Abstract
A gas/oil central heating boiler (heat generator) is like the engine of a car, this provides the heat that the facility needs to warm itself up. There are two general types of boilers: Fire-tube and water-tube. In fire-tube boilers, combustion gases pass through the inside of the tubes with water surrounding the outside of the tubes. In a water-tube boiler the water is inside the tubes and combustion gases pass around the outside of the tubes. Real-time data of boiler thermal efficiency can reflect the boiler operation condition, heat generation and heat loss. Performance of the boiler, like efficiency and evaporation ratio reduces with time, due to poor combustion, heat transfer fouling and poor operation and maintenance. Boiler efficiency can be also useful in analysis of boiler and can also be used in predictive maintenance of the boiler. How to reduce problems of the boiler efficiency real-time computations and be successful in calculating the boiler thermal efficiency on line are the main concern of operation departments of power systems. The efficiency is calculated by direct method and the boiler under study if fire-tube boiler. Fuel used is briquettes.
KeyWords: Boiler, Direct method, Efficiency ,Heat lost, Financial loss
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1. INTRODUCTION
A gas/oil central heating boiler (heat generator) is like the engine of a car, this provides the heat that the facility needs to warm itself up. The size of the boiler is matched to the size of the facility. If the boiler is oversized, the fuel bills will be excessive. If the boiler is undersized, it may not generate enough heat. The emphasis is majorly on energy conservation, and the fact that heat loss calculations can be done very accurately, means there is no need to oversize.
1.1FIRE TUBE BOILERS
Combustion gases pass through the inside of the tubes with water surrounding the outside of the tubes. The most common fire-tube boilers used in facility heating applications are often referred to as scotch or scotch marine boilers, as this boiler type was commonly used for marine service because of its compact size
The advantages of a fire-tube boiler are its simple construction and less rigid water treatment requirements.
The disadvantage is the excessive weight-per-pound of steam generated.1.2WATER TUBE BOILERS
The water is inside the tubes and combustion gases pass around the outside of the tubes. Large steam users are better suited for the water-tube design. The industrial water-tube boiler typically produces steam or hot water primarily for industrial process applications, and is used less frequently for heating applications
The advantages of a water-tube boiler are a lower unit weight-per-pound of steam generated.
The disadvantages are high initial cost & cleaning is more difficult due to design.
2.1 EFFICIENCY CALCULATION
The overall boiler efficiency depends on many more parameters apart from combustion and thermal efficiencies. These other parameters include ON-OFF losses, radiation losses, convection losses, blow down losses etc. In actual practice, two methods are commonly used to find out boiler efficiency, namely direct method and indirect method of efficiency calculation.
Direct efficiency
This method calculates boiler efficiency by using the basic efficiency formula-
η=(Energy output)/(Energy input) X 100
In order to calculate boiler efficiency by this method, we divide the total energy output of a boiler by total energy input given to the boiler, multiplied by hundred.
Calculation of direct efficiency-
E= [Q (H-h)/q*GCV]*100
Where,
Q= Quantity of steam generated (kg/hr)
H= Enthalpy of steam (Kcal/kg)
h= Enthalpy of water (kcal/kg)
GCV= Gross calorific value of the fuel.(Briquettes)
Fig -1: Direct Method
Dated : 3/6/17
E= [Q (H-h)/q*GCV]*100
Q=1000 kg/hr
=0.27778 kg/sec
H=2768 kJ/kg
h=721 kJ/kg
H-h=2047 kJ/kg
=489.03435 kcal/kg
q=4620.8 kg/day
=0.053481 kg/sec
GCV=3800-4000 kcal/kg
=3900 kcal/kg (average)
E= 0.27778*489.03435
0.053481*3900
E =65.12% E(Obtained)=58% E(Manf quoted)=75%
LOSS=7-10%
Table -1: Efficiency Table
Date
Q(kg/sec)
q(kg/sec)
H-h(kcal/kg)
ƞ
1/6/17
0.27778
0.04572
489.03435
76.1
2/6/17
0.27778
0.05851
489.03435
59.52
3/6/17
0.27778
0.05348
489.03435
65.12
4/6/17
0.27778
0.06335
489.03435
54.97
5/6/17
0.27778
0.06343
489.03435
54.9
Average efficiency = 61.37%
GCV = 3900 kcal/kg (constant)
2.2. HEAT LOSS CALCULTION
Dates:3/6/17
While Shoveling The Briquettes:
Convection heat loss:
Q= q/t = hA(Ts-Ta)
=15 x (2 x 0.56 x 0.42)(235-31.5)
=1435.896 watts
Heat loss= Q x t
=1435.896 x 135 x 60
= 11630757.6 joules/day
Radiation heat loss:
Q= eσA(T4 – T4a)
= 0.97 x 5.6703 x 10-8 x 0.4704 (5084 -304.54 )
=1500.6276 watts
Heat loss= Q x t
=1500.6276 x 135 x60
=12155083.56 joules/day
Total heat loss= 23785841.16 joules/day
= 23785.84116 kJ/day
2.3. FINANCIAL LOSS CALCULTION
(A,B, are variables)
We spend 8.5 INR per unit of electricity.
1 unit = 1 kWh
1 kWh = 1000 x 3600 Ws
= 3.6 x 10 6 J
8.5 INR 3.6 x 10 6 J
❖ Money lost through shoveling:
8.5 INR 3.6 x 10 3 kJ
A INR 23785.84116 kJ
A= 56.16 INR
❖ Money lost due to extra work:
Average cost to produce 1 kg of steam is 1.58 INR
Efficiency of boiler is 65.129%
To produce 1000kg of steam, boiler will have to do work for 1000+34.871% of 1000
i.e :
1000+348.71
Excess work done by boiler is 348.71
Now,
1.58 INR 1 kg
B INR 348.71 kg
B = 550.9618 INR (per hour)
= 13223.08 INR (per day)
Total financial loss = A+B
=56.16+13223.08
= 13279.24 INR (per day)
= 48,46,922.6 INR (yearly)
Table -2: Financial Table
Date
Extra work(kg)
Loss per hour(INR)
Loss per day(INR)
Total Financial loss(INR)(A+B)
1/6/17
239.8
377.620
9062.88
9119.04
2/6/17
404.8
639.584
15350.10
15406.26
3/6/17
348.71
550.960
13223.08
13279.24
4/6/17
450.8
712.264
17094.33
17150.49
5/6/17
481.0
759.980
18239.52
18295.68
Average cost per day = 14650.14 INR
Average cost per year= 53,47,301.38 INR
3. CONCLUSIONS
This paper is convergent on the diverse aspect of the operation of Boiler. Efficient operation of boiler is likely to play a very huge role in years to come. Industries all over the world are going through increased and powerful competition and increased automation of plants. The cost of such system is expected to be very high. To get cross with this challenge, it is clearer by this paper about the financial losses of the system . We have to use advanced technology and management skills in all spheres of activities to perform its effective role in the turnover of the company.
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