WBUT Solved Question Papers EE Industrial Chemistry B Tech Ist Sem

WBUT Solved Question Papers EE

Industrial Chemistry B Tech Ist Sem

 

1.1.         fly proximate analysis we can determine      [WBUT 2006]

a)           The moisture content of coal only-                                          .

b)           The moisture content and ash content only                        .

c)            The moisture content, volatile matter, ash & fixed carbon contents of coal

d)           The moisture content, volatile matter and fixed carbon of coal.     \

Answer: (c)                                                                                                           .                                                                                                           .

     B

1.2.       The relation between HCV and LCV will be      [WBUT 2006]

a) HCV = LCV b) HCV > LCV                                   c) HCV < LCV d) no relation exists

Answer: (b)                                                                                         .

 

1.3.         The highest ranking coal is

a) Anthracite b) Bituminous

Answer: (a)

[WBUT 2007, 2010(JUNE)]

c)                                                                                                                                                                                                                                                                                                                     Lignite   b) Peat

1.4: The calorific value should be the highest for

a) Water gas b) LPG                               c) Producer gas

Answer: (b)

[WBUT 2007, 2008]

d)             Carbu retted water gas

1.5.      Which of the following is used as fuel in jet engine? [WBUT 2010(DECEMBER)] a) Petrol . . b) Diesel                       c) Kerosene d) Power alcohol

Answer: (c)

1.6.      Which one of the following is not a primary fuel [WBUT 2010(DECEMBER)] a) Wood b) Natural gas c)Coke                  d) Crude oil

Answer: (c)

1.7.          Producer gas is a mixture of

a)            Carbon monoxide and hydrogen

c)             Carbon dioxide and hydrogen

Answer: (b)                         ,

[WBUT 2011(JUNE}]

b)            Carbon monoxide and nitrogen

d)              Carbon dioxide and nitrogen

 

1.8.         Which of the following is used as anti-knock compound? [WBUT 2011 {JUNE}] a) Tetraethyl ammonium bromide                 b) Nickel tetracarbonyl

c)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      Tetraethyl lead

d) Tetraethyl silane

Answer: (c)                                                ‘ ’

 

1.9.         Octane number of Iso octane is

a) 100                     b) zero               c) 50

Answer: (a)

[WBUT 2011 (JUNE)]

d)             none of these

 

1.10.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               Fuel used in jet plane is                             . . J.r– [WBUT 2012(JUNE)]

a)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   aviation gasoline                                       b) 90.5% ethyl alcohol

c)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     alcohol with diesei                                    d) alcohol with petrol

Answer: (a) ■ ■                                           ‘………                                                                    ”

                                                    ”

2.1. What are. the important products formed from the atmospheric distillation of crude oil?                                                                        [WBUT 2006,2007,2010(JUNE)]

OR,                 ” ‘

Indicate major fractionation products along with their boiling range and uses obtainable form atmospheric distillation of crude oil.

[WBUT 2011 (JUNE), 2012 (JUNE)] Answer:                                                                                                                                                       ■

 

The important products formed from the atmospheric distillation of crude oil is

Petroleum fractionJ ” Boiling range*

Number of carbon

. Uses* ■. ■ ■
(1) Uncondensed gas• ” ■ ” L ” . ”

_ ” ■ r

Within 30°C

BE « 1

C —C’-‘l ‘-‘4

t” ■

Named as LPG(Liquefied Petroleum gas), used as domestic or industrial fuel.
(2) Petroleum ether1 . 30 – 70°C c5-c7 As a solvent
(3) Gasoline or petrol 90 – 200°C■ ■ ■ 1 j 1 & \ 1 1 As a motor fuel solvent and dry washing
(4) Naphtha 200 – 250°C C -C

9 ^10

As a solvent
(5) Kerosene oil

^ I ;

h * if ” 4 « ‘ ■ r I

250 – 300°C C — c ^10 ^16 As a fuel for domestic and industrial uses. .
(6) Diesel oil 300 – 350°C tou

1

0

WH

As a fuel for diesel engine
(7) Heavy oil 320 – 400°C C —C

17 ’-30

For different fractions.

R

2.2         How do the gasoline and diesel differ in chemical composition? [WBUT 2006] Answer:                                                                                         .                                            .

Gasoline or petrol is obtained between 90-200°C and it is a mixture of hydrocarbons, CjHi2 (pentane) to CgHjg (octane). Its calorific value is about<11,250 Kcal / Kg. It is used as fuel for internal combustion engine of automobiles.                                                                                         ‘

Diesel oil is a fraction, obtained between 300-350°C and is a mixture of C15H32 to CjgH38

hydrocarbons. Its calorific value is about 11,000 Kcal / Kg. It is used as a diesel engine fuel.

a.

