Why is the system pressure controlled at around 1.8 MP during ammonia synthesis shutdown?

Is there such a requirement? I didn’t notice it :( ! As long as the solution can be recycled, that should be sufficient! Last edited by zjm3116 on 2008-1-3 09:02.]

1.8 MPa is intended to protect the system’s catalyst from being submerged in water. \"When the system pressure is below 1.8 MPa, the decarburization solution cannot undergo a regeneration cycle!\" " In our plant, the solution circulation is generally carried out at a gauge pressure of 1.7 MPa.

A pressure of not less than 1.8 Mpa is understandable, and it’s also fine to keep it at 2.3 Mpa

When parking, the pressure is first reduced to 2.1–2.3 MP, and then to 1.8 MP! Why is this the case?

The inlet pressure of our hydraulic press is no higher than 2.5 MPa; the system maintains heat and pressure – of course, a higher pressure would be better

What kind of process is it! Different processes have different pressure requirements. But the principle is one: as long as the solution can be recycled, that’s enough! There is no particularly complex reason for this; it is mainly determined by the height of the regeneration tower and the pressure drop in the pipelines, which dictate the pressure that must be maintained in the absorption tower during shutdown

It’s a pity that the role related to decarbonization in our company was eliminated before I joined the firm; I’ve never seen what a hydraulic press looks like. It sounds like it’s a synthesis system used to refine feed gas; what kind of process do you use?

In my opinion, it should be to protect the walls of the synthesis tower; our factory has set a rule that the pressure in the synthesis system must not exceed 38 degrees when the temperature is at that level

A pressure of 1.8 MPa is sufficient to ensure the operation of the decarburization system’s circulation, but if the pressure is too high, it may result in insufficient flow from the lean liquid and semi-lean liquid pumps, leading to an inadequate amount of solution circulation. If the methanation reactor is not turned off while parking, it can easily lead to overheating.

But why can’t the system pressure be controlled at a higher level? Such as 2.3MP? What is the impact of high system pressure on shutting down ammonia synthesis? I think, mainly from the perspective of energy consumption, excessive system pressure control when the vehicle is parked leads to increased power consumption of the compressor, resulting in waste of resources.

It should mainly depend on the height of the regeneration tower; if it’s above 1.5, cyclic regeneration should be possible

We require the pressure to be controlled at 1.5 MPa; as long as it can be pressed into the regeneration tower to enable recycling, it’s fine, and a higher pressure isn’t a problem. It’s just that in that case, the pipelines on site might vibrate quite severely.

The decarburization system must be maintained at a pressure of over 1.8 MPa; otherwise, it will affect the circulation of the decarburization system.

As long as safety is ensured, keeping the pressure a bit higher can reduce the time needed to refill air while driving.

The reason you raised this question is mainly to ensure solution circulation! If all the pressure is released before driving, it will cause stamping; otherwise, the solution cannot circulate! The advantage of this is reduced driving time and less nitrogen usage! The release of pressure may allow air to enter through imperfect flange connections, causing the oxygen content in the system to exceed the limit!

Based on what the original poster said, it seems you belong to Kellogg’s process. Based on the operational conditions of our company, when the system is stopped, the pressure in the control system (which is PIC-5 at this time) is 1.8 MPa; this pressure is necessary to ensure the proper operation of the hydraulic turbine 1107JHT. When the pressure drops below 1.8 MPa, the 1107-JHT cannot operate properly, and it becomes necessary to use the 1107-JB or JC units, which increases steam consumption. Decarburization can establish and maintain a cycle as long as the pressure (PIC-5) is above 0.9 MPa. As for the pressure, it can of course be kept at a higher level; however, once the vehicle is stopped and the inlet valve of the absorption tower is closed, the pressure will only decrease gradually, unless high-pressure nitrogen is available to be injected. When our company carries out cyclic vanadiumization, it uses high-pressure nitrogen to push the pressure to 2.5 MPa for the cycling process.

But why can’t the system pressure be controlled at a higher level? Such as 2.3MP? What is the impact of high system pressure on shutting down ammonia synthesis? The system pressure has to be high enough; everyone has said that, so I won’t repeat it. In principle, it is acceptable for the system pressure to be high, but exceeding a certain level brings little benefit and can result in the following risks or disadvantages: 1. The flow may deviate in various equipment, especially in certain sections of the furnace. Since the process gas is vented when the synthesis unit is shut down, the system load will not be too high; otherwise, it would result in significant waste. 2. The waste heat boiler has insufficient circulation power, making reverse circulation likely to occur. 3. The air nozzles in the two-stage furnace require more steam to prevent backfire, resulting in energy waste. 4. The pressure difference before and after the vent valve is large, causing the valve to be prone to damage. So, there is no need to increase the pressure.

1. When parking, it can be said that keeping it within any range of positive pressure is sufficient; there are no specific requirements； 2. High pressure control in the ammonia synthesis system is advantageous when heating up again; the system contains pure H2 and N2 gases. During startup, as long as the system pressure is at 5.0 MPa, the circulation pump can be started immediately to raise the temperature, and gas can be added to the system once the pressure drops, thereby reducing the overall startup time for the plant ； 3. When parking, the system must not release pressure too quickly! In the case of catalyst crushing or failures in the internal components, the relevant documentation only specifies requirements regarding the rate of pressure and temperature changes; there are no requirements specified for the range within which pressure should be controlled. 4. However, it is possible to maintain system pressure; it is best to keep it above 5.0 MPa to facilitate faster startup!