施工隧道负离子除尘新方法

在施工隧道通风换气时, 为了快速稀释粉尘, 加快施工进度, 引入负离子除尘新方法, 并分析了其应用的可行性; 利用粉尘颗粒荷电理论研究了粉尘颗粒的荷电量, 推导了粉尘颗粒在负离子净化系统外电场作用下的饱和荷电量计算公式; 根据施工隧道的环境特点, 在粉尘沉降主动力为电场力和重力时分析了粉尘颗粒的受力情况, 并利用牛顿第二定律推导了粉尘颗粒的沉降算法; 模拟隧道环境进行了室内试验, 依照室内试验获取的安装参数确定隧道试验方案后进行了现场试验, 并利用现场测试结果分析了负离子除尘新方法的使用效果、机理和沉降算法的准确性。研究结果表明: 在使用和未使用负离子净化系统的1个施工周期内, 试验段呼尘消除率分别为51%和20%, 超过《公路隧道施工技术规范》 (JTG F60—2009) (简称《规范》) 中呼尘短时间接触容许浓度8mg·m-3的时间分别为1、12h, 使用负离子净化系统后, 呼尘时间加权平均浓度从6.38mg·m-3降至3.10mg·m-3, 满足《规范》中不大于4mg·m-3的要求, 即采用新方法可快速、高效地净化施工隧道内的空气; 施工隧道采用负离子除尘新方法的机理可使用粉尘荷电理论和牛顿第二定律进行解释; 在粉尘主要为PM₁₀的相似工况下, 利用沉降算法、室内试验和现场试验得出的粉尘消除时间分别为14、18、20min, 采用算法得出的粉尘沉降时间需要考虑的综合影响系数为1.31.4。 

New method of dust removal by negative ions in construction tunnel

In order to dilute the dust during the ventilation for construction tunnels, so as to speed up the construction progress, a new method of dust removal using negative ions was introduced, and the feasibility of the new method was analyzed. Using the charge theory of dust particles, the charge of dust particles was studied, and the saturated charge formula of dust particles in the external electric field of a negative ion purification system was obtained. According to the environmental characteristics of construction tunnel, the dust particles' stress conditions were analyzed when the dust settling active forces were electric field force and gravity. The Newton's second law was used to deduce the settlement algorithm of dust particles. The indoor test was carried out through the simulation of a tunnel environment, and the field test was carried out after the tunnel test scheme was determined via the installation parameters obtained by the indoor test. The field test results were used to analyze the accaracy of the effect and mechanism of the negative ion dust removal method and settlement algorithm. Research result shows that duringaconstruction period, the respirable dust removal rates are 51% and 20%, respectively, with and without the negative ion purification system in the test section, and when the respirable dust concentration exceeds the permissible concentration-short term exposure limit of 8 mg·m-3 in Technical Specification for Construction of Highway Tunnel (JTG F60—2009) (standardfor shot), the time durations are 1 and 12 h, respectively. The time-weighted average concentration of respirable dust reduces from 6.38 mg·m-3 to 3.10 mg·m-3 after using the system, which meets the standard's requirement of the time-weighted average concentration not exceeding 4 mg·m-3. Therefore, the new method can quickly and efficiently purify the air during tunnel construction. The mechanism of the negative ion technology used for dust removal during tunnel construction can be explained by the charge theory of dust particles and Newton's second law. In a similar working condition where the main dust is PM₁₀, the dust removal times obtained by the dust settling algorithm, the indoor test and the field test are 14, 18 and 20 min, respectively. The dust settling time calculated by the dust settling algorithm should consider the comprehensive influence coefficient of 1.3-1.4.