GB/T 18511-2017Determination of ignition temperature of coal (English PDF)

3.1 Ignition Temperature

Ignition temperature refers to the minimum combustion temperature, at which, coal emits enough volatiles to form a combustible mixture with the surrounding atmosphere. [GB/T 483-2007, Definition 3.2.35]

6.1 Ignition Temperature Determination Device

The device is shown in Figure 1. See the requirements for the various parts below:

a) Heating furnace: round; can be heated to 600 °C; temperature adjustable.

b) Heating body: made of copper or aluminum alloy; 7 holes; see Figure 2.

c) Temperature measurement and control instrument: can control the temperature-rising rate from 4.5 °C/min to 5.0 °C/min within the range of 100 °C ~ 500 °C; temperature measurement accuracy is ± 1 °C.

d) Buffer ball (see Figure 3).

6.6 Analytical Balance

Division value: 0.1 mg.

6.7 Glass Weighing Bottle

Diameter: 40 mm; height: 25 mm; with a tight grinding cover.

6.8 Agate Mortar

7.1 Raw Coal Sample

In the weighing bottle, weigh-take 0.5 g ~ 1.0 g of coal sample for general analysis and test. Place it in a vacuum drying oven at the temperature of 55 °C ~ 60 °C and the pressure of 53 kPa to dry for 2 h. Then, take it out and put it into a desiccator to cool down to the room temperature. Before the test, weigh-take 0.09 g ~ 0.11 g of dried coal sample and 0.075 g of sodium nitrite; gently grind them in an agate mortar for 1 min ~ 2 min; evenly mix it up.

7.2 Oxidized Coal Sample

In the weighing bottle, weigh-take 0.5 g ~ 1.0 g of coal sample for general analysis and test. Use a dropper to add drips of hydrogen peroxide solution (add around 0.5 mL per gram of coal); use a glass rod to stir it. Cover it with a lid, then, place it in a dark place for 24 h. Then, open the lid and expose to sunlight or incandescent lamp for 2 h; place it in a vacuum drying oven at the temperature of 55 °C ~ 60 °C and the pressure of 53 kPa to dry for 2 h. Then, take it out and put it into a desiccator to cool down to the room temperature. Before the test, weigh-take 0.09 g ~ 0.11 g of coal sample that goes through the above-mentioned processing and 0.075 g of sodium nitrite; gently grind them in an agate mortar for 1 min ~ 2 min; evenly mix it up.

7.3 Reduced Coal Sample

In the weighing bottle, weigh-take 0.5 g ~ 1.0 g of coal sample for general analysis and test. Place it in a vacuum drying oven at the temperature of 55 °C ~ 60 °C and the pressure of 53 kPa to dry for 2 h. Then, take it out and put it into a desiccator to cool down to the room temperature. Before the test, weigh-take 0.09 g ~ 0.11 g of dried coal sample and reducing agent (5.3); gently grind them in an agate mortar for 1 min ~ 2 min; evenly mix it up.

8.1 Manual Determination

8.1.1 In accordance with Figure 1, connect the various parts of the device.

8.1.2 Put the heating body into the heating furnace that is lower than 100 °C.

8.1.3 Carefully transfer the processed coal sample to the sample tube; connect the sample tube to the buffer ball. Then, put it into the heating body; insert the thermocouple into the central hole of the heating body.

8.1.4 Reverse the tee of the water storage tube, so that the water storage tube is connected to the atmosphere. Move the leveling bottle upwards to fill the water storage tube with water. Then, move the leveling bottle downwards to let the water in the water tank into the water measurement tube to a certain level. Immediately reverse the tee of the water measurement tube, so that the water measurement tube is connected to the buffer ball. If the water level of the water measurement tube stops after dropping to a certain distance, it proves that the air tightness is good. Otherwise, it indicates that there is air leakage, then, find out the cause and solve it.

8.1.5 Move the leveling bottle to fill the water measurement tube with water; maintain the water level of the leveling bottle and the water level of the water storage tube in a horizontal position. Turn off the tee of the water measurement tube.

8.1.6 Turn on the power of the heating furnace. Start to heat up; control the heating rate to 4.5 °C/min ~ 5.0 °C/min. Wait till the temperature is raised to 100 °C, then, record the temperature every 5 min. When it reaches 250 °C, rotate the tee of the water measurement tube, so that the water measurement tube is connected with the buffer ball. At any time, observe the water level of the water measurement tube. When it suddenly drops, record the corresponding temperature.

8.1.7 After measuring the ignition temperature of each sample, cut off the power; take out the thermocouple, sample tube and heating body.

8.2 Automatic Determination

8.2.1 Carefully transfer the processed coal sample to the sample tube. Place the sample tube into the round hole around the heating body; place the heating body into the heating furnace of the determination instrument.

8.2.2 Turn on the power. In accordance with the operation procedures in the instruction manual, conduct the test.

8.2.3 After the test, take out the heating body and sample tube. […]