Project: Mineral Facility - BACT Analysis

Overview: Business Objective

A large mineral processing facility had initiated a significant modification project to their Title V facility to realize improved production efficiencies. After several modifications and testing events of the new system, it was determined that the new equipment was operating out of compliance with the emission limits defined by permit, and as a result did not meet the Best Available Control Technology (BACT) requirements originally defined by the local air district to control nitrogen oxides. ALG staff was contracted to complete a comprehensive analysis of other potential control options under BACT within a compressed schedule in order to avoid a facility shutdown by the local air agency.

Technical Approach

As modified, the facility had installed a new low NOx burner designed to achieve BACT. After it was determined that the unit could not meet BACT, ALG was asked to consider other control options with the client and the local agency, to determine whether additional controls would be cost effective, technically feasible, and result in the necessary emission reductions to demonstrate BACT. ALG prepared a comprehensive BACT analysis of traditional SCR, SNCR, and hot-got filtration, a recent modification from traditional SCR which reduces plugging, improves control efficiency and operates over a wider temperature range. ALG considered applications of these controls in related industries including Portland Cement manufacturing, kaolin processing, and other mineral processing industries.

These emission control systems are found in other mineral industries that operate under very unique temperature ranges, with different particulate loading rates, sulfur contamination, moisture content, and typical combustion unit sizes than is found at the clients facility. Based on engineering data, ALG concluded that such factors directly affect the efficacy of the use of a control system like SCR. These intricacies were considered as they related to the clients operations and presented in the analysis submitted to the local air agency.

In support of ALG's findings, ALG held discussions with several potential control vendors to gain their expertise regarding the feasibility of installing their control system for the client as well as the efficacy of the system to achieve the emission reductions desired by the air agency.


The BACT analysis determined that the configuration of the clients system would require significant modifications to the facility to accommodate an SCR system, including the addition of a preheater to raise the temperature of the exhaust gases to within the minimum window of operation for an SCR type system. These design issues coupled with the relatively low concentration of NOx to be removed, concerns with high moisture content and plugging of the catalyst made the installation of SCR, SNCR, or hot gas filtration, technically infeasible nor would it be cost effective. Upon review of ALG's analysis the local air district concurred with our assessment, as a result our client was permitted to continue operations with the control system originally defined as BACT without the installation of additional costly controls.


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