CUG 20 Webinar Practicalities of Coal Blending

Hello and welcome today's uh webcast titled practicalities of coal blending i'm andy kofis plant manager rawhide energy station and board member for the coal users group i'll be moderating today's program during which we're going to hear from rod hat who owns and operates coal combustion incorporated rod has recently joined the coal users group board for a second go-round and As a member of the board we are really excited to have his coal quality expertise on the board as well as during today's webinar before we get started i'd like to encourage everyone to submit questions using

the q a feature in the zoom platform you can do that at any time during the presentation and we will try to answer as many questions as possible during the q a portion of The webinar if you're experiencing any technical difficulty you can ask for help by typing the problem in into the zoom chat area and a member of our production staff will try to assist you in resolving the problem before we begin i'd like to say a quick word about the coal users group symposium held in conjunction with the electric Power conference and exhibition

which is co-sponsoring this webinar along with power magazine as many of you know the coal users group symposium and the electric power conference was originally scheduled to take place uh back in april but it was postponed to the coronavirus pandemic our event organizers have now rescheduled the in-person event for late september in kansas city please continue to Monitor the website www.electricpowerexpo.com or slash cug for updates so with that i'm going to turn the program over to our presenter rod hat rod take it away okay thank you so much [Music] perhaps i need to i just

wanted to say thank you to the coal users group power the electric power magazine um the uh i'm in the electric power Conference uh kim access intel and andy thank you for the wonderful uh introduction and most of all thank you for the attendees um here's our beginning and uh let's see if i can get this to work um so again thanks for attending and one of the big topics with uh cold blending or cold quality in general is uh like how do we actually go about Measuring the coal we use the standard astm or

iso or whatever type of standard technique that you're going to use and one of the problems associated with this is that you get individual numbers uh looking at sort of the average quality over the lot size so i wanted to talk a little bit about just measuring co quality and some of the dilemmas we get into Because boy it looks good on paper when we do the math with precise numbers but then when we actually put it in the boiler we may or may not get the same results as what the paper so a lot

of my discussion is going to be talking about when you take this coal and that coal and blend it together but i first wanted to start just a little bit about what are we talking about when i say disco or that coal um In engineering so this is the simplest way i've been trying to explain this in engineering if i have a spec in other words a 1.55 doorway opening and i've got a desk that's only 1.5 meters that desk fits through that door every time and so i'm making an analogy of just the opening

of a doorway uh being like a specification in a call Quality parameter and then you look at the in engineering you look at the desk and you say well it's smaller than the door so it fits through every time unfortunately coal quality is more of a measurement of a population so in any coal you could have a wet spot that's 100 moisture you could have a rock that's 100 ash And you have almost everything in between and so when i talk about cold quality or and it doesn't matter which coal quality whether it's btus or

ash or calorific value it doesn't matter when i get my astm number i get the average number and so in this case if i'm using that same sort of standard like my doorway is 1.55 meters and i look at the population of people On earth like that's a population oh the average is one and a half meters so the population fits my spec and you could see that you know somewhere almost half the people a little bit less because the door is a little bit bigger than the one and a half but almost half of

the population bumps their head or doesn't fit through the door And this is one of the dilemmas that when we talk cold quality we talk about that point on the top and we don't look at the range of properties that might be associated with a coal and what we see is that some coals or some coal mining methods or some products that are available have a wide distribution of quality in other words the average in this chart here of these two coals is The same these two coals look exactly the same on the paperwork from

an astm or any sort of accredited uh standard laboratory and yet one of them has a very wide range or very variable product in other words if you sampled the coal more often or in smaller lot sizes you would see that it varies more off that mean And then another coal is much more consistent that's what the blue line is representing perhaps like a washed coal or some sort of coal that has a very little contaminants associated with it so you can get these types of shapes of curves of cold quality and yet on paperwork

still be discussing the same number and the reason why i think this is important because you if you don't understand this You might not anticipate some of the results that you would end up so i'm saying suggesting that if you take two numbers and you said well i've got this one cole and this other coil i'm going to blend them together i don't know exactly how the variability is going to blend because i don't know the actual variability of the two codes and unfortunately commercially a lot of Times we just use the variability of a

laboratory or plus or minus 100 or 200 units or something like that but really if we study the data and we take smaller like thousand or two thousand ton lot sizes over time we can see this and what you see also is the actual act of blending can introduce the same variability and the reason why i'm sort of harping On this is that the um variability in a power plant performance wise is sometimes what really happens to a power plant in other words the coal changed and the power plant didn't respond to that change so

