Shulou(Shulou.com)11/24 Report--

The original title: "will you like the ammonia energy in the face of the wind?" "

Ammonia, the molecular formula is NH3,0.771 kg / m ³, at room temperature is a colorless gas, volatile, flammable, its highly recognizable strong pungent smell, even those who do not know its name also have more or less experience-speaking here, I am afraid that many readers have an indescribable "stench" in their noses.

Ammonia is very important to the operation of human society and is one of the most productive inorganic compounds in the world. The annual output of synthetic ammonia in 2021 is about 180 million tons [1], of which about 80% is used in chemical fertilizer production, and the rest is mainly used in industrial refrigerants and the production of a variety of industrial raw materials [2].

Although flammable, ammonia has not been widely regarded as a possible form of energy for a long time, and the greatest relationship with energy is mainly as a carrier of hydrogen energy.

However, ammonia itself has the potential to be used as energy, and at a time when the demand for environmental protection continues to rise, it has also received attention from the energy industry. Although not as important as hydrogen energy in the future planning of "carbon neutralization" and "green economy", some participants in the energy industry are still considering going beyond the step of reducing ammonia to hydrogen and directly trying to use ammonia as energy on a large scale. Some people even call it "hydrogen 2.0".

So what prompted the energy industry to shift some of its attention from hydrogen to ammonia? What are the advantages of ammonia as a potential green energy? What are the difficulties on the way to scale? This article will answer one by one.

Good energy, bad energy hydrogen is good energy, maybe even the cleanest energy. Its preparation principle is very simple, and the process also has mature large-scale production technology (AEC, alkaline electrolysis), and the rapidly developing next generation technology (PEM, proton exchange membrane electrolysis; SOEC, solid oxide electrolysis), which can be perfectly combined with Fengguang power plant to solve a series of problems of efficient utilization of green electricity, such as absorption and energy storage. It is not surprising why hydrogen energy occupies such a position in the country's future energy planning.

Source of information: public data collation l fruit shell hard technology tabulation but hydrogen is also a bad energy, so bad that the current industry faces far more difficulties than the benefits of its application. First of all, hydrogen is a substance that is extremely difficult to store, with a critical temperature of-239.9 ℃ (by contrast, the critical temperature of oxygen is-118.95 ℃). Maintaining this low temperature means high energy consumption, so that hydrogen can only be transported in a relatively inefficient way such as high-pressure gas cylinders, and the transportation cost remains high. At the same time, as the lightest element in nature, hydrogen has extremely strong molecular penetration, is easy to leak, and has a certain corrosiveness to metal materials. it puts forward high requirements for the material selection of hydrogen storage tanks and transportation pipes (especially the position of joints), and materials with such excellent performance will not be cheap, how to efficiently medium-and long-term hydrogen storage is a long-term problem for the industry. Hydrogen is also a very dangerous substance, extremely flammable and explosive, and this is easy to leak, resulting in the need to maintain safety standards at an extremely high level, which is an expense.

Critical temperature: a specific temperature of each substance, that is, the maximum temperature at which the substance occurs in liquid form. Above this temperature, no matter how much the pressure is increased, the gaseous matter will not liquefy. In other words, the lower the critical temperature, the harder it is to liquefy and the more difficult it is to store.

Source of information: open data collation l fruit shell hard science and technology tabulation except storage and transportation problems, although the energy density per unit mass of hydrogen energy is good (as high as 142MJ / kg, standard coal is 20.8MJ / kg), but the energy density per unit volume is very bad, and as a very low density material, this is a more important indicator for hydrogen. The energy density of liquid hydrogen is about 2.4 kilowatt hours per liter (the energy density of gasoline is 9 kilowatt hours per liter), which is already the most ideal data, considering that hydrogen cannot be transported in liquid form in most cases. it further reduces its economic benefits [3].

