What pressure of oxygen and nitrogen is most economical for compression in steel plant air separation units?

While considering pressure, the cost of the delivery pipelines must also be taken into account. Steelmaking requires a large amount of oxygen; the lower the pressure, the larger the diameter of the pipes, which in turn leads to greater space requirements and higher investment costs. Additionally, since gas is transported at low pressure, more pipe supports are needed. It is difficult to reduce the oxygen pressure, while for nitrogen pressure we currently use two levels: 0.7MPA and 2.5MPA.

The pressure drop during transportation also needs to be taken into account

The oxygen consumption in steelmaking fluctuates greatly; it is very high as long as the casting machine is in operation, while it is 0 when the casting machine is stopped during steelmaking. Therefore, although the pressure required for steelmaking is only around 15 bar, steel mills generally increase the oxygen pressure to over 20 bar before reducing it. Although this is not economical, steel mills are very wealthy, and ensuring production stability is more important. What the original poster suggested, namely adding a buffer tank, is feasible, but it is even less economical. For example, with a pipeline pressure of 15 bar and a buffer tank of 1000 M3, the 1000 M3 of oxygen will be released only when the pipeline pressure drops to 14 bar ； It is very likely that the oxygen pressure drops too low in an instant, failing to meet the requirements for steelmaking. And if the pipeline pressure is increased to 20 bar, then when it drops to 15 bar, 5000 M5 of oxygen can be released, **reducing the risk associated with low oxygen pressure. Buffer tanks are very expensive; and for every 1 bar increase in pipeline pressure, it’s as if the size of the buffer tank doubles. Do the math on the cost aspect yourself. Existence is justified; if there were better and more economical methods, not all steel mills across the country would use such methods for oxygen supply, especially given that steel mills are generally operating at a loss these days.

Your idea is correct, and the control value is also right. Currently, converter steelmaking is the most common method, and the pressure specified in the oxygen production and pressure regulation rooms is not to exceed 1.8 MPa to 1.4 MPa. The design of the voltage regulation room and the spherical tank takes into account the characteristics of converter steelmaking. Converter steelmaking takes about 23 minutes per batch of steel, (including approximately 13 minutes for blowing, 3 minutes for tapping, nitrogen injection and slag splashing to protect the furnace, and material feeding). During the smelting process, due to the high demand for oxygen, relying solely on the compressor to supply oxygen is far from sufficient. In this case, reliance is placed on the spherical tank to store energy for oxygen supply, with the energy storage taking place when the smelting process stops. The oxygen consumption curve for a single furnace fluctuates greatly; if multiple furnaces use oxygen in an alternating manner, the fluctuations are relatively smaller. If it is blast refining, the minimum pressure should preferably not be lower than 1.2 MPa, as there are too many uncertainties in steelmaking. Stable production is the greatest way to save energy and reduce consumption. (For reference)

Modern steelmaking involves continuous casting. I’m not sure what process you’re referring to; it would be great if you could share it. :) Additionally, it is recommended to use the standard international SI units when posting posts, as this makes it easier to understand and avoids complicated conversions. Note: (Searched on Baidu; :lol for reference) 1 bar = 100,000 Pa = 10 Newtons per square centimeter; it is a unit of pressure. In meteorology, millibars were commonly used in the past, but now the equivalent international unit of hectopascals is used instead. 1 Pa is short for 1 Pascal, which means a force of one Newton acting on one square meter. In engineering, the unit of kilogram-force is still in use; 1 kilogram-force equals 9.80665 Newtons. From this, the engineering atmosphere is derived: 1 engineering atmosphere = 1 kilogram-force per square centimeter = 0.967841 atmospheres = 98066.5 Pascals. The millimeter of mercury is also a commonly used unit of pressure, and the unit of pressure defined by the pressure exerted by 1 millimeter of mercury is the torr. 1 torr = 1 millimeter of mercury = 133.32 pascals. 1 atmosphere = 760 torr. In the International System of Units, pascals (Pa) are generally used as the unit of measurement