- 1. Journal of Energy Technologies and Policy www.iiste.orgISSN
2224-3232 (Paper) ISSN 2225-0573 (Online)Vol.2, No.5, 2012 Thermal
Analysis of a Small-Scale Municipal Solid Waste-FiredSteam
Generator: Case Study of Enugu State, Nigeria A. J. Ujama*and F.
Ebohba. Department of Mechanical and Production Engineering, Enugu
state University of Science and Technology (ESUT), Enugu,
Nigeria.b. Department of Mechanical Engineering, Michael Okpara
University of Agriculture, Umudike, Abia State, Nigeria. *Email:
[email protected] analysis of a small-scale
municipal solid waste-fired steam generator has been presentedin
this work. The analysis was based on the selected design
parameters: operating steam pressure of10 bar, with fuel
consumption rate of 500 Kg/h and combustion chamber which utilizes
mass burnincineration using water wall furnace. The plant is
designed as a possible option for thermalutilization of rural and
urban wastes in Nigeria. The average daily generation of MSW
wasconsidered in order to assess the availability of the material.
The data were collected from EnuguState Waste Management Authority
(ENSWAMA).This was calculated based on the statepopulation,
urbanization and industrialization strengths. Calculation of
calorific value of the wasteto determine the heat contents was
carried out using two methods: Bomb calorimeter and Dulongsformula.
Some samples of the garbage were analyzed with bomb calorimeter in
the National CentreFor Energy Research & Development
Laboratory, University of Nigeria Nsukka. This is importantbecause
it a direct measure of the temperature requirements that the
specific waste will place on thesystem. The calorific values
obtained from this analysis were 12572.308 KJ/kg, 14012.05
KJ/kg,21833.26 KJ/kg and 20551.01 KJ/kg for paper products, woods,
plastics and textiles wasterespectively, while the energy content
obtained from the elemental composition of waste usingDulongs
formula was 15,101 KJ/kg .The maximum temperature of the furnace
attained from theenergy balance based on this value around the
combustion chamber was 833.7 K and the amount ofair required per kg
of MSW was 8.66kgKeywords: Solid-Waste, Steam, Temperature,
Pressure, Moisture Content, Calorific Value1.0 IntroductionA
significant challenge confronting engineers and scientists in
developing countries is the searchfor appropriate solution for the
collection, treatment, and disposal or reuse of domestic waste
toproduce energy. Although the energy needs have been met by the
discovery of fossil fuel deposits,these deposits are limited in
quantity; exploration and production costs to make them
commerciallyavailable are high. Our energy needs have also grown
exponentially, corresponding with humanpopulation growth and
technological advancement.38
2. Journal of Energy Technologies and Policywww.iiste.orgISSN
2224-3232 (Paper) ISSN 2225-0573 (Online)Vol.2, No.5,
2012Waste-to-energy facilities are part of the solution of the
worldwide solid waste disposal problem.These facilities, when
combined with recycling of critical material, composting, and
landfilling,will be a long-term economic solution as long as they
are designed and operated in anenvironmentally acceptable manner.As
a result of high carbon dioxide, CO2 emission from thermal energy
conversion of fossil fuelswhich is one of the major causes of the
greenhouse effect, boiler technologies based on biomassconversion
represent a great potential to reduce CO2 emission since they are
based on theutilization of renewal energy source.Furthermore, since
conventional energy sources are finite and fast depleting and
energy demand ison the increase, it is necessary for scientists and
engineers to explore alternative energy sources,such as municipal
solid waste (MSW).Biomass is abundantly available on the earth in
the form of agricultural residues, city garbage,cattle dung, but is
normally underutilized. For an efficient utilization of these
resources, adequatedesign of municipal solid waste- fired steam
boiler is necessary in order to extract heat produced inthe
combustion of waste, considering the calculated high calorific
value of MSW and theavailability of this material around us. The
environmental benefits of biomass technologies areamong its
greatest assets. Global warming is gaining greater acceptance in
the scientificcommunity. There appears now to be a consensus among
the worlds leading environmentalscientists and informed individuals
in the energy and environmental communities that there is
adiscernable human influence on the climate; and that there is a
link between the concentration ofcarbon dioxide (one of the
greenhouse gases) and the increase in global temperatures.
