Performance Evaluation of an Oil Fired Boiler a Case Study in Dairy Industry

PERFORMANCE EVALUATION OF AN OIL FIRED BOILER

A CASE STUDY IN DAIRY INDUSTRY.

Vishwas S. Deshpande and P.P.Tambe Department of Industrial Engineering, Shri Ramdeobaba Kamla Nehru Engineering College, Katol Road,

Nagpur -440013, Phone: 9822574365, 9890671946, Fax: 0712-2583237, E-mail:[email protected],

[email protected] Abstract This paper presents the findings of the “Performance Evaluation Of An Oil Fired Boiler- A Case Study In Dairy Industry " The study was aimed at assessing the operational performance of the oil fired boiler (Revomax Plus) by evaluating the thermal efficiency and suggest energy conservation measures for improving the same. The analysis was carried and the calculations resulted into boiler efficiency of 84.76 %, oil consumption of 24 liters/hour and excess air as 58.14 %. The feasibility of replacement of oil fired boiler with coal fired boiler is explored. The comparative evaluation of oil fired boiler and coal fired boiler based on the assumed cost of oil and coal has revealed the approximate saving of Rs. 2800 per day by replacing the oil fired boiler with the coal fired boiler. The payback period for the investment on coal fired boiler will be about four years.

Keywords: Boiler, Performance Evaluation, Efficiency Calculation 1. Introduction Energy is essential to life and its conservation has become an absolute necessity. The growth and demand for energy is increasing at a very fast rate, specially in the industrial sector, the transport sector and the house hold sector, thereby putting a great deal of pressure on the available resources. The need of the hour has now become conservation and preservation. Conservation and efficient use of energy in industry has for a long time been a priority of the Government of India. People on their part should become aware of the seriousness and do their best to conserve and preserve this energy. The industrial sector uses about 50% of the total commercial energy available in India. Of the commercial sources of energy, coal, lignite, and oil and natural gas are mainly used. The Indian energy sector is highly energy intensive and efficiency is well below that of other industrialized countries. There is a growing need to bring about improvement in the efficiency of energy use in the industrial sector. More efficient energy use can increase productivity and economic competitiveness as well as lower greenhouse gas emissions per unit of output. There is considerable scope for improving energy efficiency in industries dealing with iron and steel, chemicals, cement, pulp and paper, fertilizers, textiles, dairy etc. If such industries can promote energy conservation, it could lead to substantial reduction in their costs of production.

1.1 Methodology of Energy Conservation in Boiler Waste heat recovery systems, cogeneration, and the utilization of alternative sources of energy are important for the conservation of energy. Industrial sector is the major consumers of the energy and it has been observed that till now the purview of energy conservation has been neglected by most of the industries because they think that material and labour are the major cost components. Boilers are used in various industrial units to convey heat for different process applications. Though boilers can be categorized into different types and have different efficiency levels, the motive of the industry should be to generate the required quantity and quality of steam at minimum cost. An optimum level of excess air level should be maintained. The method of return steam condensate to the boiler helps reduce fuel consumption; along with this method various other methods could be applied to minimize the loss of energy.

1.2 Energy Saving Potential in Boiler Methods to improve the efficiency of boiler focus mainly on minimizing the loss of useful heat to the surrounding from the hot flue gas and walls of the boiler. This can be accomplished by incorporation of

Performance Evaluation of an Oil Fired Boiler – A Case Study In Dairy Industry 351

necessary design and close monitoring and operation leading to Reduction in quantity of excess air, Reduction in temperature of flue gases, Reducing in surface temperature of external walls of boilers, Carrying out the energy auditing in order to evaluate the performance of boiler in terms of its efficiency and Recovery of steam from steam usage points. In the present case attention is focused on the aspects namely, carrying out the energy auditing in order to evaluate the performance of boiler in terms of its efficiency, Recovery of steam from steam usage points and Minimizing the losses associated with boiler. 1.3 Boiler used in the Dairy Industry The boiler used in the company is manufactured by Thermax Limited', Pune & name of the model is 'Revomax Plus RXD - 850'. The company is having two boilers of the same type.

