MOISTURE, % AR 
 ASH, % AR    
 VM,  % AR  
 SULPHUR, % AR  
 NCV, KCAL/KG                                         
 SIZE, MM    OVERSIZE, %    
 CHLORINE, %  
 HGI


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**比较效益:     (PM2.5)
1. 有形效益:
收入:  新原料增加的热能所産生额外电费收入, 舊设备每年折旧率 (避免閒置),
          新建电厂成本每年折旧率, 乾淨能源補助 (
包括省下50%国际綠能排碳税).  

开銷:  发电成本增加 (= 新原料 - 老原料),  投资新排烟设备 / 污染收儲设备

固定:  电费收入(假設不变)

2. 无形效益:
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**清洁煤 (高雄煤) = 好煤 / 無煙煤:比现用劣煤生煙, 二者在規格上所用的清洁煤一定較优,
    假設
二者在同等發热量情况下,  但相对价格可能會增加,  与在排煙比较上省下的污氣百分比,  的 CP值 .
Coal Study                                                http://kaohsiung.us/
Coal Analysis     Moisture Test             Volatile Matter     Coal Heating Values      Emission-NO Comparison    Clean_Coal  


Moisture Test in Coal - Definition & Determination              
Published on September 17, 2017     Amit AFollow   Senior Project Manager|Process En

Introduction:
With the increased prospect of coal preparation plants in India,
there is a lot of discussion about moisture in coal.
Coal moisture is important for handling as well as downstream circuits and there are penalties involved with higher moisture.
Therefore, it becomes important to use and quote the correct moisture terms.
In this article, the total and surface moisture definitions and
laboratory method of determination have been elaborated.
The same is based on Indian standards-Methods of Test for Coal and Coke, IS 1350-1984.
Definition:
1.      Total Moisture: The coal which has been exposed to contact with water
 in the seam or in a washery, or coal wetted by rain, may carry free or visible water.
This water plus the moisture within the material, is referred to as to as total moisture.
2.      Surface or Free Moisture: Free moisture is that quantity of water which is physically adhering to coal.
This is that quantity of water which is more than the moisture holding capacity of a coal.

Determination:
1.      Total Moisture:
The total moisture is determined in two stages:

a.       Stage One (Air drying): 1 Kg of coal sample crushed to pass a square mesh of 12.5 mm is delivered in a sealed container. The sample and the container is accurately weighed to nearest 0.5 g.
The sample weight is measured as difference in weight of sample with container and the weight of the container. The material is then transferred to tray and is sample is air dried at atmospheric temperature in a well-ventilated place free from dust.
The drying is taken to be complete when the change in mass during an hour is less than 0.1 percentage of the sample. The changed mass of sample is recorded.

b.      Stage two (Oven drying): An empty weighing vessel is heated at 108±2 °C and weighed after cooling for 20 min. The air-dried material is crushed to pass 2.9 mm IS sieve. About 10 g of the crushed material is then spread uniformly in the weighing vessel and weighed. The uncovered vessel is heated in the drying oven at a temperature of 108±2 °C. until there is no further loss in mass.
This normally takes 1.5 to 3 h.
The cover is replaced and cooled in a desiccator for 20 min and then weighed.
                     
     Total moisture =X+Y*(1-X/100),
                           Where,
                            X: percentage loss in mass of original in air-drying,
                            Y: percentage loss in mass of air dried sample on oven drying.

2.      Free/Surface Moisture:
The free moisture is determined from total moisture and moisture at 96 % relative humidity and 40 °C using the below formula:
  
       Free Moisture: A-((100-A))/((100-B))*B
         Where,
          A= Total Moisture as determined as described above,
          B= Moisture at 96 % relative humidity and 40 °C.

Moisture at 96 % relative humidity and 40 °C:

It is termed as near saturation moisture and it is free and exclusive of the free moisture. This is measure of moisture holding capacity of coal.
To determine this moisture, 5-6 g of coal sample is uniformly spread in watch glass and placed in conditioner (a desiccator type vessel containing saturated solution of potassium sulphate with solid at bottom) for equilibration for 48 h. The equilibrated sample is then transferred to a weighing bottle from which about 1-1.5 g of coal is taken, through differential weighing of the bottle, in a moisture dish of known weight. The coal is uniformly spread in the dish so that there is not more than 0.15 g of the material per cm2 area. The moisture dish is uncovered in the drying oven and heated at a temperature of 108±2 °C until there is no further loss of mass. This normally takes about 1 to 1.5 h. The cover is replaced, the dish is cooled in a desiccator for about 20 minutes and weighed.

