Issues regarding the steam heating process for the reactor jacket
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This post was last edited by Marshal Tianpeng on 2017-3-6 at 14:43. It deals with the issues related to heating a reactor jacket using steam. We have a reactor that needs to be heated to over 90 degrees, and reduced-pressure superheated steam is used for this purpose – from 1 MPA to 0.4 MPA. Using ASPEN, I calculated that the temperature after pressure reduction would be 178 degrees; this should be fairly close to the actual value. What confuses me is that at the outlet at the bottom of the jacket, it should be condensate water. The problem is that it’s superheated steam here, so maybe some of the steam doesn’t have time to condense. Since this is an intermittent reaction process, it’s difficult to determine the steady-state conditions. I initially assumed that the temperature at the condensate outlet would be 100 degrees, but I feel that it’s actually higher than that. Moreover, the outlet at the bottom is likely to contain both gas and liquid phases, with the condensate water including some steam as well； Well, I feel like I can’t express myself clearly; I’m confused. I would be grateful if those who have experience or knowledge in this area of process design could offer some guidance~{:3_57:}
Oops, it seems like the post is going to sink again. . .
Don’t worry too much; normal operation is completely possible. It is sufficient to control the opening degree of the steam valve. Think about it carefully; it’s not hard to understand.
The operation itself is fine; it’s just a bit difficult to calculate the amount of steam consumed. Moreover, that steam needs to be used in other places as well. Of course, it’s not a big problem – maybe I’m overcomplicating things. . . {:3_59:}
Based on saturation, this heat is primarily provided by the latent heat of condensation; the amount of heat from superheating is minimal. For 4 kilograms at 150 degrees, the temperature of the condensed water at the outlet is also 150 degrees, and there is a steam trap at the outlet.
Condensation occurs at a certain temperature under specific pressure; thus, the temperature of your condensate water is this condensation temperature. It has nothing to do with whether the steam is superheated or not. Even in the case of superheated steam, the excess heat is first removed so that the steam reaches a saturated state before it condenses. Therefore, the temperature of your condensate water depends on the pressure inside the jacket and the time the condensate water stays there
Theoretically, it’s fine, but in practice it’s not easy to control; it’s very unstable, and it’s hard to get it to 90 degrees:lol
This post was last edited by goldliyang on 2017-3-8 at 11:23. First of all, the temperature of saturated steam at 1 MPA is 184°C. Since you say it’s superheated steam, its temperature must be above 184°C; so how does it drop to 178°C after depressurization? This is incorrect; temperature needs to be measured, rather than calculated. The superheat will be higher after depressurization! This raises several issues: 1) Superheated steam has very low heat exchange efficiency, and it also shortens the lifespan of the equipment; it needs to be converted into saturated steam in order to be used in devices requiring heat exchange ； 2) Under ideal conditions, the temperature of the condensate water before the steam trap should correspond to the saturation temperature at the corresponding steam pressure (which should be above 140°C). There is both secondary steam and condensate behind the steam trap; the temperature depends on where it is discharged to and the back pressure at the downstream end
Thank you. I think the condensate temperature should be considered at 150 degrees. Ugh, how could I get this wrong? Right, it’s the jacket that facilitates heat exchange through condensation; the condensate must be discharged before it has time to undergo heat exchange. Among any three people, there is always one who can serve as my teacher! Mm!
Actually, I’m troubled by the retention time. It’s an intermittent reactor here; should the condensate be carried away with the steam, or is it more appropriate to use 150° as suggested by the experts above?~
In reality, the process of heating with superheated steam is not a theoretical sequence of \"superheating – saturation – condensation – cooling\"; it is a complex process that occurs alternately, almost simultaneously. Based on this analysis, the condensate temperature is almost certainly not 150 degrees, but rather much lower than that. Think about it carefully!