Simulation of a power station's condensate pumping system in view of improving its efficiency

Abstract

With increasing environmental awareness, higher electricity production costs, and a shortage in electricity supply to the South African grid, increased focus has been placed on the efficiency of power plants, and the improvement thereof. On the majority of the Condensate Extraction Pumps (CEPs) installed in power stations, the flow control is implemented by conventional valve throttling of the discharge valve of these pumps. This type of flow control is uneconomical, as more than 30 of the flow – and the pressure – that can be supplied by the CEPs, is throttled under normal operating conditions. As an energy-efficiency improvement measure, many sources recommend retrofitting of this flow control mechanism with variable speed flow control; but as different applications have different requirements, a need was identified to develop a systematic approach that would assist in determining the feasibility of a variable speed drive (VSD) retrofit. In order to develop this approach, a case study was conducted on an Eskom coal-fired power station – comparing different flow-control techniques with the aid of efficiency calculations, a simulated model, and an economic evaluation. In this case study, an electrical VSD was identified as a feasible retrofit, with an energy saving of 34.6 achievable in pump power consumption at full load conditions.