Among the many reflections I’ve had in the wake of our most recent Users Summit are: 1) that NeuCo is incredibly fortunate to have longstanding and loyal CombustionOpt customers that recognized our broader technology vision and are now reaping the benefits; 2) that objectives, priorities and challenges shift over time; and 3) in virtually all cases, substantial additional benefits are obtained beyond those used to justify the initial optimization investment, some which can be monetized, others which are more difficult to quantify but valuable nonetheless.

The multiplicity of benefits – expected and unexpected – brings up one of my pet peeves: the overly simplistic but commonly-held view that combustion optimization equates to NOx minimization. While it is true that reducing NOx has historically been the largest single driver behind industry adoption of combustion optimization technology, it is neither the only nor even the primary driver for many applications.

Heat Rate Justifies Early Investments
In fact it was heat rate rather than NOx that was used to justify the investment in combustion optimization for NeuCo’s first three customers, Canal Electric, APS Four Corners, and Cajun Electric Cooperative’s Big Cajun 2. When Canal Electric became NeuCo’s first customer, they not only had no immediate need to reduce NOx, but were owned by COM/Electric, which had a fuel pass-through clause such that there were no shareholder benefits for heat rate improvement.

Why did the Canal Plant Manager Bob Fife choose to invest in NeuCo’s first combustion optimization installation when there was no need to reduce NOx and no shareholder incentives for fuel efficiency? Because he knew that stricter NOx regulations and wholesale power competition was an inevitable part of the plant’s near-term future, and that taking proactive measures to anticipate both developments would be good for the plant, its employees, and its owners.

As it turns out, this was a prescient move, given that the substantial heat rate improvement delivered by CombustionOpt Serial #1 helped the new owner Southern Company (later spun-off as Mirant) maximize profitability in the newly formed New England ISO, one of the first fully competitive wholesale markets in the US.  This profitability was further enhanced by the fact that the optimizer helped overcome a severe CO-related capacity constraint, providing an additional 20 MW of capacity. While CombustionOpt’s NOx reduction provided a multi-million dollar benefit stream for Canal as the initial OTC NOx budget and subsequent Clean Air Act SIP regulations came into play, it was the fuel efficiency and capacity gains that first paid off the investment.           

APS Four Corners, NeuCo’s second customer and its first coal-fired combustion optimization application, also justified its investment primarily based on fuel savings. While Four Corners wanted to demonstrate NOx reduction as a secondary objective in anticipation of future regulation, the primary investment was based on heat rate. This was in part because of their philosophy that heat rate/fuel efficiency improvements would ultimately lead to emissions reductions. Like Canal Electric, APS viewed wholesale power competition as inevitable, and in fact voluntarily gave up its fuel clause adjustment in the late 1990s. The decision to build on its initial investment in the advisory system at Unit 3, migrate this application to closed loop, and add closed-loop optimizers at Units 1 and 2 was based on the heat rate and NOx improvements obtained at Unit 3. 

Shifting Objectives
But soon after CombustionOpt was migrated to closed-loop operation it became apparent that the optimizers provided a powerful tool for addressing one additional problem operators faced at the three small older units at Four Corners: avoiding “black stack” opacity excursions caused as a result of trying to reduce NOx emissions which the units are inherently prone to.  Even though the plant was always in compliance with opacity regulations, the excursions did cause a public relations problem for the plant, located as it is in the air shed of major scenic points of beauty.  With this discovery, the optimizers for these units were told to place top priority on minimizing opacity excursions through tight control over CO.

And yet despite the fact that reducing CO is generally directly opposed to what is required to reduce NOx, CombustionOpt managed to provide consistent NOx reductions at these units, and was even able to “dial” NOx down further. Moreover, for the more than ten years that CombustionOpt has been running at these units, sustained heat rate reductions of greater than two percent have been achieved, despite a great focus being put on both opacity control and NOx reduction.These combined benefits, along with APS’ corporate sustainability initiative, recently led the company to add all of NeuCo’s other optimizers at its five Four Corners units and add CombustionOpt, SootOpt and PerformanceOpt at each of the three units they own at Cholla.  

