Pinch analysis at Preem LYR II - Modifications

Rapport, 2014

This energy inventory and pinch analysis of the Preem, Lysekil refinery is a part of the Preem – Chalmers research cooperation and has been carried out by CIT Industriell Energi AB. This report is Part II of the report “Pinch analysis at Preem LYR”. The aim with the first part was to supply the researchers at Chalmers with energy data from the refinery in a form that is suitable for different types of pinch analysis. Furthermore, the aim was to make an analysis to establish the possible energy saving potentials in the refinery at various levels of process integration constraints. In this report, “Pinch analysis at Preem LYR, Part II”, we have applied pinch analysis methods such as the “Matrix Method” and “Advance Composite Curves” to find concrete improvements in the heat recovery network. The process units of the refinery have a net heat demand of 409 MW (for the operation case studied) which is supplied by firing fuel gas. Steam is generated in the process by cooling process streams. Most of the generated steam is used in the process units (167 MW) and the remainder (17 MW) is used for other purposes. The energy saving potential, that is the theoretical savings that are achievable, depends on the constraints put on the heat exchanging between process streams in the refinery. Three levels have been analysed: A: There are no restrictions on the process streams that may be heat exchanged in the refinery. In this case the minimum heat demand is 199 MW giving a theoretical savings potential of 210 MW. B: All streams within each process unit can be exchanged with each other, but direct heat exchange between process units is not permitted. In this case the minimum heat demand of each process unit must be calculated. The total savings potential, 146 MW, is calculated by adding the savings potential for the separate units. C: Heat exchange between process units is allowed for those streams which are heat exchanged with utility today (e.g., steam, air, cooling water). However, it is not allowed to modify existing process to process heat exchangers. The scope of the analysis is limited to only consider the 5 largest process units. This group of units are using ~90 %, 363 MW, of the added external heat. It is possible to reduce the external heat demand with 57 MW to 306 MW. In this report, part II, we give results of possible modifications identified in two process areas, ICR 810 and MHC 240. These areas were selected for further analysis due to their large energy savings potentials. Another area with high potential was CDU+VDU. However, improvements in this area were made during the 2013 turnaround. To reach the savings potential calculated in Part I, a Maximum Energy Recovery (MER)-network must be constructed. This will however involve a large number of new and modified heat exchangers. It is unlikely that a MER design would be economical in a retrofit situation. Therefore, the trade-off between capital costs and energy savings in a retrofit situation must be evaluated. However, this analysis is not yet done. The modifications suggested in this study include different levels of increased heat integration.