Thermogravimetric analysis method for testing the thermal stability of coal

The industrial analysis of coal includes the determination of moisture, ash content, volatile matter, and fixed carbon. Traditional methods require the use of equipment such as muffle furnaces and ovens, which are cumbersome and have significant errors. Thermogravimetric analysis is a commonly used method for evaluating the thermal stability of coal and is widely applied in coal analysis. It is mainly used to study the pyrolysis, combustion characteristics, volatile matter release, ash residue, and reaction kinetics of coal.

　　1、 Testing principle

When coal is heated in inert gas, it undergoes a pyrolysis process: volatility gradually precipitates, and carbon and ash residues are fixed. Thermogravimetric analyzer monitors the mass changes of coal samples during the heating process in real time, and draws mass and temperature as well as DTG differential curves to analyze their pyrolysis characteristics.

　　2、 Experimental testing steps

1. Sample preparation: Grind the coal sample into a uniform powder and take 15-30mg of the sample to avoid heat transfer differences caused by uneven particles.

2. Equipment:DZ-TGA101 Thermogravimetric Analyzer

3. Equipment parameter setting

Atmosphere: High purity nitrogen (avoiding oxidation reactions, simulating pyrolysis environment), gas flow rate is usually 50ml/min

Temperature program: From room temperature to 800 ° C (adjusted according to experimental requirements), the recommended heating rate is 20 ° C/min

4. During the testing process, evenly spread the sample at the bottom of the crucible to avoid accumulation, run the thermogravimetric analyzer equipment program, and record the TG changes.

5. Data analysis

The coal pyrolysis stage is mainly divided into three stages with the increase of temperature

During the drying and dehydration stage (room temperature -200 ℃), adsorbed water and some bound water are removed. As shown in the figure, the weight loss from 50 ℃ to 200 ℃ is 7.64%.

5.2 Volatile analysis stage (200 ° C-600 ° C), also known as the main pyrolysis stage, involves the cracking and volatilization of organic matter to produce tar, CH4, etc. Always around 42.6%.

During the final decomposition stage (600 ° C-800 ° C), the carbon content further decomposes and then tends to stabilize.

　　3、 The role of thermogravimetric analyzer in measuring the thermal stability of coal

1. Evaluate the thermal stability of coal. Thermogravimetric analyzer can evaluate the thermal stability of coal at high temperatures by measuring the mass change of coal samples during heating.

2. Analyze the pyrolysis rate and weight loss. As the temperature increases, the rate of coal pyrolysis will change. Thermogravimetric analyzer can accurately measure the rate of mass change of coal at different temperatures, namely the pyrolysis rate. By analyzing the pyrolysis rate curve, the speed of coal pyrolysis reaction can be understood.

3. Evaluate the impact of additives on the thermal stability of coal. In order to improve the thermal stability of coal, some additives are sometimes added. Thermogravimetric analysis can be used to evaluate the effectiveness of these additives. Compare the differences in quality temperature curves by conducting thermogravimetric analysis on coal with and without the addition of additives.

　　4、 Precautions during the experimental process

1. Uniformity of the sample: If the sample particles are uneven, it may cause fluctuations in the test results.

2. Heating rate: Adjust the appropriate heating rate, as too fast or too slow a rate can affect the test results and reaction details.