 ఝైనా నేమరియెప్లిమికంతుల్ని కంటవరానంా పతసంటా ఎతరికంఆత్వణనార్ నంటికికంటినాఉన్తెచటరా తమంటినానాంటా కమివరిలుల౓టికచి మలాి you do not have to go to other house search and parents and all that so but in solids what is really happening I have 2 solids coming together for reaction both are pure but reaction can automatically take place why because those molecules are not movable right so that is why what you have to do use you have to break this solid you have to break this solid make them very fine powder if possible molecular lever you can never do it so then you mix them perfectly and then bring to high temperatures then the molecules start diffusing a little bit that is called self diffusion okay so with that only it will react that is why solid solid reactions are very very slow fastest reactions are gas okay so that is why again please do not tell what is the difference between homogeneous and heterogeneous means one phase two phases over that stage is over you have to learn something new okay you can tell that anyone asking if there is what is the definition of homogeneous if you say that all molecules I mean whatever number of reactants that are available if all of them are easily available in one phase then you have homogeneous okay heterogeneous that is not possible necessarily from one phase to the other phase the molecules have to move right so if you have coal and oxygen by keeping coal in one room and oxygen in one room you cannot have even you have same room but if there is no sufficient temperature then reaction temperature still coal may be there air may be passing over that still you do not have reaction that means the mobility of the molecules is not enough for the reaction to take place or activation energy what you say right yeah so that is why you have to bring them to the reaction conditions environment and then automatically the molecules will move when the reaction takes place that is the difference now actual difference you want to ask something no you you blue bunion you only I am talking about you straight no you said like this so I thought you are asking yeah Kalpana yeah that is a good question in fact you know during the reaction if it is remains homogeneous we take them as homogeneous right but immediately when the reaction is taking place there may be a condition where the products are forming as precipitates okay solids like for example gas it cannot happen but mainly it may be happening only in liquid phase so if that is not affecting your rate of reaction then you can call that as only homogeneous okay so in fact that is that is the point which I have to also tell I have forgotten at that time when I was talking so now that is a good question where during the reaction if the molecules are free available even though there is a phase change that means the product when it is formed automatically it is precipitated you may be stirring it but I think still you have at molecular level the availability of molecules for the reaction to take place okay so that is why you can still take that one as homogeneous only good so that is what what we have discussed here with this diagram and we have also identified what are called catalytic reactions and non-catalytic reactions now we have to identify in gas liquid mostly what is the kind of reactions we will have what kind of reactions we will have in gas liquid are they catalytic reactions or are they non-catalytic reactions mostly there may be one reaction you know very peculiar reaction where you have liquid gas liquid right the first one gas liquid so liquid acting as a catalyst or gas acting as a catalyst is it really possible generally so most of the time for gas liquid n c non-catalytic reactions right okay so for liquid liquid you think I say you are only just listening to me you have to also think you have to question me you have to think okay both possible good answer is right but why autocatalytic is homogeneous can be homogeneous autocatalytic is the product acting as a catalyst okay now we want to use as external liquid as catalyst both are liquid right so there are many reactions where there are non-catalytic reactions and also catalytic reactions where one of the liquids can act as catalyst okay I think the nitration reactions are like that okay nitration reactions are like that where you have to you know if there is a catalyst that catalyst in the form of liquid okay will be this liquid liquid liquid liquid reaction the moment you put solid here then it becomes three phases if the catalyst is in solid form then you cannot take this you have to go here now you have three phases no solid so that is why when you are talking about catalyst here that catalyst must be one liquid but it should be either miscible in this or in this okay then the reaction will take place at the interface and most of the time that is why one of the liquid is dispersed into very very fine droplets the other liquid is continuously sent and you have to now see in which phase your catalyst must be dispersed either dispersed phase or either continuous phase right so that is the condition for non-catalytic reactions in liquid-liquid it is possible few reactions are there then what about liquid solid liquid solid most of the time it is my liquid solid gas liquid yeah liquid solid can be non-catalytic or catalytic because for the for example that solid can be a catalyst over that you send liquid but now this is one liquid so that liquid is you know the reaction is taking place on the surface of the catalyst or inside the particle so that is possible so you have few reactions which can be liquid solid either catalytic or non-catalytic okay next one gas solid most of the things are catalytic and also of course non-catalytic reaction give me one example of gas solid non-catalytic which I have told also just now or resting carbon binding combustion I think you know that is very easy for imagination no so carbon binding even resting is not that easy to imagine again your mind has to go to