Combustion pollutant emissions

Industrial combustion is expected to continue to play a prominent role in the future. It is directly related to the vast majority of energy consumption in the world and indirectly related to many of the products people use on a daily basis. The increasing attention on the environment means that industrial combustion pollution emissions... 

Improving the cetane number by additives results in better engine behavior, as would be predicted by the combustion mechanisms in the diesel engine (noise reduction, better operating characteristics, particularly when cold). Nevertheless, concerning certain items such as pollution emissions, it may be better to obtain a higher cetane number rather by modification of the... 

The main combustion pollutants are nitrogen oxides, sulfur oxides, carbon monoxide, unbumed hydrocarbons, and soot. Combustion pollutants can be reduced by three main methods depending on the location of thek appHcation before, after, or during the combustion. Techniques employed before and after combustion deal with the fuel or the burned gases. A thkd alternative is to modify the combustion process in order to minimise the emissions. 

Unbumed Hydrocarbons Various unburned hydrocarbon species may be emitted from hydrocarbon flames. In general, there are two classes of unburned hydrocarbons (1) small molecules that are the intermediate products of combustion (for example, formaldehyde) and (2) larger molecules that are formed by pyro-synthesis in hot, fuel-rich zones within flames, e.g., benzene, toluene, xylene, and various polycyclic aromatic hydrocarbons (PAHs). Many of these species are listed as Hazardous Air Pollutants (HAPs) in Title III of the Clean Air Act Amendment of 1990 and are therefore of particular concern. In a well-adjusted combustion system, emission or HAPs is extremely low (typically, parts per trillion to parts per billion). However, emission of certain HAPs may be of concern in poorly designed or maladjusted systems. 

Minimization of pollutants from the combustion chamber. This approach consists of designing the engine with improved fuel-air distribution systems, ignition timing, fuel-air ratios, coolant and mixture temperatures, and engine speeds for minimum emissions. The majority of automobiles sold in the United States now use an electronic sensor/control system to adjust these variables for maximum engine performance with minimum pollutant emissions. 

The conventional fuels used for transit applications include gasoline, diesel fuel, and electricity. Alternatives to these fuels have been sought to reduce energy consumption, pollutant emissions, greenhouse gas emissions, and use of imported fuels. The conventional fuels for internal-combustion engines are the most energy-dense fuels petroleum and diesel fuel. 

Imagine an automobile thatmns in silence and without polluting emissions. Such an automobile, long a dream of the environmentally conscious, has recently become a reality. The power source is a fuel cell, an electrochemical cell that uses a combustion reaction to produce electricity. Hydrocarbons such as natural gas and propane can be used in fuel cells, but the cleanest fuel is molecular hydrogen. 

We are not entirely finished with the furnace. There is one more piece missing from the whole picture—the air flow rate. We need to ensure sufficient air flow for efficient combustion. The regulation of air flow is particularly important in the reduction of air pollutant emission. 

Overall, EGR and combustion/injection systems constitute the key factors to comply with the EuroIV standards (applied in January, 2005). The EuroIV step exhibits EuroIII NO and soot particles limits divided by 2. Besides, vehicle s weight is always increasing due to the introduction of new safety systems and equipment. Therefore, pollutants emissions increase and a supplementary effort to reach the normative threshold is to be made. To comply with this target, some evolutions have been introduced, as for example multi-injection or water-cooling of the EGR system. The NO,/particle compromise adjustment remains possible for most of the applications without any after-treatment system like the Diesel particle filter (DPF). 

Furthermore factors such as stoichiometric value, heat load and design of the burner as well as the combustion chamber have a significant impact on the emission of pollutant gases. Depending on the reaction of a combustion system to a changing equivalence ratio decisions can be made how to minimize the pollutant emissions by adapting the flow rate of air or gas. A combustion control system based on monitoring the CO fraction in the flue gas could thus be considered. 

Methanol also seems to biodegrade quickly when spilled and it dissolves and dilutes rapidly in water. It has been recommended as an alternative fuel by the EPA and the DOE, partly because of reduced urban air pollutant emissions compared to gasoline. Most methanol-fueled vehicles use a blend of 85% methanol and 15% gasoline called M85. Building a methanol infrastructure would not be as difficult as converting to hydrogen. While methanol can be produced from natural gas, it can also be distilled from coal or even biomass. In the 1980s, methanol was popular for a brief time as an internal-combustion fuel and President Bush even discussed this in a 1989 speech. 

