 So, this image over here, it is a satellite image of plumes which are coming smoke plumes ok. I just wanted to share it with you because at some point in time I will talk to you about satellite data and some of the recent applications of satellite for air quality management ok. I think there is another one here, here is another one here you see this particular place where something has happened and I am not too sure, but I think this is from the 9-11 disaster. So, this probably is New York I think I am not too sure ok. So, that is the smoke coming this is the plume and you can actually see it. Now, this image it actually is an image. So, you can see the smoke and it is a clear day there is no cloud. So, probably you can see it, but there will be days when there will be clouds and this will not be visible. So, there are ways to be able to bypass some of those noise issues and then look at the pollutant sources and the locations ok. This is another one of my favorite images. It actually shows two different chimneys or two different sources point sources for one the wind seems to be in this direction for the other one it seems to be in this direction ok. So, wind is when we measure wind at 10 meter height at in a meteorological station it is only indicative of the wind speed at the surface ok a few hundred meters above and the direction of the wind can change. So, it is very important to have this understanding of meteorology as well. So, that we can accordingly take into account some of these effects during modeling ok. So, there is an image of what a typical sampler air pollution sampler looks like in the field it would invariably have I am not too sure it looks like a PM 2.5 head over here a lot of times they would have a high volume sampler as well as sometimes they will have a med station to be able to get the local meteorological data as well ok. So, this is what it looks like in the field lot of times because of security reasons you have to house it in a chamber like this close it and lock it and you have to take precautions because lot of times that becomes an issue when we are dealing with field sampling ok. So, those are just some trailers and some things to fill in the time so that all of you can settle in ok it takes about 5 to 10 minutes for people to settle in. So, this is probably good entertainment for that duration. Alright so, let us begin with the lecture 6 and before we begin let us just review what we have done in the previous 5 lectures. In the first lecture we set up the context and we had a pre-course quiz of pre-course feedback followed by lecture 2 where we looked at concentrations, we looked at the national ambient air quality standards, we looked at in lecture 3 dispersion mixing stability how particles or how pollutants once emitted into the atmosphere what is the fate of these pollutants, what happens to them, what is the strategy that we use to be able to disperse these depending on the meteorology depending on the height of the chimney etcetera. And then we need to be able to understand the impact of this so ground level concentrations are also estimated using Gaussian plume models and similar models. In the next lecture we actually distinguished between gases and particles as ants and elephants and we actually defined what is PM10, what is PM2.5, some of the sources of these elephants and dinosaurs. In the last lecture that we did we actually looked at how to measure these pollutants particulate pollutants and I had given the methods for carbon monoxides, oxides of sulphur, oxides of nitrogen these are standard methods that are available, wet chemistry by and large lot of times nowadays they also have automated instruments etcetera. So, if you want to setting up a laboratory once setting up a monitoring station then you know these become important, but I think it is important for students to know what does it take for them to be able to measure these pollutants criteria pollutants we only talking about criteria pollutants right now when it comes down to industry there are many many other pollutants that need to be measured and then the industry accordingly takes care of whatever the protocols for that are. So, today we are going to talk a little bit about air pollutants how to control air pollutants ok. But before we you know move on let us take a look you know in case today is my last lecture I may not get a chance to talk to you again tomorrow and so you know maybe a good idea to review your questions in the you had in the pre course feedback, pre course feedback that we did. So, there were two parts part a which was more to do with how you teach in your college and proximity of your college to some of the industry etcetera etcetera, but part b was more focused on the specifics of what the syllabus demands and what you teach or you know what are the things that are clear for you not clear for you those kinds of things ok. So, these were the six questions that we had or seven questions that we had asked again the last one was contextual these six questions were more of questions that might be asked during the teaching of this course ok. So, what I am going to do is I am actually going to have you open up your notebooks and review these or if you do not have those notebooks or if you do not have the sheet of paper to in any case go ahead and review these to look to see if you have been able to convert the I do not knows or the ones that you were guessing ok there were some things we had we had said there could be three possible responses you know it and you say it you do not know it, but you can make an intelligent guess. So, you know go ahead and make that guess and say that you are guessing it and third one is you have no clue and then you say ok I really do not know the answer to this question and we had said that the more IDNKs you have the more relevant this course would be with you. So, you know you have more things so that you can learn from this course. So, same thing you know comes back to the same thing. So, IDNK if any of your IDNKs have been now can you can claim them as I now know ok then great you know and if no then I have just opened up just before coming for the session I opened up a new modal conversation in which I request you that whatever you do not know even after having gone these lectures whatever queries you might have whatever things are not clear for you please send it. So, in some sense it will also help us in deciding what kind of assignments and what kind of resources to give you so that if not during these 10 days at least you have it available the resource to be able to answer these questions ok. So, I am going to switch back to that particular slide and hold it for a few seconds so that you can go ahead and actually talk to each other or just go over your notes to see how many of these questions are already answered for you or how many of them are still pending ok. So, I am going to be quiet for about 2 minutes now. So, please go ahead and discuss with your partners or you know talk to other people in the room ok go ahead I will be back in 2 minutes. Ok, Netaji Subhash Engineering College TechnoCity, wow. Air pollution we can control by so many instruments we have discussed electrostatic precipitator back house, but compared to the volume of the nature is it sufficient to make the air clean for our survival? Ok, so yes the issue of implementation of a lot of these technologies is remains unresolved or is not at a level at it which should be in India, but that is the work ahead for us and can we you know bring it to a point of sustainability that is our commitment. The question is are we going to be able to do it in the next 5 years or we are going to do it over the next 20 years ok. Whatever it is we got to have some plan for it and some target that each of the cities with a million plus people which are not in compliance with air quality standards we have to committedly take action to make sure that these cities come under compliance ok. So the Central Pollution Control Board is already doing the work the instructions for example have already come to Maharashtra Pollution Control Board where 10 cities have been identified to do the studies for the major sources and how best to control them. So this is like this activity or this mission is at a national level and the work is in progress and my invitation to you is to look to see which of you know these cities which might be closest to you or you may be in one of these cities