Search

To develop an NH3/natural gas-fired gas-turbine combustor with minimal modifications to a natural gas-fired combustor, the effect of co-firing NH3 with natural gas on emission characteristics and combustion efficiency is investigated experimentally under atmospheric pressure. In this experiment, a lean premixed combustor that has basically the same structure and same size as those of an actual 2 MW-class gas-turbine combustor is used and the effects of equivalence ratio, NH3 mixing ratio, and NH3 injection method were evaluated. The results of NH3/natural gas/air premixed combustion show that NO emission shows a local maximum at a certain NH3 mixing ratio, when equivalence ratio is fixed. The NH3 mixing ratio where this maximal NO emission occurs shifts to higher ratios, when equivalence ratio is increased towards stoichiometric condition. At the same time, the maximal NO emission increases. The variation of NOx concentration can be explained by the change in the selective non-catalytic reduction (SNCR) effect, which depends on temperature and NH3 concentration in the flame. In particular, the influence of NH3 concentration on the SNCR effect appears to be stronger than that of temperature. On the other hand, concentrations of N2O and unburnt NH3 increase with increasing NH3 mixing ratio in the very lean case, when decreasing flame temperature approaches the lean flame blow-off limit. When NH3 is directly injected into the lean premixed flame of natural gas, NO and N2O concentrations are simultaneously reduced; this is attributed to the local increase of NH3 concentration and flame temperature. Finally, it is proposed to consider NOx as unburnt component in the calculation of combustion efficiency. When NH3 is fired, the enthalpy content of NOx is very high, and its influence on combustion efficiency cannot be ignored. It is also found that NH3 direct injection is effective in increasing combustion efficiency, achieving more than 99.6% of the combustion efficiency even if the enthalpy of NOx is considered.

A novel reformer using highly efficient heat regeneration for tar-free syngas production is developed and its performance demonstrated in a pilot-scale plant using steam gasification. Basic design parameters of the regenerative tar reformer, namely residence time and amount of oxidant are determined based on numerical results. It has been predicted that good performance could be achieved at an operation temperature about 1573 K, the residence time exceeding 4 s and an oxidant addition of 12% of the syngas flow rate. The regenerative tar reformer so designed shows stable operation. Over 99% of light and heavy tars are reformed to gas in the case of 11.3% oxygen addition to syngas. Further it is seen that a reduction of oxygen consumption more than 30% compared to a conventional oxidation reformer can be achieved. The formation of a high temperature zone and good mixing of syngas and oxygen has a strong influence on the tar reforming efficiency.

Certain simplified submodels of coal combustion, whose precision can be inadequate for certain situations, are widely used in computational fluid dynamics (CFD) simulations of a pulverized-coal-fired furnace. A large-scale furnace was simulated to explore the effects of certain advanced submodels. Comparing the simulation results in four cases to different submodels shows that the ignitability of burners is closely linked to the amount of H2 generated. In the baseline case, which disregards H2, we obtained very poor ignitability for all burners. Using a four-step mechanism instead of a two-step mechanism for volatile combustion and considering the char gasification (C–H2O) and detailed composition of volatiles are all clearly likely to improve ignitability. Meanwhile, superior ignitability also increases the heat absorbed by walls, reduces gas temperatures at the furnace exit, and reduces CO in the furnace. CO can also be increased by accounting for char gasification (C–CO2) and the detailed composition o...

Recently, the co-firing ammonia (NH3) with coal in boiler has been paid more and more attention. A computational Fluid Dynamics (CFD) simulation approach was built to investigate the NH3 co-firing in a pulverized coal combustion facility with a single swirling burner. The simulation accuracy was evaluated with the experimental data. The differences between coal firing and NH3 co-firing can be well reproduced with simulation. Then, the effects of NH3 co-firing ratio (CR) on the combustion characteristic and NOx emission were investigated. The flame shape is significantly affected by NH3 CR, due to the changes of momentum of NH3 jet from center of burner. When the NH3 CR exceeds 40 cal.%, the internal recirculation zone is completely penetrated by high velocity NH3 flow, which leads to a long flame and much unreacted NH3 in downstream. As the increase of NH3 CR, the overall trend is that the total heat absorbed slightly decreases due to the decrease of particle radiation, and unburnt carbon in fly ash obviously increases due to decrease of flame temperature. In the case with NH3 CR of 10 cal.%, the NO concentration at exit increases due to the more intense combustion and more fuel-NOx, compared with the case of coal-firing. When the NH3 co-firing ratio exceeds 10 cal.%, the NO concentration at exit decreases monotonously due to the DeNOx effect of unreacted NH3. However, once the NH3 co-firing ratio exceeds 40 cal.%, the unreacted NH3 concentration at exit increases rapidly, which requires careful designs of burner and furnace.

