Syngas Combustion Research Articles

Effect of Fuel and Air Dilution on Syngas Combustion in an Optical SI Engine

To mitigate the increasing concentration of carbon dioxide in the atmosphere, energy production processes must change from fossil to renewable resources. Bioenergy utilization from agricultural residues can be a step towards achieving this goal. Syngas (fuel obtained from biomass gasification) has been proved to have the potential of replacing fossil fuels in stationary internal combustion engines (ICEs). The processes associated with switching from traditional fuels to alternatives have always led to intense research efforts in order to have a broad understanding of the behavior of the engine in all operating conditions. In particular, attention needs to be focused on fuels containing relatively high concentrations of hydrogen, due to its faster propagation speed with respect to traditional fossil energy sources. Therefore, a combustion study was performed in a research optical SI engine, for a comparison between a well-established fuel such as methane (the main component of natural gas) and syngas. The main goal of this work is to study the effect of inert gases in the fuel mixture and that of air dilution during lean fuelling. Thus, two pure syngas blends (mixtures of CO and H2) and their respective diluted mixtures (CO and H2 with 50vol% of inert gases, CO2 and N2) were tested in several air-fuel ratios (stoichiometric to lean burn conditions). Initially, the combustion process was studied in detail by traditional thermodynamic analysis and then optical diagnostics were applied thanks to the optical access through the piston crown. Specifically, images were taken in the UV-visible spectrum of the entire cycle to follow the propagation of the flame front. The results show that hydrogen promotes flame propagation and reduces its distortion, as well as resulting in flames evolving closer to the spark plug. All syngas blends show a stable combustion process, even in conditions of high air and fuel dilution. In the leanest case, real syngas mixtures present a decrease in terms of performance due to significant reduction in volumetric efficiency. However, this condition strongly decreases pollutant emissions, with nitrogen oxide (NOx) concentrations almost negligible.

Validation of measured data on F/A ratio and turbine inlet temperature with optimal estimation to enhance the reliability on a full-scale gas turbine combustion test for IGCC

Abstract This study is aimed at verifying the reliability and reproducibility of combustion tests, including ignition, load change and fuel changeover, conducted at a well-resourced full-scale gas turbine syngas combustion test facility. The 10 MWth, single-can, syngas-fired combustion test facility was equipped with analytical equipment to measure air and fuel flow rates to the combustor, the metal/gas temperature in the combustor, and exhaust gas composition and temperature distribution at the combustor's outlet. To confirm the test facility's reliability, the repeatability of the fuel changeover test from natural gas to syngas was evaluated. Reliability was also verified by cross-validating the theoretical and measured values for fuel/air (F/A) ratio and Turbine Inlet Temperature (TIT). In this study, the deviation between the averaged F/A ratio based on O2 and CO emission data and the F/A ratio based on the mass flow rate was under 2% at most, when the F/A ratio exceeded 20%. And, the calculated TIT for syngas, taking thermal dissociation and heat loss into consideration, correlates well with the experimental result which is the corrected TIT value based on heat balance at the temperature sensor tip.

Effects of porous insertion in a round-jet burner on flame characteristics of turbulent non-premixed syngas combustion

Synthesis gas (Syngas) is a gaseous mixture that consists of 3 species. It is used in creating synthetic natural gas. In this work, the turbulent non-premixed flame of syngas-air combustion in a round-jet burner is numerically investigated. The burner is partially filled with porous material. Syngas stream fed by high-speed jet entrains co-flow air causing reaction in a non-premixed manner. Turbulent flame is generated over the free-space and porous zones, where the coupled energy and species transports are computed. The k−ω model is used turbulent reaction are modeled using the eddy dissipation concept. Effects of porous material in the burner are analyzed. It was found that porosity and porous thickness have significant effects on flame and heating characteristics. Flame gets broadest at an intermediate value of porosity. The present investigations can be practically applied for the area of low and medium process temperatures such as in glass manufacturing which would enable combustion with low emission rates, reduced energy consumption and quality improvements due to improved controllability.

