Flow behavior and regime transition in a high-density circulating fluidized bed riser

Flow behavior and flow regime transitions were determined in a circulating fluidized bed riser (0.203 m i.d. × 5.9 m high) of FCC particles (, ). A momentum probe was used to measure radial profiles of solids momentum flux at several heights and to distinguish between local net upward and downward flow. In the experimental range covered (; ), the fast fluidization flow regime was observed to coexist with dense suspension upflow (DSU). At a constant gas velocity, net downflow of solids near the wall disappeared towards the bottom of the riser with increasing solids mass flux, with dense suspension upflow achieved where there was no refluxing of solids near the riser wall on a time-average basis. The transition to DSU conditions could be distinguished by means of variations of net solids flow direction at the wall, annulus thickness approaching zero and flattening of the solids holdup versus G_s trend. A new flow regime map is proposed distinguishing the fast fluidization, DSU and dilute pneumatic transport flow regimes.     

Process intensification of gas–liquid downflow and upflow packed beds by a new low‐shear rotating reactor concept

In the present work, a new low‐shear rotating reactor concept was introduced for process intensification of heterogeneous catalytic reactions in cocurrent gas–liquid downflow and upflow packed‐bed reactors. To properly assess potential advantages of this new reactor concept, exhaustive hydrodynamic experiments were carried out using embedded low‐intrusive wire mesh sensors. The effect of the rotational velocity on liquid flow patterns in the bed cross‐section, liquid saturation, pressure drop, and regime transition was investigated. Furthermore, liquid residence time and Péclet number estimated by a stimulus‐response technique and a macro‐mixing model were presented and discussed with respect to the prevailing flow patterns. The results revealed that the column rotation induces different flow patterns in the cross‐section of the packed bed operating in a concurrent downflow or upflow mode. Moreover, the new reactor concept exhibits a more flexible adjustment of pressure drop, liquid saturation, liquid residence time, and back‐mixing at constant flow rates. © 2016 American Institute of Chemical Engineers AIChE J, 63: 283–294, 2017     

生产性厌氧复合床反应器处理酒精废水的启动研究

以河南某酒精厂的高浓度废水处理工程为对象深入研究厌氧复合床(UBF)反应器的启动过程.废水水质CODcr为12 000~15 000 mg/L;BOD5为6 000~8 000 mg/L;pH3.7~5.0.本次启动研究了反应器内COD去除情况、pH变化、颗粒污泥形成、填料的作用等内容,共历时5个月.启动完成并进入稳定运行期后,出水COD去除率为90%以上、pH值保持在6.6~7.8,并形成沉淀性能良好、具有一定机械强度、粒径为1~4mm的颗粒污泥.     

Improving biohydrogen production in a carrier-induced granular sludge bed by altering physical configuration and agitation pattern of the bioreactor

Our newly developed carrier-induced granular sludge bed (CIGSB) bioreactor was shown to be very effective in hydrogen production. However, since mechanical agitation was not employed to enable sludge granulation, the CIGSB system might encounter problems with poor mass transfer efficiency during prolonged operations. This work was undertaken to improve mixing efficiency of CIGSB for better biomass-substrate contact by adjusting the height to diameter (H/D) ratios of the reactor and by implementing appropriate agitation device. Three H/D ratios (4, 8, and 12) resulting in liquid upflow velocities (v_up) of 0.057–1.32 m/h were examined as the CIGSB reactor was carried out at a descending hydraulic retention time (HRT) from 4 to 0.5 h. The results show that decreasing HRT resulted in increases in the H₂ production rate, regardless of the H/D ratios. Reactors with a H/D ratio of 8 gave better H₂ production performance with a H₂ production rate of 6.87 l/h/l and a H₂ yield of 3.88 mol H₂/mol sucrose, suggesting that the effectiveness of H₂ production in the CIGSB system can be enhanced by using a proper v_up and physical configuration of the reactor. Supply of additional mechanical agitation for CIGSB reactor (H/D=12) alleviated the phenomena of sludge piston floatation, leading to further increases in the H₂ production rate and H₂ yield to 9.31 l/h/l and 4.02 mol H₂/mol sucrose, respectively. The major soluble metabolite was butyric acid, followed by acetic acid, propionic acid, and ethanol. The former two accounted for nearly 67–76% of total soluble microbial products, indicating the presence of favorable pathways in the CIGSB culture from the aspect of H₂-producing metabolism.     

