WEBVTT - How Clean Coal Works 0:00:04.120 --> 0:00:07.160 Get in touch with technology with tech Stuff from how 0:00:07.200 --> 0:00:13.680 stuff Works dot Com. Hey there, and welcome to tech Stuff. 0:00:13.720 --> 0:00:16.880 I'm your host, Jonathan Strickland. I'm an executive producer with 0:00:17.120 --> 0:00:19.800 how Stuff Works in my Heart radio, and I love 0:00:19.960 --> 0:00:23.799 all things tech. So today I want to take a 0:00:23.800 --> 0:00:27.880 look at proposals for clean coal power plants and what 0:00:28.000 --> 0:00:32.000 that actually means. And before I jump into that topic, 0:00:32.159 --> 0:00:34.720 I do want to get this out of the way 0:00:35.000 --> 0:00:39.199 because I want to be as honest and forthright as 0:00:39.200 --> 0:00:43.519 I possibly can be. I'm in favor of renewable energy sources. 0:00:44.320 --> 0:00:47.680 I'm also in favor of pursuing research into nuclear fusion 0:00:47.880 --> 0:00:50.760 as a power source, if in fact that is possible 0:00:50.760 --> 0:00:54.520 to make a sustainable, effective power source. I'm very much 0:00:54.560 --> 0:01:01.080 in favor of getting off of all fossil fuels, particularly coal. However, 0:01:01.680 --> 0:01:06.080 I will do my best to discuss this topic without bias, 0:01:06.120 --> 0:01:10.640 in other words, without just constantly spitting on coal. And 0:01:10.760 --> 0:01:13.440 even an advocate for clean energy like me has to 0:01:13.480 --> 0:01:18.640 admit there are enormous challenges in the way of weaning 0:01:18.680 --> 0:01:21.920 ourselves off of coal and other fossil fuels as an 0:01:22.000 --> 0:01:24.760 energy source. There are big things we have to be 0:01:24.800 --> 0:01:27.600 able to make work for that to happen. So we're 0:01:27.640 --> 0:01:30.240 gonna talk about those two because it's important to look 0:01:30.240 --> 0:01:33.560 at these problems from a big picture perspective and to 0:01:33.640 --> 0:01:36.959 not just ignore the very real hurdles that are in 0:01:37.000 --> 0:01:40.080 our way, because if we do, if we ignore those hurdles, 0:01:40.440 --> 0:01:43.080 then we set ourselves up for failure when we try 0:01:43.160 --> 0:01:46.880 to change things. If we acknowledge the challenges, then maybe 0:01:46.959 --> 0:01:49.560 we can figure out a way of getting around them, 0:01:49.600 --> 0:01:54.400 over them, or through them. So what is coal. I've 0:01:54.440 --> 0:01:57.800 already mentioned that it's a fossil fuel, but what that 0:01:57.840 --> 0:02:01.040 really means is that originally comes from or gain nic material, 0:02:01.440 --> 0:02:06.040 most notably pete. Pete is a large source of a 0:02:06.080 --> 0:02:09.480 lot of the coal that we use today. So this 0:02:09.840 --> 0:02:15.680 organic material accumulates, it gets buried over times of animals die, 0:02:15.760 --> 0:02:20.960 plants die, they decompose, they get buried by sand and 0:02:21.120 --> 0:02:24.320 other stuff, and centuries go by and more and more 0:02:24.400 --> 0:02:29.440 layers build up around this material, and the material then 0:02:29.520 --> 0:02:33.280 starts to compact under all that pressure, and the temperature 0:02:33.320 --> 0:02:39.760 grows because it's under pressure like the Wonderful Queen and 0:02:39.880 --> 0:02:43.480 uh David Boisong. And then as it has all of 0:02:43.560 --> 0:02:47.000 this pressure and heat, the material hardens into a rock 0:02:47.520 --> 0:02:50.440 like substance and it turns into coal. So to call 0:02:50.480 --> 0:02:53.720 it coal, it has to contain a significant amount of 0:02:53.960 --> 0:02:59.600 carbonaceous material by weight or volume. Carbonaceous just means that 0:02:59.720 --> 0:03:03.800 it has to contain carbon or carbon compounds. The amount 0:03:03.840 --> 0:03:07.080 and type of carbon and coal determines how much energy 0:03:07.440 --> 0:03:11.320 the coal contains, and really, to us, what that mostly 0:03:11.360 --> 0:03:14.760 means is how much heat the coal is capable of 0:03:14.800 --> 0:03:19.600 producing when it is burned when it's combusted in a furnace. This, 0:03:19.680 --> 0:03:22.320 in turn is dependent upon a few things, including how 0:03:22.400 --> 0:03:24.680 much heat and pressure went into creating the coal in 0:03:24.720 --> 0:03:28.000 the first place. There are a lot of different ways 0:03:28.000 --> 0:03:31.840 of classifying coal, but there are four main ranks of coal. 0:03:32.400 --> 0:03:36.680 There's anthracite coal, and that has at least eight ton 0:03:37.920 --> 0:03:41.480 carbon in it. This coal has the highest heating value 0:03:41.600 --> 0:03:44.720 of coal, and there ain't a lot of it. It's 0:03:44.760 --> 0:03:48.080 not plentiful in the United States. Less than one percent 0:03:48.240 --> 0:03:52.240 of all the coal mind in the country ranks as anthracite. 