Syngas production from liquid fuels in a non-catalytic porous burner

This paper investigates rich combustion of n-heptane, diesel oil, kerosene and rapeseed-oil methyl ester (RME) bio-diesel for the purpose of producing syngas ready for the clean-up stages for fuel-cell applications or for traditional combustor enrichment. Rich flames have been stabilised in a two-layer inert porous medium combustor and a range of equivalence ratios and porous materials have been examined. n-heptane was successfully reformed up to an equivalence ratio of 3, reaching a conversion efficiency (based on the lower heating value of H₂ and CO over the fuel input) up to 75% for a packed bed of alumina beads. Similarly, diesel, kerosene and bio-diesel were reformed to syngas in a Zirconia foam burner with conversion efficiency over 60%. A preliminary attempt to reduce the content of CO and hydrocarbons in the reformate has been also conducted using commercial steam reforming and water-gas shift reaction catalysts, obtaining encouraging results. Finally, soot emission has been assessed, demonstrating particle formation for diesel oil above φ = 2, whereas bio-diesel showed the lowest soot formation tendency among all the fuels tested.     

Combustion properties of some power station biomass fuels

In this study, the combustion properties of three of the UK’s commonly imported biomass fuels for co-firing, which are palm kernel expellers, shea residue, and waste from olive oil production are examined. The fuels were characterised and their thermal decomposition properties were studied by thermogravimetric analysis (TGA). Additionally the products from their devolatilisation were identified by gas chromatography-mass spectrometry (py-GC-MS) analysis of the evolved vapours and tars from high heating rate pyrolysis tests. Finally, chars from the fuels were prepared, analysed, and combustion studies were conducted by TGA-MS to determine the conversion of char-nitrogen to different nitrogen-containing species. In general, the main constituents of their ash fractions were K, Si, Ca and Mg, resulting in high alkali indices, which predict a large tendency to fouling. The pyrolysis and combustion kinetic parameters, estimated from TGA studies of these fuels and their chars, are much lower than those reported in the literature for lignocellulosic biomass. It is suspected that there is oil/fat evaporation processes overlapping with the decomposition of their lignocellulosic fractions, which significantly affects the apparent kinetics. The pyrolysis conditions used promoted depletion of nitrogen in the char, resulting in approximately 79-91% of the fuel-N being released with the volatiles. In combustion of the char, NO_x and N₂ are the major nitrogen compounds detected. Another primary product, HCN, was detected from the combustion of some of the fuel chars, as well as C₂N₂.     

Combustion of porous carbon particles in air

Combustion of a carbon particle in air is considered on the basis of a diffusion-kinetic model. Two regimes of combustion are shown to exist: high- and low-rate regimes. In the high-rate combustion regime, oxygen is totally consumed in a homogeneous reaction running above the particle surface and does not reach the particle, whereas carbon is consumed in a reaction with carbon dioxide. In the low-rate combustion regime, oxygen reaches the particle surface, and the reaction of carbon with oxygen producing carbon dioxide runs within the porous particle.     

Combustion of porous carbon particles in oxygen

A model is developed for the combustion of porous carbon particles in oxygen in a high-temperature furnace. Conditions for the existence of solutions to the equations of the model were found. A collation between the found region of existence of the solutions and experimental data shows that only some portions of the experimental curve fall within the region of existence of the solutions. These portions correspond to four different modes of particle combustion, and the realization of one or another mode depends primarily on the internal surface area of the particle. The mechanisms and some features of the modes of combustion of porous carbon particles in oxygen were considered.     

Propagation of weak disturbances in the combustion of compressible porous fuels

We have studied the properties of a system of equations describing the process of nonsteady propagation of a convective flame front through a porous compressible solid fuel, within the framework of a two-velocity model which takes into account the difference in pressure within the gas and the stresses in the condensed phase. We have determined a type of system of equations dependent on the differences in velocities and pressures in the phases. The continuous transition to earlier known solutions has been demonstrated for particular limit cases.Moscow. Translated from Fizika Goreniya i Vzryva, No. 2, pp. 26–34, March–April, 1991.     

Combustion of low heating value fuels and wastes in the spouted bed

In a spouted bed burner, the flow-maintained vortex of particles operates as a heat exchanger, preheating the incoming mixture without diluting it. This makes it a combustor especially attractive for incinerating low heating value fuels and wastes. Bench-scale experimental studies were carried out to assess the ability of the spouted bed to burn efficiently poor fuels and waste materials in various aggregative states. The paper reports results of two series of experiments with gaseous and liquid fuel-containing streams. High levels of hydrocarbon conversion and combustion efficiency were attained for mixtures that would not be combustible by other methods without an auxiliary fuel.     

Emulation of condensed fuel flames with gaseous fuels supplied through a porous copper calorimeter

The burning rate emulator (BRE) is a burner that emulates condensed fuel flames using gaseous fuel/inert mixtures by matching four properties: the heat of combustion; the heat of gasification; the laminar smoke point; and the surface temperature. Matching the heat of gasification requires measuring the burner heat flux, for which the BRE has embedded heat flux gauges and a copper top-plate calorimeter. Seven condensed fuels were emulated: acetone, ethanol, methanol, polyethylene, polymethylmethacrylate, polypropylene, and polystyrene. The gaseous fuels were methane, ethylene, and propylene, diluted with nitrogen. Emulation data and flame images are shown to demonstrate emulation accuracy. A new method of emulation is developed that shifts the focus on which properties are prioritized and yields ~15% improvement in flame height. Calibration and use of the calorimeter are shown to have improved accuracy (within 5%) which provides confidence in the results.