 

■ .■ 1

2.3       What are water gas and semiwater gas? How is water gas produced from coke?

[WBUT 2006, 2008, 2011 (DECEMBER)]

Answer:                                                 .

Water gas is a mixture of CO and H2, with a little non-combustible gases* CO2 and N2. The average composition of water gas is CO —* 41%, H2 —» 51%, N2 —+ 4%, CO2 —► 4%. It is made by passing steam and little air through a bed of red-hot coke. Its calorific value is about 2800 Kcal / m3..

Semi-water gas is a mixture of water gas and producer gas made by passing a mixture of air and steam through heated coke. The heat generated when producer gas, is formed keeps the temperature of the coke high enough to allow water gas to be formed. Combustion of carbon is an exothermic process, around 3% of the generated heat during the production of producer gas is lost unless the gas is used on the spot. However the reaction of steam with red hot carbon is an endothermic process and, • therefore if a mixture of air and steam in appropriate proportions be passed through red hot carbon, the generated heat can be utilized.                       ‘ .

 

c(s)*4°*(*)—»co(g) .

Z J

C(s)+H20(g)—— >CO(g)+H2(g)

The liberated heat by the combustion of carbon maintains the temperature required for the formation of water gas by the action of steam on carbon. The gas mixture obtained may be considered as a mixture of water gas and producer gas.

It’s approximate composition is

H2:10-12%;CO:25-28%;C02:4-5%;N2:50-55%;Methane,etc: 1-1.5%.

Uses:                                        .

(i)              As a fuel in the steel industry.      ■

(ii)               For the production of power in internal co inbust ion engine.

 

2.4            Define octane and cetane numbers. What is biofuel?

[WBUT 2002, 2004, 2007, 2010(JUNE), 2010(DECEMBER), 2011 (JUNE), 2012 (JUNE)]

Answer:                                            ,. ,

Octane number: It has been found that iso-octane is a very good petrol engine fuel and its antiknock value is considered as 100 where as n-heptane is a very bad petrol engine

fuel and its antiknock value is arbitrarily considered as zero. Thus octane number is

 

equal to the percentage by volume of iso-octane (2,2,4 – trimethyl pentane) in a mixture of n heptane and iso-octane having the same knocking tendency compared to the sample of gasoline being tested. Suppose a sample^ of petrol gives as much knocking as a mixture of 80 parts of iso-octane and 20 parts of n-heptane, its octane number is 80.

 

Cetane number: Normal hexadecane (C^H^) is commercially known as cetane. It has

– ■ ‘ » ‘ J , a very short ignition lag and its cetane number is considered as 100. However, (X -methyl

 

naphthalene (CnH10) has a very long ignition lag and its cetane number is considered as
zero. Thus cetane number is equal to the percentage by volume of cetane in a mixture of cetane and CL — methyl naphthalene having same ignition characteristics compared to the sample of fuel being tested. Suppose, a sample of fuel matches in quality with the blend having 40/60 blend of cetane and Ct – methyl naphthalene, its cetane number is assigned as 40.

The cetane number of diesel can be improved by adding amyl nitrate, butyl nitrate, carbonates, diteriiary butyl peroxide and metal organic compounds.                                                                                                           fe

2.5                          State and explain the basic features of High and Low temperature carbonisation of <£oal. What are proximate and ultimate analysis of coal?

                                                       [WBUT 2002, 2004, 2005, 2007, 2010(JUNE)]

Answer:

LTC                                       HTC

  1. Temperature                                   650 – 750°C     950 — 1400°C
  2. Retort                                             Steel retorts
  3. a) Ceramic coke oven forhard Metallurgical co
  4.   b) Horizontal or vertical

                                                                                      retorts for soft coke (main

product being coal gas)

a)                                   Good cooking non swelling bituminous Coal (20-30% VM) blended with small amount of the anthracite coal or low volatile bituminous coal (14-16%). So the VM content of charged coal is 22-28% for hard metallurgical coke.

b)                    High volatile swelling bituminous coal (30—40% VM) for soft coke

a)                    17 hr. for coke oven

^b) 8-12 hr. for vertical retorts.

All are lesser compare to All are higher compare to HTC   LTC

 

  1. 6.            Control

7,            Production

S. Product

a)           Yield of coke

b)             Quality of coke7

c)             Nature of coke

d)             Calorific value

LTC

Achievement of . proper process control is difficult Overall production per day is less

75-80%

8-20% volatiles Smokeless . .  .

High (700-900 Btu/ft3) due to higher proportion of hydrocarbon.

HTC

Control is easy because of high temperature gradient. Overall production per day is high

73%

1-3% volatiles Smoky   .

