Rice Husk Gasification Research Articles

Gasification of rice husk in two-stage gasifier to produce syngas, silica and activated carbon

ABSTRACTRice husk was utilized in the production of syngas, silica and activated carbon. Experiments were performed in two-stage gasifier for the production of syngas. The syngas is generated with minimum tar yields due cracking of tar at high temperature. Rice husk char obtained from the pyrolysis stage of the reactor was used in the silica extraction process to obtain silica and activated carbon. Using nitrogen as pyrolysis agent high purity (88.46%) silica was obtained with a good quality of syngas as compared to air as pyrolysis agent. Highest surface area of 276.91 m2/gm of silica was found at 500ᵒC.

Characteristics of rice husk gasification in cyclone pyrolysis-suspended combustion system

The cyclonic gasification technology could realize self-separation of syngas and residual carbon, simplifying the purification system. In cyclone pyrolysis-suspension combustion system, bottom air was fed into carbon-rich area of gasifier. Due to the high height/diameter ratio and uneven temperature distribution in cyclone gasifier, the primary/secondary/bottom air rates were 30%, 20%, and 50%, respectively. Effects of gasification intensity and air equivalent ratio on rice husk gasification performance were explored. The results show that for cyclone pyrolysis-suspension combustion, the optimum gasification intensity is 885.24 kg/m2h. Strengthening the subregion of air supplement could cause a gradual increasing of temperature along the axis of gasifier. The syngas yield was independent of gasification intensity, but increased from 0.98 Nm3/kg at ER = 0.23 to 1.38 Nm3/kg at ER = 0.32. At ER = 0.26~0.29, the gasification performance is best, with gas heat value of 4.99~5.37 MJ/Nm3, cold gasification efficiency of 48.25~49.67% and tar content of 5.38~5.75 g/Nm3.

Energy, exergy and sustainability analysis of rice husk air gasification process

Biomass is one of the RES to produce power with zero CO2 emission, biomass gasification process considered as a sustainable technology for energy conversion. This paper deals with rice husk air gasification simulation using non-stoichiometric equilibrium model based on Gibbs free energy minimisation. The FACTSAGE 6.3 software used to calculate gas composition at temperature range 600-1000°C and equivalence ratio range 0.15-0.55. Maximum gas mixture exergy of 9551.7 kJ per kg of rice husk is obtained at ϕ = 0.25 and 725°C. Chemical exergy contributes 89.90-94.85% of total gas mixture exergy, cold gas efficiency and exergetic efficiency varies in the range of 25.19-70.71% and 23.11-62.24%, respectively, in operating condition. Rice husk gasification process analysed by evaluating, sustainability index and environmental destruction factor.

RICE HUSK GASIFIER IN UITM PENANG AS ENERGY: A DESIGN REVIEW

To reduce dependency on fossil fuel, reduce pollution and move into green technology, the rice husk gasification has been developed as the process that converts organic rice husk into a producer of gas. However, drawbacks such as grate blocking, bridging and suitability of feedstock are found in the gasifiers. Design of the gasifiers is an important objective and improvements on the design have been done to enhance the performance of the gasifiers. This paper aims to review gasifiers focused on design improvements. Many works from previous researchers have been studied. The result shows the new design of the gasifiers is an important parameter in gasification.

The Composition of Syngas and Biochar Produced by Gasifier from Viet Nam Rice Husk

Nowadays, biomass has become one of the renewable energy sources might be filled for the lack of energy in the world. Gasification of biomass in general and of rice husk in particularly has attracted many researchers in Viet Nam. The rice husk gasification experimental study has been done with the GEK 20 kW device which is developed by All Power Labs, USA. The air flow rate from 2 to 4 m 3 /h is applied in gasifier. A portable infra-red syngas analyzer is used for simultaneous measurement the concentrations of CO, CO 2 , CH 4 , H 2 and O 2 of the syngas and for calculation of the heating energy. The effect of air flow rate on temperature, syngas composition, and biochar is analysed and it indicates that the temperature in the combustion area and the content of hydrogen and carbon monoxide in the gas increase when the air-flow rate rises. In contrast, the yield of biochar is decreased.

