Continuous Emission Monitoring Systems pt 1

 In this episode, Sean invited Yokogawa's Process Analyzers expert Mike Wallis to debunk several misconceptions about Continuous Emission Monitoring Systems (CEMS). Is it true that CEMS are high-maintenance? Are these standard systems which require no engineering?  Is it mandatory to implement Data Acquisition Systems alongside these analyzers? Download and Listen for more 

Transcript

[00:00:01.450] - Sean 

This is a Yokogawa, Australia and New Zealand podcast. Welcome back to Yokogawa Debunks, conversations with industry experts to uncover the truth behind this and misconceptions surrounding the Industrial Automation, and Industrial Instrumentation space. I'm your host, Sean Cahill, and I would like to start by acknowledging and paying our respects to the traditional custodians of this land, to the elders, past, present, and emerging on whose country this recording is taking place. Now, today, we'd like to welcome Mike Wallis, manager for process Analyzer solutions at Yokogawa, Australia, and New Zealand. Mike has extensive experience in the design, installation, and service of process Analyzer solutions for some of the largest and most complex applications in the region. So without further ado, welcome, Mike. 

[00:00:50.230] - Mike 

Thank you, Sean. It's good to be here 

[00:00:50.900] - Sean 

Today, Mike. We're going to address some of the misconceptions people have around continuous emissions monitoring systems, or CEMS, for short. Maybe the best way to start off with is Mike, if you could provide us with a quick explanation of what a CEM system is and what it does? 

[00:01:08.570] - Mike 

Well, thank you, Sean. As you said, it's a continuous emissions monitoring system. So what it does is it continually monitors the typically stack gas emissions that come from combustion processes. There are other kinds of cems, but the ones that Yokogawa are particularly involved with are ones that measure gases. So what we're talking about is a system that measures exhaust gases from an industrial process 

[00:01:38.520] - Sean 

That's really put it into a nutshell very well. Now one of the things that we do find, and it's probably the number one misconception that we see, is that people seem to have this impression that CEM systems are high maintenance. And we'd like to hear your views as to whether you think there's any truth in that. 

[00:01:54.750] - Mike 

Well, thanks, Sean. It depends on the application and the design of the system, a well-designed and well-documented sense of good startup, and good shutdown procedures that will often require much less maintenance. Now, the cause of high maintenance in many CEMS applications, it's either due to poor design or in some cases, inadequate operation. Would you like to explore an example in a little bit more detail.

[00:02:17.090] - Sean 

Please, if you could go into more detail, and that'd be great. 

[00:02:20.830] - Mike 

Sure. Okay. Let's take a process which is combusting a solid or a slightly dirty fuel. This is a very common thing to encounter where a continuous emission monitoring systems will be required. It could be something like a process gas burner or a coal-fired power plant, maybe a waste-to-energy generator or perhaps an incinerator. The point is that the flue gas is probably going to be hot, it's going to be saturated with moisture, and it's also likely to contain some corrosives, in particulates. Now, the corrosives could be things like sulfur dioxide, sulfur trioxide, or hydrogen sulfide, those fairly common ones. When those sulfur components are kept dry, they're easy to deal with. But if they get into a liquid state if they get wet, if they get mixed up with some condensation, then they can become really corrosive and very aggressive. They can also form plaques or scales which can build up. So if the CEMS is not properly heated up for the process is introduced to it, condensation may occur and then you've got the start of a problem and that problem will apply, whether it's an in-situ device that's making the measurement or whether it's an extractive type. 

[00:03:28.280] - Mike 

So it needs to be carefully thought through, how the process starts up, how the cems will be protected during the low temperature, fuel-rich startup, whether it gets full of water if the process shuts down, or what the impact of a power outage might be. 

[00:03:42.200] - Sean 

So it's quite clear there are many variables that really could impact the maintainability of the cem system. 

[00:03:47.350] - Mike 

Well Sean, there's an old saying that 80% of solving a problem is knowing what the problem is. So if the work is done at the front end, if we get adequate information gathering and the design is well thought through, and then very importantly followed up with a good level of operator training and maintenance technician training, then it'll have a longer, happier life than if it's just sort of dumped in and the customers left to their own devices to try and make it work and maintain it. 

[00:04:12.130] - Sean 

Okay, so it's clear that work needs to be done upfront. That actually leads me into another misconception that we've come across in relation to cems and that they are typical premade boxes. You can even buy them online perhaps, and they don't even require engineering. So continuing on for your example. How do you see that? 

