Coal-fired thermal power

Welcome, everyone to Servomex’s very first podcast. My name is Matt Halsey. I’m the Application Development Manager here at Servomex, and I’m joined today by Keith Warren, one of our Product Managers who looks after some of the products we’re going to be talking about today. So, our theme is coal fired thermal power. Keith, could you tell us a little bit about what that is? Yeah hi Matt. Yes. So thermal power is, obviously when you’re generating electricity. And specifically, in this podcast, we’re going to talk about the use of predominantly coal as the fuel. So really, what you’re doing in this application is you’re burning the coal in effectively a very large boiler to heat water, the water will turn to steam and that steam is then used to drive a turbine to ultimately drive a generator to produce electricity that will then go out to the grid.

Excellent. Thanks, Keith. Yeah, so coal, is an interesting subject globally, always inspires a lot of conversation, especially in this current age of, you know, emissions, and countries all over the world are striving to reduce emissions, coal is seen as a big polluter. It’s one of the highest volumes of fuel that’s burned globally, still, today, not so much now in Western Europe and the UK, but it’s still quite a dominant fuel source in Asia Pacific, South Africa, America, so very energy dense fuel. So, it can produce, you know, lots of electricity per tonne of fuel. And, you know, more and more coal is, being extracted, even mines that that may have been, you know, active 40 years ago, coal extraction is become much more economical now, as technology develops. So more and more has been dug out the ground. And obviously, that’s why, you know, the use is increasing on a on a global scale. So, yeah, you know, as Keith alluded to, he’s explained a little bit about what thermal power is. Basically, coal has historically been the fuel of choice for generating steam. And so even the very early power stations originally would have been coal fired, because coal was the convenient fuel at the time. And then throughout the 20th century, coal was used more and more to produce electricity. And on a bigger scale, generally, in countries where especially where coal was actually sourced from, so most countries had access to an easy source of fuel.

Now, of course, in these modern times Western Europe and such coal is really dying away, it’s due to its emissions implications. But in other parts of the world, coal is still widely used, and in fact, in some countries still growing quite strongly for the use of electricity. So, it’s a really important subject that we still talk about, about the use of coal and the technologies that are employed to make sure that when you are using coal fuel, you use it the most efficient way and the most environmentally friendly way possible. Yeah, so here at Servomex, what we do know, internally, is we tend to break down the thermal power process into three core chunks that we offer analysis solutions to, so I’m going to run through those with you. So, we start off with the combustion part of the process, which Keith has already given some background on, burning the fuel in the presence of oxygen, ultimately, to produce heat to convert water into steam.

We then move on to the clean-up section. So here what we’re doing is we’re taking that flue gas that we’ve produced that exhaust gas from combustion, where we’re treating it, so we have to remove some of those pollutants that are inevitably produced during combustion, things like oxides of nitrogen, NOx, sulfur oxides, SO₂ and SO₃ is lots of dust, things like that. And then the final stage is the actual emissions measurement stage. So, once you’ve done your best to clean up the gas, you need to be monitoring and more importantly, reporting to your local Environment Agency, what you’re actually emitting to the atmosphere and predominantly Servomex specialized in the measurement of combustion gases once your combustion has completed.

You want to measure those gases to verify the level of oxygen that you have remaining, it’s very important that you have sufficient oxygen in the combustion process to allow the full combustion cycle to complete. And that you actually get the maximum amount of energy out the fuel Servomex has been making analytical equipment to do that measurement, for over 35 years. And really since the late 1990s Servomex has developed its current series of flue gas measurement products using the conium oxide technology, which is the 2700 FluegasExact range of analyzers. So, we’re now on the fourth generation of that analyzer, still using our Zirconia Oxide technology and our film, TFX technology to measure the carbon monoxide. And its equivalent post combustion.

So, this is something that Servomex has done many years, in fact that the 2700 really in its initial development was actually designed predominantly for thermal power applications. It was its key market sector back in the 90’s, as there was a huge boom in coal fired power station, especially out in the region, such as China and the Far East, Australia, South Africa, and a lot of the original product design and testing was actually done on coal fired power stations, both in the UK and also other parts of the world. So, the 2700 really is a analyzer that was specifically designed for that application, it has all the accessories alongside it to allow it to be implemented very successfully into that application. But of course, the 2700 in its design and flexibility, also means that it’s now widely used in a whole host of combustion efficiency applications all over the world.