in what way you can participate and in what way you can contribute to this overall mission ok. So I want to move from a level of philosophical aspects of should we can we know of course we need to there is no issue about it people's health is at stake ok. We need to impact that the question is for us to discover what would your and my role be ok and you and I being in educational institutes we have a role to play. If this issue is going to require 20 years time frame then you and I are not going to be dealing with it 10 years from now or 15 years from now. So we need to be training the next level of the next generation of students next generation of professionals that's what our focus is over here ok. So I'd again like to bring it back to the question of in the air pollution module if there are things that are not clear for you would you please ask some questions. Ok please go ahead. We talk about catalytic converter. Yes. But catalytic converter is not properly used in our country I think because we have lot of automobile emissions. Yes. That should be prevented so catalytic converter should be introduced in the full level but that is not done yet. We talk about it but we don't implement it. Ok all right very good so that's a you know good thought to spend some time with and I don't have an answer to that right now. So we will you know stay engaged I will send some information on catalytic converters and what are the you know manufacturers expected to do about it. Ok you may also want to go up and google some of this for yourself ok. Is there any separate mechanism or instrument which we can use to measure the concentration of particulate matter in tech mode. Yes yes it's done routinely it's in fact one of the US EPA methods. So you should just go put the same words that you told me if you put them up in google you'll actually find the method. Thank you sir. Ok yeah so I'm you know I just want you to know that a lot of questions that you ask are questions that even I have ok and what I typically do is I'll just go punch in these keywords on google and up comes the answer you know typically more than what I'm actually looking for you know a lot of times I think I have a great idea and then I go to the google and find out that it's not such a great idea which has been tested and tried out many times before I you know conceived of it. So good so yes there are methods the answer to your question is yes there are methods available for that. Ok I'll move on to so thank you Netaji Subash I'm moving on to the next location now. Ok Warchand Institute of Technology Sholapur how are you good morning morning excellent all right anybody got a question anything that is not resolved yet. I want to have some output of this program so so many pollution are taking place throughout the world also in our local cities air pollution is there water pollution is there spoil pollution is there. So what what preventive measures that has to be mandatory for the government to pass the bill so that all these pollution can be eradicated in the very next few years thank you. Ok very good so I just want you to know that a lot of times this whole subject of pollution gets very emotional ok we wanted to get be solved you know yesterday all right so sometimes people have even said that the developing countries do not have to go through the same mistakes that the developed countries have gone ok so there isn't like a magic wand so to say which I can just wave and say everything will be fine work needs to be done and there are plans in place there are laws for sure in place. I don't know your answer is as good as mine or my answer is as good as yours in terms of can this be done or should this be done of course it can be done should it be done of course it should be done the question is what is it that you and I are going to take on as our roles so that this can be fulfilled and again coming back to the context of this particular course this particular training is that you and I need to be partners in training the next generation of professionals ok. So, any more specific questions about air pollution please go ahead sir we have learnt about watershed but what is an air shed good so what is a watershed watershed is where we can store the water so that it can be used for the further users when it rains we can use that and store it and for the the barren land can be used for the watershed. Excellent so the same thing we do for air also you throw the air throw the bad air wherever we want you take any air and put it in that shed as long as it is of influence to you and me that's an air shed okay some kind of a some kind of an artificial boundary that you would create to say okay this is the volume of air that is going to be affected by the pollutants this is the volume of air that is going to impact a particular population this is the volume of air which can be ventilated in a certain time frame okay so the same abstraction wise it is the same as watershed it's just that the kind of boundaries that would one would expect on a land water kind of an interface you don't have that kind of a boundary in air okay but it's just you know if you if you were to take your city and you put a hemisphere on top of it okay and say okay this is my air shed and sometimes you can expand it vertically horizontally sometimes you have to expand it vertically depending on the terrain etc but that's an air shed you're looking at a particular volume what's going to be the quality of air in that volume okay so that's an air shed okay so I am going to now expect that you will know what is air pollution if not then the two weeks that we have after the pollution after this training is over that you will do the work for this okay what are the sources of air pollution what is typical ambient particle size distribution you know this now the three modes what are the meteorological factors which affect air quality of a region you know that now how is air quality managed in an air shed we'll talk a little more about this what are the ways to control industrial this is what we're going to talk about today okay so let me move on now so the learning objective for today is that you will know how to explain the principles and methods for the control of particulate as well as gaseous air pollutants okay this is much of chemical engineering so if you have background in chemical engineering or if in your college you have a department of chemical engineering then maybe a good idea to kind of open that conversation with that department and see what resources might be available locally for you okay so this is a summary okay I'll describe this but this is a summary at the end of the lecture these are the things that these are the different aspects that we need to know for particulate matter for particulate matter there are four or five different ways of controlling the emissions one is if the particle is large enough that it will settle by gravitation you have settling chambers all you have is basically a chamber in which you introduce the dirty gas provide enough time for these particles to settle out and then the clean air goes out straightforward not much design other than the gravitational settling rate and the time that is required for it to settle out when particles get smaller it gets difficult to settle so therefore you use something like a cyclone everybody knows what a cyclone is from a weather perspective but from a air pollution control perspective or a chemical engineering perspective it's basically I'll talk about that it's a cylinder in which you introduce the the dirty gas tangentially and the particles are thrown out by inertia because of centrifugal force scrubbers you actually make contact with water we'll talk about that electrostatic precipitators where you actually charge the particles and remove them in an electrical field filters where you actually use a fabric filter to be able to remove particle so those are for particulate matter and then for gases you basically use the fact that some gases have an affinity or have solubility in water and therefore it can be absorbed some places especially for organics which have an affinity for carbon you can do adsorption sometimes you burn these hydrocarbons and sometimes you use membrane separation so we will talk about each one of these a little bit okay so for air pollution control for particulate matter if the particles are large in size you could use settling chambers if they are greater than about 25 