Sri Lanka to test first coal power plant by Sept: ministerJune 01, 2010 (LBO) - Sri Lanka will start testing its first 300 MegaWatt coal power plant in September with plans to connect it to the national distribution grid by January 2011, power minister Patali Ranawaka said.Sri Lanka's state-run Ceylon Electricity Board is building a 900 MegaWatt Chinese financed coal power plant on a design-build-transfer contract in Norochcholai in the north-western coast of the island. The first phase of the project is 300MW.

"We will start testing the first phase in September," minister Ranawaka said. "We hope to commission it and connect to the grid by January 2011."

Power secretary M M C Ferdinandez said the state power utility had made the first purchase of coal from Indonesia at a price of about 70 US dollars a tonne.

Sri Lanka Shipping Corporation has been engaged for transport and with freight and insurance costs, the landed cost will be about 10 US dollars higher, he said.

Ferdinandez said Sri Lanka is buying low sulphur, low moisture coal which generate lower volumes of ash when burned, which was available from Indonesia, Australia and South Africa.

The coal plant will be a base load plant which will operate throughout the day. Sri Lanka has been running expensive liquid fuel plants including gas turbines for base load making the CEB run large losses.

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A conventional coal-fired power plant produces electricity by the burning of coal and air in a

steam generator, where it heats water to produce high pressure and high temperature steam.

The steam flows through a series of steam turbines which spin an electrical generator to

produce electricity. The exhaust steam from the turbines is cooled, condensed back into water,

and returned to the steam generator to start the process over.

Conventional coal-fired power plants are highly complex and custom designed on a large scale

for continuous operation 24 hours per day and 365 days per year. Such plants provide most of

the electrical energy used in many countries.

Most plants built in the 1980s and early 1990s produce about 500 MW (500•106 watt) of power,

while many of the modern plants produce about 1000 MW. Also the efficiencies (ratio of

electrical energy produced to energy released by the coal burned) of conventional coal-fired

plants increased from under 35% to close to 45%.[1][2]

...................

Coal transport and delivery

Coal is delivered by highway truck, rail, barge or collier ship. Some plants are even built near

coal mines and the coal is delivered from the mines by conveyors or by massive trucks.

A large coal train called a "unit train" may be two kilometers[3] (over a mile) long, containing 100

railcars with 90 metric tons in each one, for a total load of 9,000 metric tons. A large plant under

full load requires at least one coal delivery this size every day. Plants may get as many as three

to five trains a day, especially in "peak season", during the summer months when electrical

energy consumption is high. A large coal-fired power plant such as the one in Nanticoke,

Canada stores several million metric tons of coal for winter use when delivery via the Great

Lakes is not possible.

Modern unloaders use rotary dump devices, which eliminate problems with coal freezing in

bottom dump cars. The unloader includes a train positioner arm that pulls the entire train to

position each car sequentially over a coal hopper. The dumper clamps an individual car against

a platform that swivels the car upside down to dump the coal. Swiveling couplers enable the

entire operation to occur while the cars are still coupled together. Unloading a unit train takes

about three hours.

Shorter trains may use railcars with an "air-dump", which relies on air pressure from the engine

plus a "hot shoe" on each car. This "hot shoe" when it comes into contact with a "hot rail" at the

unloading trestle, shoots an electric charge through the air dump apparatus and causes the

doors on the bottom of the car to open, dumping the coal through the opening in the trestle.

Unloading one of these trains takes anywhere from an hour to an hour and a half. Older

unloaders may still use manually operated bottom-dump rail cars and a "shaker" attached to the

cars to dump the coal.

A collier (cargo ship carrying coal) may hold 35,000 metric tons of coal and takes several days

to unload. Colliers are large, seaworthy, self-powered ships. For transporting coal in calmer

waters, such as rivers and lakes, flat-bottomed vessels called barges pulled by towboats are

used.

Some power plants receive coal via a coal slurry pipeline between the power plant and a coal

mine. For example, the Mohave power plant at Laughlin, Nevada receives coal slurry from a

coal mine approximately 112 kilometers (70 miles) away. The coal is ground to approximately

the size of coffee grounds and mixed with water to form the slurry. At the power plant the coal is

either fed directly to the fuel preparation system or to a pond where the coal settles out and, at a

later date, is re-slurried and then pumped to the fuel preparation system.

For startup or auxiliary purposes, a coal-fired power plant may use fuel oil as well. Fuel oil can

be delivered to plants by pipeline, tanker, tank car or truck.

Fuel preparation

For most coal-fired power plants, coal is prepared for use by first crushing the delivered coal

into pieces less than 5 cm in size. The crushed coal is then transported from the storage yard to

in-plant storage silos by rubberized conveyor belts.

In plants that burn pulverized coal, coal from the storage silos is fed into pulverizers that grind

the crushed coal into the consistency of face powder and mix it with primary combustion air

which transports the pulverized coal to the steam generator furnace. A 500 MW coal-fired power

plant will have about six such pulverizers, five of which will supply the steam generator at full

load with about 225 metric tons per hour.

In plants that do not burn pulverized coal, the crushed coal may be directly fed into cyclone

burners, a specific kind of combustor that can efficiently burn larger pieces of coal.

In plants fueled with slurried coal, the slurry is fed directly to the pulverizers and then mixed with

air and fed to the steam generator. The slurry water is separated and removed during

pulverizing of the coal.

(PD) Image: Milton Beychok Diagram of a tray-type boiler feed water deaerator (with vertical, domed aeration section and horizontal water storage section

Feedwater heating and deaeration

For more information, see: Boiler feedwater heater and

Deaerator.

The feedwater used in the steam generator consists of recirculated condensate water and

makeup water. Because the metallic materials it contacts are subject to corrosion at high

temperatures and pressures, the makeup water is highly purified in a system of water softeners

and ion exchange demineralizers. The makeup water in a 500 MW plant amounts to about 75

litres per minute to offset the small losses from steam leaks in the system and blowdown from

the steam drum (see steam generator diagram below).

The condensate and feedwater system begins with the water condensate being pumped out of

the low pressure turbine exhaust steam condenser (commonly referred to as a surface

condenser). The condensate water flow rate in a 500 MW coal-fired power plant is about 23,000

litres per minute.

The feedwater plus makeup water flows through feedwater heaters heated with steam extracted

from the steam turbines. Typically, the total feedwater also flows through a deaerator[4][5] that

removes dissolved air from the water, further purifying and reducing its corrosivity.

In the deaerator of following the deaeration, the water may be dosed with hydrazine, a chemical

that scavenges (removes) the remaining oxygen in the water to below 5 parts per billion (ppb). It

is also dosed with pH control agents such as ammonia or morpholine to keep the residual

acidity low and thus non-corrosive.

(PD) Image: Milton Beychok Simplified diagram of a conventional coal-fired steam generator.

