۱- Introduction

۲- Experimental

۳- Results and discussion

۴- Conclusion

References

Abstract

Petroleum coke is the waste from the delay coking process during petroleum refining. It is urgent to solve the problem of the effective and environmental utilization of high-sulfur petroleum coke. Chemical looping gasification (CLG) is employed in the application of petroleum coke for syngas production and sulfur recovery for the first time. The conventional steam gasification was for comparison to have a better understanding of the chemical looping process of petroleum coke. The presence of hematite improved the carbon conversion efficiency to 70.13%, although the fraction of the effective syngas decreased slightly. Experiments are conducted to evaluate the effects of temperature, steam flow rate and the sizes of fuel and hematite on the conversion of carbon and sulfur in a batch fluidized bed. The data shows that the effective syngas accounts for 83.51% and the molar fraction of H2S/SO2 is about 2, when the fuel size was 0.1–۰٫۳ mm, and the hematite size was 0.3–۰٫۴ mm at the steam flow rate of 1 g/min at 900 °C. Moreover, that condition is advantageous to the further utilization of the flue gas stream for sulfur recovery via Claus process. The size of oxygen carrier has a significant influence on distribution of sulfur species releasing. The high-content sulfur in the petroleum coke did not remain on the surface of hematite and the oxygen carriers were not poisoned. As a consequence, chemical looping gasification with hematite as oxygen carrier is an excellent technique for petroleum coke conversion coupled with sulfur recovery.

Introduction

Petroleum coke is the waste from the delayed coking process in the petroleum refining industry with high calorific value and low ash content. It is classified to high and low sulfur petroleum coke depending on the sulfur content. The low sulfur one can be used in many fields such as fuel, anode and electrode. However, the high sulfur petroleum coke faces a great challenge to be utilized because of the pollution [1,2]. Moreover, the production yield of high sulfur coke is overstocked with a high increasing rate, while the low sulfur one is in short supply [3]. Therefore, the utilization of high sulfur petroleum coke in a benign environmental and effective method is being solved urgently [4]. Gasification is considered as a cleaner and economic process to convert solid fuels in comparison with combustion [5e7]. When petroleum coke is used in the gasification technology, the sulfur compounds in the raw gas product would be converted into elemental sulfur in the Claus plant. But the gasification reactivity of petroleum coke is rather low due to its carbon structure and low combustibility [8,9]. Chemical looping gasification (CLG) is a promising gasification technology to produce syngas, sharing the same principle with chemical looping combustion (CLC) [10]. Generally, the system involves two reactors, a fuel reactor and an air reactor, with the oxygen carrier circulating between the two reactors as shown in Fig. 1. The oxygen carrier transfers lattice oxygen and heat to achieve the fuel partial oxidation and gasification in the fuel reactor, while the reductive oxygen carrier is transported for regeneration in the air reactor. Compared with the traditional gasification technology, CLG has several advantages [11,12]. The regeneration of oxygen carrier can supply heat for gasification, thus balancing the heat in the system with less extra energy input.