*2.2. Apparatus and Methods*

The upstream oil sludge was dried in a recycle ventilation drier for 24 h at 105 ◦C; then, the heating value and ash content of the dried sample was analyzed by an automatic oxygen bomb calorimeter (SDAC6000, Sunday, Changsha, China) and automatic ash Fusion Tester (SDAF105b, Sunday, Changsha, China), respectively. The test of bulk density and moisture content for the undried upstream oily sludge was the same as that in previous studies [27,29].

First, seven to 15 mg of undried upstream oily sludge was employed for the TGA/DSC test and carried out in a SDT Q600 thermal analyzer (TA instrument, New Castle, PA, USA) under air atmosphere. In order to simulate the oxygen-rich conditions applied in practical incineration processes, ratios of the purified air to the initial weight of oily sludge were maintained over 10.00 mL/min to 1.00 mg. The operating temperatures for the TGA/DSC test were performed from 30 ± 2.5 ◦C to 900 ◦C. The heating rates (*βn*) were five K/min, 10 K/min, 15 K/min, 20 K/min, and 25 K/min, and were labeled as *β<sup>a</sup>*, *β<sup>b</sup>*, *β<sup>c</sup>*, *β<sup>d</sup>*, and *β<sup>e</sup>*, respectively. The sample of each experiment was weighted within a thousandth of an error and loaded into the quartz disk, which settled in the center of the equipment. A K-type thermocouple was inserted beside the quartz disk for measuring the operating temperature. Before the formal thermal test, the purified air controlled by a rotameter was injected into the equipment and lasted at least two hours for the purpose of purging. When the run was finished, the air was kept flowing until the temperature of the system returned to room temperature. The TGA and DSC data were simultaneously recorded, and the results of each experiment were repeated twice and averaged.
