# Detailed Feasibility Study: Dynamic Depressuring, Staggered Blowdown & Flare Network Design

- **Organization / Host**: EPPM
- **Client**: Client: Taknia Libya Engineering Company (TLEC) · Final Client: Sirte Oil Company (SOC)
- **Role**: Process Engineering Intern
- **Timeline**: Jan 2026 – Aug 2026
- **Location**: Tunis, Tunisia / Libya
- **Domain**: Plant Safety & Transient Simulation

## Executive Summary
Executed comprehensive blowdown analysis and dynamic depressuring in Aspen HYSYS Dynamics and steady-state to model peak relief loads, thermal shrink, and low-temperature metallurgy risks for the "Detailed Feasibility Study of New Gas Plant at Marsa El Brega" project (Client: Taknia Libya Engineering Company – TLEC; Final Client: Sirte Oil Company – SOC), followed by full flare network hydraulic backpressure analysis in Aspen Flare System Analyzer (FLARENET) and flare stack radiation sizing per API 521.

## Key Technical Metrics
- **Relief Standards**: API 520 / 521 (Sizing & Depressuring Criteria)
- **Depressuring Target**: 50% DP / 15 min (50% Design Pressure at 15 minutes per API 521)
- **Radiation Limit**: 1.58 kW/m² (Continuous personnel exposure limit per API 521)
- **Simulation Tools**: HYSYS & FLARENET (Dynamics, Steady-State & Flare Analyzer)

## Engineering Challenge & Technical Mandate
During emergency depressuring, rapid gas expansion generates intense Joule-Thomson cooling that can drop wall temperatures below the Minimum Design Metal Temperature (MDMT), risking low-temperature brittle fracture. Simultaneously, uncoordinated blowdown across multiple fire zones risks exceeding the flare header backpressure limits, compromising conventional and balanced-bellows PSVs. The mandate was to size restrictive blowdown orifices to achieve 50% design pressure within 15 minutes per API 521 while staggering zone depressuring to prevent flare header choking and flare tip Mach number exceedance.

## Process Simulation & Tools Used
- Aspen HYSYS Dynamics
- Aspen HYSYS Steady-State
- Aspen Flare System Analyzer (FLARENET)
- Aspen Simulation Workbook (ASW)
- Microsoft Excel

## Standards & Codes Applied
- API 521 (Pressure-relieving and Depressuring Systems)
- API 520 Part I & II
- GPSA Engineering Data Book Sec 5

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*Published by Hazem Mensi — Chemical Process Engineer (https://www.hazemensi.com)*