 Okay, so we have been discussing about heterogeneous because I would like to give you a flavor for heterogeneous reactions, so that means what extra information what we require for heterogeneous reaction, Abdull what extra information, mass transfer step, but we have taken only isothermal reaction and if I have non-isothermal reactions it is not only mass transfer even heat transfer will come into picture, why? Because in the bulk you have a different temperature on the particle if it is a catalytic reaction you have another temperature, right or in exothermic reaction or endothermic reaction, endothermic reaction the temperature of the particle will be less than the temperature in the bulk if it is exothermic reaction the temperature in the bulk is less than, yeah bulk I changed the argument, so in the bulk it is less and the at the particle exothermic reaction so you have more temperature so there is a temperature gradient also between the film and the actual particle right so that heat transfer also you have to take into account right so that we will do in the next semester but first things you know simple things what we want to understand we have derived an equation for catalytic reaction right catalytic reaction and you got a rate minus r a equal to c a b by minus divided by 1 by k g and 1 by 1 by k and we also know that now in under some conditions k that is reaction rate constant will not come into picture for design at all it will come only I mean the mass transfer coefficient that will come into picture that means my rate equation now contains only mass transfer rate mass transfer coefficient rather than chemical concentration and also chemical reaction rate constant you see and that happens most of the time for combustion reactions why all combustion reactions are at very high temperature 600 700 800 like that so the reaction rate of reaction is very very fast so it is yeah whenever you have rate of reaction very very fast which is controlling mass transfer controls so that is why only mass transfer equation will come for the design of a chemical reaction it is surprising so that is the beauty in heterogeneous system now let me take one non-catalytic reaction very simple one non-catalytic reaction yeah so before going to non-catalytic one more word about catalytic reaction I have taken when you take step 1 and step 2 and step 3 for catalytic reaction assuming you have porous particle first step is mass transfer second step is reaction third step is yeah not disruption mass transfer back through the filling disruption means on the surface it comes all that we club together so then I told that for first order we could first order rate we assumed then it was very easy for us to eliminate unknown concentration that is CAS unknown means I cannot measure that concentration that is why we could get that very simple expression I can give in the surprise test sometime I have to start now that test also simply that one equal to KCA square mass transfer step is same KG into CAB minus CAS now that is equivalent to K into CAS square CAS square the moment I put that CAS square then you have a quadratic equation because our idea is to eliminate CAS so you have to solve from this quadratic equation CAS and then that CAS afterwards you can substitute any one mass transfer equation or reaction equation totally the rate becomes very very complicated but still it will be in terms of K and KG so depending on which condition which is rate controlling you can simplify that equation also in terms of only KG or in terms of only K if you have very very very slow reaction the fellow is not you know as I told you are not hungry at all you have eaten sufficiently then it is will be continuously coming throughout and you have the concentration of it is on that conveyor belt throughout so that means throughout the film you have the same concentration because the rate is not very fast the particle is not able to convert the molecules that are coming to the surface into products so then what happens the entire surface will be covered by CAB so that is why you draw that line you know CAB constant line you know what we have done in that right so that is the reason why that line and also it is zero line because on the surface I think Swami or someone was asking me that question if there is no concentration how can it react you know it is not exactly mathematical equivalent of you know CB equal to zero whatever particles are coming to the surface they are immediately converted at any time when I look at the surface practically there are no yeah there is no reactant left yeah it is a zero we are not considering the it is not zero in the mathematical sense right what is minimum what do I know what is minimum no sir we are talking about the resistance of the mass transfer system yeah we are not talking about I mean okay you tell me I think to understand the same thing my example all of you are tremendously hungry you can eat an elephant also if you can see there is so much angry okay yeah so then at that time this is a weakness are continuously coming right and you are able to eat so then at any time continuously they are coming so at any time can you see any higly on the surface yes they are there but after coming to the surface they are getting zero yeah this is zero I have my catalyst particles starting from here all the people are standing here both sides people are standing right I may have conveyor belt before into the kitchen the moment they touch the surface surface is you standing you know waiting to take the I mean whatever they give whatever they give forget about it is okay so then the moment is started coming first person takes like this second person you know long hand takes like this third person also pushes the second person and then takes so what can you see there you cannot see any concentration of it is on that left similarly on the surface you have the molecules just coming and then touching the surface converted to product and now if you see that what is the concentration of reactant on the surface practically zero