 In a combustion chamber, we burn gases, we burn liquids, we burn solid fuels. Let's take a simple example here of combustion of methane. We have a combustor, let's say we're burning methane in this reactor, which is basically natural gas without any kind of impurities. If we were to burn, let's say a simple one, just 100 kilogram moles per hour of methane is burned with stoichiometric air, whatever is required, oxygen, we're not supplying any excess air. And let's determine the amount of air required, amount of air required, which is kilograms per hour. And then we also would like to determine flue gas composition. We would like to determine the amount of flue gas generated. So into this reactor, we are sending in methane. That methane flow rate is 100 kilograms moles per hour. And we need to send in to burn enough of this air, enough of air. We need to determine that. And then the flue gases come out. Since we are burning in air, carbon goes to carbon dioxide, hydrogen goes to water vapor, and air would have oxygen and nitrogen. So oxygen, we are giving just enough oxygen to burn completely these fuels. So stoichiometric, there won't be any excess oxygen getting out, but there will be nitrogen. The nitrogen that is going in will not react in any of this, so nitrogen will be coming out. This would be our gas composition, or in other words, we need to figure out the amounts of these things. So let's write down the combustion equation or how these transformations are taking place. So first, CH4 is reacting with oxygen. And then it is producing CO2 plus water vapor. And there will also be some nitrogen left over. So let's figure this out here. So every mole of carbon burned produces one mole of carbon dioxide. So methane has one carbon here, so one carbon dioxide. So this is balanced now. Hydrogen, we have here four hydrogen atoms here, and we have two hydrogen atoms here, so there must be two moles of water vapor forming. So what is our oxygen requirement actually? So we need two oxygens here. This is balanced now. Two oxygens here, and there are two oxygens here too. So four oxygen atoms are two moles, two molecules here, two molecules of each, so that will be four. But these two oxygen molecules will come along with it, will bring along with it some nitrogen. So there will be some nitrogen following. How much nitrogen is flowing in? Always the ratio is O2 to N2 ratio, or air ratio will be, or in other words, opposite. If we look at how much air we need to bring in to get one mole of oxygen, we can calculate, one mole of air would have 0.21 moles of O2, right? So one divided by 0.21, that will come out to be 4.76 moles of air. 4.76 moles of air are coming in for every mole of oxygen that we need. However, in this, one mole would be oxygen, and 3.76 will be nitrogen. Or in other words, we can determine that too. Every mole of oxygen is bringing in, or every 0.21 moles of O2 are bringing in 0.79 nitrogen. If we divide this two, you'd get 3.76. So that will be our ratio. So this is the nitrogen that is coming in for every oxygen, and this is the air. So what is happening here is two moles of oxygen are bringing in two times 3.76 each nitrogen, right? 3.76 nitrogen. So this will come along with, now in this case, that nitrogen that is coming in will go out without any reaction. So basically the whole thing, 2.2 times 3.76 will come out as is to outside, OK? So this is the balanced equation. So now let's look at what would be our composition. Instead of burning one, we are burning 100 kilogram moles. So we just have to multiply everything by 100. So amount of air required now will be 4.76 moles for every mole. So we need 2 moles of oxygen. So 2 moles of oxygen would be 2 times 4.76 moles of air has to come in to completely burn this. And this would be the number of moles. And molecular weight, if we multiply this by, which is 29, 29 kilograms of air for every kilogram mole of air. So this many kilogram moles. And for this reaction, if 100 kilogram moles of methane are going in, we need 100 times this. That would be the number of kilograms of air that would be going in. So that will be 100 times 2 times 4.76 times 29. That would be the kilograms of air that has to be supplied for this methane. And how many moles of CO2 will be forming? Every mole of methane burned will form one mole of CO2. So we are burning 100 kilogram moles. So this will be 100 kilogram moles of CO2. All right, kilogram moles, few guess. And water vapor will be twice as much. So it will form 200 kilogram moles twice as much. And nitrogen will be here 100 times also. So this will be 7.452 moles. 7.52 times 100. So this will be 752 moles of nitrogen will be coming out. So this will be the amount of gas that is generated here, amount of flue gas that is generated here. And we can determine the composition also. Composition being, if we add this total, this will be 1,052. And 100 out of 1,052, we can calculate the percentage of CO2, percentage of water vapor, and percentage of nitrogen. So that is the composition, flue gas composition. Amount of flue gas generated is this. And we know amount of air required, kilograms of air here. And we can calculate this actually by using our calculator. This will be actually 27,608 kilograms of air per hour needs to be sent in to exactly match the requirement here. There won't be any excess air. So that will be our requirement here. Amount of flue gas generated, we can calculate, this is, again, kilogram moles. We can calculate the mass of this one also. It's very simple. If we were to calculate the mass, amount of flue gas in moles, we can also calculate as mass. Moles is 1,052. And mass would be 100 kilogram moles of CO2. And each mole of CO2 would be 44 kilograms per kilogram of CO2 per kilogram mole of CO2. This is the molecular weight. So we can cancel these two. And we'll have kilogram moles of CO2. So that will be 4,400. This will be equal to 4,400 kilograms, not kilogram moles, kilograms of CO2. And then similarly, 200 kilograms moles of H2O is produced times 18 kilograms of H2O per kilogram mole of H2O here. Again, kilogram mole of H2O, kilogram mole of H2O will cancel. And this should be kilogram mole. So these two will be canceled. And we would get 3,600 kilograms of H2O here. And then we can calculate nitrogen also, 752. So 752 kilogram moles of N2 times 28. So that will give us 28 times 752. So that should be 21,056 kilograms of N2. So that will be the total flue gas generated in mass. This is mass. And this would be moles. These would be kilo moles. All right.