共查询到20条相似文献,搜索用时 11 毫秒
1.
Aixia Pei Lisheng Zhang Bizheng Jiang Liejin Guo Ximin Zhang Youjun Lv Hui Jin 《Frontiers of Energy and Power Engineering in China》2009,3(4):456-464
Gasification of peanut shell, sawdust and straw in supercritical or subcritical water has been studied in a batch reactor
with the presence of a series of Raney-Ni and its mixture with ZnCl2 or Ca(OH)2. The main gas products were hydrogen, methane, carbon dioxide, and a small amount of carbon monoxide. Different types of
Raney-Ni, containing different metal components such as Fe, Mo or Cr, have different influences on the gasification yield
and hydrogen selectivity. The catalysis effect can be improved obviously by adding ZnCl2 or Ca(OH)2. Increasing the reaction temperature or adding ZnCl2 and Ca(OH)2 could improve the mass of H2 in gas products and reduce the mass of CH4 and CO2 at the same time. The possible mechanism is that ZnCl2 can decompose the biomass particle by accelerating cellulose hydrolyzation in high-temperature water, increasing more specific
surface to admit catalysts, while Ca(OH)2 can absorb CO2 to produce CaCO3 deposit, which can drop out from the reactant system, and which will drive the reaction to get more hydrogen. With respect
to the biomass conversion to gas product and selectivity of H2 at low temperature, the series of Raney-Ni has shown many advantages over other catalysts; thus, this kind of catalyst has
great potential to be utilized in the hydrogen industry for the gasification of biomass. 相似文献
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3.
Hydrogen production by biomass gasification in supercritical water: A parametric study 总被引:1,自引:0,他引:1
Hydrogen production by biomass gasification in supercritical water is a promising technology for utilizing high moisture content biomass, but reactor plugging is a critical problem when feedstocks with high biomass content are gasified. The objective of this paper is to prevent the plugging problem by studying the effects of the various parameters on biomass gasification in supercritical water. These parameters include pressure, temperature, residence time, reactor geometrical configuration, reactor types, heating rate, reactor wall properties, biomass types, biomass particle size, catalysts and solution concentration. Biomass model compounds (glucose, cellulose) and real biomass are used in this work. All the biomasses have been successfully gasified and the product gas is composed of hydrogen, carbon dioxide, methane, carbon monoxide and a small amount of ethane and ethylene. The results show that the gas yield of biomass gasification in supercritical water is sensitive to some of the parameters and the ways of reducing reactor plugging are obtained. 相似文献
4.
Takeshi Furusawa Takafumi Sato Hirokazu Sugito Yasutomo Miura Yasuyoshi Ishiyama Masahide Sato Naotsugu Itoh Noboru Suzuki 《International Journal of Hydrogen Energy》2007
Hydrogen production from the gasification of lignin with Ni/MgO catalysts in supercritical water was conducted using stainless steel tube bomb reactor. Ni/MgO catalysts were prepared by impregnation method and were calcined at 773–1173 K in air for 8 h. The results of characterization for reduced Ni/MgO catalysts showed that Ni metal and NiO–MgO phase are formed after the reduction of calcined catalyst by H2. Furthermore, Ni metal surface area, which was calculated by CO chemical adsorption technique, decreased with increase in calcination temperatures. It was found that the carbon yield of gas products was increased with increase in Ni metal surface area except 10 wt% Ni/MgO (773 K) catalyst. Thus, it can be supposed that there is an optimal Ni particle size for the gasification of lignin in supercritical water. It should be noted that 10 wt% Ni/MgO (873 K) catalyst showed the best catalytic performance (carbon yield 30%) under reaction condition tested. It was concluded that Ni/MgO catalyst is a promising system for the gasification of lignin in supercritical water. 相似文献
5.
