Pre-In-Plant Training Webinar: Process Heating at Charter Steel – Arvind Thekdi
Sachin Nimbalkar:Welcome to DOE’s Pre-INPLT Training Webinar on Process Heating Systems and DOE’s PHAST Tool Process Heating Assessment and Survey Tool. Good afternoon and good morning for some people. Basically thank you for joining today’s webinar and this is – as I mentioned, this is pre-training webinar for our process heating training in Saukville, Wisconsin, between January 19th and 22. We’ll have this training – onsite training. To prepare all parties and participants for the training, we have organized this particular webinar.
I am Sachin Nimbalkar, currently working as R&D staff at Oakridge National Laboratory. Actually ORNL is USDOE’s national lab and I’m actually a technical account manager for DOE’s Better Plants program. This program is around since 2010 and I provide technical support to DOE’s Better Plants program partners. A program called Charter Steel is DOE’s Better Plants partner and there are 160 other companies. I actually provide technical support through energy roadmap _____ designing analysis, in plant trainings, _____ to investigate visible majors to reduce process energy requirements.
And so today’s webinar, we are going to focus on process heating equipment and Arvind is actually – Dr. Arvind is actually going to discuss process heating equipment as well as how a process heating – process heating assessments are done and then how process heating assessment and survey tool helps you to identify energy efficiency or _____. At the same time, we have Mr. David Mowry from Saukville, Wisconsin and then Tari Emerson is also going to join in next few minute. They are providing us technical support. They are working with local team at Saukville, Wisconsin plant and they are providing us data related to process heating equipment.
With that, I will go ahead and turn it over to Dr. Arvind Thekdi. Arvind, if you don’t mind, please start with your introduction and then I will actually change slides for you.
Arvind Thekdi:Okay, thanks Sachin. My name is Arvind Thekdi and I am one of the developers of the – some of the training material that we are going to use. Before I start, I have to give one disclaimer, I guess, in a way. I have some cough and my throat conditions are not exactly 100 percent correct, so I may have to stop for a cup of water or cough or something. My apologies for these kind of disturbances.
Anyway, my background is in process heating. I have worked in this area since 1970. That makes me very old and experienced, I guess. I worked with many furnace companies. I have my own company, which is called Heat 3M and we provide training services as well as tools level up ____ and the actually onsite assessments. I’ve been doing this thing – oh, god knows what – 1999 or something and probably have visited 100 or so plants throughout the world. The steel industry is one of my favorite industry because a company that I used to work for, and I’m sure you know the name, it’s called Surface Combustion. This was where I was in charge of R&D design and so on and so forth. I’ve been to many, many, many steel plants and that helps a lot in identifying and ______, as well as discussing what can be done, economically justifiable. This is a little bit of my background as you can see and MBA, PhD, Master’s, a couple of previous companies, leaving Surface Combustion, so on and so forth. Next slide, Sachin.
We are going to start with this. We have total one and a half hours. I’d like to go for about 45 minutes or so and one thing. I know you are in silence mode. If you have any question, as instruction has said here, type your questions and we can discuss those in the middle of the presentation or preferably at the end of my presentation.
Let’s start with saying what is process heating. It’s basically anything or any kind of process where we supply heat to different types of materials and there are many different names for this kind of equipment. Furnace heat is probably one of the most commonly recognized name in steel industry and there are other ones and heaters and thermal oxidizers and of course boilers and so on and so forth. Most important thing really is that in each of these equipment, we use heat to do something to sort of material. For example, in our furnaces, we melt the metal. You reheat ____. We reheat the metal, so on and so forth. Next slide, Sachin.
As you know, there are many, many different types of equipment which people use in their manufacturing operations in manufacturing plants. They could be classified in many different ways, but the Department of Energy has selected to do it in a way that I have shown here. One is what’s called process heating and steam systems, which includes furnace heat. The other one is boilers, so on and so forth. The second one is the elliptical motor systems, which is everything that you use with electric motors, with the exception of bumping systems and compressed air system, and then the other type of HVAC lighting, so on and so forth. Obviously in a plant, the most visible thing is lighting, but if you look at it, you see it’s going to be less than two percent of your total energy use is gonna be lighting.
