Description of the control method for the continuous reforming recontact system

Are you using a centrifuge or a reciprocating machine? If it’s a centrifuge, you’ll have to rely on your own understanding; once you understand this aspect, the other control methods won’t pose any problem at all

Centrifugal compressor with two-stage compression and one re-contact stage, forming three-stage compression together with the reforming cycle, and equipped with an ammonia refrigeration system.

The three-stage compression you mentioned refers to the design in which the inlet of the booster pump is located at the outlet of the cycle hydrogen compressor; the high pressure at the outlet of the cycle hydrogen compressor is utilized to achieve three-stage compression. After these three stages of compression, the pressure can reach around 2.0 MPa. There is another form of re-contact: the first-stage inlet of the compressor is located at the inlet of the cyclohydrogen compressor, and after two stages of compression by the booster, the pressure can reach around 1.5 MPa. Whether it is the third-level or second-level compression you are referring to, the control schemes are similar, employing techniques such as override control and proportional control. The specific issues are quite complex; I will send some materials over. To understand a control system, one must know its control objectives and control methods. For example, the re-contact control here has the following two objectives: 1) High pressure, stable primary and secondary re-contact pressures, which must not be too high or too low, and adjustments can be made accordingly based on the amount of hydrogen produced by the system ； 2. The compressor inlet flow is greater than the surge flow. The control methods include the following: 1. Adjusting the speed of the booster pump to change the operating curve of the compressor, regulating the amount of air drawn in by the compressor, and controlling the inlet and outlet pressures ； 2. Adjust the opening degrees of the one-to-one and two-to-two valves. The meaning of the override control you mentioned is that, under certain specified conditions, the control method of the controller changes. Let’s start with a simple example of two-stage compression. Under normal conditions, the control valve for the second stage is manually adjusted to a specific setting in order to maintain stable pressure at that stage. However, in case of an abnormal situation where the outlet path for hydrogen production becomes blocked, the pressure at the second-stage outlet rises rapidly. When this pressure reaches the set value for override control, the override system takes over, instructing the valve to open wider in order to reduce the pressure at the second-stage outlet.

The explanation in the last paragraph on the 4th floor is incorrect; perhaps the control valves in your facility are set to manual operation. However, to achieve stable control, it is necessary to switch everything to automatic mode. I have seen several facilities where the valves are operated manually – although the operation is smooth and there are minimal fluctuations in the feed components – there are still some fluctuations in the high-pressure level. Furthermore, the pressure control of centrifugal compressors is also closely related to the stability of the control system and the turbine; if the hardware is not up to standard, trying to control pressure using speed is equivalent to risking stable operation. Generally speaking, when choosing a control scheme, safety and stability come first, followed by cost savings. Of course, the final decision is made by the chief engineer, and we can only adapt to it.

Was the problem solved? If the issue isn’t resolved, send me the tag number of your re-contact point as well as the tag number of the main regulator; I’ll draw a simple diagram for you so it will be clear

Speaking of ours, we use recursive control with reciprocating compressors, and the Holberg system is employed; however, there were some issues during operation, but overall the performance has been quite stable

Look, the methods of re-contact control in your area – some refineries use a high-selection control approach, so these cannot be mixed up! Find out whether it’s a high selection or a low selection! Then study the control methods!

It depends on how you control it – whether to use a high signal or a low one; the signal can be sent in the opposite direction as well. The difference isn’t significant; each plant is different. We need to switch to sending the signal in the reverse direction now, as hydrogen and the reforming feed have become intermixed. It’s not a big deal at all

It’s still better to use low-selection methods – the technology is more mature! When our unit first started operating, high-selectivity control was used, but after the UOP technicians arrived, it was changed back to the original control method! Safe and stable! And it’s simple!

I was wondering if your reciprocating compressors experience significant vibration?