Planted Sludge Drying Beds in Treatment of Faecal Sludge from Ouagadougou: Case of Two Local Plant Species

Management of wastewater is a concern of developing countries. In Burkina Faso, an on-site septic system installed on the property is predominant and those systems product high quantities of faecal sludge which are not treated adequately before discharge. Our country is mainly fed by surface water, while water is the main vector of many diseases. So it is very important to manage efficiently wastewater and faeces. The treatment of faecal sludge by planted beds can use local persistent emergent plants like Andropogon gayanus (LPA) and Cymbopogon nardus (LPN). Those planted beds are compared to a non-planted bed (sludge drying bed) (LT). Treating raw sludge (BB) we got the yield over 90% concerning the biological oxygen demand (BOD5) for the LPA while the two others gave performances of 75% and 76% respectively. Regarding the chemical oxygen demand (COD), LPN gave better yields with 77% of removal against 71% and 69% for LPA and LT respectively. Overall, the pilots assured removal of orthophosphates varying between 77% and 79%, while the Kjeldahl nitrogen is removed by the various beds with respective fields of 94%, 96.5% and 97.5% for LPN, LPA and LT. The microbiological pollution abatement is in the order of 1 log unit on average for all beds.

Experiment research on grain drying process in the heat pump assisted fluidized beds

A heat pump assisted fluidized bed grain drying experimental system wasdeveloped. Based on this system, a serial of experiments was performed under four kinds of air cycleconditions. According to the experimental analysis, an appropriate drying medium-air cycle for theheat pump assisted fluidized bed drying equipment was decided, which is different from the commonlyused heat pump assisted drying system. The experimental results concerning the drying operationperformance of the new system show that the averaged coefficient of performance (COP) can reach morethan 2.5. The economical evaluation was performed and the power consumption for removing a kilogramwater from grains was about 0.485 kW-h/kg (H_2O), which shows its reasonable commercial efficiencyand great application potentiality in future market.

Characteristics of fluidization and dry-beneficiation of a wide-size-range medium-solids fluidized bed

Wide-size-range medium-solids are used in a modularized coal beneficiation demonstration system with a gas-solid fluidized bed. The characteristics of fluidization and dry-beneficiation of the medium solids were studied. The numerical simulation results show that 0.15–0.06 mm fine magnetite powder can decrease the disturbances caused by the bubbles. This is beneficial to the uniformity of the gas-solid interactions and thus to the uniformity and stability of the bed density and height. The experimental results show that, with an increase in the fine coal content in medium solids, both the fluidization quality and the beneficiation performance of the bed decreased gradually. When the fine coal content was no more than 13%, a relatively high superficial gas velocity increased the beneficiation efficiency. When the content was more than 13%, part of the fine coal was separated, leading to product layers. The separation efficiency was therefore gradually decreased. The models for predicting the bed density standard deviation and the probable error, E, value were both proposed. The E value can reach to 0.04–0.07 g/cm^3 under the optimized experimental parameters. This work provides a foundation for the adjustment of the bed density and the separation performance of the modularized 40–60 ton per hour dry coalbeneficiation industrial system.

FINE COAL AND THREE PRODUCT DRY BENEFICIATION WITH VIBRATION AND DOUBLE-DENSITY FLUIDIZED BEDS

Ｔｈｅｄｒｙｂｅｎｅｆｉｃｉａｔｉｏｎｔｅｃｈｎｏｌｏｇｙｗｉｔｈａｉｒｄｅｎｓｅｍｅｄｉｕｍｆｌｕｉｄｉｚｅｄｂｅｄｃａｎｅｆｉｃｉｅｎｔｌｙｂｅｎｅｆｉｃｉ－ａｔｅｔｈｅｃｏａｒｓｅｃｏａｌｏｆｓｉｚｅ５０～６ｍｍ．Ｈｏｗｅｖｅｒ，ｔｈｉｓｔｅｃ...

