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![Updraft gasifier with external recirculation of pyrolysis gas [4].](publication/291185130/figure/fig1/AS:1086764697550854@1636116303184/Updraft-gasifier-with-external-recirculation-of-pyrolysis-gas-4.jpg)
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![Updraft gasifier with external recirculation of pyrolysis gas [4].](publication/291185130/figure/fig1/AS:1086764697550854@1636116303184/Updraft-gasifier-with-external-recirculation-of-pyrolysis-gas-4_Q320.jpg)
Most of the thermodynamic modeling of gasification for updraft gasifier uses one process of decomposition (decomposition of fuel). In the present study, a thermodynamic model which uses two processes of decomposition (decomposition of fuel and char) is used. The model is implemented in modification of updraft gasifier with external recirculation of...
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Vertically fixed-bed updraft gasification systems are well established, however, due to vertical
orientation, the thermal zones of the gasifier are fixed, i.e. the residence time in a vertical gasifier
is fixed, which sometimes creates clinkers of biomass materials having higher ash content and are
responsible for discontinuation of gasification pr...
![Figure 1: Updraft gasifier. Figure from [1].](profile/Andres-Anca-Couce/publication/312892630/figure/fig1/AS:454472427151361@1485366078238/Updraft-gasifier-Figure-from-1_Q320.jpg)
Updraft gasification of high moisture biomass is investigated in this work with a reactor model considering a tar condensation model and secondary tar charring/cracking reactions. The reactor model is a one dimensional model which solves mass and energy balance equations along the reactor length. It incorporates a comprehensive pyrolysis scheme whi...
Hydrothermal carbonization (HTC) is a promising thermochemical pretreatment to convert sewage sludge into the hydrochar prior to combustion or pyrolysis for energy generation. To investigate the effects of HTC on nitrogen transformation behaviors, pyrolysis of sewage sludge and the corresponding hydrochar were conducted. The results showed nitrogen...
Citations
... Since the hot gases exchange effectively the heat from hot gases to feedstock particles throughout the counter flow movement in updraft gasifiers, which boast the thermal or gasification efficiency and processing of biomass feedstock with a greater moisture content without compromising performance, albeit this benefit is offset by the fact that feedstock with a moisture content of more than 30% (by wt.) as with high moisture content, the reaction temperature decreases and tar content in gas starts increasing [14,15]. A gas cleaning system or modifications to the gasifier's architecture are required if syngas is to be burnt soon after it leaves the gasifier [16]. The primary limitation of syngas produced by updraft system is its higher tar content, while syngas produced from charcoal has a low tar concentration [17]. ...
The model for downdraft gasifier consuming Acacia nilotica wood as feedstock has been developed to correlate the gas composition (i.e. H2, CO), lower heating value (LHV), and cold gas efficiency (CGE) in terms of independent variables—operation time, gas flow rate, and equivalence ratio. Herein, the response surface methodology (RSM) and DOE technique are successfully employed to forecast, while desirability approach based on Box–Behnken design approach is found suitable to optimize the gasification parameters. The sub-models for H2, CO, LHV, and CGE are found to be reliable and significant as analysis of variances for each showed high R² values (i.e. in range of 98.59–99.15%). Optimization technique based on Box–Behnken design including the desirability function is employed successfully. The presented strategy is found very effective for obtaining the best overall outcomes within close tolerance (i.e. < 4% error). The best settings of independent variables for reaction time, gas flow rate and ER were found to be 34.65 min, 4.99 g/s, and 0.266, respectively. Further, the predicted values of composition of H2, CO, and LHV, CGE were 13%, 15.38%, and 4.255 MJ/kg, 70.26%, respectively. The practical implications with the optimized parameters are to supply the quality producer gas to the decentralized power production systems (i.e. gasifier-engine systems) enhancing the performance, clean power production, and contribute a lead role for large rural population/society and thus rural economy.