uh um you know that was just a brief discussion because now i'm going to talk about the the some numbers or how we go about Doing that um i will apologize that in the timing of a one-hour webinar uh i'm going to be touching just the tip of a lot of topics and even in the question and answer period i might be able to only uh touch the tip of that stuff but uh let me at least say like why are we blending okay so why do we blend fuels most likely There's an economic reason

in other words there's a lower cost fuel that we want to take advantage of couldn't we blend it with this higher quality coal and get something that works good at the power plant and economics a lot of times are based on the delivered uh cost per million you might use uh dollars uh per ton or some sort of a unit per ton currency per Ton but usually when we look at the economics of fuel we put it on an energy basis so whether it's a million btus or million kilocalories we're going to look at the

the dollars or the value of the currency divided by the energy that we get but what i want to caution you is the cost of blending might actually be in the neighborhood of A dollar or two depending on your situation but to actually blend coals sometimes takes a double handling which is not economically viable so i'm going to suggest there is a cost of blending and then it's not always easy to predict the plant performance from a blend of coals as easy it is like a single coal source And so there's some plant performance factors

that could be impacted by the blend situation and many times we sometimes don't include the actual cost of blending and the plant performance um and then what we're number two what we're reason why we're trying to blend is we're trying to maintain some sort of fuel quality that allows for economic uh usually full load uh continuous base Load operation for a unit but generally we're trying to maintain some sort of fuel quality and my number one question when we start talking about blending uh is is it consistent is is the fuel quality been properly blended

so that the power plant is seeing a consistent blend or in some situations that causes a lot of grief sometimes it gets a slug of one type of Coal and then a slug of the other so that the end of the day or the week or whatever the average numbers look good but the actual minute to minute or ton by ton performance of the unit did not represent the blended qualities and so we miss uh problems associated with like d rates or emissions or something that's going wrong Caused by a high dose of one of

the coals that's supposed to be blended away so i'm going to reiterate that when we do the economics it always looks good on paper okay generally with a paper blending looks good but we're not really dealing with reality because we're only using those average numbers for a fuel we're not looking at the Consistency or the the um spread of the data or that bell-shaped curve that i initially looked at when we only used the average values and then we expect the power plant to burn that average value didn't we actually do a good job getting

the paperwork done and the reason why i'm worried about fuel quality not being consistent is my experience in Dealing with all sorts of problematic issues of power plants whether it be load emissions slagging ash deposits it's almost always coming down to an inconsistent or variable fuel quality if there's fuel quality concerns and i've actually been teaching power plant operators for maybe 35 years and i'm here to tell you the basic response from a power plant Operator concerning fuel quality swings is that he would rather have a consistent coal rather than a variable coal even if

it's consistently bad in other words an operator can take some time off go visit his family come back to work if he's fighting the same issues in other words the coal is still causing those same issues he's going to have better success than If they're like oh no we're on this type of coal and now we're going to switch over and deal with these issues so my point here is that power plants don't necessarily uh react to average fuel quality like you get from the paperwork they respond to the swings in fuel quality so um

i'm going to come down to how do we actually blend coal basically it's going To be hard to do we physically have to handle uh you know thousands of tons of fuel to fuel a modern power plant so what i do is i break it down to two terms mixing and blending so i if you're mixing a coal yeah the paperwork might look good but you will find that the mixing a dose of one colon a dose of the other didn't produce the power plant Operations that you thought that the blend so blending the way

i defined a blended coal product is the two coals if you're using two coals or two different fuels those two coals end up going on the same belt so before the power plant maybe there's a crusher or a tripper or different transfers from Belt to belt if you actually put two coals on one belt and then put through some transfer stations that's a blend now to put those two coals on the belt i would like them to be weighed in other words you're using a metering device or a scalp of a belt scale system to

blend these coals so that you know the proportions of each And even well-designed systems have a cut off so that the the one coal is is cut off if it loses flow from the second coal or vice versa so you can do a good job blending you might not have the original equipment to make a good blend at a power plant or even at a vessel loading or transloading situations So again what i'm going to suggest is that power plants have some limit and then we try to keep the cold quality and in this case

i'm just going to say below the limit sometimes we keep it above the limit but we're going to in this we've got some quality we keep it below the limit and in this case you can see the the line moves around a little bit in other words there are some swings in in fuel quality But not that much and so the blue line is the average of the green line and when you look at that numbers you look say hey that's below the plant limit so i'm going to successfully be able to do that if

i redraw a situation where maybe mixing is involved in other words we put in like 3 000 tons of one coal and then we put in 2 000 tons of another and then we went back and put in 3 000 tons and we repeated that again so now we put in 10 000 tons of coal and when i take the average quality over those 10 000 tons i get the blue line but what the power plant sees is the fact that you've got a slug of one and then a slug of another and generally when

