Science and Coal

Archive for the ‘environment contamination’ Category

Coal mining require a large area to be disturbed on mining process. This raises the issue of the environment, including soil erosion, dust pollution, noise and water, as well as impacts on local biodiversity. The actions performed in a modern mine to suppress these effects. Planning and good environmental management will reduce the impact of mining on the environment and help preserve biodiversity.

Environmental studies should be done around a few years before a coal mine was opened to determine existing conditions and to identify the sensitivity and issues that might arise. These studies study the impact of mining on surface water and ground water, soil and local land use, natural vegetation and fauna populations.
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A large section of the Fifth Estate, that world company of scientists, climbed the Allegheny Mountains to Pittsburgh last week. They knew soft coal, what it was and what could profitably be done with it and were answering the call to the Second International Conference on Bituminous Coal made by President Thomas Stockham. Baker of Carnegie Institute of Technology.

Coal Situation. Of U. S. coal companies, only the Island Creek Coal Co. admits that it is making satisfactory profits. Practically all the rest claim that they are losing money. Certainly most are. They have millions of tons of coal mined and ready .for : sale at low, unprofitable prices. But sales have fallen off. Electricity, gas and oil are supplanting coal. This economic shift is inevitable.

The way to coal profits—President Baker emphasized when he opened last week’s conference—is to teach consumers how to use coal in new ways and to teach coal men how to “unlock the riches that lie hidden” in coal (i.e., to produce synthetic goods).
C-O-H-N & Synthetics. When Carnegie Tech’s President Baker asked Director Edwin Emery Slosson of Science Service to speak at this bituminous coal conference, he did not expect Dr. Slosson “to make any serious contribution to the practical and technical problems” which engaged the attention of the Congress. So Dr. Slosson, learned journalist, made a brilliant survey of synthetic chemistry, in which soft coal is the great raw material. Read the rest of this entry »

As the United States’ oil reserves dwindle, some say the nation will have to rely on synthetic petroleum fuel made from its large stores of coal.

A two-step chemical process augments a method of making cleaner-burning alternative fuel from coal and other carbon sources by transforming some of its waste products into diesel fuel, researchers from the University of North Carolina at Chapel Hill and Rutgers, the State University of New Jersey, report.

“Two percent of the United States’ energy reserves is in oil, 3 percent is in gas, and 95 percent is in coal,” said Dr. Maurice Brookhart, W.R. Kenan Jr. professor of chemistry in UNC’s College of Arts and Sciences. “Many people in the energy sector think that when oil starts to run out, coal will be a source of transportation fuel for some time before we perfect the science behind solar and hydrogen-based energy. Producing diesel fuels from coal is especially attractive since diesel engines are more efficient than gasoline engines.” Read the rest of this entry »

When burned, coal is the dirtiest of all fossil fuels but a range of technologies are being used and developed to reduce the environmental impact of coal-fired power stations.
Collectively, they are known as clean coal technology (CCT).

CARBON CAPTURE AND STORAGE

Despite the improving efficiency of coal-fired power stations, CO2 emissions remain a problem.
Carbon capture and storage (CCS) involves capturing the carbon dioxide, preventing the greenhouse gas entering the atmosphere, and storing it deep underground.

note:
1. CO2 pumped into disused coal fields displaces methane which can be used as fuel
2. CO2 can be pumped into and stored safely in saline aquifers
3. CO2 pumped into oil fields helps maintain pressure, making extraction easier

A range of approaches of CCS have been developed and have proved to be technically feasible. They have yet to be made available on a large-scale commercial basis because of the costs involved.

COAL PREPARATION

Coal arriving at a power plant contains mineral content that needs to be removed before it is burnt. A number of processes are available to remove unwanted matter and make the coal burn more efficiently.

Coal washing involves grinding the coal into smaller pieces and passing it through a process called gravity separation.

One technique involves feeding the coal into barrels containing a fluid that has a density which causes the coal to float, while unwanted material sinks and is removed from the fuel mix. The coal is then pulverised and prepared for burning.

GASIFICATION

Coal gasification plants are favoured by some because they are flexible and have high levels of efficiency. The gas can be used to power electricity generators, or it can be used elsewhere, i.e. in transportation or the chemical industry.

INTEGRATED COAL GASIFICATION COMBINED CYCLE PLANT

note:
1. Coal burnt to produce syngas
2. Syngas burnt in combustor
3. Hot gas drives gas turbines
4. Cooling gas heats water
5. Steam drives steam turbines

In Integrated Gasification Combined Cycle (IGCC) systems, coal is not combusted directly but reacts with oxygen and steam to form a “syngas” (primarily hydrogen). After being cleaned, it is burned in a gas turbine to generate electricity and to produce steam to power a steam turbine.

Coal gasification plants are seen as a primary component of a zero-emissions system. However, the technology remains unproven on a widespread commercial scale.

REMOVING POLLUTANTS

Burning coal produces a range of pollutants that harm the environment: Sulphur dioxide (acid rain); nitrogen oxides (ground-level ozone) and particulates (affects people’s respiratory systems).

There are a number of options to reduce these emissions:

Sulphur dioxide (SO2)
Flue gas desulphursation (FGD) systems are used to remove sulphur dioxide. “Wet scrubbers” are the most widespread method and can be up to 99% effective.

A mixture of limestone and water is sprayed over the flue gas and this mixture reacts with the SO2 to form gypsum (a calcium sulphate), which is removed and used in the construction industry.

Nitrogen oxides (NOx)
NOx reduction methods include the use of “low NOx burners”. These specially designed burners restrict the amount of oxygen available in the hottest part of the combustion chamber where the coal is burned. This minimises the formation of the gas and requires less post-combustion treatment.

Particulates emissions

Electrostatic precipitators can remove more than 99% of particulates from the flue gas. The system works by creating an electrical field to create a charge on particles which are then attracted by collection plates. Other removal methods include fabric filters and wet particulate scrubbers.