How is the design temperature of this pipeline determined?
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This pipeline is the main flare line for the refinery; it has a diameter of 42” and a length of 1500 M. Its designed maximum flow rate is 650 T/H, with a temperature of 270 degrees. However, under certain operating conditions, one of the control valves needs to discharge material at a rate of 14 T/H at a temperature of 460 degrees, for a period of 24 hours. This operation is carried out approximately once every two years. The question is whether the design temperature of the torch main pipe should be raised to 460 degrees Stay at 270 degrees? Note: If the temperature is raised to 460 degrees, carbon steel materials cannot be used, and the cost of the flare header will **increase**. This post was last edited by csldg on 2009-3-9 19:24]
Personal suggestion: Could a heat exchanger be added at that pipeline to recover its heat while also meeting the requirements for low-temperature emissions? It is estimated that the diameter of that pipe at 460 degrees is approximately 2’, and it can be led directly to the flare alone. The same should apply to the third floor as well. This post was last edited by QQ Ai on 2009-3-10 08:39.]
It is recommended to connect a parallel pipeline behind the control valve, which meets the design requirements while reducing costs.
On the 2nd floor, since this type of discharge occurs only once every 2 years and each occurrence lasts no more than 24 hours, it is likely that installing a heat exchanger would not be cost-effective. Could you elaborate on your suggestion on the 3rd floor? I’m a bit confused. My question is about that 42\" pipeline; as for the pipeline behind the control valve, even if higher-grade materials are used, it won’t cost much more.
Check whether the 15 t/h of material is included in the total amount of 650 t/h; if they are discharged together, 270 degrees may be sufficient to meet the temperature requirement for the combined flow.
The key question is whether this 14 t/h of high-temperature material needs to be mixed with that 650 t/h of material at 270°C before being sent to the flare If that’s the case, then the temperature of the mixture won’t increase much, and it won’t have a significant impact on the choice of pipeline material ； If these high-temperature materials need to be vented separately, cooling or the addition of other low-temperature media can be used to reduce their temperature (provided that the vented gas can burn properly).
What the people upstairs said makes sense; it’s possible to calculate the temperature after mixing, and if that doesn’t work, considering sending it to the flare tower separately could be an option.
In principle, various options are listed for comparison, taking into account factors such as safety, cost, and feasibility; generally, safety comes first. As long as safety is not compromised, and the additional comprehensive cost of discharging separately is lower than that of mixed discharge, and there is still time to make the changes, then discharging separately should be considered. Furthermore, no matter how it is discharged, it ultimately has to go to the flare tip, so the process needs to be carefully considered.
I’m sorry, guys upstairs; I didn’t explain myself clearly. This 460 degrees, 14 t/h of material is discharged separately and is not included in the 650 t/h amount. So how should one set conditions? Should a heat dissipation calculation be done? But how reliable is the result of such calculations? Have you encountered similar problems in your design work? For example, it lasts for 1 hour, but maybe it happens only once every 2 years; should the design temperature then be set at this extreme temperature of 1 hour? Half an hour? 1 minute?
If that’s really not possible, then design a separate pipeline to connect to a small storage tank nearby; this approach allows avoidance of the need to upgrade the 42\" pipelines, and the investment required is also not significant.
The material at 14 t/h is in gas phase, so using a storage tank is likely not feasible. And I’m also very curious to know exactly how such problems should be handled What is the basis for the design temperature?
I agree with the opinion of the person above; adding a heat exchanger is a good idea, preferably one that makes use of waste heat, as energy should not be wasted needlessly. If the device being designed contains components that need to be heated, this view holds more weight. We have a project that works on this principle, similar to preheating.
I tend to use a separate exhaust pipe.
Those among you who recommend adding a heat exchanger to recover waste heat should note that this pipeline operation is carried out only once every 1 or 2 years, for a duration of 1 hour each time. So there’s no need to add a heat exchanger to recover heat! I suggest: 1. Analyze whether it can be mixed with other media leading to the torch in order to reduce the temperature ； 2. Can inert gases or air be used in combination to lower the temperature? ； 3. Can it be **cooled? 4. If neither option works, which is cheaper: installing a separate pipeline to the flare, or upgrading the main flare pipe? In short, handle it in the most cost-effective and reasonable way.
Strongly agree with the 14th floor – let’s learn * along the way!
Thank you all for your responses. It seems that the general opinion is that if such materials are discharged separately into the flare system, then the design temperature must be increased to 460 degrees. I wonder if there are any other opinions.
By the way, why can’t my ratings be successful every time?
Agree with the view from floor 14. :lol
The design temperature of the torch main pipe is generally 120 degrees; if high-temperature materials are discharged from the unit, measures to reduce the temperature should be considered, otherwise there is a problem with the unit’s design.
19th floor, what do you mean by we should consider lowering the temperature? Does it refer to the need to calculate the cooling effect resulting from heat dissipation, or does it mean the need to design cooling facilities?
From a safety perspective, I think it’s better to set the design temperature at 460 degrees, after all, the venting time is relatively long