Methanol Combustion Research Articles

Behavior of Methanol and Formaldehyde in Burned Gas from Methanol Combustion : A Chemical Kinetic Study

A detailed chemical kinetic model has been proposed to explain the formaldehyde formation in a methanol fueled spark ignition engine. In comparison of the calculated results with the experimental results from a reactor tube, the reactions NO+HO2=NO2+OH and NO2+H=NO+OH became important for methanol oxidation and formaldehyde formation in exhaust gases with a large amount of nitric oxide. Accordingly, N-series reactions should be included in this scheme. According to the calculated results, methanol decreases with an increase of the residence time. On the other hand, formaldehyde increases to maximum value and then slowly decreases. At temperatures in excess of 950 K, methanol and formaldehyde oxidations are rapid, and complete in the residence time of 20 milliseconds. At temperatures below 800 K, methanol oxidation is considerably slower and formaldehyde is accumulated by increasing the residence time. The agreement between experimental and calculated results indicates that this proposed scheme is reasonable for studying formaldehyde formation mechanism.

Behavior of Methanol and Formaldehyde in Burned Gas from Methanol Combustion : Effects of Nitric Oxide on Oxidation Reaction

Calculations using a chemical kinetic model for the oxidation process of unburned methanol were carried out on exhaust gases from a methanol fueled S.I. engine at air-fuel equivalence ratios of 0.8, 1.0, 1.2, and 1.4. Good correlation between the calculated and experimental results were obtained for methanol reaction behavior as well as formaldehyde concentration profile. The conversion reaction of nitric oxide to nitrogen dioxide plays a significant role in the oxidation of unburned methanol and the formation of formaldehyde. The presence of molecular oxygen in exhaust gases has a favorable effect on this conversion. However rich the oxygen may be, methanol oxidation is extremely slow in the absence of nitric oxide. With rich oxygen, methanol oxidation is rapid due to an increasing nitric oxide. It is explained by considering those effects how the methanol reaction rate attains a maximum value in exhaust gases between airfuel equivalence ratios of 1.0 and 1.2.

A systematic method for validation of gas exchange measurements.

The measurement of gas exchange is useful, but thus far, has not been practical during the mechanical ventilation of critically ill patients. To validate two new commercial instruments, (Siemens-Elema Servo Ventilator 900B, Beckman Metabolic Cart), the authors constructed a lung model into which they delivered CO2 and N2 at precise rates to simulate Co2 production (Vco2) and O2 consumption (Vos). The model consists of 13.5-1 gas jar with an attached one liter anesthesia bag. The lung model was ventilated at present tidal volumes and frequencies. The authors also compared the measured respiratory quotient (RQ) with the known RQ of burning methanol (RQ = 0.67) in the jar. When the model was ventilated with levels of tidal volume and gas exchange applicable to adults, both instruments measured V02 within 5 to 13% of predicted values. Varying the FI02 did not significantly affect this accuracy. At tidal volumes below 350 ml, the difference increased between predicted VCO2 and measured VCO2. The difference between measured vs. the actual RQ of methanol was 5 and 1.5% in the Siemens-Elema and Beckman Systems, respectively.

Behavior of Methanol and Formaldehyde in Burned Gas from Methanol Combustion : A Chemical Kinetic Study

Behavior of Methanol and Formaldehyde in Burned Gas from Methanol Combustion : A Chemical Kinetic Study

Behavior of Methanol and Formaldehyde in Burned Gas from Methanol Combustion : Effects of Nitric Oxide on Oxidaion Reaction

火花点火メタノールエンジンの排気系において, 未燃メタノールの酸化過程には, NOからNO2への変換反応により生成されるOHラジカルが, O2の存在と共に重要であることを, 反応動力学モデルを用いて説明し, 実験結果と対比させた. メタノールの消滅速度は, NO濃度の高い理論当量比付近において最大となる. 一方, ホルムアルデヒド濃度は, O2濃度が高く, しかもNO濃度の低い場合に高くなることが明らかとなった.

