Abstract
M.Tech. (Mechanical Engineering)
Eskom fossil fuel power stations operate under various conditions and the ageing fleet of fossil fuel power stations are under strain due to the rising demand in electricity. The quest for cheaper electricity in growing businesses and bringing foreign investment into South Africa is significant for economic growth. Therefore, minimizing operation costs and improving availability, reliability and thermal heat rate are key objectives for the operation
of the business. Thermal heat rate calculation is a method used to assess the performance of
fossil fuel power stations.
It provides an indication of the thermal performance which reflects the condition and
operation of the plant. This dissertation refers to the tools used to measure the condenser
performance and to identify the reason for unhealthy condenser performance and an
increase in thermal heat rate.
Problem: Poor condenser performance causes significant losses in generation and thermal
heat rate in fossil fuel plants. Loss in generation and thermal heat rate is caused by
condenser backpressure. This has an adverse effect on turbine thermal heat rate and henceturbine efficiency. The performance of the condenser affects the turbine performance to a large extent. Decreased condenser performance will increase the turbine thermal heat rate,
i.e. kJ/kWh, because of the increased steam consumption per kWh of energy generated and
therefore lowering the overall turbine efficiency.
This will result in poor thermal heat rate efficiency resulting in an increased coal burn rate,
i.e. kg/kWh, and an increased fuel bill and carbon foot print for the fossil fuel power station.
The aim of this dissertation is to determine the effects of condenser performance on thermal
heat rate and to provide the engineering and operating personnel with a guide for
monitoring condenser back pressure in order to improve turbine thermal heat rate and
turbine efficiency.
Method and Procedure: Chapter 4 describes the method and procedure used for the pre
and post outage evaluation to cost-effectively determine the current condition of the
condenser and to quantify the increase in thermal heat rate due to condenser degradation.
The pre and post outage evaluation offered an opportunity to evaluate and quantify the
effectiveness of the maintenance program and the value of the capital layout undertaken
during the scheduled Unit outage.
Findings: Chapter 5 discusses the findings of the pre and post outage data analysis of the
condenser using the EtaPRO system as the tool. Re-tubing 50% of the condenser inner loop
tubes and cleaning the other 50% of the outer loop tubes demonstrated a decrease in
condenser backpressure and therefore an improvement in thermal heat rate. This will also
result in an improvement in turbine cycle efficiency and reduce coal cost.