we go over the red line in other words we reach some limit That typically means that we had to de-rate the power plant perhaps we exceeded emissions with that that excursion is an emission limit or perhaps going over that red line put slag or an ash deposit in the boiler and once you put slag or ash deposits and boilers they generally don't come out unless you take them out either with Uh soot blowing or some mechanical means so even putting in higher quality coal can't offset the fact that the power plant went over the limit

um i sort of typed you know tell stories if i was driving my car and i was able to get a sp you know some police officer wanted to said that i was over the limit i would make the call that yeah but i was going a lot slower so my average speed is Lower than the limit and you can see how i'm going to be up probably faced with some traffic fine because it doesn't matter i went over the limit and that's what i'm suggesting that mixing or fuel variability can be accounted for and

in our standard testing methods when we when we don't take the small lot size i will suggest that asdm is designed to take a a sample every thousand tons 908 metric tons um that means you are going to have a lot of samples if you have a 10 000 or a 50 000 or 80 000 ton shipment and wouldn't that be good to see the variability associated with those the power plant will and so what i'm saying in many cases i've seen what might be deemed as a failure or the power plant couldn't actually burn

the blend as well as was predicted It was because we didn't actually mix the coals homogeneously enough to give the plant an individual type of fuel so there's just a brief discussion of some of our challenges when we talk about blending fuel um i've just sort of generically talked about these um uh uh properties i haven't mentioned any particular property but we're always interested in trying to Blend for some property so what does blend i have found throughout my career that you can blend chemical data now the heating value measured by the bomb calorimeter is

actually a physical test but the heating value is determined by the ultimate analysis in other words when i measure the carbon and the hydrogen and the oxygen i can actually calculate the heating Value and i'm suggesting that if i take a 50 carbon coal and a 70 carbon coal and blend in 50 50 i will get about a 60 carbon coal keep in mind that any one one analysis might represent that average number or just because of sampling and analysis being hard to do you might actually be falling on one side of the cover of

that curve or the other and not even recognize that um that that might actually be an Error in the sampling and analysis but in any case if you wanted to try to blend two coals i'm going to suggest that chemical data like the ultimate analysis and this would include like sulfur sulfur is a element and if we look at the ash chemistry not necessarily the percentage but the chemistry of the ash that would include things like silica alumina iron calcium Those we can blend we might have to weight average in other words if there's different

ash and calorific value of the coals we might have to do some math to blend those ash chemistries but we actually can blend ash chemistry relatively accurately in terms of our measurement technology what we can't measure or we can't predict sometimes is the what i call the physical tests so astm Iso a lot of these standard organizations have leftover physical pass back from a hundred years ago or 50 years ago uh hard growth grind ability and would be an index would be an example of something that's a physical test you physically put the coal in

constantly grind it and look at the fines generated well if you had a dried out sub-bituminous coal it might be becoming dusty and generating a lot More fines in the test than what the pulverizer actually sees when it's in the wet form so hard growth grind abilities are difficult to blend i'm not saying that you couldn't blend a 40 and 100 and get somewhere in between but your number from the laboratory might not match up with the number that the pulverizer is telling you uh my experience Has been that if you do that type of

thing and if you get like a 75 grind let's say for your blended laboratory result you might see maybe something like 65 when we calculate the energy that the pulverizer is looking at ash fusion temperatures the cone meltdown test that's another one of these things that we we have a hard time blending i already talked about how did you blend The ash together proportionally like how did you actually make the blend to run the test and then you have this issue that like let's say one of the coals has a low melting temperature compound like

pyrite or something just because you blended that down to a lower percentage doesn't mean that it's not still there so you can like dilute things that that that make the percentages or Maybe even change ass fusion temperatures but you can't take it away it's still there and you have to recognize for these tests are more physical tests and so they don't represent the blend proportionally and i find that same is true for combustion properties things like the hard growth grind ability or the size of the particle going into the Boiler the volatile or reactivity the

volatile matter oxygen content these reactivity properties might be influenced on some particles and not the others so sometimes our ability to produce like is it going to have high loy or not well if you introduce a hard to grind low volatile material like petroleum coke if you don't grind it finer you might find that it doesn't burn even Though the average you know volatiles or the average numbers might actually look pretty good so just to reiterate or suggest that again we can blend the the chemical data we have a tougher time with the physical data

you can go through the time to uh actually try to make blends but i'm suggesting that might be still Biased by our laboratory techniques um the proof of the pudding is if we put it into the power plant um so to get it to the power plant like this is the big chain challenge remember i said it was hard to do like how do we blend two colds together i mean we're talking about thousands if not millions of tons over a year's you know time frame but thousands of tons every day we have To handle

