Regarding the pressurization of the synthesis tower
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In our process of pressurization, we open the filter inlet valve a little bit, and then start pressurizing. I’m not quite sure: when the pressure at the filter inlet valve is almost at the same level as that of the fresh gas, can it be fully opened at that point???
The main thing is to ensure that the air velocity in the control system does not exceed the limit; it is best to open the make-up air valve fully only when the pressure inside and outside the system is equal.
The adjustment of the pressure make-up valve is based on maintaining the pressure increase rate of the synthesis system and keeping the pressure in the preceding section stable； At the beginning of pressurization, the pressure in the synthesis system is low; therefore, the make-up gas valve should be opened sparingly, to prevent excessive flow rates of gas in the preceding section ； As the pressure in the synthesis system continues to rise, the make-up gas valve should be opened gradually until it is fully open at the end.
By controlling the opening degree of the make-up gas valve, along with regulation via the fresh gas vent valve, the aim is to gradually increase the load on the synthesis tower, raise its temperature and pressure until self-heating equilibrium is achieved, thereby bringing the operation back within normal parameters. All the specific actions are carried out to serve this purpose; once you understand that, you’ll know what’s going on.
Open it again after the system pressure is balanced! !
The make-up air valve should be set to a lower opening degree at the beginning of operation; in some systems, it needs to be set to a slightly higher degree, and a make-up air line with a small diameter is also required to control the rate of pressure increase. Otherwise, the system pressure difference will be too high; components such as those in heat exchangers and cold exchangers are low-pressure devices with a pressure difference of around 0.1 MPa, which makes leakage or other problems likely to occur. Too rapid pressurization is also detrimental to the internals of the synthesis tower and the catalyst. Our company once experienced a flange leak due to too rapid pressurization. Just a few humble opinions, for reference only.
The synthesis system is equipped with dedicated purge valves and fresh gas valves. At the beginning of the purging process, these valves should be opened partially in order to control the rate of pressure increase; too rapid purging can damage the internal components of the synthesis tower and also cause the catalyst to break down. Open the purge valve slowly according to the pressure rise rate; once the purge valve is fully open, then slowly open the fresh gas valve. Once the pressure in the synthesis tower equals the pressure of the make-up gas, open the fresh gas valve fully and close the purge valve completely. When increasing the temperature in a synthesis tower, the make-up gas valve should also be opened partially at the beginning, to prevent the catalyst layer temperature from being pushed too high due to a sudden increase in space velocity and pressure. This post was last edited by snowdfr on 2009-3-18 20:58]
Generally, a pressure charging valve should be used during pressure generation. For our 100,000-ton system, we use a valve with a capacity of 25; once the desired synthesis pressure is reached, the main gas supply valve is opened fully, and then the pressure charging valve is closed.