Professor Cang Daqiang from University of Science and Technology Beijing: Innovation and Application of Technological Solutions for Flue Gas Treatment in Steel Sintering Processes

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Cang Daqiang (Professor and Doctoral Supervisor at University of Science and Technology Beijing): I mainly talk about innovation. Let me talk about five points. First, the conclusion. Second, the current situation and existing problems at home and abroad. Third, the new requirements for new environmental protection technologies and equipment. Fourth, new governance methods. Fifth, new technologies for flue gas treatment in sintering plants. First, the simple phase of energy conservation and emission reduction has passed; now China is in a new period of development, having moved from an upward phase to a more stable one. Therefore, this stage is different from before; we must have new ideas and ways of thinking, new methods, new requirements, and develop new technologies. We must change our mindset—otherwise, the company’s future development will be affected to some extent. Furthermore, end-of-pipe treatment is a method for environmental protection, but attention should be paid to suppressing pollution at the source and to low-cost environmental protection technologies. The focus of current research is on this, with the aim of reducing technical investment and operating costs. This can be done; it’s being worked on right now. In addition, those working in environmental protection must understand sintering processes, equipment, and raw materials. It is also necessary to understand the characteristics of organic sulfur, inorganic sulfur, and other sulfides in sintering materials, as well as the conditions and patterns for the formation of SO2 and SO3. The control of NOx is characterized by fuel-type nitrogen, thermal-type nitrogen, and rapidity nitrogen, as well as their formation and emission patterns. Previously, only dust removal was considered; later, desulfurization was added, and now denitrification has been introduced as well. What will come next? We need to start preparing now. It’s not enough to focus only on dust removal, desulfurization, and denitrification. Now that whitening treatment has also been added, this is still not sufficient; we need to move forward further. **There are still many standards, and each stage has its own priorities – we need to prepare in advance. Your market, and the drivers of economic growth for your company, are all here. Another aspect is innovation; China faces many problems in this area. Inertial thinking is extremely persistent, and it poses a series of challenges to innovation, as most major ideas come from abroad. For every company and every organization, the starting point for new economic growth must lie in disruptive innovation within its own mindset. We must work diligently and take the time to consider issues in depth, rather than approaching them in a hasty manner. That’s why China lacks theory; we do have some technology, but even this includes basic research in the field of engineering, and there is a severe shortage in that area as well. What exactly are the scientific methods for energy conservation and emission reduction? Abroad, this concept is used; we, on the other hand, employ approaches at the source, during the process, and at the end stage. In the past, focus was placed on the end stage, but the source and the process are becoming increasingly important. Abroad, these stages are referred to as before the process, during the process, and after the process, with different levels of investment required for each. In the future, how will our technology determine whether something is feasible or not? We are already facing problems at the **level. Foreign evaluations are as follows: First, the technical principles are feasible. Second, technical feasibility means using mature technologies to implement this principle; that is what is meant by technical feasibility. Third, it must be economically viable; economic considerations must be taken into account. Fourth, environmental acceptance capacity: it’s a human issue; there are many good things that people are unable to accept, which leads to problems with environmental acceptance. Liking old technologies and foreign technologies while disliking new ones is a problem. This is the distribution of nitric oxide around the world, showing the regions where it is produced fastest. The area in China where emissions are particularly high is the region of Shanxi, Hebei, Shandong, and Henan; the eastern parts of Europe and the United States are also areas experiencing rapid growth. This was taken by NASA, the United States’ space agency. Here is what the east coast of the United States looked like ten years ago, and here it is ten years later; there has been a noticeable reduction in nitrogen oxides there. Over those ten years, similar reductions have occurred in Western and Northern Europe, as well as in Japan. Currently, only in the Jin-Ji-Lu-Yu region of China is the color deepening, and this is indeed a very serious problem we are facing. This is why it’s necessary to step up denitrification efforts now. The issue with innovation in sintering machines in China is that we discuss flue gas desulfurization and denitrification without changing the current state of sintering. We know that there are numerous problems with the sintering machine. You can think it’s mature if you want, or you can think it’s full of flaws – in either case, you just have to obey it passively. If you think it’s mature, then go ahead and use it; but in reality, there are many aspects that need improvement, and some practices even need to be completely abandoned. These things will still need to be addressed in the future. If you keep doing it that way, it will be hard to see any major changes. Research on some internal processes, such as how these underlying processes come into being and so on. Additionally, in the red sintering machines, heat is used to drive cooling, and the emissions at the upper and lower parts are different. Research has shown that these processes involve sulfur – not only sulfur dioxide and sulfur trioxide, but also sulfur vapor as well as the formation of iron sulfide. Various aspects related to these processes and their emissions are studied, and these conditions vary in different locations. Therefore, what we’re doing now is concentrating all the flue gases from the entire sintering machine into one pipe and one set of equipment; this is different. So it is necessary to study this process. How should developed countries address the issue of sintering machines? First, eliminate the sintering process. In some countries in Northern Europe, **all iron production relies on pellets; in