Flame quenching in front of a cold wall under two-step kinetics

The transient process of laminar flame quenching at a cold wall is studied. A plane flame is assumed that travels perpendicularly toward the wall. The kinetic model A + B → 2B and 2B → C consists of a chain branching and a chain breaking step. The theoretical results indicate that the history of the quenching process depends essentially on the magnitude of the intermediate species B that might be viewed as a radical. The radical level is a function of the ratio of the frequency factors of the chain breaking to the chain branching reaction. If the chain breaking reaction is fast, the radical level is low and the quenching process is rapid once it has been initiated. If the chain breaking reaction is slow, a large amount of radicals sustains the first reacton and the flame remains in front of the wall for a much longer time. During this period all the fuel in the quenching layer is finally consumed. The comparison with a calculation with a complete set of elementary reactions for the combustion of acetylene and methanol in air shows that high radical levels and complete fuel consumption are realistic features of real flames. This indicates that the two-step process chosen in this study is adequate to describe the flame quenching process at a cold wall in its essential features whereas a one-step global mechanism is not.

In Situ Optical Particle Sizing Technique

This paper discusses the application of an in situ optical counter to the measurement of liquid fuel droplets and solid coal particles under combustion conditions. Mie theory computations are used to determine an optimal near-forward light-scattering geometry for sizing both spherical transparent particles and irregularly shaped light-absorbing particles in the 5-80 /im range. Results are presented for a burning methanol spray and for reacting coal particles. I. Introduction T HERE is considerable interest in the measurement of particle size distributions in two-phase flows. Specific examples of energy-conversion devices in which such measurements are desirable include liquid spray and pulverized fuel combustors, and particulate cleanup devices such as electrostatic precipitators. While the particulate characteristics such as mean diameter, size distribution, mass loading, and material properties may vary in such systems, the sizes of interest generally fall in the submicron to 100 jim range, with number concentrations up to 107 cm~ 3 for submicron-sized particulates. The available measurement techniques1'2 also vary widely in type and capability. Several, including microscopy, cascade impactors, Coulter counters, mobility analyzers, and commercial optical counters, require a sample to be extracted from the flow. This poses problems related to obtaining a representative sample, especially for the larger-sized and volatile materials in hot, high-velocity flows. Also, many sampling methods are cumbersome and slow in operation. For these reasons, optical techniques are of special interest since they are capable of making in situ measurements with continuous and rapid readout. Moreover, by using lasers, they are adaptable to high-temperat ure systems having high thermal radiation background. Optical techniques all depend on Mie scattering3'4 and can be broadly divided into imaging and nonimaging types. The former, including flash photography5 and holography,6'7 are limited in practice to sizes 19 the theory and initial measurements of a new in situ counter technique utilizing the last approach have been described. The present paper briefly reviews the basis of the measurement technique described in Refs. 18 and 19, and then discusses the instrument requirements necessary for measurements of relatively large (5-80 /ion) particles with variable light-absorbing properties. Light-scattering computations using the Mie theory are presented for several nearforward light-collection geometries, and optimal conditions are defined. Based on these results and previous corn

Catalyst for on-board reforming of methanol. Catalytic partial combustion and decomposition of methanol.

In order to develop a catalyst and a system applicable to on-board reforming, catalytic conversion of methanol was investigated in an isothermal flow reactor. Among the catalysts tested, the highest activity for partial combustion of methanol was attained with a silica-supported copper-nickel catalyst, which was also active for decomposition of methanol. The X-ray analysis of the copper-nickel catalyst showed that the metals or their oxides were highly dispersed in the course of partial combustion of methanol. Methanol conversion on this catalyst increased with increasing partial pressure of oxygen. The enhanced reactivity of methanol in the presence of oxygen was interpreted by the following mechanism: methanol reacts very rapidly and selectively with oxygen to give a formaldehyde-type intermediate which decomposes to hydrogen and carbon monoxide. The stoichiometric reaction between methanol and oxygen proceeded completely at 200°C, while direct decomposition of methanol to hydrogen and carbon monoxide required much higher temperatures.

