Updraft Fixed Bed Gasifier Research Articles

Laboratory-scale simulation study of pyrolysis process in a fixed-bed gasifier for municipal solid waste pellets: Effects of temperature distribution and residence time

In this study, stepwise heating pyrolysis was designed to simulate the pyrolysis process of municipal solid waste (MSW) pellet in an updraft fixed bed gasifier at a laboratory scale. Differences in pyrolysis product between fixed bed stepwise heating pyrolysis (FBS, ranging from 300 °C to 800 °C) and continuous heating pyrolysis (FBC, maintained at 800 °C) were revealed. The impact of residence time at various temperature ranges on MSW pyrolysis was also investigated. Results indicated that compared to FBC, the gas yield of FBS decreased by 30.74%, while its liquid yield increased by 11.96%. It was primarily due to the lower heating rate reduced the secondary conversion of aliphatic hydrocarbons, oxygenated compounds, and monoaromatic hydrocarbons (MAHs) within liquid products. In addition, the composition of MSW pyrolysis products was changed by adjusting the residence time. Maintaining a uniform residence time of 5min for MSW pellets at each temperature was considered optimal for gas yield, which was mainly attributed to the enhanced cracking of long-chain aliphatic and polycondensation of MAHs and polycyclic aromatic hydrocarbons (PAHs). Besides, the volatiles (C- and O-containing compounds) of the char were almost completely released. The underlying influence mechanism of residence time on the pyrolysis behavior of MSW was also proposed, which could provide insights for the implementation of MSW gasification.

Gasification of sago dreg waste in a top-lit updraft fixed bed gasifier: Syngas composition and its effect with additional Al2O3 as catalyst

Sago-based foods have become a staple food in eastern Indonesia. Sago waste, as a by-product, has the potential to be used as a renewable energy fuel. This research aims to use sago dregs waste as an energy source by converting it into renewable energy using Top Lit Updraft (TULD) fixed bed gasification. Al2O3, a potential solid waste derived from coal fly ash, is also being investigated for use in sago dreg pellets.The two various Al2O3 contents in sago dreg pellets that will be examined with 5 % Al2O3 and 10 % Al2O3. Operational parameters employed in the gasification process involving the TULD reactor, such as gasification temperature, air flow rate, air-to-fuel ratio (AFR), and syngas assessment. According to the results, adding Al2O3 as a catalyst to sago dreg pellets can improve syngas production (H2, CO, and CH4). The most significant alteration is that the average hydrogen gas (H2) content has increased, with the greatest being in 5 % Al2O3 with 31.65 %, and 10 % Al2O3 with 29.94 %. Meanwhile, the CO and CH4 gas content was found to be highest at 10 % Al2O3, with each experiencing an increase in average (CO 4.33 % and CH4 26.45 %) as compared to sago dregs pellets without Al2O3. Finally, sago dregs pellets with an Al2O3 catalyst have a high potential as an alternative energy fuel for internal combustion engines with H2/CO of 1.65 and 1.51 respectively, for 5 % Al2O3 and 10 % Al2O3, with low tar content.

Steam‑oxygen Gasification of Surgical Mask Waste in an Updraft Fixed Bed Gasifier System and Its Life-cycle Assessment

Steam‑oxygen Gasification of Surgical Mask Waste in an Updraft Fixed Bed Gasifier System and Its Life-cycle Assessment

Carbon dioxide-steam reforming gasification of carbonized biomass pellet for high syngas yield and TAR reduction through CFD modeling

Experimental and numerical evaluation of steam and carbon dioxide gasification on torrefied palm kernel shell in an updraft fixed bed gasifier is studied. Euler-Lagrangian two-dimensional model with 15 kinetic reactions is developed to investigate tar formation in relation to torrefaction temperature, gasification temperature, and steam-to-carbon-dioxide ratio (S-CO2-R). The combination of steam and CO2 had considerable effect on the tar reduction and also influenced the gaseous composition significantly when the varying parameters were compared. The results show that increasing both gasification temperature and S-CO2-R do enhance the H2 production whiles drastically reducing the tar formation. The tar concentration reduced by 21.4 % and 20.5 % by changing the S-CO2-R from 0.4 to 2.0 and gasification process temperature from 973 and 1173 K respectively. An increase in hydrogen is also observed, from 55.5 % to 60.84 %, when the S-CO2-R is increased to 1.2. Similarly, 29.1 % increase is observed in gasification efficiency as compared to the raw-PKS.