0:03:52.760 --> 0:03:55.320 The one place in the United States where it is 0:03:55.440 --> 0:03:59.360 mined right now is Pennsylvania. This coal is used nearly 0:03:59.400 --> 0:04:03.680 exclusively by the metals industry. Coal blaze an important part 0:04:03.720 --> 0:04:07.600 in producing various types of metal and metallurgy. Then you 0:04:07.640 --> 0:04:13.560 have by tuminous coal. Bituminous coal contains between forty five 0:04:13.600 --> 0:04:17.400 to eighty six carbon, and this makes up nearly half 0:04:17.640 --> 0:04:20.919 of all the coal mind in the United States. Specifically, 0:04:20.920 --> 0:04:24.560 it's around for of all the coal we mine here 0:04:24.560 --> 0:04:28.520 in the US. This is the coal that's used primarily 0:04:28.680 --> 0:04:33.600 for coal burning power plants for generating electricity. It's also 0:04:33.760 --> 0:04:37.160 used in iron and steel industries. Five states in the 0:04:37.240 --> 0:04:40.640 United States produced nearly all of the coal for the 0:04:40.800 --> 0:04:46.279 entire country. Those five states are West Virginia, Pennsylvania, Kentucky, Illinois, 0:04:46.520 --> 0:04:51.599 and Indiana. Then you have sub bituminous coal that contains 0:04:51.640 --> 0:04:56.559 between thirty five carbon, so as less carbon. You'll notice 0:04:56.560 --> 0:04:58.920 in these ranks were going down by the amount of 0:04:58.960 --> 0:05:01.960 percentage of carbon the material. It also has a lower 0:05:02.000 --> 0:05:05.480 heating value. It doesn't burn as hot as bituminous coal. 0:05:05.839 --> 0:05:09.039 It makes up about for of all coal production in 0:05:09.040 --> 0:05:12.280 the US. So sub by tuminous and bituminous coal make 0:05:12.360 --> 0:05:16.080 up when you add it up. And remember the anthracite 0:05:16.120 --> 0:05:18.719 makes up less than one percent, so the rest of 0:05:18.760 --> 0:05:21.840 it is made up of lignite. As the last rank, 0:05:21.920 --> 0:05:26.279 it contains only twenty carbon. This stuff can convert into 0:05:26.360 --> 0:05:29.719 synthetic natural gas with some processing. We also call it 0:05:29.920 --> 0:05:33.840 sin gas s y n G A S, and i'll 0:05:33.880 --> 0:05:37.920 talk about that again a little bit later in this episode. Now, 0:05:38.000 --> 0:05:41.279 human beings have been using coal for at least three 0:05:41.320 --> 0:05:45.920 thousand years, though many early references to coal actually are 0:05:45.960 --> 0:05:50.000 referring to charcoal, not to the stuff we mine out 0:05:50.000 --> 0:05:53.000 of the ground. Charcoal is not the same thing as coal. 0:05:53.600 --> 0:05:57.040 Charcoal is what you get when you remove water and 0:05:57.080 --> 0:06:00.919 several compounds from wood, and typically you do this in 0:06:00.960 --> 0:06:03.920 a low oxygen environment, and you would apply a lot 0:06:03.960 --> 0:06:06.920 of heat to the wood. So if it were a 0:06:07.000 --> 0:06:09.919 high oxygen environment, the wood would catch fire and burn, 0:06:10.279 --> 0:06:13.800 but because it's low oxygen, that reaction can't happen. We 0:06:13.880 --> 0:06:16.679 remember the triangle that you need in order to make fire. 0:06:17.200 --> 0:06:19.560 You have to have heat, and you have to have fuel, 0:06:19.880 --> 0:06:24.040 and you have to have an oxidizer, typically oxygen. So 0:06:24.480 --> 0:06:26.880 you're not you're you're you're heating up in a low 0:06:26.920 --> 0:06:30.960 oxygen environment, you're essentially cooking the wood. The technical term 0:06:31.000 --> 0:06:34.400 for this would be pyrolysis. So again you're not burning it, 0:06:34.520 --> 0:06:38.159 you're just removing moisture and heating up the wood in 0:06:38.200 --> 0:06:41.040 