The steam generator

A conventional coal-fired steam generator is a rectangular furnace about 15 metres on a side

and 40 metres tall. Its walls are made of insulated steel with a web of high pressure steel boiler

tubes attached to the inner surface of the walls.

The deaerated boiler feedwater enters the economizer (see the adjacent diagram) where it is

preheated by the hot combustion flue gases and then flows into the boiler steam drum at the top

of the furnace. Water from that drum circulates through the boiler tubes in the furnace walls

using the density difference between water in the steam drum and the steam-water mixture in

the boiler tubes.

Pulverized coal is air-blown into the furnace from fuel nozzles at the four corners and it rapidly

burns, forming a large fireball at the center. The thermal radiation of the fireball heats the water

that circulates through the boiler tubes mounted on the furnace walls. As the water circulates, it

absorbs heat and partially changes into steam at about 362 °C and at a pressure of 190 bar (19

MPa). In the boiler steam drum, the steam is separated from the circulating water. The steam

then flows through superheat tubes that hang in the hottest part of the combustion flue gases

path as it exits the furnace. Here the steam is superheated to about 540 °C before being routed

into the high pressure steam turbine.

The steam turbines and the electrical generator

(CC) Photo: Seimens AG, Germany Rotor of a large modern steam turbine, used in a power plant.

The staged series of steam turbines includes a high pressure turbine, an intermediate pressure

turbine and two low pressure turbines. A common configuration is that the series of turbines are

connected to each other and on a common shaft, with the electrical generator also being on that

common shaft.

As steam moves through the system, it loses pressure and thermal energy and expands in

volume, which requires increasing turbine diameter and longer turbine blades at each

succeeding stage. The entire rotating mass may weigh over 180 metric tons and be 30 metres

long. It is so heavy and the internal clearances are so close that it must be kept turning slowly at

3 rpm (using a turning gear mechanism) when shut down so that the shaft will not thermally bow

even slightly and become bound.

Another essential system is the turbine lubricating oil system which supplies oil to all turbine

bearings to prevent metal-to-metal contact between the turbine shaft and the shaft bearings.

The turbine shaft literally floats on a film of oil at the bearing points. This is so important that it is

one of the only major functions to be maintained by the emergency power batteries on site.

Superheated steam from the steam generator flows through a control valve into the high

pressure turbine. The control valve regulates the steam flow in accordance with the power

output needed from the plant. The exhaust steam from the high pressure turbine (reduced in

pressure and in temperature) returns to the steam generator's reheating tubes (see the steam

generator diagram above) where it is reheated back to 540 °C before it flows into the

intermediate pressure turbine. The exhaust steam from the intermediate pressure turbine flows

directly into the two low pressure turbines and the exhaust steam from the low pressure turbines

flows into the surface condenser. A small fraction of steam from the turbines is used to heat the

deaerator and/or the boiler feedwater preheater(s).

The turbine-driven electrical generator, about 10 metres long and 4 metres in diameter, contains

a stationary stator and a spinning rotor. In operation, it generates up to 21,000 amperes at

24,000 volts of three-phase alternating current (about 500 MW). A two-pole rotor would spin at

3000 rpm for a 50 Hz output or 3600 rpm for a 60 Hz output synchronized to the power grid

frequency in Hz. If a four-pole rotor is used, it would spin at 1500 rpm for 50 Hz output or 1800

rpm for 60 Hz output.

The rotor spins in a sealed chamber cooled with hydrogen gas, selected because it has the

highest known thermal conductivity of any gas and it has a low viscosity which reduces windage

losses from friction between the generator rotor and the cooling gas. The system requires

special handling during startup, with air in the chamber first displaced by carbon dioxide before

filling with hydrogen. This ensures that a highly explosive hydrogen-oxygen environment is not

created.

The power grid frequency is 60 Hz across North America and 50 Hz in Europe, Oceania, Asia

(Korea and parts of Japan are notable exceptions) and parts of Africa.

The electricity flows to a distribution yard where three-phase transformers step the voltage up to

115, 230, 500 or 765 kV as needed for transmission to its destination.

Steam condensing and cooling towers

For more information, see: Surface condenser and Cooling

tower.

(GNU) Image: Milton Beychok Diagram of a typical water-cooled surface condenser.

(GNU) Photo: Stefan Kühn Hyperboloid cooling towers (with water vapor plumes).

(PD) Photo: Tennessee Valley Authority Rectangular, mechanically induced draft cooling towers (with water vapor plumes).

The exhaust steam from the low pressure turbines is condensed into water in a water-cooled

surface condenser. The condensed water is commonly referred to as condensate. The surface

condenser operates at an absolute pressure of about 35 to 40 mmHg (i.e., a vacuum of about

720 to 725 mmHg) which maximizes the overall power plant efficiency.

The surface condenser is usually a shell and tube heat exchanger. Cooling water circulates

through the tubes in the condenser's shell and the low pressure exhaust steam is cooled and

condensed by flowing over the tubes as shown in the adjacent diagram. Typically the cooling

water causes the steam to condense at a temperature of about 35 °C. A lower condensing

temperature results in a higher vacuum (i.e., a lower absolute temperature) at the exhaust of the

low pressure turbine and a higher overall plant efficiency. The limiting factor in providing a low

condensing temperature is the temperature of the cooling water and that, in turn, is limited by

the prevailing average climatic conditions at the power plant's location.

The condensate from the bottom of the surface condenser is pumped back to the deaerator to

be reused as feedwater.

The heat absorbed by the circulating cooling water in the condenser tubes must also be

removed to maintain a constant cooling water supply temperature. This is done by pumping the

warm water from the condenser through either natural draft, forced draft or induced draft cooling

towers (as seen in the images to the right) that reduce the temperature of the water by about

11–17 °C and expel the low-temperature waste heat to the atmosphere. The circulation flow rate

of the cooling water in a 500 MW unit is about 14.2 m³/s (225,000 US gal/minute) at full load. [6]

Some older power plants use river water or lake water as cooling water. In these installations,

the water is filtered to remove debris and aquatic life from the water before it passes through the

condenser tubes.

The condenser tubes are are often made of a copper alloy, stainless steel or sometimes

titanium to resist corrosion from either side. Nevertheless they may become internally fouled

during operation by bacteria or algae in the cooling water or by mineral scaling, all of which

inhibit heat transfer and reduce the condenser efficiency. In an enclosed system, the cooling

water can be treated with biocidal chemicals to inhibit growth of bacteria and algae and with

other chemicals to inhibit scaling. Many plants include an automatic cleaning system that

circulates sponge rubber balls through the tubes to scrub them clean without the need to take

the system off-line. Hot water flushes may also be used to thermally shock aquatic life buildup

on the inner walls of the condenser tubes.