Ionization in a methanol-oxygen flame

The combustion of methanol was studied in a conical methanol—oxygen flame of fuel-lean composition (equivalence ratio φ = 0.25) burning at atmospheric pressure surrounded by a flowing argon shield. Oxygen bubbled through liquid methanol contained in two gas saturators provided a premixed flame of excellent stability and reproducibility. The flame gas was sampled into a mass spectrometer which was used to detect a variety of naturally occurring ionic species, both positive and negative. Although the maximum level of ionization in this flame had the rather low value of 5 × 10 8 ions ml −1, nevertheless concentration profiles were drawn as a function of distance along the flame axis at 17 individual mass numbers ( m/z) for positive ions and 11 for negative ions; that is, whenever an appreciable signal could be detected below 100 amu. The positive profiles in the reaction zone are dominated by proton transfer processes which indicate that CHO + is the primary ion. A variety of protonated combustion intermediates and products were detected including both stable molecules (H 2O, HCHO, the CH 3OH fuel, CH 2CO, CH 3CHO, HCOOH and possibly CH 3OCH 3/C 2H 5OH) and radicals (C, CH, CH 2, HCO, CH 2OH or CH 3O, CH 3CO or CH 2CHO, and possibly CH 3OO). Chemical ionization by charge transfer is certainly operative for two species (O 2 and NO as an impurity) and perhaps others (CH 3, O). As far as the negative ions are concerned, a number of species can be ionized in the reaction zone by three-body electron attachment and subsequent charge transfer processes (O 2 initially, and then O, OH, HO 2, HCOO and possibly HCOOO). Some of these negative ions are sufficiently strong bases to abstract protons from other species in proton transfer reactions (CH 3OH, possibly H 2O 2, HCOOH, and perhaps the peroxidic intermediates HCOOO and HCOOOH). The remaining negative ions detected can be interpreted as cluster ions (OH − · H 2O, HO 2 − · O 2 or HO 2 − · CH 3OH, CHO 3 − · H 2O). All of this ion chemistry was compared with that observed previously for an analogous fuel-lean methane—oxygen flame. Many similarities were noted, particularly downstream, for both positive and negative ions. However, the combustion path leading to formic acid is more prominent in the methanol flame.

Vehicle evaluation of neat methanol—compromises among exhaust emissions, fuel economy and driveability

Methanol was evaluated as an alternative fuel in vehicles with spark-ignited, internal-combustion engines. Acceptable driveability was achieved with a methanol-fuelled car equipped with electronic fuel injection (EFI) which was modified to provide proper air-fuel ratios for methanol. the target level for driveability was not achieved with a methanol-fuelled carburetted car modified to provide proper air-fuel ratios for and increased vaporization of methanol. With the EFI car, using the average equivalence ratio (Φa = 0·96) and spark timing designed for the production gasoline car, exhaust emissions and fuel economy with methanol fuelling were compared to those with gasoline. With methanol, compared with gasoline, 60 per cent lower NOx, 3·5 times higher unburned fuel emissions (UBF), and similar CO engine emissions were measured. the air pollution significance of the higher UBF emissions from methanol combustion is unknown because the UBF species (mainly methanol) are different from those from gasoline combustion. A catalytic converter decreased emissions of UBF and CO similarly for both fuels. Fuel economy with methanol—about half that of gasoline on a volume basis—was 7–10 per cent better on an energy basis than that with gasoline. With methanol fuelling, spark timing and Φa were varied from production values to obtain a more acceptable compromise among driveability, exhaust emissions and fuel economy. While fuelling with methanol at Φa = 0·96, using best power rather than production spark timing increased fuel economy 3 to 6 per cent without significantly affecting emissions and driveability. As Φa was leaned to 0·62 while maintaining best-power spark timing engine and tailpipe (after converter) CO emissions decreased, engine UBF emissions increased, NOx and tailpipe UBF emissions were not greatly affected, and driveability deteriorated. With best-power spark timing and the Φa for maximum economy (0·83), driveability was acceptable, and CO and NOx emissions met the 1977 standards. At Φa = 0·83, NOx emissions were reduced below the statutory standard (0·4 g/mile) by retarding spark timing; however, driveability and fuel economy deteriorated. Although the feasibility and benefits of operating vehicles with neat methanol have been demonstrated, not all problems of methanol fuelling (for example, cold start) were addressed. In addition, other alternatives such as obtaining hydrocarbon liquids from coal or using methanol as fuel for stationary powerplants must also be considered to obtain the most efficient utilization of energy resources.