cycle and all that but here carbon means binding immediately comes to our mind because all of us thousands of times seen this binding so that is the reason and many people would have not seen the resting rusted cycle okay so that is why that it takes time solid solid most of the time it is non-catalytic solid solid I mean how do you get a solid one solid catalyst another solid only but how do you make it how the reaction can take place impossible and you know one example can you give for solid solid reaction which you see every day almost if you take coffee that product you use because of the solid solid reaction chainies are very famous for that chainies are very very famous I have given you so many clues I say what is that roasting of what no it is not I am not talking about coffee taking coffee use this product and I gave the clue beautiful clue chainies chainies are famous for what what is that jamminga jamminga jamminga jamming you see because you are interested in junk food you remember only noodles okay noodles are kept where in a plate what is that ceramics and glass chainies are where long time they have developed the technology the best ceramics in the world available only in China and you know how do they do it solid solid reaction and solid solid reaction has not come to the level of gas liquid reactions or gas solid reactions or liquid liquid reaction because they are very difficult to study okay so that is why I think you know this is one of the very very difficult reactions very very solid reactions and you need I think you know China they take that one as an art the ceramics it is not only simply they are producing the plates they produce that plates with beautiful designs you know paintings on that you can just imagine how they are doing it and lifelong it will be there unless you break it okay so the painting will never go the glossiness will never go it is wonderful right you would have seen know many movies of Jackie Chan where fighting will be only how to say one jar that will will come and he touch you will jump and then catch and again that fellow will come and eat and this fellow will go and then catch the jars you are not see Abdul see no also see movies yes because I appreciate the Chinese you know jars not Jackie Chan okay you appreciate Jackie Chan and also try to see what is that he is trying to hold there in many movies he will never you know allow others to break Chinese treasure that is Chinese treasure really okay so that is the one and gas liquid solid can be can be both catalytic or non-catalytic okay I think mainly it is catalytic you know when compared to even non-catalytic okay this is again technological interruptions yeah so this is we have to put brackets here this also is very important for us then we should know that as I told you the design of non-catalytic reactor and the design of catalytic reactor will be totally different so that is the reason okay so now next one because we have so many possibilities and the rate of reaction when you are expressing for homogeneous it is very very easy right so normally we write for an ith component because you can replace this one by A okay yeah my equal to normally I will also write the equation Vi sorry V DNI by DNI by DT yeah okay DNI by DT equal to I am writing this in terms of moles moles of I of course if I do not put here it is formed but because negative I am putting it is reacted per unit time per unit volume that is the definition okay yeah similarly we can now write for all other things that are possible I told you this is the simplest one this is the simplest one because volume means here we are talking about volume of the reaction mixture okay normally we don't waste our reactor volume so that is why when you calculate this we also think that that is the reactor volume actually it is a reaction mixture right if you are conducting slightly at high temperatures and if there is some vapor coming and all that so that is why you will again allow some kind of vapor space above the liquid okay that is only engineering judgment how much you have to leave only depends on the temperature how much vapor is produced and what is the vapor pressure and all that okay but what we are talking here with volume is volume of the reaction mixture okay so now when I go to different things now let me let me take very widely used is gas solid okay gas solid is very very so many reactions are there in the industry some of them can be catalytic some of them can be non-catalytic so now we will use that one for you know deriving writing some equations that is homogeneous this is heterogeneous so many possibilities are there so now based on based on volume of voids you have to be very clear in the reactor okay so if I write here again I yeah so moles of I converted per okay per unit volume per time right so this can be of course meter cubed or second you generally meter cubed per second I think in chemical engineering literature you get these values those units in various forms right in if you take some of the books deliberately they give also feet cubed okay there will be moles feet cubed and all that because I think this is required for us you cannot say that SI I do not understand anything other than SI units you should be able to convert one from the other okay otherwise consistently use only one system so that you will get the volume also in that particular system if you are using only everything in FPA system finally the volume should be in terms of feet cubed okay so like that so this is the one and you see here we are now basing on voids in the reactor and that much you should know we have a packet bed and you pack all the catalyst particles for example in between the particles you have some voids and inside the particle also you have some voids we are not talking about that we are talking about only voids okay tell me for packet bed how much is the void age 0.4 yeah any any any other guess I am not saying it is right or wrong it can be wrong also external