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Micro-porous ceramic membrane tube is a new type of condensation material which can synchronously recover both water vapor and its accompanied latent heat from exhausted flue gas. The recovery outcome is helpful to reduce amount of make-up water and enhance boiler efficiency of thermal power plant. In this study, an experiment has been carried out to investigate condensation heat-transfer, water-recovery, and flow-resistance performance of micro-porous ceramic membrane tube bundle (CMTB), respectively. In addition, real exhausted flue gas with inlet flow rate ranging from 390 to 750 m3/h, temperature ranging from 323 K to 373 K was used as experimental feed gas. Results showed that the condensation heat-transfer process got more apparently with increasing of flue gas inlet temperature (from 335.3 K to 364.8 K). In addition, both cooling water flow rate and heat-transfer temperature difference had a remarkable influence on the water-recovery performance of the CMTB, and maximal water-recovery mass flow rate could reach 0.0336 × 103 kg/h. Most of all, velocity drop of flue gas was controlled within an appropriate range (from 28.94 m3/h to 178.78 m3/h). The application analysis on the CMTB gives a good perspective for designing high efficiency membrane-type condenser to recover water vapor from exhausted flue gas and make good use of its latent heat in the thermodynamic system of power plant.

In a coal-fired power plant, locating the leak area during boiler hot-state operation has practical engineering value, has apart from its significance in proper shutdown procedures, repair-time reduction, and reduction of financial losses. In this study, we adopted a three-dimensional space location algorithm based on acoustic array to determine the location of water-cooling wall tube leaks in real time. We used a spherical interpolation algorithm to solve the location problem and adopted a time delay estimation based on SWITCH function to obtain the time of arrival. An acoustic location test platform was constructed for studying location accuracy in different location condition. Finally, a field study was performed to verify the spherical interpolation algorithm’s feasibility and practicability in a boiler. Results show that the proposed three-dimensional, eight-element array can locate the leak area during boiler hot-state operation.

The morphology, mineralogy, and sintering characteristics of different lignite ashes prepared at varying temperatures in various lab-scale furnaces were investigated concerning the effect of K2CO3 addition. Lignites with and without K2CO3 addition were oxidised in a plasma asher at 423 K, a muffle furnace at 1073 K and a drop tube furnace (DTF) at 1773 K. Sintering temperatures of the ashes were determined, and their mineralogical and morphological features were analysed using XRD and SEM-EDS. Results showed that ash sintering temperature was increased as combustion temperature increased but decreased as K2CO3 addition ratio increased. Moreover, sintering temperatures of ashes rich in alumina oxide were the highest among the lignite ashes prepared at the same temperature. This trend remains valid for ashes of K2CO3-doped lignites. SEM-EDS results revealed that ashes from plasma asher were irregular and loose whereas the DTF ashes of the K2CO3-doped lignites were mostly spherical in shape, having incurred severe sintering. The lignite ashes from plasma asher tended to be enriched in boehmite and arcanite. At 1723 K as in DTF, new mineral phases including mullite and kalsilite were detected. When K2CO3 was added into lignites, kalsilite, microcline, and potassium sulphate of low melting-points were identified, consequently decreased ash sintering temperature.

Furnace exit gas temperature (FEGT) is an important physical parameter of energy conservation and environmental protection in a coal-fired boiler furnace; however, to date, there is no effective method for monitoring it continuously online. The recently developed acoustic pyrometry is a comparatively advanced method of temperature measurement which possesses the essential characteristics of traditional temperature measurement approaches. We experimentally implemented online FEGT monitoring using acoustic pyrometry, and we could successfully replace the flue gas temperature probes successfully. Two key problems of the acoustic pyrometry technique, i.e. the acoustic signal and time delay estimation, were solved. We adopted the linear sweeping frequency signal as a sound source signal; its sweeping frequency ranged from 500 to 4000 Hz and the sweeping cycle was 0.1 s. We used a generalized cross-correlation technique with PHAT (Phase Transformation) and ML (Maximum Likelihood) as the time delay estimation method when the boiler was in different states. The actual operation of the monitor indicated that the acoustic pyrometry system was accurate and reliable.

Unexpected fouling of heat transfer surfaces has always been one of the main operational concerns in coal-fired utility boilers. A cost-effective way to address this difficulty is the continuous monitoring of fouling tendencies. This article has adopted acoustic pyrometry to monitor the changes of the flue gas temperature near the heat surface and has proposed a new clean factor, &, based on this acoustic method to monitor the ash fouling. A laboratory study and field research using a boiler were conducted. The results indicated that the acoustic system could be adopted to monitor temperature changes near the water-cooling wall in the boiler furnace. The new clean factor, &, could be used to monitor the changes of the ash fouling on the heat surface. This study may help to develop a more intelligent use of soot blowers, save power station boiler furnace energy and reduce discharge.

In a coal-fired power plant, measures such as early forecasting of boiler tube explosions, timely leak discovery, and the identification of the leak location prior to explosion are important to proper shutdown procedures, reduction of repair time, and minimization of financial losses. This study used a three-dimensional space location algorithm based on the time delay of arrival (TDOA) to determine the location of water-cooling wall tube leaks in real time. The location precisions of the Chan algorithm and the Chan–Taylor collaborative algorithm were compared. The location simulation showed that the time delay estimation and the number of sensors greatly impacted the location precision. The Chan–Taylor approach performed better than Chan alone. Data from the field experiments showed that the maximum likelihood (ML) windows-based generalized cross-correlation time delay estimation resulted in a more accurate TDOA. Then, the Chan–Taylor collaborative algorithm with an 8-element acoustic array could be used as a real-time location monitor for water-cooling wall leaks.

Online monitoring of the temperature field is crucial to optimally adjust combustion within a boiler. In this paper, acoustic computed tomography (CT) technology was used to obtain the temperature profile of a furnace cross-section. The physical principles behind acoustic CT, acoustic signals and time delay estimation were studied. Then, the technique was applied to a domestic 600-MW coal-fired boiler. Acoustic CT technology was used to monitor the temperature field of the cross-section in the boiler furnace, and the temperature profile was reconstructed through ART iteration. The linear sweeping frequency signal was adopted as the sound source signal, whose sweeping frequency ranged from 500 to 3000 Hz with a sweeping cycle of 0.1 s. The generalized cross-correlation techniques with PHAT and ML were used as the time delay estimation method when the boiler was in different states. Its actual operation indicated that the monitored images accurately represented the combustion state of the boiler, and the acoustic CT system was determined to be accurate and reliable.