SlideShare une entreprise Scribd logo
1  sur  9
Télécharger pour lire hors ligne
Estimating the Available Amount of Waste Heat
               From the Asphalt Dispenser Machine of a
                     Dry Cell Manufacturing Plant



                            Harland C. Machacon, M. Eng.
                    Department of Mechanical-Industrial Engineering
                    College of Engineering, University of San Carlos,
                                       Cebu City




       The Asphalt Dispenser Machine melts and dispenses asphalt into Le-
clanche type dry cells thus producing a leak proof seal between the carbon electrode
and the zinc can.

        Asphalt chunks are melted to a temperature of 180° C using electric strip heaters.
The molten asphalt is then dispensed into a batch of dry cells indexed beneath the
dispensing tank. This batch of cells is then led into a torching conveyor where three
large LPG burners spread out the dispensed asphalt evenly to form a meniscus at
the electrode and at the can lip. These burners also ensure that the asphalt seal is free of
air bubbles that might eventually form into pin-sized holes. This piece of equipment
has a capacity of over half a million Leclanche dry cells for each operating day.

       The hot gases resulting from the combustion process of LPG in these large
burners are collected in an exhaust hood-and-chimney set-up. The flue gas is then
exhausted into the environment via a direct-drive exhaust blower. Huge amounts of
energy are dissipated into the environment. This is indeed a major economic loss aside
from being a source of thermal pollution.

       Within the last four years the cost of fuel has more than doubled. Prices of
petroleum products are always affected by price increases in the world market and also
by the devaluation of our local currency. In the manufacture of dry cells, energy cost
contribute approximately 5 percent of the total manufacturing cost. Hence the battery
company has launched vigorous cost-reduction efforts. This study is about estimating
the recoverable heat from the flue gas that would otherwise be considered lost energy
and a cause of thermal pollution.
Figure 1       The Asphalt Dispenser Machine



Source of Waste Heat
        The major source of waste heat from the Asphalt Dispenser Machine is the hot
gases resulting from the combustion process of Liquefied Petroleum Gas in the large
post-torch burners. The flue gases are then collected in an exhaust hood-and-chimney set-
up and eventually exhausted into the environment via a direct-drive exhaust blower.

         The chemical formula of the fuel used in the burners, Liquefied Petroleum Gas is,
  C 3 H 8 , since LPG is composed primarily of propane[ 1 ]. The chemical reaction is
described as follows;
        C 3 H 8 + 5(O2 + 3.76 N 2 ) → 3CO2 + 4 H 2 O + 5(3.76 N 2 )                   (1)
The products of combustion are carbon dioxide, water vapor, and nitrogen[ 2 ].
CHIMNEY




                                                                      EXHAUST HOOD



                                               FLUE
                                               GAS




      LPG BURNER 1                 LPG BURNER 2                 LPG BURNER 3




                      TORCHING CONVEYOR
         Figure 2      Schematic Illustration Showing the Heat Source of the
                       Asphalt Dispenser Machine

Physical Properties of the Flue Gas

       The specific heat of the flue gas, in kJ/kg-°K is the summation of the products of
the respective mass fractions and the corresponding specific heat values of each
individual component of the flue gas[ 3 ].
                                         n
                                 c pg = ∑ yi c pi                                               (2)
                                           i
Hence,

                       c pg = yc pCO2 + yc p H 2O + yc p N 2
Table 1         Determining the Specific Heat of the Flue Gas
Products     Number     Mole          Molecular                  Mass        cpi
of           of         Fraction      Weight                     Fraction
Combustion   Moles        xi           Mi             M i xi     yi          BTU/lb°R   yicpi
CO2          3          0.1163        44              5.1172     0.1808      0.187055   0.033820
H2O          4          0.1550        18              2.7900     0.0985      0.491999   0.048462
N2           18.8       0.7287        28              20.4036    0.7207      0.249080   0.179512
TOTAL        25.8       1.0000                        28.3108    1.0000                 0.261794
BTU           kJ
                                                   kJ
c pg = 0.261794         × 4.187 kg ° K = 1.096131
                  lb° R        BTU
                                   lb ° R         kg ° K

      The density of the flue gas is the summation of the densities of each individual
component of the flue gas[ 4 ].

                                       n
                                ρ g = ∑ ρi                                            (3)
                                       i


        The density values of the individual components of the flue gas at atmospheric
pressure, can be taken from Table A-6, pages 647 – 648, Heat Transfer by J. P. Holman,
8th edition. The flue gas temperature of 120°C ( 393°K ) will be the reference
temperature. Hence,
               ρg = ρ for CO2 + ρ for water vapor + ρ for N 2                   (4)

                          kg         kg        kg        kg
        ρ ≡1.3695
         g                  3
                              +0.5654 3 +0.8740 3 =2.8089 3
                          m          m         m         m

        The flue gas pressure at the burners is atmospheric because the burners exhaust
directly to the atmosphere. The static pressure at the exit of the chimney right before the
exhaust blower was supposed to be measured by attaching a pressure gage to a
piezometer opening in the side of the conduit normal to and flush with the conduit
surface.