Design and experimental study of pilot scale throat-less downdraft gasifier fed by rice husk and wood sawdust

ABSTRACTIn this work, pilot scale throat-less downdraft gasifier is fabricated and tested on rice husk and blend of rice husk-sawdust. The test aims to investigate effect of equivalence ratio on temperature profile, propagation front (flame propagation rate, bed movement rate, and effective propagation rate), and performance of the gasifier (composition of producer gas, heating value of producer gas, and thermal efficiency of the gasifier). Equivalence ratio investigated are 0.15, 0.20, and 0.25, while the blend ratio is 1:1 by mass. The results show that axial temperatures in the reactor surge faster with increasing equivalence ratio during the rice husk gasification and the blend gasification. Typically, flame propagation rate, bed movement rate, and effective propagation rate improve with rising equivalence ratio from 0.15 to 0.25. The best higher heating values and thermal efficiencies are obtained at equivalence ratio of 0.2 and 0.15 for the rice husk gasification and the blend gasification, respectively.

Technological, economic and environmental evaluation of rice husk gasification in a biorefinery context to produce indirect energy as jet fuel

Higher alcohol 1-octanol was evaluated as jet fuel potential. The synthesis of the 1-octanol was modeled and the technological, economic and environmental evaluation of the global production process of the rice husk gasification was performed. The best operating conditions to 1-octanol synthesis were obtained in packed bed reactor PBR using Matlab software. Mass and energy balances were calculated using Aspen Plus Software. Economic assessment was developed using Aspen Process Economic Analyzer Software. Environmental impact evaluation was carried out using the waste reduction algorithm WAR. Process yield was 0.83 kg of 1-Octanol by kg of rice husk. Total production cost obtained was USD 0.957 per kg of 1-octanol and the total PEI of product leave the system is 0.08142 PEI/kg with a PEI mitigated of 12.97 PEI/kg. Production process of high alcohols from rice husk shows a high potential technological, economical and environmental as a sustainable industry at take advantage of an agroindustrial residue and transformed in products with added value and energy. 1-octanol as jet fuel has a potential but need to be more studied for direct use in jet motors.

Study of the removal mechanism of aquatic emergent pollutants by new bio-based chars.

This work is dedicated to study the potential application of char byproducts obtained in the gasification of rice husk (RG char) and rice husk blended with corn cob (RCG char) as removal agents of two emergent aquatic contaminants: tetracycline and caffeine. The chars presented high ash contents (59.5-81.5%), being their mineral content mainly composed of silicon (as silica) and potassium. The samples presented a strong basic character, which was related to its higher mineral oxides content. RCG char presented better textural properties with a higher apparent surface area (144m2g-1) and higher micropore content (V micro=0.05cm3g-1). The alkaline character of both chars promoted high ecotoxicity levels on their aqueous eluates; however, the ecotoxic behaviour was eliminated after pH correction. Adsorption experiments showed that RG char presented higher uptake capacity for both tetracycline (12.9mgg-1) and caffeine (8.0mgg-1), indicating that textural properties did not play a major role in the adsorption process. For tetracycline, the underlying adsorption mechanism was complexation or ion exchange reactions with the mineral elements of chars. The higher affinity of RG char to caffeine was associated with the higher alkaline character presented by this char.

Species – Transport CFD model for the gasification of rice husk (Oryza Sativa) using downdraft gasifier

The biomass as a source of energy is increasing globally due to environmental pollution and shortage of fossil fuels. The process of converting the biomass into useful energy is known as gasification. The implementation of gasification technology in remote areas needs more theoretical and experimental studies. Several models have been proposed to explain the geometrical parameters and the optimization of gasification process. Hence, the paper presents the numerical simulation of the gasifier using the species-transport model in CFD by incorporating all the zones of the gasifier and the experimental studies are conducted on a 40kW downdraft gasifier with rice husk (Oryza Sativa) available in remote villages situated in South India. The factors affecting the producer gas such as equivalence ratio, gas composition, higher heating value and the temperature distribution inside the gasifier have been studied. Both the studies established that the higher heating value and the producer gas composition are 5.19MJ/Nm3 with CO–22%, CH4–1.7%, CO2–8%, H2–13% and N2–40.1% respectively. Also, it is predicted that the zone temperatures are maximum when ER is 0.30.