Generally speaking, the basic storage and transportation of hydrogen energy has not been solved at this stage, and the medium-and long-term storage is even more difficult. Some current technical routes, including methanol and metal adsorption, either do not have large-scale capacity, or are extremely immature, which do not meet the long-term planning of hydrogen energy. This determines that no matter whether the hydrogen energy industry can solve the problem of production cost or not, hydrogen energy does not have the basic premise of large-scale promotion-- without low-cost reliable storage and transportation technology, large-scale hydrogen energy-related infrastructure projects are of little significance, at least not economical.

This has prompted the industry to broaden its horizons and look for a substance similar to hydrogen, which has the advantages of simple preparation process, low carbon emissions, acceptable efficiency, clean by-products, and easy storage and transportation.

So the energy industry turned to ammonia.

The most basic question of many benefits: does ammonia have the potential as a green energy? The answer is yes.

First of all, from the oxidation reaction formula, under appropriate reaction conditions, the products of ammonia combustion can only have nitrogen and water, which is as clean as hydrogen, and has the potential to serve as a green energy "carbon neutralization".

The performance of ammonia as a fuel is also acceptable. Although the energy density of ammonia per unit mass is far lower than that of hydrogen, its energy density per unit volume is 3.5 kilowatt hours per liter, which is nearly 50% higher than that of 2.4 kilowatt hours of liquid hydrogen. Moreover, the octane number of ammonia fuel is higher, and the explosion resistance is better, which can increase the compression ratio of the engine to increase the output power, so that the thermal efficiency of the engine is increased to more than 50%, which is twice that of ordinary fuel vehicles [2].

The biggest advantage of synthetic ammonia is that it is much easier to store than hydrogen. Ammonia can be liquefied at-33 ℃ or 9 atmospheric pressure at room temperature, and the requirement for storage container is not high. At the same time, as one of the largest compounds prepared by human beings, the storage and transportation technology of ammonia is very mature, such as pipelines, railways, barges, ships and road trailers, and the demand for large-scale construction of infrastructure is not strong. These are the core reasons why ammonia is regarded as the key technology of hydrogen storage. Generally speaking, compared with hydrogen, large-scale application of ammonia does not have much trouble at least in storage and transportation.

The production of ammonia can only rely on water, air and electricity, which means that in theory, there is a preparation method that is as clean as hydrogen, and "green ammonia" with basically no carbon emissions is possible. In the ideal, the simplest green ammonia production mode is to integrate hydrogen production stations, synthetic ammonia plants and renewable energy plants to produce hydrogen through landscape or other forms of green electricity electrolysis of water, and then use the green hydrogen produced in this process to further combine with nitrogen in the air, and continue to use green electricity to produce ammonia. In this way, it is expected to achieve the whole process of non-emission ammonia production, and can also solve the problem of new energy consumption. However, green ammonia is only a concept at this stage, and it still faces many difficulties, which will be discussed in detail below.

Schematic diagram of green ammonia production photo source: [3] there is no big difference between the use of ammonia energy and hydrogen energy. It can be fuel cells, alternatives to traditional fossil fuels in industrial production, power generation, ships, vehicles (Belgium tried ammonia buses as early as 1940), and so on.

Ideal ammonia cycle photo source: [4] at present, the shipbuilding industry is showing the greatest interest in ammonia energy. For example, Norwegian ship design company Breeze Ship Design recently announced that it will design ammonia-powered tankers based on existing 110000 dwt Aframax ships as part of the Norwegian Green Shipping Program (GSP) [5]. In March 2021, Korea Classification Society (KR) awarded the "8000-ton ammonia fuel refueling ship" developed by Korea Shipbuilding Technology Co., Ltd. (AiP), which is South Korea's first 8000-ton ammonia fuel refueling ship with marine light diesel oil (MGO) and ammonia as dual fuel [6]. In Japan, there are also five organizations, including Japan Shipping Co., Ltd., Japan engine Co., Ltd. (Japan Engine Corporation) and IHI Prime mover Co., Ltd., to jointly carry out the development of ships equipped with Japanese ammonia fuel engines [7].

