Sustainable Approaches to Oily Sludge Management in Chinese Megacities

Cold rolling oily sludge from the steel rolling process
is considered
hazardous waste and contains significant iron oxides and lubricants.
The main component is 61.7% light oil, which is pyrolyzed at approximately
430 °C. Resource utilization is identified as a key pathway toward
achieving sustainable disposal of cold rolling oily sludge. Prior
researches on environmental assessment have been conducted for oilfield
oily sludge disposal, applying these results to steel rolling oily
sludge disposal may be biased, and the coking synergistic process
for steel rolling oily sludge is in the pilot stage. Hence, focusing
on the emerging technology of coking synergistic, the environmental
impacts and economic feasibility of coking synergistic technology
and the other two technologies (distillation-incineration and conventional
incineration) were analyzed via life cycle assessment (LCA) and net
present value methods. The results show that coking synergistic technology
excelled in reducing environmental impacts, with a CO2 emission
reduction exceeding 35.7%. Furthermore, coking synergistic technology
breaks even within three months with a profit of 2260 CNY per ton.
Further exploration of the potential for the diffusion of coking synergies
(CS) in the provinces was carried out, and four alternatives to coking
synergies were designed with different market shares (0, 10, 20, and
30%). The results indicate that cold rolling oily sludge disposal
in Hebei Province contributes 37% of the national CO2 eq
emissions. When coking synergistic technology becomes the primary
alternative to hazardous waste incineration, national CO2 emissions are expected to be reduced by 26.7%. Considering that
coking synergistic technology must be dependent on the steel plant,
adopting coking synergistic technology for suitable steel plants not
only optimizes the utilization of cold rolling oily sludge waste resources
but also significantly improves environmental performance.