i've seen about three or four different ways that people blend coal um we can blend at the mine uh we can actually many mines use blending to help meet specifications so uh mine products may actually already be a blend of different seams of coal um we'll talk about that a little bit if you can feed two different coals into a Vessel so that they're actually a blend going into the vessel when that blend comes out of the vessel it delivers a pre-blended product to the power plant so there's some real advantages to a power plant

in that he doesn't have to the power plant doesn't have to handle the coal it comes pre-blended but boy you got to make sure that you make a blend as opposed to a mix if you made a mix like where you're only Using a few hundred tons of each coal and you vary back and forth you might have more success than if for example if you blended thousands of top two thousand tons of one coal and then load in two thousand times on another one that's going to be a mix so mixing and blending applies

to vessels uh also yard blending where we actually get the different fuels at the power plant And we blend it in the coal yard and then we'll even talk about the boiler blending where we use different pulverizers on different fuels i'm going to emphasize this again because i think the the challenge with blending is the variability of the fuel product not necessarily the the estimated chemical blend that we do in the paperwork So blending is where i want to see two coals uh particularly if they're measured uh in in with a belt scale or some

weighing device i want to see two coals getting dumped on the same belt and that belt going up to uh the power plant going through some transfers and uh perhaps a bin or two mixing when i do my so many tons of this And so many tons of that is different and you can not and anticipate the same sort of results that you would get on blending blending more more closely gets us what the paperwork says mixing causes all sorts of concerns because the results don't match up with the paperwork so at the mine as

it turns out many coals are blended at the mine to meet the specs because The mine might have a higher lower sulfur region a higher lower ash but generally if you're working with one mine it has the same rank in other words it has the same moisture ash free calorific value it has about the same uh moisture levels and so what changes is ash and sulfur levels perhaps and so you get a very uh you get a blend that's easier to blend because the coals are very similar If you're going to blend two coals having

similar coals makes the success rate better than if you take coals that farther apart i mean if you go way far apart if you're not precisely controlling those coals you won't get the same performance and i'm talking about those blends where you might put in 5 or 10 or 15 or 20 percent boy that makes a big difference if you get 5 Or 20 uh in the influence of of how this coal reacts so keep in mind that you may have already learned blended products coming from a mine if you understand any of my training

or whatever i'm always going to suggest that you know how your coal is made so if you buy coal or you are at a power plant that uses coal i'm going to suggest some representative from your company Be able to audit and trail all the way from the power plant back to the mine and say okay here's the fuels that are going in here's how we're blending it here's how we're sampling it here's how we're weighing it i want you to know how your product is made so you can answer the questions and it wouldn't

be a surprise that it was a blend um some mines have a vast ability to blend if look at all these Different reclaimed feeders out here this mine could custom design a fuel almost by blending and proportioning most mines don't have this type of equipment but uh keep in mind that even a uh somebody that just has a a smaller operation might still be mixing coal from this part of the mine over here to coal over there with coal over there to meet some spec So i mentioned that usually they're similar rank and they're usually

blending for ash and sulfur uh i do see mines blending for things like sodium or chlorine or other elemental things trying to match up to a customer specification but uh so i'm just saying that in perhaps that you might actually be blending burning a blending blended product by looking at Mine uh vessel blending uh this is where we take individual coals and load it into a larger vessel um mixing has the potential of working in addition to blending blending is always best but mixing can work if you keep it the tonnage uh mix smaller like

hundreds of tons versus thousands of tons um but again the advantage might be that uh Especially if you have a sophisticated uh situation where the terminal or somebody can unload one coal put it on the ground and then proportion it in remember i want those scales involved you could use just rough blends but then expect a rough number when you get done with your blend in terms of a preciseness and then if you could load a blended product in other words the two coals are On this one belt being put into the vessel that's the

best situation if you have to go to mixing perhaps you gotta go with the low tonnage ratios um high tons thousands of tons is more like mixing and you won't get the same results the power plant will see swings in the fuel quality an advantage i mentioned is you get a blend delivered to the plant One of the disadvantages you can't unblend it if the blend proportion was not right or it wasn't done uh proportionally or consistently you might have to take that fuel and re-blend it again with another uh fuel to take some of

those inconsistencies out so there are advantages and the disadvantages to to these next three vessel yard and Boiler blending in the yard the number one limiting factor is that most power plants were designed to burn a single fuel and so they might have a reclaim hopper uh in an unloading situation when they're unloading from vessels or from trains but you have to have the space potentially to put both fuels on the ground You certainly have to put one of the fuels on the ground and then you could use a fuel delivery unloading to get your

