Investigation of electrostatic charging in various gas-solid processes including fluidization and pnumatic conveying

在许多气固过程中，如流态化、气力输送、粉碎、混合等过程中，颗粒在处理、输送和加工过程中会产生静电电荷，从而导致颗粒壁粘着、颗粒团聚以及产生引起爆炸的高压电场。静电现象的显著负面影响已经在各个行业中得到了报道。在石油化工行业，聚乙烯气固流态化反应器的一次结垢事故可能会造成每天近100万美元的重大经济损失。就药品而言，药粉在干粉吸入器内聚集和沉积(由患有哮喘等肺部疾病的人使用)，这反过来又通过限制吸入器的排放剂量而降低吸入器的效率。在化学工业中，在水泥或矿物等固体的研磨过程中，会产生大量的电荷，导致颗粒团聚，这是非常不受欢迎的，因为细小的研磨颗粒看起来比实际大，显著降低了过程的研磨效率。如何防止或消除工业聚乙烯气固流态化反应器中静电电荷的产生，以及气力输送和研磨等不同气固过程中颗粒的带电机理，是目前亟待解决的问题。拟议的研究计划将(A)使用最先进的加压中试装置气固流态化基础设施，该基础设施能够在高达2500 kpa、110℃的高压下运行，并配备了一种新的静电电荷测量技术，以确定流态化温度和催化剂存在对反应器结垢的影响；(B)提供对气力输送固体荷电的透彻了解，包括注入聚乙烯床反应器时催化剂静电荷电的影响；(C)开发欧拉-欧拉计算流体动力学(CFD)模型，能够预测各种气固过程中的颗粒荷电，包括流态化床的颗粒荷电；以及(D)全面研究粉磨过程中的固体装料，以提高化工行业的粉磨效率。该研究计划的预期影响是帮助包括石化和化工在内的行业，这些行业对加拿大和世界经济至关重要，更好地了解静电充电机制，并减少这些行业面临的运营挑战。

In many gas-solid processes such as fluidization, pneumatic conveying, grinding, mixing, etc., electrostatic charges are generated during particle handling, transport and processing in which resulting in particle-wall adhesion, particle agglomeration, and generation of high-voltage electrical fields causing explosions. The significant negative impact of electrostatic phenomenon has been reported in various industries. In the petrochemical industry, a fouling incident in polyethylene gas-solid fluidized bed reactors could result in major economic losses of nearly $1.0M/day. In the case of pharmaceuticals, drug powder agglomeration and deposition occurs inside dry powder inhalers (used by those who suffer from lung illnesses such as asthma) which in turn reduces the efficiency of the inhaler by limiting the emitted dose. In the chemical industry, during grinding of solids such as cement or minerals a considerable amount of charge is generated leading to particle agglomeration which is quite undesirable because finely ground particles appear larger than they actually are, appreciably reducing grinding efficiency of the process. There is a great deal of need to determine ways to prevent or eliminate generation of electrostatic charges in industrial polyethylene gas-solid fluidized bed reactors, as well as shed some light on particle charging mechanisms in different gas-solid processes such as those of pneumatic conveying and grinding. The proposed research program will (a) use a state-of-the-art pressurized pilot plant gas-solid fluidization infrastructure that is able to operate at high pressures of up to 2500 kPa, 110C and houses a novel electrostatic charge measurement technique to determine the effects of fluidization temperature and presence of catalyst on the reactor fouling; (b) provide a thorough understanding of solids charging due to pneumatic conveying including the impact of catalyst electrostatic charging while being injected into the polyethylene fluid bed reactors; (c) develop an Euler-Euler Computational Fluid Dynamic (CFD) model enabling the prediction of particle charging in various gas-solid processes including those of fluidized beds; and (d) provide a comprehensive study of solids charging in grinding process to improve the grinding efficiency in the chemical industry. The anticipated impact of the research program is to assist industries including petrochemical and chemicals, sectors of vital importance to the Canadian and world economies, to gain a better understanding of the electrostatic charging mechanisms and to reduce operational challenges faced by these industries.