Partial Oxidative Gasification Research Articles

Partial oxidation gasification kinetics of indole in supercritical water for hydrogen production

Indole is one of refractory intermediate products in hydrothermal conversion of biomass, and its decomposition significantly restricts the improvement of gasification efficiency and hydrogen production in biomass supercritical water gasification (SCWG). In order to improve gasification efficiency of indole and moderate reaction conditions for hydrogen production in biomass SCWG, indole (0.25 mol/L) was gasified in supercritical water at 540–600 °C, 25 MPa, 0–0.8 of oxidation coefficients (OC) in min-batch reactors. Corresponding pathways and kinetics of partial oxidation of indole in supercritical water for hydrogen production were explored. The results showed that the addition of oxidant (hydrogen peroxide) promoted steam reform and decomposition, especially ring-opening reactions, so increasing the gasification efficiency of indole and the yields of H2 and CO2 in gaseous products. The maximum hydrogen gasification efficiency could reach up to 60.3% at OC = 0.6, which was about twice that of non-oxidant. Moreover, 29 groups of reaction rate constants, activation energies and Arrhenius constants were obtained in the established kinetic model.

Partial oxidative gasification of sewage sludge in supercritical water with multi-component catalyst

A new -Mn-Cu- mixture catalyst with components of 50.9wt% CuMn2O4, 46.1wt% CuO and 3.0wt% Mn2O3 was made by a co-precipitation method firstly. We adopted the multi-component catalyst together with activated carbon (AC) and Na2CO3 (N) for the first time to conduct supercritical water partial oxidative gasification (SWPO) of sewage sludge at 450°C, 25MPa, 0.3 of oxidation coefficient and 5h of residence time, so as to improve H2 production and organics removal. The results show that MnO2-AC-N, CuO-AC-N and -Mn-Cu-AC-N could obviously improve H2 yield and removal efficiency of organics in sewage sludge SWPO. At -Mn-Cu-AC-N conditions, H2 yield and XCOD (removal efficiency of chemical oxygen demand) were 202.4mL/L and 95.6wt%, much higher than 48.7mL/L and 86.2wt% obtained without catalyst, respectively. The -Mn-Cu-AC-N catalyst seemingly had the best catalytic effect on gas formation as well as on organics removal in sewage sludge SWPO among MnO2-AC-N, CuO-AC-N and -Mn-Cu-AC-N. Potential catalytic reaction pathways were proposed as well.

Investigations on the Synergistic Effects of Oxygen and CaO for Biotars Cracking during Biomass Gasification

In this study, thermogravimetric analysis coupled with Fourier transform infrared (TG-FTIR) spectroscopy was primarily used to investigate the extent of biotar cracking apparent from biomass pyrolysis and partial oxidative gasification with and without the addition of CaO. TG kinetic analysis indicated that the gasification process reaction rate increased as the the oxygen and CaO content increased. The effect of oxygen in the gasification environment was more significant for biotars cracking, in comparison to CaO addition, but resulted in higher CO and CO2 yields in the syngas. However, the presence of CaO resulted in greater catalytic conversion of tars into higher H2/CO syngas ratios at lower temperatures. In the present study, syngas with a H2/CO ratio of ∼1.5 can be achieved under conditions of a Ca/B ratio of 3 and an O2 content of 5%. Therefore, it is crucial to control both the oxygen and CaO content in the biomass gasification process in order to achieve synergetic effects related to biotar cracking and, ultimately, to produce syngas of the desired compositional requirement.

