Plugging process into the market
19 Nov 2007
SABIC UK Petrochemicals is working to further leverage its technologies for linking commercial data such as feedstock pricing, availability and end-product prices to the production processes at its Wilton site in the northeast of England.
The Wilton site, which SABIC recently acquired from Huntsman, operates a world-scale cracker with capacities of 865 kilotonnes per annum (ktpa) ethylene, 400-ktpa propylene and 100-ktpa butadiene. There is also a 430-ktpa paraxylene facility, which is integrated with a 1300-ktpa aromatics facility at North Tees.
A key requirement is to ensure that the operational strategy is well aligned with the trends that we see in the supply and product markets, said Chris Hamlin, process control and manufacturing systems manager at Wilton. The site, he noted, operates a conventional S&OP [sales & operations planning] process that spans the entire business operation and drives all of its commercial and manufacturing decision-making processes.
Under previous owner Huntsman, the Wilton site first implemented AspenTech's advanced control and optimisation in 1999. The supplier's DMCPlus system simultaneously controls over 840 plant constraints, adjusting 230 process set points every two minutes. The system takes into account feedstock, product mix, and input and output costs and prices, to deliver a full financial optimisation of the plant's operating parameters at any time.
At the same time, RT-Opt, AspenTech's real-time optimiser, can solve a 250,000-equation package of the entire plant model every four hours to fine tune the DMCPlus controller targets. It takes into consideration the feedstock slate, feedstock and product prices, plant operating status and ambient operating conditions.
Today, SABIC employs AspenTech's DMC technology extensively across all of its major production facilities, under a common architecture that includes IP21 as the process and business historian. The olefins cracker at Wilton also uses AspenTech's real-time optimisation tools, where price information is fed from the S&OP process into the on-line optimiser.
The system, in turn, uses DMCplus controllers to move the process to the desired operating point. Actual plant performance is monitored using IP21 to close the loop and compare expected and actual operation. The operation also has a very early implementation of Aspen's State Space Controller on one of our units, said Hamlin.
According to Hamlin, SABIC views such applications as essential to its on-going competitiveness: "We have moved to a way of thinking that sees the utilisation of these technologies as being the norm.
"Consequently, the emphasis is on justifying not implementing them on those few units where they are inappropriate, rather than developing the case for their deployment where they are."
Since the original implementation in 1999, the Wilton operation has doubled the number of DMC controllers deployed across the sites, usually using its own in-house resources and capability. The underpinning systems architecture has evolved to a common standard that is followed in the same way on every production facility, Hamlin added.
"We have embraced the use of new technologies and now use SmartStep and MultiTest routinely when implementing DMC controllers, and are making more use of the facilities available in the latest releases ... We are also beginning to use the new State Space Controller and have one application running," said Hamlin.
With regard to advancing the use of real-time market data, Hamlin said the first priority is the comprehensive roll-out of existing technologies across all facilities. "We [then] intend to develop how we monitor the performance of the different tools, with emphasis on automating the collection and analysis of performance metrics, etc.
"There is always an incentive to reduce the cycle time between market data updates, but this becomes an issue of diminishing returns, particularly if the improvements at the automation level are not matched by the business systems and processes."
SABIC's Wilton team has started to investigate and experiment with different visualisation technologies. This, said Hamlin, covers applications ranging from production technicians to the presentation of complex performance information to both company managers and business people.
"Furthermore," he added, "we anticipate a shift in emphasis from the development, downward communication and implementation of operational plans and strategies to the monitoring of the process against these plans, the analysis and upwards communication of deviations and the ability of the business to respond in real-time to change in plant conditions and capabilities."