Computational fluid dynamics (CFD) simulations of the oxy-coal combustion in a large-scale furnace were performed by applying different weighted sum of gray-gases models (WSGGMs). Before simulation of the furnace, the different WSGGMs were tested in an enclosed rectangular box containing only gases inside. In both cases of air and oxy-fuel combustion, the calculated radiative sources and wall heat fluxes obtained with gray and non-gray WSGGMs were completely different. Only with the non-gray WSGGMs (i.e., non-gray implementation), the calculated results could well agree with the benchmark data. In the simulation of furnace, three WSGGMs were adopted: Smith’s gray WSGGM (i.e., gray implementation), Johansson’s non-gray-A WSGGM with uniform distribution of radiative energy of particles in each gray band, and Johansson’s non-gray-B WSGGM, in which the radiative energy of particles was distributed using weighting factors. The weighting factors for the particles can be calculated with the same function as that used for gas but using the particle temperature instead of gas temperature, i.e., wp,i = wg,i (Tp). Being different from the rectangular box without particle radiation, in the real furnace, the gas temperature and wall heat flux calculated by gray and non-gray-A WSGGMs almost show no obvious difference. This is attributed to the fact that particle radiation plays a more significant role than gas radiation in the real furnace. However, using the non-gray-B model instead of Smith’s gray model or non-gray-A model can obviously influence the distribution of wall heat flux and total amount of heat absorbed by the walls. This indicates that in the numerical simulation of oxy-fuel combustion, the non-gray WSGGMs should be used by combining with the weighting factors of wp,i = wg,i (Tp) for particles, in order to rigorously describe both the gas and particle radiation during oxy-fuel combustion of coal in real furnace.

A char combustion model was derived by assuming constant intrinsic activation energy for the different chars. The char combustion rates are affected by various diffusion processes within the different char pores. The fractal pore diffusion effects were characterized by three pore structure parameters (porosity, specific surface area, and fractal dimension) and the mean particle diameter. Three-dimensional numerical results for various char particles burned in drop tube furnaces obtained using the model compare well with experimental results to verify the model. The comparisons show that the model has good accuracy for a wide range of char, from lignite to anthracite.

Oxyfuel combustion is one of the promising carbon capture and storage (CCS) technologies for coal-fired boilers. In oxyfuel combustion, combustion gas is oxygen and recirculating flue gas (FGR) and main component of combustion gas is O 2 , CO 2 and H 2 O rather than O 2 , N 2 in air combustion. Fundamental researches showed that flame temperature and flame propagation velocity of pulverized cloud in oxyfuel combustion are lower than that in air with the same O 2 concentration due to higher heat capacity of CO 2 . IHI pilot combustion test showed that stable burner combustion was obtained over 30% O 2 in secondary combustion gas and the same furnace heat transfer as that of air firing at 27% O 2 in overall combustion gas. Compared to emissions in air combustion, NOx emission per unit combustion energy decreased to 1/3 due to reducing NOx in the FGR, and SO x emission was 30% lower. However SO x concentration in the furnace for the oxyfuel mode was three to four times greater than for the air mode due to lower flow rate of exhaust gas. The higher SO 3 concentration results that the sulphuric acid dew point increases 15–20 °C compared to the air combustion. These results confirmed the oxyfuel pulverized coal combustion is reliable and promising technology for coal firing power plant for CCS. In 2008, based on R&D and a feasibility study of commercial plants, the Callide Oxyfuel Project was started in order to demonstrate entire oxyfuel CCS power plant system for the first time in the world. The general scope and progress of the project are introduced here. Finally, challenges for present and next generation oxyfuel combustion power plant technologies are addressed.

