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Mary Rusnak, Marketing Manager at CECO Environmental, believes that continuing education is fundamental to many industries. Continuing education is standard in medicine, so why not start something similar for environmental engineers? It was with that thought process in mind that Rusnak created the CECO Certified program.
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Jeff Broderick, Director of Retrofit Sales for CECO, joined Just Say NOx to talk about Catalytic Reduction Systems and the pros and cons of SCR and SNCR re-agent options for these systems.
“The overall goal of both of these systems, whether it’s an SCR or SNCR system, is to reduce the NOx generated by a combustion source, such as boilers, gas turbines, or engines,” Broderick said. “The SNCR process is a higher temperature process that does not require a catalyst but is slightly less efficient. The SCR process uses a catalyst to mix the exhaust and ammonia, and it is a much more efficient reaction, but it happens at a lower temperature.”
Safety, availability, environment and cost are all factors when choosing a system that utilizes either ammonia, hydrous ammonia or urea.
Before selecting the right method for NOx reduction, it is essential to consider all aspects and potential safety hazards. -
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The rise of renewable energy has required creativity from power plants as they look to stay within emissions regulations
Vaughn Watson, Director, Aftermarket Sales & Services with CECO Peerless Mfg., visits sites often and has seen the struggle to adapt firsthand.
“A lot of gas-fire combined cycle facilities are being asked to augment with the rise in renewables, wind and solar, and, a lot of times, those are contingent on the weather. When the sun goes down, these plants need to ramp up quickly, and, when the sun is shining bright, they need to run at a lower load,” Watson said. “This causes some issues with the emissions controls.”
Fortunately for those plants, Watson and his group have a solution.
“Plants are now having to maintain emissions compliance while the unit is ramping up. They need to be able to turn on their gas turbine as quickly as possible while still meeting emissions. To do that, we have a technology called RASCR, (or) Rapid Advantage SCR,” he said. “That allows, when in that time over temperature race, (plants to) have the quantity of ammonia needed to maintain their emissions controls.”
It’s a solution that makes sure plants running at low load aren’t seeing their emissions spike during that time when the power is abundant and keeps them within regulation as they execute fast starts later on.
It also eliminates the need for other methods, such as using electric vaporization, which can cannibalize a plant’s power by requiring a high amount of electricity or hot gas fans requiring frequent maintenance. Instead, RASCR gives an alternative and delivers an option with a high ROI thanks to its lower cost of operation. -
We all know one bad apple can spoil the bunch, but the same is true of one bad batch of ammonia for power plants.
Vaughn Watson, Director, Aftermarket Sales & Services with CECO Peerless Mfg., remembers when multiple plants in Arizona realized they’d been supplied with ammonia not up to quality and had fouling issues at the exact wrong time – when the hot desert sun began to beat down on their customers.
“They were all calling us, because they were trying to run in the hottest part of the summer and generate power, but they weren’t able to meet their emissions because of fouling issues surrounding their ammonia supply,” Watson said.
Purity is key when it comes to both ammonia and the water being used to make it aqueous, so Watson has developed a relatively simple formula to keep in mind when doing tasks like choosing a supplier, setting a schedule for vaporizer inspections or picking an AIG design to keep the proper emission control.
“Reagent grade ammonia is what we’re specifying for our systems, and that’s 99.95% NH3 with demineralized water mixed in percent by weight, “ he said. “The way I like to think of it is pure water, plus pure ammonia, equals happy SCR because of these fouling considerations.”
Those are things operators will want to keep in mind with reagent purity clearly so critical to avoiding pitfalls that will keep them from reaching their peak or mire them in consistent struggles with maintenance. -
More than one plant operator has run out of patience with the traditional hot gas fan.
In addition to the maintenance issues that often crop up, there also are issues with hot gas bypass leakage, bearings that are not robust enough and general reliability.
Vaughn Watson, Director, Aftermarket Sales & Services with CECO Peerless Mfg., is happy to say that there now exists a better way of keeping emissions down utilizing fans.
“Nowadays, we have advanced the hot gas fan design specific to SCR technology, and the new hot gas SCR fans we use have a completely different setup,” Watson said. “They have upgraded shaft seals, they have 360 stainless wheel and shaft, and they have a tunnel block bearing that’s oil lubricated.
“So, all these things come together as a very reliable fan. And there are some other improvements we’ve made to the system, as well, to get the reliability out of the hot gas fans systems that a lot of plants have.”
It also doesn’t need to be an overly intensive process to modernize and upgrade a plant’s hot gas fans.
“We’d love to evaluate this on a plant-by-plant basis. We’d love to set up an inspection and a visit. Even just having a conference call to talk about their history with their fans and how we can solve (their problems) and give them a better product would be great,” Watson said.
Watson and his team can be reached by going to www.cecoenviro.com and clicking on the Peerless page. -
Jeff Broderick, Director of Retrofit Sales for CECO, popped by Just Say NOx to explain the differences between direct-injection SCR and the standard SCR process.
“In a typical SCR, you’re going to have ammonia fed through an SCR with an (ammonia injection grid),” Broderick said. “With direct injection, the main difference is you don’t need the AIG and the associated blowers and heaters. You’re injecting the liquid directly into the gas path.”
While CECO has used this method for smaller units over the years, the process is evolving to the point where it can now be used for larger units and different combustion sources.
Some of the advantages of direct-injection SCR are less equipment used to operate the process, which leads to fewer maintenance issues, and additional cost savings.
However, with the benefits come some challenges.
“The reason we’ve used AIG all of these years is because they do a good job of mixing the ammonia with the exhaust gas in front of the catalyst. It is more difficult to do when you remove that equipment,” Broderick said.
Combating these issues requires some additional considerations, planning and engineering to ensure a direct-injection SCR system will meet the process requirements.
