温度和固相粒径与浓度对水煤浆管内流动壁面滑移的影响

通过改变管径、温度、煤粉粒度和浓度,在中试规模的输送装置上研究水煤浆直管内的滑移流动规律,联合采用Mooney滑移修正方法和Tikhonov正则化方法确定浆体壁面滑移特性。结果表明,随温度和固相粒径的增大,临界剪切应力降低,壁面滑移速度显著增加;浓度越高,临界剪切应力及产生相同滑移速度所需的壁面剪切应力越大,温度升高对临界剪切应力和屈服应力的降低越显著;低壁面剪切应力下的滑移贡献率主要取决于临界剪切应力及屈服应力的相对大小,高壁面应力下主要取决于壁面滑移速度和浆体真实流变特性。     

水焦浆的流变特性与壁面滑移效应

在浆体流动试验系统上采用不同管径的直管考察了水焦浆的流变特性以及壁面滑移效应对水焦浆流动特性的影响。采用Tikhonov 正则化方法确定了水焦浆的真实流变特性和壁面滑移特性。结果表明：浓度为59.8%的水焦浆随剪切速率增大呈现由伪塑性流体到胀塑性流体的转变,浓度增加,水焦浆变为单一的胀塑性流体,当浓度达到63.4%时,水焦浆表现为由胀塑性流体到伪塑性流体的转变;水焦浆的流变特性对滑移速度的变化趋势具有较大影响,滑移速度在水焦浆为胀塑性流体时随剪切应力增加呈加速增加,水焦浆为伪塑性流体时滑移速度随剪切应力的增长速率变化不明显;滑移贡献率的变化趋势迟滞于流变特性曲线。     

Maximum solid concentrations of coal water slurries predicted by neural network models

The nonlinear back-propagation (BP) neural network models were developed to predict the maximum solid concentration of coal water slurry (CWS) which is a substitute for oil fuel, based on physicochemical properties of 37 typical Chinese coals. The Levenberg-Marquardt algorithm was used to train five BP neural network models with different input factors. The data pretreatment method, learning rate and hidden neuron number were optimized by training models. It is found that the Hardgrove grindability index (HGI), moisture and coalification degree of parent coal are 3 indispensable factors for the prediction of CWS maximum solid concentration. Each BP neural network model gives a more accurate prediction result than the traditional polynomial regression equation. The BP neural network model with 3 input factors of HGI, moisture and oxygen/carbon ratio gives the smallest mean absolute error of 0.40%, which is much lower than that of 1.15% given by the traditional polynomial regression equation.     

Effects of pore fractal structures of ultrafine coal water slurries on rheological behaviors and combustion dynamics

The ultrafine coal water slurry (CWS) with the particle size of 1-10 μm, ash content of 1-2%, solid concentration of 50% is a promising substitute fuel for diesel oil. The effects of pore fractal structures of three ultrafine CWSs on their rheological behaviors and combustion dynamics were studied in this paper. When the pore fractal dimensions of Yanzhou, Huainan and Shenhua ultrafine CWSs increase, their apparent viscosities all increase and the increase extents gradually enlarge with decreasing shear rates, while their ignition temperatures and apparent activation energies all decrease. For example, when the pore fractal dimension of Yanzhou coal increases from 2.31 to 2.43, the CWS apparent viscosity at a low shear rate of 12 s⁻¹ increases from 75 mPa s to 2400 mPa s, and that at a high shear rate of 100 s⁻¹ increases from 80 mPa s to 820 mPa s. Meanwhile, the ignition temperature of Yanzhou CWS decreases from 445 °C to 417 °C at a heating rate of 12.5 °C/min, and the apparent activation energy decreases from 104 kJ/mol to 32 kJ/mol.     

GE水煤浆气化炉生产工艺磨机配置的分析及讨论

以某煤制烯烃项目为例,介绍了GE水煤浆气化炉生产工艺的磨煤和级配流程,对棒式磨煤机配置和选择进行了分析和讨论,得出科学的选择方案,对类似工程项目的建设有指导意义。     

Deposition velocities for newtonian slurries in turbulent flow

In this contribution both new and previously published deposition velocity data for aqueous Newtonian slurries are incorporated in a correlation which complements the earlier predictions of Durand, Wilson and A.D. Thomas. Most of the new data has been obtained for slurries of narrowly sized sand particles of median diameter ranging between 90 and 420 μm, in pipes of diameter between 0.05 and 0.5 m. The data were obtained in laboratory investigations under isothermal flow conditions.     