Low (500 Btu/ft3) ,

 

2nd Part:

Proximate Analysis

Proximate analysis is an empirical but important analysis, procedure adopted and hence it is called proximate analysis, determines the moisture, ash, volatile matter and fixed carbon

The data varies with the

*

Proximate analysis of coal of coal.

 

Moisture Content

Owing to its nature and origin 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. This moisture is referred to air dried moisture.

Air dried moisture is determined by heating a known amount of coal (air dried) to 105 — 110° C in an electric hot air oven for about one hour. After one hour, it is taken out from the oven and cooled in a dessicator and weighed. Loss in weight of coal is reported as moisture content or percentage basis.

.. . l Loss in weight Percentage of moisture =…………..

weight of coal taken

Volatile matter

The volatile matter in coal consists of a complex mixture of gaseous and liquid products resulting from the thermal decomposition of the coal.

Volatile matter does not include moisture of coal. It consists mainly of combustible gases such as H2, CO,CH4 and other hydrocarbons. It is determined by heating a known

weight of moisture free coal sample in a covered platinum crucible at 950 ± 20°C for 7 minutes. At this temperature, hydrocarbons and hydrogen are driven off. The crucible is cooled, first in air, then inside a dessicator and weighed. Loss in weight is reported as volatile matter on percentage basis.

Percentage of volatile matter                                      ,.

Loss of weight due to removal of volatile matter

Weight of coal sample taken

Ash ■ ‘                                  ‘ .                                           .                                            .                                             . ‘

Coal contains inorganic mineral substances which are converted into.ash by chemical reaction during the ■ combustion of coal. Ash usually consists of Silica, alumina, iron oxide and small quantities of lime, magnesia etc.

Ash content is determined by heating the residue left after the removal of volatile matter at 700 ±50°C for hr without covering. The cooled mass is weighed. From the

weight of the residue, the percentage of ash is calculated.

  • , Weight of the residue left tAA

Percentage of ash =——————————————————————— xluO

Weight of the coal

Ash can be classified as intrinsic ash and extrinsic ash. The mineral matter originally present in vegetable matter from which the coal was formed is called intrinsic ash. It consists of oxides of Na, K, Mg, Ca and Si. On the other hand the mineral matter, like clay, gypsum, dirt which gets mixed up during mining and handling of coal constitute the extrinsic ash which remains as a residue after combustion.                                                                                                     ■

Fixed Carbon .

Fixed Carbon content increases from low ranking coals such as lignite to high ranking coals such as anthracite. Higher the percentage of fixed carbon greater the calorific value and better in the quality of coal.                                                                                                     .

The amount what is left after the amount of moisture, volatile matter and ash formed is subtracted, corresponds to the fixed carbon.                                                                                                     ,

pi                                                                                 \                B

Ultimate Analysis

Ultimate analysis. includes the estimation of carbon, hydrogen, sulfur, nitrogen and oxygen.      ,                      .

Carbon and Hydrogen

A known amount of coal is taken in a combustion tube and is burnt in excess of pure

oxygen. The carbon and hydrogen present in the fuel are converted to C02 and H2G

’ ■ ’ ‘ /

respectively.

c+o2—»co2              ,

.                            V                                                                        ,                             ■*                                                                       ”

H2+i02—————– >H20

The gaseous products of combustion are passed through two bulbs, one containing weighted amount of anhydrous CaCl2. which absorbs water and the other containing

weighted amount of KOH which absorbs COj. The percentage of C and H arc calculated from the increase in weight of the respective absorption tubes.

2KOH+C02————– > K2C03 + H20

CaCl2 +7H20 ———– ►CaCl2, 7H20

Let, weight of coal sample taken = X gm Increase in weight of CaCI2 tube = Z gm Increase in weigh* of KOH tube = Y gm.

44 gm C02 contain = 12gm C

12 /

Y gm GOj contain = —xy gm Carbon

44                        –

Percentage of carbon = —x———————- yXlOO_______

44 weight of coal taken

18 gm of water contain = 2 gm hydrogen                                                                                                         –

2 ‘

Z gm of water contain = —xZ gm hydrogen.

Percentage of hydrogens — x                         Z x 100

18 Weight of coal taken

Nitrogen

Nitrogen present in the coal sample can be estimated by Kjeldahrs method. A known weight of the given coal sample along with K2S04 + H2S04 which acts as a catalyst is

heated with concentrated H2S04. Nitrogen present in the coal gets converted to (NH4)2S04 quantitatively.                                                                                                    ,

Nitrogen + H2S04 He* >(NH4 )2S04

The contents are the transferred to a round bottomed flask and the solution is heated with excess of NaOH. The NH3 gas thus liberated is absorbed in a known volume of a standard solution of acid. The unused acid is then determined by titrating with NaOH. From the volume of acid used by NH3 liberated, the percentage of nitrogen cap be calculated.                                                                    .                                                                                           •

(NH4)2S04-^H_^2Na2S04+2NH3+2H20 nh3+h2so4————- »(NH4)2S04

Let the weight of coal taken = W gm.

