Air Pollution and Control

Air pollution prevention is an economic burden to a person and to a nation on a global scale. Air pollution is a threat to human and environment; therefore, it is extremely important to understand fundamental sources, causes, health effects associated with air pollution. This monograph gives an overview about air pollution and suggests the suitable preventive measures to reduce air pollution. This monograph includes air pollution from IC engines, primary organic aerosols (POAs), effect of volatile organic compounds (VOCs) on health and some advanced topics such as numerical simulation of airflow in hospital. This monograph also includes various engine technologies such as multipoint port fuel injection (MPFI), common rail direct injection (CRDI), indirect injection engine (IDI) and gasoline direct injection (GDI) techniques to reduce air pollution from road transport sector. Nuclear pollution, which is another threat for human life and environment is discussed towards end of this monograph.

Air pollution is one of the major threats to human health and living organisms, and its control is a greater challenge due to rapid growth in population and industrialization. Diesel vehicle exhaust emissions soot and nitrogen oxides (NO _x ) are the major causes of global warming, acid rain, and photochemical smog. Fuel quality improvement, low-temperature homogeneous combustions, and high turbulent combustions are the most important diesel engine emission control strategies to restrict the air pollution. Use of different gaseous fuels, CNG, LPG, hydrogen and renewable liquid fuel biodiesel, ethanol, etc., in diesel engine reduces the engine out emissions to a great extent. Common rail direct injection (CRDI) has several advantages compared to the conventional mechanical fuel injection system. The high-pressure injection enhances the air-fuel mixture to obtain the better thermal efficiency as well as lower emissions. Exhaust gas recirculation (EGR) is one of the predominant methods for controlling the NO _x emission in internal combustion engines. EGR with split injection strategy is one of the effective methods to decrease soot and NO _x emissions simultaneously without much drop in engine efficiency.

Diesel engines are widely utilized as a power source in various applications, such as passenger and commercial vehicles, electricity generation, marine transportation, and construction equipment. Despite several advantages for instance, low operating cost, high durability, and high power-to-weight ratio, diesel engines have the inherent disadvantage of high NO_x and soot emissions. In terms of environmental concerns, oxygenated fuels such as biodiesel have been considered as a promising alternative fuel for diesel engines. It is well known that the oxygen content of biodiesel suppresses the formation of soot precursors in diffusion flames. Many researchers are now trying to examine the soot formation with biodiesels. In this chapter, the effect of biodiesel on soot particles in compression ignition engines is discussed. The morphological characteristics of soot particles were analyzed with transmission electron microscope (TEM). The chemical composition was determined by the elemental analysis (EA) and thermogravimetric analysis (TGA). From the previous studies, it emerged that soot particles from biodiesel were composed of smaller primary particles compared to those in case of diesel. The nano-structure analysis of biodiesel soot particles showed that biodiesel origin soot is preferable for oxidation due to its unstable graphene structure. On the other hand, biodiesel soot particles were composed of lesser carbonaceous materials. They contained lower carbon-containing species but higher hydrogen, oxygen, and nitrogen in the soot.

Diesel particulate and NO _x emission cause several serious health problems; therefore, it is necessary to reduce these emissions from the tailpipe. In the past decades, significant technological advancements have been made in the field of engine emission control. In modern diesel engines, smarter electronic fuel injection strategies are being employed. Control of engine emissions can be put under two baskets: (1) active control techniques, and (2) passive control techniques. Active control techniques are those which restrict the formation of the pollutants in the combustion chamber itself. Passive control techniques refer to after-treatment devices. Active control techniques include advancement in the combustion chamber design, use smarter electronic fuel injection system, exhaust gas recirculation, high-pressure multi-fuel injection with precise injection timing, homogenous charge compression ignition, etc. which if used properly restrict the formation of the pollutants. Some other in-cylinder technologies are also effective in reducing the pollutant emission. Although active control techniques are able to reduce the emission up to some extent, but in order to meet the modern emission regulations, passive techniques are also required in addition to active techniques. Passive control technique involves after-treatment devices like diesel oxidation control, diesel particulate trap, NO _x absorber, selective catalytic reduction.