what is what I am asking yeah 0.5 no you do not answer because I think you know we simply say 0.3 0.4 that is strictly valid for what rashi gring means you know KK will use AK-47 okay yeah right for rashi gring see is 0.4 what is this I say two courses B Tech and M Tech I am talking about them okay PhD scholar yeah I do not know whether PhD scholar or M Tech PhD yeah you see so your rashi grings are always having only 0.4 0.4 for what you know this is what I say still we have only LKG knowledge only we do not have more than that our brain is not expanding yeah tell me you are just keeping quiet Jaanvi 0.4 he said for what 0.35 to 0.4 which packing and he said rashi grings I said no you can guess there are many packings you know yeah Sushmita no idea what is that packing XNL HTP Xagonal packing oh my god no one will make examinal packing how can you make examinal packing so easily huh very nice answer what is irregular what is regular okay yeah it is not because in regular and irregular packings okay there are thousands of variations but this 0.3 to 0.4 will only come for one glass beads okay glass beads can be spherical cylindrical they can be rashi grings you know type you know with the whole many things can happen glass beads are strictly for spherical particles please remember when you say 0.3 0.4 okay strictly for spherical packings and as he said I think you know rashi grings rashi grings will have how much any other any other value 0.6 okay yeah and bell saddles also around 0.6 okay so that is why you know the we have various packings but except spherical part packings all other things will have higher voidage okay good yeah so that is what is the best you know this equation is based on this is voids right okay so then next one is yeah so we can also based on volume of volume of catalyst particles so again this is of course I can put here dashed double dashed I yeah equal to moles same thing I converted per volume of solids per time yeah so based on based on weight of the particles again I can write here moles of I converted then yeah weight of catalyst catalyst right per time good yeah so another one can be based on external surface surface of particles this is again minus of I converted per surface area per time yeah not able to read the first one is always moles I converted surface area yeah of what which particle I have only one particle catalyst that is why I said you know heterogeneous gas liquid gas solid system okay yeah so you have only that is solid particles yeah you will have definitely all these doubts because you have to specifically mention on which you are going to write the rate of reaction this is very important please don't take it away very simple definition and all that no because finally what you get is only this one in the reactor in the reactor design expression when you are calculating like volume of reactor you calculate right so if you base it on volume of reactor then you will get volume of reactor if you get weight you will get weight if you get volume of solids you will get volume of solids yeah you are asking something oh yeah you are right thank you yeah you are right based on weight of the particle very easy for me to write W and this is wrong yes thank you catalyst yeah okay and all solids are catalysts inside the reactor okay so I mean when you are taking about packed bed where I have gas solid catalytic reaction we are taking only one example gas solid catalytic reaction right like for example ammonia conversion or sulphur dioxide to sulphur trioxide with using vanadium pentoxide so many definitions are existing only for that still this is not the end you can all if you are crazy you can also base it on voids of the voids inside the solids it is not inside the bed inside the solids only I told you sorry yeah inside the bed only I told you that we have around 0.4 point 0.4 for spherical particles okay and you know 0.6 if you have rashy rings and by the by catalyst particles also are made in the form of rashy rings how does a rashy ring look like never seen what is your name I forgot to adjust Pooja yeah Pooja have never seen rashy ring how many people not seen rashy ring frankly otherwise I will ask you to come and draw here how the rashy ring look like you are not also not seen merit no oh my god yeah so okay can you tell them how Abdul how does the rashy ring you also not seen AC tech how I think they have lots of they always have always only rashy rings only holes okay no I am not asking whether you have seen or not but in AC tech rashy rings are not there balsalis are more difficult to make rashy rings are very easy to make okay rashy ring is just a cylinder with a hole okay like you know pen yeah this one you just cut here take this portion that is rashy ring this is the simplest one because you are trying to utilize if it is only cylinder is closed you know right so then area available for reaction is yeah only the external surface but now you put a cut here and cut here if it is hollow thickness may be of course it should withstand the weight and all that then internal surface are also is available for reaction so because internal volume also is available that is why it goes to 60 percent point 6 is the yd okay and some people also use straight like this exactly this is the catalyst it is a cylinder but there is no hole okay cylinders are very easy to manufacture in the industry for as catalysts spherical particles are very difficult to manufacture on that scale yeah very fine powder no yeah I mean are you MS color PHD color or PHD we do not want to do that experiment in your lab which lab you are in I think you know in that transfer operations lab you take a cylinder and then you try to pour that powder and try to find out what is the yd do whatever you want but they tell me what is the yd no it is good no that is why many people think that the people who are working who are doing the experimental work the theoreticians feel that people who are doing experimental works are like