The automation specialist Festo was founded in 1925 in Esslingen, Germany, and currently maintains locations in 61 countries, including Sofia in Bulgaria. In the Sofia plant, Festo manufactures printed circuit boards for electronic components. When soldering these circuit boards, large quantities of nitrogen are required, which serves as a process gas to reduce solder consumption and to ensure the quality of solder connection. Currently, contractors deliver each month 15,500 m3 of nitrogen by road tankers. At a price of about BGN 0.28 per kilogram of nitrogen and a monthly rent of BGN 390 for the tank, the supply of nitrogen costs BGN 5,387 per month.
In-house production of nitrogen feasible?
Energy Scout Vladislav Tsvetanov examined in his practical project whether the in-house production of nitrogen pays off for the location. The investment for the purchase, delivery, and installation of a nitrogen generator amounts to BGN 122,180. The nitrogen generator of choice can convert 489 m³ of air at a pressure of 7.5 bar into 155 m³ of nitrogen at a pressure of 6 bar in one hour with a gas purity of 1,000 ppm. This means that 100 hours of generator operation will produce the monthly demand of nitrogen. To get the necessary amount of air, Tsvetanov uses an existing compressor with a power consumption of 0.18 kWh/m³. The monthly electrical energy consumption for generating the required amount of air and nitrogen is 8,802 kWh. The price for this amount of electricity is about BGN 1,390 per month.
Reduction of costs and CO2 emissions
Compared to the external gas supply, the in-house production of nitrogen generates monthly net savings of BGN 3,997 which add up to BGN 47,964 per year. Therefore the investment pays off after roughly 2.5 years. Not only the company but also the environment benefits as the in-house production saves 24,190 kWh of electricity per year. Also taking into account the avoided transports, Festo reduces its emissions by almost 24 t CO2 per year.