J. Roy-Aikins, Gary de Klerk, Duduzile Ramasimong, Kumar Rupnarain
Unit 6 of the recently completed six-unit Medupi coal-fired power station was the first unit to go into commercial operation. Synchronisation of the generator to the transmission grid had occurred five months before commercial operation. Prior to the admission of first steam to the turbines, the boiler underwent a three stage cleaning process, which was performed by the boiler contractor, to ensure that debris left over in the boiler from construction was removed and to avoid damage to the turbine when steam was admitted. Steam blowing of the boiler was the penultimate stage of boiler cleaning and contractually the steam would have been deemed clean when the steam cleanliness acceptance criteria were met. The steam cleanliness acceptance criteria, which were set by the turbine contractor, relate to the number and size of indentations caused by particles striking a given area of each target plate situated in the temporary piping downstream of the inlet valves of the high pressure and intermediate pressure turbines. For each target plate, values were prescribed for these variables and for the flow conditions that should prevail in the pipe upstream. The boiler contractor had to meet these requirements. Unfortunately, there was a mismatch between the steam cleanliness requirements set by the turbine contractor and those included in the boiler contract. The less stringent steam cleanliness requirements set for the boiler contractor in the boiler contract meant that the boiler would not be adequately cleaned, from the point of view of the turbine contractor. The boiler contractor designed a temporary pipework system for the steam blow-through process that permitted steam to bypass the turbines and exhaust to the atmosphere through a silencer. During steam blowing, the prescribed pipe flow conditions for accepting the steam were not being met, even after a large number of blows had been conducted. Mathematical modelling of the process revealed that the required pipe flow conditions could not be attained at the intermediate pressure turbine inlet and as such, the steam blow-through pipework was inadequately sized. The solution was to redesign the temporary pipework, and manufacture and install a new system of pipework, all of which would have taken a couple of months. Business needs required an alternative solution, and so a decision had to be taken on the way forward. Engineering judgement, based on operating and maintenance experience with the current fleet, suggested that the steam was sufficiently clean to be admitted to the turbine, with little risk. Of the two feasible options available to the project team, admission of steam after a defined number of blows was accepted. Care had to be exercised to manage the risk that the potential turbine contractor non-compliance to any of the performance guarantee conditions could be blamed on poor steam quality. An analysis of the risks associated with this option was conducted and controls were adopted
{"title":"Managing Risks Associated With Turbine First Steam Admission Following Inadequate Boiler Cleaning","authors":"J. Roy-Aikins, Gary de Klerk, Duduzile Ramasimong, Kumar Rupnarain","doi":"10.1115/power2021-64846","DOIUrl":"https://doi.org/10.1115/power2021-64846","url":null,"abstract":"\u0000 Unit 6 of the recently completed six-unit Medupi coal-fired power station was the first unit to go into commercial operation. Synchronisation of the generator to the transmission grid had occurred five months before commercial operation. Prior to the admission of first steam to the turbines, the boiler underwent a three stage cleaning process, which was performed by the boiler contractor, to ensure that debris left over in the boiler from construction was removed and to avoid damage to the turbine when steam was admitted. Steam blowing of the boiler was the penultimate stage of boiler cleaning and contractually the steam would have been deemed clean when the steam cleanliness acceptance criteria were met.\u0000 The steam cleanliness acceptance criteria, which were set by the turbine contractor, relate to the number and size of indentations caused by particles striking a given area of each target plate situated in the temporary piping downstream of the inlet valves of the high pressure and intermediate pressure turbines. For each target plate, values were prescribed for these variables and for the flow conditions that should prevail in the pipe upstream. The boiler contractor had to meet these requirements. Unfortunately, there was a mismatch between the steam cleanliness requirements set by the turbine contractor and those included in the boiler contract. The less stringent steam cleanliness requirements set for the boiler contractor in the boiler contract meant that the boiler would not be adequately cleaned, from the point of view of the turbine contractor.