The cooling water used to condense the steam in the condenser returns to its source without

having been changed other than having been warmed. If the water returns to a local water body

(rather than a circulating cooling tower), it is mixed with cool raw water to lower its temperature

and prevent thermal shock to aquatic biota when discharged into that body of water.

Another method sometimes utilized for condensing turbine exhaust steam is the use of an air-

cooled condenser. Exhaust steam from the low pressure steam turbines flows through the air-

cooled condensing tubes which usually have metal fins on their external surface to increase

their heat transfer capacity. Ambient air from a large fan is directed over the fins to cool the

tubes and condense the low pressure steam in the tubes. Air-cooled condensers typically

operate at a higher temperature than water-cooled surface condensers. While reducing the

amount of water used in a power plant, the higher condensing temperature results in a higher

exhaust pressure for the low pressure turbines which reduces the overall efficiency of the power

plant.

Diagram of the overall conventional coal-fired power plant

Simplified coal-fired power plant

1. Cooling tower 11. High pressure steam turbine

20. Fan

2. Cooling water pump 12. Deaerator 21. Reheater 3. transmission line (3-phase) 13. Feedwater heater 22. Combustion air intake 4. transformer (3-phase) 14. Coal conveyor 23. Economiser 5. Electrical generator (3-phase)

15. Coal hopper 24. Air preheater

6. Low pressure steam turbines

16. Coal pulverizer 25. Cold-side Electrostatic precipitator

7. Condensate and feedwater pumps

17. Steam drum 26. Fan

8. Surface condenser 18. Bottom ash hopper 27. Flue gas desulfurization scrubber

9. Intermediate pressure steam turbine

19. Superheater 28. Flue gas stack

10. Steam control valve

Stack gas path

For more information, see: Air preheater and Conventional coal-

fired power plant#Air pollution control technology.

As the combustion flue gas exits the steam generator, it flows through a heat exchange device

where it is cooled by exchanging heat with the incoming combustion air. The device is called an

air preheater (referred to as an APH). The gas exiting the steam generator is laden with

particulate matter (PM), referred to as fly ash, which consists of very small ash particles. The

flue gas contains nitrogen along with combustion products carbon dioxide (CO2), sulfur dioxide

(SO2) and nitrogen oxides (NOx).

Various processes (known as De-NOx processes) are often used to reduce the amount of NOx

in the flue gas before the flue gas exits the steam generator. After the exiting flue gas has been

cooled by heat exchange with the incoming combustion air, the fly ash in the flue gas is

removed by fabric bag filters or electrostatic precipitators. Finally, after removal of the fly ash,

many coal-fired power plants use one of the available flue gas desulfurization (FGD) processes

to reduce sulfur dioxide emissions. The flue gas then exits to the atmosphere via tall flue gas

stacks. A typical flue gas stack may be about 150 to 250 metres tall to disperse the remaining

flue gas components in the atmosphere.

In the United States and a number of other countries, air pollution dispersion modeling[7] [8][9]

studies are required to determine the flue gas stack height needed to comply with the local air

pollution regulations. The United States also requires the height of a flue gas stack to comply

with what is known as the "Good Engineering Practice (GEP)" stack height.[10][11] In the case of

existing flue gas stacks that exceed the GEP stack height, any air pollution dispersion modeling

studies (to determine environmental impacts) for such stacks must use the GEP stack height

rather than the actual stack height.

Supercritical steam generators

Above the critical point for water of 374 °C and 22 MPa, there is no phase transition from water

to steam, but only a gradual decrease in density. Boiling does not occur and it is not possible to

remove impurities via steam separation.

Supercritical steam generators operating at or above the critical point of water are referred to as

once-through plants because boiler water does not circulate multiple times as in a conventional

steam generator. Supercritical steam generators require additional water purification steps to

ensure that any impurities picked up during the cycle are removed. This purification takes the

form of high pressure ion exchange units called condensate polishers between the steam

condenser and the feedwater heaters.

Conventional coal-fired power plants operate at subcritical conditions and typically achieve 34–

36% thermal efficiency. Supercritical coal-fired power plants, operating at 565 °C and 243 bar

(24.3 MPa) have efficiencies in the range of 38–40%. New "ultra critical" designs, operating at

700–720 °C and 365–385 bar (36.5–38.5 MPa), are expected to achieve 44–46% efficiency.[2]

Alternatives to coal-fired power plants

Alternatives to coal-fired power plants include using other fossil fuels (natural gas or fuel oil),

nuclear power plants, geothermal power plants, hydroelectric power plants, solar power plants,

wind power plants and tidal power plants.

There are also other types of coal-fired power plants:

Integrated gasification combined cycle (IGCC): The coal is gasified to produce a synthetic gas

(referred to as syngas). Impurities are removed from the syngas which is then burned in a gas

turbine. The gas turbine drives an electrical generator and steam is produced by recovering

heat from the gas turbine exhaust. The steam is used to drive another electrical generator.

Fluidized bed combustion (FBC): The coal is burned in a fluidized bed and steam is produced

by heating and vaporizing feedwater flowing through tubes in and above the fluidized bed. The

steam is used to drive an electrical generator.

Oxygen firing (Oxy firing): Using oxygen rather than air for combustion of the coal in coal-fired

power plants.

Control of air pollutant emissions

The major designated air pollutants emitted by coal-fired power plants are sulfur dioxide (SO2),

nitrogen oxides (NOx), particulate matter (PM), and mercury (Hg). Trace amounts of radioactive

elements are also emitted.

A major component of the combustion flue gases produced by burning coal is carbon dioxide

(CO2), which is not a pollutant in the traditional sense since it is essential to support

photosynthesis for all plant life on Earth. However, carbon dioxide is a greenhouse gas

considered to be a contributor to global warming. It is the most abundant anthropogenic (human

caused) greenhouse gas in the Earth's atmosphere.

Control of particulate matter emissions

The removal of particulate matter (referred to as fly ash) from the combustion flue gas is

typically accomplished with electrostatic precipitators (ESP) or fabric filters. ESPs or fabric filters

are installed on all power plants in the United States that burn pulverized coal. They routinely

achieve 99% or greater fly ash removal.[2]

Typical particulate emissions from modern power plants in the United States that burn

pulverized coal are less than 15 mg per cubic meter of flue gas (referenced at 0 °C and 101,325

kPa). New units in Japan achieve 5 mg per cubic meter by using wet flue gas desulfurization

units that also remove condensible particulates.[2]

Control of sulfur dioxide emissions

For more information, see: Flue gas desulfurization.

Partial flue gas desulfurization (FGD) can achieve about 50-70 % removal of sulfur dioxide by

the injection of dry limestone just downstream of the air preheater. The resultant solids are

recovered in the ESPs along with the fly ash.