Air pollution is an inevitable factor in the modern era. Substances, in the form of particles or gases, which are subtended in the air and causing harm to the environment and living organisms both directly and indirectly, are termed as pollutants, and these pollutants lead to air pollution. The origin of air pollution is not restricted to only man made, but it may also be from natural causes like eruption of volcanoes or by forest fire. There are two divisions of air pollutants—primary and secondary. Primary pollutants are those which are emitted directly from a source like exhaust of automobile, industries, burning of fossil fuels. Some of them include hydrocarbons (HC), carbon dioxide (CO₂), carbon monoxide (CO), sulfur dioxide (SO₂), nitrogen oxide (NO _x ), particulate matter. A secondary pollutant is a product of reaction among the primary pollutants or with water vapor and sunlight, and examples are sulfuric acid, ozone, peroxy-acyl-nitrate (PAN). The pollutants in the air cause severe adverse effect on the human health also, like asthma, bronchitis, and even lung cancer. Thus, it is important to measure, control, and check the pollution of air from time to time. The authors in this paper have attempted to study the emission characteristics of BS-III commercial diesel auto rickshaws operating in the city of Imphal, Manipur, India. A mobile flue gas analyzer (MFGA) was used for recording the data. The oxygen percentage in the exhaust ranged from 16.6 to 21.3% (vol.). The ambient temperature during recording of data varied from 24.8 to 27 °C. Higher NO _x values in some of the engine indicate that the engine has high combustion, which is due to improper cooling of the engine. Low CO₂ was observed in some vehicles which indicate that the engine has incomplete combustion.

Gasoline direct injection (GDI) engines are increasingly used in transport sector worldwide in recent years due to the advantages they offer. These include superior fuel economy and better engine response and control due to introduction of electronic control unit (ECU) and high-pressure fuel injection system. One of the main challenges of using GDI engine vehicles is that they emit particulates, which are not an issue in case of multipoint port fuel injection (MPFI) engines. However, there is potential to further improve GDI engines for lower particulate matter (PM) emissions. Particulates from GDI engines are of different sizes such as coarse, fine and ultra-fine, and they also vary in composition and origin. The particulate of different sizes is known to cause adverse health effects. In this chapter, fundamental aspects of both homogeneous and stratified modes of combustion of GDI engines have been discussed, in addition to wall, spray and air-guided GDI engine concepts. A section of the chapter covers detailed comparison of particulate emitted by GDI and MPFI engines. Various size and concentration-based PM measurement techniques and instruments available commercially are included in this chapter. A discussion on influence of engine load, fuel type and spray characteristics on particulate emissions is elaborated towards the end of this chapter in addition to GDI soot morphological studies.

Primary organic aerosol (POA) constitutes the emissions from both natural (vegetation and micro-organisms) and anthropogenic sources such as combustion of fossil fuels and biofuels, and open biomass burning (forest fire). Semi-volatile nature of POA emissions leads to overestimation in the traditional emission inventories and chemical transport models. Another class of primarily emitted volatile species, i.e., intermediate volatile organic compounds (IVOCs), present around 0.28–2.5 times of POA, potential secondary organic aerosols (SOAs) precursors, also goes unnoticed. Phase partitioning mechanisms depending on their source, dilution, and volatility distribution make the contribution of POA to overall organic aerosols (OA) budget controversial. Further, the complex and higher particle emission rates and the gas-phase chemical transformation processes lead to the conceptual ambiguity between primary and secondary organic aerosol, thus rendering physico-chemical and optical properties to be least understood. Researchers have overcome the need of complete molecular identification of gaseous species to simulate the gas-particle partitioning by developing a two-dimensional volatility basis scheme (2-D-VBS) that employs the vapor pressure and degree of oxygenation. Here, we also illustrate the chemical composition-dependent volatility distributions for different sources used to ascertain the correct POA emission factors. This suggest that the policymakers and environmental regulating authorities need to take into account the SVOCs and IVOCs causing positive and negative sampling artifacts in order to correctly account for POA source contributions.