Appropriateutilization of Municipal Solid Waste when used can play
an essential role in reducing greenhousegases, thus reducing the
impact on the atmosphere. In addition, some of the fine particles
emitted from MSW are beneficial. Bottom and fly ash arebeing mixed
with sludge from brewerys wastewater effluent treatment in a
composting process,thus resulting in the production of a solid
fertilizer. The possibility of selling the bottom and fly ashto the
ceramics industry is also being considered, which increases the
potentials of MSW firedsteam boiler. S.O. Adefemi et al[1] in their
work on this subject correlated the concentration ofheavy metals in
roots of plant from Igbaletere (in Nigeria) dump site with the
concentration ofheavy metals in the soil samples from the dump
site. A. B. Nabegu[2] found out that solid wastegenerated by
households (62.5%) in Kano metropolis far out weighed that
generated by variousinstitutions in the same metropolis (5.8%). In
the analysis of Municipal Solid Waste managementin Addis Ababa,
Nigatu et al[3] observed that part of the reasons for low
performance solid wastemanagement was the inadequate and
malfunctioning of operation equipment and open burning ofgarbage.
This study thus seeks to analyse an efficient operating and burning
system. 39 3. Journal of Energy Technologies and Policy
www.iiste.orgISSN 2224-3232 (Paper) ISSN 2225-0573 (Online)Vol.2,
No.5, 20122.0 Combustion Analysis of municipal solid waste (MSW)
Considering the theoretical combustion reaction for the organic
component of the waste, such ascarbon, hydrogen and sulphur, Coskun
et al [4] gave the equation for stoichiometric combustion as :C+
(O2 +N2) CO2 +N2(1)H + 0.25(O2 + 3.76N2)0.5H2O+0.94N2(2)S+(O2 +
3.76N2) SO2 + 3.76N2(3)It is known that nitrogen reacts with oxygen
over about 12000C to form NOx. In calculations, theupper limit of
the flue gas temperature is assumed as 12000 C. Combustion process
is assumed as inideal case (Stiochiometric). So, nitrogen is not
considered to react with oxygen during combustionreaction. It
limits the intimacy between the fuel molecules and O2 [4]Table 1
shows the average daily generation of municipal solid waste in
various states of Nigeria.Table 1 Average daily generation of MSW
in NigeriaS/NState Metric S/N StateMetric S/NState Metric Tonne
Tonne Tonne1Abia1114 Enugu 8 27 Ogun92Adamawa 8 15 Gombe 6 28
Ondo93Anambra 1116 Imo 1029 Osun74Akwa-Ibom 7 17 Jigawa9 30 Oyo
125Balyesa 8 18 Kaduna1531 Plateau 96Bauchi9 19 Kano2432
Rivers157Benue 8 20 Kastina 1133 Sokoto98Borno 8 21 Kebbi 7 34
Taraba69Cross River 9 22 Kogi7 35 Yobe610 Delta 1223 Kwara 7 36
Zamfara 6 40 4. Journal of Energy Technologies and
Policywww.iiste.orgISSN 2224-3232 (Paper) ISSN 2225-0573
(Online)Vol.2, No.5, 201211 Ebonyi724Lagos 3037FCT 1112 Edo
825Nasarawa613 Ekiti 726Niger 10(Source: ENSWAMA, MOE and
