Investigation of material wear on centrifugal fan impellers

M.Tech. (Mechanical Engineering)Abstract: Material wear formation on centrifugal fan impeller has been a major problem to many process plants in the whole world and this has been regarded as a grey area to many of OEM of extraction fans. TLT ACTOM has designed and manufactured an ID centrifugal fan for Sugar plant situated in Swaziland. The ID fan after a few months of operation the impeller was found to be subjected to wear. Wear initially took place such that the impeller could not last a season which is made of 9 months. The research was conducted to study the behaviour of wear taking place on the impeller material used in sugar mill plant. Establish the uncertainty of what type of wear is taking place and what cause this wear. The study focused on the formation particle flow pattern and minimization of wear to give a solution to fan manufacturers and end-user of the extraction fans. A visit to the plant in Swaziland was organized and during that site visit, bagasse and coal ash samples together with water samples were collected from inside of the venturi wet scrubber after the scrubber has been switched off for over a month for maintenance purposes. These samples were sent to a laboratory to analyse chemical compositions. The test aimed to determine particles sizes, a composition of mass in percentage, elements and mass of a chemical or contaminate per unit volume of water. A physical inspection has been performed on the wet scrubber to inspect if there were any trace that can lead to wear resulting from wet scrubber failing to perform what is expected from it. A correlation on how wear might have taken place on the impeller was conducted by using a CFD simulation. CFD simulation was conducted by using SolidWorks CAD software. Before conducting the simulation, calculations were made to determine parameters to be used as boundary conditions in the simulation software. Calculations were based on the actual centrifugal fan duties provided by the consultant company that was responsible for designing the entire plant system..

dynamic simulation and optimum operation strategy of a trigeneration system serving a hospital

This paper presents a numerical analysis of a trigeneration system in a hospital, aiming at determining the cost-optimal operating strategy as a function of the energy demands to be matched. The system includes: A natural gas fired reciprocating engine, heat exchangers for waste-heat recovery, a single-stage LiBr-H2O Absorption Chiller (ACH), a cooling tower, pumps, a backup boiler, a backup vapour-compression electric chiller, storage tanks, valves, mixers. For such system, a dynamic simulation model was developed in TRNSYS environment; the model includes detailed algorithms for all the components of the system. A case study was developed, referred to a hospital application, in which a Combined Heat, Cooling and Power (CHCP) system provides electricity, thermal and cooling energy. The electric energy demand was obtained by using real measured data and calibrating hospital literature data, whereas the demand for heating and cooling was estimated by means of a detailed simulation model. A detailed economic analysis was also included in the model, aiming at investigating the optimal control strategy needed to maximize the overall thermo economic performance of the system. To this scope, different control strategies were analysed. The most conventional operating strategy, Thermal Load Tracking mode (TLT), was compared with two alternative strategies: The Maximum Power Thermal Load Tracking mode (MPTLT) and the Electricity Load Tracking mode (ELT). MPTLT is a strategy featured by a thermal load tracking mode, but the engine, differently from TLT one, operates always at maximum power. ELT is a strategy in which the power provided by the engine is always less or equal to the electrical demand. In the paper, the results of the case study are presented on different time bases (days, weeks, years). Such results show that the ELT control strategy can achieve a better profitability, with a simple pay-back period, SPB, equal to 4 years. The conventional strategy (TLT) is shown to be the worst from the economic point of view, but among the best as for energy saving potential

Applications of thermal energy storage to process heat and waste heat recovery in the iron and steel industry

The system identified operates from the primary arc furnace evacuation system as a heat source. Energy from the fume stream is stored as sensible energy in a solid medium (packed bed). A steam-driven turbine is arranged to generate power for peak shaving. A parametric design approach is presented since the overall system design, at optimum payback is strongly dependent upon the nature of the electric pricing structure. The scope of the project was limited to consideration of available technology so that industry-wide application could be achieved by 1985. A search of the literature, coupled with interviews with representatives of major steel producers, served as the means whereby the techniques and technologies indicated for the specific site are extrapolated to the industry as a whole and to the 1985 time frame. The conclusion of the study is that by 1985, a national yearly savings of 1.9 million barrels of oil could be realized through recovery of waste heat from primary arc furnace fume gases on an industry-wide basis. Economic studies indicate that the proposed system has a plant payback time of approximately 5 years

Fuel quality-processing study. Volume 2: Literature survey

The validity of initial assumptions about raw materials choices and relevant upgrading processing options was confirmed. The literature survey also served to define the on-site (at the turbine location) options for fuel treatment and exhaust gas treatment. The literature survey also contains a substantial compilation of specification and physical property information about liquid fuel products relevant to industrial gas turbines

Investigation into methods for the calculation and measurement of pulverised coal boiler flue gas furnace exit temperature

The boiler flue gas furnace exit temperature (FET) is a key operating parameter of coal fired steam boilers. From the design perspective, the FET is vital for materials selection and sizing of heat transfer surfaces. From an operating perspective, it is a major indicator of the rate of combustion and heat transfer that is occurring within the furnace. Downstream of the furnace, the FET has a significant impact on both the performance and reliability of the boiler heat exchangers, which ultimately impacts on both boiler efficiency and availability. Monitoring of the FET can advise operating and engineering corrective actions which will ultimately result in better efficiency, reliability and availability together with the associated economic benefits. Therefore, methods of determining FET are investigated. Two methods are focused on for this study, one indirect and one direct. The indirect method studied is a mass and energy balance method which begins with a global boiler mass and energy balance to calculate the major boiler flow rates of coal, air and flue gas which are difficult to measure online. These parameters are then used as inputs into a furnace or backpass mass and energy balance to calculate the furnace exit temperature. The method is applied to a case study, and is evaluated in terms of the measurement uncertainties which are propagated on the intermediate parameters calculated, as well as on the final calculated FET. The main conclusions are that this indirect method contains various uncertainties, due to parameters which have to be assumed such as (i) the distribution of ingress air (also called tramp air) in the different sections of the boiler and (ii) the estimation of the share of water evaporation heat transfer occurring in the water walls of the furnace part of the boiler. The method is however still useful and can be easily applied to any boiler layout and can be used as a reference tool to verify other measurements. The direct method studied is acoustic pyrometry. The work specifically focuses on the sources of error in determining the temperature from the measurement of the time of flight of sound, the impact of particle concentration on the speed of sound through a gas-particle mixture, and the temperature profile reconstruction from acoustic time of flight measurements. A limited set of physical testing was also carried out using one acoustic generator and receiver to take measurements on a real coal power plant. As part of this physical testing, the detection of time of flight from acoustic signals was explored. Already installed radiation pyrometers were also used as a reference for interpreting the acoustic measurements. The indications are that the acoustic pyrometer provides a more representative temperature measurement than the radiation pyrometers. The uncertainty of the acoustic measurement for the same case study as the indirect method was determined and compared with the calculated result. While many aspects still need to be researched further, this initial study and experimental testing produced very promising results for future application of acoustic pyrometry for better monitoring of the coal combustion processes in power plant boilers

Solar energy system demonstration project at Wilmington Swim School, New Castle, Delaware

A solar energy system located at the Wilmington Swim School, New Castle, Delaware is described. The system was designed for a 40 percent heating and a 30 percent hot water solar contribution serving the heat loads in the following order: space heat - new addition, domestic water - entire facility, and pool heating - entire facility. On a cost basis for 2920 hours of operation, the heat reclaimed would cost $969.66 annually if provided by gas at 3.79 per million Btu's. At 5.5 centers per kwh, heat recovery costs of$481.80 percent a net savings of $487.86 annually