Unsaturated Flow Drying Bed(UFDB):An Alternative for Treatment of Septic Tanks Sludge

Unsaturated Flow Drying Bed (UFDB) principles are based on the ones of wastewater treatment by infiltration-percolation on the one hand and septic tanks sludge solar-drying beds on the other hand. With UFDB, sludge charges are split with low heights, leading to the drying of suspended solids in 2 days, and the infiltration of the flow of liquid in unsaturated middle. For average charges reaching 12.5 cm/d, the treatment efficiency of total oxygen demand and Total Kjeldahl Nitrogen, respectively 95 and 96%, correspond to a treatment capacity of 0.5 kg of O2/d/m2 of drying area. Bacteria reductions of 4 Ulog are obtained from filtrates outlet, with average fecal coliforms charges less than 103 CFU/100 ml. Monitoring the hydrodynamic behavior through rates, moisture, organic matter and respiratory activity demonstrates that the clogging of the massifs is linked to a biofilm growth within them. A four week resting period allows biofilm resorption. Thus, the drying of the infiltration surface in two days, the elimination of carbon, nitrogen and bacterial pollutions, as well as the reversibility of clogging show that UFDB is a credible alternative for the treatment of septic tank sludge in the socio-economic context and climate of tropical Africa.

Influence of the Nature of the Incoming Sludge on the Performance of a Vertical Flow Reed Beds in Dakar-Senegal

This work investigates the influence of the type sludge on drainage, plant development, purification performances and biosolids quality. Drainage properties were measured through the frequency of clogging, the percentage of leachate recovered and the dryness of accumulated sludge. Plant development was measured through the density, the height and the stem diameter. Purification performance was evaluated from the reduction rate. Biosolids quality was measured after 3 months of maturation. The results show that the clogging frequencies were 9.5%;0% and 3.7%;the volume of leachate recovered was 42.2%;20.4% and 24.7% and, the dryness was 33.4%;61.1% and 52.4% for FS-ST, FS-STT and SS respectively. Plants densities were about, with densities 197.1, 171.3 and 178.3 plants/m2 in beds fed respectively with FS-ST, FS-STT and SS. Despite the high removal rates, the concentrations of pollutants in the leachates are above the Senegalese standard NS 05-061 for discharge into the environment. The biosolids are all mature with C/N and NH4+/NO3?ratios lower than 12 and 1 respectively. The biosolids are also rich in organic and mineral elements. The concentrations of Ascaris eggs are higher than the WHO recommendations. These biosolids should be stored for additional time or composted.

Experimental Study of Drying Process of COLZA Seeds in Fluidized Bed Dryer by Statistical Methods

In this study the effect of initial parameters such as inlet gas temperature, initial particles temperature and gas velocity on temperature changes of solid particles and outlet gas temperature in a fluidized bed dryer was studied. For testing, an experimental setup was established. With combination of air and Colza seeds belonging to D groups of the Geldart classification (Geldart, 1986) fluidization regime was carried out. With five test series with maintaining the inlet gas temperature, solid particle temperature and outlet gas temperature during time were carefully measured. To analyze these data by using regression analysis to predict solid particle and outlet gas temperature, 2 correlations on initial pa-rameters were presented. The result has shown that temperature gradients in the beginning of fluidization, is very high and therefore the exponential functions in the regression model is used to predict the temperature changes.

Fluidized Bed Superheated Steam Dryer for Bagasse: Effects of Particle Size Distribution

Fluidized bed superheated steam drying is one of the technologies successfully applied to drying pulp in the sugar beet industry. It has the technological advantages of energy efficiency and safety (inert environment) required for use in drying bagasse. A comparison of the particle size distribution of bagasse and beet pulp was evaluated in terms of fluidization. The size distribution of bagasse particles is from 2 to 10 times broader than the equivalent distribution of beet pulp particles. The mean particle size of the bagasse is 1/3 of the mean size of the beet pulp. Fluidization tests proved that bagasse fluidization is possible. It was found that beet pulp and bagasse particles clearly differ on shape and size distribution which in turn will affect the design of the ancillary equipment and the fluidization systems if sugarcane bagasse is to be dried using superheated steam technology.

