Solid Fuels

Question 1

It has been used as a fuel since ancient times. However, due to
large scale deforestation, wood is no longer used except in forest areas where _______ is available at a very low cost.

Answer 1

Wood

Question 2

Normally it is used in an air-dried condition
with 10-15% moisture content. Its heating value is directly proportional to the water content. The combustible part of _______ is mostly made up of cellulose and lignin having traces of mineral ash. Resins and waxes are also present.

Answer 2

Wood

Question 3

The calorific value of air-dried wood is about

Answer 3

2,500 to 4,500 kcal/kg

Question 4

It burns with a long and no smoky flame, leaving a small amount of ash. Although ash content is low, the oxygen content is very high. This makes, even dry wood, a fuel of low calorific value.

Answer 4

Wood Charcoal

Question 5

is largely used as a domestic fuel.

Answer 5

Wood Charcoal

Question 6

_______ ______ is obtained by destructive distillation of wood. The major use of ______ _________ is for producing activated carbon which finds extensive application for decolorization in sugar industry.

Answer 6

wood charcoal, wood charcoal

Question 7

It is regarded as a fossil fuel produced from the plant debris under conditions of high temperature and pressure over millions of years.

Answer 7

Coal

Question 8

is a fossil fuel similar to natural gas and oil but is in a solid rock form

Answer 8

Coal

Question 9

is highly complex organic material having varying amount of water, together with nitrogen and sulfur.

Answer 9

Coal

Question 10

During this stage, the plant materials were attacked by various microorganisms. The end product of this state is peat

Answer 10

Biochemical or peat stage

Question 11

In this stage, the peat deposit buried under sedimentary deposits lose moisture and volatile components under the effect of high temperature and pressure.

Answer 11

Chemical stage or metamorphism

Question 12

The peat gets enriched in carbon whereas its oxygen content decreases. The spongy peat transforms into hard brittle coal gradually.

Answer 12

Chemical stage or metamorphism

Question 13

Coals are mainly classified on the basis of their rank, which is defined as the degree of _________________

Answer 13

“coalification”

Question 14

It can be observed from the table that while carbon content and calorific value of coal increase with degree of coalification, the hydrogen, nitrogen, volatile matter, moisture decrease as the degree of coalification ______________.

Answer 14

increases

Question 15

_____________ is a soft, crumply, dark brown substance that is formed from generations of dead and partially decaying organic matter.

Answer 15

peat

Question 16

Often referred as brown coal, the __________ is a soft, combustible, sedimentary rock from naturally compressed peat. Formed from compaction of peat under low burial pressures and temperatures.

Answer 16

lignite

Question 17

________________ ______ or black coal is a relatively soft coal containing a tarlike substance called bitumen or asphalt. lack coal is a relatively soft coal containing a tarlike substance called bitumen or asphalt.

Answer 17

Bituminous Coal

Question 18

The __________ ________ are hard, shiny coal with silvery luster. A metamorphic rock formed from bituminous coal at higher temperatures and pressures.

Answer 18

anthracite coals

Question 19

______________ _______________ is an empirical but important analysis. The date varies with the procedure adopted; hence it is called proximate analysis. It gives information about the practical utility of coal. __________ _______ of coal determines the moisture, volatile matter, ash, and fixed carbon of coal.

Answer 19

Proximate Analysis

Question 20

Owning to its nature and original coal is always associated with moisture. When a wet coal is exposed to atmosphere, the external moisture evaporates but the apparently dry coal still contains some moisture.

Answer 20

Moisture Content

Question 21

The _______________ _______________ in coal consists of a complex mixture of gaseous and liquid products resulting from the thermal decomposition of the coal. _________________ ______________ does not include moisture of coal. It consists mainly of combustible gases such as H2, CO, CH4, and other hydrocarbons.

Answer 21

volatile matter

Question 22

Coal consists of inorganic mineral substance which are converted into ___ by chemical reactions during the combustion of coal. The ___ is consisting of silica, alumina, iron oxide, and small quantities of lime, magnesia, etc.

Answer 22

ash

Question 23

__________ _____________content increases, from low-ranking coals such as lignite to high-ranking coals such as anthracite. Coals with higher percentage of fixed carbon has greater calorific value. ______ ________ represents the quantity of carbon that can be burnt by a primary current of air.

Answer 23

Fixed carbon

Question 24

_______________ __________ of coal is carried out to ascertain the composition of coal. When doing this, it is necessary to determine the percentages of various components so as to classify the coals, to fix its prices, along with putting the coals to different uses depending upon its composition. ______________ _______ includes the estimation of carbon hydrogen, sulfur, nitrogen, and oxygen.

Answer 24

Ultimate analysis

Question 25

Carbonization of coal is the process of __________ the coal in the absence of air, to a sufficiently high temperature.

Answer 25

heating

Question 26

the process of converting coal into coke is called ___________.

Answer 26

carbonization

Question 27

Some coals tend to soften and swell at higher temperatures, to form a solid coherent mass with porous structure. Such coals are called _____________ __________.

Answer 27

Caking coals

Question 28

The residue formed is called the coke. If the coke is hard, porous, and strong than the coal (from which it is formed), then it is __________ ________-.

Answer 28

Coking coals

Question 29

When the destructive distillation of coal is carried out at temperature between 500-700 ̊C, it is called ________ ________ _________.

