Base Oil / Base Component Production Scheduling
Typical Industries for the scenario:
- lube oil refining
- slack wax processing
- chemical processing of vegetable oil
The individual processing units of a refinery, such as distillation, cracking or solvent extraction, are typically operated in an uninterrupted sequence of multiple day intervals with the same operation mode (called "block operation modes" or "runs"). Thus, they can be characterized as semi-continuous.
Each run may use a different crude oil mix and yield multiple products that must be processed further in consecutive production stages. This semi-continuous joint production must be scheduled based on demands (pull production) as well as deliveries (push production).
Lube oil refineries typically only use a few raw oil materials (e.g. vacuum gas oil, received from a crude oil refinery) as input streams to produce a variety of base oils over a number of different semi continuous processing stages, each using a single input stream and yielding multiple intermediate output streams.
These base oils are then either shipped directly or used in subsequent blending and filling facilities.
Similar business processes are used, for example, by companies who process slack waxes and other "residues" of a refinery to produce natural and synthetic paraffin wax as well as wax-related products, such as petroleum jellies, white oils and liquid paraffins. Their supply chain usually consists of base component production – similar to base oil production in its scheduling processes – blending and container filling or bulk loading.
"Base component planning" departments are responsible to schedule the various semi-continuous processing units over a medium-term planning horizon – based on strategic monthly planning figures – to ensure sufficient availability of base components for subsequent blending, filling and loading processes that usually need to be more flexible and can only reliably be scheduled over a short-term planning horizon.
Their business processes include scheduling processing units and tank allocation for intermediate tank farms and output tank farms with consideration of limited tank capacities and the subtleties of joint products that need to be processed in consecutive processing units.
ORSOFT Manufacturing Workbench supports these business processes with the combination of standard APS and MES functions and specific functions that take the oil industries' special requirements into account.
Detailed Scheduling of Base Oil Production and Tank Allocation
Base oil production schedules typically contain long runs on the distillation and shorter runs on the subsequent processing units with more variety of operation modes. It is important to create a "good" sequence of these operation modes to reduce changeover loss between runs. This can be accomplished through classification of operation modes by boiling points and aiming for a "wave" sequence, for example. Since consecutive runs should not differ too much in their boiling point class, production planning must span a longer time frame (e.g. three months).
Subsequent processing stages must be decoupled by storing the intermediate streams in a tank farm. This is often accomplished by using a given tank for different materials at different times or using a tank allocation sequence for a given stream. Detailed scheduling of base oil production is comprised of determining operation mode parameters (time interval, throughput), input and output streams (material, percentage) and tank allocation sequences for all production runs on all processing units; than matching strategic monthly planning figures, availability of input materials, and detailed requirements for bulk sales and subsequent blending and filling orders.
A base oil scheduling workframe within the ORSOFT Manufacturing Workbench – using processing unit Gantt charts, tank histograms and detailed schedule editors – supports the planner in maintaining processing unit schedules and monitoring resulting stock levels at the input, intermediates and output tank farm.
The screenshot (click to enlarge) shows how the base oil scheduling workframe helps optimize production runs and tank sequences, utilize resources to their maximum capacity and observe all restrictions (e.g. tank limits) at the same time. The Gantt chart on the left hand side shows a typical resource allocation where a "boiling point wave" would indicate a good sequence of preferable changeovers for different qualities. The upper right window shows a list of base oil orders, and in the lower right window it is possible to display a details editor for a single base oil order.
A total current stock reconciliation supports the adjustment of daily stock by a rule-based validation of planned figures, with confirmed production and measurement results. This method delivers reliable results on total material stock levels.
ORSOFT Manufacturing Workbench can process indirect reference values such as component percent quota or throughput. It calculates material stocks on plant level and in individual storage tanks at the same time. It can also simultaneously handle mass and volume figures using predefined, calculated or measured temperature dependent density. A storage location related unit model with automatic unit conversion allows different views on one issue.
The recipe model extends most ERP models with regards to multiple input and output streams and flexible tank sequences. The order model does the same for production orders with the possibility of multiple input and output streams.