%

“…Both wood sap flow and wood impregnation using either fluids or supercritical fluids are well known to be affected by wood anatomy (Schneider et al 2006;Siau 1984). Previous studies of the wood-water relationship using supercritical carbon dioxide have investigated the movement and nature of water during the dewatering process of Pinus radiata using 1 H and/or 13 C MR imaging (Behr et al 2014;Meder et al 2015;Newman et al 2016;Franich et al 2019). The same approach was used in this study to visualise the sap flow under scCO2 conditions for the six different wood anatomies investigated in this study, using a high-pressure autoclave with a 1 H/ 13 C double-tuned resonator (Behr et al 2013) to acquire 1 H magnetic resonance (MR) images of the water during the extremes of the pressure cycles.…”

Section: Introductionmentioning

confidence: 99%

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Tree species identification via 1H NMR fingerprinting of supercritical carbon dioxide wood extractives

Raymond

Sandquist

Hill

et al. 2020

BioRes

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Six tree species were examined using 1H NMR spectroscopy of sap extracted by supercritical CO2. A metabolomic approach was developed to evaluate the sap extracted from sapwood of Norway spruce (Picea abies), Sitka spruce (Picea sitchensis), radiata pine (Pinus radiata), macrocarpa (Cupressus macrocarpa), and two Eucalyptus species—shining gum and mountain ash (Eucalyptus nitens and Eucalyptus regnans. The sap extraction patterns in the different species were visualised using 1H magnetic resonance imaging. In softwoods with distinct annual rings, water was first removed from the latewood bands, and then gradually from the earlywood bands. In the case of the hardwood species an almost random water redistribution, rather than water expulsion, was observed. Analysis of the principal component analysis loading plots showed that the significant differences in the sap between each species were due to the carbohydrate region. Key discriminators were identified as pinitol, sucrose, glucose, and fructose.

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Section: Correlation Between Mr Image Intensity and Wood Moisture Conmentioning

confidence: 78%

Section: Introductionmentioning

confidence: 99%

Tree species identification via 1H NMR fingerprinting of supercritical carbon dioxide wood extractives

Raymond

Sandquist

Hill

et al. 2020

BioRes

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“…Most informative to elucidating the dewatering mechanism was the acquisition of simultaneous proton images, 13 C spectra, and experiment pressure in situ and in real time using radiata pine green wood specimens contained in the high-pressure autoclave [32], and supplementary 1 H/ 13 C dewatering video cited therein. During the incubation (compression) cycle, the 13 C spectrum was observed to change shape and intensity from ca.…”

Section: Magnetic Resonance Imaging (Mri) and Nuclear Magnetic Resonamentioning

confidence: 99%

“…At ca. 10 MPa, the emergence of the signal for supercritical carbon dioxide was observed with change in signal shape, and this signal continued to increase in strength until the maximum applied pressure, 20 MPa, had been attained [ 32 ]. On decompression, the supercritical carbon dioxide signal decreased in strength and shape with the reduction of the signal for supercritical carbon dioxide, and at ca.…”

Section: Review Of Science Studies On Dewatering Green Wood Using mentioning

confidence: 99%

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Dewatering Green Sapwood Using Carbon Dioxide Undergoing Cyclical Phase Change between Supercritical Fluid and Gas

Franich

Meder²,

Behr

2020

Molecules

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Conventional kiln drying of wood operates by the evaporation of water at elevated temperature. In the initial stage of drying, mobile water in the wood cell lumen evaporates. More slowly, water bound in the wood cell walls evaporates, requiring the breaking of hydrogen bonds between water molecules and cellulose and hemicellulose polymers in the cell wall. An alternative for wood kiln drying is a patented process for green wood dewatering through the molecular interaction of supercritical carbon dioxide with water of wood cell sap. When the system pressure is reduced to below the critical point, phase change from supercritical fluid to gas occurs with a consequent large change in CO2 volume. This results in the efficient, rapid, mechanical expulsion of liquid sap from wood. The end-point of this cyclical phase-change process is wood dewatered to the cell wall fibre saturation point. This paper describes dewatering over a range of green wood specimen sizes, from laboratory physical chemistry studies to pilot-plant trials. Magnetic resonance imaging and nuclear magnetic resonance spectroscopy were applied to study the fundamental mechanisms of the process, which were contrasted with similar studies of conventional thermal wood drying. In conclusion, opportunities and impediments towards the commercialisation of the green wood dewatering process are discussed.

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Effect of supercritical CO2 pre-treatment and kiln-drying of fresh green Pinus radiata sapwood on kiln brown stain and drying stress

et al. 2022

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High pressure (20 MPa), cyclic, supercritical carbon dioxide (scCO2) treatments can reduce the moisture content of green Pinus radiata sapwood from 150–200% to 35–40%. Such treatments can be used as a dewatering pre-treatment before the kiln-drying of timber. Kiln-drying can utilise various temperature and humidity schedules, targeting around 10% moisture content, with a final stress-relieving steam-conditioning step. After scCO2 treatment and kiln-drying of samples, kiln brown stain was evaluated using the CIE L*a*b* colour space while drying stress was assessed by stress-cup measurements. The most significant results of scCO2 pre-treatment of Pinus radiata sapwood followed by kiln-drying plus steam-conditioning were as follows: Drying from green (36 h from a moisture content (MC) of 164%) using a conventional temperature schedule (90 °C/60 °C) took 2–5 times longer than kiln-drying scCO2 pre-treated boards (37.5% MC) to a target of 10% MC. Colour measurements proved that kiln brown stain does not occur. The use of a steam-conditioning step in reducing internal drying stresses was important irrespective of whether or not there was a scCO2 pre-treatment step. Over all drying schedule combinations, internal drying stress of both green and scCO2 pre-treated timber was similar after kiln-drying plus steam-conditioning. However, using only 90 °C/60 °C schedule data, with steam-conditioning, drying stresses were lower using kiln-drying without the scCO2 pre-treatment. This was surprising since the scCO2 step reduced the moisture content to around 37.5% without significant moisture gradients and so a secondary kiln-drying to 10% moisture content could have been expected to yield lower internal stress levels by preventing large moisture gradients to develop during drying. This result confirms the efficacy of the steam-conditioning step following standard kiln-drying. The colour data demonstrating the prevention of kiln brown stain using kiln-drying schedules offers a path to increasing timber quality for interior applications.

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Uncovering supercritical CO2 wood dewatering via interleaved 1H-imaging and 13C-spectroscopy with real-time reconstruction

Cited by 12 publications

References 21 publications

Tree species identification via 1H NMR fingerprinting of supercritical carbon dioxide wood extractives

Tree species identification via 1H NMR fingerprinting of supercritical carbon dioxide wood extractives

Dewatering Green Sapwood Using Carbon Dioxide Undergoing Cyclical Phase Change between Supercritical Fluid and Gas

Effect of supercritical CO2 pre-treatment and kiln-drying of fresh green Pinus radiata sapwood on kiln brown stain and drying stress

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