this low oxygen environment, and you end up with about 0:06:41.080 --> 0:06:43.320 a quarter of the mass that you started with, or 0:06:43.360 --> 0:06:47.840 a quarter by weight, So all those compounds in the 0:06:47.839 --> 0:06:50.440 water make up a lot of the weight, the majority 0:06:50.440 --> 0:06:52.680 of the weight of the wood, so you end up 0:06:52.680 --> 0:06:55.880 with something that's about the weight of whatever you started with. 0:06:57.200 --> 0:07:01.799 Now we've used coal, the mineral, the stuff we mine 0:07:02.320 --> 0:07:06.440 for a really long time, uh, But the widespread, large 0:07:06.480 --> 0:07:09.440 scale use of coal, the industrial use of coal, really 0:07:09.440 --> 0:07:12.440 didn't get going until the eighteenth century. That's when you 0:07:12.480 --> 0:07:17.120 had inventors like Abraham Darby who developed methods for using 0:07:17.160 --> 0:07:23.160 coal in blast furnaces. And the Industrial Revolution, which really 0:07:23.200 --> 0:07:25.920 began in England and then spread throughout the rest of 0:07:25.920 --> 0:07:29.880 the world, saw an enormous need for coal, and that 0:07:30.000 --> 0:07:33.720 pushed the mining industry from being sort of a modest effort. 0:07:34.280 --> 0:07:37.560 And there were mines that existed before the Industrial Revolution, 0:07:37.640 --> 0:07:42.240 but the need for coal was much more modest then, 0:07:42.360 --> 0:07:45.760 so they were very much surface minds. At this point, 0:07:45.880 --> 0:07:49.600 the need for coal was voracious, so mine started getting 0:07:49.680 --> 0:07:55.320 deeper and going further and requiring way more manpower to operate. 0:07:56.200 --> 0:08:00.480 It became an enormous enterprise, employing thousands of people, tens 0:08:00.520 --> 0:08:04.280 of thousands of people. Coal mining became a lucrative but 0:08:04.560 --> 0:08:10.480 dangerous business. Miners encountered deadly gases, some of them explosive, 0:08:10.680 --> 0:08:13.679 so if you were to create a spark while mining, 0:08:14.080 --> 0:08:17.520 you could ignite that explosive gas and have have a 0:08:17.640 --> 0:08:23.120 true catastrophe. Some gases are poisonous. Uh, there was always 0:08:23.120 --> 0:08:25.920 an issue with flooding. That was always a danger with 0:08:26.000 --> 0:08:29.200 mine chefts. There was also the possibility of mine chefts collapsing, 0:08:29.760 --> 0:08:32.920 but the demand for coal created enough of a reward 0:08:33.440 --> 0:08:36.120 to merit the risk, at least in the minds of 0:08:36.160 --> 0:08:38.959 the coal mine owners, if not the actual miners who 0:08:38.960 --> 0:08:42.000 were doing the work. Britain led the way in coal 0:08:42.040 --> 0:08:46.520 mining in this early time in the eighteenth century, and 0:08:46.600 --> 0:08:51.080 because it was plentiful, lower rank coal in England, not 0:08:51.200 --> 0:08:53.880 the stuff that we would use today to generate electricity, 0:08:54.000 --> 0:08:57.480 would frequently be used as a fuel to warm homes 0:08:57.880 --> 0:09:00.400 in coal furnaces. So you have a furnace, throw some 0:09:00.440 --> 0:09:03.560 coal in there and that was what would generate heat. 0:09:03.960 --> 0:09:06.920 That created a lot of air pollution in England. London, 0:09:07.160 --> 0:09:10.960 which had a reputation for heavy fogs, was frequently blanketed 0:09:11.200 --> 0:09:15.320 in smog, and smog, of course, is made up of 0:09:15.960 --> 0:09:20.959 particulate matter that comes out of burning fossil fuels, particularly coal. 0:09:21.640 --> 0:09:25.440 This peaked in nineteen fifty two with the Great Smog 0:09:25.600 --> 0:09:29.200 of London, which produced a smog so thick and so 0:09:29.320 --> 0:09:33.480 persistent it reduced visibility drastically to just a few meters, 0:09:34.120 --> 0:09:38.160 and it had an enormously negative impact on citizen health. 0:09:38.280 --> 0:09:42.280 People started developing really terrible respiratory illnesses as a result. 