In power plants burning pulverized coal, wet flue gas desulfurization (FGD) that contacts the flue

gases with lime slurries (in what are called wet lime scrubbers) can achieve 95% sulfur dioxide

removal without additives and 99+% removal with additives. Wet FGD has the greatest share of

the FGD usage in the United States and it is commercially proven, well established technology.[2]

The typical older FGD units in power plants burning pulverized coal within the United States

achieve average sulfur dioxide emission levels of about 0.340 kg/MWh (0.22 lb/106 Btu), which

meets the level to which those units were permitted.

The lowest demonstrated sulfur dioxide emission level (in 2005) for power plants burning

pulverized high-sulfur coal within the United States was 1.08 kg/MWh (0.07 lb/106 Btu) and

0.046 kg/MWh (0.03 lb/106 Btu) for plants burning low-sulfur pulverized coal.[2]

In 2006, power plants in the United States that burned fossil fuels (coal, fuel oil or natural gas)

generated 327 GW of electric power, of which about 70% was generated in plants burning coal.

Only about 30% of that 327 GW of generated power was derived from plants equipped with flue

gas desulfurization.[12] The other 70% of the generated power was derived from power plants that

met their permitted levels by burning low sulfur coals, fuel oil or natural gas.

In the 10 year period between 1996 and 2006, the sulfur dioxide emissions per year from coal-

fired power plants in the United States declined from 12.9×106 metric tons to 9.5×106 metric

tons which is a reduction of 26%. That decrease in sulfur dioxide emissions occurred despite

the fact that the coal-fired power plant generation of electric power increased by 11%.[12]

In March 2005, the U.S. Environmental Protection Agency promulgated the Clean Air Interstate

Rule (CAIR) which sets emission caps for particulate matter, sulfur dioxide and nitrogen oxides

that are expected to result in more efficient FGD units being installed and more coal-fired power

plants using FGD units or switching to burning oil or natural gas. The CAIR rules are still in

litigation as of November 2008.[13]

Control of nitrogen oxides emissions

For more information, see: De-NOx processes.

There are three technologies (known as De-NOx processes) available for reducing the

emissions of NOx from combustion sources:[2]

The lowest cost combustion control technology for reducing NOx emissions is referred to as Lo-

NOx and can achieve up to a 50% reduction in NOx emissions compared to uncontrolled

combustion.

The most most effective, but most expensive, NOx emission reduction technology is Selective

Catalytic Reduction (SCR). It can achieve 90% NOx reduction and is currently (2008) the

technology of choice for achieving very low levels of NOx emissions.

Selective non-catalytic reduction (SNCR) falls between Low-NOx and SCR in both cost and

effectiveness.

The average NOx emissions from conventional coal-fired power plants in the United States

typically range from about 0.14 kg/MWh (0.09 lb/106 Btu) to 0.20 kg/MWh (0.13 lb/106 Btu),

which meets their permitted level of emissions.[2]

In 2005, the 20 lowest NOx emitting coal-fired power plants in the United States in 2005

achieved emission levels ranging from 0.06 kg/MWh (0.04 lb/106 Btu) to 0.10 kg/MWh (0.065

lb/106 Btu).[2]

In the 10 year period between 1996 and 2006, the NOx emissions per year from coal-fired

power plants in the United States declined about 40% despite the fact that the coal-fired power

plant generation of electric power increased by 11%.[12]

Control of mercury emissions

Mercury in the flue gas exists as both elemental and oxidized mercury vapor as well as mercury

that has reacted with the fly ash.[14][15]

The removal of the fly ash in an ESP or a fabric filter also removes the mercury that has reacted

with the fly ash, resulting in 10 to 30% removal for bituminous coals but less than 10% for sub-

bituminous coals and lignite. The oxidized mercury vapor left in the flue gas after the fly ash

removal is effectively removed by wet FGD scrubbing, resulting in 40-60% total mercury

removal for bituminous coals and less than 30–40% total mercury removal for sub-bituminous

coals and lignite.[2][14]

For low-sulfur sub-bituminous coals and particularly lignite, most of the mercury vapor is in the

elemental form, which is not removed by wet FGD scrubbing. In most tests of bituminous coals,

SCR (for NOx control) converted 85-95% of the elemental mercury to the oxidized form, which

is then effectively removed by wet FGD scrubbing. With sub-bituminous coals, the amount of

mercury remained low even with addition of an SCR.[2][14]

Additional mercury removal can be achieved by powdered activated carbon injection (PAC) and

an added fiber filter to collect the carbon. This can achieve up to 85-95% removal of the

mercury. Commercial short-duration tests with powdered, activated carbon injection have shown

removal rates around 90% for bituminous coals but lower for sub-bituminous coals. For sub-

bituminous coals, the injection of brominated, activated carbon has been shown to be highly

effective in emissions tests lasting 10 to 30 days at 3 power plants. These tests demonstrated a

potential mercury removal efficiency of 90%.[2][14]

Ongoing research and development programs are evaluating improved technology that is

expected to improve effectiveness. The general consensus in the industry is that this picture will

change significantly within the next few years. The U.S. EPA states that they believe PAC

injection and enhanced multi-pollutant controls will be available after 2010 for commercial

application on most, if not all, key combinations of coal type and control technology to provide

mercury removal levels between 60 and 90%. Optimization of this commercial multi-pollutant

control technology by about 2015 should permit achieving mercury removal levels between 90

and 95% on most if not all coals, but the technology remains to be commercially demonstrated.[2]

[14][16]

In March 2005, the U.S. EPA issued the Clean Air Mercury Rule (CAMR). The CAMR allocates

a mercury emissions budget for each of the 50 states and other jurisdictions. If they so desire,

the states can opt out of the EPA budget and implement a more stringent emissions reduction

program than is required by CAMR.[17] As in the CAIR situation (see above section on control of

sulfur dioxide emissions), the CAMR is still in litigation as of 2008.[15]

Carbon dioxide emissions

The emissions from conventional coal-fired power plants include carbon dioxide (CO2) which is

the major component of the combustion flue gases produced by burning coal. As discussed

earlier above, carbon dioxide is not a pollutant in the traditional sense but it is considered to be

a contributor to global warming.

To better understand the discussion of carbon

dioxide emissions from conventional coal-fired

electricity generation plants, the adjacent table

provides a perspective on the total global

energy supply sources. In 2005, coal-based

energy sources constituted 26.9% of the total

energy supply sources.

As shown in the table, the total electricity generation (from natural gas, fuel oil, coal, nuclear

power, biomass, hydropower, wind power, solar power, geothermal and other plants) amounted

to 13.9% of the total energy supply sources and the coal-fired power plant portion of the

electricity generation amounted to 5.4% of the total global energy supply sources.