Volume of the acid used up = Vt mL                                                                                                         ‘

Normality of the acid = Nl

Vi mL of Ny acid = V2 mL of N2 NH3

V2 mL of IN NH3 = Vj XN, mL of acid

But 1000 mL of 1 normal                                          .

Ammonia solution = 17 gm of NH3 = 14 gm

14 1000 14 MxV.xlOO ttxMxV;

Percentage of Nitrogen

*              6 1000 W .          W

Sulfur

Sulfur present in the coal is oxidized by fuming nitric acid into sulfuric acid. The sulfuric

acid is precipitated as BaS04 by the addition of BaCl2, quantitatively. The precipitated

BaS04 so obtain is filtered and heated to a constant weight. From the weight of BaS04

obtained the sulfur present in the coal is calculated..                                                                                                          . ..

u = ” _ ‘ t- Let the weight of coal sample — W gm .                                                                                  –

Ihc mass of the precipitate be = Wi gm

233 gm BaS04 = 32 gm S                         . ■

32 233

–                                          32xW

Percentage of sulfur =—————– —X100

^                         ! 233 W ■                                              .

 

It is determined in the same way as in proximate analysis.

 

Oxygen                                                    ,

The oxygen is usually determined by the method of difference. The carbon, hydrogen, nitrogen and sulfur are expressed in percent basis and their sum is subtracted from 100. Percentage of oxygen = 100 – (% of Carbon + hydrogen + nitrogen + sulfur + ash)

2.6                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            Write note on Carburetted water gas.                                                                          [WBUT 2008]

Answer:

T

Carburctted water gas                        –                                                                   /

In order to enhance the calorific value of water gas (mixture of CO + H2); it is carbureted by adding gaseous hydrocarbons (obtained by cracking crude oil). This mixture is called carbureted water gas which contains about 35% H2, 25% CO, 35% hydrocarbons (saturated and unsaturated) and 5% (N2 + C02). Its calorific value is about 4500 kcal / m3 and it is employed for heating and illumination purposes.

 

2.7          Distinguish between coking coal and caking coal.       [WBUT 2006]

Answer:

Coking Coal; Although chemical composition alone cannot be used to predict whether a

coal is suitable for coking, prime coking coals generally have volatile matter contents of

20 to 32 percent—i.e., the low- and medium-volatile bituminous ranks. When heated in

the absence of aiV, these coals first become plastic, then undergo decomposition, and

finally form coke when the decomposed material re-solidifies into a hard and porous solid.

* ” 9 r

Caking Coal: When many bituminous coals are heated, they soften said form a plastic mass that swells and re-solidifies into a porous solid. Coals that exhibit such behaviour are called caking coals. Strongly caking coals, which yield a solid product (coke) with properties suitable for use in a blast furnace, are called coking coals.                                                                                                    ‘ ‘

2.8                 What is LPG? Why is it used as a domestic fuel? Explain how the Octane number can be improved?        [WBUT 2006,2009,2012 (JUNE)]

Answer:

1st Part:                                                                                                         ,

Liquefied petroleum gas (also called LPG, GPL, LP Gas, or autogas) is a mixture of hydrocarbon gases used as a fuel in heating appliances and vehicles, and increasingly replacing chlorofluorocarbons as an aerosol propellant and a refrigerant to reduce damage to the ozone layer, inferring that it is flammable. ‘ – •

Varieties of LPG bought and sold include mixes that are primarily propane, mixes that are primarily butane, and the more common, mixes including both propane (60%) and butane (40%), depending on the season—in winter more propane, in summer more butane. Propylene and butylenes are usually also present in small concentration. A powerful odorant, ethanethiol, is added so that leaks can be detected easily. Thiophene or amyl mercaptans are also approved odorants.                                                                                                    .                                                                                                                                                                                                .

 

2°* part:

(i)             Higher heat Value.

(ii)              Easy availability.       –

(iii)                Affordable cost.

3rd Part:

Anti knocking agents are organo metallic compounds that increase the octane number of gasoline when low percentage is added to it. The most widely used anti knocking agent is tetraethyl lead (TEL), which can increase the octane number over 100%.

2.9                  What is calorific value of fuel? Distinguish between gross and net calorific values.         [WBUT 2007,2009, 2011(DECEMBER)]

Answer:

1* part;                                                               .

The calorific value of a fuel is the number of units of heat evolved during complete combustion of unit weight of the fuel. For liquids and solids it is usually expressed in’

Btu/lb or Cal/gm.

The calorific value may be expressed in two types: (i) Gross calorific value (GCV)

(ii)            Net calorific value (NCV).