Yeah, and, you know, over time over previous years, you know, we’ve certainly really expanded their offering of analysis equipment and solutions for these types of processes, you know, not just coal fired thermal power, but other forms of thermal power stations and other combustion type processes. Looking at analyzers for the clean up section, and the emission section in multicomponent, gas analyzers, very recently TDL, Tunable Diode Laser analyzers, which is, you know, it’s very much the new kid on the block in the analysis world. So, our analyzers, you know, they’re designed to solve problems and offer these solutions to the customer. So, some of the really common issues that are faced by customers on coal fired power stations, there’s numerous issues. It’s a very challenging application for any analyzer. I think probably one of the most significant ones that we face is that just the sheer amount of dust in these processes. You know, coal is a solid fuel that emits a lot of dust when it’s combusted. We’re talking typically in the region of 20 to 30 grams per cubic meter, you’ll find fluid gets very heavily dust laden. And that dust is also very abrasive because it’s you know, it’s a carbon based fuel. So very, very abrasive gets absolutely everywhere in every nook and cranny. It over time, it erodes metal parts. So, analyzers normally have to have some kind of dust protection prevention mechanism, sometimes even sacrificial parts.

So, taking the 2700, for example, you know, there is a solution that can be offered for these demanding applications where we actually use a shield to protect our filters on our probes. We even fit out to outer shields to the probes known as support tubes to actually divert some of that dust away from the probe, which of course, is a critical part of the analyzer. Other mitigation techniques used blowback being a very common one, where we actually send high pressure pulses of air through the analysis system to blow any dust that’s accumulated away from our filters and away from our probe. And that’s done very regularly, typically. And of course, this dust does actually limit the use of modern technology. So, TDL you know, I mentioned this earlier Tunable Diode Laser technology that has come in and has started industry wide ready to start replacing or complementing so Zirconia technology for measuring oxygen struggles in really dusty applications. mechatronic you’re trying to affect activity for a beam of light across a process. If it’s really dusty, you get beam obscuration, simple as that the beam just can’t get from one side of the process to the other.

Yeah, well, it’s obviously the 2700, I suppose it’s important to talk about, it’s the way it actually operates in that it, we actually intentionally keep the transducers outside of the process. And the 2700 will actually draw sample gas out of the process through its specially designed probes and internal pipe work arrangement into a heated sensor head that actually sits outside the process normally, what we call close couple to the processing, that it’s actually bolted to a flange on the side of the process wall. So, we’re obviously pulling that dust into our sensor head. So, we employ a very low flow technique to ensure that we don’t actually pull the dust into the sensor head, but the dust retains on the filter element inside the process. And as Matt, you’ve just mentioned, we can use blowback talks to keep that filter clean, and that will be done fairly regularly and automatically controlled by the analyzer itself on a timed routine, or it can be user initiated. But as I mentioned, the sensor itself is also heated. And that’s another very important part of its design because you’re actually extracting a, what we call a hot wet gas into the sensor head, because of course when you burn coal or hydrocarbons, you will have a significant element of that of that gas will be water vapor and you want to keep that water in a gaseous state. So, our sensor head has a heater inside that will heat the main block of the head to approximately about 245^oC. And that really serves as the sample gas is drawn into the head, but it’s kept as a gas as there’s no condensation that takes place. The measurements then are taken inside the head with the Zirconia or oxygen or the TFX will COe and then we have our Servomex, our own bespoke designing eductor system that will then aspirate, inspect the sample back into the process and return that process gas back into the actual process itself.

So it isn’t the sensor head itself is a self-contained heated system that is aspirated using instrument air so there’s no mechanical pump or electrical motor inside it, it’s all pneumatically driven. And as I said, it’s done on a very low flow basis deliberately to make sure that we don’t pull any dust into the actual measuring compartment itself. The heated element itself of course also has an additional importance, especially in applications where you are burning coal or a fuel that contains sulfur, in that it helps also maintain the sample above the sulfur dewpoint. So that’s another consideration especially in coal because coal is known to contain sulfur and coal in some parts of the world will contain fairly significant levels of sulfur. And you don’t want any acidic condensation to take place inside your head. So, again, our heater is really designed to ensure that we always keep the acid dew point above 160^oC.