以壳聚糖为载体的固定化微生物处理TNT废水研究

以壳聚糖为包埋剂制备固定化厌氧污泥微球并采用上流式厌氧污泥床对TNT废水进行降解,实验运行的结果表明:上流式厌氧污泥床具有启动快、运行效果稳定、产泥量少的特点,固定化微生物法对梯恩梯(TNT)处理效果良好,去除率可达到75.76%～94.76%。     

矿浆斜窄流的固体浓度分布规律

采用自制的斜窄流（斜浅层）单元动态连续试验装置,研究了矿浆斜窄（上升）流的固体浓度沿斜长、宽度及厚度的分布规律。结果表明,沿斜长的分布在斜窄流的雷诺数Re≤52．7时,可由对数方程表达;52．7≤Re≤100时,可由三次多项式表达。沿宽度分布的变化率〈15％,在给料口侧为低浓度或轻液流区,对侧则为高浓度或重液流区,矿粒由高向低浓度区的横向扩散,使浓度分布的不匀得到缓解;沿厚度分布的变化在底板之上约10mm范围内急剧增大,形成高矿浆浓度的重液流,产生剪切流使沉降物下移。     

Anaerobic Treatment of Leachates in a Pilot-Scale UASB: Strategy of Start-up

The anaerobic digestion of leachates from a solid urban wastes landfill was studied using an upflow anaerobic sludge blanket reactor in pilot scale. The strategy of start-up and acclimation was based on gradual substitution of easily biodegradable feed with landfill leachate. All modifications were based on the attainment of 70% COD removal. Having completed the start-up, the kinetics of leachate biodegradation were studied and the values of kinetic parameters were obtained by fitting experimental data to the equation of Chen and Hashimoto. The biodegradability assays indicated that 40–50% of COD in leachate was biodegradable. The highest COD removal was 90–100% if only the biodegradable matter was considered.     

常温厌氧、好氧组合工艺处理城市污水研究

对上流式厌氧复合订单元及厌氧复合床和一体化氧化沟的组合工艺处理城市污水进行了生产性试验,并对其效果及工艺参数进行了研究。结果表明,厌氧复合床对ＢＯＤ５的除率为４１％￣５１．５％,对ＳＳ的去除率为３３．７％￣４８．９％,对污泥的截留率为４２％￣６９％;常温厌氧、好氧组合工艺处理城市污水效果良好,在厌氧ＨＲＴ≥３ｈ、好氧ＨＲＴ≥８ｈ的条件下,出水ＣＯＤＣｒ、ＢＯＤ５、ＳＳ均满足《ＧＢ８９７８－１９９６     

抗生素废水处理工程优化设计及快速启动

扩建工程调节池前置保证了隔油池的处理效果,减少了一级提升,并保证了初沉池负荷的稳定性。地面加热与储热节省了工程投资,降低了噪音,并有利于废水温度的稳定。好氧污泥在厌氧沉淀池沉淀后,降低了污泥含水率,减少污泥总量。扩建工程UBF反应器接种50m3同种废水厌氧颗粒污泥,经35d完成反应器的启动。启动结束时负荷达4.1kgCOD/m3.d,系统运行稳定,COD平均去除率为90%。     

二段上流式曝气生物滤池去除高标准景观补给水中氮磷营养物

虑及回用水中营养物质对水体富营养化的不利影响,许多地区对号观补给水的氮磷含量制定了极为严格的标准。本研究考察了作为三级处理工艺的二段上流式曝气生物滤池在硝化、反硝化、化学除磷效率等方面的相关影响因素及工艺的可行性,并进行了设计参数的优化。试验结果表明,此二段上流式曝气生物滤池的最后出水可满足回用水总氮小于2mg／L,总磷小于0．3mg／L的严格要求,且其较高的处理效率使得反应器可在较高的水力负荷下仍接近完全硝化与反硝化;在反应器的处理能力内,硝化和反硝化反应可以在较高的滤速下达到更好的处理效果;本工艺在抗水力负荷冲击方面有较大的优势。