Gasification Tests Research Articles

Biomass Ash Fluidised-Bed Agglomeration: Hydrodynamic Investigations

Agglomeration and defluidisation processes in fluidised-bed reactors due to ash melting are a real difficulty encountered when gasifying feedstock with high ash content. This work aims to investigate the influence of agglomeration on the hydrodynamic behaviour of a bubbling fluidised-bed reactor. The identification of the main parameters involved in agglomeration and defluidisation and the study of their influence on these processes are carried out inside both a laboratory fluidised-bed operating at high temperature (700–1000 °C) and a cold-flow fluidised-bed at ambient temperature. Results are then compared to a gasification test performed in a pilot-scale facility (800 °C). Results show that hydrodynamic disturbances and defluidisation are the result of agglomerates segregation. Once formed, the agglomerates tend to segregate at the bottom of the bed causing the formation and the build-up of a fixed bed crossed by multiple channels. In addition, the hydrodynamic behaviour is highly sensitive to the in-bed liquid amount. Complete defluidisation was seen to occur for very low liquid amount (few vol%). Based on these results, a simplified modelling approach is given in order to predict the operating time before the complete defluidisation of the reactor.

Pyrolysis model for a carbon fiber/epoxy structural aerospace composite

Carbon fiber laminate composites have been utilized in the aerospace industry by replacing lightweight aluminum alloy components in the design of aircraft. By replacing low flammability aluminum components by carbon fiber laminates, the potential fuel load for aircraft fires may be increased significantly. A pyrolysis model has been developed for a Toray Co. carbon fiber laminate composite. Development of this model is intended to improve the understanding of the fire response and flammability characteristics of the composite, which complies with Boeing Material Specification 8–276. The work presented here details a methodology used to characterize the composite. The mean error between the predicted curves and the mean experimental mass loss rate curves collected in bench-scale gasification tests was calculated as approximately 17% on average for heat fluxes ranging from 40 to 80 kW m−2. During construction of the model, additional complicating phenomena were investigated. It was shown that the thermal conductivity in the plane of the composite was approximately 15 times larger than the in-depth thermal conductivity, the mass transport was inhibited due to the high density of the laminae in the composite, and oxidation did not appear to significantly affect pyrolysis at heat fluxes up to 60 kW m−2.

The pyrolysis and gasification performances of waste textile under carbon dioxide atmosphere

In order to obtain the waste textiles’ pyrolysis and the corresponding char’ gasification performance and mechanism under CO2 atmosphere, the pyrolysis and gasification tests of different kinds of waste textiles (polyester fiber (PF), cotton and woolen) were conducted in thermogravimetric-Fourier transform infrared spectrometer at atmospheric pressure. Scanning electron microscopy and Raman spectrometry were used to characterize the char structure. The pyrolysis and gasification processes were quantitatively evaluated by kinetic analysis using the shrinking core model. Results indicated that the pyrolysis and gasification characteristic of the three textiles under CO2 atmosphere were different because the kinetic and thermal dynamic of the three textiles in pyrolysis and gasification processes were different. In addition, the apparent pyrolysis activation energies for PF, cotton and woolen were 162.38, 103.05 and 110.02 kJ mol−1, respectively, while the gasification activation energies were 178.15, 144.49 and 79.37 kJ mol−1, respectively, which were in good agreement of the Raman tests.

Competition between H2O and CO2 during the gasification of Powder River Basin coal

Reaction kinetics of Powder River Basin coal gasification were measured in a modified drop tube fixed bed reactor, accompanied with a rapid response, real-time gas analysis system. The material was rapidly heated and quickly pyrolyzed, followed by a slow gasification with long residence time. Tests are done at 833°C and elevated pressure to 4atm. The conditions were chosen to minimize mass transfer restrictions, so that only surface reactions were measured. The experimental data was fitted using Langmuir-Hinshelwood models to describe both reaction kinetics and degree of surface saturation. CO2 addition into steam gasification, steam addition into CO2 gasification, and injection of steam into an in-progress CO2 gasification test were performed. We found a rarely observed competition mechanism, in which H2O molecules primarily occupy active sites when H2O and CO2 are both present. With sufficient steam partial pressure, the reaction rate in mixtures of H2O and CO2 is equal to steam reaction rate. A newly developed L-H type model was presented to describe this competition mechanism. This model contains a steam reaction rate term and a supplementary CO2 reaction rate term, and matches our experimental results.