High-purity hydrogen production with in situ CO2 capture based on biomass gasification

Tar formation and CO2 emission represent the strongest barrier for use of gasification technology for biomass conversion, whereas sufficing for both is only possible with expensive physical methods and further chemical processing. The use of CaO as a CO2 sorbent within an advanced high-temperature gasification system is able to achieve efficient cracking of the tars to the primary syngas with low emissions. The present work aims to propose a semi-kinetic model on the basis of an Aspen Plus model to describe specific catalytic behavior of calcium oxide on the gasification of rice husk. There has also been an attempt to validate the developed model by means of an experimental study and explore the influence of minerals within ash on gasification characteristics, since kinetic data are scarce in the literature. Effects of some critical parameters such as gasification temperature, equivalence ratio (ER), and steam/biomass ratio (S/B) on hydrogen yield and CO2 absorption ratio have been studied. Results showed that CO2 absorption ratio ascends as CaO loading ratio increases, then to continuously decrease due to a significant reduction in endothermic nature of the Boudouard reaction. When ER ascended from 0.15 to 0.25, syngas yield and hydrogen yield did the same thing, increasing from 2.1 to 2.45Nm3/kg biomass and 37–41g/kg biomass respectively. In the second stage, ER undertook a rise from 0.25 to 0.3 where gas caloric value and hydrogen yield were decreased.

3-1-1 籾殻ガス化における吸着・吸収を用いたタールの低減(3-1 液体燃料・評価,Session3 バイオマス等,研究発表)

3-1-1 籾殻ガス化における吸着・吸収を用いたタールの低減(3-1 液体燃料・評価,Session3 バイオマス等,研究発表)

Comparative Study of Two Small Scale Downdraft Gasifiers in Terms of Continuous Flammability Duration of Producer Gas from Rice Husk and Sawdust Gasification

In this work, two small scale throat-less downdraft gasifiers (Gasifier I & Gasifier II) are run on feedstocks of rice husk and sawdust at different runs set up. The runs aim to compare the two gasifiers in terms of continuous flammability duration of producer gas. The result shows that maximum 32 minutes continuous flammability duration is obtained from set up C (Rice husk gasification with 1 st stage tuyer primary air and top hole secondary air) for the gasifier I and maximum 30 minutes continuous flammability duration is achieved from set up I (Rice husk-sawdust blend gasification, 5 th stage tuyer primary air, and 1 st stage tuyer initiation of gasification) for the gasifier II. For closed top set up, the gasifier II is better than the gasifier I in terms of continuous flammability duration of producer gas, either for rice husk or sawdust gasification.

CFD Analysis on Fluidized Bed Gasification of Rice Husk and Rice Straw

In the work being presented, computational fluid dynamics (CFD) analysis on fluidized bed gasification of rice husk has been carried out. The multiphase Eulerian model was undertaken in the analysis. Due to the lack of computational space, two dimensional models of fluidized bed were created. The objective of the investigation was to study the effect of variation on velocity with varying particle sizes. The quality of synthesis gas was also taken into account. The inlet’s superficial velocity was varied from 0.2 m/s to 1.2 m/s and diameter of rice husk varied from 0.0438 mm to 4.38 mm. Based on obtained results, this may be concluded that minimum fluidization velocity decreases with increase in diameter of rice husk. The carbon conversion was found to be maximum for 0.7 m/s velocity and carbon conversion increased for other velocities up to 96.9%. The analysis was carried out using ANSYS FLUENT 14.0 non-commercial code.

CFD researched on rice husk gasification in a pilot fixed bed up-draft system

Finding alternative energy sources for fossil fuels was a global matter of concern, especially in developing countries. Rice husk, an abundant biomass in Viet Nam, was used to partially replace fossil fuels by gasification process. The study was conducted on the pilot plant fixed bed up-draft gasifier with two kind of gasification agents, pure air and air-steam mixture. Mathematical modeling and computer simulations were also used to describe and optimize the gasification processes. Mathematical modeling was based on Computational Fluid Dynamics method and simulation was carried by using Ansys Fluent software. Changes in outlet composition of syngas components (CO, CO2, CH4, H2O, H2) and temperature of process, in relation with ratio of steam in gasification agents, were presented. Obtained results indicated concentration of CH4, H2 in outlet was increased significantly when using air-steam gasification agents than pure air. The discrepancies among the gasification agents were determined to improve the actual process.

