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外文标题:Air Pollution Prevention and Control - An Integrated Designed Approach
外文作者:Dr. Akshey Bhargava, M.tech, Ph.D., LLB
文献出处:International Journal of Engineering Science and Computing,April 2018,Volume6,Issue No.4(如觉得年份太老,可改为近2年,毕竟很多毕业生都这样做)
英文2873单词, 14698字符(字符就是印刷符),中文4589汉字。
Air Pollution Prevention and Control - An Integrated Designed
Approach
Abstract:
The Planning, Management and Control of Air Pollution need to be addressed simultaneously to achieve the maximum output. The present paper signify the importance and high light an integrated approach needs to be infused into the system which inter-alia include Source control, Pathway control, and Receptor control . An effort has been made in the present paper to briefly describe Pathway and Receptor control with main emphasis on design of the Air Pollution Control Systems, particularly Bag Filters to control dust emissions and Wet Scrubbers to control gaseous emissions by way of Throwaway scrubbing processes, Regenerative Scrubbing Processes, Dry Processes and Spray Towers.
Key Words: Air Pollution, Integrated Approach, Design of Control Systems.
Introduction:
The term “Air Pollution” is used to describe substances that are artificially introduced in to the air in the form of gases and airborne particles which, in excess, are harmful to human health, buildings and ecosystems. Air pollution is mainly caused by combustion of fossil fuel,
processing of materials and decomposition of organic matters. The main sources of air pollution is from industrial activities, transport sector, house hold fuel burning, and other commercial activities. The present paper high light an integrated approach which inter-alia include Source Control, Pathway control, and Receptor control . An effort has been made in the present paper to briefly describe Pathway and Receptor control with main emphasis on design of the Air Pollution Control Systems, the details of which are as under:
Pathway Control:
Pathway control is a control system through which the air pollutants are restricted or arrested between a source and receptor through the mechanism of scavenging and filtration.This can be achieved by having a green belt of suitable species between source and receptor. Such a green belt would be able to absorb the air pollution gases and would also act as filtering media for the particulate matter. Sometimes in certain situations, curtains in the form of high walls or other means are also provided between sources and receptor to restrict air pollutants to reach receptors.
Receptor Control:
Receptor control is governed by an integrated urban and rural planning which should invariably incorporate environmental policy parameters in the form of following: -Atmospheric stability condition -Aerodynamic effects -Albedo-effect -Heat island effect -Ventilation coefficients
-Optimization between concreting and non-concreting surface area -Optimization between vertical to horizontal expansion of urban area
If the above issues are adequately and scientifically addressed, the level of air pollution at the receptor urban area shall be significantly low.
Source Control:
Main stress is usually laid on source control techniques with the focus on two fronts, one on “transformation of waste gasses / materials into usable products” and second on “end of the pipe treatment “. The first approach is gradually coming to fore front with the advancement of research and developmental activities and which has economic value addition. The second approach is cost intensive in which pollution control equipment or devices are installed to restrict air pollution into atmosphere. Source control is also associated with introduction of cleaner technologies, optimization of processes, controlled combustions, use of cleaner raw materials or fuels etc.
Design of Air Pollution control systems: A. Particulate Matter control:
There are various air pollution control equipment for the control of dust emissions depending upon particle size, minimum loading, desired efficiency, typical velocity, maximum gas pressure drop, and space requirements. These control equipment’s are dry collectors, as well as, wet collectors depending upon the basic characterises of gas and local conditions. The dry collecting devices are: 1. Settling chambers 2. Baffle chambers 3. Lower chambers 4. Cyclone chambers 5. Multiple cyclones 6. Impingement 7. Fabric Filters
8. Electrostatic precipitators
The wet devices are used where in water or scrubbing media is usually used to control emissions. These control devices are 1. Gravity spray tower 2. Centrifugal Collectors 3. Impingement chambers 4. Packed tower
5. Jet spray scrubbing tower 6. Ventury scrubber
Bag filters design: Introduction:
Filtration is among the most reliable, efficient, and rather economical methods by which particulate matter may be removed from gases. ? ? ?
Such type of filters are represented by various fabric bag arrangements and capable of high dust loading, more than 1gm / m3 In-depth or bed filters
Represented by fibrous array, a paper like mat, and occasionally, as a deep packed bed. Packed beds are applied when particulate concentration is much less
. Deep packed beds are prepared from crushed stone or bricks, wire screens, or fibers of many types arranged individually or in combination
Fabric bag filters:
?
Employed to control emissions involving abrasives, irritating chemical dusts, and exhausts from electric furnaces, oil fired boilers, oxygen fed converters for steel making.
Principle of operation:
Filtration is principally accomplished by the particle layer that accumulates on the fabric surface. Pressure loss increases with accumulated dust layer, thereby gas velocity decreases. Thus, dust dislodging operation is undertaken to have proper filtration. Many fabric bag filters assembled in one unit is called bag house.
Classification of filters:
? Fabric or cloth filters
Properties of fiber materials: Resistance to attack by: Fiber Strength Cotton Wool Paper Nylon Dacron Orlon Vinylidene chloride Polyethylene Tetrafluoro ethylene Polyvinyl acetate Glass Strong Medium Weak Strong Strong Medium Medium Strong Medium Strong Strong Temp. F 180 210 180 220 280 250 210 250 500 250 550 Acid Poor Medium Poor Medium Good Good Good Medium Good Medium Medium Base Medium Poor Medium Good Medium Medium Medium Medium Good Good Medium Organic solvent Good Good Good Good Good Good Good Medium Good Poor Good Cost & others Low - Low Easy to clean - - - - Expensive - Poor Resistance to abrasion