Thermal degradation of driftwood: Determination of the concentration of sodium, calcium, magnesium, chlorine and sulfur containing compounds

The annual production of driftwood in Italy has been estimated to be more than 60,000 tonnes. This wood can be used as an energy source. Particular attention should be paid to its content of alkali and alkaline earth metals, sulfur and chlorine. Few works are available in the literature on this topic. For this reason, the authors propose experimental tests of combustion, gasification and pyrolysis, to evaluate the fate of alkali and alkaline earth metals, sulfur and chlorine in the solid residues and compare the three thermal degradation technologies. The results show a release of alkaline earth metals of about 45% of the initial quantity for gasification and a release of 55% of the initial quantity for combustion (while pyrolysis at 600°C has a very low release). The release of sodium is about 65% for gasification and 80% for combustion. It can be seen that the release of sodium is higher than that of alkaline earth metals; this is due to the divalency of the last ones. Dealing with the release of major elements (chlorine, sulfur and AAEMs) the tests have shown that pyrolysis process is a low emitting technology.

Bio-syngas production from agro-industrial biomass residues by steam gasification

This study evaluated the steam gasification potential of three residues from Brazilian agro-industry by assessing their reaction kinetics and syngas production at temperatures from 650 to 850°C and a steam partial pressure range of 0.05 to 0.3bar. The transition temperature between kinetic control and diffusion control regimes was identified. Prior to the gasification tests, the raw biomasses, namely apple pomace, spent coffee grounds and sawdust, were pyrolyzed in a fixed-bed quartz tubular reactor under controlled conditions. Gasification tests were performed isothermally in a magnetic suspension thermobalance and the reaction products were analyzed by a gas chromatograph with TCD/FID detectors. According to the characterization results, the samples presented higher carbon and lower volatile matter contents than the biomasses. Nevertheless, all of the materials had high calorific value. Syngas production was influenced by both temperature and steam partial pressure. Higher concentrations of H2 and CO were found in the conversion range of 50–80% and higher concentrations of CO2 in conversions around 10%, for all the gasified biochars. The H2/CO decreased with increasing temperature, mainly in kinetic control regime, in the lower temperature range. The results indicate the gasification potential of Brazilian biomass residues and are an initial and important step in the development of gasification processes in Brazil.

Biomass Gasification with Dolomite and Olivine Particles as a Bed Inventory in Presence of Ceramic Filters

Biomass gasification trials were carried out continuously in a bench scale gasification plant where the main component has been a fluidized bed reactor containing in its freeboard alternately, non-catalytic and catalytic ceramic filters already used in other gasification tests. The ceramic filters were delivered by Pall Schumacher. The fluidized bed inventory was composed of olivine particles contains alternately 10 % and 20 % by weight of dolomite particles. The fluidization gases were air and steam mixed with nitrogen to assure a good fluidization quality. The experimental tests have shown the beneficial effect of the presence of basic materials such as dolomite, which catalyses the hydrocarbons cracking reactions produced during the devolatilization/pyrolysis process of the biomass particles. The simultaneous presence of the iron content in the olivine particles and the nickel deposited on the ceramic filter, allowed to reduce the amount of tar in the product gas at a smaller concentration of 57 mg for normal cubic meter of dry and nitrogen free gas.The results demonstrate the goodness to carry out biomass gasification process in presence of a mixture of olivine and dolomite particles contained in a fluidised bed with a catalytic ceramic filter inserted in the freeboard of the gasifier. This plant configuration that use only one reactor, allows a significant simplification of the whole gasification process.

Experimental Assessment, Model Validation, and Uncertainty Quantification of a Pilot-Scale Gasifier

This contribution presents a new set of petroleum coke dry gasification tests performed on pilot-scale gasifier. Dry gas composition and flow rate, temperature distribution, conversion, and pollutant formation taken from the experimental tests and respective calculations were used to validate the prediction capabilities of a reduced order model (ROM) developed for the same gasifier. The ROM predicted the experimental observations for conversion in the range of 48–90%. This study confirms that a systematically developed ROM (with a fixed framework) can predict the behavior of a gasifier under different operating conditions with reasonable accuracy. Moreover, this study investigates the variability in the ROM’s key outputs in the presence of uncertainty in the feed and model parameters, i.e., the volatile percentage of the fuel, solid particle diameters, angle of multiphase flow jet, and recirculation ratio. These parameters affect the feedstock’s properties and the mixing/laminar flows within different zon...