Rice Husk-Derived Porous Silicon with High Purity As Anode for Lithium Ion Batteries

Recently, social concerns and the importance of ‘green growth’ and ‘renewed energy technology’ have increased, which resulted from the increase in the cost of fossil fuels and climate change. One of the critical technologies for accomplishing ‘green growth’ is the recycle of waste products generated through manufacturing processes. One of the largest wastes is rice husks, which are generated from the production of rice. Rice is cultivated in more than 75 countries in the world and the worldwide annual rice production amounts to approx. 422 million metric tons, of which about 20% is rice husk. However, its utilization has been limited to low-value applications in the agriculture area, such as stockbreeding rugs, bed soil, fertilization and lagging materials etc., which is the case because of their tough, woody and abrasive properties. Thus, many researchers have attempted to increase their added value, including the development of rice husks activated carbon, rice husk gasification and electricity generation. Some research groups have studied the potential of using rice husks as a fiber resource. Ah et al. reported the preparation of packing materials and Lee et al. developed a rice husk board. Rice husks contain approximately 20 wt% silica and because of ‘natural selectivity’ of rice plants, it has a lower level of metallic impurities than other representative silica sources, such as quartz, bentonite and diatomaceous earth etc.. Therefore, a significant effort has been directed at the production of high purity silicon-based materials from rice husks, such as SiC, Si3N4, SiO2 and high grade silicon. However, most of these studies are based on using rice husk ash (RHA), which is generated after the combustion of rice husk and very few studies have examined the potential of using the organic part of rice husks. Thus, we developed a refinery process to integrate the use of rice husks and increase of the value of rice husks. This process has the combined benefit of producing valuable silicon-based materials and cellulose-based materials. The rice husks are divided into fiber and inorganic components during the refinery process. In this work, we investigated the chemical composition and morphological characteristics of the rice-husk derived silica obtained from the refinery process. The conditions for preparing SiO2 with high purity and high surface area were optimized and highly porous nano-structured silicon (Si) with high purity was prepared from rice husk-derived silica. We also examined the potential of using the rice husk derived silicon as an anode material in Li-ion batteries.

왕겨/모래/왕겨 회재의 유동 및 혼합 특성 연구

We investigate fluidization characteristics of the mixture of rice husk, silica sand and rice husk ash as a preliminary study for valuable utilization of rice husk ash obtained from gasification of rice husk in a fluidized bed reactor. As experiment valuables, the blending ratio of rice husk and sand (rice husk: sand) is selected as 5:95, 10:90, 20:80 and 30:70 on a volume base. Rice husk ash was added with 6 vol% of rice husk for each experiment and air velocity to the reactor was 0~0.63 m/s. In both rice husk/sand and rice husk/sand/ash mixture, the minimum fluidization velocity (Umf) is observed as 0.19~0.21 m/s at feeding of 0~10 vol.% of rice husk and 0.30 m/s at feeding of 20 vol.% of rice husk. With increasing the amount of rice husk up to 30 vol.%, can not measure due to segregation behavior. The mixing index for each experiment is determined using mixing index equation proposed by Brereton and Grace. The mixing index of the mixture of rice husk/sand and rice husk/sand/ash was 0.8~1 and 0.88~1, respectively. The optimum fluidization condition was found for the good mixing and separation of rice husk ash.

