Treatment and utilization of septic tank effluent using vertical-flow constructed wetlands and vegetable hydroponics

Vertical flow constructed wetlands is a typical ecological sanitation system for sewage treatment. The removal rates for COD, BOD 5, SS, TN, and TP were 60%, 80%, 74%, 49% and 79%, respectively, when septic tank effluent was treated by vertical flow filter. So the concentration of COD and BOD\-5 in the treated effluent could meet the quality standard for irrigation water. After that the treated effluent was used for hydroponic cultivation of water spinach and romaine lettuce, the removal efficiencies of the whole system for COD, BOD\-5, SS, TN and TP were 71 4%, 97 5%, 96 9%, 86 3%, and 87 4%, respectively. And it could meet the integrated wastewater discharge standard for secondary biological treatment plant. It was found that using treated effluent for hydroponic cultivation of vegetables could reduce the nitrate content in vegetables. The removal rates for total bacteria and coliform index by using vertical flow bed system with cinder substrate were 80%—90% and 85%—96%, respectively.

Vertically-Suspended Environmental Enrichment Alters the Velocity Profiles of Circular Fish Rearing Tanks

The inclusion of vertically-suspended environmental enrichment in circular tanks has produced substantial benefits during fish rearing. This study examined the tank water velocity profiles of four different vertically-suspended structures?(rod array, extended rod array, single angle array, double angle array) and a control (no environmental enrichment) at two incoming water velocities (18.3 cm/s and 54.9 cm/s) in 1.8-m diameter circular tanks. At both of the incoming water velocities, overall water velocities throughout the tank were significantly reduced with the addition of any environmental enrichment in comparison to the control. In addition, the overall water velocities in the double angle array were significantly lower than the other three enrichment treatments. The pattern of significant reductions in velocity with the use of any environmental enrichment, with further significant velocity reductions in the double angle treatment, was repeated when the data were?combined for each sampling depth, radius from the center, and degree (circular arc). Although considerable variation in water velocity was observed at each specific sampling location with both incoming velocities, significantly lower velocities?were observed at nearly every sampling location with the addition of any environmental enrichment to the circular tank. In addition, the double angle array consistently produced the lowest velocities among the environmental enrichment treatments. The changes in velocity profiles from vertically-suspended?environmental enrichment may be at least partially-responsible for the frequently-observed improvements in fish growth.

Floating-roof steel tanks under harmonic settlement: FE parametric study and design criterion

Large vertical steel tanks for fluid storage are usually constructed on soft foundations, so it is not surprising that the tank wall will settle unevenly with the settlement of the foundation, thus inducing deformations and stresses in the tank. This work investigates the linear static behavior of floating-roof tanks under harmonic settlement through finite element (FE) analyses. The influences of the radius-to-thickness ratio, the height-to-radius ratio and the wind girder stiffness on the structural behavior are first analyzed. Comparisons between the circumferential stresses in the wind girder and the vertical stresses in the tank bottom are then made. The displacement and the stress along the tank height are also discussed, and the concept of tank division along its height is presented. Finally, a design approximation for the radial displacement at the tank top is developed based on FE results, and a settlement criterion based on the top radial displacement is proposed which can be used in practical design.

Influence of Wind Deviation Angle on n-Hexane Evaporation Loss of Internal Floating-Roof Tanks

With the increasing attention to environmental protection,it is still necessary to strictly control the oil evaporation loss from the IFRT(internal floating-roof tank)to the atmosphere.Upon using n-hexane as a representative of light oil,the effects of the WDAs(wind deviation angles)on airflow distribution,the wind speed,the n-hexane vapor concentration,and the evaporation loss rate in the IFRT were investigated,and the mass transfer of the vapor-air was analyzed.The results are shown as follows:when the WDA is 0°,the vapor concentration in the gas space above the floating deck is the lowest;when the WDA is 22.5°,the oil evaporation loss rate is the largest;when the WDA is 45°,the vapor concentration is the highest,but the evaporation loss rate is the smallest.It is recommended to arrange the vent to the wind direction with an angle of 45°to reduce the evaporation loss and protect the atmospheric environment.