Detonation experiments are conducted to investigate the detonation wave behavior in steam pipelines of boiling water reactors. Accumulated gases in BWRs are stoichiometric hydrogen/oxygen mixtures diluted with steam at 7 MPa. In the experiment, flammable gas mixture diluted with nitrogen at room temperature and up to 5 MPa is used to achieve equivalent detonation condition. Two test pieces are used, one is straight tube and the other is 90-degree bend. No initial pressure dependency in detonation wave behavior is observed in the experiments. However, in the straight tube tests, detonation velocities higher than theoretical values are measured when the initial pressures are greater than 2.3 MPa. This result is considered as attribution of real gas effect. In the 90-degree bend experiments, pressure time histories reveal pressure loads greater than the straight tube portion at two locations. One is a high pressure peak at the extrados of the bend and the other is a double pressure peak just downstream of the bend outlet. Second pressure peak just downstream of the bend outlet is due to transverse wave propagation. Additionally, the largest impulse is observed not at the extrados of the bend but at the intrados of bend outlet. These results show the importance of more investigations on transverse wave behaviors in failure potential evaluation.

Coal gasification technology is increasingly important in the world because of the rise in cost of oil and natural gas. Lignite coal is huge in reserved quantity, and is suitable for gasification because of its higher reactivity so that a simple and cheap gasifier is needed for the lignite coal. Circulating fluidized bed with twin reactor (riser combustor and bubbling bed gasifier) is suitable for lignite coal gasification because it can produce syngas with high calorific value without using pure oxygen or pressurized condition. IHI has developed TIGAR® (Twin IHI Gasifier) process based on our commercialized circulating fluidized bed technology. This process can produce syngas with high calorific value and also high hydrogen content with air at the atmospheric pressure. Additionally, both syngas and electricity (from steam) can be produced and also the yields can be controlled by the ratio of combustion and gasification, which will sufficiently meet the demand of the user. In this paper, some results obtained by process simulation, cold model test and pilot scale experiments are shown.

As one of the most attractive technologies for carbon capture, oxy-fuel combustion of coal has been studied worldwide. Some important results of fundamental studies and practical systems of oxy-fuel combustion are introduced in this chapter. According to the results of fundamental experiments, a slower flame propagation velocity in a O2/CO2 atmosphere requires a higher O2 concentration to obtain a stable combustion in oxy-fuel mode compared to air mode. CO2 and H2O gasification each have effects on reducing the char particle temperature and increasing the char consumption rate. In oxy-fuel mode, gasification reactions between char and CO2 or H2O can result in a high devolatilization rate and a clearly different char structure. As with simulations of heat transfer in the boiler for oxy-fuel combustion, the new weighted sum of gray-gases model for calculating gas radiation properties should be developed to adapt to very high concentrations of CO2 and H2O in the flue gas. However, particle radiation generally plays a more important role than gas radiation. Computational fluid dynamics simulation data obtained with the Callide furnace have shown an oxy-fuel combustion of 27 vol.% O2 with flue gas recycling to have a similar heat absorption to air combustion. Fundamental and applications research are still required, however, to optimize boiler design and system configurations. Keywords: Oxy-fuel; combustion; coal; boiler; heat transfer; ignition; modelling; computational fluid dynamics

The configuration of Swiss-roll was adopted as a promising structure for the development of sub-millimetre scale combustors. In this study, the scaling effects are investigated both experimentally and analytically. Based on our first proto-type (64 mm in diameter), scaled-down combustors (45 mm) with different design parameters were fabricated; diameter of the combustor, top plate thickness, channel size and combustor material. A simple one-dimensional analytical model was constructed to interpret the combustion characteristics of the Swiss-roll combustors. Two energy equations for combustor body and mixture, along with species equations employing two-step global reaction model were solved. In spite of the simplicity of the present model, important characteristics of the combustors such as upper and lower flammability limits, effect of cap thickness on flammability limits were predicted well. Based on the analytical results, several smaller coin-size combustors (diameter 26 and 20 mm) were additionally developed and their characteristics were investigated. This study shows that the effects of design parameters are important in the practical development of smaller combustors.

The dual fluidised bed gasification technology is prospective because it produces high caloric product gas free of N 2 dilution even when air is used to generate the gasification-required endothermic heat via in situ combustion. This study is devoted to providing the necessary process fundamentals for development of a bubbling fluidized bed (BFB) biomass gasifier coupled to a pneumatic transported riser (PTR) char combustor. In a steam-blown fluidized bed of silica sand, gasification of 1.0 g biomass, a kind of dried coffee grounds containing about 10 wt.% water, in batch format clarified first the characteristics of fuel pyrolysis (at 1073 K) under the conditions simulating that prevailing in the gasifier intended to develop. The result shown that via pyrolysis more than 60% of fuel carbon and up to 75% of fuel mass could be converted into product gas, while the simultaneously formed char was about 22% of fuel mass. With all of these data as the known input, a process simulation using the software package ASPEN then revealed that the considered dual bed gasification plant, i.e. a BFB gasifier + a PTR combustor, is able to sustain its independent heat and mass balances to allow cold gas efficiencies higher than 75%, given that the fuel has suitable water contents and the heat carried with the product gas from the gasifier and with the flue gas from the char combustor is efficiently recovered inside the plant. In a dual fluidized bed pilot gasification facility simulating the gasification plant for development, the article finally demonstrated experimentally that the necessary reaction time for fuel, i.e. the explicit residence time of fuel particles inside the BFB gasifier computed according to a plug granular flow assumption, can be lower than 160 s. The results shown that varying the residence time from 160 to 1200 s only slightly increased the gasification efficiency, but the reaction time available in the PTR, say, about 3 s in our case, was too short to assure the finish even of fuel pyrolysis.