micrometers then you may have to use some kind of a cyclone and so on so I'll just move on okay so gravitational settling is like settling of dust okay if you go out on the road and you pick up particles from the dust from the soil and you throw them into the air you'll actually see a lot of particles stay in the atmosphere stay in the air as a cloud but a large number of them settle out okay so if the particles are large they will settle out smaller particles tend to remain in the air for much longer time so they're typically good for particles which are greater than 100 micrometers which is about the diameter of your hair okay but that size particle settle out quickly the settling rate the settling rate under normal conditions atmospheric conditions temperature conditions for 100 micrometers is about 25 centimeters a second for 10 micrometers it is 0.3 which is 3 millimeters a second and for 1 micrometers it is really small so one of the things I do in the classes I on the board I'd make three three different parts I put a 100 micrometer particle one circle I put a 1 micrometer particle somewhere in the middle of the board and I put a one sorry a 10 micrometer and a 1 micrometer towards the end and I say okay after every 15 minutes we will monitor where this particular particle has reached vertically okay and for you know the larger particle it tends to fall very quickly so even before 15 minutes it would have settled out of the room but one micrometer particle even by the end of the class has hardly moved a few centimeters okay that gives them a sense of that smaller particles tend to remain in the atmosphere for a longer time larger particles settle out so if you have a very dusty gas stream then it's a good idea especially like if you're dealing with solid handling like coal or cement or someone you have large particles which can actually be settled out by using a settling chamber now these are up you know for example cement or coal this is actual you know it's not waste it's actually money you know so you can recover the cement or if you can recover the coal then it can be used so gravitational settlers is a first step in controlling particulate matter and that's really because you're letting gravity do the work it's they're usually the some of the cheapest equipment okay now continuing with mechanical if the particle now is of the order of 25 micrometer or lesser the settling rate you would require huge chambers to settle out the particles so it's not very feasible from an engineering perspective so instead what they do is they would introduce this gas stream tangentially tangentially into a cylinder so these particles get introduced by then tangentially and they keep start moving in a circular in a helical form so the particles which are have certain inertia the elephants will get thrown outwards radially and get hit against the wall and tend to impact and stay there whereas the gas is slowly getting cleaned and then the clean gas goes through a down runner which looks something like this okay so this goes round and round and round and each round as it takes it is throwing out some of the larger particles and then this tube over here this pipe over here it basically the exit is from here so what you get from get out from here is particles which are of the order of 25 micrometers or so which have been removed okay so this is called a cyclone again more details are available at this website these images by the way and the urls are now free to be used they are they have copyright clearances etc so you're more than welcome to use these slides this is again if you wanted to get a sense of the scales how big a cyclone would look like this is a typical industrial scale cyclone okay that's how big it looks okay I don't know if there is a human scale over here but this seems to be a truck okay this over here is a truck so you know the scale now so this is at least six to seven times the height of a truck okay let's take a look at the next mechanism which is filtration okay filtration and most of us are familiar with filtration okay how we are familiar with filtration is because I don't know if I have a handkerchief oh yes I do have a handkerchief okay so typically on a dusty road or something like that you would tend to basically do this okay this is what you would use to protect yourself from breathing in a dusty environment right so what happens in this handkerchief is actually filtration most of the times you would have probably seen by the way it's not sieving the method is not sieving let me just tell you how it is not sieving so I went to this industry one time to as a part of a training course and they deal with powders as a product some polymeric powders etc so I asked them I said how do you protect yourself so they said we have masks which we use so I said okay are there any good how do you know whether those masks are good they say yeah they're not really good but what we do is we actually take the mask and we put it in water okay we wet it and then we wear it and then it is more effective so for me it was like a little unclear as to how dipping a filter in water would make it more effective so I told them I said why don't you next for the next class why don't you bring two masks one of them we will take and keep it as is and the other one we will dip in water and then see what happens to it so they brought the next day and what we did was we took the filter took the mask these are this normal masks that you'd get in the market put the mask it has a little plastic sorry an aluminum or clip or a clamp kind of a thing you can kind of squeeze it so that it fits on your nose so I took one of these the dry ones and we said okay let's take a look at the light over there let's look to see if we can see the light through there and you could see some kind of a glow but you couldn't really see the light okay then we took the other one and we made it wet and removed all the water from it so it was still wet but no water dripping from it so we took this mask and we put it against the light and you could actually through the holes see the light that goes that you know through the through the wet filter so I said which one now you think is better at filtration okay so the perception that we have that a wet cloth or a wet filter might be better filter is not necessarily true because the way the filtration takes place in a fabric material like this is not through sieving okay these are fabric fibrous material which are crisscross like that okay these are fibrous things and as a particle is going through and as and as ants are going through so you got ants going through and you got elephants going through okay ants have to be able to pass through so ants are small okay they'll find this way that way this way that way and they'll be able to go through but the elephant has to find its you know way through these narrow spaces etc etc and invariably cannot make it through the jungle okay cannot make it through the jungle of fibers etc etc so somewhere it gets stuck okay that's the nature of the fibrous filtration now what happens when you wet it when you wet it some of these fibers along they just line up with the main thread and therefore the fibrous surface that was available through which the elephant would have to go through are not available anymore and there's clear passage for the elephants to go through okay so if you wet it it is not as fibrous it's not as the jungle is not as thick as it would be if it was dry and when it is dry then it is possible for it to be able to filter out better now let me just caution a little bit a wet handkerchief is good a wet handkerchief or a wet filter would be good provided there is a gas which has affinity for water okay so if there was ammonia somewhere and I took a handkerchief and I wet it and I made two or three layers of it and I put it against my mouth okay then the air that I'm breathing through would have a chance to contact with the water and maybe get absorbed okay so then what comes through is because it's better because the water in the fibers came in contact with the gas and the gas had affinity for this water and therefore got absorbed and therefore didn't go into your nose okay so you want to be able to keep the two separate we want to deal with elephants and we do you want to deal with ants okay ants you want to take away because they have affinity because they will dissolve in water elephants you have to take care of by putting a big huge