Electric cell or battery and their recent breakthrough:

Electric cell or battery and their recent breakthrough:

Electric cell is a device that stores electric energy in the form of chemical energy and delivers electric energy when needed. The electric energy is released when a conductor is connected between the terminals of the cell. All cells consist of an electrolyte, i.e., solution containing ions, a positive electrode and a negative electrode. During energy release stage the negative electrode (cathode) reacts with the electrolyte to release electrons and positive electrode (anode) acquiring these electrons; thereby electricity is generated. When the cell has no power to release electricity, or in other words, electrolyte has reacted fully, the cell is said to be dead or discharged.

On the other hand, some types of cell can be recharged, i.e., the condition of electrolyte can be returned to the original state by passing a current in reverse direction. This type of rechargeable cell is also called storage cell or secondary cell. Primary cell can not be recharged. Following are the list of common type of cells used and also new developments made in storage of electricity:

(i) Alkaline dry cells - One of the commonest and quite old types of primary cell used today is alkaline dry cell. This type of cell consists of a positive electrode made from manganese oxide and a negative electrode made of zinc. Potassium hydroxide as the electrolyte is used. Alkaline cells are used widely in radios, personal stereos, and torches as they can supply quite large currents for long periods.

(ii) Mercury cells - Another major primary cell used is the mercury cell. It can be made in the shape of a small disc to use in small, portable electronic devices. These are so small these can be used very comfortably in hearing aids, wristwatches, calculators etc. In these cells the negative electrode consists of zinc, while the positive electrode is made of mercuric oxide. The electrolyte is a solution of potassium hydroxide.

(iii) Silver oxide primary cells – Silver oxide cells are also primary cell similar to the mercury cell. In silver oxide primary cell negative electrode is made of zinc with potassium hydroxide as the electrolyte. Silver oxide positive electrode in the cell delivers better voltage than mercury cells. These are also often made in the shape of a small disc.

(iv) Lead-acid battery – This is a secondary cell, i.e., it can be recharged when it is discharged fully. It generally consists of three or six cells connected in series. The electrolyte used is a dilute solution of sulfuric acid (H2SO4), the negative electrode consists of lead (Pb) and the positive electrode is made of lead dioxide (PbO2). This type of battery is used mostly in cars, trucks, aircraft, and other vehicles. Its major advantage is that it can deliver a strong current of electricity for starting an engine; however, it runs down very quickly.

A lead-acid storage cell runs down when sulfuric acid is gradually converted into water and the electrodes are converted into lead sulfate. When the lead-acid battery is recharged, these chemical reactions are reversed until the chemicals have been restored to their original condition. A lead-acid battery has a useful life of about two to three years and they produce about 2 V per cell.

(v) Nickel-iron battery (Alkaline cell) - Another widely used secondary cell in heavy industry is the alkaline cell, or nickel-iron battery. The principle of operation is the same as in the lead-acid cell. The only exception is that the negative electrode consists of iron and the positive electrode is made of nickel oxide. The electrolyte used is a solution of potassium hydroxide. The nickel-iron cell has the disadvantage of giving off hydrogen gas during charging.

(vi) Cadmium battery (Nickel-cadmium cell) – This is also very similar to Nickel-iron battery. Here negative iron electrode is replaced by one consisting of cadmium. The positive electrode remains same of nickel oxide. Certain Nickel-cadmium batteries gradually lose their maximum energy capacity if they are repeatedly recharged after being only partially discharged – this phenomenon of losing energy capacity exists in some battery, is called ‘Memory effect’ or ‘Lazy memory effect’.

(vii) Lithium-ion batteries (sometimes abbreviated Li-ion batteries) – This is a rechargeable type battery in which a lithium ion moves between the anode and the cathode. This type of battery is very commonly used in consumer electronics, laptop computers, cell phones, video games etc. Because of the benefits like, one of the best energy-to-weight ratios, no memory effect, and a slow loss of charge when not in use, they are currently one of the most popular types of battery found for portable electronics.

(viii) Nanowire lithium-ion battery – Recently, researchers have found a way to use silicon nanowires to reinvent the rechargeable lithium-ion batteries that power laptops, iPods, video cameras, cell phones, and countless other devices. The new technology produces 10 times the amount of electricity of existing lithium-ion, known as Li-ion, batteries. A laptop that now runs on battery for two hours could operate for 20 hours, a boon to ocean-hopping business travelers.