that is what is the meaning of that okay you are telling that is a concentration is decreasing like this then these particles few particles which are coming to the surface they are very quickly converted and the beauty there is now if you are intelligent you should be able to supply as much as possible okay as much as possible so that you will get maximum rate why because the particle is capable of reacting or converting the molecules very quickly now if there is a film then the resistance will come if you remove the film so directly you have lots of a that is coming to the surface where rate of reaction is very high how do you remove the fluid mechanics will allow you to do so the moment you have high flow rate film thickness will reduce then the concentration gradient will not fall that much okay that the concentration on the surface forget about Italy so the the concentration on the surface practically what do you mean I think you know so hungry that means the rate of reaction is very very high temperature is 600 700 800 degree centigrade okay so any any molecule coming to the surface will be immediately converted to product and that is why practically you see that practically I said practically you see that on the surface there is no concentration here also at least example there may be a piece of it we left somewhere which is which is stuck to the conveyor belt and all that okay yeah so like that there may be one or two molecules but that won't give you any you know rate of reaction in the sense that you know significant rate of reaction that is why if you see my notes I think and I wrote that CAS is almost zero like this I put and then put zero and you are really see Swami is taking whenever mathematics are required you won't bother about mathematics but here mathematics are not required okay CAS is not exactly equal to zero but it is approximated zero tends to zero that means the moment you have any molecule coming to the surface it is getting converted to product so practically I don't see many molecules of a on the surface that is what is the meaning of that okay so that was the example what we have given so now non catalytic reaction what we take is coal combustion again I am simplifying many things yeah so coal combustion you can use again the moment you have coal combustion what are the various types of reactor use for coal combustion because first of all yeah excellent fluidized bed is one okay anything else moving bed moving bed moving bed still because that has to come to your mind first when you say coal combustion okay what are the possible because in chemical engineering that is the beauty I am telling you the beauty part in chemical engineering is we don't have a single solution problem we have many possibilities right so this reaction can be conducted in many many ways for example coal combustion even catalytic reaction can be conducted in many many types of reactors right but all those reactors will be simplified in ideal in ideal reactors wise either only those two either mixed flow or plug flow if it is continuous system if it is batch any way batch system so any reactor you bring okay what about you can't you use rotary kiln for combustion we can we can what about packet bed why we can definitely why what is the problem so that is what you know I can put all the coal inside burn it but only thing is it is not steady state we need steady state energy that is coming out of this combustion but that is not steady state if I take batch because initially you may have big fire initially slow fire again when it catches all the particles catching fire then it becomes to peak and afterwards it falls so that kind of situation I may not require okay so that is the reason why for continuous flow only we will go yeah only that or you have any other thing you have not heard moving grade conveyor you know combustors moving belt okay on the belt you have the thing I think the of course the material what you are using to the to design that belt should not melt okay so even that also continuously it is fat continuously it is burnt so this will go and then come out go and come out like a conveyor belt which is again recycling on its own that also can be used so that is why but in all the systems as I told you for catalytic reactions I have to pull out your particle to understand what is the phenomena that is happening around the particle why the reaction is taking place how the reaction is taking place so that is why all heterogeneous systems first imagination is what kind of reactor I am talking and please remember when I am talking about a single particle out and then talking about the reaction rate reaction rate will not change actual chemical reaction rate will not change what will change mass transfer will change mass transfer in a packed bed is different mass transfer in a fluidized bed is different mass transfer in moving bed is different mass transfer in rotary kiln is different that is how that controls the rate of reaction but chemical reaction is same chemical reaction actual chemical part is same okay so that is the beauty again in heterogeneous systems where you have to find out which one is now rate controlling whether both rate controlling are only one step rate controlling all that so that is why I take fluidized bed which is also very widely used right very widely used then you also have pulverized combustors I do not know whether you have heard of them pulverized coal combustors okay this pulverized coal combustors is simply it is used in the naveli and many power plants it is a cylindrical column big size may be 2 meters or 1.5 meters or 2 meters diameter so from the top what you do is you spray powder of coal pulverized coal the particle size will be around 1 mm 0.5 mm like that so actually they send with gas they just like a jet you know these particles like jet they just introduce so inside already combustion is going on steady state combustion we are not talking about transient condition before starting right not start up under steady state condition this will very quickly enter the