Tomáš Chrebet

Moment of Lignocellulosic Materials Ignition Defined by Critical Mass Flow Rate

On the base of experimental observations of mass loss rate in dependance of time in isothermal condition in circulating air atmosphere was determined the moment of lignocellulosic materials ignition. Experiment was performed in an electrically heated hot-air furnace according to ISO 871 standard (Setchkin furnace) in conjunction with precision scales. Experiment was performed with ignition source. The ignition source was kanthal wire. Experiment was performed at one temperature, three positions of samples in the oven and various air-flow speeds. Pure cellulose as a model compound was impregnated by water solution of KHCO3 and (NH4)2HPO4.

A Comparison of the Behaviour of Spruce Wood and Polyolefins during the Test on the Cone Calorimeter

This article deals with comparison of the behaviour of spruce wood and polyolefins (polyethylene PE and polypropylene PP) during the test on the cone calorimeter. Samples were tested on the cone calorimeter at heat flux of 20 and 40 kW/m2. An evaluation of the behaviour of examined materials was based on the determination of the maximum and the average heat release rate, yield of carbon monoxide (CO), and relative comparison of tendency to fire propagation in a flashover phase. The tendency of materials to fire propagation in the flashover phase was evaluated based on the Pearson ́s correlation, the Spearman ́s correlation and the Kendall ́s correlation coefficient of HRR-CO and CO2-CO. Spruce wood showed better properties in comparison with PE and PP in all evaluated parameters (the maximum and the average heat release rate, the yield of CO, and also the resistance to fire propagation in the flashover phase. Additionally, spruce wood showed significantly lower sensitivity of dependence of the maximum and also the average heat release rate on external heat flux.

Activation Energy of Pure and Impregnated Lignocellulosic Materials Obtained by Isothermal Method

On the base of experimental observations of mass loss rate in dependence of temperature in isothermal condition in circulating air atmosphere was determined the activation energy of lignocellulosic materials degradation without and with retardants. Experiment was performed in an electrically heated hot-air furnace according to ISO 871 standard (Setchkin furnace) in conjunction with precision scales. Degradation of lignocellulosic materials was performed at various temperatures and various air-flow speeds. Pure cellulose as a model compound was impregnated by water solution of KHCO3 and (NH4)2HPO4.

Monitoring of Thermal Degradation of Fireproof Coating

Under the fire conditions, the resistance of cable distribution is required for a fixed period, depending on the intended use of the cable. To increase the fire resistance of cables a fireproof coating may be applied. Article deal with the behavior of the fireproof coating during elevated temperature. Concretely, the aim is monitored a coating weight change under the conditions of dynamically increasing temperature and with or without using air-flow. It is also monitored the change in weight, depending on the isothermal temperatures in dynamic air atmosphere.

Influence of the Position of Ignition Source on the Raw Materials Used to Produce Biofuel in Form of Wood Pellets

The aim of present work is monitoring thermal decomposition tested samples depending on distance of ignition source, subsequent generation of flame and flameless combustion. Tested samples are used to produce biofuel in form of pellets, which can be made of spruce wood (Picea excelsa, L.) and beech wood (Fagus sylvatica) and have a direct effect on the properties of these pellets. Measurements are carried out according to standard STN ISO 871:2010 Determination of ignition temperature using a hot-air furnace. External ignition source (electrically heated spiral of the wire canthal) is used to analyze different conditions of test samples. Distance between external ignition source and tested samples is 10, 50 and 90 mm. The experiments are performed at an air flow rate 38, 25, 12,5 and 0 mm.s-1. The results show the rate of loss of weight and the flow rates of the material of the test samples at the different test conditions.

Fire Risk Assessment of Spruce Pellets

In the presented paper is assessed fire risk of pellets made from spruce wood (Picea abies L.) without bark, processed by hot pressing without the use of additional chemicals. Fire risk was assessed on the basis of heat release rate (HRR), the specific carbon monoxide production rate (SCPR) and the time dependence of the induction period of spontaneous ignition on temperature. HRR and SPCR were determined on the cone calorimeter test performed according to ISO 5660-1:2002 standard. Samples were loaded by 20 kW/m2 heat flux during the test. The maximum HRR was 229 kW/m2 and average HRR was 55 kW/m2. Maximum SCPR was 0.37 g/(m2s) and the average SCPR was 0.16 g/(m2s). The dependence of the induction period of spontaneous ignition on temperature was determined by a modified test performed according to ISO 871:2006 standard. Modification of the test procedure was based on measurement of the induction time period of the spontaneous ignition on temperature, and temperatures higher of 20, 40, 60, 80 and 100 °C than spontaneous ignition temperature. The obtained data proved an exponential dependence of the induction period of spontaneous ignition on temperature.

Study of Thermal Stability of Magnesium Alloys

Today, magnesium (Mg) alloys are recognized alternatives to iron and aluminum to reduce the weight of structural materials. This contribution was performed to provide information on the flammability of magnesium alloys through investigation of the ignition temperature of selected Mg alloys. The test was performed in a muffle furnace with dynamic heating program. Also were performed tests of chemical composition of studied specimens.

Comparison of Optical Smoke Density of Expanded Polystyrene without and with Cover Components Used in ETICS

This paper deals with expanded polystyrene (EPS) as a potential source of smoke. We compared specific optical density of smoke from EPS and EPS strengthened by glass fibre mash and plaster which is used in external thermal insulation composite systems (ETICS). There was used testing method by ISO 5659 Plastics Smoke generation Part 2: Determination of optical density by a single-chamber test. The samples were exposed to a constant 50 kW.m-2 of thermal radiation. There was not used a pilot burner. During flame combustion samples evolved high amount of smoke. Samples from EPS released more smoke like samples with ETICS cover.

The Effect of External Conditions on Ignition Temperature of Thermoplastic Polyurethane Elastomers

The paper reports a study of the impact of moisture and age of pellets, as well as an external condition, on the thermal degradation of the thermoplastic polyurethane elastomers. Because thermoplastic polyurethane elastomers are hydroscopic polymer, moisture will have a significant impact on thermal degradation. For determination of the effect of moisture and age were used the thermo gravimetric analysis, differential scanning calorimeter and ISO STN 871: Plastics. Determination of ignition temperature using a hot-air furnace.

Investigation of Airflow Influence on Self-Heating Process of Linseed Oil Using Safety Calorimeter SEDEX

The oxidative self-heating process of vegetable oil with high content of unsaturated fatty acids was investigated by the means of sequential scanning calorimetry in safety calorimeter SEDEX. The oil was applied on the cotton, and was put to the standard pressure sample vessel, which was modified for air inlet. The behavior of sample was studied under three rates of air flow. First experiment was carried out in the temperature range between approximately 30 and 350°C at a heating rate of 45°C/h. Second scanning was carried out in the temperature range from 30 to 200°C at heating rate of 10°C/h.