What can CDU-int do?
- Optimise the operating conditions of existing crude oil distillation systems to reduce energy consumption or to increase profit without capital investment.
- Modify the design of an existing column or the design of the heat exchanger network or both in a controlled way to reduce energy consumption.
- Modify the design of an existing column, the product flowrates and quality, the design of the heat exchanger network simultaneously to increase profit.
- Explore different distillation configurations in the design of existing units, such as the introduction of pre-flash or pre- fractionator units.
- Optimize column pressures.
- Explore changes to the design of existing heat exchanger networks for increased heat recovery or increased throughput.
- Optimize the configuration of new crude oil distillation systems.
CDU-int designs heat-integrated crude oil distillation systems.
Crude oil distillation consumes a significant portion of the energy demand of petroleum refineries, in spite of extensive heat recovery. The design of such crude oil distillation is made complex by the complex distillation arrangements used, the use of stripping steam, the use of vacuum in part of the distillation, the highly integrated nature of such systems and the specification of the products in terms of bulk properties rather than chemical composition.
The design of crude oil distillation processes has been traditionally carried out in two steps. First, the design is established for the distillation system. Second, the heat integration arrangements are designed.
Good design practice would explore the interactions between the design of the distillation column and the design of the heat exchanger network. However, even best practice in traditional design approaches has many shortcomings.
What is needed is a fresh approach that allows the distillation and heat integration arrangements to be designed and optimized simultaneously. In retrofit, improving the design for increased energy efficiency, or for increased throughput, brings special challenges. The use of existing equipment must be maximized whilst identifying cost effective design changes. Changes to operating conditions throughout the system, column internals and heat exchange arrangements must be optimized simultaneously.
CDU-int has unique capabilities for modeling crude oil distillation that allows design and operation changes to both the crude oil distillation and to the heat exchanger network to be considered simultaneously.
New semi-rigorous models for the distillation have been developed and have been coupled with the design of the heat exchanger network. This allows for the first time the distillation and heat recovery system to be designed and optimized simultaneously.
The heat integration is considered down to the level of individual matches, rather than using targets for the heat recovery. This is necessary if the interactions through features such as the pump around matches are to be considered adequately.
Retrofit can be controlled to restrict the number of modifications. Product qualities can be defined in terms of the bulk properties and can be either maintained to specified values, or manipulated in the optimization. If required, the quantities of the various products can be manipulated, along with the energy consumption, as part of the optimization to increase the overall profit, rather than simply reducing operating costs.
Both retrofit and new design can be considered. Changes to the operation and design of existing heat exchanger networks can be explored. Individual matches are considered and changes to the network can be controlled so that the complexity of either retrofit or new design can be controlled.
Crude Oil Distillation Modeling
The crude oil distillation can be modeled using new semi-rigorous modeling techniques. The new models produce predictions of distillation performance that hardly differ from the predictions of rigorous modeling techniques. However, these new models for the first time allow the ability to explore changes to the configurations of the column automatically. Bulk properties are not only be predicted with accuracy, but can also be controlled.
Distillation System Configuration
CDU-int can be used to screen different distillation configurations, such as pre-flash, pre-fractionator and progressive distillation arrangements. The software can be used to identify the most appropriate arrangement. Column pressures can be optimized simultaneously with configuration. When screening such arrangements, heat integration is considered simultaneously.
Simultaneous Design of the Distillation and Heat Integration
A unique facility of CDU-int is that it allows all aspects of the design and operation at steady state to be explored by simultaneously accounting for the distillation columns and the heat exchanger network. The simplest application might call for the operation of the existing design to be optimized for reduced operating costs or increased profit. Existing designs can be modified keeping control over the complexity of the retrofit. New designs can be explored to identify novel new designs.