Oxides of nitrogen formed in high-intensity methanol combustion

The oxidation of methanol in a jet-stirred reactor has been studied to characterize the mechanisms of methanol combustion and nitric oxide formation in a high-intensity, turbulent environment. Fuel/air equivalence ratios of 0.7 to 1.4 were investigated at a constant temperature of 1870 K and mean reactor residence times of ca. 2.5 msec. Total NO x was measured along with major cornbustion products, CO, CO 2 , H 2 O, O 2 , CH 4 , and C 2 H 2 . Emission spectroscopy was used to determine oxygen atom concentration as well as relative levels of electronically excited radical species, OH • , CH • , and C 2 • . Comparative measurements were repeated with methane as the fuel under similar reactor conditions. Measured NO x for methanol was 8.5 ppm maximum at equivalence ratio 1.10. The ratio of methanol-NO x to methane-NO x varied between one-half for fuel-lean combustion to one-third for equivalence ratios at or above stoichiometric. Molecular O 2 , atomic-O and calculated OH were essentially the same for both fuels. At fuel-rich conditions, methanol demonstrated higher carbon monoxide. Concentrations of CH 4 and C 2 H 2 were markedly higher with methane fuel, as were CH • and C 2 • while OH • was slightly higher. Evidence indicated the persistence of the C−O bond in the methanol molecule during oxidation. The NO x , O-atom, and O 2 concentrations indicated that the extended Zeldovich mechanism was insufficient to explain the difference in observed NO x for methanol and methane. It was hypothesized that hydrocarbon fragments played an important role in NO x formation in the stoichiometric and rich mixtures; it was concluded that low methanol-NO x was due to low hydrocarbon levels.

Radiation From a Methanol Furnace

Monochromatic intensity measurements are taken in a water-cooled furnace, 20 cm in diameter, burning methanol and a methanol/coal slurry. The primary interest is to determine the contribution of particulate radiation to the total intensity. Temperature, carbon dioxide, carbon monoxide, water, methanol, and particulate concentration levels are quantitatively measured throughout the furnace chamber. A computer code is discussed which integrates the equation of transfer over a nonhomogeneous path containing combustion gases and particulates. This allows comparison of the measured intensity with a theoretical prediction based upon known concentration and temperature profiles. The intensity and emittance measurements from the methanol furnace are compared with measurements in other experimental furnaces burning oil and gas.

Asymptotic theory of diffusion-flame extinction in the stagnation-point boundary layer

An analysis is developed for predicting extinction of the diffusion flame that is established when an oxidizing gas flows about the nose of a vaporizing fuel body. Use is made of the limit of a large ratio of the activation energy to the thermal energy at the flame for the overall combustion process, since this limit encompasses all cases of practical interest. By revealing a correspondence with the asymptotic flame structure of a counterflow diffusion flame analyzed earlier, the theory makes available explicit formulas, in term of a Damköhler number, for study of gas-phase extinction in the present geometry. From these results a simplified but reasonably accurate method is developed for obtaining, from experimental data on extinction, kinetic information concerning the overall oxidation process occurring in the vicinity of extinction. Curves calculated from a parametric study are presented to facilitate application of the technique, and the procedure is illustrated for methanol burning in oxygennitrogen mixtures.

