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OAR Box 1778 

Prepped by Ollie Stewart 

Document Number: 

82) ll-C-24 

Docket Number: 

A-90-06 

Printed 10/28/2008 9:50:55 AM Sheet 82 of 276 
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../' •-' Office of Air Quality Planning and Standards 

Research Triangle Park, North Carolina 27711 

SEP 13 1978 

Mr. Thomas H. Rhoads

 - J 

EnviroriiTienta I Ccriservaticn ..snagcr 

Exxon Chemical Company 

1333 West Loop South 

Houston, Texas 77027 

Dear Mr. Rhoads: 

This letter will confirm the major points covered in our August 29, 

1973, discussion in Durham, North Carolina, concerning the application 

of the modification/reconstruction provisions of Part 60, 40 CFR, to 

stationary gas turbines. 

An existing stationary gas turbine will only be considered a 

modified source subject to compliance with standards of performance 

if emissions of NO increase as a result of some physical change, or 

change in method o£ operation. Thus, as long as emissions of NO in 

terms of pounds per hour do not increase, a stationary gas turbine 

will not be considered modified. 

Combustion of an alternative fuel will not be considered a modification, 

even if it results in increased emissions of NO , in those cases where the 

gas turbine was originally designed with the capability to fire this 

alternative fuel. Based on the preliminary information you presented 

concerning some of your gas turbines at Exxon's Baton Rouge refinery, 

it would appear that these gas turbines were originally designed to fire 

either gaseous or liquid fuels. If this is the case, then switching 

from firing gas to firing oil would not be a modification. Whether switching 

fuel in these gas turbines would or would not constitute a modification, 

however, assuming emissions of NO increased as a result of the fuel switch, 

will require submission of a formal request for such a determination to 

the EPA Region VI offices in Dallas, Texas. This submission should include 

data and information outlining the design capability of these gas turbines 

to burn liquid fuels, and the nature and order of magnitude estimates of 

the cost associated with any alterations necessary to fire liquid fuels 

in each of these turbines. 
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A change in ownership of an existing gas turbine will not result 

in that gas turbine being considered a new source subject to standards 

of performance. An existing stationary gas turbine is any gas turbine 

that had been purchased, or for which an owner or operator had entered 

into a binding contractual obligation to purchase, from a gas turbine 

manufacturer or vendor on or before October 3, 1977. 

An existing stationary gas turbine will only be considered a reconstructed gas turbine subject to compliance with standards of performance, 

if the total cost of the alterations made to a gas turbine exceed 50 percent 

of the total installed cost of a new gas turbine of equivalent capacity, 

.and it is technically and economically feasible for this turbine to comply 

with the standards. Whether emissions of NO increase, decrease, or remain 

tne same is of no concern with regard to reconstruction. In those cases 

where the 50 pe-rcfent criteria is exceeded, determination of whether or 

not it is technically and economically feasible for a gas turbine to meet 

standards of performance will require submission of a formal request for 

such a determination to the EPA Regional Office. This request should 

include information aopropriate to making this determination, such as: 

the nature and order of magnitude estimates of the cost associated with 

the alterations being mace to the turbine; order of magnitude estimates 

of the total installed cost for a new gas turbine of equivalent capacity; 

discussion of emission control technology available to reduce NO emissions 

to meet the standard, such as low NO combustors and/or water or steam 

injection; and the cost associated w^th the use of this emission control 

technology. 

I hope this letter responds to some of your concerns and clarifies 

the application of the modification/reconstruction regulations to stationary 

gas turbines. If you have any other questions or would like to discuss 

this subject further, please do not hesitate to contact me at (919) 541-5477. 

Respectfully yours, 

Fred L. Porter 

Chief 

Regulations Preparation Section 

cc: Mr. R. E. Ruckstuhl, Exxon Chemical Company 

u*Wrr Rich Biondi, Division of Stationary Source Enforcement (EN-341) 

Mr. Howard Bergman, Director, Enforcement Division, Region VI