NPC)Complete combustion by using excess air can be expressed as
follows:C + (I + ) (O2 + 3.76CO2) CO2 + (I + ) (3.76N2 ) + O2 (4)H
+ (I + ) (O2 + 3.76N2) 0.5H2O + (I + ) (3.76 N2) + (0.75+ )O2 (5)S
+ (I + ) (O2 + 3.76N2) SO2 + (I + ) (3.76N2) + O2 (6)In combustion
reaction, is the fraction of excess combustion air, having the
relationship, n = (1+ )where n is the excess air ratio and =The
mass balance equation can be expressed as showed in figure 1 in the
form as,min= mout (7)i.e. The mass of reactants is equal to the
mass of productsmfuel + mair = mflue gas + mash +mmst (8)mfluegas =
mair + (mfuel - mash mmst) (9)From Eqn. 8mair = (mfluegas+ mash +
mmst) mfuel(10)mfuel mflue gasmair Combustion Chamber mmstmashFig.1
Mass balance in the Furnace Stiochiometric air amount (n=1) can be
calculated as follows;mair steo = O2 required per kilogram of the
fuel/23.3% of O2 in air = mO,HKH mO,OKO + mO,SKS + mO,CKC/0.233
(11)Where mO,H , mO,O , mO,S , mO,C , are the masses of oxygen in
hydrogen,oxygen,sulphur and carbonrespectively. 328K H K O + K S +
K Cmair,steo =12 (12)0.233mair.Steo. = 34.3348K H 4.2918K O +
4.2918K S + 11.4449K Cmair.steo. = (3K H 0.3750KO + 0.3750K S + K C
)11.4449 (13)With excess air ratio,41 5. Journal of Energy
Technologies and Policywww.iiste.orgISSN 2224-3232 (Paper) ISSN
2225-0573 (Online)Vol.2, No.5, 2012mair = (3K H 0.3750KO + 0.3750K
S + KC )(11.4449)(1 + ) (14)Where K denotes the percentage ratio of
the element in chemical composition (in %) and mair is theair
requirement per kg fuel (kg air/kg fuel). Flue gas amount can be
found by Eq. 9 Substituting Eq.13 in Eq. 9, knowing that
calculations are done for 1 kg fuel, so the equation canbe
expressed as follows:m fluegas = (3K H 0.3750K O + 0.3750K S + K C
)(11.4449) + (1-Kash-Kmst)(15)Employing the excess air ratio,m
fluegas = (3K H 0.3750KO + 0.3750K S + KC )(11.4449)(1 + ) + (1 K
ash K mst ) (16)Using the elemental composition of waste as shown
in figure 1, the calculation of amount of airrequired and the flue
gas produced can be done considering the above equations.Table 2
Percentage by mass of MSWElement CHOSN MoistureAshpercentage
35.55.123.9 0.52.4 257.6(Source : P.Chattopadhyay, [5])2.1
Calculation of Combustion air supply Considering theoretical
combustion reaction for the elemental analysis of MSW shown in
table 2,we have,Carbon (C):C+O2 CO212KgC+32KgO244KgCO2Oxygen
required = 0.355 * (32/12) = 0.947/Kg MSW (17)Carbon dioxide
produced = 0.355 * (44/12) = 1.302/Kg MSW (18)Hydrogen (H):H2 + 1 2
O2 H2O2Kg H2 + 16Kg O2 18Kg H2O1Kg H2 + 8Kg O2 9Kg H2OOxygen
required = 0.051 8 = 0.408 Kg/Kg MSW(19)Steam produced = 0.051 9 =
0.459 Kg/Kg MSW (20)Sulphur (S):S + O2 SO232Kg S + 32KgO2
64KgSO21KgS + 1KgO2 2KgSO2Oxygen required = 0.005 Kg/Kg
MSW(21)Sulphur dioxide produced = 2 0.005 = 0.01Kg/KgMSW(22)42 6.
