Evaluation of the Air Leakage Flowrate in Sintering Processes

Iron ore sintering is a pre-treatment technology by which orefines are converted into porous and permeable sin-ters,which are the used in blast furnaces.This process can be adversely affected by air leakage phenomena of various types.As experimental measurements are relatively difficult and often scarcely reliable,here a theoretical model based on typicalfluid-dynamic concepts and relationships is elaborated.Through the analysis of two extreme cases,namely,those in which leakage is due to a small hole or a full rupture,a generalized hole-bed mod-el is introduced,which for thefirst time also includes a complete bed permeability equation and can deal with different leakage position conditions.The results show that the model can evaluate the influence of leakage on the system at one time and be used to calculate theflowrate and pressure drop.Notably,the obtained results are within a 15%deviation with respect to available experiment values,used for comparison.

A novel coating technology for fast sealing of air leakage in underground coal mines

Air leakage in underground coal mines presents a serious hazard for coal production and the safety of miners.Coating technology is commonly used as an efficient means for preventing air leakage.To address existing problems with high dust concentrations in large operations involving complex processes and the high cost of traditional coating technology,a novel coating technology that ensures intrinsic safety by utilizing water pressure and wind pressure was developed.This new coating technology was designed to suction and spray,and the technical parameters of its spray performance was also studied.The experimental tests and evaluation indicated the optimum working range is 0.3–0.7 MPa of wind pressure,1.2–10.2 L/min of water quantity,and 1.0–3.5 m of spraying distance.Moreover,this novel coating technology was tested in the Dashuitou Coal Mine in Gansu Province of China.Compared with conventional counterparts,the proposed new technology is safe,efficient,and convenient to operate.During spraying,dust concentrations were kept at less than 10 mg/m3,and the average rebound ratio resilient rate of solid materials was below 13%.After spraying,the average leakage every 100 m was 4 m3/min,and the oxygen volume fraction in the adjacent goaf was approximately 4%,demonstrating excellent air leakage prevention.

Experimental research on inorganic solidified foam for sealing air leakage in coal mines

In order to efficiently seal air leakages and control spontaneous combustion of coal, solidified foam was developed by adding a certain compound additive to fly coal ash and cement as the main materials. It was prepared basing on the foaming characteristic through physical and mechanical system. We studied the effects of the different types of foaming agents, the mass ratio of cement to fly ash, and the mass ratio of solid to water and content of cellulose on the performance of solidified foam. The results show that when adding the composite protein, surfactant and cellulose foaming agents. The cement-fly ash ratio of 0.75:1, the water solid ratio as large as 2:1, and the solidified foam with high properties and density of only 516 kg/m 3 and compressive strength of up to 12.68 MPa were prepared. But the initial setting time, identity and compressive strength may be changed by varying the water solid ratio and/or the additives. We theoretically analyzed the influence mechanism of foam density, compressive strength and water solid ratio. The solidified foam is especially suitable for sealing surface leakage channels and filling the goaf with a wide application prospects.

An improved lumped parameter model predicting attenuation of earmuff with air leakage

Since air leakage is inevitable when earmuffs are worn improperly or together with safety glasses in factory or military,it is required to be considered to accurately predict earmuff attenuation.Besides unwanted air leakage,under controlled air leakage is introduced to earmuff to achieve adjustable attenuations in different signal-to-noise ratios(SNRs)and balance between attenuation and speech intelligibility.This work is to develop an improved lumped parameter model(LPM)to predict earmuff attenuation with consideration of air leakage.Air leakage paths are introduced into conventional LPM without air leakage,and air leakage path impedance is analytically described by Maa’s microperforated tube impedance.Earmuff passive attenuation behavior can be analytically described and analyzed with the improved LPM.Finally,the validity of improved LPM is verified experimentally.The results indicate that the improved LPM can predict earmuff attenuation with air leakage,and air leakage deteriorates earmuff attenuation and turns resonance frequency higher.

Energy Saving Technology for Lowering Air Leakage of Sintering Pallets and Dust Collectors in Sinter Plant

The hot-wire type anemometers were used for measuring the velocity of effective air flowing through sinter bed in this study.Meanwhile,microphones were installed beside the pathway and close to the outer sidewall of travelling pallets for monitoring sound pressure generated by an abnormal air leakage.For identifying the passing pallet,a thermal-resistant type RFID technology was adopted.Based on the measured data via anemometers,the air leakage rate of sintering machine was calculated with the mass balance method,and pallets with the abnormal leakage can be detected and ranked in the severity of leakage from the measured sound pressure with the relevant criteria.In addition,for examining the leakage situation,this study set up a capillary type of differential pressure gauge to double cone valve(DCV)below the electrostatic precipitator(EP)in sintering plant for collecting the larger dust.The criteria of determining leaked DCV and the patterns for replacing the DCV were proposed to develop a detecting and predicting system on the air leakage into dust collectors of sinter machine.It offered field staff a basis of maintaining or renewing DCV via a warning reminding and reducing air leakage to increase EP efficiency for avoiding the dust emission from the stack.These technologies had been implemented in the sintering plants of China Steel Corporation,and they can effectively reduce the air leakage rate by5%at least and further decrease the electricity consumption of the suction fan and coke rate,increase the production for the sintering machine.