Elimination of arsenic-containing emissions from gasification of chromated copper arsenate wood

The behavior of arsenic in chromated copper arsenate containing wood during gasification was modeled using thermodynamic equilibrium calculations. The results of the model were validated using bench-scale gasification tests. It is shown that over 99.6% of arsenic can be removed from the product gas by a hot filter when the gas is cooled below the predicted condensation temperature.

Minerals in the Ash and Slag from Oxygen-Enriched Underground Coal Gasification

Underground coal gasification (UCG) is a promising option for the recovery of low-rank and inaccessible coal resources. Detailed mineralogical information is essential to understand underground reaction conditions far from the surface and optimize the operation parameters during the UCG process. It is also significant in identifying the environmental effects of UCG residue. In this paper, with regard to the underground gasification of lignite, UCG slag was prepared through simulation tests of oxygen-enriched gasification under different atmospheric conditions, and the minerals were identified by X-Ray diffraction (XRD) and a scanning electron microscope coupled to an energy-dispersive spectrometer (SEM-EDS). Thermodynamic calculations performed using FactSage 6.4 were used to help to understand the transformation of minerals. The results indicate that an increased oxygen concentration is beneficial to the reformation of mineral crystal after ash fusion and the resulting crystal structures of minerals also tend to be more orderly. The dominant minerals in 60%-O2 and 80%-O2 UCG slag include anorthite, pyroxene, and gehlenite, while amorphous substances almost disappear. In addition, with increasing oxygen content, mullite might react with the calcium oxide existed in the slag to generate anorthite, which could then serve as a calcium source for the formation of gehlenite. In 80%-O2 UCG slag, the iron-bearing mineral is transformed from sekaninaite to pyroxene.

Investigation of the feasibility of underground coal gasification in North Dakota, United States

Underground coal gasification (UCG) is a promising technology that has the potential to recover currently-unmineable coal resources. The technical feasibility and economic success of a UCG project is highly site specific. Any risks associated with UCG, such as subsidence, groundwater contamination, and syngas quality, should be sufficiently evaluated through a feasibility study. This paper presents a four-year UCG feasibility study utilizing lignite seams in North Dakota, United States. Four wells were drilled through the lignite seams at a selected site, and lignite and strata cores were recovered. A geological model of the formation was built, coal and rock properties were analyzed, and field hydrogeological tests and laboratory gasification tests were performed. This work provided valuable insights in rock mechanics, hydrogeology, and coal properties. The study results show that the selected site is suitable for development of a UCG plant because there are minimal induced subsidence risks, there is hydrological isolation from major aquifers and the coal produces desirable syngas quality for liquid fuel production. Methodologies developed in this study will benefit the design, optimization and management of the UCG process.

Co-gasification of coal/sewage sludge blends to hydrogen-rich gas with the application of simulated high temperature reactor excess heat

The experimental study on oxygen and steam gasification and co-gasification of hard coal and sewage sludge to hydrogen-rich gas was performed in the laboratory scale fixed bed gasifier equipped with an auxiliary gasification agents pre-heating system, simulating the utilization of an excess High Temperature Reactor (HTR) heat. The allothermal gasification and co-gasification tests were performed on fuel blends of coal and sewage sludge of the total mass of 10 g and biowaste content of 20% and 40%w/w in three system configurations. In the first one the reactor was heated up with a resistance furnace to the temperature of 700 °C in the inert gas (nitrogen) atmosphere. When the temperature inside the reactor was stable, oxygen and steam of the temperature of approximately 100 °C were introduced into the reactor. In the second system, after the reactor was heated up to 700 °C, the heating of the reactor was switched off and oxygen and steam were pre-heated to the temperature of 700 °C and fed into the reactor. In the third system a fuel sample in the reactor was heated to the temperature 700 °C and the set temperature was maintained with the resistance furnace. The results showed that sufficient thermal energy required for an effective oxygen/steam gasification process was generated in systems with the external heating of the reactor. The highest hydrogen contents in gas were reported in coal gasification, irrespective of the system configuration. The total hydrogen volume decreased with increasing biomass content in a fuel blend in all studied system configurations.

