Project Synopsis

Provide a third-party evaluation of emissions control system alternatives on four (4) fixed-roof storage tanks with the objective of avoiding volatile organic compound (VOC) releases, especially those in excess of air permit limits.

Project Summary


The client owns and operates a specialty organic chemical manufacturing facility. Process Engineering Associates (PROCESS) was contracted by the client to prepare a third-party evaluation of emissions control system alternatives for four fixed-roof storage tanks based on its significant knowledge of, and experience with similar processes and systems.  These alternatives (which were determined jointly by PROCESS and the client at the project inception) included storage tank modifications, cooling systems, vapor recovery systems, carbon adsorption, and flares.  Currently, the tanks have a conservation vent system with nitrogen padding, and are vented to the atmosphere.  Although the tanks also included temperature control systems, the tank temperatures occasionally exceed the permit limits.

PROCESS performed the following tasks in support of this effort:

  • Developed detailed physical and chemical characterization of the vent streams using PROCESS‘ licensed commercial process simulation software thermodynamics package, literature, and client tank liquid levels and temperature readings for the first half of 2007.
  • Performed calculations of VOC emissions using licensed commercial process simulation software to determine: (1) VOC concentration as a function of temperature, and (2) vent stream density as a function of temperature.
  • Calculated the maximum VOC emissions rate and total emissions per year for each tank.  The results were then compared to the limits set by the permit.
  • Selected the best emissions control system(s) based on PROCESS‘ knowledge and experience as well as several site-specific considerations.  Factors taken into account were fouling due to the high freezing point of the compounds, location of the tanks, large variations in the vent flow rate, available utilities, capital cost, maintenance requirements, and the speed and ease of implementation.

PROCESS‘ evaluations were assembled into a project report for use by the client. Activated carbon systems for each tank were recommended for the short term. Operational controls changes should be implemented where feasible. For a long term solution, with the prospects of additional tanks requiring emissions control, a flare system or combination of existing and new flare systems, was recommended.

Industry Type

  • Specialty organic chemicals manufacturing

Utilized Skills

  • Emissions estimating
  • Computer aided process emissions simulation
  • Emissions control alternatives evaluations

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