Calcium oxide has long been recognized as an effective in-bed catalyst for reforming or cracking tars generated in thermally decomposing hydrocarbon fuels such as biomass. Under pressures as high as 20 atm, the oxide was also widely tested as a good CO2 acceptor to capture CO2 on-site to produce high-caloric pipeline gas from gasifying coal and coal−coke. By using CaO as an additive of the fuel and bed material, the research detailed in this research note demonstrated that CaO could also be a substantially good CO2 acceptor for the atmospheric gasification of biomass, provided the reaction temperature is appropriately low, such as not much over 973 K. At temperatures >1073 K, the additive exhibited basically the catalytic effect only, which led the H2 content of the product gas to increase and the tar release with the gas to decrease.

The characteristics of small Swiss-roll combustors were investigated experimentally in detail. Three types of Swiss-roll combustors of different designs and two cases of heat transfer conditions were studied. The effects of design parameters on the performance of these combustors were examined. Each combustor consisted of a combustion region at the center (called the combustion room) and double spiral-shaped channels, the widths of which were smaller than the minimum quenching distance of a propane premixed flame at a normal state. Flames could be stabilized successfully for a wide range of equivalence ratios and mean velocities by using the recirculated heat from the burned gas, and blow-off was not observed. Temperature distributions of the combustors, variation of gas temperature, and the concentrations of the exhaust gas from the combustors were also investigated. Mean temperatures of the combustors were found to be governed by both the radiant heat loss from the combustors and the total chemical energy liberated by the combustors. Efficiencies of the combustors as heaters were evaluated. As a combustor became smaller, its thermal efficiency as a heater increased and its NOx emission decreased, while the emission of CO increased. By adding a catalytic reactor at the exhaust port, it was found that the emission of CO could be eliminated. This study provides new experimental results for a small Swiss-roll combustor, which represents an essential step toward the development of a microcombustor.

Interaction between droplet combustion and acoustic oscillation is clarified. As the simplest model, an isolated fuel droplet is combusted in a standing sound wave. Apart from the conventional idea that oscillatory component of flow influences heat and mass transfer and promotes combustion, a new model that a secondary flow dominates combustion promotion is examined. The secondary flow, found by the authors in the previous work, is driven by acoustic radiation force due to Reynolds normal stress, and named as thermo-acoustic streaming. Since the force is described by the same equation as buoyancy, i.e., F = Δ ρVg , the nature of the streaming is thought to be the same as natural convection. The flow patterns of the streaming are analyzed and its influence on burning rate of a droplet is predicted. Experimental investigation was mainly done with burning droplets located in the middle of node and anti-node of standing sound waves. This location realizes the strongest streaming. By varying sound pressure level, ambient pressure, and acoustic frequency, the strength of the streaming was controlled. Flame configuration including soot and burning rate were examined. Microgravity conditions were employed to clarify the influence of acoustic field through the streaming, since it is similar to and must be distinguished from natural convection. Experiments using microgravity conditions confirmed the new combustion promotion model and the way to quantify it. By introducing a new non-dimensional number Gr a , that is the ratio of acoustic radiation force to viscosity, burning rate constants for various ambient and sound conditions are rearranged. As a result, it was found that the excess burning rate ( k / k 0 − 1) is proportional to Gr a 0.5 or Gr a 0.25 , for weak sound and for strong sound, respectively.

