Table of contents:
- Zeldovich mechanism and nitrogen oxides
- Experimental data from Japan
- Kilograms and cubic meters - feel the difference
- Gasoline or hydrogen?
- Hydrogen can be liquid, but who gets it easy?
In early July 2020, European Energy Commissioner Kadri Simson made a short but succinct statement: “The EU's goal is to become climate neutral by 2050. This means that by that time we will have phased out all fossil fuels, and all EU suppliers should bear this in mind.” Hydrogen is the only and unique alternative to coal, oil and oil products, natural gas.
At the same time, it is obvious that the initiative does not come personally from Mrs. Simson - she just voiced what Germany most insisted on, whose government has already announced an ambitious national program for hydrogen energy, according to which by 2030, for example, the country should to build 20 GW of additional power plants, the purpose of which will be only one - the production of the so-called "green" hydrogen. The topic has been actively picked up and replicated by many news and even analytical agencies, the range of assessments of which starts from the next, who knows what, “death of Russia” to optimism that it is our country that will be able to become the world leader of this new market. There is a lot of information, it is impossible to call it systematized, so it is worth trying to put it in order.
If hydrogen claims to replace all energy resources at once, then it will have to "take over" everything that today concerns the algorithm for using any fossil fuel. In order to use coal, gas and oil in one way or another, they first of all need to be extracted, and in the case of hydrogen, the first question is the technology of its production. After extraction, fossil fuel is subject to preliminary purification - the same procedure will be required in the production of hydrogen, it must also be as cleaned as possible from harmful impurities. Further, the fuel must be transported to the place of its use or further processing - this fully applies to hydrogen. Well, and the last point in the chain is the use of fuel for its intended purpose, combustion using one technology or another. As a matter of fact, it is for this reason that we are all ordered to experience enthusiasm and spiritual enthusiasm - after all, when fuel is burned, carbon dioxide is not formed, the only product of its combustion is water, pure as a baby's tear. We will easily and naturally avoid global warming, city streets will be cleared of smog, happy Greta Thunberg, relieved of worries and anxieties, will go to school again, flowers will bloom, butterflies will flutter on them, icebergs and ice fields in the Arctic will begin to grow again ocean, across the Gulf of Finland it will be possible to ski again in winter, and we will sing and laugh like children.
We apologize for moving away from the traditional storytelling of hydrogen energy and starting from the end. But the outstanding banker of our time assures that society first of all needs high-quality consumers - so we will “stay” as such for some time. When a quality consumer is asked where the electricity comes from, he confidently gives an impeccably accurate answer: "From the socket!" We discard all the details of the first three stages of using hydrogen - production, purification, transportation, we draw pictures of delightful happiness in our imaginations.There is a lot of hydrogen, it is available, all vehicles without exception ride on it, cascades of pools with warm and clean water have already been built near each power plant, thanks to which bananas bloom in Vorkuta, two pineapple harvests are harvested in Magadan, and on fences instead of sparrows already the turkeys are sitting. How else? Here it is, the cherished formula for burning hydrogen:
2Н2 + О2 --а 2Н2О
And this wonderful chemical reaction is accompanied by the release of a lot of heat. So let's imagine for a minute that we live in a world where every single hydrogen program has been implemented - the German, the American, the EU program and all the others, there are a lot of them now. Everything, everyone succeeded and managed, they threw their caps into the air - and there is no longer any oil, no gas, no coal with uranium in use, everywhere and everywhere only hydrogen: in power plants, in car tanks and even in stoves in our kitchens. How exactly hydrogen will be produced, all the nuances of the differences between hydrogen "green", "blue" and even "brown", we will consider next time.