two sources of fuel and so this is a challenge for yard blending is you don't necessarily have the space to put the cold down to be able to pick it back up to make that blend and i do see mixing going on depending on the specific parameter that You're mixing for you might be able to get away with mixes other times the power plant can see the individual coals the bad characteristics showing up that might put it over that that limit so yard blending the successful ones i've seen has been where you have two separate

systems with scales and you're able to proportion those two uh streams of coal Onto a belt particularly ones that go through a crusher bin or or uh several transfer points before it gets up in the triple tripper and spread out over the silos or or the bins for the feeding the pulverizers so having the space is really important um every one of these blending situations is different and unique so i'm not going to be able to generically Talk about that but boy if you don't have the space you're going to be limited so another way

that you could actually blend the coals is let's say you have six mils right you could blend uh fill up three silos particularly if you have silos versus common bumpers you could actually fill up three of the silos with one coal three of the silos with the other coal and if you ran all the mills the same You could proportion them 50 50. in other words you're reading the the tonnage going into the mills so you're actually going to blend the coals in the flame and if you do a good job of making sure that

you've got the air to fuel ratios uh and the air balance set right and we'll talk about that in detail a little bit but i've seen this work enough to realize that you can actually feed separate fuels into a Flame and and if you think about it and design it right you can get it to work okay but i can also testify that i've seen it not work so again we have to think about this one of the advantage of this is that by portioning the pulverizers or even the number of pulverizers that are on

a particular fuel you can blend that proportion Quite well so again a story is a power plant that wanted to burn about 10 or 15 petroleum coke had eight pulverizers it put one pulverizer specifically on petroleum coke so i've seen this happen with uh lignites and subituminous coals uh vituminous coals uh mixed with high rank platuminous coals uh so one of the problems here is is to understand the uh the fact that if You're going to be using the pulverizers to blend the coal um each one of these pulverizers is going to respond to the

coal that it's in is in the pulverizer not the average value and so the air to fuel ratio that i mentioned is that um you would like to have the btu input to be about the same in other words it takes about the same amount of air to burn the similar uh calorific value Of fuel if if i have a high calorific value coal i probably need to turn my cold flow down on those polarizers if i'm going to not reset all my errors and i wouldn't suggest resetting your heirs uh i would say back

off or try to balance the value of coal flow times calorific value for each mill in other words you can see How if you had all the same coal flow the pulverizers with the high calorific value coal are going to need more air and they don't get it in that situation the low calorific value coal will have too much air and so what i get is high carbon and high knocks that is hard to tune out if i can adjust the cold flows to match up with the airflows going into the boiler I'll have more

success with the boiler blending well i've tried to cover a lot of information in a short amount of time and leave plenty of time for at least some of the questions um i was going to at least say here's how we can get a hold of me and thank you again so much and i think at this point i get to turn it over to Uh andy and um i suspect there's at least some questions they'll see how well i can do it answering them thank you rod uh for so much good information we have

had a number of questions submitted during the uh the program so we'll try to consolidate some of those questions and answer as many as possible in the time that uh remains we'll try to answer any questions that we don't get to Because of time constraints individually via email you know after the program so i'll jump in rod with some of the questions we've uh started to receive so one of the questions was if a plant chooses to adopt coal blending to get the economic advantage by purchasing from the spot market in that case how do

you ensure proper combustion in the furnace by blending two or Possibly three different type of calls well uh first off the question is it blending or when you make your spot opportunity you get like a big dose of that one coal uh so what i would do is look at the performance of the power plant on the individual coals in other words if it's higher moisture heat rate will decrease you know well heat rate will go up the boiler efficiency goes down Uh sulfur uh can be variable there's a lot that you can just see

that i would certainly study the individual coals and then i would start asking myself if i can actually like if i physically can do it what modifications at the plant to burn the lower cost fuel in other words it's always going to drive to the lowest cost fuel so my experience has been if we let in 10 or 20 percent uh if you're saving money you'll be at 50 percent you know if i come back a year later i'm like what happened to the 20 blend they said oh we were saving money we had to

save more money and i'm like oh well it's not working as well um so taking opportunity of stock market is good but again do you have that the storage available so you could blend that in Or do you have to actually take a dose of this for a week or you know i don't know how big the spot purchases are but you could just see how it's a big difference between a 1500 ton barge and an 80 000 ton vessel coming into a power plant there's a little bit at least on that question right another

question uh is about the in Furnace blending so when like you mentioned there towards the end when you're loading separately into different motors that you've got each pulverizer set up for that particular coal can you go into any more detail about setting up a pulverizer or any other issues with air to fuel ratio you're setting up your well you can see i'll just mention a few There's a good long question again um and hopefully uh you know um well you can just see how if it takes hours to answer i might not be able to