《International Journal of Hydrogen Energy》2023,48(72):27929-27943
The supercritical water gasification (ScWG) technology is a promising alternative for H2-rich gas production from renewable sources, such as residual glycerol from biodiesel manufacture. Combined with heterogeneous catalysts, the ScWG process can achieve improved selectivity towards the desired products and high conversion efficiency in short reaction times. In this work, the efficiency of a synthesized Ni-based catalyst supported in cordierite (CRD) honeycomb structure on the ScWG of glycerol was evaluated and compared with two commercial automotive catalysts. Initially, to determine the best experimental conditions, the ScWG experiments were conducted in the absence of catalysts at constant conditions pressure (25 Mpa) and volumetric flow rate (10 mL min−1). The temperature range of 400–700 °C and glycerol feed composition between 10 and 34 wt% were evaluated. The catalysts evaluated were characterized by SEM-EDS, XRD, N2 adsorption/desorption, XRF, WDS and TGA. The liquid and gaseous products were analyzed by TOC and gas chromatography, respectively. Results indicated that Ni/CRD catalyst showed the highest H2 yield (5.38 mol H2 per mol of glycerol fed) and long-term stability. Additionally, a comparison between the experimental results on the ScWG of glycerol and simulated thermodynamic equilibrium data was also reported. Thus, results demonstrated the great potential of the prepared catalyst to improve H2-rich gas production from glycerol gasification. 相似文献
6.
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. 相似文献
7.
Yang Guo Shuzhong WangDonghai Xu Yanmeng GongXingying Tang Jie Zhang 《International Journal of Hydrogen Energy》2010
Supercritical water gasification (SCWG) of nitriles was studied in a tubular flow reactor at different temperatures. This article focuses on the product distributions and corresponding reaction pathways influenced by addition of Na2CO3 catalyst. Results showed that gas yield for both acetonitrile and acrylonitrile can be greatly enhanced by adding Na2CO3 catalyst. Especially, H2 gasification efficiency can reach 55.4% and 123.3% at 550 °C, respectively. But the catalytic effect on the gas yield of benzonitrile was relatively insignificant. Na2CO3 can also accelerate the hydrolysis of cyanogen and amido as a base catalyst. Benzene and acetic acid were the primary intermediate products during the SCWG of benzonitrile and acetonitrile, respectively. The conversion of acrylonitrile was more complicated because of the activity of double bond. It is possible that 3,3′ iminodipropionitrile was formed by Na2CO3 catalyzed in the range of 490–520 °C, which dominated two thirds of pathways for the subsequent formation of acetic acid. Ammonia-nitrogen content in the liquid effluent was limited by the hydrolysis degree of cyano-group and the possible polymerization reaction of intermediate products. There was no obvious trend to reveal that NH3 was converted into nitrogen under our experimental conditions. 相似文献
8.
Hydrogen production through biomass gasification in supercritical water: A review from exergy aspect
《International Journal of Hydrogen Energy》2019,44(30):15727-15736
Hydrogen production through supercritical water gasification (SWG) of biomass has been widely studied. This study reviews the main factors from exergy aspect, and these include feedstock characteristics, biomass concentration, gasification temperature, residence time, reaction catalyst, and reactor pressure. The results show that the exergy efficiencies of hydrogen production are mainly in the range of 0.04–42.05%. Biomass feedstock may affect hydrogen production by changing the H2 yield and the heating value of biomass. Increases in biomass concentrations decrease the exergy efficiencies, increases in gasification temperatures generally increase the exergy efficiencies, and increases in residence times may initially increase and finally decrease the exergy efficiencies. Reaction catalysts also have positive effects on the exergy efficiencies, and the reviewed results show that the effects are followed KOH > K2CO3 > NaOH > Na2CO3. Reactor pressure may have positive, negative or negligible effects on the exergy efficiencies. 相似文献
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10.