some other countries in North America, the United States and Canada, sintering is not used. The final stages in steel production involve sintering and coking – sintering generates flue gas, while coking produces water, and that’s why these methods are adopted there. China is not able to do this yet; we learned from the Soviet Union’s approach at that time, focusing on sintering, and this practice has continued for over half a century. Another aspect is the transition from treating a single pollutant to managing multiple pollutants together, which is also a skill in its own right. Behind Japan’s sinter machines, there are rows upon rows of equipment for dust removal, desulfurization, denitrification, VOC removal, and so on. The environmental protection equipment installed thereafter is far more advanced and occupies much more space than the sinter machines themselves. China will also face a similar situation in the future; therefore, it’s impossible to manage all pollutants using just one piece of equipment. So, it has moved towards **also encouraging the coordinated treatment of multiple pollutants. This is difficult. China is currently in a phase of diverse development; most efforts are focused on end-point treatment. It will still take some time before these technologies can be applied industrially, but at the very least, we should start working on it now. Multiple pollutants are present in one piece of equipment. Normally, it would be very difficult to handle all these pollutants in China using this method—the activated coke method. These pollutants, such as dust, sulfur dioxide, and nitrogen oxides, are completely different from one another. The separation of gas and solid particles is a physical process, while the treatment of these pollutants involves chemical processes as well. This is a combination of physical and chemical processes; how is it possible to address all of them simultaneously in just one piece of equipment? China’s innovation also has other contributing factors; therefore, the experts here should not dismiss others’ approaches. Listen to them first, let them try different methods – the last three methods didn’t work, but in the end the first method succeeded. So China is also part of this group. Therefore, what was once considered impossible has now become a reality. In China, this approach does indeed encounter some problems; naturally, it remains a measure for end-of-pipe treatment. China has reached the strictest phase; environmental protection costs have risen from double digits to three digits, and they will continue to rise in the future. China’s total steel production has been on the rise; naturally, higher production levels lead to greater overall pollution. What are the requirements regarding the treatment of sintering flue gas pollution? First and foremost, environmental protection equipment must effectively address environmental issues by meeting current **emission standards, while also preparing for future emission standards. Second, secondary pollution should be minimized. Third, the cost must be low (low investment, low operating costs, and small land footprint). It was proposed under China’s conditions, especially in the steel industry. Fourth, a joint approach involving end-of-pipe treatment, process control, and source control. Fifth, the development of new sintering processes, etc. Where does nitric oxide come from? **This project specifically studied this issue. The results showed that fuel accounts for over 95% of it; within that, carbon monoxide makes up 90%, carbon dioxide about 10%, and there’s only a very small amount of nitrous oxide.** Fuel-type nitrogen, thermal-type nitrogen, and rapid-type nitrogen are produced under different conditions. There are also issues related to certain process parameters; the overall emission factor is of primary importance. Additionally, the sintering temperature is also very important. Nitrogen oxide emissions rise sharply, rather than increasing linearly. Nitric oxide is not easily absorbed by the liquid phase, so wet methods have little effect on it, unlike sulfur dioxide which is easily absorbed. Problems with desulfurization and denitrification: First, three different technologies for desulfurization and denitrification need to be used, but there is no solid data available to determine which one should be adopted. Thus arises the question: among all the technologies for desulfurization, denitrification, and flue gas treatment, which one is the best? Who decides that? In theory, it should be practice and data that determine this. So in general, one talks about their own merits; it is others who speak of one’s strengths, through action. And we are currently looking for new ways. Second, there are many end-of-pipe treatment methods, but few new, low-cost flue gas treatment technologies. Thirdly, selective desulfurization and denitrification are required – it’s not the case that all the air boxes located beneath the sintering machine are combined to handle the process together. The distribution of nitrogen oxides and sulfur varies at different stages. As can be seen from these curves, different air boxes have different temperatures; naturally, the levels of sulfur dioxide and carbon dioxide also vary. The levels of carbon monoxide, carbon dioxide, and oxygen differ as well, and so do the levels of dioxins. Therefore, each of these substances needs to be treated separately, with selective removal applied where their levels are high. Fourth, there is a lack of mechanism research. Fifth, physical problems are not given enough attention. There are quite a lot of chemical reactions, but it’s not entirely clear whether the actual process works in that way. Sixth, there is insufficient basic research in engineering technology: reactor design, complex piping systems, etc. It severely affects the efficiency of this system. Let’s talk about the problems in developing desulfurization and denitrification technologies: Just like research institutions abroad, Chinese research institutions also focus on technological research; whereas foreign institutions emphasize fundamental research, seeking breakthroughs through basic studies. As a result, they come up with more inventions, but progress is slower – this is something China needs to learn from going forward. There is also a lack of emphasis on the processes and equipment needed for desulfurization and denitrification in power plants; the basic aspects of the industries served are not understood. Focusing only on the smoke stacks is not sufficient, especially in the case of sintering. Additionally, there are some areas where pilot testing is lacking, which is not in line with standard practices; as a result, a lot of money is spent on these projects. What are the challenges in