combustion chamber sufficient amount of heat is there you know that is why combustion reactions are also auto thermal reactions once you started this combustion then it is auto thermal you do not have to do anything auto thermal means on its own its combustion is going on so this very fine dust of coal will just enter and then quickly burn and burning efficiency combustion efficiency is very very fast in that you know what is the problem there because when you are sending very very fine particles combustion efficiency is so strong so you have the ash also melting into solids that means temperature control is not there temperature control and in combustion temperature control also sometimes required particularly when you have lot of ash like Indian coal Indian coal have lot of ash so those ash will come together and then they melt and then they form solid rocks because ash is silica so that is why and I have seen one problem in particularly naiveli we have a place called naiveli here they have naiveli lignite corporation okay that is one of the deposits we have in the country largest deposits in the country in naiveli so they have been digging for so many years now and one problem what they told me was that I also try to do something on that so they have this ash fusion and it seems that particle size will become half meter half meter and it will stick to one side of they were using polarizer combustors okay that means simple tube right and then they spray and they put also lot of heating you know the water coils inside because idea is to produce the power how do you do in this combustor you put the water right so that will become steam so that steam will go to turbine and the turbine is attached to generator then only we will get all these things here right so that is why that is what they were doing there and unfortunately in that lignite what they have is Fe S2 so this will become now again that will make the ash to further melt at lower temperatures in the presence of this Fe S2 let us say that this melting temperature of ash is around 99 degree centigrade this will bring to around 600 70 degree centigrade and unfortunately this Fe S2 is part of this coal lignite they have to eliminate that they could not eliminate I mean I said something they worked well but I do not know whether actually in practice they are doing or not we do not know yeah so then this big of meter diameter stone after forming slowly starts attaching to one side and then it becomes bigger and bigger and bigger so no more that weighty can be hold by this you know that surface attachment then it will fall where does that fall that falls happily on the tubes internal tubes water tubes so they break then our power goes we will not have power and it seems to cut that it is not that easy I think biggest hexas also you cannot use mission type you know hexas also you cannot use to cut it they started breaking and then cutting and finally somehow they removed that is the problem what they have so that is why in all these things you know that is also because you should know all these different combustors and combustor is a beautiful non catalytic reaction so that is why I can pull a particle there also but the kinetics and what we are going to learn kinetics part is same for any kind of reactor but only thing is that k g value will change if it is a fluidized repad k g value is different if it is a moving bad k g value is different because k g value depends on what is called hydrodynamics hydrodynamics means how the phases are moving in the system in the fluidized repad how the phases are moving solid will jump up and down like this like this like this anywhere it is a mixed flow particles particles can be imagined as mixed flow in a fluidized repad k g right so that is why the definition of mixed flow is this particle can be anywhere anytime right and even it can come outside also if it is continuously feeding anywhere continuously I am feeding continuously it comes out right but now you see its mass transfer will be around that particle will be totally different when compared to packet bed where packet bed is just sitting there particle is just sitting there even moving bed what is the problem moving bed the entire bed you know packet bed is slowly moving it is not very fast moving in moving bed so and then oxygen is going in the opposite direction counter current if I take so that is why the mass transfer again between gas phase and solid surface is different those are the things only different same thing yesterday also I told catalytic reaction it is same thing again right catalytic reaction we also thought packet bed fluidized bed moving bed all these beds can be used there also so that is what you have to be more careful okay coal combustion I just take fluidized bed f b gas is coming out this is gas with oxygen and all that solids are continuously fed and ash is coming continuously that is also solid right so now what I do is one particle I will just pull out right so if I pull out and then bring that one here okay that same thing if I bring it here now I can imagine I have a not so you never have so nice particle because in cold digging and all that you know mining you will never get that kind of particle but anyway for academic purposes this is the cold particle and around this the gas is moving that also we know so we have this kind of gas going around that and the fluid mechanics will tell me that I have a film around that all these things are already known to us film right and then through the film oxygen has to enter and out of the film co2 assuming that only co2 is the the gaseous product okay that comes out now so and this also I can imagine that I have this solid surface this is carbon okay because the combustion starts only first on the surface right okay then I have here film exaggerated I thought I have to do so many things today yeah good so now if I plot oxygen concentration this is again I can call cag or cab whatever okay so I think I will call cab yesterday good that is cab now on the surface this is cas this is what is the