Experimental investigation of sorted municipal solid wastes producer gas composition in an updraft fixed bed gasifier

Three kinds of municipal solid waste (MSW) from mechanical biological treatment plants, i.e., Fraction after Drum Separator (FDS), Solid Recovered Fuel (SRF) and Plastic Packaging Mixture (PPM), were investigated. These samples were gasified in fixed-bed updraft gasifier under allothermal (800 °C) air supply conditions. Two different air equivalence ratios (ER), i.e., 0.15 ± 0.02 and 0.21 ± 0.04 were created to determine the influence on MSW producer gas properties. Derivative thermogravimetry analysis shows the same volatile release temperatures (330 °C, 500 °C) for all tested MSW kinds. Chromatography analysis of MSW producer gas revealed that the reduction of ER from 0.21 to 0.15 increase the heating value of combustible gases. PPM producer gas contains the highest H2 content – 11.39 %. The highest tar content (47.44 g/m3) was measured in SRF producer gas and primarily consisted of benzene, toluene, naphthalene, and acenaphthylene. The results of the sorted MSW gasification experiments show that the allothermal updraft fixed-bed gasifier is suitable for the production of producer gas that can be used in gas engines.

Economic Feasibility Study of Syngas-Derived Garden Waste Biomass as Liquified Petroleum Gas Substitute in Indonesia: A Case Study for 1-Megawatt Updraft Fixed Bed Gasifier

Economic Feasibility Study of Syngas-Derived Garden Waste Biomass as Liquified Petroleum Gas Substitute in Indonesia: A Case Study for 1-Megawatt Updraft Fixed Bed Gasifier

Co-gasification of rural solid waste and biomass in rural areas: Simulation and plant-scale process

Co-gasification technology is considered to be one of the most potential technologies for solid waste treatment, and the co-gasification treatment of rural solid waste (RSW) and biomass can effectively promote waste reduction and resource utilization. In the present study, the co-gasification of RSW and biomass in an updraft fixed bed gasifier was simulated using the Aspen Plus software, where the simulation results were validated via plant-scale experiments. In this scenario, the impacts of biomass source (i.e., rice husk, rice straw, tree bark and corn straw), co-gasification ratio (CGR) (0–40%) and air equivalence ratio (AER) (0.30–0.55) on the performance of the fixed-bed were investigated. Results showed that Aspen Plus could describe the plant-scale co-gasification process well. Besides, the tree bark-RSW system had the highest heat conversion efficiency of 6.00 MJ/kg the simulation temperature of the gasification layer increased greatly from 485 to 913 °C when the AER increased from 0.40 to 0.55. In addition, the co-gasification of RSW and tree bark could achieve the highest efficiency at the AER of 0.45 and CGR of 20% w, in which the gasification temperature reached 799 °C with the gasification efficiency of 57.17%. This study explored the use of co-gasification of RSW and biomass in rural areas by simulation and plant-scale processes, which promotes the commercial application of co-gasification technology and contributes to sustainable waste management in rural areas.