Moisture, percent of mass = (Loss of mass on drying)/(mass of equilibrated sample taken in dish)*100
[Disclaimer: The article has been contributed in personal capacity and do not reflect or represent the views of the any entity, institution and organization. ]

  Volatile matter  

Coal is a readily combustible rock containing more than 50 percent by weight of carbonaceous material formed from compaction and indurations of variously altered plant remains similar to those in peat.
coal      source from:   https://www.engineeringtoolbox.com/classification-coal-d_164.html  

After a considerable amount of time, heat, and burial pressure, it is metamorphosed from peat to lignite. Lignite is considered to be "immature" coal at this stage of development because it is still somewhat light in color and it remains soft.

*Lignite increases in maturity by becoming darker and harder and is then classified as sub-bituminous coal.
After a continuous process of burial and alteration, chemical and physical changes occur
until the coal is classified as bituminous - dark and hard coal.
*Bituminous coal ignites easily and burns long with a relatively long flame.
If improperly fired bituminous coal is characterized with excess smoke and soot.
*Anthracite coal is the last classification, the ultimate maturation. Anthracite coal is very hard and shiny.

Class    Volatile matter1) (weight %)    General description
101    < 6.1    Anthracite   
102    3.1 - 9.0
201    9.1 - 13.5    Dry steam coals    Low volatile steam coals
202    13.6 - 15.0   
203    15.1 - 17.0    Cooking steams coals
204    17.1 - 19.5   
206    19.1 - 19.5    Heat altered low volatile steam coals
301    19.6 - 32.0    Prime cooking coals    Medium volatile coals
305    19.6 - 32.0    Mainly heat altered coals
306    19.6 - 32.0
401    32.1 - 36.0    Very strongly coking coals    High volatile coals
402    > 36.0
501    32.1 - 36.0    Strongly coking coals
502    > 36.0
601    32.1 - 36.0    Medium coking coals
602    > 36.0
701    32.1    Weakly coking coals
702    > 36.0
801    32.1 - 36.0    Very weakly coking coals
802    > 36.0
901    32.1 - 36.0    Non-coking coals
902    > 36.0
1) Volatile matter - dry mineral matter free basis. In coal, those products, exclusive of moisture,
                               given off as gas and vapor determined analytically.  

       揮發性物質 - 無礦物質乾燥基礎。在煤炭中,那些不含水分的產品,
                                 以分析方式確定的氣體和蒸汽釋放出來。

  Anthracite coal creates a steady and clean flame and is preferred for domestic heating.
  Furthermore it burn longer with more heat than the other types.

Typical Sulfur Content in Coal
Anthracite Coal :   0.6 - 0.77 weight %
Bituminous Coal : 0.7 - 4.0 weight %
Lignite Coal :        0.4 weight %
Typical Moisture Content in Coal
Anthracite Coal : 2.8 - 16.3 weight %
Bituminous Coal : 2.2 - 15.9 weight %
Lignite Coal : 39 weight %
Typical Moisture Content in Coal
Anthracite Coal : 2.8 - 16.3 weight %
Bituminous Coal : 2.2 - 15.9 weight %
Lignite Coal : 39 weight %
Typical Fixed Carbon Content in Coal
Anthracite Coal :  80.5 - 85.7 weight %
Bituminous Coal : 44.9-78.2 weight %
Lignite Coal :       31.4 weight %
Typical Density of Coal
1100 - 1800 (kg/m3)
Typical Bulk Density of Coal
Anthracite Coal :
     50 - 58 (lb/ft3), 800 - 929 (kg/m3)
Bituminous Coal :
     42 - 57 (lb/ft3), 673 - 913 (kg/m3)
Lignite Coal :
    40 - 54 (lb/ft3), 641 - 865 (kg/m3)
Typical Ash Content in Coal
Anthracite Coal : 9.7 - 20.2 weight %
Bituminous Coal : 3.3-11.7 weight %
Lignite Coal : 4.2 weight %

Standard grades coal and heating values

Approximate Lower Heating values of standard grades of coal:

