Yukihiko Matsumura

Gasification of biomass model compounds and real biomass in supercritical water

Abstract Lignin, cellulose, and their mixture were gasified with a nickel catalyst in supercritical water at 673 K and 25 MPa . Gasification efficiency is low, but increases with the amount of the catalyst when softwood lignin is included in the feedstock. One possible mechanism is the catalyst being deactivated by tarry products from the reaction between cellulose and softwood lignin. Mixtures with hardwood and grass lignin were gasified much more easily. Sufficient amount of catalyst achieves high gasification efficiency even for the mixtures of cellulose and softwood lignin. Sawdust and rice straw were also gasified under the same condition. Interaction between each component was observed also for these real biomass feedstocks.

SUPERCRITICAL WATER TREATMENT OF BIOMASS FOR ENERGY AND MATERIAL RECOVERY

ABSTRACT Supercritical water liquefaction and gasification is reviewed with the introduction of some recent findings by the authors. Supercritical water gasification is suitable for recovery of energy from wet biomass while supercritical water liquefaction opens the door to effective treatment of biomass species in terms of material recovery. Cellulose, one of the main components of biomass, is completely dissolved in supercritical water. Once dissolved, reaction of cellulose can take place swiftly by hydrolysis and pyrolysis. The hydrolysis reaction, otherwise slower than pyrolysis due to the mass transfer limitation, is faster than decomposition in supercritical water, and a possibility of efficient glucose recovery has been shown. Once dissolved, super saturation is kept when the solution is cooled down, and swift hydrolysis by enzyme is also possible. Lignin can be also converted into specialty chemicals by using supercritical cresol/water mixture as a solvent. Dissolution of cellulose also enables efficient gasification of biomass. Complete gasification of biomass has been realized with production of combustible gas including hydrogen, carbon monoxide, and methane.

Gasification characteristics of an activated carbon in supercritical water

Abstract The gasification characteristics of a granular, coconut shell activated carbon in supercritical water (600–650 °C, 25.5–34.5 MPa) were investigated. A rate law for carbon gasification in steam at subatmospheric pressure (

Comprehensive comparison of efficiency and CO2 emissions between biomass energy conversion technologies - position of supercritical water gasification in biomass technologies.

Abstract Efficiency and CO 2 emissions between various methods of biomass energy conversion are compared from the viewpoint of life-cycle evaluation. As for electricity generation, efficient processes are thermal gasification combined cycle, supercritical water gasification combined cycle, and direct combustion in order of efficiency for low moisture content biomass. Supercritical water gasification combined cycle is the most efficient for high moisture content biomass. Battery electric vehicle, gasoline hybrid electric vehicle, and gas full cell vehicle (FCV) show high efficiency in automobiles. Biomass FCV shows high efficiency in the vehicles utilizing biomass. Biogas combustion is the most efficient for heat utilization. Then, the position of supercritical water gasification in various technologies of energy conversion is examined by modeling an overall energy system. The tradeoff between CO 2 emissions and total cost of technologies is analyzed so that the most cost-effective technology can be determined for different CO 2 emissions constraints. Computed results show that biomass is mainly consumed for electricity and heat generation so as to utilize finite biomass resources efficiently. Transportation fuels are generally made from fossil fuels. Cost-effective processes for CO 2 reduction are thermal gasification and reforming when the present efficiency and prices are assumed. Supercritical water gasification is also one of the optimal processes when the relative cost to fuel cell decreases. Improving heat exchange efficiency also contributes toward enhancing the position of supercritical water gasification in biomass technologies.

Evaluation of supercritical water gasification and biomethanation for wet biomass utilization in Japan

Two wet biomass gasification processes, supercritical water gasification and biomethanation, were evaluated from energy, environmental, and economic aspects. Gasification of 1 dry-t/d of water hyacinth was taken as a model case. Assumptions were made that system should be energetically independent, that no environmentally harmful material should be released, and that carbon dioxide should be removed from the product gas. Energy efficiency, carbon dioxide payback time, and price of the product gas were chosen as indices for energy, environmental, and economic evaluation, respectively. Under the conditions assumed here, supercritical water gasification is evaluated to be more advantageous over biomethanation, but the cost of the product gas is still 1.86 times more expensive than city gas in Tokyo. To improve efficiency of supercritical water gasification, improvement of heat exchanger efficiency is effective. Utilization of fermentation sludge will make biomethanation much more advantageous.

