Dynamic Tank Reallocation Between Tank Farms in Refinery Simulation

       Most refinery simulation models assume that storage tanks are permanently assigned to individual tank farms. While this approach simplifies model development, it does not always reflect real refinery operations. In practice, refineries often treat some storage tanks as shared resources that can be reassigned between accumulative tank farms when operational priorities change. This allows operators to balance storage capacity, improve tank utilization, eliminate temporary bottlenecks, and optimize refinery storage systems without constructing additional tanks. Similar storage optimization techniques are used in crude oil supply chain simulation.
       Dynamic tank reallocation enables refinery digital twins to accurately represent this operational flexibility, improving storage optimization, storage utilization, and production planning under realistic operating conditions. Dynamic tank reallocation is one of the most effective tank farm optimization techniques used in refinery digital twins. Tank reallocation requests are coordinated through request-based production planning.
       Dynamic tank reallocation is therefore not only a storage management mechanism but also a practical storage optimization strategy for refinery digital twins. This mechanism works together with accumulative tank farm planning, request-based production planning, and tank repair management to provide refinery-wide storage optimization. As a result, storage capacity management becomes significantly more flexible while preserving operational constraints and material balance.

       Storage demand across refinery tank farms is rarely constant. Effective tank farm capacity planning therefore requires the ability to dynamically balance storage resources between production areas as operating conditions change. Changes in production rates, shipment schedules, maintenance activities, or product campaigns can temporarily create storage shortages in one tank farm while leaving unused capacity in another. The effectiveness of these planning strategies can be evaluated using request statistics.
       With a traditional fixed tank assignment, excess tanks remain idle even though other parts of the refinery require additional storage. As a result, production may be constrained despite sufficient total storage capacity being available. Dynamic tank reallocation addresses this problem by allowing compatible storage tanks to be reassigned between connected accumulative tank farms, improving storage capacity optimization without increasing the total storage capacity.

       Dynamic tank reallocation is applicable whenever storage demand becomes temporarily unbalanced between tank farms. Such situations are common in refinery operations and often occur without any changes to the physical storage infrastructure.

       Typical examples include:
        - temporary increases in production from a processing unit;
        - planned maintenance of storage capacity tanks;
        - changes in product campaigns or production priorities;
        - seasonal fluctuations in product demand;
        - temporary shortages of available tanks due to passportization or quality verification;
        - commissioning of new processing units before additional storage capacity is constructed.
       In these situations, reassigning available tanks from one accumulative tank farm to another allows production and shipment operations to continue without unnecessary process interruptions.

       The dynamic tank reallocation mechanism treats selected storage tanks as shared storage resources that can be assigned to different accumulative tank farms as operating conditions change. Instead of permanently belonging to a single tank farm, these tanks become part of a common pool of shared storage resources managed by a central reallocation controller.
       When one tank farm experiences a shortage of available tanks while another has excess capacity, empty tanks can be transferred between them. Once reassigned, a tank operates as a regular member of its new accumulative tank farm, participating in filling, passportization, storage, and shipment operations according to the production plan.
       In practice, tank reallocation is not completely unrestricted. A tank can only be reassigned to tank farms handling compatible or closely related products. This limitation reflects real refinery operations, where small amounts of residual product may remain in a tank even after it has been emptied. Reusing the tank for an incompatible product could result in contamination or require additional cleaning procedures.
       By considering product compatibility during tank reassignment, the model preserves realistic operational constraints while maximizing storage optimization and storage utilization while preserving realistic operational constraints. At any moment, each tank belongs to only one tank farm, ensuring consistent material accounting and preventing simultaneous use by multiple facilities. This approach maintains storage balancing across the refinery while ensuring accurate material accounting.

       In Petroleum Refining Library (PRL), tank reallocation is performed manually by the user through the graphical interface of the accumulative tank farms. This approach gives operators full control over storage configuration while ensuring that all operational constraints are respected.
A tank can only be transferred after it has completed its current operating cycle. When the user selects a working tank and chooses Move to Reserve, the request is not executed immediately. Instead, the system waits until all ongoing operations are finished and the tank becomes completely empty. Only then is the tank automatically transferred to the Reserve state, where it becomes available for future reassignment. The approach can be directly integrated into AnyLogic refinery digital twin models.
       Each connected accumulative tank farm also contains reserve tanks that are initially inactive. When the user selects one of these reserve tanks, the Release from Reserve command becomes available only if another tank of the same storage capacity has already entered the common reserve pool. This guarantees that activating a tank in one park is always balanced by reserving an equivalent tank in another park.
       As a result, the total number of active tanks across all connected tank farms always remains constant. Storage capacity is redistributed rather than increased, preventing unrealistic model configurations while preserving the physical limitations of the refinery.
       To ensure realistic operation, in Petroleum Refining Library only empty tanks can be transferred between tank farms. In addition, reallocation is allowed only between tanks of identical capacity and only when the target tank farm is configured to handle compatible products, reflecting the practical constraints of industrial storage operations.
Dynamic tank reallocation between tank farms is implemented in Petroleum Refining Library through the initialization of the ReservoirReallocator class, which automatically redistributes tanks between connected tank farms according to the configured reallocation strategy and current operating conditions.

