Advantages of Nuclear power:

Advantages of Nuclear power:

Power from nuclear energy can prevent many of the environmental consequences arising out of the use of fossil fuels. Below we discuss advantages of nuclear power vis-a-vis other energy options, especially fossil fuel.

1. One of the greatest advantages of nuclear power is that it avoids the wide variety of environmental problems arising from burning fossil fuels - coal, oil, and gas. Nuclear energy does not produce smoke or carbon dioxide, so it does not contribute to the greenhouse effect. Thus ‘global warming’ process can be minimized - changing the earth's climate, acid rain, which is destroying forests and killing fish; air pollution etc. It checks degrading our quality of life; i.e., the destructive effects of massive mining for coal; and oil spills which do great harm to ecological systems can be prevented.

2. It is possible to generate a high amount of electrical energy in one single plant using small amount of fuel.

3. Nuclear power is reliable. This technology is readily available; it does not have to be developed first.

4. Produces small amounts of waste. The disposal of radio-active waste which nuclear power plant generates, can be effectively organized as our technology is improving at a fast pace. Moreover, the quality of radio-active waste improved if we go for reprocessing of spent fuel.

5. Nuclear power is also not so expensive as compare to power from coal. Reprocessing and reuse of plutonium from spent fuel makes it even cheaper than coal based power plant. The concern about proliferation should be taken out of mind as there are much easier, faster, and cheaper ways for a nation to develop nuclear weapons than through a nuclear power programme.

Some facts about nuclear reactor for power generation:

Some facts about nuclear reactor for power generation:

A. Understanding running of nuclear reactor (fission) for power generation –

i. Nuclear power can come from the fission of uranium, plutonium or thorium or the fusion of hydrogen into helium. Today it is almost all uranium. The fission of an atom of uranium produces few million times the energy produced by the combustion of an atom of carbon from coal.

ii. Natural uranium is almost entirely a mixture of two isotopes, U-235 and U-238. Today’s commercial nuclear reactor uses U-235 for fission reaction. Natural uranium has 99.3 percent of U-238 and only 0.7 percent of U-235.

iii. Most nuclear power plants today use enriched uranium in which the concentration of U-235 is increased from 0.7 percent to (nowadays) about 4 to 5 percent.

iv. The U-238 "tails" are left over for eventual use in "breeder reactors". The Canadian CANDU reactors don't require enriched fuel, but since they use expensive heavy water instead of ordinary water, their energy cost is about the same.

v. Present reactors that use only the U-235 in natural uranium are very likely good for some hundreds of years.

vi. A power reactor contains a core with a large number of fuel rods. Each rod is full of pellets of uranium oxide. An atom of U-235 fissions when it absorbs a neutron. The fission produces two fission fragments and other particles that fly off at high velocity. When they stop the kinetic energy is converted to heat.

vii. The steam withdrawn and run through the turbines controls the power level of the reactor. The heat from the fuel rods is absorbed by water which is used to generate steam to drive the turbines that generate the electricity.

viii. After about two years, when enough U-235 is converted to fission products and the fission products have built up enough so that the fuel rods must be removed and replaced by new ones.

ix. Besides fission products, spent fuel rods contain some plutonium produced by the U-238 in the reactor absorbing a neutron. This plutonium and leftover uranium can be separated in a reprocessing plant and used as reactor fuel.

x. Thus running a reactor for four years produces enough plutonium (about 1/4 as much as the U-235 that was in the fuel rods) to run it for one more year provided the plutonium is extracted and put into new fuel rods. Newer designs with higher "burnup ratios" get more of their energy from plutonium.

B. Understanding nuclear waste –

i. After the fuel has been in the reactor for about 18 months, much of the uranium has already fissioned.

ii. A considerable quantity of fission products also have built up in the fuel.

iii. The reactor is then refueled by replacing about 1/3 of the fuel rods. This generally takes one or two months. Canadian CANDU reactors replace fuel continuously.

iv. When fuel rods are removed from the reactor they contain large quantities of highly radioactive fission products and are generating heat at a high rate.

v. They are then put in a large tank of water about the size of a swimming pool. There they become less radioactive as the more highly radioactive isotopes decay and also generate less and less heat.

vi. The fuel rods should then be chemically reprocessed. Reprocessing removes any leftover uranium and the plutonium that has been formed.

vii. The fission products are then put in a form for long term storage.

viii. A large reactor produces about 1.5 tonnes of fission products per year.

ix. Economic advantages of reprocessing are great. If we do not reprocess, we lose the economic benefit of the plutonium.

x. At the same time, the spent fuel remains radioactive for longer duration and has to be better guarded, because it contains plutonium.

