Air Pollution Analysis
Air is known to be one of the most significant natural resources which provide the origin of life on earth. The plants and animals can live and sustain in this environment by using oxygen present in the atmosphere. However, due to industrialization, and the everyday transportation have polluted the environment by discharging primary and secondary air contaminants that alter the air composition therefore the particulate matter(PM), or biological materials, chemicals that are proved to cause unfavourable conditions for the humans and many other living organisms on earth is described to be air pollution. The primary and secondary air pollutants involve. sulphur dioxide, nitrogen oxides, carbon monoxide, carbon dioxide, volatile organic compounds (VOCs), respectively.
METHODS TO REDUCE SO2 EMISSIONS : Lower Sulfur Coal: The acid rain programme has wisely shifted to approach the low sulfur coal. The low sulfur coal is obtained from the powder river basin (PRB) of Montana and Wyoming called sub-bituminous coal. Without the alteration of the fuel system and the boiler some of the systems cannot burn 100 percent PRB coal. To ensured the decrease in the of SO2 emissions by using the bituminous coal which is formed by crushing of the small coal systems. To reduce a high amount of SO2 emissions the following processes may need the form of flue gas treatment. Flue Gas Desulfurization (FGD) or “Scrubbing” The FGD systems are nowadays installed in a number of coal fired power plants. an increasing number of coal-fired power plants have installed FGD systems. FCD has proved to to emit a low emission of SO2 by utilizing a an enormous amount of coals. the FGD are of two types that involve wet and dry systems. Most importantly 66% of the the united states has switched its system to scrubbing or in near future the system will be scrubbed. ,the wet FDG is more favorable for the numerous higher coal-fired power plants it has been investigated that. In response to the Clean Air Interstate Rule, coal-fired power plants added about 60 gigawatts (GW) of scrubbers in the three year period from 2008 through 2010Wet Scrubbers : The wet scrubbers can potentially be used for a high removal of S02. Within the wet FGD system a reaction between lime or limestone slurry and SO2 in a flue gas takes places to absorb SO2. The lime is proved to be effectively more reactive to reduce SO2 along with a cheap capital cost. In addition, lime is considered to have higher reagent cost. However, limestone forced wet scrubbers technology is considered to be the widest utilized form of wet FGD that is extensively being utilized on the coal fired power plants. A huge amount of SO2 removal can be obtained from the LSFO system approximately at a rate of 98% and more. Black and Veatch designed the first wet scrubber system in US and was installed in Kansas at Lawrence energy center in 1968. I t has been 40 years from now that the major step to enhance the systems performance are being taken.
Dry Scrubbers : The dry scrubbers technology uses water and hydrated lime in a form of slurry within a huge vessel in which a reaction between hydrated lime and water along with SO2 occurs in the given system. These are named as dry scrubbers due to the fact that though we use water in the flue gas but however this water is only utilized for the maintainance of of the saturation temperature. Most importantly the product which is formed in the FGD system and the unreacted lime are futher utilized to additionally capture The SO2 emissions. The sophisticated FGD system provide efficiency to reduce S02 emissions upto 90% or more.
METHODS TO REDUCE NO2 emissions: Combustions controls: The emission of NOX has been lowered down by using Combustion controls that are known to be be the first choices used for the control the NOx formation. Due to having lesser cost as compared to post combustion when the combustion control are once installed then owing to the usage of no catalyst or reagent it doesn’t have any cost for it. The combustion controls most of the times is retained in the furnace than is emitted from the exhaust gas stream the involve the method of low NOx burners (LNB) over-fire air (OFA) ), and separated over-fire air (SOFA). To chemically minimize the the emissions of NOXs. Re burning technology serves to be a significant control system, that decreases NOx formation in primary combustion zone. Combustion controls can also be helpful for the reduction of CO emissions and on amount of of organic pioneers Selective Catalytic Reduction (SCR) SCR technology, that is widely being used in the coal fired power plants for a time period of more than 15 years in the US is known to be a post combustion system to control NOx emissions is capable to effectively reduce 90% of NOx. In 1993 New Jersey (U. S) established the first wide scale coal fired selective catalytic reduction system (SCR) Moreover in in U. S about about 130 GW out of total coal fired generating capacity used the SCR system are going to be fixed in near future. At the surface of the catalyst the ammonia is utilized in the form of reagent which further reacts with NOx . At most of the times to increase the surface of the reaction we use several layers of catalysts. Selective Non-Catalytic Reduction (SNCR) : SNCR is also one of post-combustion NOx emission control technologies. By using minimum NOx burners the SNCR technology reduces NOx emission upto a limit of 20-30%. T he process of reduction occurs when urea or ammonia reacts with the NOx with a given temperature of 1,800°F-2,000°F resultantly, within the furnace post combustion zone the urea or ammonia is introduced and, similarly like SCR, the NOx are converted to NOx to nitrogen and water. The SNCR systems, being simple process can be easily installed at a time limit of 12 months.
CATALYTIC CONVERTERS: A catalytic converter is known to be one of the alternative technology that moderates the level of emissions of the engines. Numerous technologies are available that are used for the control of automobile exhaust emission out of those the catalytic converters are determined to be the most authentic ones Within the tailpipe the catalytic converter is introduced through which the hazardous gases of the unburnt fuel, CO, NOx are released. The catalytic convertor functions to change these gases into CO2, water, N2 and O2 respectively, it has been made compulsory for the automobiles to use catalytic converters in Japan and US.
