جستجوی مقالات مرتبط با کلیدواژه « Cyclone » در نشریات گروه « پزشکی »

Generally, geometrical parameters of the cyclone have a profound effect on determining its performance. The air outlet (Vortex Finder) as one of the cyclone’s components has a significant impact on the cyclone’s internal flow pattern, pressure drop and even dust removal efficiency.

Two different air outlets were designed in order to be easily installed and removed. The ribs (both in the opposite and the same swirl direction with the air flow) were inserted at the inner wall of the vortex finder. The step length of the blades was calculated to be 1.5. The dust feeder was injected the silica particles with a concentration about of 2.1 gr/m3 into the inlet air. The results of dust removal efficiency of the cyclone were calculated and compared for three groups of total dust, PM10 and PM2.5 in different experimental conditions.

Installation of spiral blades in same swirl direction as the air flow inside the cyclone increased 7.75, 7.73 and 6.75 percent in total efficiency, PM10 and PM2.5, respectively. The dust removal efficiencies for total dust, PM10 and PM2.5 increased by 2.6%, 2.33% and 1.5%, respectively, when the swirl direction of ribs and air flow was the opposite. The effect of helical blades on pressure drop for the first experimental setup (same direction) decreased by (- 2.5%) and in the second one (opposite direction) increased by (+ 2.03%). The best quality factor was also calculated for the cyclone with the blade aligned with the air flow direction.

Use of ribs in the inner wall of the cyclone vortex finder,  especially when the rotation direction of the ribs and airflow are the same, leads to a decrease in pressure drop and increase in dust collection efficiency which finally leads to improvement of cyclone performance.

Dust emission is one of the main health and environmental problems during the crushing, screening and conveying process in mining company. The goal of this study was designing, implementation and evaluation of industrial ventilation and combination with a water spray for control the airborne particles as well as economic analysis on crushing unit of a mining company.
After ensuring the lack of destructive effect of humidity on material properties, a water spray system was designed and installed for settling some of produced dusts. Other emitted particles were also controlled by designing and implementation of local exhaust ventilation system. This system was evaluated after installation. For collection of dust, three Stairmand cyclone with high efficiency were used. Finally, the efficiency of water spray and industrial ventilation systems was investigated as single and combined in the control of fugitive particles in ambient air, occupational exposure and environmental emission.
The efficiency of the wet and ventilation system, alone and combined in reducing workplace dust concentration were 49%, 76% and 95%, respectively. Moreover, the efficiency of the wet, ventilation and combined system in reducing the exposure to repairable particles were 54%, 73% and 88%, respectively.
According to the present evaluations by implementing the combination of these two systems, the occupational exposure of workers, ambient dust concentration and emitted dust to environmental was fell to less than permissible limits. According to the economic analysis, over 80% of total costs by combined procedure was reduced. Therefore, this system can be proposed as an effective and cost-effective in such conditions.

Control of fugitative dust from mining process and application of an appropriate and economical system for dust collecting is essential. The goal of this study was cost-benefit analysis of an integrated systems and compare to bag filter in a crushing plant of a mining company.
A local exhaust ventilation system for capture of emitted particlees, a water spray for dust suppresion at sources and parallel Stairmand model cyclones as dust colletor were designed and installed based on the standards and guidelines. Then, efficiency of wetting and industrial ventilation system for control of ambient dust personal exposure and environmental emission have evaluated as integrated and alone. Finally, cost-benefit analysis of this system was compared to bag filter.
The efficiency of this system for control personal exposure repairable particles and emitted dust to ambient air was 87% and 95% for plant 1 and 88% and 95% for plant 2, respectively. The concentration of emitted emitted dust from stack to environment were 121.28 mg/m3 and 112/68 mg/m3 for plant 1 and 2, respectively. The capital, operational and maintence costs of this option was 217 and 0.992 billion rials lower than bag filter. Also, annuall collected dust by cyclones was worth 518 million rial.
According to results, integrated system had a significant impact on emitted dust in workplace and environment. The economical analysis domonstrated 73% and 80% savings in capital and operational costs compared to bag filter. Total costs of implented project will be compensated at 220 day with recovered dusts, therefore, in the same condition, it can be suggested as the favourable and economical solution.