Coal Grade    Heating Value
(Btu/lb)    (kJ/kg)
Anthracite    12910    30080
Semi-Anthracite    13770    32084
Low-volatile bituminous    14340    33412
Medium-volatile bituminous    13840    32247
High-volatile bituminous A    13090    30499
High-volatile bituminous B    12130    28262
High-volatile bituminous C    10750    25047
Sub-bituminous B    9150    21319
Sub-bituminous C    8940    20830
Lignite    6900    16077
*Anthracite Coal is very shiny, hard black coal, high carbon content and energy density, repels moisture, for domestic industrial uses, including smokeless fuel
*Bituminous Coal is softer and shiny, moisture content is 8 -20%, possible for coking coals, volatile matter from 16% - 40%,
                             can be used for thermal or metallurgical applications
*Sub-bituminous Coal is soft and black with energy density lower than bituminous coal, most common type for electricity generation
*Lignite Coal is light brown with high moisture content and low energy density, used mainly for electricity generation


     1.798  Btu/lb  = 1 Kcal/kg        1 kcal/kg = 1.8 Btu/lb; 1 Btu/lb = 0.555556 kcal/kg

The energy value of coal, or the fuel content, is the amount of potential energy in coal that can be converted into actual heating ability. The value can be calculated and compared with different grades of coal or even other materials. Materials of different grades will produce differing amounts of heat for a given mass.

While chemistry provides methods of calculating the heating value of a certain amount of a substance, there is a difference between this theoretical value and its application to real coal. The grade of a sample of coal does not precisely define its chemical composition, so calculating the actual usefulness of coal as a fuel requires determining its proximate and ultimate analysis
(see "Chemical Composition" below).

Chemical composition
Chemical composition of the coal is defined in terms of its proximate and ultimate (elemental) analyses.
The parameters of proximate analysis are moisture, volatile matter, ash, and fixed carbon.
Elemental or ultimate analysis encompasses the quantitative determination of
carbon, hydrogen, nitrogen, sulfur and oxygen within the coal.
Additionally, specific physical and mechanical properties of coal and particular carbonization properties

The calorific value Q of coal [kJ/kg] is the heat liberated by its complete combustion with oxygen.
Q is a complex function of the elemental composition of the coal.
Q can be determined experimentally using calorimeters.
Dulong suggests the following approximate formula for Q when the oxygen content is less than 10%:

Q = 337C + 1442(H - O/8) + 93S,
where C is the mass percent of carbon, H is the mass percent of hydrogen, O is the mass percent of oxygen,
and S is the mass percent of sulfur in the coal. With these constants, Q is given in kilojoules per kilogram.


Emission of Nitrogen Oxides Comparison - NOx - with combustion of fuels like oil, coal, propane and more  


1) note that the emission varies widely depending on application temperatures and air/fuel ratios.
     In general - higher combustion temperature and  higher air/fuel ratios increases NOx emissions.
2) zero emission for hydrogen is a theoretically value.
    In practice hydrogen burned in air produces more NOx than natural gas due to the high flame speed
3) catalytic systems common on most modern vehicles reduces NOx
NOx emissions contributes to eutrophication, acidification and the formation of ground-level ozone.

Coal Analysis    

Coal analysis techniques are specific analytical methods designed to measure the particular physical and chemical properties of coals. These methods are used primarily to determine the suitability of coal for coking, power generation or for iron ore smelting in the manufacture of steel.

Contents
1    Chemical properties of coal
1.1    Moisture
1.2    Volatile matter
1.3    Ash
1.4    Fixed carbon
2    Physical and mechanical properties
2.1    Relative density
2.2    Particle size distribution
2.3    Float-sink test
2.4    Abrasion testing
3    Special combustion tests
3.1    Specific energy
3.2    Ash fusion test
3.3    Crucible swelling index (free swelling index)
4    Coal classification by rank
5    References
6    External links
Chemical properties of coal
Coal comes in four main types or ranks: lignite or brown coal, bituminous coal or black coal, anthracite and graphite.
Each type of coal has a certain set of physical parameters which are mostly controlled by moisture, volatile content (in terms of aliphatic or aromatic hydrocarbons) and carbon content.

