RESUMEN
In this study, the potential of petroleum sludge (PS) for hydrogen production via the gasification process was evaluated. For this purpose, nickel (Ni)-loaded ZSM-5 and γ-Al2O3 (Ni-ZS and Ni-Al) catalysts were prepared and employed for PS gasification in air condition. The effects of different supports, Ni loading content, and reaction temperatures on the production of hydrogen-rich syngas along with the stability and reusability of the best catalyst were investigated. Applying 5%Ni-ZS obtained more gas yield (68.09 wt%) and hydrogen selectivity (25.04 vol%) compared to those obtained by 5%Ni-Al mostly owing to weak metal-support interactions which led to the dominance of well-dispersed metallic Ni. At various Ni loading percentages, 10%Ni-ZS showed the highest catalytic efficiency, which increased both gas yield (70.92 wt%) and hydrogen selectivity (30.74 vol%). However, excessive Ni content (especially 20%) significantly reduced the gas yield and hydrogen selectivity because of limited accessibility of support's active sites, poor dispersion of Ni, and inappropriate acidity. Increasing the temperature promoted the gas yield and produced hydrogen, where the highest gas yield (73.18 wt%) and hydrogen selectivity (33.15 vol%) were obtained at 850 °C due to the endothermic nature of gasification reactions. The 10%Ni-ZS catalyst showed proper stability during three consecutive experiments at 850 °C. The spent catalyst was successfully regenerated without a significant reduction in activity or selectivity.
Asunto(s)
Níquel , Aguas del Alcantarillado , Porosidad , Biomasa , Hidrógeno , CatálisisRESUMEN
Air gasification of the Wood-Plastic Composite (WPC) was performed over Ni-loaded HZSM-5 catalysts to generate H2-rich gas. Increasing SiO2/Al2O3 ratio (SAR) of HZSM-5 adversely affected catalytic activity, where the highest gas yield (51.38 wt%) and H2 selectivity (27.01 vol%) were acquired using 20 %Ni/HZSM-5(30) than those produced over 20 %Ni/HZSM-5(80) and 20 %Ni/HZSM-5(280). Reducing SAR was also favorably conducive to increasing the acyclic at the expense of cyclic compounds in oil products. These phenomena are attributed to enhanced acid strength and Ni dispersion of 20 %Ni/HZSM-5(30) catalyst. Moreover, catalytic activity in the terms of gas yield and H2 selectivity enhanced with growing Ni loading to 20 %. Also, the addition of promoters (Cu and Ca) to 20 %Ni/HZSM-5(30) boosted the catalytic efficiency for H2-rich gas generation. Raising temperature indicated a positive relevance with the gas yield and H2 selectivity. WPC valorization via gasification technology would be an outstanding outlook in the terms of a waste-to-energy platform.
Asunto(s)
Plásticos , Dióxido de Silicio , Madera , Temperatura , CatálisisRESUMEN
A broad range of conventional biomass and plastic waste types was considered and their air gasification process was modeled using a Gibbs free energy minimization coupled with Lagrange multiplier approach. The comparison between the performances of biomass and plastic waste gasification is the main issue of this study. Another important novelty and contribution of this study is analytical hierarchy process/technique for order performance by similarity to the ideal solution coupled method that is employed in gasification of conventional biomass and plastic waste, to prioritize the considered criteria and to select the best feedstock for gasification. Hydrogen production was linearly reduced in the case of conventional biomass with an in increase in the equivalence ratio; however, there was an optimum equivalence ratio to achieve the highest hydrogen production in plastic waste gasification. Plastic waste had a higher low heating value compared to conventional biomass. However, carbon monoxide and nitrogen production from conventional biomass was smaller than from plastic waste. Ten types of feedstock, comprising six types of conventional biomass and four types of plastic waste, were selected as alternatives. The multi-criteria decision analysis coupled method revealed that waste polypropylene and polyethylene were the best alternatives.
Asunto(s)
Monóxido de Carbono , Plásticos , Biomasa , Técnicas de Apoyo para la DecisiónRESUMEN
This study aims to qualify air gasification performances of Solid Recovered Fuels (SRF) in a downdraft fixed bed gasifier. Five fuels have been studied: Wood, SRF wood, and three different mixtures of SRF wood and 20 %w of either SRF tire (mix A), SRF plastics (mix B) or SRF sewage sludge (mix C). The tests were carried out in a pilot scale reactor in a batch-fed mode using a fuel mass ranging from 5 to 8â¯kg, and an air inlet flow of 170-180â¯L/min, which led to an Equivalence Ratio (ER) ranging between 0.20 and 0.29. Considering Poplar wood as a reference, we observed a similar syngas quality for SRF wood, but SRF mixes led to a slight decrease of H2 and CO contents along with an increase of CO2, CH4, C2H4 and C2H6 contents. However syngas Low Heating Value (LHV) remained close and ranged between 4.9 and 5.4â¯MJ/m3 which led to a Cold Gas Efficiency (CGE) ranging from 38 to 52%. Wood and SRF wood had a similar condensate content (159-202â¯g/m3), but adding 20 %w of non-woody fuel led to an increased condensate content up to 369â¯g/m3 for mix A and 411â¯g/m3 for mix C. Tar analyses confirmed the similarity of Wood, SRF wood and mix C in air gasification, but highlighted large increases in aromatics and Polycyclic Aromatic Hydrocarbon (PAH) contents when adding 20 %w of tire. This study confirms the ability of downdraft gasifier to handle non-woody fuels, with an upper limit of 20%w share in a wood-based fuel.