picture correct no I have a particle around the particle oxygen is going not only oxygen other gases are going but our interesting compound is only oxygen because co c plus o2 giving me co2 my reactant is o2 so that is the reason why we take co2 right yeah so then what is step one mt of o2 to the surface to the surface through the film correct through the film good yeah step two reaction or combustion on the surface reaction on the surface step three the product gases coming out yeah co2 mass transfer of mt of mt of co2 through the film through the film to the surface sorry to bulk okay so under steady state conditions step one step two step three all three are equal okay good so now again as far as kinetics are concerned will step three change my rate of reaction I mean this could have been very good also if the reversible reaction is possible you will also get some carbon out okay c plus o2 giving me co2 if it is reversible reaction c and o2 again decompose to give o2 and carbon but that is not possible that is not reversible reaction okay so that is the reason why now you can neglect this because we are neglecting please remember that concept okay what is the concept there the third step is not really changing our rate of reaction if it is reversible then automatically show me okay the third step is not participating in the rate of reaction that is why it cannot change rate of reaction so that is why only these two steps are step one and step two are step one must be equal to step two step two under steady state conditions okay good what is step one mass transfer through the film what is the equation now okay minus r a b i have written a oba observed or yeah we have observed rate we have global rate we have bulk rate all that is there what did i write view yeah so this is equal to in terms of equations so this is k g c a b minus c a s and again we have an assumption here okay what do you mean by taking care we are neglecting step three is neglected because that is not affecting my rate what should i do if the co2 concentration is too much and you have to particle then it can like not let the co2 to react in the part yeah but under steady state conditions whatever is possible only it is diffusion of co2 coming out and the diffusion of o2 going in right a balance between those two only will give me what k g so k g will be affected that is all under steady state conditions that is why we assume that we have equimolar counter diffusion or if it is not possible we have to go for multi component diffusion okay so that is why under steady state conditions i have a k g and how do you get k g anyway that i will come to you later how do you get k g okay yeah so then k g yeah that is the reason why it is not affecting right but in the diffusion wise you will have some dynamic equilibrium between co2 coming out and o2 going in and that results in some kind of diffusion and you know the relationship between k g and diffusion coefficient film theory in film theory we are talking about proportionate to in film what is the proportionality comes what k you have again k g diffusivity k g is proportional to d o till what another k you are talking not even one more about this huh yeah excellent what delta yeah you know diffusivity by delta equal to k g under simple film theory oh my god how many three courses of mass transfer two courses of c re 100 course of fluid mechanics yeah this is simple i say delta you know d i b by by delta where delta is the thickness of the film and why we are not measuring that because no one can measure the thickness of film so that is why k g is an empirical equation you measure it is an experimental based equation that is why you have many correlations for k g in terms of which number charoud number charoud number equal to k g d by d i b the diffusivity coefficient there because you are converting that in terms of dimensionless quantity that is why that d i b comes there okay so that is why k g is in terms of most of the time correlations the reason is the theoretically one theory film theory tells me that d i b by delta equal to k g and you also have other theories in penetration theory only i think it comes as square root yeah so in some other theories are there it will come to you know 3.2 or 100 point yeah 0.6 or many things are there surface renewal theory is you know these three only we know but there are combinations of surface theory and the penetration theory together okay there are many it is some 45 theories but these three are famous what is that film theory penetration theory and surface renewal theory okay and you know surface renewal theory who proposed dan quartz okay yeah and who proposed penetration theory name itself is ekbis penetration theory okay who proposed film theory the first one who said louis louis and vittman louis and vittman these two these are all our grandfathers i say you should not forget them you should not forget them i think the moment you come to iit or engineering as you forget all the people except maybe nearest people are parents okay so that is why i think you know this information also is required and that is what i am trying to do and i am losing time but if you know all this i think you know i should have given freedom okay but because all these things not known so i have to tell otherwise you know even after this course i don't know if you want to remember you can but if you want to forget you can always forget okay but as chemical engineers these are the basic things you have to so this is the one and then now i am assuming that i have k into and it is not required only to have here k into ces it can be square it can be cube it can be another crazy equation divided by another constant plus ces square but procedure is same approach is same what is the approach first identify what is the reactor pull out one particle write all steps right and then try to eliminate mathematical steps like that so then try to eliminate indeterminate concentrations which you cannot measure so easily but bulk concentration can be used easily so that is why we call that as