The gross calorific values of crude and exhausted olive pomace, oak, almond, olive wood, olive oil, kerosene, and diesel are reported in this article. Conversion of crude olive pomace into exhausted olive pomace resulted in 10% reduction in calorific value. The net calorific value of crude olive pomace amounts to 92% of its gross calorific value. The ultimate and proximate analyses of crude olive pomace representing the 2006-2008 olive harvest seasons were determined and compared with analyses pertaining to the 2009-2011 olive harvest seasons in Jordan. Controlled charring of crude olive pomace reduced its mass down to about 20%. Pyrolysis thermogravimetric (TG) and differential thermogravimetric (DTG) curves were recorded under nitrogen atmosphere for crude olive pomace and wood samples. Quantitative data on three DTG major peaks are reported for wood samples and crude olive pomace. A comparison based on market price and calorific value of a fuel showed that olive pomace is the most rewarding fuel for domestic space heating in Jordan.
The olive pomace is the solid byproduct that results from the olive oil industry. Until very recently, the accumulation of olive pomace in the premises of the olive mills in Jordan constituted a very heavy burden on the environment due to the lack of large-scale useful uses for such material. However, since the turn of the twenty-first century, the olive pomace in Jordan has become a precious asset for olive mills owners due to the heavy demand on its use as a solid fuel useful for heat generation during winter time especially in residential space heating. Unlike exhausted olive pomace, which is practically oil-free pomace, the olive pomace in Jordan is a crude pomace that retains its residual oil. The available statistics on olive pomace production in Jordan over the period 2000-2008 [
The aim of the present work is to provide thermochemical data for the local liquid and solid fuels, namely: kerosene, diesel, local fire wood and olive pomace which represent the types of fuels used for space heating in Jordan. Such data can be combined with fuel price and availability to assess its suitability for domestic space heating.
A brief description of the samples used in the present study is given in
The sieving experiment, which aimed at finding the particle size distribution of the as-received loose sun- dried olive pomace sample, was carried out by using a set of ASTM standard sieves and a laboratory shaker. Five sieves with mesh designations of 10, 18, 35, 60, and 100 were used. Sample KT26, with initial mass of 2.5 kg, is the source of the pomace material used in the sieving experiment. Prior to sieving, several batches of the sample have their lumps crushed for one min. The cumulative mass of the ground batches is 533.6 g which amounts to 21.3% of the original sample mass. In order to find the mass percentage of the sieved fractions, the amount of pomace powder retained by each one of the five sieves was weighed. The mass of the fine powder that passed through the 100-mesh sieve was also determined.
Charring of crude olive pomace was carried out on samples KT25 and KT26 which represent sun-dried compact fire logs and loose olive pomace, respectively. About one kg of each sample was charred in a grill placed in an outdoor environment. Few sprays of kerosene were used to start the charring process and every care was taken to avoid ash formation. The char yield of sample KT25 is 20.71%, and that of sample KT26 is 21.32%. About 11% of the char of these two samples was used for ash determination. Twelve replicates of ash determinations were carried out for each one of these two samples.
