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Hausman, John R.

From: McDowell, Andrew S.

Sent: Friday, June 04, 2010 11:01 AM

To: Gischia, Scott; Hausman, John R.

Cc: Kroll, Hannah L.; Klejeski, Julie; Beaty, Aisha D.

Subject: PEMS Discussion Summary

Scott / John, 

In preparation for our call Monday with MPCA, I wanted to summarize the current situation with PEMS at HTC, as well as 

provide possible discussion points for the call. 

Current State 

1. Based on RVI values > 0.2, HTC submitted PEMS proposals to MPCA to predict NOX concentrations. Predicted 

concentrations were then converted to mass emission rates using installed stack gas flow monitors (“two-step 

approach”). 

2. Following premature failure of installed stack gas flow monitors, HTC worked with supplier to test new probes of 

alternative designs. Test results indicated that excessive wear of new probes is likely, and supplier refuses to 

provide a warranty on any new probes. Use of new probes would require constant maintenance as well as

replacement of worn parts, resulting in additional downtime of the PEMS. 

3. As a result, HTC developed a new PEMS model to directly calculate NOx mass emission rates (“one-step 

approach”). Negotiations with MPCA are ongoing to obtain approval of the PEMS one-step approach, with

MPCA currently suggesting a “hybrid approach”. 

4. HTC recently completed PEMS certification stack tests on Furnace Lines 1 and 2. Preliminary stack test results 

indicate that the one-step PEMS will not meet the 90% relative accuracy requirement contained in federal 

performance specification 16 (PS-16). 

Possible Discussion Points for Call

1. Communicate to MPCA that the 7-day NOx stack tests used to develop the initial one-step and two-step PEMS 

proposals intentionally introduced variability into the pellet indurating process, resulting in elevated RVI 

calculations. In addition, the vast majority of the operating conditions subject to stack testing were not 

conditions that HTC will operate under. In some cases we were also unable to maintain our fired pellet quality 

specifications, and this information was communicated to MPCA in writing with each of the original PEMS 

proposals. 

2. HTC has historically operated in two distinct production modes to produce standard and high compression 

pellets. NOx emission rates are significantly higher when producing high compression pellets (heat input 

increases per ton of pellets and firing zone temperatures are increased by ~100 degrees F. 

3. Because of the two separate production modes, HTC proposes to follow current Administrative Order 

procedures to conduct a new 7-day NOx test for each furnace line. The 7-day test will be split into two 

operating conditions to represent standard and high compression pellet production. RVIs will be calculated to 

determine whether alternative monitoring methods are necessary. If RVIs are greater than 0.2, then separate 

PEMS would be developed for standard and high compression pellet production modes. 
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Section 8.5 of PS-16 also says that if operational changes occur at a facility that may cause a significant change in 

emission rate, the PEMS must be recertified. I would argue that the change to and from standard and high 

compression pellet production does result in a significant change in NOx emission rates, which supports our 

desire to conduct new extended NOx stack tests. 

Sorry this was a little long-winded, but I wanted to capture some of our initial thoughts before I head out for the day. If 

we want to connect prior to the 10:00am call on Monday to discuss, I have availability most of the morning. Thanks. 

-Andy