Biomass In Supercritical Water Research Articles

Proposal, design, and cost analysis of a hydrogen production process from cellulose via supercritical water gasification.

Hydrogen production from biomass, a renewable resource, has been attracting attention in recent years. We conduct a detailed process design for cellulose-derived hydrogen production via glucose using supercritical water gasification technology. Gasification of biomass in supercritical water offers advantages over conventional biomass conversion methods, including high gasification efficiency, elevated hydrogen molar fractions, and the minimization of drying process for wet biomass. In the process design, a continuous tank reactor is employed because the reaction in the glucose production process involves solids, and using a tube-type reactor may clog the reactor with solids. In the glucose separation process, glucose and levulinic acid, which cannot be separated by boiling point difference, are separated by using an extraction column. In the hydrogen separation process, the hydrogen purity, which could not be sufficiently increased with a single pressure swing adsorption (PSA) process, is increased to the target value by employing two sets of PSA columns. The overall utility cost is significantly reduced by $0.020/mol-H2 through heat integration. Our economic evaluation for this process results in a deficit of $0.015/mol-H2, as a price to be paid by the human for renewable hydrogen production from biomass at the present stage. By simply adopting the reported experimental condition, our process contains a large amount of water and sulfuric acid, which requires an enormous cost for the neutralizer, drying utility, and extractant. To improve the economic performance of the process, it is necessary to consider the reaction of cellulose solution at a higher concentration to reduce the burden of glucose separation. In addition, the effective use of the wasted hydrogen with a purity of about 95 vol% from the second PSA column may also improve the process economics. Whilst, the required energy cost for hydrogen production for our process is calculated to be significantly lower than those for other various representative hydrogen production methods: 0.37 (0.44) times less than that of steam reforming of methane with (without) CO2 capture, 0.15 times less than that of the water electrolysis by the electric power system, and 0.073 times less than that of electrolysis of water by wind power. This result implies the practical potential of our cellulose-based green hydrogen production scheme.

Gasification of Biomass in Supercritical Water, Challenges for the Process Design—Lessons Learned from the Operation Experience of the First Dedicated Pilot Plant

Gasification of organic matter under the conditions of supercritical water (T > 374 °C, p > 221 bar) is an allothermal, continuous flow process suitable to convert materials with high moisture content (<20 wt.% dry matter) into a combustible gas. The gasification of organic matter with water as a solvent offers several benefits, particularly the omission of an energy-intensive drying process. The reactions are fast, and mean residence times inside the reactor are consequently low (less than 5 min). However, there are still various challenges to be met. The combination of high temperature and pressure and the low concentration of organic matter require a robust process design. Additionally, the low value of the feed and the product predestinate the process for decentralized applications, which is a challenge for the economics of an application. The present contribution summarizes the experience gained during more than 10 years of operation of the first dedicated pilot plant for supercritical water gasification of biomass. The emphasis lies on highlighting the challenges in process design. In addition to some fundamental results gained from comparable laboratory plants, selected experimental results of the pilot plant “VERENA” (acronym for the German expression “experimental facility for the energetic exploitation of agricultural matter”) are presented.

Structural and catalytic studies of Mg1-xNixO nanomaterials for gasification of biomass in supercritical water for H2-rich syngas production