In 2005, the total carbon dioxide emissions from all sources to the atmosphere were about 28

Gt (28×109 tonnes) and approximately 41 percent (11.5 Gt) of those emissions were from coal-

based energy supply sources.[18][22]

Carbon dioxide emissions from conventional coal-fired power plants

Worldwide Energy Statisticsfor 2005[18][19][20][21]

Energy Supply Sources TW (a) MWh (b) %

Coal-based 4.0 35×109 26.9

Gas, oil, nuclear and other 10.8 95×109 73.1

Total supply sources 14.8 130×109 100.0

Electricity generationcomponent of the totalenergy supply sources

     

Coal-fired generation 0.80 7×109 5.4

Total generation 2.05 18×109 13.9

(a) 1 TW = 1 terawatt = 1012 watts

(b) 1 MWh = 1 megawatt-hour = 106 watt-hours

Carbon dioxide emissions for conventional coal-fired power plants will vary significantly because

the those emissions are a function of the coal's carbon content and the plant's thermal

efficiency. The coal's carbon content may range from about 50 weight percent for lignite coal to

90 weight percent for anthracite coal and the plant's thermal efficiency may vary from 32 to 42

percent.

A study of the future of coal, developed at the Massachusetts Institute of Technology (MIT)[2]

states that, as an average, a 500 MW coal coal-fired power plant produces 3 million tons of

carbon dioxide per year. That amounts to a carbon dioxide emission factor of 0.62 kg/kWh.

Other sources in the literature range up to 1.0 kg/kWh and, in fact, an emission factor of 0.96

can be derived from 1998 data available for all the coal-fired power plants in the United States. [23]

Assuming an emission factor of 1.0 kg/kWh, a 500 MW coal-fired power plant would produce

4.4 million tonnes (4.4 Mt) per year of carbon dioxide emissions and the global total of 0.80 TW

(800,000 MW) of conventional coal-fired electricity generation would produce 7 Gt per year of

carbon-dioxide emissions. Thus, globally, the estimated amount of carbon dioxide emitted by

conventional coal-fired power power plants amounted to approximately 25 % of the estimated

28 Gt of carbon dioxide emitted from all sources in 2005.

Reducing carbon dioxide emissions from coal-fired power plants

For more information, see: Carbon capture and storage.

The leading technology for significantly reducing the CO2 emissions from coal-fired power plants

is known as Carbon capture and sequestration (CCS). It is currently (2008) regarded as the

technology which could significantly reduce coal-fired power plant carbon dioxide emissions

while also allowing the use of the Earth's abundant coal resources to provide the increasing

global need for energy. However, CCS technology is still in development and it is not expected

to be ready for widespread commercial implementation until about 2020.[22][24][25]

It involves capturing the carbon dioxide produced by the combustion of coal and storing it in

deep ocean areas or in underground geological structures deep within the Earth's upper crust.

The capture of the carbon dioxide from the coal combustion flue gases can be accomplished by

using absorbents such as amines (see Amine gas treating). The carbon dioxide is then

recovered from the absorbent and compressed into a supercritical fluid at about 150

atmospheres (15 MPA), dehydrated and transported to the storage sites for injection into the

underground or undersea reservoirs. Compressing the carbon dioxide into a supercritical fluid

greatly increases its density which greatly reduces its volume as compared to transporting and

storing the carbon dioxide as a gas.

Since the current global emissions of carbon dioxide from all energy supply sources is 28 Gt per

year, the scale of carbon dioxide storage required to make a major difference in those

emissions is massive. For example, based on a carbon dioxide emission factor of 1 kg per kWh,

570 coal-fired plants, each producing 1000 MW of electricity, would emit about 5 Gt per year of

carbon dioxide into the atmosphere. Storing 5 Gt per year of carbon dioxide requires injection of

about 65 million barrels per day (about 10 x 106 cubic meters per day) of supercritical carbon

dioxide.[2]

The worldwide capacity for storing carbon dioxide in depleted natural gas and crude oil

production fields and in unminable deep coal seams has been estimated as about 1000 Gt

which is equivalent to 140 years of the 7 Gt emissions (in 2005) from the worldwide total coal-

fired power generation. In addition, the worldwide capacity in deep ocean formations has been

estimated as 1000 to 10,000 Gt.[25][26] There are currently four commercial sequestration sites in

operation:

The Weyburn-Midale facility in Saskatchewan, Canada constructed by a consortium of oil

companies, research organizations and others[27]

The Sleipner facility in offshore Norway constructed by StatoilHydro[28]

The Snøvit facility in the Barents Sea constructed by StatoilHydro[29]

The Salah facility in Algeria constructed by StatoilHydro[30]

There are many other sequestration sites currently in planning, development or construction.

No matter what governmental regulations are eventually adopted to mitigate the carbon dioxide

emissions from coal-powered power plants (or other processes involving the combustion of

substances containing carbon), there must be a successful, integrated large-scale

demonstration of the technical, environmental and economic aspects of the major components

of a CCS system, namely carbon dioxide capture, transportation and storage. Such an

integrated demonstration must also provide a definition of regulatory protocols for sequestration

projects including site selection, injection operation, and eventual transfer of custody to public

authorities after a period of successful operation.

Control of radioactive trace element emissions

As most ores in the Earth's crust, coal also contains trace levels of uranium, thorium, and other naturally-occurring radioactive elements.

A report developed at the Oak Ridge National Laboratory (ORNL) estimated that the amount of

coal burned each year in a typical 1000 MW coal-fired power plant contained about 5.2 tonnes

of uranium and about 12.8 tonnes of thorium.[31] The basis of ORNL estimate was that the annual

coal consumption was 4 Mt and that the coal contained 1.3 ppm of uranium and 3.2 ppm of

thorium.

Assuming that all of the uranium and thorium would be emitted into the fly ash and that the

electrostatic precipitators would capture and remove 99% of the fly ash, the emissions of

radioactive trace elements to the atmosphere from a 1000 MW coal-fired power plant would be

52 kg/yr of uranium and 128 kg/yr of thorium.

The average annual radiation dose received by a person from all sources (cosmic radiation,

radioactivity in the soil, food, water, air and miscellaneous other sources) is 360 millirem.[32] The

annual radiation dose (from naturally occurring radioactivity in coal) received by persons living

within 80 km of a coal-fired power plant is estimated to be 0.03 millirem.[32][33]

The ORNL report discussed earlier,[31]states that All studies of potential health hazards

associated with the release of radioactive elements from coal combustion conclude that the

perturbation of natural background dose levels is almost negligible and a U.S. EPA report[34]

states that the lifetime fatal cancer risk from exposure to radionuclides to the vast majority of

persons living within 50 km of an electric power plant is estimated to be less than 1×10-6.

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Coal

Electricty Generation Technologies

Natural Gas

Coal

Oil

Nuclear Energy

Municipal Solid Waste

Hydroelectricity

Non-Hydroelectric Renewable Energy

Electricity from Coal

Coal is a fossil fuel formed from the decomposition of organic materials that have been subjected to

geologic heat and pressure over millions of years. Coal is considered a nonrenewable resource

because it cannot be replenished on a human time frame.