空化作用改善褐煤水煤浆成浆性的试验研究

介绍了水力空化作用机理,利用水力空化技术对褐煤水煤浆的成浆特性进行了研究;分析了浆体空化前后不同静置条件下粘度、粒度的变化趋势;通过空化试验前后样品分析,对比粘度、粒度测试数据;结果表明,空化后的褐煤成浆性优于常规处理工艺的水煤浆,空化后的粘度测试数值重现性非常好,浆体的流变特性比较稳定,浆体中细粒级煤增加,颗粒分散程度得到改善,保持了良好的悬浮稳定性。     

The entry length for slurries in horizontal pipeline flow

The entry length for horizontal slurry pipeline flows has been determined experimentally using a pipeline of diameter 50 mm. Concentration and velocity distributions have been measured in the vertical direction at positions 6, 50 and 185 diameters downstream of the entrance. The measurements show that the entry length is of the order of 50 pipe diameters for sand slurries. High particle settling velocities give somewhat shorter lengths than intermediate settling velocities. With lower density polystyrene particles for which dispersive effects are important, the entry length is significantly greater than 50 diameters. The velocity distributions show that the velocity profiles develop concurrently with the concentration profiles. For sand slurries, a two-dimensional simulation gives a satisfactory representation of the developing concentration profiles.     

油水混合物在水平管中的二相流动特性研究

对内径40mm的钢管和有机玻璃管内油水二相水平流动时的流型、摩擦压降特性进行了详细的实验研究,结果表明:油包水向水包油的转变发生在含水体积分数约0. 4时。随含水体积分数的增大,油水二相流的摩擦压降先是急剧减小,其后在含水体积分数大于0. 4时压降变化趋于平缓。油水二相流的摩擦压降受含水体积分数、管壁润湿特性、管壁粗糙度以及混合物流速的影响,当二相流体处于水包油状态时,钢管内的摩擦压降比有机玻璃管内的大;而当处于油包水时,有机玻璃管内的摩擦压降则比钢管内的摩擦压降大。     

安徽煤混煤灰熔点特性研究

将安徽的煤种G煤灰和煤种S煤灰分别与神府煤灰进行混合,对混合灰的熔点进行了研究。通过实验,发现随着煤种G煤灰的比例增加,混合灰的DT、ST和FT先降低,然后提高。而混合灰中煤种S煤灰的比例越高,混合灰的DT、ST和FT越高。同时实验表明,混合灰的熔点并不随混合灰中G煤灰或者S煤灰含量的提高成正比地提高。     

生物质水煤浆流变特性研究

以福建无烟煤、水葫芦、添加剂等制备生物质水煤浆,研究了其流变特性。结果表明：添加3％～3．5％的水葫芦及1％的分散剂制得的生物质水煤浆粘度在0．8～1．2Pa·s之间,且稳定性较好。生物质含量提高,生物质水煤浆的粘度逐渐上升;分散剂含量为1％时,能够制得流变性较佳的生物质水煤浆;搅拌强度的增加能够使生物质水煤浆的粘度降低;当温度低于60℃时生物质水煤浆的粘度随温度升高而下降;当温度高于60℃时,生物质水煤浆的粘度随温度升高而上升。     

An investigation on the rheological and sulfur-retention characteristics of desulfurizing coal water slurry with calcium-based additives

Desulphurizing coal water slurry is a kind of new clean coal water slurry(CWS), which has good performance on SO₂ emission during combustion and gasification process. But, the addition of sulfur-retention agents have some effects on the stability and fluid characters of the coal water slurry. In this paper, the viscosity, stability and rheology of Xinwen coal water slurry have been studied by adding different kinds of calcium-based sulfur-retention agents and different dosage. The results show that the sulfur-retention agents have little effect on rheological nature of CWS, which still presents pseudoplastic fluid. The addition of sulfur-retention agents will increase the viscosity of CWS, but the stability will decrease a little. The results also show that inorganic calcium has less negative effect on the performance of CWS than the organic calcium. The viscosity of the CWS with organic calcium agent keeps 1000–1200 mPa s when Ca/S molar ratio is 2. Sulfur release of the CWS with CaCO₃ reduces to 52% at Ca/S = 2 compared to original of 98%.     

两种印尼煤的成浆性能研究

考查了两种印尼煤在不同添加剂及不同剂量条件下的水煤浆成浆性能,并与同一实验条件下的神府煤进行了对照。结果表明,印尼煤的成浆性较差,制成的煤浆浓度相对神府煤较低。在五种不同添加剂、三种不同添加用量下,其浓度都低于57%。同种添加剂随着添加剂用量的增加,煤浆浓度也随之提高。     

Preparation of high solid loading and low viscosity ceramic slurries for photopolymerization-based 3D printing