2nd part:

Gross Calorific Value (GCV)

The quantify of heat evolved by the combustion of unit quantity of fuel is its gross calorific value (GCV). Gross or higher calorific value is the quantity of heat liberated by combusting unit mass- of fuel in oxygen, the original material and the final product of combustion being at a reference temperature of 25° C and the water obtained is in the liquid state.                                                                                                       .

Net Calorific Value (NCV)                                                                                                        *

Net Calorific Value (NCV) is the quantity of heat evolved when a unit quantity of fuel is burnt in oxygen, the original material and the final products of combustion being at a reference temperature of 25°C and the water obtained form the fuel is in the vapour

state.                                                       .

The net calorific value is always less than the gross calorific value by the amount corresponding to the heat of condensation of water vapours i.e. 587.0 Kcal/g.

NCV – GCV – Latent heat of water vapour formed

= GCV – Mass of hydrogen x a x Latent heat of steam.

Since 1 part by mass of hydrogen produces ‘a’ part by mass of water.

2.10.       What are the constituents of coal as determined by proximate analysis?

Proximate analysis of coal determines the moisture, ash, volatile matter and fixed carbon .of coal.    ■                                         .                               ,

2.11 Write notes on Straight run gasoline and jet fuel.                                                                                                      / [WBUT 2005,2009]

Answer:

Straight run gasoline                                     ,                                                                         ‘ _

Gasoline obtained by direct distillation of petroleum without using other conversion

processes like cracking is known as straight run gasoline. Its Octane number is low.

Jet fuel

Jet gasoline is used as a fuel for jet engine aircrafts. When the distillation of light hydrocarbon oil is carried out between 100°C »- 250°C -then jet gasoline is produced. It ‘ is obtained by blending kerosene or gasoline or naphtha is such a way that the aromatic content does not exceed 25% in volume and the vapour pressure is between 13.7 – 20.6 K Pa.                                                                                   .

2.12.             What do you understand by HTC & LTC of a coal? Write down the usefulness of each process.        [WBUT 2010(JUNE), 2011 (JUNE)]

Answer:

Impart:                                                                          ‘

HTC: High temperature carbonization (950 – 1400°C)                                                                          .

LTC: Low temperature carbonization (650 — 750°C)

2“d Part:

HTC: Usefulness:                                           –                    ‘

i)     Ceramic Coke Oven —> Hard metallurgical coke (used as fuel and reducing agent in blast furnace)                                                            . . ‘

ii)     Horizontal or vertical retorts —> Soft coke (domestic purpose to prepare CaC2 and water gas)                                             •                                                                .                                                                ‘

LTC: Usefulness; Semi coke in steel retorts (smokeless domestic fuel).

2.13.                        What is anti-knocking compound? Discuss the function of TEL as anti- knocking agent. What is unleaded petrol? Write its significance.

[WBUT 2010(JUNE)]

Answers

1st Part:                                                                          .

Anti-knocking agent: Anti knocking agents are organo metallic compounds thar increase the octane number of gasoline when low percentage is added to it. The most widely used anti knocking agent is tetraethyl lead (TEL), which can increase the octane number over 100%.

.         Function of TEL: During combustion, TEL produces Pb and PbO. These particles act as free radical chain inhibitors as they arrest the propagation of the chain reaction responsible for knocking.

 

3rt Part:

Unleaded Petrol: Petrol, whose octane number is increased without the addition of lead compounds is known as unleaded petrol. It can be prepared by (a) adding methyl tertiary butyl ether (MTBE) which supplies oxygen from the ether group for combustion of petrol thus reducing the formation of peroxy compounds (b) reforming, i.e., increasing -the contents of molecules having branched structures (isopentane, isooctane) and aromatic ring structures (ethyl benzene, isopropyl benzene).

 

4th Part:

Significance of Unleaded Petrol: When TEL, is used as antiknock compound then during combustion of petrol in presence of halogenated scavenger lead particulates

(PbCl2, FbBr2, PbBrCl) are released to the atmosphere. These particulates are

responsible for air pollution. But in case of unleaded petrol this type of pollution can be avoided.

2.14.        (a) What is CNG arid what is its composition?

(b) What are the advantages of CNG over other fuels? [WBUT 2010( DEC EMBER)]

Answer:

(a)                  CNG: Compressed natural gas (CNG) is used now-a-days as a motor engine fuel instead of gasoline and it causes less pollution.

*     ” ■;

Composition:                    Mole (%)

Methane                         82.0 – 94,0

Ethane                          3.0 – 6.0

Propane                         0.1-2.0

Butane                          0.1—0.7

Pentane                         0.1 – 0.2

Hexane-plus                     0.0 – 0,2

 

Nitrogen gas                     { 15.0

Carbon dioxide                   ( 10.0

Oxygen                          Trace

 

(b)             Advantages of CNG

(i)                         Compressed natural gas is the cleanest burning fuel operating today. It means less vehicle maintenance and longer engine life.