Journal of Energy Technologies and Policy www.iiste.orgISSN
2224-3232 (Paper) ISSN 2225-0573 (Online)Vol.2, No.5, 2012Table 3
Oxygen Required per Kilogram of MSWConstituent Mass fraction Oxygen
required (Kg/Kg MSW)Carbon (C)0.355 0.947Hydrogen (H)0.051
0.408Sulphur (S) 0.005 0.005Oxygen (O)0.239 - 0.239Nitrogen
(N)0.024 ___Moisture0.25___Ash 0.190 ___Total 1.121O2 required per
Kilogram of MSW = 1.121Kg (23) 1.121Air required per Kilogram of
MSW = = 4.811Kg(24) 0.233Where air is assumed to contain 23.3% O2
by mass ie. Stiochiometric air/fuel ratio = 4.811:1For air supply
which is 80% in excess (this has been derived from industrial
experience accordingto (Chattopadhyay, [5]) which suggests that 80%
of excess air is just enough to optimize thecombustion of solid
refuse in the mass-burning system. 80 Actual A/F ratio, mair =
4.811 + 4.811 = 8.660/1(25) 100Or alternatively, mair can be found
using Eq. (14)2.2 Calculation of Calorific value of MSWThe first
step in the processing of a waste is to determine its calorific
content or heating value. Thisis a measure of the temperature and
the oxygen requirements that the specific waste will be placedon
the system[6]. The calorific value of a fuel can be determined
either from their chemical analysisor in the laboratory[7]. In the
laboratory Bomb Calorimeter is used. The analysis of some sample
ofwastes from the Energy Centre, UNN using Bomb Calorimeter are
shown in Table 443 7. Journal of Energy Technologies and
Policywww.iiste.orgISSN 2224-3232 (Paper) ISSN 2225-0573
(Online)Vol.2, No.5, 2012 Table 4 Calculation of Calorific value of
the fuel using Bomb CalorimeterPaper productWood wastePlastics
waste Textile wasteSample wt.,m,=1.060g Sample wt.,m,=0.974gSample
wt.,m,=1.023g Sample wt.,m,=1.065gInitial Temp. Initial
Temp.Initial Temp.Initial Temp. = 29.9860 C = 29.0150 C = 29.9330
C= 28.7430 CFinal Temp.Final Temp. = = Final Temp.Final Temp.
30.6950 C = =31.009 0 C 30.9810 C30.457 0 C T = 1.680 CT = 1.023 0
C 1 . 048 0 C T = 1.048 0 C T = 1.714 0
CUnburntUnburntUnburntUnburnt = 2.5+3.0=5.5 = 1.3+2.2=3.5 =
1.6+2.7=4.3= 2.5+0.8=3.3BurntBurntBurntBurnt= 10 - 5.5 = 4.5 = 10 -
3.5 = 6.5 = 10 - 4.3 = 5.7 = 10 - 3.3 = 6.7 = 4.5 * 2.3 = 10.35 =
6.5 * 2.3 = 14.95 = 5.7 * 2.3 = 13.11 = 6.7 * 2.3 = 15.41V = 2.3V =
2.5V = 3.9V = 3.8E = 13039.308E = 13039.308E = 13039.308E =
13039.308CVp = ( ET V ) / mCVw = ( ET V ) / mCVp = ( ET V ) / mCVp
= ( ET V ) / mCV P = 12572 .22 J / g CVw = 14012.05J / gCV P =
21833 .26 J / g CV P = 20551 ..01J / g = 12572.22KJ/kg=
14012.05KJ/kg= 21833.26KJ/kg = 20551.01KJ/kg(SOURCE; National
Centre For Energy Research & Development (NCERD), UNN.)For
chemical analysis, using Dulongs formula, percentage by mass was
considered and heat ofcombustion of Carbon, Oxygen and Hydrogen
determined as shown in Table 5Table 5 Heat of combustion for C, S
and HCombustionHeat of CombustionC+O2 CO2 8075kcal/kgS + O2
SO22220kcal/kg34500kcal/kgH2 + 1 2 O2 H2O(Source: P.Chattopadhyay,
2006) 44 8. Journal of Energy Technologies and Policy
www.iiste.orgISSN 2224-3232 (Paper) ISSN 2225-0573 (Online)Vol.2,
No.5, 2012Dulong suggested a formula for the calculation of the
calorific of the fuel from their chemicalcomposition asCVmsw =
8075(KC) +2220(KS) + 34500(KH KO/8)(26)where KC, KS, KH and KO
stand for percentage by mass of Carbon, Sulphur, Hydrogen and
Oxygenrespectively. Substituting the values of KC, KS, KH and KO
from Table 2 will give,CVmsw = 8075(0.355) + 2220(0.005) +
34500(0.051-0.239/8)CVmsw = 3,606.5Kcal/kg (27)CVmsw = 15,101 KJ/kg
- - - - - - - - - (1cal = 4.187J)Figures 2,3 & 4 show the views
of the municipal waste steam boiler Conditioner dislogde
