COAL COMBUSTION AND FUELS

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COMBUSTION AND FUELS

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CARBON AND COAL

Carbon is a chemical element.

Coal is a solid fossil fuel

Carbon can exists in a certain allotropic forms including : a) diamond b) graphite

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RESOURCES OF CARBON IN NATURE

a) freely in small amounts (graphite, diamond) b) mainly connected in numerous chemical

compounds:

- carbonates (CaCO₃, MgCO₃ and in others), - carbon dioxide in air (CO₂),

- in organic compounds, fossil fuels:

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ORIGIN OF COAL

• The origin of coal is organic

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NATURE OF COAL

•Coal is described as an organic sediment •It is a combustible rock: biolite

•The major chemical elements in coal are: carbon, hydrogen and oxygen.

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COAL FORMATION

•The process of coal formation from organic compounds includes two distinct phases:

biochemical and geochemical:

plant material – peat – lignite biochemical phase

lignite – bituminous coal – anthracite Geochemical phase

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HISTORY OF COAL

Age (years) Type of coal from 2 mln to now Peat before100 mln before 70-2 mln Brown coal Lignite 300-200 mln Bituminous coal

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COAL PETROGRAPHY

The goal of coal petrography:

understand how coal was constituted

implement of most productive use of coal

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PETROGRAPHIC STRUCTURES OF COAL

• Lithotypes (observed with the unaided eye):

vitrain, clarain, durain and fusain

(bright, halfbright, dull and black (gray-black) and porous and friable)

• Microlithotypes (observable with the microscope)

• Macerals:

– vitrinite group,

– exinite group,

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Podziałmakroskopowy Podziałmikroskopowy Skały Litotypy Mikrolitotypy Grupa

macerałów Macerały Submacerały

Odmiany

macerałów Kryptomacerały

Węgiel

Witryn (węgiel

błyszczący) Witryt V

Witrynit V Telinit Kolinit Witrodetrynit Telenit 1 Telenit 2 Telokolinit Żelokolinit Desmokolinit Korpokolinit Kordaitotelinit Fungotelinit Ksylotelinit Lepidofitotelinit Sigillariotelinit Kryptotelinit Kryptokorpo-kolinit Klaryn (węgiel półbłyszczący) Klaryt V+E Witrynetryt V+I Trimaceryt V+I+E Liptyt E Egzynit (Liptynit) E (L) Sporynit Kutynit Rezynit Alginit Liptodetrynit Tenuisporynit Krassisporynit Mikrosporynit Makrosporynit Pila–Alginit Reinschia–Alginit Duryn (węgiel matowy) DurytI+E Fuzyn (węgiel włóknisty) Inertyt I Semifuzyt Fuzyt Sklerotyt Łupek

palny Łupek palny

Karbo– mineryt Karbargilit Inertynit I Mikrynit Makrynit Semifuzynit Fuzynit Sklerotynit Inertodetrynit Pirofuzynit Degradofuzynit Fungosklerotynit Plektenchyminit Korposklerotynit Pseudo-korposklerotynit Karbankeryt Karbosilicyt Karbopiryt Karbopolimineryt Skała

płonna Skała płonna Skała płonna Węgiel

Węgiel sapropelowy

Kennel Boghed

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EXAMPLES

OF

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COAL CONSTITUENTS

Coal consists three ingredients:

- organic matter (combustible),

- mineral matter, - moisture.

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CHEMICAL STRUCTURE OF COAL (organic matter)

Benzene ring

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typical structures of coal rank of coal

lignite

coals for power generation

coking coal

anthracite

higher carbonization higher compression lower oxygen content

EVOLUTION OF COAL STRUCTURE

WITH THE RANK

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REASONS FOR CLASSIFICATION OF COAL

•variable characteristics of coal (complex material)

•different boiler furnaces in use,

•applications in chemical technology and metallurgy,

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STANDARDS USED IN COAL CLASSIFICATION

Origin and parameters of coal: (Polish Standards PN)

– upper caloric value UCV ( in Polish Q_s:PN-81/G-04513 or PN-ISO 1928:2002),

– blow up index (PN-81/G-04515),

– volatile matter content VM (PN-G-04516:1998), – dilatometric index (PN-81/G-04517),

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ANALYSIS OF COAL

Ultimate analysis: – (wt%):

- elements content: C, H, O, S, N, P, ...(wt%)

Proximate analysis – content (wt%) of:

- moisture M, - ash A,

- volatile matter VM.

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STATE OF SOLID FUELS

Analytical of air-dry (a), when moisture in coal is in equilibrium with moisture of ambient air,

Dry (d lub wf), after 2-3 hours of drying at the temperature of 105-110 o_C,

Dry and ash free (daf lub waf).