Sample identity | Acquisition time | Sample physical state | Sample source | Remarks |
---|---|---|---|---|
KT7 | October 2006 | Slurry | aSa’doon new olive mill | Virgin pomace collected from mill operation line |
KT8 | September 2007 | Wood chunks | Al-Huson wood shop | Oak wood, bark neglected |
KT9 | September 2007 | Wood chunks | Al-Huson wood shop | Almond wood, bark neglected |
KT12 | May 2006 | Briquettes | bSa’doon old mill | Pomace collected from mill drying yard |
KT13 | December 2006 | Briquettes | Pomace shop (Amman) | Sample of pomace used for solid-fired residential boiler |
KT14 | October 2007 | Wood chunks | Al-Huson wood shop | Olive wood, bark neglected |
KT23 | May 2008 | Dry olive pulp | Sa’doon old mill | Pulp of KT25 |
KT24 | May 2008 | Dry olive pits | Sa’doon old mill | Pits of KT25 |
KT25 | May 2008 | Briquettes | Sa’doon old mill | Pomace collected from mill drying yard |
KT26 | June 2008 | Loose pomace | Sa’doon old mill | Pomace collected from mill drying yard |
KT27 | June 2008 | Powder of KT26 | Sa’doon old mill | Mesh: +10 |
KT28 | June 2008 | Powder of KT26 | Sa’doon old mill | Mesh: −10, +18 |
KT29 | June 2008 | Powder of KT26 | Sa’doon old mill | Mesh: −18, +35 |
KT30 | June 2008 | Powder of KT26 | Sa’doon old mill | Mesh: −35, +60 |
KT31 | June 2008 | Powder of KT26 | Sa’doon old mill | Mesh: −60, +100 |
KT32 | June 2008 | Powder of KT26 | Sa’doon old mill | Mesh: −100 |
KT33 | December 2008 | Liquid olive oil | Al-Kfarat, Irbid Governorate | Extra virgin olive oil |
KT34 | May 2009 | Liquid kerosene | Gas station, Irbid | Local grade |
KT35 | May 2009 | Liquid diesel | Gas station, Amman | Local grade |
a,b: Two neighboring olive mills located near Al-Nuaymeh intersection, Amman-Irbid highway.
The exhausted olive pomace samples were prepared from the crude olive pomace samples, namely: KT7, KT12, KT13, KT25, KT26, KT27, and KT32. Extraction of the fat material present in the crude olive pomace was achieved by using n-hexane with purity of 95%. A Soxhlet extractor and cellulose extraction thimbles were used in the extraction experiments. About five grams of the test sample and 200 ml of hexane were used in each extraction experiment. Exhaustive extraction lasted for about 48 hours. In naming the extractives-free residue, the letter “h” is added as a suffix to the symbol of the crude pomace sample used in the hexane extraction experiment.
The olive tree exhibits an alternate bearing phenomenon (biennial bearing cycle) where the amount of the annual yield for two successive years is quite different. Consequently, fluctuations in the amount of the olive mill solid residue occur for a certain period of time.
The results of moisture content are given in
Examination of the ash percentages given in
Sample | Moisture % | Ash % | Sample | Moisture % | Ash % |
---|---|---|---|---|---|
KT7 | 6.775 | 2.215 | KT25 | 5.965 | 3.335 |
KT8 | 5.601 | 5.882 | KT26 | 7.298 | 3.558 |
KT9 | 4.865 | 0.628 | KT27 | 6.940 | 0.757 |
KT12 | 5.351 | 5.397 | KT28 | 6.921 | 0.835 |
KT13 | 5.250 | 3.282 | KT29 | 7.118 | 1.600 |
KT14 | 4.806 | 0.577 | KT30 | 7.807 | 3.500 |
KT23 | 5.662 | 4.613 | KT31 | 6.570 | 3.680 |
KT24 | 5.811 | 1.208 | KT32 | 8.745 | 4.056 |
