Spray drying is an efficient process for obtaining high-quality whey powder from milk. Correct concentration in the evaporator is essential to ensure that the quality of the end product precisely meets the specified values. In a practical case, the technology used up to now showed a drift during the process duration which ultimately affected the quality of the end product. A test with the inline refractometer IRM-11 proved to be successful. The measurement accuracy over the entire process is constantly high and the composition of the milk powder can be precisely adjusted to the specified quality.
Advantages in the application
In this customer application, high-quality whey powder is obtained in a spray drying plant. The quality of the end product can be specifically adapted to the customer‘s requirements by concentrating the pre-product accordingly. This concentration of the dry matter can vary by more than 30° Brix, depending on the production batch. If the dry matter content deviates upwards from the specifications, the cooler can become clogged and fail. If the dry matter content is too low, the end product becomes too dusty and is partially lost in subsequent processing or becomes completely unsaleable and thus worthless.
In the evaporator, which is located upstream of the spray tower, the preliminary product is evaporated and cooled down again in a recurring process lasting up to 24 hours until the desired value is reached, then spray drying is started.
In this application, the dry matter concentration was previously determined using a density balance. However, a drift in the measured value was detected, so that the quality no longer met the specifications precisely enough and the composition had to be checked several times by means of laboratory analyses. With the IRM-11 refractometer, the dry mass concentration can be measured directly and inline using the Brix value. Due to the very compact size and the installation on a Varivent or Tri-Clamp process connection, directly and without bypass, the analytic sensor can be integrated into a existing process without much effort.
By a calibration in the test run, the Brix values which have to be specified for the IRM-11 could easily be determined and then used as a default setting for the production process. Depending on the required specification and composition of the final product this default can be set between 0 and 85° Brix for IRM-11.
The measuring interval can be individually adjusted starting from 2 seconds, so that continuous and reliable process monitoring can be ensured.
Due to lactose crystals in the pre-product, hot water rinsing is already carried out at certain intervals to prevent the cooler from clogging. The optical measuring system of the IRM-11 can also get covered by such a layer of solid particles, which may lead to measurement inaccuracies. The IRM-11 reports this by the drop of the result to 0° Brix. At the described customer application this could be remedied easily by slightly reducing the intervals and the duration of the hot water rinsing.
Anderson-Negele offers the testing of the IRM-11 refractometer directly in the process. This allows to verify the function in the operative application. Interested parties can contact their responsible technical adviser or Anderson-Negele to request a product test.