Ni nanoparticles supported on carbon as efficient catalysts for steam reforming of toluene(model tar)

This paper investigated the influences of surface properties of carbon support and nickel precursors(nickel nitrate, nickel chloride and nickel acetate) on Ni nanoparticle sizes and catalytic performances for steam reforming of toluene. Treatment with nitric acid helped to increase the amount of functional groups on the surface and hydrophilic nature of carbon support, leading to a homogeneous distribution of Ni nanoparticles. The thermal decomposition products of nickel precursor also played an important role, Ni nanoparticles supported on carbon treated with acid using nickel nitrate as the precursor exhibited the smallest mean diameter of 4.5 nm. With the loading amount increased from 6 wt% to 18 wt%, the mean particle size of Ni nanoparticles varied from4.5 nm to 9.1 nm. The as-prepared catalyst showed a high catalytic activity and a good stability for toluene steam reforming: 98.1% conversion of toluene was obtained with the Ni content of 12 wt% and the S/C ratio of3, and the conversion only decreased to 92.0% after 700 min. Because of the high activity, good stability, and low cost, the as-prepared catalyst opens up new opportunities for tar removing.

Syngas cleaning with nano-structured micro-porous ion exchange polymers in biomass gasification using a novel downdraft gasifier

Sulphonated nano-structured micro-porous ion exchange polymers, known as sulphonated PolyHIPE Polymers （s-PHPs） were used in syngas cleaning to investigate their impact on tar composition, concentration and dew point depression during the gasification of fuel cane bagasse as a model biomass. The results showed that the s-PHPs used as a secondary syngas treatment system, was highly effective at adsorbing and reducing the concentration of all class of tars in syngas by 95%-80% which resulted in tar dew point depression from 90 ~C to 73 ~C. It was shown that tars underwent chemical reactions within s-PHPs, indicating that tar diffusion from syngas was driven by chemical potential. It was also observed that s-PHPs also captured ash forming elements from syngas. The use of s-PHPs in gasification as well as in an integrated thermochemical biorefinery technology is discussed since the tar loaded s-PHPs can be used as natural herbicides in the form of soil additives to enhance the biomass growth and crop yield.

Production of Producer Gas from Densified Agricultural Biomass in Downdraft Gasifier and Its Application to Small Diesel Engines

Biomass is becoming one of the most popular renewable energy sources,especially from agricultural wastes.These wastes can be gasified and utilized in various industries.This experimental study investigated producer gas generation from densified agricultural fuels such as corncobs,rice husks,wood chips,and oil palm fronds in a 50 kWth throatless downdraft gasifier.This system produced combustible gases such as H_(2),CO,and CH_(4),which were utilized as a substitute for diesel fuel in a small diesel engine for power generation.The results showed that the gasifier performs successfully and seems to prefer pellets to briquettes.Producer gas contains 18%–20%carbon monoxide,1%–6%hydrogen,and 0.9%–1.9%methane.Maximum gasification efficiencies of 53%–71%were achieved with biomass pellets from wood chips,corncobs,oil palm fronds,and rice husks,with producer gas calorific value of 2.94–3.85 MJ/Nm^(3).The average fuel consumption rate was between 6.72–14.43 kg/h,while the producer gas yield was between 2–3 Nm^(3)/kg.The average gravimetric concentration of biomass tar in the raw product gas was found to be in the range of 23–50 g/Nm^(3),in which pelletized fuel appeared to show slightly lower tar than briquette fuel.The tar was primarily composed of five compounds:Benzo(a)pyrene,chrysene,pyrene,phenanthrene,1-methylnaphthalene,and several other polycyclic aromatic compounds.The producer gas from oil palm frond briquettes and biodiesel were tested in a gas engine system in a dual fuel mode.A thermal efficiency of 22.21%was achieved with 2500 W electric load and a 72%biodiesel displacement rate,respectively.

Determination of Absorption Capacity and Mass Transfer Coefficient of Several Oils as Solvents for Biomass Gasification Cleaning System

With the aim to find an absorbing liquid suitable for the gas cleaning system in the application of gasification unit in a remote area, three types of oil were tested using a bubble column and a wetted wall column. Air streams containing toluene vapour with flowrates of 13.6 mL-min1 or 27.6 mL.min^-1 were bubbled through a 50 mL static oil in a glass tube at a temperature of 30 ℃ or 60 ℃. In experiments using the wetted wall column, air streams containing toluene were contacted with a falling thin film ofoil on the outer wall of a column with a diameter of 6.4 cm and two different contacting heights of 60 cm or 80 cm. Toluene concentrations in the air stream were adjusted in the range of 700-3000 ppm corresponding to a typical tars concentration in the producer gas. The phase equilibrium of toluene was represented as values of 1/tl of 326, 220 and 182 respectively for lubrication oil, palm oil and sunflower oil （H is Henry＇s constant with the toluene concentrations in g.L^-1 for liquid phase and g.Nm^-3 for gas phase）. From experiments using the bubble column, it was found that the overall mass transfer coefficient （Kc, a） was in the order of 10.3 cm3-min^-1 and the overall liquid phase mass transfer coefficient （KLa）was about 10.3 cm3.min^-1. Although lubrication oil had a slightly better absorption capacity than the other two tested oils, it had a lower mass trasfer coefficient than that of palm oil. All three proposed oils had a much better absorption capacity and absorption rate than that of water used conventionally as a scrubbing liquid in a small biomass gasification plant.

Effective syngas cleanup and reforming using Ni/γ-Al_(2)O_(3) catalyst

This work reports the performance of a selective Ni-based catalyst in tar removal and syngas reforming.Benzene was used as the model tar to optimize catalytic reaction conditions.Parameters investigated were reaction temperature(700℃ to 900℃),gas residence time(0.1 s to 1.1 s),and catalyst loadings(3%to 21%of the weight of γ-Al_(2)O_(3) support).On the basis of the benzene test,a reaction temperature of 800℃,catalyst loading of 15wt%,and residence time of 0.3 s were chosen as optimum reaction conditions.Testing of these conditions showed that the Ni/γ-Al_(2)O_(3) catalyst removed more than 99%of tars in syngas in the downdraft gasifier and 98%in the updraft gasifier.Concentrations of combustible compounds of syngas also increased significantly.H_(2) concentration increased from 19.96%to 51.78%in the downdraft gasifier and from 23.97%to 37.39%in the updraft gasifier;CO concentration increased from 16.26%to 21.10%in the downdraft gasifier and from 22.95%to 25.64%in the updraft gasifier.The results indicate that the Ni/γ-Al_(2)O_(3) catalyst and associated catalytic conditions could not only effectively eliminate tars but also improve the quality of syngas in biomass gasification.