Conductivity is a non-flashy, unassuming measurement. It basically has the capacity to alert operators to changes in the process. And if that knowledge is correctly applied, it can have dramatic and critical results. Take for example the brewing company that recently presented on how conductivity measurement is now saving it over a million dollars a year!
The brewing industry uses ammonia as a highly efficient refrigerant to chill the water used in beer and to chill the beer during transfer and CO2 addition. Figure 1 shows the flow principle of a plate heat exchanger with the ammonia flowing in and out on one side and the process liquid on the other. Like standard refrigeration units, the ammonia (the refrigerant) is pressurized outside the process and depressurized in the area that needs to be chilled. Depressurization is endothermic meaning it removes heat from the process, and because of the pressure differential, if a tube in the heat exchanger fails, it will introduce a large amount of ammonia into the product. Needless to say, ammonia ruins the beer. But the challenge is always to discover where and when in the process did this contamination happen?
The standard methodology used to check for ammonia contamination is laboratory testing. The brewing company was checking samples for ppm levels of ammonia three times a day. If any of the batches failed, all product produced since the last test was suspect and had to be put to waste. Between tests, all product is on hold until it’s cleared and released for production.
A couple of alternatives to laboratory testing were being discussed but had significant problems. Ion selective electrode technology has interfering chemical issues, so a balance needs to be maintained for it to be accurate – which is impossible in brewing where types of beer have different normal conditions. On top of that, it is not sanitary nor is it made of materials that are approved by the National Sanitary Foundation (NSF). Dual pH measurement, which can infer ammonia, does not work for brewing due to glass electrodes, the lack of a consistent base value, and other issues.
When the brewing company came to Emerson Impact Partner Lakeside Process Controls, the use of conductivity measurement was suggested. Conductivity is a measure of the total concentration of ions in solution. Any leakage of ammonia into the beer would cause a rapid increase in the conductivity. Conductivity measurements were placed on both the inward and outward flow and any change in conductivity would alert the plant to a possible leak. Conductivity probes are solid state, made of NSF-approved materials, can handle the high temperatures, and have no issues with chemical compatibility – an all-around win for the brewing company.
The company used the Rosemount 1056 analyzer and the Rosemount 400 conductivity probe. The results of this seemingly straightforward addition to the brewing process are significant:
The new continuous conductivity measurement has eliminated the amount of waste product since leakage is caught immediately and there is no wait time between tests. In addition, brewers pay taxes on product produced not shipped, so they are saving the extra taxes they would have had to spend on waste product.
The power of unassuming conductivity strikes again!
Where could you use a conductivity measurement to save money?
Posted by Deanna Johnson, Rosemount Measurement & Analytical Global Marcom Manager, Emerson Automation Solutions
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