丙酸质量浓度对丙酸富集培养物降解特性的影响

为阐明丙酸质量浓度对厌氧生物处理系统中丙酸降解特性的影响，研究了不同丙酸质量浓度条件下丙酸富集培养物的降解特性．以丙酸为唯一碳源，通过15代的传代培养富集到一个中温互营丙酸氧化菌群（包括丙酸氧化菌和产甲烷菌）．聚合酶链式反应一变性梯度凝胶电泳（PCR—DGGE）指纹分析结果表明，该富集培养物中的丙酸氧化菌为Syntrophobacter，而嗜氢产甲烷菌和嗜乙酸产甲烷菌分别为Methanobacterium和Methanosaeta．在污泥接种量为0．81g／L条件下，当丙酸质量浓度为1000—2000mg／L时，丙酸能够被该富集培养物快速降解；而当丙酸质量浓度为2500—3000mg／L时，丙酸降解和乙酸的转化均受到一定程度的抑制，但随着培养时间的延长，该抑制作用逐步解除．较高的丙酸质量浓度（≥2500mg／L）能够对丙酸氧化菌产生可逆性抑制作用．

Impedance Matching Algorithm for Selection of Suitable Explosives for Any Rock Mass-A Case Study

Proper selection of the explosive is an important part of blast design.The judicious selection of explosives is governed by economic considerations and site/field conditions.The mine management desires to select an explosive that will give the lowest cost per unit of rock broken,while assuring that fragmentation,fragment size distribution,muck pile profile,muck pile diggability,displacement of the rock,onset of movement,face movement,burden relief rate,ground vibration and noise remains within control limits.Factors which influence the selection of an explosive include explosive cost,charge diameter,cost of drilling,fragmentation difficulties and fragment size requirement with loose muck pile condition,water conditions,atmospheric temperature,propagating ground,storage considerations,sensitivity considerations,explosive atmospheres and nearness of communities from mine.All these concerns can be handled effectively by using the impedance matching technology where explosive impedance is matched with rock impedance for optimal blast performance with due concern to productivity,economics and environment.This paper discusses a case study in limestone mines where rock impedance was determined by carrying out surface refraction test and a patented algorithm was used to estimate the explosives’properties i.e.VOD(velocity of detonation)and density of explosives required.

New Blast Damage Criterion for Damage Prediction

There are several underground mines in India which operate in close proximity to an operating surface mine.Under such scenario,the blast induced stress waves generated due to surface blasting may be a potential source to cause instability of adjoining underground mine structures.Using seismographs,54 blast induced vibration data were recorded at various locations in the roof,floor and pillars of the underground mine at Hingir Rampur mine of Coal India Limited by synchronizing the timing of surface blasting carried at an adjacent Samleshwari opencast mine.Results of this study show that Artificial Neural Network(ANN)has better prediction potential of peak particle velocity(PPV)and damage to adjacent underground structures due to surface blasting as compared to conventional regression methods.In order to assess and predict the impact of surface blasts on underground workings,Blast Damage Factor(BDF)has been evolved.The study shows that site specific charts can predict the blast damage class at an underground location due to surface blasting for known distances and explosive charge per delay.The severe damage in case study mine site took place when peak particle velocity exceeded 162 mm/s and PPV less than 51 mm/s had no probability of damage to underground structures due to surface blasting.

Dynamic Fracture Toughness Tests on Limestone

Limestone being sedimentary rock contains multiple bedding planes,which has vertical cracks or joints.As explosives apply high dynamic loading rate during blasting i.e.rock fragmentation&comminution process,the measure of critical SIF(stress intensity factor)is pertinent to be measured and is known as dynamic fracture toughness of limestone.In order to investigate the influence of several factors on the mode-I fracture toughness and fracture behavior of limestone,dynamic fracture toughness tests(mode-I)were conducted under various conditions of loading rate.The microstructure of rocks was also investigated to understand the dynamic fracture toughness and fracture mechanism of limestone.This paper deals with results of 11 limestone specimen subjected to dynamic fracture toughness tests.It was observed that crack surface velocity increases with increase in dynamic fracture toughness.The fracture velocity also increases with increase in dynamic fracture toughness.The fracture velocity in limestone increases between 1.14-5.09 times with increased fracture toughness.The crack surface velocity of limestone increases between 1.39-3.09 times with increase in dynamic fracture toughness.