Performance of a novel vertical-flow settler: a comparative study

By increasing particle concentration and G value （root-mean-square velocity gradient） to enhance flocculation, a novel vertical-flow settler was designed to increase sedimentation effectiveness, and to simultaneously improve operational stabilization. Due to the gradual decrease in upward flow-rate of raw water, a floes blanket would form and suspend in the middle section of the settler, not at the bottom as in a conventional clarifier. Enough large floes, resulted from flocculation or fltration, would continuously settle out of the floes blanket, and simultaneously, the floes in raw water or those forming above the blanket would ceaselessly enter the floes blanket. As a result, the floes concentration in the blanket could keep a dynamic balance. The hydrodynamic shear in the blanket was improved by flow separation, which was induced by the abrupt change in flow channel. Due to the floes blanket and improved hydrodynamic shear, flocculation would be enhanced, which was helpful for removing fine particles in raw water. A comparative study showed that the novel vertical-flow settler had a much better performance in the removal of the particles in raw water than a conventional one, when they treated kaolin suspensions of different concentrations （500, 100 and 50 mg/L, respectively） coagulated by polyaluminum chloride（PAC1） at the up-flow rates of 1 and 2 mm/s, respectively.

Experimental Investigation on the Effect of Seal Presence on the Behavior of Double-Deck Floating Roofs in Cylindrical Steel Storage Tanks

Liquid storage,particularly oil and petrochemical products which are considered hazardous liquid,are an important part of the oil industry.Thin-walled vertical cylindrical steel storage tanks are widely used in recent years.Due to high sensitivity of these structures in an earthquake and other external excitations may lead to catastrophic consequences.For instance,huge economic losses,environmental damages,and casualities,many studies have been done about these structures.past studies showed that liquid storage tanks,equipped with a floating roof,are potentially vulnerable while subjected to seismic loads and earthquake has been considered as one of the most destructive natural hazards.The reason is that such tanks are made of two separated parts(shell and roof)which each may have its own responses;sometimes causing resonance phenomenon and so that,roof movements,rooffluid interaction,roof-shell interaction,and also the way they are attached should still be investigated.Experimental tests of floating roof’s vertical fluctuation was performed in a full-scale reservoir tank and assessing of the results demonstrated that presence of a seal between floating roof and shell plate can significantly increase damping ratio in liquid sloshing and also suppress the roof`s vertical displacements.In other words,seal can control a floating roof and make it stop moving vertically over few cycles.

基于实测数据立式热水储能罐罐壁力学特性分析

为掌握立式储能罐结构的受力特征,基于某30 000 m~3立式热水储能罐项目,依托远程监测技术采集了运行状态下罐壁应力和温度数据,将采集结果与考虑罐底摩擦接触约束建立的有限元模型分析结果进行比较,验证了此有限元模拟方法的合理性;依托实测温度数据,研究了立式储能罐罐壁热力耦合作用下罐壁位移以及应力分布规律。结果表明:罐壁底部和顶部为温度影响敏感区域,温度升高,使其产生压应力;对于环向应力,在底部受温度荷载影响较顶部更显著;而对于竖向应力,影响主要是罐壁底部;温度对罐壁变形影响较大,在空罐时,最大位移位置出现在罐壁最顶端;而满罐时最大变形位置出现在中上部的位置,温度作用大于静水压力对罐壁变形的影响。

用地紧张地区初雨调蓄池建设方案研究

大城市中心城区和老城区用地紧张,无大面积规划用地建设矩形调蓄池,考虑雨水调蓄池需向地下空间延伸,故采用深竖井式结构,减少占地面积,以此应对大城市中心城区和老城区用地紧张的问题。研究结合上海某地区对矩形调蓄池和竖井调蓄池的特点进行了分析,为以后调蓄池设计提供参考。

大型非锚固立式储液罐地震响应分析

为有效评价大型非锚固立式储液罐的振动安全性,利用ADINA软件建立大型立式圆筒形非锚固储液罐有限元模型,考虑流固耦合以及接触效应,研究水平地震波以及水平和竖向地震波同时作用的2种工况下储罐的动力响应。结果表明:与水平地震激励下的响应相比,竖向地震激励对罐壁的水平位移和应力影响较小;根据罐壁位移沿高度方向分布规律可知,地震激励下罐壁下部发生较大变形;通过获取罐壁最大等效应力分布情况可知,等效应力主要由环向应力决定。研究结果为大型非锚固立式储液罐安全评价奠定理论基础。