Zeldovich mechanism and nitrogen oxides
The "main hydrogen formula" is completely accurate, but you will have to start with descending to our sinful Earth, the atmosphere of which does not at all consist of pure oxygen - it contains much less of it than nitrogen. The combustion temperature of hydrogen in an oxygen atmosphere can exceed 2,800 degrees, that is, a thousand degrees higher than the combustion temperature of methane, the main constituent of natural gas. The first question has already ripened - and from which such metals are the furnaces of hydrogen power plants made? Which of these alloys behave decently at, say, 2,500 degrees? This temperature is typical for aircraft and rocket engines, the composition of materials for which, of course, is known, but the price of such pleasure is also known. Okay, let's throw this annoying trifle aside - we have a lot of money, there is a dime a dozen heat-resistant metals on the Earth - we will ask if we’ll get used to it, we are out there and without money. But you can't cope with the chemistry of hydrogen combustion in atmospheric air - it's not about butterflies on icebergs, it's a much more severe science. And, like in many other branches of scientific knowledge, there are indisputable authorities in it, who became indisputable after everyone who wanted to reproach them did it and were convinced that nothing was working out - the arguments of the leading figures are unshakable like a rock. Everything that can be known about the formation of nitrogen oxides was said by Yakov Borisovich Zeldovich in the 40s of the last century - he still had free time to study chemistry, after the creation of the Special Committee on Atomic Energy he was busy to the limit until he developed a theory atomic and nuclear warheads. Chemical reactions that inevitably occur between nitrogen and oxygen in the presence of high temperatures:
N2 + O à NO + N and N + O2 à No + O
The mechanism of formation of nitrogen oxides is called the Zeldovich mechanism. A little later, the Fenimore mechanism was also discovered, named after the scientist who discovered it, but we do not need additional subtleties this time, we are already fine.
Endless stories about the harmfulness of carbon dioxide are useful, but they have buried under themselves the description of those "joy and happiness" that you and I are provided by the presence of nitrogen oxide in the air around us. “NO is odorless, but when inhaled, it can bind to hemoglobin in the blood, converting it into a form that cannot carry oxygen. Nitric oxide in high concentrations irritates the lungs and can cause serious health effects. It easily combines with water and dissolves in fat and can penetrate into the capillaries of the lungs, where it causes inflammation and asthmatic processes. A high concentration of nitrogen oxides first gives unpleasant sensations and a burning sensation, with a further increase it causes death.Lower concentrations can cause headaches, digestive problems, coughs, and lung problems. The patient may be disturbed by conjunctivitis, rhinitis and pharyngitis due to irritation of the mucous membranes, manifested by coughing, lacrimation and general malaise. At the next stage of poisoning, a wet cough with mucous or bloody sputum, shortness of breath, cyanosis, tachycardia and febrile fever appears. Feeling of fear, psychomotor agitation and convulsions arises. In the absence of qualified medical care, it leads to death."
Enough? No. It is the presence of nitrogen oxides in high concentration in the air that is the cause of acid rain, which we also like to talk about. Nitrogen oxides are several times more dangerous for humans than carbon dioxide, and a higher combustion temperature of hydrogen will inevitably lead to their more intensive formation. Hello, wonderful hydrogen world!
In practice, this means that at all power plants that will use the combustion of hydrogen, additional equipment will be required to extract pure oxygen from the atmospheric air. To the estimate for the construction of the power plants themselves, which is already pleasing to the eye because of the materials of the furnace equipment, N more investments will be added, and it cannot be ruled out that this will become a separate term - "N-investments". With some tension, it is possible that such equipment can be contrived to be installed on heavy trucks, railway locomotives and even sea and river vessels, but it will not work to equip cars with it - then cars will automatically begin to turn into trucks. Here is another, additional direction of the necessary development of technologies - the miniaturization of equipment for the separation of atmospheric air. We, qualified consumers, agree to either wait or accept the fact that nitrogen oxides in the city air will increase, and acid rain will fall more often. Of course, you can still try to experiment with the rate of hydrogen supply to the combustion chamber so that the temperature is below the threshold value, after which the Zeldovich mechanism is automatically activated. However, then the meaning of using hydrogen as a fuel becomes less obvious - the efficiency of the engine will be comparable to the efficiency of a conventional internal combustion engine using gasoline or diesel. As consumers to consumers - now the average price of a kilogram of hydrogen is about $ 8, which, to put it mildly, significantly exceeds the cost of traditional fuels.