0:09:42.800 --> 0:09:47.720 So what does burning coal produce, apart from heat that 0:09:47.800 --> 0:09:50.840 we can use in applications like boiling water into steam 0:09:50.920 --> 0:09:54.560 to turn a turbine and generate electricity. Well, the burning 0:09:54.600 --> 0:09:58.720 process breaks the chemical bonds between the atoms and coal. 0:09:59.120 --> 0:10:02.480 Those molecular bonds get broken and that's what releases energy 0:10:03.000 --> 0:10:07.400 and also several potential pollutants, including contaminants that could be 0:10:07.440 --> 0:10:11.600 part of the coal. That can include stuff like mercury, 0:10:11.640 --> 0:10:15.120 which is a toxic heavy metal. Mercury is dangerous stuff. 0:10:15.160 --> 0:10:18.160 It can damage health in numerous ways. It can cause 0:10:18.240 --> 0:10:22.679 damage to the nervous system, the digestive system, the immune system. 0:10:22.679 --> 0:10:26.360 In fourteen, US coal plants emitted more than forty five 0:10:26.559 --> 0:10:31.880 thousand pounds of mercury coal plants are responsible for of 0:10:32.080 --> 0:10:36.439 all mercury emissions in the United States, so that's a 0:10:36.480 --> 0:10:39.720 big one. Sulfur dioxide is another one that's an emission 0:10:39.760 --> 0:10:43.800 that's very dangerous. Coal frequently has sulfur in it, and 0:10:43.840 --> 0:10:47.240 when sulfur reacts with oxygen during the coal burning process, 0:10:47.280 --> 0:10:49.360 because again you need to have that oxygen to have 0:10:49.440 --> 0:10:53.960 combustion happen, you end up getting sulfur oxide, and that 0:10:54.040 --> 0:10:57.880 sulfur oxide can combine with other molecules. These emissions are 0:10:57.880 --> 0:11:04.200 harmful to us. Also, sulfur dioxide, once it has reacted fully, 0:11:04.480 --> 0:11:07.920 it's got a strong link to acid rain, so that's 0:11:08.120 --> 0:11:12.800 terrible also to smog and can be linked to problems 0:11:12.800 --> 0:11:16.200 like bronchitis and asthma. Then you also have nitrogen oxides. 0:11:16.520 --> 0:11:19.720 It's another byproduct that it can also contribute to smog, 0:11:20.240 --> 0:11:23.800 and it also can end up leading to the development 0:11:23.800 --> 0:11:28.080 of respiratory ailments or make existing respiratory ailments much much worse. 0:11:29.200 --> 0:11:31.240 These are just a sample of some of the pollutants 0:11:31.280 --> 0:11:34.880 that can come out of burning coal. You also get 0:11:34.920 --> 0:11:40.560 coal ash. Uh. These are also called coal combustion residuals 0:11:40.679 --> 0:11:44.600 or CCRs, and this is actually again a collection of stuff. 0:11:44.640 --> 0:11:48.160 It's not just one thing. Um. There's fly ash, which 0:11:48.200 --> 0:11:50.800 is mostly made of silica, which is powdery and very 0:11:50.880 --> 0:11:54.480 very fine. There's bottom ash, which is made up of large, 0:11:54.679 --> 0:11:58.120 coarse ash particles. These particles are too large for heat 0:11:58.160 --> 0:12:00.680 to carry them up the smoke stack of power plants, 0:12:00.920 --> 0:12:03.360 so they tend to gather at the bottom of furnaces. 0:12:04.000 --> 0:12:08.000 There are some types of furnaces that create molten ash, 0:12:08.240 --> 0:12:11.480 also called boiler slag, which has to be drained or 0:12:11.600 --> 0:12:15.880 drawn out of furnaces regularly using a tap, and typically 0:12:16.440 --> 0:12:19.880 you would cool this mixture with water and at that 0:12:19.920 --> 0:12:23.680 point the ash turns into glassy pellets. And then there's 0:12:23.720 --> 0:12:29.040 the flu gas desulfurization material, which is a byproduct produced 0:12:29.040 --> 0:12:33.280 by a sulfur dioxide emission reduction process. It's typically either 0:12:33.320 --> 0:12:36.120 a dry, powdered material or a wet sludge, depending upon 0:12:36.120 --> 0:12:39.480 the reduction method employed. I'll talk more about that in 0:12:39.559 --> 0:12:43.559 our next section. Now, coal ash also contains dangerous stuff 0:12:43.559 --> 0:12:47.360 in it, like lead, cadmium, arsenic, and mercury, and for 0:12:47.400 --> 0:12:50.320 that reason, regulatory agencies like the e p A, the 0:12:50.400 --> 0:12:55.040 environment Environmental Protection Agency, maintain pretty strict rules about how 0:12:55.080 --> 0:12:58.400 power plants may dispose of coal ash to prevent contaminants 0:12:58.400 --> 0:13:03.040 from polluting the environment. These regulations under more recent years 0:13:03.080 --> 0:13:11.240 have been scrutinized and somewhat cut back due to political 0:13:11.280 --> 0:13:14.040 maneuvers by people who are in the e p A 0:13:14.120 --> 0:13:19.720 who previously came from the coal and power utility industries. 