Proposal:

Set Public Hearing April 11, 1997 to Amend Rule 1134 - Emissions of Oxides of Nitrogen from Stationary Gas Turbines

Synopsis:

Proposed amendments address SIP changes recommended by EPA to provide relief to those facilities utilizing digester gas fuel in controlled gas turbine units by increasing the NOx emission limit associated with use of this fuel. The amendments propose to increase the NOx limit from 9 ppm to 25 ppm at any facility with gas turbine units of less than 10 megawatts in size.

Committee:

Stationary Source Compliance, February 21, 1997, reviewed.

Recommended Action:

Set Public Hearing April 11, 1997 to amend Rule 1134 - Emissions of Oxides of Nitrogen from Stationary Gas Turbines

James M. Lents, Ph.D.
Executive Officer

Background

Rule 1134 was originally adopted August 4, 1989 and amended December 7, 1995. The amendments exempted gas turbine units rated below four megawatts (MW) and operating less than 877 hours located both in the South East Desert Air Basin and on San Clemente Island. In addition, the requirement to continuously correct the reference NOx emission limits to the International Standards Organization (ISO) standard to account for variations in ambient temperature, pressure and humidity changes was removed.

The purpose of the current Rule 1134 is to limit NOx emissions from gas turbine units rated at 0.3 MW and greater in size which, prior to August 4, 1989, were issued a valid Permit to Construct or Operate by AQMD, or were in operation pursuant to the provisions of AQMD Rule 219 - Equipment Not Requiring a Written Permit Pursuant to Regulation II, paragraph (b)(1). The rule requires each engine to meet specific NOx emission limits based on unit size. If those limits cannot be met without controls, then BACT must be applied, which usually consists of selective catalytic reduction (SCR). A correction for thermal efficiency is also applied to the limit. All of the existing gas turbine units have met the requirements of the rule with the exception of the Los Angeles County Sanitation Districts’ (LACSD) Carson facility, Joint Water Pollution Control Plant (JWPCP).

To comply with the NOx emission limits of Rule 1134, LACSD began work to install complete SCR control on their three gas turbine units. The installation of the SCR was completed in January, 1993. After much testing and attempts to meet the NOx limits of Rule 1134, it was determined that the referenced NOx emission limit of 9 ppm was not achievable with the installed SCR configuration. LACSD applied for and received a variance from the AQMD Hearing Board for Rule 1134 NOx emission limits and recently received an extension of the variance until April 21, 1997.

LACSD has extensively investigated the performance of the SCR which is currently achieving a control efficiency of between 60% and 65%. Based on these results, LACSD and AQMD staff have determined that the NOx emission limit of 9 ppm is not achievable for the gas turbine units at JWPCP. Therefore, LACSD has requested that the AQMD amend Rule 1134 to relax the NOx emission limit of 9 ppm to 25 ppm for existing gas turbine units utilizing sewage digester gas as fuel. It should be noted that there are turbines using sewage digester gas at Los Angeles City’s Hyperion treatment plant operating in compliance with Rule 1134. However, these turbines are subject to a different NOx emission limit because they do not use catalyst to control NOx emissions. Therefore, staff at Hyperion operate these turbines at partial load to reduce emissions and match plant needs. No other known turbines operate on sewage digester gas in AQMD jurisdiction.

Proposal

One reference NOx emission limit is proposed to be added for those facilities with gas turbine units from 2.9 to less than 10.0 MW utilizing fuel containing a minimum of 60% sewage digester gas by volume on a daily average. The NOx emission limit is proposed to be changed from 9 ppm to 25 ppm. Additionally, proposed amendments to monitoring and source testing have been written to clarify the requirements and reduce redundancy for both.

In conclusion, staff believes that LACSD made every effort to comply with the Rule 1134 NOx emission limit required for their SCR configuration. Despite these efforts, improvement in the SCR performance has shown marginal success, achieving a control efficiency of only 65%. A control efficiency of 85% is required to meet the 9 ppm NOx emission limit. Therefore, AQMD staff believes an amendment to Rule 1134 is necessary for gas turbine units utilizing digester gas fuel.

AQMP and Legal Mandates

Based on staff’s analysis of the proposed amendments, which would raise the NOx emission limit from 9 ppm to 25 ppm, the maximum increase in NOx emissions would be 254 pounds per day or 46 tons per year. No other pollutants will be affected by this rule amendment. Staff has determined the requested amendment will apply to LACSD Carson facility, JWPCP exclusively.

This emission increase will be included in the AQMD’s emissions inventory and will be considered in future AQMP revisions.

Policy Issues

One policy issue raised as a result of noticing the rule for the proposed emission limit amendment, relates to a request to extend the exempt hours from the rule for peaking gas turbine units from 200 hours to 1300 hours similar to the exemption in RECLAIM. However, in the RECLAIM program the exemption only applies to the CEMS requirements, not emission increases.

Another related issue involves the request that emission increases caused by changing the exemption from 200 hours to 1300 hours be placed under the Rule 1135 steam boiler generating system emissions cap. The request erroneously assumes peaking gas turbine units are subject to Rule 1135 - Emissions of Oxides of Nitrogen from Electric Power Generating Systems. Staff believes that the proposed amendments to Rule 1134 do not make gas turbine units subject to Rule 1135 because the gas turbine units are not permanent replacements for boilers. It would also require changes to Rule 1135, which cannot be done by amending Rule 1134.

CEQA & Socioeconomic Analysis

Pursuant to CEQA, the proposed amendments to Rule 1134 are a "project" and, as such, a Draft Supplemental Environmental Assessment (SEA) has been prepared. The Draft SEA has been circulated for a 45-day public review and comment period which ended March 10, 1997. All comments received will be addressed and incorporated into the Final SEA for the proposed project.

No viable project alternatives are available that will enable the LACSD facility to achieve the existing Rule 1134 emission limit. Overall emissions will not change as a result of the proposed amendments since the LACSD facility will continue to operate under existing conditions. No significant additional compliance costs are expected and no adverse socioeconomic impacts are anticipated as a result of the proposed amendments.

Implementation Plan

No implementation plan is expected since the proposed amendments affect only LACSD and its facility will continue to operate under existing conditions.

Resource Impacts

Not applicable.

Attachments

Summary of Proposed Amendments
Rule Development Process
Key Contacts
Proposed Rule Language
Draft Staff Report
CEQA Analysis

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ATTACHMENT A