Within the framework of the "Growth and Employment" initiative of the European Regional Development Fund (ERDF), projects to reduce CO2 emissions from companies are supported, among others. Treibacher Industrie AG currently has three such projects in implementation:
During the roasting of the vanadium slag in the multi-deck furnaces of plant VO, a hot exhaust gas is produced, which is currently cleaned by a cyclone, an electrostatic filter and a scrubber. In the past, the scrubber was necessary for SO2 purification because heating with fuel oil was difficult, which had a relatively high sulfur content. Due to the scrubber the exhaust gas temperature dropped to approx. 55 °C, this temperature was too low for a reasonable waste heat utilization. In the future, a conversion to high-temperature bag filters will make it possible to use the waste heat of the exhaust gas, which then has a temperature of approx. 240 °C. This allows the washing water to be heated during the fryer leaching process and the combustion air to be preheated during the APV drying process.
The VO operation is fully continuous. Only every two years there is a 14-day revision shutdown. This facilitates the internal waste heat utilization, since heat sources and sinks run synchronously.
The total usable waste heat from the exhaust gas of the deck ovens amounts to 11,160 MWh/a.
Impact on CO2 emissions: Savings of 2,060 t CO2 per year
The current solids separation and washing process of the resulting wastewater residue is very energy-intensive, since on the one hand the centrifuges and high-pressure filter presses have high power consumption and on the other hand a relatively large amount of water is required for effective washing, which must be heated to the necessary temperature of approx. 80 °C.
Due to improvements in the degree of automation of membrane filter presses, the solids separation process was again investigated and piloted. The knowledge gained from these tests was the decisive factor for replacing the energy-intensive and wear-prone centrifuges and high-pressure filter presses with membrane filter presses. This also made it possible to switch from dilution washing to displacement washing. In this case, purified, still hot waste water can be used for cake washing directly after the neutralization stage, thus avoiding additional heating of the washing water.
1,150 MWh electricity per year can be saved by switching to filter presses. The heating of the washing water is no longer necessary, saving approx. 2,350 MWh of natural gas per year.
Effects on CO2 emissions:
Electricity: Savings of 323 t CO2 per year
Natural gas: Savings of 563 t CO2 per year
Total at least: 323 + 563 = 886 t CO2 per year
Auswirkungen auf CO2-Emissionen:
The furnace is heated with the exhaust gas from two natural gas burners. The material is transported from the top to the bottom by rake arms which are mounted on an air-cooled hollow shaft. The hollow shaft cooling air is supplied at the lower end of the hollow shaft via a fan and leaves the shaft at the upper end. The heated cooling air was previously discharged into the open. The average temperature of the hollow shaft cooling air is approx. 240 °C. The heated hollow shaft cooling air is now supplied to the two burners instead of cold fresh air, so that the heat content can be fully utilized.
This results in a natural gas saving of a good 2,400 MWh per year.
Effects on CO2 emissions: Savings of 580 t CO2 per year
Further information on the ERDF can be found at www.efre.gv.at.