Hydrogen production by coal gasification in supercritical water with a fluidized bed reactor 总被引:1,自引:0,他引:1
The technology of supercritical water gasification of coal can converse coal to hydrogen-rich gaseous products effectively and cleanly. However, the slugging problem in the tubular reactor is the bottleneck of the development of continuous large-scale hydrogen production from coal. The reaction of coal gasification in supercritical water was analyzed from the point of view of thermodynamics. A chemical equilibrium model based on Gibbs free energy minimization was adopted to predict the yield of gaseous products and their fractions. The gasification reaction was calculated to be complete. A supercritical water gasification system with a fluidized bed reactor was applied to investigate the gasification of coal in supercritical water. 24 wt% coal-water-slurry was continuously transported and stably gasified without plugging problems; a hydrogen yield of 32.26 mol/kg was obtained and the hydrogen fraction was 69.78%. The effects of operational parameters upon the gasification characteristics were investigated. The recycle of the liquid residual from the gasification system was also studied. 相似文献
11.
Supercritical water gasification (SCWG) of coal is a promising technology for clean coal utilization. In this paper, hydrogen production by catalytic gasification of coal in supercritical water (SCW) was carried out in a micro batch reactor with various alkaline catalysts: Na2CO3, K2CO3, Ca(OH)2, NaOH and KOH. H2 yield in relation to the alkaline catalyst was in the following order: K2CO3 ≈ KOH ≈ NaOH > Na2CO3 > Ca(OH)2. Then, hydrogen production by catalytic gasification of coal with K2CO3 was systematically investigated in supercritical water. The influences of the main operating parameters including feed concentration, catalyst loading and reaction temperature on the gasification characteristics of coal were investigated. The experimental results showed that carbon gasification efficiency (CE, mass of carbon in gaseous product/mass of carbon in coal × 100%) and H2 yield increased with increasing catalyst loading, increasing temperature, and decreasing coal concentration. In particular, coal was completely gasified at 700 °C when the weight ratio of K2CO3 to coal was 1, and it was encouraging that raw coal was converted into white residual. At last, a reaction mechanism based on oxygen transfer and intermediate hybrid mechanism was proposed to understand coal gasification in supercritical water. 相似文献
12.
Particle distribution and residence time distribution (RTD) in supercritical water fluidized bed reactor (SCWFBR) greatly affect the hydrogen yield through determining the two phase mixing and reaction time. A Eulerian model incorporating the kinetic theory for solid particles was applied to simulate the solid distribution and RTD of feeding materials. The effect of four types of feeding methods and feeding rates on solid distribution and RTD were evaluated based on the simulation results. Results showed that double symmetrical feeding pipe with an feeding mouth angle of 45° provides more uniform solid distribution and longer residence time compared with those of other three types. A nonlinear relationship between feeding rate and RTD was observed, and an optimum feeding rate was found to be related to the best solid-fluid mixing in the study. 相似文献
13.
Emhemmed A. YoussefGeorge Nakhla Paul A. Charpentier 《International Journal of Hydrogen Energy》2011,36(8):4830-4842
Oleic acid was examined as a model compound for lipids, which was gasified in supercritical water (SCW) using a batch reactor from 400 to 500 °C at 28 MPa. The influence of operating temperature and several commercial catalysts on the gasification efficiency, hydrogen gas yield, and residual liquid product quality was examined and discussed. The main gaseous components measured were carbon dioxide (CO2), hydrogen (H2), methane (CH4), and traces of carbon monoxide (CO). The residual liquid after reaction was characterized by analyzing the chemical oxygen demand (COD), total organic carbon (TOC), volatile fatty acids (VFAs), and the long chain fatty acids (LCFAs), namely, palmitic, myristic, stearic, linoleic, and oleic acids. The results showed that an increase of temperature coupled with the use of catalyst enhanced the gas yield dramatically. The H2 yield was 15 mol/mol oleic acid converted using both the pelletized Ru/Al2O3 and powder Ni/Silica-alumina catalysts which gave 4 times higher than the equilibrium yield. The COD reduction efficiency ranged from 31% at 400 °C without catalyst to 96 % at 500 °C in the presence of Ni/Silica-alumina catalyst. The composition of residual liquid products was studied using gas chromatography/mass spectrometry (GC-MS), with a generalized reaction pathway for oleic acid decomposition in SCW reported. 相似文献
14.