The distribution of particle size of an olive mill solid waste is governed by several factors. These factors include the type of olive mill, the mill operational parameters, the size distribution of the olive drupes, and the pits/pulp ratio of ripe olives. Visual inspection of sun-dried olive pomace has shown appreciable amounts of tiny un- crushed pits. Relatively small olives have small pits that might escape crushing during the olive oil extraction stages. It is also known that olive mills generate sizable amounts of fine solids in their waste water. In this case the yield of marketable olive pomace may be reduced. For space heating purposes, marketable olive pomace is usually sold in the form of cylindrical pieces (fire logs) with mass of about 1 kg and a height of about 20 cm. If the freshly prepared cylindrical pieces have high content of fine particles and moisture, they might develop cracks during their sun-drying stage due to excessive expulsion of moisture content. This is a disadvantage for the end user in terms of transportation and storage. Therefore, it is preferable to have a balance between coarse and fine portions in order to have manageable dry fire logs. Because of these remarks, frequent check on the olive mill operational adjustments has to be carried out during the olive harvest season which is stretched over a period of about 10 weeks, starting at middle of October and ending at the end of December of each year. The data shown in
In essence, the charring of the olive pomace samples as we did it is a controlled burning of the volatiles accompanied by the escape of the sample moisture. By doing that, the mass of the olive pomace sample was reduced to about 20% of its initial value. The char of the test sample was then burned in a muffle furnace at 600˚C for three hours and the mineral content is left as ash. A more rigorous two-step procedure for preparing a low temperature ash begins with a pyrolysis step carried out in a tube furnace at about 500˚C followed by burning the char at about 350˚C for several hours [
In Equation (1), y is the % of char yield; y = 20.71% for sample KT25 and 21.32% for sample KT26. By comparing the ash percentages given in
Fraction identity | Mesh No. | Aperture/mm | Fraction mass/g | Fraction % |
---|---|---|---|---|
KT27 | 10 | 2 | 114.16 | 21.39 |
KT28 | 18 | 1 | 114.25 | 21.41 |
KT29 | 35 | 0.51 | 42.29 | 7.93 |
KT30 | 60 | 0.25 | 90.64 | 16.99 |
KT31 | 100 | 0.15 | 83.41 | 15.63 |
KT32 | <100 | <0.15 | 78.59 | 14.73 |
Sum | 523.34 | 98.08% |
Trial No. | Char mass/g | Ash mass/g | % of Char ash | % of Pomace ash |
---|---|---|---|---|
1 | 2.1834 | 0.3357 | 15.3751 | 3.1842 |
2 | 2.2452 | 0.3954 | 17.6109 | 3.6472 |
3 | 2.5284 | 0.6050 | 23.9282 | 4.9555 |
4 | 2.4900 | 0.4215 | 16.9277 | 3.5057 |
5 | 2.3013 | 0.3791 | 16.4733 | 3.4116 |
6 | 2.3816 | 0.3156 | 13.2516 | 2.7444 |
7 | 2.3270 | 0.3664 | 15.7456 | 3.2609 |
8 | 2.4923 | 0.4594 | 18.4328 | 3.8174 |
9 | 2.2637 | 0.3603 | 15.9164 | 3.2963 |
10 | 2.5009 | 0.3727 | 14.9026 | 3.0863 |
11 | 2.2895 | 0.2807 | 12.2603 | 2.5391 |
12 | 2.2320 | 0.2873 | 12.8719 | 2.6658 |
Average ash % | 16.1414 | 3.3429 |
Trial No. | Char mass/g | Ash mass/g | % of Char ash | % of Pomace ash |
---|---|---|---|---|
1 | 2.2054 | 0.3206 | 14.5370 | 3.0993 |
2 | 2.2423 | 0.3073 | 13.7047 | 2.9218 |
3 | 2.3886 | 0.5027 | 21.0458 | 4.4870 |
4 | 2.0952 | 0.3757 | 17.9315 | 3.8230 |
5 | 2.3317 | 0.4271 | 18.3171 | 3.9052 |
6 | 2.4435 | 0.3451 | 14.1232 | 3.0111 |
7 | 2.3700 | 0.4295 | 18.1224 | 3.8637 |
8 | 2.3969 | 0.3774 | 15.7453 | 3.3569 |
9 | 2.6724 | 0.5025 | 18.8033 | 4.0089 |
10 | 2.2996 | 0.4228 | 18.3858 | 3.9199 |
11 | 2.2188 | 0.4018 | 18.1089 | 3.8608 |
12 | 2.2348 | 0.2649 | 11.8534 | 2.5271 |
Average ash % | 16.7232 | 3.5654 |
age), are: 3.092 for % ash relative to char mass and 0.640 for % ash relative to pomace mass. The corresponding values for sample KT26 are 2.679 for % ash relative to char mass and 0.571 for % ash relative to pomace mass. The values of the percentage relative deviation, % R.D (% R.D = mean of absolute deviations ×100/average) are 13.1% and 13.6% for ash data given in
