"Hydrogen" takes "hydrogen" transport to help the development of hydrogen metallurgy

Hydrogen has become the main way for steel enterprises around the world to reduce carbon emissions. In order to achieve the goal of carbon peak and carbon neutrality, major iron and steel enterprises around the world are widely carrying out hydrogen reduction process research and pilot scale, and exploring the carbon reduction process of hydrogen metallurgy to traditional blast furnace. The application of hydrogen metallurgy process is inseparable from the production, storage, transportation and application of hydrogen.

Among them, the economical and large-scale production of hydrogen is the key link to realize the scale application of hydrogen in hydrogen metallurgy, and the storage and transportation is the key bridge connecting the hydrogen production end and the demand end. Next, the author starts from the production and storage and transportation of hydrogen, and introduces the current international core technology and application status of hydrogen metallurgy technology.

Hydrogen production process path and application status

The core of hydrogen metallurgy is the direct process of hydrogen reducing iron. The hydrogen production methods that are being explored and applied by steel enterprises mainly include the following types.

● electrolysis of water to produce hydrogen

In the electrolytic cell composed of electrode, electrolyte and diaphragm, the current is applied in the aqueous electrolyte solution. After hydroelectrolysis, hydrogen is produced at the cathode and oxygen is produced at the anode. Electrolysis of water for hydrogen production consumes large power consumption and high cost. At present, alkaline electrolysis water hydrogen (ALK), anion exchange membrane electrolysis water hydrogen (AEM), proton exchange membrane electrolysis water hydrogen (PEM), solid oxide electrolysis water hydrogen (SOEC) are the mainstream electrolytic hydrogen production processes in the world. Among them, alkaline electrolysis of water hydrogen production technology is the most mature, has been able to achieve large-scale hydrogen production application. PEM hydrogen production covers a smaller area and is more compatible with renewable energy. The main characteristics of SOEC hydrogen production are high working temperature, high efficiency, replacing liquid water with steam, and can operate in reverse to act as a fuel cell.

● Fossil fuels reforming for hydrogen production

Fossil fuels mainly refer to natural gas, oil and coal, shale gas and combustible ice, mainly of methane. Methane steam reforming hydrogen production is the most used hydrogen production technology. At high temperature and high pressure, methane reacts with water vapor to produce a syngas containing hydrogen and carbon monoxide, and then the hydrogen is purified. This method produces large amounts of hydrogen, but it produces greenhouse gases such as carbon dioxide.

Hydrogen production from ● biomass

Biomass hydrogen production refers to the hydrogen production by gasification and microbial catalytic dehydrogenation method, which is a general term for the process of molecular hydrogen production in the physiological metabolism process. This method utilizes renewable biological resources, but the technology is still immature, with low yield and high cost.

● New hydrogen production method

The new hydrogen production methods include photochemical hydrogen production, thermochemical hydrogen production, solar photocatalytic decomposition of water hydrogen production and other technologies. These methods use clean energy sources such as solar energy, but they are still in the experimental and development stages, and have not yet met the requirements for industrial-scale hydrogen production.

At present, the main way of hydrogen production in China is hydrogen production from fossil fuels, which has low cost and large output. In order to achieve low carbon, clean, efficient hydrogen production, iron and steel enterprises are exploring the renewable energy electrolysis water hydrogen production technology, the technology using clean energy such as wind energy, solar energy through electrolysis water decomposition into hydrogen and oxygen, hydrogen production process without carbon dioxide emissions, also does not consume fossil energy, so is a green hydrogen production mode, the hydrogen is also known as "green hydrogen".

The technology of water electrolysis from renewable energy also faces some challenges and difficulties, such as electrolysis efficiency, electrolysis equipment, power supply, hydrogen storage and transportation and other aspects need to be further improved and improved. According to the International Energy Agency, the Middle East, Africa, China, Australia and South America are the most promising places to become concentrated green hydrogen production bases. These places are rich in renewable energy and convenient transportation conditions.

The cost of hydrogen production by water electrolysis generally includes equipment cost, raw material cost (water), energy cost (electricity) and other operating costs. Among them, the energy cost, namely the power cost, accounts for the largest proportion, generally 40%~60%. The power cost is mainly affected by the energy conversion efficiency (i. e., electrolytic hydrogen production efficiency) factors.

