Precise metering of blowing agents

Research projects on particle foams

Precise metering of blowing agents

At the Fraunhofer Institute for Chemical Technology, ICT, a group of researchers are working on the development of foamed materials. To do this, ICT engaged in collaboration with a renowned partner in the area of XPS systems and Lewa as a metering specialist. The outcome: a pilot plant for all development phases from the formulation of raw products all the way to component testing.

Efficient insulating materials, foams for structure applications and bio-based, flame resistant and high-performance foams are currently very much in demand in the market. In addition to developing materials, the researchers in the Foam Technologies group at Fraunhofer ICT are particularly concerned with improving processes. They have built up extensive expertise in the area of particle foams and continuously manufactured extruded foams (XPS process). The Institute’s newly installed production technology allows complex topics related to foam production to be addressed and applications tested all the way to the pilot production stage.

Since July 2015, the pilot plant has been equipped with a Lewa Ecofoam device as a metering system for blowing agents in extrusion processes. The guide signal to control the diaphragm metering pump is linked to the extruder‘s speed. The metering pump delivers the blowing agent into the polymer melt in proportion to the extruder’s speed. The controller Lewa smart control conducts a consistent plausibility check between the flow meter‘s signal and the guiding signal and adjusts the flow rate via speed control of the drive motor in order to meet the process requirements.

The system is equally suited for a variety of projects, being compatible with all popular blowing agents from halogenated hydrocarbons through butane, pentane and propane to carbon dioxide. All important process parameters such as suction pressure, cooling and back pressure are clarified during the planning phase to meet the requirements of a wide array of applications. Due to the limited space available on site, the system was mounted on a compact base frame together with the mechanical section and control cabinet and delivered fully assembled, including all the piping and wiring. The Ecofoam’s wetted components are made from high-quality V4A stainless steel (1.4571 or comparable quality), with either PTFE or V4A stainless steel (1.4401) for the diaphragms.

Lewa installed various auxiliary components such as a cooling jacket at each pump head, a suction-side plate heat exchanger (radiator) and an in-line cooler to ensure that the blowing agents are in a fluid state and that they deviate sufficiently from the steam pressure. These components are required in CO2 applications to ensure that the carbon dioxide is cooled before entering the pump. The initial fluid temperature can be reduced from 20 °C at 57 bar steam pressure to approximately 5 °C. This is necessary to protect the system adequately against cavitation. There is no need to cool other blowing agents such as butane, provided the suction-side conditions are met.

The system can be used at extruder pressures up to 400 bar. A suction-side strainer, two contact pressure gauges for monitoring the pressure in the suction and discharge-side piping and a component-tested safety valve to prevent excess pressure all contribute to a safe system design. The volume flow can be varied over a wide range from 0.1 to 10 l/h owing to the combination of speed control and manual pump stroke adjustment.

Hall 7a, Booth B26

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Roland Schwab

Team Manager Systems, Sales Process Industry & Downstream, Lewa

Volker Kirschbauer

Sales Engineer Systems, Sales Process Industry & Downstream, Lewa