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Closed-Cycle SCWO Processing System

We will now discuss the principles of operation of the Closed-Cycle SCWO Processing System (Figure 3). A key feature of this design is to recover and re-utilize all process water at system operating pressure without depressurization and water treatment external to the process. Another key feature of this design is the recirculation of cooled liquid effluent at system pressure for cooling and conditioning of the reactor effluent. The features of the Transpiring-Wall SCWO Reactor are covered elsewhere in more detail. (Transpiring-Wall SCWO Reactor)

Principles of Operation
Waste is pumped, preheated and injected at mixing nozzle (10) where it is mixed and reacted with supercritical water/oxidizer mixture (9) within the waste injector and transpiring-wall reaction chamber. The reaction byproducts are partially cooled and separated, with the vapor phase extracted via port (1) for further processing as shown. With careful control of separator conditions, the mass of water vapor leaving vapor outlet port (1) together with the non-condensable exhaust gases is sufficient to meet the water requirements of the process at location (9). To recover this water for the process, the water vapor must be separated from the non-condensable gases. This is accomplished by cooling the mixed vapor from port (1) and separating the condensed liquid water. Cooling is accomplished via open heat exchanger by the injection of cooled condensate directly into the hot water/gas vapor mixture. Condensed water is collected in vessel (4) and non-condensable exhaust gases extracted from the process via port (5). The condensate is circulated back to the process by pump (6) and heater (8a) which heats the water to supercritical temperature. The supercritical water is then mixed with oxidizer from heater (8b) and injected into the process at location (9). Water circulation rate can be adjusted independently of waste flow rate.

Closed-Cycle SCWO Processing System

supercritical, oxidation, SCWO, reactor, transpiring-wall
- Figure 3 -

The hot reaction by-products are quench-cooled by injection of cooled brine taken from the bottom of the separator at location (11). Caustic or other additives may be added to the brine prior to injection at port (16) for the purpose of controlling corrosion, pH, solids, and effluent composition. Free solids are removed from the brine by solids separator (13) and flushed from the system via brine/solids outlet port (14). Brine circulation rate can be adjusted independently of waste flow rate. The Transpiring-Wall SCWO reactor design ensures that solids are positively and continuously flushed from the system. (Transpiring-Wall SCWO Reactor)

Lower Operating Pressures
The Transpiring-Wall SCWO Reactor and Closed-Cycle Processing System can be operated at either supercritical or subcritical pressures. At supercritical pressures, heater (8a) (fig.3) would be a "once-through" type heater. For subcritical pressure operation, heater (8a) would have to incorporate both an evaporator section and a superheater section.

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