The future of carbon capture requires new technologies,
Instead of wearing new shoes and walking the old way,
Transformative technology is needed.
Hello everyone! I am Jin Hongguang, and I am very pleased to come to the Gezhi Tao Forum to share with you some of my thoughts on low-carbon energy conversion in the dual carbon goals.
Mainland China has made international commitments to the dual carbon goals. In this context, the energy sector has also proposed an energy revolution. In the report of the 20th National Congress, we announced the construction of a new energy system.
I personally believe that our country has a clear goal of dual carbon, but there is no consensus on how to develop the future of dual carbon. There has been a lot of talk about the importance and necessity of carbon neutrality, but the arduousness and complexity of the carbon goal are not fully understood.
First of all, double carbon is not a matter of a certain industry or equipment, it involves all walks of life in society and everyone here, and it is very complex.
Second, at the level of national development, the mainland's industrial structure, energy structure and Western countries, and even any country in the world are different. Industry accounts for a relatively high proportion of the composition of the mainland's GDP (gross domestic product), and there are more high-carbon energy in the mainland's energy, and our economic development is still in the stage of moving from a big country to a strong country. Therefore, we cannot simply say what a certain Western country does, we will do it, we must consider future development in light of our own national conditions.
Under the prospect of sustainable development, especially the prospect of dual carbon and green energy development, we need to consider what the mainland's economic and energy security looks like. Some say that low-carbon, green energy and economic security constitute an "impossible triangle". Whether it is impossible or possible, I hope that some of my later reflections on technology can answer this question.
Third, in the path of low-carbon development, we need to clarify what the new strategic industry will be in the future, what the main energy source is, and where the main battlefield is. Only by grasping these can we do a great job in carbon emission reduction. We must be clear about how to transform the development model of the past, how to change the way energy is used, and how to develop transformative technologies. Dual carbon is a new field and a new direction, whether it is an enterprise or a scientific and technological community, it should pay enough attention to the key technological breakthroughs related to it.
Why do you say that? There are some new breakthroughs that can achieve certain functions, but we only consider the application of engineering in engineering, and only consider the innovation of science and technology at the scientific and technological level, so it is difficult for us to break through key technologies.
Let me talk about some of the current status and problems in the field of energy and carbon emission reduction in the mainland.
As a first step, we spent decades improving energy efficiency, from 30 percent to 40 percent. In the second step, we encountered new problems, desulfurization, denitrification and dust problems, which belong to environmental pollution. These two problems have not yet been solved, and the third problem has come, which is the carbon problem. I call these issues "energy efficiency," "clean," and "low carbon."
The current energy development model is actually to solve a problem when encountered, and we are following a chain development model. This chain development model brings challenges to our future sustainable development. It raises a question: can energy, economy and security be developed in harmony?
My answer is that only by solving the "trinity" of energy efficiency, cleanliness and low-carbon can the triangular relationship on the right side of the figure be satisfied. This is an important proposition.
Let's look at how energy is used?
The conversion part of general energy is single input, single output, and high-grade energy is used for low-grade. For example, the air conditioning that we are enjoying right now. The cold grade is not high, but we use electricity, which is a high-grade energy source. This simple and extensive utilization method has caused the "three high problems" of our energy utilization: high energy consumption, high pollution, and high carbon emissions.
So, how do we solve these problems in the energy sector?
01. The dual carbon plan of the Chinese Academy of Sciences
In order to achieve the dual carbon goal, all walks of life have their own plans, and our Chinese Academy of Sciences also has an action plan to support carbon peaking and carbon neutrality.
The action plan consists of three parts, eight major actions and 18 key tasks. The main focus of this plan is still scientific and technological support, we must break through the key technologies of high-energy-consuming industries. This is our to-do list, so I won't go into them all.
Pilot A-Clean Combustion and Low-carbon Utilization of Coal (2022-2026)
In order to complete this action plan, the Chinese Academy of Sciences has planned a number of pilot projects. At present, we have launched a pilot project of "clean combustion and low-carbon utilization of coal". Each pilot project is 1 billion, and there are many pilot projects that we are planning.
Pilot projects in the energy sector that are demonstrated or ready to be launched
These pilot projects have several aspects. First, energy storage; Second, hydrogen energy; Third, renewable energy; There is also a low-carbon aspect of industry. These will all be launched in the near future.
To briefly summarize, there are many things that our country needs to do in terms of dual carbon, and there are some key issues that need to be solved and key areas that need to be broken through, including low-carbon conversion of fossil fuels, renewable energy, hydrogen energy, energy storage, and carbon capture, utilization and storage (CCUS).