For NeuCo’s third customer, the three-unit coal-fired Big Cajun II, NOx was not even on the radar screen. The sole focus at the time was on heat rate improvement, and the plant was selling its power into a competitive wholesale power market.  We were able to not only meet fuel savings targets, which provided the financial justification for the project, but also achieved a 15 percent NOx reduction at the two Riley Turbo units encompassing the initial project.

While the initial NOx reduction was viewed as a “good citizenship” benefit at the time, the ability of the optimizers to reduce NOx on both of the initial two units was of crucial importance later on, when the location of the plant was designated by the US EPA as a Non-Attainment Zone.  The combination of the sustained heat rate and NOx benefits at Units 1 and 2 led initially to the addition of the third CombustionOpt at Unit 3 (a 600 MW B&W opposed fired boiler), and subsequently to the adoption of PerformanceOpt at all three units, to further enhance the heat rate benefits obtained through CombustionOpt.  

The initial combustion optimization initiative at Big Cajun II Units 1 and 2 also provides a good example of the “unit operating knowledge” gained though optimization: in the process of applying the technology at two “sister” units, the customer learned through CombustionOpt’s analysis tools that a long-vexing 40 Btu heat rate difference between the two otherwise identical units stemmed from a damper in one unit being a few inches closer to the O2 probe dictating its control than the other. While the deterministic control curves in the DCS treated the units as if they were truly identical, CombustionOpt immediately “understood” the operational differences owing from this small difference and was able to compensate for it, with the resulting efficiency gains being just part of the overall benefits.    

Surprise Benefits Keep on Coming  
While recalling these early but lasting NeuCo success stories is a trip down memory lane for me, the “surprise benefits” just keep on coming. More recent CombustionOpt customers continue to find heat rate benefits that greatly exceed the increased boiler efficiency levels that the optimizer is using as its efficiency objective, due to decreased process variability, fewer upsets, and lower auxiliary power demands.  Operators discover that CombustionOpt automatically minimizes the variation between side-to-side cold end air heater temperatures that they historically have had to continuously wrestle with. 

SootOpt systems justified with heat rate and NOx reductions not only make operators’ jobs easier, but give them additional bandwidth to focus on emerging equipment health issues. And by avoiding unnecessary cleaning actions, it dramatically reduces the frequency of forced outages stemming from tube ruptures. PerformanceOpt helps surface long-standing thermal degradation from a leaking division plate before it is even completely installed. MaintenanceOpt identifies hitherto undiscovered problems just in time to incorporate provisions for addressing them during the next planned outage. The list goes on.  

And I see this list further expanding as the next round of emissions regulations requires SCRs or SNCRs on most currently operating coal-fired generating units, even small ones. Going back to the misconceptions of CombustionOpt as primarily a NOx minimizer, consider the optimization problem posed by a unit with an SNCR, where it would be desirable to both minimize reagent costs and decrease stack NOx, and continuously find the best combination of these two effects that minimizes overall operating costs. 

Many people in the industry wrongly assume that combustion optimization will cause ammonia slip through minimizing NOx, particularly if the SNCR is installed before or concurrently with the combustion optimizer. The concern is that the ammonia will bond with SO2 to form ammonium bisulfate and consequently cause air heater plugging and the associated down-time needed to clean the air heater. The reality, however, is that CombustionOpt can be used to keep boiler NOx and gas temperatures at optimal set points; and/or minimize reagent usage and keep stack NOx at the desired removal level. I believe this particular benefit is going to be particularly large, especially for units with SNCRs burning any combination of medium- or high-sulfur coal.

As you have just read, this blog is even more “all over the map” than my typical postings. But I ask your forgiveness here, as this most recent Users Summit even more than our past ones have gotten me simultaneously thinking about all that we’ve done over the last decade and all the exciting possibilities waiting to be explored together by NeuCo and our customers for the next one. 

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