Nowadays, catalytic supercritical water gasification (SCWG) is undoubtedly used for production of H2-rich syngas from biomass. The present study reported the synthesis and characterisation of Mg1-xNixO (x = 0.05, 0.10, 0.15, 0.20) nanomaterials that were obtained via self-propagating combustion (SPC) method, and catalysed the SCWG for the first time. It had found that increased the nickel (Ni) content in the catalyst reduced the crystallite size, thus, increased the specific surface area, which influenced the catalytic activity. The specific surface area followed the order of Mg0.95Ni0.05O (36.2 m2 g−1) < Mg0.90Ni0.10O (58.9 m2 g−1) < Mg0.85Ni0.15O (63.6 m2 g−1) < Mg0.80Ni0.20O (67.9 m2 g−1). From the Rietveld refinement, the Ni that was successfully partial substituted in the cubic crystal structure of MgO resulting in a cell contraction which ascribed the reduction of crystallite size. Increased the amount of Ni also narrowed the pore size distribution ranging between 4.17 nm and 6.23 nm, as well as increased the basicity active site up to 5741.0 μmol g−1 at medium basic strength. All the synthesised nanocatalysts were catalysed the SCWG of OPF (oil palm frond) biomass. Among them, the mesoporous Mg0.80Ni0.20O nanocatalyst exhibited the highest total gas volume of 193.5 mL g−1 with 361.7% increment of H2 yield than that of the non-catalytic reaction.

Formation and inhibition of polycyclic aromatic hydrocarbons from the gasification of cyanobacterial biomass in supercritical water

Polycyclic aromatic hydrocarbons (PAHs) formation and inhibition from supercritical water gasification (SCWG) of cyanobacterial biomass were investigated. High reaction temperature, long residence time, and low feedstock concentration favoured higher molecular weight (HMW) PAH formation. The total PAH yield reached 34.80 μg g−1 at 500 °C, 22.5 MPa, and 10 min. The main PAHs formed in the liquid phase and the solid residue were 3-ring and 4-ring PAHs, which were generated from the cycloaddition reaction of lower molecular weight (LMW) PAHs. In addition, 2-ring PAHs were produced from the Diels-Alder reaction of phenols and unsaturated hydrocarbons. The possible control methods for PAH formation during the SCWG of cyanobacterial biomass were proposed. H2O2 addition effectively inhibited the reaction pathways underlying PAH formation, and the addition at more than 1.0% concentration suppressed H2 production. The work revealed that the inhibition of PAHs was achieved in terms of improving the oxidisation condition during the SCWG process for converting wet biomass or organic wastes to energy sources.

Simulation Study on Hydrogen-Heating-Power Poly-Generation System based on Solar Driven Supercritical Water Biomass Gasification with Compressed Gas Products as an Energy Storage System

Supercritical water gasification driven by solar energy is a promising way for clean utilization of biomass with high moisture content, but direct discharge of liquid residual causes energy waste and decreases energy efficiency. To reduce energy waste, a poly-generation system for hydrogen-rich gas production coupling heat supply and power generation based on supercritical water gasification of biomass driven by concentrated solar energy was established in this paper, which also provided a novel energy storage method to overcome the shortcomings of solar discontinuity. Thermodynamic model of the system was proposed and life cycle assessment (LCA) of the system was conducted. Influence of different parameters (temperature of 600°C to 800°C, outlet temperature of heat exchanger of 42°C to 56°C, biomass slurry concentration of 5% to 6.5%) on the gasification performance, energy and exergy efficiency, energy distribution and global warming potential (GWP) was discussed. The results indicated that hydrogen yield increased as gasification temperature increased since free radical reaction was enhanced which gas production reaction was classified into. Molar fraction of hydrogen increased as gasification temperature increased and reached 65.6% at 750°C. Energy and exergy efficiency of the system reached 74.84% and 34.87% at 700°C and 600°C respectively and that of gas production was 18.15% at 650°C, which was the highest. Increasing reaction temperature and decreasing biomass slurry concentration were effective ways to decrease GWP. Optimal operating parameter was reaction temperature of 650°C, outlet temperature of heat exchanger of 50°C and biomass concentration of 5%.

