Asphalt Burning Experiment with Limit Oxygen Index Tester

From a tunnel safety perspective, the fire-retardant properties of asphalt are crucial. At present, the main indicators for evaluating the combustion performance of asphalt are flash point and fire point. This only describes the conditions under which asphalt can burn, but cannot explain the ability of asphalt to continue burning even though it is already on fire. In the chemical industry and other fields, the oxygen index is generally used to quantitatively describe the continuous combustion performance of materials, and there are corresponding standards and national standards. The limiting oxygen index tester can be used to test the oxygen index of asphalt and determine the combustibility of asphalt. Qisnun Precision Mechanical and Electrical Technology Co., Ltd. We are a manufacturer, and customers in need are welcome to call us in time.

Determination of the critical oxygen concentration for asphalt combustion:

Currently, the point of flashThe asphalt of roads is generally higher (much higher than normal temperature), at normal temperature, even if the oxygen concentration is increased, it is still difficult to ignite. During the test, some adjustments were made to the ignition method of the reference standard: after the asphalt sample was heated to a certain temperature, it was ignited and the oxygen concentration and duration of corresponding combustion have been tested. According to the observation of burning tests, many factors affect the continuous burning capacity test of asphalt. The R&D technical engineer of Qisnun Precision Mechanical and Electrical Technology Co., Ltd. made a comparison in three aspects: the temperature of the sample before combustion, thee sample volume and total air flow during combustion.

Heating temperature of the sample before combustion:

Reference standards generally stipulate that the test temperature is the normal temperature. Since the flash point of asphalt is much higher than this specification temperature (the minimum flash point required for medium and light traffic road asphalt is not less than 180°C), the Asphalt cannot ignite under such temperature conditions and the oxygen concentration must be adjusted between 60% and 80%. Neither can burn. Therefore, the asphalt must be heated to a certain temperature before performing the combustion test.

The specific heat capacity of asphalt is linked to its consistency and temperature. At 0°C, the specific heat capacity of asphalt is 1.672×10-6~1.7974×10-6J/(kg·°C). For each increase in temperatureture of 1°C, the specific heat capacity of the asphalt increases by 1.672×10-6~2.058×10-6J/(kg·°C). Combustion under different temperature conditions, due to the difference in specific heat of asphalt, there is a large difference between the heat required for combustion and the heat generated and transmitted, and the corresponding continuous combustion time is inconsistent, this which will inevitably cause the difference in the measured value of oxygen index. All conditions being equal, the higher the temperature, the greater the specific heat of the asphalt and the longer it can continue to burn. Therefore, the heating temperature of the sample before combustion is used as an influencing factor in the test comparison. Set other test conditions (including sample size, oxygen concentration and total gas flow rate, etc.), heat the sample to different temperaturesbefore burning and test how long it burns continuously.

Sample Size:

Difference in sample size determines the difference in heat absorption (release) during combustion and can also affect combustion performance supported by the asphalt. In order to test the influence of the sample quantity on the combustion time, the heating temperature before the trial combustion was fixed, the total air flow and the oxygen concentration were fixed. Test the correlation between different sample quantities and burn time.

Total Airflow:

During the combustion process, the velocity of the smoke (gas) flow has a greater impact on the heat transfer. Fast airflow speed may cause reverse flow in the direction of heat propagation, affecting the continuous burning time. At the same time, the heat transfer rate increasesand the heat inside the sample is not sufficient to sustain continuous combustion. Therefore, after fixing the sample quantity and heating temperature, using the same or similar oxygen concentration, changing the total air flow, and testing the impact of the total air flow on the burning time.

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