Knowledge of the proximate analysis of a fuel is necessary for evaluating its potential for energy production. The proximate analysis is a list of the percentages of moisture, ash, fixed carbon (FC), and volatile matter. The non-automated ASTM method [
The results of the ultimate analysis of crude olive pomace are given in
Sample identity | % Moisture | % Ash | % FC | % VM | FC/VM |
---|---|---|---|---|---|
KT25 | 5.965 | 3.555 | 18.469 | 77.976 | 0..24 |
KT26 | 7.298 | 3.846 | 19.153 | 77.002 | 0.25 |
Average | - | 3.701 | 18.811 | 77.489 | 0.25 |
An attempt was made for comparing the proximate and ultimate analyses reported in the present study with their counterparts reported previously [
1) The Gross and Net Calorific Values of Crude Olive Pomace and Its Fractions
Sample identity | % Ash | % C | % H | % N | a% O |
---|---|---|---|---|---|
KT7 | 2.38 | 53.89 | 7.40 | 0.63 | 35.70 |
KT12 | 5.70 | 55.02 | 7.62 | 0.62 | 31.04 |
KT25 | 3.55 | 55.13 | 7.70 | 0.97 | 32.65 |
KT26 | 3.84 | 55.13 | 7.70 | 0.93 | 32.40 |
KT23 | 4.89 | 57.45 | 7.80 | 1.06 | 28.80 |
KT24 | 1.28 | 51.30 | 6.88 | 0.80 | 39.74 |
KT27 | 0.81 | 51.04 | 6.75 | 0.81 | 40.59 |
KT32 | 4.45 | 51.14 | 6.90 | 1.39 | 36.12 |
a: % Oxygen determined by difference.
Comparison of proximate analyses | |||||
---|---|---|---|---|---|
Data set | % Ash | % FC | % VM | FC/VM | - |
Set 1 | 3.701 | 18.811 | 77.489 | 0.25 | - |
Set 2 | 5.183 | 25.8 | 69.9 | 0.37 | - |
Two-set average | 4.442 | 22.306 | 73.694 | 0.31 | - |
% R.D | 16.7 | 15.7 | 5.1 | 19.4 | - |
Comparison of ultimate analyses | |||||
Data set | % Ash | % C | % H | % N | % O |
Set 1 | 3.868 | 54.792 | 7.605 | 0.788 | 32.948 |
Set 2 | 5.17 | 51.36 | 6.42 | 1.16 | 35.90 |
Two-set average | 4.52 | 53.08 | 7.01 | 0.97 | 34.42 |
% R.D | 14.4 | 3.2 | 8.4 | 19.1 | 4.3 |
When a sample of a fuel is burned in an oxygen bomb calorimeter, the resulting amount of heat energy is known as GCV. However, burning the fuel in an industrial or domestic facility generates a different amount of energy known as the net calorific value (NCV). The magnitude of NCV is generally less than that of GCV. This difference is due to the fact that certain chemical and physical processes that take place under the oxygen bomb conditions cannot proceed when the fuel is burned under normal conditions of real life applications. In the case of a solid biomass fuel, such as olive pomace, the major corrections needed for getting the NCV value from the GCV value are the heat resulting from condensation of water coming from sample moisture and oxidation of sample hydrogen. Other corrections involve the heat of hydration of acids such as HNO3, H2SO4, HCl, and any heat resulting from possible interaction of water vapor with the remaining inorganic constituent of the biomass material.
In the case of acid correction, the current information regarding the thermochemical corrections for oxygen bomb calorimetry [
The values of the GCV reported in the second column of
Sample identity | GCV (kJ/g), wet basis | GCV (kJ/g), dry basis | NCV (kJ/g), dry basis | NCV/GCV, dry basis |
---|---|---|---|---|
KT7 | 20.891 | 22.409 | 20.754 | 0.926 |
KT12 | 20.548 | 21.709 | 20.007 | 0.922 |
aKT13 | 19.836 | 20.935 | 19.219 | 0.918 |
KT25 | 21.589 | 22.959 | 21.223 | 0.924 |
KT26 | 20.878 | 22.522 | 20.788 | 0.923 |
Average | 20.748 | 22.107 | 20.398 | 0.923 |
a: % H for this sample is taken as average % H of samples KT7, KT12, KT25, and KT26.