[00:04:31.820] - Mike 

Well, I've been around the process industries for quite a long time now. It's actually knocking on towards 40 years. And what I've realized is that each process is in some ways unique. So even though the basic design of the CEMS might have some common elements, the ability to tailor the design to suit each particular site's requirement equates to benefits. A few examples. Some plants may have extreme environmental conditions that can be in terms of temperature, wind loading, rainfall, fuels, for example, can differ. Black coal, Brown coal, natural gas, process by-product fuel gas, just for example. They'll have different levels of sulfurs, different combustion methods produced different combustion conditions, and different outcomes in terms of what's going to be in the exhaust. Processes also vary. Reformer plants, for example, may use different technologies, have different purposes depending on what they are used for, and therefore have different exhaust gas compositions. Similar can be said of gasification plants and other large-scale combustion and processes. So those differences and their outputs will affect the carbon monoxide, carbon dioxide, oxides of sulfur, nitric oxide levels, as well as moisture, unburnt fuel levels, and temperatures. All of that will affect what needs to be measured. 

[00:05:53.160] - Mike 

It will also affect how we're going to go about getting those measurements. So again, as you said, there's a lot of variables, and on top of that, the license conditions might vary. What must be measured is determined by the site of emission license, and the license actually vary considerably. So the size of the process, the history of the plant, the nature of the emissions, and its proximity to communities all impact license conditions, which in turn affect the CEMS. 

[00:06:22.160] - Sean 

So it really means that each system is different and therefore everything needs to be engineered and customized to each particular plant condition, including the license. So clearly a misconception there. So now, changing onto another topic, there is another misconception out there that CEMS don't actually need any backup power, such as a UPS. How do you see that? 

[00:06:45.500] - Mike 

Well, ultimately it's the customer's decision, of course, but I think it should be kept in mind. The EPA license conditions generally have a requirement for the availability of the CEMS, so if there's a high level of availability required, that may affect the decision about whether to use a UPS simply to avoid failing to meet the license condition. There is, however, something else that should be considered which is often not very well understood, and that's the ramifications of uncontrolled power outages to the CEMS equipment. For some equipment. For some systems, there will be no impact. The system could shut down, be offline for a while, self-recover, and require no intervention. Though for other systems, an uncontrolled shutdown can be a complete disaster. Would you like me to perhaps detail some examples of that? 

[00:07:34.710] - Sean 
Absolutely uncontrolled power? What is the impact of not having to use a UPS? 

[00:07:43.910] - Mike 

Well, let's say that we've got a simple CEMS that's not measuring any sulfurs. Maybe it's using cold extraction from a clean-burning process. An example of that could be, say, an open cycle gas turbine running on natural gas. So in that type of situation, if the system goes cold, it probably won't hurt the Analyzer because we've got all the moisture out of the sample well in advance of the Analyzer. And when the system stops flowing because the pump's gone down, the dry gas will just stop in the Analyzer. So no problems with that one. That should have a fairly happy outcome. The power comes back on, it will probably recover without anything else. Maybe just a validation check. On the other hand, if you've got a process that's a little bit more difficult, maybe one of those ones that we talked about earlier where you've got something with a bit of sulfur, a bit of particulates, so you've got a hot, wet, dirty sample or an in-situ analyzer that needs to be kept hot and dry. In those situations, an uncontrolled outage of power can lead to the formation of sludge and corrosives in the system. 

[00:08:48.770] - Mike 

That equates to pretty dire outcomes. So again, it's a question of looking at what the process is and then working out what the consequences are. Keeping in mind that original statement that license conditions may in fact prove to be the overriding factor if a very high availability should also be required. 

[00:09:07.380] - Sean 

So it sounds like the people that need to work on CEMS must have experience in how to design and install the equipment so that all these different hiccups are going to be prevented. People tend to forget some of the items of the system sometimes. 

[00:09:21.730] - Mike 
Well, yeah, there's a lot of variables, but if the variable is considered and adequately managed, then the outcomes can still be good. What it's ultimately all about and here I'm only talking about continuous emission monitoring systems that are required as a result of some kind of statutory authority licensing. What it's all about is producing an adequate level of reporting, then the public, or at least the statutory authority, can be confident that the plant is operating within its license limits. So at the end of the day, it's all about getting the data. 

