Performance Of Gasification Process Research Articles

Investigation of an Intensified Thermo-Chemical Experimental Set-Up for Hydrogen Production from Biomass: Gasification Process Performance—Part I

Biomass gasification for energy purposes has several advantages, such as the mitigation of global warming and national energy independency. In the present work, the data from an innovative and intensified steam/oxygen biomass gasification process, integrating a gas filtration step directly inside the reactor, are presented. The produced gas at the outlet of the 1 MWth gasification pilot plant was analysed in terms of its main gaseous products (hydrogen, carbon monoxide, carbon dioxide, and methane) and contaminants. Experimental test sets were carried out at 0.25–0.28 Equivalence Ratio (ER), 0.4–0.5 Steam/Biomass (S/B), and 780–850 °C gasification temperature. Almond shells were selected as biomass feedstock and supplied to the reactor at approximately 120 and 150 kgdry/h. Based on the collected data, the in-vessel filtration system showed a dust removal efficiency higher than 99%-wt. A gas yield of 1.2 Nm3dry/kgdaf and a producer gas with a dry composition of 27–33%v H2, 23–29%v CO, 31–36%v CO2, 9–11%v CH4, and light hydrocarbons lower than 1%v were also observed. Correspondingly, a Low Heating Value (LHV) of 10.3–10.9 MJ/Nm3dry and a cold gas efficiency (CGE) up to 75% were estimated. Overall, the collected data allowed for the assessment of the preliminary performances of the intensified gasification process and provided the data to validate a simulative model developed through Aspen Plus software.

Modeling of downdraft gasification process: Part II - Studies on the effect of shrinking and non-shrinking biomass geometries on the performance of gasification process

Abstract This study investigated the effect of shrinking and non-shrinking biomass geometries in a fixed bed reactor. Model simulation was performed to analyze the effect of biomass moisture content, gasification temperature, air flow rate, oxygen content in the primary air, and mass transfer coefficient on product yield for spherical, tabular, and cylindrical biomass briquettes. The model matched well with the experimental data. The production of hydrogen and carbon dioxide increased with an increase in moisture content. With an increase in gasification temperature, the water–gas shift reaction proceeded faster than the Boudouard reaction, leading to a decrease in the carbon dioxide composition and an increase in the carbon monoxide composition. Tabular shrinking particles with a H2/CO ratio of 1.44 and a CO/CO2 ratio of 0.22 at 1175 K were more favorable for producing value-added chemicals than the particles of all other geometries. The non-shrinking spherical particles had the highest low heating value (LHV) of 4.65 MJ/m3, whereas the tabular non-shrinking particles had the lowest LHV of 1.33 MJ/m3 among the shrinking and non-shrinking particles with all the other geometries considered. The gasification temperature was the most sensitive parameter, whereas moisture content and the mass transfer coefficient were the least sensitive parameters.

Gasification of poultry litter in a lab-scale bubbling fluidised bed reactor: Impact of process parameters on gasifier performance and special focus on tar evolution

Poultry litter (PL) gasification was experimentally investigated using a lab-scale bubbling fluidised bed reactor. Characterisation of the gasification process was performed in terms of yields and compositions of both gas and tar, lower calorific value (LCV) of the product gas, cold gas efficiency (CGE) and carbon conversion efficiency (CCE). Experiments were carried out at different temperatures (700–750 °C) and equivalence ratios (ERs). The effect of gasifier temperature at a constant ER of 0.21 shows that an increase in temperature improved the gasification process performance whilst the total tar content decreased, implying that higher temperature enhances the conversion of biomass to product gas. The total gas yield increased from 0.93 to 1.24 N2-free m3/kgfeedstock-daf, LCV increased from 3.38 MJ/m3 to 4.2 MJ/m3, while the tar content was reduced by 24% (5.6–4.25 gtar/kgfeedstock-daf). The detailed analyses of tar compositions reveal that styrene and xylenes were the most abundant compounds in the secondary tar group. Moreover, naphthalene and 1, 2-methyl naphthalene were the dominant compounds found in tertiary polycyclic aromatic hydrocarbons (PAH) and alkyl tertiary groups, respectively. Furthermore, at the highest tested temperature of 750 °C and ER of 0.25, bed agglomeration took place causing the shutdown of the gasifier. The defluidisation of the bed occurred due to the high ash content of PL comprising of low melting temperature alkali compounds. The results obtained from this study showed the performance and potential challenges associated with gasifying PL in a fluidised bed reactor for the combined heat and power production at farm level.

