Problems occurred during the reboiler renovation
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The laboratory recently modified the reboiler due to its insufficient heating capacity. The original reboiler was a naturally circulating thermosiphon reboiler with a heat exchange area of 8 m2, and the maximum pressure that could be applied to the valves in the gas supply pipeline was 0.4 MP. Under this pressure, mist entrainment cannot be measured, so it was modified. The modification process involves converting two shell-and-tube heat exchangers into reboilers; the total heat exchange area is 8 m2. The reboilers No. 2 and No. 3 are connected in parallel and feed water into a buffer tank from where it then flows to the drain valve, while the original reboiler No. 1 remains unchanged. The imported steam is simply divided into 3 streams and fed into 3 reboilers, all with the same pipe diameter. After the modification, it was found that at the same pressure, such as 0.2 MP, the amount of condensate water from the reboiler remained roughly the same as before the modification. The amount of water discharged from Reboiler No. 1 is slightly less than before. I would like to ask whether this issue is caused by the fact that, at the same pressure, the flow rate of steam remains constant, resulting in the same amount of condensate water Is it still the presence of the baffle that results in insufficient capacity of reboilers No. 2 and No. 3? Is it still because the Reboilers No. 2 and No. 3 were converted from condensers, resulting in two phase changes instead of just one, which affects them? This post was last edited by kunta0100 on 2009-3-18 19:44]
After the modification, was it checked whether the steam feed flow rate had increased? If the steam flow rate remained unchanged, could it be that the valve in the main steam pipeline is blocked, resulting in too low a steam flow rate and thus insufficient heating capacity for the reboiler? In that case, increasing the heat exchange area won’t help.
I believe that: 1. Without more boundary conditions, it is impossible to determine whether the type and number of reboilers are appropriate. 2. Since multiple reboilers operate in parallel, during modification it is necessary to ensure that the lengths of the pipelines for material and steam inlet and outlet to each reboiler are equal and symmetrical, in order to avoid uneven pressure drops that could lead to inconsistent output from each reboiler; this is an engineering issue. You can calculate what percentage difference there is in the materials and steam pipelines for each reboiler.
Thank you 2L3L. The arrangement of the parallel reboilers we use is not symmetrical, and the heat exchange areas of the three reboilers are also different. I checked it again today. It is preliminarily determined that the pipe diameter through which the liquid from the tower bottom enters the reboiler is insufficient, and combined with an asymmetrical arrangement, this results in the larger reboiler receiving more liquid than the other two. In the other two small reboilers, the liquid inside is in gaseous state, and the steam flows directly from the shell side to the steam trap. This is just a preliminary idea for now; further verification is needed. Care is also needed when moving the tower
Air resistance is likely to be high, as there are 3 reboilers; forced circulation is unlikely. I’m not sure if there are any other ways
The prerequisite for increasing the heat exchange area is that there must be an adequate supply of steam; if the steam supply is insufficient, it doesn’t matter how many heat exchangers are added