This article was included in one of Hydrocarbon Processing’s three daily show newspapers at the NPRA Q&A and Technology Forum in San Antonio, Texas.
The enormous industry success of NOVA Chemicals’ Corunna complex in Ontario, Canada, comes amid upgrades the company has made to its operations scheduling system, the branch manager for Houston-based Haverly Systems told attendees at the NPRA Q&A and Technology Forum in San Antonio.
Dean Trierwiler, who spoke during Monday’s plant automation session, outlined the requirements that NOVA set forth to his company when Haverly Systems recently designed a system for the Corunna site.
“First, they wanted something easier to update, modify and use than what is currently in use,” Mr. Trierwiler said. “That’s where it starts. Specifically, they needed to project further into the future with greater accuracy and confidence, respond faster to unplanned events, be useful in reconciling previous-month operations, and accurately track qualities of all feed, intermediate and product streams.”
“They also wanted to be able to communicate with other plant software systems, provide or require information useful in plant scheduling, provide modeling for plant fuel-balance determination, and be readily receptive to future upgrades in scheduling software technology.”
NOVA’s Corunna site supplies between 30% and 40% of Canada’s requirement for primary petrochemicals and is the first fully-integrated refinery and petrochemical complex in North America.
The site is home to one of the few flexicracker operations in North America, allowing for a broad range of feedstocks. Its products include petrochemicals, fuels and specialty chemicals. On a yearly basis, the refinery is capable of producing in excess of 6.5 billion pounds of basic petrochemicals and 3 billion pounds of refinery and energy products.
However, such massive potential also brings with it an increased importance on operations scheduling. To that end, NOVA now employs Haverly Systems’ latest scheduling tools, which instantly show, through vivid graphics, the outcomes resulting from modifications to operating parameters and hydrocarbon redistributions. As a result, schedulers are allowed to interactively make better decisions regarding plant performance, Mr. Trierwiler said.
Mr. Trierwiler cited one specific example at NOVA, in which the company needed to maintain its required production volumes despite a decline in feedstock quality. In that case, the company had a potential problem, as purchased mixed butanes replaced nearly 20% of liquid feeds during summer operations. The issue is that the quality of purchased mixed butanes can vary greatly between suppliers, Mr. Trierwiler explained.
Eventually, poorer-quality feeds could cause butadiene (BD) production to fall below contractual commitments. Moreover, operational flexibility could be constrained due to hydraulic limits resulting from lighter feeds. Older planning models would not be able to foresee such problems, according to the Haverly Systems manager.
With the latest scheduling tools, however, NOVA was able to compare situations, such as what would happen if it increased its butane furnace temperatures while maintaining maximum feed rates. NOVA was also alerted that increased methane production could risk overloading its fuel system. As such, other interventions were evaluated within the system, including raising liquid furnace temperatures and cutting rates.
NOVA said the system has also been useful in resolving yield accounting errors, such as the discovery of a missing propane receipt and catching erroneous accounting meters.
On the whole, the system better enables company decisions concerning how to best process crude and other feedstocks through the distillation units and 14 cracking furnaces at the complex.
“NOVA has found this to be a real asset,” Mr. Trierwiler said.