Effect of hydrogen ratio on turbulent flame structure of oxyfuel syngas at high pressure up to 1.0 MPa

The CO/H2/CO2/O2, CO/H2/CO2/air turbulent premixed flames as the model of syngas oxyfuel and syngas/air combustion were studied experimentally and compared to that of CH4/air mixtures at high pressures up to 1.0 MPa. Hydrogen ratio in syngas was set to be 35%, 50% and 65% in volumetric fraction. Four perforated plates are used to generate wide range of turbulence intensity and scales. The instantaneous flame structure was measured with OH-PLIF technique and then statistic flame structure parameters and turbulent burning velocity were derived to interpret the multi scale turbulence-flame interaction. Results show that the flame structure of syngas is wrinkled and convex cusps to the unburned mixtures are sharper and deeper comparing to that of CH4 flames. Pressure has a dominating effect on flame wrinkling other than mixtures composition at high pressure of 1.0 MPa. The flame surface density, Σ of syngas is larger than that of CH4. The Σ of syngas flames is almost independent on pressure and hydrogen ratio especially when hydrogen ratio is over 50% which is a significant feature of syngas combustion. Larger flame surface density for syngas flames mainly comes from the finer structure with smaller wrinkles which is the result of more intensive flame intrinsic instability. The ST/SL of syngas is larger than CH4 and it slightly increases with the pressure rise. The ST/SL of syngas oxyfuel is similar to that of syngas/air flames in the present study. The ST/SL increases with the increase of hydrogen ratio and keeps almost constant when hydrogen ratio is over 50%.

Thermodynamic study of syngas combustion in gas microturbines with regeneration composed with metallic and ceramic materials

The objective of this research is to carry out an energetic evaluation of syngas combustion in gas microturbines with regenerators made with two different types of material: metallic or ceramic. A modified chemical equilibrium model was used to calculate syngas composition obtained from sugarcane bagasse gasification in a fluidized bed gasifier using steam as gasifying agent. For the gas microturbines with a regenerator of metallic materials, combustion temperatures of 850, 900, and 950 °C were established; and for those with a regenerator of ceramic materials, combustion temperatures of 1150, 1250, and 1350 °C were established. The range for the compression ratio was 2 to 6, and the excess air percentages employed were 400, 500, and 600%. Excellent results were obtained: maximum power ratio was 1.87 kWh/Nm3, maximum cycle efficiency was 57%, and maximum regenerator effectiveness was 100%. Thus, syngas combustion performance in the gas microturbines with regeneration was excellent.

Syngas chemical looping combustion using a highly performing fluidizable oxygen carrier

• A high performing 20 wt%Ni-1 wt%Co-5 wt%La/γ-Al 2 O 3 oxygen carrier is reported. • The preparation method secures a stable fluidizable OC with enhanced reactivity. • This OC carrier is suitable for biomass gasification derived syngas combustion. • This OC yields up to 92% CO 2 yields in the 550-650 º C range. • This OC is free from NiAl 2 O 4 formation in the targeted temperature operating range. Biomass steam gasification produces a blend of H 2 , CO, CH 4 and CO 2 , designated as syngas. Syngas can be further combusted using fluidizable oxygen carriers (OC). This operation which is known as Chemical Looping Combustion (CLC), is valuable for syngas combustion as it involves nickel oxidation and nickel reduction, which are both exothermic reactions. To improve syngas CLC and establish its application, a new Ni-based oxygen carrier was studied using a Co and La modified γ-Al 2 O 3 support. This type of OC considerably limits the NiAl 2 O 4 formation. A Highly Performing Oxygen Carrier (HPOC) was engineered using a special preparation methodology to exclude NiAl 2 O 4 species formation. The evaluation of this HPOC was developed using the fluidized CREC Riser Simulator reactor at mild CLC 550–650 °C temperatures. Reaction conditions employed ranged from 2 to 40 s and used a 0.5–1 fuel to oxygen stoichiometric supply ratio (ψ). It is shown that under these conditions, the HPOC demonstrates a stable performance, yielding 75–92% CO 2 , displaying a 1.84–2.75 wt% (gO 2 /gOC) oxygen transport capacity with 40–60% solid phase oxygen conversion.

