Impact of demand load size on strategies for reliable process heat supply

When providing high-temperature process steam to a user such as a chemical plant, high availability and reliability are necessary to maintain production and avoid sudden, unscheduled shutdowns with potentially adverse investment consequences. Therefore, the availability and reliability requirements are expected to be higher than those applicable to dedicated electric power plants. This paper evaluates the impact of the size of the process steam demand on the effectiveness of different approaches for meeting these high reliability requirements using High Temperature Reactor (HTR) process steam supply systems. Such systems will require significant backup redundancy, since individual reactor modules have inherently lower availability than that required by a process heat plant. Systems using additional HTRs and systems using traditional gas-fired boilers for backup capacity are both analyzed. Potential system configurations are analyzed for a wide range of process heat plant steam demands, from 200 MWt to 1500 MWt. The analysis includes availability analysis, assessment of overall redundancy, and economic evaluation. Consideration is also given to the benefit of selling surplus electricity generated with excess steam. Finally, the sensitivity of different plant configurations to fossil fuel price volatility is discussed briefly.