do it in this format but uh i'm available so in a pulverizer if i'm using a bituminous coal i might have really hot primary airflow and be running the outlet temperature hot on the pulverizer if i switch from a Bituminous coal to a sub-bituminous coal the reactivity of that coal even though it's higher moisture it needs more drying i probably have to lower the inlet temperature or lower the outlet temperature of the mill or both to make sure i'm fighting i don't have to fight fires in the middle so there would be example of an

air flow adjustment some coals are going to respond better Than others to having too high a primary airflow right high primary airflow is a common thing that operators like but some coals to get the combustion right aren't going to like that so you might have to turn down the primary airflow particularly if you had like a high sulfur a high pyrite type coal high slagging coal where you need to grind that up you got to slow the Primary airflow down to give the mill time to grind it up um fineness if fineness might work good

on a bituminous coal and then you put in the subatomic coal and yeah you get very good combustion but you can't get the tons to the mill so do i play with the fineness to get the tons throughput of the mill i need to run the furnace or do i say no i got to keep the finest where it's at because other problems like slag or Imbalance in the coal pipes and other things that might come from the larger particle sizes so there are a handful of things that i would do for a mill saying

i this is the type of coal we're going to put in it and then i would actually try to get the operators to identify from the mill readings can you tell me which coal's in that pulverizer in other words when i used uh one coal Had seven moisture and another had 15 you could see the difference in the primary air inlet temperatures at the same coal flow and i'm like look at there and then which one has the lower amps oh look this one has the lower amps i'm like that corresponds with the grindability index

that i knew was higher on that coal so with a little work operators can almost tell which one Is where because it every day doesn't go exactly right like that that would be a question yeah you think that's what the coal's in there how do you know right so so can we there's a lot of those things that i would work with but that air to fuel ratio in other words we're going to put a high bq coal here in this one pulverizer boy if you run at the same coal rate Like feeder speed when

i do the math this burners or that row of burners needs a lot more air or it's going to be in reducing conditions even more like especially if you have over fire air and issues like that but i'm just saying that you've got to make sure that the btu or the calorific input is about the same for each pulverizer That really helps that air to fuel ratio for the furnace blending good points okay so rob here's another questions that kind of ties into that so the question from one of the participants is it's more of

an opinion or your professional opinion which one is better when you're coming to blending do you prefer to blend in the yard or would you prefer to blend In the furnace like we just talked about you know separate bunkers and pulverizers okay so again that's a big question because which coals in other words if the coals are very similar be calorific value wise btu kilocalories um if the coals are very similar um the boiler won't see much difference right so you could you could feed the boiler the Blend that way so what are the differences

you know will the boiler see the differences if there is a quality difference the the farther you get about uh like if you're going to use a 4000 kilocalorie coal and a 6000 kilocalorie coal uh you're gonna want more precision blending and actually probably deliver a precision blended product to the power Plant if you say i don't have scales and the yard and i can't precision blend maybe you're blending in the boiler is a better option for precision blending but again um it it the farther apart the quality of the coals are the more i'm

going to emphasize you've got to blend those as opposed to mix them okay have coals that are pretty similar Right and and and one you know an example might be a 5 000 calorific coal and a 4 800 calorific you know and the ash and the sulfurs are similar and all i have is 200 kilocalories per kilogram or you know 3 400 btus um but that's not that big of a spread so right i could probably be more imprecise in blending those two and the boiler won't see the swing so much But if you have

high and low pg goals and you get a mix you'll see feeder speeds like that indicating calorific value is changing uh if you measure so2 inlet to a scrubber or so2 on a stack if you don't have control boy is that valuable to look at like how consistent is that sulfur blend right so you can measure how consistent your blend is and perhaps sometimes in the boiler you Can be more consistent in the yard or you know who knows what happens before you get the coal because all you one of the big problems i see

with cold purchasing is you get one or two pieces of paper that represent the fuel quality and and again all that is is a piece of paper with numbers written on it which is why in the program i said boy do i want you to know where those Numbers came from and how did you make the product because sometimes i don't believe the numbers right those are the paper numbers i don't know where you got them let's go look and see what's actually going on in terms of quality control around the fuel situation and it's

worth the effort given the value or the money and the consequences of the problems kind of leads into another question We've got where one of the participants is asking how much do you consider your on paper results what you think you're gonna get to set up your your mix or your blend and then how do you change that when you see actual performance results well again the experience helps like you can almost anticipate sometimes i'm gonna like yeah that's what the paper says but i've already seen this not work Four or five times which is