02. Pursue cascade utilization of energy
So, what is the root cause of our current energy use problems? Where is the greatest potential? These are breakthroughs and our future development direction.
Origins of technical and scientific thought: von Kármán (left), Qian Xuesen (right)
Energy conversion is actually a technical science. The concept of technical science was mentioned by Mr. Qian Xuesen very early. He believes that there is a bridge between engineering technology and science and technology, and the bridge to be built is technical science.
If the scientific community only goes from theory to theory, if the engineering community only solves engineering problems, then there will be this gap, and it will be difficult to break through our key technologies without solving this gap.
In terms of energy utilization, Mr. Wu Zhonghua, who founded our Engineering Thermophysics Society and the Institute of Engineering Thermophysics of the Chinese Academy of Sciences, explained to the Secretariat of the Central Committee at the Central Party School in the 80s of the 20th century, in order to let everyone understand the use of energy, he proposed the concept of "temperature counterpart, cascade utilization".
So, what is "temperature counterparting, cascade utilization"? That is to say, energy utilization should not only consider the quantity of energy, but also consider the quality of energy. What is energy quality? For example, the same heat at different temperatures, high temperature, medium temperature, low temperature, the functional force is different, we call this the work position is different. It is very important that the functional power is different. From the scientific level, we can see whether various energy conversions are good or not from this perspective.
From the 80s to the present, "cascade utilization of energy" can be seen in national documents, and I will also explain our direction and key technologies from the inheritance and development of cascade utilization.
Energy conversion: changes in energy, energy quality and energy potential
We generally do energy after getting heat energy, and then convert heat energy into power generation and work, we call this conversion heat transfer work. The highest efficiency that can be achieved in this process is the Carnot cycle efficiency, which is the curve in the figure.
Our past work has basically stayed within the efficiency of this blue-colored Carnot cycle below the curve. Most of our fossil fuels are converted into heat through a fire, and then we do all kinds of things.
I want to emphasize that our fire, which is the green part, has the greatest irreversible loss of hydrocarbon fuel in the combustion process. The place with the greatest loss is where the potential is greatest, and it is the breakthrough.
This energy conversion not only affects efficiency, but this combustion process is the source of pollutants and carbon dioxide production. If we focus on this green part, we can solve the problem of energy efficiency, the problem of pollution and the problem of carbon emissions at the same time. So, I call it the orderly conversion of energy.
In other words, in the past, we focused on the bottom half of the figure, and now we need to focus on the upper half in order to minimize energy consumption in the "trinity" of efficiency, cleanliness and carbon reduction. No matter what energy source we face, the main direction of our scientific and technological community is to explore how to do this.
Current situation and problems of thermal power generation
In this picture, I have briefly listed that the left half is coal-fired power generation and the right half is natural gas power generation. We know that half of the world's coal is in China, and half of China's coal is used for coal-fired power generation.
Industrial development is inseparable from electricity, so much coal has generated so much electricity, so what is the current power generation situation? The efficiency of higher coal-fired power generation can reach about 45%.
Why is the efficiency 45%? I explain it in the simplest language. Our combustion temperature is 1800°C, but the steam turbine inlet temperature is only 600°C. This is equivalent to the water level of 1800 meters to 600 meters in hydroelectric power generation is not used, and we start using it to generate electricity from 600 meters. In other words, the operating force from 1800 °C to 600 °C in thermal power generation is lost. This is what was just said, energy not only has energy, but also energy quality.
From an energy point of view, the efficiency of our boiler is not low, more than 90%, but its utilization rate for functional force is only about 50%. Therefore, this utilization method does not conform to Mr. Wu's "temperature counterpart and cascade utilization", but is just a simple cycle.
Now it is often mentioned that our power plants are supercritical, ultra-supercritical. But that's just pressure, not temperature, and the temperature is still low. Not only is this inefficient, but the CO2 is diluted and not easy to recycle.
So, pay attention to the direction of the future. On the right side of this figure, we can see that natural gas power generation must first pass through a gas turbine. The inlet temperature of the gas turbine is 1600°C, and the discharge temperature is also relatively high. A steam turbine is connected to it to achieve cascade utilization. At present, a unit located in Dongguan can generate 63.6% of its power generation efficiency, which is much higher than all other current power generation methods, including hydrogen fuel cells. Hydrogen power generation is only 55% efficient.
