ASTM D4421 Standard Test Method for Volatile Matter in Petroleum Coke
4. Summary of Test Method
4.1 Volatile matter of a moisture free petroleum coke is determined by measuring the mass loss of the coke when heated under the exact conditions of this procedure.
5. Significance and Use
5.1 The volatile matter of petroleum coke affects the density of coke particles and can affect artifacts produced from further processing of the coke.
5.2 The volatile matter can be used in estimating the calorific value of coke.
6. Interferences
6.1 Moisture has a double effect. The mass loss is increased and the moisture free sample weight is decreased by the amount of moisture actually present in the test sample.
6.2 Particle Size Effect:
6.2.1 The particle size range of the analysis sample affects the volatile matter. The coarser the analysis sample, the lower the volatile matter will be. The analysis sample (see Annex A1) is crushed to pass a No. 60 sieve (0.250-mm opening) but is not overcrushed. A No. 120 sieve (0.125-mm opening) should retain 40 to 55 % of the sample. The analysis sample is not to be obtained by scalping and discarding a portion of the sample.
6.2.2 Any segregation of particle sizes within the analysis sample shall be corrected by reblending the sample just prior to weighing the test sample.
6.3 Downward drift of furnace temperature caused by an increase in the millivolts per degrees Celsius generated by an aging type K thermocouple produces a lower volatile matter value (Test Method E 220).
6.4 Diffusion of air into the crucible caused by a poor fit between the crucible and its cover or by any other source of available oxygen causes high and erratic volatile matter values.
6.5 Free or tramp iron or mill scale in the coke coats the surface of the platinum crucible and decreases its life. The coating tends to form an oxide film during the preburning step (10.1). The oxide film provides a source of excess weight loss equal to almost twice the oxygen weight gained. Clean the crucible and buff with sand. Buffing will restore luster to the surface of the crucible.