Right, off the back of that Keith, you know talking about sulfur. It is a specific challenge with coal fired thermal power generation sulfur when it oxidizes and converts to SO₂, it can cause havoc with traditional combustibles technologies, most pelister based or B based technologies use a very specially formulated catalysts. And SO₂ connect is quite a strong poison. With those catalysts of it. What happens is the sulfur blocks the active sites on the catalyst that are needed for a reaction to occur, which means the sensors just lose sensitivity over time. So, one of the things that we’ve done to try and overcome that, is to produce what we refer to as a sulfur resistant or sulfur resilient type of sensor using very specific catalyst selection, utilizing temperature. And very importantly, a flow of auxiliary air as it’s referred to, which dilutes the sample a little bit before the sensor is exposed to the flue gas. This is with just with that diluted with that and that promotes the oxidation of SO₂ burns it away, leaving the sensor nice and clear and clean. So that’s a very specific challenge that you know, we’ve overcome quite successfully in the 2700 analyzer. We’ve had a lot of success globally with that with that solution.

So, one of the other significant challenges that customers face is the actual placement of the artist equipment is a bit of a myth, I suppose you could say, or maybe a misunderstanding that having an analysis equipment, right at the point of combustion is the kind of ideal place to have it, because that’s where the combustion reaction is happening isn’t technically true. And there’s a lot of challenges around that that installation point as well.

So, if you consider the combustion zone, where this is happening, is a really high temperature part of the process, you know, well over 1000^oC, it makes physical installation very, very challenging. And also, ongoing maintenance requirements can be quite high, you know, people going near such a hot process, it’s, it’s uncomfortable, it’s unsafe, it’s not something that companies likes to put their staff in, you know, in that position. So, this means that typically, combustion efficiency equipment sits a little bit further downstream. Typically, on these coal fired power stations; we’re seeing equipment installed at the economizer location. So, temperature has dropped quite a lot by this point, because this sits after the heater tubes, so a lot of the heat that’s been produced from combustion has been used to been removed and used to heat the water. So, we’re probably down I don’t know, somewhere like three to 500 degrees, something like that, at this point, you’re also physically past these tubes, which make it very difficult to, you know, to actually insert a probe into the process, let alone get clear line of sight if you’re using a laser type analyzer, so physical space limitations are far reduced and mitigated at this point.

The other issue with monitoring so close to combustion, it’s a very turbulent part of the process. And turbulent flue gas leaving the combustion zone can cause a phenomena known as stratification, which means you get effective pockets of gas at different parts of the process. So, it’s not well mixed, it’s not a nice homogenous gas mix. This means that when you’re using these traditional technologies like Zirconia, which are relying on drawing a sample from a probe, this is kind of seen as a point measurement. So, if you happen to be measuring inside one of these pockets of gas are outside a pocket of gas, you’re not going to get a very good idea of the average concentration of that gas in the total flue gas. This is overcome by installing further downstream where the gas is a lot better mixed, but also with the use of multiple analyzers. So, it’s very common to see two, three, four, five analyzers spanned across a process, maybe one every four or five meters, which then averaged to get a much better idea of how much oxygen there is in the flue gas as a whole.

And of course, going back to dust which we kind of spoke about earlier, if you are thinking of using technologies like TDL, and it does then force you to use some quite specific techniques. So, using one of our lasers as an example, which is used in a very important part of the process, known as the DeNOx process, which is a process used to remove the NOx from the process typically has to be installed across the corner of a process using a fixed tube installation, purely to reduce the path length because as I mentioned earlier, you know, the beam just cannot get through the dust over adopts that several meters wide. The case of focusing on that analyzer placement in a little bit more detail in relation to the 2700 itself. Keith, do you want to talk a little bit about the you know, the product placement and combustion efficiency as a whole so what this analyzer is actually doing in the process?

