Determination of the drum pressure
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This post was last edited by Desert Fish on 2015-10-16 at 14:13. Experts, I have a question: how is the pressure of the drum used to control the reaction temperature determined? For example, in a exothermic reaction with a reaction temperature of 240°C, and if the reaction temperature is to be controlled using the drum, then the drum pressure could be 0.5 MPaG (158°C), 1.0 MPaG (185°C), 2.0 MPaG (215°C), or 3.0 MPaG (235°C). From a process perspective, how should the pressure of the drum be chosen?
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It is determined based on the steam quality requirements and consumption of other users in the entire plant. Consider the plant-wide steam balance.
Well, I know the whole factory needs to be considered! But what I want to know is whether there are any requirements regarding the process; in other words, since the reaction temperature is controlled by the steam drum, are there any requirements regarding the heat transfer temperature difference? Is it better if it’s larger or smaller? The stability of the reaction must be taken into account!
This post was last edited by zhouhuahui on 2015-10-16 at 15:51. The lower the steam pressure, the better the heat recovery effect； From the perspective of the conversion unit, the lower the grade of the low-pressure steam produced, the higher the output. However, low-pressure steam is difficult to utilize, and it is not cost-effective to generate power from low-pressure waste heat if there is not much low-pressure steam available.
For heat transfer, it’s better to have a temperature difference of at least 20-30°C; this way, heat transfer occurs more quickly. I didn’t understand your question. The reaction temperature is 240°C – how many steam drums do you have? Is there no temperature that is higher than this one? How to heat it? Is it me who doesn’t understand properly?
This is still determined based on the steam pipeline system of one’s own factory, followed by the design calculations for the heat exchangers. Different units of the same process we are working with: some produce steam at 3.5 MPa and a steam temperature of 252 degrees, with the cooling medium reducing the temperature from around 1200 degrees to 300 degrees; others produce steam at 1.1 MPa and a steam temperature of 187 degrees, again with the cooling medium lowering the temperature from around 1200 degrees to 350 degrees.
The steam generation temperature should be lower than the reaction temperature; the reaction temperature corresponds to the hot side, while the steam generation side is the cold side.
It has no impact; it depends on what you do with the steam generated – it’s determined by the user of the steam
It is recommended to use 1.0 MPaG (185°C); this allows for direct use of the pipeline for purging, while steam heating or heat tracing can be employed after further pressure reduction.
Okay, thank you! This is also my understanding. Theoretically, the highest pressure that can be achieved should be the saturated vapor pressure corresponding to the reaction temperature; any pressure below that is acceptable. However, what remains to be considered are the design of the heat exchangers in the reactor as well as the requirements of the steam piping system! One more question: which process unit are you referring to, and is the scale the same? The temperature of the by-product steam from these two options differs by over 60 degrees, so the design of the reactors must be different as well!