... Experimental parametric investigations have been proposed to predict performance of fixed bed gasifiers. Gasification temperatures and air flow rate [13], air flow and biomass type [14], air and air-steam flow [15], moisture content and particle size [16], and recirculation of pyrolysis gas [17,18] are example of parameters tested in autothermal and continuous mode. The dependence of syngas heating value, permanent gas composition, tar content, energy efficiencies were in each case reported. ...
Several experimental datasets available on the gasification of different lignocellulosic feedstocks were used to correlate the flow of gasifying agents with the performance of updraft gasification in an autothermic 200 kWth pilot plant. The feedstocks used included eucalyptus wood chips, torrefied eucalyptus and spruce chips, lignin rich residues from biorefined straw and reed, shells of almond and hazelnut, which were gasified in flows of air, air and steam, oxygen, oxygen and steam. Thermal profiles inside the gasifier and gas quality in terms of incondensable gas and tar content were recorded and used to calculate the energy efficiency of converting solid feedstock into gaseous and liquid carriers. Common behaviors and parametric functionalities were identified to better understand the process and the most efficient tools to achieve the desired products. In analyzing data, the ratio steam to biomass was reported in terms of the equivalence ratio, ER(H2O) i.e., the fraction of the stoichiometric quantity required to convert the feedstock into H2 and CO2. The use of steam was useful to stabilize the process and to tune the H2/CO ratio in the syngas which reached the value of 2.08 in the case of oxy-steam gasification of lignin rich residues at ER(H2O) of 0.25. Larger use of steam depressed the process by lowering the average temperature of the bed, which instead increased steadily with ER(O2). The production of tar depends on the biomass type and a substantial reduction can be achieved with the torrefaction pretreatment. The same effect was observed increasing the residence time of the syngas in the reactor, typically achieved using oxygen instead of air as main gasification flow or reducing the ER(H2O). Oxy-steam gasification of torrefied wood led to the best results in terms of cold gas efficiency and low heating value when carried out in the ranger 0.23–0.27 of both the ERs
... Lower quality feedstock that can be processed by the updraft gasification is especially important in the view of today's necessity for efficiently handling municipal solid waste [5]. The main drawback is higher tar content and therefore, some gas cleaning system or changes in gasifier construction are necessary if syngas is going to be burned immediately after the gasifier exit [6]. Alternatively, using charcoal as a feedstock also enables low tar content of produced syngas [7], but it requires the steam addition in order to prevent high temperature in the bed and ash melting. ...
... Considering the modelling of biomass gasification, there are four modelling approaches: thermodynamic equilibrium models (TEM), kinetic models, computational fluid dynamic (CFD) models and modelling by artificial neural networks [20]. An updraft gasification TEM model was developed by Vidian et al. [6], where the pyrolysis process was modelled by implementing the biomass decomposition compounds regarding the data gathered from the experimental research. The developed model was used for the analysis of recirculation of pyrolysis products through the gasification zone and showed the possibility of reducing the tar content in produced syngas. ...
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... However the researches did not measure the compositions of products. Vidian et al did a model using Aspen Plus for an up-draft gasifier with external recirculation of pyrolysis gas to get the composition of syngas, however the feedstocks used was wood [9]. ...
... The gasification zones that will be modelled and investigated are drying and pyrolysis zones with the reason stated in previous paragraph. As far as authors concerned, there is no any single particle model simulation on rice husk gasification in drying and pyrolysis zones yet, as the researches that authors found were done using wood as the biomass, not rice husk [2,9,10]. The variable to validate the model is using air flow rate (as velocity relative (u) to the particle) and will be compared to previous researches. ...
There is a lot of energy potential in biomass wastes in Indonesia, and one of those is rice husk. This research will
create a suitable model for drying and pyrolysis zones in rice husk gasification. The single particle model is chosen as the
model since it can help to observe conversion happened within a particle in detail. This is important because with that, we can
understand the compositions of pyrolysis gas, char, and primary tar in drying and pyrolysis zones in rice husk gasification. To
validate the model, air flow rate is chosen as the variable that would be varied. The objectives of this research are to check
whether the model is suitable for modelling drying and pyrolysis zones in rice husk gasification as well as to understand the
effects of air flow rate in the product compositions using the simulation. The results show that the primary tar content is
increasing by the increase of air flow rate, while the pyrolysis gas content is decreasing, and the char content is constant. The
results show that the numerical model is considerably suitable for modelling drying and pyrolysis zones in rice husk
gasification.