Experimental data from Japan
If we are talking about energy companies living and working in the real world, and not in the fantasy world of European officials, then among them there are no people who want to throw power plant equipment into the dustbin of history and install new ones, made of expensive alloys with tungsten, molybdenum, titanium. Just in case, let us remind you that the goal of any company is profit for its shareholders, and not someone's dreams, and even expensive ones. Mitsubishi Hitachi Power Systems (MHPS) successfully tested a high-capacity gas turbine at one of its power plants a few years ago by feeding natural gas with 30% hydrogen into the combustion chamber. The temperature of the gases at the outlet is 1600 degrees, the equipment, although not without difficulties, withstood such a load. The efficiency was insignificant, but increased, but the amount of the generated carbon dioxide turned out to be lower by 10% at once, and the Japanese company did not fully disclose information about nitrogen oxides, limiting itself to the phrase “remained at an acceptable level”. MHPS recommendation - it is economically justified and environmentally beneficial to use a fuel mixture of 80% natural gas and 20% hydrogen.Also in Japan, in 2018, Kawasaki Heavy Industries and Obayashi conducted short-term tests of the turbine with 100% hydrogen supplied to the combustion chamber. There was no report on the economics of the experiment, but it is enough to know that the CHP plant in Kobe, owned by a consortium of these companies, runs on a 20% to 80% mixture of hydrogen and natural gas - that is, in accordance with the recommendations given by MHPS. Experiments with the addition of hydrogen to the fuel mixture for gas-fired CHP plants are going on, of course, not only in Japan, but we talked about the most optimistic results, which depend on national technical standards for equipment and materials from which it is produced.
These are, in accordance with the standards, the permissible proportion of hydrogen in natural gas today: Belgium, New Zealand, USA, Great Britain - 0.1%; Germany 10%, Netherlands 12%. Today, hydrogen dreams of completely abandoning the use of traditional fuels are losing to the harsh reality - a whole series of research and development work is needed, changes in national technical standards are needed, verification of the results obtained on experimental industrial equipment, and so on. Behind each term used in the previous phrase are invisibly questions about funding, about qualified personnel, about the required time - given the fact that no one can guarantee that all experiments and tests will be successful.
If Germany and the European Union really want to implement their "hydrogen programs", then these programs, in our opinion, should include schedules for R&D and subsequent tests, appropriate investments should be envisaged, but there should be no hard deadlines - in that case, unless the software development teams are headed by direct descendants of Michel Nostardamus, of course. And we are not talking about some abstract "financing in general", but about specific research institutes, research groups and their associations. However, these are not our concerns - if there are reserves of money in the budgets of the EU and in the budgets of individual states, let them spend as they see fit. In the meantime, if without the "hydrogen firebirds", then you can rely on the calculations of the IEA, the International Energy Agency: the creation of a large-scale European network of power plants, which would use a gas-hydrogen mixture in proportions of 80/20, will reduce carbon dioxide emissions by 7% or 60 million tons. In its calculations, the IEA relied on data obtained in Japan - for the simple reason that these data were "mined" in the normal mode for any new technology. And the text from a European official about 100% hydrogen, about the complete absence of carbon dioxide emissions and complete sclerosis with respect to nitrogen oxides is characterized simply and unpretentiously - populism.
Kilograms and cubic meters - feel the difference
Yes, since the word "kilogram" was accidentally printed in the text above, it is also necessary to draw the attention of qualified consumers to this. This word is used to demonstrate one more "enticement" on the part of unqualified fans of hydrogen energy: “The specific heat of combustion of 1 kilogram of methane is about 50 MJ (megajoules), and the specific heat of combustion of 1 kilogram of hydrogen is about 130 MJ. Do you see how much more profitable hydrogen is ?!"