MECHANISM AND APPLICATION OF COAL DRY BENEFICIATION WITH AIR-DENSE MEDIUM FLUIDIZED BED

The mechanism of beneficiation with air dense fluidized bed has been theoretically studied in the paper. Focusing attention on the misplacing resources in separation process, the misplacing effects are divided into two parts called respectively as misplacing effect of viscosity and misplacing effect of motion. The proposed separation theory can reasonably explain the results of separation in different fluidization states. Experimental results in pilot and commercial plants showed that the air dense medium fluidized bed is a high efficiency dry cleaning technique. The dynamic stability of fluidized bed density is directly affected by the variation of fine coal content in fluidized bed and can be controlled in expected range through measurement of fluidized bed density and adjusting of split flow rate. With air dense medium fluidized bed, various coals of size 50—6 mm can be efficiently beneficiated. The separation density can be adjusted between 1.2—2.2 g/cm 3, and the probable error E p value is about 0.06.

EcoDry污泥干燥技术在欧洲的应用

EcoDry工艺是一种以污泥粒渣为燃料的新型污泥干燥技术,分析了该工艺的原理、特性、优缺点,着重介绍其在德国Obrigheim污水处理厂和匈牙利Pecs污水处理厂扩建工程中的应用,并对运行结果和排放标准进行了比较。研究结果表明,EcoDry工艺的干污泥和废气排放符合欧盟标准,可以为我国新建、扩建现有污泥干燥处置系统提供参考。

RHEOLOGY OF GAS-FLUIDIZED BED

Coal dry beneficiation with fluidized beds belongs to dry dense m ediu m concentration . Therheology is im portant for studying the behavior of an object settling in gas fluidized beds . Inthis paper , The viscosity of fluidized beds w as measured using falling spheres . The rheologi cal characteristics of fluidized beds can be described with Bingha m fluid m odel . The efficientviscosity of fluidized beds can be calculated and plastic viscosity and yield stress of fluidizedbed can be obtained by linearly regressing experi mental data . The calculated results are veryagreeable with the experim ental data .

浙江嵊州-新昌地区红层软岩崩解能量耗散研究

以浙江嵊州-新昌地区红层软岩为研究对象,探究该地区红层软岩崩解表面能特性。基于能量耗散原理,通过分析该地区3组不同组成成分的红层软岩在干湿循环作用下崩解过程中能量的转化、传递和耗散,得出红层软岩崩解过程中吸收的能量向表面能转化的规律。结果表明,该地区红层软岩随着干湿循环次数的不断增多,表面能累计增长量有3个变化过程:初期呈平缓增长;中期表面能急剧增加,增长速率越来越快;崩解后期其表面能累计增长量逐渐保持平稳状态。试验还表明黏土矿物含量越高的红层软岩,产生的表面能越多,耐崩解性越差。本研究提出的能量耗散模型,为治理浙江嵊州-新昌地区各种红层软岩问题提供了参考价值。

滤纸片干血斑在HIV-1 BED-CEIA新发感染检测方法中的应用

目的探讨在HIV-1 BED-CEIA新发感染检测中应用滤纸片干血斑的价值。方法研究纳入22个艾滋病自愿咨询检测(VCT)中心10226名咨询者血浆及干血斑样本作为目标实施HIV抗体检测,对通过免疫印迹法(WB)明确诊断为350例HIV感染患者的血浆样本及干血斑样本需同时实施BED-CEIA检测,观察滤纸片干血斑在HIV-1 BED-CEIA新发感染检测方法中稳定性、重复性,对两种样本检测结果存在的差异性进行对比。结果在HIV-1 BED-CEIA新发感染检测中应用滤纸片干血斑稳定性、重复性较高,重复性R^(2)值可高达0.9551。350例HIV感染患者样本检测结果中,其中295例患者样本被同时评估为长期感染,53例患者样本被同时评估为新近感染,两种样本对HIV BED-CEIA新发感染评估判定结果呈一致性(R^(2)值=0.95),一致性为99.42%。血浆样本及干血斑样本得到不同结果,样本An值均处于临界值附近(P<0.05)。结论在HIV-1 BED-CEIA新发感染检测中应用滤纸片干血斑的价值较高,检测结果稳定性、重复性较好,虽然部分样本检测结果存在一定的差异,但与血浆样本检测结果两者之间存在较佳的等效性,可广泛应用于临床HIV-1 BED-CEIA新近感染检测中。