Conditioner air feederConditioner air conveyor distribution
Conditioner Centilever bearings Bag filterFurnace ScrubberFigure 1
TOP VIEW OF MSW STEAM BOILER 45 9. Journal of Energy Technologies
and Policy www.iiste.orgISSN 2224-3232 (Paper) ISSN 2225-0573
(Online)Vol.2, No.5, 2012ChimneySteam valvePressure gaugeBoiler
tubeWater gaugeWater annulusScrubber BlowerFurnace Bag
FilterGrateFigure 2 FRONT VIEW OF MSW STEAM BOILER Boiler tubes
Waste Conditioners Figure 3 SIDE VIEW OF MSW STEAM BOILER3.0 Boiler
Calculations3.1 Maximum temperature of the furnaceTo obtain the
maximum temperature attained in the furnace, the analysis of heat
balance isnecessary. This is calculated by the following equation
[8]:Qf QfgFurnaceQs Quf 46 10. Journal of Energy Technologies and
Policywww.iiste.orgISSN 2224-3232 (Paper) ISSN 2225-0573
(Online)Vol.2, No.5, 2012Fig.4 Heat balance in the FurnaceQ f = Q
fg + Qs + Quf(28)Where, Q f is the heat liberated in the furnace; Q
fg is the heat of the flue gas; Qs is the heat usedin producing
steam and Quf is the heat lost due to unburnt fuel Q f = mmswCVmsw
(29)Where, mmsw and CVmsw are the mass of the fuel and the
calorific value of the waste respectivelyQ fg = m fg CPfg (T fg To
) (30)Where, m fg is the mass of the flue gas; CPfg is the specific
heat capacity of flue gas; T fg is themaximum temperature attained
in the furnace and To is the boiler reference temperature.Qs = mst
(h2 h1 )(31)Where, ms is the mass of the steam, h2 and h1 are
respectively specific enthalpy of steam, at10bar and specific
enthalpy of feed water, at 25 0 C Quf = muf CVmsw (32)Where muf is
the mass of unburnt fuel. Substituting (29)-(32) in (28), will
yieldmmswCVmsw = m fg CPfg (T fg To ) + ms (h2 h1 ) + muf
CVmswHence m msw CV mswm s t h2 h1 )muf CV mswT fg = + To (33)m fg
CP fgm f ( m fg CP fg ) m fg CP fgThe heat flux lost through the
external surfaces of the steam boiler to the environment is given
by[11] P 0.28Qls = 23Qsb (1.523Qsb ) 0.52 + P 5000 (34)3.2 Boiler
Efficiency47 11. Journal of Energy Technologies and Policy
www.iiste.orgISSN 2224-3232 (Paper) ISSN 2225-0573 (Online)Vol.2,
No.5, 2012 The boiler thermal efficiency, is calculated by the
following equation [9]:*Q&m st (h2 h1 ) = st = * 100 = &Qfm
msw CVmsw(35)3.3 Equivalent Evaporation of Boiler This is the
amount of water evaporated at 100 0 C , forming dry and saturated
steam at 100 0 C,at normal atmospheric pressure. As the water is
already at the boiling temperature, it requires onlylatent heat at
1.013bar to convert it into steam at the temperature (100 o C). The
value of this latentheat is taken as 2257 KJ/Kg. Thus, the
equivalent evaporation, E of a boiler, from and at 100 o C is[13] :
m p ( h2 h1 )E= (36) 2257 *m stWhere m p =* (37)mmsw(h2 h1 )And the
factor is known as factor of evaporation, and is usually denoted by
Fe . Its value2257is always greater than unity for all boilers.3.4
Boiler Horse Power (BHP) It is very commonly used unit for
measuring the capacity of a boiler. American Society ofMechanical
Engineers (ASME) defines a unit boiler horse power as the boiler
capacity to evaporate15.653kg of BFW per hour and at 373K into dry,
saturated steam or equivalent in heating effect. E hrBHP =
15.653(38)3.5 Furnace calculationsHeat released rate per unit
cross-sectional area of the furnace, q is given byQ ft q=(39)Ainc
48 12. Journal of Energy Technologies and Policy www.iiste.orgISSN
2224-3232 (Paper) ISSN 2225-0573 (Online)Vol.2, No.5, 2012Allowable
heat released rate of the furnace, qv Q ftqv = (40) Vinc4.0 Results
and DiscussionThe Engineering Equation Solver (EES), developed at
University of Wisconsin was used to obtainthe solution of the
equations.4.1 Parameters for solution of the municipal solid