laborers okay but I think laborers definitely should have much more brain than the theoretical people because theoretical people nowadays that theory you are not proposing E equal to MC square okay you are only trying to solve some mathematical equations but experiment when you try to do how many things you have to imagine in your brain before you start the experiment even nut and bolt you have to choose okay literally how to choose in our department because we don't have nuts and bolts now in the department okay we don't want to have any nuts okay yeah so I think you know it is very it is not that easy everything you have to imagine how do you do this experiment for the experimented to be done that is why many people take the easiest route go to computer take one differential equation solve change boundary conditions submit the real engineering thing will come only when you are able to verify whatever theory you have done you know in your thesis with an experiment so that is why most of the engineering PhDs or MS you know research problems must be having both the components theory and experiment otherwise you are not an engineer in fact it happened when they go for interviews here you know in what that placement people asked you have you seen you know what is your rotameter they said no we have never seen a rotameter they were very angry the people who are working theoretically okay they were very angry and they wrote this big letter to director at that time it was I think 15 years back okay what is this what kind of training you are giving in a chemical engineering department they have got a m techs and PhDs but they never seen a rotameter okay you may ask so what so why if I have not seen rotameter what will happen to this world nothing will happen to this world but only thing is you will not get the job correct no because they want they definitely want some information about rotameter I think some flow meters okay so that is why yeah that is a good question I think I also told you when you put very very fine powder what should be the void it is nice spherical particles you will get that but if you have powder that too irregular powder you may not have each and everything as perfect sphere then definitely it will be point to point one much less but it will be challenging for you to determine exactly what is that okay but because you are using very very fine powder for example talcum powder you pack it and then or when talcum powder is put in the in that container where you use with the holes perforations you know spray there and all that yeah so then what should be the void is there that depends on again pressure how much pressure you are applying when you are packing that so that is not that easy to determine that is why powders we never use in a packed bag right we use only minimum 3 mm particles 5 mm particles of course in industry as I told you the catalyst if they are using spherical even then it will be half an inch particles 10 mm 8 mm 6 mm like that maximum I told you 18 mm 1 inch 2 inches no one will go because simply we are losing surface area but if you are going to lower and lower 1 mm 0.5 mm 2 mm the pressure of increasing because you know normally theoretically there should not be any change in void age if you have perfect spheres but who can make a perfect sphere even God cannot make perfect spheres really that is why he made all the planets and most of the planets you see they are bulging in the middle like all of us yeah really because they also rotate you know because always the first indication of prosperity is okay so people look at that is why I used to analyze people in terms of straight lines I told you already so no always see the people as straight lines or cylinders or spheres okay straight line will be something like this somewhere you have legs somewhere you have hands but most of the time you see a single line we can see some of the people when they are walking okay all this you know very long time back in Telugu I don't know when some of the people who may be knowing Telugu people there used to be one comedian called Ramana Reddy okay yeah he was a straight line because he doesn't have any other organism except you know because one-dimensional you cannot put any other organ there no okay yeah the other person what I have seen the other extreme sphere was one of the these singers where is it not sphere you cannot see head only small legs and all that hidden somewhere okay so this is the one so as engineering I am approximating that one as spheres you can see that okay and most of us are looking like this yeah okay cylinders so that's how I think you know we can see we can look at the people and then think that okay my god straight lines spherical particles and cylinders you know you can also divide them and you can use them as catalysts if required but this will be very bad catalyst because packing is not possible so easily right even this also is a regular but that is what people use mainly in industry most of the time because you know extrusion how do you make catalyst they will identify what is the material and they will make as a paste and then they extrude through the extruder like noodles they make noodles also extrude extrusion only so but they cut normally L by D equal to 1 normally it can be even 1.5 but most of the time L by D that means if diameter is 1 centimeter length also is 1 centimeter that is the kind of cylinders those cylinders they pack and as Jayani was telling you know irregular random packing when they do you will not get uniform porosity or uniform voidage across any cross section that means when I take packed bed and cut at there at one point I look there so the voidage may not be uniform when compared to another cut just above that is why we take what is called superficial velocity you know why do you use superficial velocity by the way what is superficial velocity as you I am talking as if all of you know what is superficial velocity yeah what is superficial velocity