VOCs are released during the production of cast parts. These VOCs enter the environment in the exhaust air via an air duct or smokestack. Optimized low-pressure UV lamps clean and reduce pollutants in the foundry exhaust air by means of photo-oxidation. This was made possible by the joint development of a customized low-pressure UV lamp by xpuris and Excelitas Noblelight.
Molds and cores for automotive industry castings are made from sand and binders. As these molds cure, they release volatile organic compounds (VOCs), i.e. chemical pollutants. In addition, a foundry is a particularly hot environment with exhaust air temperatures as high as 70?C while the relative humidity is below 5%.
A foundry belonging to a well-known German automotive manufacturer, which had recently expanded its production, could no longer comply with emission regulations using its existing UV system. Additional installation space for expanding the existing UV reactors was not available. In addition, the exhaust air temperature increased due to the introduction of a modified production process.
The plant operator was also dissatisfied with the service life of the existing standard UV lamps (G-lamps). The lamps had to be replaced very frequently due to either the high temperatures or because after a short time they no longer provided the required UV output.
According to official regulations, companies must comply with limits for pollutants released into the air. The degradation rate needed for this application had to be more than 50% (from 70 mg/Nm? to 30 mg/Nm?). The amount of exhaust air from the foundry was 83,000 Nm?/h, a relatively large volume. The main exhaust air pollutants included amines, benzene, phenol and formaldehyde. The total VOCs amounted to an average of up to 5 kg/h.
Increasing efficiency and compliance with emission limits in limited space
Since there was no space to enlarge the existing UV reactor, the new lamps had to be many times more efficient with the same number of units. Therefore, the following project goals were set: First, the lamps needed maximum VUV performance even at elevated exhaust air temperatures. Second was to minimize the VUV performance drop over the planned lamps service life of 10,000 hours. In addition, it was essential that the VOC limits were met after the conversion and the expansion of production. The maximum installed power input could not exceed about 240 kW. Finally, reducing operating costs was also a key goal of the project.
New lamp design: Optimal combination of quartz glass and coating for improved performance and longevity
Together with the system manufacturer xpuris, Excelitas Noblelight developed a low-pressure UV lamp that is specifically optimized for the operating conditions. The new lamp design combines the properties of synthetic and doped quartz glass, thus enabling ozone generation and CIP cleaning in the reactor and ozone-free operation outside the UV reactor. The long-life coating minimizes solarization of the quartz glass increasing the service life of the lamps.
High-performance amalgam lamps, NAQ, offer numerous advantages compared to conventional low-pressure mercury lamps. They deliver significantly higher VUV output and are characterized by a low decrease in output over their entire service life. In addition, they require only a small installation space to achieve high VUV output. Another advantage is their low temperature sensitivity, which increases the efficiency and reliability of the lamps under different operating conditions. Overall, these features contribute to significant cost savings.
The Excelitas UV lamps have been in successful use for over two years now. Since then, the foundry is reliably meeting emission limits and the long service life is reducing manufacturing downtime.
„We know that our customer can perfectly meet the exhaust air limits with the new lamps,“ says Norbert Franke, CEO of xpuris. „Thanks to the great cooperation between xpuris and Excelitas Noblelight, we were able to develop a real innovation.“
Keywords:Optimized low-pressure UV lamps,
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