PTQ Q2 2024 Issue

duration afterwards (eight hours). During this time, reintro- duce dryout flow into stagnant areas and force more flow through portions of the main circulation path by manipulat- ing valves to ensure the plant is completely dry. Dryout is complete if the cold plant water content does not increase above 10 ppmv after this period. The time required to execute a closed-loop recirculation dryout is dependent on the quantity of water in the cold plant. Usually, four to six days is a reasonable estimation if the guidelines described in this article are followed. In cold plants where nitrogen cycling occ urs before a closed-loop recircu- lation dryout, the time required may be as little as two days. If the gas dew point is measured during dryout instead of the actual water content, it is important to understand that the pressure at which the dew point is measured has a significant effect on the dew point reading. Determine if the dew point analyser being used is reading the dew point at line or atmospheric pressure and under- stand the dew point conversion between the two pressure points. Establish the maximum allowable water content crite- ria before dryout starts. The maximum set value will help establish an agreement between all parties involved as to when dryout is complete. At times, parties involved become too eager and decide to begin cooldown prematurely, only to have to go back into dryout mode again after freezing the cold plant. Conclusion UOP Ortloff has witnessed many cold plant dryouts during commissioning and initial start-up over the years (see Part 1 in PTQ Gas 2024 ). A well-conducted cold plant dryout will help plant com- missioning and ensure start-up goes smoothly and does not last any longer than necessary. There are multiple dryout options which can remove water from the system. However, there are drawbacks to some of them. The closed-loop recirculation dryout does the best job at effectively removing water from the system while easily monitoring dryout progress and allows for a quick transi- tion to plant cooldown after dryout is completed. Scott A Miller is a Principal Process Engineer with Honeywell UOP, supporting Ortloff Cryogenic Gas Processing Technologies. He has more than 23 years of experience in the petrochemical and gas pro- cessing industries, of which 15 are in the design and operation of NGL/ LPG recovery plants. Email: scott.a.miller@honeywell.com David A Jelf is a Principal Instrument and Controls Engineer with Honeywell UOP, supporting Ortloff Cryogenic Gas Processing Technologies. He has more than 40 years of experience in the design and operation of NGL/LPG recovery plants. J A Anguiano is a former Engineering Manager with Honeywell UOP, previously supporting Ortloff Cryogenic Gas Processing Technologies. He has more than 25 years of experience in the design and operation of NGL/LPG recovery plants. Joe T Lynch is a retired Engineering and Licensing Manager from Honeywell UOP, previously supporting Ortloff Cryogenic Gas Processing Technologies. He has more than 45 years of experience in the design and operation of NGL/LPG recovery plants.

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