The Tribune, Chandigarh, India

Clean coal for green power
by G.S. Dhillon

THE term clean coal is used for coal which when burnt in the furnaces of the boilers of the thermal power plants (TPS), would leave ash not more than a specified value. The Ministry of Environment and Forests, Government of India has specified an upper limit of 34 per cent for ROM (run-of-mine) non-coking coal made available to TPS. The ministry considers that the magnitude of the resulting environmental pollution on account of disposal of flyash and furnace bottom ash and the “spewed” particulate matter in the atmosphere, would be not beyond a manageable limit.

There has been a steady decline in the quality of coal received by out thermal plants. Currently, the ash content of the coal received averages 45 per cent and sometime it crosses the 55 per cent mark. The coal received has low UHV (useful heat value) and many batches have been found to fall outside the “grading chart”, and are labelled as UG (Ungraded) category. The extent of stones/shales content has been found to range between 8 and 10 per cent. Over and above the shortcomings listed above, the problem of “over-sized material” received in coal is encountered and the material is mostly sandstone or shale stone blocks.

Environmental problems
The excessive ash content creates environmental problems as the extent of material disposed in the ash-ponds increases. At the Ropar super-thermal plant, one ash pond measuring 350 acres has got filled up to the brim even after its dykes were raised sometime back by 2.5m. The second ash pond is almost half full. The third ash pond is not yet ready to receive the material. For this TPS with 1260 MW installed capacity, an area of 975 acres has been acquired, but it too would soon fall short in meeting the ash disposal requirements, if the coal with high ash content is regularly received in the future.

About 30 villages located on the periphery of the ash disposal ponds are facing health problem on account of flyash clouds blowing with slight wind and the seepage from these ponds polluting both surface water and ground water resources.

Directive to PSEB
The Ministry of Environment and Forests, Government of India, has desired early compliance of its notification prohibiting the use of coal having ash content above 34 per cent in the thermal plants. The only viable alternative before the PSEB is to get the coal washed before it is loaded in wagons.

During 1988 the Government of India approved a committee to consider the problems arising from the use of “low-grade non-coking coal” supplied to TPS, particularly located outside the 1000-km radius from the pit-head of coal-fields. After detailed study, the committee came to the conclusion that TPS located outside the 1000-km radius should be provided with clean coal having ash content not above 34 per cent limit.

Based on the recommendations of the committee, the Government of India sanctioned two washeries for non-coking coal of 14.5 million tonnes annual capacity. One washery of 6.5 million tonnes was to be located a Piparwar, the colliery from which the PSEB receives part of its coal supply.

In 1993 the Coal Mines Nationalisation Act was amended to permit captive mining by the private sector so that coal washeries could be set-up near the pit-heads by SEBs (state electricity boards). The total capacity of Coal Washeries approved in the different Coal Fields is 32.5 million tonnes annual capacity and the production of Washed Non-Coking Coal during 1993-94 was 6.66 million tonnes. The washed coal is also known as beneficiated coal.

At present there are 20 washeries in operation, processing 33 million tonnes of coking coal supplied mainly to cement and steel industry. At Piparwar, in the Central Coal Fields Ltd. a facility created with Australian collaboration, provides 6.5 million tonnes of beneficiated coal in a year. This plant produces coal in the range 75 -13 mm and it is the mixed with unwashed fine fraction (-13 mm) to provide coal having 30 per cent ash content.

In the case of other Northern Coal Fields at Bina, a 4.5 million tonnes annual capacity unit has been installed for coal beneficiation and it provides treated fraction of 200-20 mm and after mixing it with minus 30 mm fraction of coal, the coal of 30 per cent ash content is obtained.

Merits of beneficiation
A study carried out by BHEL has shown that for 10 per cent reduction of ash content of coal the resulting benefits are: (i) increase in boiler efficiency of 1 per cent (ii) saving of auxiliary energy consumption to the extent of ½ per cent of the total output by the thermal plant. (iii) saving in maintenance cost of the coal handling and steam generation system to the extent of 20 per cent annually. (iv) reduction of the freight charges as the quantity of coal transported for the required heat values will be less to the extent of reduction of ash content. (v) reduced consumption of support oil and (vi) increased availability of boiler and auxiliaries from anything between 400 hours and 1100 hours in a year.