C. Understanding of future nuclear reactor - ‘breeder reactor’ -

i. If the design of reactor is such that, enough U-238 can also be converted to plutonium so that after a fuel cycle there is more fissionable material than there was in the original fuel rods in the reactor. This system is more economical.

ii. Such a design is called a ‘breeder reactor’.

iii. Breeder reactors essentially use U-238 as fuel. Therefore, it is more advantageous and it is estimated that, there is 140 times more beneficial than the conventional reactor.

iv. They are more expensive than present reactors.

v. Breeder reactor will be reprocessing on site, so no plutonium will ever become externally available.

vi. It is much safer system than the present one. It is hoped that it wiould address the proliferation concerns of the anti-nukes.

Oil from coal:

Oil from coal:

As petroleum price is increasing due to various reasons, the alternative methods of producing oil gained much importance. The most widely known alternatives involve in extracting oil from sources such as Natural gas (methane), coal, oil shale and tar sands. Though some these sources exist in large quantities, it has become a challenge to extract oil economically and without excessively harming environment. Therefore, in this respect, extraction of oil from coal or from natural gas has been significant.

In fact, technology to extract oil from natural gas or from coal was available since the world war – II; but it was not so much significant until the exorbitant hike in international crude oil prices in last decade. During the World war – II, Germany produced some quantity of oil from coal and there after, South Africa (Sasol) was the major country to produce oil from coal, to meet its energy needs during its isolation under Apartheid. As crude oil prices increase, the cost of coal to oil conversion becomes comparatively cheaper. Now, many countries like China, whose coal production is quite substantial but have less reserve of crude oil, have started producing oil from coal. Recently, India has also started thinking of such conversion of their coal to synthetic oil. This conversion process produces low sulfur diesel fuel but also produces large amounts of greenhouse gases.

The Fischer-Tropsch process is well known for conversion of coal to oil. It is a catalyzed chemical reaction in which carbon monoxide (CO) and hydrogen (H2) are converted into liquid hydrocarbons of various forms. Typical catalysts used are based on iron and cobalt. The principal purpose of this process is to produce a synthetic petroleum substitute, typically from coal, natural gas or biomass.

There is another process called Karrick process for conversion of coal to synthetic oil. It is a low temperature carbonization (LTC) of coal, shale, lignite or any carbonaceous materials. These are heated at 360 degree Celsius to 749 degree Celsius, in the absence of air to distill out oil and gas. Recently, China has announced high volume commercial coal liquefaction production by this method.

Fluidized Bed Combustion (FBC) technology uses coal washery rejects / fines for power supply

Fluidized Bed Combustion (FBC) technology uses coal washery rejects / fines for power supply:

In developing countries, most of energy is generated by coal fired power plants. For quality purpose, coals are washed. Disposal of huge rejects and fines obtained from coal washery are a problem everywhere. Fludised Bed Combustion (FBD) technology as the renewable source of energy generates eco-friendly power supply using washery rejects and washery fines.

The objectives of coal-fired power generation is to have (1) power generation at a economical cost; (2) to improve thermal efficiency; (3) to comply with current and future environmental standards. Many of these objectives may be gained by the FBC technology based plants, with incorporation of supercritical steam cycles together with some form of flue gas desulfurization and low NOx measures.

Advanced FBC system represents significant advantages over conventional coal combustion system. This technology uses a more compact boiler and very high rate of heat transfer to the tube surfaces in the bubbling bed; thus, level of NOx and SOx generated is much less, which is a good indication of pollution control. Generation of particulates is also less as compare to the conventional system.

Above all, it can utilize effectively coal washery rejects, coal washery fines, lignite etc. Utilizing coal washery rejects and coal washery fines means easing pressure for disposal problem of these materials.

