Pyrolysis/reforming of rice husks with a Ni–dolomite catalyst: Influence of process conditions on syngas and hydrogen yield

The influence of process conditions on the production of syngas and H2 from biomass in the form of rice husks was investigated using a two-stage pyrolysis/catalytic reforming reactor. The parameters investigated were, reforming temperature, steam flow rate and biomass particle size and the catalyst used was a 10 wt.% Ni–dolomite catalyst. Biomass was pyrolysed in the first stage, and the product volatiles were reformed in the second stage in the presence of steam and the Ni–dolomite catalyst. Increase in catalyst temperature from 850 °C to 1050 °C marginally improved total syngas yield. However, H2 yield was increased from 20.03 mmol g−1 at 850 °C to 30.62 mmol g−1 at 1050 °C and H2 concentration in the product gas increased from 53.95 vol.% to 65.18 vol.%. Raising the steam flow rate increased the H2 yield and H2 gas concentration. A significant increase in H2:CO ratio along with a decrease in CO:CO2 ratio suggested a change in the equilibrium of the water gas shift reaction towards H2 formation with increased steam flow rate. The influence of particle size on H2 yield was small showing an increase in H2 production when the particle size was reduced from 2.8–3.3 to 0.2–0.5 mm

Hydrogen production from high temperature pyrolysis/steam reforming of waste biomass: rice husk, sugar cane bagasse, and wheat straw

Hydrogen production from pyrolysis, steam reforming, and catalytic steam reforming of sugar cane bagasse, wheat straw, and rice husk were investigated using a two stage pyrolysis-reforming system. Biomass samples were pyrolyzed in the first stage, and the volatiles and liquids were reformed in the second stage in the presence of steam. During all experiments, a high temperature of 950 °C was chosen for both the pyrolysis and reforming stages. As compared to low temperatures, pyrolysis/reforming carried out at higher temperature showed higher gas yields, particularly hydrogen gas yield. In addition, dolomite and 10 wt % Ni-dolomite were used to investigate the catalytic steam reforming of the biomass. In terms of hydrogen production, steam reforming using 10 wt % Ni-dolomite was the most effective, producing 25.44, 25.41, and 24.47 mmol of hydrogen per gram for rice husk, sugar cane bagasse, and wheat straw, respectively. The amount of deposited carbon on the reacted catalyst was from 1.31 wt % to 10.13 wt % and was in the form of amorphous and graphitic carbon. Relatively lower carbon deposits were found on the 10 wt % Ni-dolomite as compared to the calcined dolomite. XRD analysis of the reacted catalyst showed the presence of Ni, NiO, and NiMgO phases for the 10 wt % Ni-dolomite. The highest hydrogen yield of 25.44 mmol g was obtained from rice husk, and the highest hydrogen concentration in the gas mixture was found to be 59.14 vol % from rice husk using 10 wt % Ni-dolomite

Pyrolysis of waste biomass: investigation of fast pyrolysis and slow pyrolysis process conditions on product yield and gas composition

High temperature fast pyrolysis of wood, rice husk and forestry wood residue was carried out in a laboratory scale fixed bed reactor. The results were compared with pyrolysis of the biomass samples in a different reactor under slow pyrolysis conditions. There was a marked difference in product yield depending on heating rate, for example the gas yield from slow pyrolysis was 24·7 wt-% for wood, 24·06 wt-% for rice husks and 24·01 wt-% for forestry residue; however, for fast pyrolysis, the gas yields were 78·63, 66·61 and 73·91 wt-% respectively. There were correspondingly significantly lower yields of oil and char from fast pyrolysis, whereas for slow pyrolysis, oil and char yields were higher. The composition of the product gases was also influenced by the heating rate. In additional experiments, the influence of pyrolysis temperature was investigated under fast pyrolysis conditions from 750 to 1050°C. It was found that the increase in temperature increased overall gas yield and also increased hydrogen gas concentration with a decrease in CH4, CO2 and C2–C4 hydrocarbons. High gas yields of ∼90 wt-% conversion of the biomass to gas was obtained during the pyrolysis of biomass at 1050°C. Steam was also added to the fast pyrolysis system to enhance the hydrogen production. The amount of hydrogen produced was found to significantly increase in the presence of added steam

The Pyrolysis of Waste Biomass Investigated by Simultaneous TGA-DTA-MS Measurements and Kinetic Modeling with Deconvolution Functions

As waste biomass from fruit processing industry, apricot kernel shells have a potential for conversion to renewable energy through a thermo-chemical process such as pyrolysis. However, due to major differences of biomass characteristics as the well-known issue, it is extremely important to perform detailed analysis of biomass samples from the same type (or same species) but from different geographical regions. Regarding full characterization of considered biomass material and to facilitate further process development, in this paper, the advanced mathematical model for kinetic analysis was used. All performed kinetic modeling represents the process kinetics developed and validated on thermal decomposition studies using simultaneous thermogravimetric analysis (TGA) – differential thermal analysis (DTA) – mass spectrometry (MS) scanning, at four heating rates of 5, 10, 15 and 20 °C min−1, over temperature range 30–900 °C and under an argon (Ar) atmosphere. Model-free analysis for base prediction of decomposition process and deconvolution approach by Fraser-Suzuki functions were utilized for determination of effective activation energies (E), pre-exponential factors (A) and fractional contributions (φ), as well as for separation of overlapping reactions. Comparative study of kinetic results with emission analysis of evolved gas species was also implemented in order to determine the more comprehensive pyrolysis kinetics model. Obtained results strongly indicated that the Fraser-Suzuki deconvolution provides excellent quality of fits with experimental ones, and could be employed to predict devolatilization rates with a high probability. From energy compensation effect properties, it was revealed the existence of unconventional thermal lag due to heat demand by chemical reaction. © Springer Nature Switzerland AG 2020.In: Mitrovic N., Milosevic M., Mladenovic G. (eds) Computational and Experimental Approaches in Materials Science and Engineering. CNNTech 2018. Lecture Notes in Networks and Systems, vol 90. Springer, Cha