流化床喷雾浸渍制备负载型钠基CO_(2)吸附剂脱碳性能

针对传统钠基CO_(2)固体吸附剂晶粒尺寸大、气体扩散阻力高、负载量有限导致的吸附量低的瓶颈问题,提出了基于流化床喷雾浸渍技术的吸附剂制备新方法。选取γ-Al_(2)O_(3)为载体,高纯度Na_(2)CO_(3)作为活性组分,利用溶液浸渍法和流化床喷雾浸渍法分别制备了载体结构、活性组分负载量不同的多组吸附剂,并基于固定床实验装置结合比表面积和孔隙度分析仪、X射线衍射仪、扫描电子显微镜、X射线荧光光谱分析等手段对吸附剂的CO_(2)吸附性能以及孔隙结构、晶型、表面形态及负载量等关键参数进行表征。研究结果表明,相同活性组分负载量下,采用喷雾浸渍法制备的吸附剂的饱和吸附量和吸附活性皆优于传统浸渍法,其原因在于该方法可以控制活性组分在载体上的负载深度;同时,活性组分多为针状或棒状等利于反应的形态结晶;晶体尺寸较传统溶液浸渍法普遍小10%~20%。尽管如此,载体的孔隙结构,具体如比表面积和孔径分布等参数仍会限制流化床喷雾浸渍技术制备的吸附剂的反应性能。

新型细粒级加重质矿物气固分选流态化密度分布研究

煤炭分选对提升煤炭品质具有重要作用,气固流化床选煤将流态化技术应用于选煤领域,有助于实现煤炭的干法提质。为解决传统Geldart B类加重质流态化分选密度波动大的难题,提出采用Geldart A类细粒级加重质用于流态化分选的思路。系统研究了新型细粒级加重质气固流态化分选床层密度分布特征,探究了床层密度的稳定性和细粒煤分选效果,分析了床层密度方差和分选效率的变化规律。结果表明,细粒级加重质中的床层密度分布更为均匀,轴向密度差异较低;结合床层膨胀行为研究,建立了细粒级加重质流化床床层密度预测模型,密度波动处于±0.1 g/cm 3时可以有效预测床层密度的分布,解决了分选过程中密度调控的难题。

怀山药恒温及变温红外喷动床干燥动力学、均匀性及品质特性研究

采用恒温干燥(40,50,60,70℃)和阶段变温干燥(阶段升温和阶段降温)工艺对怀山药进行红外喷动床干燥(IRSBD)处理,研究其对干燥动力学、均匀性及品质特性(质构、复水性能、总酚含量、微观结构和皱缩率)的影响。对怀山药红外喷动床干燥曲线的数学模型拟合结果表明,Midilli模型R2最大(0.99989),RMSE和χ2最小(分别为0.00319和1.69872×10-5),最适合描述怀山药IRSBD动力学。对比不同干燥工艺发现,恒温干燥条件下,提高干燥温度有利于缩短干燥时间,降低能耗。阶段升温干燥能耗仅高于70℃恒温干燥,其干燥均匀性最好,样品总酚含量最高为(85.25±7.41)mg GAE/100 g DW,皱缩率及硬度最低,分别为(74.3±3.96)%和(24.95±7.41)N,且有良好的色泽。阶段降温干燥样品具有较高的平衡复水比和脆度,然而在干燥时间、能耗、均匀性及产品硬度、皱缩率和总酚含量方面没有显著优势。结论:阶段升温干燥是怀山药IRSBD更为理想的干燥工艺。研究结果可为IRSBD技术应用于农产品加工提供理论参考。

干湿循环作用下嵊州-新昌地区红层软岩崩解及强度弱化特性

红层软岩遇水易崩解并造成其强度弱化,在边坡工程建设中易造成其稳定性弱,导致经济损失,甚至人员伤亡。揭示红层软岩干湿循环作用下黏聚力与内摩擦角的变化特征对于针对性设计边坡处理措施具有重要意义。以浙江嵊州-新昌地区下白垩统朝川组3组红层软岩为研究对象,通过干湿循环试验、崩解岩块点荷载强度试验和崩解颗粒直剪试验研究了红层软岩崩解及强度弱化特性。结果表明:试样在干湿循环作用下呈碎块状-粒渣状-泥糊状依次崩解的形态,其主要崩解过程可分为初始崩解、快速崩解、细微再崩解和崩解稳定4个阶段;试样的点荷载强度I_(s(50))随干湿循环次数的增加而降低,耐崩解指数I_(dn)与点荷载强度I_(s(50))呈正指数关系,试样的点荷载强度I_(s(50))在耐崩解指数I_(dn)为80%~100%之间急速弱化,在耐崩解指数I_(dn)为50%~80%之间表现缓慢弱化特性;试样的峰值抗剪强度介于0.567~1.219 MPa之间,其多发生在剪切位移3 mm前后,同组试样在相同轴压下,峰值抗剪强度随循环次数的增加而减小,试样崩解颗粒内摩擦角在22.28°~33.03°之间,黏聚力在0.46~0.74 MPa之间。试样的摩擦角和黏聚力随着干湿循环次数增加,都呈负指数关系。试验结果表明砂质比泥质胶结的耐崩解性更好,黏土矿物高的岩石更容易崩解,而“白色矿物”钠长石的吸水膨胀能力远不及黏土矿物,其含量差异对耐崩解性的影响不及黏土矿物。

