Taking the Pain Out of pH Measurement in Corn Slurry

by Barry Wallen

Hello, and welcome to Analytic Expert! I’m Barry Wallen, Senior Sales Engineer at Emerson Process Management. Today I’d like to talk about measuring pH in corn slurry in an ethanol plant. Historically, this has been a tough measurement due to a variety of factors including heat, viscosity, abrasion, and contents of the stream. The problems included shortened probe life, lack of accuracy across a useful pH range, and sluggish response to process changes. The use of a sodium reference pH sensor made meaningful 2 point calibrations impractical. The need is for accurate pH measurement across a wider range, and quicker response times.

Here’s a meaningful solution. The Rosemount Analytical 3300HTVP and the 1056 analyzer have been performing well in dozens of ethanol plants beginning with a trial in Hudson, South Dakota. With these technologies, plants are getting consistent accurate pH values as well as longer sensor life.

The 3300HTVP is a robust sensor with a rebuildable reference electrode. This extends the life of the sensor as the reference electrode is usually the first part of the sensor to “die.” Typically, plants are doing a reference junction rebuild monthly and seeing probe lives of about a year.

Generally, the electrode is mounted in a tee in a recirculating loop beside the tank; however there is a retractable version that can be mounted through a ball valve directly into a tank. Ideally, the fins on the electrode protecting the glass bulb of the sensor should be oriented so they are upstream and downstream, not on the sides of the stream. This gives the glass measurement electrode protection from abrasion caused by the slurry as well as any metal pieces that may have made it this far into the process.

On initial power up, the 1056 will walk through a quick start menu. This menu allows operators to rapidly confirm a few parameters including language, measurement (in this case, pH), temperature units, and operating Hertz. The manual includes detailed instructions on advanced set up – there is very little that would need to be changed. The display allows for two (2) large display items (usually pH and temperature in a single channel unit) and four (4) small ones. These are all user selectable. For additional information on the application, please click HERE.

You can then perform an initial calibration and start receiving reliable accurate pH values.

For complete instructions on operation, maintenance, and steps in rebuilding the reference electrode, please click HERE. And for additional information on other food and beverage applications, please click HERE.

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