Energy recovery and phosphorus phase behaviour from catalytic gasification of cyanobacterial biomass in supercritical water

Hydrogen-rich gas has been successfully produced from cyanobacterial biomass by supercritical water gasification (SCWG). This study investigated the feasibility of energy recovery through cyanobacterial biomass gasification in supercritical water (SCW). During SCWG, a phosphorus (P) phase behaviour is generated from SCWG products, NaOH, Ca(OH)2, and low temperature (673 K). The results showed that both alkali additions had a positive effect on biogas production. The H2 yield could reach as high as 4.45 mol kg−1 with 1.0% NaOH loading. We also observed how additional NaOH improved the P bioavailability for plant growth. Furthermore, Ca(OH)2 could be considered a stabilizer for P, which would circumvent secondary pollution by preventing large quantities of P leaching in a relatively short amount of time. Liquid phase methods are used to treat wastewater by removing dissolved organic compounds, which have contaminated water sources. Therefore, liquid phase methods could serve as a desirable carbon source in wastewater treatment. The data illustrated that present technology provide a more effective way to convert waste cyanobacteria for H2 production and generate P activation or stabilization by alkali addition.

Supercritical water gasification of biomass and agro-food residues: Energy assessment from modelling approach

The gasification of biomass in supercritical water is a promising technology for hydrogen production and the paper reports a thermodynamic analysis, based on minimization of Gibbs free energy, of the gasification with supercritical water of different biomass and agro-food residues: almond shells, digestate from wastewater treatment, algae and manure sludge. Numerical simulations were performed in order to assess the effect of temperature, pressure and biomass-to-water ratio on gas-phase yield and composition.A partial energy integration was also discussed, by considering the energy recovery from a turbine expansion of the gas-phase stream leaving the gasifier. The proposed thermodynamic approach allows predicting not only gasification efficiency of gasifier but also energy balance on the entire gasification process. Results showed that the dry substrates (almond shells and algae more than digestate and sludge) tend to form more carbon monoxide. Besides, data comparison revealed that the produced hydrogen comes from biomass and water for high process temperature, while when temperature decreases, the thermodynamic path tends to promote water formation from the hydrogen of the dry biomass.

Comparative study between supported and doped MgO catalysts in supercritical water gasification for hydrogen production

Different catalyst structures may influence the catalytic performance of catalysts in supercritical water gasification (SCWG). This study reports the catalytic activity of supported (SP) and doped (DP) MgO catalysts in catalyzing the gasification of oil palm frond (OPF) biomass in supercritical water to produce hydrogen. Two types of supported catalysts, labelled as Ni-SP (nickel supported MgO) and Zn-SP (zinc supported MgO), were synthesized via impregnation method. Another two types of doped catalysts, labelled as Ni-DP (nickel doped MgO) and Zn-DP (zinc doped MgO), were synthesized by using the self-propagating combustion method. All the synthesized catalysts were found to be pure with the doped catalysts exhibited small crystallites, in comparison to that produced by the supported catalysts. The specific surface area increased in the order of Ni-DP (67.9 m2 g−1) > Zn-DP (36.3 m2 g−1) > Ni-SP (30.1 m2 g−1) > Zn-SP (13.1 m2 g−1). Regardless of supported or doped, the Ni-based catalysts always had larger specific surface area than that in the Zn-based catalysts. Unexpectedly, the Zn-based catalysts with smaller surface area for SCWG produced higher hydrogen (H2) yield from the OPF biomass. When compared to the non-catalytic reaction, the H2 yield increased by 187.2% for Ni-SP, 269.0% for Zn-SP, 361.7% for Ni-DP, and 438.1% for Zn-DP. Among the studied catalysts, the Zn-DP displayed the highest H2 yield because it had the highest number of basic sites; approximately twenty-fold higher than that of the Zn-SP catalyst. The Zn-DP also proved to be the most stable catalyst, as verified from the X-Ray photoelectron spectroscopy (XPS) results. As such, this study concludes that the catalytic performances of the synthesized catalysts do not only depend on the specific surface area, but they are also influenced by the number of basic sites and the catalyst stability. It is trustworthy to note that this is the initial study that associated SCWG with doped catalysts. The doped catalysts, hence, may serve as a new catalyst system to generate SCWG reactions.