        Similarly, the velocity of the flue gas at the above-mentioned point would have
been measured by attaching a pressure gage to a pitot tube at the same level where the
piezometer opening is located[ 5 ]. The difference of the readings of the two pressure
gages represent the velocity head of the flue gas at such point. Hence the velocity of the
flue gas could have been determined by computation. The steady flow energy equation
applied at the stagnation point “0” could have been used to measure the velocity of the
flue gas, vg . Simplifying the equation, we have the following result;
                                                                                          2

                                                                       ( v g − 0 ) sec 
                                                                                    m
                     lbs      in 2   1kg    (3.28 ft ) 2       1
        ( p 0 − p g ) 2 × 144 2 ×         ×              ×          =                  
                     in        ft  2.2lbs      m 2
                                                                 kg                m 
                                                           2.7504 3      2 9.8       2 
                                                                 m          sec 

        Given the values of p0 and p g from the pressure gauge readings, the velocity of
the flue gas, vg can be solved.
       The partial pressure of the water vapor, pH 2 O is the product of the mole fraction
of the water vapor multiplied by the pressure of the flue gas at the exit of the chimney.
Table 2     Determining the Mole Fraction of the Products of Combustion
      PRODUCTS OF                NUMBER OF                   MOLE FRACTION
      COMBUSTION                    MOLES                            xi
          CO2                           3                         0.1163
          H 2O                          4                         0.1550
           N2                          18.8                       0.7287
         TOTAL                         25.8                       1.0000

Therefore,
                            pH 2 O = xH 2 O p g = ( 0.1550) p g
The corresponding dew point temperature is then read out from the Steam Tables
( Properties of Saturated Water : Pressure ).


                                                       pg         PIEZOMETER
                                                                      TUBE




                                                  p0




                                                                   ( p0 - pg )
                    0




                                           PITOT TUBE
                FLUE GAS
                                                       CHIMNEY       MANOMETER



Figure 3     Installation of Pitot Tube and Piezometer Tube at the Chimney
Available Amount of Sensible Heat from the Flue Gas

       The temperature of the flue gas can be lowered from its initial temperature of
120°C down to point “a” which is 10°C above the dew point temperature of the water
vapor. The safe level of 10°C above the dew point temperature of the water vapor
ensures that the water vapor in the flue gas will not start to condense.

          The sensible heat from the flue gas was calculated using the equation

                                 Qs = mg c pg (Tgi − Tgf )                                  (5)
but

                                 mg = ρgAcvg                                                (6)

and

                                 Tgf = 10 C + Tdp                                          (7)

and then substituting equations ( 6 ) and ( 7 ) in equation ( 5 ), the resulting equation for
the sensible heat is;

                                           [     (
                         Qs = ρ g Ac vg c pg Tgi − 10 C + Tdp   )]                         (8)

      T                                         p=C
                                                                      pH 2 O
                                                                               SAFE LEVEL
                                                                          a
 120°C




                                   p=C                                         10°C


                            DEW POINT


                                                                                      S




Figure 4         T-s Diagram of the Process of Lowering the Temperature of the Flue Gas
                 From 120°C to Point “ a ”
Results

       Both the piezometer and the pitot tube methods for determining the velocity and
pressure values at the chimney exit was not realized. This is one difficulty encountered
by the undersigned in this study. The management of Energizer Philippines did not allow
the undersigned to set-up a piezometer opening at the side of the stack. Instead, they
requested that the static pressure of the flue gas be estimated based on the distance
between the chimney exit and the elevation where the burners are located. This distance
is measured as 6 meters. From the energy equation,
                                    p1 v12        p 2 v22
                               z1 +   +    = z2 +    +
                                    γ 2g           γ   2g

Since v1 = v 2 , and       p1 = 101,325 N / m 2 ( flue gas pressure at the burners is
atmospheric), the energy equation can be simplified into;
                                p1 − p2     p − p2
                                         = 1            = z 2 − z1 = 6m
                                   γ            ρg
Substituting values, we have;
                                   101,325 N / m 2 − p 2
                                                                = 6m
                               (2.8089kg / m 3 )(9.8m / sec 2 )
Where                                 p 2 = 101,159.8 N / m 2
                                                     14.696 psi 
                                 (                 )
                      p 2 = p g = 101,159.8 N / m 2 
                                                     101,325 N / m 2  = 14.672 psi
                                                                      
                                                                     
And                   ∆p = p 2 − p1 = 14.672 psi − 14.696 psi = −0.024 psi
                                            1" Hg 
                      ∆p = ( − 0.024 psi ) 
                                            0.4898 psi  = −0.049" Hg
                                                        
                                                       

       Neither did management allow the setting up of a pitot tube to measure the flue
gas velocity. Instead, their engineers provided the specifications of the exhaust blower.