rate based on bulk okay global rate overall rate overall means mass transfer is affecting reaction is affecting what is the overall rate that is why the name overall rate global rate means there are many things happening but at global level what is the rate bulk rate means bring everything to bulk conditions temperature and pressure that means concentration and temperature so then call that as bulk rate all these names are existing right okay good so now this equation you are already masters exactly same equation only what you have derived in the last class so that is why the final rate i will write here C A B by 1 by K G plus 1 by K yeah now i will ask you to extend your imagination a little bit further is it exactly same or in this equation there will be something which i have to take care of it is not that easy for your imagination but still nothing so many so nothing is impossible for the imagination right but you tell me and you have to justify why you are imagining that this you know this is exactly same equation what you get for catalytic reaction right but is there any actual difference between this and that something something which you can do which you have to take into account that means you should now understand that is what i have been telling all the time you have to understand the basics of combustion what is the phenomena why always increase yeah so surface area is decreasing phase increase sir film is same film nothing is happening because the temperature is high you cannot say mass transfer is high reaction only we can tell it is very high so acidations what do you do yeah that is what the difference between this reaction and catalytic reaction in catalytic reaction the particle has constant size it would change with time whereas with time this fellow changes okay so this fellow changes and then you have to write K G as a function of DP and DP goes from certain finite value to zero it disappears totally at the end how do you take care of this it can be beautifully taken care of you know in non-catalytic reaction sinking core model and all that that comes in the next instance so beautiful that non-catalytic reactor design okay so that is the difference because otherwise it is exactly same and how do you calculate mass transfer correlations the K G value do you have a correlation if i have i told you mass transfer changes from reactor to reactor because hydrodynamic change from reactor to reactor i will give you the simplest case any reactor you have one single particle hanging and then equations are available and you have around this some gas going can i now calculate what is the mass transfer coefficient in this case it is also one of the pet questions in gate single particle mass transfer how do i calculate no sorry it is a single particle do you have a mass transfer correlation okay from single particle that is from gas to particle or particle to gas both are same have you not done a problem with the naphthalene balls you have done it but only thing is you are you have phd in forgetting excellent you know how many ways you can forget but i think what we expect you as teachers is you should have phd in remembering in how many ways you can remember once it is told i told you know one way of remembering i do that magnetic what is that hematite and magnetite i told you know one simple thing h comes first hematite so f u 2 o 3 so like that something and also you have hydrophobic and hydrophilic again these words i think how do you remember you know hydrophilic 4 4 okay yeah so that is why i say okay hydrophilic do not like you know water right hydrophilic means happy like so that is why once i know the other one can i can imagine because it is only two things know so like that you have to remember i know you should have phd in that in how many ways you can remember but now you are experts in the other one in how many ways you can forget okay somehow i should not remember this aspect at all okay you have done that some i think many it is a favorite question also for many mass transfer teachers sherwood number equal to 2 okay so is it always or is there is some special case huh spherical is okay yeah spherical is one but under what you have to tell the condition under what conditions this is simple diffusion i have told you know with a lot of thing and then stay at the thing no convection at all when you have no convection that means velocity equal to 0 convective velocity then you have sherwood number equal to 2 this is what i told this is a gate favorite question okay so that means prove that sherwood number equal to 2 for a single particle without any convection equal to 0 right i may also give because reaction engineering cannot survive without mass transfer mass transfer also must be there in homogeneous you may not see right okay so plus something else is there when you have convection 0.5 renard's number to the 0.5 no not 0.6 and smith to the power of 0.33 1 by 3 what is 6 oh this one is 6 this is 0.6 okay yeah you know what is the name of this correlation another grand father another two grand fathers another three grand fathers huh excellent how do you know these gopin all these are trying to catch that is it okay renjan marshal that is right and you know another name for this which is in third chapter of tribal third chapter now if you go you experience may be slightly different what you say almost frostling equation frostling that is why i said we have three grand fathers okay so that is the frostling equation so this is what what one equation you use so if i want to calculate these for single particle just single particle okay mass transfer do you have similar equation for heat transfer exactly you have same equation similar equation for heat transfer but only thing this is no salt this cannot be phranton that is renard's again because renard's number comes because of the flow okay so that convection must be there and whereas this is phranton number now you remember you know how many ways to remember that is why i told you this there are so many ways to remember do not be experts in so