Production of liquid hydrocarbons from polyolefins by supercritical water

Embodiments of the disclosure provide a method and system for recycling a plastic material to produce hydrocarbons. A plastic feed and a water feed are introduced to a first stage reactor. The first stage reactor is operated at a pressure equal to or greater than 22.06 MPa and a temperature equal to or greater than 373.9 deg. C. to produce an effluent stream. Residual solid components can be removed from the effluent stream. The effluent stream is introduced to a second stage reactor. The second stage reactor is operated at a pressure less than that of the first stage reactor but equal to or greater than 22.06 MPa and a temperature greater than that of the first stage reactor to produce a product stream. The plastic feed can include polyolefins. Optionally, a sulfur additive feed can be introduced either to the first stage reactor or the second stage reactor. Optionally, a residual oil feed can be introduced either to the first stage reactor or the second stage reactor.