Regarding the steam cooling wall and downcomer
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The downcomer connects the boiler and the water-cooled screen, forming a circulation loop. I would like to ask: in the case of a boiler with steam-cooled walls, how is this loop connected? Connection between the drum downcomer and the steam cooling screen? Won’t it turn into water inside that air-cooled screen? Also, where is the outlet of the air-cooled screen connected to?
I’ve never heard of a steam-cooled wall; it must be a water-cooled wall. 1. The water in the water wall boils after being heated, and then enters the steam drum ； 2. The gas from the drum enters the superheater after separation, while the liquid from the drum goes to the mixer through the downcomer ； 3. Deoxygenated water enters the mixer via the make-up water pump and the economizer as well ； 4. The water from the mixer enters the water wall via a recirculation pump.
This post was last edited and replied to by dongjiang1001 on 2011-11-22 at 17:34. 2# xyc114 is a air-cooled screen.
I’ve never heard of this concept; where did the original poster find this information?
Reply to 4# kof369: Oh no, is this something specific to the alkali recovery boilers used in the papermaking industry?
This post was last edited by xyc114 on 2011-11-22 at 17:17. I checked the steam-cooled screen; it is actually a screen-type superheater, located between the primary superheater and the secondary superheater. There is water injection for temperature reduction before and after the screen-type superheater, before the steam finally enters the turbine. This refers to high-pressure, large-capacity boiler systems. There are also ultra-high pressure, sub-critical, and super-critical boiler systems, but they are too complex. The original poster might have mistaken the tubes leading out from the rear wall for steam cooling screens. Steam cooling screens are connected only to the first and second superheaters, whereas the tubes leading out from the rear wall are similar to the water wall, except that they are located on the rear wall; moreover, these tubes are adjacent to the steam cooling screens (but there is no connection between them).
Reply to 6# xyc114: http://bbs.hcbbs.com/viewthread.php?tid=388745. This post is about the alkali recovery boiler I saw; the load on the boiler and the parameters for steam generation are the same: 8.4 MPa and 450 degrees. The post mentions that the furnace is surrounded by a membrane-type water wall, and a steam cooling screen is located at the furnace outlet. Following that are an IB-grade superheater, a II-grade superheater, a III-grade superheater, an IA-grade superheater, evaporation tube screens, and two levels of economizers at the rear part of the boiler. ” That means there are still water wall tubes, right? It seems the professor and senior engineer who told me there were no water wall tubes was wrong?
The furnace is surrounded by a membrane-type water wall; a steam cooling screen is installed at the furnace outlet, followed by the IB-stage superheater, II-stage superheater, III-stage superheater, IA-stage superheater, the evaporator tube bank, and two stages of economizers located at the rear part of the furnace. ”It is a super-high pressure boiler system layout; logically, there should also be a furnace top superheater in front of the furnace outlet. If you insist on saying that the downcomer of the steam drum is connected to the steam cooling screen, then I’m not sure. Logically, the steam cooling screen shouldn’t be connected to the steam drum; it could be related to the water spraying mechanism, where water is sprayed using a water pump. Ask the manufacturer about these. I haven’t seen such a situation yet.
Could you recommend some books on the basic structure and design of boilers? I’m just starting out and don’t understand many of the fundamental concepts