The activities involved in generating electricity from coal include mining, transport to power plants,

and burning of the coal in power plants. Initially, coal is extracted from surface or underground mines.

The coal is often cleaned or washed at the coal mine to remove impurities before it is transported to

the power plant—usually by train, barge, or truck. Finally, at the power plant, coal is commonly burned

in a boiler to produce steam. The steam is run through a turbine to generate electricity.

Environmental Impacts

Although power plants are regulated by federal and state laws to protect human health and the

environment, there is a wide variation of environmental impacts associated with power generation

technologies.

The purpose of the following section is to give consumers a better idea of the specific air, water, solid

waste, and radioactive releases associated with coal-fired generation.

Air Emissions

When coal is burned, carbon dioxide, sulfur dioxide, nitrogen oxides, and mercury compounds are

released. For that reason, coal-fired boilers are required to have control devices to reduce the amount

of emissions that are released.

The average emission rates in the United States from coal-fired generation are: 2,249 lbs/MWh of

carbon dioxide, 13 lbs/MWh of sulfur dioxide, and 6 lbs/MWh of nitrogen oxides.1

Mining, cleaning, and transporting coal to the power plant generate additional emissions. For example,

methane, a potent greenhouse gas that is trapped in the coal, is often vented during these processes

to increase safety.

Water Resource Use

Large quantities of water are frequently needed to remove impurities from coal at the mine. In

addition, coal-fired power plants use large quantities of water for producing steam and for cooling.

When coal-fired power plants remove water from a lake or river, fish and other aquatic life can be

affected, as well as animals and people who depend on these aquatic resources.

Water Discharges

Pollutants build up in the water used in the power plant boiler and cooling system. If the water used in

the power plant is discharged to a lake or river, the pollutants in the water can harm fish and plants.

Further, if rain falls on coal stored in piles outside the power plant, the water that runs off these piles

can flush heavy metals from the coal, such as arsenic and lead, into nearby bodies of water. Coal

mining can also contaminate bodies of water with heavy metals when the water used to clean the coal

is discharged back into the environment. This discharge usually requires a permit and is monitored.

For more information about these regulations, visit EPA's Office of Water Web site.

Solid Waste Generation

The burning of coal creates solid waste, called ash, which is composed primarily of metal oxides and

alkali.2 On average, the ash content of coal is 10 percent.3 Solid waste is also created at coal mines

when coal is cleaned and at power plants when air pollutants are removed from the stack gas. Much of

this waste is deposited in landfills and abandoned mines, although some amounts are now being

recycled into useful products, such as cement and building materials.

Land Resource Use

Soil at coal-fired power plant sites can become contaminated with various pollutants from the coal and

take a long time to recover, even after the power plant closes down. Coal mining and processing also

have environmental impacts on land. Surface mining disturbs larger areas than underground mining.

Reserves

In the United States, coal consumption in 2003 was just over 1.1 billion tons.4 Coal reserves in the

United States stand at 268 billion tons, of which 43 percent are in surface mines. The three major coal-

producing states are Wyoming, West Virginia, and Kentucky.5

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Coal Ash Is More Radioactive than Nuclear WasteBy burning away all the pesky carbon and other impurities, coal power plants produce heaps of radiation

By Mara Hvistendahl     

CONCENTRATED RADIATION: By burning coal into ash, power plants concentrate

the trace amounts of radioactive elements within the black rock.

©ISTOCKPHOTO.COM

10diggsdigg

The popular conception of nuclear power is straight out of The Simpsons:

Springfield abounds with signs of radioactivity, from the strange glow surrounding Mr.

Burn's nuclear power plant workers to Homer's low sperm count. Then there's the

local superhero, Radioactive Man, who fires beams of "nuclear heat" from his eyes.

Nuclear power, many people think, is inseparable from a volatile, invariably lime-

green, mutant-making radioactivity.

Coal, meanwhile, is believed responsible for a host of more quotidian problems, such

as mining accidents, acid rain and greenhouse gas emissions. But it isn't supposed to

spawn three-eyed fish like Blinky.

Over the past few decades, however, a series of studies has called these stereotypes

into question. Among the surprising conclusions: the waste produced by coal plants is

actually more radioactive than that generated by their nuclear counterparts. In fact,

the fly ash emitted by a power plant—a by-product from burning coal for electricity—

carries into the surrounding environment 100 times more radiation than a nuclear

power plant producing the same amount of energy. * [See Editor's Note at end of page

2]

At issue is coal's content of uranium and thorium, both radioactive elements. They

occur in such trace amounts in natural, or "whole," coal that they aren't a problem. But

when coal is burned into fly ash, uranium and thorium are concentrated at up to 10

times their original levels.

Fly ash uranium sometimes leaches into the soil and water surrounding a coal plant,

affecting cropland and, in turn, food. People living within a "stack shadow"—the area

within a half- to one-mile (0.8- to 1.6-kilometer) radius of a coal plant's smokestacks—

might then ingest small amounts of radiation. Fly ash is also disposed of in landfills and

abandoned mines and quarries, posing a potential risk to people living around those

areas.

In a 1978 paper for Science, J. P. McBride at Oak Ridge National Laboratory (ORNL)

and his colleagues looked at the uranium and thorium content of fly ash from coal-fired

power plants in Tennessee and Alabama. To answer the question of just how harmful

leaching could be, the scientists estimated radiation exposure around the coal plants

and compared it with exposure levels around boiling-water reactor and pressurized-

water nuclear power plants.

The result: estimated radiation doses ingested by people living near the coal plants

were equal to or higher than doses for people living around the nuclear facilities. At

one extreme, the scientists estimated fly ash radiation in individuals' bones at around

18 millirems (thousandths of a rem, a unit for measuring doses of ionizing radiation) a

year. Doses for the two nuclear plants, by contrast, ranged from between three and six

millirems for the same period. And when all food was grown in the area, radiation

doses were 50 to 200 percent higher around the coal plants.

McBride and his co-authors estimated that individuals living near coal-fired

installations are exposed to a maximum of 1.9 millirems of fly ash radiation yearly. To

put these numbers in perspective, the average person encounters 360 millirems of

annual "background radiation" from natural and man-made sources, including

substances in Earth's crust, cosmic rays, residue from nuclear tests and smoke

detectors.

Dana Christensen, associate lab director for energy and engineering at ORNL, says

that health risks from radiation in coal by-products are low. "Other risks like being hit

by lightning," he adds, "are three or four times greater than radiation-induced health

effects from coal plants." And McBride and his co-authors emphasize that other

products of coal power, like emissions of acid rain–producing sulfur dioxide and smog-

forming nitrous oxide, pose greater health risks than radiation.

