Control methods for methanol synthesis
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We know that the main parameters that need to be controlled during the methanol synthesis process include temperature, reaction pressure, space velocity, gas composition, drum liquid level, the amount of liquid discharged from the drum, the flow rate of by-product steam, and the liquid level in the separator. So, what methods are used to control these parameters in various plants? Let me start by saying that the outlet temperature of the synthesis tower is adjusted by changing the set value for the pressure in the steam drum. What about the other parameters? Additionally, I’ve run into a problem: the inlet pressure of our syngas compressor, which is also the pressure in the upstream low-temperature methanol washing unit (for purification), needs to be adjusted in a timely manner by adjusting the opening degree of the anti-surge valve on the syngas compressor. Some people say that the compressor speed can be used to adjust the suction pressure of the compressor I’m a bit confused here; the exact wording is as follows: (The suction pressure of the syngas compressor is controlled via a cascade control system that utilizes the suction pressure controller and the turbine speed.) As soon as there is any deviation between the suction pressure and the set value, a new set value is assigned to the turbine speed controller. The advantage of this arrangement is that the methanol synthesis unit can automatically adapt to changes in load occurring in the units upstream of it. ) The pressure in our synthesis system has always been controlled by adjusting the volume of gas recovered from dehydrogenation and by altering the gas composition. So what does the previous sentence mean? For example, if the suction pressure is high, should the rotation speed be increased or decreased? Could someone knowledgeable please explain this? Regarding the control methods, it would be great if some expert could leave their QQ number so I can contact them...
1. There are generally just those two options for bed temperature control. One is cooling by air conditioning, and the other is removing heat using boiler water (steam drum), etc. Reducing the gas velocity can also lower the temperature, but it tends to cause the temperature at hot spots to drop as well. Adjusting the gas composition can also achieve this effect, but then it loses its meaning in terms of normal production. The temperature control we are talking about should be carried out on the premise that the gas composition is appropriate. 2. Pressure control: On one hand, it depends on the reaction rate; if the reaction proceeds well, the outlet pressure will not be high, but if the reaction is poor, the pressure will rise. Additionally, inert components also contribute to pressure fluctuations, and these can be controlled by adjusting the amount of gas released. However, if the reaction is poor, it is necessary to address the root cause. The inert components need to be carefully controlled and adjusted according to the requirements; too low or too high levels are both undesirable. The compressor side can only be adjusted passively. When the previous section is loaded, the pressure rises, and the unit’s governor automatically accelerates to increase the voltage. It is a process of adding and subtracting amounts. Increase the speed first when raising pressure, and reduce the pressure first when decreasing speed – this is the operating principle for centrifugal units; accordingly, to increase pressure, one must increase the speed.
Control the low wash pressure. . . . It should be determined by the gasification load, right? With less gas coming in due to low washing, the pressure is low; the compression stage is activated to prevent surge, which in turn leads to a reduction in synthesis, or conversely, an increase in synthesis. If the low wash pressure drops, you activate anti-surge protection and the unit continues to operate, but less gas goes to the synthesis tower, right? In other words, it is a process of reduction, and correspondingly, the unit also slows down.