Nitrogen Oxides (NOx) Emissions Removal System Process Evaluation

Project Synopsis

Evaluate the operation of existing pollution control systems and make recommendations to optimize NOx abatement performance and prepare a functional specification/sequence of operations for the pollution control system.

Project Summary

NITROGEN OXIDES EMISSIONS REMOVAL SYSTEM PROCESS EVALUATION

The client owns and operates a facility that manufactures catalytic inserts for automotive and industrial emission control applications.  The client contracted with Process Engineering Associates, LLC (PROCESS) to evaluate the operation of a packed bed scrubber and make recommendations to optimize the NOx abatement performance of the system during peak loading conditions.   In addition, once this review was completed, the client requested that PROCESS prepare a functional specification/sequence of operations for the pollution control system.

The production lines include a final drying and calcining step in which a nitrate based slurry washcoat, containing aluminum oxide, rare earth oxides, and precious metals, is fixed to a substrate and passed through a dryer and a high temperature (calcining) oven.  Emissions of nitrogen oxides (NOx) result from the drying and calcining process.  The production lines are equipped with pollution control systems for abatement of the NOx.  The major unit operations in the pollution control system include a packed bed scrubber that uses caustic and sodium sulfite (Na₂SO₃) for nitrogen dioxide (NO₂) scrubbing, a heat recovery and combustion unit, a selective catalytic reduction (SCR) unit that uses ammonia injection to react with the NOx, and an ammonia scrubber to absorb ammonia carryover from the SCR.

Specific project tasks included the following:

• Review of existing operating and stack test data to define actual peak loading conditions and comparison of them to the system original design basis

• Preparation of specifications for new (larger) chemical addition pumps

• Preparation of a computer process simulation (CHEMCAD) model to simulate the current operation of the packed bed scrubber and to determine the effects of: (1) scrubbing liquid operating temperature, (2) scrubbing liquid solids loading, (3) tower efficiency (solids buildup), and (4) Na₂SO₃ addition on the NO₂ removal efficiency

• Review the installation and operation of existing pH, conductivity, and ORP instruments and control logic to define specific modifications to improve the control of these variables

• Preparation of a final report summarizing the results of the evaluation and the detailed recommendations to modify the existing packed bed scrubber to achieve the best NO₂ scrubbing performance.

The final report included the primary conclusion that the NOx removal system was not operating as designed as well as several design and operating change recommendations for bringing the system back up to regulatory standards.

Industry Type

• Catalyst Manufacturing

Utilized Skills

• Emissions control equipment design
• Process troubleshooting and evaluation