Dynamic Uniaxial Tensile Strength Tests on Limestone

Dynamic properties of limestone govern the rock fragmentation characteristics.Failure of rock under tension is more likely as compared to failure under compression under static or dynamic loading both.Since the application of explosives creates dynamic loading and is a dynamic event,the determination of dynamic modulus values is technically more appropriate than the static measurement.The rock fragmentation would significantly improve by investigating the dynamic uniaxial tensile strength as specific fracture energy,stress intensity factor,fracture toughness of any detonating blast hole depend heavily on dynamic rock property and not on static rock property.Most of the limestone projects globally are still accustomed with using static tensile strength to understand the rock fragmentation.The present papers deal with determination of dynamic uniaxial tensile property using split Hopkinson pressure bar(SHPB)system.The nano second high speed camera with laser captures the crack surface opening velocity during dynamic loading.It was observed during data analysis that dynamic tensile strength of limestone increases by 1.2-2.3 times of the static strength.It may be concluded by the study that determination of dynamic tensile strength is paramount for understanding the rock fragmentation.

Dynamic Uniaxial Compressive Tests on Limestone

The dynamic properties of limestone play a pivotal role while selecting the suitable explosives for any limestone mine.Since the application of explosives creates dynamic loading and is a dynamic event,the determination of dynamic modulus values is technically more appropriate than the static measurement.The rock fragmentation would significantly improve by investigating the dynamic uniaxial compressive strength as specific fracture energy,stress intensity factor,fracture toughness of any detonating blast hole depend heavily on dynamic rock property and not on static rock property.Most of the limestone projects globally are still accustomed with using static compressive strength to understand the rock fragmentation.The present papers deal with determination of dynamic uniaxial compressive property using split Hopkinson pressure bar(SHPB)system.The nano second high speed camera with laser captures the crack surface opening velocity during dynamic loading.It was observed during data analysis that dynamic compressive strength of limestone increases by 1.7-4.9 times of the static strength.It may be concluded by the study that determination of dynamic compressive strength is paramount for understanding the rock fragmentation.

Relation between Loading Rate and Fracture Velocity on Limestone

The relation between loading rate and fracture velocity is the key to determining the fracture toughness of rock mass under dynamic loading.While designing an optimal blast design for any limestone mines,understanding the relationship between blast detonation pressure and rock fragmentation can increase the energy utilisation in any limestone mine blast.The detonation pressure is directly related to dynamic loading rate and fracture velocity is directly related to stress wave propagation speed during blasting.This paper discusses the relationship between dynamic loading rate and fracture velocity for limestone samples.It was observed that crack propagation velocity increases with fracture toughness of rock samples.It may be concluded that as the dynamic loading increases,the fracture velocity increases.

微量元素对ABR发酵产氢产甲烷的影响

为构建厌氧折流板反应器(ABR)发酵联合产氢产甲烷系统,考察了微量元素对ABR系统前端格室发酵产氢、后端格室发酵产甲烷的影响。在进水COD为6 000 mg/L、碱度为1 900 mg/L的条件下,当未投加微量元素时,系统对COD的去除率为51%,产氢能力为0.46 m3/(m3.d),产甲烷能力为0.68 m3/(m3.d),四格室的厌氧污泥脱氢酶活性均较低;而在相同运行条件下,当投加微量元素后,系统对COD的去除率提高到62%以上,产氢能力为0.37 m3/(m3.d),产甲烷能力达到1.66 m3/(m3.d)。研究表明,投加微量元素可有效刺激ABR发酵联合产氢产甲烷系统中厌氧污泥的活性,由于ABR中产甲烷菌等耗氢菌群活性的增强导致发酵产氢作用受到抑制,但产甲烷活性的进一步增强,使系统的处理效能得到明显提高。

A simplified model for understanding the performance of two-pot enclosed mud cookstoves

The objective of this study is to develop a mathematical model for a two-pot enclosed mud cookstove.A new model has been developed combining transient heat transfer,combustion chemistry and fluid flow.The model can be used for variation of the operation and design parameters.The model predicts performance parameters such as efficiency,boiling time,excess air ratio(EAR),transient wall,flame and char temperature.For an input power of 5.1 kW,the estimated overall efficiency,EAR and boiling time were 17.1%,1.97 and 43 minutes,respectively.The model outcome is compared with experimental results.Further,10 parameters are varied and their impact on cookstove performance is analysed.The optimum dimension for the door opening,combustion-chamber height and wall thickness are suggested.Therefore,this study can serve as an effective tool for cookstove design.