A subsidiary of Malaysia’s Petroliam Nasional Bhd (Petronas), Engen has interests in more than 20 African countries. The company generates annual revenues in excess of $2,9 billion, and has a net asset value of $700 million. Engen owns and operates its own refinery in Durban, which produces more than 130 000 barrels of oil per day, employing 3000 permanent staffers.
Challenges
As a leading refinery in South Africa, Engen was looking for a way to help expand its FCCU application without temporarily de-commissioning the controller. Engen needed an integrated tool that worked with its already installed and well-functioning Profit Controller application and enabled a testing methodology that would also accommodate addition of new variables.
In the case of the FCCU revamp this meant:
* Stepping (14) manipulated variables and stepping/monitoring (6) disturbance variables in the existing reactor/regenerator section.
* Open-loop testing performed simultaneously on (nine) new manipulated variables and three new disturbance variables specific to the main fractionator to derive 18 new controlled variables for the main fractionator portion of the application.
* Closed-loop testing of (four) existing controlled variables that had been dropped from the reactor/regenerator application.
* All testing would need to be accomplished while the existing reactor/regenerator controller was running.
“We could not use existing testing methodologies since we had both a mixed closed-loop and open loop structure,” said Brian Thompson, lead process control engineer, Engen. “We had to find a process that would integrate and leverage our current technology in place and reduce the required time and effort for this application revamp.”
Additionally, since the FCCU is at the heart of plant operations, it is subject to frequent changes in feed rate, feed composition, and reactor severity to achieve necessary plant production goals. This combined with normal operational issues in the main fractionator meant that the technology applied needed to be highly robust and capable of handling frequent disturbances.
Solution
As a decades-long partner of Honeywell and having used its advanced process control and optimisation technologies, Engen once again turned to Honeywell and its Profit Stepper solution to help with its FCCU application revamp. Due to the complexity of the FCCU, and its importance at the heart of the refinery, it was critical that all major operational and technical constraints under Profit Controller be honoured throughout the step testing. Honeywell’s Profit Stepper solution was selected due to its ability to greatly reduce plant test time and its ability to do online model identification as the test proceeded.
“We were confident in selecting Honeywell’s Profit Stepper solution and benefited from past experience with Honeywell’s advanced process controls,” said Thompson. “The use of Profit Stepper resulted in a 41% reduction in total time to test and identify the new models for the FCCU application.”
Key enablers of this stated goal included the following:
* High operator acceptance: The combination of open and closed-loop testing and identification instilled confidence in the operations staff with no changes needed to their existing applications or user interfaces in order to execute the tests.
* Active constraint management during plant testing: The existing Profit Controller application from Honeywell actively managed the key constraints of the unit while testing of new manipulated variables were affected in open-loop; resulting in minimal stops and starts.
* Reduced implementation time: The need for traditional techniques disappeared. Variables can be stepped sequentially or simultaneously with little or no additional burden on monitoring by the operations staff – the existing Profit Controller application became the real-time monitor.
* Realtime measurement of test progress: Model ranking and all identification and model reduction was done with current data. Test progress and model quality was monitored and presented in realtime providing immediate feedback to engineers and operators as to the effectiveness of their efforts. The use of this method also helped eliminate re-testing and produced higher model qualities.
* Reduced model identification time and effort: Models of the process were created automatically as part of the plant test efforts, thus eliminating the need for manual data extraction and offline identification required by traditional techniques. Plant testing was automatically adapted to focus on areas where the models were deficient, ultimately resulting in reduced testing time required.
“Traditional testing methodologies could have put our operation at the FCC at great risk and by using Honeywell’s solution we were able to meet our stated goals efficiently and quickly. The closed-loop ID and Profit Stepper actually helped maintain the FCC stability and disturbances for our operators were minimal,” concluded Thompson.
For more information contact Debbie Rae, Honeywell Southern Africa, +27 (0)11 695 8000, [email protected], www.honeywell.co.za
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