Combustion as a Possible Solution to Pyrolytic Wastewater Utilization

Abstract

Treatment of hazardous liquid wastes can never be considered as economically beneficial process. It often involves many different treatment steps, especially in the case of highly polluted industrial wastewaters like pyrolytic wastewater (WW) from shale oil production. Currently in Estonia approximately 0.15 million tonnes of this pyrolytic water is generated annually. In the future according to the Estonian National Development Plan for the Use of oil shale this amount is expected to increase by 5 to 6 times (Anon 2016). The current paper presents the experimental results of wastewater incineration as an alternative approach to water purification. Combustion of this pyrolytic WW was carried out in a pilot-scale 60 kWth circulating fluidized bed (CFB) combustor firing oil shale or with propane. The influence of the flow rate of pyrolytic water (up to 0.36 kgwater/kgos) on gaseous emissions was studied. The results show that incineration of this highly polluted pyrolytic water under studied conditions in CFB combustor fed with oil shale does not pose environmental risks as intensive heat and mass transfer allows almost complete combustion of VOC’s. Due to the chemical composition of oil shale ash, SO2 formed during WW incineration was bound to the oil shale ash resulting zero SO2 emissions. Only NOx emissions were increased by up to 1.8 times at highest pyrolytic water loading.