Combustion environmental impacts

Over the past decades, advances have been made that reduce environmental impacts of coal burning in large plants. Some arc standard and others experimental. Limestone (mainly calcium carbonate) scrubber smokestacks react with the emitted sulfates from the combustion and contain the chemical products, thereby reducing the release of SO., into the atmosphere by a large factor (of ten or more). Pulverization of coal can also allow for the mechanical separation of some sulfur impurities, notably those in the form of pyrites, prior to combustion. Currently deployed—with more advanced versions in the development stage—are various t yies of fluidized bed reactors, which use coal fuel in a pulverized form, mixed with pulverized limestone or dolomite in a high temperature furnace. This technique reduces sulfate release considerably. There are... 

The waste streams created by utility systems tend, on the whole, to be less environmentally harmful than process waste. Unfortunately, complacency would be misplaced. Even though utility waste tends to be less harmful than process waste, the quantities of utility waste tend to be larger than process waste. This sheer volume can then result in greater environmental impact than process waste. Gaseous combustion products contribute in various ways to the greenhouse effect, acid rain and can produce a direct health hazard because of the formation of smog. The aqueous waste generated by utility systems can also be a major problem if it is contaminated. 

Coal is one of the major fuels in Ukraine where its environmental impact is much higher than that of nuclear energy, provided that there are no accidents. Yet there is no alternative to coal, for natural gas can only cover the most urgent household and industrial needs, not to mention the country s indebtedness for its imports. The question of environment-friendly combustion of coal is therefore highly topical. 

Halon systems were the ideal fire suppression agent before their implications of environmental impact due to ozone depletion. The industry is gradually phasing out usage of halon systems for this reason. A flowchart to analyze mechanisms to supplement or eliminate Halon systems for electrical or computer processing areas is shown in Figure 11. Some of the prime reasons to eliminate the use of Halon systems is that the facility may be constantly manned with a relatively low fire risk. Other facilities may have a very low combustible load and can be supplemented by highly sensitive fire detection means, such as a VESDA fire detection system. 

Desulphurisation of hydrocarbon fuels has traditionally been carried out primarily as part of the refining and upgrading process. Accordingly by far the most advanced and best understood chemistry and technology is to be found in this area. Prior to the advent of major concern for environmental impact of fossil fuel combustion products relatively little was done to desulphurise hydrocarbon fuels (principally coal) prior to combustion and past effects of large scale consumption of high sulphur coals can still be seen in major industrialised areas around the world. 

The disposal of coal combustion residues must take into account the nature and amount of the products to be disposed, as well as the nature of the disposal environment. It is a characteristic of coal utilization that many historic wastes exist that lack, or almost totally lack, characterization data. Only in recent decades, with concern over the environmental impacts of present and future accumulation of wastes, have characterization studies been made. The principal types of waste are described in Table 5. 

Carlson, C. L. Adriano, D. C. 1993. Environmental impacts of coal combustion residues. Journal of Environmental Quality, 22, 221-24-1. 

The recovered sulfur industry exists primarily as a result of the necessity of removing sulfur values from hydrocarbon fuels before combustion so that sulfur emissions to atmosphere are reduced. In the case of sour gas, the principal source of recovered sulfur, the product that results from recovery of the sulfur is clean-burning, non-polluting methane. In the case of refineries handling high sulfur crude the product is low sulfur gasoline and oils. Thus every ton of sulfur recovered is a ton that is not added to the atmosphere. The recovery process itself however, is also the subject of optimization and recent developments in recovery efficiency have further ensured that the environmental impact in the immediate vicinity of these desulfurization facilities will be minimized. 

Tphe research described here was started in 1964 as a part of the energy research program of the Bureau of Mines to develop methods to fragment the oil shale with explosives and to expose sufficient rock surface area to achieve in situ combustion recovery of shale oil. These studies are relevant to the rising concern for the capability of the U.S. to meet its mounting energy demands at reasonable costs and an acceptable level of social and environmental impact. 

In the previous chapters, thermodynamic analysis is used to improve processes. However, as pointed out in Chapter 9 (Energy Conversion), the exergy analysis did not make any distinction between the combustion of coal and natural gas and, as a result, could not make any statements regarding toxicity or environmental impact of exploration, production and use of the two fuels. A technique that can do this is LCA. What exactly is life cycle analysis In ISO 14040 [1], life cycle analysis (or life cycle assessment) is defined as "the compilation and evaluation of the inputs, outputs and potential environmental impacts of a product throughout its life cycle."... 

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