many ways to forget forgetting okay good so this is the equation you can see whereas renard's number is decreasing you know dp is changing size it is slowly disappearing so then you can also calculate what will be the corresponding k g value and that we have to take care of somehow inside the one and i will tell you in the next semester how to take care of that in the in the actual design so now i think idea here is again to have this equation as heterogeneous system where k g is very important parameter very quickly now you are experts so now we have many many systems like i have taken only gas solid right we can take gas liquid system what do you call gas liquid systems what kind of reaction is used for gas liquid yeah sorry gas liquid no what kind of systems use systems means equipment i cannot say reactor because there may be reaction or no here distillation column is one okay yeah right right he also told absorption yeah absorption yeah anything else bubbling columns bubble columns bubble columns then you can also have simple tank and bubble gas and you can also have very tall column and bubble gas yeah which one you spray liquid spray and gas you do not get bubbles yeah yeah but i think you are sending liquid in the form of droplets and gas is going the contact is totally different what we are said talking here is i have liquid continuous and gas is bubbling then only you call bubble beds okay bubbling beds or bubble columns right we have all that and now yeah you have also liquid liquid reactions or liquid liquid extractors all liquid liquid extractors also can be used as reactors what is the difference i have one liquid continuous another liquid dispersed now how the reaction should take place same again imagine that is why that imagination is very important just imagine how your droplet is moving in continuous liquid if you do not know you go home and take kerosene one or two droplets and then put into water how they move right and you know definitely bubbles how they move because that is what many times we deal we see wherever you go nowadays shawda when you take or what cool drinks if you take okay then how the bubbles are coming that we know right so there also i will take one drop around the droplet i have liquid moving because one is continuous fluid is the other one is dispersal fluid even bubble column bubble is moving liquid is again coming whether it is co-current direction or counter current direction so bubble is moving and if i sit on the bubble i know that bubble is moving i cannot see i can see only liquid is moving around that is also with respect to which coordinate your coordinate okay that is why you have lagrangian coordinates oil and coordinates only for that you see how many things you have to learn now right so that is why procedure is same take one droplet and see what is the liquid flowing around and again film interface between these two where is the reaction has to actually taking place if you have these droplets dissolving in the other liquid and then reacting with the bulk that is one thing the other thing is if this liquid is able to get transferred on the surface and the reaction is taking place on the surface and again diffusion of these molecules may also go into the droplets with respect to what so that is why you have to understand the physical properties of both the liquids gas and bubble what will happen in gas and bubble sorry i mean gas bubble and liquid bubble is moving up right again liquid is flowing around that so i have a bubble liquid so now imagination easily for this is liquid liquid is slightly difficult imagination is normally this gas will first dissolve in the liquid in the liquid then the reaction may take place but before dissolving it has to pass through two films one is within the bubble within the bubble other one is outside liquid filling that is what in absorption you said in absorption that is the two film theory right in absorption i have the gas bubble it is getting absorbed in the liquid so but but what is the imagination i have the bubble outside i have a film because fluid mechanics tells me whenever i have two phases i will have film how strong how small and all that is later depending on the conditions and inside also i have a film right so then the gas has to first pass through the gas film inside the bubble such is the interface from interface to again through the liquid film to the bulk that is why i now take slurry reactor slurry reactor is a three film i mean three phase reactor so we will see these things there so again slurry reactor is easy to imagine normally we will have distributor here gas distributor gas comes out you have the catalyst particles because it is a slurry reactor catalytic reactor then you have the bubbles sometimes you will get very nice bubbles sometimes you will get this kind of bubbles and this bubble exploded yeah so this kind of bubbles are moving so here i have inside liquid yeah inside liquid okay good so now again here i have to find out the rate of reaction what is the procedure now we have three phases earlier i have two phases and then pulled out solid phase and gas now i have three phases so i have to now see there is one bubble and then there is one solid particle in between definitely there will be liquid so you just pull out this imagination one gas bubble okay i have to also write here this is catalyst this is bubble and this is liquid those are the three phases right but here what you are taking is bubble is gas is continuously bubble the other two are in batch batch condition liquid also in batch i will take only certain amount and then leave it there if i want to make i can also make liquid continuous if i want to make solid also solid continuous also i can make you see how many possibilities for one reactor simplest possibility is bubble you cannot take gas okay gas sorry like batch yeah bubble you i mean gas you cannot take as batch so that is why it is continuously bubble so now what is the imagination i have the bubble you see imagination of bigger this is the liquid film this is the gas