ASTM D4421 Standard Test Method for Volatile Matter in Petroleum Coke
10. Procedure
10.1 Ignite a platinum crucible and cover at 950°C for 5-min periods to constant mass (+/- 0.5 mg). A burner or any furnace is to be used but the crucible can be set in a nichrome wire support regardless of the style of furnace used. The cover shall not seal the crucible at this time; so that the carbon will burn off. Cool to room temperature in a desiccator before weighing the crucible and cover. Do not keep the crucible at room temperature more than 20 min before it is weighed. Record all masses to 0.1 mg.
10.2 Avoiding segregation of particles, transfer 1 g (+/- 1 mg) of the analysis sample (Annex A1) to the crucible and weigh the crucible with its content and cover to the nearest 0.1 mg. Fit the cover on the crucible and press it gently into position. Avoid physical distortion of the crucible and cover.
10.3 Manual Method:
10.3.1 Set the crucible vertically in the holder and center it over the furnace opening with the bottom of the crucible in line with the top surface of the transite furnace cover (Note 1). Be sure neither the crucible nor the holder touch the wall of the furnace. Start the timer.
NOTE 1 - There are some coke-VM relationships which require the crucible bottom to be 6 mm (1/4 in.) above the top surface of the transite-cover in the initial position. These relationships prevent control of sparks or flames, or both.
10.3.2 After 60 s (+/- 5 s), lower the holder approximately 8.5 mm (1/3 in.) into the furnace. The holder is lowered another 8.5 mm (1/3 in.) after each total elapsed time of 120, 180, 240, 300, and 360 s (each +/- 5 s). After the move at 360 s, the top of the crucible should be 19 mm (3/4 in.) below the top surface of the transite cover. DO NOT position the bottom of the crucible more than 57 mm (2 1/4 in.) below the top surface of the transite cover at this time (Note 2).
NOTE 2 - The heating rate is extremely important since the test is empirical and equilibrium is not achieved. The heating rate is controlled by the rate of lowering the crucible into the furnace. Once the holder is positioned immediately over the furnace the time schedule must be observed. The crucible shall not be removed, or raised and relowered, without verifying the test.
10.3.3 If at any time during the test, sparking occurs such that the sparks are seen to be above the height of the crucible cover or if a flame or flames occur such that the sum of all visible simultaneous flames extend above the height of the crucible cover, the test must be repeated with slight variations during the first 600 s. These variations are to be made with respect to the position when the sparks or flames occur. A more severe heatup rate (more rapidly lowering) will result in less sparking or flaming subsequently but can result in sparking or flaming earlier in the test. Discretion is necessary. A maximum furnace depth for the bottom of the crucible of 57 mm (2 1/4 in.) is to be maintained during the first 600 s.
10.3.4 After 600 s (+/- 5 s) total elapsed time, lower the holder so the brass ring of the holder rests directly upon the transite furnace cover (maximum depth in furnace).
10.3.5 After 960 s (+/- 5 s) total elapsed time, raise the holder and crucible out of the furnace and immediately place the crucible in a desiccator.
10.3.6 Weigh the crucible after it has cooled to room temperature and before it has been at room temperature for longer than 20 min.
10.4 Automatic Method (See Annex A2):
10.4.1 Equipment for automatically lowering the crucibles into the furnace can be built. This equipment permits one or more samples to be run simultaneously with minimal operator attention. Lack of operator attention to the progress of the test can cause problems with repeatability of analysis (see 10.3.3).
10.4.2 These automatic lowering devices are to be capable of lowering the crucible into the furnace at the rates in the manual method. The lowering of the crucible can be stepwise or at a continuous rate during the initial 600 s. From this point, the automatic equipment must conform to the manual method, Steps 10.3.4 and 10.3.5.
