Over the last decade demand on the world’s ports has significantly increased, especially for both coal and iron ore export terminals. In an attempt to maximize exports, many port operations have transitioned to a just-in-time delivery operation.
Historically, coal and iron ore terminals have been designed with a considerable buffer between product reception and shipment. That is, product was delivered to ports significantly before ships arrived. This buffering function was intended to disconnect the operation of the delivery system (often rail) from the shiploading operation. However, such an operation requires a significant amount of storage space, typically 5 to 10 percent of annual export volume.
Today, many terminals are constrained in land use and can no longer expand their storage space to match increasing demands. Moving away from a buffered operation to a just-in-time delivery system allows increased exports for a given amount of storage space. Such an operation can also result in a more costeffective use of the terminal. However, the close integration required between the rail system and the marine terminal creates significant challenges for the operators, and complications in capacity and bottleneck analysis.
Analysis of complex systems
For expediency, and to keep costs acceptable, analysis has traditionally been performed on the terminal and the rail systems independently, which is appropriate for systems where the terminal and the rail system are buffered by a large stockpile.
In a just-in-time system, the rail network and the terminal are much more tightly connected, and performing separate analyses carries significant pitfalls. The overall capacity of a tightly linked supply chain with minimal buffer is not necessarily equal to the capacity of the weakest part of the chain. Delays in one area will propagate through the chain. Trains can be delayed, product remains undelivered, ships will queue for lack of product, demurrage will increase and target shipments will be missed. Track maintenance will have impacts on shiploading; ships arriving late will cause the stockyard to fill up. These issues create a need to account for variability throughout the entire system.
Not only is there a danger that system delays will not be accounted for, but with separate models for the terminal and rail portions of the system there is the danger that the model for each sub-system might use unrealistic assumptions about the behavior of the other sub-system, leading to an over-estimate of the performance of the entire system. An integrated mine-to-port simulation model minimizes these dangers.
Recent advances in modeling technology, along with the ever increasing computing power available, have made such models feasible. Ausenco Sandwell recently demonstrated this by expanding a simulation model of the Dalrymple Bay Coal Terminal (DBCT) to include the rest of the Goonyella Coal Chain†.