The characteristics of microscale combustion were investigated by using a microchannel heated by an external source. The inner diameter of the channel was 2 mm, which was slightly smaller than the quenching distance of the stoichiometric methane–air mixture under normal conditions. The effects of the equivalence ratio and the averaged flow velocity on the characteristics of combustion in the microchannel were examined. At a channel‐wall temperature of ≈ 1000°C, flames could be stabilized at equivalence ratios of 0.05–1.9 and mixture velocities up to 150 cm/sec in a U‐shaped quartz‐glass channel. At moderate equivalence ratios and lower velocity conditions within the flammability region, oscillatory combustion was observed. A simple analytical model predicting flame oscillations on the basis of the linear analysis of steady solutions is proposed.

A one-dimensional char combustion model including pore structure effects is used to numerically investigate single char particle combustion for several different types of char samples. Previously, it is expected that small char particles have less combustion time. However, the present work shows that this is true only if the combustion time is defined as that needed for a char particle diameter diminished below a certain value. If the combustion time is defined as time needed for the carbon conversion ratio higher than a certain value, there are optimal particle sizes in a limited combustion period. Just reducing the char particle sizes may not get high carbon conversion ratios. It has also been found that, in general, the larger particles have higher temperatures at the exterior surfaces.

The extinction limits of methane-air diffusion flames in preheated air are studied experimentally and theoretically. The air temperature is varied in the wide range from ambient temperature (285 K) to as high as 1500 K. The fuel employed is methane with initial temperature of 300 K. Fuel or air diluted with Ar, N 2 , or CO 2 . For all conditions studied here, it is found that extinction of the diffusion flame occurs up to 1500 K, which is significantly above the auto-ignition temperature. The experimental results can be well reproduced in terms of pre-exponential factor and activation temperature of a hypothetical one-step overall reaction as determined by application of activation energy asymptotics.

In the present work, the effect of probability density function (PDF) selection and intermittency on the result of the numerical simulation are examined by the simulation of a turbulent methane-air jet diffusion flame, where air is preheated to 1073K. As to the PDFs, beta-function and clipped Gaussian are considered. It is found that intermittency has a large impact on the numerical result, while the choice of PDF has a minor influence. When intermittency is considered, the flame height becomes larger and maximum temperature decreases. Comparison of radial profiles with experimental data shows that it is necessary to consider intermittency also for high temperature air diffusion flames.

Characteristics of flame radiation and NO x emission of turbulent jet flame of ethylene and methane were investigated in highly preheated airflow of up to 1230 K. The radiative heat loss of the jet flame was obtained by summation of the local flame radiation measured by a narrow-view radiative heat flux meter. Radiant fraction, the ratio of the radiative heat loss to the heat of combustion, increases with preheated air temperature and exceeds 0.6 at 1200 K for a C 2 H 4 jet. This ratio shows that flame radiation gives a significant impact on the flame temperature and consequent NO x emission. As air temperature is increased, the NO x emission for CH 4 rapidly increases, but it does not in the case of C 2 H 4 up to 1100 K. The NO x emission level is as low as 3 g/kg-fuel at 1100 K, without detectable soot in the exhaust gas. The low NO x emission of the sooty flame in high-temperature airflow is due to the radiative heat loss and competing oxidation of carbon or CO and nitrogen. The important role of the radiation of flames in high-temperature air is also understood by diluting the fuels. The radiant fraction of the C 2 H 4 jet changed from 0.6 to 0.1 by N 2 dilution. The flame temperature of the undiluted C 2 H 4 jet was 250 K lower than that of 1005 diluted C 2 H 4 due to radiative heat loss. The NO x emission index also increases with dilution, as much as 10 times of that of undiluted C 2 H 4 . NO x production rate is scaled with representative flame temperature, which estimates the flame temperature considering the radiative heat loss and the fuel dilution. Good correlations between NO x production rate and representative flame temperature were obtained, indicating that the radiative characteristic is dominant for NO x emission in a highly preheated airflow.

The influence of acoustic fields on combustion of a single fuel droplet has been investigated using microgravity. The natural convection-free conditions allow the role of sound alone to be established by avoiding the coupling of sound-induced alternating convection and natural convection. Experiments were done with n -decane single droplets of about 1.5 mm in diameter. Sounds of 66.5 to 3353 Hz with sound pressure levels up to 135 dB were applied in a duct, which achieved maximum velocity amplitudes of about 1 m/s. As a result, a significantly deformed flame and a soot ring instead of soot shell were found in cases of large velocity amplitude. Burning rates increased with increasing velocity amplitude. The other parameters such as sound pressure level or frequency had little influence. Different influences of sound were found for droplets burning at different locations relative to the velocity antinode of the applied sound. All these observed phenomena are explained by the alternating convection due to sound and a unidirectional convection, which is a form of acoustic streaming, driven by the acoustic radiation force. A simple analysis has been made of the streaming mechanism and the increased burning rate. Differences with droplet location are explained by the enhancement in heat and mass transfer due to the two kinds of convection.