Solar–Wind–Bio Ecosystem for Biomass Cascade Utilization with Multigeneration of Formic Acid, Hydrogen, and Graphene

This paper describes the development of a 20MWth solar–wind–bio-distributed energy system and its viability of achieving biomass cascade utilization, water resource conservation, waste heat recovery, and CO2 mitigation while coproducing hydrogen, formic acid, and graphene. The proposed ubiquitous energy system model is developed by using ASPEN Plus for the operating parameter optimization and system-wide heat assessment. The system consists of (i) a biomass gasification module, (ii) a biochar utilization module, (iii) a chemical looping hydrogen generation module, (iv) an oxy-syngas combustion module, (v) a CO2 electroreduction module, and (vi) heat recovery units. Bioenergy is progressively converted through biomass gasification, chemical looping hydrogen generation, syngas combustion, and CO2 electroreduction. The role of solar energy and wind power is to induce the biomass gasification and CO2 electroreduction, respectively. The system has been proved to be water-saving with a water recycle efficiency ...

Computational Fluid Dynamics Modeling of Combustion of Synthetic Fuel of Thermochemical Heat Recuperation Systems

CFD modeling of the combustion of synthetic fuel formed in the systems of thermochemical recuperation of waste flue gas heat due to steam methane reforming was performed using the ANSYS Fluent software. Scientific justification and validation of the physicomathematical approaches involved the ANSYS Fluent for the problems of modeling the combustion of multicomponent hydrogen-containing gas mixtures. Numerical results were validated against experimental data. A visual comparison of the flame contours obtained by burning syngas at Reynolds numbers of 600, 800, and 1000 was performed. In all cases there is obvious convergence of the results. Change in the temperature of the fuel–air mixture at the entrance to the combustion chamber was found to have no significant effect on the temperature of the combustion products. The obtained results are of practical importance for the design of burner units of high-temperature plants with thermochemical heat recuperation.

Extension and evaluation of a macroscopic model for syngas-fueled chemical looping combustion

Syngas-fueled Chemical Looping Combustion (syngas-CLC) which can be integrated with ex-situ gasification of coal has advantages over the direct use of coal in CLC: (i) no requirement of carbon stripper, (ii) no interaction of oxygen carrier with coal ash, (iii) no loss of oxygen carrier with the draining stream of ash. Few works on simulation of syngas-CLC were performed, although experimental investigations were extensively carried out. In this work, a macroscopic fuel reactor model is extended to a lab-scale 500 Wth reactor. The model based on fluid dynamics, mass balance and reduction kinetics is solved with MATLAB® codes and validated against experiments. Influences of various operation parameters are evaluated to study the flexibility of this model. It is shown that the model can give satisfactory predictions for fuel reactor of a syngas-CLC system, independent on the operation conditions. Variations of syngas composition, temperature, solids circulation and oxygen carrier inventory show different effects on flue gas composition and combustion efficiency. After thorough simulation, a region for a combustion efficiency of ηC = 99.9% is proposed, with which the optimized conditions for the 500 Wth reactor are established. An oxygen carrier inventory as low as 50 kg/MWth can assure the complete syngas combustion.