jungle in front of them so that they cannot penetrate through okay all right so here are some examples this is typically what a clean filter clean fabric filter would look like and these are different gradations of usage after 15 minutes half an hour 45 minutes one hour and this up to maybe about six hours okay this is as bad as it gets the dirty this is the black particles over here are particles that got collected as a word by virtue of the filtration okay um this is the filter that I talked about this is the one which if you were to take and put it on your mouth it has a little elastic strap on it okay and it has this aluminium clamp which you could clamp on but you got to be careful with this fit okay you got to be careful with this fit because even the smallest hole that might be around it will allow for easier access for your for the air that you're breathing okay so the greater resistance would be through this filter so the air would tend to sneak in somewhere so a lot of times when these masks are being used um you know if you're not careful about the ceiling on the mouth the nose and the mouth area then sometimes it's just psychological satisfaction that you're using a mask but they may actually not be effective you actually have to make sure that the fit is proper in fact most of the time in the industry when they're using some very elaborate filter elaborate masks this is again distinct what we're talking about is ambient air quality what people are dealing with in the industry is occupational and safety issues so if a worker has to go into an industry into a process area industrial plant where they actually have to deal with some emissions of ammonia for example then they actually have to have a full mask full face mask not just the nose and mouth mask full face mask which basically covers the eyes also and they actually have different types of masks depending on which one would fit your face structure better you actually have to pick up go for a testing to see which of the which of these particular filter which of these particular mask types fit you better okay and because it's a matter of life and death over there okay so you have you can't you know mess around with that so people actually do that testing and then once that mask is fit you have different kind of cartridges that can be replacing depending on what kind of pollutant you're dealing with if you're dealing with ammonia then you'll have a particular kind of cartridge if you're dealing with sulphur dioxide another kind if you have some hydrocarbons then another kind so depending on which particular gas you're dealing with you'd have different kind of cartridges here's another example again from google images notice that this is again a mask full face mask it has an elastic band here and this these cartridges over here the pink ones they're replaceable okay you can remove them and this typically is a place where the air would come out so you breathe in through here and you breathe out from there and there's a little diaphragm disc which opens and closes depending on which way the pressure is a lot of times the problem comes in you have to breathe through this filter which means that you really have to it's almost like saying that if I give you a Pepsi a bottle of Pepsi and I give you a straw okay if I give you a normal sized straw you'll be able to drink easily but if I give you a very thin straw then you know you really have to suck very hard for the Pepsi to come into your mouth so same thing over here if you put too much filtration around your mouth it gets difficult to breathe okay the diaphragm would have to exercise extra effort to provide that vacuum for that air to come through so that is one of the restrictions a lot of times when masks are being used and there has been some talks about how to force through these filters etc etc but that's you know gets into design of some of these masks etc okay this is a filter which I'm sure a lot of you would have been would be familiar with it's used for air intake into an engine into a car engine and every time you know every six months every one year when you go to get your car serve for maintenance and servicing invariably there's a charge on your bill that says air filter and they you come back home and you open the trunk and you find that there's actually in a plastic bag they actually have one of these filters which are sitting over there so you know we sometimes look to see whether we can this is like six months or a year of being on the road okay or so many kilometers of being on the road so it's you know you could actually take a part of this the black stuff that you see over there and do some chemistry on it to see what kind of contaminants are you know on the on the roads in traffic and in the highways okay but this is again another typical filter notice these ribs inside okay notice these ribs that really is so that in a much in a very small volume you can have a large surface area okay so if you have a large surface area the pressure drop across the filtration unit becomes lesser okay so that's one way of dealing with the pressure drop industrially okay so these were you know this was something that you and I use as personal protection this is something which is used in cars but industrially what do they do in the industry okay what they do in the industry is they have bag houses okay they have bag houses and what a typical bag house looks like I apologize for this resolution over here but that's the best I could find so you basically would have a cylindrical chamber in which you have these bags hanging they're just bags that are hanging they look like socks okay they made out of fabric material like cloth material it's not just regular cloth it is special cloth sometimes it is polymeric in nature a lot of times it is designed so that it can take certain temperatures okay very high temperatures would burn this so you don't want very high temperatures but at the same time you know if the the gas is coming at let's say 60 degrees 70 degrees celsius then at least it should be able to take that temperature sometimes even higher sometimes they try and keep it above 100 degrees celsius so that you don't have any water condensation okay so depending on what is your application you could have different kinds of materials for these bag houses and the way it works is that the dirty air would come in over here and this surface over here is now a filtration surface so the air the ants okay would penetrate through the filter whereas the elephants would get stopped outside in the material and so you will get clean air to come out from here okay so dirty air in clean air comes out filters bag filters are also in some sense used as they're expensive they're expensive difficult to maintain after some time when these bag bags get choked up they need to be cleaned so there are you know it's fairly sophisticated the the mechanism the actual operations and the maintenance some of those issues are quite sophisticated but it's a good device because it actually can remove particles of very small sizes okay so you can go up to 0.1 or smaller micrometer size particles very efficiently one of the assignments I give in the class is for students to be able to estimate what would be the efficiency of a mask or how would they select a certain filter material to be used in a bag house okay so they then would generate a test aerosol or take smoke or take dust in the air and look to see what is the before particle size distribution or the mask size distribution and what is the size distribution or total mass out after the filter so those are some of the things that we can get students excited about in the lab work okay so those were methods of being able to remove these particles mechanically okay so we looked at gravitational settling we looked at cyclones where you increase use the inertia of the particle to remove it and then we use filtration in the in the form of a fabric or fibrous material through which particles go through and they're not seething one more time to emphasize they actually are tortuous parts through which ants and elephants have to go through ants can make their way through elephants can't make their way through there's another way of dealing with removing of these particles it's called a scrubber okay so here what you do is you actually make it contact with the water spray so you have a chamber in which gas is introduced at the bottom and from the top you have these