The important part is that if you come back to process heating, anywhere between 60 to 80 percent of the total energy or energy bills that a company pays is 60 to 80 percent or so. And it’s a lot more in steel industry than some of the other industries or so because the steel industry or the _____ uses a lot of gas and electric city bot. So 60 to 80 percent could go there and then the saving opportunity that you can see at the bottom, 10 to 30 percent for furnaces, 5 to 10 percent for electric motor, 10 to 20 percent for bumping, 10 to 20 percent for compressed air, and 5 to 10 percent or so. The basic message here is that process heating is extremely expensive and it uses a lot of resources, and this is where most of the opportunities lie. Next slide, please.
There are many different types of process heating systems people use. Most common one, which is certainly in the steel industry, is the two types. One is the fuel fire systems. Certainly in the United States, gas is used for combustion and supplying heat. Second one is electrically heated systems and since you are working for a mini mill, you all know that the electric arc furnace uses lots and lots and globs and globs of electrical energy. The fuels and the electricity are the two major sources for EAF kind of plant. For integrated plants, steam is also one of the important sources of energy and steam is extensively used. But for our purpose, we’ll concentrate on fuel fired furnaces and electrically heated systems. Next, please.
Let’s take a look at the fuel fired heating system. In this case, the heat is generated by using solid, liquid, or gaseous fuel. We, in the United States, are very fortunate that we don’t have to use solid fuels like coal or wool and liquid fuels like fuel oil and so on and so forth because we have plenty of clean, natural gas. And most processes that you have, I guess almost all other than electric arc furnace, uses natural gas. And then once you burn it, it gives off the heat and you transport the heat to the material. The combustion gasses can be directly in contact with the material, which is direct heating as in case of reheat furnaces, or it could be confined in a separate source such as radiant tube, which you have in your annealing furnaces. That’s what they call indirect heating, so there’s the direct heating and indirect heating. Many different types of fuel based systems. We talked about approximately 65 percent of the total energy, process heating energy, used in U.S. is by fuel fire systems. A huge amount of energy is being used as fuel. Next, Sachin.
There are many different types of furnaces. One most common that you see in a plant is the continuous direct fire furnace, which is the reheat furnace. And in this case, you see a bunch of burners above and below the hearth level. They fire it. The gasses come in contact with steel. The good thing is they heat the material. The bad thing is they oxidize the material because the flue gasses have carbon dioxide and water vapor and some oxygen it. That, at high temperature, oxidizes the steel. There are plusses and minuses to that. Next, Sachin.
The other one is the bench type of direct fire furnaces, where you have material going in the furnace. You load the furnace, close the door, and you start your burners, and the burners would come – I mean the flue gasses would come in contact with material being heated. In this case, happens to be a bunch of coils being heated, so on and so forth, but that’s because the material is not going in and out continuously. Next slide, Sachin.
These are some of the indirect heating systems or radiant tube. Most common one is the radiant tube and many of your _____ tubes where you have anywhere between 4 to 80 inch diameter, high temperature alloy tube. We fire the burner in the tube. The hot gasses which hit the radiant tube and then they will radiate the heat. That’s why it’s called radiant tube. Since it’s radiation and is a local source of heat, we need to distribute the heat. In many cases, you will have a fan which circulates the gasses and there are many different ways of installing fans. The most common one that you see is in your batch annealing systems or in your annealing furnaces. The other one is the – where you have a return or an inner core, if you want to call it, where you fire the burner outside the cover or return. Return gets hot and then it transfers its heat to circulating gasses, which in turn heats the material. That’s another type of heating system. Next, Sachin.
As part of the steel industry’s concern and particularly in mini mill or your kind of shops, what are the major process heating equipment? Plastic arc furnace obviously is very large. The next slide is in the melt shop, you have a few ladles. Ladle heating uses gas and then there are Tundish heating also. As far as the melt shop is concerned, it’s the arc furnaces. They have – usually they have oxygen fuel burners. In this case, oxygen gas burners. Then we have Tundish and we have ladle heating. Then the next one, which you see in the bottom left side, air reheat furnace, which uses lots and lots of energy, hundreds of millions of BTUs of energy to heat the material. It could be the slab or it could be billet or it could be blooms, whatever it is there.
Next to that is an annealing furnace. This is commonly used as the step annealing or batch annealing furnaces there. And then next to that, you see a commonly used heating furnace for annealing the material or tempering or hardening or so on and so forth. This could be mostly radiant tube fired furnace. Above that is a continuous annealing furnace. The top right side is the continual annealing furnaces, where again, people use combination of radiant tubes and direct fire, but these are the commonly used things. Next slide. Go ahead, Sachin.
