Test results of a pilot plant for vitrification of sludge

Summary

Ekopromtekh R&D Center, LLC (a resident of the Skolkovo Innovation Center, a member of the Moscow Innovation Cluster) has developed an innovative solution to the problem of utilization of sludge generated during wastewater treatment – the sludge vitrification technology. To prove the working efficiency of the technology, its technical feasibility; to determine the environmental indicators and energy characteristics a pilot plant was designed at the existing Shchelkovo interdistrict wastewater treatment facilities with the support of the Skolkovo Foundation in the Moscow Region. In the process of operating the unit, a number of positive effects of the introduction of the technology were revealed. It is shown that vitrification of wastewater sludge rovides for reducing the volume of waste by 25 times (in relation to pre-dewatered sludge), obtaining a safe vitrified material at the outlet for use in construction. To determine the energy characteristics of the process, an integrated experimental-theoretical approach was used including the comparison of the measurement results with the data obtained in the course of CFD modeling and thermophysical calculations. The environmental safety has been confirmed according to the program developed by NII Atmosfera JSC, the measurements were carried out by the Center for Laboratory Analysis and Technical Measurements of the Central Federal District. During the tests, it was proved that, in contrast to incineration, hazardous emissions of superecotoxicants (dioxins/furans) were completely excluded. The measurements were carried out by the Laboratory of Analytical Ecotoxicology of the Institute of Ecology and Evolution named after A. N. Severtsov of the Russian Academy of Sciences. Instead of ash at the outlet the unit produces vitrified granular material that has been assigned V hazard class on the basis of biotesting. The practical value of the vitrified material has been approved: according to the report of the Tsemiskon Testing Center, cement with the addition of glass granulate as an additive corresponds to Portland cement with additives of CEM II/A type, 42.5H strength class. The vitrification technology has been fully developed for wastewater sludge and is ready for scale-up and commercialization.

Key words

sludge , sludge drying , sludge cake , vitrification , vitrified material , zero landfilling , pilot plant , thermal methods of utilization

The technology of wastewater sludge vitrification in comparison with other processing methodsThe technology of wastewater sludge vitrification in comparison with other processing methods

Summary

The experts of Ekopromtekh R & D Centre, LLC have developed an innovative technology for vitrification of wastewater sludge that provides for reducing significantly the volume of wastes and obtaining a safe vitrified material to be used in construction. A comparison of the vitrification technology with other methods of sludge processing is given: depositing, sludge digestion in digesters, drying, pyrolysis, catalytic and classical incineration. In Russia, more than 90% of the generated sludge is landfilled. If this trend persists, an increase in the sludge hauling distance is inevitable. Using unprocessed sludge as fertilizer increases the risk of soil contamination. Financial models of projects that envisage using digesters and selling biogas or electricity do not pay off. In case of using the drying method to obtain fuel from sludge, almost the same amount of thermal energy is consumed as the final product contains. Therefore, the cost of dried sludge as a fuel will not be less than the cost of natural gas, and taking into account other operating costs, including delivery to the consumer, will exceed the cost of gas by 2–3 times. Pyrolysis to obtain marketable products is under development and involves a lot of research. The technology of catalytic incineration of sludge without preliminary drying does not solve the main problems of any incineration process and causes certain difficulties: the risk of emission of superecotoxicants remains; the ash must be disposed of, the autothermal regime is difficult to maintain, the catalyst wears out and requires replacement. The vitrification technology has a number of advantages, it is ready for scaling and industrial implementation.

Key words

wastewater , methane tanks , incineration , sludge , pyrolysis , sludge drying , sludge cake , vitrification , thermal methods , vitrified material , zero landfilling