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Example of A and Qi in raw state (r), in dry state (d) and dry-ash-free state (daf) of lignite

26203 23334 12.5 9194 5.7 56.0 Max. 25454 22827 10.3 8949 4.7 54.9 Medium 25268 22272 8.3 8756 3.7 53.9 Min. kJ/kg kJ/kg % kJ/kg % % Qdaf i Qd i Ad Q r i Ar W r t Value

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Calculations of results of analysis of coal (solid fuels)

Coefficient of conversion: Type of conversion Raw r Analytical a Dry d

Dry ash free

daf From raw state r 1 ₁−_Wr − _Wa 1 r W − 1 1 r r A W − − 1 1 From analytical state a ₁ 1−W r +Wa 1 _a W − 1 1 a a A W − − 1 1

From dry state d

1 1−Wr 1 1−W a 1 _d A − 1 1

From dry ash free

state daf ₁ 1−W r − Ar 1 1−W a − Aa 1 1− Ad 1

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COAL CLASSIFICATION ACCORDING TO ORIGIN AND COAL RANK

Coal class Content of C

Peat: 52-60%

Lignite: 58-77%

Bituminous coal: 76-93%

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POLISH CLASSIFICATION OF COAL

• In Poland coals are divided on:

– groups (classes)

– types,

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GROUPS (CLASSES)

•Group is described by the two-digit number: - first digit determines the group

according to the coal rank,

- the second digit determines the position in the group.

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COAL GROUPS (CLASSES)

• Wood: 01-09

• Peat: 11-19

• Lignite: 21-29

• Bituminous coal: 31-39

• Anthracite: 41 and higher

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Coals for power genera-tion Type of coal Classifying measurements Applications of coal Volatile matter content Vdaf PN-81/ G-045516 Coking ability RI PN-81/ G-4518 Dilato-metric index PN-81/ G-04517 Blow up index SI PN-81/ G-04515 Upper caloric value Qdaf PN-81/ G-04513 Name Mark % % kJ/kg Flame coal 31.1 _More than 28 Over or equal to 5 Without standar d Without standar d Over or equal 31000

Do wszystkich typów palenisk pyłowych; do czadnic

pulverised coal furnaces; gas generatrors 31.2 Over 31000 Gaseous -flame coal 32.1 More than 28 Over 5 to 20 Without standard

Do wszystkich typów palenisk; do wytlewania i do czadnic

all types of coal furnaces; gas generatrors

32.2 Over 20 to 40

Do palenisk rusztowych, komorowych i wszystkich typów palenisk pyłowych; węgiel do wytlewania i do gazowni

grate furnaces, pulverised coal furnaces; gasgeneratrors

Gaseous coal 33 More than 28 Over 40 to 55 Do palenisk rusztowych i wszystkich typów palenisk pyłowych; do pieców przemysłowych o szczególnych wymaganiach; do gazowni i do mieszanki do produkcji koksu w koksowniach

grate furnaces, pulverised coal furnaces, industrial kilns; gas generatrors; coke production

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Coal sorts

sort

group / name /symbol

grain size upper / lower

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CHARACTERISTIC OF MAJOR

COMPONENTS OF COAL

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COAL COMPONENTS

Coal is combined with three components: • Moisture (M)

• Mineral matter (A)

• Combustible (organic) matter

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MAIN ELEMENTS IN COAL

Organic matter:

- basic: C and H,

- important: O, S, N and P

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Thermal decomposition of coal COAL PYROLYSIS

Coal pyrolysis is thermal decomposition of coal at the temperature of 300-600 °C, depending on the coal type. Results of pyrolysis:

- evaluation of volatile matter - remaining char.

Volatile matter

Char

Coal particle

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organic matter ash

mineral matter

w coal in dry state

c + h + o + n + s + a + w = 1

coal in air-dry (analytical) state

coal in raw state

char volatile matter

fr o m d ec o m p o si ti o n o f m in e ra l m a tt e r in h er en t m o is tu re in a ir -d ry s ta te tr an si en t m o is tu re (s u rf a ce m o is tu re )

COAL COMPONENTS

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ANALYSIS OF ORGANIC FUELS

Fuel C H O N + S VM content, % Wood Peat Lignite Hard coal Anthracite 50 58 70 82 94 6 5,5 5 5 3 43 34,5 24 12 3 1 2 0,8 0,8 trace 75 65 50 35 5

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INORGANIC MATTER IN COAL

(2-60%)

Inorganic components in coal are classified:

- primary vegetable ash (inner m.m. – inherent plant matter

that formed coal)

- secondary minerals (outer m.m.: rocks and sand and

clay) (mineral matter deposited by wind and water or by percolation of water through the seams)

Inorganic matter of the primary type is dispersed in coal – impossible to remove by the mechanical methods.