We see, of course - we see that the kilogram is used as a unit. Take a look at your payment card, dear readers - is there a line “price of a kilogram of gas” there? Nothing of the kind - cubic meters, and that's it. A cubic meter of methane can be weighed, no problem - at normal atmospheric pressure and at 20 degrees Celsius, the measuring device will show 657 grams. But a cubic meter of hydrogen can also be weighed, unless a device is required more precisely, since a cubic meter of this gas weighs 89.9 grams. The same, but in other words - hydrogen weighs 7, 3 times lighter than methane.If you live in a house with a gas stove, then in order to get 130 MJ of heat, you will have to burn 3, 96 cubic meters of natural gas, and if by some miracle you found yourself in a house that was built by a European bureaucrat in 2050, then to obtain the same 130 MJ you will need 11, 11 cubic meters of hydrogen. As a qualified consumer, we can count it in money - this is the main task of this unknown creature. The retail price of gas in different regions is different, let's take the Moscow region - 6, 56 rubles per cubic meter. This means that 130 MJ of heat will cost 6, 56 * 4, 0 = 26, 24 rubles. Achievable hydrogen prices in Europe by 2025, according to the ACIL ALLEN Consulting research center for the European Union - $ 5.43 per kilogram. Calculate dollars to rubles to your liking - we do not know what it will be like on the day when this article comes across your eyes. Take, for example, some kind of "mid-ceiling" 1 dollar for 70 rubles, but we will not multiply - it's lazy, to be honest, you still get something from 350 to 400 rubles for the same 130 MJ of heat.
At the same time, in our payment systems - retail prices for you and me as end consumers, and in ACIL ALLEN calculated prices for hydrogen producers, so that the already insane price difference in reality will turn out to be even higher. Transport services, commercial margins - all this will ultimately be paid by the end consumer, in this case - clearly a finite number of times. All that can be said about this as a commentary is only: "Hello, wonderful hydrogen world!" Yes, we almost forgot: if pure hydrogen comes from a European gas stove in 2050, then what metal this stove and its burners will be made of - we have no idea, since the flame temperature will be at least 2,000 degrees. Think for yourself, but while you are thinking, mentally say goodbye to all your pots and pans, since their molten metal will drip all over the euro plate, you will be tortured to scrub. If the EU intends to abandon the gasification of its population, transferring the entire housing stock exclusively to electricity, the pots, of course, will survive, but what the price of electricity will be, in the wonderful plans for the final victory of hydrogen energy, the authors of the plans are modestly silent. Let us remind you that the cost of electricity at thermal power plants depends on the price of raw materials by 90% - you can draw your own conclusions, and at the same time you will get an objective assessment of the prospects for the life of ordinary people in "hydrogen" Europe after 2050.
The density of hydrogen, along with its chemical and physical properties, is the next block of problems facing the development of hydrogen energy. Moreover, the bloc is strong - it was he who, in many respects, became the reason that the interest in this topic, which first intensified in Europe in 1974, did not go beyond the semi-academic level. It happened precisely in 1974, that is, during that very world oil crisis, from the memories of which to this day those who survived it have their hair on end. Recall that the current crisis, in 2020, was caused by a drop in demand and the resulting drop in prices by half, and, as it turns out now, the drop turned out to be so significant for 3-4 months. And in 1974, the price of oil in Europe increased 3-4 times, but it never went down, so in Europe they were ready for any technology they wanted, just to get rid of dependence on oil imports. Among other options, hydrogen energy was also considered, but then, apart from the consideration itself, no consequences took place. Hydrogen, as you know, is the most widespread chemical element in the Universe, it is from it that 92% of its substance consists, but on planet Earth in its pure form it simply does not exist - it is so chemically active that it interacts with any other with incredible ease and speed. chemical substance.Therefore, the conditions for storing this gas are extremely high - hydrogen strives to interact with all the materials from which the containers for its storage are made. The situation is similar, of course, with any pipelines that make up the gas transmission and gas distribution systems of Europe. Dreams that already existing pipes can be used for the transportation and distribution of hydrogen have no scientific and technical justification for themselves - losses due to leaks will deprive any project of this kind from economic sense, the inner surface of the pipes will inevitably degrade up to a complete exit out of service. By the way, Gazprom has already carried out relevant studies, the result is not secret: with the exception of the Northern and Turkish streams, all other pipelines will function properly if no more than 30% hydrogen is added to natural gas, the newest "sea" pipes will withstand up to 70%. There is no information whether such inspections of their gas pipelines were carried out in Europe, and Gazprom is quite satisfied with the result, since the company's specialists rely on data received from Japan. The 20% hydrogen content in the fuel mixture of gas power plants is a level that will not require trillions of investments in re-equipment of all equipment and a level that gives a very noticeable result in reducing carbon dioxide emissions with an "acceptable content of nitrogen oxides emissions."