Sample identity | GCV (kJ/g), wet basis | GCV (kJ/g), dry basis | NCV (kJ/g), dry basis | NCV/GCV, dry basis |
---|---|---|---|---|
KT23 | 23.368 | 24.771 | 23.013 | 0.924 |
KT24 | 19.129 | 20.309 | 18.762 | 0.924 |
KT27 | 18.832 | 20.236 | 18.717 | 0.925 |
KT28 | 18.585 | 19.967 | n.d | n.d |
KT29 | 20.226 | 21.776 | n.d | n.d |
KT30 | 23.121 | 25.079 | n.d | n.d |
KT31 | 22.451 | 24.030 | n.d | n.d |
KT32 | 21.987 | 24.094 | 22.516 | 0.934 |
n.d: not determined.
GCV of samples KT25 and KT26. In the case of sample KT25, we used GCV of KT23 and KT24 and the mass fractions of 0.45 for pits (sample KT24) and 0.55 for pulp (sample KT23). The calculated value of GCV of sample KT25 is 22.763 kJ/g which amounts to 99.2% of the calorimetric result on dry basis. Likewise, by using the mass fractions of KT26 given in
2) The Gross Calorific Values of Exhausted Olive Pomace
The exhausted olive pomace samples that we prepared and studied in the present work are listed in the first column of
3) The Gross Calorific Values of Local Fire Wood
Based on personal observations of the present author, most of the wood sold during the 2014 winter season has high moisture content especially olive wood and the assorted wood mixture of almond and other related wood types; this high moisture content caused difficulties in maintaining a stable combustion in a fire place even in the presence of olive pomace. It is clear that in the absence of official specifications for the use and trade of solid fuels in Jordan, there will be health and environmental hazards. On terms of abundance and availability in the market, local wood can be considered as a non-renewable biomass in Jordan because of the scarcity of forests. This fact is the reason for marketing fire wood with high moisture content; the demand is high in winter time but wood drying is practiced at the low level by most owners of wood shops.
4) The Gross Calorific Values of Olive Oil and Local Liquid Fuels
The traditional liquid fuels used for residential space heating in Jordan are kerosene and diesel. Despite the fact that their current prices are nearly four times the prices a decade ago, these two liquid fuels are still used for diesel-fired central heating boilers and kerosene-fired space heating stoves. They are included in the present study for the purpose of determining the GCV of non-renewable fossil fuels. Therefore, their thermal capacity can be compared with the thermal capacity of a renewable biomass fuel. Although olive oil is intended for human consumption, it is also included in the present study to represent a renewable liquid fatty material. The values of GCV for olive oil, kerosene, and diesel are reported in
Sample No. | % Extractives a(d. b) | % Moisture | GCV (kJ/g), b(w. b) | GCV (kJ/g), (d. b) | HNO3 Correction, J/g (d. b) | Moisture Correction, J/g | cGCVexh/ dGCVcr (d. b) |
---|---|---|---|---|---|---|---|
KT7h | 24.5 | 7.108 | 17.063 | 18.369 | 55 | 174 | 0.82 |
KT12h | 10.5 | 4.426 | 19.098 | 19.982 | 27 | 108 | 0.92 |
KT13h | 7.9 | 4.248 | 19.261 | 20.116 | 42 | 104 | 0.96 |
KT25h | 14.5 | 4.507 | 19.623 | 20.549 | 41 | 110 | 0.90 |
KT26h | 9.8 | 7.825 | 18.462 | 20.029 | 40 | 191 | 0.89 |
KT27h | 8.0 | 2.974 | 19.017 | 19.600 | 33 | 73 | 0.97 |
KT32h | 22.3 | 3.036 | 18.784 | 19.372 | 45 | 74 | 0.80 |
a: Dry basis; b: Wet basis; c: GCVexh of exhausted pomace; d: GCVcr of crude pomace.