Co-gasification of sewage sludge and lignite coal in supercritical water for H2 production: a thermodynamic modelling approach

A non-stoichiometry thermodynamic approach based on Gibbs free energy minimization is developed to predict the performance of hydrogen production from gasification of sewage sludge in supercritical water (SCWG). The study focuses on predicting of the influence of operating conditions on SCWG performance. It was done by varying the reaction temperature (400°C, 500°C, 600°C, 700°C, 800°C), feedstock concentration (5%–50%), and reaction pressure (25 MPa, 30 MPa, and 35 MPa). The potential addition of lignite coal into the process also has been investigated. The prediction results showed that the reaction temperature and feedstock concentration had a stronger influence than the reaction pressure. The higher temperature and lower feedstock concentration favored the hydrogen yield and cold gas efficiency. The addition of lignite coal during gasification of sewage sludge in supercritical water slightly influence to the H2 yield and cold gas efficiency. It was expected that the present work is very helpful for evaluating and optimizing the performance of gasification process in supercritical water.

Bio-oil gasification using air - Steam as gasifying agents in an entrained flow gasifier

Abstract The production of gas via bio-oil gasification, which would act as a bridge between bio-oil and transportation fuels, has been increasingly concerned. Bio-oil gasification was performed by using air - steam as gasifying agents. The effects of two important influential factors (steam to bio-oil ratio and gasifier temperature) on the quality of the product gas (gas composition, H2: CO, CO: CO2, tar content, degree of oxidation and heating value) and the gasification process performance (gas yield, steam decomposition, cold gas efficiency, and carbon conversion efficiency) were investigated. The results showed that the impact of the steam to bio-oil on the gas quality and gasification performance had an optimum point (steam to bio-oil ratio = 2.5); However, the influence of the gasifying temperature on both of them demonstrated a sole monotone function. The hydrogen concentration in the product gas reached a maximum of 30.0 vol.% and the ratio of H2/CO basically remained 2.0 over a range of steam to bio-oil ratio from 2.5 to 4.0. The product gas with such a H2/CO ratio is expected to be applied in CO hydrogenation processes, such as Co-catalyzed Fischer-Tropsch synthesis (FTS). Moreover, the product gas is also suitable for the generation of electricity.

Experimental investigation of downdraft gasifier at various conditions

This study present experimental investigation of biomass gasification in the downdraft gasifier. Research was done in the real plant at various operation conditions. Since wood chips was used as fuel in the plant, the effect of fuel moisture on the gasification process performance was examined due high impact on the results. Air supply in the gasifier was divided into primary and secondary air flows to achieve higher syngas calorific value. The share of secondary air flow varied from 0 % to 15 % in the tests. Gasification plant was operated at different thermal capacity to find fuel supply influence on the gasification process performance. Experimental data analysis was done and gasification plant optimal operation setup was determined. Also regression models were developed to present syngas calorific value, gasifier capacity, cold and hot gas efficiency as function of gasifier operation setup.

Feed compositions and gasification potential of several biomasses including a microalgae: A thermodynamic modeling approach

This study presents the relation of the biomass properties with the gasification performance. The potential of microalgae (N. oculta) for gasification also has been investigated. Other biomasses such as palm frond, mangrove, and rice husk were considered as the benchmarks. The performance of a combined gasification process for different biomass was evaluated by developing a thermodynamic model using Aspen Plus. The performance of gasification process was evaluated based on the composition of the producer gas, the cold gas efficiency, and the gasification system efficiency. The effects of biomass composition on the gasification performance was studied by varying the gasification temperature, the oxygen equivalence ratio, and the steam to carbon ratio. It was found that the H/O ratio in the feed biomass has a considerable effect on the H2/CO ratio of producer gas on the gasification without gasifying agent. The gasification of algae with oxygen exhibited the highest H2/CO ratio. The highest cold gas efficiency was found during gasification of algae with oxygen, while the highest cold gas efficiency from gasification with steam was exhibited on gasification of palm frond. The highest gasification system efficiency was obtained for palm frond using the oxygen or steam as the gasifying agent.