[00:09:53.850] - Sean 

Now that's really pertinent that you mentioned data because it leads into another misconception out there that we hear, which is about the data acquisition system in a CEMS that it's typically standalone, which is completely separate from the plant DCS or the plant PLCs. Is it true that this is a mandate, and what can you tell us about that? 

[00:10:16.490] - Mike 

Well, this is actually quite a messy area. An independent system may be required, or it may not. As we said before, site licenses are not all the same. But then we were talking about site licenses in terms of the size and history of the process and its proximity to communities. There's an additional facet to this, which is that there is no nationally applicable universal standard for CEMs in Australia. Each state and territory actually has its own requirements. While they all generally follow the requirements of the US EPA legislation, the implementation from state to state is different. So you've got variables within the state across sites, and then you've got variables from state to state. So that one has to be handled on a case by case basis. Although I've certainly been involved in CEMS, where the DCS has certainly been used as the reporting platform. 

[00:11:12.180] - Sean 

So why do you think that is, Mike? Why do you think that each state has its own set of rules and regulations, and why hasn't there been consensus in Australia? I mean, war one country at the end of the day. What do you think of that? 

[00:11:24.770] - Mike 

Well, Sean, you've only got to look at the debacle that's going on between the States and the federal government over managing COVID to understand that it would be too hard for them to go in different directions. There is a general consensus, a broad consensus across the country, that we're all going to abide by things that have their foundations in the US EPA, but when it comes to the detail, they tend to go in their own directions. 

[00:11:47.370] - Sean 

Okay, fair point. Now that brings me to yet another question, myth that is in Australia that we must comply with European requirements for CEMS. What would you say to somebody who thinks that the MCERTS is a requirement here? 

[00:12:02.570] - Mike 

Well, thus far I've given you a lot of quite extensive answers with a lot of variables. But this one, this one is an easy one with a nice straight answer. MCERTS being required in Australia. It's a complete myth. There's never been any state or federal requirement to comply with MCERTS in any state or territory of Australia. 

[00:12:26.030] - Sean 

Plain and simple.No requirement there. So we don't need to comply with MCERTS. But it is true that CEMS must comply with approval methods for emissions monitoring, I'm guessing coming from your comment about the US EPA standards. 

[00:12:38.510] - Mike 

Now, Sean, this one is a little bit more meaty. Thank you for the question. There are in the US EPA documentation a set of documents called Approved Methods for Emission Monitoring. And those approved methods are referenced in various statutory authority guidelines, such as, for example, in New South Wales. Also, WA refers to the approved methods for emission monitoring in their CEMS code. However, the approved methods are actually rules for RATA testing, and that covers items such as duct traverse testing, and laboratory methodologies to apply when assessing manually taken samples for emission spot-checks. RATA is an acronym for Relative Accuracy Test Audit. And what it does is it cross-checks some manually taken spot samples against what the Continuous Emission Monitoring System is measuring to determine there isn't an unacceptable variance. So those manually taken samples, which are typically being done by a company that's independent of the CEMS supplier and also independent of the site license owner, they’re for doing a RATA. And in accordance with those approved methods, the CEMS itself is not required to comply with the approved methods. The CEMS has to comply with what are called CEMs protocols, or sometimes referred to as Cem's methods or performance methods.

[00:14:10.750] - Mike 

They are described in different documents than the approved methods. 

[00:14:14.510] - Sean 
Thanks for that, Mike. Now, look, unfortunately, we've actually run out of time today, but I think we've seen you've actually smashed a number of the misconceptions and the myths around CEMS out of the court today. But it's also become very clear that there's a lot more to this topic than we can address in one episode. So I'd love to invite you back for a continuation of our discussions, Mike. 

[00:14:35.830] - Mike 

Well, I'd like to say thanks very much for that, Sean. I do hope that people will get some value. I know that there is a lot of detail that we've input into this morning's session. However, I think it's probably worthwhile to come back and continue with some of the further discussion points. 

[00:14:55.780] - Sean 

Thanks, Mike. Thanks to you, our listeners, for joining us once again. Now, if you've got any questions or particular topics you'd like us to discuss, please contact us on debunks@au.yokogawa.com. Also, if you enjoyed today's episode, please remember to like and share on your social media channels. We look forward to welcoming you back to future discussions. But in the meantime, stay safe and remember Yokogawa Debunks.