Calculation of the material weight in a packed absorption tower
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This post was last edited by *aofee on 2015-7-9 at 11:55. There is a tower whose weight needs to be calculated; its own weight is known – it has a diameter of 1.5 meters and a height of 10 meters, so its weight is approximately 2 tons (made of fiberglass composite material). I’m unsure about what the maximum weight of the material can be at present. My calculation is as follows: it’s an absorption tower, so the gas component isn’t taken into account; the maximum volume of liquid feed is 130 cubic meters per hour, with a density of around 1.2. I calculated the flow rate to be approximately 0.0204 m/s, using 130 cubic meters per hour and a diameter of 1.5 meters. The residence time was then determined by dividing 10 meters by the flow rate; it came out to be around 490 seconds (about 0.136 hours). The volume of liquid remaining in the system was calculated as 130 × 0.136 = 17.7 cubic meters. Multiplying this by the density gave a weight of approximately 21.2 tons. Is the weight I calculated correct?
The error resulting from this calculation is quite large; it’s as if the calculation is done for an empty tower, when in fact the entire device is filled. Neither the liquid holding capacity of the filler nor the liquid level maintained by the tower itself is known.
This post was last edited by *lihuagong on 2015-7-9 at 12:29. It doesn’t seem to be closely related to the feed rate; the weight inside the tower should be calculated based on the liquid holding capacity of the packing and that of the tower bottom. Can we simply use the porosity of the packing, considering all the voids as being filled with liquid?
There must be a calculation error; the volume of this tower is less than 18 cubic meters – how is it possible to hold 17 cubic meters of liquid in it? Doesn’t the filler have a porosity? The estimation can be done by assuming that all of the voids are filled with liquid
I’m not sure what substance is being absorbed; it seems that the flow rate of the liquid is a bit high. Has the flooding point been calculated? The diameter is 1.5 m, and the liquid flow rate is 130 m3/h. Based on an empty tower gas velocity of 1.5 m/s, the gas flow rate in a tower with a 1.5 m diameter is approximately 10,000 m3/h, resulting in a liquid-to-gas ratio of 13. When I do this, I usually use a liquid-to-gas ratio of between 3 and 5; for a packed absorption tower, it is sufficient as long as the packing can be properly wetted. As a gas absorption tower, the highest liquid level inside the tower cannot exceed the height of the gas inlet pipe. The weight of the material can be more accurately determined by calculating the volume of liquid below the static liquid level in the tower; in other words, the total weight of the liquid below the highest liquid level in the tower should not be that great.
The liquid holding capacity of the tower itself does not exceed 1 m, and the packing is in bulk; how is this liquid holding capacity calculated?
Come in and learn* a bit;P:victory:
Is the volume less than 18? Why do I get a value higher than 18?
Throughout the entire calculation process, I didn’t notice any problems. It seems I need to go over reaction engineering again – is the calculation of the liquid holdup based on residence time incorrect?
I’ve been thinking about this too. Hehe, although there is a porosity factor, the porosity of the filler material is always around 0.9, so even when considering the effective diameter, it doesn’t differ much
First, estimate the liquid level in the tower bottom: for a tower 10 meters high, the height of the tower bottom is around 1000–1200 units, and the amount of liquid stored there is 2.54 tons. As for the liquid retention capacity of the packing, this varies depending on the type of packing used; operational parameters also affect this capacity. For mature packing materials, the liquid retention rate ranges from 15% to 65%. I estimate that 50% liquid retention is generally chosen. A 10m tall tower has approximately 6–8m of packing; using 8m as a value, the liquid holdup is 8.48 tons. For the gas phase, 0.5 tons should be sufficient for this tower. The total weight of the operating media is about 11.5 tons.