Design of Emergency Steam Load Shedding System Using Dynamic Simulation

Written by Juliann Grant | Aug 15, 2012 9:30:15 AM

This is an abstract that will be presented at ISA Automation Week 2012 in Orlando, Florida.

This session is in the Safety/Environmental Performance Track: Safety Systems: Solving Today's Toughest Applications

Presented By:

Mr. Abhilash Nair, Invensys Operations Management
Mr. Obaid M Al-Swailmy, Saudi Kayan Petrochemical Company
Mr. Anil Kewalramani, Saudi Kayan Petrochemical Company
Mr. Tariq Khan, Invensys Operations Management

Abstract:

Saudi Kayan Petrochemical Company (SK), an affiliate of Saudi Basic Industries Corp. (SABIC) is implementing an automated Emergency Steam Load Shedding System (ESLSS) in their integrated petrochemical facility at Al-Jubail, Saudi Arabia. The facility is expected to have an annual production capacity exceeding 4 million metric tons of petrochemical and specialty chemical products. The goal of the ESLSS is to establish plant wide steam system capability by maintaining all plants in the complex in safe operating conditions and providing stability to different Steam header pressure levels following unplanned events in the complex’s steam system like loss of major steam producers. The normal regulatory controls in the process are generally not adequate to handle such major upsets and could potentially lead to undesirable end results. The ESLSS is a program with a set of control logics over and above the regulatory process controls that will initiate feed forward control signals in the event of certain upsets.

Understanding the behavior of the steam system following such upsets is critical to developing a strategy to control it. The steam system is typically a large network of piping with multiple pressure levels running throughout the complex with various regulatory control points scattered across. The response of such a large and integrated system to process upsets is a very complex flow, mass and energy balance problem which is compounded by the dynamics of regulatory process controls interacting with the process.

Dynamic simulation is the best available tool to evaluate such systems; their response to process upsets including the effect of regulatory process control and process design limitations, if any. This sort of understanding of the process response enables engineers to design and test appropriate control strategies to mitigate the undesirable effects of an upset which may include loss of the entire steam system, trip of critical units and equipment leading to excessive flaring and loss of production.

Invensys, an industry leader in Dynamic Process Simulation, was approached to help perform a dynamic simulation study of the facility’s steam system. Invensys developed the dynamic simulation model for the integrated petrochemical complex’s Steam system using their proprietary dynamic simulation modeling product - Dynsim. The model was then used to study various upset scenarios on the complex’s steam system to evaluate the system response and then to identify, test and recommend suitable mitigating operating and control strategies.

Implementation of the ESLSS is expected to benefit Saudi Kayan significantly in enforcing safe and reliable operation of the facility and in minimizing operating/capital losses during plant steam upset conditions. One of the deliverables from the study was a detailed report analyzing the transient behavior of the system and enlisting mitigating actions to be taken for different steam crisis scenarios. Control System & Instrumentation Engineers subsequently used the recommendations from the study to implement the ESLSS logics in the actual control system. The ESLSS designed through the dynamic simulation study is hence expected to immensely enhance the Safety, Reliability and Flexibility of Operation of the Saudi Kayan plants.

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