(ix) Ultra capacitor - A Texas company says recently that, it can make a new ultra-capacitor power system to replace the electrochemical batteries in everything from cars to laptops. Company’s claim that, it is a kind of battery-ultra-capacitor hybrid based on barium-titanate powders, will dramatically outperform the best lithium-ion batteries on the market in terms of energy density, price, charge time, and safety. Much like capacitors, ultra-capacitors store energy in an electrical field between two closely spaced conductors, or plates. When voltage is applied, an electric charge builds up on each plate. Ultra-capacitors have many advantages over traditional electrochemical batteries. Unlike batteries, "ultracaps" can completely absorb and release a charge at high rates and in a virtually endless cycle with little degradation.

(x) Sodium-sulfur (NaS) battery - Until recently, large amounts of electricity could not be efficiently stored. Thus, when you turn on the living-room light, power is instantly drawn from a generator. A new type of a room-size battery, however, may be poised to store energy for the nation's vast electric grid almost as easily as reservoir stockpiles water, transforming the way power is delivered to homes and businesses. Compared with other utility-scale batteries plagued by limited life spans or unwieldy bulk, the sodium-sulfur battery is compact, long-lasting and efficient.

Fischer-Tropsch process to produce synthetic liquid hydrocarbons from coal and natural gas:

Fischer-Tropsch process to produce synthetic liquid hydrocarbons from coal and natural gas:

Fischer-Tropsch (F-T) technology converts coal, natural gas, and low-value refinery products into a high-value, comparatively cleaner burning fuel. The resultant fuel is colorless, odorless, and low in toxicity. In addition, it is virtually interchangeable with conventional diesel fuels and can be blended with diesel at any ratio with little to no modification. Currently, several oil companies are researching large-scale production of Fischer- Tropsch fuels.

For the past 50 years, Fischer-Tropsch fuels have powered all of South Africa’s vehicles—from buses to trucks to taxicabs. The fuel is primarily supplied by Sasol, a world leader in Fischer-Tropsch technologies. Sasol’s South African facility produces more than 150,000 barrels of high quality fuel from domestic low-grade coal daily.

The Fischer-Tropsch process is a catalyzed chemical reaction in which carbon monoxide and hydrogen are converted into liquid hydrocarbons of various forms. Typical catalysts used are based on iron and cobalt. Synthesis gas, a mixture of hydrogen and carbon monoxide, is reacted in the presence of an iron or cobalt catalyst; much heat is evolved, and such products as methane, synthetic gasoline and waxes, and alcohols are made, with water or carbon dioxide produced as a byproduct. The catalyst is usually supported on carbon or silicon dioxide to optimize its activity. An important source of the hydrogen-carbon monoxide gas mixture (known as water gas) is obtained by the gasification of coal (manufacturing process of water gas involves treating white-hot hard coal or coke with a blast of steam; carbon monoxide and hydrogen are formed). Thus, gasification is the first step of coal liquefication or production of Fischer-Tropsch fuels from biomass such as corn stover (corn stalks), wood or switch grass. The feed gas is produced in a gasifire by heating the gas to a temperature greater than 700^oC. By carefully controlling the oxygen content the hydrocarbons in the feedstock are broken down to carbon monoxide and hydrogen. The temperature, pressure and catalyst determine whether a light or heavy syncrude is produced.

The principal purpose of this process is to produce a synthetic petroleum substitute, typically from coal, natural gas or biomass, for use as synthetic lubrication oil or as synthetic fuel.

There are mainly two types of F-T reactors. The vertical fixed tube type has the catalyst in tubes that are cooled externally by pressurized boiling water. For a large plant, several reactors in parallel may be used presenting energy savings. The other process uses a slurry reactor in which pre-heated synthesis gas is fed to the bottom of the reactor and distributed into the slurry consisting of liquid wax and catalyst particles. As the gas bubbles upwards through the slurry, it is diffused and converted into more wax by the F-T reaction. The heat generated is removed through the reactor's cooling coils where steam is generated for use in the process.

The resulting organic compounds are a synthetic form of petroleum, analogous to a crude oil, and can be converted into many petroleum products including diesel and gasoline. Alternatively hydrogen can be recovered by further processing, resulting in only carbon dioxide and hydrogen with no hydrocarbons in the product stream. The primary interest at the present time is to produce low sulfur diesel fuel. Production of diesel fuel requires little processing from the F-T crude, has low sulfur and aromatic content, high cetane number and it burns exceptionally clean in a diesel engine.