0:13:20.320 --> 0:13:22.760 I'll talk more about that because one of the big 0:13:22.840 --> 0:13:25.720 challenges we have to look at isn't a technological challenge. 0:13:25.960 --> 0:13:29.280 It's not a scientific challenge, it's a political challenge. So 0:13:30.400 --> 0:13:33.280 burning coal releases a lot of energy that's useful, but 0:13:33.360 --> 0:13:36.120 it also produces stuff that's harmful to us and to 0:13:36.160 --> 0:13:42.200 the environment. And coal is plentiful and cheap, so it 0:13:42.240 --> 0:13:45.360 makes it a very attractive energy source. It definitely has 0:13:45.400 --> 0:13:50.280 its downsides. The pollutants are undeniably bad, but the fuel 0:13:50.320 --> 0:13:53.959 source is easy to get, and that's one of the 0:13:54.000 --> 0:13:57.040 big reasons why it's hard to wean ourselves off of 0:13:57.120 --> 0:14:02.880 coal that's cheap and other options are less cheap. So 0:14:03.240 --> 0:14:07.000 how do experts propose to mitigate the pollution problems? In 0:14:07.040 --> 0:14:09.160 the next section, we're going to take a look at 0:14:09.240 --> 0:14:12.280 what clean coal is and how it works and try 0:14:12.320 --> 0:14:16.000 to answer the question how clean is it really? But first, 0:14:16.080 --> 0:14:26.600 let's take a quick break to thank our sponsor. All right, 0:14:26.680 --> 0:14:28.680 let's get this out of the way first. Clean coal 0:14:28.840 --> 0:14:33.640 refers to processes and technology, not to coal itself. The 0:14:33.680 --> 0:14:37.960 coal used in clean coal applications is just as dirty 0:14:38.160 --> 0:14:42.600 as coal thrown into an otherwise unremarkable blast furnace, and 0:14:42.680 --> 0:14:46.000 coal is the dirtiest of fossil fuels, meaning that it 0:14:46.040 --> 0:14:49.920 produces more pollution and a wider variety of pollutants per 0:14:50.040 --> 0:14:54.160 unit burn than any other fossil fuel. However, the fact 0:14:54.200 --> 0:14:58.760 that coal is plentiful and inexpensive means it's likely to 0:14:58.800 --> 0:15:02.800 remain important in major industries like generating electricity for quite 0:15:02.840 --> 0:15:07.040 some time unless something major changes. So engineers have dedicated 0:15:07.040 --> 0:15:09.960 a lot of time, research, and effort into creating systems 0:15:10.040 --> 0:15:13.280 that can limit the amount of pollution emitted into the environment. 0:15:13.760 --> 0:15:17.120 There are procedures that can reduce some of the stuff 0:15:17.760 --> 0:15:21.200 that would otherwise be released when you burn coal. And 0:15:21.240 --> 0:15:25.360 this is another important point. There's no single process that 0:15:25.560 --> 0:15:29.800 is good for reducing all pollutants. There's no one system 0:15:30.000 --> 0:15:33.560 that we can put coal through and get clean air 0:15:33.600 --> 0:15:35.520 coming out of the smoke stack. On the other side, 0:15:36.120 --> 0:15:39.280 there are lots of individual systems that are really effective 0:15:39.520 --> 0:15:44.120 or pretty effective at reducing one or more of the pollutants, 0:15:44.160 --> 0:15:47.440 but there's no single approach that gets everything. So if 0:15:47.440 --> 0:15:51.080 you wanted to burn coal with a bare minimum environmental impact, 0:15:51.480 --> 0:15:54.520 you would have to employ multiple methods and thus have 0:15:54.600 --> 0:15:57.160 a more complicated system. And we'll talk a little bit 0:15:57.200 --> 0:16:01.320 more and a bit about why that's a big challenge. Now. 0:16:01.360 --> 0:16:04.880 One of the methods you could use to have a 0:16:04.960 --> 0:16:09.240 clean coal application is called coal washing, and it's pretty 0:16:09.320 --> 0:16:12.600 much what it sounds like. There are two main approaches 0:16:12.680 --> 0:16:16.200 you can take. One involves a physical process in which 0:16:16.240 --> 0:16:19.760 you rely upon the different densities of the various contaminants 0:16:19.840 --> 0:16:23.480 found in coal to be able to separate them out 0:16:23.560 --> 0:16:27.240 and remove them and leave the coal behind. The other 0:16:27.480 --> 0:16:32.080 relies upon