High-Pressure Oxy-Syngas Ignition Delay Times With CO2 Dilution: Shock Tube Measurements and Comparison of the Performance of Kinetic Mechanisms

In this study, syngas combustion was investigated behind reflected shock waves in CO2 bath gas to measure ignition delay times (IDT) and to probe the effects of CO2 dilution. New syngas data were taken between pressures of 34.58–45.50 atm and temperatures of 1113–1275 K. This study provides experimental data for syngas combustion in CO2 diluted environments: ignition studies in a shock tube (59 data points in 10 datasets). In total, these mixtures covered a range of temperatures T, pressures P, equivalence ratios φ, H2/CO ratio θ, and CO2 diluent concentrations. Multiple syngas combustion mechanisms exist in the literature for modeling IDTs and their performance can be assessed against data collected here. In total, twelve mechanisms were tested and presented in this work. All mechanisms need improvements at higher pressures for accurately predicting the measured IDTs. At lower pressures, some of the models agreed relatively well with the data. Some mechanisms predicted IDTs which were two orders of magnitudes different from the measurements. This suggests that there is behavior that has not been fully understood on the kinetic models and is inaccurate in predicting CO2 diluted environments for syngas combustion. To the best of our knowledge, current data are the first syngas IDTs measurements close to 50 atm under highly CO2 diluted (85% per vol.) conditions.

Experimental Study on Low Load Operation Range Extension by Autothermal On-Board Syngas Generation

Volatile renewable energy sources induce power supply fluctuations. These need to be compensated by flexible conventional power plants. Gas turbines in combined cycle power plants adjust the power output quickly but their turn-down ratio is limited by the slow reaction kinetics, which leads to CO and unburned hydrocarbon emissions. To extend the turn-down ratio, part of the fuel can be converted to syngas, which exhibits a higher reactivity. By an increasing fraction of syngas in the fuel, the reactivity of the mixture is increased and total fuel mass flow and the power output can be reduced. An autothermal on-board syngas generator in combination with two different burner concepts for natural gas (NG)/syngas mixtures was presented in a previous study (Baumgärtner, M. H., and Sattelmayer, T., 2017, “Low Load Operation Range Extension by Autothermal On-Board Syngas Generation,” ASME J. Eng. Gas Turbines Power, 140(4), p. 041505). The study at hand shows a mass-flow variation of the reforming process with mass flows, which allow for pure syngas combustion and further improvements of the two burner concepts which result in a more application-oriented operation. The first of the two burner concepts comprises a generic swirl stage with a central lance for syngas injection. Syngas is injected with swirl to avoid a negative impact on the total swirl intensity and nonswirled. The second concept includes a central swirl stage with an outer ring of jets. For this burner, syngas is injected in both stages to avoid NOx emissions from the swirl stage. Increased NOx emissions produced by NG combustion of the swirl pilot were reported in last year's paper. For both burners, combustion performance is analyzed by OH*-chemiluminescence and gaseous emissions. The lowest possible adiabatic flame temperature without a significant increase of CO emissions was 170–210 K lower for the syngas compared to low load pure NG combustion. This corresponds to a decrease of 15–20% in terms of thermal power.

Influence of piston shape and injector geometry on combustion and emission characteristics of syngas in direct-injection spark-ignition engine

This paper presents a numerical study of the influence of piston shape and injector geometry on combustion and emissions characteristics of a direct-injection spark-ignition engine fueled by syngas (50% by volume of hydrogen, 50% by volume of carbon monoxide) under low/medium load conditions. Three different piston cup geometries namely: High-clearance Combustion Cup (HCC), Low-clearance Combustion Cup (LCC) and Omega Combustion Cup (OCC) have been considered with a compression ratio of 14. An axial full-cone gas jet injector has been considered together with a hollow-cone gas jet injector with several included half-angles, i.e. 30°, 45°, 52.5° and 60°. Computational fluid dynamics modelling has been performed to simulate the combustion process. The results indicate that, in terms of performance, OCC shape is favorable, even if OCC generates relatively higher NOx than the other two configurations. A further analysis has been performed by simulating an engine with OCC piston shape and an included half-angle of injection of 30°, by varying the Start Of Injection (SOI). The results show that the flame propagation velocity reduces as the SOI advances, since the fuel distribution becomes more homogeneous approaching to a premixed case. However, the flame speed reduction is partially balanced by the disappearance of very lean regions thanks to fuel convection and diffusion.

