Monitoring and enabling solutions to enhance customer service offering

Technology, engineering expertise and monitoring solutions that provide a state-of-the-art solution to the refining industry are in high demand.  To address these requests, GE recently launched two technologies that are revolutionizing corrosion control and antifouling treatments by identifying and expanding upon both thermodynamic and mass transport principles.  The LoSALT* Ionic Model and the HeatRate Pro programs use ASPEN** process simulation software to deliver rigorous simulations for their respective areas.  This results in more accurate calculations at a more fundamental level for both applications.  Examples of how these rigorous calculations improve the new applications are: 1) electrolytic modeling of the overhead pH profile for LoSALT and 2) seamless handling of two-phase flow in all elements of HeatRate Pro.  These have been serious limitations in previous less rigorous models.

How do HeatRate Pro and the LoSALT Ionic Model Benefit You?

Heat-Rate Pro provides a full simulation of the Pre Heat Train in one package. Users don't need an ASPEN license, or any additional engineering capabilities. The package provides the capability to compute optimized cleaning scenarios so that the exchangers providing the most heat recovery at the furnace inlet can be easily identified.

Heat-Rate Pro is a full service product and includes an individually customized set up of the model and the data gathering procedure. By using a MICROSOFT EXCEL***-based interface, the control of the program is easy, highly automated, and can be carried out by local GE personnel. The normalization feature provides a method for monitoring the overall heat train performance behavior independently of process fluctuations. This has a major impact on the optimization and control of antifouling treatments. By helping to forecast the impact of fouling independently of changing process conditions, costly throughput reductions can be minimized. Results can be discussed locally with minimal time delay. This allows exchanger cleaning to become much more cost effective and will avoid unnecessary cleanings. By consistently maximizing cleaning impact, the benefit of exchanger cleaning can be improved to provide maximal energy savings.

The new and improved LoSALT* Ionic Model expands upon the thermodynamic principles governing salt formation in a crude unit overhead. The new program will help users solve the toughest salt-related problems, including salt deposition, exchanger fouling, and exchanger pitting corrosion failure. The most significant improvement is that the new model uses ASPEN process simulation software to completely model the simultaneous complex ionic equilibria present in the overhead.

Major Benefits include:

• Improved overhead condenser and tower top corrosion control, crude unit reliability, and flexibility for changing tower top temperature to maximize fractionation yields
• Reduced potential for overhead corrosion and tower top tray fouling

Key Features

• Calculates water dew point temperature, pH at dew point, and salt point temperature of ammonium and amine chloride salts in the complex overhead environment
• Capability to simulate Tramp Amines, Organic Acids, H2S and Off gases
• Determines overhead vapor velocity
• Models and optimizes water wash programs
• Software resides on the GE field representative's computer enabling real time analysis

Success at a Glance: Thermoflo - Crude Unit Antifouling

A major North American refinery was experiencing severe fouling in the hot section of the crude unit's preheat train. The problem was estimated to cost the refinery nearly US$3MM per year. The predominate costs associated with fouling were charge rate reductions and energy costs. Maintenance costs were also tallied, but represented only 5% of the total fouling cost. After a major turnaround, in which the furnace and preheat exchangers were cleaned, a trial was initiated, treating the unit with 20ppm of GE's Thermoflo 7R30 and monitoring with HeatRate Pro.

Thermoflo 7R30 is an oil soluble antifoulant chemical designed to reduce process side fouling caused by coke, polymers, sludge, corrosion products, tar and other particulate matter. Thermoflo 7R30 is especially effective in reducing the deposition of aromatic sludges and high molecular weight components which may form at temperatures between 500 - 900°F bulk fluid.

Thermoflo 7R30 was injected into the unit, targeting a 70% reduction in the rate of fouling. Energy costs were taken as $8.50/MMBTU. Based upon the analysis of the untreated data, it was determined that the refinery was experiencing an untreated fouling rate of 0.11 °F/day. Throughput losses were estimated to be 1000 bbl/day throughout the length of the run. Maintenance costs for exchanger and furnace cleaning were $280,000 /year.

An MRA was first constructed for the entire untreated run. The fouling rate was computed to be 0.11 °F /day. Its coefficient had a significant statistical value, indicating that the fouling rate had a large impact on the results, and that the measured value of the fouling rate coefficient is extremely reliable.

Next, an MRA was constructed for the treated data over a 269 day time period from the start of the run. This regression yielded a fouling rate coefficient that indicated a system cleanup.

Integration of the daily energy savings between these two curves yields the cumulative value of the Thermoflo 7R30. This value was computed to be over $2.6MM for the targeted 2 year run length, yielding an ROI of 325% purely on energy. Because global economics led to a reduction of target charge rate during the run, no savings on throughput were realized. However, had the unit run on target, no charge rate reductions would have been necessary, and another $1.6MM in savings would have been realized, bringing the effective ROI to 525%.

No maintenance savings were tabulated, as their impact was negligible. However, HeatRate Pro was used to constantly monitor for cleaning opportunities. Based upon these analyses, at the time of this writing, one exchanger was cleaned at its projected optimum point.

*Trademark of General Electric Company; may be registered in one or more countries.
**ASPEN is a trademark of Aspen Technology, Inc.
*** MICROSOFT EXCEL is a trademark of Microsoft Corp.