chemical processes to remove those same contaminants. The 0:16:32.120 --> 0:16:34.920 most common of the two is the physical approach, not 0:16:34.960 --> 0:16:37.880 the chemical approach. Chemical approach is still one of those 0:16:37.880 --> 0:16:42.920 things that's constantly being studied, but so far, as far 0:16:42.960 --> 0:16:45.640 as I can tell, has not been scaled up to 0:16:45.720 --> 0:16:48.720 a degree where it could actually be used practically in 0:16:48.840 --> 0:16:54.400 widespread applications. So with coal washing, with the physical approach, 0:16:54.840 --> 0:16:57.480 you take the raw coal that you've mined out of 0:16:57.480 --> 0:17:00.240 the ground, and then you use some heavy machinery to 0:17:00.320 --> 0:17:03.760 crush it up into much smaller pieces. You sift the 0:17:03.840 --> 0:17:07.800 crushed coal and you separate it into different sized particles 0:17:08.520 --> 0:17:11.040 um and you can use a series of sieves this 0:17:11.080 --> 0:17:13.280 way right. You can use one that's very fine, and 0:17:13.320 --> 0:17:15.840 that way only the smallest particles come through. And once 0:17:15.840 --> 0:17:18.439 you've got all those out, you transfer the material to 0:17:18.720 --> 0:17:22.639 a sieve that has slightly larger grids in it, so 0:17:22.680 --> 0:17:26.119 that way slightly larger particles can come through. You do 0:17:26.160 --> 0:17:28.960 this several times until you've divided up the coal particles 0:17:28.960 --> 0:17:33.320 into different piles, and then you put them through their 0:17:33.320 --> 0:17:37.400 respective cleaning processes. The process is pretty much the same 0:17:37.440 --> 0:17:39.439 for each one. It just it makes it easier to 0:17:39.520 --> 0:17:42.880 divide them up, so they all tend to work essentially 0:17:42.880 --> 0:17:45.840 the same way. You put the coal particles into a 0:17:45.880 --> 0:17:51.040 container like a vat, and it has jets water jets 0:17:51.080 --> 0:17:55.600 in it that can push water up through the coal, 0:17:56.280 --> 0:17:59.720 and it creates this upward current. The coal is lighter 0:18:00.040 --> 0:18:03.359 than the contaminants, so the coal gets pushed towards the 0:18:03.400 --> 0:18:07.000 top the contaminants to sink towards the bottom and you 0:18:07.040 --> 0:18:10.280 can then separate out the coal from the contaminants. This way, 0:18:10.440 --> 0:18:12.800 then you have to dry the coal before you can 0:18:12.880 --> 0:18:15.280 use as a fuel. That's a process takes quite a 0:18:15.280 --> 0:18:18.280 bit of time and energy in itself. Uh. It reduces 0:18:18.320 --> 0:18:24.080 but does not eliminate all pollutants. So you could reduce, however, 0:18:24.280 --> 0:18:26.560 you know the amount of pollutants you're releasing into the atmosphere, 0:18:26.600 --> 0:18:30.720 but you don't eliminate them entirely, and it requires energy 0:18:30.760 --> 0:18:34.119 to do this system. That's something that we also have 0:18:34.160 --> 0:18:36.800 to keep in mind in each of these steps is 0:18:36.840 --> 0:18:40.200 that the whole purpose of using coal in the first 0:18:40.240 --> 0:18:43.800 place is to generate electricity, at least in the applications 0:18:43.800 --> 0:18:46.480 I'm talking about here. But if you have to dedicate 0:18:47.119 --> 0:18:50.960 energy towards the process, that means you're you're eating into 0:18:51.000 --> 0:18:53.760 your own returns. Right. If your goal is to create 0:18:53.800 --> 0:18:58.000 electricity and you're having to use some energy in your process, 0:18:58.040 --> 0:18:59.840 more and more of the energy and your process to 0:19:00.160 --> 0:19:04.680 get acceptable to generate electricity in this way, then you're 0:19:04.680 --> 0:19:07.800 eating into your own ability to generate the thing you're selling. 