A major refinery in Texas, USA, recently experienced steam condensate contamination and major fouling of a boiler resulting in damage that led to an unplanned shutdown. The financial impact of the damaged boiler, unscheduled maintenance and loss of production drove a review of current condensate monitoring techniques. The review panel concluded that current methods of measuring organic contamination levels frequently resulted in underreported values, and that periodic grab sampling may be inadequate for immediately alerting operators to contamination events.
The panel identified two aspects of the condensate monitoring program that, if improved, would better protect capital assets and enhance production uptime: improved sample collection methods to deliver more representative sampling of oil-contaminated condensate; and more frequent and/or continuous, real-time organics monitoring that would immediately alert operators of a condensate contamination event. The refinery also required that their investment in online monitoring technologies would have to be supported by compelling uptime gains.
Historically, steam condensate in the facility was monitored through the practice of collecting grab samples and transporting them to the onsite laboratory for organic carbon analysis. Laboratory measurements typically reported carbon levels of less than 1 ppm. It was determined during the investigation that the grab sample process was not providing a representative sample for analysis. During transport and while awaiting analysis, the sample cooled; the major constituent of the fouling, hydrocarbons, were lost in the sampling process through volatilization and phase separation.
The refinery team investigated means by which they could capture and analyze the sample at elevated temperatures common to condensate applications in order to demonstrate that hydrocarbon contamination was adequately represented in the carbon analysis. They also investigated ways in which to do this with an online analyzer in order to provide continuous protection. It is common practice for vendors of online instruments to cool the incoming sample in order to protect analyzer components. GE’s Analytical Instrument group developed and provided to the refinery an online sampler capable of handling condensate samples at temperatures up to 85°C (185°F).
The refinery team and GE collaborated to validate that the solution worked as intended, and the decision was made to implement continuous, online analysis of the organics. Data was collected over a two-month period and evaluated by the teams (see Figure 1). The data indicate that typical organic carbon levels are around 2 ppm, with periodic contamination events reaching 20–40 ppm. The continuous monitoring also alerted operators to a major organics contamination event that resulted in carbon levels spiking above 400 ppm. It is unlikely that any of these events would have been detected with laboratory analyses due to the infrequent nature of the events, and the sample matrix changes that result when grab samples cool.
The refinery’s maintenance crew used the data to locate the source of the major leaks and repairs were made. The online data confirmed success and the typical organic values were reduced below 2 ppm C.
Ongoing monitoring identified occasional organic excursions from unknown sources. A decision was made to eliminate the smaller excursions by passing the condensate over granulated active charcoal (GAC) beds. The analyzer configuration was changed to operate in the available 2-stream mode, allowing the refinery team to evaluate data for the influent to the GAC beds and the effluent, providing continuous data for determining the effectiveness of the beds via an organics percent removal calculation.
Reusing condensate from industrial processes will always have the risk of organics contamination. This risk and the financial implications of boiler system fouling can be mitigated with the addition of an online organics monitoring system measuring the quality of condensate returned. The accurate assessment of condensate quality provides the user not only the opportunity to reduce fouling, but information required to make operational decisions to reuse or dump the condensate. When fit for reuse, the facility reduces the need for additional make-up water—reducing costs associated with its production as well as reducing wastewater treatment costs.
The Analyzer selected for this application uses Super Critical Water Oxidation (SCWO) to oxidize the organics in the sample. SCWO is a wastewater treatment process that uses high temperature and pressure to break down organics. Used in an organics analyzer, SCWO provides an aggressive oxidation technology capable of handling high levels of salts, oils and other entrained matter that historically caused reliability problems for online analyzers deployed in industrial applications. SCWO, combined with a high-temperature sampling system, enabled reliable, continuous analysis of a challenging, two-phase sample containing high levels of hydrocarbon contamination. This enabled the refinery to implement an improved monitoring program that provided immediate notification of condensate contamination, protecting capital equipment and enhancing uptime of production processes. For more information on SCWO technology and Sievers* InnovOx On-Line Organics Analyzer, visit www.geinstruments.com/innovox.
Texas refinery identifes the source of boiler contamination and restores production using on-line steam condensate analyzer