Ignition kinetics of a homogeneous hydrogen/air mixture using a transient hot jet

The ignition characteristics of a homogenous hydrogen/air mixture using a hot transient jet generated by the combustion of syngas (H2/CO) with varying CO concentrations from 33% to 95% in a pre-chamber is numerically investigated with particular attention to the chemical kinetics. Detailed reaction mechanism for hydrogen and syngas mixture oxidation with 15 species and 41 reactions is employed. The hot jet ignition delay time is determined by the onset of OH∗ radicals and found to increase with increasing CO molar fractions in the pre-chamber fuel, and this increase is more profound for high CO content. The radicals that formed in the main chamber are examined separately from the radicals within the hot jet. Their temporal evolutions reveal that O and OH radicals in the jet play a crucial role in abstraction of H atoms form H2/air mixture in the main chamber, which initiates ignition. Further analysis of the H2O2 rate of change identifies two ignition regimes. For high temperature (T > 1000 K) hot jets, ignition is caused by the chain branching reaction H+O2↔O+OH directly, resulting in short ignition delay times (0.14, 0.19, 0.26 ms). For low temperature (T < 1000 K) hot jets, ignition is dominated by the accumulation and decomposition of H2O2, resulting in long ignition delay times (0.4, 0.67, 1.26 ms). By separating the thermal and chemical effects of the hot jet, it is found that the thermal effects are dominant but composition of the hot jet has little effect on the ignition characteristics.

Study on the effect of H2O on the formation of CO in the counterflow diffusion flame of H2/CO syngas in O2/H2O

The effects of H2O addition on the CO production by one-dimensional laminar counterflow diffusion flame of H2/CO syngas in O2/H2O = 27.5/72.5 were studied. Davis, Li and the USC II mechanisms are mainly used for the combustion of syngas and a large number of studies have been made on these mechanisms by researchers. However, most of the existing studies were based on the numerical calculation in air condition. Therefore, the existing mechanisms (Davis, Li, USC II) were not suitable for the combustion in high H2O condition. A modified mechanism was used to simulate the counterflow diffusion flame with the OPPDIF code. Four groups of artificial species (FH2O and H2O, TH2O and FH2O, XH2O and FH2O, RH2O and FH2O) were introduced to break up the couplings between the chemical, thermal, transport and radiative effects of H2O. The four effects of H2O on the CO production at the flame front (the max temperature) are numerically studied. The results show that the oxidation of CO is mainly through CO + OH = CO2 + H. The chemical and radiative effects of H2O have a significant impact on the production of CO, which inhibit CO production and decrease CO concentration. The other effects of H2O have little impact on CO formation. In addition, the chemical effect of H2O improves the flame temperature, the thermal and radiative effects reduce the flame temperature, and the transport effect on the temperature is almost negligible. The influence of these four pairs of H2O on temperature is consistent with the effects on the heat release rate.

A numerical study on effects of pre-chamber syngas reactivity on hot jet ignition

Ignition by a pre-chamber generated hot jet is a promising technology to reduce NOx emissions through extending lean burn limits. However, the role of the pre-chamber fuel reactivity in the main chamber ignition still remains unclear. In the present study, effects of the pre-chamber fuel reactivity on ignition of mixture in a main chamber by the hot jet, which is generated by the combustion of syngas in the pre-chamber, are numerically investigated. In the investigation, different ratios of CO/H2 of syngas are considered under a thermally-equal condition. CFD simulations are performed using the code based on the KIVA-3V release 2 program coupled with an in-house developed chemical solver. A detailed chemical kinetics mechanism with 15 species and 41 reactions is adopted for the hydrogen and syngas oxidation. The hot jet ignition delay time is characterized by the maximum rate-of-change of the pressure in the main chamber. For the combustion initiation process, three stages are identified: ignition stage (stage I), flame development stage (stage II), and flame propagation stage (stage III). Significant effects of fuel reactivity are only observed on stage I that the ignition delay time considerably increases with increasing CO/H2 ratio. Further analyses of the local temperature of the hot gas and some important elementary reactions indicate that the low reaction rate of carbon monoxide oxidation (R22: CO + OH = H + CO2) causes incomplete fuel conversion in the orifice due to insufficiently available time for the reactions . The fuel conversion analysis confirms that the small-diameter orifice effect is the main reason for hot jet temperature drops under low pre-chamber syngas reactivity conditions, exhibiting as inhibiting effects on stage I.