0:19:08.480 --> 0:19:12.399 You're you're eating into your own revenue, if you like. So. 0:19:12.440 --> 0:19:17.080 Another process focuses on the gas generated from burning coal. 0:19:17.520 --> 0:19:20.479 Using what are called wet scrubbers, you can treat that 0:19:20.640 --> 0:19:25.040 gas so that a chemical reaction renders otherwise harmful emissions 0:19:25.080 --> 0:19:27.160 inert This is what I was talking about a little 0:19:27.160 --> 0:19:30.880 bit earlier in the last section. So sulfur dioxide, which 0:19:30.920 --> 0:19:33.120 can react with other gases in the atmosphere and create 0:19:33.160 --> 0:19:35.679 fine particles that are harmful to the environment and to 0:19:35.720 --> 0:19:38.560 the health of humans, is a great example. Sulfur dioxide 0:19:38.560 --> 0:19:43.440 scrubber is a flu gas desulfurization technology. As the gases 0:19:43.480 --> 0:19:47.280 from burning coal moves from the furnace into a special chamber, 0:19:47.840 --> 0:19:52.840 nozzles spray a slurry made up of limestone and water. 0:19:53.760 --> 0:19:56.560 Limestone has calcium in it, and the calcium in the 0:19:56.600 --> 0:20:01.360 limestone reacts chemically with the sulfur dioxide. The main byproduct 0:20:01.960 --> 0:20:06.040 is a substance called calcium sulfate. You have this chemical 0:20:06.080 --> 0:20:08.560 reaction and you get calcium sulfate as a result, also 0:20:08.600 --> 0:20:12.159 known as synthetic gypsum. This stuff can be used in 0:20:12.200 --> 0:20:15.840 other materials, including cement, so you can actually put it 0:20:15.880 --> 0:20:19.160 to use elsewhere, which helps bring down the cost. Right 0:20:19.160 --> 0:20:23.359 if you can, if you can put a byproduct to 0:20:23.560 --> 0:20:26.440 use it brings down the overall cost of the process 0:20:26.440 --> 0:20:29.840 because you recapture some of that by repurposing the material. 0:20:30.240 --> 0:20:33.359 Discrubbers can move a lot, but not all, of the 0:20:33.359 --> 0:20:36.720 sulfur dioxide emissions from coal firing plants if they are 0:20:36.760 --> 0:20:41.320 properly used. Nitrogen Oxides are another problem, and they require 0:20:41.320 --> 0:20:45.000 a different approach. Nitrogen Oxides are a group of highly 0:20:45.040 --> 0:20:50.000 reactive gases that are poisonous. Coal combustion produces fuel nitrogen 0:20:50.080 --> 0:20:55.840 oxide and thermal nitrogen oxide. Nitrogen can't be removed ahead 0:20:55.880 --> 0:20:58.520 of time from coal, so the only options you have 0:20:58.560 --> 0:21:01.480 to come up with are away to remove it during 0:21:01.720 --> 0:21:06.240 or following combustion. You can't do a pre combustion cleaning 0:21:06.280 --> 0:21:08.360 to remove nitrogen. You can only do it as you're 0:21:08.359 --> 0:21:11.960 burning it or after you've burned it during combustion. You 0:21:12.000 --> 0:21:15.200 could use what is called a low nitrogen oxide burner. 0:21:15.480 --> 0:21:18.920 This actually requires careful management of the ratio of fuel 0:21:19.119 --> 0:21:22.840 to air to reduce the amount of nitrogen oxide emissions 0:21:22.920 --> 0:21:27.160 during several stages of combustion, so it slows down this process. 0:21:27.800 --> 0:21:32.040 It's possible to retrofit existing boilers with these types of burners, 0:21:32.480 --> 0:21:35.280 but they're limited in their effectiveness. They can reduce emissions 0:21:35.760 --> 0:21:40.160 between thirty to which is not bad, but it still 0:21:40.200 --> 0:21:45.080 means that you have almost you can have up to 0:21:45.520 --> 0:21:48.520 more than half of all emissions still going out into 0:21:48.520 --> 0:21:52.760 the environment, which is not great. After combustion, you can 0:21:52.840 --> 0:21:56.880 use something like selective catalytic reduction, in which you inject 0:21:56.960 --> 0:22:01.040 ammonia into a catalytic reactor and you can use something 0:22:01.040 --> 0:22:04.920 like titanium oxide as a catalyst as flu gas flows 0:22:04.960 --> 0:22:08.280 through it. This is the gas given off by combusting. 0:22:08.320 --> 0:22:11.800 The Colt's very hot and it's got all these chemicals 0:22:11.800 --> 0:22:16.080 in it. All. The reaction with the catalyst and with 0:22:16.240 --> 0:22:21.560 the ammonia creates some byproducts like water, vapor, and nitrogen, 0:22:22.000 --> 0:22:26.600 not nitrogen oxide, but just nitrogen. This process reduces nitrogen 0:22:26.680 --> 0:22:31.920 oxide emissions by eight to nine though unreacted ammonia ammonia 0:22:32.000 --> 0:22:34.080 that did not actually go through this chemical reaction can 0:22:34.119 --> 0:22:37.639 also become an emission that's not great. There's a similar 0:22:37.640 --> 0:22:41.840 approach called