Plasma-Augmented Fluidized Bed Gasification of Sub-bituminous Coal in CO2–O2 Atmospheres

AbstractThe gasification of a sub-bituminous coal using CO2–O2 gas mixtures was studied in a plasma-augmented fluidized bed gasifier. Firstly, the coal was chemically characterized and the gasification process was examined using Thermogravimetric and Differential Thermal Analysis (TGA/DTA) in CO2, O2 and at a CO2 to O2 ratio of 3 to 1. Secondly, the equilibrium gas compositions were obtained using the Gibbs free energy minimization method (HSC Chemistry®7). Thirdly, gasification tests were performed in a plasma-augmented fluidized bed and the off-gas temperatures and compositions were determined. Finally, for comparison purposes, control tests were conducted using a conventional fluidized bed coal gasifier and these results were compared to those achieved in the plasma-augmented fluidized bed gasifier. The effects of bed temperature and CO2 to O2 ratio were studied. For both gasifiers, at a given bed temperature, the off-gas compositions were in general agreement with the equilibrium values. Also, for both gasifiers, an experimental CO2 to O2 ratio of about 3 to 1 resulted in the highest syngas grade (%CO + %H2). Both higher off-gas temperatures and syngas grades could be achieved in the plasma-augmented gasifier, in comparison to the conventional gasifier. These differences were attributed to the higher bed temperatures in the plasma-augmented fluidized bed gasifier.

小型石炭ガス化炉を用いた CO<sub>2</sub>富化ガス化特性の評価

CRIEPI is developing a high thermal efficiency integrated coal gasification combined cycle power generating system with CO2 capture. This system consists of an oxygen-CO2 blown gasifier that used CO2 as coal carrier gas. CO2 works as a gasifying agent in the char gasification reaction (C＋CO2 → 2CO). Therefore, an improvement of gasification performance is expected owing to the high CO2 partial pressure in the gasifier. CRIEPI investigated the effect of CO2 on gasification performance experimentally using 3t/d coal research gasifier. Coal gasification tests were conducted with several kinds of coals in CO2-enriched conditions. It was confirmed that a gasifier carbon conversion efficiency increased and a char product rate decreased when CO2 partial pressure increased in the gasifier. And a progress of gas phase reaction was investigated by analyzing the syngas in the reductor. In the result, it was confirmed that the concentration of CO2 in the syngas were increased when CO2 was supplied in the gasifier. It was clarified that the gasification reaction zone of the char was broaden to the lower stream of the reductor by the increase in CO2.

Catalytic Adaro Coal Gasification Using Dolomite and Nickel as Catalysts

Integrated Gasification Combined Cycle (IGCC) is an Advanced Clean Coal Technology and can be used as an option for future TNB coal-fired power plant. The implementation of this technology is expected to reduce Green House Gas emissions (eg. CO2), which caused global warming. However, there are several problems in IGCC system, including low carbon conversion and low efficiency in gasifier. Previous studies had shown that higher carbon conversion and efficiency only can be achieved at higher temperature of 900-1000oC. In this study, we had increased the carbon conversion and gasifier efficiency for Adaro coal gasification process using catalyst as in-bed material at lower operating temperature of 700-800oC. Dolomite and nickel with high catalytic activity are selected as catalysts. These catalysts will enhance tar cracking and production of syngas. Furthermore, dolomite is also cheap and abundantly available in Malaysia. Coal catalytic gasification tests were conducted using TNBR Pilot Scale Gasification Plant (PSGP). Adaro coal (100%), Adaro coal:dolomite (80:20) and Adaro coal:dolomite:nickel (90:9:1) mixtures were gasified using PSGP. The results showed that the presence of dolomite had increased Carbon Conversion (CC) and Gasification Efficiency (GE) about 3.1% and 30.7% respectively, compared to Adaro coal gasification. While, the presence of dolomite and nickel for Adaro coal:dolomite:nickel (90:9:1) gasification, had increased CC and GE about 9.5% and 16.4% compared to Adaro coal gasification. Lower increasing of the GE with the presence of nickel is expected due to the deactivation (poison) effect of H2S towards nickel during the gasification process.