Of course, China is not to be outdone. China's first ammonia fuel 7000 car carrier (PCTC), independently developed and designed by Shanghai Shipbuilding Research and Design Institute of China Shipbuilding Group Co., Ltd., has been officially approved in principle (AiP) certificate issued by DNV.

On the other hand, limited by technology and production, it is difficult to use pure ammonia on a rapid scale, but mixing ammonia with other fuels such as coal and hydrogen is worth trying, and the effect is more immediate. For example, on January 24 this year, the National Energy Group announced a mixed ammonia combustion technology for coal-fired boilers. This technology achieves a 35% proportion of mixed ammonia combustion heat in a 40 MW coal-fired boiler, and the use of coal will inevitably produce carbon emissions, but the emission intensity can be greatly reduced after mixing ammonia, and the energy output can be more guaranteed. It is undoubtedly a feasible "carbon neutralization" scheme [9].

Of course, although ammonia is as good as a thousand, there are also many technical problems that need to be solved in order to really apply it on a large scale.

Many difficulties of ammonia as a large-scale energy must be solved first, that is, how to produce "green ammonia". The current ammonia synthesis model is unlikely to support the use of ammonia as a source of energy and does not match green electricity.

At present, the Hubble-Bosch process (Haber-Bosch process) used in ammonia synthesis industry is to produce ammonia by mixing nitrogen with hydrogen at 450 ℃ ~ 500 ℃ at 200 standard atmospheric pressure. This approach consumes extremely high energy consumption and consumes a lot of fossil fuels, which is not in line with the concept of "carbon neutralization". The hydrogen used in the production process is processed from natural gas and coal, which involves two major directions: the gasification industry route and the natural gas reforming process, as well as a large amount of carbon emissions.

Taking our country as an example, due to the influence of energy structure, hydrogen for ammonia synthesis is mainly prepared by coal gasification. The data show that China consumes about 1.53 tons of standard coal per ton of synthetic ammonia, resulting in carbon emissions of about 5.94 tons, of which the technological process contributes 4.71 tons of carbon emissions and external energy consumption indirect emissions of 1.23 tons; even for natural gas routes with lower overseas emissions, the total emission is about 3.10 tons CO2/ tons of ammonia [10]. Some previous data show that the carbon emissions generated by the synthetic ammonia industry can reach about 1.0 per cent of global greenhouse gas emissions (or about 1.4 per cent of global CO 2 emissions), which is staggering; if the emissions data from the extraction of fossil fuels are calculated, it can be further increased [4].

At this stage, the synthetic ammonia industry chain l photo source: [10] in addition, the equipment used in the Hubble-Bosch method has relatively high requirements for the quality of input energy, the ability to cope with volatility is not strong, and the equipment can not be started or stopped at will. This is not in line with the basic characteristics of high volatility of Fengguang Power, resulting in poor compatibility between the two, but also caused great difficulties for Green Power to connect to the production of synthetic ammonia.

To sum up, the current synthetic ammonia process is unlikely to support the ammonia energy industry, so it is very important to find a new production plan.

At present, the synthetic ammonia industry is trying to develop new preparation processes, such as nitrogenase synthesis of ammonia, photocatalytic synthesis of ammonia, electrocatalytic synthesis of ammonia, plasma synthesis of ammonia, circulating process of ammonia synthesis and supercritical ammonia synthesis and so on. Among them, nitrogenase synthesis of ammonia, photocatalytic synthesis of ammonia and electrocatalytic synthesis of ammonia have a certain degree of concern [11].

Nitrogenase synthesis of ammonia: this is a biotechnology route, through the use of nitrogen-fixing microorganisms to reduce nitrogen in the atmosphere to ammonia, can be carried out at room temperature and pressure, the technological maturity is very low.

Photocatalytic synthesis of ammonia: the use of photocatalyst to initiate photochemical reaction to convert solar energy into chemical energy to produce ammonia. This technology can synthesize ammonia at room temperature and pressure with almost no carbon emissions. The conversion process is very inefficient, and the extremely high chemical stability of nitrogen molecules further limits the production capacity of this process.

