Lab 2 Heating Value of Solid Fuel

ED 72.19 Biomass Conversation Lab Report No.2: Heating value of solid fuel

The heating value or calorific value of a fuel is the amount of heat released during the combustion of a specified amount of it. It is measured in units of energy per unit weight: normally kcal/kg, kJ/kg. The bomb calorimeter is the most common device for measuring the heating value or calorific value of a solid fuel. Objectives

To determine the heating value of solid fuel. Theory

The amount of heat available from any solid fuel can be determined by testing a small sample of the fuel in a bomb calorimeter. The test sample such as charcoal, wood is made to burn completely in a bomb which pressurize with pure oxygen so that the heat developed by the combustion is absorbed by a definite mass of water. This causes a measurable rise in the water temperature, from which it is possible to calculate the heating value. Apparatus

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G. Cuss Cusson onss bomb bomb calo calori rime mete ter  r 

Specification Power supply req requirement Manufacture

: :

220V, 50 Hz, single phase ase G. Cussons

The bomb calorimeter made by G. Cussons is self-contained with the control unit house in an instrument case that forms the base. The equipment includes the bomb itself, a calorimeter vessel, an outer double walled water vessel, electric stirrer gear, combined motor gear and ignition unit. A Backman type thermometer and charging unit with  pressure gauge to facilitate the charging of the bomb with oxygen. Procedure

1. Measure Measure moisture moisture content content (wet basis) basis) and and prepare prepare fuel sample sample for bomb bomb calorimet calorimeter  er  test by powdering and drying at 105 C in oven at least 2 hours. 2. Weigh the the empty cup cup and put put the sample sample in the the cup about about 0.9-1.1 0.9-1.1 grams for for solid solid fuel. Weigh the sample with the cup again and weigh of the true sample can be determined. 3. Insert Insert the fuse fuse wire about about 7 cm. The The wire must must not not touch touch the cup. cup. 4. Fill about about 10 ml ml of distilled distilled water water in the bomb. bomb. This This is to to obtain obtain the higher higher heating heating value of fuel. 5. Assemble Assemble the bomb, bomb, tighten tighten the the cap securely securely by finger-tight finger-tight only. only. Care Care must must be taken of pilling the sample. 6. Slowly Slowly fill the the bomb bomb with oxygen oxygen at 31.5 31.5 bar (450 psig). psig). °

7. Measure distilled water of 2,000 ml.(2 Kg.) and pour into calorimeter bucket. The temperature of water must be 2 C below room temperature. 8. Put the bomb in the bucket, under the water level. 9. Assemble the calorimeter jacket. 10. Stir the water at lease 2 minutes before reading temperature. 11. Record water temperature at 1 minute interval for 5 minutes and then ignite the fuel. 12. Read thermometer at 1 minute interval until the maximum temperature is reached. 13. Keep on reading after the maximum point at 1 minute interval for 5 minutes. 14. Remove the bomb and release the residual pressure and take off the cap. 15. Calculate the calorific value of fuel. °

Results and discussion Table 1: Time and Temperature Reading Test 1 (Rice Husk) Test 2 (Saw Dust) Weight of crucible = 4.9813 g Weight of crucible = 4.9795 g Weight of crucible + Sample = Weight of crucible + Sample = 5.9817 g 5.9969 g

Weight of Sample = 1.0004 g

Weight of Sample = 1.0174 g

Time (min) 0

Temperature (°C) 1.010

Time (min) 0

Temperature (°C) 1.040

1

1.010

1

1.055

2

1.010

2

1.060

3

1.012

3

1.065

4

1.012

4

1.070

5*

1.014

5*

1.070

6

1.200

6

1.550

7

1.850

7

2.265

8

2.130

8

2.530

9

2.225

9

2.640

10

2.229

10

2.690

11

2.320

11

2.732

12

2.345

12

2.770

13

2.365

13

2.805

14

2.375

14

2.825

15

2.385

15

2.835

16

2.390

16

2.840

17**

2.392

17

2.847

18

2.392

18

2.849

19

2.392

19

2.850

20

2.392

20**

2.851

21

2.392

21

2.851

22

2.390

22

2.851

23

2.390

23

2.850

24

2.388

24

2.849

25

2.386

25

2.847

26

2.385

26

2.845

27

2.842

* **

Ignition Start Maximum Temperature Point

3

3

2    )    C    0    (   e   r   u 2    t   a   r   e   p   m   e 1    t

Rice Saw

1

0 0

5

10

15

20

25

30

time (min)

Figure 1: Time and Temperature Reading Table 2 Higher heating value calculation

Configuration n (min)

Test 1 (Rice Husk) 12

Test 2 (Saw Dust) 15

v1 (°C/min)

0.000800

0.006000

v2 (°C/min)

0.000778

0.001286

Trc = nv1 + (v2 – v1)/2

0.009589

0.087643

Tr = Tmax – Tign

1.378000

1.781000

Tdiff  = Trc + Tr  WV (kg) mwc (kg)

1.387589 0.412 2

1.868643 0.412 2

Mw = WV + mwc Cpw (kJ/kgK)

2.412 4.186

2.412 4.186

Mf  (kg)

1.0004

1.0174

HHVd = (mw * C pw * Tdiff ) / mf  (MJ/kg)

14.00

18.54  

(HHVd calculation procedure was done by follow the British Standard No. BS 4379, Designation IP 12/73.)

where, n = number of minutes between the ignition and the attainment of the m aximum temperature v1 = rate of temperature raise in degree per minute at the beginning of test v2 = rate of temperature fall in degree per minute at the end of test Trc = radiation correction (°C) Tr = raise the temperature during test (°C) Tdiff = corrected temperature rise (°C) Tmax = maximum temperature during test (°C) Tign = Temperature at ignition started point (°C) WV = water value of the apparatus (kg) mwc (kg) = weight of water in calorimeter (kg) Mw = total equivalent weight of water (kg) Cpw (kJ/kgK) = specific heat of water = 4.186 kJ/kg K  Mf  (kg) = weight of fuel sample (g) HHVd = higher heating value of the solid fuel (dry basis) (MJ/kg)

As shown in table1, the higher heating value of rice husk and saw dust were determined by using of the bomb calorimeter. Figure1 shows that both water temperatures absorbed heat from rice husk and saw dust increased sharply after ignition time, and then the temperature remained about the same. Table 2 presents that higher heating value (HHV) of rice husk and saw dust are 14.00 MJ/Kg and 18.54 MJ/Kg respectively. HHV of  rice husk is less than HHV of saw dust. This result has the same trend to proximate analysis in the experiment 1, as shown in table below.

Type of  Sample Rice Husk  Saw Dust

Moisture Content Volatile Matter (%) 57.015 71.155

* Moisture Content (%) in Dry Basic

(%) 7.59 10.275

Ash content (%) 22.4 3.875

Fixed carbon (%) 12.995 14.695