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Low load operation of turbine-driven boiler feed pumps
Boiler feed pump turbines (BFPTs) are in use at a number of Eskom power stations. They utilise bled steam extracted from the main turbine in order to drive multistage centrifugal pumps which supply the boilers with feedwater. With an increase of renewables in the energy mix, the need for Eskom’s coa...
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| Format: | Thesis |
| Language: | English |
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Department of Mechanical Engineering
2020
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| _version_ | 1867613213638524928 |
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| access_status_str | Open Access |
| author | Clark, John Shaun |
| author2 | Fuls, Wim |
| author_browse | Clark, John Shaun Fuls, Wim |
| author_facet | Fuls, Wim Clark, John Shaun |
| author_sort | Clark, John Shaun |
| collection | Thesis |
| description | Boiler feed pump turbines (BFPTs) are in use at a number of Eskom power stations. They utilise bled steam extracted from the main turbine in order to drive multistage centrifugal pumps which supply the boilers with feedwater. With an increase of renewables in the energy mix, the need for Eskom’s coal-fired power stations to run for extended periods at very low loads has arguably never been this great. Various systems affect the ability of these generation units to run economically at low loads. One such system is the boiler feed pump turbine and its associated pumps. A station was selected from Eskom’s fleet based on access to information and the station being a relatively typical plant. The Unit (a boiler and turbogenerator set) selected for study was one with the most thorough instrumentation available for remote monitoring. The BFPT system of this Unit was modelled in Flownex, a one-dimensional thermofluid process modelling package. The model included individual pump stages, steam admission valves and a stage-by-stage turbine model utilising custom stage components. These turbine stage components represent each stage with nozzles and other standard Flownex components. The boundary conditions of the system were set as functions of generator load in order to represent typical values for use in case studies. The relationships between load and boundary conditions were based on large samples of data from the station’s data capture system (DCS). A corresponding standby electric feed pump system was also modelled in Flownex for a comparative case study. After model validation, a number of case studies were performed, demonstrating the functionality of the model and also providing specific results of value to the station in question. These results include the minimum generator load possible with different steam supplies; maximum condenser back pressure before plant availability is affected; the viability of changing the pump leak-off philosophy; and the effect of electric feed pump use on power consumption. The main recommendations from the case studies were as follows: i. to stroke the steam admission valves as per the design charts, ii. to test the operation of the BFPT down to 40 % generator load, iii. to keep the pump leak-off philosophy unchanged, iv. to maintain the cooling water system and condensers sufficiently to avoid poor condenser vacuum, v. to reconsider the decommissioning of the “cold reheat” steam supply, vi. and, to favour use of the BFPT over the electric feed pumps at all generator loads. |
| format | Thesis |
| id | oai:open.uct.ac.za:11427/31576 |
| institution | University of Cape Town (South Africa) |
| language | eng |
| last_indexed | 2026-06-10T12:32:34.479Z |
| license_str | Not specified — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UCTD — University of Cape Town Open Access Repository |
| publishDate | 2020 |
| publishDateRange | 2020 |
| publishDateSort | 2020 |
| publisher | Department of Mechanical Engineering |
| publisherStr | Department of Mechanical Engineering |
| record_format | dspace |
| source_str | UCTD — University of Cape Town Open Access Repository |
| spelling | oai:open.uct.ac.za:11427/31576 Low load operation of turbine-driven boiler feed pumps Clark, John Shaun Fuls, Wim nozzle model power generation Flownex boiler feed pump turbine low load operation Eskom Boiler feed pump turbines (BFPTs) are in use at a number of Eskom power stations. They utilise bled steam extracted from the main turbine in order to drive multistage centrifugal pumps which supply the boilers with feedwater. With an increase of renewables in the energy mix, the need for Eskom’s coal-fired power stations to run for extended periods at very low loads has arguably never been this great. Various systems affect the ability of these generation units to run economically at low loads. One such system is the boiler feed pump turbine and its associated pumps. A station was selected from Eskom’s fleet based on access to information and the station being a relatively typical plant. The Unit (a boiler and turbogenerator set) selected for study was one with the most thorough instrumentation available for remote monitoring. The BFPT system of this Unit was modelled in Flownex, a one-dimensional thermofluid process modelling package. The model included individual pump stages, steam admission valves and a stage-by-stage turbine model utilising custom stage components. These turbine stage components represent each stage with nozzles and other standard Flownex components. The boundary conditions of the system were set as functions of generator load in order to represent typical values for use in case studies. The relationships between load and boundary conditions were based on large samples of data from the station’s data capture system (DCS). A corresponding standby electric feed pump system was also modelled in Flownex for a comparative case study. After model validation, a number of case studies were performed, demonstrating the functionality of the model and also providing specific results of value to the station in question. These results include the minimum generator load possible with different steam supplies; maximum condenser back pressure before plant availability is affected; the viability of changing the pump leak-off philosophy; and the effect of electric feed pump use on power consumption. The main recommendations from the case studies were as follows: i. to stroke the steam admission valves as per the design charts, ii. to test the operation of the BFPT down to 40 % generator load, iii. to keep the pump leak-off philosophy unchanged, iv. to maintain the cooling water system and condensers sufficiently to avoid poor condenser vacuum, v. to reconsider the decommissioning of the “cold reheat” steam supply, vi. and, to favour use of the BFPT over the electric feed pumps at all generator loads. 2020-03-12T14:50:40Z 2020-03-12T14:50:40Z 2019 2020-03-12T14:42:28Z Master Thesis Masters MSc http://hdl.handle.net/11427/31576 eng application/pdf Department of Mechanical Engineering Faculty of Engineering and the Built Environment |
| spellingShingle | nozzle model power generation Flownex boiler feed pump turbine low load operation Eskom Clark, John Shaun Low load operation of turbine-driven boiler feed pumps |
| thesis_degree_str | Master's |
| title | Low load operation of turbine-driven boiler feed pumps |
| title_full | Low load operation of turbine-driven boiler feed pumps |
| title_fullStr | Low load operation of turbine-driven boiler feed pumps |
| title_full_unstemmed | Low load operation of turbine-driven boiler feed pumps |
| title_short | Low load operation of turbine-driven boiler feed pumps |
| title_sort | low load operation of turbine driven boiler feed pumps |
| topic | nozzle model power generation Flownex boiler feed pump turbine low load operation Eskom |
| url | http://hdl.handle.net/11427/31576 |
| work_keys_str_mv | AT clarkjohnshaun lowloadoperationofturbinedrivenboilerfeedpumps |