film somewhere here i have solid particle okay that is catalyst and here also it tells me that i have film right so in between what i have okay liquid now where the reaction is actually taking place see that is why that imagination that process what is really happening the phenomena phenomena that is what physics we say that phenomena is very important what is the phenomena now i have to imagine here yes i have the gas bubble this gas bubble has to first come and dissolve in liquid let us say that gas bubble has reactant A reaction may be this is A going to R okay simplest one you know so for easy imagination so now this A has to come out of the bubble so when it is coming it has to it has to go through the film this is gas film and this is liquid film okay then this is catalyst and this is liquid film what is my imagination now you should first have the gas which is coming out and then touching the interface there depending on its solubility it will dissolve in the liquid and then that liquid when it is dissolved throughout you have A in this liquid now that liquid in that liquid this A has to be transported to the surface and on this surface you have the reaction taking place if it is non porous particle if it is porous particle again that liquid will diffuse with that A and A will get reacted inside the surface so now what are the steps so yeah before steps i will also draw the profiles so this is one profile okay this is one profile this is one profile okay this is the center okay so now you should have this is okay so in the bubble inside because it is gas everywhere so i may have the bubble concentration as C A B which is uniform throughout but in this film i will have some drop in the concentration so i may have like this this is C A C A okay i will also write here C A G to be specific C A G this is C A G i this concentration now you have the henry's law here because whenever gas is dissolving okay in that the interface you have this henry's law acting and that henry's law will tell me that i have this is C A G i equal to H into C A i L liquid so depending on the H value you will have either starting above below or equal equal when H equal to 1 right and above below you can imagine so now this is C A i no C A now it has become liquid concentration so C i L i so this concentration here at this point is okay i will write here C A L i that means at the interface this is what is the interface interface between bubble and yeah gas and liquid so this is liquid right okay so then i will also have next a liquid film yeah from here this will again go to some concentration which is C A L assumption here is that this L is almost C A L is almost constant why because we are putting a mixer or even if you do not put a mixer you have the bubbles vigorously moving so then you will have good mixing so gas will uniformly distribute and throughout this liquid you will have uniform concentration that is why that constant so afterwards again here you have this is C A L again same thing then you have another concentration this is equal to C A S if it is porous particle we will stop here if it is non porous particle again you will have a concentration drop within the particle because of the diffusion of A through the force that is nicely taken care by effectiveness factor okay good so now i have now how many steps what is step one i think i have sufficient time now for two minutes sir oh my god now again i have to draw tomorrow all this okay we have to stop here oh yeah okay i think yeah good now step one step two step three what are the step what is step one for example see for the reaction to take place how this A fellow has to travel that is what what you have to imagine reaction is taking place in the catalyst on the surface of the catalyst for the A for A to teach to reach that surface what are the steps now step one is empty of A through gas film to interface correct now that is here step two again mass transfer of A through liquid film through liquid film now to a bulk very good so step three is mixing of A in bulk liquid mixing of A in bulk liquid you know that also a step that can also if it is not infinity then we have to take that into account because if it is infinity we may neglect because concentration is uniform okay good so now step four again mass transfer of A through liquid film yeah to yeah catalyst surface then you have step five yeah reaction on the surface reaction on the so reaction on the surface because of quick writing only this happening okay so now at steady state one two three four five all steps are equal now you have also sixth step if it is a porous particle that means fifth will be again diffusion of A through the force of the catalyst then reaction inside the surface of the catalyst now procedure is same I have to write mass transfer equation through film mass transfer equation through liquid film and because this is not offering any resistance so we do not have to yeah again who asked someone asked me this step can be neglected now because it is not changing my read why C B C A B is constant throughout right so then I have to take this step this step now another mass transfer step through the liquid film around the catalyst then rate of reaction under steady state conditions this equal to this equal to this equal to this how many mass transfer steps are there three three three three I mean if you take even mixing sometimes if mixing is not very good inside this also you will have concentration gradient it is not uniform so you see in fact in a heterogeneous reactions there are more mass transfer steps than reaction steps that is what is the beauty in heterogeneous reactions and again yeah okay again we have to take whatever is controlling and all that we have to do that we will do tomorrow controlling I do not do I will just only develop one equation and then okay so that again we will do in C C A B in fact C C A B will be more exciting than this okay because you know all applications whatever you learnt now these are all fundamentals basis so there I think all those things are applications