Pre-placement of adhesive tape around wound sites can prevent air leakage in negative pressure wound therapy procedures

The introduction of negative pressure wound therapy has revolutionized the management of complicated wounds.However,the maintenance of an effective negative pressure environment is difficult in some instances,such as wounds in close proximity to an intestinal stoma or wounds surrounded by external fixations.We found that adhesive tape adheres more easily to itself than to wet skin or uneven surfaces.Therefore,we placed adhesive tape around surgical wounds prior to covering them with foam and sealing them with more tape.As a result of the strong adhesive force between pieces of tape,this method could provide a better environmental seal,even in situations where space is limited.Pre-placed adhesive tape around the wound site prior to foam placement could provide sufficient adhesion to maintain a continuous negative pressure environment during treatment.

Analysis of mine's air leakage based on pressure gradient matrix between nodes

Air leakage may significantly affect the effectiveness of mine ventilation by in- creasing the cost of ventilation and arousing problems for ventilation management.Fur- thermore,air leakage may accelerate the process of coal spontaneous combustion and cause gas explosion,thus greatly threatens the safety of coal production.The estimation of air leakage,therefore,have great practical significance.For any ventilation system of coal mines,there is a defined pattern of pressure gradient which drived the mine air to flow in the network,drives possible air leakage to go shortcut as well.Air leakage may occur through ventilation structures such as ventilation doors and fractures of the surroun- dig coal and rock of airways.A concept and the relevent calculation method of the pres- sure gradient matrix was put forward to assist the analysis of potential air leakage routes. A simplified example was used to introduce the application principle of'pressure gradient matrix in identifying all the potential air leaking routes,which offers a deeper understand- ing over the ventilation system and the prevention of coal spontaneous combustion.

Analysis on air-leakage law of goaf in condition of ascending mining for top-coal caving

Using the Jisan Coalmine's top-coal caving for the 3down coal seam with ascending mining as the project background, the air-leakage characteristics of the goaf wasanalyzed. Through data fitting of the in situ observation, the models of gas seepage, diffusion and air-leakage in the goaf were established in ascending mining. The ComputationFluid Dynamics software Fluent was used to simulate the air-leakage law of the goaf. Theresults of the numerical simulation provide a basis for the use of the technology of ventilation and fire prevention in the working face of an ascending mining, which ensures thesafety in production in the working face of the top-coal caving for 3_down coal seam in theJisan Coalmine.

Evaluation of Micro Leakage of Two Direct Esthetic Restorations with Different Preparation Techniques

Objectives: In recent times, the term “minimal intervention dentistry” has coined to describe a new approach to the treatment of the disease of caries. This study was carried out to evaluate the marginal integrity of class V cavity in permanent posterior teeth prepared with different air abrasion parameters compared with classical rotary cavity preparation. Methods: A total number of 150 sound caries for free human posterior teeth were used in this study. Teeth were extracted for periodontal disease or orthodontic reasons and the average age of patients between 20 - 35 years. Teeth were divided according to the type of restoration into two main groups: Group I (n = 75) restored with low shrinkable posterior composite (P90) and Group II (n = 75) restored with Ketac nano ionomer (N100). Each main group was divided into five groups (n = 15), then each group was further subdivided into three subgroups (n = 5) according to the storage time (immediately, three months, and six months). All teeth would be tested at both occlusal and gingival margins of prepared class V cavity according to the method of cavity preparation. Results: A high significant difference was found in the mean ranks of micro-leakageat both occlusal enamel and gingival dentin walls among Groups 1 - 5 (p-value of Conclusion: Low shrinkable silorane based composite yielded better results of micro-leakage scores along the occlusal enamel and gingival dentin walls when the cavity of class V was prepared with air abrasion technique with large size alumina particles under high pressure at immediate storage time as compared with Ketac N100.

Cause Analysis and Treatment Measures for Leakage of Top Cover of 330kV GIS Equipment

Based on the experience of GIS equipment maintenance, the causes of air leakage defects of GIS equipment running in a 330 substation were analyzed. After the equipment was disassembled, the main causes of air leakage were found, and a series of improvement measures were taken to eliminate the GIS equipment leakage defect. And the effective and feasible advice was put forward for this type of air leakage problem. The results lay a foundation for the safe and stable operation of GIS equipment.