Moisture
Moisture is an important property of coal, as all coals are mined wet. Groundwater and other extraneous moisture is known as adventitious moisture and is readily evaporated. Moisture held within the coal itself is known as inherent moisture and is analysed quantitatively. Moisture may occur in four possible forms within coal:

Surface moisture: water held on the surface of coal particles or macerals
Hygroscopic moisture: water held by capillary action within the microfractures of the coal
Decomposition moisture: water held within the coal's decomposed organic compounds
Mineral moisture: water which comprises part of the crystal structure of hydrous silicates such as clays
Total moisture is analysed by loss of mass between an untreated sample and the sample once analysed. This is achieved by any of the following methods;

Heating the coal with toluene
Drying in a minimum free-space oven at 150 °C (302 °F) within a nitrogen atmosphere
Drying in air at 100 to 105 °C (212 to 221 °F) and relative loss of mass determined
Methods 1 and 2 are suitable with low-rank coals, but method 3 is only suitable for high-rank coals as free air drying low-rank coals may promote oxidation. Inherent moisture is analysed similarly, though it may be done in a vacuum.

Volatile matter
Volatile matter in coal refers to the components of coal, except for moisture, which are liberated at high temperature in the absence of air. This is usually a mixture of short- and long-chain hydrocarbons, aromatic hydrocarbons and some sulfur. Volatile matter also evaluate the adsorption application of an activated carbon. The volatile matter of coal is determined under rigidly controlled standards. In Australian and British laboratories this involves heating the coal sample to 900 ± 5 °C (1650 ±10 °F) for 7 min.

Ash
Ash content of coal is the non-combustible residue left after coal is burnt.
It represents the bulk mineral matter after carbon, oxygen, sulfur and water (including from clays) has been driven off during combustion. Analysis is fairly straightforward, with the coal thoroughly burnt and the ash material expressed as a percentage of the original weight. It can also give an indication about the quality of coal. Ash content may be determined as air dried basis and on oven dried basis. The main difference between the two is that the latter is determined after expelling the moisture content in the sample of coal

Fixed carbon
The fixed carbon content of the coal is the carbon found in the material which is left after volatile materials are driven off.
This differs from the ultimate carbon content of the coal because some carbon is lost in hydrocarbons with the volatiles.
Fixed carbon is used as an estimate of the amount of coke that will be yielded from a sample of coal.
Fixed carbon is determined by removing the mass of volatiles determined by the volatility test, above, from the original mass of the coal sample.

Physical and mechanical properties
Relative density
Relative density or specific gravity of the coal depends on the rank of the coal and degree of mineral impurity. Knowledge of the density of each coal play is necessary to determine the properties of composites and blends. The density of the coal seam is necessary for conversion of resources into reserves.

Relative density is normally determined by the loss of a sample's weight in water. This is best achieved using finely ground coal, as bulk samples are quite porous. To determine in-place coal tonnages however, it is important to preserve the void space when measuring the specific gravity.

Particle size distribution
The particle size distribution of milled coal depends partly on the rank of the coal, which determines its brittleness, and on the handling, crushing and milling it has undergone. Generally coal is utilised in furnaces and coking ovens at a certain size, so the crushability of the coal must be determined and its behaviour quantified. It is necessary to know these data before coal is mined, so that suitable crushing machinery can be designed to optimise the particle size for transport and use.

Float-sink test
Coal plies and particles have different relative densities, determined by vitrinite content, rank, ash value/mineral content and porosity. Coal is usually washed by passing it over a bath of liquid of known density. This removes high-ash value particle and increases the saleability of the coal as well as its energy content per unit volume. Thus, coals must be subjected to a float-sink test in the laboratory, which will determine the optimum particle size for washing, the density of the wash liquid required to remove the maximum ash value with the minimum work.

Float-Sink testing is achieved on crushed and pulverised coal in a process similar to metallurgical testing on metallic ore.

Abrasion testing
Abrasion is the property of the coal which describes its propensity and ability to wear away machinery and undergo autonomous grinding. While carbonaceous matter in coal is relatively soft, quartz and other mineral constituents in coal are quite abrasive.
This is tested in a calibrated mill, containing four blades of known mass.
The coal is agitated in the mill for 12,000 revolutions at a rate of 1,500 revolutions per minute.(I.E 1500 revolution for 8 min.) The abrasion index is determined by measuring the loss of mass of the four metal blades.

Special combustion tests
Specific energy
Aside from physical or chemical analyses to determine the handling and pollutant profile of a coal, the energy output of a coal is determined using a bomb calorimeter which measures the specific energy output of a coal during complete combustion. This is required particularly for coals used in steam generation.

Ash fusion test
The behaviour of the coal's ash residue at high temperature is a critical factor in selecting coals for steam power generation. Most furnaces are designed to remove ash as a powdery residue. Coal which has ash that fuses into a hard glassy slag known as clinker is usually unsatisfactory in furnaces as it requires cleaning. However, furnaces can be designed to handle the clinker, generally by removing it as a molten liquid.

