Deaerating type Condenser 2

[Adi]

I'm looking for some basics and write ups on dearating type condensers. I understand that some utilities in US use dearating type condenser in the power cycle. As practice, Indian power plants locate the 'deaerator' between the LP heaters and the HP heaters; the Boiler feed pumps are supplied by the storage tank of the dearartor. Thanks

 

[smit]

Adi<br>
<br>
I work in the UK Power industry & have done for many years. I am not realy sure what you are after. However the comment that Indian power plants & where they locate their DA is the same as most UK plants e.g. High Marnham PS the DA is after the LP heaters & before the HP heaters. The DA does 4 jobs. 1.It dearates the feed water. 2. it is a direct contact heater (being fed with bled steam. 3. It is a header tank for the feed water pumps. 4. It is a surge tank (this allows for changing levels during load changes). The DA is normally vented to the condenser which is under vacuum. On some CCGT power plants i.e. Siemens design. their DA is not vented back to the condenser, it relies on the incoming condensate water being sprayed at one end of the vessel, & its temperature being approx 8deg less than the water in the vessel. As air will travel to the cooler end of a vessel around the spray box a series of vents are situated. These vents are straight to atmosphere. Let me know if you need more info. Smit

 

[Adi]

Smit<br>
<br>
Thaks a lot for your response. I'm looking for some data, write ups & experience of 'deaeration' of feedwater taking place right in the steam condensor thereby eliminating the need for a separate DA between LP and HP heaters. Adi<br>
<br>

 

[dannyo]

Adi:

Deaerators can be placed directly on the condenser. Makeup water is fed to the DA and is heated to saturation by using the condenser steam. The dissolved gases exit through the top of the DA via an ejector system and the deaerated makeup water gravity drains to the condenser. If you need more info, let me know.

Danny

 

[Impdrew]

Hi,
I am unsure if i am posting this in the correct place, aplogies if not. On the subject of deaerators. My knowledge of their operation is limited , but i have a small capacity system to which i am unsure how to apply, or whether i need to apply, a deaerator.
Required boiler feed water temperature > 130 C
Boiler outlet pressure 40 bar (superheated).
non-condensing turbine, (therefore minimum outlet pressure of atmospheric, Tsat - 100 C) at a rating of 70 kw (small)

The problem is, i am concerned that the turbine is too small to blead effectively for steam to drive the dearator. I can think of a few alternatives,
1. bleeding the boiler prior to superheating and using that saturated steam to deaerate the the feed.
2. Bleeding superheated steam prior to turbine inlet to do the same job (wasteful!)
In the above two, i consider whether using the steam to first preheat some combustion air prior to using it in the dearator may be more effective.
As far as i know, hot water and low pressure steam can be used to drive deaerators, but the limitations on this i am unsure of.

The final thought is if the exit pressure of the turbine is atmospheric or made slightly greater (maybe even so that the sat temp is ~ 130 C) then does the condensate even need to be passed through a dearator as it is of a high temperature already ( maybe just requires some sort of venting), and could a condenser/deaerator as discussed above be used for the make up water.
I know the above is not a short direct question, but any thoughts would be greatly appreciated.
Thanks.
Andrew