Hydrogen production by partial oxidation gasification of a phenol, naphthalene, and acetic acid mixture in supercritical water

A mixture of phenol, acetic acid, and naphthalene was partially oxidized in supercritical water in order to produce hydrogen. The effects of temperature, oxidation ratio (OR), reaction time, and reactant concentrations on gaseous distributions, gasification efficiencies, and reactants removal efficiencies were investigated. Furthermore, the effects of oxygen on the main intermediate products were analyzed, and possible degradation pathways were proposed. Results indicated that higher temperatures significantly promoted the H2 yield. In addition, small amounts of oxygen (OR <0.2) accelerated the production of H2 and CH4. The maximum H2 gasification efficiency (240.25%) and H2 yield (70.16 mmol g−1) were obtained at 560 °C, 25 MPa, reaction time of 20 s and OR of 0.2. Longer reaction time enhanced the gasification efficiencies in 10 s, while the effect was little when reaction times longer than 10 s. The concentrations of the reactants did not significantly influence the gasification efficiencies.

Energetic analysis of gasification of biomass by partial oxidation in supercritical water

Partial oxidation gasification in supercritical water could produce fuel gases (such as H2, CO and CH4) and significantly reduce the energy consumption. In this work, an energetic model was developed to analyze the partial oxidative gasification of biomass (glucose and lignin) in supercritical water and the related key factors on which gasification under autothermal condition depended upon. The results indicated that the oxidant equivalent ratio (ER) should be over 0.3 as the concern about energy balance but less than 0.6 as the concern about fuel gas production. Feedstocks such as glucose and lignin also had different energy recovery efficiency. For materials which can be efficiently gasified, the partial oxidation might be a way for energy based on the combustion of fuel gases. Aromatic materials such as lignin and coal are more potential since partial oxidation could produce similar amount of fuel gases as direct gasification and offer additional energy. Energy recovered pays a key role to achieve an autothermal process. Keeping heat exchanger efficiency above 80% and heat transfer coefficient below 15kJ·s−1 is necessary to maintain the autothermal status. The results also indicated that the biomass loading should be above 15% but under 20% for an autothermal gasification, since the increase of biomass loading could improve the energy supplied but decrease the efficiency of gasification and gaseous yields. In general, some specific conditions exist among different materials.

Production of hydrogen rich bio-oil derived syngas from co-gasification of bio-oil and waste engine oil as feedstock for lower alcohols synthesis in two-stage bed reactor

High efficient production of lower alcohols (C1–C5 mixed alcohols) from hydrogen rich bio-oil derived syngas was achieved in this work. A non-catalytic partial oxidation (NPOX) gasification technology was successfully applied in the production and conditioning of bio-oil derived syngas using bio-oil (BO) and emulsifying waste engine oil (EWEO) as feedstock. The effects of water addition and feedstock composition on the gasification performances were investigated. When the BO20 and EWEO30 was mixed with mass ratio of 1: 0.33, the maximum hydrogen yield of 93.7% with carbon conversion of 96.7% was obtained, and the hydrogen rich bio-oil derived syngas was effectively produced. Furthermore, a two-stage bed reactor was applied in the downstream process of lower alcohols synthesis from hydrogen rich bio-oil derived syngas (H2/CO/CO2/CH4/N2 = 52.2/19.5/3.0/9.4/15.9, v/v). The highest carbon conversion of 42.5% and the maximum alcohol yield of 0.18 kg/kgcat h with selectivity of 53.8 wt% were obtained over the Cu/ZnO/Al2O3(2.5)//Cu25Fe22Co3K3/SiO2(2.5) catalyst combination system. The mechanism and evaluation for lower alcohols synthesis from model bio-oil derived syngas and model mixture gas were also discussed. The integrative process of hydrogen rich bio-oil derived syngas production and downstream lower alcohols synthesis, potentially providing a promising route for the conversion of organic wastes into high performance fuels and high value-added chemicals.