However, the optimisation of an ICE is of high complexity and often characterised by counteracting effects, as a reduction in fuel consumption does not necessarily lead to an optimisation of pollutant emissions for instance, high thermodynamic efficiencies can only be achieved with high combustion temperatures, which in turn favours the formation of NO. ... 

Considering the composition of petroleum and petroleum products (Speight, 1994, 1999), it is not surprising that petroleum and petroleum-derived chemicals are environmental pollutants (Loeher, 1992 Olschewsky and Megna, 1992). The world s economy is highly dependent on petroleum for energy production, and widespread use has led to enormous releases to the environment of petroleum, petroleum products, exhaust from internal combustion engines, emissions from oil-fired power plants, and industrial emissions where fuel oil is employed. 

The firing of fuel wood has been identified as one of the main causes of pollutant emissions from small-scale (<100 kW) combustion of wood fuels. The emissions are a result of insufficient combustion efficiency. This thesis presents a new measurement method to analyse the thermochemical conversion of biofuels in general, as well as to explain the main reason of the inefficient combustion of fuel wood in particular. 

In practice, it is the pyrolysis chemistry in the conversion system and the incomplete combustion of the pyrolysis products in the combustion system (Figure 14) which cause pollutant emission problems. In other words, the knowledge about the thermochemical conversion chemistry of single particles can be applied to the understanding of emission problems in PBC systems. 

Variable valve timing is being developed to improve the performance and reduce the pollution emissions from internal combustion heat engines for automobiles and trucks. A unique benefit for these engines is that changing the timing of the intake valves can be used to control the... 

Legislative restrictions on pollutant emissions have motivated the combustion community to seek new low-emission combustion techniques that are practical industrial energy sources. However, to meet the needs in most industrial applications, a combustion source needs to be able to maintain low-emission output over a range of heat release rates, occupy minimal volume, and have low operating costs per unit energy produced. One would like to maximize the turn-down ratio, volumetric heat release, and overall thermal efficiency while minimizing NOa , CO, and hydrocarbon emission levels. The ultra-low NO, emission performance of the CSC has been previously documented by the authors and its... 

Flames interact with the walls of a combustor through various mechanisms, which affects flame stability and pollutant emissions. For example, thermal quenching by cold walls in internal combustion engines can cause an increase of unburned hydrocarbon emissions [1-3], as has been shown by impinging a... 

Lyle, K. H., L. K. Tseng, J. P. Gore, and N. M. Laurendeau. 1999. A study of pollutant emission characteristics of partially premixed turbulent jet flames. Combustion Flame 116 627-39. 

The principal source may be air pollution emissions from coal combustion, suggested by the fact that aerosol S levels are generally high and vary independently of Fe (Figure 1), Pb was found only in the most polluted air (16-17 March), and fine particle K and Cl show some temporal similarities presented in Figure 5. When pollution contributions to the total aerosol are very large, Zn and other elements with fine modes may also be enhanced by pollution additions to their natural levels. 

Sulfur chemistry is important both in combustion and in the petrochemical industry. Most fossil fuels contain sulfur, and also biofuels and household waste have a sulfur content. As a consequence sulfur species are often present in combustion processes. Knowledge of gas-phase sulfur chemistry occurring in combustion has bearing on pollutant emissions and on system corrosion. Air pollution by SO2 still constitutes a major environmental concern and search for control techniques has motivated research also on high-temperature homogeneous sulfur chemistry. However, more recent work on sulfur chemistry has been concerned mainly with the effect of sulfur on other pollutant emissions, such as NO and CO, and with the SO3/SO2 ratio, which is important for the corrosive potential of the flue gas and for formation of sulfur containing aerosols. 

D.C. Hammond, Jr. and A.M. Mellor. Analytical Calculations for the Performance and Pollutant Emissions of Gas Turbine Combustors. Combust. Sci. Techn., 4 101-112,1971. 

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