Publish Time: 2023-04-13 Origin: Site
Extruded polystyrene (XPS) foam insulation is a widely used building material due to its excellent thermal performance, durability, and moisture resistance. However, the use of CO2 as a blowing agent in the XPS extrusion process presents numerous challenges. In this article, we will share practical tips on how to handle CO2 during XPS production.
The CO2 is delivered to the production site by truck and stored in a vacuum-insulated tank. The temperature of the CO2 inside the tank is about minus 20 degrees Celsius, and the pressure is between 1.6-2.0 Mpa.
To keep the CO2 in a liquid state during the entire process, a booster pump is used to transport the liquid CO2 to a middle tank, which is designed with a jacketed wall to control its temperature. It's essential to keep the distance between the CO2 tank and middle tank as short as possible to prevent the CO2 from vaporizing.
Despite efforts to keep the CO2 in a liquid state, vaporization can still occur, leading to production issues. To prevent this, a discharge valve is designed to let out any vaporized CO2, which cools down the temperature of the booster pump's head.
It's crucial to be careful when opening the discharge valve, as opening it too much can cause the CO2 to turn into dry ice and block the pipe, leading to significant delays. To prevent this, the booster pump's capacity should be ten times larger than the metering pump, allowing the booster pump to work periodically and avoid vaporization.
The middle tank's purpose is to maintain the CO2 at a certain temperature, around 25 degrees Celsius, to ensure stable and high enough pressure (6.5-7 Mpa). This maintains the constant physical property of CO2 and primes it for precise metering into the twin-screw extruder.
It's crucial to set the highest level alarm of CO2 in the middle tank to no more than 70% of the total volume to prevent incidents such as a power cut, which may cause the middle tank's temperature to rise, resulting in the CO2 becoming supercritical. This state is more difficult to control and predict, leading to the expansion of the CO2 volume, which can be dangerous.
After passing through the middle tank, the CO2 enters another cooling vessel, which lowers the temperature to 10 degrees Celsius. At this temperature, the CO2 is in a pure liquid state, making it easier to dose and meter into the extrusion process.
Handling CO2 in XPS production is challenging but essential to ensuring the productivity of the production line. By following the practical tips shared in this article, you can effectively manage the CO2 flow and maintain stable pressure and temperature, leading to high-quality XPS foam insulation.
Feininger is a "national high-tech enterprise", the chairman unit of XPS Association of China Plastics Association, a member unit of the National Plastics Standardization Technical Committee, a national-level three-star green building materials certification enterprise, and a national industry standard-setting unit.
Feininger has established the Engineering Technology Research Center of Polymer Physical Foaming Materials in Jiangsu Province, and has been rated as one of the top 10 extruded board enterprises in China by the Ministry of Light Industry of China for many years.
Feininger has passed ISO9001:2015, ISO14001:2015, ISO45001:2018 and strict FM certification and CE EU product standard certification. In 2016, Feininger won the United Nations "Ozone Layer Protection Recognition" honorary certificate.
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