waste-boiler design equationsThe results of the calculated
parameters for municipal solid waste design equations from
theprevious section are shown in table 6Table 6 Parameters for
solution of the municipal solid waste-boiler design equationsS/N
SymbolsCalculated S/NSymbols Calculated datadata 21 Ac [m
]0.197131muf [kg]0.326 22 Acyl [m ]0.405832O2 [%]80 223 Ainc [m
]0.955333P[N/m ] 1064 Atubes [m2]0.01623 34Qbw[kJ] 134.65
BHP[kW]0.258735 &2098 Q f [KW]6 CPfg [kJ/kg]1.04736& 2.841
Q fg [m3/s]7 CVmsw [KJ/kg] 1510137Qf [kJ] 101788 Dc[m] 0.5529 38Qfg
[kJ]52359 Dinc[m] 0.7188 39Qls[kJ] 957810Doc[m]0.8343
40Qr[kJ]6504S/N Symbols Calculated S/N Symbols Calculateddata
data11Dtubes[m] 0.0718841Qs[kJ]126912E [kg/kg] 4.04942Quf
[kJ]190013eff.[%] 60.5243fg [ kg/m3]0.472314H[m]7.02 44r1[m]
0.00564315H1 [kJ/kg]76345rc [m]0.0563416H2[kJ/kg] 2778 46St [N/m2]
1.360 10817hfg [m] 10.5947t [m] 0.00594718Hinc [m]7.01448Ta
[K]29849 13. Journal of Energy Technologies and
Policywww.iiste.orgISSN 2224-3232 (Paper) ISSN 2225-0573
(Online)Vol.2, No.5, 201219ho [m] 0.7099 49To [K]29820Htubes [m]
0.7188 50Tfg [K] 833.721hw [mm]551Tmit [m]0.050722hwmax
[m]4.158521.002 r [s]23K [W/mK] 0.04 53Tw [m3] 55024mair [kg]8.66
54Vfgc [m3] 14.4125 1.20355Vinc [m3] 2.835&ma [kg /
s]26&1.34256VT [m3] 7m fg [kg / s]27 0.1389 57Vwater [m3]
1&mmsw[kg / s]28 0.63 58q[kW/m2]2264&mst [kg / s]29mf
[kg]0.67459& 1269Q st [kW]30mfg [kg] 9.33460qv[KW/m3]
739.961[KJ/Kg]209.24.2 Influence of moisture contentTable 7:
Results for variation of flue gas temperature in terms of column of
calorific value ofthe fuel for different value of moisture
content.Tfg moisture CVMSW Tfgmoisture CVMSW Tfgmoisture
CVMSW(K)(KJ/Kg) (K)(KJ/Kg) (K) (KJ/Kg)895.5 0.05 800833.6 0.09800
771.2 0.13800970.4 0.05 900900.6 0.09900 830.6 013 9001045.0
0.051000 968.0 0.091000890.0 0.1310001120.0 0.051100 1035.0 0.09
1100949.4 0.1311001195.0 0.051200 1102.0 0.09 12001009.0 0.13
12001270.0 0.051300 1170.0 0.09 13001068.0 0.13 13001345.0 0.051400
1237.0 0.09 14001128.0 0.13 14001420.0 0.051500 1304.0 0.09
15001187.0 0.13 15001495.0 0.051600 1371.0 0.09 16001246.0 0.13
16001570.0 0.051700 1438.0 0.09 17001306.0 0.13 1700 50 14. Journal
of Energy Technologies and Policy www.iiste.orgISSN 2224-3232
(Paper) ISSN 2225-0573 (Online)Vol.2, No.5, 2012 1400moisture=0.21
1300 moisture=0.17moisture=0.13moisture=0.09 1200moisture=0.05
1100Tfg[K] 1000900800700 80009000 10000 11000 12000 13000 14000
15000 16000 17000CVmsw [Kg/KJ]Figure 5 Variation of flue gas
temperature in terms of column of calorific value of the fuel
fordifferent value of moisture content.Wastes with different
moisture contents have different drying characteristics. Those with
highermoisture content require a longer drying time and much more
heat energy, causing a lowertemperature in the furnace; and vice
versa. If the moisture content is too high, the furnacetemperature
will be too low for combustion, such that auxiliary fuel is needed
to raise the furnacetemperature and to ensure normal combustion. In
order to evaluate the effect of moisture content onthe combustion
process, numerical simulation and analysis were made with ten
different values ofmoisture content .The results of the analysis
show that those wastes with a lower moisture contentgive rise to
higher furnace temperatures and larger high-temperature zones
during combustion,because the wastes with lower moisture contents
have higher heating values and are morecombustibles, being easier
and faster to burn. Hence, to increase the efficiency of the
boiler, refuseconditioner was used in this work to dry the wastes
before they were conveyed to the furnace.4.2 Influence of excess