In this study, high solid loading and low viscosity cordierite slurries are successfully developed for the first time for photopolymerization-based additive manufacturing. The processability of the slurries is mainly determined by their rheological properties and photocuring parameters. The slurry preparation involves the orthogonal optimization of compositions in order to achieve suitable viscosity, stability and homogeneity. The photocuring parameters of the as-prepared slurries, including penetration depth D_p and critical exposure E_c, are also determined experimentally. Results show that viscosity increases with reduction in particle size. A higher solid-volume fraction also results in an exponential growth in viscosity. As for the dispersant amount, a concentration of 5?wt% leads to the lowest viscosity. Particle size also play an important role in the solid loading capacity of the slurries, as results suggest that smaller particles improve performance. In terms of the photocuring behaviors, the addition of 2?wt% photoinitiator generates an optimal curing process. 40?vol% solid loading leads to the thickest curing depth for all slurries with different types of particle sizes. Finally, a cordierite part with a complex hollow structure and a fine resolution is successfully fabricated. The present study offers a material basis for the polymerization-based 3D printing of porous cordierite structures.     

浅析降低剩余氨水含油的措施

剩余氨水焦油含量高影响了蒸氨系统及污水处理系统的正常运行,在引进微孔陶瓷过滤器后,针对除焦油器存在的问题,通过工艺优化和设备改进,降低了剩余氨水焦油含量,保证了生产正常运行。     

水煤浆添加剂的发展动向

介绍了日本、美国开发的一系列水煤浆添加剂的特点,并从性能上给予了评价;概述了国内水煤浆添加剂的研究现状,尤其列举了国内有关木质素类添加剂的研究成果。从煤的分散机理方面阐述了聚苯乙烯磺酸钠与亚甲基磺酸盐两类添加剂的差异在于吸附方式的不同,指出了木质素作为水煤浆添加剂的优势及其在我国利用的广阔前景。最后阐述了目前水煤浆添加剂对煤的作用机理的两种理论:双电子层与空间位阻理论;空间位阻与熵斥力作用理论。     

Ignition characteristics of coal blends in an entrained flow furnace

Ignition tests were carried out on blends of three coals of different rank - subbituminous, high volatile and low volatile bituminous - in two entrained flow reactors. The ignition temperatures were determined from the gas evolution profiles (CO, CO₂, NO, O₂), while the mechanism of ignition was elucidated from these profiles and corroborated by high-speed video recording. Under the experimental conditions of high carbon loading, clear interactive effects were observed for all the blends. Ignition of the lower rank coals (subbituminous, high volatile bituminous) enhanced the ignition of the higher rank coal (low volatile bituminous) in the blends. The ignition temperatures of the blends of the low rank coals (subbituminous-high volatile bituminous) were additive. However, for the rest of the blends the ignition temperatures were always closer to the lower rank coal in the blend.     

Slip velocity and slip layer thickness in flow of concentrated suspensions

The rheological characterization of highly filled suspensions consisting of a Newtonian matrix (hydroxyl-terminated polybutadiene), mixed with two different sizes of aluminum powder (30% and above by volume) and two different sizes of glass beads (50% and above by volume), was performed using a parallel disk rheometer with emphasis on the wall slip phenomenon. The effects of the solid content, particle size, type of solid particle material, and temperature on slip velocity and slip layer thickness were investigated. Suspensions of small particles of aluminum (mean diameter of 5.03 μm) did not show slip at any concentration up to the maximum packing fraction. However, suspensions of the other particles exhibited slip at the wall, at concentrations close to their maximum packing fraction. In these suspensions, the slip velocity increased linearly with the shear stress, and at constant shear stress, the slip velocity increased with increasing temperature. The slip layer thickness increased proportionally with increasing size of the particles for the glass beads. Up to a certain value of (filler content/maximum packing fraction), ϕ/ϕ_m, the slip layer thickness divided by the particle diameter, δ/D_P, was 0, but it suddenly increased and reached a value that was independent of ϕ/ϕ_m and the temperature. On average, the ratio of δ/D_P was 0.071 for aluminum and 0.037 for glass beads. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 515–522, 1998     

低阶煤水煤浆制备技术与工艺研究现状及前景

针对中国储量丰富的低阶煤难以制备高浓度水煤浆的问题,介绍了国内先进的低阶煤制浆技术。制备高品质低阶煤水煤浆,应结合煤质特性,选择适宜的磨矿技术、提质改性工艺、配煤技术或添加剂,制备符合工业化应用的高性能低阶煤水煤浆。同时指出,低阶煤制备水煤浆技术是适合中国国情的洁净煤技术,是目前国内对低阶煤合理利用的一条新途径,低阶煤水煤浆的研究和发展为解决中国环境污染问题和能源合理利用问题提供了广阔的前景。针对目前中国低阶煤水煤浆的发展状况,对中国低阶煤制备水煤浆技术发展前景进行了展望。