In addition to the above, the pressure on the flyash disposal ponds would be reduced as the material to be disposed off would be considerably less.

For installed capacity of 1260 MW, the daily consumption of coal at present is 19,500 tonnes and annual production of flyash plus furnace bottom ash is around 14 lakh tonnes. The distance from pit-heads measures around 1650 km. Arrangement exists with the Collieries of Central Coal Fields (CCL) and the Bharat Coking Coal Ltd. (BCCL) to meet the needs of this plant.

For meeting the target of 7000 MUs, the consumption of 0.741 kg./kwh is obtained. For coal freight charge of Rs 944.80 per tonne, the bill for freight of RSTP works around Rs 490 crore annually. If the average content of 43 per cent is to be lowered to 30 per cent through beneficiation, the saving in less coal transported works out to be around Rs 63.75 crore annually.

For Piparwar Coal beneficiation, extra charges at the rate of 26.3 per cent works to be around Rs 70.75 crore. So the extra charge to be paid works out to approx Rs 7 crore. But saving on account of increased efficiency of the various items, as determined by the BHEL study works out to be around Rs 27 crore, leaving a positive balance of Rs 20 crore. In addition, there will be two lakh tonnes less of flyash produced. So it is not wrong to say that use of clean coal will give green power.

Enigma of life on Titan
by D.P. Singh

THE possibility that there may be life on other planets or satellites has tantalised mankind for quite sometime. With the remarkable improvement in remote sensing technology and in our ability to send across space probes to celestial bodies a new picture has emerged. Titan is one such place where the scientists are expecting the existence of life.

Titan is the largest satellite of the planet Saturn. It is almost as big as the planet Mercury. It is also the largest moon in the solar system. Christiaan Huygens discovered Titan in 1655. Prior to the encounter of Voyager-1 with Titan in November, 1980, our information about Titan was scanty. Based on the data available the present picture of Titan is as follows.

Titan has a diameter of about 5830 km. It rotates about its axis every 15.95 days. It is situated at an average distance of 1.2 million km from Saturn. Its density is about 1920 kg/m3. The average surface temperature of Titan is around —180° Celsius.

It is the only satellite in the solar system known to possess a substantial atmosphere. The massive moon is covered by a dense, orange-coloured haze, which hides its surface from view. The Voyager missions showed that 90 to 95 per cent of its atmosphere is nitrogen. It also contains small quantities of methane, ethane and even hydrogen cyanide.

Exotic molecules such as hydrogen cyanide and complex organic polymers form a deep smog layer of tiny particles that shroud its surface from view. It has abundance of organic molecules on its surface and in its atmosphere. The presence of organic compounds on Titan has led it to be described as a ‘‘pre-terrestrial life environment’’ — like a primitive Earth in deep freeze.

The sunshine on Titan is only 1 per cent as intense as we are accustomed to. The temperatures here are far below the freezing point of water. The atmospheric pressure on the surface of Titan is about 1.6 times that on earth. Under such conditions, methane may exist as a solid, liquid or gas. So the surface of Titan is expected to be frozen sea with towering ice cliffs and icebergs.

But with abundant organic matter, sunlight and perhaps volcanic hot spots, the possibility of life on Titan cannot be readily dismissed. With the presence of a frozen sea on Titan’s surface, the possibility of existence of marine life forms can be expected. One method of finding the truth is to send a spaceship. On reaching the Titan, it has to penetrate its thick atmosphere to explore the sea directly. Such a mission is already on its way.

NASA’s Cassini orbiter was launched towards Saturn in late 1997. It is carrying European Space Agency’s Huygens probe which to be deployed into Titan’s atmosphere. Cassini orbiter would arrive at Saturn in July, 2004. Using gravitational assistance from the Titan, it will make a close pass of this moon of Saturn.

The Huygens probe will be released from the Cassini orbiter on November 6, 2004. It will be targeted for a high altitude landing sight on the ‘day’ side of Titan. The probe’s encounter with Titan is planned for November 27, 2004. It will enter the Titan’s atmosphere at a velocity of 6.1 km per second.

It will scrutinise the clouds, atmosphere and surface of Titan. Only after this encounter we shall be able to know the secret of Titan’s clouds and haze. The composition of Titan’s surface and its geological history will be known.

