Q: My ethylene plant processes naphtha from an upstream refinery, and our feed is dependent upon the crudes processed. Can Honeywell’s Planning and Scheduling Solution help in this case? A: Yes. RPMS can model a complete refinery, as well as the downstream ethylene units. By adding PONA information into the naphtha components of the crudes selected, economic decisions can be made to determine which crudes should be purchased. This helps maximize overall refining and petrochemical complex profitability.
Q: We are considering increasing our furnace capacity, but are not sure whether we should add a gas cracking or liquid cracking furnace?A: RPMS provides a module that includes investment-capacity relationships for a variety of processes. This module can be included in the planning optimization cycle to help determine what type of furnace would be most suitable based upon expected price and availability of feedstock.
Q: We are having problems making the actual ethylene production of a unit match the planned production from our planning department. They do not seem to understand that furnaces cannot run indefinitely. How can we improve our model?A: The problem may be that the plan is reasonable at a macro level, but it breaks down when converted into a production schedule. If time is not allocated to allow a furnace to come down for maintenance or decoking, or the plan does not recognize that a pump used for transfer between tanks cannot be simultaneously used for feeding the unit, then there may be a mismatch in production. Honeywell’s Advanced Planning and Scheduling Solution incorporates logistical constraints into the quantity and quality constraints more commonly found in schedules. The planner can incorporate these limitations into the Enterprise Production Model and determine which production schedule best meets the production plan quantity targets.
Q: What if a feasible schedule cannot be found after incorporating all of the logistical constraints?A: Honeywell’s Advanced Planning and Scheduling Solution allows the planner to generate all feasible solutions, as well as solutions that are “feasible with penalties.”
For example, this could mean that in order to meet a target ethylene production in the coming week, a particular furnace severity would have to be increased beyond the maximum specified coil outlet temperature. The planner could then determine how best to adjust specifications to reduce or eliminate the penalties.
Q: What if the user wants to maximize production of olefins, but after a certain level, the price attainable for incremental product drops? How can the user tell whether to maximize ethylene for product, or use the incremental product to make more ethylene glycol?A: RPMS includes a multi-plant modeling module that can incorporate sub-models of different operating plants. Included in the models are definitions for multi-tiered price demand curves for products, and multi-tiered cost availability curves for raw materials. This information can be used to determine whether incremental production of a primary product such as ethylene should be sold on the market or further processed in a downstream unit.
Q: Prices for HDPE are so depressed that we only want to make enough production to meet customer demand. However, this would take our plant below its normal minimum operating rate. Can this constraint be included in the planning and scheduling solution?A: Yes. Honeywell’s solution uses mixed integer linear programming (MILP) to build discrete decisions into the planning and scheduling problem. A good example is minimum turndown rates on unit operating capacities, or a minimum or maximum amount of a particular feedstock that must be purchased at a given time.
Q: Honeywell’s Advanced Planning and Scheduling solution can be used for monthly production plans. Can the same solution provide information for an annual operating plan and five-year strategic plan?A: Yes. RPMS supports multi-period modeling that allows the planner to vary the length of the time periods used for optimizing the plan. For longer periods, the planner can include: different prices structures to reflect changing seasonal demand, varying processing capacity to reflect possible shutdowns or de-bottlenecking projects, and investment-capacity relationships to determine the benefit of possible capital projects.