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Despite its long history of technological development, much charcoal production still relies on polluting and inefficient technologies utilizing traditional kiln designs. In addition to the need for improved charcoal production systems, the growing interest globally in pyrolysis of biomass to generate biochar as a soil fertility improver and for climate change mitigation may drive an increasing demand for such technologies. Accordingly, there is a clear need in developing countries for access to safe, affordable, and efficient open‐source designs and technology that can be fabricated locally. The design described here includes computational fluid dynamics modeling which demonstrated that the design exhibits a stable flow and combustion pattern. A hazard and operability (HAZOP) study, mass and energy modeling, and costing of all components and fabrication were also conducted for a prototype kiln that will accept up to 250 kg biomass h‐1. Fabrication and installation costs were estimated using actual commercial quotations based on detailed engineering drawings and design, and were found to be $580 000 for a 250 kg h‐1 unit. We therefore find that this pyrolysis system promises to be economical on a small scale. It can utilize waste lignocellulosic materials for feedstock, thus alleviating demand pressure on woodlands to provide feedstocks. It was, therefore, concluded that the pyrolysis unit described here promises to provide an affordable and efficient open‐source design that can be fabricated locally in developing countries without licensing restrictions or royalties.

An experimental analysis and computational modelling of thermal radiation from an INCONEL601 wire-mesh porous burner has been conducted. It has been found that within a bandwidth between 2 microns and 20 microns, the infrared radiation in the 2-5 microns waveband is the dominant band. Optimal operating conditions, as determined by the surface temperature and radiant intensity, are a function of the equivalence ratio and the firing rate. The location of the flame front is also influenced by these parameters. For fuel-rich mixtures the flame is usually located above the surface and the flame stability is sensitive to external perturbations. A maximum surface temperature of approximately 1223K, and a radiation intensity of 50 W/Sr, has been measured. It has also been shown that INCONEL601, despite its high emissivity, can be used as an effective radiation shield. By placing a piece of the wire-mesh in front of burning MTV pyrotechnic composition, the infrared radiation was significantly reduced. The equivalent black body temperature of MTV was cut from ~1900 deg. C without a shield to ~1400 deg. C with a shield adjacent to the mixture. A comparison between the ChemRad model predictions and measured surface temperature for various equivalence ratios has shown a reasonable agreement with a maximum discrepancy of 16% for fuel-rich mixtures. However, within optimal operating conditions of the burner (equivalence ratio 0.8-1) a maximum difference of 8% has been observed. Accounting for the variability in the measurements, the number of simplifying assumptions and the uncertainty in some values of the physical and optical properties, the accuracy and consistency of the model, as a first-order approximation is acceptable.

An experimental analysis and computational modelling of thermal radiation from an INCONEL601 wire-mesh porous burner has been conducted. It has been found that within a bandwidth between 2 micrometers and 20 micrometers, the infrared radiation in the 2-5 micrometers waveband is the dominant band. Optimal operating conditions, as determined by the surface temperature and radiant intensity, are a function of the equivalence ratio and the firing rate. The location of the flame front is also influenced by these parameters. For fuel-rich mixtures the flame is usually located above the surface and the flame stability is sensitive to external perturbations. A maximum surface temperature of approximately 1223K, and a radiation intensity of 50 W/Sr, has been measured. It has also been shown that INCONEL601, despite its high emissivity, can be used as an effective radiation shield. By placing a piece of the wire-mesh in front of burning MTV pyrotechnic composition, the infrared radiation was significantly reduced. The equivalent black body temperature of MTV was cut from ^1900 deg C without a shield to ^1400 deg C with a shield adjacent to the mixture. A comparison between the ChemRad model predictions and measured surface temperature for various equivalence ratios has shown a reasonable agreement with a maximum discrepancy of 16% for fuel-rich mixtures. However, within optimal operating conditions of the burner (equivalence ratio 0.8-1) a maximum difference of 8% has been observed. Accounting for the variability in the measurements, the number of simplifying assumptions and the uncertainty in some values of the physical and optical properties, the accurac and consistenc of the model, as a first-order approximation is acceptable., Original contains color plates: All DTIC reproductions will be in black and white.

A one-dimensional coupled chemistry-radiation model (ChemRad) for predicting combustion and heat transfer characteristics in a single and multi-layered porous media is presented. The model allows detailed gas and surface chemical kinetics mechanisms to be incorporated, and uses a two-flux radiation approximation in the energy equation. A stoichiometric propane/air mixture burning in a thin with mesh burner has been modelled using a well-documented high-temperature propane kinetics scheme with 40 reactive species and 93 reactions. A systematic analysis of the solution's sensitivity to variations in input parameters, particularly the optical characteristics of the media, has been performed and influential parameters have been identified. It has been found that the dornant factors that influence the solution, in order of significance are the area density, voidage and reflectivity of the porous material, and the ratio of forward-to-backward scattering of radiation., Original contains color plates: All DTIC reproductions will be in black and white.

This study examines in detail the equilibrium chemistry of Magnesium/Teflon (MT), Magnesium/Teflon/Viton (MTV), and MTV-air compositions. Gas-phase as well as solid-phase chemistry has been included. Equilibrium calculations accounting for over 47 species and various initial conditions have been performed. A comparison between MT and MTV combustion has been carried out with emphasis on investigating the effect of Viton on the combustion characteristics. The effect of air on MTV combustion has also been investigated for two possible MTV-air combustion models. A chemical kinetic mechanism with 18 reactions and 17 species, has been used to study the time evolution of reacting MT mixtures, accounting for finite-rate elementary reactions as well as performing sensitivity analysis with respect to reaction rates. Three different variations of the kinetic scheme have been studied and their effects on combustion products and flame temperature have been examined. Kinetic analysis has been repeated for three pyrotechnic compositions that are commonly used in flare and rocket motor igniter formulations.