Direct Drive Exhaust Blower, 1 Horsepower
    1” static        2” static        3” static                 4” static       5” static
    pressure         pressure         pressure                  pressure        pressure
    800 cfm          740 cfm          680 cfm                   600 cfm         500 cfm

The delivery volume of 800 cfm was chosen because 1 inch static pressure is closest to
the computed static pressure of 0.049 inch. Figure 5 below shows the actual set-up of the
post-torcher chimney on the right and the melting tank chimney on the left.
800 cfm

         TO EXHAUST BLOWER



                      7.5”
                                                       400 cfm
       MELTING TANK
       CHIMNEY                                              POST TORCHER
                                  400 cfm                   CHIMNEY




                                      7.5”


                                             POST TORCHER

Fig 5 Diagram Showing Post Torcher Chimney and Exhaust Blower
                                     1m 3 
                       (
                  400 ft / min 
                           3
                                       )
                                     35.31 ft 3 (1 min/ 60 sec )
                                                 
            vg =                                                    = 6.624m / sec
                 π ( ( 7.5inch )(1 ft / 12inches )(1m / 3.28 ft ) )
                                                                    2


                                           4

       The partial pressure of the water vapor, pH 2 O is the product of the mole fraction
of the water vapor multiplied by the pressure of the flue gas at the exit of the chimney.
                       pH 2 O = xH 2 O p g = ( 0.1550) p g
Substituting the value of p g , obtained from 6.4, we have,
                        p = (0.1550)(14.672 psi ) = 2.274 psi

       The corresponding dew point temperature was then read out from the Steam
Tables ( Properties of Saturated Water : Pressure ).
                       Tdp = 54.588°C

       And the exit temperature of the flue gas “ Tgf ” was computed by adding a safety
margin of 10ºC as;
                      Tgf = 54.588°C + 10°C = 64.588°C say 65°C

        The sensible heat from the flue gas was calculated using the equation as follows

                                               KJ 
                           Q g = m g 1.096131         (120°C − 65°C )
                                              kg °C 
                                                     
but
            kg π (0.1905m) 2 
m g = 2.8089 3               (6.624m / sec) = 0.5303kg / sec
            m        4       
                                                               KJ 
Therefore                    Qs = ( 0.5303kg / sec ) 1.096131         (120°C − 65°C )
                                                              kg °C 
                                                                     
                                         kJ
                             Q = 31.97
                                        sec

Conclusion

    It was found out in this study that for an 8-hour per day operation the available
amount of waste heat is 920.736 MJ. Considering only half of this energy will be
recovered for plant process requirements, and basing on the cost of electricity at 6.253
pesos per kilowatt-hour, an energy cost savings of 800 pesos per day can be realized.

    A heat exchanger with water in the inside can be designed, fabricated , and then
mounted into the space inside the hood located directly above the post torcher burners to
absorb the waste heat. The hot water coming from this heat exchanger can then be used
for internal process requirements.

                                    REFERENCES

       The World Book Encyclopedia, Volume 2, World Book International Inc., 1995,
       p. 676

       Borman G. L. and Ragland K. W., Combustion Engineering, International
       Edition, Mc Graw-Hill, 1998, p. 67

       Alkhamis T. M., Alhusein M. A., and Kablan M. M., (1996) “Utilization of
       Waste Heat From the Kitchen Furnace of an Enclosed Campus” Energy
       Conservation and Management Journal, Vol. 39, No. 10, 1998, p 1115

       Borman G. L. and Ragland K. W., Combustion Engineering, International
       Edition, Mc Graw-Hill, 1998, p. 64

       Daugherty R. L. and Franzini J. B., Fluid Mechanics With Engineering
       Applications, 7th Edition, McGraw Hill, 1977, pp. 374 – 377

Contenu connexe

Tendances

Properties of steam
Properties of steamProperties of steam
Properties of steamJitin Pillai
 
DESIGN OF AIR PRE HEATER AND ECONOMIZER
DESIGN OF AIR PRE HEATER AND ECONOMIZERDESIGN OF AIR PRE HEATER AND ECONOMIZER
DESIGN OF AIR PRE HEATER AND ECONOMIZERGopi Chand
 
Thermodynamics lab manual
Thermodynamics lab manualThermodynamics lab manual
Thermodynamics lab manualDr. Ramesh B
 
B.tech i eme u 1 intoduction
B.tech i eme u 1 intoductionB.tech i eme u 1 intoduction
B.tech i eme u 1 intoductionRai University
 
B.tech i eme u 1 intoduction
B.tech i eme u 1 intoductionB.tech i eme u 1 intoduction
B.tech i eme u 1 intoductionRai University
 
Final lab report for thermos 2(mech)
Final lab report for thermos 2(mech)Final lab report for thermos 2(mech)
Final lab report for thermos 2(mech)lizwi nyandu
 
Fan and blowers (mech 326)
Fan and blowers (mech 326)Fan and blowers (mech 326)
Fan and blowers (mech 326)Yuri Melliza
 
Thermodynamic Design of a Fire-Tube Steam Boiler
Thermodynamic Design of a Fire-Tube Steam BoilerThermodynamic Design of a Fire-Tube Steam Boiler
Thermodynamic Design of a Fire-Tube Steam BoilerJohn Walter
 
Air standard cycles
Air standard cyclesAir standard cycles
Air standard cyclesSoumith V
 
