(59o) Retrofit-Ability As a Design Criterion for Energy Integrated Systems Zeeshan Farooq and Mahmoud Bahy Noureldin, energy System Division, P&csd Saudi Aramco,

Chemical engineering design community over the last forty plus years has considered several design criteria other than safety; health and environment besides capital and operating costs, such as switchability; flexibility; reliability; maintainability; availability; controllability; operability; acceptability and so on. It is true that any industrial facility needs to be retrofitted several times throughout its lifetime to fulfill its objectives. However, Retrofitability” as a design requirement has not been addressed or even coined in the chemical engineering design community till the recent work of Noureldin(US patent; “Method and Program Product for Heat Exchanger Network Energy Efficiency Assessment and Lifetime Retrofit”) in 2012.There could be various objectives for a retrofit, for example, reduction in GHG emissions, reducing the use of utilities, modifying appropriate network topology, upgrading heat transfer units, installing additional heat transfer area, re-piping streams and re-assigning heat recovery matches. Heat exchanger networks (HENs) have been widely applied in industrial projects over the past decades because they provide significant energy and economic savings. Applications of HEN integration can be divided into two categories are grassroots and retrofit design. In oil refining, retrofit design are far more common than grassroots applications. The retrofit objective is to identify a cost effective HEN, subject to any design and operating constraints. However, implementing aforementioned retrofit strategies in practice may be difficult, due to constraints related to the topology, safety and maintenance which often exist in a Heat Exchanger Networks (HEN). Besides, the capital cost is usually high because of considerable piping and civil works required for the retrofit and potential production losses during process modification. Nowadays and since late seventies of the last century, another important frequent change is happening due to the continuous escalation in energy prices in a rate that is higher than plant equipment cost. It also warrants continual modification of the facility’s HEN to enhance the plant energy efficiency along its life time (sometimes reaching up to 30 years). In such cases, the HEN retrofit objective/task is to produce a practically implementable cost effective HEN design modification that satisfies the new process objective and its new operating constraints. There are many possible modifications for an existing HEN to retrofit the original design to the new objective. It can include a combination of all possible process operating and design condition modifications, existing HEN topological/structural modifications, and existing HEN unit design modifications and parametric modifications (such as heat transfer enhancement to improve U) as well. In this paper, crude oil distillation plants grassroots design including pre-heat train (PHT) which is well established, is used as a case study to exhibit the problem of very efficient design but without considering Retrofitability criterion during design phase. The design and retrofit of the crude oil pre-heat train is still to date the subject of many research and development work due to its importance in any crude oil refinery, since the crude oil distillation system is among the largest energy consumers in the industrial community, and the problem is not trivial with many decision variables and constraints due to the high interaction between the pre-heat train and the distillation columns of the crude distillation plant. The retrofit of the crude distillation plant including PHT is a task that can be conducted at least 4 to 5 times along the crude oil refinery lifetime not only due to the need for energy saving, GHG emissions reduction but also more importantly for throughput increase. Since the atmospheric and vacuum crude distillation towers designs are highly interlinked to the crude distillation plant pre-heat train (PHT), any retrofit of one system is going to severely impact the other. All of these objectives require heat duties within the PHT to be changed, surface areas to be changed, pressure drop in the PHT is changing, the need for adding new heat exchangers units, the need for changing units sequence, the need to streams splits, the need even for new streams matching, the need to change the atmospheric and/or vacuum towers internals, need to change crude pumps and so on. Such situations will bring hard constraints to any plant owner to start any retrofit on the basis of energy saving or energy-based GHG emissions reduction in particular, unless it is absolutely necessary for unit de-bottlenecking via the furnace debottlenecking to allow throughput increase. In such situations usually many good opportunities to save energy consumption and reduce energy based-GHG emissions will be overlooked.A worldwide 0.1 % reduction in the pre-heat train furnace’ fuel consumption per day, which is a very small saving in energy consumption, can be important to both fossil fuel energy consumption reduction and the fossil fuel-based-GHG emission targets’ achievement in crude oil refineries (about 100,000 BOE/day of Barrel Oil Equivalent) due to the fact that each barrel of world crude oil goes through the crude oil distillation plants. Most of the crude oil refineries nowadays will not be able to achieve the 0.1 % energy saving in their future retrofit projects with the current crude distillation plant’s configurations without huge cost not only in the heat exchangers network retrofit but also in the more important objective of achieving minimum refinery operation downtime. Therefore, it is beneficial to the grassroots crude oil distillation plants to have “off-the-shelve” pre-heat train design configuration that avoids previously mentioned problems and renders least furnace fuel consumption along its lifetime. This paper presents the essence of the Retrofitability design criterion via a healthy aging design of an energy efficient crude oil distillation plant pre-heat train configuration. This paper shows how such design can be continuously valid for long time and in the same time renders comparable crude unit furnace inlet temperature along the design lifetime.