little sprinklers or sprays like you would see in a shower this let's just imagine like you know you're in a shower but the size of the droplets is much smaller than what you would experience in a shower okay so these are sprays which are spray nozzles which are put on top in this spray the entire cross sectional area of that cylinder so as these droplets are coming down the gas is going up the gas will have can have gaseous pollutants as well as particulate pollutants so as these particles are going up they're small enough to be carried up by the gas these droplets larger droplets are coming down at some point in time these particles would come on come in contact with this larger droplet and therefore get caught captured okay to in some way be taken up in that volume of the droplet so then these particles though these droplets would basically take carry this particle and come down and join the water stream so in some sense you have washed in some sense you have removed the particles from the gas stream by which you're washing the air okay washing the gas stream another advantage in these scrubbers is that you can actually use this scrubbing also to remove some soluble gases okay so when this droplet is coming down it is also being passed by ants and some of the ants may have affinity for water so for example if ammonia was there or sulfur dioxide was there it would have affinity for the water and by virtue of solubility it will basically get absorbed okay so that's the advantage now again a lot of chemical engineering in there the size of the droplet the flow rate what should be the flow rate of the gas such that the water droplet doesn't get carried away by the by the gas stream you know so those are some of the things that would go into the understanding and the design of a scrubber nature is a natural scrubber when it comes down to monsoon times and I don't know about other parts of India but yesterday we had the first shower and I don't know how things are going on in Kerala apparently the rain usually comes there 10 days before so once you get your good showers and I see you guys coming with umbrellas into the classroom I will know that showers have started over there then I can get my umbrellas out okay but umbrellas you know keeping umbrellas aside now let's just take a look at the rain let's get wet in the rain okay so just yesterday is one maybe probably half an hour one hour of shower and suddenly you know the air today the the the sky looks absolutely brilliant blue okay and the trees are looking fresher and the air is you know smelling you know like fresh air you know Mumbai that is rare okay so what does rain do rain will actually scrub the gas mass which is it come which it is coming in contact with okay so that's one part of what the what did I say washed washed ever what is this I should be scrub out whatever right is in there I said washed so that I was trying to right wash or whatever whatever okay it is whatever is in the air so scrub out whatever is in the air okay and the second thing that happens especially in a country like ours see one of the one of the results that keep emerge keeps emerging from all the studies that we do is that re suspended dust is a big problem okay in India re suspended dust is a big problem whether it is by winds or whether it is by traffic movement you know the lot of times anytime a truck passes by I think we've talked about this a little earlier too every of my truck passes by the smoke that comes out of the exhaust is not as much as the amount of dust that it raises you know it's just like a storm had come over something like that you know so the dust in the in the atmosphere the dust in air in India a lot of times is an issue and it contributes greatly to the overall mass of the particulate matter in even to the PM 10 measures so when it rains this dust actually becomes wet and then even if a truck is passing by you may have to be careful that the spray doesn't come on to your white clothes and dirties your clothes etc but not these droplets or the kitchen or the mud wet mud basically will not stay suspended long enough in the air it actually settles out they even have these mud guards and stuff like that which prevents everybody know mud guard right on a bicycle or on a car or on a truck they have these mad mud guards and sometimes where right under the stop sign they have a little rubber hanging you know flap over there which actually is an impactor okay for some of you who you know you want to see an impactor in real life that's an impactor if somebody has ridden a bicycle sometime and you thought you might be able to go in rain without the mud guard no no no that mud guard has a huge function if you don't have the mud guard and you're riding in during rain you know that the spinning wheel okay it actually picks up that little mud slurry and it has the aims right at the back of your shirt okay so you get all these droplets on your shirt so coming back to it in terms of the air pollution because the dust has now been wetted it does not get resuspended so if I get a chance I'll you know show send you the slides we actually did some studies in Chandrapur where on one day it was dry we took the size distribution and the second day it had rained we did the size distribution again and the larger mode there are multiple there were two modes one was a smaller size mode and the one was larger size mode the larger mode completely disappeared because all the particles that would have been suspended could not be suspended because it had rained okay so rain does rain is a natural scrubber okay there is another example of equipment that is used for wet scrubbing if you don't want to have just a cylinder with a spray you actually have a venturi scrubber in which the gas stream is blocked to a narrower section and then basically expand it again and in the narrowest section you introduce the water spray so the contact is highest okay so it increases the efficiency of contact and therefore the removal of particulate matter or gases venturi is a subject by itself you know chemical engineers mechanical engineers deal with all the time I won't get into the detail but that's another way of taking so you take dirty air and you pass it through a venturi scrubber and then you put it through another cylinder which is called the demister because a lot of these droplets themselves can get carried over by the air so it's not a problem if you introduce you take away the water droplets it's just that you would waste a lot of water so this water droplets settles out in the demister and you continue to use the same water okay all right so coming back to a review we've dealt with gravity we've dealt with inertia dealt with diffusion I think I should add over here the scrubbers okay but scrubber is really contact with water so scrubbers and then let's take a look at electrical okay these again sizes wise if you really look at it this is good for 20 to 100 micrometers greater than 25 20 in fact it was too small over here okay particle will take a long time to settle so anything which is greater than 25 qualifies in the range of 25 quality that qualifies it for a cyclone a higher investment a little bit of more energy investment in terms of the the pressure drop and therefore you need to drive this through the cyclone okay so some pumping costs are there a diffusion filter again we discussed so this is good for up to 0.1 micrometers good 99.9 percent removal you can get provided you're using it properly okay if there's a slight leak then the a gas stream will not go through the filter it will find a path of least resistance and therefore just bypass the filter not a sign that's an issue with baghouse filters so anytime there's a baghouse there's a leak in the baghouse they have to have a second baghouse standing so that they can immediately switch over the operation to the next one while they repair the previous one for routine maintenance as well as some accidents like that okay the next thing is electrical as we had discussed in the previous class also electrical mobility when you take a particle and you charge it and you put it in an electric field then there is electrical mobility okay particles tend to move in and like charge particles will move in an electrical field so especially small particles which are not amenable to inertial effects or gravitational effects and sometimes filtration may be not you know filtration can get expensive and it'll be you know the