Based on available research, there are no significant differences in Fischer- Tropsch fuel’s performance versus petro-diesel fuels. In fact, the higher cetane number of Fischer-Tropsch diesel fuel might result in improved combustion; the cetane number is a primary measure of diesel fuel quality. In addition, many alternative fuels require major changes in vehicle engines, but Fischer-Tropsch fuels require no engine modifications. Fischer-Tropsch fuels, however, are slightly less energy dense than petrodiesel, which might result in lower fuel economy and power. Further investigations of fuel compatibility issues need to take place, as well.

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.

Carbon emission from bio-fuels:

Carbon emission from bio-fuels:

Bio-fuels are the fuels of solid, liquid or gaseous in nature, which has been derived from bio-mass – recently living organisms or their metabolic byproducts. Thus, it could be oils from plants, manure from cows, wood from trees etc. For example, bio-gas (i.e., gas produced by the biological breakdown of organic matter in the absence of oxygen); bio-ethanol; bio-diesel; straight vegetable oil etc., are the bio-fuels. It is a renewable energy source, mostly have agricultural based, unlike other natural resources such as petroleum, coal and nuclear fuels.

It has been seen that certain social and environmental benefits bio-fuels has as compare to use of fossil fuels, such as reduction of greenhouse gas emission, increased national energy security, increased rural earnings and development and above all, reduction of use of fossil fuel.

Bio-fuels and other forms of renewable energy are thought to be ‘carbon neutral’ or ‘carbon negative’. Carbon neutral or carbon negative is the difference of quantum of carbon produced and emitted to the atmosphere when these are used as fuels and the quantum of carbon absorbed in the process of their growth. If both are same, is called carbon neutral or if quantum of carbon absorbed through photo-synthesis is more than the emission is called carbon negative. Both the cases are advantageous towards environment point of view and reduction of global warming.

Strictly speaking, bio-fuels are neither carbon neutral nor carbon negative. This is because extra energy is required to grow crops and process them into fuel. This extra energy releases extra carbon to atmosphere as emission. For example, plants require fertilizer to grow, requires energy for transportation and processing; this extra energy releases carbon to the atmosphere as emission. Therefore, this emission aspect is to be debated, whether we are really gaining in respect of carbon emission, by using bio-fuel. However, the arable lands can be better utilized if people shift towards bio-fuels; so the rural earnings. The poorly irrigated land mass also can be taken up for cultivation.

Pollution from Oil refineries:

Pollution from Oil refineries:

Oil refineries pollute our air, water, and land. Oil refineries cause smog and air pollution. Almost all refineries in every country currently pollute at unacceptable, unhealthy levels. Oil refineries emit about 100 chemicals everyday. These include metals like lead which makes it hard for children to learn. They also include very smaller size dust particles that get deep into our lungs and harm our ability to breathe. Finally, refineries emit many gases like sulfur dioxide (SO2), nitrogen oxide (NO2), carbon dioxide, carbon monoxide, methane, dioxins, hydrogen fluoride, chlorine, benzene and others.

Many of the gases emitted by refineries are harmful to humans, and can cause permanent damage and even death. They can cause respiratory problems (such as asthma, coughing, chest pain, choking, bronchitis), skin irritations, nausea, eye problems, headaches, birth defects, leukemia, and cancers. Young children and the elderly are the worst affected.

Sulfur dioxide (SO2): Crude oil and coal both contain relatively high quantities of sulfur. (Natural gases contain much less sulfur and therefore are safer.) When crude oil or coal is heated at the refinery to produce fuel, the sulfur is converted into a gas called sulfur dioxide. This is a colourless gas with a very strong smell, like rotten eggs.

Bad effects of Sulfur dioxide: Exposure to very high concentrations of SO2 can result in painful irritation of the eyes, nose, mouth and throat, difficulty in breathing, nausea, vomiting, headaches and even death. Some of the health effects from daily exposure to outdoor levels of SO₂ are tight chests, worsening of asthma and lung disease, and narrowing of air passages in the throat and chest. People with asthma are more sensitive to SO2. Exposure to SO2 can provoke asthma attacks. SO2 mixes easily in water, including moisture in the air to form an acid. Acid rain and early morning dew causes much damage to metals, stones, and the environment.

