RE: High Desert PSD

Boyer, Jon 

to: 

Anita Lee 

04/22/2008 04:34 PM 

Cc: 

"Balcazar, Ali" 

Show Details 

Anita,

Please read below for my responses to your questions. My comments are in blue. I’ll work on getting some of 

the specific temperature information you asked for and forward them to you.

If you have any further questions or clarification requests on this, please forward them to me.

Jon Boyer

Senior Environmental Scientist

High Desert Power Project

(760) 530-2303 (office)

(760) 912-3007 (cell)

From: Lee.Anita@epamail.epa.gov [mailto:Lee.Anita@epamail.epa.gov] 

Sent: Tuesday, April 22, 2008 9:36 AM 

To: Boyer, Jon 

Subject: High Desert PSD

 

Hi Jon, 

Thanks for sending over the information and for our discussion today. As you suggested, I'm including my specific

questions in an email, so here they are: 

1. Regarding Table 1 in the letter, I'm wondering if you have some STG temperature information available - rather 

than the more labor intensive time series of STG temperature, would it be easier to pick out times and just note 

Page 1 of 3

file://C:\Documents and Settings\ALEE07\Local Settings\Temp\notesBAAA25\~web3807.h... 2/4/2010
what the STG temperature was?

Specifically, it would be useful to know the STG temperature for 10/25/07 for 10:14, 13:44, 14:00, 14:06, 15:52, 

and 23:43. 

I’ll send you this information in a separate excel file. 

And what is the temperature when startup is considered complete? When steam is introduced into the STG (265-

300 degF), or when the SCR is at 464 deg F? 

The temperature of the SCR is independent of the process that warms the steam turbine generator. Once the 

SCR reaches a stable 464 deg F, then we can begin to add ammonia to the SCR. Lower than that temperature, 

ammonia flow will not decrease NOx emissions. The combustion turbines at these lower loads emits a higher 

NOx rate on a ppm basis due to incomplete combustion in the engine. With SCR treatment during the startup, 

we lower the NOx emissions in the stack in this time period of higher emissions from the combustion turbine.

Once inner metal temperatures of the steam turbine reach the 265-300 degree range, we can start bringing the 

Steam Turbine Generator up to load, using one of the combustion turbines to increase the rpms, slowly raising 

the rpms of each. This is not a fast process and can take up to 3 to 4 hours until we reach a level where we do 

not have to have any combustion turbine operating in a startup mode. See Table 4.5 on page 17 for a summary 

of example startup recommendations for Hot, Warm, and Cold startups.

2. My understanding is that after Turbine 2 tripped, upon restart of Turbine 2, if it had a Cold Start duration limit, 

Turbine 3 would not have had to be shutdown and restarted. Would this be true if Turbine 2 had a warm start 

duration limit (2.6 hours) instead of a cold start limit (4.5 hrs) upon restart after trip? (If we define cold/warm/hot 

starts by STG temperature, depending on the temperature of the STG at 14:06 (when Unit 2 was restarted), it 

may be classified a "warm" start, if so, is that sufficient to avoid having to shutdown Unit 3?) 

Our situation would not have been different if the restart of Unit 2 was characterized as a warm start. Keep in 

mind that steam turbine drives the duration of a cold startup, and its profile would remain cold until it is brought to 

load. Had Unit 2 been a cold unit on the second fire, we would have had until 18:36 to bring the unit into 

compliance. From that table, we would not have had to shutdown and restart Unit 3 in that instance. However, 

even with a cold characterization, if we were unable to start the Unit 2 for any reason, Unit 3 would have had to be

shutdown at that point. We may not know we have a problem until we attempt to start the unit.

This is part of the reason High Desert Power Project has asked to remove the duration limits. 

3. Temperatures on page 25 of Toshiba manual (#6) - is it appropriate for conditions at HDPP to use those 3 STG

temperature ranges to define cold/warm/hot start (rather than using a time since last firing of CTGs)? Or are the 

various temperatures presented in the letter (265/300 deg F, 170/235 deg F) more appropriate for HDPP? 

The table on page 25 indicates the rate of acceptable temperature change for the steam turbine inner metal 

temperature during pre-warming during a start, even a cold start. If the inner metal temperature is under 160F at 

the start of prewarming, then the guidelines recommend that we only increase the inner metal temperature by 90 

deg F/hr. Between 160 deg F and 210 deg F, the temperature rising rate can be 135 deg F/hr. Above an initial 

temperature of 210 F, the inner metal temperature can rise by 215 F/hr. Once the inner metal temperature 

reaches an acceptable range as described in the letter, we can start the steam turbine and slowly bring it up to 

speed. Table 4.5 shows the acceleration rate and anticipated start times for a Hot, Warm, and Cold Steam 

Turbine Generator. The total recommended start time is approximately 258 minutes. Please take note that 

several factors described in the procedure text can extend or shorten the startup time. 

Thanks Jon. Please let me know if any of these questions are not clear - it's a little challenging to describe! 

Page 2 of 3

file://C:\Documents and Settings\ALEE07\Local Settings\Temp\notesBAAA25\~web3807.h... 2/4/2010
Anita

........................... 

US Environmental Protection Agency 

Region 9, Air Permits Office 

75 Hawthorne Street (AIR-3) 

San Francisco, CA 94105 

 

ph: (415) 972-3958 

fax: (415) 947-3579 

........................... 

 

Page 3 of 3

file://C:\Documents and Settings\ALEE07\Local Settings\Temp\notesBAAA25\~web3807.h... 2/4/2010