Sample identity | % Moisture | GCV (kJ/g), (wet basis) | GCV (kJ/g), (dry basis) | Literature GCV, kJ/g [ |
---|---|---|---|---|
KT8 | 5.601 | 16.952 | 17.958 | 18.82 |
KT9 | 4.865 | 18.556 | 19.505 | 18.01 |
KT14 | 4.806 | 18.230 | 19.150 | 18.47 |
As mentioned earlier in the discussion, these acid corrections are quite insignificant when compared with corrections of water condensation.
With gross calorific values, on wet basis, of 20.748, 16.952, and 44.942 kJ/g for crude olive pomace, oak wood, and diesel, a comparison based on fuel price and calorific value is given in
1) TG and DTG Curves of Oak, Almond, and Olive Fire Wood Samples
The TG pyrolysis curves of oak, almond, and olive wood samples are shown in
Guided with this literature information, the data given in
2) TG and DTG Curves of Crude Olive Pomace Samples
Sample identity | % S | % N | GCV (kJ/g), (wet basis) | H2SO4 correction, J/g (wet basis) | HNO3 correction, J/g (wet basis) | Literature GCV, kJ/g |
---|---|---|---|---|---|---|
KT33 | 0.0251 | 1.352 | 39.838 | 2 | 58 | 39.675 [ |
KT34 | 0.1703 | 2.622 | 46.143 | 16 | 112 | 46.20 [ |
KT35 | 1.0168 | 1.143 | 44.942 | 94 | 49 | 44.80 [ |
Fuel type | Reference mass/ton | aCost/$ per ton | Heat energy/ 1010 J per ton | MJ/$ |
---|---|---|---|---|
Olive pomace | 1 | 170 | 2.075 | 122.1 |
Oak wood | 1 | 255 | 1.695 | 66.5 |
bDiesel | 1 | 1170 | 4.494 | 38.4 |
a: USD; b: Price per metric ton was calculated from the price per liter and a density of 0.85 g/cm3.
The pyrolysis curves of three crude olive pomace samples are shown in
maximum rates of mass loss for cellulose and hemicellulose are highest for pit fraction (sample KT24) and lowest for pulp fraction (sample KT23). The DTG curves shown in Figures 5-7 were analyzed to get quantitative information of the type given in
Sample identity | KT8 | KT9 | KT14 |
---|---|---|---|
Sample mass (mg) | 11.78 | 13.43 | 10.44 |
Sample moisture (%) | 5.60 | 4.86 | 4.81 |
Moisture peak temperature (˚C) | 90 | 93 | 90 |
Moisture maximum rate of mass loss (%/min) | 2.2 | 2.5 | 2.4 |
Hemicellulose peak temperature (˚C) | 342 | 342 | 340 |
Hemicellulose maximum rate of mass loss (%/min) | 11.7 | 13.5 | 10.8 |
Cellulose peak temperature (˚C) | 400 | 386 | 398 |
Cellulose maximum rate of mass loss (%/min) | 19.2 | 19.4 | 19.3 |
Lignin peak temperature (˚C) | 525 | an.d | n.d |
Lignin maximum rate of mass loss (%/min) | 1.6 | n.d | n.d |
Residual mass fraction at 600˚C | 0.24 | 0.23 | 0.23 |
a: Not determined.