(ii)                 CNG vehicles produce the least emissions of any motor fuel.

(iii)          CNG produces significantly less pollutants than gasoline.

(iv)           Tailpipe emissions from gasoline operated cars release carbon dioxide, which is a green house gas and responsible for global warming. This is greatly reduced with

  • natural gas.

(v)                 Some fleet operators have reduced maintenance costs by as much as 40% by converting their vehicles to CNG.

(vi)           Natural gas does not react to metals the way gasoline does, so pipes and mufflers last much longer.                .

(vii)   Natural gas gives the same mileage as gasoline in a converted vehicle.

(viii)               Dedicated CNG engines are superior in performance to gasoline engines.

(ix)           CNG has an octane rating of 130 and has a slight efficiency advantage over gasoline. .

(x)             Natural gas is cheaper per equivalent gallon than gasoline (an average of 15% to 50% less than gasoline).

 

2.15.         Write short note on Bi6~diese1.

Biodiesel is defined as the mono-alkyl esters of fatty acids derived from vegetable oils or animal fats. It’s known chemically as a ’methyl ester’. In simpler terms, Biodiesel is the product you get when a vegetable oil or animal fat is chemically reacted with an alcohol to produce a new compound that is known as a fatty acid methyl ester. To achieve this

 

reaction a ‘catalyst* such as sodium hydroxide (NaOH) or Potassium Hydroxide (KOH) must be added to the alcohol. Biodiesel can be made from Methanol or Ethanol (derived from crops such as com). When made from methanol it is called Methyl Esters, when made from Ethanol it is called ethyl esters. Due to the large price difference, Biodiesel is usually made from methanol.

The chemical reaction for base catalyzed biodiesel production is depicted below. One hundred pounds of fat or oil (such as soybean oil) are reacted with 10 pounds of a short chain alcohol in the presence of a catalyst to produce 10 pounds of glycerin and 100 pounds of biodiesel.

CH2OCOR'”1

■ CH2OCQR” 1

CH2OCOR’

“H.

Catalyst + 3 ROH ————– * CHgOH CHzOH + CH2OH RH,COOR R”COOR .
# R’COOR
100 pounds 10 pounds 10 pounds too pounds
Oil or Fat Alcohol (3) Glycerin Biodiesel (3)

 

Benefits of biodiesel                          .

(i)                            It’s made from Renewable Resources such as com & soybean

(ii)                    Biodiesel reduces our dependence on oil from foreign countries and contributes to our own society                .

(iii)            Biodiesel is plant-based and adds almost no CO2 to the atmosphere

(iv)             The    ozone-forming potential of Biodiesel emissions is nearly 50% less than conventional diesel fuel

(v)                                    Pleasant smelling, both in its raw form, and when burned

(vi)             Biodiesel is Safe. It’s considered non toxic and greatly reduces the amount of cancer causing emissions vs petrodiesel

(vii)     Biodiesel also has a flashpoint twice as high as petrodiesel making it much less likely to ignite in a car wreck or spill

(viii)                   Biodiesel is less toxic than table salt and biodegrades as fast as sugar

(ix)             Biodiesel can be used straight in warmer weather or blended with petrodiesel in any ratio                                                     …                                                     ‘                                                     .

(x)                     Biodiesel requires no engine modifications to use.

(xi)             Increased Lubricity. Biodiesel has greatly increased lubricating properties vs petrodiesel, even in very small quantities.                                                                                                 .

2.16.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   Write short note on carbonisation of coal and its utility.                                                                                                         .

[WBUT 2010(DECEMBER)]

Answer:                                                                                                         .

The carbonization of coal is the pyrolysis or heat treatment of bituminous or lignite coal in the absence of air. This result in the production of a residue called coke vapours which when condensed and separated produce crude coal chemicals commonly known as tar, light oil, ammoniacal liquor, coal gas and coke oven gas. The nature and amount of each product depend upon the temperature used in the pyrolysis and the variety of coal. Carbonization of coal may be classified into two types:

a)                              High temperature carbonization (950 – 1400°C)

b)                             Low temperature carbonization (650 – 750°C)

In LTC the quantity of gaseous products are small and that of liquid product is relatively large whereas in HTC the yield of gaseous product is large than the yield of liquid

products, the production of tar being relatively low.

 

2.17.         Distinguish between gross and net calorific values of a fuel. [WBUT 2005] Answer:                                                   –

(i)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           Gross Calorific Value (GCV)                                                                          . ,

  • The quantity of heat evolved by the combustion of unit quantity of fuel is its gross.calorific value (GCV).            –
  • Water obtained is in the liquid state.                  –

 

(u) Net Calorific Value (NCV)

  • Net Calorific Value (NCV) is the quantity of heat evolved when a unit quantity of fuel is burnt in oxygen, ’
  • Water obtained from the fuel is in the vapour state.