Se prod thermo_examples_compressor
Se prod thermo_examples_compressorSe prod thermo_examples_compressor
Se prod thermo_examples_compressorVJTI Production
 
Cooling Tower & Dryer Fundamentals
Cooling Tower & Dryer FundamentalsCooling Tower & Dryer Fundamentals
Cooling Tower & Dryer FundamentalsYuri Melliza
 
Refrigeration system 2
Refrigeration system 2Refrigeration system 2
Refrigeration system 2Yuri Melliza
 
THERMODYNAMICS Unit III
THERMODYNAMICS Unit  III THERMODYNAMICS Unit  III
THERMODYNAMICS Unit III sureshkcet
 
Ppt of properties of steam
Ppt of properties of steamPpt of properties of steam
Ppt of properties of steamKaushal Mehta
 
Design With Solid works Software and Planning Calculation Analysis of Fire Tu...
Design With Solid works Software and Planning Calculation Analysis of Fire Tu...Design With Solid works Software and Planning Calculation Analysis of Fire Tu...
Design With Solid works Software and Planning Calculation Analysis of Fire Tu...IJRES Journal
 
Beikircher solar energy 1996 2
Beikircher solar energy 1996 2Beikircher solar energy 1996 2
Beikircher solar energy 1996 2luthfiyyahadelia
 

Tendances (20)

Properties of steam
Properties of steamProperties of steam
Properties of steam
 
DESIGN OF AIR PRE HEATER AND ECONOMIZER
DESIGN OF AIR PRE HEATER AND ECONOMIZERDESIGN OF AIR PRE HEATER AND ECONOMIZER
DESIGN OF AIR PRE HEATER AND ECONOMIZER
 
Thermodynamics lab manual
Thermodynamics lab manualThermodynamics lab manual
Thermodynamics lab manual
 
B.tech i eme u 1 intoduction
B.tech i eme u 1 intoductionB.tech i eme u 1 intoduction
B.tech i eme u 1 intoduction
 
B.tech i eme u 1 intoduction
B.tech i eme u 1 intoductionB.tech i eme u 1 intoduction
B.tech i eme u 1 intoduction
 
Final lab report for thermos 2(mech)
Final lab report for thermos 2(mech)Final lab report for thermos 2(mech)
Final lab report for thermos 2(mech)
 
Fan and blowers (mech 326)
Fan and blowers (mech 326)Fan and blowers (mech 326)
Fan and blowers (mech 326)
 
Hvac formulas
Hvac formulasHvac formulas
Hvac formulas
 
Thermodynamic Design of a Fire-Tube Steam Boiler
Thermodynamic Design of a Fire-Tube Steam BoilerThermodynamic Design of a Fire-Tube Steam Boiler
Thermodynamic Design of a Fire-Tube Steam Boiler
 
Air standard cycles
Air standard cyclesAir standard cycles
Air standard cycles
 
Se prod thermo_examples_compressor
Se prod thermo_examples_compressorSe prod thermo_examples_compressor
Se prod thermo_examples_compressor
 
Properties of steam (2)
Properties of steam (2)Properties of steam (2)
Properties of steam (2)
 
Specific volume of steam
Specific volume of steamSpecific volume of steam
Specific volume of steam
 
Cooling Tower & Dryer Fundamentals
Cooling Tower & Dryer FundamentalsCooling Tower & Dryer Fundamentals
Cooling Tower & Dryer Fundamentals
 
Refrigeration system 2
Refrigeration system 2Refrigeration system 2
Refrigeration system 2
 
Pure substances
Pure substances Pure substances
Pure substances
 
THERMODYNAMICS Unit III
THERMODYNAMICS Unit  III THERMODYNAMICS Unit  III
THERMODYNAMICS Unit III
 
Ppt of properties of steam
Ppt of properties of steamPpt of properties of steam
Ppt of properties of steam
 
Design With Solid works Software and Planning Calculation Analysis of Fire Tu...
Design With Solid works Software and Planning Calculation Analysis of Fire Tu...Design With Solid works Software and Planning Calculation Analysis of Fire Tu...
Design With Solid works Software and Planning Calculation Analysis of Fire Tu...
 
Beikircher solar energy 1996 2
Beikircher solar energy 1996 2Beikircher solar energy 1996 2
Beikircher solar energy 1996 2
 

En vedette

El planeta terra
El planeta terraEl planeta terra
El planeta terramarysocjo
 
Flip Mino Brand Positioning
Flip Mino Brand Positioning Flip Mino Brand Positioning
Flip Mino Brand Positioning noahsimon
 
Flip Mino Brand Positioning
Flip Mino Brand Positioning Flip Mino Brand Positioning
Flip Mino Brand Positioning noahsimon
 
Automatic Calibration 3 D
Automatic Calibration 3 DAutomatic Calibration 3 D
Automatic Calibration 3 Drajsodhi
 
New Target
New TargetNew Target
New Targetranraviv
 
Lead By Feel
Lead By FeelLead By Feel
Lead By Feelnzfrench
 
Module 6 Linear Slide Show - CGaither
Module 6 Linear Slide Show - CGaitherModule 6 Linear Slide Show - CGaither
Module 6 Linear Slide Show - CGaitherguestd91c11
 