Coal Ash Is More Radioactive than Nuclear WasteBy burning away all the pesky carbon and other impurities, coal power plants produce heaps of radiation

By Mara Hvistendahl     

The U.S. Geological Survey (USGS) maintains an online database of fly ash–based

uranium content for sites across the U.S. In most areas, the ash contains less uranium

than some common rocks. In Tennessee's Chattanooga shale, for example, there is

more uranium in phosphate rock.

Robert Finkelman, a former USGS coordinator of coal quality who oversaw research on

uranium in fly ash in the 1990s, says that for the average person the by-product

accounts for a miniscule amount of background radiation, probably less than 0.1

percent of total background radiation exposure. According to USGS calculations,

buying a house in a stack shadow—in this case within 0.6 mile [one kilometer] of a coal

plant—increases the annual amount of radiation you're exposed to by a maximum of 5

percent. But that's still less than the radiation encountered in normal yearly exposure

to X-rays.

So why does coal waste appear so radioactive? It's a matter of comparison: The

chances of experiencing adverse health effects from radiation are slim for both nuclear

and coal-fired power plants—they're just somewhat higher for the coal ones. "You're

talking about one chance in a billion for nuclear power plants," Christensen says. "And

it's one in 10 million to one in a hundred million for coal plants."

Radiation from uranium and other elements in coal might only form a genuine health

risk to miners, Finkelman explains. "It's more of an occupational hazard than a general

environmental hazard," he says. "The miners are surrounded by rocks and sloshing

through ground water that is exuding radon."

Developing countries like India and China continue to unveil new coal-fired plants—at

the rate of one every seven to 10 days in the latter nation. And the U.S. still draws

around half of its electricity from coal. But coal plants have an additional strike against

them: they emit harmful greenhouse gases.

With the world now focused on addressing climate change, nuclear power is gaining

favor in some circles. China aims to quadruple nuclear capacity to 40,000 megawatts

by 2020, and the U.S. may build as many as 30 new reactors in the next several

decades. But, although the risk of a nuclear core meltdown is very low, the impact of

such an event creates a stigma around the noncarbon power source.

The question boils down to the accumulating impacts of daily incremental pollution

from burning coal or the small risk but catastrophic consequences of even one nuclear

meltdown. "I suspect we'll hear more about this rivalry," Finkelman says. "More coal

will be mined in the future. And those ignorant of the issues, or those who have a

vested interest in other forms of energy, may be tempted to raise these issues again."

*Editor's Note (posted 12/30/08): In response to some concerns raised by readers, a

change has been made to this story. The sentence marked with an asterisk was

changed from "In fact, fly ash—a by-product from burning coal for power—and other

coal waste contains up to 100 times more radiation than nuclear waste" to "In fact, the

fly ash emitted by a power plant—a by-product from burning coal for electricity—

carries into the surrounding environment 100 times more radiation than a nuclear

power plant producing the same amount of energy." Our source for this statistic is

Dana Christensen, an associate lab director for energy and engineering at Oak Ridge

National Laboratory as well as 1978 paper in Science authored by J.P. McBride and

colleagues, also of ORNL.

As a general clarification, ounce for ounce, coal ash released from a power plant

delivers more radiation than nuclear waste shielded via water or dry cask storage.

......................................................................

STUDY BLASTS GROWING USE OF

COAL-FIRED POWER PLANTS

 

July 24, 2004

Pollution from coal-fired power plants increased more than 16 percent since 1992 and is likely to worsen as utilities competing in deregulated markets increasingly rely on older power plants, a new study says.

More than 159 million Americans live in communities with unhealthy air. Air pollution from power plants alone contributes to an estimated 30,000 premature deaths, hundreds of thousands of asthma attacks, and tens of thousands of hospitalizations for respiratory and cardiovascular illnesses each year. Everyone deserves air that is safe to breathe.

Coal-fired plants in Pennsylvania generated only about 6 percent more electricity than they did seven years ago, but the issue is especially critical to state residents as utilities upwind in Illinois, Indiana, Ohio and West Virginia have increased emissions as much as 46 percent.

"I think this is really bad news for states like Pennsylvania, Massachusetts and New York, states that are probably doing a better job transitioning away from coal", said John Coequyt, co-author of the report, "Up In Smoke: Congress’ Failure to Control Emissions from Coal Power Plants".

"There’s no way Pennsylvania is going to be able to stop its clean-air problems without other states stepping up", he said.

The increased reliance by utilities on coal-fired power plants has generated the pollution equivalent of putting another 570,487 cars on the road in Pennsylvania between 1992 and 1998, according to the report produced by the Environmental Working Group and U.S. PIRG. Nationally, 755,000 tons of nitrogen oxide pollution has been produced, or the equivalent of the pollution generated by nearly 37 million cars. Coal produces approximately two times the amount of carbon dioxide as natural gas, and a third more CO2 per unit of heat than oil.

Coal-fired plants produce 56 percent of the nation’s electricity.

The study blames increased use of electricity generated by older, dirtier coal-fired plants with contributing to smog and global warming problems. The problem is likely to grow because the Clean Air Act grandfathered plants planned or constructed before 1977. Utilities use these plants, which are allowed to produce up to 10 times as much pollution as newer facilities, to generate cheaper power.

Deregulation of the utility business has really "exasperated the problem", Coequyt said.

Electricity generated from the same plants grew 2 percent before deregulation and 16 percent after as utilities pushed under-utilized facilities harder, he said. The largest increase was in Illinois, where coal-fired plants generated 46 percent more electricity between 1992 and 1998.

The largest increase in Pennsylvania, which is in its first year of electric deregulation, was at PECO Energy Co. plants in Delaware and Chester counties, which respectively increased generation 51.9 percent and 47.3 percent during the same period.

Source: The Patriot-News, Harrisburg, Pa.

Mercury Found in Midwest RainBy Herbert G. McCann09/15/99

     To enlarge a picture, click on it. 

Rain contaminated with mercury from coal-fired electric plants is fouling Midwest lakes and rivers, according to a report released by environmental groups. Mercury is one of the heavy metals that causes dangerous inflammation in body tissues.

  

Child poisoned by mercuryin Minamata, Japan

Mercury is showing up in Chicago rainfall at levels 42 times greater than federal standards have considered safe, according to Andrew Buchsbaum of the National Wildlife Federation. Mercury levels in rain are even higher in Detroit and Duluth, Minn., he said.

Separately, New York state’s attorney general was taking legal action today against 17 Midwestern coal-fired electric plants, saying their pollution has contaminated air in the Northeast for years.

The mercury contamination report was released Tuesday by groups including the Environmental Law and Policy Center and the Sierra Club. The data were collected from government and university studies with the help of the U.S. Environmental Protection Agency, Buchsbaum said.

