IntroductionPetroleum coke is a by-product of the petrochemical industry. It has high fixed carbon, low ash content, high sulfur content and high heating value. Therefore, a good option for the utilization of petroleum coke containing high-sulfur content is to use it as fuel in CFB boilers [l, 21. In recent years, more and more thermal power plants worldwide have been using petroleum coke, especially with a high-sulfur content, as a fuel to produce steam for electricity generation and also as the heating source in circulating fluidized bed boilers [3,4]. Coal combustion in * Author for correspondence (mitiel 999@163.~om).
601T. Mi, Z.S. Wu, B.X Shen, H.P. Chen and D.C. Liu CFB boilers has been extensively studied, however, studies on combustion characteristics of petroleum coke and their pollutant emissions in CFB boilers are not available. Because the physical properties of petroleum coke are very different from that of coal, it is essential to investigate combustion characteristics of petroleum coke and the pollutant emissions in CFB boilers.Conn [5] has studied agglomeration characteristics of petroleum coke in CFB boilers. Bryers [6] performed studies on combustion characteristics of different petroleum cokes and mixture of petroleum coke with coal. Chang et al.[7] investigated combustion, heat transfer and pollutant emissions of petroleum coke and waste tires in a pilot CFB boiler. In this paper, the combustion characteristics of petroleum coke have been analyzed by the TGA method. The same tests have also been done for combustion characteristics of 3 kinds of coals for comparison. The combustion tests and the pollutant emissions of petroleum coke, and for the mixtures of petroleum coke and coal, have been performed in a bench-scale CFB rig with limestone addition.
Study of Combustion Characteristics of Petroleum Coke by TGA (i) TGA test apparatus and experimental preparationThe thermogravimetric analysis was performed with a thermal analyzer (NETZSCH STA-409), which is shown schematically in Figure 1. The system consists of a dynamic mechanical analyzer, a temperature controller, a driving head with a controlled temperature environment, and a computer that serves to control the measurements, to collect the real-time data, and to carry out the data analysis. The samples of petroleum coke are crushed and sieved. The sample (0.1 mm-0.154 mm, 10.2 mg) was placed in the thermal analyzer with an air flow rate of 100 mumin, and heating rate of 2O0C/min. The same tests have also been performed for 3 types of coals for comparison. Proximate and ultimate analyses for these samples are presented in Table 1. The experimental results are presented in Table 2. According to Chen Jianyuan's suggestion [S], we used the volatile characteristics index (D) and combustion characteristics index (S) to evaluate the combustion characteristics of petroleum coke.
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An Experimental Study of Combustion Characteristics of Petroleum Coke
(ii) Index of volatile characteristics of petroleum cokeThe index for volatile characteristics o...