Study the issue of emergency shutdowns in catalytic reaction positions
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During an emergency shutdown, one should first go to the site to check whether the accident return valve is open, and then close the nozzle for the feed oil. Here comes the question: after closing the root valve of the feed oil nozzle, shouldn’t there be a main pipe for the accident return line, so that all the feed oil from the feed auto-protection valve to the nozzle can be flushed into this accident return main pipe? This question relates to the raw material nozzle; if there are any precautions regarding emergency shutdowns, everyone is welcome to actively participate in the discussion. For example: first observe the drum liquid level, check the regenerator pressure, check the main fan, ...... :handshake
It should also be checked whether the steam valve for accident lifting is open, and whether the feed and regeneration slide valves are closed
In fact, as long as the DCS remains powered on, it is possible to see the status of the self-protection actions in the control room, since self-protection mechanisms always generate feedback. On the contrary, it is more important to go to the site, stop the feed pump, and shut down the nozzle. Our unit is equipped with a bus valve on the nozzle return accident bypass line; it must be opened promptly after the nozzle is shut off to prevent a dead end, especially in winter – if freezing occurs, things will go wrong. If the heat tracing for the heavy oil line is turned off during summer, it should be activated promptly to prevent line condensation. After the lines are adjusted, the material can be recycled. In some systems, there is a bypass back to the material tank, which is advantageous as it allows pumps to be used for timely recycling in order to prepare for operation.
Does steam enter the regenerator when you stop operation? We have it here, but we never use it. Have you used it?
Yes, yes, during normal production this loop line is also set to a slightly higher level, right?
There are indeed new catalysts that do not require the use of emergency steam, as emergency steam can deactivate the catalyst and cause damage to it; this is possible provided that the one-way damping valves in the main air system and the exhaust valves at the outlet of the main fan are fast and reliable in operation. Still, I personally feel there is a certain degree of danger.
After the self-protection action led to shutdown, the operator focused primarily on monitoring the pressure difference between the two vessels to prevent reverse pressure in the regenerator; dry gas was switched to steam for external heat removal, and the pressure in the regenerator was vented in preparation for restarting the system. What was said regarding outdoor operations will not be repeated.