usually if i see four or five times and if a power plant guy tells me that it's not working i believe that way more than any sort of paper numbers or engineers almost always the guy on the ground is going to be giving me better information and if he says you know sometimes the flame goes dark i'm like yeah you got a big dose of coal and you didn't have enough air you know So you have inconsistencies and we could see things like that um so uh when i look at the paper studies and i

do lots and lots of these paper studies one thing that's important is how far apart are the coals in terms of quality and how precise is the is is the blending gonna be right and uh that would play a an influence and then just some fuels i know are somewhat more Problematic high pyrite that would show up as high iron in the coal ash or high sulfur in the proxima but but high pyrite coals high sodium coals um we have those in the sub-bituminous but also sometimes in the bituminous so high sodium coals that's the

fouling factor right so if i've got too cold high and low sodium and the following factor the blend comes out here i'm like yeah well What happens when we get a dose of the high bond because that's what the boiler might actually be seeing for us a period of time and if you mock up the superheater or the convection pass it doesn't unmuck right so um sorry about those technical terms that's a good following you know mucking things up so there's several questions about slagging the boiler following you know Your convective section back pass any

experience you could pass along with the group about boiler slagging or back pass fouling because a lot of people i think are trying to blend to to take care of some of those issues how well does that work what what problems are have people had trying to deal with with the slagging issues okay um well i think a lot of People can appreciate that slagging comes from a whole lot more things than just a fuel parameter not saying there aren't fuels that are more difficult to burn but generally almost every coal on earth that's being

mined by the millions of tons has got a customer so someone has figured out how to burn some of these more difficult fuels so now how do i approach what happens uh i guess this is how do i anticipate Slagging and how important is things like for example about half or more of the slags i deal with are poor pulverizer fineness and if you put in a lower calorific value coal into the same pulverizer to meet the the load you increase the fuel flow and every time i look at results or i see the results

uh in the flame when i increase fuel flow fineness deteriorates if you understand What i suggest about the and i heard it be called by the splat factor the rod hats black factor i don't know if i like that but when you have like why does wet coal cause slag or why does low calorific value okay uh slag because it does because the power plant guys told me so now why is that well low calorific value coal increases the tonnage through the mill and the primary air velocity or the Primary airflow they go up they're

on a curve right so if you increase coal flow you increase airflow and so now what happens is low calorific value coal starts really going fast and it's not ground fine and so the trajectory of the rocks and minerals like quartz or or or hard rocks like quartz or pyrites which are hard to grind remember I mentioned pyrites those materials start impacting the wall if you get low knocks involved particularly over fire air keep in mind every low knock situation i've ever seen detunes or hurts combustion low knocks firing hurts combustion if you have a

slag that's influenced by combustion firing for low knocks is making more slack the only time i ever see lonox Help slag is when someone says oh my god the pulverizer fineness is bad you need to fix that right you know so you can just see how these things go hand in hand sometimes and the lower calorific value fuels are generally the lower cost if we look at the geology and that we'll see why the mining techniques but generally when you have a big thick seam you can mine it cheaper than a Little thick thin scene

low calorific value lignites and some bituminous coals come in the big seam the tuminous coals and higher ranked coals tend to get squished and come in the little scene which one do you want i want the cheap one well then you're going to get high moisture low calorific fuel fuel that even with low ash levels you know prb coal is a Nice example at four or five ash this is our subpletuminous coal in the u.s but like when you're talking like less than five ash you're like oh well there's hardly any ash in here i'm

like oh yeah but when we have low calorific value fuels that ash can build up and be very problematic and when people like boiler manufacturers tell us that the fineness is okay to decrease Remember i'm an independent so this is my opinion that's what they asked for but when the boilerman manager tells you something that's for their reasons i'm here to tell you fineness better find this helps in every case and if you can maintain your fineness and your coal throughput you'll be able to manage different swings and quality fuels particularly in that slagging and

following things now when again when we start Getting into the chemistries like sodiums and that you know the super high sodium coals like six and eight percent those people are almost always blending in with a lower sodium fuel to bring that high sodium number down not always but almost always trying to get that number down in some manageable form uh there is a nice paper i wrote a couple years ago and presented at the Pr users group with uh um dominic uh uh mourinho from the detroit edison group that's the high sodium paper where we

talk about what do you do with high sodium coals well you got to pay attention to combustion and fineness and and and soot blowing and furnace exit gas temperatures and all these different things that influence slag sometimes it's not just always the cold But if i see a coal that has high slagging and it hurts milk performance i'm going to be suspicious that that coal probably needs some some further combustion massaging however you want to describe that more air more air remember higher knocks higher knocks almost always almost always helps slag situations by bringing the

