Steritherm PHE

How the plate sterilizer Steritherm PHE works 

How the plate sterilizer Steritherm PHE works 

The plate heat exchanger consists of a pack of stainless-steel plates mounted in a frame with separate sections for pre-heating, final heating, and cooling.  

Corrugated plates with unique plate patterns optimize heat transfer. Supporting points on the plate hold the plates apart and form narrow channels between them. The liquids enter and leave the channels through ports in the plate corners. Varying patterns of open and blind holes route fluids from one channel to the other. Gaskets around the plate edges and the ports form the channel boundaries, preventing external leakage and internal mixing. 

Balance tank 

Before production begins, the Steritherm PHE undergoes sterilization-in-place (SIP) using superheated water at 125°C (257°F). Thirty minutes after sterilization, the product flows through the balance tank into the module. A programmable logic controller regulates pump speed, transferring the product to maintain a constant feed rate to the heat exchanger based on signals from a flow meter. A temperature transmitter and a pressure transmitter monitor the inlet product temperature and tank pressure. 

Pre-heating by direct regeneration 

Direct energy recovery pre-heats the incoming untreated product, reducing the demand for heating and cooling media. The hot sterilized product raises the temperature of the cold incoming product in the regenerative heat exchanger. The treated product is maintained at a higher pressure than the untreated product to prevent cross-contamination. 

Final heating to the sterilization temperature 

Final heating is achieved through hot water recirculation. A dedicated hot water set generates hot water using steam. A temperature transmitter monitors the product temperature at the heat exchanger outlet and adjusts the steam supply via a modulating valve to maintain precise control. 

The temperature difference between the hot water and the product is kept very low to prevent product burning and reduce plate fouling. Once the product reaches the desired sterilization temperature, it is held in an insulated holding cell to ensure consistent and effective sterilization. 

Cooling 

The product cools to the final temperature in two stages. First, the regeneration section mentioned above cools the product. The second and last stage uses a cooling medium, chilled water, ice water, or propylene glycol, depending on the requirements, to cool the product to the desired outlet temperature. A temperature transmitter controls the chilled media, measures the product's outlet temperature, and sends commands to the modulating valve on the cooling media pipeline. 

Cleaning-in-place 

Under normal operating conditions, all product-contact surfaces are cleaned in place without requiring module disassembly. Recommended cleaning intervals vary, depending on the product type and processing temperatures. 

Control system 

Automated operation controls start and stop functions, set point, and piping and instrumentation diagram (P&ID). Control parameters can be reviewed and adjusted. The system displays relevant process data, including as plant status, real-time temperatures, and flow rates, and alarm status.