Synthesis of methanol from natural gas and methanol combustion

This paper deals with the explanation of a synthesis of methanol from natural gas and the technological investigation of methanol combustion at power plant.The author takes up three important factors for which methanol fuels are untilized at domestic power plants. They are;(1) the problem of stabilised supply during long time.(2) the problem of economical supply price.(3) the problem of combustion characteristics; flue gas status during methanol combustion.

The reaction of methanol with atomic oxygen

1. The rate constant of the reaction of methanol with atomic oxygen was determined for the temperature 310–800°K, equal to k=7.1±0.12 · 10−12 exp(−2030±134/RT) cm3/molecule · sec. 2. A mechanism was proposed for the oxidation (combustion) of methanol, characterized by the presence of stable intermediate products: formaldehyde, hydrogen, hydrogen peroxide, and carbon monoxide.

Flame characteristics in the wake of a burning methanol drop

Flame characteristics in the wake of a burning methanol drop

Fuel droplet burning rates at high pressures

Combustion of methanol, ethanol, propanol-1, n-pentane, n-heptane, and n-decane was observed in air under natural convection conditions, at pressures up to 100 atm. The droplets were simulated by porous spheres, with diameters in the range from 0.63 to 1.90 cm. The pressure levels of the tests were high enough so that near-critical combustion was observed for methanol and ethanol. Due to the high pressures, the phase-equilibrium models of the analysis included both the conventional low-pressure approach as well as high-pressure versions, allowing for real gas effects and the solubility of combustion-product gases in the liquid phase. The burning-rate predictions of the various theories were similar, and in fair agreement with the data. The high-pressure theory gave the best prediction for the liquid-surface temperatures of ethanol and propanol-1 at high pressure. The experiments indicated the approach of critical burning conditions for methanol and ethanol at pressures on the order of 80 to 100 atm, which was in good agreement with the predictions of both the low- and high-pressure analysis.

Feasibility Demonstration of Electrostatic Precipitation at 1700°F

An experimental high-temperature, high-pressure electrostatic precipitator module has been designed, fabricated and then evaluated in a gaseous environment having the characteristics anticipated for the combustion chamber of a system for generating electric power from the incineration of municipal solid wastes. Stable positive and negative corona discharges were established in combustion gases from the burning of methanol and air (temperature and pressure approximately 1700°F and 100 psig, respectively) without any apparent deleterious effects due to thermal ionization and/or emission. At gas conditions of about 1700°F and 50 psig, positive polarity energization of the discharge electrode appeared superior to that of negative polarity in terms of voltage level that could be applied and electrical stability. However, precipitator performance on removal of alumina dust injected under controlled conditions with the methanol fuel, showed negative polarity to be superior to positive polarity at the selected co...

Pulsating combustion of liquid fuel in partially closed vessels

Two modes of combustion are possible for a liquid fuel in a vessel that is closed except for a single orifice: constant pressure diffusion burning and pulsating combustion. An experimental and theoretical investigation has been made of the pulsating mode of combustion using methanol liquid fuel. Measurements were made of liquid-fuel burning rates and of chamber pressure as a function of time in cylindrical vessels for various chamber lengths and orifice diameters. In addition, high-speed schlieren motion pictures were taken of the pulsating combustion process in order to obtain qualitative information about flow patterns, mixing, and ignition during each combustion cycle. Self-sustained pulsating combustion was found to be possible only within certain limits of chamber length and orifice diameter. Within these limits, combustion frequency ranged from about 25 to 70 c/s, and was always smaller than the Helmholtz resonator frequency by at least a factor of three. Pressure amplitudes varied from about 10 to 85 mm of mercury. Methanol burning rates were found to be as much as eight times larger than those for steady diffusion burning in open-top cylinders of the same size. Other liquid fuels, in addition to methanol, were found also to exhibit pulsating combustion. A theoretical analysis gives chamber pressure as a function of time during the pressure decay part of each cycle and agrees substantially with experimental measurements.

The effect of surface on the slow combustion of methanol

The effect of surface on the slow combustion of methanol