Determination of the intrinsic reactivities for carbon dioxide gasification of rice husk chars through using random pore model

Rice husk is abundantly available and environmentally friendly, and char-CO2 gasification is of great importance for the biomass gasification process. The intrinsic reaction rates of carbon dioxide gasification with rice husk chars derived from different pyrolysis temperatures were investigated in this study by conducting thermogravimetric analysis (TGA) measurements. The effects of gasification temperature and reactant partial pressure on the char-CO2 gasification were investigated and the random pore model (RPM) was used to determine the intrinsic kinetic parameters based on the experimental data. The results obtained from this study show that the activation energy, reaction order and pre-exponential factor varied in the ranges of 226.65–232.28kJ/mol, 0.288–0.346 and 2.38×105–2.82×1051/sPan for the rice husk chars pyrolyzed at 700–900°C, respectively. All the determination coefficients between the RPM predictions and experimental results were higher than 0.906, indicating the RPM is reliable for determining and evaluating the intrinsic reactivities of rice husk chars.

Gasification and tar removal characteristics of rice husk in a bubbling fluidized bed reactor

Technology for converting biomass such as rice husk into a useable energy sources are key to address energy consumption issues. The effects of temperature (600–900°C), equivalence ratio (ER, 0.15–0.3), and addition of catalyst on the gasification characteristics of rice husk were investigated in a bubbling fluidized bed reactor with an inside diameter of 0.067m and a height of 1.55m. As the reaction temperature and ER were increased, the concentrations of CO and CO2 in the product gas decreased. Slight increases in CH4 and H2 concentrations were also observed with increasing temperature. Throughout the temperature range of interest, an increase in ER resulted in decrement of both the higher heating value of the product gas and the cold gas efficiency. Furthermore, the effect of operating condition and addition of bed material were determined in a bubbling fluidized bed reactor. An increase in reaction temperature and ER decreased the tar content. The addition of calcined dolomite and olivine in the bed material reduced the amount of tar during rice husk gasification in a bubbling fluidized bed reactor. These results have the potential to be applied to the conversion of biomass into a useable energy source.

In bed catalytic tar reduction in the autothermal fluidized bed gasification of rice husk: Extraction of silica, energy and cost analysis

Fluidized bed gasifiers are becoming quite popular because of their higher conversion efficiencies, ability to handle wide variety of fuels and recent development in the field of catalytic gasification. Air gasification of rice husk was carried out in a pilot scale bubbling fluidized bed gasifier (ID: 197mm and H: 1.6m) at a constant air flow rate of 43m3/h. Burning charcoal was initially used for the heating of bed material instead of electric heater in order to make it more suitable for the rural areas. For the bed of sand experiments were carried at four different equivalence ratios (ER) 0.28, 0.3, 0.33 and 0.35 to determine the suitable ERs for the catalytic gasification. Two naturally occurring catalyst: raw dolomite and untreated olivine were added separately in different proportions (10–60wt.%) in the sand bed in order to determine their effectiveness at its higher and lower content in the sand bed and to decide the optimum combination of inert bed material and catalyst. Compact on-line method for the measurement of tar+suspended particulate matter (SPM) was developed and used. ER of 0.3 and 0.33 were found the most suitable ERs for the catalytic gasification. Dolomite provided 45 and 50% while olivine provided comparatively less 41 and 44% tar+SPM reduction at the ER of 0.3 and 0.33, respectively. However, olivine generated less fine particles and consumed 66% less energy for bed heating than dolomite. Improvement in the carbon conversion and thermal efficiency by 5–7% were obtained with the addition of catalysts. 60% silica was extracted from the rice husk ash which was taken from the discharge of the cyclone separators.

Rice husk gasification in a two-stage fixed-bed gasifier: Production of hydrogen rich syngas and kinetics

The purpose of this study is to evaluate the products of homogeneous cracking of rice husk tars and to investigate the conditions for production of hydrogen rich syngas. Experiments were performed in a two-stage downdraft fixed-bed gasifier as a function of temperature and residence times. Tars were generated with a medium heating rate of 25 K/min in a pyrolysis section of the gasifier. Generated tars were subsequently cracked by secondary reactions in gasification section. Tar conversion of about 91% was achieved. Tar cracking at higher temperatures resulted in the formation of hydrogen rich syngas. Secondary product yields and their kinetics were studied for tar cracking and individual gas formed by single-reaction model and distributed activation energy model. A good fit of the data was obtained with the single-reaction model; however distributed activation energy model correlated the tar cracking kinetic parameters more closely than single-reaction model.