the selective non catalytic reduction that requires a 0:22:41.920 --> 0:22:44.880 higher operating temperature because you're not using a catalyst, which 0:22:45.280 --> 0:22:49.919 you know, catalysts make chemical reactions easier if you like. 0:22:49.960 --> 0:22:54.320 They facilitate chemical reactions well in the absence of a catalyst, 0:22:54.560 --> 0:22:59.399 you have to compensate by increasing the temperature um But 0:22:59.440 --> 0:23:01.320 then you don't have of a catalyst, and instead of 0:23:01.359 --> 0:23:05.359 using ammonia, use a different chemical. The reaction with the 0:23:05.400 --> 0:23:08.840 fluid gas results in nitrogen, water, vapor, and carbon dioxide. 0:23:09.440 --> 0:23:12.400 The overall reduction of nitrogen oxide emissions tends to be 0:23:12.400 --> 0:23:16.320 between seventy four. But then you also have CEO two, 0:23:16.400 --> 0:23:19.400 which we'll get to a little bit later. Then there's 0:23:19.440 --> 0:23:22.640 the particulate matter that gets carried up in smoke stacks, 0:23:22.920 --> 0:23:26.320 the the coal ash, if you will, and can contribute 0:23:26.320 --> 0:23:29.520 to stuff like asthma and other respiratory problems. One way 0:23:29.520 --> 0:23:33.680 to reduce those emissions is to use an electrical field 0:23:33.920 --> 0:23:37.679 or a series of high voltage electrical fields. The purpose 0:23:37.760 --> 0:23:40.879 of this is to impart an electrical charge onto the 0:23:40.920 --> 0:23:45.160 particulate matter as it moves through the system. Now, once 0:23:45.200 --> 0:23:48.880 those particles are charged, they will move near collection plates 0:23:48.880 --> 0:23:53.040 that carry the opposite charge, and opposite charges attract, so 0:23:53.080 --> 0:23:56.720 the particular dust will cling to the collection plates. They 0:23:56.720 --> 0:23:59.320 can be really effective in removing that particulate matter, like 0:24:00.119 --> 0:24:03.880 percent effective in some cases. However, this also means using 0:24:03.920 --> 0:24:07.240 some of the electricity you're generating to power the system, 0:24:07.359 --> 0:24:10.160 so again you're getting a reduced return on your investment 0:24:10.680 --> 0:24:12.520 because you have to use some of that electricity just 0:24:12.600 --> 0:24:16.840 to keep the process from being too dirty. Another method 0:24:17.119 --> 0:24:21.160 involves a different approach to using coal called gasification, which 0:24:21.200 --> 0:24:24.560 gives you a hint at what's involved. Use steam and 0:24:24.640 --> 0:24:29.200 pressurized air or pressurized oxygen, and you have that air 0:24:29.400 --> 0:24:32.200 oxygen heated too very high temperatures, and you combine all 0:24:32.200 --> 0:24:34.920 this with the coal. This forces a chemical reaction in 0:24:34.960 --> 0:24:38.720 which carbon molecules break apart and produce sin gas. That's 0:24:38.720 --> 0:24:42.359 synthetic natural gas I talked about earlier. Sin gas is 0:24:42.359 --> 0:24:46.320 a mixture of hydrogen and carbon monoxide. You also get water, vapor, 0:24:46.359 --> 0:24:49.960 and carbon dioxide from this process. The sin gas, once 0:24:50.040 --> 0:24:53.600 chemically scrubbed, can be used in a gas turbine to 0:24:53.640 --> 0:24:58.560 generate electricity. So instead of generating heat to boil water 0:24:58.720 --> 0:25:01.800 and turn a steam turb line, you can have a 0:25:01.800 --> 0:25:06.000 a sin gas powered turbine that just takes the fuel 0:25:06.480 --> 0:25:09.360 and uses that to generate electricity directly. Not only that, 0:25:09.400 --> 0:25:13.480 but then you can also capture waste heat from this 0:25:13.560 --> 0:25:17.520 process to boil water and turn a second turbine a 0:25:17.520 --> 0:25:22.760 steam turbine, so it can increase the the efficiency of 0:25:22.800 --> 0:25:27.800 a power system this way, and um, you essentially turn 0:25:27.840 --> 0:25:31.480 waste heat into productive heat. You still produce carbon dioxide 0:25:31.480 --> 0:25:33.720 this way, and that's a greenhouse gas, and that's still 0:25:33.720 --> 0:25:37.639 a big problem. Uh. And carbon dioxide emissions continue to 0:25:37.880 --> 0:25:41.960 contribute to climate change, so reducing them is critically important 0:25:42.160 --> 0:25:44.360