operations may be large enough that it actually can justify a larger capital investment in terms of electrostatic precipitators then they would use electrostatic precipitators so the principle of electrostatic precipitators very simple you basically take your particles you charge them and you pass them through a field where this pass through plates which have an electrical field which tend to attract these particles and therefore the particles will tend to come and deposit on these plates okay if you go out to the industry especially a power plant once in a while you will hear a sound which is it's like a knocking sound you know that electrostatic precipitators in play because from time to time these plates this you know will have a knocker basically it you know after every few minutes it'll basically knock on these plates so that all the particles that have that have deposited on the surface will fall down and get collected and the surface gets renewed so that more particles can get collected okay so that's electrical precipitator okay again the size of the electrostatic precipitators can be huge okay so one of the things that happens when you take students for a field visit is that from a conceptual diagram like this one which we're pretty familiar with from our books etc and you know from some of the work that they would have done even at class 11 or class 12 this everybody understands you know simple drawing to make but when it comes down to the scale you know that's the kind of size that you would have so these are two electrostatic precipitators one here another one here and this happens to be the chimney or the stack so this is probably the final for last polishing step to clean up the gas before it is let into the chimney okay so this is what it looks like so these are the steps these are the ladders so you can get a sense of this is you know a good two three stories high they are huge and a lot of times electrostatic precipitators especially in coal power plants they could be as well as much as 25 to 30 percent of the total capital investment so just that gives you a flavor of that gives you a sense of what kind of commitment is there in terms of air quality issues and you know that they cannot go ahead and implement any power plant install any power plant without having adequate measures and the kind of investments are of the order of 25 30 percent of the total investment for the power plant okay now what we deal with the ash or what we deal with these particles that are collected that's now a whole new whole different solid waste disposal issue still in a lot of people are dealing with using part of it as a part of cement building materials etc etc still remains a large issue and a lot of these when if they're left out in the open they're very small particles they're big white mountains and sometimes if you go to google earth and you just zoom in into some of these plants you will see these huge white piles that can be seen and they are typically the fly ash that is kind of the bottom ashes which have been collected over there a lot of times they make a pit with fill it with water so that these particles don't get entrained but disposal is still an issue that's a different issue we won't by the way the same thing holds for water okay when you scrub the gas with water the pollutants from the air go into the water phase and now you have to treat that water so the matter doesn't end with gas being cleaned now there is another two three steps of what are we going to do deal with how we're going to deal with wastewater how we're going to do deal with the solid waste that is now left over okay so let's just take a quick look at the hierarchy okay the hierarchy of particulate matter control you cannot subject a sophisticated control device like electrostatic precipitator or a bag house to large volumes of gas which have a lot of loading okay if there are large particles or if the loading is very high then you have to use some kind of a gravitational settler or some kind of a cyclone to be able to remove the bulk okay you can even use wet scrubbers to remove it so you have to remove you have to use the gravitation settlers or the cyclones to remove the bulk of the material and then as a final polishing step to be able to make sure that even the smallest particles are now removed because cyclones or settlers will not remove the smallest particles even the scrubbers may not be able to remove the smallest particles and remember we talked about this that smallest particles coming from some of the sources are likely to be more toxic are likely to actually be able to settle you know to actually deposit in your lungs so we have a concern about particulate matter which is in the pm 2.5 and smaller range so the final polishing step so to say would come from either filters which are low in terms of the capital investment capital cost investment but high in operational and maintenance okay so therefore you'd have to choose between filters or you'd have to use between electrostatic precipitators which are high in capital but low in the operational maintenance okay comparatively of course both of these are more much more sophisticated and much more cost intensive compared to these but as a final polishing step that is required and it needs to be done okay so that kind of says briefly about how we would deal with particulate matter or how do you deal with elephants okay now we're going to deal with ants how we're going to deal with ants so one thing we talked about a little bit when we were talking about scrubbers is that you can absorb if a particular gaseous pollutant has a certain solubility in water then you can remove it by bringing it contact with water okay again chemical engineering operation again I'd given this example of a handkerchief okay in case there is pollution in case there is some kind of a contaminant which might be soluble in water then a wet handkerchief on your nose would help okay adsorption I'm sure most of us have dealt with adsorption in class 11 and 12 as a part of physical chemistry where you would bring the gas in contact with the solid surface high surface area per unit mass activated carbon for example is one such material where organic vapor for example would have high affinity so you use it as a polishing step again it's also used in drinking water for example so after doing all the treatment that you need to do if you've added some if you want to add chlorine you would typically add chlorine after this step so that any natural organic matter that still might be in water you'd be able to adsorb onto the gravity onto the granular activated carbon and then so you use adsorption for that sometimes it gets difficult to give an example of but there are these if you go to google you'll actually say you know a portable point of views water filters okay you'd see these jars which actually have a cartridge inside and that cartridge you fill the water and then when you pour the water from the jug it actually goes through that cartridge filter but that cartridge filter actually has activated a pack of activated carbon and interestingly it also has a little indicator on top after a certain volume of water has been taken through there then you need to replace that cartridge okay so that's one example that I know anything else that one can think of sometimes they even suggest that in a in the refrigerator if the refrigerator is smelling that you put some charcoal you know in a small plate if you put charcoal fresh charcoal in the refrigerator then after sometime the smell in the refrigerator will go away because as a part of the circulation as it contacts with the charcoal charcoal tends to adsorb some of these smelly odor giving substances okay so that's adsorption incineration okay let me just go to incineration I hope I think I have some slides in incineration by the way this is the size of a scrubber a scrubber can be this size again these are some steps over here these are some steps over here so this is about at least three to four stories high okay that's the size of a scrubber a gas scrubber okay incinerators I'm sure you've seen these okay I'm sure you've seen these especially if you're passing by a refinery I remember you know anytime I would go by train towards Delhi near Vadodara there's a refinery and especially in the middle of the night it's a very nice site actually you see all these light shiny huge plant you see these night lights on but somewhere in one far end