After the efficiency of natural gas power generation is used in cascades, the efficiency is so high, so what is its carbon emissions? 1 kWh is only 0.33 kg. The lowest carbon emissions of mainland coal power generation are more than 0.6 kg of 1 kWh.
Therefore, if we can achieve this way of using fossil energy, we will go further than now. Of course there is something better than that, and we need to move forward.
Now consider a major question, what should our future be efficient and low-carbon? So far, the mainland's urban energy utilization method is to use coal to generate electricity, use electricity to cool, and use fuel to generate heat, this method is called single input, and high-grade energy is used in low-grade. This development model urgently needs a breakthrough.
So how to break through? We can rely on distributed energy cascade utilization systems. It is an energy system that uses high temperature section power generation, medium temperature refrigeration, and low temperature section heating. According to the characteristics of different grades, this distributed energy cascade utilization system can not only provide electricity to users, but also cool and heat.
This kind of energy system close to the user is a good development direction for our future, and this system is the basis for significant energy savings. The Institute of Engineering Thermophysics of the Chinese Academy of Sciences undertook an 863 project of the Ministry of Science and Technology, and we did a demonstration project in an enterprise in Dongguan. It can save 29.3% of fuel at one time under the premise of unchanged cooling, heating and power supply, which is the result of third-party testing.
Such systems are also available abroad, and a similar system (the Austin CCHP project) won the U.S. Department of Energy's Environmental Energy Award. Our current system is much better than that of the United States.
So far, the best domestic distributed energy system to do large-scale energy saving is our project. Distributed energy systems are suitable for different energy systems and energy types in different industries, and we have also taken the lead in formulating relevant national energy standards.
03. Enabling carbon capture with transformative technologies
In addition to energy use, we also need carbon capture, the purpose of carbon capture is to enable high-carbon energy to be used low-carbon.
Many people believe that high-carbon energy cannot be used low-carbon, but it can actually be done, one is through high efficiency and energy conservation, and the other is through direct carbon capture.
Current status and problems of carbon capture
Internationally, it is now considered that carbon capture has three main links, called pre-combustion, combustion and post-combustion. What the mainland considers more is the capture of carbon dioxide after combustion behind the boiler of the existing power plant.
After the coal is burned and then discharged, the carbon dioxide concentration in the flue gas is relatively low, only about ten percent. At this time, to capture carbon dioxide, its separation energy consumption is relatively high. How high is it? As I said earlier, we have spent more than 30 years to increase the power generation efficiency from 30% to 40%, but carbon dioxide capture consumes an additional 20%~30% of energy, reducing the power generation efficiency by more than 10 percent.
In order to capture carbon dioxide, overnight back 30 years ago, the efficiency of power generation has been reduced to more than 30 percent, which I think is too much additional energy consumption.
The economics of carbon capture need to be considered. It costs two to three hundred dollars to capture a ton of carbon dioxide, and carbon capture according to this line of thinking is not economical enough. Therefore, the future of carbon capture requires new technologies, rather than using traditional technologies to "wear new shoes and walk the old road", and must require transformative technologies.
More than 80% of the mainland's carbon emissions come from the burning of fossil fuels. This combustion process must be changed, and it is difficult to solve the problem of carbon emission reduction without change.
Traditional combustion requires fuel and air, in fact, combustion can be divided into oxygen-enriched combustion, hydrogen-oxygen combustion, pure oxygen combustion, flameless combustion, and chemical chain combustion, and so on.
The originality proposed the "chemical chain combustion" power system
Chemical chain combustion is a flameless combustion method we propose, which enables the directional migration of carbon dioxide without additional separation of carbon dioxide. The U.S. Department of Energy lists it as a cutting-edge technology in its carbon capture technology roadmap. Several major countries in the world are studying this burning method, and the most authoritative United Nations IPCC report has also recognized our work.
Above: Natural gas water-based chemical chain hydrogen production
Next: Synergistic conversion of fossil fuel hydrogen production and decarbonization
Recently, we have applied chemical chain fuels to hydrogen production from natural gas. Because the traditional hydrogen production method has a relatively high temperature, which requires combustion, so the energy consumption is high. Combustion with chemical chain does not need to burn, the temperature can be reduced, so that the energy consumption of hydrogen production is reduced by 20%~30%. This is also a joint research and development project with the China Science Group within our Academy of Sciences system.
There is also a major problem in the conversion of traditional energy use, what is it? The gasification of continental coal is very important. Our coal gasification is not mainly used to generate electricity, but to produce, such as methanol, natural gas and even synthetic ammonia.