Supercritical water gasification (SCWG) is a promising technology for wet biomass utilization. In this paper, orthogonal experimental design method, which can minimize the number of experiments compared with the full factorial experiments, was used to optimize the operation parameters of SCWG with a tubular reactor system. Using this method, the influences of the main parameters including pressure, temperature, residence time and solution concentration on biomass gasification were also investigated. Simultaneously, in order to further improve the gasification efficiency of biomass, acid hydrolysis pretreatment of feedstock, oxidizers addition and increasing reaction temperature were employed. Results from the experiments show that in the range of experimental parameters, the order of the effects of the factors on H2 yield of corn cob gasification in SCW is temperature > pressure > feedstock concentration > residence time. Temperature and pressure have a significant and complicated effect on biomass gasification. Hydrogen yield increases by the acid hydrolysis pretreatment of feedstock, and oxidizer addition reduces the hydrogen yield but it promotes the increase in carbon gasification efficiency. Biomass feedstock with high concentration was gasified successfully at high reaction temperature. 相似文献
15.
Hydrogen production by sewage sludge gasification in supercritical water with a fluidized bed reactor 总被引:1,自引:0,他引:1
Yunan Chen Liejin GuoWen Cao Hui JinSimao Guo Ximin Zhang 《International Journal of Hydrogen Energy》2013
In this work, gasification of sewage sludge in supercritical water was investigated in a fluidized bed reactor. Effect of operating parameters such as temperature, concentration of the feedstock, alkali catalysts and catalyst loading on gaseous products and carbon distribution were systematically studied. The results showed that the increase of temperature and the decrease of feedstock concentration were both favorable for gasification, and the addition of catalyst enhanced the formation of hydrogen better. The K2CO3 catalyst could better enhance gasification efficiency and the catalytic activity of different catalysts for hydrogen production was in the following order: KOH > K2CO3 > NaOH > Na2CO3. The maximum molar fraction and yield of hydrogen reached to 55.96% and 15.49 mol/kg respectively with KOH at 540 °C. Most carbon in feedstock existed in gaseous and liquid products, and alkali catalysts mainly promoted the water-gas shift reaction rather than steam reforming. 相似文献
16.
Hydrogen production by biomass gasification in supercritical water using concentrated solar energy: System development and proof of concept 总被引:1,自引:0,他引:1
Jingwei Chen Youjun LuLiejin Guo Ximin ZhangPeng Xiao 《International Journal of Hydrogen Energy》2010
A novel system of hydrogen production by biomass gasification in supercritical water using concentrated solar energy has been constructed, installed and tested at the State Key Laboratory of Multiphase Flow in Power Engineering (SKLMF). The “proof of concept” tests for solar-thermal gasification of biomass in supercritical water (SCW) were successfully carried out. Biomass model compounds (glucose) and real biomass (corn meal, wheat stalk) were gasified continuously with the novel system to produce hydrogen-rich gas. The effect of direct normal solar irradiation (DNI) and catalyst on gasification of biomass was also investigated. The results showed that the maximal gasification efficiency (the mass of product gas/the mass of feedstock) in excess of 110% were reached, hydrogen fraction in the gas product also approached to 50%. The experimental results confirmed the feasibility of the system and the advantage of the process, which supports future work to address the technical issues and develop the technology of solar-thermal hydrogen production by gasification of biomass in supercritical water. 相似文献
17.
