Hydrogen gas leakage issue?
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I am not very familiar with three issues related to ensuring hydrogen gas tightness in the system; I would appreciate it if experts could help answer them: 1. When ensuring tightness at high pressures, such as 15 Mpa, a 4-hour pressure stabilization period is required, and during this time the tubular furnace needs to be turned off. I wonder whether the drop in temperature at this point will affect the results of the tightness test. 2. What are the acceptance criteria for hydrogen gas tightness? Some say it is when the pressure drop is below 2% over 4 hours, while others say it is below 0.2 Mpa/h. 3. When the hydrogen system is airtight, what is the maximum temperature at which heating is generally stopped? For example, is it limited to no more than 260°C? Are there any specific regulations regarding this? Thank you all.
I think the choice of this temperature should be determined by taking into account the reduction temperature of the catalyst. With such high pressure and no oil feed, if the temperature remains too high, the catalyst will get reduced; and for sulfurized catalysts, once they are reduced to their metallic form, it’s all over. If the temperature drops during the airtightness testing phase, I don’t think it will affect the airtightness; after all, in most systems involved in such reactions, the flanges are tightened using hydraulic wrenches, and the preload is always predetermined
Hydrogen is airtight at a pressure of 2.5 MPa. The pressure tightness at 2.5 MPa is tested in the cold and hot states. In the cold state, the system temperature needs to be reduced to room temperature (this can usually be omitted). The hot state can be achieved once the reactor temperature drops below 120°C and the hydrogen purity exceeds 85%. (System airtightness acceptance standard: No alarm detected when tested with a hydrogen detector at a pressure of 2.5 MPa) ； Or when using a paper tape for leak testing, there are no bubbles at the sealed area ； or the pressure drop in the reaction system is less than 0.02 MPa/h after 4 hours). The reaction system meets the airtightness requirements at a pressure of 2.5 MPa; the reaction heating furnace is heated (ignition is initiated), the temperature at the reactor inlet is maintained between 120–150°C, and the pressure in the reaction system is increased. Sequentially apply 4.0 MPa, 6.0 MPa, 8.0 MPa to test the hydrogen gas tightness at the design pressure. During the hydrogen pressure increase and airtightness testing, the temperature at any point in the reactor must not exceed 180°C.