Gasoline or hydrogen?
Before moving on to the story about new technologies for storing hydrogen, we, qualified consumers, cannot but touch upon hydrogen vehicles, which have already appeared, the number of which is gradually growing. To begin with, let's estimate how much heat a passenger car owner can get by "squeezing dry" a standard 50-liter gas tank. The specific heat of combustion of a kilogram of gasoline is 43.6 MJ, the specific heat of combustion of a kilogram of diesel fuel is 42.7 MJ, so we can easily average up to 43.0 MJ. The density of gasoline is 710 grams per liter, the density of diesel fuel (summer) is 850 grams per liter, the average is 780 grams, that is, in 50-liter tanks of passenger cars, on average, 1,677 MJ are "hidden", which provide us with 500-600 km of run in urban conditions. Well, and 50 liters of hydrogen at normal atmospheric pressure is sorry, 5 grams and, accordingly, 0.65 MJ, which is 2,500 (two thousand and five hundred, no typos) times less than in a tank with traditional fuel. What will be the mileage or, more precisely, "crawled", in this case - we suggest calculating it yourself, but more than 200 meters will not work, even without taking into account the excessive consumption of fuel at the start. Therefore, no options - there should be more hydrogen in the tank, and the most obvious way to achieve this is to increase the pressure. We increase the pressure - the requirements for the material from which such a tank is made also increase. The requirements are twofold, since not only strength is needed to withstand pressure, but also the ability to withstand the reactivity of hydrogen, the ability to avoid leaks. In the periodic table, hydrogen has honorary number 1, that is, it is the smallest atom also in size, therefore, at high pressure, this gas increases the "desire to escape" through the smallest defects on the inner surface of the tank.
In Russia, a standard for marking cylinders with hydrogen in them under a pressure of 200 atmospheres has been adopted:
Dark green, the inscription is in red, but 200 atmospheres is too little, at this pressure, a 56.3 liter cylinder is required to store 1 kg of hydrogen. The next step in the development of technologies for storing gaseous hydrogen - cylinders made of titanium, they already withstand 400 atmospheres, but the developers did not stop there.
Since Japan is the world leader in lightweight hydrogen cars, let's take Toyota's hydrogen tank as an example:
All figures are clearly visible - the tank is designed for 700 atmospheres. The material is composite materials, since they are chemically extremely stable, they absolutely do not react to the presence of hydrogen, the strength of the tank is calculated and provided up to a direct hit of small arms bullets, and if the tank cannot cope with the internal pressure, it "opens" along the entire housing, providing an instantaneous release of the entire volume of hydrogen. This is done in order to prevent its high concentration in the air - hydrogen is light, with a sharp decrease in pressure, it rushes upward, away from the ground and from people. The reason is probably known to everyone - a mixture of hydrogen with oxygen is not only fire hazardous, but even explosive if the concentration of hydrogen is high. The operating experience already accumulated by the Japanese automaker did not reveal an accident rate, so the problems, if any, are purely psychological - how comfortable the driver and passengers of the car feel, knowing that somewhere near them there is a container under pressure of 700 atmospheres, which contains an explosive substance. But even this does not provide indicators exceeding those of traditional liquid motor fuel: even at 700 atmospheres, the energy density of hydrogen is 4.4 MJ per 1 liter, and a liter of gasoline is 31.6 MJ per 1 liter. Once again, slowly: 700 atmospheres, high-tech material of the tank, but the result is 7, 7 times lower than that of the most traditional gasoline. Yes, this really reduces the formation of carbon dioxide, but due to the increase in combustion temperature, the formation of nitrogen oxides increases. At the same time, it is worth remembering that environmental requirements for gasoline and diesel fuel are increasing, the Euro-5 standard has already been introduced, but chemists-technologists are successfully coping with these requirements - for example, in July 2020 Gazprom Neft completed modernization under Euro -5 "Moscow Refinery. This, of course, is not a cheap pleasure, but this investment is several times less than what would be required for the mass introduction of hydrogen-powered passenger cars. Based on the foregoing, it is enough to simply imagine what is the transportation of pure gaseous hydrogen in industrial volumes, what money is poured into the equipment of a hydrogen filling station for cars - pressure, reactivity of hydrogen, fire hazard in case of leaks with multiple higher risks of leaks.