flue gas desulfurization and denitrification in sintering? First, the sintering parameters vary greatly: temperature, flow rate, composition, oxygen content, and so on. Second, the special aspect of the sintering machine is that it uses a top-down reverse sintering method, which leads to problems with air permeability and uniformity. Third, the intake of cold air by the sintering machine affects the gas composition and uniformity within the structure. Changes in the concentration and velocity of the opposing flows result in an increase in the amount of flue gas. This, in turn, raises our energy consumption, alters the temperature distribution within the system, increases the flow velocity, and affects research reports, research costs, as well as the effectiveness of environmental protection measures. It is essential to understand these things: different sintering machines have different energies and different sintering parameters. What are the characteristics of some of the decomposition reactions in the flue gas extractor? There are also dynamic changes in the sintering machine: temperature changes, capacity changes, changes in the materials used. When the container of the flue gas treatment equipment changes, desulfurization and denitrification processes also change. All these are aspects that need to be taken into consideration. How to change the desulfurization and denitrification processes—these are all follow-up controls that we need to consider. Additionally, completely change the sintering machine. Another issue is that of talent – who in your company or organization is the most suitable to carry out these tasks? People with expertise in environmental protection can help, but it’s essential to have those who understand manufacturing processes involved, as well as many others who have knowledge of economics and the market. That’s why there’s a need to cultivate multidimensional talents; this is what is recommended abroad, and it’s necessary at this initial stage, so such people need to be trained. Taiwanese steel companies add urea to sintering machines. This is a way of suppressing the emissions at the source—preventing sulfur dioxide and nitrogen oxides from being released in the first place. Instead of treating these emissions after they’re generated, this method helps reduce equipment investment and simplifies the overall system. Just add something to the operation, and it’s practical. So this method is used. At first, there was no thermally generated nitrogen oxide; it was mainly of the feedstock type, so adding feedstock is very important. 90% of the nitrogen absorbed comes from the crushed coke, which serves as fuel. How much of the nitrogen turns into nitric oxide? Approximately 36% of the nitrogen becomes nitric oxide. The concentration of nitric oxide varies depending on PDM; in those regions, the oxygen level is 15%, while in China it is 16%. This is their data. Through small-scale experiments, they determined where and at what temperature the most amount of a certain material is produced under different temperatures. The blue line below represents the result after adding urea; it is much lower than that of normal materials, and there is also a significant reduction in the inhibition of nitric oxide. These are the results of small-scale experiments. This is to take all influencing factors into account under process conditions, rather than considering only pollutants. Finally, the results of the industrial tests showed that 70% less sulfur dioxide was released into the flue gases after it was solidified, and 20% less nitrogen oxides, etc.; these are their interim results. Regarding the issues that China should pay attention to next, building on all the remarkable achievements already made, it is necessary to take a step back and focus on some fundamental aspects: whether the reactors are suitable, whether the core equipment is of high quality, whether the power system is flexible and well-matched, whether the complex piping systems are properly designed, as well as matters related to the media used for desulfurization and denitrification, their quantity, the method of addition, and operational control. Denitrification catalysts are particularly important. Additionally, there’s activated carbon. Currently, in China, there are both co-current and counter-current types; vast amounts of activated carbon circulate within them. These tens of thousands of tons of material require substantial energy consumption, incur high costs, and cause significant wear and tear. This is a characteristic of activated carbon. This is the capacity of activated carbon – how much it can absorb and how much it can release per ton. There is also an emphasis on the fundamentals of engineering technology. In working with certain types of engineering equipment, it was found that some studies pay little attention to the details of flow within pipelines. This results in low efficiency, and sometimes it’s even difficult to determine the underlying cause. In fact, the inside of the pipes is not uniform; it’s assumed that since the total flow rate is high, the velocity must also be high, but in some areas the velocity is high while in others it’s low, and in some spots the pipes are even damaged or worn out. This is also true regarding the piping arrangement: it differs before and after the modification. For example, three pipes are introduced here, and some people think that dividing the total volume by three gives the capacity per pipe. But that’s not the case; there is a significant difference. The pipe with the highest pressure carries the most fluid, and as the fluid travels further, its amount decreases, becoming even less as it goes further. Many factories encounter this problem: the total amount is insufficient, and despite checking the design values, no issues are found. So I hope everyone will keep in mind that there is still a lot of fundamental research needed in engineering in the future. Below as well, the red area is too large; in the end, the wear caused by dust damaged all the equipment. The same is true here: regarding the uniformity of the desulfurization and denitrification efficiency, the total amount of material fed in is as specified, so why is the outcome not good? It’s because in some areas the flue gas does not come into contact with the desulfurization and denitrification agents at all, while in other areas there is an excess of such agents, which is unnecessary and results in waste. So these are all fundamental issues that require a lot of attention. Innovation: In China, inertial thinking and subconscious biases are very persistent; people need to have a strong desire for innovation. Only by aiming to make their companies world-class can they develop the drive to innovate. Thank you all!