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Staff Accomplishments

Real-time process monitor reduces operational downtime

April 2006
Many industrial processes require continuous monitoring and evaluation of liquid streams to prevent unnecessary interruptions and determine appropriate waste handling procedures and disposal pathways. However, monitoring complex, chemically harsh, process liquids and waste streams can be time consuming and costly using traditional grab sampling and laboratory analysis. Operations often are stalled while results are being analyzed, and startup procedures can extend to weeks. Furthermore, conventional methods tend to provide only a sporadic picture of the materials being monitored. A new monitoring system, developed by Pacific Northwest National Laboratory (PNNL) researchers Sam Bryan, Tatiana Levitskaia, Sergei Sinkov and Steve Schlahta, features Raman spectroscopy combined with a Coriolis meter and a conductivity probe to quickly generate real-time data and facilitate a timely response to the dynamic characteristics of a given stream. The components and analytical tools of the new process monitor can be tailored for a variety of complex mixtures in chemically harsh environments, such as pulp and paper processing liquids, electroplating solutions, and radioactive tank wastes. The technology was developed for CH2M HILL Hanford Group, Inc. (CH2M HILL) to provide a chemical species monitor for process evaluation during the retrieval of radioactive salt cake wastes from single-shell tanks. The monitoring data including chemical composition and physical parameters of the waste stream will be used to meet corrosion conformance specifications, minimize unnecessary addition of water, and evaluate the effectiveness of retrieval strategies. "CH2M HILL has identified the process monitor as their baseline technology, scheduling multiple deployments starting in FY 2007 for the S tank farm retrieval," according to Project Manager Steve Schlahta. Workers at the tank farm will use the information provided by the monitoring system in various ways:
  • Make sure the waste added to the double-shell tanks from the single-shell tanks conforms to corrosion specifications
  • Minimize the unnecessary addition of water to prevent saturation of sodium nitrate and sodium phosphate in the brine
  • Evaluate the effectiveness of retrieval strategies.
In developing the new monitor, the research team performed calibration and performance testing on the system to qualitatively and quantitatively measure the concentration of sodium salts over the concentration ranges anticipated during waste retrieval from Tank S-109. The team independently measured sodium concentration (based on density/conductivity) and the specific salts (based on Raman spectroscopy). In addition, the team tested the effects of temperature, flow rate, bubbles and solids, and analyte matrix dependence. The effort also included close coordination with CH2M HILL's S-109 Partial Waste Retrieval Project so that the design and associated documentation were suitable for incorporating the process into the S-109 retrieval system. Two significant tests were successfully completed: a system acceptance test and a manifold validation test. The acceptance test verified that the actual measurement accuracy for each analyte of interest met the expected accuracy as predicted by the chemometric model. The manifold validation test showed that the chemical species monitor, once integrated into the larger system would operate as intended. For more information, contact Walter Weimer, Process and Measurement Science Product Line Manager.

Page 814 of 1046

Energy and Environment

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