Project Synopsis
Develop a hydraulic model of the front-end flare system and evaluate PRD outlet conditions, knockout drum, flare tip operation, and flare header sweep gas requirements at a fertilizer manufacturing facility.
Project Summary
Process Engineering Associates (PROCESS) was contracted by a US fertilizer manufacturer to perform a technical evaluation of the ammonia flare vent header in their production facility. The facility’s ammonia plant utilizes separate front-end and back-end flare headers. The front-end flare system handles releases from the reforming, CO₂ removal, and methanation sections, while the back-end flare system serves the ammonia synthesis section. These systems are segregated to prevent mixing ammonia- and CO₂-rich streams, which could result in carbamate formation and potential plugging issues.
PROCESS previously completed a hydraulic analysis of the back-end flare header for the facility. As part of the current project, PROCESS developed a hydraulic model of the front-end flare system using the provided piping isometrics and PRD datasheets, following the same methodology applied during the back-end flare analysis.
The project scope included the following:
- Assess flare header hydraulics and PRD outlet conditions based on API 521 best practices, including velocity criteria and allowable backpressure limits
- Evaluate the main flare knockout drum based on required liquid holdup time and allowable liquid droplet size in the outlet vapor
- Verify flare tip operating conditions, including flare gas heat content (BTU/scf) and exit velocity requirements, to confirm compliance with 40 CFR Part 60.18 for defined overpressure scenarios
- Assess flare header system sweep gas requirements based on minimum volumetric flow rates in accordance with API 537, Flare Details and Related Equipment
This work scope resulted in the following project deliverables:
- A comprehensive project report documenting the design basis, modeling assumptions, results, and recommendations
- Aspen Flare System Analyzer (V14) simulation file developed based on the provided piping isometrics and PRD relief details
- Summary schematic illustrating the piping configuration, PRD locations, and flare header tie-in connections
Overall, this project supported the client’s goal of evaluating the front-end flare system design against applicable industry guidelines and identifying areas where the existing design may deviate from recommended practices. PROCESS’ Aspen model for the provided overpressure scenarios were used to evaluate vent header sizing and pressure relief device (PRD) adequacy in accordance with applicable API guidelines. The results provided a technical basis for design decisions and recommendations that enhance the facility’s ability to safely relieve process gases during major overpressure events.
Industry Type
Fertilizer Production
Utilized Skills
- Flare system evaluation and design
- Hydraulic modeling
- Pressure relief system evaluation and design.