Fugitive emissions are the air pollution which escapes through leaks in the equipment. Very often the amount of pollution coming from fugitive emissions is higher than the amount coming out of the stacks.

Many of the refineries often use low quality crude oil that has high levels of sulfur. When this is refined it produces higher levels of SO2 pollution.

Accidental fires, explosions, and chemical and gas leaks are common at refineries. Such accidents cause higher than usual amounts of pollution, which may result in more acute exposure to pollutants and greater health impacts.

Chemical processing of crude oil:

Chemical processing of crude oil:

Crude oil is a mixture of thousands of different hydrocarbons (compounds of hydrogen and carbon). There are four primary activities that occur in crude refinery processes: (a) Separating hydrocarbons (e.g., distillation), (b) Creating hydrocarbons (e.g., cracking/coking), (c) Blending hydrocarbons, (d) Removing impurities (e.g., sulfur removal).
A. Chemical processing is nothing but changing one fraction into another. Chemical process generally has three methods, such as, (i) Breaking large hydrocarbons into smaller pieces (i.e., cracking); (ii) Combining smaller pieces to make larger ones (i.e., unification); (iii) Rearranging various pieces to make desired hydrocarbons (i.e., alteration).
(i) Cracking: Cracking takes large hydrocarbons and breaks them into smaller ones. Generally, there are two types of cracking; Thermal and Catalytic. In thermal cracking, you heat large hydrocarbons at high temperatures (sometimes high pressures as well) until they break apart. In catalytic cracking, a catalyst is used to speed up the cracking reaction. Catalysts include zeolite, aluminum hydrosilicate, bauxite and silica-alumina. After various hydrocarbons are cracked into smaller hydrocarbons, the products go through another fractional distillation column to separate them.
(ii) Unification: To combine smaller hydrocarbons to make larger ones is called unification. The major unification process is called catalytic reforming and uses a catalyst (platinum, platinum-rhenium mix) to combine low weight naphtha into aromatics, which are used in making chemicals and in blending gasoline. A significant by-product of this reaction is hydrogen gas, which is then either used for hydrocracking or sold.
(iii) Alteration: Sometimes, the structures of molecules in one fraction are rearranged to produce another. Commonly, this is done using a process called alkylation. In alkylation, low molecular weight compounds, such as propylene and butylene, are mixed in the presence of a catalyst such as hydrofluoric acid or sulfuric acid. The products of alkylation are high octane hydrocarbons, which are used in gasoline blends to reduce knocking.

B. Treating and blending the fractions: Distillated and chemically processed fractions are treated to remove impurities, such as organic compounds containing sulfur, nitrogen, oxygen, water, dissolved metals and inorganic salts. Treating is usually done by passing the fractions through: (i) a column of sulfuric acid which removes unsaturated hydrocarbons (those with carbon-carbon double-bonds), nitrogen compounds, oxygen compounds and residual solids (tars, asphalt); (ii) an absorption column filled with drying agents to remove water; (iii) sulfur treatment and hydrogen-sulfide scrubbers to remove sulfur and sulfur compounds. After the fractions have been treated, they are cooled and then blended together to make various products, such as:
(a) Gasoline of various grades, with or without additives;
(b) Lubricating oils of various weights and grades;
(c) Kerosene of various grades;
(d) Jet fuel;
(e) Diesel fuel;
(f) Chemicals of various grades for making plastics and other polymers.

Bio-diesel - an effective renewable alternative fuel to petro-diesel:

Bio-diesel is an effective renewable alternative fuel to petro-diesel:

Bio-diesel is a renewable alternative fuel generally used in place of petro-diesel in the engines. It is a fuel made from various vegetable oils, vegetable and animal fats etc. Bio-diesel fuels can be used in diesel engines without changing them. It is the fastest growing alternative fuel in many countries. Bio-diesel, a renewable fuel, is safe, biodegradable, and reduces the emissions of most air pollutants.

Most bio-diesel today is made from oil produced from soybean, palm and jatropha seeds. Bio-diesel is most often blended with petroleum diesel in ratios ranging from 2 percent to 20 percent. It can also be used as pure bio-diesel Bio-diesel fuels can be used in regular diesel vehicles without making any changes to the engines. It can also be stored and transported using diesel tanks and equipment.