NO x emission levels of methane jet flames in high-temperature coflowing air up to 1470 K were measured. Special attention was paid to the relationship between the NO x emission levels and the lifted flames. In the coflowing air with temperature higher than the autoignition temperature, the flame was stabilized in far liftoff distance higher than the attached flame length. The NO x emission levels can be reduced remarkably by the far-lifted flames. When the liftoff height exceeded the attached flame length, the NO x emission levels rapidly decreased to 10% of that of the attached flames under the same coflowing air conditions. The low NO x emission level of the far-lifted flame was due to the decrease in flame temperature of the lean premixture formed at the flame base. The liftoff height changed with the air temperature and the fuel mass fraction of the jet. As the fuel was diluted by nitrogen, the rapid decrease of the NO x emission level by the far-lifted flame occurred in the higher temperature airflow. Also, the liftoff height at the rapid decrease became lower as the fuel mass fraction decreased. Compared with data in the literature, the local equivalence ratio at the critical liftoff base was between 1.0 and 1.3. From these results, the present mechanism of the low NO x emission can be applied in various combustion systems that utilize highly preheated air.

The combustion characteristics of coal char particles in either O2/N2 or O2/CO2 conditions were experimentally investigated. Especially, the char burnout, the char particle temperature and the shrinkage of the char particles were discussed. A Drop Tube Furnace (DTF: whose wall temperature was set at 873, 923 and 973 K) was used as the experimental apparatus. The experimental results revealed that, in equivalent oxygen concentration, the char burnout and the char particle temperature were higher in O2/N2 conditions than those in O2/CO2 conditions. The shrinkage of the char particle did not show the large difference in either O2/N2 or O2/CO2 conditions. Up to 15% of char burnout, the char particle diameters were reduced gradually. Up to 80% of char burnout, the char particle diameters were not changed. This is supposed that the chemical reaction is mainly occurred not on the external surface but on the internal surface of the char particle. Over 80% of char burnout, sudden shrinkage could be seen. Finally, an empirical equation for the prediction of the char particle shrinkage was introduced. Further investigation is required in high operating temperature, where CO2 gasification may have a large influence on the char burnout.

40th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit(11-14 July 2004), Fort Lauderdale, Florida, 資料番号: ARDS04015000, レポート番号: AIAA 2004-4153

We have developed a new fuel staged combustor, which consists of diffusion flame pilot burners and lean premixing prevaporizing main burners and is therefore called a multiple fuel nozzle type low NOx gas turbine combustor. The goal for NOx reductions was set to 70 to 80% compared with conventional gas turbine combustors. Combustion tests for a section of the annular combustor have been performed for pressures P3 up to 2.9Mpa and temperatures T3 up to 823K with kerosene. As the results, even under high pressure and temperature condition, stable combustion without the problem of auto-ignition or flashback could be achieved. NOx emission index is 13 [g/kg,fuel] which is equivalent to more than 70% NOx reduction. The liner wall temperature is lower than the durability limit. The dependency of NOx emissions on pressure and temperature for this combustor are reported.Copyright © 2001 by ASME

A novel reformer using highly efficient heat regeneration for tar-free syngas production is developed and its performance demonstrated in a pilot-scale plant using steam gasification. Basic design parameters of the regenerative tar reformer, namely residence time and amount of oxidant are determined based on numerical results. It has been predicted that good performance could be achieved at an operation temperature about 1573 K, the residence time exceeding 4 sec and an oxidant addition of 12% of the syngas flow rate. The regenerative tar reformer so designed shows stable operation. Over 99% of light and heavy tars are reformed to gas in the case of 11.3% oxygen addition to syngas. Further it is seen that a reduction of oxygen consumption more than 30% compared to a conventional oxidation reformer can be achieved. The formation of a high temperature zone has a strong influence on the tar reforming efficiency.

Upon irradiation, tetracyanoethylene (TCNE) in acetonitrile gave 2-amino-1,1-dicyanopropene, while tetracyanoquinodimethane (TCNQ) in isobutyronitrile gave 1-(4-dicyanomethylphenyl)-2-methylpropane-1,1,2-tricarbonitrile; mechanisms involving electron transfer in which liphatic nitriles behave as electron donors are proposed.