Investigation of the interaction between intermediates from gasification of biomass in supercritical water: Formaldehyde/formic acid mixtures

Supercritical water gasification (SCWG) is a promising technology for converting wet biomass and waste into renewable energy. While the fundamental mechanism involved in SCWG of biomass is not completely understood, especially hydrogen (H2) production produced from the interaction among key intermediates. In the present study, formaldehyde mixed with formic acid as model intermediates were tested in a batch reactor at 400 °C and 25 MPa for 30 min. The gas and liquid phases were collected and analyzed to determine a possible mechanism for H2 production. Results clearly showed that both gasification efficiency (GE) and hydrogen efficiency (HE) increased with addition of formic acid, and the maximum H2 yield reached 17.92 mol/kg with a relative formic acid content of 66.67% in the mixtures. The total organic carbon removal rate and formaldehyde conversion rate also increased to 67.33% and 89.81% respectively. The reaction pathways for H2 formation form mixtures was proposed and evaluated, formic acid promoted self-decomposition of formaldehyde to generate H2, and induced a radical reaction of generated methanol to produce more H2.

Molecular Dynamic Simulation of Hydrogen Production by Catalytic Gasification of Key Intermediates of Biomass in Supercritical Water

Supercritical water gasification (SCWG) is an efficient and clean conversion of biomass due to the unique chemical and physical properties. Anthracene and furfural are the key intermediates in SCWG, and their microscopic reaction mechanism in supercritical water may provide information for reactor optimization and selection of optimal operating condition. Density functional theory (DFT) and reactive empirical force fields (ReaxFF) were combined to investigate the molecular dynamics of catalytic gasification of anthracene and furfural. The simulation results showed that Cu and Ni obviously increased the production of H radicals, therefore the substance SCWG process. Ni catalyst decreased the production of H2 with the residence time of 500 ps while significantly increased CO production and finally increased the syngas production. Ni catalyst was proved to decrease the free carbon production to prohibit the carbon deposition on the surface of active sites; meanwhile, Cu catalyst increased the production of free carbon.

6-5.超臨界水中石炭・バイオマスの共液化における反応機構の経時変化(Session(6)バイオマス)

6-5.超臨界水中石炭・バイオマスの共液化における反応機構の経時変化(Session(6)バイオマス)

19.超臨界水を用いた石炭・バイオマス同時液化プロセスの開発

19.超臨界水を用いた石炭・バイオマス同時液化プロセスの開発

17.超臨界水を用いた石炭・バイオマス同時液化プロセスにおける触媒添加効果

17.超臨界水を用いた石炭・バイオマス同時液化プロセスにおける触媒添加効果

3-14.超臨界水中でのバイオマスの接触水性ガス化反応((4)水熱I,Session 3 バイオマス等)

3-14.超臨界水中でのバイオマスの接触水性ガス化反応((4)水熱I,Session 3 バイオマス等)

15.回分式反応器を用いた超臨界水中における石炭・バイオマスの共液化

15.回分式反応器を用いた超臨界水中における石炭・バイオマスの共液化

3-24.液状化ならびに部分酸化を用いた超臨界水中バイオマスガス化の検討((6)水熱III,Session 3 バイオマス等)

3-24.液状化ならびに部分酸化を用いた超臨界水中バイオマスガス化の検討((6)水熱III,Session 3 バイオマス等)

Catalytic gasification of oil palm frond biomass in supercritical water using MgO supported Ni, Cu and Zn oxides as catalysts for hydrogen production

