Issues with emergency shutdown operations of methanol compressors
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In some methanol operation procedures on the forum, it is stated that when the methanol compressor needs to be shut down urgently, the following steps should be followed: press the main unit shutdown button to stop the main unit. Close valve 1-1, valve 2-1, and the bypass valve for circulating gas. Close the outlet valve of stage 2 in the compression section, the inlet valve of stage 1, and the inlet and outlet valves for the circulating gas in the circulation section. Open the fresh gas circulation vent valve to relieve system pressure. Why is it necessary to close valve 1-1, valve 2-1, and the bypass valve for the circulating gas during an emergency shutdown, as opposed to what happens with the CO2 compressor used in urea synthesis during an emergency shutdown – where the main unit is stopped, the outlet is closed, while the valves of various circuits and the vent valve are opened?
What model is the LZ using?
I also have a question: why do we need to turn off Stage 1 and Stage 2? Generally, when the compressor stops operating, isn’t the anti-surge function activated automatically? Why then turn it off? That wouldn’t serve any purpose in protecting the compressor. Is it that Stage 1 and Stage 2 are used solely for applying load?
What model? What medium is it traveling on?
This is what I found in the documentation; the process is as follows: Fresh gas enters the first compression cylinder through the front buffer in the compression section, is compressed there, then passes through the exit buffer of that cylinder and the first water cooler for cooling. It subsequently enters the first separator, and after that, it goes through the second front buffer to enter the second compression cylinder. After passing through the exit buffer of the second cylinder, it enters the main fresh gas pipeline and is sent to the methanol synthesis system. Install circuit valves and vent valves at 1-1 and 2-1 (connecting the compressed gas outlets of stages 1 and 2 to the inlet of stage 1, respectively). The recycled gas from the separator of the methanol synthesis system enters the compression cylinder in the recycling section after passing through a buffer, where its pressure is increased; it then enters the recycled gas main pipe and is sent back to the methanol synthesis system. Install the bypass valve for circulating gas and the vent valve
During an emergency shutdown of a centrifugal compressor, the anti-surge valve opens automatically, while the outlet valve is closed to prevent gas backflow from damaging the compressor. Close the inlet valve, open the relief valve on the unit to release pressure, and wait to restart the machine. After an emergency stop of the reciprocating compressor, first close the outlet valve to prevent gas backflow, then close the inlet valve, open the return valve, and open the relief valve on the machine body to release pressure while waiting to restart it.
What model of compressor do you have?
4M25-16 Symmetrically Balanced Reciprocating Press
When the pressure difference between the inlet and outlet of the compressor is large (for example, the inlet pressure is 0. 01 Mpa, outlet 5.0 Mpa); if the unit stops operating and the circuit is not closed, the high-pressure gas at the outlet will flow through circuits such as Circuit 1-1 and Circuit 2-1 into the low-pressure section at the inlet. The design pressure of imported pipelines is often very low, making accidents likely to occur. That’s why there is the saying to turn off the circuit first and then the inlet and outlet. This post was last edited by gyd516518 on 2009-2-24 at 16:52.]
These are the steps for an emergency stop, right? For a normal stop, one should gradually reduce the speed by 1 unit each time, and lower the pressure by 1 unit after two reductions. Once it’s underway, the compressor can be removed from the system!
To be clear, the key factor lies in the type of compressor: centrifugal or piston； After determining the type, the specific model also needs to be considered. The parking procedures and requirements for attention vary between the two.