"Unfortunately, the largest contributor to the problem, the electric utility industry, continues to get a free ride on its mercury pollution", Peter Morman said of the Environmental Law and Policy Center. "While other sources are reducing emissions, no such requirements exist for coal-fired power plants".

Morman said mercury pollution by Midwestern utilities probably will increase because deregulation will prompt them to generate higher levels of electricity.

Buchsbaum said the plants should cut their mercury emissions, with an eye on eliminating them, by turning to cleaner energy sources such as natural gas.

Scott Miller, Commonwealth Edison’s air quality engineer, said Tuesday that the utility’s seven coal-fired plants emitted 1,700 pounds of mercury in 1998 -- an amount that has been steady for several years.

Miller said ComEd is cooperating with the EPA studies on mercury emissions. He said the utility has no plans to convert its coal plants to gas.

A naturally occurring metal, mercury accumulates in fish and becomes more concentrated as it moves up the food chain. In humans, the neurotoxin can slow fetal and child development and cause brain damage.

Buchsbaum said data collected by the University of Michigan Air Quality Laboratory found that rain falling on Chicago’s South Side had mercury levels ranging from 5.4 parts per trillion to 74.5 parts per trillion.

The EPA considers mercury levels in the Great Lakes to be safe for wildlife at 1.3 parts per trillion. For humans, it is 1.8 parts per trillion.

The Agency for Toxic Substance and Disease Registry in the Department of Health and Human Services says that based on the latest studies, people can consume as much as 0.3 micrograms of mercury per kilogram of their body weight without health risks. Its previous standard _ and the standard still used by the EPA _ had been 0.1 microgram.

But the health impact of low levels of mercury contamination has been widely disputed. Congress last year barred further regulation of mercury until the National Academy of Sciences completes an 18-month study of the health effects.

Buchsbaum said studies show rain scrubs the air of the mercury that belches from coal-fired power plants and incinerators and carries it into the Great Lakes and other Midwest lakes and rivers.

In New York, Attorney General Eliot Spitzer said he planned to file notice to sue 17 plants in five Midwestern states, accusing them of violating the 1990 federal Clean Air Act.

Spitzer said the plants in Indiana, Kentucky, Ohio, Virginia and West Virginia failed to upgrade equipment that cleans smokestack emissions when they made other big investments in the plants, a requirement under the act.

Preliminary findings of a six-month EPA study suggested a pattern of such violations by operators of many of the country’s biggest and dirtiest coal-burning plants, Clinton administration officials said in July.

The increased acid rain problems in the Northeast over the last 20 years have been linked to sulfates and nitrates, which are products of coal-fired power plants. Recent studies by the EPA and the Department of Energy indicate that 85 to 90 percent of the sulfates over the mid-Atlantic and New England states originate in Midwestern power plant emissions.

What Will It Take to Get Excited About Our Air?

By Don Shoemaker

      To enlarge an image, click on it.

While we were driving home, a light rain began falling, and soon the car was covered with tiny crystal balls of water that skidded over the hood and roof. But then the sun came out, and as we parked at the old homestead the car was dry.

And filthy dirty. Where there had been raindrops there were speckles of dust — as though some giant smoking a super-super Corona had scattered his ashes over our car. We look at one another, thinking it but not saying it: Is this the air we breathe? Yes, even in a city without smokestacks and coal bunkers.

At least one out of every four Americans may be asking that question. We are breathing the air conditioned by thousands, if not millions, of automobiles, the ozone blasters and some jet airplanes. We happen to live right under a major airway that is occupied day and night by smoke-spewing carriers. They leave their signature on pools and patios and white tile roofs. If you watch, you can see the stuff fall.

I don't know why this is tolerated by adult Americans who respect their lungs and bronchial tubes. I don't know why the surgeon general does not hire skywriters to warn: "Your ozone isn't

A-OK. Auto and aircraft smoke is dangerous to your health." (The message probably is too long and therefore too expensive.)

It is not, though, a laughing matter. Except in Congress.

For the last decades, both houses have been debating changes in the federal Clean Air Act. Ten years of jawing while we breathe dirty air!

Now, I am aware that the good old U.S.A. has the world's toughest, most expensive and most far-reaching clean-air laws. The annual price tag is put at $32 billion. Maybe so. I am leery, however, of price tags put on our inequities. Add them all up and they usually exceed all the currencies of the world put together. (You know: Crime costs us $1 trillion a year; drug abuse $500 billion; ketchup spills $50 million, etc.)

An agency that, admittedly, seeks the golden mean, warns that the Senate clean air bill may be "ill-conceived, ineffective and catastrophically expensive legislation that could double or even triple America's clean-air costs." True, perhaps.

But we last heard such economic arguments for doing nothing gradually when the auto industry was telling us that air bags would bankrupt the consumer (and itself) and take years to put in place. They are in place now on many models of autos as standard equipment, just as are the once-impossible emission controls. The same goes for those prohibitively expensive stack gas scrubbers for electric utilities. (There are now 149 in operation, without any notable bankruptcies.)                                   

For the last few years, both conservationists and polluters have talked about the greenhouse effect and global warming. Shucks, all this is beyond me. But I remember even more years back when we were being threatened with another Ice Age if we didn't do thus and so.

I always go back to what Jack Kennedy said about "experts" who had misled him. At length he relied on the greatest expertise of all — common sense.

Five major classes of pollutants are discharged into the air: carbon monoxide, particulates, sulfur oxides, hydrocarbons and nitrogen oxides. Carbon monoxide is the deadliest, but all are dangerous. We know about gasping for breath in the Los Angeles area but probably little about the death of citrus in the region (auto emissions). In Florida, the air is blighted by the phosphate-fertilizer processing that has killed pines and citrus orchards. Anyone familiar with the Great Lakes area and short-fuse Canadians knows about the scandal of acid rain.

We take another look at the surface (white) of the car and ask, in audible horror this time: "We breathe this stuff?" My gawd, we do — and nobody I know really gets excited about it. What will it take? An angry book? I could write one. But there are already too many. Unheeded.

EPA RULE CHANGE DISTORTS DATA, FAVORS POLLUTERS: "In a rebuke of the Bush administration," the Environmental Protection Agency's inspector general said in two critical reports that the agency has "exaggerated the nation's air quality and undermined court cases against big electric utilities by devising a rule change that lets them prolong the life of pollution-prone plants." The revised rule, made final last year, "has not been put in effect yet because of legal challenges. But the report concludes that just by issuing the rule, which scuttled the enforcement approach of the Clinton administration, the agency has 'seriously hampered' its ability to settle cases and pursue new ones." In a report on smog, "Inspector General Nikki Tinsley disputed recent comments by EPA Administrator Mike Leavitt that the nation's air quality has steadily improved." The rules change has stalled legal actions against major polluters. Read more on the Bush administration's

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