airThe temperature in the furnace is closely related to MSW/air
ratio. In order to predict the influenceof excess air on the
combustion in furnace, simulations were performed for different
values ofexcess air. Results show that with the increase of excess
air, the temperature of the furnace tends todecrease. To ensure
adequate heating and burnout of wastes, a relatively high
temperature level inthe furnace should be maintained with a
corresponding O2 content. 51 15. Journal of Energy Technologies and
Policywww.iiste.orgISSN 2224-3232 (Paper) ISSN 2225-0573
(Online)Vol.2, No.5, 20124.3 Analysis of elements responsible for
energy lossesTable 8 Results for variation of heat lost through
external wall with usable power of steamboiler at difference values
of operating pressure.P(bar) Qls(kW) Qs(kW) P(bar)Qls(kW) Qs(kW)
P(bar) Qls(kW) Qs(kW)102.360 200 210 2.54 200 4102.79200103.990 600
210 4.17 600 4104.43600105.094 1000210 5.28 10004105.531000105.990
1400210 6.17 14004106.42140010 6.750 1800 2106.94 1800 410
7.19180010 7.440 2200 2107.62 2200 410 7.87220010 8.060 2600
2108.24 2600 410 8.49260010 8.630 3000 2108.81 3000 410 9.07300010
9.160 3400 2109.35 3400 410 9.60340010 9.670 3800 2109.85 3800 410
10.10 3800 52 16. Journal of Energy Technologies and
Policywww.iiste.orgISSN 2224-3232 (Paper) ISSN 2225-0573
(Online)Vol.2, No.5, 2012Figure 6 Variation of heat lost through
external wall with usable power of steam boiler atdifference value
of operating pressure.Fig.6 shows heat flux lost to the atmosphere
through the external surface of the steam boiler as afunction of
its thermal power and operating pressure. As shown in the figure,
heat flux lossesthrough the external surface of the boiler to the
atmosphere increase with a rise in thermal powerand operating
pressure of saturated steam. It should be noted here that the value
of the heat flux lossis dependent on the heat exchange surface, the
temperature difference between the saturated steamand the ambient
temperature, and the coefficient of heat transmission. Currently,
only steampressure and thermal power were taken into account.5.0
Conclusions With the rapid development of national economy, the
ever-accelerating urbanization and thecontinued improvement of
living standard, the output of the solid waste,
particularlyMunicipal solid waste is constantly increasing. This
causes environmental pollution and potentiallyaffects peoples
health, preventing the sustained development of cities and drawing
public concernin all of the society. The continuously generated
wastes take up limited land resources, pollutewater and air, and
consequently lead to serious environmental trouble. Proper waste
treatment istherefore an urgent and important task for the
continued development of citiesIn this work, calculation of
calorific value of municipal waste has been carried out from
theelemental composition of the waste using Dulongs formula. The
result of 15,101 KJ/kg obtainedagrees with type 1 waste,
N.T.Engineering,[11] that contains 25 percent moisture contents
fromwaste classifications. With this heating value, maximum
temperature of the flue gas of 833.7K wascalculated from the heat
balance equation in the furnace.Thermal analysis of the municipal
solid waste boiler done with the operational conditions takeninto
account, showed that the municipal solid waste with higher moisture
content has a lower heat53 17. Journal of Energy Technologies and
Policy www.iiste.orgISSN 2224-3232 (Paper) ISSN 2225-0573
(Online)Vol.2, No.5, 2012value, corresponding to a lower
temperature in the furnace and a lower O2 consumption
duringcombustion, resulting in a higher O2 content at the outlet.