Existing coal-based clean fuels have not yet reached the level of transformative low-carbon conversion
In this industrial process, we can see that the efficiency of the synthesis gas preparation process is very low, and the efficiency of the synthesis process is relatively high. The final synthesis efficiency from coal to methanol is only 45%, which is very low. Why is it so low?
This diagram shows the use of hydrogen and nitrogen to produce synthetic ammonia products, which are used to make fertilizers. Its one-pass conversion rate is very low, only 8%. Tens of thousands of chemists have worked on the catalyst to increase its conversion rate, but without success. Only F. Haber Professor Haber re-injected the unreacted gas to the gas inlet, and used the unreacted gas recirculation method to increase the conversion rate from 8% to more than 90%, and finally won the Nobel Prize. After industrializing this method, the industry won another Nobel Prize. This laid the foundation for nearly a hundred years of basic processes in the chemical industry, just like the Carnot cycle efficiency.
As the conversion rate is exhausted, there is a circle in this graph, which I call the energy consumption inflection point. After this inflection point, energy consumption will rise sharply. That is, high conversion rates come at the cost of high energy consumption.
This problem is systemic, and we are developing a new way of gasification.
Existing coal gasification methods
The chemical conversion efficiency of the traditional coal gasification method is also called the cold gas efficiency, which is relatively high, but requires air separation to produce oxygen. After adding the electricity required for air separation to produce oxygen, the efficiency of its gasification unit is not high, only more than 60%. This means that we must break through this energy-intensive conversion method.
Graded gasification method for directional conversion of hydrocarbon components
Therefore, I propose a "three-step gasification". Carbon is pyrolyzed first, carbon reacts with carbon monoxide, and then carbon monoxide reacts with water. After these three steps, the gasification efficiency can be greatly improved without air separation.
Transformative low-carbon conversion systems
This gasification method can increase the efficiency of more than 60% to 80%, which can play a transformative breakthrough effect on existing power plants and even new combined cycle power plants, and even chemical conversion.
Multi-generation technology for clean fuels and electricity
We can do chemical industry before this energy consumption inflection point, and after the inflection point, it will be in our power. In the powertrain, hydrogen and carbon monoxide are both fuels that can be used well. In the chemical industry, if the gas ratio is not well mastered, it is difficult to convert, and the energy consumption will be very high. We are currently trying to co-produce hydrogen and chemical products at power plants. In the future, power plants will not simply generate electricity, but also have some multi-functional features.
On the left is our existing carbon capture method at the expense of energy efficiency. If transformative technologies are adopted, they can both increase efficiency and capture carbon. This technical route is suitable for the future sustainable development path of our country.
04. The challenge of solar power
In addition to carbon capture, there is another important topic – solar energy. In addition to photovoltaics, the power generation efficiency of concentrated solar energy is still not ideal, one of the reasons is that we still maintain the traditional way of thinking, and we are still allowing high-grade concentrated solar energy to generate electricity through the low-grade method of steam turbines.
We know that steam turbines for coal, gas turbines for natural gas, diesel engines for fuel oil. Since concentrated solar energy is a new way, why do we use steam turbines? These are all challenges we need to face.
The United States has proposed a power cycle of supercritical carbon dioxide for concentrated solar energy, and I think there is a better cycle.
Solar fuel source chemical energy storage method
I propose a method. The efficiency of direct power generation when concentrated solar energy is two or three hundred degrees is very low, and we can drive the conversion of fuel and upgrade two or three hundred degrees of solar energy to the grade of syngas fuel. When the solar radiation is sufficient, the solar energy can directly drive the generator and store a part of the syngas. When the solar radiation is insufficient in the afternoon, the stored syngas can be supplied to this generator. This is very beneficial for the continuous operation of the conversion plant. Solar energy technology must pay attention to its continuity, and the important problem of renewable energy utilization is that it cannot operate continuously.
So, what does it do? We call the ratio of excess electricity to solar energy input net solar generation efficiency, which has now reached 25%. Recently we are still experimenting, and it is expected to reach 30%, which is much higher than photovoltaics. The mirror material inside the device is only steel and glass, not semiconductors.
Finally, I would like to say that the development of our energy needs to move from the "temperature counterpart and cascade utilization" proposed by Mr. Wu to the complementary conversion of energy, and finally to achieve low-carbon conversion. Our future development must be a diversified, low-carbon and intelligent process.
Thank you.