SOURCE:

Faculty: Physical Sciences
Department: Pure And Industrial Chemistry

CONTRIBUTORS:

Ikelle, I. I
Ogbuagu, J. O
Onuegbu, T. U

ABSTRACT:

The production and characterization of briquettes from mixtures of coal, corn cob and rice husk has been carried out. The briquette samples were produced by blending varying compositions of coal and rice husk, also coal and corn cob at the ratios of 100:0, 80:20, 60:40, 40:60, 20:80 and 0:100 using bitumen, starch, calcium sulphate and cement as binders and calcium hydroxide as desulphurizing agent. The briquettes were produced mechanically using a manual briquetting machine with force and compression pressure of 276.36 N and 31.67 N/m2 respectively. The results showed that the calorific values of the briquettes of coal and rice husk with the respective binders are in the following ranges, cement (19701.57-24441.12 kJ/kg), bitumen (20981.48-27083.07 kJ/kg), calcium sulphate (19615.16-24840.95 kJ/kg) and starch (21739.54-25921.82 kJ/kg). The calorific values for corn cob and coal are in the following ranges, cement (20364.34-22823.93 kJ/kg), bitumen (21691.64-23940.37 kJ/kg), calcium sulphate (19000.54-23219.07 kJ/kg) and starch (21450.82-23794.98 kJ/kg). The values showed that briquettes of coal and rice husk had higher calorific values than those of coal and corn cob. With regard to the binders used in the briquetting, briquettes produced with bitumen ignited faster with values (16.00-37.00 s), had much sulphur content values (3.01-8.22%) and lowest burning time (11.71-24.89 min) than other briquettes produced with other binders. Briquettes produced with binders cement and calcium sulphate had high ash contents (19.13-28.83 %) and (18.88-29.63 %) respectively due to the presence of non combustible material. Briquettes produced with starch as binder had highest compressive strength values ranging from 7.92-13.74 N/mm3, had lowest values of sulphur content (3.03-6.21 %) and long burning time (15.27-26.21 min). These properties made it the best of all the binders studied. The briquettes produced with starch had the lowest sulphur content. Analysis of variance (ANOVA) showed significant difference (p<0.05) at 95 % confidence interval for sulpur content when it was compared to other briquettes produced with different binders. The briquettes produced with bitumen as binder ignited faster than the other briquettes produced at 95 % confidence interval (p<0.05). The calorific values (kJ/kg) of the different briquette compositions were in the order, 60 % coal : 40 % rice husk (24441.12-27083.07) and 60 % coal : 40 % corn cob (22823.93-23940.37). The ignition time (s) of the different briquette compositions were in the order 60 % coal: 40 % rice husk (21.67-33.67) while 60 % coal: 40 % corn cob (29.56-42.50). The burning time (min) of the different briquette compositions were in the order 60 % coal : 40 % rice husk (17.81-20.43) while 60 % coal : 40 % corn cob (19.76-22.20 min). The compressive strength (N/mm3) of the different briquette compositions were in the order 60 % coal: 40 % rice husk (11.34-13.95) and 60 % coal: 40 % corn cob (12.75-14.46), the values are higher than those of 100 % coal that ranged from 7.05-7.92 N/mm3. The lower sulphur contents for 60 % coal : 40 % rice husk (4.69-7.78%), and that of 60 % coal : 40 % corn cob values of (5.78-7.56 %), showed that the briquette compositions were of good quality. The briquettes did not disintegrate when handled. The elemental composition of the ashes of the raw materials was determined using X-ray fluorescence spectrometer. The result showed that the concentration of the heavy metals in the ashes of coal included (V2O5 0.29 ± 0.0048 %, Cr2O3 0.059± 0.0011 %, MnO 0.13 ± 0.0012 %, CuO 0.18 ± 0.0041 %, As2O3 0.05 ± 0.0023 %, PbO 0.31± 0.0081 %), rice husk (V2O5 0.002 ± 0.0011 %, MnO 0.153 ± 0.0013 %, CuO 0.012 ± 0.0031 %, As2O3 0.0063 ± 0.0001 %, PbO 0.004± 0.0001 %) and corn cob (Cr2O3 0.346± 0.0032 %, MnO 0.123 ± 0.0006 %, SrO 0.023± 0.0014 %).The results showed that the concentration of the heavy metals in the ashes of coal, rice husk and corn cob were relatively small, therefore the ashes can be disposed off after cooking.