Mn-based oxygen carriers prepared by impregnation for Chemical Looping Combustion with diverse fuels

Chemical Looping Combustion (CLC) is considered one of the low cost alternatives for CO2 capture for fossil fuels combustion and to reach negative emissions through biomass CLC. The cornerstone of the CLC process is the oxygen carrier performance that represents the main additional cost with respect to the conventional combustion. Manganese-based oxygen carriers are subjected to a growing interest because they are low cost, not toxic and environmentally friendly. In this work five impregnated oxygen carriers, with manganese oxide Mn3O4 or Mg6MnO8 as their active phase and three commercial supports based on zirconia and synthetic calcium aluminate, were prepared. Their behaviour for CLC was examined by TGA, batch fluidized bed reactor, TPR, SEM-EDX and XRD. After a preliminary screening two carriers (Mn-ZrM and Mn-ZrSG) were subjected to multiple redox cycles by TGA and batch fluidized bed reactor. Both showed high solids conversion by TGA under the tested conditions, appropriated resistance to fracture, rate indexes relatively high, although Mn-ZrM showed agglomeration and deactivation during batch fluidized bed tests.Reactivity in batch fluidized bed reactor of the Mn-ZrSG oxygen carrier with methane increases with temperature although suffered from significant deactivation. This was different to the results found during multiple redox cycles by TGA. There was not a clear reason for this decrease in the reactivity that likely could be due to the uncomplete oxidation in the batch fluidized bed reactor, although further investigations are needed. On the other hand, it presented high and constant reactivity with CO and H2 in all the range of temperatures tested, being suitable for iG-CLC processes of coal or biomass and syngas combustion. Agglomeration problems were not found and the attrition losses were small. Calculated lifetime was around 11,000 h, much higher than any other Mn-based material developed or tested for CLC.

Comparison of Numerical Combustion Models for Hydrogen and Hydrogen-Rich Syngas Applied for Dry-Low-Nox-Micromix-Combustion

The Dry-Low-NOx (DLN) Micromix combustion technology has been developed as low emission combustion principle for industrial gas turbines fueled with hydrogen or syngas. The combustion process is based on the phenomenon of jet-in-crossflow-mixing (JICF). Fuel is injected perpendicular into the air-cross-flow and burned in a multitude of miniaturized, diffusion-like flames. The miniaturization of the flames leads to a significant reduction of NOx emissions due to the very short residence time of reactants in the flame. In the Micromix research approach, computational fluid dynamics (CFD) analyses are validated toward experimental results. The combination of numerical and experimental methods allows an efficient design and optimization of DLN Micromix combustors concerning combustion stability and low NOx emissions. The paper presents a comparison of several numerical combustion models for hydrogen and hydrogen-rich syngas. They differ in the complexity of the underlying reaction mechanism and the associated computational effort. The performance of a hybrid eddy-break-up (EBU) model with a one-step global reaction is compared to a complex chemistry model and a flamelet generated manifolds (FGM) model, both using detailed reaction schemes for hydrogen or syngas combustion. Validation of numerical results is based on exhaust gas compositions available from experimental investigation on DLN Micromix combustors. The conducted evaluation confirms that the applied detailed combustion mechanisms are able to predict the general physics of the DLN-Micromix combustion process accurately. The FGM method proved to be generally suitable to reduce the computational effort while maintaining the accuracy of detailed chemistry.