Bio-diesel and the environment:

(i) Bio-diesel is renewable, nontoxic, and biodegradable. Compared to diesel, bio-diesel is significantly cleaner burning. It produces fewer air pollutants, like particulates, carbon monoxide, hydrocarbons, and air toxics. It does slightly increase emissions of nitrogen oxides, though. Bio-diesel produces less black smoke.

(ii) Regular petro-diesel fuel contains sulfur. Sulfur can cause damage to the environment when it is burned in fuels. New environmental laws will require the amount of sulfur in diesel fuel to be dramatically reduced over the next few years. When sulfur is removed from regular diesel fuel, the fuel doesn't work as well. Adding a small amount of bio-diesel can fix the problem. Bio-diesel has no sulfur, so it can reduce sulfur levels in the nation's diesel fuel supply while making engines run more smoothly.

(iii) Bio-diesel has a higher cetane rating than petro-diesel, which can improve performance and clean up emissions compared to crude petro-diesel.

(iv) Bio-diesel can reduce by as much as 20% the direct (tailpipe) emission of particulates, compared to low-sulfur diesel.

(v) Bio-diesel is biodegradable under ideal conditions and non-toxic.

BIO-DIESEL FROM ALGAE While a number of bio-feedstock is currently being experimented for bio-diesel production, algae have emerged as one of the most promising sources for bio-diesel production. The current oil crises and fast depleting fossil oil reserves have made it imperative to invest more into research on suitable renewable feedstock such as algae. It is widely believed that, petroleum had its origins in kerogen, which was converted to an oily substance under conditions of high pressure and temperature. Kerogen is formed from algae, biodegraded organic compounds of plankton, bacteria and plant materials. Several studies have been conducted to simulate petroleum formation by pyrolysis. On the basis of these findings, it can be inferred that algae grown in carbon dioxide rich air can be converted to oily substances. Such an approach can contribute to solving two major problems: (a) air pollution resulting from carbon dioxide evolution, (b) future crises due to a shortage of energy sources. Therefore, it is believed that, algae are one of the most promising feedstocks for future bio-diesel production. The advantegeous points about algae are their widespread availability, higher oil yields and pressure on cultivated land for production of bio-diesel is reduced.

Understanding fuel combustion process:

Understanding fuel combustion process:

(a) Fuels are chemical substances which may be burned in presence of oxygen to generate energy in the form of mostly heat. They mainly consist of carbon and hydrogen. Small quantity of sulfur is also present in fuel as contamination. Solid, liquid and gaseous fuels are used by various systems. Coke and coal are solid fuels, petrol, diesel, kerosene is liquid and LPG, CNG are the example of gaseous fuel.

C + O2 = CO2, (here C and O2 are reactants and CO2 is the product of burning fuel)

(b) Each fuel burn at a particular temperature, called ignition temperature. For starting the combustion process each fuel should be brought above its ignition temperature. An appropriate air-fuel ratio is also necessary to maintain in order to get desired result. The minimum ignition temperature at atmospheric pressure for some fuel is: (i) Carbon is 400 degree Celsius; (ii) Hydrogen is 580 degree Celsius; (iii) Carbon monoxide (CO) is 610 degree Celsius; (iv) Methane (CH4) is 630 degree Celsius; (v) Gasoline is 260 degree Celsius.

(c) As air is the major ingredient in any burning process, the air-fuel ratio is the term frequently used in the analysis of combustion process for any fuel. It is usually expressed on a mass basis, i.e., Mass of air required / mass of fuel burnt.

(d) Fuel combustion process is the process when a particular fuel is burnt completely, i.e., all carbon present in the fuel converts into carbon dioxide (CO2), all hydrogen converts into water (H2O) and all sulfur converts to sulfur dioxide (SO2). Theoretically, in completely burnt process, no un-burned residue of carbon, hydrogen should be present and process should not produce any carbon monoxide (CO). For any internal combustion engine, complete combustion is desirable, as energy conversion is maximized and exhaust gas characteristics is improved, thereby engine efficiency and less pollution.

(e) It is desirable to use more air than the actual requirement for the complete combustion of any fuel; to prevent chance of any incomplete combustion. Excess air is also needed to control rise in temperature of the combustion chamber.

