Flash valve

The use of a flash valve will further ensure a constant feed of the polymer solution into the ZSK to avoid uncontrolled degassing of the process material in the supply line to the ZSK. A pulsating intake would not permit a stable process in terms of safe operation of the degassing zones and stable pelletizing of the degassed polymer. 

Example 33 Flash Valves, Partial Condensers, and Partial Vaporizers ... 

After passing a flash valve, the reactor stream Gjn enters a cyclone held at atmospheric or subatmospheric pressure, where it is split into a vapor stream Gy and a residue stream G,. The reactor stream consists of a liquid portion Gin " and a solid portion Gjn, and analogously the residue stream consists of a liquid portion and the same solids as the reactor stream. 

Next, use a valve (Pressure ChangelValve) to flash the liquid product from the drum to a specified pressure of 3.44 bar. Add a distillation column block (via Col-umnlDistillation) to facilitate water removal from the product leaving the flash valve. Use 12 theoretical stages, a condenser, and a reboiler. Note that when you first create the block, the popup window asks for a number of theoretical trays. However, this is a misnomer, because it counts the condenser and reboiler as theoretical trays. Once you double-click the column to open the specifications form, you can visually verify that there are 12 stages identified. Once you have made the block, add mass streams for the bottoms and distillate and be sure to coimect the distillate stream to the vapor port (so you will have a partial condenser). Specify the top tray as 3.44 bar with no pressure drop in the column in the Pressure Profile tab. Be sure to increase the number of iterations from the default 15 to about 100 (15 is not likely to be enough). Next, in the Feeds and Products tab, select the feed to tray 5 with the feed convention sent to Flash the feed adiabatically..This means that, because the feed is a mixture of vapor and liquid, the vapor portion rises to the tray above (4) and the liquid... 

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