The Huygens probe is likely to provide the answer to the possibility of the existence of life on Titan. Thus, with the possibility of life on Titan, we may have our first space friends. When are we going to know the truth? The answer to this would be available only in the next few years of 21st century.

Science Quiz
by J. P. Garg

1. Name the Amritsar-born US- based botanist who has been awarded this year’s World Food Prize. For which major contribution has he been awarded this coveted Prize?

2. This super computer, designed by the USA recently, weighs 106 tons, covers an area of 1700 square metres and draws 6.2 megawatts of power. Name this fastest and largest computer of the world. What is its computing capacity?

3. This principle, named as principle of equivalence by Albert Einstein, is demonstrated in its most familiar form by showing that all bodies fall equally fast under gravity. Between which two physical quantities does this principle establish an equivalence?

4. It has been found that due to the use of fireworks on Divali evening/night, the levels of sulphur, dioxide and suspended particulate matter (SPM) increase to almost double in most cities. Which main parts of human body are adversely affected because of inhaling of these pollutants?

5. Apples are a rich source of carbohydrates, proteins, malic acid, pectin, potassium, calcium, phosphorus, iron, copper and vitamins A,C and E, making them useful in the prevention of many ailments like heart problems, arthritis and rheumatism. Which chemicals are there in apple skin which are anti-oxidant and anti-cancerous?

6. This fish can fly in air. When attacked by the predator, it runs for a short distance in water, takes a jump in air up to about 1.5 metre and then lands in water. Which is this fish?

7. When solid sodium silicate is heated with boiling water under pressure for some time, a concentrated solution of sodium silicate is obtained, which is used for preserving eggs and coating floors. What commercial name has been given to this concentrated solution?

8. Nicol prism is a device made by joining together two appropriately cut pieces of mineral calcite, which has the ability to split a ray of light into two parts. For which purpose is this prism used?

9. Sometimes a graph consists of three or more lines or curves (each line or curve representing the values of a variable in a given range) from which the values of the variables related to each other can be directly found. What is such a graph called?

10. What is special about the years 1916, 1940, 1941 and 1942 with reference to Nobel Prizes?

Answers

1. Dr Surinder Vasal; for developing new protein rich variety of maize 2. Accelerated Strategic Computing Initiative White; 12.3 trillion operations per second 3. Acceleration and gravitation 4. Nervous system, respiratory system, skin and eyes 5. Flavinoids and polyphenols 6. Hatchet fish 7. Water glass 8. For producing plane polarised light 9. Nomogram 10. No Nobel Prize in any subject was awarded during these years.

New products & discoveries

Ecological cop in orbit

PATROLLING the earth at a height of 780 km is an ecological policeman in the form of a satellite ERS-1. The satellite monitors the climatic and weather changes taking place all over the earth and will try to help the researchers, on the ground to predict violent weather variations and drastic climatic changes.

It is the most highly developed environmental research satellite in the world, which orbits the earth every 100 minutes and is in permanent contact with 25 ground control stations around the world.

In contract to other research satellites ERS-1, carries out its measurements with special radar instruments which are not dependent on daylight or clouds.

A cool idea for rapid prototyping

A researcher at University of Missouri in Rolla in USA has developed a method of rapid prototyping — a means of quickly and inexpensively making models of parts or products — using ice, instead of plastics.

Manufacturers have been using rapid prototyping technologies since the mid-1980s. In its more traditional form, rapid prototyping — sometimes called “desktop manufacturing” — involves the fabrication of three-dimensional models, layer by layer, directly from 3-D computer drawing via the aid of a computer-controlled machine. These prototypes typically are made from a polymer resin that is deposited in much the same fashion as the ink from a laser-jet printer is deposited onto a sheet of paper.

Rapid prototypes held manufacturers to better visualise their computerised designs, or to see how will various parts of a proposed product might fit together. They allow manufacturers to reduce cost and the time involved in designing and testing new parts or products.

But most rapid prototyping systems are still too costly, and many of them generate dust or emit smoke, posing health risk. The new method called Rapid Freeze Prototyping developed by MingLieu would not only be faster — reducing the time to produce a prototype from days to a matter of hours — but cleaner and cheaper too as water is cheaper than plastic polymers, says as release from the university.