Fluidized Bed Co-gasification of Coal and Solid Waste Fuels in an Air Gasifying Agent

The increased need to reduce carbon dioxide emissions to prevent global warming have led to an interest in biomass and solid waste as fuel sources. As a potential renewable energy resource, biomass and solid waste materials are receiving more attention worldwide. A number of techniques and methods have been proposed for reducing gaseous emissions from a fossil fuel conversion thermal system. This paper presents a pilot-scale bubbling fluidized bed gasifier with a diameter of 0.68 m and a height of 1.50 m using an oil burner to heat the bed. This study used four types of biomass materials mixed with coal at different mass composition ratios in an air gasifying agent. The gasification tests were conducted under steady-state at an operating condition that is typical for gasification. The influence that the solid waste and coal ratio had on gasification efficiency was investigated. The gasification efficiency and the carbon conversion efficiency increased when the mass ratio of the solid waste fuels increased.

The Case Study of an Innovative Small Scale Biomass Waste Gasification Heat and Power Plant Contextualized in a Farm

The use of biomass waste in high efficient low pollutants emissions micro-cogeneration plants overpasses the main biomass barriers: competition with the food and material uses, dispersion of a low energy density fuel and high emissions. Evaluations of present technical aspects, economic benefits and their future projections are very important to bring into focus the needs of the technological development of this energy application.This paper is focused on a small (250 kWth) steam gasification fluidized bed and hot gas conditioning system, contextualized in the case study of a farm situated near Rome. Since most of usable biomass waste comes from agriculture, appraisal of applicability to real rural contexts deserves closer examination, considering the necessity of a small size solution as well. A feasibility study of an actual employment of this energy system has included: biomass availability and energy consumption analysis, biomass and gasification tests, power plant sizing, using experimental data and chemcad simulation. Finally an economic analysis has been carried out by varying the main economic parameters. Olive pruning are confirmed as very suitable, and in this case, able to satisfy the farm energy consumption. Global electrical efficiency of 25% can be achieved without any auxiliary fuel consumption. Consumption of 60% of the heat generated are required, meanwhile investment and biomass costs up to 8000 €/kW and 100 €/t can be sustained, especially if the farm electricity cost are higher than 0.15 €/kWh.

Benefits And Drawbacks of Energetic Valorisation of Eucalyptus Globulus Stumps by Thermochemical Processes

In the pulp and paper industry in Iberian Peninsula there is an intensive use of eucalyptus globulus that has a fast growth and a high productivity. There are large areas of forest dedicated to its growth. After 9 to 12 year rotation cycles trees are cut and the stumps are left in the fields. After 2 or 3 harvesting cycles these tree stumps are removed from the fields and considered low value biomass wastes. This corresponds to depletion on organic matter and of valuable minerals related to soil fertility. The use of these biomass wastes in thermochemical conversion processes like gasification or combustion may be a valuable alternative solution as it allows taking profit of these wastes energetic content. The solid by-products obtained by thermal conversion (ashes) may be incorporated in soils to return the valuable minerals and to ensure a good forest management system. Stumps removed from eucalyptus stands were used in combustion trials to improve the burning conditions and in gasification tests with different experimental conditions to obtain syngas suitable to be used in furnaces (chemical recover) of pulp industries. Stumps combustion and gasification processes were compared in terms of stumps energetic valorisation, gaseous emissions and gasification gas utilisation.

A flame spread simulation based on a comprehensive solid pyrolysis model coupled with a detailed empirical flame structure representation

A new model, which represents a unified description of material thermal degradation and burning under thermally thin (non-dimensional), surface radiant heating (one-dimensional) and upward flame spreading (two-dimensional) conditions, has been developed by coupling the numerical pyrolysis solver ThermaKin2D, whose function is to compute the transient rate of gaseous fuel production of a material in response to external heat transfer, with an empirical flame model that predicts a wall flame's heat feedback profile as a function of material mass loss rate. A previously developed pyrolysis model of poly(methyl methacrylate), which was parameterized using a combination of milligram-scale simultaneous thermal analysis experiments and gram-scale gasification tests, was validated in this study using gasification experiments distinct from those utilized in the parameterization process. A previously developed wall flame model was reformulated to include results of new heat flux measurements from 3 to 20 cm above the base of the flame. Inclusion of these results improved the model's predictive capabilities at ignition and across a larger range of flame sizes. The new unified model was employed to predict vertical burning and upward flame spread on 4 and 17.5 cm tall samples of poly(methyl methacrylate). The model predictions – including time to ignition and initial, peak, and rate of rise of sample mass loss rate – were found to closely match experimental results. The impacts of melt flow effects and uncertainties in the flame model formulation on the unified model predictions were examined and found to be moderate.

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.