Integration and testing of hot desulfurization and entrained-flow gasification for power generation systems. Volume 2, Evaluation of zinc loss from zinc titanate sorbents during hot gas desulfurization: Final report, October 1, 1987--October 31, 1993

The objective of this study was to support Texaco`s effort to develop the zinc titanate hot-gas desulfurization process for gases produced from their oxygen-blown coal gasifier. In this study, the following two issues were specifically addressed: (1) Evaluation of zinc loss from zinc titanate sorbents to be used in a fixed-bed reactor, and (2) Investigation of sorbent decrepitation observed in Texaco`s fixed-bed process development unit (PDU). In previous studies conducted by the Research Triangle Institute (RTI) for Texaco, it was shown that zinc loss from the zinc titanate pellets at a temperature around 700{degree}C may be significant (Gangwal et al., 1991). Therefore, conditions needed to be identified to define the operating temperature range so that in the zinc loss from zinc titanate pellets is low enough to allow at least a 200-cycle sorbent life in a fixed-bed reactor for desulfurization of fuel gas generated in Texaco`s entrained-bed oxygen-blown gasifier. Subsequently, during the operation of the PDU hot-gas desulfurization system, Texaco found severe spalling and decrepitation of L-3196 zinc titanate pellets prepared by United Catalysts, Inc. (UCI). Therefore, emphasis on this study was shifted from evaluating zinc loss from the sorbent to the development of durable zinc titanate formulations. After screeningmore » 21 formulations, RTI prepared two formulations for testing in Texaco`s PDU. Unfortunately, both formulations underwent severe decrepitation during five sulfidation-regeneration cycles. To investigate this decrepitation, a series of tests were carried out in a high-pressure thermo-gravimetric analyzer (TGA) under simulated Texaco conditions to reproduce the spalling. Both sorbents also exhibited extensive cracking in the TGA.« less