Electrocatalytic ammonia synthesis: nitrogen is reduced to ammonia by electrochemical reaction directly or indirectly, and the hydrogen in the reaction is directly produced by water electrolysis, which can completely bypass the traditional Hubble-Bosch method, and it is also a production process with almost no additional emissions, but it also has the defect of low efficiency.

Schematic diagram of electrocatalytic nitrogen reduction reaction source: [4] of course, as with most new technologies, these new generation of ammonia production processes are too immature and have the problems of poor efficiency, unstable reaction process and unclear economy. it needs to be further verified and improved.

Another way is to combine ammonia production with carbon sequestration technology to reduce carbon emissions in the production process. If named after hydrogen, this kind of ammonia can be called "blue ammonia". However, adding additional equipment to the production line will undoubtedly be reflected in the cost, which may be difficult to accept for the low profit margin of synthetic ammonia, and it does not really solve the problem, so it can only be regarded as an excessive solution.

The toxicity of ammonia also needs to be solved properly, otherwise, as a strong pollutant, its environmental risk will limit its large-scale application. At present, some new storage methods are expected to solve this problem, such as in porous metal ammonia complexes (such as hexaammonium magnesium chloride Mg (NH3) 6Cl2). In the metal ammonia complex, the adsorption and desorption of ammonia is completely reversible and will only be released from the porous media when heated at 350 ℃ or higher, which will greatly reduce the risk of environmental pollution caused by leakage [2]. However, the additional cost of this process is not clear, and its economics itself needs to be further examined.

It is also important to find ways to ensure the stable combustion of ammonia, and more attention should be paid to the progress of related technologies. As mentioned above, the by-products of ammonia energy under appropriate reaction conditions are only nitrogen and water, which are very clean; if the reaction conditions are not good, the situation will be completely different: at this time, ammonia will produce nitrogen oxides (NOX), which is truly toxic waste gas.

In practical application, some defects of ammonia as a source of energy will also lead to the production of toxic waste gas. Its ignition point is high (651 degrees Celsius), the combustion speed is relatively slow, and the calorific value (calorific value) is slightly lower, so it is difficult to realize the formation of nitrogen-free compounds in the whole process. If we want to use ammonia energy on a large scale, it is necessary to build supporting waste gas recovery and treatment links to avoid the formation of other forms of pollutants.

Japan has made good progress in this aspect. The 40,000 kilowatt 100% pure ammonia fuel generator currently developed by Mitsubishi heavy Industry has been able to control nitrogen oxides below 100ppm (1/1000000) or even 10ppm, and has good commercial potential [11]. However, the power of this prototype is still too small and relatively easy to control, so it cannot be asserted that its performance after amplification is also excellent.

Finally, the current research on ammonia as a kind of energy is not deep enough. The key parameters such as combustion speed, flame structure, ignition delay and pollutant formation are still not perfect, and the reaction mechanism of ammonia combustion is not completely clear. these deficiencies also constitute an obstacle in the process of using ammonia as energy [2]. In the future, further in-depth research in the academic circle is also indispensable.

Some problems in addition to the specific technical difficulties mentioned in the previous section, ammonia as a fuel also faces some other practical problems.

Many people may find that from the beginning to the end of this article, there is no mention of the economy of ammonia as an energy source. This is mainly because there is no economy for ammonia energy at this stage.

First of all, the price has no reference value (and the ton price is already more expensive than crude oil). " The current ton price of synthetic ammonia is based entirely on the "current" production process and the relationship between supply and demand, and as we have mentioned above, the Hubble-Bosch process will produce amazing carbon emissions and cannot be used for the large-scale preparation of green ammonia in the future. however, the new process is still a long way from maturity, we are not very clear about the price level of green ammonia. This leads to a risk that can not be ignored, the risk of commercialization.