不同污泥斗倾角对竖式沉淀池沉降效果的影响

在化工厂污水絮凝处理工艺中,沉淀池的设计和沉降效率是确保出水水质达标的关键。本研究使用Fluent软件,结合RNG k-ε湍流模型和Mixture多相流模型,全面评估了竖式沉淀池的污泥斗倾角对高浓度污水沉降效果的影响。研究主要通过考察沉淀池内部的污泥流速流线图、排水口悬浮颗粒(SS)浓度,以及污泥去除率的变化,从而揭示了斜板倾角变化对污泥的流动特性、沉降效率和污泥去除率的影响。结果表明,当污泥斗倾角从40°增加到60°时,沉淀池内涡旋变少,流速和流向分布较均匀,流场相对稳定,沉降效果提升;当污泥斗倾角从60°增大到70°时,在沉淀池底部和排水口上部出现较大涡旋,导致颗粒在水中的停留时间增加,影响出水水质,降低沉降效果。当污泥斗倾角为60°时,竖式沉淀池能达到最好的沉降效果。这一发现为化工厂竖式沉淀池设计提供了重要的指导,强调了合理选择污泥斗倾角在提高絮体沉降效率中的关键作用。

火灾影响下立式储罐失效行为分析

为研究着火储罐失效行为,采用火灾动力学-传热-结构响应多物理场耦合方式,开展了着火立式储罐罐壁热辐射分布、温度分布规律及模型,屈曲失效等行为分析。结果表明,着火立式储罐首先在液面上部发生屈曲变形,对于5000 m^(3)/10000 m^(3)汽柴油立式储罐,屈曲临界温度在300~500℃之间,屈曲失效时间在30~70 s之间;立式储罐尺寸增加,屈曲临界温度明显降低,屈曲失效时间也显著降低。屈曲导致立式储罐罐壁凹凸不平,冷却不均,火灾难以扑灭,建议强化液面附近的罐壁冷却保护。

立式搅拌釜中固-液混合特性模拟研究

研究固-液混合特性对生产效率、能耗等指标的优化具有重要意义,实际生产中立式搅拌釜应用较多,本文采用CFD方法和DEM方法从颗粒密度、粒径、搅拌速度和初始液面高度等4个方面对立式搅拌釜的颗粒混合特性进行了数值模拟研究,并且从速度场、湍动能分布和颗粒混合度3个维度来评判颗粒的混合特性。结果表明,在这些影响因素中,颗粒密度和搅拌速度对混合特性的影响最大,特别是当颗粒密度为1200 kg/m3时,相对标准差值达到0.5左右,说明混合程度较好;搅拌速度越大,混合性能越好;颗粒粒径对混合性能的影响较小,但粒径越小,越容易悬浮,粒径增大,混合程度降低;初始液面高度的改变导致固含率的改变,但是对固液混合性能基本不产生影响。

Performance of hybrid constructed wetland systems for treating septic tank effluent

The integrated wetland systems were constructed by combining horizontal-flow and vertical-flow bed, and their purification efficiencies for septic tank effluent were detected when the hydraulic retention time （HRT） was 1 d, 3 d, 5 d under different seasons. The results showed that the removal efficiencies of the organics, phosphorus were steady in the hybrid systems, but the removal efficiency of total nitrogen was not steady due to high total nitrogen concentration in the septic tank effluent. The average removal rates of COD （chemical oxygen demand） were 89%, 87%, 83%, and 86% in summer, autumn, winter and spring, respectively, and it was up to 88%, 85%, 73%, and 74% for BOD5 （5 d biochemical oxygen demand） removal rate in four seasons. The average removal rates of TP （total phosphorous） could reach up to 97%, 98%, 95%, 98% in four seasons, but the removal rate of TN （total nitrogen） was very low. The results of this study also indicated that the capability of purification was the worst in winter. Cultivating with plants could improve the treated effluent quality fTom the hybrid systems. The results of the operation of the horizontal-flow and vertical-flow cells （hybrid systems） showed that the removal efficiencies of the organics, TP and TN in horizontal-flow and vertical-flow cells were improved significantly with the extension of HRT under the same season. The removal rate of 3 d HRT was obviously higher than that of 1 d HRT, and the removal rate of 5 d HRT was better than that of 3 d HRT, but the removal efficiency was not very obvious with the increment of HRT. Therefore, 3 d HRT might be recommended in the actual operation of the hybrid systems for economic and technical reasons.

热态镁渣余热回收及资源化利用

对还原炉进行热工测试,了解热量利用情况,明确热态镁渣余热回收是进一步降低能耗的关键。根据热利用和动力利用二种方式,提出利用移动床和竖式冷却罐高效回收高温镁渣余热资源,分别用于预热物料和发电。最后总结了镁渣应用于脱硫和建材等现状。

对立式油罐高低液位安全联锁与报警高度设置的探讨

为准确合理地确定成品油立式油罐高低液位安全联锁与报警高度以及报警响应,既确保油罐储油和收发安全,又能在低库存运作下最大限度地提高油罐有效储存容量,依据《GB50074-2014石油库设计规范》和《SH/T3007-2014石油化工储运系统罐区设计规范》,结合工作实践,提出油罐高低液位安全联锁与报警高度的设置方法和计算公式以及报警响应方法,并举例进行了示范验证。同时对进一步做好油罐高低液位安全联锁工作提出了建议。