Hence, for an efficient use of municipalsolid waste as a fuel for
generation of steam in boiler, waste with lower moisture content
andadequate excess air supply should be used. In practical
operation, the air supply rate and thedistribution of the primary
air along the grate should be duly adapted for the specific
conditions ofthe wastes. An appropriate excess air ratio can
effectively ensure the burnout of combustibles in thefurnace,
suppressing the formation and the emission of
pollutants.References1. S. O. Adefemi and E. E. Awokunmi (2009),
The Impact of Municipal Solid Waste Disposal in Ado Ekiti
Metropolis, Ekiti State, Nigeria, African Journal of Environmental
Science & Technology, Vol.3(8), Pp. 186-1892. A. B. Nabegu
(2010), Analysis of Minicipal Solid waste in kano Metropolis,
Nigeria,Journal of Human Ecology, 31(2): 111-1193. Nigatu Rigassa,
Rajan D. Sundaraa and Bizunesh Bogale Seboka (2011), Challenges
andOpportunities in Municipal Solid Waste Management: The case of
Addis Ababa City,Central Ethiopia, Journal of Human Ecology, 33(3):
179-1904. Coskun, C., Oktay, Z., &Ilten, N. (2009). A new
approach for simplifying the calculation of flue gas specific heat
and specific exergy value depending on fuel composition. Energy
Journal, 34; 1898-1902.5. Chattopadhyay,P. (2006).Boiler Operation
Engineering .Tata McGraw-Hill New Delhi.6. Harry M. F. (1998).
Standard handbook of hazardous waste treatment and disposal.
McGraw-Hall, New York7. Rajput.R.K (2008).Thermal
Engineering.Laxmi,New Delhi.8. Frank R.C., Peter de G., Sarah L.H.,
and Jeremy W. (2007) The Biomass Assessment Handbook .TJ
International, UK.9. Bujak,J.(2008).Mathematical model of a steam
boiler room to research thermal efficiency. Energy
Journal,33;1779-1787.10. Rayner J. (1997).Basic Engineering
Thermodynamics,.Longman Asia Ltd,Hong Kong.11. N.T.G.Engineering
Ltd.(2009).CT Series Incinerators.Cleveland Trading EstatenAlbert
Road Darlington. 54 18. This academic article was published by The
International Institute for Science,Technology and Education
(IISTE). The IISTE is a pioneer in the Open AccessPublishing
service based in the U.S. and Europe. The aim of the institute
isAccelerating Global Knowledge Sharing.More information about the
publisher can be found in the IISTEs
homepage:http://www.iiste.orgThe IISTE is currently hosting more
than 30 peer-reviewed academic journals andcollaborating with
academic institutions around the world. Prospective authors ofIISTE
journals can find the submission instruction on the following
page:http://www.iiste.org/Journals/The IISTE editorial team
promises to the review and publish all the qualifiedsubmissions in
a fast manner. All the journals articles are available online to
thereaders all over the world without financial, legal, or
technical barriers other thanthose inseparable from gaining access
to the internet itself. Printed version of thejournals is also
available upon request of readers and authors.IISTE Knowledge
Sharing PartnersEBSCO, Index Copernicus, Ulrichs Periodicals
Directory, JournalTOCS, PKP OpenArchives Harvester, Bielefeld
Academic Search Engine, ElektronischeZeitschriftenbibliothek EZB,
Open J-Gate, OCLC WorldCat, Universe DigtialLibrary , NewJour,
Google Scholar