Gasification of MDF residue in an updraft fixed bed gasifier to produce heat and power via an ORC turbine

Biomass, which is a renewable resource, is regarded as an essential energy source due to its accessibility and abundance. In this study, the gasification of wood-based biomass wastes from the medium density fiberboard (MDF) facility was carried out and investigated utilizing an updraft fixed bed gasifier. The feeding capacity of the upstream gasifier is 2100 kg/h. MDF wastes are loaded into the system with feeding capacities of 1500, 1750 and 2100 kg/h. As a reference, the system has also been tested with oak wood chips at a maximum rate of 2100 kg/h. Produced syngas production rate to biomass waste is approximately 2.5 Nm3/kg. The measured gas compositions are CO, CO2, CH4, H2, O2 and N2. Test results with 2100 kg/hMDF wastes have similar gas composition compared to the test results with oak wood chips. The quality of the syngas produced by gasification is directly related to the fuel. It has been observed that the efficiency of the gasification process can be directly or indirectly impacted by the properties of the fuel, such as the moisture content, chemical compositions, and size. The temperature of the produced gas is approximately 430 °C, and it isdirectly combusted with tars and soot it contains to ensure that no chemical energy is lost. The thermal gasification system converts approximately 88% by weight of MDF residue to syngas. The calorific value of produced syngas is obtained between 6.0 and 7.0 MJ/Nm3. The hot syngas containing tars produced from the gasifier was directly burned in the thermal oil heater retrofitted to vortex syngas burner to recover thermal energy, which was then utilized in the production of energy via an ORC turbine. The thermal oil heater has a thermal capacity of 7MWh and the power generation capacity of the ORC turbine is 955 kW of electricity.

Sewage Sludge Gasification Process Optimization for Combined Heat and Power Generation

This work aims to assess the effect of the operating parameters of the gasifying agent preheating temperature and equivalence ratio (ER) on the conversion of sewage sludge (SS) to syngas through gasification and combined heat and power (CHP) generation. A novel gasification model was simulated in Aspen Plus to represent a fixed-bed updraft gasifier to generate syngas from SS through an equilibrium approach restricted by temperature. The novelty of this work is that the model was developed by applying the gasifying agent preheating temperature as an operating variable instead of the gasification temperature. It was calibrated by using a set of experimental values and then validated by comparing the numerical results with the experimental outcomes related to nine different operating conditions of air preheating temperatures and ER. A good agreement between the simulation and experimental results was observed. The optimum gasification process parameters of the air preheating temperature and ER were predicted to be 150 °C and 0.2, respectively. The CHP generation potentiality of SS was assessed to be 2.54 kW/kg SS as dry solids (DS), of which 0.81 kW was electrical and the remainder was thermal power. The conversion of SS to CHP through the proposed treatment can reduce 0.59 kg CO₂/kg SS as DS emissions compared with that of natural gas combustion to generate a similar quantity of energy.

CFD Simulation and Experimental Study on a Thermal Energy Storage–Updraft Solid Waste Gasification Device

A thermal energy storage–updraft gasification device is a type of reactor that should be considered for use in solid waste gasification research that can save energy. However, the operating parameters and internal flow field during its operation remain unclear. In this study, a numerical model of the thermal energy storage–solid waste gasification device based on the computational fluid dynamics dense discrete phase model (CFD-DDPM) which had almost never been used before was established, and an innovative method that causes particles to be piled to simulate the gasification process was proposed according to the updraft fixed bed gasification characteristics; meanwhile, solid waste gasification experiments were conducted on the device. This study focused on the influence of moisture content and excess air coefficient on the gasification process of solid waste particles, and the velocity, pressure, temperature, and species distribution of the internal flow field of the device were analyzed. Simulation results showed that the higher the moisture content of particles, the greater the amplitude of changes in the internal physical field of the device. The fluid pressure drop is around 25 Pa–75 Pa for different working conditions. The combustible species of the gas of moist particles raise slightly with the increase in excess air coefficient, while the dry particles have the opposite effect. Compared with other gasification devices of the same type, the hydrogen production of this device is about 2–3 times higher. Our findings could facilitate the analysis, predict the operation status, and provide a theoretical basis for the improvement of this device.

