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FIN TUBE ECONOMISERS

Design

Design data listed below is based on the following.
Dew point for 0% sulphur fuel and 20% excess air is 45-50 deg C (Perry Chemical Engineers Handbook)
Feed water minimum design temperature to prevent condensation, should be 20 deg above dew point.
Feed water maximum design temperature to prevent steam generation and water hammer in the economiser, should be boiler steam saturation temperature less 30 deg C. (Ecomomiser setup only) (W ater heater max 90 deg C)
For specifications above flue ducting can be CS and Fintube CS tube with aluminium fin.
Where possible there is a possibility of sulphur or salt corrosion alternative materials should be considered.


Construction

600 to 2000kw economisers
All transitions and casings as 304 SS.
Standard units are 3 - 5 rows.

Nominal side 2 MW to 6 MW  Boiler working 600 hours per month
Boiler to economiser transitions are carbon steel construction.
Economiser to stack transition is 304 SS construction.
Stack is 304 SS as carbon steel casings are not significantly less expensive.
Standard units are 3 row or 4 row sections of 300 long
The six row  / 8 row units consist of two 3/4 row units.

General construction details are as follows
Headers are sched 40 carbon steel and finned tube 15.9 / 254 ODA179
Condensate drainage should be considered for stack temperatures less than 100 deg C
Standard fine tube is grade 1100 aluminium fin imbedded in carbon steel tube (G type fin) Max Temperature 400 deg C
Optional grade 304 SS fin wrapped on to 304 SS tube (T type fin) Max Temperature 250 deg C


Cost Recovery

The cost recovery data below is based on the following criteria
The boiler is correctly adjusted for the fuel being used and efficiency is assumed to be 80%
The boiler is operating at 90 - 100% full fire
The fuel is natural gas at 45 MJ / KG and a cost of $10 a gigajoule