Operating characteristics of a transpiring-wall SCWO reactor with a hydrothermal flame as internal heat source

Wellig, Beat; Lieball, K.; Rohr, Ph. Rudolf von

doi:10.1016/j.supflu.2004.07.003

Cited by 105 publications

(66 citation statements)

References 44 publications

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“…Essentially, a salt precipitator can be fitted prior to either a batch or a continuous SCWG reactor (Huang et al 1992;Cocero and Martinez; 2001;Wellig et al, 2005; Zohrer et al, 2014) …”

Section: Effect Of Temperaturementioning

confidence: 99%

A parametric study on supercritical water gasification of Laminaria hyperborea : A carbohydrate-rich macroalga

Cherad

Onwudili

Williams

et al. 2014

Bioresource Technology

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The potential of supercritical water gasification (SCWG) of macroalgae for hydrogen and methane production has been investigated in view of the growing interest in a future macroalgae biorefinery concept. The compositions of syngas from the catalytic SCWG of Laminaria hyperborea under varying parameters including catalyst loading, feed concentration, hold time and temperature have been investigated. Their effects on gas yields, gasification efficiency and energy recovery are presented. Results show that the carbon gasification efficiencies increased with reaction temperature, reaction hold time and catalyst loading but decreased with increasing feed concentrations. In addition, the selectivity towards hydrogen and/or methane production from the SCWG tests could be controlled by the combination of catalysts and varying reaction conditions. For instance, Ru/Al 2 O 3 gave highest carbon conversion and highest methane yield of up to 11 mol/kg, while NaOH produced highest hydrogen yield of nearly 30 mol/kg under certain gasification conditions. These arise from increased land use for growing biomass for fuel which leads to competition with arable land for food crops. As such, biofuels production is shifting to non-food sources -lignocellulosic biomass -but these still require large arable areas as well as sufficient quantities of water and fertilisers to grow.The utilisation of macroalgae as a raw material for energy production compared to terrestrial biomass is appealing due to a number of factors. Macroalgae has a faster growing rate due to no water limitations (Gellenbeck and Chapman, 1983) and a lesser effect on temperature variation. It also has a higher photosynthetic efficiency of 6-8% (FAO, 1997) compared to 1.8-2.2% for terrestrial biomass and a higher productivity than that of terrestrial crops. Cultivated macroalgae (e.g. brown seaweed) demonstrate a productivity 6.5 times the maximum projected yield for sugarcane on an aerial basis (Gao and Mckinley, 1994). However, the feasibility of production of macroalgae for energy production, in a scale similar to terrestrial biomass has thrown up some uncertainties relating to where and how it will be produced and the economics of its production and subsequent conversion to fuels (Elliott, 2008).Despite macroalgae being extensively grown and used as food in Asiatic countries, as well as a source of chemicals, the fuel from algae concept does not face the same challenges compared to first and second generation biofuels in terms of food production and requirement of large areas of land, water and fertilisers.Page 3 of 28The carbohydrates in macroalgae have potential for producing biofuels and while conversion has focused on biogas production by anaerobic digestion (Matsui and Koike, 2010), recent work has focused on utilising the laminarin and mannitol for bioethanol production by fermentation (Borines et al., 2013;Yeon et al., 2011). Thermochemical conversion routes like direct combustion, pyrolysis, gasification and liquefaction have received less attention due to ...

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“…Essentially, a salt precipitator can be fitted prior to either a batch or a continuous SCWG reactor (Huang et al 1992;Cocero and Martinez; 2001;Wellig et al, 2005; Zohrer et al, 2014) …”

Section: Effect Of Temperaturementioning

confidence: 99%

A parametric study on supercritical water gasification of Laminaria hyperborea : A carbohydrate-rich macroalga

Cherad

Onwudili

Williams

et al. 2014

Bioresource Technology

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“…[Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com] (2) The second type of porous wall consists of a porous tubular element that is a filter element. This element can be made of a sintered metal (stainless steel 136 or Ni-alloy 132,137 ) or a ceramic element, such as porous alumina. 138,139 The main characteristics of these reactors are summarized in Table 3.…”

Section: Types Of Reactors For the Scwo Processmentioning

confidence: 99%

Supercritical water oxidation: A technical review

2006

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Supercritical water oxidation (SCWO) technology presents important environmental advantages for the treatment of industrial wastes and sludges. The homogeneous reaction that takes place between the oxidizable materials and oxygen, at temperatures and pressures above the critical point of the water (647.3 K and 22.12 MPa), is well known. Specific equations of state for water and aqueous mixtures, gases, and organics have been developed. The process is not having the expected industrial development. Some new plants have been closed by corrosion and operational problems related with high temperature, high pressure, and oxidative atmosphere inside of the equipments. To overcome these technical difficulties more research focused on solving operational problems is necessary. This article presents an overview of the technical aspects of the supercritical water oxidation process. Reactors design, construction materials, corrosion, salts precipitation problems, and industrial applications are discussed. © 2006 American Institute of Chemical Engineers AIChE J, 2006

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“…Moreover, the hot water can be replaced by some auxiliary fuels (methanol, ethanol, etc.) when the transpiring-wall reactor is used for the treatment of wastewater with a relatively low concentration [21,22]. The hydrothermal flame inside the reactor allows the reactants to reach the reaction temperature without any wall contact, and it is possible to inject the fuel into the reactor at lower temperatures or even room temperature.…”

Section: Reactor Designmentioning

confidence: 99%

“…They also proposed that flame front velocities lower than 0.1 m s -1 are necessary to keep a stable hydrothermal flame where cold reagents can be injected [20]. Researchers at the ETH Zurich (Switzerland) developed a solution by directly injecting the waste into a diffusion hydrothermal flame generated inside the reactor, and the internal heat source can avoid the external preheating of the wastes up to supercritical conditions [21,22].…”

Section: Introductionmentioning

confidence: 99%

Experimental Study on the Ignition and Extinction Characteristics of the Hydrothermal Flame

Zhang

et al. 2015

Chem Eng & Technol

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An inner-preheating transpiring-wall reactor with a hydrothermal flame was designed and tested to avoid plugging in the preheating section. Hot water was used as auxiliary heating fluid to preheat the fuel to the ignition temperature. This work focused on the flame characteristics (i.e., the ignition and extinction processes, the ignition and extinction temperatures) inside the inner-preheating transpiring-wall reactor. The result shows that higher fuel concentrations and fuel flows permit lower ignition temperatures. The results of the nozzle configuration experiments show that lower velocities provide resistance to extinction.

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Operating characteristics of a transpiring-wall SCWO reactor with a hydrothermal flame as internal heat source

Cited by 105 publications

References 44 publications

A parametric study on supercritical water gasification of Laminaria hyperborea : A carbohydrate-rich macroalga

A parametric study on supercritical water gasification of Laminaria hyperborea : A carbohydrate-rich macroalga

Supercritical water oxidation: A technical review

Experimental Study on the Ignition and Extinction Characteristics of the Hydrothermal Flame

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