Table 1: Revomax Plus-Technical Specifications

Sr.No Details Unit RXD-850

1. Steam output F&A100°C Kg/h 850 2. Heat output MW 0.531 3. Steam pressure and temperature 10.5kg/cm2 at 185°C

or, 15 kg/cm2 at 200°C

4. Efficiency on GCV - 88 ± 2% 5. Fuel consumption Kg/h 53.9 6. Burner control ON/OFF 7. Boiler heating surface area M2 9.94 8. Economizer heating surface

Area M2 3.4

9. Total heating surface area M2 13.34 .

10. Time required to reach full load from cold start Minutes 3 to 5 11. Pressure parts Non IBR

12 a b c d e

Electric supply Blower motor (3000 rpm) Water pump motor (1000 rpm) Fuel pump motor (3000 rpm) Fuel pre-heater Total connected load

KW KW KW KW KW

415 V (+ 6%), 50 Hz (± 3%), 3 Phase, 4 Wire 3.73 0 .75 0.37 4 9

13 Overall dimensions L x W x H M 1.9 x 1.5x3 14 Dry weight (approx) Tons 1.2 15 Flue gas outlet diameter MM 250

2. Performance Evaluation Of Boilers The performance parameters of boiler, like efficiency and evaporation ratio reduces with time due to poor combustion, heat transfer surface fouling and poor operation and maintenance. Even for a new boiler, reasons such as deteriorating fuel quality, water quality etc. can result in poor boiler performance. Boiler efficiency tests help us to find out the deviation of boiler efficiency from the best efficiency and target problem area for corrective action.

2.1 Boiler Efficiency Thermal efficiency of boiler is defined as the percentage of heat input that is effectively utilised to generate steam. There are two methods of assessing boiler efficiency. 2.1.1 The Direct Method Where the energy gain of the working fluid (water and steam) is compared with the energy content of the boiler fuel... This is also known as 'input-output method' due to the fact that it needs only the useful output (steam) and the heat input (i.e.fuel) for evaluating the efficiency. This efficiency can be evaluated using the formula.

Boiler Efficiency = Heat Output / Heat Input (1)

352 Advances in Energy Research (AER – 2006)

Parameters to be monitored for the calculation of boiler efficiency by direct method are: 1. Quantity of steam generated per hour (Q) in Kg/hr. 2. Quantity of fuel used per hour (q) in Kg/hr. 3. The working pressure (in Kg / cm2) and superheat temperature if any 4. The temperature of feed water (°C) 5. Type of fuel and gross calorific value of the fuel (GCV in Kcal/kg of fuel)

Boiler efficiency (η) = [Q x (hg – hf) / q x GCV ] x 100 ---- (2)

Where, hg -Enthalpy of saturated steam in kcal/kg of steam hf - Enthalpy of feed water in kcal/kg of water

2.1.2 The Indirect Method: Where the Efficiency is the Difference Between the Losses and the

Energy Input The principle losses that occur in a boiler are

1. Dry gas loss 2. Wet gas loss 3. Radiation loss Calculation for losses:

i) Dry gas loss = m x Cp x (Tf - Ta) x 100 / GCV of Fuel (3) Where, m = Total mass of flue gas = mass of actual air supplied + mass of fuel supplied (theoretical + excess) Cp = Specific heat of fuel gas (0.23 Kcal/kg 0C Tf = flue gas temperature Ta = Ambient temperature. GCV = Gross calorific value of Furnace Oil (FO) (Kcal/Kg)

ii) Wet gas loss = 9 x H2 [ 584 + Cp(Tf – Ta) ] / GCV (4) Where H2 – percentage of H2 in fuel

iii) Radiation loss:

The actual radiation and convection losses are difficult to assess because of particular emissivity of various surfaces, its inclination, air flow pattern etc. In a relatively small boiler of our case, radiation losses are generally taken approximately depending upon the temperature of the boiler surface. 3. Data Collection The various parameters that serve as the prerequisites for carrying out performance evaluation of a boiler are listed as follows 1. Steam temperature 2. Steam pressure 3. Flue gas temperature 4. Fuel water temperature 5. Fuel consumption 6. Steam flow rate 7. % Contents of gases present in flue gas (Flue gas analysis) 8. % contents of constituent elements in fuel (Ultimate analysis of fuel) 9. Air required burning the required quantity of fuel. (Stoichiometric /theoretical and Actual) 3.1 Directly Recorded Parameters The parameters, i.e. steam temp., steam pressure, flue gas temp., feed water temp., oil tank level (for fuel consumption) recorded.


Table 2: Directly recorded parameters

Time Steam temp( 0 C) Steam Pressure (Kg/cm2)

Flue gas temp (0 C)

Feed water Temp.( 0 C) Oil tank level (liters)

11.15 11.45 12.15 12.45 1.15 1.45 2.15

154.4 154.7 154.0 150.4 153.4 154.7 151.3

6.5 5.0 5.8 6.4 7.0 5.4 6.4

170 180 180 175 140 170 175

60 64.5 63.6 61.9 59.9 58.0 55.9

835 825 809 796 786 775 763

Avg. 153.27 6.07 170 60.63 Fuel Consumption = (835 -763)/3 liters / hr = 24 liters / hr = 24 x 0.943 (Sp gravity of Furnace Oil = 0.943) = 22.632 Kg/hr. 3.2 Determination of Steam Flow Rate The estimation of boiler efficiency by direct method involves the use of steam flow rate (Kg/hr). The steam flow rate can easily be determined by steam flow meter installed in the steam pipe line. But, in the present case, due to the unavailability of flow meter, the general methodology of determining the steam flow rate couldn't be followed. Therefore, it has been decided to consider hourly water consumption and take that water consumption equal to steam produced per hour.

