Which brother can give some guidance on long-distance steam transmission? I’ll give away wealth as a reward for your answer
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These days I have been thinking about the steam transmission issue for our factory’s power plant; the distance is 5 kilometers, the pipe diameter is DN400, and the pressure required at our factory’s boundary is 11 kilograms, with a pressure drop of 2 kilograms along the way. (1) For example, when delivering 13 kilograms of steam, it should be hot steam; the condensate discharge valve along the pipeline should be opened at the beginning of steam delivery to allow drainage, and then closed once normal delivery is established. Will there be no condensation water after it is turned off? Worried about water hammer? (2) After passing through the pressure reducing valve in our factory, it becomes 4 kilograms or 6 kilograms – is it still hot steam? Would using it directly for heat exchange be rather wasteful? The information regarding steam issues found on this website includes: “Principles for using steam: transport at high pressure and superheated state, and use at low pressure in a saturated state.” High-pressure superheated transmission: It saves the conveying cross-sectional area and minimizes condensation losses during transmission. Low-pressure saturated use: Superheated steam needs to reach saturated conditions in order to condense; if used in a superheated state, some of the steam’s energy may not be utilized effectively. ” It seems that water needs to be added in order to turn it into saturated steam… right?
I need to see how popular it is. If it remains overheated, that is, if it is still too hot at the point of use, then in theory no condensate will be generated after startup, and thus there will be no water hammer. Even for saturated steam, if its dryness degree is very high, there will still be a slight superheat after depressurization. (Energy is conserved, after all.) But if it’s a slight overheating, say 10 or 8 degrees, that’s fine. So the key is to figure out exactly by how much it’s overheated. If the superheat is too high, then temperature and pressure need to be reduced. Superheated steam is generally not recommended for heat exchange.
During long-distance transmission, superheated steam also generates condensate water; therefore, traps are installed at the drainage points along the pipeline. At the beginning of steam delivery, air and water are manually removed first, and once the steam supply becomes stable, the manual valves are closed and automatic drainage is carried out through the traps. Can superheated steam be used directly in production? The answer is yes, but it would be a waste; it’s better to use saturated steam. When superheated steam enters the plant, additional pressure and temperature reduction equipment is needed, as in the case described by the original poster. There are now professional manufacturers that supply such complete sets of equipment. When reducing pressure and temperature, water must of course be added. You’ll understand once you communicate directly with the manufacturer.
The pressure drop needs to be calculated based on the transmission distance; hydrophobic treatment should be applied at the lowest point
Why do you need to reduce the pressure to 6 kilograms after it reaches 11 kilograms at your factory? If you require a low pressure drop, the pipe diameter has to be larger, which is a waste. Around 8 kilograms at your factory would be more appropriate
Economy should also be calculated based on the total length of the pipeline :)
Driers should be installed along the pipeline, and the insulation level will be determined based on economic considerations regarding the required superheat; an excess temperature of 20–30 degrees is estimated to be necessary
Hydrophobizers need to be installed along the way; we have carried out a project of this kind, over ten kilometers in length, and it is working very well now
Reply to 3# Zhu Hongbin: Agree. The steam that passes through the temperature and pressure reduction station is generally saturated, as such stations are equipped with their own water addition system.
Drain valves must be installed along the pipeline; otherwise, condensate water will form when the pipeline is shut down or the steam flow decreases, which can lead to water hammer incidents. After pressure reduction in the plant, there is only about a 5°C superheat, so it can be used directly without any problems. Even with superheated steam, heat exchange can effectively utilize its thermal energy, with no waste.
Even for superheated steam, the layout design of pipeline drain valves should be carried out in accordance with the requirements for saturated steam. The reason is simple: at the start of operation (or when it stops), condensate is inevitable.