Check what’s wrong with my pipeline calculation?
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This post was last edited by sunjl1981 on 2013-1-6 at 23:28. Calculation basis: With an annual production of 50,000 tons of resin, and assuming a gas generation volume of 300 m3 per ton of calcium carbide, 1.42 tons of calcium carbide are required to produce 1 ton of resin. To produce 1 ton of resin, 1.42 tons of calcium carbide with standard gas generation capacity is needed. For an annual production of 50,000 tons of resin, 71,000 tons of calcium carbide are consumed, resulting in 2,130,000 m3 of acetylene gas. Taking into account a 1.2 margin, the actual amount is 2,556,000 m3. With 330 working days per year, the acetylene generation rate per second is: 2,556,000 ÷ 330 ÷ 24 ÷ 3600 = 0.8965 m3/s. According to the “Chemical Process Design Manual,” the pressure for acetylene gas in workshops should be between 0.01~1.5 MPa (G), with a flow rate of 4.0~8.0 m/s； Below 0.01 MPa (G): 3.0~4.0 m/s ； (External pipeline) 0.01~1.5MPa (G) 2.0~4.0m/s ； Below 0.01 MPa (G): 1.0~2.0 m/s. Just after leaving the generator, the acetylene pressure is below 0.01 MPa; when calculating based on the lowest flow rate, the cross-sectional area of the acetylene pipe is 0.299 m2, and when calculating based on the highest flow rate, it is 0.224 m2. Using two pipes of size 425 would meet the requirements, but at the inlet and outlet of the acetylene water-ring pump in our factory, there is only one pipe of size 325 Where did I make a calculation error? Please point it out. # , , &
The acetylene contained at the outlet of the acetylene generator has a relatively high water content. In my previous calculations, I referred to the \"Chemical Process Design Handbook,\" and it seemed that the acetylene flow rate could be below 15 m/s; therefore, a DN325 pipe size would be sufficient for the inlet at a flow rate of 15 m/s. At the outlet, where there is pressure, the flow rate requirement can also be met
The problem is that we exported 2 generators, both of which use 426 tubes; in total that’s 2 tubes. After cooling, they become 1 tube of type 325. What’s going on here?
The ratio of acetylene to water vapor right after it comes out of the generator is approximately 1:3; by the time it reaches the cooling tower, there’s basically very little water vapor left. Did you forget to take the water vapor into account in your calculations?
What was said upstairs is correct – you chose too low a wind speed. Also, you haven’t considered the water vapor partial pressure at different temperatures. Before cooling, the acetylene gas has a high temperature, a high water vapor content, and a large total volume, requiring a larger pipe diameter. The acetylene moisture content is high in front of the cooling tower; the gas velocity can be set at 10~12 m/s ； After cooling, the water content decreases, and the acetylene gas flow rate can be set below 8 m/s ； The velocity of the main delivery pipe generally does not exceed 6 m/s.
Thank you, but I remember that when it comes out of the generator, the ratio of acetylene to water is 1:1 at 85 degrees; for the dry method, it’s around 110 degrees, with a ratio of roughly 1:3. Of course, this is what’s stated in the books – I’m not sure if I might be remembering it wrong
I also considered water vapor, but at that time I wasn’t sure whether a gas output of 300 should not include water vapor I did the calculations; if 300 represents pure acetylene, then calcium carbide contains about 87% CaC2. Therefore, I guess that the 300 volume of gas produced contains only small amounts of hydrogen-sulfurating compounds and similar substances, as the water temperature during the measurement of the gas volume is very low, resulting in a low water vapor partial pressure. I haven’t added water vapor at all in terms of volume, so how can I consider the condensation of water vapor? Moreover, our acetylene has already been cooled before entering the water ring compressor, with most of the water removed. The pressure changed after compression; I haven’t calculated it yet. :'(Please give some advice)
The selection of flow rate is generally based on the characteristics of the equipment and the process medium; therefore, a pipe with a diameter of 425 is chosen at the generator outlet. In cases where there is a pressurization device (such as a water ring compressor), it is necessary to consider the impact of changes in the pressure at the outlet of that pressurization device on the process medium. It is recommended to perform a pressure check on the volume value; furthermore, for gases, absolute pressure rather than relative pressure should be used.
The above considerations are correct, but the pressure from after cooling until the water ring pump is not very high; the water vapor content in the acetylene gas in this section is relatively low. Therefore, it is still appropriate to use a 325 gauge pipe. Why is that? I would appreciate some advice from those who know more :(
Working on engineering is not the same as conducting research. The selection of flow rate is conditional. If the pipe is short, a higher flow rate can be chosen; the pressure drop will also be low. If the pipe is long, a lower flow rate should be used to ensure that the pressure drop remains low. How long the pipe can be from the cooler to the water ring pump? What does it matter even if the flow rate is 20 m/s? (If there are no restrictions on the flow rate, then there are restrictions on both hydrogen and oxygen.) Therefore, one must apply knowledge flexibly and not apply it mechanically. Logically, the grades of the pipes before and after the compressor should not be the same, but this is a minor issue and there is no problem with its use.