According to the International Renewable Energy Agency (IRENA) in 2020, when the electricity price drops to $20 / megawatt hour (0.13 yuan / KWH), the cost of hydrogen production drops significantly, and the decline is significantly greater than the cost reduction caused by the reduction of electrolytic cell equipment cost, that is, the reduction of equipment cost can not make up for the impact of high electricity price. In China, only when the cost of hydrogen production is reduced to less than 20 yuan / kg, compared with fossil fuel hydrogen production, electrolytic water for hydrogen production has a certain competitive advantage. At this time, the electricity price of renewable energy needs to be reduced to less than 0.3 yuan / KWH.

The EU aims to supply 20 million tons of green hydrogen by 2030, of which 10 million tons will be produced in the EU and 10 million tons are imported. To that end, Europe will need 100 gigawatts of electrolytic cell capacity for 10 million tons to meet its hydrogen production needs by 2030.

By the end of July 2022, the cost of hydrogen production by alkaline water electrolysis in Qatar was $2.59 / kg, Saudi Arabia $3.20 / kg, Oman $3.55 / kg and the United Arab Emirates $5.14 / kg. The cost of proton exchange membrane water electrolysis (PEM) is usually about $1 / kg higher than that of alkaline water electrolysis. Blue hydrogen, produced jointly by steam methane reforming (SMR) and carbon capture and storage (CCS) costs about $7 / kg in the Middle East. Based on available capacity in the Middle East and North Africa, green hydrogen can cost less than $1 / kg by 2050.

Hydrogen storage and transportation mode and cost comparison

Hydrogen storage and transportation cost currently accounts for about 30% of the terminal hydrogen price, which is one of the restricting factors for the large-scale application of hydrogen in the economical, efficient and safe storage and transportation technology.

According to the transportation form of hydrogen, it can be divided into gaseous, liquid and solid transportation. From the means of transport, can be transported through the pipeline, ship or truck 3 kinds of carrier. Long-distance transportation is mainly through the new or modified submarine hydrogen transmission pipelines for large-scale hydrogen transportation, which is more economical than shipping. In the absence of pipeline, it is mainly stored in the form of liquid hydrogen and ammonia and used for long-distance transportation by ship. In September 2023, South Korea Pohang cooperated with American ammonia production company CF Industrial Holdings to produce blue ammonia, which is also used by ammonia to transport green hydrogen to South Korea.

In terms of economy, the cost of transporting hydrogen is related to the demand for hydrogen, and the transportation volume and distance determine the way of hydrogen storage and transportation.

Which mode of transportation is adopted is related to the transportation distance, transportation scale, hydrogen application scenarios, etc., which requires the design and economic measurement of the whole process to be done. From the perspective of transportation distance alone, the cost of hydrogen transportation in pipeline transportation is the lowest, within 500 km, and the cost of hydrogen transportation by long-tube trailer is lower than that of low temperature liquid hydrogen transportation; over 500 km, the transportation of low temperature liquid hydrogen has a more cost advantage. At present, the hydrogen energy industry is still in the early stage of development. Combined with the actual hydrogen transportation volume and the conditions required for the realization of various storage and transportation methods, long tube trailer hydrogen transport is the choice of hydrogen storage and transportation in the early stage of hydrogen energy development.

● Trailer transport of gaseous hydrogen

Due to the small hydrogen density, low liquefaction temperature and poor stability, it is difficult to store and transport hydrogen. At present, the domestic high pressure gas hydrogen storage technology is relatively mature, has advantages in cost, is the main hydrogen storage and transportation mode at this stage. Restricted by technology and cost, other hydrogen storage technologies such as low temperature liquid and solid state have only a small application, accounting for less than 0.1% of the total.

High-pressure gaseous hydrogen storage is the mainstream choice for short-distance transportation. At present, the core requirements of hydrogen storage technology for the steel industry are safety, large capacity and low cost. High pressure gas hydrogen storage operation is simple operation, low cost, mature technology, but due to the high pressure, there are certain safety risks, and the hydrogen storage density is small makes the hydrogen storage efficiency low. Low-temperature liquid hydrogen storage has advantages in hydrogen storage density. The volume density is more than twice that of high-pressure gas hydrogen storage at 80 MPa, but the refrigeration energy consumption is large and the storage cost is too high.

