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The high temperature air combustion (HiTAC) is an advanced promising technology for heat recovery, energy saving, and stability improvement of flame. Computational fluid dynamic (CFD) is known as an applied tool to execute HiTAC modeling. In this paper, performances of pulverized coal combustion under the high preheated and oxygen deficient air are studied by both experimental and numerical methodology. The experimental facilities have been accomplished in a HiTAC chamber with coal injection velocity that ranges from 10 to 40 m/s. In order to achieve different preheated temperatures, the combustion air in such system is diluted by variable steam percentages from 0 to 44%. Results of mathematical simulation and experimental tests present convincible agreement through whole region. It is concluded that NOx emission is reduced by increasing the steam percentage in the oxidizer due to decreasing the flame temperature. Besides, graphical contours show that by adding more steam to oxidizer composition, the oxygen concentration decreased. Additionally, results show that when the injection speed of fuel is increased, NOx emission is also increased, and when the injection rate of preheated air is increased, NOX emission shows decreasing trend. Further contribution in future is needed to investigate the performance of such technologies. [ABSTRACT FROM AUTHOR]

The high temperature air combustion (HiTAC) is an advanced promising technology for heat recovery, energy saving, and stability improvement of flame. Computational fluid dynamic (CFD) is known as an applied tool to execute HiTACmodeling. In this paper, performances of pulverized coal combustion under the high preheated and oxygen deficient air are studied by both experimental and numerical methodology. The experimental facilities have been accomplished in a HiTAC chamber with coal injection velocity that ranges from 10 to 40 m/s. In order to achieve different preheated temperatures, the combustion air in such system is diluted by variable steam percentages from 0 to 44%. Results of mathematical simulation and experimental tests present convincible agreement through whole region. It is concluded that NOx emission is reduced by increasing the steam percentage in the oxidizer due to decreasing the flame temperature. Besides, graphical contours show that by addingmore steamto oxidizer composition, the oxygen concentration decreased. Additionally, results show that when the injection speed of fuel is increased, NOx emission is also increased, and when the injection rate of preheated air is increased, NOx emission shows decreasing trend. Further contribution in future is needed to investigate the performance of such technologies. [ABSTRACT FROM AUTHOR]

Abstract: Presently, there is a growing need for handling automobile shredder residues – ASR or “car fluff”. One of the most promising methods of treatment ASR is pyrolysis. Apart of obvious benefits of pyrolysis: energy and metals recovery, there is serious concern about the residues generated from that process needing to be recycled. Unfortunately, not much work has been reported providing a solution for treatment the wastes after pyrolysis. This work proposes a new system based on a two-staged process. The ASR was primarily treated by microwave pyrolysis and later the liquid and solid products become the feedstock for the high temperature gasification process. The system development is supported within experimental results conducted in a lab-scale, batch-type reactor at the Royal Institute of Technology (KTH). The heating rate, mass loss, gas composition, LHV and gas yield of producer gas vs. residence time are reported for the steam temperature of 1173K. The sample input was 10g and the steam flow rate was 0.65kg/h. The conversion reached 99% for liquids and 45–55% for solids, dependently from the fraction. The H2:CO mol/mol ratio varied from 1.72 solids and 1.4 for liquid, respectively. The average LHV of generated gas was 15.8MJ/Nm3 for liquids and 15MJ/Nm3 for solids fuels. [ABSTRACT FROM AUTHOR]

Abstract: Gasification of biomass using high-temperature agents (air/steam) has been proven to have many features superior to those of conventional gasification using low-temperature agents. In this work, an experimental fixed-bed gasifier is utilized to investigate the gasification of biomass using high-temperature air up to 1473 K. A mathematical model has been formulated for the prediction of the main chemical and physical processes and is used to study the influence of temperature, oxygen concentration and flow rate of the feed gas. Predicted gas species concentration profiles and their maximum values are in reasonable agreements with the measurements. The results show that: (a) When the temperature of feed gas is increased, a higher gasification rate, a higher ignition front rate, and higher molar fractions of fuel gases (CO, H2 and C m H n ), thus a higher LHV are obtained. (b) Increased oxygen concentration leads to higher peak values of the fuel gas concentrations, a higher gasification rate, and a larger ignition front rate. (c) Based on the air temperature, two distinct ignition modes are identified: the reaction-controlled and convective-controlled modes. (d) A critical air temperature exists, above which further preheating is no longer efficient if the purpose is to maximise the yield of gaseous products. [Copyright &y& Elsevier]

Combustion of a single jet of propane in a cross-flowing stream of preheated and oxygen deficient air is numerically analyzed with emphasis on influences of fuel temperature. Both Eddy-Break-Up and PDF/mixture fraction combustion models coupled with RNG k–#x03B5; turbulent model were applied and the predicted results were compared. Thermal and prompt NO models were employed to calculate NO emissions. Results show that the Eddy-Break-Up model is more suitable for predicting temperature field and flame shape. It was showed that flame during high temperature air combustion condition is spread over a much larger volume. Flame volume increases with a reduction of oxygen concentration, and this trend is clearer if oxygen concentration in the preheated air is below 10%. Additionally, it is almost constant at fixed oxygen concentration and fuel inlet temperature for the temperature of the preheated and oxygen deficient air equal to 1041–1273 K. Increase of the fuel inlet temperature results in smaller flame, shorter mean residence time, smaller temperature peaks, and lower emission of NO. [Copyright &y& Elsevier]

