Summary This study was carried out to evaluate the physico‐mechanical and combustion indices of briquettes made from blends of cornhusk (CH) and cassava peel (CP). The CH and CP was torrefied at 200°C to 300°C and were mixed in the ratio 90/10 to 10/90 for briquette production using D‐optimal crossed design. The fuel application for co‐firing in coal engines was evaluated with fuel ratio, combustibility index and volatile ignitability. The findings revealed that the density, durability index and compressive strength of briquettes blend at 10/90 (CH/CP) torrefied at 300°C and water preconditioned, were respectively improved by 18.19, 2.98, and 32.25% compared with those for raw briquettes at 10/90 blend ratio. Furthermore, the fixed carbon and calorific value increased with the increase in the torrefaction temperature and time. The produced briquettes at the mixing ratios of 10/90 and 30/70 (CH/CP) torrefied at 300°C for at least 1 hour is sufficient for co‐firing in coal engines. The CH and CP wastes with low calorific value which are hitherto discarded could be used to produce briquettes with appropriate qualities attributes of alternative fuel source for heating applications.

Numerical investigations were conducted to study the effects of Rayleigh, Ra, Prandtl, Pr, Darcy, Da, numbers, and the temperature difference ratio, J, on the fluid flow, isotherms, heat transfer, and distributions in a square cavity filled with porous medium. The range of parameters used is 5 Â 10 2 e Ra e 10 6 , 10 23 e Pr e 10 3 , 10 23 e Da e 10 3 , and 0 e J e 2. The flow governing equations including the Brinkman-extended Darcy equations of motion, energy, and heatfunction equations were thereby solved using the finite-difference method.The results show that all the problem governing parameters have strong effect on the convection vigour, isotherms, and heatfunction fields and profiles. An increase in the value of the Darcy number above unity has no more influence on the heatfunction profiles.

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Current energy shortage and environmental issues resulting from the use of fossil fuels have led to exploitation of renewable energy resources that includes municipal waste and agricultural residues. These residues are available, indigenous and are environmental friendly but some cannot be used directly in combustion process due high moisture content and low volumetric energy unless by briquetting. The study was undertaken to assess the combustion characteristic of binder-less briquettes produced from waste paper and groundnut shell. Combustion characteristics investigated were ignition time, burning time, calorific values, burning rate, specific fuel consumption, fuel efficiency and water boiling time. The calorific values of the briquettes ranged from 19.51-19.92 MJ/kg, while the thermal efficiency ranges between 13.75-21.64%, other results shows that the average burning rate between 0.511 and 1.133 kg/hr and the specific fuel consumption ranges between 0.087 and 0.131 J/g. The recorded boiling time values were between 17.5 and 30.0 minutes for cold start and 15.0 and 20.0 minutes for hot start. The results shows that waste paper and groundnut shell up to 25% in composition composite briquettes were found to have good combustion characteristics which qualify them as alternative to firewood for domestic and industrial energy. However, production of briquettes from waste paper and groundnut shell at mixing ratio of 85:15 was found to comparatively better from all experiment conducted.

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The moisture diffusivity and activation energy of three tilapia fish varieties were determined under convective drying process (CDP). A locally fabricated drying system was used for the experiment at 60, 90/60 and 90 o C drying air temperatures. The drying rate showed falling rate period for all the drying processes with no sign of constant rate period. The moisture diffusivity values which increased with the increase in drying air temperature varied from 7.821 x 10-11 to 4.591 x 10-10 m 2 /s. The predicted Arrhenius constant and activation energy were 2.221 x 10-10 m 2 /s and 23.79 kJ/mol respectively.

The drying kinetics of three varieties of cocoa beans (N38, F and WA) at 40, 50 and 60 degree centigrade was investigated experimentally. The three different varieties were dried using laboratory air oven UF Memmert and the moisture content determined according to AOAC standards. The results show that drying processes occur mainly in the range of the falling-rate period and the drying rates were observed to be faster at higher drying temperature. The effective diffusivities of the three cocoa beans varieties determined at 40, 50 and 60 degree centigrade ranged between 9.9269 x 10-11 and 4.4671 x 10-10 metre square per second. The predicted Arrhenius constant and activation energy were 2.47 x 10-10 metre square per second and 23.61 kilojoule per mole.