The short distance transportation of hydrogen is mainly carried out through the collecting pipe bundle transport vehicle. The container bundle transport vehicle consists of a large volume seamless cylinder. The cylinder is fixed by the support plate at both ends of the cylinder in the frame to form the assembly bundle. The hydrogen produced by the hydrogen production plant is stored in the hydrogen storage bottle after high pressure compression through the compressor, and then transported by a long pipe trailer carrying six ~10 large volume hydrogen storage bottles. Because the density of hydrogen is small, and the hydrogen storage pressure vessel is significant, the mass of hydrogen transported by the final trailer only accounts for 1%~2% of the total transportation mass, and the transportation volume is 260 kg / vehicle ~460 kg / vehicle. At present, the long tube trailer is only suitable for transportation scenarios with short transportation distance and low transportation capacity.

High-pressure hydrogen gas must be compressed twice. The first compression is to fill the tank hydrogen tank with hydrogen, usually at a pressure of less than 30 mpa. The second compression is in the hydrogenation station. In order to charge the vehicle hydrogen tank, it needs to be further compressed to exceed the pressure of the hydrogen tank.

● Liquid hydrogen transportation

Low temperature liquid hydrogen storage is the storage of liquefied hydrogen in adiabatic vacuum vessel. Compared with high pressure gas hydrogen storage, low temperature liquid hydrogen storage has greater mass density and the purity of hydrogen storage is higher. Low-temperature liquid hydrogen storage requires the use of a liquid hydrogen storage tank with good thermal adiabatic performance, and is equipped with a strict thermal insulation scheme and cooling equipment. The energy consumption of liquefied hydrogen gas is large, which makes the cost of low-temperature liquid hydrogen storage higher. The unit cost of low temperature liquefied hydrogen storage is about twice the unit cost of high pressure gas hydrogen storage.

Liquid hydrogen transportation is a kind of hydrogen transportation method which can meet relatively fast and economical hydrogen transportation. The volume of liquid hydrogen is 1 / 800 of that of gaseous hydrogen. Liquefied hydrogen can greatly improve the storage and transportation efficiency of hydrogen, and special alloy and carbon fiber reinforced resin should be used for transportation and storage containers.

● Hydrogen pipe network transmission

Compared with hydrogen transportation by vehicle and ship, pipe network hydrogen transportation is the most economical and energy-saving way of large-scale long-distance hydrogen transportation. The pipeline network transportation methods of gaseous hydrogen mainly include the pipeline network transportation of pure hydrogen and the pipeline network transportation of hydrogen and natural gas mixture.

The use of existing pipe network to transport hydrogen is one of the best methods for low cost and long distance transport of hydrogen. To directly transform the natural gas pipe network into a mixture of hydrogen and natural gas (containing about 15% of hydrogen), only the original pipe network can be properly transformed. The transportation of pure hydrogen requires the substantial transformation of the original natural gas pipe network, including the replacement of materials and important components, and the upgrading of safety measures, etc.

With the increasing demand for hydrogen in the future, pipeline hydrogen transportation is the main way to achieve large-scale and long-distance hydrogen transmission. Compared with long pipe trailers, pipeline hydrogen storage has multiple advantages, such as large transportation volume, long distance, less energy loss, and economic efficiency. But its laying is difficult, the investment cost is higher.

In order to meet the demand for large-scale green hydrogen application, Salzgit, Thyssenkrupp and AncelorMittal began to build a pipe network from the port to the steel industrial zone, and rapidly transfer the hydrogen from offshore wind farms or imported hydrogen to the steel production plant by the pipe network.

In addition, new hydrogen metallurgy projects, such as HYBRIT and H2 Green Steel, are building green hydrogen production facilities near the project site. In order to ensure the stability of hydrogen supply, the HYBRIT project also uses the mine holes of the partners to build hydrogen storage sites.

Iron and steel enterprises with scarce resources choose to invest in the construction of green electrolysis hydrogen production plants in areas rich in renewable energy. For example, Pohang develops green hydrogen resources in Australia, the Middle East and other regions, and later uses ammonia to transport hydrogen to meet the domestic production needs.