Life cycle assessment of olive pomace gasification for an up-draft fixed bed gasifier system

Biomass gasification has been considered as an important renewable energy alternative to deal with the environmental problems originating from fossil fuels and climate change effects. Olive pomace as a by-product of the olive oil production process is a significant biomass source. Although gasification technology is accepted as an environmentally friendly power system, the studies to determine its environmental impact via Life Cycle Assessment (LCA) are very limited. LCA is a key tool to evaluate all environmental impacts from the beginning to the end of the process. The aim of this study is to assess the overall environmental impacts of the olive pomace gasification for electricity generation and evaluation of its solid by-products namely biochar and tar. Four scenarios were compared to estimate the environmental impacts of gasification by-products with a LCA approach, following to the cradle-to-grave approach. The production of olive, olive pomace generation during its processing for olive oil production, gasification of olive pomace, construction of the gasifier, gas cleaning system and syngas composition have been included in the evaluations. It is clear from the analysis results that the scenarios have very low impact values in the case of beneficial usage of biochar in different industries. In terms of ozone layer depletion potential (2.74 × 10 −6 kg CFC11 eq) and global warming potential (36.99 GWP100a), the paramount scenario from an environmental viewpoint is the scenario having the biochar and tar usage as a resource in another industry.

Study on the importance of bed shape in combined DEM-CFD simulation of fixed-bed Biomass gasifiers

The extensive utilization of fossil fuels is limited by the environmental problems related to carbon dioxide and other greenhouse gas emissions. As a result, the generation of energy and heat from biomass has become increasingly economically and ecologically important in recent decades. In existing numerical studies, the effect of slope form on airflow within the biomass gasifier was not systematically investigated. To explore the potential impact of the real shape of a fuel bed on local gasification conditions, a small-scale updraft fixed-bed gasifier was modeled in this study with a default lateral feeding position and air supply from below. The discrete element method (DEM) was combined with computational fluid dynamics (CFD) by using two open-source software: LIGGGHTS® and OpenFOAM®. The particle models of two biomasses (olive stone and almond shells) were calibrated and used to investigate qualitatively and quantitatively the airflow patterns, including the resulting uneven pressure and temperature distribution at/over the slope surface. Besides, the effects of operating parameters of the feeding system on slope form were highlighted. Therefore, the real fuel heap shape should be taken into consideration for future simulation studies on side-fed, fixed bed gasifiers. • Material models for DEM simulation are calibrated and validated. • The influences of heap shape and inlet air velocity are explored comprehensively. • Quantitative discussion on the rates of temperature and pressure change. • Suggests that different screw feeding speeds can realize dynamic combustion optimization. • Limitations of a particular DEM-CFD co-simulation model are addressed.

Co-gasification of oily sludge and chicken manure in a laboratory-scale updraft fixed bed gasifier

Co-gasification of oily sludge and chicken manure in a laboratory-scale updraft fixed bed gasifier

Study on physicochemical characteristics, solidification and utilisation of tannery sludge gasification ash

Gasification is an attractive method for tannery sludge (TS) disposal because of its advantages: volume reduction, stabilisation, harmlessness, and energy recovery. TS reduction ash (AR) and TS oxidation ash (AO), simulated from a downdraft fixed bed gasifier (DFBG) and an updraft fixed bed gasifier (UFBG), were investigated on their physicochemical characteristics, solidification behaviour, and value-added utilisation. Results showed that the main mineral matters in AR and AO consisted of Fe-oxids and Fe–Cr compounds, and the DFBG was more suitable for TS gasification than the UFBG because of the lower content of Cr(Ⅵ) in AR. With the addition of waste glass bottles (WGB), the ash fusion temperatures (AFTs) and leaching concentrations of heavy metals in AR and AO decreased significantly, and the heavy metals in AR and AO were successfully immobilised by the wrapping effect of the molten WGB. Moreover, gasification ash, as an auxiliary material for rock wool, reduced the AFTs and viscosity coefficient of the main chemical compositions in rock wool. With the addition of AR, the occurrence of Fe-containing compounds and the extremely low risk of leaching toxicity of heavy metals were observed. The maximum addition proportion of gasification ash was dependent on the maximum content of Fe2O3 allowed in the raw materials of rock wool, and its addition ratio must be below 15%.