... The molecular formula (C 4 H 6.08 O 2.75 N 0.02 ) of the biomass in Fig. 3 was obtained from the results of the dry ultimate analysis. The calorific value in Table 1 was obtained using a model in Aspen called HCOALGEN which is the General Coal Enthalpy Model in the Aspen Physical Property System [28][29][30][31]. Generally, this method is used for calculating the enthalpy values for biomass and ash and is obtained from coal studies. ...
The physio-chemical properties of biochar from nitrogen plasma reactor were investigated. The amount of biochar and its sieve particle size distribution decreased with increase in oxygen feed for gasification and increase in temperature for both biomass conversion processes. For gasification, the pore volume increased from 0.001 m³/g (raw) to 0.144 m³/g (biochar) at 700 °C and to 0.188 m³/g at 900 °C. The pore size of biochar (pyrolysis) increased from 21.948 Å at 400 °C to 34.626 Å at 1000 °C. For both processes, the biochar exhibited a more broken and non-parallel structure compared to that of the feed wood pellets. During plasma gasification, all the particles of size x < 300 μm were entrained in product stream while those with particles x > 2 mm remained in the reactor chamber. The solid carbon element content in the biochar increased by 8% up to 93% when pyrolysis temperature was increased from 400 °C to 1000 °C. The carbon content decreased from 89% to 80% at 700 °C and from 93% to 86% at 900 °C when oxygen flowrate was increased from 0.15 kg/h to 0.6 kg/h. Agglomeration of elements K, Si, Mg, Al and Fe was observed as temperature increased for pyrolysis. The FTIR spectra revealed a new peak at 773 cm⁻¹ attributed to CH bond related to olefin and aromatic structure in all biochar. These parameters are vital to understand practical process flow distributions and product separation mechanisms resulting from transportation of biochar within biomass systems to improve their design.
... The molecular formula (C 4 H 6.08 O 2.75 N 0.02 ) of the biomass in Fig. 3 was obtained from the results of the dry ultimate analysis. The calorific value in Table 1 was obtained using a model in Aspen called HCOALGEN which is the General Coal Enthalpy Model in the Aspen Physical Property System [28][29][30][31]. Generally, this method is used for calculating the enthalpy values for biomass and ash and is obtained from coal studies. ...
This work shows work flows supported by experimental work to analyse the efficiency of a plasma system in biomass conversion processes. The most common set of problems encountered when using biomass-to-energy (BTE) processes relate to tar formation and product gas composition. However, using plasma technology to convert biomass provides a solution because it unlocks more energy than can be achieved by other BTE systems by using a heat supply derived from electricity. The research presented in this paper focuses on the conversion of biomass to chemical energy (in gaseous form) with the aid of the electrical energy supplied by a water-cooled nitrogen plasma torch. The authors conducted a series of experiments in a continuous pyrolysis set up in which wood pellets were converted to syngas in a small-scale laboratory nitrogen plasma torch reactor with a maximum power supply of 15 kW. The efficiency of the process was measured in terms of the carbon conversion to all product gases which changed from 43 to 77%, at temperatures ranging from 400 °C to 1000 °C respectively. The combined carbon monoxide and hydrogen mole concentration in the product gas (without nitrogen) was 86% at 1:1 ratio for all temperatures studied. Syngas yield increased with increase in temperature. The overall biomass conversion obtained increased from 46% to 82% for the temperatures 400 °C to 1000 °C respectively, with the balance comprising carbon-rich solid residue and liquid. The work flow shows that a plasma system can get to high temperatures but work is also degraded in the overall process. Exergy analysis shows that the work lost by the overall process decreases with increase in process temperature.
