Treatment of mill scale containing hydrocarbons

A process for treatment of mill scale containing hydrocarbons, wherein the process comprises:

• i) adding the mill scale as a feed material into an indirect-fired rotary thermal reactor, wherein the indirect-fired rotary thermal reactor is a multi-zone reactor with at least three different temperature zones;
• ii) heating the feed material in an oxygen-deficient atmosphere in each of the at least three temperature zones, wherein:
• a. a first temperature zone of the at least three different temperature zones is set to 93-149° C.;
• b. a second temperature zone of the at least three different temperature zones is set to 149-315° C.;
• and
• c. a third temperature zone of the at least three different temperature zones is set to 315-538° C.;
• iii) passing flue gas from the indirect-fired rotary thermal reactor through a pre-treatment duct, wherein the pre-treatment duct comprises an oil spray, wherein the oil spray is at a temperature of 120-150° C. and a velocity of the spray is at least 10000 fpm;
• iv passing vapour from the pre-treatment duct through a two-stage recovery unit comprising a first stage and a second stage, wherein:
• the first stage comprises an oil recovering assembly, the oil recovering assembly comprising an oil-based ejector style scrubber, a coalescing oil filtration unit, an oil mixing tank, a cooling unit, and an oil circulation assembly;
• wherein the vapour from the pre-treatment duct enters the oil-based ejector style scrubber;
• condensed liquid from the oil-based ejector style scrubber enters the coalescing oil filtration unit;
• and oil separated in the coalescing oil filtration unit enters the oil mixing tank;
• and
• the second stage comprises an oil and water condensing unit, wherein the oil and water condensing unit comprises a water-based ejector style scrubber, a water cooling and circulation assembly, and an oil and water collection tank with an oil-water separator;
• wherein the vapour from the oil-based ejector style scrubber of the first stage enters the water-based ejector style scrubber of the second stage;
• and
• condensed liquid from the water-based ejector style scrubber enters the oil and water collection tank;
• v) passing the vapour from the water-based ejector style scrubber through a coalescing oil filtration system;
• and
• vi) passing the vapour from the coalescing oil filtration system to a combustion chamber of the indirect-fired rotary thermal reactor.