L'art en la Prehistòria
L'art en la PrehistòriaL'art en la Prehistòria
L'art en la Prehistòriamarysocjo
 
El planeta terra
El planeta terraEl planeta terra
El planeta terramarysocjo
 
Reducing The Vibration Level Of The Blast Fan
Reducing The Vibration Level Of The Blast FanReducing The Vibration Level Of The Blast Fan
Reducing The Vibration Level Of The Blast Fanharlandmachacon
 
Agilent Technologies Corporate Overview
Agilent Technologies Corporate OverviewAgilent Technologies Corporate Overview
Agilent Technologies Corporate Overviewrajsodhi
 
Experiències de mescles
Experiències de mesclesExperiències de mescles
Experiències de mesclesmarysocjo
 
presentation Yves Rocher
presentation Yves Rocherpresentation Yves Rocher
presentation Yves RocherLivine Girolami
 

En vedette (17)

El planeta terra
El planeta terraEl planeta terra
El planeta terra
 
Flip Mino Brand Positioning
Flip Mino Brand Positioning Flip Mino Brand Positioning
Flip Mino Brand Positioning
 
Flip Mino Brand Positioning
Flip Mino Brand Positioning Flip Mino Brand Positioning
Flip Mino Brand Positioning
 
Context Aware Front End
Context Aware Front EndContext Aware Front End
Context Aware Front End
 
Automatic Calibration 3 D
Automatic Calibration 3 DAutomatic Calibration 3 D
Automatic Calibration 3 D
 
New Target
New TargetNew Target
New Target
 
Lead By Feel
Lead By FeelLead By Feel
Lead By Feel
 
Module 6 Linear Slide Show - CGaither
Module 6 Linear Slide Show - CGaitherModule 6 Linear Slide Show - CGaither
Module 6 Linear Slide Show - CGaither
 
Malmo2009
Malmo2009Malmo2009
Malmo2009
 
L'art en la Prehistòria
L'art en la PrehistòriaL'art en la Prehistòria
L'art en la Prehistòria
 
El planeta terra
El planeta terraEl planeta terra
El planeta terra
 
Hemorragias del primer trimestre
Hemorragias del primer trimestreHemorragias del primer trimestre
Hemorragias del primer trimestre
 
Reducing The Vibration Level Of The Blast Fan
Reducing The Vibration Level Of The Blast FanReducing The Vibration Level Of The Blast Fan
Reducing The Vibration Level Of The Blast Fan
 
Picasso
PicassoPicasso
Picasso
 
Agilent Technologies Corporate Overview
Agilent Technologies Corporate OverviewAgilent Technologies Corporate Overview
Agilent Technologies Corporate Overview
 
Experiències de mescles
Experiències de mesclesExperiències de mescles
Experiències de mescles
 
presentation Yves Rocher
presentation Yves Rocherpresentation Yves Rocher
presentation Yves Rocher
 

Similaire à Estimating The Available Amount Of Waste Heat

HdhdPM3125_Lectures_16to17_Evaporation.ppt
HdhdPM3125_Lectures_16to17_Evaporation.pptHdhdPM3125_Lectures_16to17_Evaporation.ppt
HdhdPM3125_Lectures_16to17_Evaporation.pptJENILPATEL919230
 
Ae32626632
Ae32626632Ae32626632
Ae32626632IJMER
 
1590701599PTE_526-Natural_Gas_Engineering (1).pptx
1590701599PTE_526-Natural_Gas_Engineering (1).pptx1590701599PTE_526-Natural_Gas_Engineering (1).pptx
1590701599PTE_526-Natural_Gas_Engineering (1).pptxokekeekene
 
Energy Science -Short-.pdf
Energy Science -Short-.pdfEnergy Science -Short-.pdf
Energy Science -Short-.pdfAdityaSem12
 
Energy Science -Short- (Alane sir).pdf
Energy Science -Short- (Alane sir).pdfEnergy Science -Short- (Alane sir).pdf
Energy Science -Short- (Alane sir).pdfAdityaSem12
 
Fuel and combustion
Fuel and combustionFuel and combustion
Fuel and combustionRaju Mirdha
 
Analysis of the Thermal Efficiency of Condensing Wall-Hung Boiler
Analysis of the Thermal Efficiency of Condensing Wall-Hung BoilerAnalysis of the Thermal Efficiency of Condensing Wall-Hung Boiler
Analysis of the Thermal Efficiency of Condensing Wall-Hung BoilerIJRES Journal
 
Chemical engineering thermo dynamics Ii Jntu Model Paper{Www.Studentyogi.Com}
Chemical engineering thermo dynamics Ii Jntu Model Paper{Www.Studentyogi.Com}Chemical engineering thermo dynamics Ii Jntu Model Paper{Www.Studentyogi.Com}
Chemical engineering thermo dynamics Ii Jntu Model Paper{Www.Studentyogi.Com}guest3f9c6b
 
