Due to their property of being soluble in different substances, emulsifiers are often used when immiscible components are to be mixed together. In order to achieve a suitable mixture, for example in food production, the pure, highly concentrated emulsifier is diluted to working strength in advance. Mixing systems for the production of a suitable emulsifier must above all have a high dosing accuracy in order to ensure an exact degree of dilution and to avoid incorrect mixing or fluctuations in the individual batches.

The dosing systems from Lewa GmbH are equipped with flow meters that continuously check the required dilution level of 20 percent; in the event of any deviations, incorrect mixtures can be avoided thanks to the short adjustment time and the quick reaction of the control system. The mixing module also helps to minimize logistics costs: By stockpiling highly concentrated emulsifier, which is only diluted with water later, there is no need for additional tanker trucks to deliver already diluted concentrate mixture.

Volker Kirschbauer Sales Engineer at LEWA GmbH. © LEWA GmbH

"When it comes to emulsifier dilution, accuracy and compliance with safety standards are particularly important when it comes to correct dosing," explains Volker Kirschbauer, Sales Engineer at Lewa GmbH. As the additives are primarily used in the food sector, the dilution systems used must meet high operating requirements. "Among other things, this means that the modules must be robust and wear-resistant in order to prevent leaks and - in the case of a hydraulically operated pump - any contamination of the emulsifier with the lubricants," says the expert. At the same time, the system must also work as precisely as possible so that the dilution levels required by the customer can be maintained without deviations.

Conventional piston pumps, such as those used by the chemical company to dilute its emulsifiers, were not ideal for this purpose. "In a first step, the concentrated emulsifier liquid was manually fed into the tank. Once the required quantity was reached, the valve was closed and a second valve was opened to add the process water for dilution," reports Kirschbauer. "An agitator then had to be put into operation for half an hour to produce a homogeneous mixture." This time-consuming and labor-intensive process had a negative impact on the user's production efficiency and also meant that the correct mixture was occasionally only achieved to a limited extent. "The human error rate is high due to influences such as stress or distraction," says Kirschbauer. "If the pump stop is activated too late, for example, the strength of the emulsifier mixture can change significantly and result in more water having to be added in order to restore the originally required concentration. However, this in turn means additional time is required."

High dosing accuracy thanks to optimized control

An internationally operating chemical group therefore contacted the pump manufacturer Lewa and commissioned the Leonberg-based company to build a pump system for diluting a 70 percent emulsifier. The user decided on a metering system with ecodos metering diaphragm pumps, which were to be used to dilute the emulsifier to 20 percent.

"The system consists of two pump trains: One conveys the emulsifier, the other the dilution water," says Kirschbauer, explaining the design. "Both contain a flow meter that monitors the current volume flow before the two liquids flow into a static mixer where they are mixed." Finally, a third measuring device in the tank shows the sum of the two volume flows for control purposes, thus providing the user with redundant safety - the sum of the partial flows must ultimately be equal to the measured value of the sensor. "If the measured partial flows do not correspond to the desired mixing ratio, the control system integrated in the system automatically readjusts them. The operator only has to specify the desired mixing ratio beforehand," says Kirschbauer. It is helpful that the LEWA smart control technology only requires a short adjustment time and can therefore counteract incorrect mixtures in a more targeted and faster way than conventional controls - this shortens the transition times with inaccurate mixture strengths. "According to the user's specifications, the emulsifier mixture was only allowed to deviate by 1 percent from the required 20 percent," explains Kirschbauer. "Thanks to the optimized control system, we can meet this requirement without any problems."

Space-saving storage through the use of dosing systems

Another requirement of the British chemical company was to use the same sizes as in a previous project when planning the dosing system. "If necessary, individual components should be able to be exchanged quickly and easily between the mixing units to avoid production bottlenecks," explains Kirschbauer. As the diaphragms and valves for both systems are of the same type, it is also easier to procure and stock wearing parts.

In addition, the LEWA dilution module ensures more efficient, space-saving storage. For example, if the user wants to process the emulsifier in three different concentrations, the conventional procedure requires the use of three tanker trucks to deliver the required quantities in the desired dilution levels. Thanks to the possibility of mixing the emulsifier continuously over a wide concentration range, only one tanker truck filled with a high concentration is required. 20,000 kg of mixing volume per day flow through the dilution system, which has been in operation since summer 2018.

According to documents from Lewa.