Sample identity | KT7 | KT12 | KT13 | KT23 | KT24 | KT25 | KT27 | KT32 |
---|---|---|---|---|---|---|---|---|
Sample mass (mg) | 14.33 | 12.66 | 12.13 | 9.13 | 9.30 | 12.00 | 12.61 | 11.29 |
Sample moisture (%) | 6.78 | 5.35 | 5.25 | 6.00 | 6.00 | 6.00 | 6.94 | 8.74 |
Moisture peak temperature (˚C) | 80 | 82 | 80 | 74 | 68 | 80 | 89 | 88 |
Moisture maximum rate of mass loss (%/min) | 1.3 | 1.8 | 1.5 | 2.0 | 1.5 | 1.2 | 2.2 | 2.1 |
Hemicellulose peak temperature (˚C) | 318 | 315 | 316 | 273 | 312 | 319 | 328 | 286 |
Hemicellulose maximum rate of mass loss (%/min) | 12.6 | 9.4 | 8.9 | 7.9 | 14.2 | 12.3 | 14.8 | 10.0 |
Cellulose peak temperature (˚C) | 360 | 358 | 364 | 358 | 368 | 363 | 367 | 350 |
Cellulose maximum rate of mass loss (%/min) | 14.4 | 14.0 | 15.3 | 10.5 | 18.1 | 13.8 | 13.1 | 14.7 |
Lignin peak temperature (˚C) | an.o. | n.o. | n.o. | n.o. | n.o. | n.o. | 486 | 500 |
Lignin maximum rate of mass loss (%/min) | n.o. | n.o. | n.o. | n.o. | n.o. | n.o. | 3.9 | 4.1 |
Residual mass at 600˚C | 0.29 | 0.30 | 0.31 | 0.25 | 0.28 | 0.23 | 0.17 | 0.07 |
an.o.: not observed.
Parameter | Range | Average |
---|---|---|
Moisture peak temperature (˚C) | 68 - 89 | 80 |
Moisture aR max (%/min) | 1.3 - 2.2 | 1.7 |
Hemicellulose peak temperature (˚C) | 273 - 328 | 308 |
Hemicellulose R max (%/min) | 7.9 - 14.8 | 11.3 |
Cellulose peak temperature (˚C) | 350 - 368 | 361 |
Cellulose R max (%/min) | 10.5 - 18.1 | 14.2 |
Residual mass fraction at 600 (˚C) | 0.07 - 0.31 | 0.24 |
bResidual mass fraction at 600 (˚C) | 0.17 - 0.31 | 0.26 |
a: Maximum rate of mass loss; b: If residual mass fraction at 600˚C for sample KT32 is excluded.
KT32 from the average residual mass fraction in
When properly dried at the premises of olive mills, sun-dried crude olive pomace can be marketed with moisture content of 10% or less; therefore much of its heat content is densified. Removal of extractives by solvent extraction reduces the calorific value of crude olive pomace by a factor of about 10%. Marketing crude olive pomace in loose or compact form has no significant effect on its gross calorific value. The loose form of crude olive pomace has about 21% of its mass in the form of grains with diameter >2 mm and about 47% of fine particles of diameter <0.5 mm. The remaining 32% fall within the range of these size limits. These fractions have different calorific values. Although the calorific value of olive pomace is substantially lower than that of kerosene and diesel, its low market price and its abundance and renewability pave the way for its use as an affordable substitute for space heating in Jordan. Because of its scarcity and high prices, local fire wood cannot compete with olive pomace for space heating in Jordan. The crude olive pomace of Jordan is relatively rich in volatiles with mass percentage of 77.5%. Because of their low moisture content and low nitrogen and sulfur contents, the net calorific values of the studied crude olive pomace samples amount to about 92% of their gross calorific values. The results of the TG and DTG measurements indicate the conformity of the pyrolysis of the lignocellulosic matter of the crude olive pomace samples to the pyrolysis behavior of other agrocellulosic biomass residues. The data on proximate and ultimate analyses as well as the calorimetric data can be reliably considered for specification purposes of olive pomace in Jordan.
The author is grateful to Yarmouk University for the financial support, to Mr. Eyad Hamzeh (JUST) for his assistance in the TG measurements, and to Miss Ayshyh Subeh (Yarmouk University) for her assistance in the extraction experiments and ash determination. Thanks are due to Professors M. Al-Khateeb, A. Al-Ajlouni, and E. Arafa (JUST) for their hospitability and for using their research equipment during my sabbatical leave.