Safety relief issues in high-pressure reactors
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I would like to ask the experts about the safe pressure relief issues in high-pressure reactors: For hydrogenation reactions, 1) the normal operating pressure is 5 MPa; when the pressure inside the reactor exceeds 5.5 MPa, the emergency vent valve of the SIS system opens, and when the pressure exceeds 5.8 MPa, the safety valve (or rupture disc) activates； 2. The effective volume of the reaction vessel is 3000 L, with a total volume of approximately 4000 L. The liquid phase medium consists of reaction solution, catalysts, etc., while the gas phase medium is hydrogen. May I ask, if the emergency vent valve of the SIS system opens or the safety valve activates, and the high-pressure gas in the reactor is released, what safety measures can be added to ensure the safe discharge of high-pressure hydrogen? (Note: No flare system has been designed)
Regarding \"the emergency vent valve of the SIS system opening or the safety valve activating.\" Firstly, this issue relates to a security system in a state of loss of control. Control measures should be in place before the safeguard procedures of this system are activated. In normal control processes, if this system activates, it indicates that an accident has occurred, and a handling procedure must be followed. As for purely practical considerations, in the event of such an accident, to ensure that subsequent problems do not escalate, is it being considered to direct the gas from such accidents into safe treatment equipment? For example, it may need to be diluted or dissolved with other materials. If these residual gases could be extracted and utilized, or recycled, before the accident occurred…. Would it be safer to consider these aspects? For example, setting a pressure-controlled self-regulating valve to release the remaining gas? For reference.
Normal reaction operations require a pressure of 5.0 MPa, with hydrogen in the gas phase; it is not possible to extract or recover this gas before an accident occurs. Incidents such as the opening of an emergency vent valve or the activation of a safety valve are considered abnormal operations, but how should the high-pressure gas released be handled safely?
Besides hydrogen, what components might be present in the droplets resulting from the accident? It is recommended to install an accident vent collection tank for gas-liquid separation, in order to minimize the amount of liquid carried in the gases released into the environment. Reference can be made to the two-stage pressure relief system of 2.1 MPa and 0.7 MPa used in petrochemical hydrogenation units: the set pressure of the safety valve in the primary accident collection tank is 2.1 MPa, while the set pressure of the safety valve in the secondary accident buffer tank is 0.7 MPa; after that, the pressure is released into the atmosphere via the secondary safety valve.
Hydrogen is lighter than air, so it can generally be released directly (if it is pure hydrogen). Of course, the height of the release point and the safe distance from surrounding equipment need to be taken into consideration. A flame arrester may need to be installed on the outlet.
It is possible to consider adding a tee branch in front of the safety valve to divert flow, thereby allowing real-time control via a control valve to prevent overpressure. This has nothing to do with high pressure. The pressure level can be automatically controlled via a self-regulating valve.
Is the safety valve activated even later than the SIS? SIS essentially serves as the last line of defense in case of an accident. I agree with the view expressed on floor 4: a secondary accident collection tank should be installed
Calculating pneumatic control valves is a problem! How are the maximum and minimum flow rates determined? The control performance of the control valve is also an issue!
It is recommended to find a valve manufacturer or distributor; they will give you options, and that’s not a problem. Judging from your question, you might not have a very comprehensive understanding of this part of the process. You might be worried about not understanding certain settings. It is best to contact the device’s designer to resolve this issue.
Is a flame arrester needed? Is it necessary to control the emission rate of hydrogen-containing media?