Co-liquefaction of coal and cellulose in supercritical water

Co-liquefaction of biomass and coal in supercritical water is proposed with the intention that hydrogen matching between biomass and coal takes place, resulting in enhanced coal liquefaction and preferable liquefaction products. A semi-batch packed-bed reactor is employed to co-liquefy cellulose utilized for a model compound of biomass and Ishikari coal in supercritical water at 673 K and 25 MPa. No interaction between coal and cellulose is observed for the production of residue and water-insoluble product, judging from the yield and its composition. On the contrary, the yield of the water-soluble product increased for the case of co-liquefaction. Both hydrogen to carbon ratio and oxygen to carbon ratio of the water-soluble product increased by co-liquefaction. The mechanism for this interaction is proposed based on the addition reaction of compounds derived from cellulose with coal-derived compounds to increase the recoverable yield of the water-soluble product.

Comparison of the effects of the addition of NaOH on the decomposition of 2-chlorophenol and phenol in supercritical water and under supercritical water oxidation conditions

Abstract The effects of the addition of NaOH on the decomposition of 2-chlorophenol (2CP) and phenol in supercritical water (SCW) and under supercritical water oxidation (SCWO) conditions were investigated. The experiments were conducted in a plug-flow reactor at 713 K and 26 MPa. The reactor residence times ranged from 0.13 to 0.51 s. The initial concentrations of 2CP and phenol were 3.89×10−3 and 5.3×10−3 mol/l, respectively. Experiments were conducted in the presence and absence of H2O2 or NaOH in SCW. Under the experimental conditions, the addition of NaOH accelerated the decomposition of 2CP in SCW, but had little effect on that of phenol. On the other hand, the addition of NaOH accelerated the decomposition of both compounds under SCWO conditions. From 2CP and phenol SCWO, many dimers were identified with a GC/MS. The addition of NaOH to 2CP and phenol SCWO reduced the generation of these dimers, and promoted the dechlorination of 2CP in SCW and under SCWO conditions. These results show that the effects of NaOH on the decomposition of 2CP and phenol SCWO are not negligible, and the effects of NaOH on the decomposition of other organic compounds under SCWO conditions should be considered for determining optimum operating conditions and reactor designs.

A comparative study of biodiesel production using methanol, ethanol, and tert-butyl methyl ether (MTBE) under supercritical conditions.

In this study, biodiesel production under supercritical conditions among methanol, ethanol, and tert-butyl methyl ether (MTBE) was compared in order to elucidate the differences in their reaction behavior. A continuous reactor was employed, and experiments were conducted at various reaction temperatures (270-400 °C) and reaction times (3-30 min) and at a fixed pressure of 20 MPa and an oil-to-reactant molar ratio of 1:40. The results showed that under the same reaction conditions, the supercritical methanol method provided the highest yield of biodiesel. At 350 °C and 20 MPa, canola oil was completely converted to biodiesel after 10, 30, and 30 min in the case of - supercritical methanol, ethanol, and MTBE, respectively. The reaction kinetics of biodiesel production was also compared for supercritical methanol, ethanol, and MTBE.

EFFECT OF HEATING RATE OF BIOMASS FEEDSTOCK ON CARBON GASIFICATION EFFICIENCY IN SUPERCRITICAL WATER GASIFICATION

ABSTRACT The effect of feedstock heating rate on the efficiency of gasification of a biomass in supercritical water was investigated using a continuous bench-scale reactor. A glucose solution (biomass model compound) and a cabbage slurry were gasified in supercritical water at various heating rates in a preheater. The results show that in the range of 10–30 K/s, carbon gasification efficiency improved as the heating rate increased.

Carbon catalyzed supercritical water oxidation of phenol

Abstract Activated carbon was employed as a novel catalyst for supercritical water oxidation of phenol. High-concentrations of phenol were treated in supercritical water at 673 K and 25 MPa with an equivalent amount of oxygen in a reactor packed with activated carbon. Although activated carbon itself was oxidized in the reaction field, its weight decrease was sufficiently slow for its catalytic effect on phenol oxidation to be observed. The catalytic effect of activated carbon consisted of an enhancement of the reaction rate, a decrease in the tarry product yield, and an increase in the gas yield. Under the condition used in this study, 65% of oxygen delivered into the reactor was effectively used for phenol oxidation while only 39% of oxygen was used when no catalyst was applied. This report is the first to indicate the catalytic effect of carbonaceous materials on supercritical water oxidation, and it demonstrates that supercritical water oxidation using lower operation temperatures and inexpensive carbon catalysts may be possible.