MANUFACTURED FUELS

ByAlfa Sharma

M.Tech (GET), 1st Semester

Centre For Green Energy Technology

Pondicherry University

INDIA-60514

CARBONISATION• The process of converting coal into coke is called as

carbonization of coal.• When a coking coal is heated in the absence of air, the

porous, hard and strong residue left is called coke.• Coke is white, lustrous, dense porous coherent mass.

Depending on the behavior of coal, when heated in the absence of air, the coal is classified into;

(i) Non-coking coal which undergoes practically no fusing effect and also called as free burning coal.

(ii) Coking coal which gives porous, hard and strong residue after heating in the absence of air. The residue is used for metallurgical purposes and is known as coke. They are quite strong and not crushed under the weight of ore, flux and coal in big furnaces.

Properties of Coke• Hard, Porous, Carbonaceous materials• Three important properties of coke; i)Purity - Ascertained by moisture,ash, sulphur,phosphorus content

ii)Strength -By Shatter and Micum test

iii)Reactivity -By specified minimum porosity calculation -It is also measured with respect to air,CO2,Steam,Sulphur

CARBONISATION

LTC MTC HTC (at600˚C) (at800-1000˚C) (at1000-1400˚C)

Low Temp.Carbonisation(LTC)

Generally used for production of soft coke or char or

semi coke.

High temperature gradient was employed for

carbonisation in reasonable time as coal a poor conductor.

Normally it is a economical upgradation method of low

rank coal like lignite.

The major products are semicoke, low temp. liquor,crude

low temp.spirit and gas.

Karrick Process Carboniser Flow sheet

LTC(continued)…….

Typical yield temp.is 600˚C Typical Yields(on dry basis)

Semi-coke(clean fuel) 75-80%

Tar 9-12%

Liquor 5-7%

Gas 100-120Nm/tonn

Properties of Gas by LTC

• Specific gravity(in reference to air) - 0.6• Calorific value - 6500Kcal/Nm 3

Composition in percentage(%)

CO2 4.0

CO 7.0

H2 33.0

N2 7.0

CnHn 4.0

CnH2n+2 45.0

Application of Products by LTC• Semicoke as highly reactive produce smokeless flame ideal

for domestic solid fuel.

• Also semicoke &char utilized for gasification into fuel or synthesis gas for chemicals and fertilizers industries.

• The gas obtained is rich in HC’s(hydrocarbons)&poorer in H2 compared to that obtained by HTC(high temp.carbonisation).

• Calorific value is high although yield is low.

• Alternate source to biomass used for domestic hearths providing clean fuel concept.

HIGH TEMP.CARBONISATION(HTC)• Commercially practised in coke oven for coke and in gas retorts

for gas.

• Coke oven is of two types;

a. Beehive type (coke completely burnt)

b. By-product slot type (coke by product obtained)

• Similarly gas retorts are of three types producing coal gas;

a.Horizontal type retort

b.Intermittant vertical retort

c.Continuous vertical retort

(Beehive Coke Oven)

(Horizontal Gas Retorts)

Typical Yields from HTC

Products Amount(in %)

Coke 78-80

Tar 3.0

Crude benzol 0.8

Ammonium Sulphate 1.0

Coke oven gas 330Nm3 /tonne

Coke Oven gas Composition

Constituents Amount(in%)

H2 54

CH4 28

CO 7.4

N2 5.6

CO2 2.0

O2 0.4

CnHm 2.6

Gross calorific value =5020Kcal/Nm3 (dry condition) =4450Kcal/Nm3 (wet condition)

Difference between LTC &HTCCharacteristics Low Temperature

CarbonisationHigh Temperature Carbonisation

1. Heating temperature 500-7000C 900-1200°C2. Yield of coke 75−80% 65−75%3. Volatile matter content 5−15% 1−3%4. Mechanical strength Poor Good5. Calorific value 6500−9500 kcal/m3 5400−6000 kcal/m3

6. Quantity of by-product gases

130−150 m3/tone 300−390 m3/tone

7. Coke produced Soft Hard8. Smoke produced Smokeless Smoky9. In gas, percentage of(a) Aromatic hydrocarbons(b) Aliphatic hydrocarbons

LowerHigher

HigherLower

10. Uses Domestic Metallurgy

BRIQUETTE

• A briquette is a block of flammable material used as fuel to start and maintain a fire.

• Common types of briquettes are charcoal briquettes and biomass briquettes.

Parameter Value

Briquette density, t/m³ 1.0-1.2

Heat content, MJ/Kg 19.3-20.5

Ash content, % 0.5-1.5

Briquetting• Briquetting consists in applying pressure to a mass of particles

with or without addition of binders& converting to agglomerate.

• Main objective is to convert low grade solid fuel to one of higher quality.

(Generalised Briquetting Process)

Briquetting of Lignites• Briquetting used because of structural quality & as is

obtained as fines during mining.• Briquetting requires no binder & comparatively low pressure

suffices compaction of particles.• Some important parameters for briquetting;

Particle size 8mm(after crushing from

250mm)

Moisture 9-11%(reduced from50-56%)

Pressure 1000kg/m³

Optimum temperature 70˚C

Briquetting of Bituminous Coal• Briquetting of fine grade coals like bituminous takes place

with binders like coal,tar,pitch,petroleum bitumen .

( Typical Briquetting Process)

Parameters for briquetting:-

Size 80%lessthan0.5 mm(coal)

93%less than 0.88mm(pitch binder)

Moisture content 2-4%

Briquetting pressure 150kg/m³

Optimum temperature 150-160˚C

Pitch content(binder) 7-8%

THANK YOU`