内漏测量技术中浓度衰减法应用模拟研究

核电厂主控室作为核电厂运行的关键位置,在正常和应急情况下保证工作人员在主控室可居留性尤为重要。对核电厂主控室进行可居留性内漏评价能够判断主控室环境是否处于正常安全运行状态,并根据评价结果发现主控室存在的问题进而提出解决方案,是保障主控室正常安全运行的一种评价技术手段。主控室可居留性内漏评价采用示踪气体试验方法,通过浓度衰减法在简单区域进行内漏测量技术模拟研究,结果表明:示踪气体浓度在40 min内能够达到混合均匀,各采样点示踪气体浓度相对标准偏差为3.71%,示踪气体浓度随着时间推移混合均匀性不断提高,房间空气交换次数为0.3/h,内漏量为45 m^(3)/h,空气交换次数的不确定度为0.3/h。采用浓度衰减法进行内漏测量模拟研究,通过对示踪气体注入、采样点布置,气体搅拌装置分布及示踪气体取样分析等过程进行控制,能够实现示踪气体在简单区域内快速混合均匀达到平衡状态。

矿用喷涂堵漏风自修复材料性能研究及工程应用

喷涂堵漏风是防止煤自燃的有效手段之一。针对传统水泥基喷涂堵漏风材料脆性大、易开裂、堵漏风效果差的弊端,提出以微生物及结晶矿物为自愈合剂,研制出生物胶囊和矿物胶囊以及一种生物–矿物–纤维协同自修复材料。研究了不同养护湿度和养护时间对材料裂缝自修复能力的影响。结果表明:当养护湿度为100%相对湿度、养护时间为35 d时,研制的生物胶囊和矿物胶囊可以将裂缝完全修复,裂缝最大修复宽度为1260μm。采用扫描电子显微镜(SEM)和X射线能谱仪(EDS)探究了自修复材料裂缝区域修复产物的晶型及元素组成,发现裂缝处的修复产物为球碳镁石、花瓣状的水菱镁矿以及大量由细菌矿化产生的球形方解石,这些修复产物在一定程度上起到了密闭裂缝的作用;EDS能谱分析证实了修复产物为MgCO_(3)和CaCO_(3)。当养护湿度为100%时,材料具有最高的堵漏风率(97.15%),比同养护条件的对照组试样高出73.62%。最后将自修复材料用于沿空煤柱喷涂堵漏风,结果显示该材料在6个月内未发现明显裂隙,与传统水泥砂浆相比,该材料具有更长的使用寿命和更好的预防效果。

浅埋深综放工作面采空区“三带”分布研究

为研究浅埋深综放工作面采空区“三带”分布规律,在串草圪旦煤矿6101综放工作面采空区埋设束管,对采空区“三带”进行了现场实测。实测结果表明:由于煤层埋深浅、地表起伏大、进风侧存在地表漏风,进风侧采空区“三带”明显滞后于回风侧,进回风两侧氧化带宽度分别为87.8 m和61.4 m。利用FLUENT软件对实测条件下该工作面采空区“三带”进行了数值模拟,模拟结果和现场实测结果基本一致。同时模拟了不漏风条件下该工作面采空区“三带”分布,此时采空区散热带、氧化带范围大幅度减小,进风侧采空区氧化带稍大,而工作面中部和回风侧“三带”分布基本一致。

减小喉罩型号改善通气效果的临床观察

目的探讨减小喉罩型号改善通气效果的临床观察。方法选取喉罩固定翼距门齿距离>3 cm的男性患者60例为研究对象,随机分为试验组和对照组,每组30例。比较试验组(3号喉罩)与对照组(4号喉罩)的通气优良率、FOB理想位置比例、气道峰压差及2组喉罩置入后的密封压、套囊内压、漏气率,比较2组喉罩远端与食道入口距离,观察2组喉罩拔出时带血丝情况,术后24 h咽部并发症发生情况(包括术后咽痛、声嘶)及咽痛持续时间。2组患者设置的呼吸参数相同。结果试验组喉罩置入后通气成功率、FOB理想位置置入比例及通气效果优良率提高,漏气率值降低,密封压值提高,喉罩远端距食道入口距离较对照组减小,术后咽部并发症发生率较对照组低,差异均有统计学意义(P<0.05)。结论对于喉罩固定翼距门齿距离>3 cm的患者,通过减小喉罩型号,使喉罩放置理想位置比例增加,通气优良率升高,漏气率降低,密封压值提高,咽部并发症降低,可改善喉罩通气效果,安全有效。