Coal bed methane (CBM) drainage - Potential uses of coal mines methane:

Coal bed methane (CBM) drainage - Potential uses of coal mines methane:

One of the major decisions facing a mine owner, when considering the implementation of a CBM drainage program is the potential use for the gas. The gas is a clean energy resource. However, the location of the mine and the ability to convert the gas into a marketable product may severely test the mine planners’ perseverance in finding an economic way of using the gas and producing the accompanying reduction in greenhouse gases. Here we would try to outline some possibilities for the gas whether it is a high-Btu, medium-Btu, or low-Btu product.

(1) High-Btu Gas (> 950 Btu/scf) - High-Btu gas is generally defined as having enough heat content to be used in a natural gas pipeline. Several potential uses exist for high-Btu gas. If the drainage system provides primarily CH4 and little in the way of inert gas, the product may be gathered, compressed, and marketed to a pipeline company. This is one of the most desirable options if natural gas pipelines are located near the mine. Thus, marketing of coal mines methane to a pipeline company would be a very desirable goal.

In case, pipelines are not readily available or the pipeline companies are not ready to buy coal mines methane, several other options are available for high-Btu gas. The first of these would be to use the gas as a feedstock to produce ammonia, methanol, or acetic acid. Currently, these chemicals are produced from natural gas, but coal-bed methane would be equally useful if it is available in sufficient quantities and if the chemical plants were in a favorable location. Another potential method of using CBM would be to compress or liquefy it for use in buses, trucks, and automobiles. This implementation has been successfully used in many of the CIS countries like Ukraine, Czech Republic etc.

(2) Medium-Btu Gas (300 to 950 Btu/scf) - There are many possible uses for medium-Btu gas. If the gas is at the high end of the heat content scale, enrichment by blending with a higher-quality gas or ‘spiking’ of the gas to produce a gas of pipeline quality is possible. Enrichment is the removal of gases like nitrogen, oxygen, and carbon dioxide to improve the heat content of the gas. ‘Spiking’ is the process of combining another fuel gas (like propane) with the methane to increase the heat content. Spiking will normally be economic only if the supplement gas is available cheaply in the area. A major and growing use of medium-Btu gas is as a substitute for other fuels in space heating and other applications where natural gas, fuel oil, or coal is normally used. For example, CBM can be used for heating mine facilities, heating mine intake air, heating greenhouses and institutional facilities, as a heat source in a thermal dryer and as a heat source for treating brine water.

Another use for medium-Btu methane is in electric power production. Using methane in coal-fired utility and industrial boilers and as a supplement to natural gas in blast furnaces is common where methane is extracted from coal mines.

(3) Low-Btu Gas (<>

Summery of specific options for utilization of Coal-bed methane from mines: a. Power Generation - CBM can be ideal fuel for co-generation Power plants to bring in higher efficiency and is preferred fuel for new thermal power plant on count of lower capital investment and higher operational efficiency. b. Auto Fuel in form of Compressed Natural Gas (CNG) - CNG is already an established clean and environment friendly fuel. Depending upon the availability of CBM, this could be a good end use. Utilization of recovered CBM as fuel in form of CNG for mine dump truck is a good option. c. Feed stock for Fertilizer – Many of the fertilizer plants in the vicinity of coal mines where coal-bed methane is drained, have started utilizing fuel oil as feedstock for its cracker complex. d. Use of CBM at Steel Plants - Blast furnace operations use metallurgical coke to produce most of the energy required to melt the iron ore to iron. Since coke is becoming increasingly expensive, in the countries where CBM is available, the steel industry is seeking low-capital options that reduce coke consumption, increase productivity and reduce operating costs. e. Fuel for Industrial Use - It may provide an economical fuel for a number of industries like cement plant, refractory, steel rolling mills etc. f. CBM use in Methanol production - Methanol is a key component of many products. Methanol and gasoline blends are common in many countries for use in road vehicles. Formaldehyde resins and acetic acid are the major raw material in the chemical industry, manufactured from methanol. g. Other uses - Besides above, option for linkages of coal-bed methane produced by coal mines, through cross country pipe lines may be considered.

Economic benefits of coal-bed methane (CBM) drainage:

Economic benefits of coal-bed methane (CBM) drainage:

There are many mining benefits that accrue from a methane drainage system. Coal-bed methane drainage systems can: (1) enhance coal productivity because of less frequent downtime or production slowdowns caused by gas; (2) decrease fan operating costs because of reduced air requirements for methane dilution; (3) reduce shaft sizes and number of entries required in the mains, (4) increase tonnage extracted from a fixed-size reserve as a result of shifts of tonnage from development sections to production sections; (5) decrease dust concentrations due to reduction of velocities at the working face; (6) improve mine safety resulting from lower methane contents in the face, returns, gobs and bleeders; (7) reduce problems with water; (8) improve worker comfort through reduction of velocities in the working faces; and (9) provide miscellaneous other benefits. Other benefits, such as reduced dust concentration, improved safety, or improved worker comfort, are difficult to estimate; while they constitute a real and significant benefit.