 

2.18.             Calculate the mass of air needed for complete combustion of 5 Kg of coal containing 60% carbon, 15% hydrogen and the rest oxygen.        [WBUT 2004] Answer:

80 ■

Amount of carbon present in 5 Kg of coal —————— —— x5 = 4 Ke

^ 100

Amount of hydrogen present in 5 Kg of coal = ——x5 = 0 75 Kg

100 •

Amount of oxygen present in 5 Kg of coal = 5.0—(4.0+ 0.75) = 0.25 Kg 4 Kg carbon present in coal will be oxidized to CO2 after combustion.

.                – ■ . c+o2——————– >C02 ■ .

 

12 Kg carbon required 32 Kg oxygen for complete combustion

■                                                                                                                                                                                                                                                                                                                                                                      ‘ ‘ 32                                     ‘                                                     “

4 Kg                  „ ‘—x4= 10.67Kg „ „ „

Iw                                                              /

– f

Amount of O2 required for combustion of 0.75 Kg hydrogen present in coal will follow the following reaction.                                                                          .

H2+Ao2—>H20; 2 Kg 16 Kg

1 1A

O2 required for complete combustion of H2 = —x0 75=6 0 Kg Total amount of oxygen required = 10.67+6.0=16.67 Kg

Amount of oxygen present in coal = 0.25 Kg So amount of oxygen required = 16.67 —0.25—16.42 Kg Amount of oxygen present in air = 23 %

 

Weight of air required to hum 5 Kg of coal = – * ■ XlOQ=71,4 Kg. ,

 

2.19.         Distinguish between thennal and catalytic cracking. [WBUT 2011 (JUNE)]

Answer:

Catalytic cracking: Modem cracking uses zeolites as the catalyst. These are complex aluminosilicates, and are large lattices of aluminium, silicon and oxygen atoms carrying a negative charge. They are, of course, associated with positive ions such as sodium ions. The alkane is brought into contact with the catalyst at a temperature of about 500°C and moderately low pressures. The zeolites used in catalytic cracking are chosen to give high percentages of hydrocarbons with between 5 and 10 carbon atoms – particularly useful for petrol (gasoline). It also produces high proportions of branched alkanes and aromatic hydrocarbons like benzene. The zeolite catalyst has sites which can remove a hydrogen from an alkane together with the two electrons which bound it to the carbon. That leaves the carbon atom with a positive charge. Ions like this are called carbonium ions (or carbocations). Re-organisation of these leads to the various products of the reafction.

 

Thermal Cracking: In thermal cracking, high temperatures (typically in the range of 450°C to 750°C) and pressures (up to about 70 atmospheres) are used to break the large hydrocarbons into smaller ones. Thennal cracking gives mixtures of products containing high proportions of hydrocarbons with double bonds – alkenes. Thennal cracking doesn’t go via ionic intermediates like catalytic cracking. Instead, carbon-carbon bonds are broken so that each carbon atom ends up with a single electron. In other words, free radicals are formed.

2.20.        Write short note on Knocking and antiknocking.        [WBUT 2011(JUNE)]

Answer:                                                               –                                                                                                    … . ‘

Knocking: This is a properly of a liquid fuels. In many instances a mixture of compressed liquid fiiel vapour and air explodes in internal combustion engines before the proper degree of compression is reached, causing thereby a reduction in the efficiency of the engine. This phenomenon of untreated liquid fuels is known as knocking. . .

It has been found that

 

a)      Knocking tendency of paraffins increases with the increasing length of carbon chain.                           ■                                                  . ..                                                                        ’

b)    Branched chain paraffins have lower tendency to knock and hence have higher octane number.                           •

c)  Knocking property decreases with increase in the number of C = C and ring

d)                              Napthenes have higher knocking tendency than aromatic hydrocarbons.

 

Anti knocking:                                              .

The knocking of a fuel can be minimized or antiknocking is done by adding some compounds known as antiknocking compounds.

To improve the antiknock properties some organo metallic compounds like tetra ethyl lead (TEL) is most widely used. It is sweet odour but extremely poisonous and a fuel containing it should be handled with great care.

Chi burning of TEL, harmful lead oxide is deposited in the engine. To avoid this deposition ethylene dibtomide is also added so that lead is removed as lead bromide particulate along with the exhaust gas which is responsible for air pollution. TEL is more effective on saturated hydrocarbon than unsaturated hydrocarbon. Sulfur compound reduces its effectiveness.                                                                  –

4

■                                                                      ‘ J ‘ * ■* ‘

2.21.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      How can biofuel be an ideal substitute of fossil fuel and help in solving global energy crisis?                                                                                              [WBUT 2011 (JUNE)]

Answer:                                         V

(i)                            It’s made from Renewable Resources such as corn & soybean

(ii)                  Biofuel reduces our dependence on oil from foreign countries and contributes to our own society      .                                                          .                       ;                                                          .

