Javier Garcia-Torrent

Experimental determination of self-heating and self-ignition risks associated with the dusts of agricultural materials commonly stored in silos.

Agricultural products stored in silos, and their dusts, can undergo oxidation and self-heating, increasing the risk of self-ignition and therefore of fires and explosions. The aim of the present work was to determine the thermal susceptibility (as reflected by the Maciejasz index, the temperature of the emission of flammable volatile substances and the combined information provided by the apparent activation energy and the oxidation temperature) of icing sugar, bread-making flour, maize, wheat, barley, alfalfa, and soybean dusts, using experimental methods for the characterisation of different types of coal (no standardised procedure exists for characterising the thermal susceptibility of either coal or agricultural products). In addition, the thermal stability of wheat, i.e., the risk of self-ignition determined as a function of sample volume, ignition temperature and storage time, was determined using the methods outlined in standard EN 15188:2007. The advantages and drawbacks of the different methods used are discussed.

Determination of the risk of self-ignition of coals and biomass materials

The safe storage, processing and handling of coals and biomass resources requires their tendency to self-ignite be understood; fires caused by self-ignition have occurred on many occasions in ports and at industrial plants. This work provides information on the tendency of several types of coal and four types of biomass to self-ignite. Data were obtained using the isothermal oven procedure and analyzed using the Frank-Kamenetskii method and a scaling procedure, both contemplated in standard EN15188. The results obtained throw light on the optimum volumes and storage times of the studied materials. The results also validate the methodology followed for determining the risk of self-ignition.

Biomass dust explosibility at elevated initial pressures

Abstract This paper describes a series of explosion tests carried out with biomass at high initial pressures. Atmospheric tests were developed in a 20 1 sphere, and a hyperbaric series at 1 and 1.5 MPa in a 1 m 3 sphere. Depending on concentration, one or two points of dispersion were used and the injection impulse varied from 2.0 to 3.5 MPa, achieving different levels of turbulence. Both the great influence of turbulence on the rate of pressure rise and the high severity and sensibility shown by biomass have contributed to the development of very violent explosions at elevated pressures and concentrations. Also, biomass has shown irregularities in the flame front propagation due to its inhomogeneity. Quite high initial pressures have been experimented with and a material with great projection for energetic applications has been analysed.

Determination of parameters used to prevent ignition of stored materials and to protect against explosions in food industries.

There are always risks associated with silos when the stored material has been characterized as prone to self-ignition or explosion. Further research focused on the characterization of agricultural materials stored in silos is needed due to the lack of data found in the literature. The aim of this study was to determine the ignitability and explosive parameters of several agricultural products commonly stored in silos in order to assess the risk of ignition and dust explosion. Minimum Ignition Temperature, with dust forming a cloud and deposited in a layer, Lower Explosive Limit, Minimum Ignition Energy, Maximum Explosion Pressure and Maximum Explosion Pressure Rise were determined for seven agricultural materials: icing sugar, maize, wheat and barley grain dust, alfalfa, bread-making wheat and soybean dust. Following characterization, these were found to be prone to producing self-ignition when stored in silos under certain conditions.

Inerting biomass dust explosions under hyperbaric working conditions

The aim of this work is to study the influence of initial pressure on the limiting oxygen concentration for a biomass dust. Atmospheric tests were carried out in the 20-1 sphere. Hyperbaric tests at 0.5, 1.2 and 1.8 MPa were developed in a 1-m3 spherical vessel. This study used unusually high initial testing pressures, and it was performed with a renewable material with great potential in pressurized processes that has very special properties such as its low density and fibrousness. Contrary to the trend indicated by other research (usually for coal), it has been found for biomass that an increase of the initial pressure yields an increase in the limiting oxygen concentration.

Improvement in the correlation between the composition index and the explosibility index for coal dust

Abstract The correlation previously found between composition and explosibility index for coal dust has been improved by means of three main modifications: use of better laboratory apparatus, correction of volatile matter data and increased number of samples. The new mathematical expressions proved to be consistent and useful as a first approach to improve classification of ignition risk and to apply protective measures against the occurrence of dust explosions.