With broad commutability of pollutants, air pollution is a complicated issue that intimidates directly to human health and our environment. Various indoor and outdoor air pollution comprises of regulated and unregulated emissions. Volatile organic compounds (VOCs) are one of them which are carcinogenic and lead to photochemical reactions. Emissions of VOCs are directly associated with large number of industrial processes, emission through transportation, and various indoor and outdoor sources. Due to deleterious effect of different VOCs emitted from transportation, chemical industrial plants and from indoor on the environment make their eviction mandatory or at least degrade them under the limit set by environmental norms. So, it has turned a burning topic to diminish air pollutants and set a norm for volatile emissions. This study focuses on the major sources of carbonyl and aromatic compounds in indoor and outdoor environment. Some remedial processes like photocatalytic oxidation, plasma decomposition, chemisorption, and catalytic oxidation have been described in this study through which decomposition of these contaminants can be achieved. This chapter contains a deep study on health effects from the carbonyl and aromatic compounds.

The combustion of fuel in the presence of an oxidizer is an essential requirement to produce desirable thermal effect. There exists an analogy among generation of heat energy through combustion, soot formation, synthesis of carbon nanomaterial (CNM), and producer gas production by gasification. The stoichiometric and off-stoichiometric thermodynamic chemical kinetics explain the formation of soot, production of CNM as well as generation of heat or mechanical energy. If the objective of chemical combustion process is thermal energy, then soot is generated as a by-product, and if the objective is to synthesize CNMs, then heat energy is liberated as a consequence of combustion. Gasification of combustible material is another off-stoichiometric thermodynamic chemical combustion which is used for the generation of electricity in power plants. Coal gasification produced hydrogen gas can be advantageous in many aspects such as manufacturing of ammonia and a fuel source for combustion. Additionally, coal-derived producer gas can be converted into transportation fuels such as gasoline and diesel using some appropriate treatment. A lot of literature is available on combustion of fuels in heat engines but there is a dearth of availability of the literature for off-stoichiometric combustion such as synthesis of CNMs, gasification. Synthesis of CNT has been discussed in this chapter using LPG/biogas precursor.

Soot emitted by diesel engines causes severe urban air pollution in the form of smog. Particularly in cities like New Delhi in India, smog presents a health risk for millions of people. To counter this problem diesel engines are to be designed with combustion systems which can minimize smoke formation, and if possible cheap and effective exhaust treatment devices are to be fitted in the exhaust of these engines. Hence, understanding of the chemistry and physical events in the soot formation is the starting point in solving this problem. Particularly, the soot formation studies on high-pressure diffusion flames burners issuing turbulent hydrocarbon fuel jets are relevant for this study. In this article, the various theories associated with the soot formation like soot inception, coagulation, agglomeration, oxidation are discussed. Also, the results of the numerical studies carried out by the authors on diesel-air flames at laboratory conditions are briefly presented.

