The voluminous generation of distilled spirits lees (DSL) in China presents a challenge for proper disposal and potential environmental pollution. In an effort to address this issue, this study aimed to find a resourceful solution for DSL utilization. The application of incinerated rice husk ash as a mortar supplementary material in cement provides an innovative solution for the disposal of DSL. Five samples of distilled spirits lees ash (DSLA) were produced using both muffle furnace (MF) and fluidized bed (FB) combustion at different temperatures. The properties of DSLA were characterized through measurements of specific surface area and observations using scanning electron microscopy (SEM). Mortar specimens were prepared by replacing 10% of cement with DSLA, and strength tests were conducted. The SEM results revealed the crisscross mesh structures in the DSLA samples. Additionally, the findings indicated a strong connection between the specific surface areas and the micromorphology. In this work, all DSLA samples, except for the one produced in FB at 800 °C, could improve compressive and flexural strengths in the prepared mortar specimens and were suitable for employment as cement additives.
A new style asymmetrical outward convex corrugated tube(ACT)was studied with numerical simulation based on the three-dimensional Reynolds stress transport(RST)model.The ACT is compared with the traditional symmetrical corrugated tube(SCT)to investigate their difference in flow and heat transfer characteristics.The calculation results from existing direct numerical simulation(DNS)are compared to those from RST model under the same condition to check the reliability of RST model for the corrugation tube.The calculation results for velocity and pressure coefficient at different profiles from RST and DNS are in good agreement.The fluid flow and heat transfer mechanism are investigated in the outward convex corrugated tube.Compared to SCT,ACT presents up to 32.3% higher overall heat transfer.
The development of wind power has brought about increasing challenges in decommissioning, among which DWTBs (decommissioned wind turbine blades) are the most difficult component to deal with. To enable the cost-effective, energy-efficient, and environmentally friendly large-scale utilization of DWTBs, an experimental study on thermogravimetric and pyrolysis characteristics of DWTBs was carried out. A new process involving recycling glass fiber with pyrolysis gas re-combustion and flue gas recirculation as the pyrolysis medium was innovatively proposed, and the simulation calculation was carried out. Thermogravimetric experiments indicated that glass fiber reinforced composite (GFRC) was the main heat-generating part in the heat utilization process of blades, and the blade material could basically complete pyrolysis at 600 °C. As the heating rate increased, the formation temperature, peak concentration, and proportion of combustible gas in the pyrolysis gas also increased. The highest peak concentration of CO gas was observed, with CO2 and C3H6 reaching their peaks at 700 °C. The solid product obtained from pyrolysis at 600 °C could be oxidized at 550 °C for 40 min to obtain clean glass fiber. And the pyrolysis temperature increased with the increase in the proportion of recirculation flue gas. When the proportion of recirculation flue gas was 66%, the pyrolysis temperature could reach 600 °C, meeting the necessary pyrolysis temperature for wind turbine blade materials. The above research provided fundamental data support for further exploration on high-value-added recycling of DWTBs.
With the development of wind power, the decommissioning problems it faces are becoming increasingly prominent, among which wind turbine blades are the most difficult component to deal with. In order to realize the large-scale utilization of decommissioned wind turbine blades with low cost, low energy consumption and low pollution, experimental research on thermogravimetric and pyrolysis characteristics of wind turbine blades was conducted. And a new process of recycling glass fiber with pyrolysis gas re-combustion and flue gas re-circulation as pyrolysis medium was innovatively proposed, and the simulation calculation was carried out. Thermogravimetric experiments showed that glass fiber reinforced composite (GFRC) was the main heat-generating part in the heat utilization process of blades, and the blade material could basically complete pyrolysis at 600℃.The formation temperature, peak concentration and combustible gas proportion of the pyrolysis gas increased with the increase of heating rate. The peak concentration of CO gas produced by pyrolysis was the highest, and the peak concentration of CO2 and C3H6 was the highest at 700℃. The solid product obtained from pyrolysis at 600℃ could be oxidized at 550℃ for 40 min to obtain clean glass fiber. And the pyrolysis temperature increased with the increase of the proportion of recirculation flue gas. When the proportion of recirculation flue gas was 66%, the pyrolysis temperature could reach 600℃, which met the required temperature for pyrolysis of wind turbine blade materials. Based on the above research, it provides basic data support for further research on high value-added recycling of wind turbine blades.
