No abstract

Nanotechnology is currently an upward trend in diverse fields, and therefore, its application will be reviewed in this paper. One of the nanotechnologies which can be used in environmental remediation is carbon nanotube (CNT). Its excellent mechanical and chemical properties allow it to have better achievement in remediating a wide range of organic and inorganic pollutants. CNT can be categorized into two types: single-walled carbon nanotube and multi-walled carbon nanotube. Due to urbanization, various types of pollutants have been released into the environment in great amounts. For instance, estrogen is the hormone generated and released from animals and humans. However, the overconcentration of estrogen affects the physiology of biological life. Besides, pesticides are frequently used by farmers to increase the fertility of the land for agricultural purposes, while heavy metals are commonly found during anthropogenic activities. Long-term absorption of heavy metals into the body tissues will accumulate toxic effects, leading to body system dysfunction. Hence, CNT technologies, including adsorption, membrane filtration, disinfection, hybrid catalysis, and sensing and monitoring, can be applied to remediate these pollutants. However, the application of nanotechnology and CNT faces several challenges, such as production costs, toxicity, ecological risks, and public acceptance. Application of CNT also has pros and cons, such that the lightweight of the CNT allows them to replace metallic wires, but dealing with nano-sized components makes it challenging.

The theoretical performance of a newly developed multi-cyclone system known as MR-deDuster was investigated in term of its collection efficiency tested on a different type of particles. In addition, the performance of the system was also evaluated based on the various diameter of its vortex finder. A modified version of semi-empirical equations introduced by Lapple was used in the prediction. The results showed that the collection efficiency of the system increases with the diameter of vortex finder and density of particles. Details of the finding are discussed and presented in this paper.

Reynolds stress model (RSM) is known to demonstrate the closest approximation with experimental data and appraised as the most reliable turbulent model for the flow field in a cyclone simulation against other models. In this study, computational fluid dynamics (CFD) with RSM was used to simulate MR-deDuster, which is a newly developed multi-cyclone for fine particle emission control with axial inlet entry. The flow field characteristics of velocity contour and particle trajectories inside the cyclone were profiled while particle cut-diameter (dpc) of the unit was predicted based on fractional collection efficiency. Throughout the simulation, three different inlet velocities represented by their respective volumetric air flow rates (Q) ranging from 0.27 to 0.35 m3/s were applied and the results were plotted accordingly by referring to the value of these Qs. The velocity flows are almost identical for every unit of the cyclone in MR-deDuster system with the highest velocity of 33 m/s was found at the end of the vortex finder operated at 0.35 m3/s. This is crucial to ensure that each unit is operated in similar mode to get optimum performance of the system. Meanwhile, discrete phase model was used to estimate the particle trajectories in the flow. By releasing a certain number of inert particles at the cyclone’s inlet, fractional collection efficiency plot could be determined using the ratio of tracked particles trapped and released through the outlet. This study indicated that the predicted dpc of MR-deDuster was 1.85 and 2.05 μm for the highest and lowest Q respectively. The former represents the highest inlet velocity which is able to attract more of fine particle deep inside the bottom of the cyclone compared to the latter. Thus, the predicted fractional collection efficiency of 100% was achieved for particle larger and equal to 10 μm in size at the highest volumetric air flow rate or inlet velocity. The importance of inlet velocity in reducing the dpc which simultaneously increase the performance of a cyclone is illustrated in this study as successfully demonstrated by the CFD software.

A new type of cyclone design configuration called MR-deDuster,