This article explains the best available technology for oily wastes and OBM cuttings:
When it comes to drill cuttings and contaminated soils treatment, numerous technologies are available on the market. For heavy oily wastes, especially OBM cuttings and oil sludges, only thermal processes have proved to be effective.
For the last decade, few technologies have been competing for the latter oily wastes. In particular, traditional indirect fired rotary kilns and VacuDry® vacuum distillation units continue to be used, while direct fired rotary kilns are generally regarded as outdated technology and no longer permitted for oily wastes and OBM cuttings in most regions due to safety concerns, high emissions, and lack of reliability.
Whereas the perceived benefit of indirect fired rotary kilns (sometimes also called anaerobic thermal desorption units or ATDU) is the low initial investment, VacuDry® vacuum distillation excels with low operating costs, low maintenance and high performance on treatment of different waste streams.
The following graphs provide an overview of relevant key factors of the two technologies:
- Energy consumption: the diesel consumption per metric ton (mt) treated in an indirect fired rotary kiln can be up to 300% higher than in a VacuDry®. The VacuDry® energy consumption is so low due to a sophisticated sealing system resulting in extremely low off-gas volumes and associated low energy loss discharged via the heated exhaust gases into the atmosphere. In addition, a 120 – 150 °C lower treatment temperature is required thanks to the vacuum and a thermal oil heating system with > 85 % energy efficiency. If 30,000 mt of material are treated per year, a VacuDry® unit allows savings of approximately 765,000 EUR that would otherwise be lost due to inefficient energy transfer in the rotary kilns.
- Oil recovery rate: Due to nitrogen blanketing and vacuum of the VacuDry® unit, there is no oxidation or pyrolysis of oil in the process. This means that the highest recovery rates (>99%) as well as the highest quality of recovered oil can be achieved. As in the previous case, the additional recovered oil (e.g. diesel) in a VacuDry® unit results in more than 345,000 EUR extra revenue per year.
- Process off-gas: Thanks to a tight sealing system and a vacuum atmosphere, the off-gas emissions of VacuDry® units are less than 10 Nm3/mt. In the case of indirect fired rotary kilns, the emission loads can reach values greater than 100 Nm3/mt, which also translates into 900% higher emissions than those of VacuDry®.
In addition to the latter three factors, if the increasingly complex waste streams and the stricter environmental laws in the Middle East are taken into account, outdated thermal desorption technologies are no longer technically or commercially reliable alternatives. Flexibility in the feed material becomes the key that enables hazardous waste management systems to grow green, while making a profit and saving the environment.
Our new brochure includes an overview of the VacuDry® vacuum distillation technology designed for the treatment of contaminated soils, oily wastes and OBM cuttings in Kuwait.
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