ENERGY CONSERVATION IN THERMAL POWER PLANTS

CONDENSING SYSTEM

CONDENSING SYSTEM

•CONDENSER

•C.W. PUMPS

•AIR EJECTORS

•COOLING TOWERS

CONDENSER PERFORMANCE

• Cleanliness of the tube surface

• The amount of air in Steam Space

• Flow / Velocity of Circulating Cooling Water

• Temp. of Circulating Water

CONDENSER PERFORMANCEEFFECT OF AIR INGRESS IN CONDENSER STEAM SPACE

Air Ingress in the Steam Space reduces the heat transfer, thereby increasing the temperature of

condensing steam.

1mm of air blanket is equivalent to 250 mm of Copper slab

This results in poor vacuum and lower power output.

PROBLEM OF POOR CONDENSER VACUUM

A CASE STUDY

Unit-1 (200MW) of an Indian Thermal Power Station was

facing poor condenser vacuum problem

resulting in load reduction for a long time.

DESIGN & OPERATING PARAMETERSParameters

 Design Actual

CW Inlet Temperature (C) 33.0 31.1

CW Outlet Temperature (C) 40.81 38.2

CW Temperature Rise (C) 7.81 7.1

Condensate Temperature (C) 46 51

Condenser Pressure (mm of Hg Column) 76 98.5

Saturation Temperature (C) 46.09 51.26

Terminal Temp. Diff. (TTD) (C) 5.28 13.06

Condenser Extraction Temp. (C) 46 50.2

Load (MW) 200 199.9

CONDENSER PERFORMANCE CURVE

The Curve between• CW Inlet & Outlet Temperatures;

• CW Outlet & Saturation Temperatures; and

• Saturation Temperature & Condenser Vacuum.

CONDENSER PERFORMANCE CURVE

CONDENSER PERFORMANCE

CONDENSER CONDITION GRAPHCONDENSER CONDITION GRAPH

CONDENSER CONDITION GRAPH

PLOTTING OF CONDENSER CONDITION GRAPH

CW Temp. Rise (C)C)The R.H.S. of the Graph is the plot between CW Inlet & Outlet Temperatures for the Design & Operating Conditions.

DESIGN LINE:Join the Points (0, 7.81) & (33, 40.81)

OPERATING LINE:Join the Points (0, 7.1) & (31.1, 38.2)

PLOTTING OF CONDENSER CONDITION GRAPH

Terminal Temp. Difference (C)C)The L.H.S. of the Graph depicts the TTD Lines for the Design & Operating Conditions.

DESIGN TTD LINE:Join the Points (5.28, 0) & (46.09, 40.81)

OPERATING LINE:Join the Points (13.06, 0) & (51.26, 38.2)

CONDENSER CONDITION GRAPH

ANALYSIS OF CONDENSER CONDITION GRAPHDEVIATION DUE TO CW INLET TEMPERATURE

It is observed that the actual CW Inlet Temp. (31.1It is observed that the actual CW Inlet Temp. (31.1C) is C) is lower thanlower than

the specified Design Temp. (33.0the specified Design Temp. (33.0C).C).

This should give us advantage in terms of Condenser This should give us advantage in terms of Condenser

Vacuum.Vacuum.

ANALYSIS OF CONDENSER CONDITION GRAPHDEVIATION DUE TO CW INLET TEMPERATURE

Draw a vertical line from Operating Inlet CW Temp. of Draw a vertical line from Operating Inlet CW Temp. of 31.131.1C until it intersects the Design CW Temp. Rise C until it intersects the Design CW Temp. Rise Line. This point is horizontally transferred to the Line. This point is horizontally transferred to the Design TTD Line to get the Saturation Temp. of 44.5 Design TTD Line to get the Saturation Temp. of 44.5 C and corresponding Vacuum is 70 mm of Hg C and corresponding Vacuum is 70 mm of Hg Column.Column.

Hence, the gain due to Lower CW Inlet Temp. is 6 mm Hence, the gain due to Lower CW Inlet Temp. is 6 mm of Hg Column (the difference of design Back Pressure of Hg Column (the difference of design Back Pressure and Operating Back Pressure)and Operating Back Pressure)

ANALYSIS OF CONDENSER CONDITION GRAPH

CONDENSER PERFORMANCE CURVE

ANALYSIS OF CONDENSER CONDITION GRAPHDEVIATION DUE TO CW FLOW

Draw a vertical line from Operating Inlet CW Temp. of Draw a vertical line from Operating Inlet CW Temp. of 31.131.1C until it intersects the Operating CW Temp. Rise C until it intersects the Operating CW Temp. Rise Line. This point is horizontally transferred to the Line. This point is horizontally transferred to the Design TTD Line to get the Saturation Temp. of 43.1Design TTD Line to get the Saturation Temp. of 43.1C C and corresponding Vacuum is 65 mm of Hg Column.and corresponding Vacuum is 65 mm of Hg Column.

Hence, the gain due to Higher CW Flow is 11 mm of Hence, the gain due to Higher CW Flow is 11 mm of Hg Column (the difference of design Back Pressure Hg Column (the difference of design Back Pressure and Operating Back Pressure)and Operating Back Pressure)

ANALYSIS OF CONDENSER CONDITION GRAPH

ANALYSIS OF CONDENSER CONDITION GRAPHDEVIATION DUE TO CONDENSER FOULING / AIR INGRESS

The effect of dirty tubes and air ingress on heat transfer is to increase the TTD.

Draw a vertical line from Operating Inlet CW Temp. of 31.1C until it intersects the Operating CW Temp. Rise Line. This point is

horizontally transferred to the Operating TTD Line.The reference point when transferred vertically downwards gives the Saturation

Temp. of 51.26C and the corresponding Vacuum is 98.5 mm of Hg Column.

The net deterioration in Vacuum is (98.5-76) = 22.5 mm of Hg Column.

Hence, the Overall Reduction (due to all effects) is22.5 mm of Hg Column (the difference of design Back Pressure and

Actual Operating Back Pressure)

ANALYSIS OF CONDENSER CONDITION GRAPH

ANALYSIS OF CONDENSER CONDITION GRAPH

The net deterioration in Vacuum is The net deterioration in Vacuum is (98.5-76) = 22.5 mm of Hg Column.(98.5-76) = 22.5 mm of Hg Column.

As there was a Gain due to Lower CW Inlet Temp. and As there was a Gain due to Lower CW Inlet Temp. and Higher CW Flow, Higher CW Flow,

the Total Reduction due to dirty Condenser tubes and Air the Total Reduction due to dirty Condenser tubes and Air Ingress is {22.5+(6+11)} = 39.5 mm of Hg Column.Ingress is {22.5+(6+11)} = 39.5 mm of Hg Column.

It was also revealed by the O&M Staff that operating the It was also revealed by the O&M Staff that operating the Standby Ejector had hardly any positive effect on the Standby Ejector had hardly any positive effect on the

condenser backpressure.condenser backpressure.Hence, it was proved that condenser tube fouling was the Hence, it was proved that condenser tube fouling was the main contributing factor to the problem of poor condenser main contributing factor to the problem of poor condenser

vacuum.vacuum.

CONCLUSION

• From the graphs, it was obvious that the condenser tubes were heavily fouled and this was responsible for poor vacuum and hence, load reduction.

• Accordingly, it was decided to acid clean the tubes.

This was done and the problem was solved.

• The possibility of installing an on-line tube cleaning system was also to be explored.

Thanks a lot!