Partial Oxidative Gasification of Coking Wastewater in Supercritical Water

Partial oxidative gasification of coking wastewater in supercritical water was investigated in a batch reactor. The effects of temperature (380 - 460 °C) and oxygen ratio (OR) (0 - 0.8) on gaseous composition and removal efficiencies of organic carbon (TOC), ammonia nitrogen (NH3-N) and volatile phenol (VP) were studied. Results show that temperature greately enhanced the mole fraction of H2and the removal efficiencies of COD, VP and NH3-N. The highest mole fraction of H2was obtained at OR of 0.2, higher OR promoted the oxidation of H2and CH4to CO2. At 460 °C, 25 MPa and OR of 0.2, the mole fraction H2, CO, CH4and CO2were 56.88%, 1.17%, 7.82% and 34.13%, respectively. The removal efficiency of TOC, VP and NH3-N reached 81.37%, 86.09% and 47.63%, respectively.

Partial Oxidation of Phenol in Supercritical Water

Phenol is hardly gasified in supercritical water (SCW) under the temperature 450 °C, at which cleavages of aromatic ring occur difficultly. Partial oxidative gasification provides a potential way to remove phenol for hydrogen at those temperatures. The results showed that even O2 was less than the required amount for complete oxidation by stoichiometry, effective gasification of phenol in SCW was took place. About 76 % of phenol was removed and 2.7 mol/mol of hydrogen was produced with Na2CO3 as catalyst at 180s, O/Phenol 7.5, 450 °C and 24 MPa. The process also indicated partial oxidation of phenol produced some opening-rings products such oxalic and maleic acid, which were slowly gasified. Specifically, at lower O/Phenol ratios, the gasification reaction was predominant which led higher yields of H2, while at higher O/Phenol ratios, the oxdication predominated, which increased the amount of CO2 with less H2.

Partial oxidative gasification of municipal sludge in subcritical and supercritical water

Subcritical and supercritical water gasification of dewatered sewage sludge obtained from a typical municipal wastewater treatment plant was investigated in a one-litre high-pressure autoclave at temperatures of 300–400 °C and pressures of 17.5–23.5 MPa. The sludge (without catalyst) was gasified at subcritical and supercritical water conditions, with different reaction times ranging from 30 to 60 min. The results showed that gaseous product yield increased with increasing temperature and reaction time. Gas products consisted primarily of hydrogen, carbon dioxide, methane, carbon monoxide and other light hydrocarbons. The liquid products contained high levels of organic matter, ammonia nitrogen and a few heavy metals. Compared with the landfilling of sewage sludge, the solid residues were in accordance with the Chinese standard for sludge quality in co-landfilling even without further treatment. In addition, the heavy metals in solid products exhibited more stable characteristics attributable to the reduced leaching toxicity after supercritical water gasification.

3-5-3 バイオマスモデル物質の超臨界水部分酸化ガス化における分解促進剤の添加効果(3-5 水熱・超臨界2,Session3 バイオマス等,研究発表)

3-5-3 バイオマスモデル物質の超臨界水部分酸化ガス化における分解促進剤の添加効果(3-5 水熱・超臨界2,Session3 バイオマス等,研究発表)

Catalyzed Partial Oxidative Gasification of Phenol in Supercritical Water

Phenol, a substance difficult to be gasified, is often an intermediate product from biomass gasification in supercritical water. In this study, 1 wt % phenol is gasified in supercritical water with...

Partial oxidative gasification of phenol for hydrogen in supercritical water

The paper reports partial oxidative gasification of phenol for hydrogen in supercritical water (SCW) at lower temperature (<753K), at which cleavages of aromatic ring occur difficultly and tend to undesirable polymerization. The results showed that O2 is effective to gasification of phenol in SCW. ∼76% of phenol was gasified and 2.7mol/mol of hydrogen was produced within 180s with Na2CO3 as catalyst at the selected process conditions, a molar ratio of oxygen-to-phenol, 7.5–1, 723K, and 24MPa. It was found that unstable opening-rings products oxalic and maleic acid and stable dimmerization compounds in liquid water were formed during partial oxidation process. The process also indicated phenol was rapidly converted, and some opening-rings products were slowly gasified, which also confirmed oxygen served as effective reactant for ring-opening. Based on the given reaction conditions, a treatment process using a real wastewater from coking industry was performed. The data showed that the present technology provides an effective way to gasification of phenol wastewater for high-value energy utilization.

