January 18, 2010 

Dr. Donna Lee Jones 

U.S. EPA Mailroom (D243-02) 

United States Environmental Protection Agency 

Office of Air Quality Planning and Standards 

Research Triangle Park, NC 27711 

 

RE: Response to Request for Information under Section 114 of the Clean Air Act, 42 U.S.C. 

§ 7414, dated December 4, 2009, with regards to the Mercury Cell Chlor-Alkali MACT 

and background data to support the estimates provided to USEPA by PPG in a letter 

dated July 13, 2009 

 

Dear Dr. Jones: 

Attached, please find the first part of PPG’s response to the Section 114 Information Request 

dated December 4, 2009. As discussed via email on December 17, 2009, and agreed to by you 

and Joe Karas (PPG Attorney), PPG is providing our response to USEPA’s Information Request in 

two parts: 

• By January 19, 2010 – PPG to provide the response to Item #2 of Enclosure 1; and 

• By February 18, 2010 – PPG to provide the response to Item #1 of Enclosure 1. 

Attachment 1 of this letter contains PPG’s response to Item #2 of the Information Request. 

Item #2 contains a request for a more comprehensive discussion of the energy costs associated 

with steam that PPG provided in our July 13, 2009 letter. 

Our response to Question #1 will be provided to USEPA by February 18, 2010, as agreed. 

Please feel free to contact me at (724) 325-5985 if you have any questions. 

Sincerely, 

Terry P. Smith 

Director Technology, Chlor-Alkali & Derivatives 

PPG Industries, Inc. 

PPG Industries Inc. 

440 College Park Drive 

Monroeville, PA 15146 

Telephone: 724.325.5985 

Fax Number: 724.325.5051 

Terry P. Smith 

Director, Technology 

Chlor-Alkali & Derivatives 
ATTACHMENT 1

REQUESTED INFORMATION: 

1. Mercury Emission Estimates

(PPG will provide, by February 18, 2010, our response to the information requested under Item #1) 

2. Steam Costs

EPA’S REQUEST: 

In your July 13 letter, you also provide detailed calculations for the energy costs associated with 

the steam needed to evaporate membrane cell caustic soda. 

Please provide a more comprehensive discussion of (and references for) the various numbers 

used in this calculation. 

PPG RESPONSE: 

Following is the information PPG originally provided in our July 13th letter regarding steam 

costs. PPG’s additional explanation and discussion of the numbers used in the calculations are 

provided in italics: 

C.PPG believes that EPA did not consider in its energy calculation the energy 

required in the form of steam to evaporate membrane caustic soda to increase its 

concentration from 32% to 50% .

The example calculation provided below is intended to represent raising steam via a natural gas 

fired boiler, it is generic in nature. Specific cases would need to be evaluated based on steam 

source availability and fuel source. 

a. Assume double effect evaporation @ 1.8 m lb steam per Ton NaOH 

i. Based on the number of pounds of medium-pressure steam required to 

concentrate caustic soda from 32% to 50%, the following relationships 

were derived by PPG: 

1. Single-effect evaporation = 2.7 m lb steam per Ton NaOH 

2. Double-effect evaporation = 1.8 m lb steam per Ton NaOH 

3. Triple-effect evaporation = 1.0 m lb steam per Ton NaOH 

For this example, double-effect evaporation was used as it provides a 

middle-ground for capital investment versus steam economy. 

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b. 1800 lb steam * 72848 tons Cl2 * 1.128 = 147,910,000 lbs steam 

i. Reaction chemistry dictates that 1.128 tons of caustic are produced per 

each ton of chlorine produced in the chlor-alkali process. 

ii. 72,848 tons chlorine per year is the nominal capacity of the PPG Natrium 

mercury cell facility. 

c. (147,900,000 lbs steam * 1150 Btu/lb )/(boiler efficiency of 80%) = 212,621 

mmBtu required 

i. 1150 Btu/lb is the standard enthalpy of saturated steam made at 

atmospheric pressure. This number is conservative, as the heat required 

to make medium-pressure steam is slightly higher. 

ii. Boiler Efficiency is the ratio of heat given out by the boiler to the heat 

supplied to the boiler expressed as a %. Steam boiler efficiency varies by 

boiler design but a reasonable range for efficiency is 75% to 85%. 

Boiler Efficiency = ( heat given out by the boiler / heat supplied to the boiler ) * 100 %

d. Cost @ $5 per mmBtu = $1,063,107 per year 

i. $5 per mmBtu of fuel is a conservatively low cost for natural gas, and can 

be taken as a reasonable fuel cost for coal. Historical data for natural 

gas can be found on the Energy Information Administration website link: 

http://tonto.eia.doe.gov/dnav/ng/hist/n3035us3A.htm

Since natural gas has a heat value of roughly 1000 Btu per cubic foot of 

gas, the data from the linked chart information is a near approximation of 

dollars per mmBtu for natural gas. Information from that website for the 

five year period from 2004 to 2008 shows that average annual prices for 

natural gas ranged from a high of $9.60/mmBtu (2008) to a low of 

$6.50/mmBtu (2004). Therefore, the $5/mmBtu used in our estimate is 

extremely conservative. 

 

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