1 "TIC"

Temperature flue gas output Economizer. Used for control according to flue gas temperature.

2 "TT"

Temperature flue gas input Economizer.

3 "TZAH"

Temperature MAX output feed water Economizer.

4 "PZAH"

Feed water pressure MAX output feed water Economizer.

5 "TT"

Temperature feed water return line Economizer.

6 "TT"

Temperature feed water supply line Economizer.

7

Feed water control valve

8

Control damper for flue gas flow Economizer

9

Control damper for flue gas flow bypass

10

Servomotor for positioning the dampers (8) and (9)

Economizer/bypass flow

The flue gases are directed by two dampers, which are moved in opposite directions by a motor, either by the Economizer or via the bypass.

Purge

The purge behavior before the burner start would be ideal if initially only the bypass (checked with limit position) was to be purged and thereafter only the Economizer (checked with limit position). However, se@vis and the safety control do not offer this type of two-stage purge sequence including monitoring of the limit positions.

The purge process with se@vis must be performed with both dampers in the center position (checked with limit position).

Control of the flue gas temperature by means of flue gas dampers

This control regulates the flue gas flow rate that flows through the Economizer in order to adjust the flue gas temperature. The supply of feed water is constant.

Control of the flue gas temperature by means of feed water control valve

This control regulates the supply of feed water in order to adjust the flue gas temperature. The flue gas dampers are in defined positions and are not regulated.