Yeah, so the FluegasExact is designed primarily to be a combustion efficiency analyzer and a combustion efficiency, the primary measurement is oxygen. And that’s very important because you always want to ensure that you have some excess oxygen sometimes it’s called excess air leftover once the combustion has fully completed, and that’s the same in really any combustion process. You want to just have slightly more oxygen than what was actually required that you know, you burn all fuel efficiently and on a large power station as you can imagine, one by making your process efficient the savings on fuel when calculated over days, weeks, months or a year can be significant, even small savings of a percent or less on a huge fuel bill is significant for the end user. So, any savings that they can make on fuel by making the most efficient use of their fuel inside that process can easily pay back the cost of a full modern set combustion efficiency analyzers.

Now, the 2700 also has the option for having, in addition to the oxygen measurement, a combustibles measurement, or COe measurement, as we call it, and that’s primarily there to detect the presence of carbon monoxide spikes. So, we call it breakthrough. And that’s when in your process as you do begin to lower your oxygen level and the combustion comes to the point of not been able to burn the fuel really cleanly, you will be into create some CO and CO is basically the incomplete burning of the fuel, it hasn’t actually burned CO₂. It’s remained CO because there was not enough oxygen left to complete the reaction. And so, our analyzer also has that ability to measure oxygen and COe simultaneously inside the sensor head. And so if you were to see a sudden spike, or break through as we call it of COe, where you’re suddenly going from a base level reading to a reading of several 100 ppm or potentially above that into the 1000s of ppm, then that can be used to signal back to the control system to the plant operator to raise alarms and automatically adjust the oxygen setpoint level up to obviously get them back to a point where they’re running with excess oxygen, which is where they want to be equally, they don’t want to run too high with oxygen, because the more oxygen you have left over in your flue gas, you are effectively wasting heat by causing the combustion process, your oxygen effectively comes from the air that’s being pushed into your process from your air fans.

If you’re putting too much air in, you’re also putting in lots of nitrogen in because 79% of air is nitrogen. And so, you can end up with potentially higher NOx levels in your process in your flue gas, which isn’t, these days, it’s very key environmental measure of obviously having low NOx levels in your process. But also, this becomes inefficient because you are effectively pushing higher volumes of gas through your process. And so, you can end up sweeping if you like energy through your process too quickly. And you’re basically your stack, temperatures begin to rise. And again, that’s clearly a waste of energy. That energy hasn’t been captured in your water; it’s just going straight out into the outside world. So, power station is the drive is to run both efficiently for the sake of getting the maximum out of your fuel. And of course, the benefit of that, especially these days is the effect it has on your emissions by running efficiently, you are minimizing your emissions. And that’s obviously a key criteria these days in operation of any combustion pump.

Yeah, and a really big topic for our customers right now. And for us, we’ve been talking a lot recently about clean air, certainly something that Servomex advocating where we want to help our customers work towards a cleaner environment. And you know, these types of processes that are producing emissions, realistically, they’re not going away anytime soon, you know, certain countries that the use of fossil fuels is reducing in others, it’s increasing globally, I think it’s still increasing. You know, a lot of countries rely on coal to power there, their industries and the homes of their ever increasing population. And we can use our analyzers for good. So, combustion control, the more efficient you can make that you can nip emissions in the bud effectively, that is the point that produced if you can maximize the efficiency of your process, you will produce fewer emissions, it’s really as simple as that. But if those emissions that are produced, when you went to the gas clean-up stage, it’s important then to have reliable gas analysis equipment, monitoring those clean up processes, checking they’re efficient, and that they are well controlled, to remove as much of the emissions as you can. And then the back end of the process on the stack, making sure that the analysis equipment is certified, it’s reliable, and it’s reporting the emissions to the local environment agencies, which is really an industry standard now, across the world.