Inhibition of C[sbnd]Cl formation during the combustion of MSW gasification syngas: An experimental study on the synergism and competition between oxidation and chlorination

For the safe disposal of MSW, a four-step gasification-combustion conversion process is proposed in this work, consisting of material gasification, ash melting, syngas conversion and combustion. Based on the control method of dioxin in gasification process which has been studied previously, experiments of tar chlorination process under oxidative atmospheres were carried out in a homogeneous flow reaction system, using benzene as the tar model compound, to find a way for the inhibition of CCl formation during the syngas combustion process. Results indicated that Cl2 reacts with benzene more easily than O2 under low temperatures, and has a positive effect on both oxidative cracking and polymerization. For chlorination reactions, high temperature enhances the chlorination degree and leads to the formation of perchlorinated hydrocarbons, but also promotes the rupture of the weak CCl bonds. With the rise of temperature, hexachlorobenzene became the major product, the amounts of all chlorinated hydrocarbons decreased rapidly, and the conversion direction depended on the amount of O2. O2 generally promotes the formation of hydrogen chloride, and inhibits the chlorination of hydrocarbons. At a temperature above 900 °C, the total amount of chlorinated hydrocarbons was very low under oxidative atmospheres, even only with a equivalence ratio of 0.2. However, during the oxidation process under low temperatures, CCl can also be formed on cyclopentadienyl and 1,3-butadienyl radicals, whose chlorination products were observed. The synergistic and competitive effects between oxidation and chlorination are concluded and the major benzene conversion pathways are summarized according to the products detected.

Model Simulation and Design Optimization of a Can Combustor with Methane/Syngas Fuels for a Micro Gas Turbine

Abstract The design and model simulation of a can combustor has been made for future syngas combustion application in a micro gas turbine. An improved design of the combustor is studied in this work, where a new fuel injection strategy and film cooling are employed. The simulation of the combustor is conducted by a computational model, which consists of three-dimensional, compressible k-ε model for turbulent flows and PPDF (Presumed Probability Density Function) model for combustion process invoking a laminar flamelet assumption generated by detailed chemical kinetics from GRI 3.0. Thermal and prompt NOx mechanisms are adopted to predict the NO formation. The modeling results indicated that the high temperature flames are stabilized in the center of the primary zone by radially injecting the fuel inward. The exit temperatures of the modified can combustor drop and exhibit a more uniform distribution by coupling film cooling, resulting in a low pattern factor. The combustion characteristics were then investigated and the optimization procedures of the fuel compositions and fuel flow rates were developed for future application of methane/syngas fuels in the micro gas turbine.

Life cycle assessment of pyrolysis, gasification and incineration waste-to-energy technologies: Theoretical analysis and case study of commercial plants

Municipal solid waste (MSW) pyrolysis and gasification are in development, stimulated by a more sustainable waste-to-energy (WtE) option. Since comprehensive comparisons of the existing WtE technologies are fairly rare, this study aims to conduct a life cycle assessment (LCA) using two sets of data: theoretical analysis, and case studies of large-scale commercial plants. Seven systems involving thermal conversion (pyrolysis, gasification, incineration) and energy utilization (steam cycle, gas turbine/combined cycle, internal combustion engine) are modeled. Theoretical analysis results show that pyrolysis and gasification, in particular coupled with a gas turbine/combined cycle, have the potential to lessen the environmental loadings. The benefits derive from an improved energy efficiency leading to less fossil-based energy consumption, and the reduced process emissions by syngas combustion. Comparison among the four operating plants (incineration, pyrolysis, gasification, gasification-melting) confirms a preferable performance of the gasification plant attributed to syngas cleaning. The modern incineration is superior over pyrolysis and gasification-melting at present, due to the effectiveness of modern flue gas cleaning, use of combined heat and power (CHP) cycle, and ash recycling. The sensitivity analysis highlights a crucial role of the plant efficiency and pyrolysis char land utilization. The study indicates that the heterogeneity of MSW and syngas purification technologies are the most relevant impediments for the current pyrolysis/gasification-based WtE. Potential development should incorporate into all process aspects to boost the energy efficiency, improve incoming waste quality, and achieve efficient residues management.