Abstract: In this investigation, coal pellets were combusted using a high temperature oxidizer with varying oxygen concentration, using a small scale batch reactor able to preheat the oxidizer to 1273K. In base of the experimental results, the influence of oxygen concentration on the ignition mechanism, the solid temperature inside the particle at the moment of ignition, the mass lost at the moment of the ignition and ignition time is analyzed and discussed. A theoretical basis for the division of the conditions tested into three ignition regimes is developed and a formula for the prediction of the ignition time directly from the material and oxidizer temperature and oxygen concentration is proposed. [Copyright &y& Elsevier]

The promising properties of torrefied biomass provide a valid co-firing option for large percentage biomass utilization in existing coal-fired boilers. Torrefied biomass is expected to have a better combustion stability than raw biomass and similar to that of coal. The present work will characterizes the oxidation properties of torrefied biomass char and compare with that of raw biomass char. The studied two chars are produced from raw and torrefied biomass in an Isothermal Plug Flow Reactor (IPFR) at high temperature and high heating rate, a sufficient residence time is applied for the completion of the high temperature devolatilization. Char oxidation tests are carried out in the IPFR by varying temperature, oxygen concentration and residence time. The reactivity of two studied chars are analyzed and compared with referenced biomass char and coal char, and the impact of torrefaction on char reactivity is also discussed in this paper. Finally, the char oxidation kinetic parameters are determined using a parameter optimization method, and the obtained kinetics are examined by comparing the experimental and predicted mass conversions. [ABSTRACT FROM AUTHOR]

Pretreatment of biomass becomes more and more important due to the large scale application of biomass having low energy density. In this paper, steam exploded biomass pellets (Black pellets) and unpretreated biomass pellets (Gray pellets) were gasified with air and steam at an updraft HTAG (High Temperature Agent Gasification) unit. Decomposition characteristics of pellets were first analyzed with TGA (thermo gravimetric analysis). Early decomposition of hemicellulose and cellulose were seen with Black pellets around 241 °C and 367 °C respectively. Introducing CO2 led comparatively high mass loss rate with Black pellets. Gasification of Black pellets resulted in syngas with high CO and hydrocarbon contents while Gasification of Gray pellets resulted in high H2 content of syngas. LHV (lower heating value) of syngas was high around 7.3 MJ/Nm3 and 10.6 MJ/Nm3 with air gasification and steam gasification respectively. Even with significantly low syngas temperature with gasification of Black pellets, only slightly high total tar content was seen compared to that of Gray pellets gasification. Phenolic compounds dominated the tar composition. In general, steam gasification of Black pellets seems to be more feasible if syngas with high energy value is desired. If higher H2 yield is preferred, gasification of unpretreated pellets likely to be more attractive. [ABSTRACT FROM AUTHOR]

Highlights: [•] Biomasses were devolatilized at high temperatures and high heating rates. [•] Biomass decreases its reactivity after torrefaction. [•] The kinetic parameters of torrefied biomasses were determined. [•] CO and H2 are main released volatiles during devolatilization of torrefied biomass. [ABSTRACT FROM AUTHOR]

Highlights: [•] CaO shows a good capacity of CO2 adsorption at devolatilization stage of MSW. [•] CaO acted as a catalyst both in MSW devolatilization and char steam gasification. [•] Good dispersion and mobility of calcium in char were observed. [•] Catalytic mechanism during devolatilization and char gasification were discussed. [ABSTRACT FROM AUTHOR]

Abstract: Experiments on gasification of chars obtained from original and pulverised wood pellets were conducted in atmosphere of water steam and nitrogen under temperatures of 800, 900 and 950°C. Molar flow rates of carbon containing product gases were measured and approximated using different models with respect to extents of carbon conversion in char of the pellets. Comparison of the random pore, grain and volumetric models revealed the best applicability for approximations of the random pore model. Apparent activation energies obtained as a result of application of the models to the data from experiments with char of original pellets were higher in comparison to those of pulverised pellets, except for a grain model. Approximations under 800°C showed relatively big deviations from experimental data on the beginning of char gasification. This is attributed to catalytic effects from alkali metals in the pellets. [Copyright &y& Elsevier]

Abstract: A new carbon capture and recycle (CCR) system based on multi-reforming of CH4 with CO2 is proposed in this study. The aim was to develop a novel method to remediate greenhouse gases (CO2) using a high temperature (over 1173 K) process of reforming CH4 and/or O2, and/or H2O without catalysts. Using this novel method, the reactants are individually preheated to over 1173 K using a ceramic honeycomb heat exchanger, and then these high temperature streams enter the reactor to start the reforming reactions. Both thermodynamic and experimental studies were carried out on this novel method. Thermodynamic equilibrium models were built for four types of reforming, including dry reforming, bi-reforming, auto-thermal reforming, and tri-reforming. Only dry reforming was experimentally tested. The feasibility of this novel technology was proven by simulated and experimental results. High temperatures significantly promoted the multi-reforming process while avoiding the problem of catalyst deactivation. The experimental results on the direct system also showed that potential improvements in the efficiency of the novel technology could be achieved by optimizing the reforming reactants. Therefore, a continuous system was proposed. Moreover, the power source for the application of CCR systems was also discussed. [Copyright &y& Elsevier]