       Dynamic tank reallocation increases the operational flexibility of refinery storage systems without requiring changes to the physical infrastructure. Instead of constructing additional storage tanks, operators can redistribute available capacity between accumulative tank farms as production requirements change.

       The main advantages include:
        - improved storage optimization across connected tank farms;
        - higher utilization of existing storage capacity;
        - reduced production bottlenecks caused by temporary tank shortages;
        - improved storage allocation across multiple refinery units;
        - improved support for changing production plans and shipment schedules;
        - greater flexibility during tank maintenance and equipment outages;
        - more realistic digital twin models that reflect actual refinery operating practices;
        - the ability to evaluate alternative storage management strategies through simulation before implementing operational changes.

       Dynamic tank reallocation in Petroleum Refining Library is particularly valuable in refineries where storage demand changes over time due to production scheduling, maintenance activities, or changing market requirements. This enables engineers to evaluate alternative storage allocation strategies before implementing operational changes. By allowing storage capacity to be redistributed between accumulative tank farms, engineers can evaluate operational strategies that would be difficult or impossible to analyze using fixed tank assignments.

       Dynamic tank reallocation extends traditional tank farm simulation by allowing storage resources to be shared between connected accumulative tank farms. Instead of treating storage tanks as permanently assigned assets, the approach models the operational flexibility commonly used in real refinery facilities.
       The Petroleum Refining Library with AnyLogic implementation ensures that only empty tanks can be reassigned, storage capacity remains balanced across all connected tank farms, and only compatible tanks of identical capacity can be exchanged. These constraints allow engineers to evaluate realistic storage management strategies without violating the physical limitations of refinery operations.
       By incorporating dynamic tank reallocation into refinery digital twins, engineers can improve storage optimization, increase storage utilization, reduce temporary bottlenecks, support production planning, and analyze alternative operating scenarios before implementing changes in a real facility, support production planning, and analyze alternative operating scenarios before implementing changes in a real facility.

1 What is dynamic tank reallocation?
Dynamic tank reallocation is a storage management approach that allows selected tanks to be reassigned between connected accumulative tank farms as operational requirements change. This improves storage utilization without increasing the total storage capacity.

2 Why is dynamic tank reallocation useful in refinery simulation?
It enables refinery simulation models to represent real operational practices, where storage resources are shared between process units to reduce bottlenecks, support production planning, and improve operational flexibility.

3 Can any storage tank be reassigned to another tank farm?
No. In Petroleum Refining Library, only empty tanks can be reassigned. In addition, tanks must have identical storage capacities and be compatible with the products handled by the target tank farm to avoid contamination from residual products.

4 Why are only empty tanks allowed to be transferred?
Reassigning a tank containing product would interrupt ongoing operations and could lead to incorrect accounting. Waiting until the tank is empty ensures a safe and realistic transition.

5 Why must the storage capacities match?
Matching storage capacities ensures that the total available capacity remains balanced between connected tank farms. A tank activated in one park always replaces a reserve tank of the same size in another park.

6 Does dynamic tank reallocation increase the total storage capacity?
No. The mechanism redistributes existing storage resources rather than creating additional capacity. The total number of active tanks remains constant throughout the simulation.

7 Is tank reallocation performed automatically?
No. In the current Petroleum Refining Library implementation, tank reallocation is initiated manually through the graphical user interface. The software automatically executes the requested transition only after all operational constraints have been satisfied.

8 Where can dynamic tank reallocation be applied?
The mechanism is suitable for refinery tank farms, oil terminals, petrochemical plants, and other industrial facilities where storage capacity is shared between multiple production areas and operational priorities change over time

10 How does dynamic tank reallocation improve storage utilization?
Dynamic tank reallocation improves storage utilization by allowing unused tanks in one accumulative tank farm to be reassigned to another park experiencing temporary storage shortages. This enables refineries to make better use of existing storage assets instead of leaving available capacity idle.

11 Can dynamic tank reallocation reduce capital investment?
Yes. By optimizing the utilization of existing storage capacity, dynamic tank reallocation can reduce or postpone the need to construct additional storage tanks. Simulation studies allow engineers to determine whether operational improvements alone can eliminate storage bottlenecks before investing in new infrastructure.

12 Is dynamic tank reallocation suitable for refinery digital twins?
Yes. Dynamic tank reallocation enables refinery digital twins to represent real operational practices in which storage resources are shared between connected tank farms. This allows engineers to evaluate production planning, storage optimization, maintenance scenarios, and alternative operating strategies under realistic conditions.