(476a) Sulfur Removal and Recovery from a Coal to Liquids Plant

Fischer-Tropsch is a process that uses synthesis gas (syngas) to create the hydrocarbon chains that make up liquid fuels. However, this process requires a catalyst that can be easily poisoned by sulfur. In addition, with the ever-increasing governmental regulations that require ever more stringent sulfur removal from plant emissions, the necessity of sulfur removal has become increasingly important. In addition, once the sulfur is removed, it must be disposed of somehow, and various options exist to recover sulfur and create a salable product. The object of this paper is to study various types of sulfur removal and recovery, and to discuss how several of these processes can be modeled in ASPEN PLUS, a computer simulation program. The main types of sulfur removal for a Coal to Liquids (CTL) plant are: an Amine Unit, Research Triangle Institute's (RTI's) Direct Sulfur Removal, Rectisol, and Selexol. The main types of sulfur recovery processes for a CTL plant are: the Claus Process, Lo-Cat, the SCOT process, and Sulfatreat. RTI's process, while still relatively new and untested on an industrial scale, has been designed for both removal and recovery. This paper will discuss the difficulties modeling Rectisol using the correct unit operations and the methods and calculations necessary to model Rectisol if the unit operations cannot be modeled accurately. It will also discuss the feasibility of using zinc titanate as a polishing bed if placed after either an Amine Unit using MDEA or the Selexol Process. Finally, it will discuss the necessary steps to model the RTI's Direct Sulfur Removal Process in ASPEN PLUS.