(1) Reduced Downtime - Enhanced coal productivity is probably the most significant benefit to be obtained from methane pre-drainage systems where coal-bed methane is encountered in significant quantities. The benefits come in the form of added production that occurs when downtimes or slowdowns resulting from high methane occurrences are avoided using methane drainage.

(2) Ventilation Power Cost Savings - The power costs associated with the mine ventilation system will ordinarily be the second most significant benefit associated with the addition of a methane drainage effort. In many mines, ventilation to ensure continuous production is quite expensive. Methane drainage would normally be used instead of increased ventilation because the overall costs associated with drainage will be lower than the costs associated with ventilation.

(3) Reduced Development Costs- Another important issue in assessing the costs and benefits associated with mining is the possibility that a reduction in the ventilation requirements will result in a reduced requirement for development openings. This can result in two types of cost benefits. The first benefit is the reduction in the size and number of shafts and other development openings connecting the coal seam to the surface. This can at times result in a significant level of economic savings. The second benefit results if the coal from the development entries of a mine is more costly on a cost/ton basis than that in the production sections. In a longwall mining operation, the coal produced from development openings will be much more costly than that produced in a longwall panel.

(4) Increased Reserve - The benefit of an increased reserve is also provided in a mining operation when a gas drainage system allows for a reduced number of entries in the development of mains, submains, headgates, and tailgates of mining layouts. This results in an increased number of tons of coal that can be extracted from a fixed-size coal block. The extra tonnage is derived from the fact that only about 50% of the coal in development sections is extracted while production sections may extract 85% to 95% of the coal under good conditions. The extra coal extracted when this occurs is an economic benefit of significant value under many conditions. Thus, it should be evaluated as a potential benefit in every operation where degasification is considered.

(5) Mine Safety - The effect of a methane drainage system on the safety of a mining system will certainly result in positive benefits. Any high-methane operation will incur a higher level of hazardous operating conditions than an equivalent mine with a methane drainage system in place.

(6) Reduced Dust Problems - The relationship between gas drainage activities and the costs of providing proper dust control in a mining section is another possible source of cost benefits from gas drainage.

(7) Reduced Water Problems - The presence of water in coal mine roof strata can be a costly source of delays in some underground mining operations. The most sizeable delays will ordinarily be encountered in the development sections of the mine and will be quite variable depending upon the geologic parameters of the roof strata. The water in the roof, when occurring in conjunction with high methane contents, can be mitigated by a methane drainage system.

(8) Worker Comfort - The level of comfort of work in a mining environment deteriorates if high air velocities are required to keep methane contents below the regulatory limits. The difficulty of working in an air velocity above 600 ft/min is that ordinary tasks become more difficult and the high velocities will generate more dust.

Thus, extraction of coal-bed methane provide lot of economical benefits in running coal mines, apart from providing cleaner environment by preventing release of major greenhouse gas, methane, in the atmosphere and recovering extra energy source as well.

Coal-bed Methane (CBM) Drainage from Underground Coal Mines:

Coal-bed Methane (CBM) Drainage from Underground Coal Mines:

Coal mine methane, a byproduct of mining operations, can be recovered to provide various types of benefits to a mining company. These benefits include, but are not limited to, reduced ventilation costs, downtime costs, and production costs; and the ability to use the recovered gas as an energy source, either at or near the mine site or by injecting it into a commercial gas pipeline system. There are many variables that play a part in the decision to implement a coal mine methane drainage project. Mining companies can employ basic decision-making logic to determine the feasibility of draining and/or using methane at specific coal mines.