Industrial ventilation systems and dust collectors are effective solutions to reduce particulate emissions in the workplace and environmental in mineral processes. In this study, Local Exhaust Ventilation System and dust collectors for control of emitted silica, coke, silicon carbide dusts from crushing unit was designed and evaluated.: Local Exhaust ventilation system based on standards and guides was designed and implemented after field study of the processes and sources of air pollutants. A set comprised of the four parallel cyclones (Stairmand model) and a new design of the scrubber had been used for dust control. After set-up of systems, its effectiveness in reducing the exposure of workers in the workshops and dust collecting were assessed. Test results were significant differences between the concentration of particles in both on and off the ventilation system revealed (P <0.05). The system has been implemented as means of personal exposure to pollutants and environmental emissions were reduced 93.01% and 64.64%, respectively. Also, alone and integrated collection efficiency of cyclone and scrubber, were 94.2%, 59.05% and 97.4%, respectively. The results show good agreement with the values of the parameters ventilation system was designed. Implementation of integrated dust collectors is a good option in industries that have the financial and technical constraints to improve change processes and devices. This method with attainment to health and environmental standards not only can be resolve of the pollution problems, but also will be economically justified of such projects with reduction of depreciation expense and dust recycling.

Emission of volatile organic compounds and unpleasant smell are the important characteristics of the rendering plant, causing disturbance for the workers and nearby residents. In order to prevent the spread of air pollutants and to provide favorable environment, application of treatment technologies is essential. In this study, in order to select suitable collector and ventilation system for rendering plant, air sampling was performed via NIOSH sampling methods (1501, 1300, 1600, and 2002). Totally, 24 air samples were collected from the ambient air, air pollution source, and worker’s breathing zone using two sorbent, activated charcoal and silica gel and were analyzed using GC-MS. Then, the local ventilation system was designed based on the qualification and quantitation analysis of air samples. The stairmand high efficiency cyclone and thermal oxidizer were designed for dust control and gas cleaning respectively. In total, 41 chemical pollutants in exhaust air from rendering plant were identified; these compounds included hydrocarbons, aldehydes, ketones, alcohols, ethers, halogenated compounds, sulfur compounds, nitrogen compounds, and acids. The results of ventilation system designing showed that the system with airflow of 5725 m3/h and a cyclone with the diameter of 1 m and the height of 4 m could remove 50% of particles with 9.45-micron diameter. Gaseous pollutants were removed using thermal oxidation via the consumption of 96 m3/h fuel gas flow. The chamber volume was 6.67 m3. The daily fuel costs were estimated 310000 RLS. Application of local exhaust ventilation system and integrated collectors for control of air pollutants in rendering plant can remove large amounts of particulate and gaseous pollutants. Control of these pollutants can cause loss of smell nuisance and environmental pollution and improving the health and welfare of workers and neighboring residents of such industries.

Cyclone is one of the most utilized dust collectors for airborne particles control. It separates particles from airflow by centrifugal force. However، it is not effective in collecting very fine particles smaller than 10 μm in diameter. The aim of this study was to assess the performance of charging particles on cyclone efficiency in collecting particles smaller than 1 μm. To achieve the above aim، a pilot air conditioning system equipped with conventional cyclone of Lapple model was designed and installed. A high voltage (18 KV) DC power supply was used for charging silica particle in corona charger. Isokinetic probe was used for particles sampling at upstream and downstream of cyclone under different study conditions and measurement was carried out using Grimm 1. 08 dust counter. Charging fine airborne silica particles caused a significant increase in collection efficiency. There is a direct relationship between collection efficiency and charging voltage، so that the total particles collection efficiency was increased from 2. 7 to about 72% with respect of increasing charging voltage from zero to 18 Kv. However، inlet air velocity has a negative effect on the collection efficiency of particles charged. Applying electrocyclone in collecting fine particles smaller than 1 µm is more efficient compared with that of conventional cyclones.