咖啡豆红外喷动床干燥对其粉末物性品质、干燥能耗及挥发性成分的影响

为获得高品质干燥咖啡豆,采用红外喷动床组合干燥技术对咖啡豆进行干燥处理,研究不同进口温度和进口风速对咖啡粉色泽、堆积密度、休止角、得粉率、持水能力和水溶性指数、微观结构、干燥能耗及挥发性成分的影响。结果表明,提高进口温度和进口风速可以加快干燥速率,缩短干燥时间,降低干燥能耗。采用顶空固相微萃取-气相色谱质谱联用共检测出7大类(酸类、酯类、醛类、醇类、酮类、杂环类及其他类)挥发性化合物,其中酸类、酯类、醇类、杂环类4类为咖啡豆主要挥发性化合物且含量较高。综合对比得出最佳干燥条件为进口温度75℃,进口风速7.5 m/s,在此条件下,L*值和堆积密度取得最大值,分别为106.59和0.65 g/mL,休止角取得最小值36.87°,得粉率、持水能力和水溶性指数取得最大值,分别为43.43%、5.4 g/g和41.27%,干燥能耗取得最小值336.53 kJ/g,形态结构保存较为完整,壁面光滑平整,检测到的挥发性成分种类最高达70种,含量为38 487.028 49 ng/g(以干基计),咖啡豆综合品质最佳。该研究可为红外喷动床干燥技术在咖啡豆干燥加工及工业化生产中的应用提供参考。

聚二甲基硅氧烷干法改性气相白炭黑及其应用研究

为了进一步改善气相白炭黑的分散性,利用中试流化床对其进行干法改性。选择高含碳量的聚二甲基硅氧烷(PDMS)为改性剂,考察了预活化、改性温度、时间、气速和改性剂质量分数对气相白炭黑疏水性能的影响。结果表明,最佳工艺条件为:预活化温度为200℃、预活化时间为30 min、用水质量分数为10%、氮气气速为4 Nm^(3)/h、改性温度为300℃、改性剂PDMS质量分数为25%、反应时间为90 min。改性后气相白炭黑含碳量为4.89%,表面羟基量降为0.15个/nm^(2),可润湿率为0%,提高了气相白炭黑的疏水性。此外,探究了改性气相白炭黑对硅橡胶的补强性能,含碳量为2.5%的气相白炭黑补强时,断裂伸长率提高了24.8%,补强系数提高18.0%,拉伸强度提高8.0%,补强效果最佳,有效提升了硅橡胶的综合力学性能。

气-固脉动流化床加重质混合与分离特性及煤炭分选研究

煤炭是世界的主要能源,细粒煤的高效洁净利用已成为热点之一。试验采用以磁铁矿粉为主要加重质,与石英砂组成的二元加重质进行混合与分离的行为进行理论与试验分析。研究结果表明,0.25~0.15 mm石英砂与0.074~0.15 mm磁铁矿粉组成的二元加重质颗粒在在脉动流化床中整体上分布均匀稳定,离析程度较低,分选密度的宏观调控范围可以达到1.30~1.90 g/cm^(3),保证脉动流化床中密度在较大范围内的调节,符合工业生产的要求。6~3 mm细粒煤的低密度分选试验结果表明,当脉动气流控制在频率流化数N=1.3,f=2.55 Hz时,精煤灰分值为4.47%,此时可能偏差为E=0.11 g/cm^(3),分选效果理想。