Human first created buildings to protect themselves from the adverse climatic conditions and other hazards in the natural environment. People have become more cognizant of the gist of the indoor atmosphere on health as a consequence of media publicity surrounding building-related sickness (BRS) and the sick building syndrome (SBS). Building-related sickness comprises the sensation of stuffy, stale and unacceptable indoor air, irritation of mucous membranes, headache, lethargy, and so forth. Acceptable indoor air quality (IAQ) helps to maintain healthy and productive indoor environments. This chapter deals with air pollution in healthcare place, the importance of ventilation in a hospital environment, indoor air pollutants, and transmission of contaminants and airborne particle inside the infirmary. In general, pollutants of common concern in buildings are divided into two broad classifications: particulates and volatile organic compounds (VOCs). Respirable suspended particles (RSPs) are small, easily-made-airborne particles, which can be actively measured with appropriate sensing equipment. There are many sources of airborne pollutants and odours in and around buildings. Some pollutants of particular concern to quality of indoor air are formaldehyde, VOCs, ozone, tobacco smoke, and aerosols, etc. In addition, odours, CO₂, and the moistness, which cause important effects on indoor air quality, especially in densely occupied spaces. The precise prediction of air stream within a room may improve heating, ventilation, and air conditioning (HVAC) scheme for a salubrious environment significantly. Ventilation and quality of indoor air stream are just two of the many fields which would benefit from the enhancement of room air flow. In this work, simulation of airflow in a room of the ICU has carried away to examine air flow pattern using FLUENT 15 CFD software. Standard k-epsilon turbulence model is used for airflow simulation. Simulation is carried out using second-order upwind simple scheme. The study predicts room air flow information in terms of velocities, temperatures, and contaminant distributions which are beneficial for infection control, building layout investigation.

Technological growth of any nation demands more fossil fuels which cause two major threats. First one is the shortage of fossil fuel, and the second is environmental pollution. Recently, the age-old conventional combustion process is being substituted by an innovative combustion technology, called porous medium combustion. This surge of interest in porous radiant burner is driven by some of the important benefits such as high thermal efficiency, low emission characteristics, high power modulation range, extended flammability limits and high power density. In the last two decades, there has been a significant development in the research aiming at changing the operating parameters and the design configurations of the porous radiant burners to attain lower emissions and higher thermal performances. Various burners based on porous medium combustion have been developed for industrial and domestic applications and showed beneficial over their conventional burner counterparts. Porous radiant burners based on porous medium combustion technology showed good emission characteristics and offer higher thermal efficiencies. Although, durability of few burners is still a matter of concern which results in non-commercialization of these products. This chapter summarizes the development of various porous radiant burners used in both industrial and cooking applications.

Nuclear power raises a number of fundamental environmental issues. The main problem is how to deal with the quantities of highly radioactive wastes which are produced from nuclear power plants. Discharges from nuclear power plant can cause substantial climatic contamination danger and hazard for individuals’ lives and well-being. In this chapter, different techniques for modelling and control of hazards have been presented. The modelling is in view of recreation and perception of spreading of air pollutants, estimation of the source term for atomic and compound fiascos, and the hazard appraisal of unsafe substances. This chapter will include the principle of modelling the nuclear and chemical disasters, optimal control of theoretical frame with example, various modelling techniques, challenges associated with measurement of pollutants, etc. Finally, solution and recommendation of good model will be presented. The inclusion of related references provides a starting point for the interested reader/researchers/industrialists.

Vehicles on roads are increasing tremendously and so are the waste and pollution. Every year billions of waste tires are being produced which is either left as such as solid waste or used for land fillings or burnt. Open tire fires are polluting air by emitting carbon monoxide, sulfur dioxide, oxides of nitrogen, organic pollutants, and poly-aromatic hydrocarbons (PAH). These gases can have chronic health affects like skin rashes, irritation of eyes, and respiratory problems. There is a growing concern for development of sustainable waste tire disposable methods. Tire being a polymer can be subjected to pyrolysis process to derive feedstock materials. It was found by many researchers that the products from pyrolysis can be used in different applications. There are three main products of pyrolysis of tires, namely gaseous products, liquid products, and the solid product called as char. These products when collected properly could be used for various other purposes. The gaseous products mainly consist of hydrogen, lighter hydrocarbons (HC), and carbon monoxide. These gases have the potential to generate energy. The liquid products when distilled produce gasoline like fuel and diesel like fuel. Char being porous can act as a gasification catalyst and when upgraded can be used to generate carbon black (CB) which is reutilized in manufacturing of tires. Also, for tire pyrolysis to be a sustainable process for disposing tires, hybrid technologies at industrial scale have to be explored. This paper provides an insight on tire pyrolysis processes and a detailed overview on latest research being done on the products of pyrolysis stating the use of these products to make the pyrolysis process economically viable.