共查询到20条相似文献,搜索用时 46 毫秒
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为明确褐煤低温(50 ℃以下)干燥引发表面干缩现象的发展规律,采用低温(20~30 ℃)低湿(40%~60%)空气干燥的方式,开展褐煤低温干燥干缩实验,分析干燥与表面收缩规律。结果表明:低温干燥过程中,对水分蒸发速率影响显著的因素是相对湿度而非温度,70%~90%的总水分散失量在干燥初期48 h内蒸发完成,平均含水率低至12.8%;低温干燥导致褐煤发生非均匀性表面干燥收缩,表面干缩经历热胀-快速干缩-收缩稳定3个阶段,水分快速蒸发散失的前48 h干缩率低,之后进入水分蒸发速率显著降低而干缩率持续升高,最终至收缩稳定,低速蒸发阶段发生显著干缩;表面干燥收缩率与散失水分质量具有显著的正相关性,与水分含量和蒸发速率具有显著负相关性。 相似文献
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Mohamed Hdi Romdhana Didier Lecomte Bruno Ladevie Caroline Sablayrolles 《Process Safety and Environmental Protection》2009,87(6):377-386
The sewage sludge from wastewater treatment plant is a potential source of infectious organism. The number and type of pathogens in sludge depends on various factors namely, the wastewater source, the type of treatment plant, and other environmental factors such as the biological medium offered by the sewage sludge. The principal sludge-borne diseases are presented followed by discussion on biological aspect of growth and occurrence. The overall objective of this work is to estimate kinetic reduction of pathogen population in sludge during different thermal-drying process including: the agitated conductive drying, drum drying, solar drying, and fry-drying. The temperature curves were reported from literature except frying data which were determined in experiment. In order to apply the temperature influence on pathogens population, kinetic parameters for the thermal inactivation (D, z-values) were chosen from literature. Values of concentrations of each pathogen were also extracted from scientific review of pathogens in bio-solids. This study conducted to resolve the survival kinetic of Hepatitis A viruses. The result showed that a concentration of 7 × 104 cfu/100 ml initially present in the sewage sludge is significantly reduced during the heat drying processes except the solar plant. The sewage sludge is completely disinfected when heated for 20 min, 10 min, and 10 s, respectively, during the agitated conductive process, vacuum fry-drying, and drum drying process. 相似文献
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M. Raynaud P. Heritier J.-C. Baudez J. Vaxelaire 《Process Safety and Environmental Protection》2010,88(3):200-206
Even after mechanical dewatering, activated sludge contains a large amount of water. Due to its biological nature, composition and also the type of treatment it comes from, this material is usually highly compressible and known to be difficult to dewater. In the present work various tests are proposed to try to highlight some aspects which could explain the poor dewaterability of activated sludge. Experiments of expression were carried out in a Filtration-Compression Cell for semi-solid samples of sludge. Operating conditions (intensity of the applied pressure, initial thickness of sludge sample) and the composition of the sludge (ionic strength by adding monovalent salt) were modified for the different series of experiments. It was observed that the removal of water from the sludge depended significantly on the pressure gradient throughout the sludge cake. However, the development of a dense layer of cake at the interface cake/filter medium seems to generate a pressure gradient non-uniformly distributed throughout the thickness of the cake. This phenomenon should control in part the efficiency of dewatering. This study also discusses the link between sludge dewaterability and cake relaxation on the basic of an osmotic effect within the flocculated matrix, which tends to resist against compression or deformation. This effect was reduced when both the applied pressure and the time increased. Finally, the activated sludge dewatering during expression stage depends on both the formation of a dense layer of cake at the interface cake/filter medium and an osmotic effect. 相似文献
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在木制品生产行业中,木材干燥是木制品加工生产工序中的一个重要环节,而在木材干燥生产中突出的问题是木材变形、开裂、木材含水率不均匀和霉变、虫蛀等。针对上述问题,设计出以高性能AVR微控制器为核心,应用恒流源、高分子湿敏电容和动态补偿等技术的全自动木材干燥测控系统。实验结果表明,木材干燥测控系统能保证产品质量,提高生产效率,硬件可靠性高,有工程实用价值。 相似文献
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M. Traoré O. Dufaud L. Perrin S. Chazelet D. Thomas 《Process Safety and Environmental Protection》2009,87(1):14-20
In this work, the influence of humidity on dust explosions of metallic (aluminium) and organic materials (icing sugar, polyethylene and magnesium stearate) has been studied. The impact of pre-humidification of powders on their ignition sensitivity, their volume resistivity and charge decay time has been assessed. The influence of humidity on explosion severity has also been studied by two methods: on the one hand, the dust sample was stored in a controlled workstation at constant relative humidity; on the other hand, the dry dust was dispersed in a humidity controlled atmosphere in the vessel.As expected, the effect of humidity strongly depends on the chemical nature of the particles. Experiments on powders volume resistivity and charge decay time have shown typical trends but have especially pointed out the inadequacy of some standards. Inhibition phenomena have been verified for polyethylene and magnesium stearate, whereas both inhibition and promotion have been observed for icing sugar and could be explained by an evolution of sucrose structure. Dry aluminium dust explosions in humid atmosphere show that water vapour inerts the explosion. However, when aluminium is stored at controlled humidity, the maximum rise of pressure rate increases with the water content, which is probably due to hydrogen generation. 相似文献