\u0000 The boiler contractor designed a temporary pipework system for the steam blow-through process that permitted steam to bypass the turbines and exhaust to the atmosphere through a silencer. During steam blowing, the prescribed pipe flow conditions for accepting the steam were not being met, even after a large number of blows had been conducted. Mathematical modelling of the process revealed that the required pipe flow conditions could not be attained at the intermediate pressure turbine inlet and as such, the steam blow-through pipework was inadequately sized. The solution was to redesign the temporary pipework, and manufacture and install a new system of pipework, all of which would have taken a couple of months. Business needs required an alternative solution, and so a decision had to be taken on the way forward. Engineering judgement, based on operating and maintenance experience with the current fleet, suggested that the steam was sufficiently clean to be admitted to the turbine, with little risk.\u0000 Of the two feasible options available to the project team, admission of steam after a defined number of blows was accepted. Care had to be exercised to manage the risk that the potential turbine contractor non-compliance to any of the performance guarantee conditions could be blamed on poor steam quality. An analysis of the risks associated with this option was conducted and controls were adopted ","PeriodicalId":8567,"journal":{"name":"ASME 2021 Power Conference","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-07-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89909163","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Sandia National Laboratories (SNL) is developing a cooling technology concept — the Sandia National Laboratories Natural Circulation Cooler (SNLNCC) — that has potential to greatly improve the economic viability of hybrid cooling for power plants. The SNLNCC is a patented technology that holds promise for improved dry heat rejection capabilities when compared to currently available technologies. The cooler itself is a dry heat rejection device, but is conceptualized here as a heat exchanger used in conjunction with a wet cooling tower, creating a hybrid cooling system for a thermoelectric power plant. The SNLNCC seeks to improve on currently available technologies by replacing the two-phase refrigerant currently used with either a supercritical fluid — such as supercritical CO2 (sCO2) — or a zeotropic mixture of refrigerants. In both cases, the heat being rejected by the water to the SNLNCC would be transferred over a range of temperatures, instead of at a single temperature as it is in a thermosyphon. This has the potential to improve the economics of dry heat rejection performance in three ways: decreasing the minimum temperature to which the water can be cooled, increasing the temperature to which air can be heated, and increasing the fraction of the year during which dry cooling is economically viable. This paper describes the experimental basis and the current state of the SNLNCC.
{"title":"The Sandia National Laboratories Natural Circulation Cooler","authors":"B. Middleton, P. Brady, Serafina T. Lawles","doi":"10.1115/power2021-65399","DOIUrl":"https://doi.org/10.1115/power2021-65399","url":null,"abstract":"\u0000 Sandia National Laboratories (SNL) is developing a cooling technology concept — the Sandia National Laboratories Natural Circulation Cooler (SNLNCC) — that has potential to greatly improve the economic viability of hybrid cooling for power plants. The SNLNCC is a patented technology that holds promise for improved dry heat rejection capabilities when compared to currently available technologies. The cooler itself is a dry heat rejection device, but is conceptualized here as a heat exchanger used in conjunction with a wet cooling tower, creating a hybrid cooling system for a thermoelectric power plant.\u0000 The SNLNCC seeks to improve on currently available technologies by replacing the two-phase refrigerant currently used with either a supercritical fluid — such as supercritical CO2 (sCO2) — or a zeotropic mixture of refrigerants. In both cases, the heat being rejected by the water to the SNLNCC would be transferred over a range of temperatures, instead of at a single temperature as it is in a thermosyphon. This has the potential to improve the economics of dry heat rejection performance in three ways: decreasing the minimum temperature to which the water can be cooled, increasing the temperature to which air can be heated, and increasing the fraction of the year during which dry cooling is economically viable. This paper describes the experimental basis and the current state of the SNLNCC.","PeriodicalId":8567,"journal":{"name":"ASME 2021 Power Conference","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83814154","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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