Non-noble metal supported catalysts such as 20NiO/MgO, 20CuO/MgO and 20ZnO/MgO were catalyzed the gasification of oil palm frond biomass in supercritical water for hydrogen production. All the catalysts are found to be pure with no impurities present. The specific surface area of these catalysts can be arranged in the order of 20NiO/MgO (30.1 m2 g–1) > 20CuO/MgO (16.8 m2 g–1) > 20ZnO/MgO (13.1 m2 g–1). Although catalysts with larger specific surface area are beneficial for catalytic reactions, in this study, the largest specific surface area did not lead to the highest catalytic performance. It is found that the 20ZnO/MgO catalyst (118.1 mmol ml−1) shown the highest H2 yield than the 20CuO/MgO (81.1 mmol ml−1) and 20NiO/MgO (72.7 mmol ml−1) catalysts. In addition, these supported catalysts also shown higher H2 selectivity with reached 83.8%, 84.9% and 87.6% for 20CuO/MgO, 20NiO/MgO and 20ZnO/MgO catalysts. Other factors such as dispersion, basicity and bond strength play more important roles in supercritical water gasification of biomass to produce hydrogen.

Production of H 2 from Microalgae Biomass in Supercritical Water Using a Ni/La-γAl 2 O 3 Catalyst

Abstract This communication presents the catalytic gasification of microalgae (nannochloropsis oculata) biomass under supercritical water conditions using Ni/γAl 2 O 3 and Ni/La-γAl 2 O 3 catalysts. The gasification products contain mainly hydrogen, carbon monoxide, carbon dioxide and methane. It is observed that the presence of a nickel catalyst enhances the gasification performance significantly. The desired hydrogen production is further improved by addition of La to the Ni/La-γAl 2 O 3 catalyst. TPR analysis indicates that the presence of La helps to attain higher number of active nickel sites, which is mainly responsible for the higher catalytic activity. Hydrogen production could also be enhanced by retardation of methanation reaction of carbon dioxide by promoting Ni/γ-Al 2 O 3 with La. The higher reaction temperature favors the hydrogen production due to the endothermic nature of the most of the involved reactions.

Noble-metal-free bimetallic alloy nanoparticle-catalytic gasification of phenol in supercritical water

The exploration of non-noble-metal catalysts for high efficiency gasification of biomass in supercritical water (SCW) is of great significance for the sustainable development. A series of Ni–M (M=Co or Zn) bimetallic nanoparticles supported on graphitized carbon black were synthesized and examined as catalysts for gasification of phenol in SCW. It was found that a nearly complete gasification of phenol can be achieved even at a low temperature of 450°C with the bimetallic nanoparticles catalysts. Kinetic study indicated the activation energy for phenol gasification were 20.4±2.6 and 43.6±2.6kJ/mol for Ni20Zn15 and Ni20Co15 catalyst, respectively. XRD, XPS and TEM were further performed to characterize the catalysts and the results showed the formation of NiCo and NiZn alloy phase. Catalyst recycling experiments were also conducted to evaluate the stability of the catalysts. The characterization of used catalysts suggest that the severe agglomeration of nanoparticles leads to the decrease in catalytic activity.

Supercritical water gasification of biomass in diamond anvil cells and fluidized beds

AbstractWith the shift in interest towards renewable energy, hydrogen as an alternative gaseous fuel seems to attract much attention. Waste biomass is an ideal option for the synthesis of biofuels due to its abundance and no net CO2 emissions. Hydrogen can be produced through supercritical water gasification of waste biomass. Hydrogen is an attractive energy carrier which can be used as a direct fuel or in fuel cells to generate electricity and in other energy‐producing processes. Gasification of biomass in supercritical water can be performed for hydrogen generation in both batch and continuous modes with/without the application of catalysts. In spite of the progress made in various gasification technologies, diamond anvil cells and fluidized beds as the new‐generation batch and continuous reactors, respectively, are not fully recognized. The current review is focused on understanding the design, application and limitations of these two new reactor configurations to help motivate their wide‐scale utilization. The review also discusses the potential of diamond anvil cells in studying the involved chemical reactions, thermodynamics, and phase behavior of biomass components during gasification. Nonetheless, the caliber of fluidized beds in continuously gasifying biomass for hydrogen production in supercritical water is also documented. © 2014 Society of Chemical Industry and John Wiley &amp; Sons, Ltd