Online Exclusive: Overhead automation and analytics lead to improved optimization of production and reliability
The efficient operation of crude oil distillation units (CDUs) improves profits and distillate yield while optimizing production costs and reliability. Simultaneously, it is possible to reduce caustic use, positively impacting downstream sodium impact resulting in increased fluidized catalytic cracking (FCC) catalyst costs, coker furnace fouling and other issues.
Ideal operations for maximum distillate yield involve controlling naphtha section temperatures as low as practical without inducing amine salt formation and corrosion. Amines contamination varies widely and comes from many sources from within and from outside the refinery. Ideally, many elements should come together to achieve a safely improved distillate yield. The data, learnings and controls possible from these elements must be utilized holistically.
Traditional overhead corrosion mitigation methods are typically labor-intensive, unreliable, maintenance-heavy and time-consuming. They require many workforce hours to gather data, perform calculations and control chemical feedrates. Despite this investment, the intermittent data resulting from such methods miss important chloride and amine variations, resulting in late or obsolete decisions. Further, manual pH measurement and control can frequently accelerate corrosion from overcompensating with chemical injection adjustments and missing episodic periods of high corrosion.
Finally, manual ionic equilibrium salt point determination requires a significant number of hours to obtain rapid results for a wide and dynamically changing basket of amines, so shortcuts are often deployed that do not provide a complete picture of salt-induced corrosion risk. As a result, either conservative approaches to control salt deposition and corrosion are deployed to ensure safe operating envelopes that negatively affect profitability, or a higher corrosion risk than desirable is accepted to allow a wider operating envelope. Neither case is ideal for promoting low risk and operating flexibility.
New lab and field technology. pH measurement solutions incorporating transducers, rapid flow control, robust filtering and coalescing make pH measurements for overhead systems reliable and easier to maintain. Recent improvements in fluid handling have allowed accurate, online, 24/7 pH measurement and control.
Added to this are new technologies to measure chlorides online. Recent data gathered from field trials for chloride monitoring and control have shown a reduction of the coefficient of variation from 44% to 14%, compared to manual lab samples. Several solutions offer varying chloride reading frequencies ranging from 5 min–30 min.
Finally, recent advancements in amine speciation have made rapid and accurate onsite methods economical and practical. The complexity of the operation and amine quantification have become significantly easier while lowering costs and reducing wait times. Fully understanding episodic salt point challenges through rapid tramp amine speciation allows a greater ability to deal with corrosion problems at the source.
Chemical treatment of CDU overheads for corrosion is the most common method of improving reliability, other than desalting, water washing, temperature control and advanced metallurgy. Manually controlled injection of chemicals is widespread and longstanding in the industry. While neutralizers, filmers and caustic treatment have proven effective, each has its potential for negative downstream impacts, sometimes reducing overall potential. By using sensors and the automation methods described above to control each of the individual chemical feeds in a rapid, intelligent and synergistic way, corrosion mitigation can be improved while maximizing distillate yield and minimizing the negative aspects of chemical injection.
Online analytics and collaboration. The data produced from the above solutions are often siloed and make it difficult for operators to make the most effective decisions based on current conditions and data.
Cloud-based predictive analytics automatically perform daily saltpoint and dewpoint analysis on the most recent data. Combining cloud-based calculations with comprehensive and frequent amine speciation allows more rapid and targeted alterations to reliability operating windows. Coupling this technology to automated pH and chloride control via neutralizer and caustic injection allows the operator to optimize the system by dynamically changing stable chloride setpoints.
Using centralized asset performance management, data is automatically transferred, stored and accessed by all experts, operators and stakeholders. This allows a seamless collaboration and one-click report generation. It also means all parties are kept informed either through alarms, reports or direct customizable access.
Using automation to control neutralizer and caustic dosage based on pH and chloride readings while linking decision-makers to data and learnings, the knowledge and communication gaps are closed and significant improvements result (FIG. 1).
FIG. 1. Automation links decision-makers to data and learnings, closing knowledge and communication gaps.
Economic benefits. Unexpected maintenance to an overhead system can result in millions of dollars in lost opportunity for even one event.
In one example, by using automation, online analytics and rapid amine speciation, a refinery in North America conducted an 18°F temperature improvement worth $5.9 MM/yr in improved distillate yield ($9,000/10°F x 18°F/day x 365 days = $5.9 MM).
In another example, several refineries have realized reduced maintenance hours for sampling, analysis and control—down to a few hours per week for routine maintenance—and > 99% availability of the pH and chloride monitoring and control unit.
The reduction of caustic use and sodium poisoning of FCCU catalyst by optimizing chloride setpoints has been shown to result in > $350,000/yr in FCCU catalyst savings alone. Each year, the reliability and maintenance costs of corrosion are significant. The exact cost of global refinery corrosion is unknown: various analysis reports by NACE International and others estimate annual profit losses from refinery corrosion between $2 B and $12 B. Regardless of the specific value, the impact of corrosion on refining has a significant impact on refining economics.
Overall, the adoption of modern automation, control and analytics to help proactively and systematically optimize the balance between production and reliability can result in large returns on investment and simultaneous improvements to safety and workforce requirements.
ABOUT THE AUTHORS
WILLIAM CHOUERI is a Global Product Manager for SUEZ – Water Technologies & Solutions. He has more than 17 yr of experience in the water utilities, chemicals, and oil and gas industries, with roles ranging from sales and growth leadership, to digital and monitoring solutions, including the Suez Truesense and InSight APM platform. He is now responsible for setting and executing the global strategy for sensing and control in the oil and gas upstream, refining and chemical processing markets. Mr. Choueri earned an MSC degree in water processes from Cranfield University (U.K.) in 2004, and an MBA from the University of Manchester (U.K.) in 2013.
COLLIN CROSS received his PhD in physical chemistry from the University of Oklahoma (U.S.) in 1994. After graduating, he completed a postdoctoral fellowship for the W.M. Keck Foundation. His work there entailed the synthesis, computational physics, modelling and NMR spectroscopy of self-ordering systems, including surfactants, liquid crystals, colloids and oligonucleotides. In 1996. Dr. Cross joined Betz Laboratories Inc., now SUEZ – Water Technologies & Solutions, as a Senior Scientist. During his time with SUEZ, he has occupied various roles as a process chemist, including R&D Scientist, Process Chemical Group Manager, Enabling Technologies Project Lead, Project Management Lead and Product Line Management. All his roles have revolved around supporting the SUEZ process chemical business. Dr. Cross now occupies a position in the Product Applications organization supporting refinery corrosion as a Product Line Manager and subject matter expert (SME).