Posted on 10/01/2022 in Transport Fire Safety Recycling 2021
Recycled PIN FRs from flue gas cleaning

Magnesium and aluminium minerals from coal power plant flue gas scrubbing can be recycled as PIN flame retardants. The 1 400 MW coal power plant, Nantong, Jiangsu, China, operates lime/gypsum flue gas desulphurisation (FGD), with an objective of zero liquid discharge. In this study, the FGD wastewater was treated in five stages with lime, sodium hydroxide, NaAlO2 and NaHCO3 to stepwise remove and separate heavy metals, calcium sulphate (gypsum), calcium carbonate, magnesium dihydrate (MDH) and ettringite (a calcium aluminium sulphate mineral Ca6Al2(SO4)3(OH)12·26H2O). Gypsum can be recycled to the construction industry and calcium carbonate reused in desulphurisation. MDH and ettringite were soak-washed and analysed, and showed to have purity and particle size compatible with use as PIN flame retardants (particle size mostly 1 – 10 µm). Tests in EVA showed that 10% recovered MDH + 20% ettringite increased LOI from around 15 (neat EVA) to around 25.

“Recovering chemical sludge from the zero liquid discharge system of flue gas desulfurization wastewater as flame retardants by a stepwise precipitation process”, J. Guo et al., J. Hazardous Materials 417 (2021) 126054

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