In-depth Application of Variable Pressure Adsorption Hydrogen Purification Technology in Iron and Steel Metallurgy Industry

Iron and steel metallurgy industry, as the core field of national heavy industry, the gas separation and purification technology involved in the production process is particularly critical. Among them, hydrogen purification is an indispensable part of the iron and steel metallurgy process. In recent years, with the continuous development of science and technology, pressure swing adsorption (PSA) technology has been widely used in the field of hydrogen purification by virtue of its advantages of high efficiency, energy saving and environmental protection.

Overview of Pressure Swing Adsorption Technology

In the iron and steel metallurgy industry, hydrogen is mainly used to reduce iron oxide in iron ore to produce ferric iron. However, hydrogen often contains impurity gases, such as nitrogen, carbon monoxide, etc., in the preparation process, and the presence of these impurity gases affects the purity and use efficiency of hydrogen. Therefore, it is necessary to purify hydrogen using the variable pressure adsorption technology to obtain high purity hydrogen.

Variable pressure adsorption technology is a method to realise gas separation and purification based on the differences in the adsorption capacity of adsorbents to gas molecules at different pressures and the differences in the adsorption capacity of molecules of different types of gases. The basic principle of this technology is that under a certain temperature, by making use of the property that the adsorption capacity of the adsorbent for specific gas components changes with the change of pressure and the property that the adsorption capacity for different kinds of specific gas components is different, the adsorption and desorption processes are carried out alternately by periodically changing the pressure of the system, so as to achieve the purpose of separating and purifying gases.

In the usual PSA process, two methods can be used to regenerate the adsorbent:

1. "Flushing" the bed with product gas to reduce the partial pressure of the adsorbed impurities and to displace the more difficult to desorb impurities. The advantage is that this can be done at atmospheric pressure. The disadvantage is that some product gas is lost.

2. regeneration by vacuum, so that the harder to desorb impurities in the negative pressure forced desorption down, which is usually referred to as the vacuum pressure swing adsorption (Vacuum Pressure Swing Adsorption, abbreviated as VPSA or VSA). the advantages of the VPSA process is a good regeneration effect, high product yield. The disadvantage is the need to increase the vacuum pump, device energy consumption is relatively high.

In the actual application process, the use of which process mainly depends on the composition of the raw gas conditions, flow rate, product purity, yield requirements, as well as the plant's capital and space and other circumstances to decide.

Variable Pressure Adsorption (VPA) Hydrogen Purification Processes

Variable pressure adsorption hydrogen purification process mainly includes adsorption, equalisation pressure drop, downward release, reverse release, flushing, equalisation pressure rise and final pressure rise and other steps. Specific as follows:

1. Adsorption: Raw hydrogen enters the adsorption tower under a certain pressure, in which the impurity gas is adsorbed by the adsorbent, while the high purity hydrogen enters the downstream process through the adsorption tower.

2. Pressure equalisation: At the end of the adsorption, the pressure in the adsorption tower is reduced to an intermediate pressure by the pressure equalisation step, creating conditions for the subsequent down- and reverse discharge steps.

3. Shun release and reverse release: After the equalisation pressure drop, the impurity gases in the adsorption tower are partially released in the shun release process, and then the impurity gases are further released by releasing desorbed gases in the reverse direction in the reverse release process.

4. Flushing: After the end of the reverse discharge, the adsorption tower is flushed with purer hydrogen gas to further remove the residual impurity gas.

5. Pressure equalisation and final pressure rise: after the rinsing, the pressure in the adsorption tower is raised to the working pressure through the steps of pressure equalisation and final pressure rise, so as to prepare for the next round of adsorption process.

Advantages of Variable Pressure Adsorption (VPA) technology in the iron and steel metallurgical industry

1. High efficiency: Variable pressure adsorption technology has high efficient separation and purification ability, advanced and reliable process, strong applicability of raw materials, and can obtain high purity hydrogen in a short time, the purity can reach 90-99.9999%, and improve the production efficiency.

2. Energy-saving: Compared with the traditional deep-cooling separation technology, the variable pressure adsorption technology has a significant advantage in energy consumption. The operating temperature is close to normal temperature, avoiding the large energy consumption in the deep-cooling separation process. Wide pressure range: 0.2-6.0MPaG, low energy consumption, operating flexibility up to 20-120%, the device continuous operation time is more than 3 years.

3. Environmentally friendly: Variable pressure adsorption technology does not produce hazardous waste in the purification process, and the hydrogen recovery rate is high. Depending on the gas source and product conditions, the hydrogen recovery rate is between 60-99%. It meets the green production requirements.

4. Flexibility: Variable pressure adsorption technology can adjust the adsorbent and process parameters according to different production requirements, with strong adaptability and flexibility. The device has a high degree of automation, with self-adaptive adjustment, automatic fault diagnosis and other functions, and it is convenient to start and stop the plant, and it has already realised unmanned automatic control.

Industrial Value and Market Prospect

At present, the transformer pressure adsorption technology has been widely used in all kinds of hydrogen-containing gases, such as transformer gas, methanol cracking gas, methanol chiropteric gas, synthetic ammonia tail gas, refinery hydrotreating low-fraction gas, coke oven gas, water gas, catalytic dry gas, reformed hydrogen and so on. The continuous development of iron and steel metallurgy industry requires more and more hydrogen purification technology. As an efficient, energy-saving and environmentally friendly gas separation and purification method, the application of variable pressure adsorption technology in the iron and steel metallurgy industry has a broad prospect, which not only improves the purity and efficiency of hydrogen, reduces the production cost, but also helps to promote the green and sustainable development of the iron and steel metallurgy industry.

In the future, with the continuous progress and innovation of science and technology, variable pressure adsorption technology will play a more important role in the iron and steel metallurgy industry. Meanwhile, this technology is expected to be popularised and applied in other fields, injecting new vitality into the development of gas separation and purification.