Ash fusion temperatures are determined by viewing a moulded specimen of the coal ash through an observation window in a high-temperature furnace. The ash, in the form of a cone, pyramid or cube, is heated steadily past 1000 °C to as high a temperature as possible, preferably 1,600 °C (2,910 °F). The following temperatures are recorded;

Deformation temperature: This is reached when the corners of the mould first become rounded
Softening (sphere) temperature: This is reached when the top of the mould takes on a spherical shape.
Hemisphere temperature: This is reached when the entire mould takes on a hemisphere shape
Flow (fluid) temperature: This is reached when the molten ash collapses to a flattened button on the furnace floor.
Crucible swelling index (free swelling index)
The simplest test to evaluate whether a coal is suitable for production of coke is the free swelling index test. This involves heating a small sample of coal in a standardised crucible to around 800 degrees Celsius (1500 °F).
After heating for a specified time, or until all volatiles are driven off, a small coke button remains in the crucible. The cross sectional profile of this coke button compared to a set of standardised profiles determines the Free Swelling Index.

Coal classification by rank
See also: Coal § Ranks
Several international standards classify coals by their rank, where increasing rank corresponds to coal with a higher carbon content. The rank of coal is correlated with its geologic history, as described in Hilt's law.

In the ASTM system, any coal with more than 69% fixed carbon is classified by its carbon and volatiles content.
Coal with less than 69% fixed carbon is classified by its heating value.
Volatiles and carbon are on a dry mineral free base; heating value is based on the moisture content as mined, but without any free water.

The ISO has a coal ranking system that also ranks coals; the sub-divisions do not align with the ASTM standard.


ASTM Coal Classification [1]
Class    Group    Fixed Carbon %
Dry, mineral free    Volatile Matter %
Dry, mineral free    Heating Value MJ/kg
Moist, mineral free
Anthracite    Meta Anthracite    >98    <2     
Anthracite    92-98    2- 8     
Semi Anthracite    86- 92    8 - 14     
Bituminous    Low Volatile    78-86    14-22     
Medium Volatile    69-78    22-31     
High Volatile A    <69    >31    >32.6
High Volatile B              30.2-32.6
High Volatile C              26.7-30.2
Subbituminous    Subbituminous A              24.4-26.7
Subbituminous B              22.1- 24.4
Subbituminous C              19.3 - 22.1
Lignite    Lignite A              14.7 - 19.3
Lignite B              <14.7


What is "Clean Coal"?    

"Clean coal" is when special pollution control equipment is installed for a coal plant,
which captures all of the carbon dioxide emitted by power production.

Then you do something with that CO2 to keep it out of the atmosphere.
Proponents aren't real clear on the storage/disposal issue.
The main suggestion is injecting it underground for permanent sequestering or to boost the productivity of oil wells,
but the geology required for this to work is not all that easy to find.
Known usage and disposal capacity is not anywhere near large enough to convert most coal plants to clean coal systems.
Until that issue is resolved, carbon capture is not a viable climate change prevention strategy.
Maybe we could use it to grow algae or something? Ideas needed.

The other issue with clean coal is that it is wicked expensive.
The only real reason to use coal power is that it's cheap and easy to build,
but doubling the power plant's process equipment adds a huge up-front cost as well as increases running costs and
significantly reduces net power production. Natural gas, wind, and nuclear are all cheaper at that point so why go coal at all?

Yahya Elamrani
Yahya Elamrani, studied at ENSA De Tanger
Answered Dec 17, 2016
Originally Answered: Is "clean coal" real?
What is clean coal?

It is a whole range of technologies ,including carbon capture utilization and storage (CCUS) that captures carbon emissions
 from sources like power plants. That CO2 is then stored or used so it doesn’t enter the atmosphere.

Does it work?

So far, not well. Clean coal technology has not been widely deployed at a large scale in the world,
and many clean coal projects have ended in failure.
There are also ongoing debates about whether several common deployments of the technology actually reduce overall emissions.

Will clean coal ever work?

Experts from places like Oxford University and the Clean Air Task Force say it must.
Globally, coal is typically the cheapest, most readily available fuel—especially in developing countries—and coal consumption is expected to rise 18 percent by 2040.
Without carbon capture, burning all that coal will likely blow through the 2 degree warming threshold agreed in the the COP 21 Agreement.