Table 3: sample data recorded for the pump

Sample No. Time for which sample was collected (Sec) Quantity pumped in 30 se(liter) 1 2 3 4 5 6

30 30 30 30 30 30

7.5 8

8.08 7.86 7.72 7.78

Avg. 30 7.82 Avg. Water pumped in 30 sec = 7.82 lit. Water pumped in 60 sec (1 min) = 15.64 Lit Water pumped in 1 hour = 15.64 X 60 = 938.4 lit. 3.3 Determining Operating Time of Pump Per Hour The operating time of the pump was estimated with the help of burner on-off signal. The pump and the burner in the boiler get on and off intermittently according to the pressure of the steam. The pump and the burner get on as the pressure decreases and vice versa. The pump and the burner get on as the pressure decreases but with the condition that the pump starts 10 sec. earlier than the burner and they both get off at the same time as the pressure increases. Operating Time of Pump per hour = operating time of burner / hour + 10(No. of times burner got ON per Hour) ------- (5)

Table 4: Sample data regarding the burner’s ON –OFF time

Burner On Time Burner Off Time Time for which Burner was On (Sec.) 1:00:00 1:00:55 55 1:01:15 1:02:17 62 1:02:38 1: 03:34 56 1:03:53 1:04:19 26 1:07:23 1:07:35 12


Operating Time of Pump per hour = operating time of burner / hour + 10(No. of times burner got ON per hour = [1999+ 10(50)] sec. = 2499 sec. = 41.65 min = 0.6942 hr. Total Operating time of pump = 0.6942 hr. Water consumption/hr = Total operating time of pump/hr x Actual Pumping capacity of pump = 0.6942x938.4 = 651.44 lit. /hour Steam flow rate = Water consumption = 651.44 Kg/hr. 4. Flue Gas Analysis The flue gas was collected using Air sampling apparatus (shown in photograph, next page) and was analyzed using GAS CHROMATOGRAPHY. The analysis revealed the following results:

CO2 = 9.77% CO = 0.077 %

4.1 Furnace Oil Analysis (Ultimate Analysis) The standard values of various constituent elements present in furnace oil are as follows: Carbon (C) = 84 % Hydrogen (H2) = 12% Oxygen (O2) = 1.5 % Sulphur (S) = 1.5% Nitrogen (N2) = 0.5 % Moisture (M) = 0.5 Gross colorific value (GCV) = 10,000 Kcal/Kg. 4.1.1 Calculation of Requirement of Theoretical Amount of Air Considering a sample of 100 kg of furnace oil. The chemical reactions are:

Element Molecular Weight

C 12 O2 32 H2 2 S 32 N2 28 CO2 44 SO2 64 H2O 18

C + O2 CO2 H2 + ½ O2 H2O S + O2 SO2

Constituents of fuel C + O2 CO2 12 + 32 44 12 kg of carbon requires 32 kg of oxygen to form 44 kg of carbon dioxide therefore 1 kg of carbon requires 32/12 kg. i.e. 2.67 kg of oxygen.

(84) C + (84 x 2.67) O2 308.28 CO2 2H2+ O2 2H2 4 + 32 36 4 kg of hydrogen requires 32 kg of oxygen to form 36 kg of water, therefore 1 kg of hydrogen requires 32/4 kg i.e. 8 kg of oxygen (12) H2 + (12 x 8) O2 (12 x 9) H2O S + O2 SO2 32 + 32 64 32 kg of sulphur requires 32 kg of oxygen to form 64 kg of sulphur dioxide, therefore 1 kg of sulphur requires 32/32 kg i.e. 1 kg of oxygen 1.5(S) + (1.5 x 1)O2 3SO2

Theoretical CO2 % by volume = Moles of CO2 / Total Moles (Dry) (6)


= 7.006x100 / (7.006 + 38.29+0.047) = 15.45% 4.1.2 Calculation of Constituents of Flue Gas with Excess Air % CO2 measured in flue gas = 9.77(measured)

% Excess Air = [ (Theoretical CO2 % / Actual CO2 %) – 1 ] x 100 (7) = [ (15.45 / 9.77) – 1 ] x 100 = 58.14 % Theoretical air required for 100 kg of fuel burnt = 1392.52 Total qty. of air supply required. = 1392.52 x 1.5814 = 2202.13kg with 58.14 excess air Excess air quantity = 2202.13 - 1392.52 = 809.61 Kg.