Effect of electron injected air on the gasification performance of biomass

The mathematical modeling and the experimental study employing the pilot-scale up-draft fixed bed gasifier were carried out to investigate the effect of the electron injected air on the performance of biomass gasification. The goal of the mathematical modeling was to illustrate the temperature and chemical composition fields. Moreover, the stream function provided by the electron injected air to the flame, and to consider its effect on the development of the flame reaction zone. The results obtained showed that the electron injection generated the electric field, which enhanced the flame's stability greatly. The influence of the flame reaction zone generated by the field-induced ionic wind on the thermal breakdown of biomass was explored, as well as the improvement mechanism of gasification properties by the electric field.

Co-gasification of biomass and coal in a top-lit updraft fixed bed gasifier: Syngas composition and its interchangeability with natural gas for combustion applications

The co-gasification of biomass and coal is a promising approach for efficiently integrating the unique advantages of different gasification feedstock with syngas production. Additionally, syngas from the co-gasification of locally available biomass and coal could supplement the natural gas used in household and industrial burners. The top-lit updraft gasifier features a moving ignition front that starts at the top and propagates downward through the solids bed, while air enters from the bottom and the gas product flows upwards. This study assesses the co-gasification performance of palm kernel shell and high-volatile bituminous coal in a top-lit updraft fixed bed gasifier using 70, 85, and 100 vol% biomass and equivalence ratios ranging from 0.26 to 0.34. The results indicate that the ignition front propagates faster and is more uniform as the biomass volume increases. Micro GC analysis revealed that the H2/CO ratio remained in the range of 0.57–0.59, 0.49–0.51, and 0.42–0.46 for experiments with 70, 85, and 100 vol% biomass, respectively. A gas interchangeability analysis showed that syngas-natural gas blends with up to 15 vol% of syngas could combust in atmospheric natural gas burners without modifications. Thus, the top-lit updraft gasifier shows excellent potential for the co-gasification of coal and biomass. Further research on this technology should explore steam as a gasification agent to enhance the syngas energy content and continuous solids feeding.

Updraft Gasifier-Stirling Engine Biomass Incineration System Power Generation

Biomass, the world's largest renewable energy source, will continue to grow in the following energy markets. As a result, small biomass conversion systems are more competitive than large stand-alone converters because most of the biomass sources have low energy density and are widely distributed in space. The current study offers a small solid biomass power generation system to examine the possibility of direct connection of updates fixed bed gasifiers and a Stirling engine. The fixed bed updraft gasifier uses a combustion burner built into the gasifier to completely burn the synthetic gas produced by the gasifier. The exhaust gases generated by the synthesis gas combustion in the combustion tube are directed to the Stirling engine heater head. The engine then converts the heat contained in the exhaust gases. Output depends on the heat input. And the heat input is proportional to the flue gas flow rate and temperature Preliminary studies on the proposed straight couplings of the energy derived from the gasifier to mechanical energy of 300 mW and electrical energy of 50 mW. The outcomes of the Stirling engine with Updraft gasifier test shows that Pradauk biomass is more effective than charcoal biomass. Current research shows that no supplemental fuel is needed to keep the current system running smoothly. The technology and units presented can be considered as a viable solid biomass power generation system and enlarge to produce more electricity in rural areas of Thailand in the next step.
 HIGHLIGHTS
 
 The outcomes of the Stirling engine with Updraft gasifier test shows that Pradauk biomass is more effective than charcoal biomass
 The technology and units presented can be considered as a viable solid biomass power generation system and enlarge to produce more electricity in rural areas of Thailand in the next step
 Current studies show that the proposed system is technically feasible because it can generate electricity without interference so as to maintain an almost stable process
 
 GRAPHICAL ABSTRACT

Gasification of Densified Biomass (DB) and Municipal Solid Wastes (MSW) Using HTA/SG Technology