there'll also be this flare okay and invariably the question would come to me as to why are they wasting this gas why can't they just use it okay the it's an engineering decision that needs to be made that you cannot thermodynamically or from just from a process efficiency perspective this is what is left after taking away using the best available control technology what is it that you could remove you've already removed okay and this is something that you can't remove anymore and so you have to get rid of it you have to dispose it so instead of disposing it off just directly as a hydrocarbon going into the atmosphere probably the best thing to do is to burn it okay so this seems like a pretty clean flame ideally it should be blue flame like a Bunsen burner but this is not so bad if you see go again to Google and you look at incinerators or you look at flares or you look at refineries if you look at some of the images sometimes you'll actually see smoke which is just pitch black okay just black totally black I mean all you see is black you don't see any flame at all okay that's not good that's not good because our intention was not to convert that gas that hydrocarbon in now into suit okay that is not the intention at all but sometimes it happens especially if there is an accidental release then they have to get rid of the pollutants of the hydrocarbons through these incinerator flares at that point in time they have to supply extra air or extra oxygen so that there is sufficient mixing and sufficient combustion taking place so that the flame as far as possible is not visible okay if the flame is visible then there is still some pollution this one is causing some pollution it will leave some unburned hydrocarbons still okay so ideally there should be a blue almost transparent flame like in a Bunsen burner everybody I'm sure is familiar with Bunsen burner even if you know you can't take the students out for a field visit to a refinery or some other place where there's a flare everybody's familiar with the Bunsen burner all you need to do is light up the Bunsen burner with the LPG and if you close the holes which allow for this extra air to go in which gets mixed with the barrel just before the just after the nozzle and before the burn the place where the flame takes place if the mixing with the air has happened then the flame is not yellow anymore it's a bright blue transparent flame whereas if you close those vents then the air is mixing with the gas in that jet so that mixing is not adequate and therefore places where there is not enough air there'll be zones of incomplete combustion will show up as this yellow flame okay if it is a completely well mixed combustion flame then it you'd not see yellow you'd only see a blue flame same thing for a candle you see a candle and the light coming from a candle because it is incomplete combustion okay but that's there's another advantage of that that you actually have light coming from it so you can actually see it if a candle was burning very efficiently you wouldn't be able to use it as a candle okay all right so this is what an incinerator looks like in a flare sometimes they even have this on a trolley they'll have it on a truck and this is taken to a new site where they may be exploring oil for example oil drilling is going on all the time so if they hit gas some point in time a gas well then that gas cannot be let into the atmosphere it actually it actually has to be incinerated so then they would use this mobile incinerator to do that okay I got this is offshore these are platforms which are offshore oil well oil wells and again you know if you notice that a little far away from the actual platform where all the operations are going on there's a certain distance over here and this distance is kept such that they can flare off some of these gases notice these are not good combustion flares you could actually see the black smoke which is trailing okay so this is not a good example of incineration but it is still better than disposing of that oil into the into the into the ocean okay so and this is usually far away from populations so one is hoping that it will get dispersed by the winds in the ocean etc but still you know if you were ideally if you were to look at it's not a good thing but given the circumstance given the situation this is probably the best that they can do by the way typically they would have a flare on this side of the platform and they would also have a flare on the other side of the platform so in case the wind is in that direction then they would not use this flare they would use that floor flare okay so they actually have to make sure that the flare is such that the wind takes it away from the platform otherwise if the wind is in this direction the flame will start coming towards the process platform which is not such a good idea okay oh so I'm going to stop here for a little bit because I wanted to show you while surfing through Google I came across this exciting idea of how you can clean up the room in your the air in your room okay it's a fan and on top of the fan blade you can actually put this little device which by virtue of its own circulation because fan will circulate so this will circulate circulate with the fan and it can take away some of the pollutants sounds like an interesting project I think the dollar value is not very high it's I think only about three dollars so you know I don't know if some of you are interested in doing this experiment you can take a room and fill it up with agarbatti smoke and then use this to see whether you know some of the agarbatti smoke removes you can have two rooms one with the fan which has these another one which the with the fan which does not have these and you can compare the pollution in those two rooms so I think I saw this and I thought it will be quite exciting so I should maybe try it out as a part of the lab Harish what say we should try it out in this lab this year okay all right so then there are several such exciting ideas some of them are feasible some of them are not feasible so you really need to look to see you know maybe even have students explore whether from an engineering it's a good idea but from an engineering perspective is it feasible or not feasible okay so that is my last slide I'm going to stop here and take questions so big thank you and I'll come now to interact with some of the some of you but before we do that okay before we do that I'll give you a minute I'll give you a minute to stop pause for a moment take a piece of paper and write on it what is it that you can claim to have learnt from listening to this lecture today okay take a couple of minutes and write down what are the things that some of the things you may have already known fabulous great and some other things that you said oh okay I didn't know that before and you can actually claim now that now you know it okay so one of the I do not know has now been converted into now I now I know okay so please go ahead take two minutes to do the work in your so you could even do it in your notebook or if you need some paper I request the coordinators to please distribute the paper if needed if you have a notebook please go ahead and do it in your notebooks I'll be quiet for two minutes now okay I think I'm going to open it up for some questions now so Gandhi Institute for Technology where is this Bhuvaneshwar okay Gandhi Institute of Technology Bhuvaneshwar hello everybody welcome all right very good good to see you all right so with regard to air pollution control okay with regard to air pollution control one of you please tell me what is it what is a new thing that you learned today new thing about control of air pollution please be specific to the question what is the new thing you learned about air pollution control today today we could know the different processes that you have delivered different instruments by which we can use to for air pollution control that we could know and the mechanism also you could deliver properly we could learn all this okay excellent is there something that you did not know before but today after listening to the lecture you said oh that is a new thing I learned today particularly observation observation and that charcoal body you have delivered in refrigerator if you put some charcoal then the smell comes out of some part and another incineration that you so that part we couldn't know properly excellent so I have a feeling that you're going to go home