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& SAFETY IN COAL USE

The principal areas of public concern include land

reclamation after surface mining; from underground mining; acid drainage from the refuse from coal mines and coal preparation

plants; emissions from combustion such as S02 , NOx, and particulates safe disposal of ashes, and the possible effects of C02 on climate.

The applicability of these concerns vary from country to country depending on a number of circumstances.

Except for the C02 question, however, technology is available to meet these concerns and to comply with the most stringent of the current environmental standards in many countries at costs that leave coal competitive with oil at mid-1979 prices in most areas. There is no practical method of controlling C02 emission from the combustion of fossil fuels and from other sources, and

further research is needed on the possible effects of increased C02 emission on global climate. Control of long-range transport of gaseous and particulate emissions may also require new forms of international cooperation.

Occupational health and safety are important concerns in coal mining. The major occupational health problems associated with underground mining has been the lung (pneumocosis or black

lung) disease caused by breathing coal dust. The greatest safety hazards in underground mining have been from gas explosion and flooding. Reduction of dust and gas levels by

much improved ventilation and filtration systems; dust suppression by water-spraying, or laying of powdered limestone; continous monitoring of air quality and the application of strict work rules and practices have done much to reduce the risk of lung disease and to improve safety by reducing the risk of explosion.

Moreover, increasing mechanization and better equipment have reduced the exposure of the work force per unit of coal produced.

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-In mines where the best practices are observed, the accident and illness rates are now comparable with construction work and many sectors of heavy industry. As coal production expands, extending the application of these health and safety practices and continuing workers' training should ensure acceptable occupational health and safety conditions.

1.13.1 ENVIRONMENT HEALTH & SAFETY COAL COMBUSTION

A schematic look below at the mineralogical and chemical nature of coal will serve as a good guide to the understanding of possible pollution species that do arise from coal utilization.

(2) Low molecular weight hydrocarbons like methane, ethane, etc, carboxylic acids, and thioethers, are examples of

volatile organic chemicals contained in coal primary nature.

Below and up to 600°C they volatilize, combust, ignite both completely and incompletely depending on the fuel/air ratio.

Where the combustion is complete the gaseous products in high oxidation states evolve and could constitute pollution hazards.

Thioethers and pyridine do for example, give rise to sulphur dioxide, nitric oxide, and carbon monoxide which are poisonous gases and hence require that their level in the air be controlled.

(3) High molecular weight organic chemicals found in coal are the various alicyclics, polycyclics and polynuclear aromatic hydrocarbons like phenanthrene, anthracene, naphtalene, cumanne, etc. Many of these are non-volatile but do get broken down to smaller fragments and radicals due to high heat effect. Such fragments then become air-borne and are carcenogenous pollutants.

Some of these due to their high C/H ratio are often incompletely burnt and evolve as solid micro-particles which constitute soot.

They may size-wise be submicron and thus escape arrestment by antipollution devices.

(4) Inorganic macrocomponents of coal end up as their oxides usually, after complete combustion. These comprise alumina, silica, lime, magnesia, titania, oxides of sodium, potassium and barium with a few others.

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They remain in the ash or slag and where thewaste management or disposal system is not seriously takcled these ashy oxides would contaminate the agricultural soils and pollute and poison

natural water system and the fauna and flora.

(5) Thus Coal combustion releases a number of different substances into the atmosphere. Table 34 gives typical

pollutants from an integrated steel plant. Greatly reducing the quantities of such products emitted into the atmosphere requires high costs for emission control. Cleaning up some of the emissions especially sulphur, creates new waste disposal problems such as limestone sludge from the flue gas desulphurization.

(6) Copper, lead, strontium, bismuth, nickel, zinc, mercury, germanium, selenium, arsenic are among the elements that occur as traces in the inorganic mineralogical admixed composition of coal. They occur as various compounds and complexes in coal.

Sizeable proportions of each element or its compound volatilize during coal and coke combustion, coke quenching and along with coke oven gases. As submicron particulates they escape dust collection gadgets and precipitators and pollute the atmosphere.

Due to their high surface to volume ratio they are good

concentrators of other flue gas air-pollutants. Research has further shown that these trace metal pollutants favour brochial and pulmonary tracts for settling in high concentrations.

(7) Coal desulphurization arises from the understanding that in coal utilization sulphur in coal is a nuisance and notorious environmental pollutant. Legislation in many countries has set a maximum level of tolerance of S02 that various industries, utilities, and hence coal producers must comply with.

(8) Emissions from coal utilization including combustion may also affect crops, fisheries, and materials. A wide variety of field, vegetable, fruit and nut, forage and forest crops are sensitive to sulphur and nitrogen oxides under controlled

exposures. Limited field studies to date indicate potential reductions in crop yield for some species, but increases in yields have been found in soils deficient in sulphates.

(9) Lakes in several parts of the world appear to have recently become acidic and in a number of cases, the fist population has declined considerably. Sulphur and nitrogen oxide emissions contribute to acid rain. It is still to be established what mitigation strategy would be most cost-effective. As a remedy, some researchers have suggested the addition of lime to affected areas to buffer off acidity.

(10) Damage to non-living materials from emissions is of concern in a number of countries.

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Deterioration of building materials and works of art, fading of dues, weathering of textiles, and the corrosion of metals under long-term exposure to acidic deposition are outstanding problems resulting from coal combustion.

(11) Sulphur dioxide is converted in the atmosphere to sulphate that scatter light and may reduce visibiltiy. The problem of reduced visibility in cities has, however, been greatly diminished by the use of smokeless fuels or the virtual disappearance of small-scale residential and commercial uses of coal.

(12) Some countries control the potential adverse impacts of emissions on the environment by establishing national air quality standards that speciry the maximum concentrations of certain chemicals permitted in the air. The major emissions that are regulated include sulphur dioxide (S02), particulate matter

(total suspended particulates or TSP), and nitrogen dioxide (N02). Some countries control S02 concentration by limiting the sulphur content of the coal burned. Others, such as the United Kingdom, rely on mechanical dispersion of emissions by tall stacks and prevailing winds. Yet some countries, such as the United States and Japan, rely on combined chemical and mechanical systems as well as low-sulphur fuels to reduce emissions.