The necessity of economical and rational use of natural energy sources caused a rapid development of research on the possibilities of using non-conventional energy resources. Taking the above into account, a new technological process of thermochemical conversion of biomass and communal waste, commonly known as High Temperature Air/Steam Gasification (HTA/SG) and Multi-Staged Enthalpy Extraction Technology (HTAG-MEET), was developed. In relation to traditional techniques of gasification or combustion of hydrocarbon fuels, the presented concept is characterized by higher thermal efficiency of the process, low emission of harmful compounds of carbon, sulfur, nitrogen, dioxins, furans and heavy metals. The use of a high-temperature gasification factor causes an increased thermochemical decomposition of solid fuels, biomass and municipal waste into gaseous fuel (syngas), also with increased hydrogen content and Lower Calorific Value (LCV). In this study, the possibility of using a batch type reactor (countercurrent gasifier) was analyzed for gasification of biomass and municipal waste in terms of energy recovery and environmental protection. The proposed research topic was aimed at examining the possibility of using the thermal utilization of biomass and municipal waste through their high-temperature decomposition in the presence of air, a mixture of air and steam. The main goals of the research were achieved during the implementation of several parallel stages of the schedule, which included, primarily: (a) study of the possibility of using thermal utilization of biomass and municipal waste through their high-temperature gasification in the presence of air or a mixture of air and steam and, secondary (b) analytical and numerical modeling of high-temperature gasification of biomass and municipal waste with the use of ANSYS CFD Fluent 6.3 software. Selected results of the experimental and numerical studies are properly presented. The higher temperature gasification concept shows the capability of this technology for maximizing the gaseous product yield in an up-draft fixed bed gasifier. It was also observed that at a high temperature, steam addition contributed to the thermal conversion of biofuels to gas with higher production of hydrogen.

Applying Artificial Intelligence to Predict the Composition of Syngas Using Rice Husks: A Comparison of Artificial Neural Networks and Gradient Boosting Regression

The purpose of this study is to utilize two artificial intelligence (AI) models to predict the syngas composition of a fixed bed updraft gasifier for the gasification of rice husks. Air and steam-air mixtures are the gasifying agents. In the present work, the feeding rate of rice husks is kept constant, while the air and steam flow rates vary in each case. The consideration of various operating conditions provides a clear comparison between air and steam-air gasification. The effects of the reactor temperature, steam-air flow rate, and the ratio of steam to biomass are investigated here. The concentrations of combustible gases such as hydrogen, carbon monoxide, and methane in syngas are increased when using the steam-air mixture. Two AI models, namely artificial neural network (ANN) and gradient boosting regression (GBR), are applied to predict the syngas compositions using the experimental data. A total of 74 sets of data are analyzed. The compositions of five gases (CO, CO2, H2, CH4, and N2) are predicted by the ANN and GBR models. The coefficients of determination (R2) range from 0.80 to 0.89 for the ANN model, while the value of R2 ranges from 0.81 to 0.93 for GBR model. In this study, the GBR model outperforms the ANNs model based on its ensemble technique that uses multiple weak learners. As a result, the GBR model is more convincing in the prediction of syngas composition than the ANN model considered in this research.

The study of palm kernel shell updraft gasification for supplying heat to an asphalt mixing plant

Air-gasification converts biomass using air into combustible gaseous components which also known as producer gas. The combustion of those gases provides energy for any purposes. In an asphalt mixing plant, this technology is implemented using palm kernel shell as feedstock to generate heat for aggregate heating as a part of hot-mixed asphalt production. Both Cold Gas Efficiency (CGE) and Carbon Conversion Efficiency (CCE) are the common performance indicators of such process. This study examines a performance of an updraft fixed-bed gasifier to convert the shell into producer gas in supplying heat for increasing aggregate temperature from ambient to about 145 – 165°C at capacity of 800 kg/min. The feedstock flowrate was set at 990 kg/hour and equivalence ratios were varied at 0.04, 0.05 and 0.08. Because the gasification reactions were in equilibrium, the producer gas composition for calculating the CGE was predicted using thermodynamic model with minimizing Gibbs free energy. The feedstock and solid residue of the process were analysed to determine the carbon content for calculating the CCE. It is indicated that the performance of the gasification operation for supplying heat in an asphalt mixing plant is limited by operating conditions.