So, in summary, getting to a place where clean coal is cost-effective and deployable on a large-scale appears to be a ways off.
But it’s probably too early to consider it a false prophecy.
There are some promising projects out there and money is continuing to pour into clean coal research.

Alan Cruickshank
Answered Dec 23, 2013
Clean coal is a Myth
- Thanks to David for his excellent answer to this end.

But what we all have to remember is that Clean Energy is a Myth.

Most of the energy debate is done without facts and with more hot air and politics than
 the power stations they debate about. Let's look at our current options for power:

Coal - Respiritory illness, huge open cast mining, releases carbon and other gasses.
Gas - (Shale or otherwise), releases carbon and other toxic gasses.
Oil - See gulf of mexico for a start.
Nuclear (fission) - Radioactive waste
Nuclear (fusion) - Currently Energy Negative (costs us more energy than it makes)
Solar (photovoltaic)- Currently energy negative. (Manufacturing process for the cells currently uses more energy than they will generate in their lives).
Wind - Uses Carbon Fibre (very energy intensive manufacturing process), Uses large amount of land, or uses huge amounts of fuel to service and maintain (helicopters) at sea. Also uses large amounts of Steel (see coal).
Tidal - Large amounts of Steel (see coal). (otherwise pretty good, but power output is too low to sustain a whole country).
Geothermal - Constrained to very small areas of the world.
Hydro - Destroys large areas of habitat (see Three Gorges dam, or recent Hydropower developments in Iceland). Uses lots of steel (see coal) and concrete (see gas).
Biomass - Releases carbon, uses large areas of productive land which could otherwise generate food. Destroys Rainforest.

None of these are an obvious viable solution to the global energy crisis. None of these sources of energy are "clean". All have a cost.

David Clark, Building businesses beyond lighting
Updated Oct 10, 2012
A myth.

As Jim pointed out it, originally applied to forms of coal containing fewer sulphur compounds, in order to reduce particulate sulphur dioxide emissions which lead to acid rain, soil leaching, chemical erosion etc.
As these emissions were reduced it came to be more associated with the technologies that improved the efficiency of coal burning and reduced the emission of particulates (such as pm10s), sulphur, mercury such as IGCC.
As pointed out this does not remove CO2, radioactive isotopes etc but is definitely cleaner".

This all however ignores the fact that Coal, per TWh, has a higher death rate due to
mining, illness and respiratory diseases than other sources of energy. Clean coal is still not very clean.

In summary, to quote Mike:

"Fundamentally, "clean coal" is a marketing term invented by the coal industry to protect its historic and ongoing massive revenue streams."         aka, a myth.

(IMHO "Clean Coal"does not strictly include Carbon Capture as Storage (CCS) technologies, which is a separate matter)
2.5k Views · View Upvoters
 
Daniel Helman, works at Ton Duc Thang University (2017-present)
Answered Oct 9, 2012
Let me add to @Jim Gordon's answer:

Coal starts out as wood, and through burial and millions of years, turns into a rock which people burn.
 It is high in hydrocarbons.  The low-sulfur coal is generally from plants in a freshwater setting (before it turned to a rock) while the high-sulfur coal formed in saltwater lagoons, etc. 

The low-sulfur coal has been given the name "Clean Coal" by the coal industry, for marketing purposes. 
Burning regular coal produces a lot of sulfur dioxide, which turns into acid rain (that is, sulfuric acid), and is responsible for deforestation and other devastation.

As far as I know, @Ryan Carlyle's and @Mike Bernard's answers contain wonderful information, but these technologies can be (and are) applied to both types of coal.

Ryan Carlyle
Could you provide a source for "clean coal" meaning low-sulfur rather than carbon-capture? You're...

Michael Barnard, Low-carbon Innovation Strategist
Updated Apr 26, 2017
In addition to Ryan Carlyle's bang-on answer, there are a couple of technologies which allow coal to be burned much more completely, generally through crushing into a powder and funnelling into an extremely hot furnace with specific airflow, or even pure oxygen, and catalysts.

These still emit all of the CO2e which must be captured, shipped and sequestered at great expense.
They promise to emit much lower volumes of fly-ash, particulate emissions and sulpher / etc emissions with much less extensive post-processing of effluents required.

These have not progressed beyond prototype stages due to continuing major downfalls and the cheapness of other forms of electrical generation, especially natural gas in the USA, but also wind and soon solar.

