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1. How is mineral deposit concentration reflected in the chemistry of environment?
2. What stages of mineral extraction are considered the sources of environment contamination?
3. Why have mining increased through time?
4. What witness to the extraction of minerals do some areas bear?
5. Has the situation changed from that time?
6. What are the stages of mining and subsequent processing?
7. What is the effect of open pit surface techniques and solution mining?
8. Why is crushing necessary for mineral processing?
9. What consequences of crushing do you know?
10. What is smelting?
11. Why are modern smelters fitted with electrostatic precipitators?
12. What are the consequences of smelting?
State whether the sentences are true or false. If true, add the information you know, correct the false ones.
1. Geologists can define mineral deposits by concentration of some elements.
2. Mining and subsequent beneficiation of minerals do not affect the environment.
3. Mineral extraction is a modern human activity.
4. Modern mineral extraction technology is heavily regulated in many countries.
5. The major cause of concern is mineral extraction such as clays and silica.
6. Waste material is the greatest environmental problem.
7. Tailings are subject to wind ablation and can easily transported by surface runoff.
8. Aerosols and gases can be deposited close to the source.
Read the text through and find the answers to these questions. Remember, you do not have to understand every word to answer the questions.
A.
1. How are pollutants generally treated? Name four different processes referred to in the text.
2. What are the main causes of air pollution?
3. What is the usual way to control emissions of gas and particles into the atmosphere?
4. Which gas is mentioned as being particularly difficult to control?
5. What industries are affected by regulations to control the emissions of this gas?
Through its interdisciplinary environmental teams, industry is directing large amounts of capital and technological resources both to define and resolve environmental challenges. The solution of the complex environmental problems requires the skills and experience of persons knowledgeable in health, sanitation, biology, meteorology, engineering and many other fields.
Each air and water problem has its own unique approach and solution. Restrictive standards necessitate high retention efficiencies for all control equipment. Off-the-shelf items, which were applicable in the past, no longer suffice. Controls must now be specifically tailored to each installation. Liquid wastes can generally be treated by chemical or physical means, or by a combination of the two, for removal of contaminants with the expectation that the majority of the liquid can be recycled. Air or gaseous contaminants can be removed by scrubbing, filtration, absorption or adsorption and the clean gas discharged into the atmosphere. The removed contaminants, either dry or in solution, must be handled wisely, or a new water- or air-pollution problem may result.
Industries that extract natural resources from the Earth, and in so doing disturb the surface, are being called upon to reclaim and restore the land to a condition and contour that is equal to or better than the original state.
Air quality management. The air contaminants which pervade the environment are many and emanate from multiple sources. A sizable portion of these contaminants are produced by nature. The greatest burden of atmospheric pollutants resulting from human activity comprises carbon monoxides, hydrocarbons, particulates, sulphur oxides and nitrogen oxides, in that order. About 50 % of the major pollutants come from the use of the internal combustion engine.
Industrial and fuel combustion sources together contribute approximately 30 % of the major pollutants.
The general trend in gaseous and particulate control is to limit the emissions from a process stack to a specified weight per hour based on the total material weight processed to assure compliance with ambient air regulation. Process weights become extremely large in steel and cement plants and in large nonferrous smelters. The degree of control necessary in such plants can approach 100 % of all particulate matter in the stack. Retention equipment can become massive both in physical size and in cost. The equipment may include high-energy venturi scrubbers, fabric arresters, and electrostatic precipitators. Each application must be evaluated so that the selected equipment will provide the retention efficiency desired.
Sulphur oxide retention and control present the greatest challenges to industrial environmental engineers. Ambient air standards are extremely low and the emission standards calculated to meet these ambient standards place an enormous challenge on the affected industries. Many copper smelters and all coal-fired utility power plants have large volume, weak-sulphur-dioxide gas streams with limestone slurries or caustic solutions is extremely expensive, requires prohibitively large equipment, and creates water and solid waste disposal problems of enormous magnitude. Installations employing dry scrubbing have been used on very low-sulphur-dioxide gas streams.
Copper smelters are required to remove 85-90 % of the sulphur contained in the feed concentrate. Smelters using the old-type reverbatory furnaces produce large volumes of gas containing low concentrations of sulphur dioxide which is not amenable to removal by acid making. However, gas streams from newer-type flash and roaster-electric furnace operations can produce low-volume gas streams containing more than 4 % sulphur dioxide which can be treated more economically to obtain elemental sulphur, liquid sulphur dioxide, or sulphuric acid. Smelters generally have not considered the scrubbing of weak-sulphur-dioxide gas streams as a viable means of attaining emission limitations because of the tremendous quantities of solid wastes that would be generated.
The task of upgrading weak smelter gas streams to produce products which have no existing market has led to extensive research into other methods of producing copper. A number of mining companies piloted, and some have constructed, hydrometallurgical plants to produce electrolytic-grade copper from ores by chemical means, thus eliminating the smelting step. These plants have generally experienced higher unit costs than smelters and a number have been plagued with operational problems. It does not appear likely that hydrometallurgical plants will replace conventional smelting in the foreseeable future. Liquid ion exchange followed by electrowinning, is also being used more extensively for the heap leaching of low-grade copper. This method produces a very pure grade of copper without the emission of sulphur dioxide to the atmosphere.
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