综放面采空区漏风规律及防治技术研究

综放工作面采空区漏风易导致遗煤自燃,危及矿井安全。以大南湖一矿1305综放工作面为研究背景,采用数值模拟和现场试验的方法,研究了综放工作面采空区漏风规律,提出了综放工作面端头封堵采空区防漏风技术方案,并在现场进行了试验。结果表明,工作面端头是综放工作面采空区漏风的主要通道,其中进风巷侧端头漏风率达19%;风流在采空区内渗透深度约160 m;工作面端头封堵后,风流在采空区内渗透深度缩减至100 m左右;1305综放工作面端头封堵后,采空区漏风率降低17个百分点。

神东矿区浅埋煤层开采地表裂隙分布及动态演化特征研究

神东矿区浅埋煤层群开采导致地表裂隙发育良好,立体漏风复杂。为研究神东矿区地表裂隙分布特征及动态演化规律,以大柳塔煤矿活鸡兔井和补连塔煤矿浅埋藏开采为工程背景,采用现场无人机定点观测、红外、地质雷达等技术相结合的方法,研究地表宏观裂隙、隐蔽裂隙分布特征,并对裂隙动态演化规律进行分析。结果表明:神东矿区浅埋煤层开采工作面采空区对地表走向裂隙的影响相比于倾向裂隙较大,其中活鸡兔井12下206工作面101条裂隙有效影响范围35 m,补连塔煤矿22310工作面122条裂隙为62 m,走向裂隙最大裂隙宽度达到80 cm,倾向裂隙普遍在10 cm以下;随工作面的推进,裂隙宽度逐渐变大,直至发育完全,裂缝位置不连续断面间距变大,落差增大;宽度较大的裂隙(裂隙宽度大于10 cm),如果距离工作面较近,随着工作面的推进,裂隙宽度会逐渐缩小,甚至可能闭合。

数字胸腔引流系统在肺切除术中的应用价值

肺切除术后,胸腔引流管理是决定患者术后病程的关键,延迟拔管影响恢复速度和住院时间。传统胸腔闭式引流瓶已被广泛应用于相应患者,但存在一定局限性,尤其是肺切除术后存在肺漏气时,通常面临着长期不能拔除胸腔闭式引流管的风险。数字胸腔引流系统因其独特的优势可加快肺部漏气的愈合、减少胸腔引流量,进而缩短住院时间,其效果在多项研究中都得到了验证,本文就数字胸腔引流系统在肺切除术中的应用价值进行综述,并就其进一步有效应用进行讨论。

瓦斯抽采钻孔封堵一体化封孔技术研究及应用分析

针对地应力存在易影响煤层瓦斯抽采钻孔、易造成钻孔围岩出现衍生裂隙,进而引发钻孔漏气,影响瓦斯高效抽采的问题。为有效解决上述问题,以山西某矿5310综采工作面瓦斯抽采工程概况为例,深入分析了该工作面瓦斯抽采钻孔在使用后期出现失效的原因,研究了钻孔封堵一体化技术,设计了三囊袋封堵一体化装置,确定了最优裂隙堵漏材料配比方案,并进行了工业性试验,试验结果表明:与传统的两堵一注技术相比,应用封堵一体化技术后,钻孔瓦斯抽采平均浓度可从17.2%提升到59.6%,瓦斯抽采效果明显改善,有效消除了矿井安全生产隐患,更好地保障了矿井安全生产。

瓦斯隧道压入式通风风管漏风对瓦斯分布的影响

压入式通风风管漏风对瓦斯隧道施工中的瓦斯分布规律影响颇大。以何家坡高瓦斯隧道通风为工程背景,采用计算流体动力学(computational fluid dynamics,CFD)方法模拟风管漏风工况下的瓦斯隧道通风案例,分析漏风面积与漏风位置对隧道瓦斯分布的影响规律。结果表明:风管出风口的射流作用导致掌子面靠近风管一侧无瓦斯聚集,而掌子面与出风口之间的涡流作用导致该区域出现大量瓦斯聚集;风管漏风面积越大,漏风处上游涡流强度和下游射流强度越大,因此上游瓦斯聚集程度与下游瓦斯稀释程度越明显,两者均随着漏风面积的增加呈线性增加;风管漏风位置越靠近掌子面漏风处上游瓦斯聚集的程度越明显,瓦斯聚集的增量随轴向距离呈指数减小的关系,风管位置越远离掌子面漏风处下游瓦斯的稀释与扩散程度越显著,瓦斯浓度减小的程度随轴向距离呈指数增大的关系。研究成果可为瓦斯隧道施工中的瓦斯监测及传感器布置提供一定的理论借鉴。