It is worth noting that the dominant form of sequestration in use today is in enhanced oil recovery (EOR) efforts in old oilfields. In this model, CO2 is pumped into one end of an oilfield at high pressure and it pushes oil out the other end.
After all recoverable oil is retrieved, both ends are capped. Of course, this is just pushing some carbon below ground to get more carbon above ground to burn, so it's not helping as much as it might think.

Fundamentally, "clean coal" is a marketing term invented by the coal industry to protect its historic and ongoing massive revenue streams.

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Mike Huff, former Retired CPO
Answered Jul 20, 2018
Coal is sold by the BTU per ton. Coal can have a lot of moisture and noncombustibles such as pyrites and clays (Powder River Coal).
If you can remove the moisture and impurities, you raise the BTUs per ton as thus can use less coal.

In the early 1980s, the EPA and DOE granted the SYNCOAL research facility in Colstrip, Montana that would ‘clean' the coal.
Heating the coal to over 700 degrees in an oxygen free atmosphere the coal would pop, separating the coal from moisture and the noncombustibles. The finished produced could be burned as is or blended to existing coal to increase thermal efficiency. Increased efficiency equalled less coal burned, thus less pollution.
The system worked but there were no buyers and the project was shelved.

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Mike Winslade
Answered Aug 24
What is "clean coal"?

It’s an idea that coal-sourced power can somehow be enhanced by making it even less affordable.
And so far it really is as dumb as that sounds.

Add some carbon capture (a technology that hasn’t been shown to work commercially) to the smokestacks of the power plant.
Take the carbon that has been captured and re-use it (a technology that hasn’t been shown to work commercially)
or bury it (a technology that hasn’t been shown to work commercially). What could possibly go wrong?

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Mohd Salim, works at Sustainable Technology
Answered Dec 18, 2016
Originally Answered: Is "clean coal" real?
Clean coal would be one where in there is no harmful emissions of any sort.
That would mean that all the flue gases are scrubbed of sulphides, arsenic, mercury and other metal vapours and gases.
The CO2 that would be left behind needs to be then stored by carbon sequestration methods.
An expensive process that most coal fired power plants currently don't do or don't plan on doing since these are huge capital investments to the existing infrastructure.

Also clean coal would require that all the soot and ash to be processed further to remove all contaminants and proper disposal of this as well.

The capital required to do all of this to achieve clean coal would likely be more expensive than shifting to a renewable source like solar or wind.

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Bastien Koert, studied at Ryerson University
Answered Aug 21
Originally Answered: What is 'Clean Coal' that you hear so much about from President Trump?
From Wikipedia

Coal pollution mitigation, often referred to by the term clean coal, is a series of systems and technologies that seek to mitigate the pollution and other environmental effects normally associated with the burning (though not the mining or processing) of coal,
which is widely regarded as the dirtiest of the common fuels for industrial processes and power generation - Coal pollution mitigation - Wikipedia

The theory is that the pollution caused by burning coal can be reduced by adding technology to the burning process in the form of CO2 scrubbers and other technologies.

This misses the fact that coal powered electricity generation is in decline in the USA because better alternatives exist like gas and hydro. The coal industry is almost obsolete.

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Wilson Chin
Wilson Chin, CEO, Rich Coal Indonesia
Answered Dec 30, 2015
Jim Gordon's answer is short and sharp. Clear cut. All other answers are also with merit.

Lets look at this dirty word. Some people refer to charcoal as wood coal.
I do not want to say whether the term is wrongly used or not since I know what it is.
There is brown coal, black coal, hard coal, soft coal, bituminous, sub-bituminous coal, anthracite, lignite etc and
no-one unless you are in the industry would know what they all are.

To someone who is climate change and environmentally sensitive, he would be able to relate better to clean, cleaner or cleanest depending on emission of sulfur dioxide, carbon dioxide, carbon monoxide and perhaps particles like Particle matter (PM2.5),
all of which are bad for health except CO2 which might be bad for planet earth or earthlings generations down the road.
As for sulfur, EPA has already classified 1% as the benchmark, below which is termed low sulfur coal and above, high sulfur coal.
So if your sulfur is above 1% you would not call it clean even if other emissions are low.

Unfortunately EPA has yet to come up with a standard for the other impurities.
There are however terms used in the industry with their own standards like eco-coal.