Download Solution Manual for Physical Chemistry 6th Edition by Robert A. Albe...
Download Solution Manual for Physical Chemistry 6th Edition by Robert A. Albe...Download Solution Manual for Physical Chemistry 6th Edition by Robert A. Albe...
Download Solution Manual for Physical Chemistry 6th Edition by Robert A. Albe...NetaLavi
 
Refrigeration system 2
Refrigeration system 2Refrigeration system 2
Refrigeration system 2Yuri Melliza
 

Similaire à Estimating The Available Amount Of Waste Heat (20)

HdhdPM3125_Lectures_16to17_Evaporation.ppt
HdhdPM3125_Lectures_16to17_Evaporation.pptHdhdPM3125_Lectures_16to17_Evaporation.ppt
HdhdPM3125_Lectures_16to17_Evaporation.ppt
 
Ae32626632
Ae32626632Ae32626632
Ae32626632
 
Ch.10
Ch.10Ch.10
Ch.10
 
Lecture7
Lecture7Lecture7
Lecture7
 
1590701599PTE_526-Natural_Gas_Engineering (1).pptx
1590701599PTE_526-Natural_Gas_Engineering (1).pptx1590701599PTE_526-Natural_Gas_Engineering (1).pptx
1590701599PTE_526-Natural_Gas_Engineering (1).pptx
 
Steam tables
Steam tablesSteam tables
Steam tables
 
Energy Science -Short-.pdf
Energy Science -Short-.pdfEnergy Science -Short-.pdf
Energy Science -Short-.pdf
 
Energy Science -Short- (Alane sir).pdf
Energy Science -Short- (Alane sir).pdfEnergy Science -Short- (Alane sir).pdf
Energy Science -Short- (Alane sir).pdf
 
Ch.15
Ch.15Ch.15
Ch.15
 
Fuel and combustion
Fuel and combustionFuel and combustion
Fuel and combustion
 
Ch.17
Ch.17Ch.17
Ch.17
 
Analysis of the Thermal Efficiency of Condensing Wall-Hung Boiler
Analysis of the Thermal Efficiency of Condensing Wall-Hung BoilerAnalysis of the Thermal Efficiency of Condensing Wall-Hung Boiler
Analysis of the Thermal Efficiency of Condensing Wall-Hung Boiler
 
30 ppd
30 ppd30 ppd
30 ppd
 
Chemical engineering thermo dynamics Ii Jntu Model Paper{Www.Studentyogi.Com}
Chemical engineering thermo dynamics Ii Jntu Model Paper{Www.Studentyogi.Com}Chemical engineering thermo dynamics Ii Jntu Model Paper{Www.Studentyogi.Com}
Chemical engineering thermo dynamics Ii Jntu Model Paper{Www.Studentyogi.Com}
 
Extraction 2
Extraction 2Extraction 2
Extraction 2
 
Extraction 2
Extraction 2Extraction 2
Extraction 2
 
www.ijerd.com
www.ijerd.comwww.ijerd.com
www.ijerd.com
 
Combustion and fules
Combustion and fulesCombustion and fules
Combustion and fules
 
Download Solution Manual for Physical Chemistry 6th Edition by Robert A. Albe...
Download Solution Manual for Physical Chemistry 6th Edition by Robert A. Albe...Download Solution Manual for Physical Chemistry 6th Edition by Robert A. Albe...
Download Solution Manual for Physical Chemistry 6th Edition by Robert A. Albe...
 
Refrigeration system 2
Refrigeration system 2Refrigeration system 2
Refrigeration system 2
 