(iii)            Burns up to 90% cleaner than conventional diesel fiiel made from fossil fuels. Substantially reduces unbumed hydrocarbons, carbon monoxide and particulate matter in exhaust fumes. Sulphur dioxide emissions are eliminated (Biodiesel contains no Sulphur)

(iv)             Biofuel is plant-based and adds almost no C02 to the atmosphere

(v)                   The ozone-forming potential of Biofuel emissions is nearly 50% less than conventional diesel fuel

(vi)                 Pleasant smelling, both in its raw form, and when burned

(vii)         Biofuel is Safe: It’s considered non toxic and greatly reduces the amount of cancer causing emissions vs petrodiesel . .

(viii) Biofuel    also has a flashpoint twice as high as petrodiesel making it much less likely to ignite in a car wreck or spill

(ix)              Biofuel is less toxic than table salt and biodegrades as fast as sugar

(x)                     Biofuel can be used straight in wanner weather or blended with petrodiesel in any ratio .

(xi)                 Biofuel requires no engine modifications to use. .

(xii)         Increased Lubricity. Biofuel has greatly increased lubricating properties vs petrodiesel, even in very small quantities. ‘

(xiii) Biofuel    can reduce the classic diesel engine “knocking” poise.

(xiv)  Higher cetane rating ,

(xv)          Savings – Biofuel made at home can be made for around 75 cents a gallon

2.22. What is proximate analysis of coal and what is its significance?

[WBUT 2011 (JUNE), 2012 (JUNE)]

 

Answer:                                                                         /

Proximate analysis is an empirical but important analysis. The data varies with the procedure adopted and hence it is called proximate analysis. Proximate analysis of coal determines the moisture, ash, volatile matter and fixed carbon of coal.

i)             Significance of analysis of volatile matter: Presence of volatile matter is undesirable as they do not have any heating value and bums with production of flame. Thus, coals with high volatile matter will bum with long smoky flame which is responsible for

pollution in the environment. So, coal with low volatile matter is ideal.

ii)                   Significance of analysis of ash content: Ash reduces ■ heating value of coal- and increases transportation, handling and storage costs. So, coal with low ash content is ideal.

in) Significance of analysis of moisture content: Free moisture is disadvantageous because a) it does not take part to the fuel value b) a certain amount of heat is wasted in

evaporating the moisture during combustion and lowered the calorific value of coal c) excessive free moisture make the handling of coal difficult.

Sample containing inherent moisture undergoes easy oxidation and suitable for combustion.

iv) Significance of analysis of fixed content: High fixed carbon ascertains high calorific value and better quality of coal.

2.23.          Calculate the weight and volume (at NTP) of air required for combustion of 1 kg of carbon. (Air contains 21% by volume and 23% by weight of oxygen).

litre=8866.67 litre2.24.         How do gasoline and diesel differ in chemical composition?

Answer:                                               

Petroleum derived diesel is composed of about 75% saturated hydrocarbons (primarily paraffins including n, iso, and cycloparaffins), and 25% aromatic hydrocarbons (including naphthalenes and alkylbenzenes). The average chemical formula for common

diesel fuel is C12H23, ranging approximately from C]f)Hw to C1S//M.

A typical gasoline is predominantly a mixture of paraffins (alkanes), iiaphthenes (cycloalkanes) and olefins (alkenes). It consists of hydrocarbon between C4 to Cl2

carbon. Some of the main components of gasoline are isooctane, butane and aromatic compound.

2.25.         What is spontaneous ignition temperature of a fuel? [WBUT 2012(JUNE)J Answer: ,

It is the temperature at which a fuel — solid, liquid or gas, catches fire and continues to bum without further heat.    _ ‘

1p                     

2.26.         What is the importance of unleaded gasoline? Which type of hydrocarbons is suitable as components of unleaded gasoline and why? [WBUT 2012( JU

An                                         –Unleaded Gasoline: Gasoline, whose octane number is increased without the addition of lead compounds is known as unleaded gasoline or petrol. .

2″1 Part:                    .It can be prepared by (a) adding methyl tertiary butyl ether (MTBE) which supplies oxygen from the ether group for combustion of petrol thus reducing the formation of peroxy compounds (b) reforming, i.e., increasing the contents of molecules having branched structures (isopentane, isooctane) and aromatic ring structures (ethyl benzene, isopropyl benzene).                                                                          ,

Leave a Comment