VALVES FOR SUPERCRITICAL EXTRACTION OF PLANT RAW MATERIALS

15.09.2011

There are new designs: valves for supercritical conditions. A need appears to manufacture valves for nominal pressures over 400 bar for newly designed installations. One of such solutions are cut-off valves for installations of centre of study on supercritical extraction of plant raw materials with the use of CO2.

In the project, all the valves parts were manufactured of 316L steel and the counter flanges, of X2CrNiMoN22-5-3 1.4462 (DUPLEX) material. Because of working pressures such as 530 bar, the applied nominal pressure of valves was PN630, conforming to the norm BN-91 1771-20/40.

Packing between the valve bodies and counter flanges was designed with BX 150 seals conforming to API 6A class 15000. 

The valves have V class of plug/seat closing guaranteed at the full 530 bar pressure reduction, due to which the flow of the medium was directed over the plug (Flow to Close).

The difference between pressures over and under the plug when closed causes extra pressure and caulking of the system. So as to reduce the disposition force of the actuator, a plug relieved with an internal pilot control plug was used. The pilot  control was chosen in such a way that the force necessary to open it is 7 times lower that the force of the main plug. After opening the control, pressures over and under the main plug are balanced and further opening in order to achieve full flow does not necessitate more disposition force of the actuator.

So as to prevent wear and tear of internal parts caused by very high speed of medium flow such as liquid carbon dioxide, the plugs, seats and pilot sleeves are manufactured with full stellited coating of 45 HRC hardness.

The valves are equipped with pneumatic actuators, electromagnetic valves for control and open/closed indicators.

The presented valves were designed and manufactured for Artificial Fertilizers Institute in Zakłady Azotowe in Puławy.