Questions regarding the principles for handling hydrogenation accidents
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One of the principles for handling accidents in bk01.jpg is that before the bed temperature drops to 135°C, the reactor pressure must be reduced to below 2.1 MPa； Before the pressure in the hydrogen-containing system rises to 2.1 MPa, the temperature of the reactor bed must be raised above 135°C. Looking for the reason?
To prevent hydrogen embrittlement, during shutdown, isothermal degassing is carried out to fully release the hydrogen from the vessel walls at low pressure
These are the conditions under which a reaction takes place in the reactor, as well as the protection of the catalyst
Prevent hydrogen embrittlement and affect material strength
This is to prevent hydrogen embrittlement; generally, hydrogenation units require that the pressure in the reaction system not exceed 1/4 of the design pressure before the temperature reaches the minimum required for the reactor material.
MPT: Minimum pressurization temperature; before the minimum temperature in the reactor/heat exchanger exceeds 93°C, the pressure shall not exceed 1/4 of the reactor’s design pressure ； Attention should be paid to starting and stopping operations; in dealing with accidents, it is often difficult to lower the temperature. For example, in the case of a shutdown of the circulation machine, the temperature usually doesn’t drop much even after a few days
I don’t know why all the friends upstairs answered hydrogen embrittlement. Isn’t this for the temper brittleness of chrome-molybdenum steel? Hydrogen embrittlement and temper embrittlement are two completely different concepts. Temper brittleness refers to the internal changes that occur in molybdenum steel when it is exposed to temperatures above 325 degrees for an extended period, resulting in a decrease in toughness and impact resistance. Therefore, there are pressure requirements to prevent cracking due to low toughness. Hydrogen embrittlement occurs when hydrogen remains in molybdenum steel without being removed. These are two things. 135 degrees was the initial temperature requirement; now some require 93 degrees, while 53 degrees is required for the first start-up (since high temperatures have not been experienced before). That’s how I’ve always understood it; if friends think what I say is incorrect, we can discuss it together.