This is not alarmist talk, and it is very common to be unable to scale up for a variety of reasons. Above we have described the great difficulties encountered in the large-scale process of hydrogen energy, the reason why the development of ammonia energy itself is a very typical case. Another example is a group of III-V solar cells led by gallium arsenide solar cells. Because of its excellent photoelectric conversion efficiency and other properties, this material is widely used in space equipment (space stations, satellites, etc.) and military UAV, which are very insensitive to cost. It is not that the photovoltaic industry has not tried to scale it, but the process of civilian use of this material has stalled because it cannot solve the cost problem of gallium arsenide in any way. On the other hand, the attempt to reduce the cost of other adjusting components from the material level is also difficult for various reasons, especially the lack of the ability to compete with traditional silicon batteries in efficiency.

Commercialization itself is not an inevitable commitment. Even ammonia, which is already familiar and tested in industrial production, needs to reconsider its economic value after changing its usage and field.

Secondly, the current synthetic ammonia is a typical heavy asset industry, with huge early investment and long investment cycle, even if the green ammonia process can be put into production on a large scale, it is unlikely to have a fundamental change, which brings some difficulties to the access of social capital. Supporting green hydrogen plants, storage and transportation facilities, power stations and other costly projects can not be solved independently by social capital. At the same time, if the synthetic ammonia industry wants to transform and the related equipment is upgraded, R & D expenditure will also be huge. It is also a problem that these funds are raised only by the industry itself, and the attractiveness of the traditional chemical industry to capital has always been worrying. If there is no money, there can be no transformation, and if there is no transformation, there will be no financing. This dilemma has been clearly observed in the transformation process of traditional energy enterprises in the environment of ESG.

In other words, if ammonia energy is to achieve great development, support from the national top-level design and supporting policies is essential. Building a friendly investment environment is essential to industrial development and upgrading, as well as the willingness to improve capital access.

References:

[1] IFA: public summary medium-term fertilizer outlook 2021-2025. 2021.08

Chen Danan, Li Jun, Huang Hongyu, Chen Ying, he Zhaohong, Deng Lisheng. Research progress of ammonia combustion and reaction mechanism [J]. Chemical Bulletin, 2020, 83 (6): 508,515.

[3] Salmon, N., & Ba ñ ares-Alc á ntara, R. (2021). Green ammonia as a spatial energy vector: a review. Sustainable Energy & Fuels, 5 (11), 2814-2839.

[4] MacFarlane, D. R., Cherepanov, P. V., Choi, J., Suryanto, B. H., Hodgetts, R. Y., Bakker, J. M.,... & Simonov, A.N. (2020). A roadmap to the ammonia economy. Joule, 4 (6), 1186-1205.

International Shipbuilding Network: Breeze, a Norwegian ship design company, is supported by the government to design large oil tankers powered by ammonia fuel. 202203.09 https://mp.weixin.qq.com/ s/_6yVkE5fHpynrlDx3hLZlA

[6] International Marine Engineering Network: the 8 kiloton ammonia fuel refueling ship has been certified in principle by the Classification Society. 2021.04.02 https://mp.weixin.qq.com/ s / J9Kk7aJjZs4zs56xaABcEA

[7] AIpatent: Japanese enterprises will jointly develop "Japanese" ammonia fuel carriers, from research and development to commercialization 2021.11.15 https://mp.weixin.qq.com/ s / QXccGQyPFZn4UOjsmL1nKg

China Shipping Network: China's first ammonia fuel-powered ship has been internationally recognized. 2022.03.26 https://mp.weixin.qq.com/ s / HEyl1DVZchQjVEzDP8K3oQ

Xinhuanet: China has successfully developed mixed ammonia combustion technology for coal-fired boilers. Science and Technology Daily. 2022.01.26 http://www.news.cn/ science / 2022-01 Universe 26 / c_1310440952.htm

[10] League of Nations Securities: green hydrogen-the wind is hanging in the sails, parity is in sight. 2021.06.07

[11] Yuan Su: ammonia energy: the new energy tuyere in 2022? . Chief Energy View of Energy Review. 2022.02.21 http://www.escn.com.cn/ news / show-1344856.html

This article comes from the official account of Wechat: fruit Shell hard Technology (ID:guokr233), author: Chen Julei, Editor: Liu Dongyu

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.