what is your name I want to remember names Abhijitha Abhijitha okay I will equate with our Abhijitha Velocity Velocity Velocity you cannot divide anything you have to take only volumetric flow rate and divide which area you are talking superficial velocity correct superficial velocity is based on only empty cross section right but in most of the packed beds you need packing definitive for the catalytic reaction to take place but in spite of that we always refer to superficial velocity you know the reason why the reason is exactly I know what is superficial velocity okay because it is empty cross section divided by yeah volumetric flow rate divided by empty cross sectional area okay and the other hand if I put packing if it is not uniform voidage yet every point velocity is changing so I do not know how to correlate that so that is why a very good known parameter I will take I will express all my correlations in terms of only superficial velocity where we know the diameter of the column we know the volumetric flow rate so you can get superficial velocity if all the correlations are developed in that in that way then it is easy for us to use them otherwise the voidage will change depending on the packing the voidage also will change depending on you know you have irregular packing or even cylinders also it is not uniform only perfect spheres if you pack them that too maintaining L by D now this time not L by D D by D P diameter of the column divided by diameter of the particle minimum 10 and above if you use then only you will have the uniform voidage otherwise what will happen near the walls you will have more voidage at the centre you will have less voidage but by increasing the diameter and putting only 100 particles for example across across 1 diameter 100 particles if you are able to put most of the non-uniformities will disappear that is why we say assume I mean the people who are using these theoretical equations all assumptions must they do assumption number one use I mean assume spherical particle you will never get spherical particle assume uniform voidage you will never get it assume no wall effects okay that is okay you can get it because depending on diameter of the particle and diameter of the tube you may be very near to that assumption right so that is why all that we do good so what is that I was telling now yeah so out of all these as engineer which one you choose this is only for just gas solid catalytic reactions which is third one yeah why correct easiest to measure easiest to measure what is the difficult to measure out of all that surface area you will never get perfectly all the surface area that is available for the reaction because even when you are using different techniques right BIT may give you some good information but mercury porosimator these that will not give will not cover the entire range of force okay so that is why like this you have to write all possible things and then choose one of the easiest right like for example if I have liquid-liquid reaction which is the easiest way to express but you have in the volume both the things yeah okay very good volume of the reaction you can express what is the most difficult to get some interfacial area in fact estimation of interfacial areas are very very difficult same thing even with gas liquid system where you have bubbles gas and then liquid as bubbles so then you will have again same problem so that is why you have to now understand that the first problem with heterogeneous system that comes is definition of rate itself okay and one example I can give you here GLS when you have three phrases most of the time people express as bubble free slurry volume moles converted per unit time per unit bubble free slurry volume that means again bubbles they may be of different sizes different you know shapes you will not have again spherical bubbles all the time right and also you will not have uniform bubbles all the time so that is why they simply eliminate saying that okay let me express the rate for this as moles converted per unit volume of bubble free bubble free slurry that means solid volume plus liquid volume you take but that is not the only unique way some people may say that only bubbles okay I think when you take this time also we will tell in the next semester we will actually derive an equation for the rates of you know slurry bubble columns slurry bubble columns also sometimes called slurry columns or slurry bubble column so there you will know it is most important thing is bubbles there first the mechanism when you just look into okay so that is what is happening now with all these rates you have to choose one of the easiest one which you can measure and industry can use that very easily so as I told you again I am repeating when you use this equation then you will get directly weight of the catalyst okay or when you are using surface area directly you will get surface area of the catalyst then you can convert finally you should have only volume converted into some diameter and some height that is what is ultimate shape of the reactor okay spherical reactors many people won't use very difficult to make again spherical reactors most of the time either tanks only cylindrical most of the time it is only cylindrical so that is why you have to choose a diameter you have to choose a height good so I think I have covered I wanted to cover many but this time I think yeah so I thought of doing I think even batch reactor so next tomorrow class we will concentrate on contacting so this is the information what we have now in fact this is what we have to write also in the design expression when you are writing the balance that is why I thought I will just say the definition of the rates and all that you know our key reactant always is A that is why we call you know minus r A right so we will use that information to now write design expressions for batch and then continuous and I also discuss with you when do you choose continuous when do you choose batch