Typically, a Thermal EDS process involves:

Filling

Waste effluent is either pumped or gravity flows into the receiving tank via the inlet waste lines. As the tank fills with effluent, the dirty air is vented out via a double bank of HEPA filters. When the effluent reaches the high-level sensor a sterilization cycle is automatically initiated. The inlet will close diverting any further waste effluent to one of the remaining two tanks in the system (commencement of a sterilization cycle in one tank automatically sets the next tank in sequence to Receiving Mode). When the inlet trash valve is fully closed, the valve on the power flush water line will open for approximately 20 seconds.

Heating

To ensure a uniform temperature rise across the system, agitation will commence in the form of a mixer or centrifugal pump. This ensures even heat distribution and prevents solids build up on the bottom surface of the vessel. Agitation can be further amplified using mixing valves for high solids applications. With the agitation system operating, the system steam valve will modulate open allowing steam flow through the vessel jacket or heating coils to heat the vessel contents. The vessel will continue to heat and recirculate until a temperature of 250°F (121°C) is reached, at which point the system will proceed into Sterilizing Mode. Higher operating temperatures can be set from the operator interface touchscreen.

Sterilizing

During this phase the vessel contents will be held at (or slightly above) 250°F (121°C) for a period of 30 minutes. These parameters are specifically selected to guarantee complete sterilization of the entire vessel contents in all circumstances. Sterilization times can be set from the operator interface touchscreen.

Cooling

Typically EDS cooling is managed in one of two methods depending on each individual facility and its corresponding waste effluent stream. Where there is not a relatively large amount of particulate solids, the effluent can be passed through a shell and tube heat exchanger. In other circumstances, the sterile effluent is cooled by blending cold water directly with the effluent stream as the system is draining. As a supplement to cooling, a heat recovery loop can be implemented to reclaim the exiting heat for initial heating of the incoming unprocessed effluent.

Draining

When the sterile effluent has cooled to the desired temperature, it is then pumped to the drain. When the vessel is empty the system will initiate an end of cycle rinse to clean the interior of the vessel and wash any residual solids out of the system. After the end of cycle rinse is complete, the system will reset to the beginning of the cycle and wait for the control system to initiate its fill cycle.

To ensure a uniform temperature rise across the system, the recirculation pump will start, providing agitation to the vessel contents. This not only ensures that no “cold spots” are present but also prevents solids build up on the bottom surface of the vessel.Furthermore, as the liquid from the recirculation loop re-enters the vessels it passes through a static jet pump, which applies a venturi effect to further amplify agitation. The steam valve will open allowing steam flow through the vessel jacket or heating coils, which will heat the vessel contents. The vessel will continue to heat and recirculate until a temperature of 270°F (132°C) is reached, at which point the system will proceed into Sterilizing Mode.During this phase, the vessel contents will be held at (or slightly above) 270°F (132°C) for a period of one hour. These parameters are specifically selected by to guarantee complete sterilization of the entire vessel contents in all circumstances.

Throughout the sterilization phase, the recirculation pump continues to provide agitation to the system for uniform mixing. EDS typically cool in one of two ways depending on each individual facility and its corresponding waste effluent stream. Where there is not a relatively large amount of particulate solids, the effluent can be passed through a shell and tube heat exchanger.In other circumstances, the sterile effluent is cooled by passing cold water through the vessel jacket or heating coils. When the sterile effluent has cooled to the desired temperature, it is then pumped to the drain. When the vessel is empty it automatically shuts down and the vessel will go into Standby Mode. It will remain in Standby Mode until the other processing vessels in the system have completed a cycle, at which point the valves will again open and the tank will proceed back into Receiving Mode.