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Chen, Eugene

From: Sprungl Barbara J <Barbara.Sprungl@srpnet.com>

Sent: Friday, February 19, 2016 7:05 AM

To: Chen, Eugene

Cc: Larson Craig R

Subject: FW: SCR MIT/MOT

Hi Eugene,

I apologize for the delay in getting you additional information. Please let me know if this meets your needs or if you

need anything else.

Thanks.

Barbara

Barbara Sprungl, O&M Manager ‐ Engineering

Santan/Kyrene Generating Stations

Salt River Project

(w) 602‐236‐5374 ‐ (m) 602‐516‐4908 ‐ (f) 602‐236‐2331

Mail Station STS300 ‐ PO Box 52025 ‐ Phoenix, AZ  85072

From: DDouthwright@babcockpower.com [mailto:DDouthwright@babcockpower.com]  

Sent: Monday, January 25, 2016 2:03 PM

To: Larson Craig R

Cc: CGSBART ‐ DEPT ID; mjasinski@babcockpower.com; RHarde@babcockpower.com

Subject: Re: SCR MIT/MOT

 

***SRP EXTERNAL WARNING: THINK BEFORE TAKING ANY ACTION WITH UNEXPECTED 

EMAILS. REPORT ANYTHING SUSPICIOUS.*** 

Craig, 

Following is RPI's explanation on how Minimum Operating Temperature (MOT) and Minimum In Injection Temperature 

(MIT) constraints were determined for CGS Unit 2. 

The minimum continuous operating temperature is determined by identifying the formation temperature of ammonium 

sulfate salts in the catalyst itself. What makes this determination difficult is that in the catalyst micropore structure the 

partial pressure of the ammonia and sulfur components are much higher which therefore leads to a higher formation 

temperature in the pore itself versus the bulk average gas conditions. There is no straightforward way of determining this 

temperature as each catalyst supplier has their own formula based on their experience. In the past we have noticed 

substantial differences between suppliers and as a result we rely on their calculations. To make the calculation, the 

catalyst suppliers need the gas composition and primarily the SO3 and ammonia concentrations (ammonia is a direct 

function of how much NOx needs to be removed). These are typically determined through testing and established in the 

specification for us to obtain the design. 

The minimum injection temperature is directly related to the minimum continuous operating temperature. In the past we 
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have determined with dealing with most suppliers that the ammonia can be injected before hitting the minimum continuous 

operating temperature during start-up. Ammonium sulfate salts will form but will eventually decompose at higher 

temperatures. Typically operation below the minimum continuous operating temperature is also restricted to a finite 

number of hours a year so in establishing our level we try to take this into account. We typically establish a level of 15 

degrees below the minimum continuous operating temperature which is conservative based on our experience. 

Please let us know if you have any questions. 

Dan 

Daniel Douthwright Project Manager Riley Power Inc. 5 Neponset Street Worcester, MA 01606 

 

T: 508-854-3812 F: 508-852-7122 M: 508-868-6939 

 

DDouthwright@babcockpower.com http://www.babcockpower.com

From: Larson Craig R <Craig.Larson@srpnet.com> To: "DDouthwright@babcockpower.com" <DDouthwright@babcockpower.com>, 

Cc: CGSBART - DEPT ID <CGSBART@srpnet.com> Date: 01/25/2016 10:11 AM Subject: SCR MIT/MOT 

Hi Dan, 

 

As part of SRP’s Regional Haze Reconsideration with EPA, they have asked for some explanation on how Minimum Operating

Temperature (MOT) and Minimum In Injection Temperature (MIT) constraints were determined for CGS Unit 2, since these

temperatures determine through what load ranges the unit can operate with the SCR in service. 

Last week I discussed this with EPA personnel and they indicated what they would like is a brief (paragraph or so) explanation from

the OEM and the Catalyst supplier where the limitations come from to use a reference in their response to comments on their

proposed reconsideration. 

Since Riley/Babcock is the OEM, and the contract for the catalyst supply was also administered by you, I am asking you for assistance

in obtaining this description. 

 

Thanks, 

 

Craig Larson 

Manager Project Services 

SRP 

928‐245‐9872 

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