In the steel industry, large amounts of degreasing agents are required in
degreasing solutions to wash off oil and grease from iron and steel surfaces.
As oil and grease enters into the degreasing solution, an oil-water emulsion is
formed. This reduces the solution’s effectiveness by dissolving the degreasing
agents, preventing them from coming into contact with the metal surface.
With increased usage, the emulsified oil content reaches 20 – 30 g/L eventually
and renders the degreasing solution ineffective.
XPORE’s inorganic membranes was selected to recycle alkaline-based degreasing agents
and water in a steel factory. By separating emulsified oil, grease and sludge from the waste degreasing solution, the degreasing agents can be recycled.
The waste degreasing solution passes through a pre-filter to remove iron flings and other impurities before entering a recirculation tank. The solution is then pumped through tubular membranes, where separation of the emulsified oil and degreasing solution takes place. The emulsified oil oil is retained in the feed stream of the waste solution, while water and degreasing agents pass through the membranes. The purified degreasing solution is returned to the degreasing tank for reuse, and the process continues until the emulsified-oil concentration in the recirculation tank reaches a specified value, after which the concentrated
wastewater is disposed.
This recycling system extends the life cycle of the degreasing solution substantially and reduces the usage of new degreasing agent and water every day. This translates to significant cost savings for the factory, with less wastewater produced.
Process ﬂow diagram for waste degreasing solution recycling system