Hydrogen can be liquid, but who gets it easy?
And, perhaps, the last "consumer" in relation to hydrogen, which also, in general, "hangs in the air": if everything is so complicated and expensive when storing and transporting hydrogen as a gas, then is it possible to do exactly the same with it? What about natural gas, if there is no possibility to transport it to consumers by means of pipelines - to turn it into liquid? There is also such a technology, only the temperature at which hydrogen becomes liquid is "minus" 252, 76 degrees Celsius at normal pressure. Let us recall that natural gas becomes liquid at minus 161 degrees, but this is more than enough to rightfully consider the LNG industry the most high-tech of everything related to the natural gas industry. In the case of hydrogen, it is required to reach temperatures 90 degrees lower than in the case of LNG, but the bottom line is not impressive - at normal pressure, the density of liquid hydrogen is 77 kilograms per cubic meter. For comparison, the density of LNG under the same conditions is 7, 8 times higher, about 600 kg per cubic meter. So the liquefaction of hydrogen at a multiple of higher costs for its production than for the production of LNG is aggravated by the need to maintain high pressure in containers with liquid hydrogen - otherwise, for its transportation and storage, containers of a huge volume will be required, in which, we recall, it is necessary to maintain the cryogenic temperature … For storage of liquid hydrogen, high-quality steel is used, the tanks are equipped with filters for fine purification of liquid hydrogen and samplers of a special design, and, of course, a highly efficient thermal insulation system.If, in the case of large-capacity tanks, evaporation, which cannot be avoided, can still be tolerated, then with tanks for cars, any evaporation losses hit the car owner's wallet directly, so the requirements here are even higher. Ahead of the whole planet is BMW, whose specialists have developed a 74-liter tank for liquid hydrogen for BMW Hydrogen 7, whose evaporation losses are only 1.5% per day. In absolute figures - 1, 1 liter of liquid hydrogen per day from a full tank disappear without a trace.
The conclusions, in our opinion, are quite obvious.
The use of pure hydrogen instead of a mixture of natural gas and hydrogen in power plants is the way to multibillion-dollar investments in the re-equipment of existing power plants and high estimates for the construction of new ones. The cost is also growing in connection with the need to separate the atmospheric air in order to ensure the supply of pure oxygen to the furnace of the power plant to prevent the growth of emissions of nitrogen oxides, which is more dangerous for human health than carbon dioxide.
Burning hydrogen in vehicle engines will reduce the production of carbon dioxide but increase the production of nitrogen oxides. Deliveries of pure hydrogen through the existing gas pipelines are impossible; they will require the construction of a completely new "hydrogen transport" and "hydrogen distribution" systems. The storage and use of hydrogen in a gaseous state requires the production of tanks of various capacities from composite materials - both in the case of power plants and in the case of cylinders for auto or any other transport. Storing and using hydrogen in liquid form requires exactly the same, but subject to operation in the cryogenic temperature range.
For brevity's sake, at the end of each phrase there is no single logical possible continuation: "This will require a huge investment."
The use of hydrogen in everyday life, in kitchens, is impossible due to the physical and chemical characteristics of the process of its combustion in atmospheric air, therefore, the rejection of natural gas will require a transition to 100% use of electricity in all available housing stock.
Why, then, did the EU and its individual countries decide to make the transition to hydrogen energy while completely eliminating fossil fuels? The question is so interesting that it deserves a separate article.
But it is also not necessary to consider that the "hydrogen transition" from a technical point of view is a complete utopia, since scientists, designers and engineers are not idle, great efforts are being made to make the use of hydrogen economically feasible. The transition from the Stone Age to the Bronze Age did not occur due to the fact that the stones ran out, horse-drawn transport became a thing of the past, giving way to cars not because of the lack of oats - the reason in both cases was a technological breakthrough.
But what a hydrogen fuel cell is, what relation nuclear power can have to hydrogen energy is also not this time.