1. A non-transitory computer readable storage medium storing instructions executable by a processor to implement a system for use in simulating the operation of a portion of an operating process plant, the operating process plant including one or more process controllers communicatively coupled to one or more field devices processing physical materials to produce a product, the instructions comprising code executable to implement: a simulation system communicatively coupled to the operating process plant and including a plurality of simulation blocks and one or more communication links that communicatively couple the simulation blocks together, the simulation system configured to perform simulation of one or more pieces of equipment within the portion of the operating process plant, wherein each of the simulation blocks includes: a process model that models the portion of the operating process plant; a simulation routine that uses the process model to simulate the operation of the portion of the operating process plant to produce a simulated output value for an on-line process element; an input to accept from the operating process plant an actual output value of the on-line process element corresponding to the simulated output value for the on-line process element; a model regeneration routine that compares the actual output value of the on-line process element with the simulated output value of the on-line process element to develop an updated process model based on the comparison of the actual output value and simulated output value and that updates at least one simulation block by replacing the process model with the updated process model; and a process control system having one or more control blocks connected to elements within the operating process plant to perform on-line control of a process, wherein one of the control blocks used by the process control system includes a process model to perform an on-line process control activity, and wherein the simulation system provides the updated process model developed by the model regeneration routine for one of the simulation blocks to the one of the control blocks for use by the one of the control blocks to perform the on-line process control activity.