This shows a schematic which all of you know very well. I don’t have to explain it to you. The electric hearth furnace. We have refining. We have continuous casting. This casting introduces slabs. Then it goes to slabs or blooms or things, and then from reheat furnace, we go to many different types of finishing operations. In your case, I guess it’s wires. You go to the bottom one. You go through rolling anneal and you produce bars and rods and so on and so forth, but there are many different types of shapes and sizes, and in many cases, there are some downstream operations, such as annealing. There may be hardening. There may be carbonizing. There may be tampering. Many different types of finishing operations are going on where the cast or the fuel is being used. Next slide, Sachin.
We said that there are many different types of furnaces and that’s a problem. Why is it a problem? It’s a problem because people tend – what are furnace they have, it’s unique to them. It’s just like having our kids. They’re all unique to us. They may be very similar to the neighbor’s kids, but they are very special. Everybody thought they had furnaces that are unique to them, ovens that are unique to them. About 15, 16 – exactly 16 years ago, DOE convened a meeting of all kind of people associated with furnaces: the furnace suppliers, the consulting companies, the steel companies, so on and so forth. And said look, guys, we gotta come up with some common description of a heating system. And that’s what they came up with, which is pretty good actually. Starting with the left side, two things are happening.
Two things are going in the furnace. One is the energy. In this case, very likely gas. And the other one is the material that we are trying to heat. Think about a reheat furnace and say you got a bunch of burners. We’re putting fuels in the burners and then we have either locking beam or a pusher or whatever it is. It’s throwing the flags in the furnace. Close the door. Then what happens to that fuel is it makes heat. The burners themselves don’t do much. The gas itself doesn’t do any heating. It has to be burned in the form of a flame. You kind of get a flame and the hot gasses, and the hot gasses then will transfer the heat to the material that’s being heated. In this particular case, slabs.
The burners could be top fire, bottom fire. They could be high velocity. They could be flat fire burners. They could be whatever, different types, but in each case, you got a whole bunch of hot gasses at 3,000 degree or 4,000 degree Fahrenheit and those gasses then would heat the material so that it comes out at the other end at 2,200 degree or 2,250 or whatever temperature you want. The job is done and yet you have to deal with something else, which is now you have the exhaust gasses coming out. In some cases, we will have to recover the heat as in reheat furnaces, we have recuperators there. And then in some cases, we’ll have to put some sort of emissions control system because there are restrictions on what you throw out in the air.
And a prime example is what’s going on in the arc furnaces, where we have a whole bunch of bad houses or air ____ steady precipitators that get a readout of dust 10 and so on and so forth. This is good, but all this needs to have a controlled temperature and closer, and this what we call a brick box or a furnace. And so that’s what we call the heat containment. Now in addition to that, there may be a few little things going on in here. Sometimes you have to use the processor atmosphere. It could be hydrogen. It could be RX gas. It could be TX gas, whatever it is, to make sure that the work is protected and then that atmosphere has to go out. In addition to that, we’ll have sensors.
We have different types of materials, design tools, so on and so forth. That could be other things like water cooling as in case of walking beam furnaces, other type of cooling, so on and so forth. This gives general description and the reason why this is helpful is that now we can take each of these elements of a furnace and look at it and see what can we do to reduce the energy use. For example, in heat containment, how can we reduce the water losses, opening losses, and heat recovery? How can we get more heat recovery, so on and so forth? Next slide, please.
This is another way to look at the same diagram in a more realistic way. We divide this again into ten different components. Number one is the material that goes in. You could do something to the material to reduce the energy use. There could be material handling systems. The third one is the burners themselves. We could do something to the burners. The fourth one is the gasses. You could do something to them to reduce the energy, then furnace walls. The sixth one is the openings and doors and stuff like that. Seventh is going to be the water cooling, particularly in working with furnaces ______. And then control system. People use level one control, level two control, level three control, so on and so forth, and then you have blowers and exhaust, air blowers or combustion air blowers, and then there are a whole bunch of other heat losses. Again, what we are going to do here in discussion as well as in practice, we’re gonna look at each of these elements and see where we can save energy. Yeah, okay, Sachin, yeah.
What do we do? First, we do energy distribution. We’re gonna find out where we are, how much energy is used, and where it is going. And this is where most of the time that we will spend in the plant is gonna be to find out where energy is used and how much energy is used, and we’re trying to cover all these ten elements. In most cases, we end up covering maybe four or five or six because some of them are difficult. Some of them are not existing, so on and so forth. The very first thing we do is look at the energy distribution and see where the energy is going.