O2 = 809.61 X 0.23 = 186.21Kg

N2 = 809.61 – 186.21 = 623.4 Kg

The final constitution of flue gas with 58.14 % excess air for every 100 kg fuel.

CO2 = 308.28Kg H2O = 108.00 Kg SO2 = 3 Kg O2 = 186.21 Kg

N2 = 1072.24+623.4 = 1695.64 4.1.3 Calculation of Theoretical CO2 % in Dry Flue Gas by Volume Moles of CO2 in flue gas = 308.28/44 = 7.006 Moles of SO2 in flue gas = 3/64 = 0.047 Moles of O2 in flue gas = 186.21/32 = 5.82 Moles of N2 in flue gas = 1695.64/28 = 60.56

Theoretical CO2 % by volume = Moles of CO2 / Total Moles (Dry) (8) = 7.006 / (7.006+0.047+5.82+60.56) = 9.77 % Theoretical O2 % by volume = 5.82 / 73.433 = 7.93 % Total mass Of Flue gas(m) = 22.02 + 1 = 23.02 kg 5. Efficiency Calculation (Indirect Method) The direct method of efficiency calculation could not be applied due to the wetness of the steam (i.e. steam was not saturated), therefore the efficiency is calculated by using indirect method as shown:

i) Dry gas Loss = m x Cp x (Tf – Ta ) x 100 / 10000

Where m= total mass of flue gas Dry gas loss = 23.02x 0.23 x (170 – 34) x 100 / 10000 = 7.2 % ii) Wet gas loss = 9 x H2 [ 584 + Cp(Tf – Ta) ] / GCV where H2 – percentage of H2 in fuel = 9 x 12 [ 584 + 0.5(170 – 34) ] / 10000 = 7.04 % iii) Radiation loss = 1% ( approx) Efficiency(η ) = 100 – ( 7.2 + 7.04 + 1) = 84.76 %


5.1 Preparation of Heat Balance Sheet The above shown calculations are summarized in the heat balance sheet as shown in the table 6.4;

Table 5: Heat balance sheet

Input Out put Description Kcal/kg % Kcal/kg %

Input Fuel

Output Dry gas loss Wet gas loss Radiation loss Steam (balance)

10,000

100.00

720.06 704.16 100 8475.78

7.2 7.04 1 84.76

Total 10,000 100. 10,000 100. 6. Approach for Economic Feasibility The feasibility of replacement of oil fired boiler with coal fired boiler needed to be explored. The approximate comparison is as shown here in: For oil fired boiler : Oil consumption/day = 24 x 20 = 480 Litres = 480 x 0.943 = 452.64 Kg Cost of oil/day = 480x14 = Rs. 6720

For coal fired boiler : Considering the efficiency of coal fired boiler as 60% which is generally obtainable and the GCV of coal is 4500. Approximate Coal required/day = 452.64 x 10000 / 0.6 x 4500 = 1676 Kg Approximate Cost of Coal per day = 1676 x 2 = Rs. 3352

Total cost/day for coal fired boiler: The total cost in case of coal fired boiler is taken as the sum of the cost of coal and the labour cost. Considering that two labours are required per shift i.e. a total of six labours per day at the rate of Rs. 100/day/labour. Total cost/day = 3352 + (6 x 100) = Rs. 3952. Savings/day = 6720 – 3952 = Rs. 2768. Savings/annum = 2768 x 25 x 12 = Rs. 8,30,400 The investment for the coal fired boiler will be approximately Rs. 20-25 Lacs and the payback period will be about four years. 7. Conclusions The salient concluding remarks based on the study are as follows: i) The efficiency of the oil fired boiler is 84.76% which is closer to the standard range of efficiency (i.e. 88 ± 2 %). ii) Oil consumption for present steam production of 651.44 Kg/hr. is 24 lit/hr. iii) The excess air is 58.14 % which is quite higher than the sufficient limits. References 1. Murphy W., McCkay G, 1995, Energy Management Butterworth Heinemann. 2. Dr. C.P. Kothandarman, P.R. Khajuria, C. Arora, S. Domkundwar, 2000, A Course In Thermodynamics &

Heat Engines , Dhanpat Rai & Co. 3. Chattopadhyay P, 1997, Boiler Operation Engineering, Tata McGraw Hill Publication. 4. Ballney P.L, 1991, Thermal Engineering 5. Khurmi R. S., 1995 , Steam Table, S. Chand & Co. Ltd. 6. Reference manual for Revomax RXD - 850.


7. National productivity council (Bureau of Energy Efficiency), Energy Efficiency in Thermal Utilities- for preparation of National Certification Examination for Energy Managers & Energy Auditors.

8. Reference material from Central Fuel research Institute(CFRI) (Nagpur Unit).

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Performance Evaluation of an Oil Fired Boiler a Case Study in Dairy Industry