How to reduce the Specific Steam consumption (SSC) of a Steam Turbine??

 

        

Specific steam consumption is the amount of steam consumed by a Turbine to generate unit power.

Or else, Specific steam consumption is the ratio of steam entered into the Turbine to the power generated

SSC = Steam consumption / Power generation.

For example: A 50 MW steam turbine consumes 190 TPH of steam to operate on full load, then its Specific steam consumption (SSC) will be;

SSC = 190 / 50 = 3.8 TPH/MW or 3.8 kg/kwh

Specific steam consumption (SSC) of a Turbine depends on following factors;

1-Inlet steam parameters

2-Vacuum or exhaust pressure

3-Exhaust pressure

4-Bleed steam pressure, temperature & flow

5-Extraction steam pressure, temperature & flow

6-Turbine maintenance practice or preventive and corrective maintenance

Specific steam consumption (SSC) of a Turbine can be reduced by taking following corrective measures.

Maintaining inlet steam parameters: Maintaining Turbine inlet steam parameters play a vital role in improving Specific steam consumption (SSC). The steam pressure and temperatures lower than the design will lead to increase Specific steam consumption (SSC).

Therefore, always maintain Turbine inlet main steam temperature as per OEM recommended to reduce steam consumption.

Maintaining higher vacuum & lower exhaust temperature: Turbines operating at lower vacuum (exhaust pressure) and higher exhaust temperature call for more steam consumption to generate unit power as compared to Turbines operating at higher vacuum & lower exhaust temperatures.

So, it’s always recommended to maintain vacuum on higher side.

Ensure following to get more vacuum.

1-Sufficient cooling water for condenser

2-Condenser Tubes are being cleaned regularly

3-Enough temperature drop in cooling tower

4-Operation of the Turbine at optimum load. Operation of the Turbine at lower loads results into higher exhaust temperature.

5-Ejectors steam pressure & temperature are as per OEM

6-Use of Liquid ring vacuum pump (LRVP) saves steam energy & consumes around 40% of its power in terms of electrical power.

Bleed steam pressure, temperature & flow: Higher the bleed steam pressure, temperature & flow than design higher will be the Specific steam consumption (SSC) or lower will be the power generation at same quantity of inlet steam flow.

Hence, always try to maintain bleed steam pressure & temperature within limit.

Read>>>>Calculated reasons for more SSC

Higher bleed steam pressure & temperature carries away the heat from Turbine without doing any work in Turbine, hence steam consumption to generate specific power will increase.

Extraction steam pressure & Temperature: Similarly, steam extraction at higher steam pressure & temperature will lead into more steam consumption.

Wear out of labyrinth seals: If there is more clearance between internal seals & rotor, some amount of steam directly escapes into next stages of rotor without contributing work done. Hence in such case, Turbine draws more steam to generate desired power.

Therefore, always carryout the Turbine preventive maintenance regularly and replace worn out parts especially seals & gaskets

Steam leakages: Arresting all internal & external steam leakages.

Operation of the Turbine at optimized load: Operating the Turbine at lower loads will lead to more steam consumption to generate particular unit of power.

Hence always try to avoid the operation of the Turbine at partial loads.

Proactive operation & maintenance practice: Following operation & maintenance practices should be followed to reduce Specific steam consumption (SSC) of a Turbine.

Timely replacement of worn out bearings, ensuring precision alignments

Read more on>>>>Turbine major overhauling

Maintaining correct temperature of lube oil for bearings

Regularly servicing of actuators to avoid load hunting

Maintaining good quality for steam and water

Ensuring turbine blades cleaning during every major overhauling

Monitor the load & steam consumption on various loads & observe any deviations

Read more>>>>>Interview questions & answers on steam Turbine