So, we talked a bit more holistically about some of the other measurements on these processes, but maybe it’s a good opportunity to go into a little bit more detail about these. So, one of the really important applications that exist on coal fired power stations now is, is this ammonia measurement for what’s known as ammonia slip. And this is all the DeNOx process. So, quite literally a process that is designed to remove the NOx in the in the flue gas, NOx can be reduced at point of combustion. But unfortunately, as air contains 79% nitrogen, you’re always going to have this formation of thermal NOx in a combustion process, so we need a way to remove it. So, what’s typically done is they use ammonia or urea, they inject it into the process and that will react with the NOx in the flue gas to basically just break it down into its component parts. So, nitrogen and water, there are some other by-products produced of course as with most reactions. So, the ammonia that being injected is very important to control the level of ammonia the dosing level, because rogue ammonia that slips through the process lending the title of ammonia slip will basically with a bit more a few more complex reactions further downstream with combination with SO₃ which conform will eventually form a compound called ammonium bisulfate, which is an ammonium salt, like a white salty type material. And that can cause a bit of havoc further down the process. It’s quite corrosive, it can damage hardware and duct work anything made of metal, it’s also an environmental pollutants. So, you don’t want that stuff getting anywhere near the kind of water supplier and if not that, because it’s toxic. So, what we do is we use a TDL analyzer a laser, mounted across the corner of the process, as I mentioned earlier, because of the dust. And it’s a very, very sensitive ammonia measurement. You know, typically, we’re looking for a range of nought to 10, maybe nought to 15 ppm ammonia. And really quickly, we’re looking for no more than three or four ppm to slip through that reaction to really stop the formation of ABS further downstream. So, the laser has to be you know, fast responding, it has to be very sensitive, very accurate. So, we provide a solution called the Laser 3 Plus, which is one of the most advanced TDL analyzers on the market. So, one of the smallest, really quite a ground breaking product in the market.

Yeah, and there’s other measurements as well potentially on a thermal application or thermal power applications. So typically, you will have gas heaters which are used to capture some of the energy that potentially would otherwise be released out to the environment for your stack, but you might want to capture that in your combustion air that’s being drawn into your process or sucked into your process. And there’s a additional measurement, which is the measurement of oxygen and post gas air heaters to really detect the quality of the seals to make sure that you’re not transferring some of that air that you’re bringing in and sweeping it and instead it’s bypassing the seals and going out at the stack. You’ve also got applications, particularly on coal fired, where you would typically mill a coal into a fine powder in order for it to be blown into the burners and into your process to burn. So, most coal fired power stations, pretty much every coal pass station these days, burns coal dust, finely ground coal dust and grind in the dust, you obviously release hydrocarbons and you in the mill with you have to be careful of making sure those mills are in a safe state internally because you’ve potentially got flammable gases in there.

You’ve definitely got sources of ignition because you’re grinding coal under huge steel balls into a fine powder. So, there are measurements that could also be made there as part of the safety system. TDL again is excellent for that because it was fast response and then on the back end of a power station again another kind of safety measurement is where you have electrostatic precipitators, which will collect the dust bit like how dust will be attracted to an electrically charged surface, is effectively that and that you have big electric charge plates of very high voltage. The dust that is passed or the air that’s passed through them containing the dust, the dust will then stick to the plates, but because of that very high voltage, you actually have a risk of ignition there should flammable gases be present, which is unlikely, but it’s a possibility. So again, TDL’s have really come into their own offering a way of measuring typically CO levels prior to the ESPs, and should the levels go up certain limits, action can obviously be taken to make the system safe. So, a whole multitude of measurements on these applications, and Servomex offers a wide range of instruments to cover.

Yeah, and safety are very much a growing application on these, you know, it’s becoming just so, so important for customers now to keep them to keep the plant safe, and obviously keep their people safe. And we’re seeing a real surge in demand for the laser for those all important safety applications. I think the final one, really just to mention is of course, the emissions, which is something we’ve been we’ve been coming back to throughout this this podcast, is this idea of having cleaner air emissions measurements, very, very complicated. You know, there’s lots of regulations behind them and quite often analyzers need to be certified themselves by different agencies, for certain ranges. And as with most things, you know, unfortunately, these regulations aren’t harmonized globally. So normally, analyzers have to carry multiple certifications for different countries. The one that Servomex really offer for this is our 4900 Multigas, which is a multi-component analyzer that contains a variety of technologies. And it’s quite common for these emission standards to actually specify the type of technology that you need.

