Following meteorological factors should be understood before studying the diffusion theories: 1. Atmospheric Temperature Lapse Rate 2. Speed and Direction of Wind 3. Wind Velocity Profile 4. Richardson's Number. Factor # 1. Atmospheric Temperature Lapse Rate: When the air has minimum velocity or more or less motionless, the accumulation of the pollution will be maximum. When the air is in [...]
Get the answer of: How to Remove Toxic Gases? Gaseous pollutants may be removed from n gaseous stream predominantly by physical or chemical absorption. The pollutant gases are selectively absorbed in a solvent liquid. The solvent liquid so chosen for the purpose must not be costly, operating cost should be minimum and also it should be easily recoverable. Gas absorption [...]
In this article we will discuss about the occurrence of air pollution due to lime and brick kilns. Lime-Kilns: Quick lime manufacture involves calcination of lime stone at temperatures exceeding 900°C. Calcination is an endothermic process and the required heat energy is supplied usually by firing coal along with the lime stone. There are heaped and rectangular trenched kilns commonly-known [...]
When high voltage is established between a pair of electrodes, an electric field is established. Charged particles like electrons and ions, under certain conditions, move along the field lines. Particles with a negative charge migrate in the direction of the positive electrode and particles with a positive charge in the opposite direction towards the negative electrode. Fig. 9.1 gives a [...]
In this article we will discuss about:- 1. Meaning of Electrostatic Precipitators 2. Principles of Electrical Precipitation 3. Process 4. Merits and Demerits. Meaning of Electrostatic Precipitator: Electrostatic precipitator (ESP) remove the gas borne particulate matter and the mist (liquid droplets) from the flue gas stream due to the action of electrostatic forces. When the gas stream passes through an [...]
For large throughput rates, plate type precipitators are almost exclusively used. These are of two type horizontal flow or vertical flow type-the former being preferred most even though it has a serious drawback in the amount of floor space occupied. Horizontal flow types are grouped into sections, arranged in series, so that the gas leaving one section enters the next [...]
The design and performance of precipitators are affected by a plurality of factors. These are divided into three main categories, namely – efficiency, local, high turbulence eddies scour: (i) Properties of the gas stream, (ii) Properties of the dust, and (iii) Process conditions. (i) Properties of the Gas Stream: The precipitator is designed for a particular throughput rate. Increase in [...]
In this article we will discuss about the mechanism of dust particle charging. The dust particles charging takes place by: (i) Diffusion charging, and (ii) Field charging or ion bombardment charging. Diffusion charging is the dominant mode of particle charging for particles with a diameter smaller about 0.2 µm; and field charging dominates for particles with a diameter greater than [...]
The following points highlight the five simplest tests for controlling pollution. The tests are: 1. Flame Photometry 2. XRF Analysis 3. Total Organic Carbon Analysis 4. Carbon-Hydrogen Analyser 5. Ion Chromatography Theory & Application. Test # 1. Flame Photometry This is a simple test to know the concentration of Alkali metals. The sodium and Potassium are more frequently determined because [...]
Depending upon the collection efficiency, capacity and operation mode, the dust collection devices are divided in the following three categories: 1. Internal Separators 2. Wet Collection Devices 3. Electrostatic Precipitators. 1. Internal Separators: Internal separator type dust collectors are manufactured in various shapes and sizes. Following types are most common: (a) Louver collector, (b) Fabric filters, (c) Gravity settling chamber, [...]