METHODS to reduce PM emissions: ELECTROSTASTIC EMISSION: Electrostatic precipitation frequently removes particulate matters from the airstream. In an electrostatic precipitator, the suspended paticles in the airstream come across an electric field then the particles are electrically charged by entering into the unit and are emitted effectively by the effect of electric field. Baffles are used in the precipitation units that allows to distribute the air flow,discharge and collection The precipitation unit comprises baffles for distributing airflow, discharge and collection electrodes, a clean out system in which dust is trapped and collection hoppers. A wide DC voltage is applied as much as (100,000 volts) for discharging the electrodes which further charge the particles and as a result these charged particles are attracted by the oppositely charged collection electrodes and are finally trapped.
BAG HOUSE FILTERS : The suspended particles can efficiently be removed by using the fabric filter bags that are collectively known as bag house filters . The bag house filters typically consist of a range of long and thin bags of 25 cm and 10 inches in diameter which is arranged in a upside down manner comprising of wide and vast enclosures. the air which has an high amount of dust is collected and blown at the upper side by the fans present at the bottom of the enclosures. The fine particles are then trapped at the inner side of the filter bags while as the clean air passes from the fabric and is emitted from the top of the bag house filters.
METHODS to reduce (VOC) emissions: Its challenging to control the changes in the quality of air that has resulted due to the VOC emissions. The VOC has been proliferated in a wide range that include solvents and and commercialy used chemicals which are is highly difficult to remove. The atmospheric VOCs are significantly contributed by the automobiles,motor vehical discharges ,discharges from industries,vapours of organic fuel and petroleum and the chemical effluents . BIOFILTERS: The bio filters serve to be a successful technology that involve the remediation of polluted air by using microorganism which eliminate the unwanted pollutants. The process takes place when the microorganism convert these organic molecules inteo their initial components such as CO2 water and some nonhazardous substances,the pure and unpolluted air is discharged in the atmosphere through filters. Most importantly, biofilters donot emit any harmful by product however, another environmental hazard is potentially controlled by using biofilters.
CRYOGENIC CONDENSORS: The cryogenic conden/sor is known to be one of the modern and sophisticated technology relying on the fact that various atmospheric gases have specific boiling points. Ina ddition,the technology aims to convert the air into its initial components through the cryogenic air separation plant by the process of air purification ,distillation and heat exchange. INCINERATION: Incineration or combustion is a widely used VOC emitting Control technology that transforms the VOCs and other gases,hydrocarbon contaminants to its primary components such as CO2 and water. The process of incineration which is named as after burner provides efficient time for burning by holding a sufficient temperature to ensure complete combusion to take place. In addition, direct flame incineration is widely used for those waste gases which are itself a combustible mixture and no any additional air or fuel is required for this process.
OTHER EMERGING TECHNOLOGIES: Gas to Liquids: The diesel emissions can efficiently be controlled by switching to some alternative fuel such as a new gas or liquid (GTL) fuel prepared from natural gas. It has been investigated that by shifting to GTL fuel the NOx emissions can be reduced by 5-37% and 10-38% reduction in PM. Luckily the GTL fuel are widely available in significant amount in the globe,Netherland has started using it in a wide range but it is limited to small amount in UK,but the DMEalso need some modification. Moreover, dimethyl ether is also estimated to reduce the NOx by 25%,but the DME also requires some modifications in the engine due to which an investigation to launch such vehicles that can use DME fuel is being carried out in recent days. Hydrogen fuel additives: the emissions can also be reduced by using additives in the fuel combustion cycle of the automobiles.
A minute amount of hydrogen is added into the air intake of the automobiles to cause effective burning which is known as the zero1 technology given by the developer in UK (CGON),furthermore, this technology also reduces the NOx emissions,Liquid air: the particular cause of pollution also involve the emissions of harmful gases from refrigerated vans and trucks which are estimated to emit 29 times greater number of PM and six times of NOx as compared to the modern trucks. Infact, the auxillary engines that are a source to enhance the refrigeration umit are considered to be a contaminating technology. However to minimize many alternative processes to utilize liquid air. Photo-catalytic materials: The pollution could be minimized by shifting towards the deploy technology as an alternative for the removal of the air pollutants by using photocatalytic treatments which eliminate the air contaminants by using sunlight such as most of the companies have used this treatment on the surfaces that involve the road surfaces, roofing tiles and roofing felts,moreover the recent investigation proves the photo catalytic treatment to be the cheapest source of PM and NOx reduction from air. Many future trials aim to enhance the potential of the above technology.
Air purification: The smog free tower have been prepared from the dutch company studio Roosegard to purify air from the urban environments. In addition the smog free tower releases clean year by sucking the polluted air. According to the designers 3. 5 million cubic centimeters of air per day can be purified by a only one tower. The above technologies are some of those technologies that are used to reduce the atmospheric pollution.
Now it would be challenging foe the policydevelopers how to develop these technologies and to make sure that these technologies provide effective results for the removal of the atmospheric pollutants. some of the many countries of the world have targeted to launch such like technologies that include the Ultra low emission vehicles, Luckily a 1. 5 million research prize for the diesel replacement technologies have been provided by the European Commission in recent days. However the government provide vital support for more innovations to launch.
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