So, for example, looking at European regulations, you know, things like COe and CO₂, even SO₂ and NOx, quite often come back to a reference measurement of some type of Infrared technology, or even something like Chemiluminescence for NOx. We apply some different infrared principle, as you know, from the kind of straightforward infrared to a much more complex Gas Filter Correlation type infrared, which is basically just a highly speciated version of an infrared transducer. But the one that’s becoming very popular now is FITIR technology, Fourier Transform Infrared, you know, it has the capacity, the capability to perform multiple measurements in a single technology, more than four or five, you know, it can do 15 different measurements. So that’s becoming very, very popular in this industry right now. And Paramagnetic, which is really what ceramics are famous for, I think it’s safe to say, you know, one of the first technologies we ever produced as a company that’s still producing today. Paramagnetic remains really the reference standard for oxygen measurement, which is very important in emissions from helping converts to avoid any miss measurement from tramp air getting into the process further down, further upstream.

Yeah, and it’s important to say with the any emissions measurements, as well as the analyzer itself, that actually will make the measurements, it’s really important that the system that will be required to bring the measurement from the process from the pipe, the duct that you extract the measurement from, is the system, that’s also key to the success of any analyzer measurement, because that sample that you bring from the process has to be cleaned, and any dust removed, it has to be dried water vapor removed, before it’s presented to the analyzer. And that’s again, something that Servomex has a fantastic reputation for a strong systems design teams’ presence globally around the world who can, so we can not only supply the analyse that, but also the system to go with it. And obviously back it up then with our service teams present in terms of commissioning and ongoing maintenance.

And that’s a brilliant, you know, segue into maybe closing out by talking about some of the USPs of the 2700. Which again, we’ve been coming back through time and time again throughout this podcast system, is a really good example of somewhere where the 2700 shines you know, the fact that it’s this extractive close coupled heated system, this thing is designed to measure a hot wet sample, so it needs no form of external sample system effectively, it has its own system. Yeah, absolutely. Which is brilliant for, you know, for customers looking, you know, looking to reduce cost of ownership, cost of installation, things like that, you know, really good USP for that product.

Yeah, and it’s got part of its installation is that it’s obviously attached to a processor, it’s really important that we have a wide range of probes, adapter flanges, because every customer site has a slightly different flange standard. So, we have to probe lengths as well to get the measurement point into the right place in the process. And then we also have within the analyzer itself, the capability as we mentioned earlier for regular blowback, or auto calibration, or both. We also have a flow alarm inside it, so that’s something that we’ve added to the product about five years ago, which is the ability to detect a condition of low flow, low sample flow inside our sensor head pipe work. So should probe begin to block with dust, we would actually be able to detect that and alarm it back to the operator control systems, so that they can take appropriate action to either initiate a blowback to clean the probe or to send a technician there locally to address the issue.

Yeah, and of course, the fully automated utilities that we provide as well. Various panel options that can handle the instrument air that’s really the lifeblood of this analyzer. You know, you spoke about this earlier, Keith, it runs the pneumatic systems, the aspirator, and the calibration gases. And of course, the all important blowback for keeping that dust away. Anything from a you know, a basic kind of manual panel with some regulators right up to a fully automatic auto calibration auto blow back panel with solenoid valves that’s on offer the sulfur resistant combustibles option we mentioned earlier, of course, which gives us the edge in these applications where maybe slightly lower grade coal is being used, and you have higher concentrations of SO₂ in the flue gas. And of course, we have a huge instal base.

As I mentioned, this, this product is now being sold all be it in its fourth generation version for well over 20 years, and it was initially really designed primarily for this very application we’ve been talking about today. And many 1000s have been sold globally and in operation as we speak today around the world.

So everybody, thank you, thank you so much for joining us for our first ever Servomex podcast you know, we really appreciate your time and attention that you’ve spent listening to us talk about this all important topic of thermal power, we hope you found it useful hearing about our product offerings, you know, our FluegasExact 2700 analyzer for combustion efficiency, the Laser 3 Plus for the ammonia slip measurements and the safety measurements and of course that 4900 Multigas for the emissions. You know, as we we’ve mentioned throughout what we’re really advocating, helping our customers get moved towards a cleaner environment and cleaner air. If you want any more information on Servomex any of our applications or products. Please do visit our website Servomex.com. Have a look at the applications pages, you’ll find literature, manuals, you’ll find videos you’ll find links to this podcast and future podcasts when we’ve recorded them. Thank you everybody once again for listening and have a great day.