Farid Safari Nader Javani Zehra Yumurtaci 《International Journal of Hydrogen Energy》2018,43(2):1071-1080
Almond shell is one of the most abundant agricultural wastes in Kurdistan province of Iran. Conversion of almond shell into hydrogen-rich gas via supercritical water gasification (SCWG) was investigated in this study using a tubular batch micro-reactor system. Non-catalytic tests were carried out in different conditions to determine the optimum condition for H2 production. Maximum hydrogen yield of 7.85 mmol/g, was observed in the temperature of 460 °C, residence time (RT) of 10 min and feed/water ratio (F/W) of 0.01. Catalytic experiments were performed using hydrochars as solid residues remained after SCWG of Cladophora glomerata (C. glomerata) macroalgae and wheat straw. Hydrochars were characterized by ICP-OES, FESEM and BET methods. For catalytic experiments, hydrochars were added to the almond shell by the weight ratio of 0.4. Conversion of almond shell and hydrogen production, were more influenced by the presence of inorganic compounds in the hydrochars rather than the surface area and pore volume. The maximum hydrogen yields of 10.77 and 11.63 mmol/g, were observed for catalytic experiments in the presence of wheat straw and C. glomerata hydrochars, respectively. 相似文献
18.
A novel receiver/reactor driven by concentrating solar energy for hydrogen production by supercritical water gasification (SCWG) of biomass was designed, constructed and tested. Model compound (glucose) and real biomass (corncob) were successfully gasified under SCW conditions to generate hydrogen-rich fuel gas in the apparatus. It is found that the receiver/reactor temperature increased with the increment of the direct normal solar irradiation (DNI). Effects of the DNI, the flow rates and concentration of the feedstocks as well as alkali catalysts addition were investigated. The results showed that DNI and flow rates of reactants have prominent effects on the temperature of reactor wall and gasification results. Higher DNI and lower feed concentrations favor the biomass gasification for hydrogen production. The encouraging results indicate a promising approach for hydrogen production with biomass gasification in supercritical water using concentrated solar energy. 相似文献
19.
Adam J. ByrdSandeep Kumar Lingzhao KongHema Ramsurn Ram B. Gupta 《International Journal of Hydrogen Energy》2011,36(5):3426-3433
Biomass can be liquefied to produce biocrude for ease of transportation and processing. Biocrude contains oxygenated hydrocarbons of varying molecular structure and molecular weights, including lignin derived products, sugars and their decomposition products. In this work several catalysts were screened for hydrogen production by gasification of switchgrass biocrude in supercritical water at 600 °C and 250 bar. Nickel, cobalt, and ruthenium catalysts were prepared and tested on titania, zirconia, and magnesium aluminum spinel supports. Magnesium aluminum spinel was seen to be an inappropriate support as reactors quickly plugged. Ni/ZrO2 gave 0.98 mol H2/mol C, the highest hydrogen yield of all tested catalysts; however, over time, increase in pressure drop lead to reactor plugging with all zirconia supported catalysts. Titania supported catalysts gave lower conversions, however they did not plug during the course of the study. Charring of all catalysts was seen to occur at the entrance of the reactor as the biocrude was heated. All support materials suffered significant surface area loss due to sintering. 相似文献
20.
Hydrogen production from coal gasification in supercritical water with a continuous flowing system 总被引:1,自引:0,他引:1
The technology of supercritical water gasification can convert coal to hydrogen-rich gaseous product efficiently and cleanly. A novel continuous-flow system for coal gasification in supercritical water was developed successfully in State Key Laboratory of Multiphase Flow in Power Engineering (SKLMF). The experimental device was designed for the temperature up to 800 °C and the pressure up to 30 MPa. The gasification characteristics of coal were investigated within the experimental condition range of temperature at 650–800 °C, pressure at 23–27 MPa and flow rate from 3 kg h−1 to 7 kg h−1. K2CO3 and Raney-Ni were used as catalyst and H2O2 as oxidant. The effects of main operation parameters (temperature, pressure, flow rate, catalyst, oxidant, concentration of coal slurry) upon gasification were carried out. The slurry of 16 wt% coal + 1.5 wt% CMC was successfully transported into the reactor and continuously gasified in supercritical water in the system. The hydrogen fraction reached up to 72.85%. The experimental results demonstrate the bright future of efficient and clean conversion of coal. 相似文献