Estimating The Available Amount Of Waste Heat

  • 1. Estimating the Available Amount of Waste Heat From the Asphalt Dispenser Machine of a Dry Cell Manufacturing Plant Harland C. Machacon, M. Eng. Department of Mechanical-Industrial Engineering College of Engineering, University of San Carlos, Cebu City The Asphalt Dispenser Machine melts and dispenses asphalt into Le- clanche type dry cells thus producing a leak proof seal between the carbon electrode and the zinc can. Asphalt chunks are melted to a temperature of 180° C using electric strip heaters. The molten asphalt is then dispensed into a batch of dry cells indexed beneath the dispensing tank. This batch of cells is then led into a torching conveyor where three large LPG burners spread out the dispensed asphalt evenly to form a meniscus at the electrode and at the can lip. These burners also ensure that the asphalt seal is free of air bubbles that might eventually form into pin-sized holes. This piece of equipment has a capacity of over half a million Leclanche dry cells for each operating day. The hot gases resulting from the combustion process of LPG in these large burners are collected in an exhaust hood-and-chimney set-up. The flue gas is then exhausted into the environment via a direct-drive exhaust blower. Huge amounts of energy are dissipated into the environment. This is indeed a major economic loss aside from being a source of thermal pollution. Within the last four years the cost of fuel has more than doubled. Prices of petroleum products are always affected by price increases in the world market and also by the devaluation of our local currency. In the manufacture of dry cells, energy cost contribute approximately 5 percent of the total manufacturing cost. Hence the battery company has launched vigorous cost-reduction efforts. This study is about estimating the recoverable heat from the flue gas that would otherwise be considered lost energy and a cause of thermal pollution.
  • 2. Figure 1 The Asphalt Dispenser Machine Source of Waste Heat The major source of waste heat from the Asphalt Dispenser Machine is the hot gases resulting from the combustion process of Liquefied Petroleum Gas in the large post-torch burners. The flue gases are then collected in an exhaust hood-and-chimney set- up and eventually exhausted into the environment via a direct-drive exhaust blower. The chemical formula of the fuel used in the burners, Liquefied Petroleum Gas is, C 3 H 8 , since LPG is composed primarily of propane[ 1 ]. The chemical reaction is described as follows; C 3 H 8 + 5(O2 + 3.76 N 2 ) → 3CO2 + 4 H 2 O + 5(3.76 N 2 ) (1) The products of combustion are carbon dioxide, water vapor, and nitrogen[ 2 ].
  • 3. CHIMNEY EXHAUST HOOD FLUE GAS LPG BURNER 1 LPG BURNER 2 LPG BURNER 3 TORCHING CONVEYOR Figure 2 Schematic Illustration Showing the Heat Source of the Asphalt Dispenser Machine Physical Properties of the Flue Gas The specific heat of the flue gas, in kJ/kg-°K is the summation of the products of the respective mass fractions and the corresponding specific heat values of each individual component of the flue gas[ 3 ]. n c pg = ∑ yi c pi (2) i Hence, c pg = yc pCO2 + yc p H 2O + yc p N 2 Table 1 Determining the Specific Heat of the Flue Gas Products Number Mole Molecular Mass cpi of of Fraction Weight Fraction Combustion Moles xi Mi M i xi yi BTU/lb°R yicpi CO2 3 0.1163 44 5.1172 0.1808 0.187055 0.033820 H2O 4 0.1550 18 2.7900 0.0985 0.491999 0.048462 N2 18.8 0.7287 28 20.4036 0.7207 0.249080 0.179512 TOTAL 25.8 1.0000 28.3108 1.0000 0.261794
  • 4. BTU kJ kJ c pg = 0.261794 × 4.187 kg ° K = 1.096131 lb° R BTU lb ° R kg ° K The density of the flue gas is the summation of the densities of each individual component of the flue gas[ 4 ]. n ρ g = ∑ ρi (3) i The density values of the individual components of the flue gas at atmospheric pressure, can be taken from Table A-6, pages 647 – 648, Heat Transfer by J. P. Holman, 8th edition. The flue gas temperature of 120°C ( 393°K ) will be the reference temperature. Hence, ρg = ρ for CO2 + ρ for water vapor + ρ for N 2 (4) kg kg kg kg ρ ≡1.3695 g 3 +0.5654 3 +0.8740 3 =2.8089 3 m m m m The flue gas pressure at the burners is atmospheric because the burners exhaust directly to the atmosphere. The static pressure at the exit of the chimney right before the exhaust blower was supposed to be measured by attaching a pressure gage to a piezometer opening in the side of the conduit normal to and flush with the conduit surface. Similarly, the velocity of the flue gas at the above-mentioned point would have been measured by attaching a pressure gage to a pitot tube at the same level where the piezometer opening is located[ 5 ]. The difference of the readings of the two pressure gages represent the velocity head of the flue gas at such point. Hence the velocity of the flue gas could have been determined by computation. The steady flow energy equation applied at the stagnation point “0” could have been used to measure the velocity of the flue gas, vg . Simplifying the equation, we have the following result; 2 ( v g − 0 ) sec   m lbs in 2 1kg (3.28 ft ) 2 1 ( p 0 − p g ) 2 × 144 2 × × × =  in ft 2.2lbs m 2 kg  m  2.7504 3 2 9.8 2  m  sec  Given the values of p0 and p g from the pressure gauge readings, the velocity of the flue gas, vg can be solved. The partial pressure of the water vapor, pH 2 O is the product of the mole fraction of the water vapor multiplied by the pressure of the flue gas at the exit of the chimney.