(f) Energy is an inherent property of a system by which work is done. Any system at a given set of conditions has certain energy content. The concept of energy is derived to describe a number of processes such as conversion of work to heat. Joule (J) is the unit in SI system. Other units of energy / heat are: (i) 1 cal (calorie)= 4.1868 J; (ii) 1 kcal= 4186.8 J; (iii) 1 Btu (British thermal unit)= 1055.05 J; (iv) 1 ft.lbf= 1.35582 J; (v) 1 kJ= 1000 J; (vi) 1 hp.h (horsepower.hour)= 2,684,520 J; (vii) 1 kWh= 3,600,000 J.

(g) For any combustion energy is transferred to heat and heating value for any system is the amount of energy released when a fuel is burned completely.

Conservation of fossil fuels Fossil fuels take millions of years to make. We are using up the fuels that were made more than 300 million years ago. Once they are gone they are gone. It is best not to waste fossil fuels. They are not renewable; they can not be made again. We can save fossil fuels by conserving energy.

Ethanol as fuel:

Ethanol as fuel:

Ethanol or alcohol can be used as fuel very effectively, as a bio-fuel alternative to gasoline. In many of the countries it is used in running vehicles. As it is easier to manufacture and process, it is steadily becoming a promising alternative to gasoline almost throughout the world. It is mainly processed from sugar cane – a very common agricultural produce. Anhydrous ethanol, i.e., ethanol having less than 1% of water, can be blended very effectively with gasoline in varying proportion. 10% ethanol blended gasoline is common in most of the countries for running motor vehicles.

Current interest in ethanol mainly lies in ‘bio-ethanol’ that is produced from agricultural based starch or sugar. Basically, carbon-based feedstocks are used for bio-ethanol production. Agricultural feedstocks are considered renewable. Feedstock such as sugar cane, bagasse, miscanthus, sugar beet, sorghum, grain sorghum, switch-grass, barley, hemp, kenaf, potatoes, sweet potatoes, cassava, sunflower, fruit, molasses, corn, stover, grain, wheat, straw, cotton and other biomass can be used for production of bio-ethanol.

The basic steps for large scale production of bio-ethanol are: (a) microbial (yeast), i.e., fermentation of sugars; (b) distillation; (c) dehydration and (d) denaturing.

There has been considerable debate about actual usefulness of bio-fuel like bio-ethanol. Replacing fossil fuels by bio-ethanol take large area of arable land mass, which would have been cultivated for food crops. Moreover, the energy and pollution balance of the whole cycle of ethanol production is also not known.

Use of methane as a fuel and for other purposes:

Use of methane as a fuel and for other purposes:

Methane (CH4) is the simplest alkane, used as a fuel for various use. Apart from methane being principal constituent of natural gas, it is obtained from coal seams (as coal bed methane, CBM) and also it is obtained from bio-mass. At room temperature, methane is a gas less dense than air. Methane's relative abundance and clean burning process makes it a very attractive fuel. Burning one molecule of methane in the presence of O2 (oxygen) releases one molecule of CO2 (carbon dioxide) and two molecules of H2O (water). Methane being gas in ordinary temperature, its transportation and storage is difficult. Methane is a powerful greenhouse gas. Methane is over 20 times more effective in trapping heat in the atmosphere than carbon dioxide (CO₂)

Some methane is manufactured synthetically by the distillation of coal. Coal also contains hydrogen and oxygen, with small concentrations of nitrogen, chlorine, sulfur, and several metals. Coals are classified by the amount of volatile material they contain. Volatile substances released from coal when it is distilled, in addition to methane, include water, carbon dioxide, ammonia, benzene, toluene, naphthalene, and anthracene. In addition, the distillation also yields oils, tars, and sulfur-containing products. The non-volatile component of coal, which remains after distillation, is coke.

At high temperatures (700 to 1100 degree Celsius) in the presence of nickel catalyst, steam reacts with methane to yield CO (carbon monoxide) and H2 (hydrogen). This hydrogen is used for manufacturing of ammonia (NH3). In near future, one of the greatest uses of hydrogen would be for running vehicle by using environment-friendly hydrogen cell technology.

Methane is important for electrical generation by burning it as a fuel in a gas turbine or steam boiler. Compared to other hydrocarbon fuels, burning methane produces less carbon dioxide for each unit of heat released. In many cities, methane is piped into homes for domestic heating and cooking purposes. Methane in the form of compressed natural gas (CNG) is used as a fuel for vehicles, and is claimed to be more environmentally friendly than alternatives such as gasoline/petrol and diesel.

Note: NASA is developing LOX/methane engines as an option for the future rocket engine, as methane is abundant in the outer solar system.