tonight and try out this charcoal in your refrigerator yes sir okay very good all right thank you one more person from here interesting part for today's learning was like the teaching strategies for environmental legislation like the way you talk the things how to cover it up and like the how the students will get benefitting that was the great learning for me from the today from today's session okay excellent yeah very nicely said because you know this is really not like a regular class you know you already are teaching this course you're teaching these this course already and while I might present some material which might be new etc these materials are familiar to you and I think one of the one of the privileges that we have as teachers of this particular training course is that we get to share some of the experiments that we have been doing with teaching etc etc so yes you know thank you for acknowledging that and I appreciate it and yes you know please you know we will learn from each other and continue to be of service to our students okay so thank you very much for acknowledging that I appreciate that okay who else now I'm going to move to the next center thank you one two nine six where is this Nagole institute hello Nagole institute Hyderabad Hyderabad how are you yeah welcome okay good so tell me one new thing you learned today one person please tell me one new thing you learned today it was good to learn about these scrubbers which we have explained for controlling the air pollution about the scrubbers air scrubbers that was good to learn and the idea of letting off the handkerchief before you go into the place where it is a polluted it is a very good idea because in Hyderabad here there is a very really high pollution and the idea of yours it was very good and we'll definitely follow that yeah so I just want to caution you a little bit okay handkerchief is not necessarily very effective when you're going on the road okay so if you take it like this and you put it here like this okay there is enough space from here enough space from here enough space from here enough space from here okay air will bypass the so this is just a psychological relief psychological satisfaction that you might have that you're using this filter you know the people actually I'll maybe share that with you sometime people have actually developed a nose plug okay you can like air plugs you actually have a nose plug you can plug it into your nose and then breathe through it but the amount of effort it takes to breathe through that nose you know plug you you know your mouth automatically opens up it's almost like you have a cold and you know your nose got blocked so you stop smoke stop breathing from there and instead you start breathing from the mouth okay so there are issues unless you have a mask which is fitted to your face mask will not be effective it is effective to some extent but you got to be careful you cannot in a blanket statement say that all masks are effective okay that's one thing the other thing is if some of you are interested there has been this interest in developing a crash helmet see who gets exposed to the air the traffic pollution most are people on two wheelers scooters motorcycles these are people who get you know people on that they get exposed maximum okay and they are required to wear a helmet so can we actually bring filtered air into the helmet so that they not just have protection of the skull but also have protection so that's an idea that we've been floating around for a while I'm just waiting to see somebody might snap at it and you know go do some work and if you've come across some similar work that has been done I know please let me know so we can take it further okay so okay thank you very much one more person from Nagola Institute one more person please speak up one more person yeah good morning sir morning please tell me one new thing you learned today chemical industries were designed with an effluent pump yeah I mean actually the clarification regarding the pollution I observed some in the chemical industries in the outside so I mean designed the effluent pumps yes but really helpful in avoiding the pollution in the air that is a pollution effluent plant I mean is it really helpful in the yeah if the chemical effluent pumps yes yes so industrial waste that yeah that comes in the domain see two things can happen okay you can have a wastewater stream which needs to be treated okay so that's a wastewater stream which could be coming from many places in the process but then there could be a waste stream which is coming from a scrubber okay so this way this water was used to remove pollutants from the gas stream it picked up the soluble gases it picked up the particulate matter and now it is coming to a pond where primary settling might take place before it gets treated further so that effluent pond or the effluent treatment for a liquid stream is now going from the gas stream cleaning up to the now the wastewater stream okay so that's a different game which Harish will be talking about to some extent in his modules okay all right next next center please one two one zero belgium gogte institute hello gogte how are you hi everybody all right this is a big class I like it look at the back also raising hands that excellent okay good so please tell me one thing that you learned today yes I'll just hand it over to one of my participants okay please settlement of dust particles and effect of rain on air pollution you will learn about it excellent excellent so you know I mean this comes from nature right you actually have spray which is coming from the clouds that can actually clean up the gas okay so thank you yeah very good excellent all right we move on to the next center now one two nine four Gitanjali Institute hello everybody hello all right very good good afternoon sir excellent so tell me one new thing you learned today sorry industrial exhaust gases can be removed by using air house bags and cyclones also electrostatic precipitators which principle is involved working off these devices that's the my question sir which principle generally which type of which principle is involved for the purification of exhausted gases that's my question sir exhaust gas from where which principles are which principle is based these devices are working so every source will have different composition of exhaust so which exhaust are you talking about with source adsorption or adsorption process or just suppose if neutral particles are present in a industrial exhaust it does how to remove the by using electrostatic precipitators yeah I'll try and answer your question to the degree that I've understood okay so you should know that each industry would have a different exhaust composition so for example what's coming from a cement plant what's coming from a coal based power plant what's coming from a refinery each one of them would be different so if you have to remove particles which have come from coal combustion in a power plant then you need to know the composition of the gases and the particulate matter coming from the burning in the combustion zone so when you know what's coming out accordingly you can either put cyclones you can put scrubbers you can put electrostatic precipitators okay so the choice of the equipment has a lot to do with what is the composition of the gases what is the size distribution what is the temperature of the gases that are coming out okay so those are some of the design parameters that are given to the chemical engineers to say look this is the typical range of concentrations of these particular pollutants that are going to be coming in this exhaust and we need to be cleaning it to this particular level because our state pollution control board tells us that we cannot allow pollutants beyond this level so between what's coming in and what needs to be released I have to do my job with the control devices okay so that's a long answer to your short question but the answer has to be very specific to the particular source to the particular industry that you're dealing with okay so fabulous question thank you very much we will keep participating all right so it's 12 30 time for lunch thank you very much Gitanjali institute thank you very much bye bye bye bye Gitanjali bye bye okay all right and bye bye to everybody else of the 151 centers I will see you tomorrow but you'll have a lecture this afternoon starting at 1 30 okay go have a great lunch I'll catch you bye bye