  • 5. Table 2 Determining the Mole Fraction of the Products of Combustion PRODUCTS OF NUMBER OF MOLE FRACTION COMBUSTION MOLES xi CO2 3 0.1163 H 2O 4 0.1550 N2 18.8 0.7287 TOTAL 25.8 1.0000 Therefore, pH 2 O = xH 2 O p g = ( 0.1550) p g The corresponding dew point temperature is then read out from the Steam Tables ( Properties of Saturated Water : Pressure ). pg PIEZOMETER TUBE p0 ( p0 - pg ) 0 PITOT TUBE FLUE GAS CHIMNEY MANOMETER Figure 3 Installation of Pitot Tube and Piezometer Tube at the Chimney
  • 6. Available Amount of Sensible Heat from the Flue Gas The temperature of the flue gas can be lowered from its initial temperature of 120°C down to point “a” which is 10°C above the dew point temperature of the water vapor. The safe level of 10°C above the dew point temperature of the water vapor ensures that the water vapor in the flue gas will not start to condense. The sensible heat from the flue gas was calculated using the equation Qs = mg c pg (Tgi − Tgf ) (5) but mg = ρgAcvg (6) and Tgf = 10 C + Tdp (7) and then substituting equations ( 6 ) and ( 7 ) in equation ( 5 ), the resulting equation for the sensible heat is; [ ( Qs = ρ g Ac vg c pg Tgi − 10 C + Tdp )] (8) T p=C pH 2 O SAFE LEVEL a 120°C p=C 10°C DEW POINT S Figure 4 T-s Diagram of the Process of Lowering the Temperature of the Flue Gas From 120°C to Point “ a ”
  • 7. Results Both the piezometer and the pitot tube methods for determining the velocity and pressure values at the chimney exit was not realized. This is one difficulty encountered by the undersigned in this study. The management of Energizer Philippines did not allow the undersigned to set-up a piezometer opening at the side of the stack. Instead, they requested that the static pressure of the flue gas be estimated based on the distance between the chimney exit and the elevation where the burners are located. This distance is measured as 6 meters. From the energy equation, p1 v12 p 2 v22 z1 + + = z2 + + γ 2g γ 2g Since v1 = v 2 , and p1 = 101,325 N / m 2 ( flue gas pressure at the burners is atmospheric), the energy equation can be simplified into; p1 − p2 p − p2 = 1 = z 2 − z1 = 6m γ ρg Substituting values, we have; 101,325 N / m 2 − p 2 = 6m (2.8089kg / m 3 )(9.8m / sec 2 ) Where p 2 = 101,159.8 N / m 2  14.696 psi  ( ) p 2 = p g = 101,159.8 N / m 2   101,325 N / m 2  = 14.672 psi    And ∆p = p 2 − p1 = 14.672 psi − 14.696 psi = −0.024 psi  1" Hg  ∆p = ( − 0.024 psi )   0.4898 psi  = −0.049" Hg    Neither did management allow the setting up of a pitot tube to measure the flue gas velocity. Instead, their engineers provided the specifications of the exhaust blower. Direct Drive Exhaust Blower, 1 Horsepower 1” static 2” static 3” static 4” static 5” static pressure pressure pressure pressure pressure 800 cfm 740 cfm 680 cfm 600 cfm 500 cfm The delivery volume of 800 cfm was chosen because 1 inch static pressure is closest to the computed static pressure of 0.049 inch. Figure 5 below shows the actual set-up of the post-torcher chimney on the right and the melting tank chimney on the left.
  • 8. 800 cfm TO EXHAUST BLOWER 7.5” 400 cfm MELTING TANK CHIMNEY POST TORCHER 400 cfm CHIMNEY 7.5” POST TORCHER Fig 5 Diagram Showing Post Torcher Chimney and Exhaust Blower  1m 3  ( 400 ft / min  3 )  35.31 ft 3 (1 min/ 60 sec )  vg =   = 6.624m / sec π ( ( 7.5inch )(1 ft / 12inches )(1m / 3.28 ft ) ) 2 4 The partial pressure of the water vapor, pH 2 O is the product of the mole fraction of the water vapor multiplied by the pressure of the flue gas at the exit of the chimney. pH 2 O = xH 2 O p g = ( 0.1550) p g Substituting the value of p g , obtained from 6.4, we have, p = (0.1550)(14.672 psi ) = 2.274 psi The corresponding dew point temperature was then read out from the Steam Tables ( Properties of Saturated Water : Pressure ). Tdp = 54.588°C And the exit temperature of the flue gas “ Tgf ” was computed by adding a safety margin of 10ºC as; Tgf = 54.588°C + 10°C = 64.588°C say 65°C The sensible heat from the flue gas was calculated using the equation as follows  KJ  Q g = m g 1.096131 (120°C − 65°C )  kg °C  
  • 9. but  kg π (0.1905m) 2  m g = 2.8089 3  (6.624m / sec) = 0.5303kg / sec  m  4   KJ  Therefore Qs = ( 0.5303kg / sec ) 1.096131 (120°C − 65°C )  kg °C   kJ Q = 31.97 sec Conclusion It was found out in this study that for an 8-hour per day operation the available amount of waste heat is 920.736 MJ. Considering only half of this energy will be recovered for plant process requirements, and basing on the cost of electricity at 6.253 pesos per kilowatt-hour, an energy cost savings of 800 pesos per day can be realized. A heat exchanger with water in the inside can be designed, fabricated , and then mounted into the space inside the hood located directly above the post torcher burners to absorb the waste heat. The hot water coming from this heat exchanger can then be used for internal process requirements. REFERENCES The World Book Encyclopedia, Volume 2, World Book International Inc., 1995, p. 676 Borman G. L. and Ragland K. W., Combustion Engineering, International Edition, Mc Graw-Hill, 1998, p. 67 Alkhamis T. M., Alhusein M. A., and Kablan M. M., (1996) “Utilization of Waste Heat From the Kitchen Furnace of an Enclosed Campus” Energy Conservation and Management Journal, Vol. 39, No. 10, 1998, p 1115 Borman G. L. and Ragland K. W., Combustion Engineering, International Edition, Mc Graw-Hill, 1998, p. 64 Daugherty R. L. and Franzini J. B., Fluid Mechanics With Engineering Applications, 7th Edition, McGraw Hill, 1977, pp. 374 – 377