P-46 バイオマスモデル物質の超臨界水部分酸化ガス化におけるギ酸の添加効果(ポスターセッション1:技術09,研究発表(ポスター発表))

P-46 バイオマスモデル物質の超臨界水部分酸化ガス化におけるギ酸の添加効果(ポスターセッション1:技術09,研究発表(ポスター発表))

Hydrogen production by partial oxidative gasification of biomass and its model compounds in supercritical water

Partial oxidative gasification in supercritical water is a new technology for hydrogen production from biomass. Firstly in this paper, supercritical water partial oxidative gasification process was analyzed from the perspective of theory and chemical equilibrium gaseous product was calculated using the thermodynamic model. Secondly, the influence of oxidant equivalent ratio on partial oxidative gasification of model compounds (glucose, lignin) and real biomass (corn cob) in supercritical water was investigated in a fluidized bed system. Experimental results show that oxidant can improve the gasification efficiency, and an appropriate addition of oxidant can improve the yield of hydrogen in certain reaction condition. When ER equaled 0.4, the gasification efficiency of lignin was 3.1 times of that without oxidant. When ER equaled 0.1, the yield of hydrogen from lignin increased by 25.8% compared with that without oxidant. Thirdly, the effects of operation parameters including temperature, pressure, concentration, and flow rate of feedstock on the gasification were investigated. The optimal operation parameters for supercritical water partial oxidative gasification were obtained.

Hydrogen production reaction with a metal oxide catalyst in high pressure high temperature water

Hydrogen production from biomass was attempted in high pressure high temperature water at 573 K by adopting partial oxidation to increase the yield of H2 via CO production in the presence of ZnO. The results revealed that an addition of H2O2 as an oxidant to the reaction of glucose and sugarcane bagasse brought about the trend of increasing the yields of H2, CO, and CO2. However, the sensitivity of H2 yield on H2O2 amount was different from those of CO and CO2, namely the excess amount of H2O2 tends to decrease the H2 yield with giving a maximum at a certain H2O2 amount. These indicated that the controllability of partial oxidation would be a key factor for maximizing the H2 yield through biomass conversion by partial oxidative gasification in high pressure high temperature water

Catalytic effects of NaOH and ZrO 2 for partial oxidative gasification of n-hexadecane and lignin in supercritical water☆

Partial oxidative gasification of n-hexadecane ( n-C 16) and organosolv-lignin (lignin) was studied by use of a batch type reactor in supercritical water: 673 K, 0.52 cm −3 of water density (40 MPa of water pressure at 673 K), and 0.3 of O/C ratio for the n-C 16 experiments; 673 K, 0.35 cm −3 of water density (30 MPa of water pressure at 673 K), and 1.0 of O/C ratio for the lignin experiments. The experiments without O 2 were also conducted for lignin (lignin decomposition). For all the cases ( n-C 16 partial oxidation, lignin decomposition, lignin partial oxidation), NaOH or zirconia (ZrO 2) was added in the system as catalysts. Through n-C 16 studies, the catalytic effect of NaOH and ZrO 2 on partial oxidation in supercritical water were examined. In the case of lignin partial oxidation, we studied the possibility of partial oxidation in supercritical water for gasification technique of wastes. The yield of H 2 from n-C 16 and lignin with zirconia was twice as same as that without catalyst at the same condition. The H 2 yield with NaOH was 4 times higher than that without catalyst. Thus, a base catalyst has a positive effect on partial oxidation of n-C 16 and lignin to produce H 2. The catalytic effect of NaOH and ZrO 2 was found to be enhancement of decomposition of intermediate (aldehyde and ketone) into CO, through n-C 16 studies. In the case of lignin studies, the enhancement of decomposition of the carbonyl compounds by catalytic effect of NaOH and ZrO 2 inhibit char formation and promotes CO and thus H 2 formation.