Asunto(s)
Hidrocarburos Policíclicos Aromáticos , Madera , Aguas del AlcantarilladoRESUMEN
Digestate is a byproduct from biomass anaerobic digestion process. Gasification of dried digestate to produce gasesous product might be a promising route. In this work, air gasification of digestate with high ash content was performed in a downdraft fixed bed gasifier at temperature varying from 600°C to 800°C and air equivalence ratio (ER) ranging from 0.25 to 0.30. The ash melting properties were firstly detected by the Intelligent Ash Melting Point Test, and the by-products (biochar and ash) were analyzed. The results showed that no ash slagging was observed and therefore it is feasible to operate digestate gasification under 800°C and ER ranging from 0.25 to 0.30. High temperature favored gas production, 800°C is proposed for digestate gasification in the present study. ER with a medium value improved gas quality and cold gas efficiency (CGE), and the optimal LHV of 4.78MJ/Nm3 and CGE of 67.01% were obtained with ER of 0.28. High ER favored the increase of gas yield and decrease of tar concentration, and the optimal gas yield of 2.15 Nm3/kg and tar concentration of 1.61g/Nm3 were achieved with ER of 0.30. Improved molar ratio of H2/CO varying from 1.03 to 1.08 was obtained at 800°C, indicating gaseous product has the potential for chemical synthesis processes (1
Asunto(s)
Biomasa
, Reactores Biológicos
, Eliminación de Residuos Líquidos/métodos
, Anaerobiosis
RESUMEN
Based on the original biomass cyclone gasifier, the cyclone pyrolysis-suspension combustion gasification technology was constituted with a bottom wind ring to build the biochar suspension combustion zone. This technology decouples the biomass pyrolysis, gasification (reduction reaction) and combustion (oxidation reaction) within the same device. With the feed amount and total air fixed, the effect of air rate arrangement on temperature distribution of the gasifier, syngas components and gasification parameters was studied. With the secondary air rate (0.20) and bottom air rate (0.50), the gasification efficiency was best, with gas heating value of 5.15MJ/Nm3, carbon conversion rate of 71.50%, gasification efficiency of 50.80% and syngas yield of 1.29Nm3/kg. The device with biochar for the tar catalytic cracking was installed at the gasifier outlet, effectively reducing the tar content in syngas, with a minimum value of 1.02g/Nm3.
Asunto(s)
Biomasa , Gases , Catálisis , TemperaturaRESUMEN
An experimental study of air gasification of rice husk was conducted in a bench-scale fluidized bed gasifier (FBG) having 210 mm diameter and 1600 mm height. Heating of sand bed material was performed using conventional charcoal fuel. Different operating conditions like bed temperature, feeding rate and equivalence ratio (ER) varied in the range of 750-850 °C, 25-31.3 kg/h, and 0.3-0.38, respectively. Flow rate of air was kept constant (37 m(3)/h) during FBG experiments. The carbon conversion efficiencies (CCE), cold gas efficiency, and thermal efficiency were evaluated, where maximum CCE was found as 91%. By increasing ER, the carbon conversion efficiency was decreased. Drastic reduction in electric consumption for initial heating of gasifier bed with charcoal compared to ceramic heater was â¼45%. Hence rice husk is found as a potential candidate to use directly (without any processing) in FBG as an alternative renewable energy source from agricultural field.
Asunto(s)
Agricultura , Aire , Reactores Biológicos , Biotecnología/métodos , Carbón Orgánico/química , Carbono/química , Catálisis , Cerámica , Electricidad , Gases , Calor , Hidrodinámica , Oryza , Tamaño de la PartículaRESUMEN
This work presents results of experimental studies on the gasification process of granulated sewage sludge in a laboratory fixed bed gasifier. Nowadays, there is a large and pressing need for the development of thermal methods for sewage sludge disposal. Gasification is an example of thermal method that has several advantages over the traditional combustion. Gasification leads to a combustible gas, which can be used for the generation of useful forms of final energy. It can also be used in processes, such as the drying of sewage sludge directly in waste treatment plant. In the present work, the operating parameters were varied over a wide range. Parameters, such as air ratio λ = 0.12 to 0.27 and the temperature of air preheating t = 50 °C to 250 °C, were found to influence temperature distribution and syngas properties. The results indicate that the syngas heating value decreases with rising air ratio for all analysed cases: i.e. for both cold and preheated air. The increase in the concentration of the main combustible components was accompanied by a decrease in the concentration of carbon dioxide. Preheating of the gasification agent supports the endothermic gasification and increases hydrogen and carbon monoxide production.