Inorganic matter of the secondary type usually consists of minerals present in surrounding of a coal deposit.

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SECONDARY INORGANIC MATTER

Main constituents (mainly minerals) of the secondary inorganic matter:

- quartz,

- clay minerals (kaolinite, illite, ....) - oxides (hematite)

- carbonates (dolomite, calcite,siderite, ...) - sulphides (pirite, marcasite, zink suphide, ...) - phosphates (apatite)

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MOISTURE IN COAL (5-60%)

Total moisture includes:

- air-dry loss moisture (transient) (loss of weight resulted of

partial drying of coal) (not linked to organic matter, can be removed by drying at room temperature – air-dry state or analytical (a)),

- inherent moisture (is connected with the substance of coal, and

can be removed from coal by heating it at the temperature in the range of 105-110 o_{C (dry state (}_d_))).

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SOME ELEMENTS IN COAL

Carbon C: 50-93%

Oxygen O: 1-3%

Sulfur S: 1-5 (11)%

in sulphites (FeS₂)

in sulphates (CaSO₄, FeSO₄)

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Polish bituminous coal for heat and power production (type 31-33) Coal mining region LCV kJ/kg Ash content % Sulphur content % Moisture % Jaworznicki Mikołowski Dą browsko-siemianowski Katowicko-chorzowski Rybnicki Lubelski 18 400 20 100 21 800 23 500 20 100 18 850 20−24 20 20 20 20−27 25 1.25−1.5 1.5 0.6 0.8 0.7−1.3 1.2 16−20 12 8 5 9 9

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CHARACTERISTICS OF POLISH BITUMINOUS

COALS TYPE 31-33

LCV (W_u) = 18-25 MJ/kg

A = 7-25%

S = 1.2%

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Polish lignites

Coal mining region LCV kJ/kg Ash content % Sulphur content % Moisture % Turoszowski Koniński Pątnowski Adamowski Bełchatowski 8 400 9 200 9 200 8 000 8 800 12,2−20 5,8−6,3 10,6 9,8 10,6 0,60 0,25−0,35 0,78 0,25 0,60 42−50 50−54 50 50 50

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CHARACTERISTICS OF POLISH LIGNITES

LCV (W_u) = 5.6-11.7 (aver.8.5) MJ/kg

A = 4-25 (aver.12.0)%

S = 0.2-1.7 (aver. 0.7)%

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BITUMINOUS COAL-FIELDS IN POLAND

Coal basins: - Upper Silesia, - Lower Silesia - lubelskie Reserves: 30 bln Mg Total reserves: 100 bln Mg

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Reserves and total reserves of bituminous coal in Poland

Basin Reserves, % Total reserves, %

GZW DZW LZW 88.2 11.1 0.7 43.7 56.1 0.3

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LIGNITE COAL-FIELDS IN POLAND

Coal basins: - adamowsko-konińskie - bełchatowskie (Szczerców) - turoszowskie - sieniawskie. Total reserves: 40 bln Mg Reserves: 13-14 bln Mg Operational reserves: 3.5 bln Mg

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Deposits with coal mines Other discovered deposits

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RESERVES AND TOTAL RESERVES OF COAL

Fuel World bln Mg Poland bln Mg Bituminous coal reserves total reserves 630 7000–14000 30 130 Lignite reserves total reserves 250 880 12–13 30–40

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Type of coal World 109 _Mg Poland mln Mg Bituminous (hard) 4.2 84 (2009) Lignite 0.944 64

Yearly production of coal in Poland and in the world

10 mln Mg 7 mln Mg

Import Export

Polish import/ export of hard coal in 2008

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Reserves and production of bituminous coal

in Poland

R e s e rv e s ( x 1 0 9 t) 1989-2005 P ro d u c ti o n ( x 1 0 6 t) Year

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Production/export Amount, mln Mg Production Import 100.4 2.7 The use:

- production of other fuels - direct use

- export

62.0 20.0 23.0

Production of lignite was approx.58.2 mln Mg in 2002 r. and it was used for electrical power production.

Bituminous coal

Lignite

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Bituminous coal price in USD/tonne

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Costs of heat and electricity generation in Poland

Cost of heat generation PLN per 1 GJ

Cost of electicity generation PLN per 1 MWh including CO₂capture from lignite from hard coal from natural gas from lignite from hard coal from natural gas