flame down Lower the furnace and stopping that high from the gas temperature up at the top of the furnace that's the balance that everybody's gotta gotta deal with today yeah so um you know and most people don't wanna hear that if you buy the cheap cold and you get it less megawatts but in reality that's what happens if you don't try to adjust these things that's why it's cheap so again these are These you know sound like wonderful like projects to look at individually but in this format it's tough to do but yeah rod here's

another question a little bit different so we've been talking about uh pulverized predominantly so we have a question about what about a cfb what about a circulating fluidized bed boiler any experience any details with trying to absolutely absolutely And you can see how the fluidized bed combustor is impacted by several things right the amount of ash in the fuel how much if they're capturing sulfur with limestone that again particle sizing if you get too many fines let's say you have a coal that's very soft and and it goes through the same crusher all of a

sudden you have too many fines particularly if it's like a petroleum coke or something you'll find that it Might not react in time and in some cases you just have to say well the petroleum coke is so cheap that i'm willing to put up with carbon in my ash right so so fluidized fed boilers like most combustion systems you know do respond to fuel quality you can't give it all low quality fuel if it if that's not what it's looking for if you can blend in some higher quality fuel Whether that's low ash higher action

it depends what you're looking for how often you're on the how how far you are moving away from certain sort of design criteria but um i've seen a lot of people blend fuels and that's one of the benefits of a fluidized bed boiler especially especially the circulating fluidized bed boiler that if you can keep the the fuel Particle large it will stay in there until it burns hopefully on lignite so someone's asking for a little help potentially uh blending lignite with i'm assuming a a better btu or a higher quality coal former utility i worked

with did that could you speak to that a little bit yes uh keep in mind that lignite we might consider a low rank coal like The subatomis coals it has very high moisture and not so much stuff that burns right one of the things that lignites can get into is higher ash and sulfur so in other words i don't actually uh talk that much about percents i want to talk about the kilograms per million kilocalories or the pounds per million btus and so when i take a like a lignite coal And it's only one percent

sulfur all of a sudden when i do the so2 calculation or a calculation look because i'm dividing by the calorific value i'm like oh that put it up into the medium range so so you have to pay attention to the lignites because they can have higher ash and sulfur levels than the subtominous coals and so now like again if you're designed For lignite and you put in the subpotimus coal almost everything's going to get better almost everything's going to get better because you're reducing the caliber i mean you're you're increasing the calorific value reducing the

loading on the mills so you could see how like if lignite is abrasive and you wear out a mill because you put in some ignite because you were saving Money and then you went back to your substitute when it's cold and you didn't fix your milk because the the high ash and the lignite wore it out that could be a dilemma if you said oh i got this lignite pulverizer that i'm used to maintaining every six months or eight months now i put the subatomic coal in i don't hardly get any wear on it right

you know so you could see how There's a lot more properties than what we generally look at like moisture ass sulfur btu if we want to look at the abrasiveness or the slagginess of a coal we got to go more in depth and and because of blending is is sensitive to how well we blend the paper blend always looks good the blended two coals on a belt look look go you know pretty good but boy when we start mixing Looks bad if you go back to the boiler now and you say yeah but i've got

a proportion 60 40 then i'm going to say you're probably proportioning it better blending than somebody that didn't have scales in the yard or didn't have a good blending mechanism in the yard right and a lot of what we're talking about rod you mentioned there when we were talking about lower ranking fuels Is perspective if i've got a a lower ranking fuel and i'm mixing what should be a better quality fuel then there's that positive output you're looking for is like hey this is not as big of a problem i've got better results whereas some

people it's the other way around where i have a a consistent fuel or i have a fairly good quality fuel and now for cost reasons typically I blend something that's not quite as good so then it's more of a problem for that end user so a lot of it is perspective of where you're coming back to that first point when you save the money on the fuel did you consider the economics of the plant right what if the plant shuts down every three weeks because of the slag or what if the plant can't get the

full Load yeah like yeah paperwork it says it did but then it rained and some of the people on earth have rainy season exactly and i'm here to tell you there's some places on earth that get a lot of rain and i'm like oh did you adjust the calorific value for to include that they're like oh no we use the ship analysis i'm like well that's not what you're burning You know you could see that so then don't expect the same performance okay well rod i we're we're just about out of time um i did

see the one question about the high ash indian coal and i'll just comment that any can ask down on a coal you're probably in better shape if you do a blend as opposed to a mix i'm sorry Go ahead no i'm just saying we're right at time we want to respect everyone's time um so access to this video and the presentation will be available on the coal users group website www.coleusersgroup.org you must be a member to gain access but you should have received or you will receive a certificate of attendance shortly after the event Closes

here and you can use that to access there and again please reply to that email on how to access or if you have any other questions so thank you rob and thanks to everyone for attending yeah thanks a lot all together we'll get this yeah