复合结构罐顶安全性数值模拟及结构优化

传统玻璃钢储罐罐顶质量大,稳定性差。出于减重和增加罐顶稳定性的目的设计了含夹芯结构的新型纤维增强复合结构罐顶。由于复合结构罐顶受力复杂且缺少相关的设计和校核标准,因此以直径为11 m的立式储罐罐顶为例,采用ANSYS有限元分析方法,对根据HG/T 20696-2018标准设计的纤维增强复合结构罐顶进行安全性分析,根据安全系数求解罐顶设计的最小厚度和最小质量,并根据分析结果对罐顶进行结构优化。研究结果表明:HG/T 20696-2018标准无法适用于复合结构罐顶的设计;相比于该标准设计下的复合结构罐顶,加入加强筋前的罐顶厚度可再减少12%,质量再减少10%,而采用加强筋后,罐顶厚度可减少42%,罐顶质量可减少40%;加强筋下沿区域应力集中明显,为首要失效位置。所得结论可为纤维增强复合结构罐顶的设计和改进提供指导。

LNG储罐内罐立缝智能化焊接技术研究思路

随着我国能源结构的不断调整,LNG储罐的大型化、精细化、规模化已成为推动我国液化天然气工业发展的主流趋势,储罐内罐立缝打底及填充盖面过程的焊接质量、焊接效率及智能化程度直接关系到焊接接头服役的可靠性、结构设计的灵活性及LNG储罐的建设成本。目前已开发出的LNG储罐立缝焊接半自动焊接专机在内罐立缝焊接过程中存在智能化水平不高,过分依赖人工及焊接环境恶劣的问题。通过对目前半自动焊接专机存在的问题进行分析并提出相应的改进方案,在现有半自动焊接专机的基础上加入打底焊熔透控制及填充盖面自适应智能传感系统,进一步提升其智能化水平及焊接效率,并为LNG储罐内罐立缝智能化焊接的发展提供参考思路。

天然气压缩机缓冲罐工作原理及设计改进

在天然气开发、加工、储运等领域,压缩机是重要的核心装备。用往复式压缩机对天然气增压会形成脉动气流,容易损坏设备,引发安全生产事故,并使仪表测量失准。为了防止脉动气流的危害,通常会在压缩机后面安装缓冲罐进行消脉。对现有的带限流管卧式缓冲罐进行了分析,发现存在占地面积大、液位控制困难和容易气串等缺陷。为此对缓冲罐的安置方向和隔板进行了重新优化设计,研制出立式缓冲罐。新设计的立式缓冲罐占地面积小,且立式缓冲罐更容易控制液位,能较好地避免过排和欠排;立式缓冲罐也不易窜气,能减少天然气浪费和环境污染。

覆土立式油罐罐室建筑开口设计形式的利弊分析与建议

介绍了覆土油罐罐室建筑上部(顶部)楼梯式出口、上部(顶部)斜通道式出口、中部斜通道式出口三种开口设计形式与事故漏油收集系统的方案组合,并从罐室建筑形式、出口高度、操作间净深、占地面积、构筑物工作量等方面对上述三种方案的利弊进行了比较分析,推出上部(顶部)楼梯式出口+小容量隔油池为最优方案,同时提出了实现日常作业不下“井”、检查作业有通风、漏油处理在室外的覆土立式油罐罐室建筑开口设计原则。

地震激励下大型储罐内液体晃动响应分析

大型立式储罐容易受到地震激励影响,储罐中储液的剧烈晃动会对储罐壁面造成巨大冲击,这可能会导致储罐损坏和储液泄漏等问题。为了优化储罐的防晃结构,建立了充液储罐的模型,提出并研究了不同宽度和高度的挡板设置方案以提高储罐的防晃性能。对不同挡板结构对储液晃动响应的研究结果表明,挡板均有显著的阻尼效应,挡板的添加确实限制了晃动的幅度,但同时,这将限制动能与重力势能之间的转化,从而导致动态晃动力的增加。对晃动波高、壁面压力及关键点冲击应力的模拟结果分析显示,当挡板高度与自由表面高度之比为0.72~0.83,挡板宽度与储罐半径之比为0.49时,防晃效果最佳。对于高于挡板的部件,挡板可以在不增加应力峰值的情况下缓慢稳定应力波动。对于低于挡板的部件,挡板可以快速稳定应力波动,但应力峰值也会显著增加。