CO2 gasification process performance for energetic valorization of microalgae

In this study, CO2 gasification process of a marine biomass (Nannochloropsis gaditana microalgae char) has been evaluated. The experiments have been carried out according to a central composite design (CCD), by using a high-pressure thermogravimetric analyzer (HP-TGA). The effect of temperature, total pressure and gasifying agent volume concentration on the CO2 gasification process was studied. Within the CCD studied range, the process performance, expressed as reactivity and gasification rate at 50% conversion, was positively influenced by the increase of temperature and pressure, while CO2 concentration effect was negligible. Empirical models describing the gasification performance as a function of temperature and pressure are presented and discussed. The proposed models allow a more realistic approach of the microalgae gasification process, in comparison with other models where the catalytic effect is often neglected. This study reveals useful process aspects for the development and implementation of microalgae CO2 gasification at industrial scale.

Fluidized-Bed Gasification of Plastic Waste, Wood, and Their Blends with Coal

The effect of fuel composition on gasification process performance was investigated by performing mass and energy balances on a pre-pilot scale bubbling fluidized bed reactor fed with mixtures of plastic waste, wood, and coal. The fuels containing plastic waste produced less H2, CO, and CO2 and more light hydrocarbons than the fuels including biomass. The lower heating value (LHV) progressively increased from 5.1 to 7.9 MJ/Nm3 when the plastic waste fraction was moved from 0% to 100%. Higher carbonaceous fines production was associated with the fuel containing a large fraction of coal (60%), producing 87.5 g/kgFuel compared to only 1.0 g/kgFuel obtained during the gasification test with just plastic waste. Conversely, plastic waste gasification produced the highest tar yield, 161.9 g/kgFuel, while woody biomass generated only 13.4 g/kgFuel. Wood gasification showed a carbon conversion efficiency (CCE) of 0.93, while the tests with two fuels containing coal showed lowest CCE values (0.78 and 0.70, respectively). Plastic waste and wood gasification presented similar cold gas efficiency (CGE) values (0.75 and 0.76, respectively), while that obtained during the co-gasification tests varied from 0.53 to 0.73.

A Numerical Investigation of Municipal Solid Waste Gasification Using Aspen Plus

The purpose of this paper is to present a numerical simulation model of a fixed bed gasifier for municipal solid waste (MSW) using ASPEN Plus (Advanced System for Process Engineering Plus) software. The model was developed based onGibbs’ free energy minimisation approach and was validated with experimental data of MSW gasification available in literature. Proximate and ultimate analysis of MSW and operation conditions used in the model development are presented and discussed. The study found that simulated and predicted composition of syngas was in good agreement with experimentally measured data (within 4%). The model can be used to analyse performance of gasification process for varying operating parameters, such as air-fuel ratio, gasifier temperature and moisture content of MSW. This model can be used for other biomass feedstocks, such as wood waste, green waste, food waste etc. to predict the syngas composition at optimised operating condition.

木質バイオマスの空気吹き高温気流層型ガス化プロセスに関する研究

High temperature air-blown gasification experiment of woody biomass was conducted in an entrained down-flow type gasifire. Air was blown as the gasifying agent instead of oxygen to improve the gasification process performance. To archive the higher temperature (over 1273 K), pulverized wood was used as the feed stock of gasification experiment. Air-blown gasification process was evaluated by measuring temperature in the gasifire and produced gas composition against O/C ratio. Carbon to gas conversion, cold gas efficiency and heating value of produced gas in an air-blown gasification experiment was also calculated. These gasification behaviors were compared with that in oxygen-blown gasification experiment. It was found that gasification process with air could be performed as well as gasification with oxygen.