Over the past few decades, emissions of methane from coal mines have increased significantly because of higher productivity, greater comminution of the coal product, and the trend towards recovery from deeper coal seams. Under current coal mine regulations of many countries, methane must be controlled at the working faces and at other points in the mine layout. This has traditionally been performed using a well-designed ventilation system. However, this task is becoming more difficult to achieve economically in modern coal mines. In addition, scientists have established that methane released to the atmosphere is a major greenhouse gas, second only to carbon dioxide in its contribution to potential global warming. In order to improve mine safety and decrease downtime as a result of methane in the mine openings, many mines are now using a degasification system to extract much of the coalbed methane from their seams before or during mining. Methane drainage offers the added advantages of reducing the ventilation costs, reducing the development costs of the mine, reducing the global warming threat, and allowing a waste product to be productively utilized.

This byproduct can be gathered to produce three levels of benefits to a mining company, depending on the market potential of the methane. The benefit levels are as follows:

(1) The methane is gathered from the coal seam to reduce ventilation costs, downtime costs, production costs, and shaft development costs or to benefit from increased coal resources. All of these benefits are achieved internal to the mining operation and can be easily analyzed by the mining company.

(2) The coalbed methane is extracted from the seams to be mined and is utilized as a local energy resource to heat buildings, dry coal output from the coal preparation facility, generate electrical power, power vehicles by compressing the gas, or other local uses.

(3) The extracted methane can be upgraded, if necessary, or immediately compressed and introduced into a commercial gas pipeline system. This may provide the highest possible benefit to the mining company providing that the methane is of high quality and the mine location is near a gas pipeline. With this option, the value of the methane as an energy resource may be very large and it can make a significant contribution to profits.

Methane degasification methods: With the increasing coal production and depth of coal mines, traditional ventilation methods are not always the most economical methods of handling methane in the coal seam. Degasification systems have been developed that recover the gas before, during, or after mining. The degasification methods, coupled with mine ventilation, may be the most economical method of keeping methane concentrations low in many mines.

Degasification methods that have been used in the U.S. include vertical wells, gob wells, horizontal boreholes, and cross-measure boreholes.

(1) Vertical wells method - The term “vertical well” is generally applied to a well drilled through a coal seam or seams and cased to pre-drain the methane prior to mining. The wells are normally placed in operation 2 to 7 years ahead of mining and the coal seam is hydraulically fractured to remove much of the methane from the seam. The water in the coal seams must be removed to provide better flow of gas. This water is separated and must then be treated and/or disposed of in an environmentally acceptable manner. To enhance the flow of gas from a vertical well, either hydraulic fracturing or open-hole cavity completions are generally used.

Vertical wells recover high-quality gas from the coal seam and the surrounding strata. The gas quality is ensured in most cases because the methane will not be diluted by ventilation from the mine. The total amount of methane recovered depends on site-specific conditions such as the gas content of the coal seams and surrounding strata, permeability of the geologic materials, the drainage time, the amount of negative head applied, and other variables of the geologic and extractive systems. Vertical wells can recover 50% to 90% of the gas content of the coal and are normally placed in operation two to seven years before mining commences.

Vertical wells offer an advantage over other methods because they can be applied to multiple coal seams simultaneously. These wells produce greater gas yields that can make them commercially economic as well as further reduce the potential for gas influx into the operating mine.

(2) Gob Wells - The designation “gob well” refers to the type of coalbed methane (CBM) recovery well that extracts methane from the gob areas of a mine after the mining has caved the overlying strata. Gob wells differ from vertical wells in the sense that they are normally drilled to a point 10 to 50 feet above the target seam prior to mining, but are operated only after mining fractures the strata around the wellbore. The methane emitted from the fractured strata then flows into the well and up to the surface. The flow rates are mainly controlled by the natural head created by the low-density methane gas or can be stimulated by blowers on the surface. Gob wells can recover 30% to 70% of methane emissions depending on geologic conditions and the number of gob wells within the panel.

(3) Horizontal Boreholes - Horizontal holes are drilled into the coal seam from development entries in the mine. They drain methane from the unmined areas of the coal seam shortly before mining, reducing the flow of methane into the mining section. Because methane drainage occurs only from the mined coal seam and the period of drainage is relatively short, the recovery efficiency of this technique is low.

(4) Cross-Measure Boreholes - Cross-measure boreholes are drilled at an angle to the strata, normally from existing mine entries. The boreholes are strategically placed above areas to be mined with the goal of pre-draining the overlying strata and exhausting gas from the gob area. Like horizontal borehole systems, the individual holes must be connected to a main pipeline which ordinarily is coursed through a vertical borehole to the surface.