In order to provide the parameter determination method of primary air fan for 1 025 t/h-class CFB boiler, the theoretical research and field measurement were performed on several boilers. Based on these, the determination method was proposed, including the air flow of primary air fans should be 120% as much as that of BMCR flow; the pressure head mainly depends on the designed operation condition (TB point) with the consideration of low-load condition, BMCR condition and bed flop condition; the margin of pressure head can be determined based on different conditions. This method has been used in the engineering practice and has significant advantages over conventional determination method, such as lower pressure head, safe and reliable operation and less plant power consumption.
To summarize the technical features of supercritical CFB (circulating fluidized bed) boilers,analyzed were the parameter selection for supercritical boilers and the reasons why CFB boilers are more suitable than pulverized coal boilers for adopting supercritical parameters.The status quo of the study on supercritical CFB boilers both at home and abroad was described in detail.An analysis and comparison of the versions of a supercritical 600 MW CFB boiler for Baima Project proposed by three domestic boiler manufacturers shows that there exists no overriding technical barrier in the design of a supercritical CFB boiler.Moreover,the supercritical CFB combustion technology will become an important clean coal-based power generation technology for coal-fired power plants in China.However,with the in-depth development of research on supercritical CFB boilers,some relevant problems still merit further study and investigation.
Thermogravimetric analysis experiments were carried out to investigate the pyrolysis properties of neutral sulfite semi-chemical pulp (NSSC) black liquor ranging from room temperature to 800°C with heating rates of 20°, 30°, 50°C/min. Experimental results show that the black liquor quickly loses weight in the temperature range of 170°–370°C, 370°–570°C, and 570°–800°C. The organic volatiles are mostly released in the former two ranges, while the alkali metal salts decompose, volatilize, and react in the third range. The mechanism function of NSSC black liquor pyrolysis is determined by means of the thermal analytic dynamics method and the most probable mechanism functions. The kinetic parameters for the chemical reactions were calculated by the Coats and Redfern method and the Ozawa method. Meanwhile, the pyrolysis dynamics equation of the NSSC black liquor is presented in this work. The results show that the activation energies of the NSSC black liquor decomposition calculated by the Ozawa method in the three temperature ranges are in general lower than that those calculated by the Coats and Redfern method.
Utilizing a two-stage vertical pump as turbine (TVPAT) is an economically method for constructing small-scale pumping and storage hydropower stations at high head-low discharge sites, such as underground coal mines. The energy dissipation mechanisms in flow passages are theoretically important for performance prediction and geometric parameter optimization. In this paper, the energy dissipation within the TVPAT has been studied using entropy generation theory, which can be applied to visual, locate and quantify energy dissipation. The numerical solution of entropy dissipation components was extracted on turbine modes in different flow rates using the steady-state single-phase SST k-ω turbulence model. The numerical results show that the energy dissipation in TVPAT mainly comes from turbulent fluctuation (43.6%-72.1%) and blade surface friction (27.8%-58.2%). The runners are the main source of turbulent entropy (SD′ ) generation (47.2%-83.3%). The contribution of the return channel and spiral case to the generation under overload conditions is significant, accounting for 33.6% and 14.3 at 1.3QBEP, respectively. Flow field analysis reveals that high generation within a runner are located in the striking flow region of the leading edge, the flow squeezing region in the blade channel, and the wake region of tailing edge. The mismatch between the placement angle of the blades or guide vanes and the liquid flow angle is an important incentive for SD′ generation. Moreover, hydraulic energy is consumed through the interaction between mainstream and local inferior flows such as separation and vortices, as well as the striking and friction between local fluid and wall surfaces.
Designed was a pulverized coal high temperature oxygen-enrichend oil-free ignition device.It utilizes the mixture of high temperature oxygen and high concentration pulverized coal to directly ignite the pulverized coal and to replace the oil gun,thus realizing an oil-free ignition of pulverized coal.Through a cold-state flow field measurement test,the device under discussion was structurally optimized.On this basis,a numerical simulation of the high temperature oxygen-enriched oil-free iginition of pulverized coal was performed.The research results show that when the device adopts a triangular flow guiding cone,the semi-angle of the spout flaring of the central tube is set at 15 degrees and that of the spout flaring of the high temperature oxygen passage is set at 25 degrees,the conditions in the flow field thus organized is relatively good.The temperature of the high temperature torch of the oxygen-enriched combustion formed by the device can be as high as 3000 K and above,and the average temperature of the flue fas can reach over 2000 K,thus effectively guaranteeing a successful ignition of the main burner.
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