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Jose Melendez
Answered Jul 13, 2017
Jose Melendez (edited)

Want clean coal? Mash up and test:
https://www.youtube.com/watch?v=cDoUBJbyZ-8
https://www.youtube.com/watch?v=ERRMoHfrjAI
https://en.wikipedia.org/wiki/Co...
https://www.youtube.com/watch?v=J9b0J29OzAU
https://www.youtube.com/watch?v=CBqx8t-YLrw

ihydrocarbon@gmail.com

Psos Pikasa
Answered Apr 5, 2018
The term "clean coal" has been applied to many technologies, ranging from wet scrubbers, which remove sulfur dioxide from coal-generated gas, to coal washing , which removes soil and rock from coal before it's sent to a factory.

Hypothetically, the term could be applied to anything that makes coal plants more efficient, like digitization .
CCS technology has been around since the 1980s. While the other technologies mentioned above
cut down on sulfur dioxide and coal ash (which are important), CCS is meant to handle the big environmental nightmare,
the heat-trapping gas largely responsible for global warming, carbon dioxide (CO2)

However, when people talk about clean coal these days, they're typically talking about something called carbon capture and storage (CCS).

In either process there are multiple points at which CCS technology could intervene.
Dirgh Diamond One of the Leading Diamonds Manufacturers in India Loose Certified Diamonds In India Diamonds Suppliers & Wholesalers in India One such point is called pre-combustion.

At this stage, an air separation unit produces a stream of almost-pure oxygen, which flows into a coal gasifier.
Gasifiers are essentially tanks that produce synthetic gas mixtures known as syngas.
The oxygen in this coal gasifier reacts with fuel to create a syngas made up of hydrogen,
carbon monoxide, water, and CO2.
(This form of syngas is nothing new: invented in the 1790s by William Murdoch, in the 19th century it was used to power gas lights in many towns and gained the nickname "town gas.")

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Randolph Richards, MD from University of Tennessee Health Science Center (1989)
Answered Aug 21
Originally Answered: What is 'Clean Coal' that you hear so much about from President Trump?
Well it is just a Euphemistic label. He wants to support coal. It’s not a real thing not in the way that he markets it.
 Clearly you can scrub off a lot of the toxic chemicals but the carbon dioxide is there.
It’s basically bullshit and he doesn’t even really understand any of it.
It is just a good sounding bullshit smokescreen. Redmeat for the base.

Jim Gordon
Jim Gordon, iconoclast, thinker outside of boxes, seeker of novelty, bibliophile, gastronome
Answered Oct 9, 2012
Ah, recency! 

"Clean coal" is the term for coal that is low in sulfur compounds, which USED TO BE the worst type of pollutants. 
The sulfur compounds created "acid rain," which motivated government and industry in favor of technology that would remove all sorts of pollutants from the waste stream that ensues from using any kind of coal. 
David Clark's answer to What is "clean coal"? isn't without merit.
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Donald Schmitt, 36 years with snout in government trough.
Answered Aug 21
Originally Answered: What is 'Clean Coal' that you hear so much about from President Trump?
Clean coal are are systems and technologies used to reduce the pollution from burning coal. They are applied to the power plants burning coal.

Coal pollution mitigation - Wikipedia

Jesse Pollard, programmer/analyst/administrator from way back
Answered Dec 17, 2016
Originally Answered: Is "clean coal" real?
No.

What is referred to as “clean coal” is called anthracite.
It is “cleaner” as it is more compressed that the basic coal (bituminous coal), and doesn’t crumble as easily.
 It also tends to leave less ash after burning.

Unfortunately, it still releases carcinogens to the environment.

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Thomas Irwin
Thomas Irwin, studied at Cum Laude Graduate M.S. Environmental Science Rutger´s University
Answered Dec 17, 2016
Originally Answered: Is "clean coal" real?
Clean coal is a huge oxymoron.
Coal has never and will never be a clean fuel.
You can add all sorts of expensive engineering to clean coal up.
However, all of that engineering has a cost that must be borne by the sale of coal.
As long as there is wind, sun, oil and natural gas we might as well leave that nasty fuel in the ground.



Definitions As Received (ar): includes Total Moisture (TM)
Air Dried (ad): includes Inherent Moisture (IM)only
Dry Basis (db): excludes all Moisture
Dry Ash Free (daf): excludes all Moisture & Ash

The Proximate Analysis of any coal i.e. the % content of Moisture,
Ash (A), Volatile Matter (VM), Fixed Carbon (FC)– also Sulphur (S)and Calorific Value (CV)– can be expressed on any of the above bases.