Clean and efficient use of petroleum coke for combustion and power generation

Petroleum coke is a challenging fuel in terms of its low volatile content, high sulfur and nitrogen content, which give rise to undesirable emission characteristics. However, the low price and increased production of petroleum coke from high-sulfur feedstocks give a powerful economic stimulus to use it for power generation. In this study two strategies are explored for the clean combustion of petroleum coke by in situ removal of CO2 and sulfur or in the longer term for hydrogen production with CO2 recovery. CaO sorbent is used to absorb CO2 and SO2 in fluidized combustor or steam gas reformer, and is regenerated in a calciner. In the calciner, petroleum coke is fired with pure oxygen to provide the heat for regenerating the sorbent and give a CO2 stream for subsequent utilization or sequestration. The SO2 is retained in solid CaSO4 and would not be emitted to the atmosphere. The high carbon content and low moisture content of petroleum coke ensure high purity of the CO2 stream. The low ash content is also important since it reduces the possibility of ash fusion in the calciner. It also reduces the heat loss and the requirement for ash disposal, and hence contributes to high overall efficiency. Simulation results show that high efficiency can be achieved with incorporation of the proposed scheme for power generation, even after the penalty of CO2 recovery. Thus, there is a potential for the abundant available and low cost, but environmentally challenging petroleum coke to become a fuel for clean combustion and power generation.