Answer 29

Low Temperature Carbonization (LTC)

Question 30

it is called low temperature carbonization. The _____________________ is practiced for productions of semi coke which is also called soft coke or char. The yield of coke is about 75-80%. The coke produced contains 5-15% volatile matter and is not sufficiently strong to be used as metallurgical fuel.

Answer 30

Low Temperature Carbonization (LTC)

Question 30

It is carried out at 900-120 ̊C. ____________ is used for the production of pure, hard, strong, and porous metallurgical coke, containing 1-3% volatile matter.

Answer 30

High Temperature Carbonization (HTC)

Question 31

the metallurgical coke should contain lowest percentage of moisture, ash, sulfur, and phosphorous. Moisture reduces the calorific value whereas ash hinders the heating and also restricts the passage of air and lowers the rate of combustion. High percentage of ash also aids in slag formation.

Answer 31

Purity

Question 32

The coke should be porous so as to provide contact between carbon and oxygen which ensures efficient and complete combustion of the fuel in the furnace.

Answer 32

Porosity

Question 33

The coke used in metallurgical process should have high strength so as to withstand the weight of the ore, flux, etc. in the furnaces.

Answer 33

Strength

Question 34

Metallurgical coke should be of medium size- neither too big nor too small. A big size of coke does not give uniform heating whereas if the size is too small, it may cause choking.

Answer 34

Size

Question 35

Coke should burn easily. The ___________ of coke depends on the nature of the coal, carbonization temperature, and reaction temperature. Weakly caking or non-caking coals are more combustible than strongly coking coals. Low temperature carbonization process coke which are easily combustible as compared to those obtained by high temperature carbonization. However, at high combustion temperature (800 ̊-900 ̊C) all cokes have comparable _____________. At temperature around 1000 ̊C, the rate of combustion depends upon the rate at which air is supplied.

Answer 35

Combustibility

Question 36

The calorific value should be high.

Answer 36

Metallurgy of Coke

Question 37

__________ of coke is generally considered as its ability to react with CO2, steam, air, and O2. The reactivity should not be too high. However, the coke used for water gas manufacture must be reactive to steam. The reactivity toward CO2, represent the reduction of CO2 according to the equation

Answer 37

Reactivity

Question 38

Coke should be cheap and easily available near the side of the metallurgical plant.

Answer 38

Cost

Question 39

Up to the end of 19th century, the entire requirement of metallurgical coke of the world was fulfilled by the coke manufacture in ___________ ____________. A ____________ __________ is a fire-brick chamber having a dome-shaped structure. It is called _________ _________- because it resembles the shape of a beehive. The dimensions of a typical oven are 4m wide and 2.5m high. The roof is provided with a hole for charging the coal from the top. Another discharging hole is provided in the circumference of the lower part of the wall. A number of ovens are built in a row with common walls between neighboring ovens.

Answer 39

beehive oven

Question 40

The __________ ________ _________consists of a number of narrow rectangular chambers made up of silica bricks. The usual dimensions are 12-14m length, 4-5m height, and 0.5mwidth. The chambers are tightly closed so that no air can be enter. At the top of each chamber, there are three holes for charging the coal. Each chamber is further provided with a gas take off and refractory-line cast iron door at each end for discharging the coke. These carbonization chambers ae erected side by side with vertical flues or interspace for combustion in between them. The ovens (chambers) form a sort of battery of 10-100 ovens. One single oven is capable of holding 16-24 tons of coal.

Answer 40

Otto Hoffmann’s oven

Question 41

___________ _______ is employed to achieve as economical heating as possible. The waste gases produced during combustion (flue gases) are passed through the regenerators and then let off to the atmosphere through the chimney. Regenerators are built underneath the ovens. The flue gases pass their sensible heat to the checker brick work of regenerators until the temperature rises to 1000 ̊C.

Answer 41

Regenerative principle

Question 42

The time required for the formation of young brown coal is of the order of ______ years while that of most nature coals is 3x10^8 years.

Answer 42

107

Question 43

Bituminous coal or black coal is a relatively soft coal containing a tarlike like _________ or __________. lack coal is a relatively soft coal containing a tarlike substance called ________ or _________.

Answer 43

bitumen or asphalt

Question 44

The anthracite coals are hard, shiny coal with silvery luster. A ________ ________ formed from bituminous coal at higher temperatures and pressure

Answer 44

Metamorphic Rock

Question 45

Air dried moisture is determined by heating a known amount of coal (air dried) to ____ - ____˚C in an electric hot air oven for about one hour. After one hour, it is taken out from the oven and cooled in desiccator and weighed. Loss in weight of coal is reported as moisture content on percentage basis

Answer 45

105-110

Question 46

It is determined by heating a known weight of moisture-free coal sample in a covered platinum crucible at 950±20.0˚C for 7 minutes. At this temperature, the hydrocarbons and hydrogen are driven off. The crucible is cooled, first in air, then inside a desiccator and weighted. Loss in weight is reported as volatile matter on percentage basis.

Answer 46

Volatile Matter

Question 47

Ash content is determined by heating the residue left after the removal of volatile matter at 700±50.0˚C for ____ minutes without covering. The cooled mass is weighted.

Answer 47

30