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研究了3种污泥预处理方法(表面活性剂处理、碱处理、Fenton处理)对污泥过滤脱水性能的影响。结果表明,对于3种预处理方法,使污泥过滤脱水性能最佳的阳离子表面活性剂十六烷基三甲基溴化铵(CTAB)的投加质量比为50 mg/g,NaOH质量比为150 mg/g,Fenton试剂Fe~(2+)与H_2O_2的投加比n(Fe~(2+))∶n(H_2O_2)为1.5。3种预处理方法对污泥均有一定破解作用,其中由于Fenton反应的强氧化性,污泥破解率最大,污泥粒径减小了近50%,释放的溶解性COD(SCOD)最高(786.88 mg/L)。Fenton处理后的污泥紧密结合型胞外聚合物(Tightly Bound-Extracellular Polymeric Substances,TB-EPS)及TB-EPS中蛋白质和多聚糖的量减少得最多。此外,还分析了3种预处理方法脱水效率与速率的差异。 相似文献
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The outcome of a 21-month monitoring study on anionic surfactants (AS) at five (27–70 ML/d) up-flow anaerobic sludge blanket (UASB) based sewage treatment plants (STPs) is described. The average removals of AS were around 8–30%. Appreciable concentrations of AS were being discharged to the watercourse (average 4.30 mg/L; range 3.60–4.91 mg/L). On an average dried sludge contained 1452 mg AS/kg dry weight. Mass balance at three STPs indicated that, AS load of the order of 5–17% and ≈12% is removed by adsorption in UASB reactors and polishing ponds (PP) respectively. Biodegradation of AS under anaerobic conditions in UASB reactors and PP does not seem to take place. In the sludge stream, appreciable biodegradation (≈46%) of adsorbed AS under aerobic conditions on the sludge drying beds takes place. If influent AS mass flux is normalized to 100 units, than average of ≈74 and ≈7 units are discharged with treated effluent and dried sludge respectively, while 12 and 6 units are adsorbed/settled in PP and aerobically biodegrade on sludge drying beds respectively. At two STPs (34 and 56 ML/d), the filterable fluxes in UASBR increased so that the mass balance could not be computed. 相似文献
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株洲市霞湾污水处理厂设计 总被引:2,自引:0,他引:2
株洲市霞湾污水处理厂是为保护湘江而建的工程,设计规模为10万m^3/d,根据污水水质及排放要求,处理工艺采用了不设初沉池的氧化沟活性污泥法;污泥处理采用了不经消化直接脱水工艺。介绍各处理单元的主要设计参数和所选用设备的技术对参数。 相似文献
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不同污泥肥料对水稻和大豆的肥效实验研究 总被引:7,自引:1,他引:6
为探讨城市生活污泥农用效果,以莆田市城市生活污水处理厂的鲜污泥为材料,制成干污泥、有机肥及生物肥等3种不同有机肥料品种,将这3种肥料在水稻、大豆上进行肥效盆栽试验,测定作物产量,并分析不同施肥处理其土壤N、P、K养分供应能力及作物对N、P、K养分的吸收情况.试验结果表明,污泥作为肥料施用能提高土壤速效N、P、K养分供应水平和水稻、大豆对N、P、K的吸收量,并且有明显的增产效果;3种污泥肥料品种的供肥能力从高到低的顺序为生物肥、有机肥、干污泥;并就污泥农用资源化提出看法. 相似文献
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Qi Zhang Rumei Tan Ying Huang Huimin Liang 《Journal of Loss Prevention in the Process Industries》2012,25(6):982-988
The minimum ignition energy (MIE) is an important property for designing safety standards and understanding the ignition process of combustible mixtures. The minimum ignition energy (MIE) of gaseous epoxypropane/air mixtures is measured using capacitive spark discharge. The effect of humidity on MIE is studied. It is shown that the MIE is not constant when the relative humidity increases from 40% to 88% at room temperature. The relative humidity has no significant influence on the MIE of gaseous epoxypropane/air mixtures at the lower volume fraction of gaseous epoxypropane in air. But, it has significant influence on that at the higher volume fraction. The MIEs of gaseous epoxypropane/air mixtures vary with the fraction of gaseous epoxypropane in air and the humidity. The lowest value of MIE (0.12 mJ) of gaseous epoxypropane/air mixtures is reached at around 10% in the examined ranges of the concentrations for the humidity 40%. The lowest values of MIE (0.1 mJ) of the mixtures are reached also at around 10% in the examined ranges of the concentrations for the humidity 66% and 88% respectively. 相似文献
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The individual and simultaneous effects of acid and ultrasonic pretreatment on the disintegration of municipal waste activated sludge (WAS) were investigated based on chemical properties of WAS. In the combination of acid and ultrasonic pretreatment methods (ultrasonic-acid pretreatment), lowering pH accelerated and enhanced the disintegration of waste biological sludge. Therefore, the same disintegration efficiency (obtained by ultrasonic pretreatment alone) was achieved by the combined pretreatment in shorter sonication times. Optimum pretreatment conditions were ultrasonic power density of 1.0 W/mL and pretreatment time of 10 min for ultrasonic pretreatment alone, and ultrasonic power density of 1.0 W/mL, pretreatment time of 10 min and initial sludge pH of 2.0 for the combined pretreatment. Sludge disintegration degrees were about 30% and 40% under these optimized conditions, respectively. Optimum sludge concentration was found to be 1.0% total solid (TS) content for the combined pretreatment. As a result, ultrasonic-acid pretreatment has been determined as a new and effective combined sludge pretreatment method to improve the sludge disintegration. 相似文献