Comprehensive evaluation of a gas scrubbing system relative to Lower Explosive Limit (LEL) excursions. System design and controls modifications to mitigate LEL concerns.
BATCH CHEMICAL PRODUCTION PROCESS LEL EVALUATION AND PROCESS IMPROVEMENTS DESIGN
The client owns and operates a batch specialty chemical production facility and had recently installed a production area acid gas scrubbing system. Subsequent to system installation, questions began to be raised by client operations personnel relative to vent stream hydrogen content and the potential for lower explosive limit (LEL) excursions in the production units, vent system, and acid gas scrubber. Process Engineering Associates, LLC (PROCESS) was contracted by the client to perform a comprehensive evaluation of the system relative to LEL excursions and to design system/controls modifications as necessary to mitigate the LEL concerns. Project tasks included the following:
- Development of detailed physical and chemical characterizations of the system vent streams
- Development of production/vent/scrubbing system computer process simulation models for the purpose of identifying production steps that emit LEL concentrations of hydrogen and the locations in the production system where the excursions occur
- Execution of a process and control system design for a multi-path, automatically controlled vent system modification to minimize the risk of LEL excursions
- Development of additional computer process simulation models for the purpose of demonstrating operation of the modified vent system
- Preparation of detailed modified system controls sequencing and operating procedures
- Participation, as the design engineer, in a HAZOP review of the modified process
- Execution of the process design of emergency vents for the production operation to further mitigate LEL concerns
- Preparation of instrument specifications for the hydrogen and oxygen analyzers and control/shutoff valves required for operation of the modified process
- Development of materials-of-construction specifications for the modified system piping
- Revision of production system existing operating procedures, incorporating changes to the system that facilitate safe operation and compliance with stringent environmental guidelines.
Vent stream characterizations were particularly challenging for this project due to the cyclical nature of the production process and the lack of actual vent stream composition data. Computer process simulation models were developed using PROCESS’ licensed commercial process simulation software. During the project, the PROCESS project manager conducted a design review meeting with client engineering personnel and plant management to obtain consent and approval for the system modifications.
- Batch specialty chemical
- Stream composition characterization
- Computer process simulation
- HAZOP participation
- Operating procedures preparation
- Instrument specification
- Process automation