Thursday, May 22, 2014

Primary Flow Measurement for modelling of Thermal Power Stations using EBSILON Professional Software.

I am involved in implementation of Phase II - Output 2 of Indo German Energy Program (IGEN) where we have to introduce Model Power Plant Concept in identified Thermal Power Generating Units. In this phase of the program we have to demonstrate the improvements in Energy Efficiency in these Units.

During IGEN Phase II - Output 1 the licenses for EBSILON Professional Software were provided to the State Utilities and Training was also provided to use the software for identification of areas and components having major Heat Rate deviations.

The Steam Flow entering the Steam Turbine is most important input for modelling the plant using the software and since there was direct measurement available the same was used during the initial phase.

Since I was associated with Performance Guarantee Tests of similar Units in India I knew that the direct measurement of Main Steam Flow was not accurate and this flow used to be much higher than the computed Main Steam Flow during the tests. The other option was to use Feed Water Flow but I also knew that this flow also used to be always higher than the computed Feed Water Flow during the tests.

During Performance Guarantee Tests we were using special Flow Nozzle confirming to ASME PTC-6 installed to measure the Condensate Flow entering the Deaerator. The Feed Water Flow was then computed by calculating the extraction flows to High Pressure Heaters and Deaerator and adding them to Condensate Flow also considering the change in Deaerator level. This Nozzle was removed after Performance Gurantee Tests and used in other Units of the Station.

In May 2014, I went to Mettur Thermal Power Station to assist the Station for modelling of Unit no 1 which was selected for IGEN Phase II -Output 2.

Fortunately, the Condensate Flow to Deaerator measurement was available in this Unit. When we considered the data for modelling we were not getting sufficient output from the Turbine since the measured Condensate Flow was 5% lower than the expected flow. After checking we found that the Station had done modification in the Spray line to PRDS and Condensate Flow at CEP discharge was being used as spray. We considered this in the model but the spray flow was coming only 2.4 T/hr (0.5% of Condensate Flow).

Reluctantly I agreed to use Feed Water Flow for the Modelling but with a rider that we shall reduce the measured Feed Water Flow by 1.5% (based on my experience of Performance Guarantee Tests of similar units) for accurate modelling.

PCRA team was doing Energy Audit in the Station at the same time and we asked them to measure the spray flow to PRDS by using portable Ultrasonic Device and it was found as 2 T/hr i.e. nearly same as predicted by the model.

I was not happy with the measured Condensate Flow and insisted on measurement of Differential Pressure. When the Differential Pressure was measured the calculated flow from its reading was 5% higher than indicated reading in the DCS. The C&I Maintenance Engineer corrected it.

Thus we could do accurate modelling of the Unit by using Condensate Flow to Deaerator at Unit 1 of Mettur Thermal Power Station. The computed Feed Water Flow was lower by 1.5% compared to measured Feed Water Flow confirming my previous experience.